EPA 560/6-76-012
THE MANUFACTURE AND USE
OF SELECTED INORGANIC CYANIDES
TASK III
JANUARY 15, 1976
FINAL REPORT
...JNMENTAL PROTECTION AGENCY
OFFICE OF TOXIC SUBSTANCES
401 M STREET, S.W.
WASHINGTON, D.C. 20460
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STUDY ON CHEMICAL SUBSTANCES FROM INFORMATION CONCERNING
THE MANUFACTURE, DISTRIBUTION, .USE, DISPOSAL,
ALTERNATIVES, AND MAGNITUDE OF EXPOSURE TO
THE ENVIRONMENT AND MAN
Task III - The Manufacture and Use of Selected Inorganic Cyanides
by
Ralph R. Wilkinson
Gary R. Cooper
FINAL REPORT
April 2, 1976
EPA Contract No. 68-01-2687
MRI Project No. 3955-C
For
Environmental Protection Agency
Office of Toxic Substances
4th and M Streets, S.W.
Washington, D.C. 20460
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NOTICE
This report has been reviewed by the Office of Toxic Substances,
Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency. Mention of tradenames
or commercial products is for purposes of clarity only and does not
constitute endorsement or recommendation for use.
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PREFACE
This report presents the results of Task III of a project entitled
"Study on Chemical Substances From Information Concerning the Manufactur-
ing, Distribution, Uses, Disposal, Alternatives, and Magnitude of Exposure
to the Environment and Man," performed by Midwest Research Institute under
Contract No. 68-01-2687 for the Office of Toxic Substances of the U.S. En-
vironmental Protection Agency. Mr. Thomas E. Kopp has been the project of-
ficer for the Environmental Protection Agency. This program had Midwest Re-
search Institute Project No. 3955-C.
Task III, "The Manufacture and Use of Selected Inorganic Cyanides,"
was conducted from June 13 to November 14, 1975, by Dr. Ralph R. Wilkinson,
Associate Chemist, who served as task leader, and Mr. Gary R. Cooper, As-
sistant Chemist. Dr. Thomas W. Lapp has served as project leader on this
contract under the supervision of Dr. E. W. Lawless, Head, Technology As-
sessment Section. The following individuals were consultants on this task:
Professor Roger Clifford, Department of Metallurgical Engineering, Univer-
sity of Missouri, Rolla; Dr. Leslie Lancy, Lancy Laboratories Division,
Dart Industries, Inc., Zelienople, Pennsylvania; and Mr. Gerald Alletag,
President, Alta Chemical Company, San Diego, California.
Midwest Research Institute expresses its sincere appreciation to the
many companies, who provided technical information for this report.
Results of Task I of this project, "Manufacture and Use of Selected
Aryl and Alkyl Aryl Phosphate Esters," and Task II, "Production and Uti-
lization of Selected Alkyltin Compounds," are presented in separate reports.
Approved for:
MIDWEST RESEARCH INSTITUTE
at.
L. J.
^^•^-e*^A^-o«w—
lannon, Assistant Director
PhysioaJL Sciences Division
April 2, 1976
iii
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CONTENTS
Chapter Page
I Introduction 1
Cyanide Stability 1
Chemical Classes. 2
Objectives and Report Organization 2
II Summary 5
Merchant Cyanide Production Quantities,
Sites and Manufacturers 6
Manufacturing Processes That Produce Cyanides . . 8
Waste Management 8
Industrial Usage Patterns of Cyanides 8
Future Trends in Cyanide Usage. 8
Environmental Burden of Cyanides. . 10
III Conclusions and Recommendations 11
IV Historical Development and Future Outlook of
Cyanides 13
Historical Development to 1948 13
Hydrogen Cyanide 15
Alkali Metal Cyanides 19
Alkaline Earth Cyanides 21
Heavy Metal Cyanides 22
References to Chapter IV 23
V Market Input-Output Data 24
Manufacturers 24
Production and Capital Value 24
Importation and Capital Value 41
Exportation and Capital Value 47
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CONTENTS (continued)
Chapter Page
Usage Patterns 47
Final Products and Disposal 50
References to Chapter V 52
VI Manufacturing Processes 53
Hydrogen Cyanide. . 53
Sodium and Potassium Cyanide 58
Calcium Cyanide 60
Ferrocyanides and Ferricyanides 60
Iron Blue 61
Heavy Metal Cyanides. . . 63
Transportation Rates and Regulations 64
References to Chapter VI 68
VII Areas of Utilization 69
Metal Finishing (62.5%) 69
Pigment (Iron Blue) (16.9%) 83
Metal and Mineral Recovery (8.2%) . . . 88
Metal Heat Treatment (5.6%) 116
Photographic Processing (3.1%) 123
Anti-Caking Agents (3.1%) 129
Agricultural and Pest Control Chemicals (0.6%). = 130
References to Chapter VII 135
VIII Cyanide Treatment Methodologies 141
Destructive Techniques 143
Recovery Techniques 145
Engineering Methodologies 147
Effluent Treatment Costs 149
References to Chapter VIII 153
IX Alternative Materials, Processes and Uses 156
Alternate Raw Materials and Synthetic Methods . . 156
Alternates to Cyanides in Various Industrial
Sectors 157
References to Chapter IX. 169
vi
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CONTENTS (concluded)
Chapter
X Material Balance and Energy Consumption 172
Raw Materials 172
Energy Consumption for Production 173
Waste Material Product 174
Material Balance of Cyanide by Industrial Sector . 177
Exposure to Man and the Environment. 177
References to Chapter X 191
Appendix A - Thermally Generated Cyanide Sources 193
Appendix B - Results of the Written Questionnaire 204
vii
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FIGURES
No. Title Page
1 Industrial Patterns of Cyanides as Percentages of
Merchant Sales 9
2 Domestic HCN Production 20
3 NaCN Production, Importation, and Exportation in
1975 29
4 Distribution of NaCN Equivalent Available for
Merchant Sales 30
5 Iron Blue Consumption 34
6 Cyanide Importation , 46
7 NaCN Exportation 48
8 Inorganic Cyanide Consumption and Disposal Pattern ... 51
9 Manufacture of Hydrogen Cyanide 54
10 Acrylonitrile (SOHIO) Process for Hydrogen Cyanide . . 55
11 Manufacture of NaCN 59
12 Iron Blue Manufacture 62
13 Homestake Process Schematic 90
14 Carlin Process Schematic .... 92
15 Knob Hill Process Schematic 94
viii
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FIGURES (concluded)
No. Title
16 Magma Process Schematic 95
17 Gold Ore Production 97
18 Sodium Cyanide Consumption for Gold Recovery by
Cyanidation 98
19 Generalized Selective Flotation Process Schematic . . . 102
20 Lead-Zinc Flotation Circuits 104
21 Cyanide Consumption as a Flotation Reagent 112
22 Copper Bearing Ore Production and Beneficiation by
. Flotation 113
23 Lead-Zinc Bearing .Ore Production and Beneficiation
by Flotation. ................ 114
24 Fluorspar Ore Production and. Beneficiation,.by
Flotation 115
25 Estimated Consumption of Sodium Cyanide for Metal Heat
Treating 124
26 Possible WPW Processs Treatment for Metal-Cyanide .
Wastes 148
27 Closed-Loop Evaporative'Recovery System . .-.. 150
28 Material Balance for the Production of HCN and other
Cyanides as NaCN Equivalent . 178
29 Estimated Total Amount of Ferrocyanide and Iron Blue
As Environmental Burden, 1950-1985 189
IX
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TABLES
No. Title
1 Merchant Cyanide Production, Quantities, Sites and
Manufacturers in 1975 . 7
2 Manufacturers of Selected Cyanides in 1975. 25
3 Domestic Production of Selected Cyanides. ....... 26
4 Comparison of Estimated Hydrogen Cyanide Production . . 26
5 Capital Value of Selected Cyanides - Domestic
Production. 28
6 Estimated Domestic Production of NaCN for Merchant
Sales 32
7 Estimated Domestic Production of KCN for Merchant
Sales 33
8 Current and Former Manufacturers of Iron Blue 35
9 Major Companies Manufacturing and/or Distributing
Cyanide Salts for Industrial Use 36
10 Sodium Cyanide Equivalent Consumption in Metal
Finishing in 1975 40
11 Cyanide Imports and Capital Value - Sodium Salts. ... 42
j
12 Cyanide Imports and Capital Value - Potassium Salts . . 43
13 Calcium Cyanide Imports and Capital Value 44
14 Iron Blue Consumption, Importation, and Capital
Value 45
x
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TABLES (continued)
No. Title
15 Estimated Cyanide Importation in 1975 .......... 45
16 Sodium Cyanide Exports 49
17 Usage Patterns for Hydrogen Cyanide 49
18 Manufacturers of Hydrogen Cyanide By the Andrussow
and the SOHIO Acrylonitrile Processes 57
19 Hydrpgen Cyanide Process Waste Disposal Techniques. . . 58
20 Manufacturing Processes for Heavy Metal Cyanides. ... 64
21 Regulations for Shipment of Cyanides 65
22 Motor Carrier Shipping Charges, Chicago to
Kansas City 66
23 Rail Carrier Shipping Charges, Chicago to
Kansas City 66
24 Cyanide Cadmium Electroplating Bath Compositions. ... 71
25 Solutions for Stripping Electroplated Cadmium ..... 72
26 Cyanide Zinc Plating Bath Compositions 73
27 Solution for Electrochemically Stripping Zinc ... . . 74
28 Cyanide Copper Plating Bath Compositions 74
29 Approximate Composition of Major Commercial Copper
and Zinc and Copper and Tin Alloys 75
30 Cyanide Brass Plating Bath Compositions ........ 76
31 Cyanide Bronze Plating Bath Compositions 78
32 Cyanide Silver Plating Compositions 79
33 Cyanide Gold Plating Bath Compositions 80
xi
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. TABLES (continued)
No* Title Page
34 Major Companies Supplying Proprietary Plating Baths
and Chemical Formulations to the Metal Finishing
Industry • • • 82
35 NaCN Equivalent Consumption in Metal Finishing in
1975-1985 • . 83
36 Annual Consumption of Iron Blue of a Kansas City
Paint Manufacturer, 1971-1975 84
37 Consumption of Iron Blue by Market Use in 1975 85
38 Current Major Ink Manufacturers in Order of Business
Volumes • • 86
39 Size Classification of Printing Establishments in
1972 86
40 Major Operations Recovering Gold and Silver by
Cyanidation . 89
41 Cyanide Consumption for Recovery of Gold. 96
42 Factors Influencing Cyanide Consumption for Gold
Recovery • 99
43 Effect of Cyanide on Various Minerals 100
44 Typical Additions of the Cyanides to Ores 101
45 Leading Copper Producing Mines. • .. 107
46 . Leading Lead Producing Mines 108
47 Companies Concentrating Fluorspar 109
48 Consumption of Cyanides as Flotation Reagents in
Pounds. 110
49 Factors Affecting Cyanide Consumption 110
50 Consumption of all Depressants (Including Cyanides)
per Ton of Ore Ill
xii
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TABLES (continued)
No. Title
51 Compositions of Liquid Carburizing Salt Baths 117
52 Preferred NaCN Content in Relation to the Bath
Temperature . 117
53 Different Liquid Nitriding Salt Bath Compositions . . . 119
54 Preferred Salt Bath Composition for Liquid
Carbonitriding 120
55 Estimates of the Number of Commercial and Captive
Heat Treating Shops ..... 121
56 Factors Influencing Consumption of NaCN for Metal Heat
Treating 125
57 Composition Range of Bleach Solutions 126
58 Photographic Chemicals Manufacturers •• 126
59 Estimated Annual Consumption of Sodium Ferrocyanide
and Sodium Ferricyanide in Photographic Processing. . 127
60 Ferricyanide Consumption in Three Typical Film
Processing Laboratories 128
61 Comparative Regeneration and Disposal Costs of
Various Techniques 129
62 Estimated Cost of Ozonation Equipment 129
63 Estimated Consumption of Cyanides for Agricultural and
Pest Control Purposes 131
64 Principal Manufacturers of Fumigants. ......... 133
65 Principal Manufacturers of Warfarin-Type
Rodenticides 134
66 Direct Chemical Cost Comparison Alkaline Chlorination
Versus Carbon Cyanide Removal 146
67 Comparison of Treatment Costs, $ (1972) 152
xiii
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TABLES (concluded)
No. Title Page
68 Estimated Distribution of Zinc Plating Baths by Type. . 157
69 Products Currently Available for Use by Metal
Finishers ..... 159
70 Manufacturers of Cobalt Blue and Ultramarine Blue ... 160
71 Processes for Recovery of Gold and Silver 162
72 Alternatives to Liquid Carburizing. ... 164
73 NaCN and NaCN Equivalent by Industrial Sector 179
74 Estimated Amount of Cyanide as NaCN Equivalent in Use
and Exposed to the Environment and Man, 1965-1985 . . 184
75 Estimated Amount of Cyanide as NaCN Equivalent in Use
and Exposed to the Environment and Man, 1970-1985 . . 185
76 Estimated Amount of Cyanide as NaCN Equivalent in Use
and Exposed to the Environment and Man, 1975-1985 . . 186
77 Estimated Amount of Cyanide as NaCN Equivalent in Use
and Exposed to the Environment and Man, 1980-1985 . . 187
78 Estimated Amount of Cyanide as NaCN Equivalent in Use
and Exposed to the Environment and Man in 1985. ... 188
xiv
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CHAPTER I
INTRODUCTION
Inorganic cyanides are widely used in industry because of their unique
chemical properties. Industrial uses include:
* Metal finishing - stripping and electroplating
* Pigments for paints, inks, carbon paper, and plastics
* Mining - flotation and extraction of ores
* Metal heat treatment and case hardening
* Photographic processing
* Anti-caking agent
* Agriculture and pest control.
In addition, hydrogen cyanide is present during coking, smelting, and blast
furnace operations.
CYANIDE STABILITY
Generally speaking, inorganic cyanides are not contained in consumer
and household products, but are confined to the industrial, mining, and
agricultural sectors because of the extreme toxicity of hydrogen cyanide
gas, HCN, and the cyanide ion, CN~. Two exceptions are photo processing
chemicals and pigments which contain ferrocyanide, Fe(CN)x-~^, and/or fer-
ricyanide, Fe(CN)g~3. Cyanide in this form is not particularly toxic nor
hazardous to handle because of the great stability of the iron cyanide rad-
ical ion toward dissociation and oxidation-reduction reactions. However,
some experimental data indicate that even the iron cyanide radical ion can,
under certain conditions, slowly release cyanide ion.
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CHEMICAL CLASSES
Inorganic cyanides are primarily ionic compounds consisting of a metal
cation associated with one or more cyanide radicals, e.g., sodium cyanide,
NaCN, and zinc cyanide, Zn(CN)2« Special cases are the complex iron cyanide
radical ions previously mentioned and double salts such as NaCu(CN)/>. To
this inorganic listing, gaseous hydrogen cyanide, HCN (or hydrocyanic acid),
must be added, since it serves as a starting point in the synthesis of many
other metal cyanides. Hydrogen cyanide is essentially a covalent compound
in contrast to the above ionic cyanides.
Organic cyanides are largely covalent compounds and are liquids or
solids and are called nitriles. The cyanide grouping, CN, is attached to
a hydrocarbon or other complex grouping having a skeleton or backbone of
carbon atoms. The simplest nitrile is acetonitrile, CHoCN (also known as
methyl cyanide or cyanomethane).
Nitriles are generally less toxic than inorganic cyanides, and are
extensively used in the synthesis of other organic compounds, e.g., dyes,
drugs, synthetic fibers, plastics, etc. Organic cyanides lie outside the
scope of this report. The term cyanide will be used throughout the body
of the report and will refer to inorganic cyanides only. Cyanides selected
for study on this task are:
* Hydrogen cyanide, HCN * Sodium and potassium ferricyanide
* Sodium cyanide, NaCN * Iron Blue (ferric ammonium ferro-
cyanide)
* Potassium cyanide, KCN
* Heavy metal cyanides as cadmium,
* Calcium cyanide, Ca(CN)2 copper, gold, silver, and zinc
* Sodium and potassium
ferrocyanide
OBJECTIVES AND REPORT ORGANIZATION
The primary objectives of this study are to collect information on
the production quantities, manufacturers and their processes, formulators
and their products, users and their processes, alternatives to cyanide ma-
terials, the environmental management of cyanide-containing effluents, and
the magnitude of exposure to the environment and man.
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This information is organized into a format which will assist the
governmental agencies in the evaluation of any regulatory alternatives for
these materials. The goal of Task III of the study has been to assist the
Environmental Protection Agency (EPA) in the evaluation of the potential
for environmental contamination by cyanides.
The report is organized into 10 chapters and two appendices. The Sum-
mary and Conclusions and Recommendations chapters are given early in the
body of the report to allow an immediate overview. References are given at
the end of each chapter for convenience. Chapter contents are as follows:
Chapter I - Introduction; Overview of industrial cyanide uses, chem-
ical classes, specific cyanides selected, objectives of present study.
Chapter II - Summary; Degree to which objectives were met, production
data of specific cyanides, manufacturing processes and waste management, us-
age patterns as percentage of total merchant cyanide, future trends in usage,
environmental burden.
Chapter III - Conclusions and Recommendations.
Chapter IV - Historical Development and Future Outlook of Cyanides;
Manufacturing processes, economic growth from 1965 to 1975, industrial fu-
ture of cyanides to 1985.
Chapter V - Market Input/Output Data; Identification of cyanide man-
ufacturers, cumulative data regarding production, importation, exportation,
and capital value, usage patterns by production quantity, final products and
disposal of cyanides.
Chapter VI - Manufacturing Processes; Hydrogen cyanide by Andrussow
and SOHIO acrylonitrile processes, manufacturers by capacity and site, other
cyanide manufacturing processes, waste disposal, transportation rates and
regulations.
Chapter Vtl - Areas of Utilization; Metal finishing, pigment, mining
operations, metal heat treatment, photography, anti-caking agents, agricul-
ture and pest control, waste disposal, economic considerations, future growth
patterns.
Chapter VIII - Cyanide Treatment Methodologies; Destruction and recov-
ery techniques, engineering methodologies, comparison of treatment costs.
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Chapter IX - Alternative Materials, Processes, and Use; Alternate
raw materials and processes for cyanide synthesis, alternatives to cyanides
by industrial sector.
Chapter X - Material and Energy Balance and Environmental Exposure;
Raw materials, energy balance, plant capital investment, process waste ma-
terial, material balance by industrial sector, estimated environmental bur-
den by industrial sector from 1950 to 1985.
Appendix A - Thermally Generated Cyanide Sources; Coke pro'duction,
blast furnace operations, estimated hydrogen cyanide production as by-
product.
Appendix B - Results of Written Questionnaire.
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CHAPTER II
SUMMARY
The primary objectives of this project were to collect information
on environmental aspects of U.S. production and use of inorganic cyanides,
alternatives to cyanides, environmental management, and exposure to the
environment and man. The information was to be organized and presented in
a form which will assist the EPA in assessing environmental impacts of in-
organic cyanide.
The present study accomplished all the objectives and in particular
indicates which cyanides are being phased out by industry and which may
have continuing use in the next 10 years. The environmental impact of these
cyanides is assessed.
Information acquisition and evaluation activities were designed to
identify proven or potential sources of cyanides and the environmental ef-
fects of these substances. The commercially important cyanides were identi-
fied through manufacturers, formulators, distributors, users, and surveys
of technical literature. The cyanides include:
* Hydrogen cyanide
* Sodium and potassium cyanide
* Calcium cyanide
* Sodium and potassium ferrocyanide
* Sodium and potassium ferricyanide
* Iron blue (ferric ammonium ferrocyanide)
* Heavy metal cyanides, including cyanides of cadmium, copper, gold,
s i1ver, and . zinc
The scope of the study for each of these chemicals included identifi-
cation of production sites and quantities, descriptions of manufacturing
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processes and environmental aspects, description of waste disposal methods,
and identification of commercial uses for these products.
Sources of the project team's information included several standard
and reference publications, technical literature for the chemical process
industry, telephone and letter inquiries to producers, trade organizations,
government agencies, formulators, distributors, users, and a written ques-
tionnaire submitted to the seven producers of hydrogen cyanide.
The major findings in this study are briefly described in the follow-
ing subsections.
MERCHANT CYANIDE PRODUCTION QUANTITIES, SITES AND MANUFACTURERS
Production data for the 14 cyanides of interest are presented in Table
1. '''"'".'''''
The production rates, sites, and manufacturers range from two manufac-
turers of gold cyanide in New Jersey at 200,000' lb annually to seven manufac-
turers of hydrogen cyanide at 375 million pounds annually. Production sites
of hydrogen cyanide are located in Texas (3), Louisiana, Tennessee, Ohio,
and New York State.
Sodium cyanide is the next most prominent cyanide with a production
of about 56.5 million pounds annually. Other cyanides are manufactured in
relatively small quantities and are derived from either hydrogen cyanide
or sodium cyanide. Total metal cyanide production is 79.2 million pounds.
The total of all cyanides is 454.2 million pounds.
Emphasis is placed on the quantity of cyanides produced for merchant
sales in contrast to cyanides produced for captive use. Statistical data
are more generally available for merchant trade cyanides and are considered
proprietary information when applied to captive cyanides. Thus, a reasonably
accurate estimate (5 to 10%) of merchant trade cyanides can be given but es-
sentially no production information is available for cyanides used internally.
Captive cyanides are used as raw materials in the production of other
materials. For example, sodium cyanide is captively consumed in the manufac-
ture of chelating agents, EDTA and NTA, but no production figures are avail-
able for these purposes. Adiponitrile is now principally manufactured via
cyclohexane and adipic acid and no longer requires hydrogen or sodium cyanide.
Potassium cyanide is captively consumed in the manufacture of cyanogen
gas and malpnic acid. Cyanogen is an intermediate for medicinals, photo-
graphic chemicals, and military poison gas. Malbnic acid is an intermediate
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Table 1. MERCHANT CYANIDE PRODUCTION, QUANTITIES, SITES
AND MANUFACTURERS IN 1975
a/
Cyanide—
Hydrogen cyanide
Sodium cyanide .
Calcium cyanide-
Iron blue
Zinc cyanide
Sodium and potassium
ferrocyanides
Potassium cyanide
Copper cyanide and
sodium and potassium
copper double salts
Cadmium cyanide
Silver cyanide
Sodium and potassium
ferricyanides .
Potassium gold cyanide-
Total
Total ,.
productIon-
go6 Ib/year)
375.0
56.5
8.0
7.0
2.5
2.0
1.5
0.6
0.5
0.4
Production
sites
in U,S«
7
1
3
2
3
2
1
1
2
2
Number of
manufacturers
7
1
3
2
3
2
1
1
2
2
aj The cyanides are listed in descending order of total production.
b/ Midwest Research Institute (MRI) estimated 1975 production.
£/ There are no domestic producers of calcium cyanide. Imports amounted
to 8.0 million pounds in 1975.
d/ Chemical Week, p. 23. April 23, 1975.
for polymethine dyes, synthetic caffeine, and medicinals. No production
figures for potassium cyanide for these purposes are available.
Calcium cyanide is captively consumed for organic synthesis and for
production of heavy metal cyanides, including ferro- and ferricyanides,
and iron blue.
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MANUFACTURING PROCESSES THAT PRODUCE CYANIDES
Hydrogen cyanide is produced as a primary product by the Andrussow
process. It is estimated that.275. million pounds are produced in this man-
ner. A second pfoce'ss, SOHIO-acrylonitrile', yields hydrogen cyanide as a
by-product. It is estimated that 200 million pounds are produced by this
process but that 100 million pounds are incinerated. Of. the total 375 mil-
lion pounds available for use, only about 11% enters the inorganic sector,
principally as sodium cyanide, and the remainder is used for organic syn-
thetic purposes.
Other cyanides are manufactured by simple replacement and/or oxidation-
reduction reactions. Hydrogen cyanide is also produced as an unwanted by-
product from coke ovens and blast furnaces. There are approximately 60 million
pounds of hydrogen cyanide generated by coke ovens annually. Coke oven gases
are used in blast furnaces as an additional fuel.
WASTE MANAGEMENT
The wastes produced by the various manufacturing processes generally
involve solids as complex iron cyanides and are handled by landfill or by
deep well injection. Liquid wastes occurring as cyanide liquors and nitriles
are generally treated by alkaline chlorination. Waste gases as hydrogen cya-
nide and as volatile nitriles are incinerated.
INDUSTRIAL USAGE PATTERNS OF CYANIDES
The usage patterns of industrial cyanides are given in Figure 1. Metal
finishing operations including cleaning, stripping, plating, bath makeup,
and maintenance account for about 62.5% of total merchant cyanide as NaCN
equivalent. Principally, sodium cyanide is employed but heavy metal cyanides,
especially zinc cyanide, are important. Iron blue (ferric ammonium ferrocya-
nide) is an important article of commerce, and accounts for 16.9% of cyanide
consumption as pigment. All other sectors account for less than 10% each.
FUTURE TRENDS IN CYANIDE USAGE
Substitutes for cyanides in some industrial processes are being sought
and utilized. Specifically, it is forecast that metal finishing usage of
sodium and heavy metal cyanides will decrease by at least 25% over the next
10 years as noncyanide plating baths, especially zinc baths, are developed.
The same trend is noted in metal heat treatment as noncyanide liquid baths
and gaseous processes involving methane and/or ammonia are developed.
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Metal
Finishing
for Stripping
and Plating
62.
5%
TOTAL CYANIDES FOR
MERCHANT SALES
Iron Blue
as Pigment
for Ink
16.
9%
(100%)
Mining
Chemicals
Ore Flotation
and Extraction
8.2%
Metal Heat
Treatment
and Case
Hardening
5.6%
Photographic
Chemicals for
Development
3.1%
Anti-Caking
Agents for
De-icers
3.
1%
Agricultural
and
Pest Control
0.6%
Figure 1. Industrial patterns of cyanides as percentages
of merchant sales (NaCN equivalent)
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Photographic chemicals using ferro- and ferricyanides are declining
as systems based on ferric ion and EDTA become more prominent. Agricul-
tural uses of cyanides as fumigants and insecticides and for pest control
as rodenticides are no longer economically significant.
A continued usage of cyanides as iron blue for pigment in inks, car-
bon paper, as a plastics colorant and for industrial paints is forecast.
Likewise, mining applications for ore flotation and extraction, principally
as sodium cyanide, and anti-caking agents for de-icers, principally as fer-
rocyanide and iron blue, continue to consume a small but significant quan-
tity of cyanide.
ENVIRONMENTAL BURDEN OF CYANIDES
Practically all industrial cyanide is handled by one or more waste
treatment processes to yield cyanate or carbon dioxide and nitrogen and
heavy metal hydrated oxides. Cyanides as ferrocyanide and iron blue are
dispersed in runoff waters, along highways from de-icing operations and
may eventually be degraded and oxidized by sunlight, heat and normal wea-
thering conditions. Much cyanide as iron blue is disposed by landfill op-
erations. The fate of iron blue in anaerobic condition in the absence of
light and heat is unknown at present. If the anaerobic degradation process
is relatively slow, e.g., only 5% degradation per year, a significant
amount of iron blue could be accumulating in the environment. Fortunately,
iron blue is not toxic.
10
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CHAPTER III
CONCLUSIONS AND RECOMMENDATIONS
The following conclusions are drawn on the basis of this study.
1. Overcapacity for hydrogen cyanide exists at present. The needs
of hydrogen cyanide could be met with existing SOHIO-acrylonitrile plants
yielding by-product HCN and one or two large Andrussow process facilities.
2. Rapidly changing industrial processes and markets are causing a
decrease in long-term demand for hydrogen cyanide which will likely con-
tinue for the next 10 years.
3. Metal cyanides are very prominent industrially with the two larg-
est sectors being metal finishing (62.5%) and pigment (16.9%).
4. Chemical substitutes for cyanides are being researched and devel-
oped. If successful, these will largely replace cyanides and cause a signi-
ficant drop in cyanide usage in all sectors, with the possible exceptions
of mining operations, pigments and as anti-caking agents. By 1985, cyanide
consumption will be 50 to 757o of its present usage, i.e., a drop to 40 to
60 million pounds from the present 80 million pounds of NaCN equivalent.
5. Over the next 10 years, a 2 to 37o growth rate is forecast for
iron blue by industry sources. Consumption of cyanides by mining operations
will continue at present levels over the next 10 years as will anti-caking
agents usage.
6. In general, proper cyanide waste management has been observed by
nearly all major cyanide users since 1970. Alkaline chlorination and land-
fill operations are the more prominent of several options available.
!• Very little regeneration of cyanides has been observed. One ex-
ception lies in the photographic chemicals sector where conversion of fer-
rocyanides to ferricyanides by persulfate oxidation or ozonation is becom-
ing prominent. The economics are favorable for regeneration.
11
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8. Environmental burden due to ferrocyanides and iron blue as anti-
caking agents and iron blue as pigment may become prominent in the future.
Fortunately these chemicals have low toxicity.
The following recommendations are offered:
1. Continue encouragement of lower cyanide waste levels in the metal
finishing area through the establishment of effluent guidelines and stan-
dards of performance.
2. Continue to monitor mining waste operations and encourage good
housekeeping and safety practices regarding tailings ponds.
3. Encourage research and development toward regeneration or recyc-
ling of cyanides particularly in the metal finishing and photographic sec-
tors.
4. Encourage research and development to find economic and easily
degradable blue pigments as a substitute for iron blue.
5. Encourage the development of economical and easily degradable
anti-caking agents for de-icers as substitutes for ferrocyanides and iron
blue.
6. Determine decomposition kinetics and mechanism for ferrocyanides
and iron blue in runoff waters from highway de-icing operations.
7. Determine decomposition kinetics and mechanism for ferrocyanides
and iron blue under landfill management conditions.
12
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CHAPTER IV
HISTORICAL DEVELOPMENT AND FUTURE OUTLOOK OF CYANIDES
The historical development of cyanides for industry, mining, and ag-
riculture is reviewed. The future outlook of cyanides from 1975 to 1985 is
discussed from a generalized viewpoint.
HISTORICAL DEVELOPMENT TO 1948
Cyanides have been employed in electroplating since 1840 when special
solutions for gold and silver plating were developed by Elkington. Photo-
graphic applications date from 1884 with Farmer's Reducing Solution uti-
lizing ferro- and ferricyanides. In 1888, MacArthur and Forrest developed
a gold cyanidation process and commercial extraction of low-grade gold and
silver ores began the following year.
The usage of cyanides in metal finishing, i.e., stripping and electro-
plating operations, constitutes the largest industrial sector today. Other
uses of cyanides are economically significant, e.g., metal heat treatment
and case hardening and pigments, but they do not rate even a close second
in overall utility of cyanides when compared to metal finishing.
Cyanide synthesis and commercial production has had a long history and
has been reviewed by a number of authors.JL' In general, the historical syn-
thetic routes extend back at least to Scherlein 1782, and have been modified
by various talented individuals, culminating in two very successful processes,
namely, the Castner process (1900) and the American Cyanamid process (1917).
The early routes relied on nitrogenous organic matter, ammonia, or
nitrogen gas as the source of nitrogen, and the reaction with carbonates
and coke was carried out at high temperatures near 900 to 1000°C in iron
vessels. The products were always impure and contained traces of iron.
A very successful process by Beilby (1891) in Scotland utilized po-
tassium and sodium carbonates, carbon and ammonia:
13
-------
Na CO + K CO .+ 8C + 4NH ^
2NaCN + 2KCN + 6CO + 6H
The process could not be made to yield pure sodium cyanide.
World production of metal cyanides by 1897 reached 13 million pounds
annually, and rose to 50 million pounds by 1915. This increased production
was largely the result of the Castner process (1900) which yielded a high
grade of sodium cyanide and largely displaced the more expensive potassium
cyanide except for electroplating operations.
The Castner process combines metallic sodium, charcoal, and ammonia
as follows:
2Na + 2C + 2NH ^. 2NaCN + 3H
It takes place in stages involving sodamide as an intermediate. The raw
materials are heated to 800°C in iron vessels, and the molten water-like
cyanide can be easily cast into "eggs" containing 98% NaCN. The hydrogen
can be recovered in high purity. Even as late as 1964, plants operating
in England, Spain, France, and Germany were using an updated form of the
Castner process.
Large quantities of alkali cyanide have been made in the U.S. by
heating calcium cyanamid with coke or charcoal in electric furnaces above
1000°C to form "black" cyanide, Ca(CN)2- Thus,
CaNCN + (excess) C 1100°C> Ca(CN)
NaCl
From calcium cyanide other cyanides can be made by treating it with metal
carbonates. For example,
Ca(CN)2 + Na2C03 ^ 2NaCN + CaC03
American Cyanamid Company has been largely responsible for development of
these processes starting in 1916 as a direct result of World War I. With
several of these processes operating simultaneously in various parts of
the world, total annual consumption of sodium cyanide reached 160 million
pounds in 1963, excluding the Communist Bloc, for which consumption data
are lacking.
14
-------
Sodium cyanide or calcium cyanide can be utilized to form many other
cyanides, including hydrogen cyanide by direct acidification, ferro- and
ferricyanides, iron blue, heavy, metal cyanides, and a host of organic de-
rivatives (nitriles).
Hydrogen cyanide can also be made by catalytic dehydration of forma-
mide (1932). Thus:
0
NaOCH ||
CH OH + CO —T > CH -C-OH
J ' J
0 0
CH C-OH + NH3 > HC-NH + CH OH
(formamide)
The final step requires temperatures up to 650°C with an alumina catalyst.
This process was popular in Germany.
HYDROGEN CYANIDE
In 1948, the major American producers of hydrogen cyanide were E» I.
du Pont de Nemours and Company and American Cyanamid Company. The combined
production of hydrogen cyanide (by acidification as described above)
amounted to 40 .million pounds annually. Hydrogen cyanide was also obtained
from coke oven gas during coking operations. In 1948, Pittsburgh Coke and
Chemical Company (now Shenango Company) recovered 1 million pounds of hydro-
gen cyanide from coke oven gas.2/ This process also constituted a source of
sodium cyanide, since HCN could be trapped in caustic and sold for electro-
plating and organic synthesis purposes. Recovery of cyanide from coke oven
gas ceased about 1960.
However, in 1948, the synthetic route for hydrogen cyanide and metal
cyanides changed dramatically with the introduction of the world's first
plant for the captive production of HCN from natural gas, ammonia, and air
by Rohm and Haas Company at Deer Park (Houston), Texas*!' The principal
use of the hydrogen cyanide was for the production of acetone cyanohydrin,
an intermediate of methyl methacrylate. Two other companies, Carbide and
Carbon Chemicals (now Union Carbide Company) and Monsanto Chemical Company
15
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soon entered the field, and byi!953 over 200 million pounds capacity of
HCN was in existence.
The synthetic route involved the oxidation of ammonia in the presence
of methane, and was devised by Andrussow in 1933 • Thus:
2CH4 + 302 + 2NH3 2HCN
3/
Hydrogen cyanide occurs to the extent of 7% by volume in the reaction gas.—
More recent adaptations of the synthetic route to HCN include the
Degussa process (West Germany, 1958) which uses no air or oxygen, just am-
monia and methane. The two reactants are passed through externally heated
ceramic tubes containing a platinum catalyst at 1200 to 1250°C. The reac-
tion is:
OT + CH
4 1250
This process is limited to a smaller scale than is the Andrussow process
because of a lower production rate and relatively fragile equipment.
The Shawinigan Chemicals Division of Gulf Oil Canada, Ltd., developed
an alternate route for the production of HCN from ammonia and propane in
the absence of air using an electrothermal fluidized bed of coke at 1500°C
with no catalyst. The plant operated from I960 to 1968 , and was closed for
economic reasons, not technical problems. The HCN produced was transitory
and converted directly to sodium cyanide.
U«S« production capacity by the Andrussow process or modifications
thereof grew rapidly from 1948 to 1965 as new companies entered the field,
and as older facilities expanded. Published annual capacity in 1963 was
415 million pounds, and production rose from 40 million pounds prior to
the Andrussow process in 1948 to more than 450 million pounds in 1965.
This figure supplied by the Bureau of Census is known to be understated
since interplant transfers of HCN are not counted as consumption in pro-
ducing plants. Hence, total consumption was more nearly 550 million pounds.
The principal uses for HCN from 1948 to I960 were for plastics and
organics (acrylonitrile, methyl methacrylate, adiponitrile, chelating ag-
ents, lactic acid, Pharmaceuticals, alkylamines, etc.). Only a small amount
of hydrogen cyanide was converted to alkali cyanides, pigments (iron blue),
ferro- and ferricyanides, and heavy metal cyanides. It has been estimated
that the combined market for all inorganic cyanides accounted for approxi-
mately 10 to 20% of HCN production. This estimate holds true today as well.
16
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In 1960, Standard Oil of Ohio (SOHIO) developed a new process for
acrylonitrile production which yielded HCN as a by-product. Thus, acrylo-
nitrile, instead of being an important consumer of HCN, became an important
producer of HCN. The first SOHIO-based acrylonitrile plant was placed in
operation by Vistron Corporation (a subsidiary of SOHIO) in 1962 at Lima,
Ohio. This plant produced 8 million pounds of HCN annually. Approximately
0.15 to 0.20 lb of HCN are produced as by-product for every pound of acryl-
onitrile that is produced.^./
From 1962 to 1965 the hydrogen cyanide producers expanded their ca-
pacity, and HCN production rose from 170 to 450. million pounds (and higher
if interplant transfer is counted) as demand for HCN for use in organics
rose. The inorganic needs for HCN grew slowly, as no new markets were de-
veloped.
From 1965 to 1967 many of the original acrylonitrile plants using HCN
as a raw material converted to the SOHIO process, causing demand and pro-
duction of HCN to slide downward from the peak of 450 to 250 million pounds.
Much of the by-product HCN was incinerated as demand slumped. The last HCN-
based acrylonitrile plant which was operated.by Monsanto at Texas City,
Texas, closed in August 1970. From an estimate of nearly 80% production ca-
pacity in 1965, the industry fell to a level near 55% of production capacity
in 1970 Jt/
However, beginning in 1967, strong interest was shown in nitrilotriace-
tic acid (NTA) as a replacement for phosphate as a builder in detergents.
This trend rejuvenated the HCN market, since HCN is. a raw material for NTA.2/
The methyl methacrylate market began growing rapidly and production of HCN
rose again to a peak near 370 million pounds (or higher) in 1969.
In 1970, Ethyl Corporation planned an 85 million pound HCN facility
along the Houston Ship Channel and contracted Chemico (Chemical Construction
of New York) to design the plant.~.' Ethyl Corporation planned to use HCN for
manufacture of NTA. If completed, the HCN capacity would rise to near 650
million pounds.
Meanwhile, the Hampshire Division of Grace Chemical Company expanded
its original 20 million pound NTA plant (1967) to 60 million pounds capa-
city by 1970.-t' By 1969 Monsanto was producing 75 million pounds of NTA in
Alvin, Texas, and planned to expand to a 350 million pound NTA plant in
Texas City, Texas. Other companies indicated an interest in NTA production,
e.g., E. I. du Pont de Nemours and Company.
These very hopeful estimates of perhaps 500 million pounds annual pro-
duction of NTA, with a consequent rise to perhaps 500 million pounds of HCN
17
-------
annually, were made in the face of an unresolved nitrate pollution poten-
tial arising from NTA degradation JJ Thus, although NTA was considered a
biodegradable product and a possible substitute for phosphates in deter-
gents, it was also a potential cause of nitrate pollution.
In December 1970, the EPA released results of an NTA study which
showed that NTA, in combination with cadmium and methyl mercury, could
cause a high incidence of fetal injuries in rats and mice. The EPA recom-
mendation was to stop using NTA pending further tests and review.
The EPA report caused Proctor and Gamble to make a clean break with
NTA. The result of the report was to cause the HCN producers to drop ex-
pansion plans of more than 750 million pounds annually. The Ethyl Corpora-
tion cancelled plans for its NTA plant. The property remains vacant today.
Monsanto Company halted construction of 450 million pound NTA facilities
at Alvin and Texas City, Texas. W. R. Grace Company suspended plans for a
100 million pound NTA plant in Ontario, Canada..§/
The latest information regarding hazards of NTA came from the National
Cancer Institute and the National Institute of Environmental Health Sciences.
Long-term studies show that NTA causes the development of urinary tract can-
cers in rats and mice.—' Thus, NTA seems to offer no future markets for hy-
drogen cyanide.
The result of these actions has slowed HCN growth significantly to date.
Since 1970, HCN production has hovered near 300 million pounds annually. Pres-
ent capacity is more than adequate to handle present markets.
The most recent estimate of HCN future production is by the Chemical
Marketing Reporter, December 10, 1973. This source estimates HCN growth at
5.5%/year through 1977. Growth will occur principally because of methyl
methacrylates and other plastics and synthetics. Hopes for NTA revival ap-
pear nil. The inorganic cyanide market provides no growth opportunity for
HCN since this market is amply supplied by current production and facili-
ties in existence.
Finally, an opinion from T. C. Ponder, Petrochemicals Editor of Hy-
drocarbon Processing, is offered regarding the future of hydrogen cyanide:
"New technology for the major consumers of hydrogen
cyanide have almost killed this old standby. Never a real
tonnage petrochemical, HCN is now reserved for those spe-
cialties products where its chemistry makes the reaction
simple.
18
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"However, large tonnages of HCN are produced in most
industrialized areas of the world but most of this is in-
cinerated for disposal.
"Acrylates are now made from propylene; acrylonitrile
is now made from ammonia and propylene. These direct pro-
cesses no longer require HCN as a raw material. Conversion
to the SOHIO process throughout the world is almost com-
pleted for acrylonitrile and all new acrylonitrile plants
will use this or the Ugine or Snamprogetti technology. Any
new acrylic acid or ester processes will continue to use
propylene directly and the melamine business has converted
to urea. There just doesn't seem to be any good reason for
making HCN."I°/
These erratic trends in HCN production are well illustrated in Figure
2 and are primarily due to shifts in demand for certain organic chemicals,
e.g., acrylonitrile, methyl methacrylate, and NTA.-Iil.il/
ALKALI METAL CYANIDES^/
The two commercially prominent alkali metal cyanides are sodium cy-
anide and potassium cyanide. Of these, sodium cyanide is produced and uti-
lized to a much greater degree than potassium cyanide, perhaps by a factor
of 20. Only in special applications, e.g., special electroplating baths, is
potassium cyanide specified over sodium cyanide. Potassium cyanide is con-
siderably more expensive than sodium cyanide, primarily because of the low
production volume, and also because of the high cost of potash relative to
soda ash. Since these two cyanides are so similar in nature, they are grouped
together for discussion and they will be differentiated only if it is rele-
vant to the discussion.
Alkali cyanide manufacture has been described earlier in connection
with hydrogen cyanide. The historical methods of manufacture are no longer
of significance. The modern method of preparation involves neutralization
of hydrogen cyanide by NaOH or KOH solution. The process appears straight-
forward and simple, but this is, in fact, not the case. The resulting solu-
tion of alkali cyanide must be evaporated under reduced pressure and in a
highly controlled manner to avoid loss of hydrogen cyanide through hydroly-
sis of the cyanide ion.
After evaporation of the cyanide solution, a fine powder is obtained
which is then briquetted or fused to obtain a product conveniently han-
dled. Purity is greater than 99%. E. I. du Pont de Nemours and Company is
the principal manufacturer of sodium and potassium cyanide, and markets
19
-------
700
to
600
500
Ii 400
300
200
Sources:
A Bureau of Census
• Chemical Marketing Reporter
• 6.5%
4.5%
100'
1955
1960
1965
1970
YEAR
1975
1980
1985
Figure 2. Domestic HCN production
-------
these products as a briquette or in granular form. Some sodium cyanide is
sold as a solution containing 30% by weight.
The historical markets for alkali cyanides have remained unchanged.
Considerable amounts are used as such in mining for flotation and extrac-
tion of ores, for metal heat treating and case hardening as proprietary
salt baths, for electroplating and metal stripping as proprietary baths,
for the preparation of heavy metal cyanides for electroplating, for the
preparation of complex metal cyanides, e.g., ferro- and ferricyanides and
iron blue, for agricultural uses as pest control agents and fumigants,
and in the manufacture of a host of organic cyanides (nitriles).
Commercial potassium cyanide is made in a manner similar to sodium
cyanide, but is of slightly lower purity, 97 to 99%. The principal con-
taminants are sodium cyanide and potassium carbonate.
The principal use of potassium cyanide is in electroplating, wherein
the salt has superior "throwing power" over the sodium salt; in other
words, potassium cyanide electroplating solution has a higher current ef-
ficiency. Some potassium cyanide is used in conjunction with sodium cyanide
for metal heat treating salts and in salt mixtures for metal coloring by
chemical or electrolytic processes.
As a group, the alkali cyanides have shown little significant commer-
cial growth other than as a result of the general expansion of the economy.
No new uses of alkali cyanides are anticipated. The normal growth via ex-
pansion of the economy may be offset to some extent by the introduction of
noncyanide salt baths into the metal heat treatment and electroplating sec-
tors. Historically, a 3%, growth in sodium cyanide has taken place between
1965 and 1970, and new applications for cyanides appear unlikely in the fu-
ture.
ALKALINE EARTH CYANIDES-i/
Only calcium cyanide is of any commercial importance in the class of
alkaline earth cyanides. Other alkaline earth cyanides are known and have
been characterized, but they offer no advantage over calcium cyanide and
are much more expensive.
Calcium cyanide is generally manufactured by heating crude calcium
cyanamid with carbon in an electric furnace to 1000°C in the presence of
sodium chloride. The resulting melt is cooled rapidly to prevent reversal
of the reaction. The crude calcium cyanide is called "black cyanide" and
is sold in blocks, flakes, granules, or powder form.
21
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Uses of calcium cyanide include fumigation wherein the powder form
rapidly hydrolyzes in moist air to release hydrogen cyanide. Some calcium
cyanide is used in metal heat treatment and some is sold as a 15% solution
for gold extraction. Sodium or potassium ferrocyanide utilizes calcium cy-
anide as a starting material.
Much calcium cyanide has been imported from American Cyanamid Ltd.,
of Canada. However, the market for calcium cyanide has been declining rap-
idly since 1970, since its use in agriculture as a fumigant and pest control
agent has been supplemented by other chemicals. Some proprietary salts for
heat treating have been developed that do not contain calcium cyanide.
HEAVY METAL CYANIDES
This class of cyanides contains a transition metal and the cyanide
radical. They can be simple compounds like copper cyanide or complex cya-
nides as sodium ferrocyanide, sodium ferricyanide, or ferric ammonium fer-
rocyanide (iron blue). The heavy metal cyanides are prepared by simple re-
placement reactions from a metal salt and sodium cyanide.
The commercially important heavy metal cyanides include those of cop-
per, cadmium, gold, silver, and zinc. These are generally used in electro-
plating applications. Accurate marketing data are difficult to obtain since
the manufacturers consider this information proprietary. However, the future
market for these materials in the electroplating area is tied to the general
economy; also noncyanide plating baths are becoming significant, which may
lower heavy metal cyanide consumption especially in zinc plating.
The historical market for iron blue as a paint pigment has recently
shifted to that of chemical coatings, printing ink, carbon paper, paper
manufacture, and plastics. The market for inks and carbon paper is growing
rapidly and iron blue consumption will rise and fall with the general econ-
omy.
22
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REFERENCES TO CHAPTER IV
1. Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd ed., Vol. 6,
Interscience Publishers, Inc., New York (1965).
2. Sherwood, P. W., Petroleum Processing, 9(2):384-389, February 1954.
3. Kent, J. A., Riegel's Industrial Chemistry, John Wiley and Sons, Inc.,
New York (1974).
4. Fallwell, W. F., Chemical and Engineering News, 48_:22, December 7, 1970,
5. Anonymous, Chemical and Engineering News, 48:11, April 6, 1970.
6. Anonymous, Chemical and Engineering News, 43:15, November 30, 1970.
7. Anonymous, Chemical and Engineering News, 46:16, November 14, 1968.
8. Anonymous, Chemical and Engineering News, 49:15, January 4, 1971.
9. Anonymous, Chemical and Engineering News, ,53j7, August 18, 1975.
10. Ponder, T. C., Petrochemicals, Hydrocarbon Processing, Personal Com-
munication, September 22, 1975.
11. Chemical Marketing Reporter. 183_, May 27, 1963; 191., May 22, 1967; 19£,
September 28, 1970; 198, October 5, 1970; 20.3, December 10, 1973; MRI
estimates.
12. U»S» Department of Commerce, Bureau of Census, Series No. M22a-13.
23
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CHAPTER V
MARKET INPUT-OUTPUT DATA
This chapter identifies manufacturers of industrially important cya-
nides and presents cumulative data for the selected cyanides during the
years 1965 through 1973. The data are considered in terms of production,
importation, exportation, use patterns, and final disposal.
MANUFACTURERS
Table 2 lists manufacturers of industrially important cyanides in
1975. Historical changes in this select group of companies are presented
in detail when dealing with a specific cyanide or classes of cyanides.
PRODUCTION AND CAPITAL VALUE
Hydrogen Cyanide
The total annual production quantities of selected cyanides for the
last 10 years and for a 10-year projection from 1975 to 1985 are shown in
Table 3. The table requires a number of comments in order for the reader
to understand the limitations of these data. Production figures for HCN
are based on Census Bureau data, which are known to be understated. Actual
production of HCN was probably 25% higher in most years since interplant
transfers are not counted by the Census Bureau. Further, all HCN that is
produced but not isolated is not reported, e.g., direct conversion to NaCN.
Some HCN is produced as a by-product of acrylonitrile manufacture and is at
present being incerated. Future growth of HCN is assumed to be linear at
4.5%/year, and was adjusted downward from an estimate of 5.5%/year by the
Chemical Marketing Reporter JL'
A comparison of Census Bureau, Stanford Research Institute, and Chem-
ical Marketing Reporter production estimates for HCN is given in Table 4.
24
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Table 2. MANUFACTURERS OF SELECTED CYANIDES IN 1975
Ul
Company HCN NaCN KCN Ca(CN)2
a/
American Cyanamid Company X X~
C, P. Chemicals, Inc.
City Chemical Corporation
Dow Chemical Company X
E. I. du Pont de Nemours and Company XXX
Engehard Industries, Inc.
Fisher Scientific Company X X
Harshaw Chemical Company
Harstan Chemical Company
Hercules, Inc. X
M&T Chemicals, Inc.
Mallinckrodt Company X
Monsanto Chemical Company X
Phillips Brothers Chemical Company
Rohm and Haas Chemical Company X
Vistron Corporation (SOHIO) X
Ferrocyanides, Heavy metal
f erricyanides Iron blue cyanides
X
X
X
X
X
X X
X
X
X X
X
X X
X
-
a^l Imported from Canadian affiliate.
-------
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
451
323
252
304
370
321
282
272
322
356
375
453
530
32.0
34.0
35.0
38.3
45.0
42.8
46.1
41.1
45.1
45.1
43.0
38.0
32.0
Table 3. DOMESTIC PRODUCTION OF SELECTED CYANIDES
(million Ib annually)
a/ b/
Year HCN NaCN— KCN Iron blue Heavy metal cyanides—
1.7 11.0
1.7 11.0
2.0 11.6
2.2 12.0
2.1 11.6
2.3 10.4
2.5 10.8
2.3 10.4
2.3 10.1
2.1 9.0
2.0 8.0 13
1.7 10.3
1.6 11.8
al Domestic production for merchant sales but excluding exports.
V Including ferro- and ferricyanides.
Table 4. COMPARISON OF ESTIMATED HYDROGEN CYANIDE PRODUCTION
Year SRI CMR Census Bureau
(million Ib HCN annually)
1963 440 293 293
1964 480 - 350
1965 530 . 451
1966 . 450 220 323
1967 390 218 252
1968 430 - 304
1969 500 247 370
1970 - .285 321
1971 ' - - 282
1972 - 320 : 272
1973 - 345 322
:26
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2/
The large discrepancies between Census Bureau production data,— SRI esti-
mates of consumption,—' and CMR estimates of consumption are related to in-
adequate information, differences in counting methodology, possible double
counting, and to the point made earlier, that HCN is sometimes produced but
not isolated. This report will draw upon Census Bureau data since these data
are more complete, readily available, and do not require estimates of HCN
which has only a transitory existence. (The rationale behind the erratic
production history for HCN has been given in Chapter IV.)
The present manufacturers of HCN are given below:
American Cyanamid Company,
Dow Chemical Company,
E. I. du Pont de Nemours and Company,
Hercules, Inc.,
Monsanto Company,
Rohm and Haas Texas, Inc., and
Vistron Corporation Division of SOHIO.
Other companies no longer producing HCN are: B. F. Goodrich Company; Union
Carbide Corporation; and Ethyl Corporation which planned an HCN facility in
1970, but never built.
Table 5 presents the capital value of selected cyanides by type or
grade as raw materials. Estimates of capital value for 1975 through 1985
are given, and assume a linear rise of 8% annually on prices.
Sodium Cyanide
Sodium cyanide is a prominent industrial cyanide, and a complete pro-
duction, importation, and exportation history of this compound is given in
this chapter. Total sodium cyanide available for merchant sales is given by
domestic production plus imports. The total amount produced, domestically is
given by domestic merchant sales plus exports. Figure 3 illustrates these
relationships and estimates these quantities for 1975.
Figure 4 presents the distribution of sodium cyanide as merchant sales
in various industrial sectors in 1975. The total of 80 million pounds of
NaCN equivalent was obtained by independently estimating the quantity used
in each sector and summing. The overall standard deviation of this estimate
is + 6.6 million pounds, which is an 8% relative uncertainty. The principal
source of uncertainty is the metal finishing sector.
27
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Table 5. CAPITAL VALUE OF SELECTED CYANIDES - DOMESTIC PRODUCTION
(million dollars)
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
51.9
37.2
29.0
35.0
42.6
36.9
32.4
31.2
37.0
41.0
67.5
113.0
170.0
6.23
6.63
6.82
7.36
8.65
8.22
8.86
8.33
9.35
15.0
14.5
17.8
19.1
d/
Iron blue—
6.16
6.32
6.73
7.26
7.26
7.06
6.80
6.65
7.07
7.06
7.20
12.90
18.90
a/ Tanks, liquid HCN, 98% works.
b/ Drums, briquettes or granulated, 99% minimum, 24,000-lb lots,
delivered.
£/ Drums, 20,000-lb lots, delivered, 99% minimum.
cl/ Bags, regular grade, ton lots, delivered.
&j Domestic production of NaCN for merchant sales excluding exports.
Source: U.S. Department of Commerce, Bureau of the Census, Series
M28A-13; MRI estimates.
28
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Total NaCN Produced Domestically
56.5 M
I
NaCN for Merchant Sales
43.OM
NaCN Imports
10.OM
Total NaCN
Available for
Merchant Sales
53.OM
NaCN Exports
13.5 M
Figure 3. NaCN production, importation, and exportation in 1975
(million Ib)
29
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TOTAL NaCN EQUIVALENT
AVAILABLE FOR MERCHANT SALES
80M
Metal
Finishing
for Stripping
and Plating
50M .
Iron Blue
as Pigment
for Ink
13.
5M
Mining
Chemicals
Ore Flotation
and Extraction
6.5M
Metal Heat
Treatment
and Case
Hardening
4.5M
Photographic
Chemicals for
Development
2.5M
Anti-Caking
Agents for
De-icers
2.5M
Agricultural
and
Pest Control
0.5M
Figure 4. Distribution of NaCN equivalent available
for merchant sales
(million Ib)
-------
The term "NaCN equivalent" refers to the fact that some NaCN is con-
sumed as a raw material for the production of other metal cyanides, e.g.,
ferro- and ferricyanides and heavy metal cyanides. Consumption of NaCN
equivalent in these areas is estimated at 27 million pounds in 1975 as
heavy metal cyanides, iron blue pigment, photographic chemicals, anti-caking
agents, mining chemicals, and for agricultural and pest control.
Large amounts of NaCN are used directly in electroplating baths, metal
heat treating salt baths, and as a mining chemical. Consumption of NaCN in
these areas is estimated at 53 million pounds. Thus, total consumption is
80 million pounds of NaCN equivalent in the merchant sector.
The previous information on NaCN was utilized to develop Table 6 for
the years 1965 to 1985 inclusive. Exports and imports for the years 1965 to
1973 inclusive are accurately known; all other data are estimates. Merchant
sales plus imports were assumed to increase 3% annually from 1965 to 1969,
with no growth from 1970 to 1972. Projections to 1985 are based on a decline
in sodium cyanide usage due to introduction of noncyanide processes and ma-
terials; e.g., noncyanide plating baths and gaseous carbo-nitriding for case
hardening metals.
E« !• du Pont de Nemours and Company is the principal manufacturer of
sodium and potassium cyanide and guard the production figures of each. How-
ever, Mr. James McNutt and Mr. Robert Pieslik of the Industrial Chemicals
Department assisted this survey by providing a limited amount of information
on these chemicals. ?'
Potassium Cyanide
Production of potassium cyanide for merchant sales is also an unknown
quantity but has been estimated at T/a of domestic production of sodium cy-
anide for merchant sales and imports. Table 7 presents estimated domestic
production of potassium cyanide for merchant sales plus importation data.
The figures for domestic production are corroborated by a Du Pont source
which estimated production at less than 5 million pounds annually.—' Imports
are known accurately for 1965 to 1973; potassium cyanide is not exported in
significant quantities.
Calcium Cyanide
There are no sources for domestically produced calcium cyanide. Ameri-
can Cyanamid Company imports large amounts of this chemical from its affil-
iate in Canada. Degussa, Inc., also imports calcium cyanide from Europe.
31
-------
Table 6. ESTIMATED DOMESTIC PRODUCTION OF NaCN FOR MERCHANT SALES
(million Ib annually)
Year
. Domestic
production
for merchant
sales
Exports Imports
Domestic
production
for merchant
sales plus
imports
Domestic
production
for merchant
sales plus
exports
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
32.0
34.0
35.0
38.3
. 45.0
42.8
46.1
41.1
45.1
•45.1
43.0
38.0
32.0
8.5
8.1
10.2
11.4
12.3
23.0
18.3
8.7
12.0
12.5
13.5
16.0
19.0
21.5
20.9
21.4
19.7
14.7
18.7
13.9
17.2
11.6
10.0
10.0
10.0
10.0
53.5
54.9
56.4
58.0
59.7
61.5
60.0
58.3
56.7
55.1
53.0
48.0
42.0
40.5
42.1
45.2
49.7
57.3
65.8
64.4
49.8
57.1
57.6
56.5
54.0
51.0
Note: Data on exports and imports from Bureau of the Census for
1965 to 1973. Exports to grow by 5%/year 1975 to 1985.
Imports to remain unchanged.
32
-------
Table 7. ESTIMATED DOMESTIC PRODUCTION OF KCN FOR. MERCHANT SALES
(million Ib annually)
Domestic production Domestic production
Year for merchant sales Imports Exports plus imports
2.2 0 3.9
2.3 0 4.0
1.9 0 3.9
1.8 0 4.0
2.1 0 4.2
1.9 0 4.2
1.4 . 0 3.9
1.6 0 3.9
1.5 0 3.8
1.7 0 3.8
1.6 0 3.6
1.6 0 3.3
1.6 0 3.2
Note: KCN domestic production and imports set at 7% of the corresponding
NaCN domestic production for merchant sales and imports. MRI es-
timates.
Iron Blue
The production history of iron blue is readily obtainable, and manu-
facturers are relatively open on this subject. Table 3 presents .production
data and Figure 5 presents total consumption data for iron blue with pro-
jection estimates to 1985. This information was gathered with the assistance
of representatives from American Cyanamid Company, Reichhold Chemicals, Inc.,
and the Bureau of Mineg.6"8/
/
Table 8 presents.current and former manufacturers of iron blue and
the estimated market share of the two principal manufacturers.
Heavy Metal Cyanides,- Including Ferro- and Ferricyanides
Table 9 presents a listing of various cyanide salts including heavy
metal cyanide manufacturers and distributors. Those companies.with an en-
closed symbol (D) are .former distributors.
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974.
1975
1980
1985
1.7
1.7
2.0
2.2
2.1
2.3
2.5
2.3
2.3
2.1.
2.0
1.7
1.6
33
-------
u>
20 r-
18
16
o 14
12
10
8
Total Consumption
I I I I I I I
I I I I I
4%
Domestic Production
2%
Approximate
Growth Rates
4%
2%
I I I I I I I 1
1960
1965
1970
1975
1980
1985
Figure 5. Iron blue consumption
-------
Table 8. CURRENT AND FORMER MANUFACTURERS OF IRON BLUE
Company
American Cyanamid Company
Pigments Division
Hercules, Inc.
Imperial Division
The Harshaw Chemical Company
Pigments and Dye Department
u> Chemetron Corporation
E. I. du Pont de Nemours and
Company, Inc.
Pigments" Department
Hilton-Davis Chemical Company
H. Kohnstamm and Company, Inc.
Reichhold Chemicals, Inc.
Location
Comment
Willow Island, West Virginia Principal manufacturer
Glens Falls, New York
Louisville, Kentucky
Holland, Michigan
Wilmington, Delaware
Cincinnati, Ohio
New York, New York
White Plains, New York
Principal manufacturer
Alkali-resistant grade
manufacturer
Discontinued 1973
Discontinued 1965
Discontinued 1972
Discontinued 1970
Discontinued 1972
Estimated
market
70
25
<. 5
-------
Table 9. MAJOR COMPANIES MANUFACTURING AND/OR DISTRIBUTING CYANIDE SALTS FOR INDUSTRIAL USE
Metal
cyanide
NaCN
KCN
Company
Ashland Chemical Company
C. P. Chemicals, Inc.
Degussa, Inc. (import)
E. I. du Pont de Nemours and Company, Inc.
Fisher Scientific Company
Harshaw Chemical Company
Imperial Chemical Industries, Ltd. (import)
J. T. Baker Chemical Company
M&T Chemicals, Inc.
Phillips Brothers Chemical Company
Sobin Chemicals, Inc.
United Mineral and Chemical Corporation
Ashland Chemical Company
C. P. Chemicals, Inc.
Degussa, Inc. (import)
E. I. du Pont de Nemours and Company, Inc.
Fisher Scientific Company
Harshaw Chemical Company
Harstan Chemical Company
Imperial Chemical Industries, Ltd. (import)
J. T. Baker Chemical Company
Mallinckrodt Chemical Company
M&T Chemicals, Inc.
Phillips Brothers Chemical Company
United Mineral and Chemical Corporation
Location
Columbus, Ohio
Sewaren, New Jersey
New York, New York
Memphis, Tennessee
Fair Lawn, New Jersey
Cleveland, Ohio
Wilmington, Delaware
Phillipsburg, New Jersey
Rahway, New Jersey
New York, New York
Boston, Massachusetts
New York, New York
Columbus, Ohio
Sewaren, New Jersey
New York, New York
Memphis, Tennessee
Fair Lawn, New Jersey
Cleveland, Ohio
Brooklyn, New York
Wilmington, Delaware
Phillipsburg, New Jersey
St. Louis, Missouri
Rahway, New Jersey
New York, New York
New York, New York
Manufacturer ,
distributor
D
D
D
M,D
M,D
D
D
D
D
D
D
D
D
D
M,D
M,D
D
D
D
D
M,D
D
D
(D)
-------
Table 9. (continued)
Metal
cyanide
Ca(CN)2
American
Degussa,
Company
Cyanamid Company (import)
Inc. (import)
Location
Wayne, New Jersey
New York, New York
Manufacturer,
distributor
M,D
D
Cd(CN)2
Ferrocyanide
to
Ferricyanide
CuCN
City Chemical Corporation
American Cyanamid Company
Ashland Chemical Company
Hercules, Inc.
Mallinckrodt Chemical Company
Philip A. Hunt Chemical Company
United Mineral and Chemical Corporation
American Cyanamid Company
Degussa, Inc. (import)
Eastman Kodak Copmany
Mallinckrodt Chemical Company
Philip A. Hunt Chemical Company
United Mineral and Chemical Corporation
Ashland Chemical Company
E. I. du Pont de Nemours and Company, Inc.
Fisher Scientific Company Ltd.
Harshaw Chemical Company
Harstan Chemical Company
Imperial Chemical Industries, Ltd. (import)
Phillips Brothers Chemical Conpany
New York, New York M,D
Wayne, New Jersey M,D
Columbus, Ohio D
Glens Falls, New York M
St. Louis, Missouri M,D
Palisades Park, New Jersey (D)
New York, New York (D)
Wayne, New Jersey M,D
New York, New York D
Rochester, New York M,D
St. Louis, Missouri M,D
Palisades Park, New Jersey D
New York, New York D
Columbus, Ohio D
Niagara Falls, New York M,D
Fair Lawn, New Jersey M,D
Cleveland, Ohio D
Brooklyn, New York D
Wilmington, Delaware D
New York, New York M,D
-------
Table 9. (concluded)
Metal
cyanide
Company
Location
Manufacturer,
distributor
Zn(CN)2
Na(K)Cu(CN)2
oo
AgCN
KAu(CN)2
Ashland Chemical Company
C. P. Chemicals, Inc.
E. I. du Pont de Nemours and Company, Inc.
Harstan Chemical Company
Imperial Chemical Industries, Ltd. (import)
Phillips Brothers Chemical Company
Ashland Chemical Company
C. P. Chemicals, Inc.
E. I. du Pont de Nemours and Company, Inc.
Harstan Chemical Company
Ashland Chemical Company
Engelhard Industries, Inc.
Fisher Scientific Company, Ltd.
Mallinckrodt Chemicals Company
Ashland Chemical Company
Engelhard Industries, Inc.
Fisher Scientific Company
Columbus, Ohio D
Sewaren, New Jersey M,D
Niagara Falls, New York M,D
Brooklyn, New York D
Wilmington, Delaware D
New York, New York M,D
Columbus, Ohio D
Sewaren, New Jersey M,D
Niagara Falls, New York M,D
Brooklyn, New York M,D
Columbus, Ohio D
Newark, New Jersey M,D
Fair Lawn, New Jersey M,D
St. Louis, Missouri M,D
Columbus, Ohio D
Newark, New Jersey M,D
Fair Lawn, New Jersey M,D
a/ ( ) Denotes.former distributor.
-------
The production history of ferro- and ferricyanides and of heavy metal
cyanides, principally zinc, cadmium, copper, gold, and silver cyanides, is
largely unknown at present. Companies such as CP Chemicals, Inc., and E. I.
Du Pont are producers of metal cyanides such as copper, zinc, and the double
salts of these metals, i.e., sodium copper cyanide, sodium zinc cyanide, etc.,
but consider their production statistics confidential information.
Trade and professional associations such as the American Electroplat-
ers1 Society, The Silver Institute, Metal Finishing Magazine, Manufacturing
Chemists Association, Metal Finishing Suppliers Association, etc., simply do
not possess consumption data on cyanides. Representatives from these organi-
zations were sympathetic to the needs of the survey, but could offer no data
on industry usage rates and/or considered this proprietary information. Typi-
cal of comments from Metal Finishing Magazine editor Nathaniel Hall, was the
following:
"I can sympathize with your obvious frustration at the
lack of any figures ... of chemical usage in the finishing
industry. You are not the first since, unfortunately, no one
has even been able to compile any figures in our industry,
aside from a handful of chemicals and metals."I/
Thus, due to lack of hard data, it is not possible at present to develop
complete tables of production statistics for ferro- and ferricyanides and
other heavy metal cyanides and arrive at an estimate of capital value for
these chemicals.
In order to calculate a total cyanide material balance in Chapter V
it will be necessary to estimate the 1975 heavy metal cyanide consumption
in the electroplating sector using data from various sources. Table 10 pre-
sents annual consumption of NaCN, KCN, and heavy metal cyanides in the elec-
troplating sector. The consumption estimates of the various cyanides are re-
duced to a common basis, NaCN equivalent weight. This is reasonable since
NaCN is the principal constituent of all plating baths except gold and high-
speed copper.
Bath makeup occurs at initial start-up and is repeated on rare occa-
sions due to accidental dumping, leakage, and contamination. Soluble anodes
are generally used in conjunction with direct NaCN additions. Estimated
heavy metal cyanide consumption is about 10 million pounds or 7.3 million
pounds of NaCN equivalent.
39
-------
Table 10. SODIUM CYANIDE EQUIVALENT CONSUMPTION
IN METAL FINISHING IN 1975JL/
Category I - Bath makeup
Metal cyanide
(million Ib)
Consumption as NaCN
equivalent
(million Ib)
7.0 Zn(CN)2
1.5 CuCN
0.6 Cd(CN)2
0.5 AgCN
0.2 KAu(CN)2—
Subtotal 9.8
5.8
0.8
0.4
0.2
0.07
Subtotal 7.3
Category II - Plating bath maintenance
Metal cyanide
plating process
Zinc
Copper and brass!2'
Cadmium!^/
Silver!!/
Gold (jewelry)
Metal consumed
in plating
(million Ib)
°- 100 Zn
10 Cu
4.4 Cd
2.4 Ag
0.01 Au
Maintenance
requirements
by NaCN
°- 30% ., 30
"- 25-30% 3.0-'
•*• 25-30% 1.2
*• 30-50% 1.0
*• 10X 0.1
Subtotal 35.3
Category III - Stripping, cleaning, deburring, tumbling, etc.
Total
_8
50.6
a/ Source: MRI estimate.
b/ Includes 0.3 M KCN.
40
-------
IMPORTATION AND CAPITAL VALUE
Importation is generally confined to the following cyanides: sodium
cyanide, potassium cyanide, sodium ferrocyanide, potassium ferrocyanide,
potassium ferricyanide, calcium cyanide and iron blue (ferric-ammonium fer-
rocyanide).
Various heavy metal cyanides, e.g., cuprous cyanide, zinc cyanide,
mercury cyanide, etc., are imported in relatively small quantities; less
than 1 million pounds each and having capital values of less than $1 mil-
lion each. Other cyanides are classed merely as Mixtures of Inorganic Com-
pounds, Chief Value Cyanide, TSUSA No. 423820 and are of negligible amounts.
Tables 11 through 14 present importation data and capital value for
various cyanides over the years 1965 to 1973 inclusive with extrapolations
for the years 1974, 1975, 1980, and 1985. From 1975 to 1985, a linear price
rise of 8% annually was assumed. It may be seen that large amounts of vari-
ous cyanides have been imported in the past.
As developed earlier in Chapter V, the quantity of NaCN equivalent
used industrially is very large, of the order of 80 + 6.6 million pounds
annually. Present imports account for nearly 29 million pounds of NaCN
equivalent annually. The estimated amount of cyanides imported in 1975 is
given in Table 15 for purposes of summary.
Figure 6 presents the cyanide importation historical record for the
years 1960 to 1973 inclusive with projections to 1985. In the past, much
calcium cyanide has been imported, principally by American Cyanamid Com-
pany from its Canadian operation at Niagara Falls. Over the years 1960 to
1970 inclusive some 200 million pounds of calcium cyanide were imported for
an average of 33 million pounds annually. However, in 1971 and the follow-
ing years importation dropped to less than 10 million pounds annually.
American Cyanamid Company told us that the plant was voluntarily shut down
when the Canadian government imposed effluent restructions on the operation.
This decision was also influenced by rapidly rising power costs required to
operate the electric furnaces which convert calcium cyanamid to calcium
cyanide.
After some period of negotiations, American Cyanamid Company and the
Canadian government agreed to jointly fund the necessary modifications to
allow the plant to come back on stream. Beginning in 1975 the flow of cal-
cium cyanide from Canada should rise somewhat, but probably will not match
the previous historical record because of a projected decrease in overall
industrial cyanide demand. This opinion differs from one source at American
Cyanamid who suggested that the importation rate would return to the level
of 20 to 30 million pounds annually by 1980-1985
41
-------
Table 11. CYANIDE IMPORTS AND CAPITAL VALUE - SODIUM SALTS
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
Sodium
Million
pounds
21.5
20.9
21.4
19.7
14.7
18.7
13.9
17.2
11.6
14.4
10.0
10.0
10.0
cyanide
Million
dollars
2.62
2.46
2.64
2.48
1.89
2.42
1.94
2.47
1.73
2.70
2.02
2.84
3.64
Sodium
Million
pounds
3.4
5.7
6.4
6.5
5.0
4.0
3.0
1.8
0.4
0.5
0.5
1.0
1.0
ferrocyanide
Million
dollars
0.45
0.60
0.66
0.67
0.54
0.41
0.32
0.22
0.06
0.08
0.08
0.23
0.29
Total
Million
pounds
24.9
26.6
27.8
26.2
19.7
22.7
16.9
19.0
12.0
14.9
10.5
11.0
11.0
Million
dollars
3.07
3.06
3.30
3.15
2.43
2.83
2.26
2.69
1.79
2.78
2.10
3.07
3.93
Source: U.S. Department of Commerce, Bureau of the Census, FT 246, MRI
estimates.
42
-------
Table 12. CYANIDE IMPORTS AND CAPITAL VALUE - POTASSIUM SALTS
Potassium
cyanide
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
Million
pounds
2.2
2.3
1.9
1.8
2.1
1.9
1.4
1.6
1.5
1.7
1.6
1.6
1.6
Million
dollars
0.51
. 0.54
0.40
0.41
0.44
0.41
0.30
0.36
0.36
0.44
0.45
0.63
0.81
Potassium
ferrocyanide
Million
p ounds
2.3
4.3
3.8
4.4
1.5
2.4
2.1
2.0
1.8
1.7
1.7
1.7
1.7
Million
dollars
0.47
0.80
0.71
0.94
0.27
0.46
0.39
0.42
0.44
0.45
0.48
0.68
0.87
Potassium
ferricyanide
Million
pounds
1.3
1.3
1.3
1.6
2.1
1.5
1.7
2.1
1.4
1.7
1.7
1.7
1.7
Million
dollars
0.41
0.41
0.41
0.52
. 0.67
0.46
0.59
0.73
0.58
0.76
0.82
0.87
0.93
Total
Million
p ounds
5.8
7.9
7.0
7.8
5.7
5.8
5.2
5.7 ,
4.7
5.1
5.0
5.0 .
5.0 .
Million
dollars
1.39
1.75
1.52
1.87
1.38
1.33
1.28
1.51
1.38
1.67
1.75
2.18
2.61
Source: U.S. Department of Commerce, Bureau of the Census, FT 246, MRI
estimates.
43
-------
Table 13. CALCIUM CYANIDE IMPORTS AND CAPITAL VALUE
Calcium cyanide
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
Million pounds
35.8
.35.3
33.0
32.3
32.4
31.6
10.9
4.9
7.8
7.5
8.0
9.0
10.0
Million dollars
1.46
1.44 .
1.35
1.32
1.29
1.31
0.46
0.28
0.58
0.61
0.71
1.13
1.62
Source: U.S. Department of Commerce, Bureau of the Census,
MRI estimates.
44
-------
Table 14. IRON BLUE CONSUMPTION, IMPORTATION, AND CAPITAL VALUE
Domestic
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
Million
pounds
11.0
11.1
11.6
12.1
11.7
10.4
10.8
10.4
10.1
9.0
8.0
10.3
11.8
Capital
value (.$)
6.16
6.32
6.73
7.26
7.26
7.06
6.80
6.65
7.07
7.06
7.20
12.90
18.90,
Imports
Million
pounds
0.9
1.1
0.9
1.2
1.7
2.1
2.7
4.3
5.3
5.1
5.0
5.3
6.0
Capital
value ($)
0.40
0.48
0.40
0.50
0.63
0.87
04
65
2.21
50
50
70
5.40
Totals
Million
pounds
11.9
12.2
12.5
13.3
13.4
12.
13,
14,
15.4
14,
13.0
15.6
17.8
Capital
value ($)
6.56
.80
,13
,76
,89
.93
.84
8.30
9.28
9.56
9.70
16.60
24.30
6.
7,
7,
7.
7.
7.
Source: U.S. Department of Commerce, Bureau of Census, FT 246, M28A-13,
MRI Estimates.
Table 15. ESTIMATED CYANIDE IMPORTATION IN 1975
Cyanide
NaCN
KCN
Ca(CN)2
Iron blue
Heavy metal and
ferro- and
ferricyanides
Total
(million Ib)
Quantity
10.0
1.6
8.0
5.0
~ 5.0
NaCN Equivalent
10.0
1.2
8.5
5.2
«*• 3.7
Principal exporting
countries
U.K., West Germany, Japan
Canada, Japan
U.K., Japan
Europe, U.K., Japan
U.K., West Germany, Japan
29.6
28.6
45
-------
70 r-
1960 1965 1970 1975
YEAR
Source: Bureau of Census & MRI Estimates
Figure 6. Cyanide importation
1980
Total
Cyanides
iNa CPDS.
Ca(CN)2
Iron Blue
IK CPDS.
1985
-------
EXPORTATION AND CAPITAL VALUE
Exportation of cyanides is essentially confined to sodium cyanide.
No other separate cyanide listing was given by the Bureau of the Census.
Principal areas or countries receiving sodium cyanide are South America,
United Kingdom, Canada, and Mexico. The historical data and capital value
are given in Figures 7 and Table 16. A linear rise of 5% annually is pro-
jected for NaCN exportation.
USAGE PATTERNS
The cyanides of sodium and calcium as well as hydrogen cyanide gas
have been used extensively as agricultural and pest control chemicals in
the past but this is no longer true. The use of cyanides in these areas
has all but disappeared and likely will not return. Data in the Encyclo-
pedia of Chemical Technology by Kirk and Othmer are largely incorrect in
this area.i2/
Sodium cyanide and to a much smaller extent calcium cyanide and so-
dium ferrocyanide are used directly as mining chemicals for flotation and
ore extraction. Sodium cyanide is also added directly to electroplating
baths for replenishment. Aside from these three examples; agricultural,
mining, and for plating bath maintenance, cyanides are not used as final
products but instead are the raw materials for the manufacture of other
products.
Cyanides find use in the preparation of electroplating baths, metal
heat treatment and case hardening baths, photographic chemicals, pigments,
inks, metal strippers, paints to a limited extent, and a host of organic
compounds, e.g., Pharmaceuticals, plastics, agricultural chemicals, chelat-
ing agents, and other organic intermediates. Essentially all cyanides are
derived from hydrogen cyanide today except for calcium cyanide which is
made from calcium cyanamid.
The Chemical Marketing Reporter estimates of hydrogen cyanide usage
patterns are given in Table 17.
The range for NaCN usage is between 7 to 10% of HCN production over
the last 12 years. The organic sector will probably consume 90% of HCN
production with NaCN being produced in the largest quantity in the inor-
ganic sector to 1985.
47
-------
-p-
oo
30 r
o 20
-, 10
0
1960
1965
1970
.. 5.0%
2.5%
1975
1980
1985
YEAR
Source: Bureau of Census
Figure 7. NaCN exportation
-------
Table 16. SODIUM CYANIDE EXPORTS
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1980
1985
NaCN
Million pounds
8.5
8.1
10.3
11.4
12.3
23.0
18.3
8.7
12.0
16.2
13.5
16.0
19.0
Million dollars
1.29 .
1.15
1.41
1.67
1.58
2.79
2.61
1.42
2.16
. 3.93
2.97
4.80
7.60
Source: U»S« Department of Commerce, Bureau of Census,
FT 410, MRI Estimates.
Table 17. USAGE PATTERNS FOR HYDROGEN CYANIDE (%)
Methyl
Adipo- Acrylo- meth- Acrylic
nitrile nitrile aerylate acid Chelates NaCN Other
May 27,
1963
May 22,
1967
October 5,
1970
December 10,
1973
14 52
34
_
•• ••
18 1
38 5
61
61
7
8 10
21 10
21 10
8
5
8
8
aj Ref. 4, Chapter VI.
49
-------
FINAL PRODUCTS AND DISPOSAL
As stated earlier cyanides are not generally used as final products
except for flotation and ore extraction, for electroplating bath replen-
ishment, as anti-caking agents, and as agricultural and pest control chem-
icals. Cyanides are used extensively as raw materials in proprietary plat-
ing baths, case hardening metal heat treating baths, as photographic
chemicals, as pigments for paints, inks, carbon papers, and as colorants
in plastics*
Hydrogen cyanide principally enters the organic sector as a raw ma-
terial in the manufacture of a host of organic chemicals. Sodium cyanide
is derived from hydrogen cyanide and is used in large quantities in pro-
prietary plating baths, in metal heat treating baths, and as a direct
replenishment chemical as stated above. Calcium cyanide is used directly
for mining applications but is more generally used for organic synthesis
purposes and to make other metal cyanides, e.g., ferro- and ferricyanides.
Iron blue is made from ferrocyanides. Heavy metal cyanides are made from
sodium cyanide and the corresponding metal ion or by reacting metal ion
with hydrocyanic acid.
Some idea of the vastness of the use of sodium cyanide and other mer-
chant cyanides as industrial chemicals is shown in Figure 8. The industrial
applications are many in the metal finishing and electroplating sector and
include electronic, jewelry, automotive, aircraft, and consumer items. The
figure indicates captive use of potassium cyanide and calcium cyanide for
organic synthesis purposes. The route of each metal cyanide from introduc-
tion through consumption and ultimate destruction and disposal is given ex-
plicitly on a weight basis.
Iron blue appears to be a chemical that is not of great concern at
present due to its innocuous nature. Thus, iron blue may enter the indus-
trial sector as pigment for ink, carbon paper, or as trash bag colorant.
Ultimately, iron blue enters the consumer sector and reaches the municipal
waste collection system where it is incinerated or becomes part of land-
fill. A portion of iron blue enters the environment directly as an anti-
caking agent in highway de-icing operations.
One study indicated that the action of UV illumination of ferro- and
ferricyanides in solution can generate significant amounts of cyanide ion.—-!/
A similar study for iron blue has not been performed nor has an incineration
study of iron blue to determine if noxious gases are liberated been carried
out to our knowledge.
50
-------
KCN
Co(CN)2
Inorganic
NaCN
KCN
Ca(CN)2
Ferrocyanides
Ferricyanides
tron Blue
Heavy Metal
Cyan ides
Total Cyanid
Disposal £/
Methods
55
4 . i
Mining
5.3M
0.1
0.3
1.5
0.1
7.3 M
Sector
= 89% 375M
HCN
3.0M Captive Uses
7 2M »• •
10. 2M
rV
By-Product A
41 .2M HCN =111%
Inorganic Sector
NaCN
Iron Blue
Ferrocya
Ferricyar
Heavy N
KCN
^
nides(78.1M)
ides
eta Cyanides —
Merchant Uses 1 83. 7M
i 4 4
Photographic
Chemicals
0.
2.
2.
*
Disposal
Tailing Pone
Recycle
NaOH. CI2
8M
0
8M
Disposal
>/
Metal Heat
Treatment
4.4M
0.2
0.2
4.8M
Metal
Finishing
43. OM
0.3
9.8
53. 1M
Pigments
12. OM
12. OM
, L_
Disposal
Municipal Sewers NaOH, CI2
NaOH, CI2 Electrolysis
H202
KMNO4
H202
Municipal Sewer
Landfill
Regeneration
Dispose
NoOH, CI2
Electrolysis
Ozone. UV
H202
Municipal
Sewer
Sodium Persulfate
Ozone, UV
Electrolysis
Disposal
Irr
-•" E>
V
Land Fill
Municipal
ncine ration
Weathering
Municipal
Sewer
°J Major met
-S/ Including
crylonitrile Process 100M HCN
Incinerated 100M HCN
ports as NaCN, KCN, ~| Nef
Ferro- and Ferricyonides, I , ^
Iron Blue, Ca(CN)2 f ,™P,™
ports as NoCN J
4 4
Agricultural
Pest Control
0.5M
0.5M
• 1
Disposal
Air
Weathering
Anticatcing
Agents
2.2M
1.0
3.2M
I
Disposal
Weathering
Runoff
tods of disposal are underlined.
disposal methods for consumer products.
Figure 8. Inorganic cyanide consumption and disposal pattern
(million pounds)
-------
REFERENCES TO CHAPTER V
' / l .
1. Chemical Marketing Reporter. 203_(24):9, December 10, 1973.
2. U.S. Department of Commerce, Bureau of Census, Series M22a-13.
3. Stanford Research Institute, Chemical Economics Handbook, Menlo Park,
California, January 1971.
4. McNutt, J. E., E. I. du Pont de Nemours and Company, Technical Ser-
vices Laboratory, Industrial Chemicals Department, Wilmington,
Delaware, Letters of September 28 and October 28, 1975.
5. Pieslik, R., E. I. du Pont de Nemours and Company, Sales and Marketing
Department, Industrial Chemicals Department, Wilmington, Delaware,
Telephone Contact.
6. Confidential Industrial Source.
7. Sistino, J. A., Technical Director, Reichhold Chemicals, Inc., Brooklyn,
New York.
8. Jones, T. S., Physical Scientist, U.S. Department of the Interior,
Bureau of Mines, Division of Ferrous Metals, Washington, D.C.
9. Hall, N., Metal Finishing Magazine, Hackensack, New Jersey.
10. Murphy, J. A., Surface Preparation and Finishes for Metals, McGraw
Hill Book Company, New York, Chapter 4 (1971).
11. Anonymous, Chemical Week, p. 23, April 23, 1975.
12. Withers, D., American Cyanamid Company, Mining Chemicals Department,
Wayne, New Jersey.
13. Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd ed., Vol. 6,
Interscience Publishers, Inc., New York (1965).
14. Burdick, G. E., and M. Lipschurtz, Trans. Amer. Fisheries Soc., 78,
192 (1948); CA 44, 10939 (1950).
52
-------
.CHAPTER VI
MANUFACTURING PROCESSES
This chapter presents manufacturing processes for hydrogen cyanide
and other cyanides in detail. Two principal synthesis routes for hydrogen
cyanide are the Andrussow direct process and the SOHIO-acrylonitrile pro-
cess which produces the cyanide as a by-product. Manufacturers are identi-
fied by site location and capacity. The chapter closes with a discussion
of manufacturing wastes disposal and transportation rates and regulations.
HYDROGEN CYANIDE
The general manufacturing process for hydrogen cyanide is the
Andrussow method which is given schematically in Figure 9.JL' The method
consists of passing ammonia, air, and natural gas over a platinum-rhodium
catalyst at elevated temperature.— The net reaction is:
1100°C
2 NH_ + 2 CH. + 30 —~ > 2 HCN + 6 H00
j "r 2. Cat. 2.
After reaction, the mixture is quenched to below 400°C to prevent
dissociation of the hydrogen cyanide. The gaseous mixture is scrubbed with
dilute sulfuric acid to remove ammonia for recycling. Hydrogen cyanide is
absorbed in the water phase. The final product (994% purity) is obtained
by distillation and stabilized by addition of 0.17o phosphoric acid to pre-
vent polymerization. The hydrogen cyanide yield is near 757o based on recy-
cled ammonia and 65% based on methane.
Waste gases include hydrogen, nitrogen, carbon monoxide and dioxide,
and water. The wastewater from the still residue is treated with caustic
chlorine to yield carbon dioxide, nitrogen, and dissolved salt. Other
waste disposal methodologies are employed and are mentioned later in this
section.
Hydrogen cyanide is also produced as a by-product in the manufacture
of acrylonitrile. Since 1970 all plants in the U.S. use the SOHIO process
or some modification^-' Figure 10 presents a schematic flow diagram of the
SOHIO process for acrylonitrile with hydrogen cyanide as a by-product.i'
53
-------
630 Ammonia .
890 Air
600 Natural Gas
Ol
Catalytic _
^ Cc
Converter
f
1 Am
Rec
Dilute
Suifuric
Acid
1
. Ammonia
•oler -i — • ., , —
Absorber
monia
overy
Water
1 r+ Waste Gases
HCN _
Absorber
HCN
^ Still "
.1
Wastewater
Treatment
I
Wastewater
25-75
1000
— ^ Hydrogen
Cyanide
Caustic
Chlorine
Dissolved Solids
Figure 9. Manufacture of hydrogen cyanide (Andrussow process)
-------
Ul
Ln
2500 Steam
Air-
560 Ammonia
1200 Propylene-
H2O
NH3
N2
CO2
02
H2O Propylene
150
HCN
1000
Acrylohitrile
t
Catalytic
Converter
Scrubber
Separator
Dryer
Distillation
450° C
H2O-
Dryer
I
Acrolein
Distillation
75
Acetonitrile
Other Nitriles
Figure 10. Acrylonitrile (SOHIO) process for hydrogen cyanide
-------
It is estimated that in 1975 approximately 25 to 30% of all hydrogen cya-
nide produced was by the SOHIO process.
In the SOHIO process propylene, ammonia, air,,and steam are mixed and
passed over "catalyst 41" (probably consisting of cerium and molybdenum ox-
ides supported on a silica carrier) at 450°C. The propylene Is converted to
acrylonitrile in approximately 75% yield. The net reaction is:
2 CH. + 2 NH,. + 30, 4 ° > 2 CH0 = CH-CN + 6 H00
36 3 2 Steam 2 2
Scrubbers remove various inert gases and unreacted propylene from the re-
action effluent. The crude acrylonitrile is separated from acetonitrile,
hydrogen cyanide, and water and is then distilled. Approximately 150 Ib of
HCN (994% purity) are recovered for each 1,000 Ib of acrylonitrile produced.
If the HCN is not wanted, it is incinerated.
Some hydrogen cyanide has a transitory existence only and is immedi-
ately converted to sodium or potassium cyanide or ferrocyanides or is used
for synthesis purposes internally by" the producer. Hydrogen cyanide manu-
factured and handled in this manner is generally not counted by the Bureau
of Census. The same is true for hydrogen cyanide which is incinerated. These
facts account for doubt over the yearly amount of hydrogen manufactured.
The- manufacturers of hydrogen cyanide are given in Table 18 and are
classified as to primary (Andrussow process) or by-product (SOHIO acrylo-
nitrile process) producers. Some companies have both kinds of operations
and use hydrogen cyanide as a captive product and/or market it for merchant
trade. The history is complicated since membership in this select group has
radically changed over the years 1948 to 1975. Individual company capacity
and production data are guarded closely. Sources for the data presented in
Table 18 include the Chemical Marketing Reporter, a questionnaire circulated
by Midwest Research Institute, various trade journals and publications, and
contact with industry representatives.
Table 19 presents a listing of various hydrogen cyanide process waste
disposal techniques. Some degree of variability exists in disposal metho-
dology as more efficient, economic, and environmentally desirable means are
sought. Alkaline chlorination is the most prevalent treatment methodology
among the manufacturers, with landfill and incineration prominent.
Transportation details for all cyanides, including handling and ship-
ping regulations, rates, and safeguards are described later in this chapter.
Detailed rate data for cyanides by class and transportation mode are given
in tabular form.
56
-------
Table 18. MANUFACTURERS OF HYDROGEN CYANIDE BY THE ANDRUSSOW AND THE SOHIO ACRYLONITRILE PROCESSES-
4/
Ul
Estimated capacity
(million pounds annually)
Company
American Cyanamid
Dow
Du Pont
B. F. Goodrich
Hercules
Monsanto
Rohm and Haas
Union Carbide
Vistron (SOHIO)
Total capacity
Location
South Kenner, Louisiana
Freeport, Texas
La Place, Louisiana
Memphis, Tennessee
Memphis, Tennessee
Beaumont, Texas
Victoria, Texas
Calvert City, Kentucky
Glens Falls, New York
Texas City, Texas
Alvin, Texas
Deer Park, Texas
Institute, West Virginia
Lima, Ohio
Remarks
B,
P,
P,
P,
P,
B,
B,
P,
B,
P,
P,
B,
P,
P,
B,
C
c,
c,
C
c,
c,
c,
c
M
C
c,
C
c,
c
M
M 1954-1966
1958-
M
M
1970-
1952-
1948-
1963
.
32
5
100
-
-
40
5
5
70
-
40
35
8
340
1967
13
(32) Standby
5
20
115
-
-
40
5
5
70
32
80
35
30
450
1970
27
(32)
5
20
130
27
30
40
7
5
75
55
180
35
30
666
1973
27
(32)
5 ;
20
130
27
30
40
Dis. 1972
5
75
55
180
Dis. 1971
30
624
1975
27
(32)
5
20
130
27
30
40
-
5
75
55
180
-
30
624
P = Primary, Andrussow Process.
B = By-product, SOHIO-aerylonitrile process.-
C = Captive consumption.
M = Merchant sales.
-------
Table 19. HYDROGEN CYANIDE PROCESS WASTE DISPOSAL TECHNIQUES
Company Technique
American Cyanamid DeepLweIT injection and alkaline chlorination
Dow Chemical ' -
E. I. du Pont Calcium hypochlorite, incineration and landfill
Hercules
Monsanto Alkaline chlorination and sodium hypochlorite
Rohm and Haas Activated sludge and landfill
Vistron (SOHIO) Deep well injection, incineration and aerobic
bio-oxidation
Note: MRI source.
The capital value of a 220 million pounds per year acrylonitrile pro-
duction facility has been estimated at $23 millionJl' Assuming that this
estimate applies to 1970, the capital value of the same plant in 1975 may
be close to $34 million.
The portion of the acrylonitrile. plant capital value attributable to
hydrogen cyanide is difficult to assign. In some cases the HCN may be a
valuable captive or salable intermediate chemical. In other cases, the prob-
lem of its disposal may be a liability.
The capital value for a plant producing hydrogen cyanide by the
Andrussow process is estimated to be $3.5 million for 50 million pounds
per year capacity. This relatively low capital value results from the sim-
ple and straightforward process.
SODIUM AND POTASSIUM CYANIDE ... • .
Production of sodium and potassium cyanide is principally carried out
by E. I. du Pont and Company, in Memphis, Tennessee. The neutralization
process involving NaOH (or KOH) and hydrocyanic acid is schematically given
in Figure 11.—' Essentially no wastes are generated by this process as the
balance between caustic and hydrocyamic acid is critical to avoid loss of
cyanide values.through hydrolysis. Purity of these cyanides is 99+%.
Production estimates are given in Tables 6 and 7 for NaCN and KCN, re-
spectively. Capacity of the facilities is unknown. These data'are closely
guarded by E. I. du Pont de Nemours and Company and other manufacturers.
58
-------
816 NaOH -
Hydrocyanic
Acid Solution
Neutralization
Tank
^
Water Vapor
t
Dryer
1000 Sodium
Cyanide Product
Figure 11. Manufacture of NaCN
59
-------
Environmental management at Du Pont has been described previously in
Table 19. These techniques presumably apply to sodium and potassium cya-
nides as well.
The capital value of a plant producing 50 million pounds of sodium cy-
anide and 5 million pounds of potassium cyanide per year would be $750,000
if operated in conjunction with the Andrussow hydrogen cyanide plant men-
tioned previously.
CALCIUM CYANIDE
American Cyanamid Company imports large amounts of calcium cyanide
from Niagara Falls, Canada. The manufacturing process involves heating cal-
cium cyanamid with coke or charcoal in a salt bath as the heat conducting
medium at or near 1000°C in an electric furnace.—' Thus,
CaNCN + C ^ > :Ca(CN) ' '
o £1J. U 2. •'- t • '
Other details of this process such as capacity, materials, and energy re-
quirements are lacking. '""..-,
Presumably waste disposal methodologies for this facility are the same
as those included in Table 19 for American Cyanamid Company. It is known the
Canadian government and American Cyanamid are jointly involved in funding
major changes in the facility to reduce pollution and emissions.
FERROCYANIDES AND FERRICYANIDES
The principal manufacturers of sodium and potassium ferro- and ferri-
cyanides are American Cyanamid Company, Fisher Scientific Company, and the
Mallinckrodt Chemical Company. The manufacture of ferrocyanides and ferri-
cyanides is accomplished by replacement and oxidation-reduction reactions
in general•£/ Thus sodium ferrocyanide is formed by combining calcium cy-
anide, ferrous sulfate, and sodium carbonate with water and heating with
live steam: . . ., .
Na CO
3 Ca(CN)0 + FeSO, r > Ca. Fe(CN), + CaSO.
2. 4 ^ i. o 4-
Ca0 Fe(CN), + 2Na0 CO., r—> Na. Fe(CN), + 2CaC00
60
-------
The final product as sodium ferrocyanide is obtained by evaporation, cool-
ing, and crystallization.
Potassium ferricyanide is obtained by oxidizing potassium ferrocyanide
with chlorine. Thus,
2 K. Fe(CN), + Cl > 2 K0 Fe(CN), + 2 KCl
462 Jo
The final product is obtained by evaporation and crystallization. Alterna-
tively, ferrocyanide may be electrolytically oxidized in a diaphragm cell
with nickel electrodes.
Capacity and production data on ferro- and ferricyanides are lacking.
Again, these data are held as confidential and proprietary information by
manufacturers.
Environmental management and waste disposal techniques are the same
as those for other cyanides except that ferro- and ferricyanides are much
less toxic than the simple cyanides and landfill disposal of wastes is the
most prevalent method used.
IRON BLUE
Principal manufacturers of iron blue are American Cyanamid Company
at Willow Island, West Virginia, and Hercules, Inc., at Glens Falls, New
York. One additional manufacturer, Harshaw Chemical Company at Lexington,
Kentucky, offers a special alkali-resistant grade of; iron blue but in
rather small amounts, probably 500,000 Ib annually.
Figure 12 illustrates the manufacture of iron blue. Sodium ferrocya-
nide, ferrous sulfate, and ammonium sulfate are combined in aqueous solu-
tion which is heated with live steam.JL' A white precipitate of ferrous am-
monium ferrocyanide, Berlin white, is obtained. The slurry is transferred
to a heated digestion tank which contains dilute sulfuric acid to leach
out soluble salts. The reaction tank may then be recharged.
After digestion, the slurry is transferred to an oxidation tank wherein
sodium chlorate is added to oxidize the ferrous ion to the ferric condition.
Thus, the overall reactions are:
61
-------
Reaction
Tank
///
// -
_^ Digestion ^ Ox
Tank Tar
/
i? o?
.0 /<•
£ o
' &*
idation ^ Filter ^ ^
k * &.Wash * Dlye'
1
' Treatment m 27
1 1
Solid Residue Liquid Effluent
~ . , <- IUUU
_^ Qnnd Screen _^ |ron B|ue
& Package Product
6 Ca(OH)2
507 CaSO4
25 Fe4(Fe(CN)6)3
190 Fe2O3
32 Fe(OH)2
Water +
70 NaCI
1016
300 (NH4)2SO4
Figure 12.. Iron blue manufacture
-------
Fe(CN)6 + 2 Na2 S04
and ...
6 Fe(NH,)0 FeCCN). + NaClCL + 3 H0SO. > 6 Fe(NH.) Fe(CN). +
426 3.24 4 6
3 (NH ). SO + 3 HO + NaCl
The final product, ferric ammonium ferrocyanide or iron blue, is filtered,
washed, dried, ground, and packaged. The so-called "soluble blues" are in
reality colloidal dispersions in water and are made by peptization of iron
blue with oxalic acid.
Much is known of production data for iron blue but little of the ca-
pacity. At present the market is of the order of 8 million pounds annually
but in the past as much as 12 million pounds were manufactured domestically.
Excess capacity will probably exist for the near future.
Approximately one-third of total iron blue consumption is due to im-
portation and resale. The economics are favorable for importation, $0.38/
Ib versus $0.65/lb for domestically produced iron blue.
Waste management problems hinge on solids disposal since approximately
0.75 Ib are produced per pound of iron blue. These wastes are most likely
disposed of by landfill. The liquid effluent contains ammonium sulfate and
sodium sulfate primarily. It appears that recovery of ferrous and sulfate
values would be possible but probably not economically desirable since these
chemicals are low cost items.
HEAVY METAL CYANIDES . ;
Less is known of'the manufacture of these compounds than any other
cyanide class. Production, capacity, and capital value data are completely
lacking. Further, companies such as C. P. Chemicals, Inc., and E. I. du
Pont de. Nemours and Company are very reluctant to discuss their operations.
Table 20 describes various processes for making heavy metal cyanides.
According to E. I. du Pont de Nemours and Company, cyanide wastes are
currently and historically have been mixed with large excesses of calcium
hypochlorite in the manufacturing plant process sanitary sewer prior to dis-
charge to the City of Niagara Falls treatment plant. Plant pretreatment fa-
cilities to prepare heavy metal cyanide wastes for final treatment by the
City of Niagara Falls will be in operation by December 1976, but details
are lacking.
63
-------
Table 20. MANUFACTURING PROCESSES FOR HEAVY METAL CYANIDES
Cyanide Process description
CuCN Continuous chlorination with direct precipitation of
CuCN from copper chloride and a cyanide. Recovery of
cyanogen chloride for organic synthesis purposes.—'
Na Cu(CN) Dissolve CuCN in NaCN or KCN solution; evaporate and col-
K Cu(CN>2 lect crystals.-/
Zu (CN) Direct precipitation from zinc sulfate and sodium cyanide
with evaporation and crystallization.^'
K Au(CN) Dissolve gold anodically in solution of KCN. Cathode com-
partment contains KOH.—/
Ag CN Direct precipitation with cyanide.—
a/ E. I. du Pont de Nemours and Company.
b/ Ref. 6.
TRANSPORTATION RATES AND REGULATIONS
The regulations regarding the shipment of inorganic cyanides are de-
tailed in the Code of Federal Regulations.— These regulations detail pack-
aging, labeling and classification of materials to be shipped. Table 21 lists
the class and labeling requirements for some of the inorganic cyanides. The
responsibility of proper packaging and labeling of articles for shipment lies
with the shipper.
Table 22 shows typical charges for shipment of goods from Chicago to
Kansas City by motor carrier. The low rate shown is most likely a commodity
rate, which may not apply depending on amount and regularity of shipments.
Table 23 gives typical shipping charges for shipment from Chicago to Kansas
City by rail. This example was chosen since E. I. du Pont de Nemours and
Company has a large distribution facility in Chicago.
Air transportation rates were not determined, as they are of little
consequence. Barge rates were not determined but should be comparable to
rail rates.
64
-------
Table 21. REGULATIONS FOR SHIPMENT OF CYANIDES-
II
Cyanide
Hydrogen cyanide,
stabilized
Hydrogen cyanide,
unstabilized
Hydrogen cyanide
Sodium cyanide
Potassium cyanide
Calcium cyanide
Copper, zinc, lead,
or silver cyanides
Ferrocyanide .. .
Ferricyanide
Form
liquid,
solution > 5%
liquid
solution <, 5%
solid, mixtures,
solutions
solid, mixtures,
solutions
solid, mixtures,
solutions
solid, mixtures,
solutions
solid, mixtures,
solutions
Class
Required
label
Poison A Poisonous gas
Unacceptable for shipment
Poison B
solid, mixtures,
solutions Poison B
Poison B
Poison B
Poison B
Poison
Poison
Poison
Poison
Poison
65
-------
Table 22. MOTOR CARRIER SHIPPING CHARGES, CHICAGO
TO KANSAS CITY3
Shipping charges ($/100 Ib)
Weight range Low High
Minimum: 13.40
< 500 7.37 9.63
500-1,000 6.36 8.61
1,000-2,000 5.50 7.52
2,000-5,000 5.08 7.11
5,000-24,000 4.14 . 5.77
24,000 and up 2.01 2.72
_a/ Distance is about 500 miles.
Source: Consolidated Freightways, Yellow Freight System, Inc.
Table 23. RAIL CARRIER SHIPPING CHARGES,
CHICAGO TO KANSAS CITY-3'
Weight range . Shipping charges ($/100 Ib)
20,000-30,000 2.29
30,000-40,000 1.75
40,000-50,000 . 1.44
50,000-60,000 1.37
60,000-80,000 1.22
80,000 and up 1.14
al Distance is about 500 miles.
Source: Illinois Central Gulf Railroad.
66
-------
It should be noted that cyanide transportation rates do not differ
from rates for other goods because of their toxicity. Essentially all
commodities may be shipped from one point to another at the same rate
for each type of carrier. The carrier, however, may be regulated as to
what other goods may be shipped along with cyanides in the same load.
67
-------
REFERENCES TO CHAPTER VI.
1. Anonymous, "Assessment of Industrial Hazardous Waste Practices, In-
organic Chemicals Industry," U.S. Environmental Protection Agency,
EPA 68-01-2246, National Technical Information Service, Springfield,
Virginia (1975).
2. Sherwood, P. W., Petroleum Processing. 9(2):384-389, February 1954.
3. Kent, J. A., ed., Riegel's Industrial Chemistry, John Wiley and Sons,
Inc., New York (1974).
4. Chemical Marketing Reporter. 183_, May 27, 1963; 191, May 22, 1967;
198, September 28, 1970; 198, October 5, 1970; 203, December 10,
1973; MRI estimates.
5. Stobaugh, R. B., S. G. McH. Clark, and G. D. Camirand, "Acrylonitrile:
How, Where, Who-Future," in Hydrocarbon Processing, 50_(1):109-120
January 1971.
6. Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 6, Interscience
Publications, Inc., New York, 2nd ed. (1965).
7. Code of Federal Regulations, Title 49, Transportation, Parts 100 to
199, U.S. Government Printing Office, Washington, D.C., October 1,
1974.
68
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CHAPTER VII
AREAS OF UTILIZATION
The use of cyanides by industry, mining, and agriculture is discussed
under separate headings of this chapter. Each usage involves a unique set
of circumstances or parameters, and no overall generalizations can be drawn
as to the usage rate or the future of cyanides. For this reason each appli-
cation is individually described, and details as to the growth rate over
the years 1965 to 1975 are given together with a comment on the future cy-
anide usage to 1985. The percentage of total cyanide usage as NaCN equiva-
lent for each sector is given by the headings.
METAL FINISHING (62.5%)
Sodium, potassium, and various heavy metal cyanides are used exten-
sively in metal finishing operations. In fact, this industrial sector con-
stitutes the largest single use of cyanides other than for organic synthe-
sis purposes, which lie outside the scope of this report.
The metal finishing industrial sector is very large, geographically
diffuse, and largely unknown in the distribution and magnitudes of the
numbers of captive, semicaptive, and independent job shops. Estimates by
industry sources of the number of metal finishing shops range from 15,000
to 60,000 or even 80,000 establishments•!' Of these, there are perhaps
5,000 to 20,000 electroplating operations, of which approximately 75% uti-
lize cyanides .in one or more plating lines. The sizes of the establishments
range from shops employing fewer than 10 persons to captive shops employing
approximately 500 operators.
The 1972 Census of Manufactures indicates some 3,265 establishments
in the SIC 3471 - Plating and Polishing category^.' The number of employ-
ees is approximately 55,000, with a payroll of over $400 million. This es-
timate of 3,265 plating shops differs considerably from those above by. in-
dustry sources. The high estimates have been suggested by private individ-
uals and trade and professional associations such as the National Association
69
-------
of Metal Finishers, the Metal Finishing Suppliers' Association, and the
American Electroplaters1 Society. The differences among the various es-
timates are due to the difficulty of locating an electroplating operation
within a company. For example, the Census of Manufactures may locate a
luggage manufacturer in Denver and identify the company as belonging in
SIC 3161 - Luggage Manufacturing category, but would not classify the
company in SIC 3471 - Plating and Polishing. On the other hand, a lug-
gage hardware manufacturer SIC 3429 Cutlery, Hand Tools, and General Hard-
ware (including luggage hardware and cartop racks) might be included in
the Plating and Polishing category as well, since the plating operation
is one of the few principal steps in the manufacturing process. No one
individual, organization, or agency knows even approximately the number
of plating operations and establishments in the U.S.; or what fraction
of these locations utilize cyanides. Further, a cyanide plating line may
be placed in operation or taken out of operation at any time with a very
short turnaround time.
The term "metal finishing" includes a multitude of operations, but
cyanides are employed principally in electroplating, metal cleaning, and
to a much smaller extent in metal stripping. "Electroplating" refers to
the electrochemical process by which a conductive substrate receives a
metal coating or layer from an appropriate solution for the purposes of
protecting, altering, and/or enhancing the substrate surfaces. "Metal
stripping" refers to chemical removal of a previously deposited metal
layer by immersion in an appropriate solution, often containing cyanide.
Much has been written on the subject of electroplating and metal
stripping, including several EPA documents for the development of efflu-
ent guidelines for the electroplating industry. The references at the
end of this section include some of the principal sources of information,
but are not intended to be an exhaustive compilation. Cyanides as the so-
dium, potassium, cadmium, zinc, copper, silver, and gold salts are used
in electroplating of cadmium, zinc, copper, silver, gold, brass,, and
bronze.
Cadmium
Electrodeposits of cadmium are used extensively to protect steel
and cast iron against corrosion. Most cadmium plating is done in cyanide
baths made by dissolving cadmium cyanide or cadmium oxide in a caustic
sodium cyanide solution. Brighteners include aldehydes, ketones, alcohols,
dextrin, etc., plus proprietary materials obtainable from various metal
finishing materials companies. The anodes for cadmium plating usually
consist of ballshaped cadmium metal held in a bare steel cage. Typical
•
bath compositions for cadmium electroplating are given in Table 24.
70
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Table 24. CYANIDE CADMIUM ELECTROPLATING BATH COMPOSITIONS^/
Ratio of total
sodium cyanide to Composition (oz/gal)
Solution cadmium metal CdO Cd metal NaCN NaOH
1 4 to 1 3.00 2.62 10.4 1.90 4.0 to 10.0
2 7 to 1 ' 3.00 2.62 18.4 1.90 4.0 to 6.0
3 5 to 1 3.50 3.06 15.3 2.10 4.0 to 8.0
4 4.5 to 1 5.50 4.82 21.7 3.44 4.0 to 6.0
Note: Solution 1 - for use in still tanks and bright barrel plating.
Solution 2 - for use in still tanks and automatic plating. Not for
, use in barrel plating.
Solution 3 - for use in still tanks, automatic plating, and barrel
plating.
Solution 4 - for plating cast iron; high-speed.
Sodium carbonate forms in the bath because of slow decomposition of
cyanide and general absorption of carbon dioxide from the air. In addi-
tion, oxygen released by insoluble or polarized anodes decomposes cyanide
and one of the products is carbonate. Excessive buildup of sodium carbon-
ate can result in anode polarization and irregular, dull deposits. The
simplest method of carbonate removal is by "freezing," i.e., cooling the
bath to slightly below 15°C for about 24 hr, after which the bath is de-
canted from the solid sodium carbonate. Calcium sulfate or cyanide may be
used to form calcium carbonate as a bulky precipitate.
Solutions for chemically stripping cadmium plate are composed of
ammonium nitrate, ammonium persulfate, and ammonium hydroxide, and other
materials. Electrolytic stripping is accomplished by making the substrate
to be stripped anodic and immersing it in a solution of caustic sodium
cyanide. Compositions of various cadmium stripping solutions are given in
Table 25.
Zinc
Zinc plating is often preferred for coating ferrous parts for protec-
tion against atmospheric corrosion because it is relatively cheap and red-
ily applied in barrel, tank, or continuous plating facilities. It is esti-
mated that zinc deposition accounts for approximately 80% of all cyanide
plating performed today*-' Typical zinc bath compositions are given in Ta-
ble 26.
.71
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3/
Table 25. SOLUTIONS FOR STRIPPING ELECTROPLATED CADMIUM-
Itnmersion
Solution Composition (oz/gal) time (min)
1 Ammonium nitrate (14-18) 10-20
2 Hydrochloric acid (22° Be), undiluted 10-20
Antimony trioxide (2)
3 Chromic acid (27) 5-10
Sulfuric acid (95%) (6.4 fluid oz.)
4 Ammonium persulfate (6.7) 5-10
Ammonium hydroxide (13 fluid oz.)
5 Sodium cyanide (8-12) 10-20
Sodium hydroxide (2-4)
Note: Solutions listed in order of preference. Immersion times are for
removal of deposits 0.3-0.5 mil thick. Solution 5 for electrolytic
stripping at 50-100 amp/sq ft and 6-8 volts, room temperature.
72
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Table 26. CYANIDE ZINC PLATING BATH COMPOSITIONS-
Ratio of total
sodium cyanide
Solution to zinc
1 2.7-3.0 to 1
2 2.5-3.0 to 1
3 2.0-2.5 to 1
4 2.7 to 1
5 2.3 to 1
Composition
Zn(CN)2
8-11
8-11
8-12
5.6
7.5
NaCN
5.2-8.8
4.3-8.8
2.1-6.5
12.3
14.0
(oz/gal)
Sodium
NaOH Polvsulfide
10-12
10-12
10-12
5.0
7.4
0.2
0.2
0.2
0.2
0.2
Note: Total sodium cyanide equals the sum of the sodium cyanide and the
sodium cyanide equivalent of the zinc cyanide or the zinc metal
equivalent in zinc oxide.
Solutions 1 and 5 are used for barrel plating.
Solutions 2 and 4 are used for still tank plating.
Solution 3 is used for conduit tubing and strip plating.
Solutions 4 and 5 utilize zinc ,oxide instead of zinc cyanide.
Brighteners for zinc cyanide plating include dextrin, pyrogallol,
gum arabic, etc., and proprietary materials. Zinc anodes in the form of
balls or elliptical bars are often used and held in a spiral steel cage.
Insoluble steel anodes are also employed.
Zinc metal may be chemically or electrochemically stripped. Table
27 presents a typical bath composition for electrochemically stripping
zinc. Chemical stripping baths do not contain cyanide.
Copper
Copper plating is widely performed in electroforming, plating on
zinc die-castings, leaded brass, as stop-offs, for heat transfer, etc.
Typical bath compositions for copper electroplating are given in Table
28.
Proprietary additives are essential in the high concentration plat-
ing baths (Solutions 5 and 6 of Table 28) in order to prevent pitting
and guarantee brightness of the deposits. The potassium complexes formed
by the combination of potassium ion and copper cyanide are more soluble
73
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3/
Table 27. SOLUTION FOR ELECTROCHEMICALLY STRIPPING ZINC—
Composition (oz/gal)
NaCN
8-12
NaOH
2-4
Immersion time (min)
5-10
Note: Immersion time for stripping deposits 0.2 to 0.3 mil thick. Anodic condition at 50-100 amp/sq ft
at 6-8 volts, room temperature. "
3/
Table 28. CYANIDE COPPER PLATING BATH COMPOSITIONS-
Solution
1
2
3
4
5
6
Ratio of
copper to
free cyanide
2.1 to 1.0
1.75 to 1.0
3.10 to 1.0
2.0 to 1.0
2.3 to 1.0
5.6 to 1.0
Composition (oz/gal)
CuCN
3.0
6.0
3.5
6.0
16.0
8.0
NaCN
4.5
9.0
4.6
7.0
18.0
12.5
Na GO
2.0
-
4.0
8.0
2.0
2.0
NaOH
To pH 12.0-12.6
To pH 12.0-12.6
To pH 13.0
4.0 (pH > 13.0)
-
Rochelle
KOH salt ;
1.0-2.0 6.0-10.0
6.0 .
. - 12.0
.-•--.
5.6 (pH > 13.0)
Note: Solution 1 is a dilute cyanide bath for strike coating.
Solution 2 is a standard barrel plating solution.
Solution 3 is used for copper strikes.
Solution 4 is used for plating up to about 0.3 mil thickness.
Solutions 5 and 6 are used for producing deposits of 0.3 to 2.0 mils thick.
-------
than those formed with sodium ion. Hence, higher metal contents and higher
deposition rates are possible. In addition, the potassium bath has a more
flexible set of operating characteristics and permits a higher current den-
sity with less danger of "burning" the deposits.
Additives for copper baths include gelatin, glue, glycine, etc.,
which result in smoother and finer-grained deposits. Some brighteners are
proprietary formulations.
High-purity copper anodes are recommended for use in high-efficiency
baths. Steel anodes are often used with the dilute cyanide baths. Often
a film of cuprous oxide, or occasionally cupric oxide, is formed during
electrolysis. When this happens, the anodes must be removed and cleaned.
Anode bags of cotton or nylon or diaphragm systems have been used to pre-
vent migration of anode particles to the cathode with resultant roughness
to the copper deposit.
Brass and Bronze
Brass and bronze plating principally refers to the electrodeposition
of alloy coatings containing copper and zinc, and copper and tin, respec-
tively. Proportions of these alloys included in major commercial applica-
tions are listed in Table 29.
Table 29. APPROXIMATE COMPOSITION OF MAJOR COMMERCIAL COPPER
AND ZINC AND COPPER AND TIN ALLOYS^/
Approximate composition (%)
Alloy Copper Zinc Tin
.Brass 70 30
White-Brass 30 70 -
Bronze-Brass 90 10
Tin-Bronze 85-90 - 10-15
Speculum metal (brass) 55-60 - 40-45
Of these alloys, the conventional brass formulation, 70-30 copper-
zinc, and the tin-bronze formulations are the most important.
Brass plate is deposited for decorative purposes, e.g., various hard-
ware and electrical fittings. The deposit is also used to promote adhesion
of rubber to steel and other metals. Typical brass plating bath composi-
tions are given in Table 30.
75
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Table 30. CYANIDE BRASS PLATING BATH COMPOSITIONS-
Solution
1
2
3
4
5
6
PH
10-11
-
-
12
13
10-11
CuCN
3.5-4.2
5.4
9.4-14.1
13.4
5.9
7.0
Zn(CN)2
1.2-1.5
1.6
0.4-1.2
2.4
2.3
3.6
Composition (oz/gal)
Na CO K CO NH Rochelle
NaCN KCN 2323 3 NaOH KOH salt NaSCN
6.0-8.0 - 4.0 - 0.1-0.4 - ' -
1.6 - - - - - - -
12.0-18.0 - - - - 6.0-10.0 -
20.1 - - - 1.5 -
16.8 - 4.0 - - 2.0 - 1.5
12.0 - 4.0 - 0.7-1.6 - - 6.0
Note: Solutions 1 and 2 are conventional baths, low current density, < 10 amp/sq ft.
Solutions 3 through 6 are high speed plating baths with current densities up to 160 amp/sq ft,
The NH is added as a 28% solution in fluid ounce.
-------
The high-speed baths operate from 5 to 160 amp/sq ft, but more
generally in the range 20-40 amp/sq ft. The increased rates are pos-
sible due to an increase in metal content, substitution of potassium
for sodium cyanide, an increase in pH by the addition of sodium or
potassium hydroxide, the addition of Rochelle salt, and higher bath
temperatures.
Organic .brighteners such as thiourea and piperonal are often
added. Antipitting agents of a proprietary origin are available. A
small quantity of ammonia has been found to improve appearance and
brightness of the brass deposit.
The composition of the anodes should be nearly the same as that
of the desired deposit, since anode corrosion occurs during electrol-
ysis and could change the bath composition.
Bronze plating is commercially important as a decorative and pro-
tective finish on various kinds of hardware and steel wire products.
Bronze is employed as a stop-off in gas nitriding of steel, for "build-
ing up" or restoring worn or undersized parts, and as a coating on
bearings. Bronze plate is occasionally a substitute for nickel plate
and can serve as a basis metal for subsequent plating by chromium or
nickel.
Typical bronze plating bath compositions are given in Table 31.
Proprietary brighteners for bronze plating baths are available.
Bronze anodes can be used, but should not contain more than 127o tin.
A preferred variation is to use copper anodes and add the tin com-
pounds as needed for bath maintenance.
Stripping of electroplated bronze is accomplished by caustic cya-
nide solution or by ammonium persulfate in an ammonia solution.
Silver
Various silver plating baths are available for industrial uses,
including aircraft engine bearings, electronics applications, jewelry,
silverware, etc. Silverplate may vary from less than 1 mil to 1/4 in.
in thickness depending on the application. Cyanide plating bath compo-
sitions are given in Table 32.
A silver strike is generally performed first in order to prevent
the formation of loosely adhering deposits. Strike solutions have
relatively low silver content and a high cyanide concentration.
77
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Table 31. CYANIDE BRONZE PLATING BATH COMPOSITIONS-
3/
Composition (oz/gal)
Solution
1
2
3
4
pH CuCN
12.6 4.7
3.9
13 5.4
2.0
Na9SnO_ • 3R90
£» -J £»
5.1
4.7
2.7
2.0
NaCN
7.2
8.6
8.7
6.0
NaOH
1.0
1.3
1.0
1.0
Rochelle
salt Tin deposit (%)
10
6.0 12
15
16
Note: All baths are operated from 20 to 100 amps/sq ft. Solution 2 uses potassium salts rather than
sodium salts and the values given are for potassium salts.
oo
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3/
Table 32. CYANIDE SILVER PLATING COMPOSITIONS-
Cproposition (oz/ga1)
Solution
1
2
3
4
AgCN
0.1-0.2
0.5-0.7
3.3-4.4
6.0-7.3
NaCN Na2C03
5-8
8-12 1.2
-
KCN
-
4-6
6.0-7.3
K2C03
-
3-12
3.0-10.7
KN03 ROM
-
-
3.0-12.0 0.4-1
Note: Solutions 1 and 2 are for silver strikes on nickel plated steel
and nonferrous metals} respectively. Solution 3 is a conven-
tional cyanide silver bath. Solution 4 is a high speed, high
efficiency bath. The pH is not controlled in any of the above
baths. .
Striking time and voltage must be controlled since prolonged application
can produce a powdery, loosely adhering deposit, thus defeating the pur-
pose of the strike. After striking, the conventional or high-speed baths
are used.
Various sulfur compounds, carbon disulfide or ammonium thiosulfate,
are sometimes added to insure deposit smoothness and brightness. Other
proprietary additives are available to increase plate hardness, tarnish-
resistance, and brightness. The additives may contain selenium, antimony,
or lead in conjunction with wetting agents, and sulfur compounds.
Anodes may be of silver or stainless steel. In the first case, op-
eration of the bath will cause the silver content to rapidly increase
beyond the normal limits at which point the excess silver must .be re-
moved by electrolysis, using a steel anode. In the second case, the sil-
ver content falls arid must be replenished.
Gold
Gold plating is industrially important in the areas of electronics
applications and in jewelry. It is ideal for electronics applications
because of resistance to tarnishing and corrosion, low electrical con-
tact resistance and ease of soldering.
Typical gold plating bath compositions are given in Table 33.
79
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Table 33. CYANIDE GOLD PLATING BATH COMPOSITIONS!/
Composition (oz/gal)
Au
Solution (troy oz.) KCN K2HP04 K2C03
1 . 0.25 2 2 -
2 0.125 0.01-2.0 2
3 1.0 2.7 2.7 2.7
4 0.5 4.0 4.0 4.0
5 2.7 - - - 27
Note: Solution 1 - for flash and alloy plating.
Solution 2 - for flash and gold alloy plating of jewelry.
Solution 3 - for thick plate (0.05-1.0 mil).
Solution 4 - for barrel plating.
Solution 5 - for high efficiency, high-speed plating (deposits
1.0 mil in 30 min).
pH maintained between 10.5 and 11.8.
The metal content is furnished by complex sodium or potassium
gold cyanides, Na(K)Au(CN)2« Soluble anodes are rarely used. Gold is
added routinely as the cyanide salt. The potassium salts are preferred
for the high efficiency, high concentration solutions because they are
more soluble than the corresponding sodium salts.
Insoluble anodes may be of stainless steel, platinum-clad tantalum,
platinum plated titanium, or carbon rods.
Gold stripping can be accomplished by anodic- oxidation in a warm
cyanide solution containing a small amount of hydrogen peroxide as a
catalyst. Other solutions not requiring electrolysis consist of 5% po-
tassium cyanide and sufficient amounts of 30% hydrogen peroxide to
cause dissolution. The latter solution can be dangerous if too much
peroxide is used since it can act on the cyanide ion as well, releas-
ing large volumes of gases.
Chemical Consumption
The previous detailed listing of various cyanide plating bath com-
positions permits a number of important points to be developed regard-
ing cyanide consumption. Heavy reliance is made on sodium cyanide as a
80
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complexing agent for metals. Only in relatively rare cases is the more
expensive potassium cyanide used for its superior solubility properties
in the formulation of high-speed plating baths. The cost difference is
substantial, amounting to nearly 56% more at October 1975 prices. Fur-
ther, since cyanide atmospheric oxidation in the bath occurs slowly and
continually, the added cyanide salts for replenishment become a signifi-
cant cost factor over the long run. It is estimated that approximately
one-half of cyanide consumption is due to oxidation of cyanide ion and
one-half is lost by drag-out as work pieces are removed from the plat-
ing solution*!'
Plating baths are generally purchased from a metal finishing sup-
plier as a complete bath only once for startup. Beyond this point, and
excluding the rare occasions of bath disposal because of irreversible
contamination, bath replenishment is accomplished by additions of so-
dium cyanide (or potassium cyanide) and the metal cyanide as salts
when plating with insoluble anodes. Small additions of the metal cya-
nide salt may be made infrequently to adjust the solution composition
balance.
Except for gold plating baths, platers generally buy raw chemicals
and formulate the plating bath themselves. Proprietary brighteners and
levelers to insure uniform metal deposits are purchased only when re-
quired. Metal finishers purchase proprietary formulations for brighteners
mainly. Sodium cyanide is conveniently purchased and handled in 100 Ib
drums.
Metal Finishing Suppliers
The major suppliers of cyanide salts and proprietary plating baths
and chemical formulations are given in Tables 9 (Chapter V) and 34,
respectively.
Outlook for Cyanides in Metal Finishing
Various industry sources have been contacted regarding the future
of cyanides in metal finishing. A general consensus has emerged which
indicates that cyanide usage has declined over the last 5 years but has
stabilized at least temporarily as electroplaters adopt a wait-and-see
attitude regarding effluent restrictions.
81
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Table 34. MAJOR COMPANIES SUPPLYING PROPRIETARY PLATING BATHS
AND CHEMICAL FORMULATIONS TO THE METAL FINISHING INDUSTRY
Company
Udylite Corporation
Sel-Rex Corporation
Du Tone Corporation
Mac Dermid, Inc.
Lea-Ronal, Inc.
R. 0. Hull and Company, Inc.
C. P. Chemicals, Inc.
M&T Chemicals, Inc.
Technic, Inc.
Enthone, Inc.
E. I. du Pont de Nemours and Company,
Allied Research Products, Inc.
Aldoa Company
Engelhard Industries, Inc.
The 3M Company
Enquist Chemical Company, Inc.
Frederick Gumm Chemical Company, Inc.
Location
Warren, Michigan
Nut ley, New Jersey
Waukegan, Illinois
Waterbury, Connecticut
Freeport, New York
Cleveland, Ohio
Sewaren, New Jersey
Rahway, New Jersey
Providence, Rhode Island
New Haven, Connecticut
Wilmington, Delaware
Baltimore, Maryland
Detroit, Michigan
Murray Hill, New Jersey
St. Paul, Minnesota
Brooklyn, New York
Kearny, New Jersey
Three pieces of evidence are offered to substantiate this viewpoint:
1. No recent major facility expansions have occurred.
2. A definite .shift to the use of low cyanide or noncyanide plating
baths has occurred, particularly for zinc processes. This trend is dis-
cussed more fully in Chapter IX.
3. Approximately 70% of the small plating shops have switched to
noncyanide baths J^'
On balance MRI forecasts cyanide consumption in the metal finishing
sector to decrease by at least 25% over the next 10 years, but that a
substantial amount of cyanide, principally NaCN, will continue to be used
as it has been historically. The estimated NaCN equivalent consumption
for 1975 to 1985 is given in Table 35.
82
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Table 35. NaCN EQUIVALENT CONSUMPTION IN METAL
FINISHING IN 1975-1985
Year Estimated usage (million Ib)
1975 50
1980 43.8
1985 37.5
In the absence of an expanding economy the drop in cyanide con-
sumption might be more dramatic. However, as the economy expands and
affects the amount of metal processed, the larger metal finishing
shops will probably continue to use cyanides, with the smaller shops
completely shifting to noncyanide systems.
PIGMENT (IRON BLUE) (16.9%)
In the past, iron blue, ferric ammonium ferrocyanide ^
Fe(CN)x-3 has been widely used as a pigment in paints, enamels, lacquers,
inks, carbon paper, typewriter ribbons, crayons, linoleum, composition
tile, blueprint paper, laundry blues, plastics, chemical coatings, etc.
The previous listing was true in 1965 but.is not accurate today.— Iron
blue is no longer an important pigment in consumer household paint,
crayons, linoleum, composition tile, etc. The major uses are now as
pigment for various types of inks, carbon papers, and for coloration of
plastics. A small amount of iron blue is used in industrial paints,
e.g., safety paint.
The reason for the decline in the general area of consumer paint
is due to the characteristic color instability of iron blue in alka-
line media. The trend in consumer paints is to latex water-based paints
which are moderately alkaline. Iron blue is simply incompatible as a
pigment in such a system. Special alkali-resistant, high purity grades
of iron blue are sometimes available, but their cost is relatively
high, the supply is scarce and uncertain, and the long-term stability
is not enough improved to warrant continued use .in alkaline media.
One paint manufacturer in Kansas City, Missouri, offered consump-
tion figures for iron blue listed in Table 36.—'
83
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Table 36. ANNUAL CONSUMPTION OF IRON BLUE
OF A KANSAS CITY PAINT MANUFACTURER,
1971-1975
Year Pounds of iron blue consumed
1971 2,000
1972 800
1973 180
1974 147
1975 (8 months) 36
The products currently using iron blue amounted to only 600 gal.
in 1975 and were special paints for industrial use, e.g., safety paint
and other enamels requiring bright, deep blue colors which are durable.
Other paint manufacturers contacted indicated that usage of iron blue
is rapidly decreasing on an industry wide basis.
The only significant usage of iron blue is in paints and enamels
having special industrial product applications, e.g., safety signs,
farm implements, trucks, tractors, etc. For these uses, there are no
organic or inorganic pigments with suitable durability and economics
to replace iron blue. Little change in the use of iron blue for these
applications is anticipated in the future.
Large amounts of iron blue were also used in the manufacture of
chrome green for paint pigment, the latter being a mixture of chrome
yellow and iron blue.— However, chrome yellow contains lead and chro-
mium. These elements have been tagged as being ecologically undesir-
able and a health hazard. Again, the iron blue market in nearly all
paints, enamels, and lacquers has decreased to a very low level and
accounts for much less than 5% of the total iron blue consumption by
industry..!!'
Iron blue has been used in art materials, paints, and crayons
because of its extremely high tinctorial power. However, it has been
replaced by copper phthalocyanine blue, an organic pigment of high
tinting strength and excellent heat and oxidation resistance. Further,
a major manufacturer of floor tiles in Lancaster, Pennsylvania, in-
dicated that any future use of iron blue in this sector is negligible.
The markets for iron blue are rapidly decreasing as organic pigments
having greater oxidation resistance are developed.
84
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The current major uses of iron blue are in the formulation of
various types of inks for carbon paper, printing, and typewriter rib-
bons. According to one industry spokesman, the market for iron blue
is divided in the manner indicated in Table 37.
Table 37. CONSUMPTION OF IRON BLUE BY MARKET USE IN 1975^
4/
Iron blue consumption in 1975
Printing ink (including publishing
gravure inks and typewriter
ribbons)
Carbon paper ink (including one-
time and multiple-copy types)
Coloration of plastics, especially
polyethylene
All other uses, including paint,
enamels, papermaking and as an
anti-caking agent
Total
Approximate
of market
45
35
10
10
100
Approximate consump-
tion (million Ib)
5.5
4.5
1.5
All printing ink contains a small amount of iron blue, typically
2 to 10% iron blue plus other pigments including carbon black, the
principal material. Carbon paper ink may contain 10 to 25% iron blue
plus other pigments. Iron blue is the lowest priced blue pigment ac-
ceptable for these applications.
There are approximately 350 domestic ink manufacturers of which
six firms may account for 60 to 70% of the total printing ink manu-
factured according to one estimate. The major manufacturers of print-
ing ink are listed in Table 38.
The value of iron blue pigment in ink in 1972 amounted to $3.5
million and the value of ink (retail sales) amounted to $4.25 million.
Temple Patton estimated some 9 million pounds of iron blue were consumed
in ink manufacture in 1972.^.'
85
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Table 38. CURRENT MAJOR INK MANUFACTURERS IN ORDER OF
BUSINESS VOLUMES
Company Location
IPI Printing Inks New York, New York
Division of Inmont Corporation
Sinclair and Valentine Company New York, New York
Division of Wheelabrator-Frye, Inc.
General Printing Ink New York, New York
Division of Sun Chemical Corporation
Flint Ink Corporation3.' Detroit, Michigan
Borden Chemical Company—' Columbus, Ohio
Division of Borden, Inc.
Sleight and Hellmuth, Inc. Chicago, Illinois
Acme Printing Company, Inc. Chicago, Illinois
aj Merged with Gal/Ink Division of Tenneco, Inc., San Francisco,
California.
b/ Merged with Levey Division, Cities Service Company, Inc.,
Cincinnati, Ohio.
Source: MRI estimates.
The ink manufacturers serve a vast and diffuse market. It has been
estimated that the size distribution of printing establishments in 1972
was that as listed in Table 39.
Table 39. SIZE CLASSIFICATION OF PRINTING
ESTABLISHMENTS IN 19721/
Approximate
Size classification number of shops
Small (< 50 employees) 18,000
Medium (50-250 employees) 850
Large (> 250 employees) 150
Total 19,000
86
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The printing establishments include all printing and publishing
facilities,.e.g., newspapers, periodicals, books, commercial, business
forms, etc.
The recent historical growth (1955 to 1972) of the printing ink
industry.averaged 5 to 6%/year and is expected to continue in the near
future.— This growth is related to the growth in the entire communi-
cations field and could be even greater over the next 10 years.
Three segments of the printing ink industry showing the most growth
in recent years are:
Lithographic ink - printing from a planar surface
Flexographic ink - printing from raised type
Rotogravure ink - printing from a recessed or engraved type
All these techniques are used for publications, packaging and
labels. These ink types accounted for approximately 457o of all printing
ink produced in 1972. Growth rates for the three segments as a: group
averaged 10% per year from 1963 to 1972 with a growth rate of nearly
15% for the lithographic sector.^-
Carbon paper is a general term describing a paper coated with
hardened ink and used for duplicating purposes. A distinction may be
made between one-time, pencil, and typewriter carbon papers, and the
applications range from single use, to sales books, to maximum repeat
requirements. Performance depends in part on the ink composition of
which iron blue is a prominent pigment.
Growth in this field has been related to growth of the entire
communications and business areas and has been approximately 5%/year
over the last 10 years. Recently, carbonless paper has become avail-
able which contains organic dyes as microencapsulated color agents.
Future iron blue consumption in the carbon paper ink area is estimated
to decrease as organic carbonless paper becomes more prominent.
Finally, iron blue is used as a colorant for polyethylene and
other plastics. The principal application appears to be the manu-
facture of green refuse bags. This market is significant but small
and accounts for approximately 0.5 million pounds of iron blue an-
nually.
87
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The overall growth of iron blue consumption is difficult to fore-
cast because of individual rising and falling trends of the various
industrial sectors. Industry spokesmen indicate slow growth over the
next 10 years. Figure 5 of Chapter V illustrates total consumption of
iron blue for a 2 and 4% annual increase. Growth is estimated to be
3% annually.
Environmental management of inks, dyes, and pigments containing
iron blue is a difficult concept to apply in the case of iron blue.
Certainly the two domestic manufacturers of iron blue, American Cyanamid
Company and Hercules, Inc., are point sources worth monitoring. Data
on iron blue manufacture are included in Chapter V in this report.
Processors utilizing iron blue as a pigment are more diffuse and
as an industry segment are phasing out iron blue as a raw material,
especially for paint. The six major ink manufacturers are.potential
point sources. When the final product, as carbon paper, ink or trash
bags, is manufactured, distributed and consumed, the geographic factor
coupled with the consumer dilution of the products, make environmental
management difficult except at the municipal or county waste disposal
areas. Since iron blue is nontoxic and harmless except perhaps when
incinerated, there should be no danger to animal or plant life.
METAL AND MINERAL RECOVERY (8.27»)
Cyanides are used extensively in the extraction and beneficiation
of metals and minerals in the United States. Cyanides are principally
used (a) to extract gold and silver from ore, i.e., cyanidation; and
(b) as a depressant in the selective flotation of copper, lead, zinc,
and fluorspar ores.
Cyanidation
The use of cyanide to extract gold was introduced domestically in
South Dakota in 1899.— Cyanidation currently is the single most impor-
tant method of recovery for gold. In 1972, nearly 5570 of the U.S. gold
production resulted from cyanidation.—'
Cyanidation is also a method of recovery for silver? however, very
little silver is recovered by cyanidation domestically, except as a by-
product of gold production. This discussion will be limited to gold
production, with the understanding that silver is recovered as a by-
product of cyanidation recovery of gold.
88
-------
Process Descriptions - Five major operations currently recover gold by
cyanidation, Table 40. Numerous other gold mining operations are in ex-
istence with the bulk of these recovering gold by various methods of
gravity concentration; a few of these employ cyanidation on a small scale.
The Homestake Mining Company is the largest domestic producer of
gold. A simplified description of the Homestake operation is shown in
Figure 13.
Table 40. MAJOR OPERATIONS RECOVERING GOLD AND SILVER
BY CYANIDATION^
7
Company
Homestake Mining
Company
Carlin Gold Mining
Company
Cortez Gold Mines
Location
Lead, South
Dakota
Carlin,
Nevada
Cortez,
Nevada
Ore type
Gold
Gold
Gold
Knob Hill Mines, Inc. Republic, Gold-silver
Washington
Magma Copper Company, San Manuel, Copper
San Manuel Division Arizona
Mill capacity,
tons/24 hr
5,600
2,500
2,400
250
12
The Homestake method is unique in that the sands and slimes are
treated in separate cyanidation circuits. The sand portion is leached
in vats by percolating alkaline sodium cyanide solution through the
sands, and the gold is recovered by precipitation with zinc dust.
The slime portion is treated by the Bureau of Mines' developed
carbon-in-pulp method. Carbon-in-pulp treatment at Homestake constitutes
mixing the thickened slimes with 6 x 16 mesh activated coconut charcoali'
in four agitated vats. The carbon and the pulp flow counter-currently
and are separated between each vat by screening.
89
-------
Barrel
Amalgamation
-To Refinery
Cqrbon in Pulp Plant
Ume "I Sands (60%)
NaCN 1 ,
1
Residue
to Fill
Mine
Stopes
Barren Solution
ach Vats
Zinc
- { Dust
Precipitation
i
Filtration
r
Bullion
to Refinery
Adapted from Gold and Silver
Cyanidation Plant Practice.
Thi
Mnf~M -L - Con
-I-
Adsorption Agi
NaCN
NaOH 1
_
1
r
Sponge to
Refinery
Slimes 1
i '
clceners
i r
ditioning
tators "^~*
^ x-.^L.
Lime
& Air
•To Tailing
Screen
Undersize
to Refinery
Figure 13. Homestake process schematic
90
-------
The gold is adsorbed by the carbon and then desorbed by leaching
with hot sodium hydroxide- sodium cyanide solution. The gold- loaded
caustic-cyanide solution is then electrolyzed, recovering the gold on
stainless steel wool cathodes*^/ The caustic-cyanide solution is re-
cycled; the desorbed carbon is reactivated by heat and is also recy-
cled.
The Carlin Gold Mining Company is the second largest domestic
gold mining operation and in 1972 the third largest producer of gold,
behind Kennecott Copper Corporation's Utah copper mine. The Carlin
venture is relatively recent with production started in 1965 and full-
scale production reached in 1966.
The ore processed at Carlin presents a different set of complica-
tions than at Homestake, in that part of the ore is of a carbonaceous
origin. Gold ores containing active carbon adsorb gold from the cyanide
solution much the same as in a carbon-in-pulp plant, except that the
goldloaded carbon cannot be separated from the gangue. Attempts in the
past to overcome the deleterious effects of the carbon have included
roasting the ore to oxidize the carbon and blanking with kerosene or
fuel oil, with varying results.
The Carlin operation (Figure 14) oxidizes the carbonaceous ore
with chlorine gas introduced into the pulp. The oxidized, carbonaceous
ore then enters the production stream with the oxide ore for agitation
dissolution with alkaline cyanide. Gold is recovered as bullion by pre-
cipitation with zinc dust and lead acetate. By-product mercury is re-
moved from the gold precipitate by retorting.
Operation at the Cortez mill would appear much the same as the
oxide ore portion of the Carlin schematic, Figure 14, except the
Cortez mine does not produce by-product mercury. This schematic would
apply to ore above 0.08 oz of gold per ton of ore, the mill cutoff
grade .-
Another part of the process at the Cortez facility is heap leach-
ing of initial development ore and mill cutoff ore less than 0.08 oz/ton.
The ore to be leached is piled on an impervious pad, alkaline cyanide
solution is sprayed over the heap and the pregnant solution collected
in ditches prior to recovery of the gold. The gold is adsorbed onto
activated carbon much the same as the Homestake procedure. The carbon
is stripped with caustic soda and the, gold precipitated onto stainless
steel wool cathodes by electrolysis.—
It has baen reported that Carlin also heap leaches using cyanide
solution, but details and the extent of the operation are not avail-
91
-------
Ore
Carbonaceous Ore
i
I
Crushers
Oxide Ore
Ball Mill
Classifier
IT
Lime
NaCN
Ball Mill
Classifier
CI2
Agitation
Agitation
Thickeners
Filter
Tailing
• Zinc Dust
Precipitation
I
Presses
I
Retort
Mill
Water
•Mercury Recovery
Adapted from Gold and Silver
Cyanidotion Plant Practice.
Bullion to Refinery
Figure 14. Carlin process schematic
92
-------
Knob Hill Mines presents an entirely different operation in that
85% of the gold is recovered by flotation and only the tails (15%) are
cyanided. The Knob Hill schematic appears in Figure 15. The gold-silver
precipitate from the cyanidization of the flotation tailings is shipped
to a smelter along with the flotation concentrates J;'
The Magma Copper Company, San Manuel Division, recovers gold by
cyanidation of molybdenite concentrates, arising from flotation of
copper ore. This process is novel in that most gold in copper sulfide
ores follows the copper flotation concentrate and is recovered as a
by-product at the smelter.
The Magma process schematic is shown in Figure 16. The process in-
cludes vat leaching of the molybdenite concentrates and precipitation
of the gold with zinc dust. The molybdenite is further processed to re-
move water before final shipment ..i/
Environmental Aspects - Treatment for the destruction of cyanides result-
ing from cyanidation of gold ores generally entails use of a tailings
pond. Tailings ponds can generally be described as reservoirs for reten-
tion of water and solids not recovered from the ores.
Retention times for tailings ponds vary from a few days to indefi-
nitely depending on various conditions such as: (a) size of pond; (b)
water reclaimed; (c) climate; and (d) water runoff from surroundings.
The cyanides may be destroyed in the tailings pond by air oxida-
tion and sunlight. The cyanides may also become immobilized by com-
plexation with metals in solution or by attachment to gangue materials.
Chemical destruction of cyanides at present is not actively prac-
ticed. One gold recovery operation has a chlorinator on standby for
treatment of tailings pond effluent in case of dam leaks or breaks Ji/
Homestake in the past has discharged the water and tailings from
the slime portion of their cyanidation operations to Whitewood Creek.i'
It has been reported that a treatment process for cyanides is under
development.— It is not known if this treatment process has yet been
applied to the effluents.
Consumption of Cyanides for Cyanidation - No data are available detail-
ing the actual consumption of cyanides in the gold recovery industries.
Figures are available in some cases on consumption of cyanide per ton
of ore processed and on the amount of ore processed each year. However,
operating conditions affecting the consumption of cyanide per ton of ore
processed can change at any given time.
93
-------
Ore
Adapted from Gold and Silver
Cyonidotion Plant Practice.
Crushers
I
Ball Mill
NaCN-
Mill
Tail
I
Jig
I
Hutch Concentrate
Classifier
I
Cyclone
I
Rougher
Flotation Cells
Concentrate
Regrind
Thickener
li
I
Classifier
Aeration
Cleaner Tail
Cleaner
Flotation Cells
Agitation
1
Thickener
-Zinc Dust
Precipitation
±i
Thickener
I
Filter
Mill
Water
Shipment to Smelter as
Flotation Concentrates
Figure 15. Knob Hill process schematic
94
-------
Molybdenite
Concentrate
Zinc Dust
Lead Acetate
Adapted from Gold and Silver
Cyanidization Plant Practice.
NaCN
Precipitate
to Refinery
Molybdenite
for Shipment
Figure 16. Magma process schematic
95
-------
Conditions changing the consumption of cyanide per ton of ore in-
clude: (a) ore grade; (b) cyanicides in the ore; and (c) process changes^
Table 41 details the data for the five major gold cyanidation opera-
tions. Figures 17 and 18 detail ore production and total annual cyanide
consumption, respectively.
Table 41. CYANIDE CONSUMPTION FOR RECOVERY OF GOLD
Mining operation
Homestake Mining Company
Carlin Gold Mining Company
Cortez Gold Mines
Knob Hill Mines, Inc.
Magma Copper Company, San
Manuel Division
Pounds of NaCN per
ton of ore
Sand portion 0.25
Slime portion 0.75
0.28
(0.25)
(0.35)
55.3
Reference
7
1
Note: ( ) = MRI estimate.
The projection of future consumption of sodium cyanide for cyani-
dation of gold and silver ore hinges on several variables. Table 42
lists the variables and the probable effect of each variable.
Selective Flotation
Inorganic cyanides as sodium cyanide, potassium cyanide, calcium
cyanide, sodium ferrocyanide, and sodium ferricyanide have been used
extensively as chemical additives in froth flotation.
96
-------
4.Or
vo
Homestake
Carl in
Cortez
Total
1965
1970
1975
1980
1985
Figure 17. Gold ore production
-------
VO
oo
i.8r
1.6
c
o
:= 1.4
--*-
Z
u
o
Z
^ 1.2
•?
J
1.0
m.^- c»»:
Estimate
1965
1970
1975
1980
1985
Figure 18. Sodium cyanide consumption for gold recovery
by cyanidation
-------
Table 42. FACTORS INFLUENCING CYANIDE CONSUMPTION FOR GOLD RECOVERY
Variable
Effect
Heap leaching -H
Price of gold +
Availability of developable ore
Environmental considerations +
Availability of capital
Comments
Low capital cost
Smaller operations
Lowers economical ore grade
Extends life of mine
Increases bullion production
Exploration costs high
Amalgamation not acceptable
Cyanide destruction costly
Froth flotation, simply stated, entails separation of mineral
values from gangue by the use of (a) a surface active agent; (b) agi-
tation; and (c) air bubbles. The valuable mineral particles are coated
with an organic collector; and when a collector-coated particle collides
with an air bubble, they will stick together and float to the surface
as froth and overflow the flotation cell. Undesirable gangue materials
remain in the flotation cell, leaving the bottom of the flotation cell
as tailings. Selective froth flotation generally implies the separation
of two or more valuable minerals from each other and from the gangue in
successive steps.
Froth flotation has been described as being the most important
metallurgical process developed in the 20th Century.— Froth flotation
allows the processing of many millions of tons of ore that otherwise
would never have qualified as
Cyanides are used in flotation as depressants to inhibit the attach-
ment of certain minerals to the froth, thereby effecting selective sep-
aration. Table 43 shows the general effect of cyanide on various minerals.
The use of cyanide in selective flotation has become widespread and in-
dispensable.—
99
-------
Table 43. EFFECT OF CYANIDE ON VARIOUS MINERALS—2—
Effect
Mineral name
Chemical composition
Strong
depressant
Moderate
depressant
Not
depressant
Pyrite
Pyrrhotite
Marcasite
Arsenopyrite
Sphalerite
Chalcopyrite
Enargite
Tennantite
Bornite
Galena
Iron sulfide
Iron sulfide
Iron sulfide
Iron, arsenic sulfide
Zinc sulfide
Iron, copper sulfide
Copper, arsenic sulfide
Copper, iron, zinc, silver,
arsenic sulfide
Copper iron, sulfide
Lead sulfide
Ore classifications on which cyanides are used as depressants
domestically include:
Copper
Copper-molybdenum
Copper-lead-zinc
Copper-zinc-iron-sulfide
Lead-zinc
Lead-zinc-silver
Zinc
Fluorspar
Other ores on which cyanides are used as depressants, but which are
not commonly processed in the U.S. are:
Nickel
Cobalt
Antimony
These ores will not be considered in this report.
The use of cyanide in flotation is generally applied to sulfide
minerals, although many oxide ores may be conditioned to respond as
the corresponding sulfide mineral.
100
-------
The most commonly used cyanide as a depressant is sodium cyanide.
Calcium cyanide is still in use, but to a much smaller extent than
previously, most likely because it is less pure, hence, less easily
adapted to automated processes. Sodium ferrocyanide and sodium ferri-
cyanide are used mainly in the flotation separation of copper and
molybdenum sulfides* Potassium cyanide is used very little because
of higher cost.
Sodium, calcium, sodium ferro- and sodium ferricyanides are usually
fed to the flotation circuits as 5% solutions and may be added to the
circuit at .different points and multiple points depending on the ore
treated.—
Usual amounts of the various cyanides fed to the flotation circuit
per ton of ore appear below in Table 44.
Table 44. TYPICAL ADDITIONS OF THE CYANIDES TO ORES—
Addition
Reagent (Ib/ton)
Sodium cyanide 0.01-0.5
Calcium cyanide 0.01-0.5
Sodium ferrocyanide 0.1-2.0
Sodium ferricyanide 0.1-2.0
Process Descriptions - A generalized description of flotation processes
for each ore considered appears in Figure 19.
Ores are difficult to class by type such as copper ore versus
copper-molybdenum ore. This will be more evident in Figures 22 and 23
shown later. It should also be noted that when an ore is referred to
as a copper-lead-zinc ore, it is actually a copper sulfide (CuFeS2),
lead sulfide (PbS), and zinc sulfide (ZnS) ore.
Preparation of the ores for flotation includes size reduction and
classification. Minerals vary as to the size most suitable for flotation
and ores vary as to the amount of grinding necessary to obtain a sub-
stantial degree of mineral liberation. Sulfide minerals can be floated
101
-------
o
ro
Ore
*
Crushing
*
Rod Mills
*
;Ball Mills
_. ....
Classification
t
/- !•.- • —
— »
Copper Ore
Flotation
— ^ Copper Concentrates
Copper - Molybdenum Ore
Bulk Q
Flotation
Copper
Msslw
Cone.
Copper - Lead - Zinc Ore ft
Selective ©
Flotation
Selective ~
Flotation -
— »j Flotation \-
-------
in the size range of 5 to 420 y,, but flotation should be done at the
largest size practicable. Reagent consumption is higher for small par-
ticles, and the flotation separation becomes very inefficient for par-
ticles less than 5 p, in diameter.
Flotation circuits (Figure 20) generally consist of a bank of
roughing cells and a bank of cleaner cells for each mineral recovered.
The roughing cells produce a-concentrate relatively impure, but con-
taining nearly all of the respective floatable mineral value. The
cleaner cells in turn refloat the rougher concentrate, producing a more
pure concentrate. The tailings from the cleaner cells are returned to
the roughing cells. This dual circuit conserves chemical reagents, pro-
duces a higher grade final concentrate and higher percent recovery for
each mineral value.
Circled numbers in the following discussion correspond to the num-
bers in Figure 19 under the respective ore headings.
Copper ore - The vast majority or copper ores are beneficiated by
flotation alone or in combination with acid leaching. Sodium and calcium
cyanides are used as depressants for iron sulfides commonly associated
with copper sulfide deposits. Care must be used when using cyanide as
a depressant; when used in excess, it also depresses copper sulfides.—
Lime is used as a pH regulator and also to help depress the iron
sulfides, except when gold is present. Sodium carbonate can substitute
for the lime to prevent solubilization of gold and silver.
Copper-molybdenum ore - Molybdenum recovery from copper-molybdenum
ores would be virtually impossible were it not for flotation, and cya-
nides are very important in this separation. Sodium and calcium cyanides
are used to depress iron sulfides in the initial flotation (l) to sepa-
rate both copper and molybdenum sulfides from the gangue. Then (2j so-
dium cyanide, sodium ferrocyanide and sodium ferricyanide may be used
to depress the copper sulfides in the bulk concentrate to produce two
concentrates, i.e., molybdenum sulfide from the froth and copper sulfide
from the tailing.
Copper-lead-zinc ore - In the flotation of the copper-lead-zinc
ores sodium or calcium cyanide tnay be used to first depress zinc sulfide,
sphalerite, while floating a bulk copper-lead concentrate (3j • In this
initial step the zinc follows the tails to the zinc flotation circuit.
Zinc sulphate is commonly used with cyanide to depress the zinc sulfides.
The zinc sulfide is recovered by the addition of copper sulfate which
activates the zinc sulfide and renders it floatable.
103
-------
Adapted from Ref. 13
•*-[ Middlings | [ Froth [
Concentrate Storage Bin
Figure 20. Lead-zinc flotation circuits
-------
The bulk copper-lead concentrate in turn is usually selectively
floated f4J . The mineral which is less abundant is usually floated
away from the more abundant mineral. One method of separation is to
depress the copper sulfides with excess sodium or calcium cyanide
while floating the lead. The copper remains as a tailing to be further
cleaned by flotation to produce a copper concentrate.
Copper-zinc-iron-sulfide ore - In the flotation of copper-zinc-
iron-sulfide ores sodium or calcium cyanide may be used to depress the
zinc and iron sulfides {5*} while floating the copper sulfides. In
ores of this type copper salts have always coated or activated at least
part of the zinc minerals .-ii' The cyanide may be helpful by leaching
copper from the surface of the zinc minerals, thereby enhancing the de-
pression of the zinc. The cyanide also complexes any stray copper ions
in solution. Again care must be used because excess cyanide depresses
copper sulfide flotation, and excess copper ions tend to activate the
iron sulfides.
The zinc and iron sulfides follow the tailings to the zinc flota-
tion circuit. The separation of the zinc from iron sulfides is usually .
accomplished best by using sulfide promoters and a pulp pH 8.5 to 11.5.-^
Copper sulfate is used to reactivate the depressed sphalerite. The cop-
per is adsorbed on the surface of the sphalerite particle, which then
acts as a copper mineral.
Lead-zinc ore - In the selective flotation of lead-zinc ores
sodium and calcium cyanides again are used to depress sphalerite anc
iron sulfides, much the same as discussed above. Lead-zinc ores often
are highly complex, requiring additional grinding to liberate the lead
and zinc minerals. Also gold and silver often are present in lead-zinc
ores. In these cases the cyanide is usually added in several stages
and in small amounts at each stage. In the above cases, recovery effi-
ciency may not be as good as in less complex ores.
Lead-zinc-silver ore - The flotation recovery of lead-zinc-silver
ores (i\ is approximately the same as discussed for lead-zinc ore above.
The distinction between the two ores is in the amount of silver present
and the economics of recovering the silver. Silver values should be re-
covered with the lead concentrates to minimize silver dissolution by
cyanide and, therefore, the loss of silver.
Zinc ore - The use of sodium and calcium cyanides in the flotation
of zinc ore Co) is small. The cyanide is used occasionally to depress
sphalerite while recovering lead and copper values. Also the cyanide
may be used in small quantities to activate the sphalerite by cleaning
the sphalerite particle surface prior to activation with copper sulfate.
105
-------
Fluorspar ore - Sodium and calcium cyanides are used in the flo-
tation of fluorspar (GaF?) ores (9j to depress small amounts of zinc
and iron sulfides. This greatly improves the purity of the fluorspar
concentrates. In some cases the zinc values may be high enough for
recovery, after the removal of the fluorspar values. The recovery of
by-product zinc can improve the economics of the fluorspar recovery.
Processing Sites - Table 45 lists in order the 25 leading copper pro-
ducing mines and corresponding concentrators. In some of the concen-
trators copper is also recovered by leaching and where possible the
capacity for leaching was excluded from the capacity reported.
Table 46 lists in order the 25 leading lead producing mines and
corresponding concentrators, if known. These 25 mines produced 99% of
the domestic primary lead in 1972. Most of the lead mines situated in
Missouri are in the "New Lead Belt" in the southeastern part of the
state and account for about 81% of the U.S. production. This area is
of recent development since many of these mines began operations in
the mid-to-late 1960's.
Table 47 lists companies concentrating fluorspar ores. Some of
these companies buy ore and do custom concentration only. Table 47 is
not in order of production. The individual company production in most
cases has been withheld by the Bureau of Mines to-avoid disclosing pro-
prietary data.
Consumption of Cyanides as Depressants - Data on the consumption of
the cyanides used as depressants are not complete. The Bureau of Mines
has published data outlining the consumption of chemicals used in flo-
tation each 5 years since 1Q6n.8»21,22/
Table 48 below details the consumption of cyanides as depressants
in the flotation of minerals.
The estimated consumptions in the above Table 48 were made assum-
ing that the consumption of cyanide per ton of ore processed by flotation
did not change since 1965.
Table 49 lists various factors affecting the consumption of cya-
nide per ton of ore.
Table 50 details the consumption (Ib/ton) of all depressants in-
cluding cyanides used in the flotation of the various ores discussed
previously.
106
-------
Table 45. LEADING COPPER PRODUCING MINES 15-17/
1965 1972
RanW Rank Mine County and state
I 1 Utah Copper Salt Lake, Utah
5 2 San Manuel Final, Arizona
2 3 Morenci Greenlee, Arizona
3£/ 4 Berkeley Pit Silver flow, Montana
5 Ray Pit. Final, Arizona
20 6 Pima Pima, Arizona
7 Tyrone Grant, New Mexico
8 Twin Buttes Pins, Arizona
9 Sierrita Pima, Arizona
9 10 White Pine Ontonagon, Michigan
4 11 Chino Grant, New Mexico
7 12 New Cornelia Pima, Arizona
11 13 Inspiration Gila, Arizona
10 14 Mission Pima, Arizona
6 15 Ruth Pit White Pine, Nevada
12 . 16 Yerington Lyon, Nevada
8- 17 Copper Queen Cochise, Arizona
19 18 Mineral Park Mohave, Arizona
17 19 Copper Cities Gila, Arizona
15 20 Silver Bell Pima, Arizona
3^ 21 Butte Hill Silver Bow, Montana
g- 22 Lavender Pit Cochise, Arizona"'
16 23 Bagdad Yavapai, Arizona
18 24 Magma Final, Arizona
25 Copper Canyon Lander, Nevada
a/ Berkeley Pit and Butte Hill mines combined.
b/ May be included with Butte Hill mine data.
c/ Excludes acid leaching plant.
d/ Now a joint venture with American Metal Climax
Mining Company.
e/ Includes acid leaching plant.
f/ Copper Queen and Lavendar Pit combined.
£/ Miami Copper Operations, Gila, Arizona.
h/ May be included with Copper Queen data.
i/ Superior Division, Final, Arizona.
j/ Battle Mountain Properties, Lander, Nevada.
Operator
Kennecott Copper Corporation
Magma Copper Company
Phelps Dodge Corporation
The Anaconda Company
Kennecott Copper Corporation
Pima Mining Company
Phelps Dodge Corporation
The Anaconda Company—
Duval Sierrita Corporation
White Pine Copper Company
Kennecott Copper Corporation
Phelps Dodge Corporation
Inspiration Consolidated
Copper Company
American Smelting and
Refining Company
Kennecott Copper Corporation
The Anaconda Company
Phelps Dodge Corporation
Duval Corporation
Cities Service Company
American Smelting and
Refining Company
.The -Anaconda Company
Phelps Dodge Corporation
Bagdad Copper Corporation
Magma Copper Corporation
Duval Corporation
Ccrapany called Anamax
Products
Cu, Mo, Au, Ag, HjSC^,
Se, Pd, Ft, Re, Te
Cu, Mo, Au, Ag
Cu, Au, Ag
Unknown #
Cu
Cu, Mo, Au
Cu, Au, Ag
Cu
Cu, Mo, Ag
Cu, Ag
Cu, Mo
Cu, Au, Ag
Cu, Mo, Ag, Au, Se, Rh
Cu, Ag, Mo
Cu
Cu
Cu, Au, Ag
Cu, Mo, Ag
Cu
Cu, Mo, Ag
Cu, H2S04, Ag, Au, Se
Cu, Au, Ag
Unknown
Cu i
Cu, Au, Ag-1
Capacity
(ton/ day)
108,500
65,000
60,000b/
Unknowrt-
c/
25,400-
46,000
50,000
30,000
80,000
25,000
22,000
34,000
20,000
22,500
21,000
e/
14,000-
20,000
17,000
14,000-**
11,000
50,000
w
Unknown
i/
3,500-
4.000-1
Flotation
Yes
Yes
„*" »/
Unknown
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Unknown
Yes
Yes
Yes
Unknown y
Yes"
Yes
Yes
h/
Yes
i/
YeSI/
YesJ
-------
Table 46. LEADING LEAD PRODUCING MINEsl6'18'
o
oo
1965
Rank
IS/
2
li/
3
5
17
IS/
7
8
6£/
16
24
12
15
18
14
1972
Rank
1
2
3
4
5
6
7
8
9
10-
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
£/
Mine
Buick
Fletcher
Magmont
Ozark
Viburnum No. 29
Federal
Viburnum No. 28
Bunker Hill
Lucky Friday
Burg in
Viburnum No. 27
Star Morning
Indian Creek
No. 32
Idarado
Leadville
Dayrock
Indian Creek
Sunnyside
Camp Bird
Ground Hog
Mayflower
Austinvllle
Ivanhoe
Eagle
Pend Ore i lie
Bulldog Mountain
Brushy Creek
County and state
Iron, Missouri
Reynolds , Missouri
Iron, Missouri
Reynolds, Missouri
Washington, Missouri
St. Francois ,
Missouri
Iron, Missouri
Shoshone, Idaho
Shoshone , Idaho
Utah, Utah
Crawford , Missouri
Shoshone , Idaho
Washington, Missouri
Ouray and San Miguel,
Colorado
Lake , Colorado
Shoshone , Idaho
Washington, Missouri
San Juan, Colorado
Ouray, Colorado
Grant , New Mexico
Wasatch, Utah
Wythe, Virginia
Eagle, Colorado
Pend Ore I lie,
Washington
Mineral, Colorado
Reynolds, Missouri
Operating company
AMAX Lead Company of Missouri
St. Joe Minerals Corporation
Cominco American, Inc.
Ozark Lead Company
St. Joe Minerals Corporation
St. Joe Minerals Corporation
St. Joe Minerals Corporation
The Bunker Hill Company
Hecla Mining Company
Kennecott Copper Corporation
St. Joe Minerals Corporation
Hecla Mining Company
St. Joe Minerals Corporation
.Idarado Mining Company
American Smelting and
Refining Company
Day Mines, Inc.
St. Joe Minerals Corporation
Standard Metals Corporation
Federal Resources Corporation
American Smelting and
•Refining Company
Hecla Mining Company
New Jersey Zinc Company
New Jersey Zinc Company
Pend Orel lie Mines and
Metals Company
Home stake Mining Company
St. Joe Minerals Corporation
Products
Pb, Zn, H2S04
Pb, Zn, Cu
Pb, Zn, Cu, Ag
Pb, Zn
Pb, Zn, Cu
Unknown
it
Pb, Zn, Ag
Pb, Cu, Zn, Au, Ag
Cd
Pb, Zn, Ag, Cdt/
i/
Zn, Pb, Ag
Pb, Zn
Zn, Pb, Cu, Au, Ag,
Cd
Pb, Zn, Ag
Pb, Ag, Zn, Cu, Au
£/
Zn, Pb, Ag, Cd, Au
Pb, Zn
Zn, Pb, Cu, Ag
Unknown
Zn, Pb
Zn, Pb, Cu, Ag-7
Pb, Zn
Pb, Ag
Pb, Zn
Capacity
(ton/day)
5,000
5,000
4,200
6,000
7,000
Unknown
a/
2,400
800
soot/
a/
1,000
2,200
1,700
700
240
£/
700
500
450
Unknown
2,600
1.20&
2,400
300
5,000
Flotation ' Cooxoents
Yes
Yea Mill started 2/67
Yes Mill started 6/68
Yes
Yea
Unknown Closed 1972
Yes
Yes
Yes*/
a/
Yes
Yes
Yes
Yea
Yes
£/
Yes
Unknown
Unknown
Unknown
Yes
Yes!'
Yes
Yes
Yes Mill started 6/7;
a/ Viburnum No. 28 and No. 27 included with Viburnum No. 29.
b/ Tintic Division, Utah, Utah.
£/ Indian Creek No. 23 included with Indian Creek No. 32.
-------
Table 47. COMPANIES CONCENTRATING FLUORSPAR*6?20/
Company
Ozark-Mahoning Company
Minerva Oil Company,
Fluorspar Division
Cerro Spar Corporation
Roberts Mining Company
E. G. Sommerlath
Enterprises
Win Industries, Inc.
Bullion Monarch Company
Concentration location
county and state
Hardin, Illinois
Jackson, Colorado
Hardin, Illinois
Hardin, Illinois
Livingston, Kentucky
Ravalli, Montana
Crittenden, Kentucky
Cochise, Sierra
New Mexico
Lander , Nevada
Products
(in addition
to fluorspar)
Zn, Pb
None
Zn, Pb, BaSO,
None
Zn, Pb
None
Barite, Zn
Pb, silica
None
Sb, Ag, Au,
Pb, Zn, W
Capacity
(ton/day)
576
600
434
250
a/
Unknown—'
1,200
250
150
800
Flotation
Yes
Unknown
Yes
Yes
Unknown3.'
Unknown
No
Yes
Yes
Reynolds Metals Company Maverick, Texas
None
500
Unknown
a/ Concentrator to open in 1974.
-------
Table 48. CONSUMPTION OF CYANIDES AS FLOTATION REAGENTS
IN POUNDS
Calcium cyanide
Sodium cyanide
Potassium cyanide
Sodium ferrocyanide
Sodium ferricyanide
19601/
806,285
2,805,900
(small)
514,467
(small)
19651V
85,509
3,224,208
(small)
941,053
(small)
1970J2/
(small)
(4,000,000)
(small)
(1,500,000)
(small)
( ) = MRI estimate.
Table 49. FACTORS AFFECTING CYANIDE CONSUMPTION
Factor
Effect
Comments
Automated process control
Change from calcium to sodium cyanide
Environmental considerations
New, more specific depressants
Lower grade ores
Smelter specifications
Resulted in discontinued
use at Friedensville
+
+
110
-------
Table 50. CONSUMPTION OF ALL DEPRESSANTS (INCLUDING CYANIDES)
PER TON OF ORE8?21?22/
Total depressant consumption
(Ib/ton)
Ore type I960 1965 1970
Copper 0.008 0.004 0.006
Copper-molybdenum 0.048 0.065 0.054
Copper-lead-zinc 0.801 0.444 0.626
Copper-zinc-iron-sulfur 0.222 0.163 0.191
Lead-zinc 0.060 0.037 0.269
Lead-zinc-silver - 0.502 0.564
Zinc - 0.034 0.070
Fluorspar 2.790 2.275. 2.695
Figure 21 shows graphically the consumption (millions of pounds
as NaCN) of cyanides used as depressants in the flotation of minerals,
and also the projected consumption (as NaCN) of cyanides through 1985.
Figures 22, 23, and 24 depict the total production of copper,
lead-zinc and fluorspar bearing ores as well as the beneficiation of
the respective ores by flotation. The apparently greater tonnage of
ore beneficiated than produced most likely results from the overlap
of the types of ores. Copper-lead-zinc and copper-zinc-iron-sulfide
ores would likely appear not only in copper bearing ores beneficated
by flotation, Figure 22, but also in lead-zinc bearing ores beneficated
by flotation, Figure 23.
Environmental Considerations - Disposal of.flotation solutions contain-
ing cyanides generally entails the use of tailings ponds, much the
same as discussed in the preceding section on cyanidation of gold and
silver ores (p» 93).
No active chemical destruction of cyanides is generally practiced
in the flotation recovery of minerals and metals. Alkaline chlorina-
tion, ozonation or other .chemical oxidation of cyanides could be ap-
plied technically to the flotation industry} however, in nearly all
instances the costs would be prohibitive because of the extremely
large gallonage of water consumed. Of consideration also is the generally
low consumption of cyanides per ton of ore processed by flotation and
the usual practice of recycling water to the mill where possible.
Ill
-------
N>
7.5
7.0
6.5
6.0
5.5
Z 5.0
u
D
z 4.5
-S 4:0
c
<£ 3.5
I 3'°
I 2.5
2.0
1.5
1.0
0.5
0
Total Consumption (as NaCN)
Consumption (as NaCN ) for Flotation of Copper, Copper-Molybdenum Ores
Consumption (as NaCN) for Flotation of Lead, Zinc Bearing-Ores
Consumption (as NaCN) for Flotation of Fluorspar Ores
All 1970 Figures Estimated
Estimate
1960
1965
1970
1975
1980
1985
Figure 21. Cyanide consumption as a flotation reagent (as NaCN)
-------
300
280
260
240
220
200
S 180
O
o
c
o
Copper, Copper-Molybdenum Ore Production
Copper Ore Beneficiated by..Flotation
160
140
I 120
100
80
60
40
20
0
Strike
1960
1965
1970
1975
Figure 22. Copper bearing ore production and
beneficiation by flotation
113
-------
30
28
26
24
22
20
Ǥ ">
ut
.0
c
o
16
14
12
10
8
6
4
2
0
Lead, Zinc Bearing Ore Production
Lead, Zinc Bearing Ore Beneficiated by Flotation
Strike
1960
1965
1970
1975
Figure 23. Lead-zinc bearing ore production and
beneficiation by flotation
114
-------
1.5
1.4
1.3
1.2
1.1
1.0
O 0-9
14-
O
£ 0.8
o
I 0.6
0.5
0.4
0.3
0.2
0.1
0
Fluorspar Ore Production
Fluorspar Ore Beneficiated by Flotation
Labor Dispute
J L
Estimate
1960
1965
1970
1975
Figure 24. Fluorspar ore production and
beneficiation by flotation
115
-------
Most of the cyanide is adsorbed strongly on the surfaces of the minerals
in the tailings pond, and is not found in the water in the tailings
pond.
The proper use of tailings ponds seems the only feasible method of
cyanide destruction.
METAL HEAT TREATMENT (5.6%)
Sodium cyanide and occasionally potassium cyanide, calcium cyanide
and sodium ferrocyanide are used in metal heat treating to produce case
hardness. The processes for case hardening of metals using cyanides are:
(a) liquid carburizing; (b) liquid nitriding; (c) liquid carbonitriding,
These processes vary mainly in salt bath composition and temperature as
will be discussed under separate subsections.
Case hardening is a process for treating metals producing a hard,
wear-resistant, relatively thin surface (case) leaving the interior
(core) strong and tough.•=/
Process Descriptions
Liquid Carburizing,- Case hardening by carburizing adds carbon to the
surface of steel.^ The nature of the source of carbon distinguishes
between gas, liquid, or pack carburizing. Gas carburizing, using carbon
monoxide or methane, is the most prevalent, and pack carburizing, using
coke, the least used. Liquid carburizing uses cyanide as the source of
carbon.
Liquid carburizing is accomplished by submerging the part to be
case hardened in a molten salt bath containing sodium cyanide. The im-
mersion time and the temperature of the bath depend on depth of the
case desired. The pot containing the salt bath may be externally heated
with oil or gas or internally heated with immersed electrodes. After
holding the part in the salt bath for the period of time required, the
part is quenched in water, brine or oil, depending on final properties
desired.
Typical bath compositions for liquid carburizing are shown below
in Tables 51 and 52. Bath compositions vary depending on the desired
depth (thickness) of the case and the operating temperature of the bath.
116
-------
3/
Table 51. COMPOSITIONS OF LIQUID CARBURIZING SALT BATHS-
Compound
Sodium cyanide
Barium chloride
Calcium or strontium chloride
Potassium chloride
Sodium chloride
Sodium carbonate
Accelerators^'
Sodium cyanate
7o Composition
Light case
10-23
0-40
0-10
0-25
20-40
30 max
0-5
1.0 max
Deep case
6-16
30-55
0-10
0-20
0-20
30 max
0-2
0.5 max
aj Possible accelerators include: manganese dioxide, boron
oxide, sodium fluoride, silicon carbide.
Table 52. PREFERRED NaCN CONTENT.IN RELATION TO THE BATH
TEMPERATURE-
Bath temperature (°F)
1500
1550
1600
1650
1700
1750
Min.
14
12
11
10
8
6
NaCN Content (%)
Preferred
18
16
14
12
10
8
Max.
••WBi^VB
23
20
18
16
14
12
The salt baths are usually operated using a carbon or graphite
cover floating on the salt bath to retard oxidation of the cyanide.
Bath temperature is adjusted for the case depth desired. A tem-
perature range of 1550 to 1650°F generally is used to produce a case
depth in the range 0.003 to 0.030 in. The range 1650 to 1750°F is used
to develop case depths of 0.020 to 0.120 in. Higher temperatures can
be used, but the life of the salt bath and the equipment is shortened.
Carbon penetration is more rapid at elevated temperatures, which may
be advantageous to production.^.'
117
-------
Liquid carburizing produces a case containing mostly carbon through-
out the case, and some nitrogen on the exterior portion of the case.—'
3/
Reactions taking place in the bath include the following:—
1. 2 NaCN ^ Na^CN,, + C
2. 2 NaCN + 0,
3.. NaCN + CO,
4. NaOCN + C
5. 4 NaOCN + 202
6. 4 NaOCN + 4COr
2 NaOCN
NaOCN + CO
NaCN + CO
2 Na CO + 2 CO + 4N
^ j
2 Na CO + 6CO + 4N
and in high temperature baths
7. Ba(CN),
BaCN2 + C
3/
The case is formed on the part by the following reactions:—
8. 3Fe + 2CO > Fe.C + CO
9. 3Fe + C > Fe C
Liquid Nitriding - Liquid nitriding is a process for case hardening
of steel by the addition of nitrogen to the surface. Liquid nitriding
produces an extremely hard, wear-resistant surface, resisting softening
by temperature and corrosion Ji'
The major differences in practice between liquid carburizing and
liquid nitriding are (a) bath temperature, and (b) bath compositions.
Liquid nitriding salt bath operating temperatures are normally between
950 to 1050°F.l/
Table 53 lists three liquid nitriding salt bath compositions.
Case depth in liquid nitriding varies with the different steels
nitrided, but generally is less than 0.020 in. and often in the range
0.002 to 0.005 in.
118
-------
Table 53. DIFFERENT LIQUID NITRIDING SALT BATH COMPOSITIONS-
Composition (7a)
Compound 1 2
Sodium cyanide 30.00 max. 58-68 60-61
Sodium carbonate 25.00s- max. 1.5-1.8
Sodium cyanate 0.3-0.35
Potassium cyanide 29-38
Potassium carbonate aj 0.2 15-15.5
Potassium cyanate 0.2-0.3
Potassium chloride remainder 0.2 23-24
Other active ingredients 4.00 max.
aj Potassium carbonate may be substituted for sodium carbonate
Equipment used for liquid nitriding can be the same as that used
for liquid carburizing.
The nascent nitrogen at the metal surface necessary for nitriding
is produced by the cyanate which results from the oxidation of cyanide
(see the reactions Nos. 5 and 6, p. 118). For this reason, liquid ni-
triding salt baths must be aged prior to introduction of metal to be
nitrided. In aging, the salt bath is held at 1050 to 1100°F for at
least 12 hr.^- The liquid nitriding salt bath, unlike the liquid car-
burizing salt bath, is operated without a floating graphite cover.
Liquid Carbonitriding - Liquid carbonitriding is a process for production
of a file hard, wear-resistant surface on ferrous parts.— Liquid car-
bonitriding is commonly referred to as cyaniding.
Liquid carbonitriding is essentially a combination of liquid car-
burizing and liquid nitriding. The hardened case is produced by nitrogen
and carbon both reacting with the iron near the surface.
A preferred bath composition for liquid carbonitriding appears
in Table 54.
119
-------
Table 54. PREFERRED SALT BATH COMPOSITION
FOR LIQUID CARBONITRIDING4/
Compound Composition (%)
Sodium cyanide 30
Sodium carbonate . 40
Sodium chloride 30
Case depths are usually on the order of 0.010 in. thick. Bath op-
erating temperatures vary usually between 1400 and 1600°F.— Salt bath
equipment is the same as employed for liquid carburizing or liquid ni-
triding. The salt baths are generally operated without a graphite cov-
ering material, but if a cover is used, oxygen or carbon dioxide must
be bubbled through the salt bath to oxidize the cyanide.
Below are reactions taking place in the bath producing nascent
carbon and nitrogen necessary for the case hardening by liquid carbo-
nitriding4'
. 2NaCN + 0 ^ 2NaOCN
4NaOCN > Na CO + 2NaCN + CO + 2N
2CO
NaCN + C02 > NaOCN + CO
Another much less used method for carbonitriding in selective case
hardening is to heat the part to red heat, sprinkle on a cyanide salt
and reheat in a forge or lead bath. Sodium cyanide or sodium ferrocya-
nide may be used in this application. Sodium ferrocyanide is preferred
due,to its less toxic nature.—'
Processing Sites
The number of commercial and captive heat treaters is large. Com-
mercial heat treaters may be thought of as a "jobber" doing business
with one or more outside customers on the open market. Captive heat
treaters may be described as being owned and operated by the company
for which the work is being done. Table 55 summarizes the various esti-
mates of numbers for the different categories of heat treaters. The
distribution of heat treating shops is closely aligned with industrial
activity.
120
-------
Table 55. ESTIMATES OF THE NUMBER OF COMMERCIAL
AND CAPTIVE HEAT TREATING SHOPS
Type
Commercial
Captive
Commercial
Captive
Number
938
9,000-10,000
600
9,500
Reference
7
7
8
8
Comments
in 1972
in 1972
20 employees
It should be pointed out that the majority of the above commercial
and captive heat treaters do not use cyanide salt baths for heat treat-
ing. An estimated 2,500 commercial and captive heat treaters may use
cyanide salt baths for liquid carburizing, liquid nitriding and liquid
carbonitriding .-•
Due to the capital investment required to dispose of cyanide wastes,
only the larger commercial heat treaters offer heat treating processes
utilizing cyanide salt baths. Captive shops may differ somewhat, due
to the backing received from the parent company. Also, captive shops
may tend toward more specific requirements, some of which may include
use of cyanide salt baths.
Environmental Management
Cyanide wastes or losses in metal heat treating processes arise
generally from two sources: (a) quenching and (b) pot cleanout. By
far the most important of these is the losses incurred during quenching.
The processes for case hardening by liquid carburizing, liquid
nitriding and liquid carbonitriding all include: (a) submerging the
parts in the cyanide salt bath; (b) maintaining the salt bath at the
required temperature; (c) holding the parts submerged for the required
time; (d) withdrawing the parts while hot; and (e) quenching the parts.
When the parts are withdrawn from the bath, liquid salt adheres to the
surface of the parts. This salt is removed when the parts are quenched.
The quenching medium may be water, water containing dissolved
salts, or oil. In the event an aqueous quenching medium is used, the
salt adhering to the parts is dissolved in the quenching solution. If
oil is used for the quench, then the adhering salt is not soluble and
settles to the bottom of the quenching tank as a sludge.
121
-------
A less significant source of cyanide wastes results from cleaning
out the pot containing the salt bath. The pot may need to be cleaned
out for replacement of the salt because of sludge buildup or for re-
placement of the pot due to the corrosive and erosive action of the
salt and heat.
Disposal of cyanide wastes produced by heat treating is predom-
inantly accomplished by oxidation of an alkaline solution containing
the cyanide with chlorine gas, sodium hypochlorite or calcium hypo-
chlorite. In the cases where oil quench sludges or concentrated salts
from pot cleanout must be disposed of, the cyanide wastes must be dis-
solved in water prior to treatment.
i
Less used waste treatment systems include: (a) electrolytic de- .
struction;— (b) peroxide-formaldehyde oxidation (Kastone process);-^1—
(c) ozonation; (d) solid waste disposal in landfills; and (e) concen-
tration and recovery.^
In many cases, a combination of electrolytic and alkaline-chlorination
may offer ah economic advantage; for instance, initial treatment of
concentrated cyanide wastes by electrolysis to a low level of cyanide
concentration, followed by chlorination to reduce the cyanide to less
than 1 ppm concentration.
Another consideration in the waste treatment of heat treating
wastes is that complex iron cyanides will likely be formed from the
reaction of cyanide with the ferrous salts. Iron cyanides do not re-
spond well to conventional alkaline chlorination. The alkaline chlor-
ination may need to be supplemented with heat.
The disposal of solid wastes to landfills could be potentially
hazardous due to the solubility of many cyanide salts used in metal
heat treating. The disposal of solid cyanide wastes in landfills
may lead to leaching of the cyanides and eventual contamination of
water courses.
Cyanide Consumption
Currently there are five major companies supplying salt baths
containing cyanide for metal heat treating, as follows:
1. Heatbath Corporation, Springfield, Massachusetts
2. E. F. Houghtpn and Company, Norristown, Pennsylvania
3. Kolene Corporation, Detroit, Michigan
122
-------
4. The Mitchell-Bradford Chemical Company, Milford, Connecticut
5. Park Chemical Company, Detroit, Michigan
No definitive data have been collected on the usage of cyanides
for metal heat treating. MRI based the consumption of sodium cyanide
for metal heat treating, Figure 25, on estimates from the four compa-
nies above, except the Mitchell-Bradford Chemical Company, which did
not estimate annual consumption.
Estimates were based on individual company data and knowledge of
their relative position in sales. Estimates ranged from 3 to 7 million
pounds of sodium cyanide consumed annually, with the average 4 to 5
million pounds.
Figure 25 shows a general decline in the consumption of sodium
cyanide over the past 10 years. The projection to 1985 also anticipates
a continued decline in consumption.
Table 56 includes some of the factors most likely to influence
future consumption.
In summary, even though cyanide salt baths have advantages over
alternatives, the future consumption will likely decrease.
PHOTOGRAPHIC PROCESSING (3.1%)
Potassium and sodium ferro- and ferricyanides are used in photo-
graphic processing as a silver bleach for color motion pictures, color
TV film, and in color photofinishing. Other uses of these cyanides are
for image reduction (i.e., density reduction) and silver recovery from
black-and-white film. However, the latter two uses represent very small
and limited application areas.
All major modern color processes utilize a silver halide emulsion
as the light sensitive portion of the film. The latent image is de-
veloped to a black silver image and a color dye image formed coinci-
dently through use of a color developing agent. Some color couplers
are contained in the emulsion while others, as with certain color re-
versal films, are introduced by the developing solutions. The color
developing agents and details of the emulsion are proprietary and
lie outside the scope of this report.
123
-------
z
u
o
u>
o
I
:= 2
1964
1970
1975
1980
1985
Figure 25. Estimated consumption of sodium cyanide
for metal heat treating
-------
Table 56. FACTORS INFLUENCING CONSUMPTION OF NaCN FOR
METAL HEAT TREATING
Factor
Influence
Comments
Environmental concern
Work hazards
Disposal, treatment costs
Noncyanide salts
Overspecification
Cyanide advantages
Experience
Salt costs
Energy shortage
To comply .with OSHA stan-
dards—"
. 13/
Require more attention-
Parts may not require case
hardening
Better case depth control,
faster
Cyanides have been used for
several years
Presently cheaper than non-
cyanide ealt-.slO/
Natural gas may be used in
place of cyanide
For our purposes in describing the use of cyanides in photoprocess-
ing chemicals it is important to focus on the silver image in the emul-
sion. Color processing of films involves "bleaching-out," or removing
the original silver image. The resulting color negative or positive
image contains essentially no silver, only the color dye images. All
silver bleaches are solutions of oxidizing agents which convert the
metallic silver to soluble silver compounds.
Among the most widely used bleaches are those based on ferricyanide
and bromide; e.g., the solution may contain 10% by weight of potassium
or sodium ferricyanide and 5% by weight of sodium bromide. Most bleaches
contain buffers to keep the pH value of the solution between 5 and 10.
Strongly acidic solutions are avoided since ferricyanide tends to be
unstable in acids. Typical compositions of bleach solutions containing
ferricyanide and bromide are given in Table 57.—1J*
The starting point in any study of the manufacturers of such color
processing chemicals is Eastman Kodak Company of Rochester, New York,
which manufactures an estimated 75 to 857o of all color photochemicals
in use today. Table 58 indicates the estimated market share of photo-
chemicals.
125
-------
Table 57. COMPOSITION RANGE OF BLEACH SOLUTIONS
Sodium or potassium ferricyanide
Sodium or potassium bromide
plus other chemicals to stabilize,
buffer, or harden, etc.
50 to 170 g/liter
10 to 30 g/liter
Table 58. PHOTOGRAPHIC CHEMICALS MANUFACTURERS
Company
Eastman Kodak Company
Philip A. Hunt Chemical Corporation
Agfa Gevaert, Inc.
Minnesota Mining and Manufacturing
Company
General Aniline and Film Corporation
Ilford
and others
Total
Market share
Location
Rochester
New York
Palisades Park,
New Jersey
Teterboro,
New Jersey
St. Paul,
Minnesota
Binghamton,
New York
Paramus,
New Jersey
75-85
10-15
<, 5-10
100
These figures are rough estimates only.— Exact market information
is lacking. Each of the above companies formulates photoprocessing chem-
icals, but only Eastman Kodak manufactures ferricyanides. American
Cyanamid Company manufactures ferrocyanides for resale to formulators.
The Hunt Chemical Corporation has in the past imported ferro- and ferri-
cyanides for photoprocessing formulations and resale. Production and
capacity data are considered proprietary information. The capital value
of ferro-ferricyanide formulations is unknown.
Table 59 presents estimated annual consumption of sodium and potas-
sium ferro- and ferricyanides in photographic processing chemicals. The
estimates are approximations only and are subject to a deviation of ap-
proximately + 20%. An assumed annual growth rate of 57o for the years 1965
through 1970 accounts for the rise in ferro- ferricyanide usage.
126
-------
Table 59. ESTIMATED ANNUAL CONSUMPTION OF SODIUM FERROCYANIDE
AND SODIUM FERRICYANIDE IN PHOTOGRAPHIC PROCESSING!*^!/
Sodium Potassium Total
Year ferrocyanide ferricyanide (million Ib)
1965 0.8 3.2 4.0
1970 1.0 4.0 5.0
1975 0.5 2.0 2.5
1980 0.25 1.0 1.25
1985 0.2 0.8 1.0
The estimate of 5 million pounds in 1970 of ferro- and ferricyanides
is by Alletag.— The subsequent decline in consumption of these chem-
icals is the result of economic regeneration processes which are avail-
able to photoprocessors and the increasing use of an alternate bleach
reaction not using ferro- ferricyanides.
Photographic processing of color TV film and general photofinishing
of amateur color films takes place throughout the U.S., whereas color
motion picture processing is concentrated in southern California (greater
Los Angeles area), the New York City-New Jersey metropolitan area, and,
on a somewhat smaller scale, the metropolitan Chicago area. There are
scattered independent photoprocessing laboratories and captive facilities
in every city of approximately 200,000 or greater population. Television
studios are an example of captive photoprocessing facilities. The total
number of photofinishers, TV studios, and motion picture laboratories
is probably near 2,000.— The industry is quite diffuse and data on the
size, distribution, and geographic locations of the various processes
are largely unknown to other than major film manufacturers. Some idea
of the distribution of commercial photoprocessing laboratories can be
obtained from the Sustaining Membership of the Society of Motion Picture
and Television Engineers and the Society of Photographic Scientists and
Engineers.
Three typical film processing laboratories located in Washington,
D.C.j San Fernando, California; and Kansas City, Missouri; were contacted
regarding ferricyanide consumption. The estimated consumption data are
given in Table 60.
This average consumption may represent 0.1% of the total ferricy-
anide consumption by all photoprocessing laboratories. Thus, the total
consumption may be of the order of 1.5 million pounds of ferro-ferricyanide.
This particular consumption figure is an "educated guess" but is in-
structive. The proposed consumption figure given in Table 59 is 2.5
million pounds of ferro- and ferricyanide for the year 1975.
127
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Table 60. FERRICYANIDE CONSUMPTION IN THREE TYPICAL
FILM PROCESSING LABORATORIES
Annual ferro-
ferricyanide
consumption
Company Location (Ib)
A Washington, B.C.
B San Fernando, California
C Kansas City, Missouri
Average 1,500
Environmental management by photoprocessing laboratories, TV sta-
tions, captive processors, etc., usually involves repeated regenera-
tion of the spent ferricyanide bleach solutions, wherein relatively
large amounts of ferrocyanides are present, and eventual disposal of
the solutions.—' Disposal is uneconomical but occurs when a tank of
processing chemicals has become contaminated, springs a leak, or has
drifted so far out of chemical balance that regeneration is no longer
possible. Disposal is generally by flushing into municipal systems
witx large quantities of water. Parenthetically, some chemical losses
occur spontaneously through drag-out or carry-over of the solutions
through normal operations of passing the film through the processing
solution. This carry-over is diluted with wash water which is largely
recycled but is eventually disposed down the drain. Drag-out losses
are kept to a minimum by use of squeegees and probably amounts to
only 1% of the solution volume. Disposal and drag-out losses are kept
at a minimum throughout the industry for economic as well as environ-
mental reasons.—
Potassium ferricyanide is a somewhat expensive chemical and several
methods have been proposed to regenerate the exhausted solution. Each
method involves oxidation of ferrocyanide to the active ingredient, fer-
ricyanide. The three most prevalent methods of regeneration today are
persulfate oxidation followed by bromite oxidation and ozonation. Other
methods involve peroxide, permanganate, or electrolytic oxidation.
Persulfate oxidation probably accounts for 70% of all regeneration pro-
cesses.i' Regeneration has caused a significant decline in overall ferro-
and ferricyanide consumption in photoprocessing chemicals.
Hendrickson has compared regeneration and disposal costs by various
techniques*!' The results of this comparison are given in Table 61.
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Table 61. COMPARATIVE REGENERATION AND DISPOSAL COSTS
OF VARIOUS TECHNIQUES
Cost or saving ($/gal
including estimated
Bleach treatment method material and labor)
Precipitation with iron as iron blue -0.30
Persulfate regeneration +0.75
Collecting and hauling away bleach -0.54
Ozone regeneration +2.05
These cost figures neglect capital investment, which is substantial
in the case of an ozonation unit. The estimated cost of ozonation equip-
ment is given in Table 62 according to Sober and Dagon.—
Table 62. ESTIMATED COST OF OZONATION EQUIPMENT
(four processing machines)
10 Ib/day ozone generator $12,000
Automatic pH control unit and acid pump 700
Sparger system, tanks, plumbing 2,000
Ozone detection device 1,000
Connection to exhaust system 1,000
Installation and assembly 1,000
Conversion to automatic 24-hr operation 1,000
Total
ANTI-CAKING AGENTS (3.1%)
$18,700
Sodium ferrocyanide and iron blue are used as anti-caking additives
in various salt mixtures for highway de-icing. .Current practice utilizes
approximately 0.2 to 0.5 Ib of sodium ferrocyanide decahydrate and 0.1
to 0.2 Ib of iron blue per ton of highway de-icing salt. The latter is
principally sodium chloride to which is added calcium chloride in a
ratio of approximately 95:5 by weight, respectively.
The estimated total amount of highway de-icing salt used in the
winter of 1966 to 1967 was approximately 6.5 million tons, and it is
assumed current usage is approximately the same. The cyanide additions
129
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amount to 1.3 to 3.2 million pounds of sodium ferrocyanide and 0.6 to
1.3 million pounds of iron blue annually. This is equivalent to 0.8
to 2.0 million pounds of NaCN and 0.6 to 1.3 million pounds of NaCN, •
respectively, for a total NaCN equivalent of 1.4 to 3.3 million pounds
or 2.5 million pounds of NaCN as an annual average.
An EPA environmental impact study was completed in June 1971 out-
lining the use and environmental factors related to highway de-icing
agents and additives•!/ The above quantitative data were obtained from
the EPA report and were updated by contacting the Salt Institute in
Alexandria, Virginia, which supplied current application rates of cya-
nide additives*=• Further details regarding the runoff for ferrocyanides
and iron blue as anti-caking agents in highway de-icing agents may be
found in this EPA document.
No change in the general usage of sodium ferrocyanide and iron
blue as anti-caking agents for de-icers is anticipated to 1985. Further,
the application rate has probably stabilized since 1970 and no change
to 1985 is expected.
AGRICULTURAL AND PEST CONTROL CHEMICALS (0.6%)
In past years two cyanides, liquid hydrogen cyanide and calcium
cyanide, have been employed extensively in agriculture as insecticides,
fumigants, and rodenticides. However, these uses have largely been
superseded by synthetic insecticides and rodenticides or by volatile
chlorinated hydrocarbons because of economic and safety reasons.
The principal company marketing cyanides for agricultural purposes
and pest control purposes has been American Cyanamid Company, Agricultural
Chemicals Division, Wayne, New Jersey, which supplied hydrogen cyanide
and imported large amounts of calcium cyanide from Canada. The latter
material, often called "black cyanide," is marketed as flakes, powder,
or in block form under several trademarks, Aerocase, Cygon, Cyanogas,
Cyano-A-Dust, Cyano-G-Fumigant, etc.
Exact consumption figures for cyanides as an agricultural and pest
control chemical are unknown, but it was never a significant quantity,
even during the grain surplus years. The use of hydrogen cyanide for
this purpose has been discontinued and is not anticipated again unless
grain surpluses return. Estimated consumption of calcium cyanide and
hydrogen cyanide for agricultural purposes is given in Table 63.
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Table 63. ESTIMATED CONSUMPTION OF CYANIDES,FOR
AGRICULTURAL AND PEST CONTROL PURPOSES'^
Million pounds
Year Ca(CN>2 annually
1965 2
1970 1
1975 0.5
1980 Nil-7
1985 Nil-'
_a/ If grain surpluses are again present, consump-
tion could return to 1 to 2 million pounds
annually.
Sources: American Cyanamid Company, Private In-
dustry Sources, MRI Estimates.
Sources at American Cyanamid.Company admitted this area was highly
profitable, but was never large and did not represent a truly significant
portion of the Agricultural Chemicals Division business volume.
Liquid hydrogen cyanide was dispensed by a small number, approxi-
mately 10, of specially trained persons authorized by American Cyanamid
Company to fumigate grain elevators and storage bins in the 1950's and
the 1960's. This activity principally related to the large grain sur-
pluses held under U»S» government supervision. This practice was finally
abandoned about 5 years ago when the grain surpluses disappeared.—
Hydrogen cyanide was used for many years as a fumigant for tobacco,
cotton, and other imports, for citrus fruit, for tobacco seedlings
against soil nematodes, and for general greenhouse use. Tree fumigation
was accomplished by spreading a tent over the tree and releasing a pre-
determined amount of cyanide from a cylinder of liquid hydrogen cyanide.
Hydrogen cyanide is still used to a very limited extent as an agri-
cultural fumigant. It is estimated that 50,000 to 60,000 lb of liquid
HCN are used annually. The liquid HCN is obtained from E. I. du Pont de
Nemours and Company and is repackaged in small steel cylinders by the
Fumico Company of Amarillo, Texas. Fumico Company than acts as a distributor-
retailer to trained persons who actually apply the liquid hydrogen cya- .
nide for fumigation purposes, principally for imported goods and citrus.—
131
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Fumico Company plans to market the HCN as a discoid of pressed porous
wood impregnated with liquid hydrogen cyanide. The discoid would be about
3 to 4 in. in diameter and 1/8 to 1/4 in. thick. Several discoids would
be placed in a steel container and the fumigation operator would, using
appropriate protection, open the container and take out one or more dis-
coids and place these strategically for maximum fumigation effect. After
treatment, the discoids would be retrieved.
Orchard fumigation has also been accomplished by spraying with re-
fined petroleum oil or by use of malathion (0-0-dimethylphosphorodithioate
of diethyl mercaptosuccinate). A case study of malathion is contained
in an EPA report*?-'
Other chemical fumigants used in the past have been Lindane (hexa-
chlorobenzene) and methyl bromide. Both these substances are covered in
EPA report s.-k-
Present solid fumigants include Phostoxin and Detia GAS-EX-B which
are aluminum phosphides in a paraffin base. The active ingredient is phos-
phine gas, PH , which is released by hydrolysis of aluminum phosphide.
Present liquid fumigants include mixtures of carbon tetrachloride
and carbon disulfide, generally in a ratio of 80 to 20 parts by volume.
Other chlorinated or brominated hydrocarbons, ethylene dichloride or
ethylene dibromide, may be added to this mixture.—'
The principal manufacturers of these materials are given in Table
64.
In the area of general pest control, including rodents, either
liquid hydrogen cyanide or calcium cyanide (flake, powder or bait) has
been extensively used. Calcium cyanide was a convenient product to dis-
pense and slowly released hydrogen cyanide gas when in contact with
moist air. At present, American Cyanamid Company has a very small market
in agricultural cyanides and pest control chemicals and may abandon this
sector in the near future .i'
A new use for sodium cyanide (and presumably calcium cyanide) has
been proposed by the EPA in 1974 for coyote, fox, and other predatory
animal control. An experimental use permit was approved for Texas for
coyote control in April 1974.—' The proposed method of application was
the "M-44 Coyote Getter," a spring-loaded gun that shoots a cyanide
charge into any animal that tugs at the bait attached to the gun.—'
132
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Table 64. PRINCIPAL MANUFACTURERS OF FUMIGANTS
Fumigant
Principal manufacturer
Carbon disulfide Stauffer Chemical Company
Carbon tetra-
chloride
Detia GAS-EX-B
Ethylene
dibromide
Ethylene
dichloride
Lindane (RGB)
Malathion
Methyl bromide
Phostoxin
E. I. du Pont de Nemours
and Company, Inc.
Chemische Fabrik Company
Dist. by Research
Products Company
Ethyl Corporation
Shell Chemical Company
Stauffer Chemical Company
American Cyanamid Company
Dow Chemical Company, USA
Degesch Company
Dist. by Phostoxin Sales,
Inc.
Location
Delaware City, Delaware;
Le Moyne, Alabama
Corpus Christi, Texas
Laudenbach, West Germany
Kansas City, Missouri
Magnolia, Arkansas
Deer Park (Houston), Texas
Louisville, Kentucky
Warners, New Jersey
Midland, Michigan
Frankfort, West Germany
Alhambra, California
The experimental program has been expanded to the degree that the
U»S» Department of the Interior was issued an experimental use permit
by the EPA covering the period September 2, 1975 to September 2, 1976.
The permit allows the use of 1,500 liters of a 33% sodium cyanide solu-
tion in up to 3,000 collars to be placed on tethered lambs. Other in-
formation relevant to restrictions on the use of the device, safety
regulations, and geographic locations were included in'the permit.—'
The program as described will not be economically significant in
any event. Environmental and safety hazards are of primary concern.
Safer alternate chemicals are available for predatory animal control,
e.g., nonfatal repellents and emetics such as lithium compounds.
Small animal pest control is presently accomplished by use of com-
mercially formulated substances which contain warfarin, an anticoagulant,
as the active ingredient. Warfarin is 3-(oi-acetonylbenzyl)-4-hydroxycoum-
arin, and the sodium salt is marketed under a series of trade names as:
Marevan, Prothromadin, Tintorane, Warfilone, Waran, etc. Manufacturers
are listed in Table 65.
133
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Table 65. PRINCIPAL MANUFACTURERS OF
WARFARIN-TYPE RODENTICIDES
Manufacturer Location
Velsicol Chemical Corporation Chicago, Illinois
Stephenson Chemical Company College Park, Georgia
Prentiss Drug and Chemical Company Newark, New Jersey
The J. J. Dill Company Kalamazoo, Michigan
Warfarin has been quite successful over the last 25 years as a rodenti-
cide, but recently tolerance in rodents, lessening warfarin effective-
ness, has spread.
Other pest control chemicals have included DDT as a "tracking powder"
against mice, arsenious oxide, sodium fluoroacetate or "1080", strychnine
sulfate, and zinc phosphide.
Rohm and Haas Chemical Company has developed a rat poison based on
carbamates, a well-known class of insecticides. The new rodenticide has
the advantage of broad-spectrum activity against rodents, single-dose
effectiveness, and is relatively innocuous to other animals .2'
The total market potential for rodent control represents about $8
million annually in chemical raw materials, $15 to $20 million at the
wholesale level, and $30 to $40 million at the retail level. The world
market is estimated at more than $100 million annually.—
134
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REFERENCES TO CHAPTER VII
Metal Finishing
1. Lancy, L. E., Dart Industries, Inc., Lancy Laboratories Division,
Zelienople, Pennsylvania.
2. U.S. Department of Commerce, Census of Manufactures, 1972, Bureau
of the Census, Industry Series MC72(2)-34D, February 1975.
3. American Society for Metals, Metals Handbook, 8th ed., Metals Park,
Ohio (1964).
Pigments
1. Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd ed., Vol. 6,
Interscience Publishers, Inc., New York (1965).
2. Bernard, D., Technical Director, Pratt and Lambert Paint and Varnish
Company, North Kansas City, Missouri.
3. Preuss, H. P., Metal Finishing, June/August/September 1972.
4. Confidential Industry Source.
5. Patton, T. C., Pigment Handbook, Wiley-Interscience Publications,
Inc., New York (1973).
6. Renson, J. E., American Ink Maker, May 1968.
Mining
1. McQuiston, F. W., Jr., and R. S. Shoemaker, Gold and Silver Cyanida-
tion Plant Practice, The American Institute of Mining, Metallurgi-
cal and Petroleum Engineers, Inc., New York, New York (1975).
2. West, J. M., "Gold," in Minerals Yearbook. 1972. Vol. I. Metals,
Minerals and Fuels, Bureau of Mines, U.S. Department of the
Interior, U.S. Government Printing Office, Washington, D.C.
(1974).
.3. Connolly, T., "Hpmestake Mine - Largest United States Gold Producer,"
Mining Engineering, %(3):24-27, March 1974.
4. Shoemaker, R. S., "Minerals Processing in 1973," in Mining Congress
J._, 60(2):28, February 1974.
135
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5. Terlecky, P. M., Jr., Calspan Corporation, Buffalo, New York, Private
Communication to R. R. Wilkinson, October 9, 1975.
6. Hallowell, J. B., J. F. Shea, G. R. Smithson, Jr., A. B. Tripler,
and B. W. Gonser, Water-Pollution Control in the Primary Nonferrous-
Metals Industry. Vol. II. Aluminum, Mercury, Gold, Silver, Molyb-
denum, and Tungsten, Battelle Memorial Institute, prepared for
Office of Research and Monitoring, U.S. Environmental Protection
Agency, U.S. Government Printing Office, Washington, D.C. (1973).
7. Dorr, J. V. N., and F. L. Bosqui, "Sand Treatment," in Cyanidation
and Concentration of Gold and Silver Ores, McGraw Hill Book Company,
Inc., New York, New York (1950).
8. Merrill, C. W., and J. W. Pennington, "The Magnitude and Signifi-
cance of Flotation in the Mineral Industries of the United States,"
in Froth Flotation 50th Anniversary Edition, D. W. Fuerstenau,
Ed., The American Institute of Mining, Metallurgical, and Petroleum
Engineers, Inc., New York, New York, pp. 55-90 (1962).
9. Anonymous, Chemical and Engineering News, in 48(42):10-11, October 5,
1970.
10. Gandin, A. M., "Modulation of Collection," in Flotation, McGraw Hill
Book Company, New York, New York (1957).
11. Anonymous, "Mineral Dressing Notes No. 26," Mining Chemicals Handbook,
American Cyanamid Company, Mining Chemicals Department, Wayne,
New Jersey.
12. Weast, R. C., Handbook of Chemistry and Physics, 50th ed., Chemical
Rubber Publishing Company, Cleveland, Ohio (1969-1970).
13. Sather, N. J., and F. L. Prindle, "Milling Practice at Bunker Hill,"
in Mining and Concentrating of Lead and Zinc, p. 356, D. 0. Rausch,
and B. C. Mariacher, Ed., The American Institute of Mining, Metal-
lurgical, and Petroleum Engineers, Inc., New York, New York (1970).
14. Anonymous, "Applications of Flotation," in Flotation Fundamentals
and Mining Chemicals, pp. 57-74, The Dow Chemical Company, Midland,
Michigan (1970).
15. Schroeder, H. J., "Copper," in Minerals Yearbook, 1972. Vol. I. Metals,
Minerals, and Fuels, p. 490, Bureau of Mines, U.S. Department of
the Interior, U.S. Government Printing Office, Washington, D.C.
(1974).
136
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16. Nielson, G. F., Editor-in-Chief, International Directory of Mining
and Mineral Processing Operations, pp. 113-158, McGraw Hill Mining
Publications, New York, New York (1974).
17. Wideraan, F. L., "Copper," in Minerals Yearbook, 1965. Vol. I. Metals
and Minerals, p. 359, Bureau of Mines, U.S. Department of the Interior,
U.S. Government Printing Office, Washington, B.C. (1966).
18. Ryan, J. P., "Lead," in Minerals Yearbook. 1972. Vol. I. Metals,
Minerals, and Fuels, p. 713, Bureau of Mines, U.S. Department of
the Interior, U.S. Government Printing Office, Washington, D.C. .
(1974).
19. Moulds, D. E., "Lead," in Minerals Yearbook. 1965. Vol. I. Metals
and Minerals, p. 573, Bureau of Mines, U.S. Department of the In-
terior, Washington, D.C. (1966).
20. Wood, H. B., "Fluorspar and Cryolite," in Minerals Yearbook, 1972.
Vol. I. Metals, Minerals and Fuels, Bureau of Mines, U.S. Department
of the Interior, U.S. Government Printing Office, Washington, D.C.
(1974).
21. Merrill, C. W., and J. W. Pennington, "Technologic Trends in the
Mineral Industries," in Minerals Yearbook, 1965. Vol. I. Metals^
and Minerals, pp. 67-93, Bureau of Mines, U.S. Department of the
Interior, U.S. Government Printing Office, Washington, D.C. (1966).
22. Morning, J. L., and G. Greenspoon, "Technologic Trends in the Mineral
Industries," in Minerals Yearbook, 1970. Vol. I. Metals, Minerals,
and Fuels, pp. 80-104, Bureau of Mines, U.S. Department of the
Interior, U.S. Government Printing Office, Washington, D.C. (1972).
23. Pellett, J. R., and W. C. Spence, "Milling at the Friedensville Mine,"
in Mining.and Concentration of Lead and Zinc, pp. 466-482, D. 0.
Rausch and B. C. Mariacher, Eds., The American Institute of Mining,
Metallurgical, and Petroleum Engineers, Inc., New York, New York
(1970).
Metal Heat Treating
1. Schwarzkopf, A. J., "Metal Surface Treatments, " in Kirk-Othmer En-
cyclopedia of Chemical Technology, Vol. 13, 2nd completely revised
ed., Interscience Publishers, Division of John Wiley and Sons, Inc.,
New York, New York, pp. 304-315 (1969).
137
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2. Haga, L. J., "Principles of Heat Treating," in Heat Treating, 6_(2):
29-30, February 1974. ~
3. Lyman, T., H. E. Boyer, P. M. Unterweiser, J. E. Foster, J. P. Hontas,
and H. Lawton, Eds., "Liquid Carburizing," in Metals Handbook, Vol.
2, Heat Treating, Calening and Finishing, 8th ed., American Society
for Metals, Metals Park, Ohio, pp. 133-145 (1961).
4. Haga, L. J., "Principles of Heat Treating," in Heat Treating, 6(3):13-
14, March 1974. ~
5. Lyman, T., H. E. Boyer, P. M. Unterweiser, J. E. Foster, J. P. Hontas,
and H. Lawton, Eds., "Liquid Nitriding," in Metals Handbook, Vol.
2, Heat Treating, Cleaning and Finishing, 8th ed., American Society
for Metals, Metals Park, Ohio, pp. 146-148 (1961).
6. Lyman, T., H. E. Boyer, P. M. Unterweiser, J. E. Foster, J. P. Hontas,
and H. Lawton, Eds., "Cyaniding," in Metals Handbook, Vol. 2, Heat
reating. Gleaning and Finishing , 8th ed., American Society for
Metals, Metals Park, Ohio, pp. 129-131 (1961).
7. Anonymous, "Commercial Heat Treaters in 1972," in Heat Treating, 6(4),
April 1974. ~"
8. Peck, F., Metal Treating Magazine, private communication to R. R.
Wilkinson, October 9, 1975.
9. Lancy, L. E., of Lancy Laboratories, Division of Dart Industries, Inc.,
Zelienople, Pennsylvania.
10. Lancy, L. E., R. L. Rice, Waste Treatment - Upgrading Metal - Finish-
ing Facilities to Reduce Pollution, U.S. Environmental Protection
Agency, Technology Transfer Seminar Publication, Washington, D.C.,
July 1973.
11. Barber, D. R., Heatbath Corporation, Springfield, Massachusetts,
private communication to R. R. Wilkinson, August 13, 1975.
12. White, L., Metallurgical, Inc., Kansas City, Missouri, private com-
munication to R. R. Wilkinson, July 18, 1975.
13. Foreman, R. W., Park Chemical Company, Detroit, Michigan, private
communication to R. R. Wilkinson, September 11, 1975.
138
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Photographic Processing
1. Alletag, G. C., President, Alta Chemical Company, San Diego, California.
2. Roosen, R., G. Vanreusel, and R. G. L. Verbougghe, J. Soc. Motion
Picture and Television Engineers (SMPTE), 82, 542 (1973).
3. Alletag, G. C., "Truth in Pollution Abatement," PURE Meeting, Washington,
D.C., April 6, 1971.
4. Source: MRI estimate.
5. Hendrickson, T. N., and L. G. Daignault, J. SMPTE. 82_, 727 (1973).
6. Cooley, A. C., "Regeneration and Disposal of Photographic Processing
Solutions Containing Hexacyanoferrate," SMPTE Meeting, Los Angeles,
California, September 28, 1975.
7. Hendrickson, T. N., "Status of Pollution Control Legislation as Related
to the Photographic Processing Industry," SMPTE Meeting, Los Angeles,
California, September 19, 1972.
8. Sober, T. W., and T. J. Dagon, Image Technology, August/September
1972.
Anti-Caking Agent
1. Environmental Protection Agency, "Environmental Impact of Highway
Deicing," EPA No. 11040GKK 06/71, June 1971.
2. Dickinson, W. E., President, The Salt Institute, Alexandria, Pennsylvania.
Agricultural and Pest Control Chemicals
1. Clark, D., Market Research Manager, Agricultural Chemicals Division,
American Cyanamid Company, Wayne, New Jersey.
2. Dines, F., President, Fumico Company, Amarillo, Texas.
3. Environmental Protection Agency, "Production, Distribution, Use and
Economic Impact Potential of Selected Pesticides," Midwest Research
Institute, EPA No. 540/1-74-001, Kansas City, Missouri, January
1974.
4. Environmental Protection Agency, "Survey of Industrial Processing
Data - Hexachlorobenzene and Hexachlorobutadiene," Midwest Research
Institute, EPA No. 560/3-75-003, Kansas City, Missouri, March 1975.
139
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5. Allen, J. R., Vice President, Research Products Company, Fumigants
Division, Kansas City, Missouri.
6. Anonymous, Environmental Science and Technology, j3, 299 (1974).
7. Anonymous, Chemical Marketing Reporter, July 21, 1975.
8. Federal Register. 40(190):44865, September 30, 1975.
9. Anonymous, Chemical and Engineering News, p. 21, October 23, 1972.
10. Anonymous, Chemical Week, p. 34, August 27, 1975.
140
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CHAPTER VIII
CYANIDE TREATMENT METHODOLOGIES
Much has been written concerning cyanide effluent treatment, princi-
pally in the metal finishing sector. All techniques to be discussed are ap-
plicable to cyanide waste effluents. Metal finishing wastes are much more
difficult to treat than simple cyanide wastes because of the presence of
heavy metals, organic brighteners, and other proprietary additives.
Several EPA development documents for guidelines are included in the
bibliography together with other pertinent references to effluent treatment.
This information is readily available and is well known within the industry.
This report will bring together all the treatment methodology that is known
in a summary form and present a current evaluation of these for an overview
of cyanide effluent.treatment. . ,
A list of various treatment techniques for cyanides includes, but are
not limited to, the following:!.'
Destructive Techniques
1. Destruction of cyanide by alkaline chlorination, including the use
of hypochlorites for dilute solutions (batch or continuous).
2. Destruction by electrolysis for concentrated solutions (batch).
3. Destruction by ozonation with/without ultraviolet radiation (batch).
4. Kastone Process (Du Pont) using hydrogen peroxide and formalin
(batch).
. 5. Destruction by hydrolysis at an elevated temperature (batch or con-
tinuous).
6. Cyanide removal, by activated carbon adsorption (batch or continuous).
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Recovery Techniques for Metal and Cyanide Values
1. Reverse osmosis (batch or continuous).
2. Ion exchange (batch or continuous).
3. Precipitation of heavy metals (batch).
4. Evaporative recovery (batch or continuous).
Engineering Methodologies
To these techniques the following engineering methodologies should
be added:
1. Countercurrent rinsing (cascade rinsing).
2. Integrated chemical rinse systems•
3. Effluent segregation.
The relative proportion of plating establishments using the above de-
struction and recovery cyanide techniques is as follows:—
Alkaline chlorination =* 90%
Electrolysis «*• 1%
Ozonation =- 1%
All others °- 8%,
1007,
The popularity of alkaline chlorination including the use of hypochlo-
rite is due to the dependability, ease of operation if properly engineered,
and the efficiency of cyanide destruction to very low levels, ''£ 0.1 mg/literi
Essentially, all metal finishing facilities employ one or more of the
above mentioned effluent handling methodologies. Effluents are no longer
combined and treated in total because of potential increased complexity of .
the resulting solution, increased chemical costs to destroy additional or-
ganic materials in the effluent, and the loss of any recovery possibility
of specific chemicals.
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DESTRUCTIVE TECHNIQUES
Alkaline chlorination is used to treat approximately 90% of cyanide
effluents on an industrywide basis. Capital investment costs for chlorine
gas storage, handling and metering are significant. Chemical costs, includ-
ing caustic and chlorine gas, are considerable on a continuous basis. How-
ever, the system does work well and, when properly installed, is dependable,
Holding tanks and lagoons are necessary for handling the resulting metal
sludges of hydrated heavy metal oxides.
Cyanide ion is oxidized to cyanate ion or to carbon dioxide and nitro-
gen gas depending on the chlorination conditions. Thus, with chlorine gas
the following reactions may occur:
NaCN + Cl + 2NaOH > NaCNO + 2NaCl + HO
and/or
2NaCN + 5C1 + !2NaOH > N + 2Na CO + lONaCl + 6 HO
A toxic intermediate compound, cyanogen chloride gas, CNCl, is formed but
a pH value of 10.5 or higher causes the cyanogen chloride to be rapidly
transformed to cyanate ion which is one-thousandth as toxic as cyanide or
cyanogen chloride. Usually 20 min are allowed for the reaction to continue
if heavy metal cyanides are present. These materials are more difficult to
oxidize than sodium or potassium cyanide. Some heavy metal cyanides are es-
sentially unchanged by alkaline chlorination, e.g., ferri- and ferrocyanide,
hence the distinction of "cyanides amenable to chlorination" is made.
The final oxidation stage to nitrogen and carbon dioxide proceeds rap-
idly at pH 7.5 to 8.0 in 10 to 15 min, but at pH 9.0 to 9.5 the reaction is
slow. The processes utilize one or more holding tanks to accomplish the ox-
idation and at the same time allow for sludge formation of hydrated metal
oxides.
Alternatively, sodium or calcium hypochlorite may be used as a solid
or as a solution to destroy cyanide. The oxidation may proceed to cyanate
or to completeness as indicated previously.
NaCN + NaOCl > NaCNO + NaCl
and/or
2NaCN + SNaOCl + HO > N + 2NaHCO + SNaCl
143
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The process is simpler than with gaseous chlorine and the hypochlorite
needs no additional caustic. Agitation is essential for efficient conver-
sion. Costs of capital equipment are less with hypochlorite, but chemical
costs are higher. It is believed that the hypochlorite treatment technique
is more applicable to smaller plating shops. In either case, effluent cy-
anide levels can be as low as ^ 0.1 mg/liter. Direct dischargers in some
states, e.g., Pennsylvania, are held to 0.02 mg/liter cyanide amenable to
chlorination.2/
Electrolytic decomposition of cyanide wastes can be effective, but
works best for higher cyanide concentration levels such as in spent plat-
ing baths at 45,000 to 100,000 mg/liter. The method is inefficient for cy-
anide in rinse waters. The time factor for complete destruction may extend
from 7 to 21 days, depending on the initial cyanide level, and the final
cyanide level may be in the range 0.1 to 0.4 mg/liter. It is probably bet-
ter to treat only the higher concentration levels to an intermediate level,
500 to 1,000 mg/ml, and then utilize chlorination. Metal recovery may be
easier by electrolysis, since electrodeposition may occur, and this can re-
duce overall operating costs. The electrolysis technique is used only for
'•«« 1% of cyanide treatment techniques.
Ozonation with and without ultraviolet radiation is an attractive
alternative for cyanide destruction, but is performed =*• 1% of the time at
present. Heavy metal cyanides are essentially resistant to direct ozona-
tion.
At least one company, PCI Ozone Corporation of West Caldwell, New
Jersey, markets an ozonation system for cyanide wastes. Houston Research,
Inc., of Houston, Texas, is proposing the combination ozonation-UV illu-
mination system.
PCI installed the first ozonation system for an industrial plant at
the Sealectron Corporation at Mamaroneck, New York, in February 1974. The
project was undertaken and financed in part by an EPA demonstration grant.
The cyanide effluent contained 60 ppm cyanide, 32 ppm Cu, and 3.4 ppm Ag.
It was treated with 1 to 1-1/270 ozone in air. After ozonation, the efflu-
ent was mixed with acid plating waste containing 14 ppm Ni, 2 ppm Sn, and
0 to 8 ppm Pb. Cyanide in solution was not detected. The previous metals
were precipitated as hydrated metal oxides. It is not stated if any cya-
nides which might have escaped ozonation were in the sludge.—'
The combination of ozonation and ultraviolet radiation is quite ef-
fective against resistant heavy metal cyanides. Ferricyanides may be re-
duced to 0.1 mg/ml in 20 min at 150°F with a 5% ozone concentration in
air and with 16 watts of UV illumination. This system is being readied
for market by Houston Research, Inc., and is undergoing a series of field
tests at various installations in the U.S. and France^-t'
144
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E. I. du Pont de Nemours and Company markets a cyanide waste treat-
ment system (Kastone process) utilizing hydrogen peroxide, formalin, and
a metal salt (usually magnesium sulfate) which converts cyanides to cya-
nates and other compounds of organic acids, e.g., glycollates. For zinc
cyanide wastes the cyanide level is generally 0.1 ppm and the hydrated
zinc oxide is settled, filtered, and can be recycled to the plating bath.—'
Hydrolysis of cyanide solutions at high pressure and elevated tem-
perature converts metal cyanides to ammonia and formate. Typical condi-
tions involve holding the cyanide solution at 150 to 200°G for 5 to 10
min in steel reactors. The resulting solution contains =- 4 mg/liter cya-
nide ion as compared to alkaline chlorination or the Kastone process
which is capable of attaining reductions of cyanide to £ 0.1 mg/liter.
Transition metal cyanides require longer retention times and/or higher
pressures and temperatures .-1'
Cyanide can be adsorbed on activated charcoal and the associated
metal recovered. For example, zinc cyanide can be adsorbed on carbon
with 99% cyanide removal. Recovery of the zinc is accomplished by pass-
ing dilute acid through the charcoal column, producing soluble zinc ion
and hydrocyanic acid. Pilot-plant operations conducted at Battelle Me-
morial Institute indicated feasibility of metal finishing waste treat-
ment by this process.—'
Cyanides can be oxidized after adsorption on activated charcoal.^/
Thus, when a copper cyanide solution containing dissolved oxygen is passed
through an activated charcoal column, the cyanide radical is oxidized to
cyanate. The cyanate in the presence of copper is hydrolyzed to bicarbon-
ate ion and ammonia. The net result is that cyanide is converted to bicar-
bonate or carbonate and ammonia and the copper precipitates on the granu-
lar carbon as copper carbonate.
The system fails with solutions of cadmium or iron cyanide but is
partly successful for zinc cyanide. The differences in effectiveness are
due to differences in the metal cyanide complex bond strengths.
Cyanide effluent levels are of the order of 0.1 mg/liter. The copper
can be recovered and the carbon regenerated. Cost estimates for alkaline
chlorination versus catalytic carbon adsorption and oxidation (catalytic
oxidation) are given in Table 66.
RECOVERY TECHNIQUES
Reverse osmosis (RO) is a technique of potentially great importance
since it offers recovery rather than destruction with chemical cost sav-
ings.—— The concentrate of metal salt and cyanide obtained by RO can
be returned to the plating bath and the alter-effluent can be returned to
145
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Table 66. DIRECT CHEMICAL COST COMPARISON ALKALINE
CHLORINATION VERSUS CARBON CYANIDE REMOVAL^'
a/
A. Cost basis-
Flow - 25 gal/min, 24 hr/day, 5 days/week
[CN] - 100 rag/liter 30 Ib/day
Cyanide destruction catalyst 2507Ib - 25% active
Oxygen (industrial) - 244 ft3 cylinders - 160/lb
Liquid chlorine (150 Ib cylinder) - 11.50/lb
. Liquid caustic (50% NaOH - 55 gal. drum) - 13£/lb
B. Feed rates
Alkaline chlorination -
Chlorine to cyanide - 10:1
Caustic to cyanide - 6:1
Catalytic oxidation -
Catalyst:cyanide:oxygen - 1:1:1
C. Estimated direct chemical costs
Complete destruction -
Catalytic oxidation - $1.25/lb
Alkaline chlorination - $1.93/lb
_a/ Cost figures are averages for 1972.
b/ Includes carbon change once per year. After start-up,
cost may be reduced to $1.00/lb.
146
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the rinse cycle in principle. Field demonstrations have been conducted
to identify problem areas and to test membranes and equipment on actual
cyanide plating wastes.—' The difficulty is that membranes able to with-
stand high alkalinity and high pressures are not available at present,
thus RO application to cyanide wastes is awaiting the development of suit-
able membrane materials.
A recent experimental program using ion exchange has been reported
by Rohm and Haas Company wherein a cyanide waste stream is treated with
ferrous sulfate at pH 8 to 11. After the resulting sludge of ferrous hy-
droxide is removed by filtration or flocculation, the resulting ferroxy-
anide solution is absorbed onto a weakly basic ion exchange resin. Once
loaded with the ferrocyanide, the ion exchange resin is regenerated with
dilute NaOH resulting in a stream of ferrocyanide. The latter material
can be disposed of by a number of methods, none of which is totally sat-
isfactory: preparation of iron blue, concentration and incineration, or
i X /
landfill, etc^i£' This technique is new, but is posing additional environ-
mental concern in view of the photodecomposition of the leachable iron cy-
anides and the potential release of toxic hydrogen cyanide.
Recovery of metal from cyanide effluents can also be accomplished
by the so-called waste-plus-waste (WPW) process developed at the Bureau
of Mines, Rolla, Missouri J^t' Various acid and alkaline cyanide wastes
were combined to completely precipitate the metals and cyanide as metal
cyanides and hydrated metal oxides. The metals and the cyanides can be
recycled. Common metals from electroplating wastes, including zinc, cop-
per, and cadmium, were successfully treated. Free cyanide ions in the
resulting filtrate was ^ 0.03 mg/liter. Only small amounts of HCN were
detected during neutralization.
Figure 26 presents a possible WPW recovery process for silver wastes.
The recovered silver was 99.1% pure and contained 0.03% Cu and < 0.001% Ni
and Fe.
The WPW process may find use in industry as an inexpensive first step
to remove cyanides and most metals from effluents. Provision for control
or incineration of possible hydrogen cyanide evolution is mandatory. After
precipitation of the metals and cyanide, other more conventional treatment
techniques could be applied.
ENGINEERING METHODOLOGIES
Much of the operating expense of waste.treatment can be reduced by
using cascade or countercurrent rinses, concentrating the drag-out chem-
icals and recycling them. A second technique which lowers costs is the
147
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Acid Waste
TT
Cyanide Waste
Mixing Tank
.HCN Entrapment
or Incineration
Filter
•Clear Solution
Mixed Metal
Cyanides
I
Furnace
Mixed Metal
Oxides
Hydrochloric Acid'
Filter
Solution
Caustic
Filter
Solution
•Silver Chloride
Iron Hydroxide
Electrolysis
Nickel Chloride Solution;
Pure Copper
Figure 26. Possible WPW process treatment for metal-cyanide wastes
148
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integrated treatment system wherein chemical rinses are employed to chem-
ically treat the cyanide drag-out during the rinsing operation. Each tech-
nique has the advantage of simpler and more economical treatment proce-
dures since the volume of water is lower and the treatment is applied to
the source rather than to a complex total-waste stream.
Countercurrent rinsing 'techniques are those wherein fresh water en-
ters a second rinse tank, overflows into the bottom of the first rinse
tank after the plating bath and thence flows to a treatment or recovery
system. In this manner, the last rinse tank is insured of clean water
without excessive contamination from a preceding rinse tank. Each addi-
tional rinse tank through which water flows, allows a reduction in water
usage by a factor of 10 or somewhat less. Fresh water costs have been
shown to be a major cost factor, particularly for electroplating rinsing
and waste treatment.ii'
The integrated treatment system can be part of a self-contained
closed-loop system in which the chemical rinse stations are enjoined to
a reservoir tank. This has the advantage of reducing cyanide in the sub-
sequent water rinse to a level < 0.02 mg/liter by simple dilution before
discharge. Effluent guidelines prescribe average permissible levels and
require knowledge of the total amount of cyanide released in a given time,
i.e., volume x average concentration.
Evaporative recovery may be employed in conjunction with cascade rins-
ing for recovery of cyanide and metal values as an alternative to destruc-
tion and precipitation. Such a system is shown in Figure 27 which shows
countercurrent rinsing in two tanks followed by a recovery-evaporation step
wherein concentrated metal and cyanide salts are returned to the plating
solution concentrate and the distillate is returned to the last rinse tank.
This is a closedloop system with essentially no discharge except for acci-
dental leakage, spills, bath contamination, etc.
EFFLUENT TREATMENT COSTS
Cost estimates for any plating recovery or destruction system must
include the following considerations: capital investment, special monitor-
ing apparatus, chemicals, modification of existing apparatus, fresh water,
maintenance, treatment of concentrated solutions and/or sludges, hard wa-
ter softening, pH adjustment, sewer rental charges, etc.
Many authors simply compare chemical costs, but the total of all
costs is what is important. A small advantage in chemical costs may be
overshadowed by a large capital investment or higher overall operating
costs.
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WORK FLOW
DISTILLATE
Ul
o
PLATING TANK
RINSE #1 RINSE #2
RINSE FLOW
CONCENTRATE FLOW
CONCENTRATOR
Figure 27. Closed-loop evaporative recovery system
-------
A cost comparison for the above factors has been given by Lancy,
Nohse, and Wystrach for three techniques: ion exchange, continuous treat-
ment, and integrated treatment. The facility chosen for economic study
consisted of two automatic plating lines which contained a cyanide copper
strike, acid copper, double.nickel, and .chromium plating cycles.ii'
Ion exchange may remove the chemical content and allow reuse of rinse
waters. Up to 80 to 90% of the rinse water may be recirculated for economi-
cal use of water. Hence, the total effluent volume is reduced.
Continuous instrumented treatment is based on continually sensing the
flowing effluent stream and precipitating the metal salts by chemical treat-
ment. Caustic chlorination oxidizes the soluble cyanides. The precipitates
are settled in a clarifier to collect the hydrated metal oxides. This is
followed by sludge concentration, dewatering, and drying.
Integrated waste treatment employs a chemical rinse following the
plating step and prior to the work entering the second or later' rinse
tanks. Heavy metals are precipitated in the first tank and removed from
the rinse water.
Table 67 presents a comparison of total treatment costs for ion ex-
change, continuous treatment, and integrated treatment. It is seen that
the integrated treatment system yields a lower total cost annual ly.JJL'
The most significant costs for metal finishing waste treatment for
this plating facility are capital investment and amortization cost of in-
stallations, water cost, sewer rental charges, treatment of concentrates,
and sludge-handling costs. Chemical costs are relatively minor. Environ-
mental management of metal finishing effluents is a complex and difficult
topic, and requires an engineering overview of all potential costs for
each option. Merely focusing on chemical costs and ease of operation does
not necessarily yield the most effective, trouble-free, and economical
process.
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Table 67. COMPARISON OF TREATMENT COSTS, $ (1972)
Continuous Integrated
Ion exchange treatment treatment
Fresh water 187 28,894 165
Ca, Mg precipitation
of hard water salts 21 4,597
pH.adjustment for oxida-
tion-reduction control - 4,367
Neutralization - 2,784 79
Sewer rental charges 157 24,143 138
Deionized water 289 289 289
Treatment and concentra-
tion of solids and sludge
handling 33,589 27,981 2,588
Electric energy 1,289 3,405 960
Chemicals 6,759 1,743 6,084
Wages 3,863 4,017 2,008
Amortization 31,091 16,966 4,809
Maintenance 3.999 12.767 1.443
Total cost annually 81,244 131,953 18,563
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REFERENCES TO CHAPTER VIII
1. Watson, M. R., "Pollution Control in Metal Finishing," Noyes Data •
Corporation, Park Ridge, New Jersey (1973).
2. Lancy, L. E., Lancy Laboratories Division^ Dart Industries,..'.Inc.,. ,.''•'.
Zelienople, Pennsylvania.
3. Bollyky, L. J., "Ozone Treatment'of Cyanide and Plating Waste," PCI
Ozone Corporation, West Caldwell, New Jersey. '
4. Mauk, C. E., H. W. Prengle,-and R. W. Legan, "Chemical Oxidation of
Cyanide Species by Ozone and UV Light," Society of Mining Engineers
Meeting, Salt Lake City, Utah, Houston Research, Inci, Houston,
Texas, September 10-12, 1975.
5. Malin, H. M., Environmental Science and Technology, 5^496 (1971).
6. Anonymous, Plating, 59_:817 (1972).
7. . Environmental Protection Agency, "An Investigation of Techniques for
Removal of Cyanide From Electroplating Wastes," EPA No. 12010 EIE,
November 1971.
8. Hoffman, D. C., Plating. 60jl57 (1973).
9. Golomb, A., Plating. 59_:3x6 (1972).
10. Environmental Protection Agency, "New Membranes for Reverse Osmosis
Treatment of Metal Finishing Effluents," EPA No. 660/2-73-033,
December 1973.
11. Luttinger, L. B., and G. Hoche, Environmental Science and Technology,
18:614 (1974).
12. McNulty, K. J., D. C. Grant, A. Gollan, and R. L. Goldsmith, "Field
Demonstration of Reverse Osmosis Treatment of Cyanide Rinse Water,"
American Electroplaters1 Society, 62nd Annual Technical Conference,
Toronto, Canada, June 1975.
13. Avery, N. L., and W. Fries, "Selective Removal of Cyanide From In-
dustrial Waste Effluents With Ion-Exchange Resins," I&EC Product
Research and Development. 14:102 (1975).
153
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14. Cochran, A. A., and L. C. George, Bureau of Mines Report of Investi-
gations, No. 7877 (1974).
15. Lancy, L. E., W. Nohse, and D. Wystrach, Plating, 59:126 (1972).
Other Waste Treatment References
16. Environmental Protection Agency, "A State-of-the-Art Review of Metal
Finishing Waste Treatment," EPA No. 12010 EIE, Battelle Memorial
Institute, Columbus, Ohio, November 1968.
17. Environmental Protection Agency, "Recommended Methods of Reduction,
Neutralization, Recovery, or Disposal of Hazardous Waste." Vol.
XIV. Summary of Waste Origins, Forms, and Quantities, EPA No.
670/2-73-053-m, TRW Systems Group, August 1973.
18. Environmental Protection Agency, "Development Document for Interim
Final Effluent Limitations Guidelines and Proposed New Source
Performance Standards for Metal Finishing," EPA 440/1-75-040-a,
April 1975.
19. Environmental Protection Agency, "Development Document for Interim
Final Effluent Limitations Guidelines and Proposed New Source
Performance Standards for the Common and Precious Metals," EPA
No. 440/1-75-040-b, April 1975.
20. Environmental Protection Agency, "Economic Analysis of the Proposed
Effluent Guidelines - The Metal Finishing Industry," EPA No. 230/1-
74-032, September 1974.
21. Environmental Protection Agency, "Treatment of Complex Cyanide Com-
pounds for Re-use or Disposal," EPA No. R2-73-269, June 1973.
22. Environmental Protection Agency, "Upgrading Metal-Finishing Facili-
ties to Reduce Pollution," EPA Technology Transfer Seminar on Waste
Treatment, U.S. Government Printing Office 1974-546-315:240, July
1973.
23. U.S. Department of the Interior, "Industrial By-Product Recovery
by Desalination Techniques," Off ice of Saline Water, Research and
Development Progress Report No. 581, October 1970.
24. U.S. Department of Commerce, "Wastewater Treatment Technology," 2nd
ed., National Technical Information Service, PB 216-162, Illinois
Institute for Environmental Quality, February 1973.
154
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25. Lund, H. F., Industrial Pollution Control Handbook, Chapter 12,
McGraw Hill Book Company, New York (1971).
26. Lowe, W., "The Origin and Characteristics of Toxic Wastes With Par-
ticular Reference to the Metal Industries," J. Insti. Water Pol.
Con.. £9:270 (1970).
27. Lawes, B. C., Plating. 59:394 (1972).
155
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CHAPTER IX
ALTERNATIVE MATERIALS, PROCESSES AND USES
In this chapter alternate raw materials and methods of production of
cyanides are discussed. The presentation also includes alternative chemi-
cals to cyanides in the various industrial sectors.
ALTERNATE RAW MATERIALS AND SYNTHETIC METHODS
The present methods of HCN manufacture by the Andrussow or the Degussa
process seems to offer no immediate suggestions for alternate raw materials.
Certainly HCN is the simplest cyanide to make and also the most versatile;
offering easy access to either the organic or the inorganic sector. The
present processes start with the simplest of materials; ammonia, methane,
and air (absent in the Degussa process). Methane from natural gas could be
in relative short supply in the distant future but there are alternates to
methane production, e.g., cracking of crude oil.
Of course, each synthesis process could conceivably be made to operate
better through use of a more efficient catalyst which would allow a lower
reaction temperature, higher flow rates, a shorter contact time, etc.
The production of acrylonitrile at present is around 1.4 billion
pounds annually which yields approximately 200 million pounds of HCN as
by-product. If all the primary HCN plants across the country would cease
production except the Rohm and Haas facility having a capacity near 180
million pounds, the total production of 380 million pounds would meet our
current needs for HCN. Thus, a tremendous capacity exists far exceeding
our present needs for HCN. This situation which combines overcapacity
from two processes yielding HCN arouses little enthusiasm to seek alter-
nate paths to cyanides today.
If a crisis in crude oil and/or natural gas does develop in the fu-
ture, cyanides can be made by the time honored historical techniques de-
scribed earlier in Chapter IV. The Bucher high temperature process which
combines sodium carbonate, coke, and nitrogen in an iron vessel will yield
sodium cyanide, another versatile chemical. The older Beilby process com-
bining soda ash, carbon, and ammonia could be revived. The key is to man-
ufacture either hydrogen cyanide or sodium cyanide; from these all other
156
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organic and inorganic cyanides can be made. Fortunately, there are many
routes to these two fundamental cyanides.
ALTERNATES TO CYANIDES IN VARIOUS INDUSTRIAL SECTORS
In this section various substitute materials for cyanides are dis-
cussed. Some trend toward cyanide replacement because of waste treatment
problems and costs has already been observed by industry spokesmen. A
countertrend is also emerging which, in essence, holds that cyanides are
so superior for certain industrial uses that the alternate materials are
a poor second choice. Further, the substitute chemicals have potential
waste effluent problems themselves. At least cyanides are well understood,
the treatment technology is on a sound basis, and the treatment costs
could conceivably drop in the near future as new technology is developed.
Metal Finishing
Zinc plating constitutes the largest plating sector in the U.S. to-
day. With the advent of restrictions on cyanide effluents, much research
and development has gone into development of mid-to-low-to-noncyanide zinc
baths in the last 10 years. The noncyanide baths include acid chloride,
acid sulfate, and fluoborate. Some plating baths substitute ammonia and/
or chelating agents as zinc complexers instead of cyanide. Table 68 indi-
cates the composition and estimated distribution of bright zinc plating
baths in 1975 according to Geduld«i/
Table 68. ESTIMATED DISTRIBUTION OF ZINC PLATING BATHS BY TYPE
Cyanide concentration Estimated
Zinc bath type (g/liter as CN) % of market
Regular cyanide 45 36
Mid-cyanide . 15-45 25
Low-cyanide 3-11 15
Micro-cyanide 0.75-1.0 8
Noncyanide alkaline 0 7
Acid 0 9
Total 100
157
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The shift to noncyanide zinc baths has largely been accomplished in
small plating shops (60 to 80%) as the result of stringent effluent regu-
lations coupled with general inability or reluctance of the small platers
to invest heavily in treatment facilities for cyanides. The larger shops
are still using cyanide zinc baths with effluent alkaline chlorination
primarily and account for a very large fraction of all zinc plating. The
larger shops have invested heavily in cyanide treatment equipment and mon-
2 / '
itor treatment expenses through careful accounting practices^'
Several companies are now heavily promoting noncyanide zinc processes.
Among these are: Lea Ronal, Inc., Freeport, New York; R. 0. Hull and Com-
pany, Inc., Cleveland, Ohio; the Udylite Company, Division of Metal Indus-
tries Corporation, Warren, Michigan; The Aldoa Company, Detroit, Michigan;
and Conversion Chemical Corporation, Division of 3M Company, Rockville,
Connecticut. One company, Lea Ronal, Inc., assisted Tracer, Inc., of Des
Plaines, Illinois, in converting some 400,000 gal. of zinc plating bath to
a noncyanide system for barrel plating. The changeover also included tin
and cadmium plating lines and was accomplished over one weekend.^.'
The alkaline and acid bright zinc noncyanide plating baths are not
without some compromises, however. Some baths are not as efficient, do not
have the same throwing power, ease of operation and control, etc., as the
historic cyanide bath which has the distinct advantage of some 100 years
of development. Recent research has reduced these shortcomings through use
of special organic brightening and leveling agents. It now appears acid
bright zinc baths have a distinct advantage over alkaline baths as regards
brightness, higher current efficiency, the option of direct plating on
cast iron without intermediate deposits, etc.
Some noncyanide zinc baths utilize chloride, ammonia, or chelating
agents in addition to organic wetting agents and proprietary brighteners.
The presence of these materials in effluents may have deleterious effects
themselves. For example, high concentrations of ammonia in an effluent
may cause difficulty in subsequent treatment since ammonium ion can very
effectively complex zinc, nickel, and copper, for example, and prevent
precipitation of the hydrated metal oxide. Chelating agents, such as EDTA,
complex zinc salts to such a degree that precipitation as zinc hydroxide
from reuse waters is impossible at any pH range, the residual zinc concen-
tration remaining near 20 rag/liter.— Ammonia in an effluent reacts with
chlorine to form chloramines which are toxic to fish. In addition, the
presence of ammonia increases chlorination costs during effluent treatment.
The zinc plating bath of the future may well be composed of zincate
(zinc hydroxide dissolved in excess caustic soda), easily degradable che-
lates, nonionic wetting agents, and proprietary brighteners.
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In the areas of alkaline copper, brass, and bronze plating there are
no commercially available noncyanide. processes as yet. Development in these
areas is continuing. A noncyanide .cadmium plating bath has been developed
by Conversion Chemical Corporation for/plating steel but has not received
wide application. • , •
Engelhard Industries markets a series of alkaline noncyanide gold
plating baths covering varying degrees of deposit hardness. The bath pro-
perties appear to be equally as desirable as the traditional cyanide baths.
Cyanide-based silver plating baths have been the subject of many re-
searchers since their discovery in 1840, but only in 1975 has a noncyanide
bath become comercially available. The new, noncyanide silver bath is based
on a derivative of succinic acid. Technic, Inc., of Providence, Rhode Island,
markets the proprietary bath and has applied for patent rights. The technical
reports claim high quality deposits with nearly the same costs as the tradi-
tional cyanide processes.
Finally, various noncyanide metal stripping, descaling, and cleaning
solutions are available. Table 69 indicates the products currently avail-
able for use by metal finishers.
Table 69. PRODUCTS CURRENTLY AVAILABLE FOR USE BY METAL FINISHERS
Noncyanide
solution Source Location
Nickel stripper Enthone, Inc. New Haven, Connecticut
Nickel stripper MacDermid, Inc. Waterbury, Connecticut
Brass detarnisher Frederick Gumm Chemical Kearny, New Jersey
and burnisher Company
In summarizing it may be said that there are noncyanide processes
commercially available for many metal finishing operations. What remains
to be seen is whether or not they are equal to the task, are economical,
and do not contribute effluent treatment problems of their own. These fac-
tors are important to metal finishers and the public alike.
Pigments
Substitutes for iron blue as paint and ink pigment have been devel-
oped in recent years. The current inorganic pigments for blue coloration
159
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in paints include cobalt blue, a mixture of cobalt, chrome, and aluminum
oxides, and ultramarine blue, a complex sodium aluminum sulfosilicate.—
These materials have poor hiding power (translucent) but are alkali re-
sistant. Ultramarine blue is used in latex and alkyd resin-based paints
and in automobile and agricultural implement enamels and finishes. Cobalt
blue is used for pale tints and toning of white. Both of these pigments
are more expensive than iron blue. Manufacturers of cobalt blue and ultra-
marine blue are given in Table 70.
Table 70. MANUFACTURERS OF COBALT BLUE AND ULTRAMARINE BLUE
Company
Chemetron Corporation
Frank D. Davis Company
Ferro Corporation
Hercules, Incorporated
Naftone, Incorporated
Sheperd Chemical Company
Whittaker, Clark and
Daniels Company
Location
Holland, Michigan
South Plainfield,
New Jersey
Cleveland, Ohio
Glens Falls, New York
New York, New York
Cincinnati, Ohio
South Plainfield,
New Jersey
Pigment
Ultramarine blue
Cobalt blue
Cobalt blue
Cobalt blue
Cobalt blue
Cobalt blue
Ultramarine blue
Many of these companies also offered iron blue as a pigment in .recent past
years.
The environmental impact arising from substitution of cobalt blue or
ultramarine blue is unknown at present. Chrome oxide is one of the compon-
ents of cobalt blue and is environmentably undesirable as a waste product.
Any contamination problems by cobalt blue would be more probable at the
point of manufacture than at the final disposal at a municipal or county
facility. Ultramarine blue appears to be innocuous, but no evidence is
available to make a sound judgment.
Organic blue pigments include two general types: copper phthalocyar-
nine blue and indanthrene blue. The former has excellent tinctorial power
and heat and chemical resistance but is semitranslucent. It has been used
in ink and textile manufacture and now increasingly for paint applications,
particularly for coil coating and high-temperature operations.— In 1963,
approximately 4.3 million pounds were produced domestically._'
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Indanthrene blue is an anthroquinone derivative and is relatively
expensive as is phthalocyanine blue. This material has good acid and al-
kali resistance and withstands temperatures up to 150 C.
A third group of dyes based on triphenylmethane and containing amino
and sulfonic acid groups are represented by peacock blue and alkali blue.
These have brilliant colors but poor alkali resistance and light-fastness.
Other organic blue colors certified by the U.S. FDA are available as pig-
ments for limited applications, e.g., FD&S Blue No. 6, Indigotin.
Manufacturers of these organic blue pigments include many of the
former list for inorganic pigments plus others, e.g., E. I. du Pont de
Nemours and Company, Wilmington, Delaware, and Ciba-Geigy Corporation,
Ardsley, New York, etc.
The environmental impact of the various organic pigments is unknown
but each could be incinerated easily. Only copper phthalocyanine offers
any hint of environmental problems. This material is actually the copper
salt of phthalocyanine, a porphyrin. It is unusually stable and can be
sublimed at 550°C in an inert atmosphere without decomposition. Ultimate
destruction of the porphyrin still leaves copper or copper oxide as a
residue depending on the incineration technique employed.
Industry spokesmen indicate a future decline in iron blue consump-
tion as pigment with phthalocyanine blue becoming more prominent in the
paint and ink sectors. The advantages of phthalocyanine blue as paint pig-
ment are related to its stability in alkaline media and its better heat
resistance^.' The advantages as ink and textile pigment are related to its
stability in acid and alkaline media, its cleaner shade, its higher tinc-
torial power, and its resistance to bleed of oils and solvents.—'
Mining Chemicals and Processes
Presently, cyanidation is the single most important method of recov-
ery for gold, domestically. In discussing the alternatives to cyanidation,
a brief description of the five processes currently employed to recover
gold and silver is in order. The processes are outlined in Table 71.
Gravity concentration is used on gold occurring in a relatively coarse
native state (occurring as metallic gold). This is generally descriptive of
placer deposits, although some lode deposits are amenable to gravity concen-
tration. In processes using gravity concentration, the gold would ultimately
be recovered by amalgamation, smelting or cyanidation, and therefore the
percent recovered in Table 71 is somewhat low. Very little gold production
can be supported by gravity concentration alone. In conclusion, gravity con-
centration is not a viable alternative to cyanidation.
161
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Table 71. PROCESSES FOR RECOVERY OF GOLD AND SILVER
% Gold recovered
Process Use cyanides (1972)—
Gravity concentration No < 1
Amalgamation No < 1
Flotation No a/
Smelting No 44
Cyanidation Yes 55
&l Reported in Smelting.
Amalgamation can be used to recover native gold with no dependence
on the size of the gold particles. Gold ores with a high percentage of
slimes are not recovered by amalgamation as the losses of mercury and
consequently gold are too high. Prior to 1971, approximately 25% of the
domestic gold production resulted from amalgamation. However, due to en-
vironmental concern, amalgamation is currently limited chiefly to recov-
ery of gravity concentrates in the processing of lode deposits. Like
gravity concentration, amalgamation does not appear to be an alternative
to cyanidation.
Flotation, as a method of recovery for gold, can be applied only to
(a) gold occurring with tellurides, (b) when in solid solution with com-
plex iron sulfides, or (c) when occurring with copper, lead and zinc sul-
fides (base metal ores). Flotation recovery of the telluride and complex
iron sulfide-gold ores is not an important source of gold domestically
and cannot be considered as an alternative to cyanidation. The flotation
recovery of gold from copper, lead, and zinc production is important, but
the gold is a by-product and therefore subject to the economics of recov-
ery of the base metal. Likewise, by-product gold recovery cannot be con-
sidered as an alternative of cyanidation.
The recovery of gold by smelting is the second most important source
of gold in the U.S. Recovery by smelting includes the gold produced by
flotation of telluride and iron sulfide ores discussed in the previous
paragraph. However, the majority of the gold produced by smelting is de-
rived as a by-product from the smelting of copper, lead and zinc concen-
trates. Of the 25 leading mines producing gold in 1972, 15 were copper
based ores and two were lead-zinc ores. In the absence of cyanidation,
smelting would continue as a source of gold. However, since the gold pro-
duced by smelting is largely a by-product, the gold production depends
almost entirely on the production of the base metals.
162
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The use of malonitrile for chemical leaching of gold has been stud-
ied by the Bureau of Mines.!' but is not an alternative for cyanidation
because of lower efficiency and higher costs.
In conclusion, currently there are no alternatives to the use of
cyanides in the production of gold, if the approximate level of produc-
tion is to be continued.
Cyanides are used in flotation as depressants, thereby inhibiting
the flotation of certain minerals while recovering other mineral values.
As shown in Table 43, cyanides strongly depress the iron and zinc sul-
fides while cyanides moderately depress copper sulfides.
In copper ores and lead ores cyanides might be replaced by reducing
agents or in some cases no depressants might be used for flotation recov-
ery. Adverse effects would probably be monetary penalties paid to smelters
for increased sulfur loads in the form of iron sulfides and increased
transportation costs for hauling worthless gangue minerals. Without the
use of cyanide in the lead-zinc-copper separation, some zinc would be lost
to the copper and lead concentrates, and smelting penalties would be asses-
sed for the removal of zinc. The definite possibility also exists that the
concentrates may not be marketable if they contain the impurities which
the cyanides depress.
The literature indicates that cyanides are the most prevalent depres-
sant used for the flotation recovery of molybdenum from copper-molybdenum
ores wi' Reference is also made to the use of roasting, steaming, sodium
sulfide, potassium dichromate, and Moke's Reagent (?2S5 or AS2S5 plus NaOH)
as methods of depressing copper while floating molybdenum. Alternatively,
dextrin may be used to depress molybdenum while floating copper; however,
this method of separation is usually much less efficient than depressing
the copper sulfides. In the case of roasting, the surfaces of the copper
grains are oxidized and become nonfloatable while the molydenite remains
floatable.—' Roasting may be an expensive method of copper depression and
SC>2 is a by-product. Steaming is an energy intensive operation. Potassium
dichromate is a powerful oxidant which oxidizes the collector from the
copper sulfide surface. Moke's Reagent is a powerful depressant, but I^S
fumes can be evolved if care is not taken in its preparation.
In the use of cyanide to depress zinc, no current viable alternatives
seem available. In the absence of cyanide used as a depressant for zinc,
zinc recovery would surely decline. Smelting of lead concentrates contain-
ing zinc results in loss of zinc to the slag._t' The use of cyanide to de-
press zinc would be included in most of the processes recovering mineral
values from copper-lead-zinc ore, copper-zinc iron-sulfide ore, lead-zinc
ore and lead-zinc-silver ore.
163
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Fluorspar ore flotation may have no substitute for cyanide. The low-
est marketable grade of fluorspar.must contain less than 0.3% sulfide sul-
fur, and the highest grade must contain less than 0.170 sulfide sulfur.
In conclusion, the substitution of other depressants for cyanides
to depress copper and iron sulfides would probably increase the sulfur
load at copper smelters and may lessen the recovery of molybdenum. The
elimination of cyanides to depress zinc would surely lower the recovery
of zinc and likely result in smelter penalties.
Metal Heat Treatment
Liquid Carburizing - Alternatives to liquid carburizing and some disad-
vantages of each alternative follow in Table 72.
Table 72. ALTERNATIVES TO LIQUID CARBURIZING
1.
Alternative
Gas carburizing using
natural gas, propane
and derivatives
2.
Solid carburizing using
coke or charcoal
3. Noncyanide salt baths
Disadvantages of Alternative
a. Toxic CO produced
b. Generally not as fast
c. Less maximum case depth
d. Flammable, explosive atmosphere
e. Furnaces generally, more expensive
f. Gas metering equipment necessary
g. Equipment less versatile
h. Requires more skilled operation
a. Much harder to control case depth
b. Much slower
c. Cannot be directly quenched
d. Equipment less versatile
e. Less efficient heat utilization
a. Requires more skilled operationi'
b. Not as versatil&i/
c. The salt is presently more expensive
In summary, gas carburizing and use of noncyanide salt baths for li-
quid carburizing will likely continue to displace the use of cyanide for
case hardening. This is especially true for smaller heat treating shops.
Gas carburizing currently is more widely practiced than liquid carburizing!
164
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Liquid Nitriding - A direct alternative to liquid nitriding is gas nitrid-
ing. Gas nitriding uses ammonia and dissociated ammonia as the gaseous at-
mosphere.
The disadvantages of gas nitriding are essentially the same as for
gas carburizing except toxic carbon monoxide is not produced. However,
ammonia is discomforting and must not be allowed to permeate the working
environment.
Two additional disadvantages with gas nitriding are firstly, that it
is not applicable to case hardening of plain carbon steel.—' Secondly, the
case produced by gas nitriding is more brittle than that produced by liquid
nitriding.I/
However, gas nitriding will likely continue to replace liquid nitrid-
ing in the future. Currently, gas nitriding is more prevalent than liquid
nitriding.
Liquid Carbonitriding - The alternative to liquid carbonitriding is a com-
bination of gas carburizing and gas nitriding, commonly called gas cyanid-
ing, dry cyaniding or nicarbing.
The same general disadvantages apply to gas carbonitriding as to gas
carburizing and gas nitriding. Again, gas carbonitriding will most likely
continue to replace liquid carbonitriding.
Less Specific Alternatives - Other methods of case hardening could also
replace the use of cyanides in specific instances..These methods include:
Induction hardening
Flame hardening
Surface alloying
Siliconizing
These processes are currently in use to varying degrees.
Photographic Processing Chemicals
A substitute for ferro-ferricyanide photographic bleach is the so-
called "blix" solution based on an EDTA-Na-Fe redox system.!/ The term
"blix" is short for bleach-and-fix and refers to a process in which the
bleaching and fixing steps are combined. In the normal bleach bath (ferro-
ferricyanide-bromide) the silver present in the film is oxidized and con-
verted to silver bromide. A subsequent fixing bath (hypo) dissolves the
silver bromide so that it may be washed from the film and the normal se-
quence of operations is bleach, rinse, fix, and rinse.
165
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A bleach-fixing bath (blix) can accomplish the same results in one ,
step followed by a rinse. In general, the blix bath consists of a ferri-
EDTA complex and hypo. The former component oxidizes silver and is reduced
to a ferro-EDTA complex. As this happens the hypo complexes the silver ion
so that" it can be washed from the film. The ferro-EDTA complex may be re-
acted with dissolved oxygen provided by aeration and reoxidized to the or-
iginal ferri complex. Silver may be removed by iron displacement, ion ex-
change methods, or electrolytically to rejuvenate the bath.
The blix solution is kinetically slower than a conventional ferro-
ferricyanide bleach solution. A catalyst such as a polyglycol, a stabili-
zer such as sulfite, and pH control are essential in satisfactory blix
bath operation.
The advantages of a blix bath are a shorter overall processing times
due to elimination of fix and rinse steps, elimination of ferricyanide,
and avoidance of potential iron blue precipitation in the bleach bath.
Disadvantages of the blix bath are that the system requires closer
control during operation than conventional ferricyanide bleach baths, that
additional chemical components must be present for an active yet stable
bath, and that silver metal is not as easily recovered by electrolysis due
to the ferri-EDTA complex. Further, the usual film hardening agents such
as formalin or potassium alum cannot be used in a blix bath because of
conflicting pH requirements.
Research on blix baths has been an active field of investigation
for the past 30 years and remains so today. According to Roosen and his
co-workers, no known blix bath has the simultaneous advantages of good
activity, stability, and hardening properties without some unwanted side
effects.—'
Equipment changes are minimal in converting from a conventional
bleach-rinse-fix-rinse operation to a two-step blix operation. The equip-
ment in many film processing laboratories consists of a combination of
hand-made developing and rinsing tanks and/or those modified from commer-
cial units to suit a particular need. Conversion from one system to another
is relatively simple and inexpensive and there appears to be no overriding
economic factors to hinder the conversion. There appears to be a definite
economic advantage in converting to the blix system since the overall pro-
cessing time is shorter with no. loss in film quality.
The ferri-EDTA-hypo blix solution has not yet completely replaced
the ferricyanide bleach bath but is gaining prominence. Conventional color
print processes were the first to use blix baths with color negative pro-
cesses following. Color reversal processes and motion picture film devel-
oping primarily still depend largely on conventional ferricyanide bleach
166
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baths. Industry sources .anticipate cpntinued growth in blix bath usage
over the next 10 years. The ecological implications of large-scale (sev-
eral millions of pounds) usage of ferri-EDTA complex are not clear.-' On
the other hand, ferro- and ferricyanide regeneration and effluent treat-
ment is well known and poses no insurmountable problems. According to
Cooley, ferricyanide bleach bath will remain in wide use in the foresee-
able future.—'
Anti-Caking Agents
There are no recommended alternate chemicals as substitutes for
iron blue or sodium ferrocyanide as anti-caking agents in de-icers for
highway use. According to the Salt Institute, Alexandria, Virginia, iron
blue or ferrocyanide have been used for this purpose since 1921 and no
adverse effects related to these chemicals have been noted«i/ Hence,
there is no good reason to make a change.
Common table salt does contain anti-caking agents such as ferric
ammonium citrate and sodium ferrocyanide. Ferrocyanide has been approved
by the FDA for use as an anti-caking agent at 500 ppm.£'
Agricultural and Pest Control Chemicals
Hydrogen cyanide and calcium cyanide have all but disappeared as ag-
ricultural and pest control chemicals. It is estimated that perhaps 50,000
to 60,000 Ib of liquid hydrogen cyanide are dispersed annually for fumiga-
tion purposes. This amount could increase significantly in the future if
grain surpluses return, for then vast amounts of grain in storage bins and
elevators across the country would require fumigation.
Present solid and liquid fumigants work well and no significant
change in their usage pattern is indicated at present. A slight increase
of usage in the future is indicated if food production continues to in-
crease. The development of new fumigants is not anticipated in the near
future unless some of the present ones are shown to be detrimental for
one reason or another. The current market appears to have stabilized.
There is quite a bit of activity in the pest control sector, prin-
cipally for rodenticides.!/ Sorex, Ltd. (London), now markets Neosorexa
in Britian and Europe. The active agent is difenacoum and kills rodents
which are resistant to other anticoagulants such as Warfarin. Sorex in-
tends to market Neosorexa in the U.S. through ICI United States of
Wilmington, Delaware. Sorexa CR which combines Warfarin with calciferol,
vitamin D-2, is an alternate rodenticide.
167
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Rohm and Haas has recently, developed Vacor, a new rodenticide, based
on a derivative of p-nitrophenyl urea. It is marketed as a 2% grain-bait,
and a bentonite tracking powder for mice is planned.
Other new rodenticides based on Vitamins D-2 or D-3 in conjunction
with warfarin are being tested for both rats and mice. Sorex Limited
(London) and Bell Laboratories, Inc., of Madison, Wisconsin, are the de-
velopers.
Finally, chemosterilization has potential as a pest control tech-
nique, but no product has yet emerged. Research and development in ster-
oids and chloroaliphatic diols are continuing.
168
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REFERENCES TO CHAPTER IX
Metal Finishing
1. Geduld, H., "Bright Zinc Plating, 1975 - The Platers' Choice," Plating
and Surface Finishing. 64:687 (1975).
2. Lancy, L. E., Lancy Laboratories Division, Dart Industries, Inc.,
Zielenople, Pennsylvania.
3. Anonymous, "Littelfuse Plant Goes Noncyanide Over One Weekend," Plating
and Surface Finishing. 61jl8 (1974).
4. Todt, H. G., "Acid Bright Zinc Electrolytes and Their Significance
for Electroplating," Presented at the American Electroplaters1
Society's 62nd Annual Technical Conference, Toronto, Canada,
June 1975.
Pigment
1. Preuss, H. P., "Pigments in Paints: Inorganic Blue," in Metal Finish-
ing, 70(8), August 1972.
2. Preuss, H. P., "Pigments in Paints: Organic Blue," in Metal Finishing,
70(9), September 1972.
3. Clark, G. L., ed., Encyclopedia of Chemistry, 2nd ed., Reinhold Pub-
lishing Company,.New York, New York (1966).
4. Maida, S. M., "Pigments for Rotogravure and Flexographic Inks," in
American Ink Maker. 46(7), July 1968.
169
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Mining Chemical and Processes
1. West, T. M., "Gold," in Mineral Yearbook. 1972. Vol. I. Minerals,
Metals, and Fuels, p. 585, Bureau of Mines, U.S. Department of the
Interior, U.S. Government Printing Office, Washington, D.C. (1974).
2. Heinen, H. J., "Malononitrile Extraction of Gold From Ores," Bureau
of Mines Report of Investigations, RI 7464, U.S. Department of the
Interior, Washington, D.C., December 1970.
3. Anonymous, "Mineral Dressing Notes No. 26." Mining Chemicals Handbook.
American Cyanamid Company, Mining Chemicals Department, Wayne, New
Jersey. .
4. Heindl, R. A., "Zinc," in Mineral Facts and Problems, Bureau of Mines,
U.S. Department of the Interior, U.S. Government Printing Office,
•Washington, D.C., p. 806 (1970).
Metal Heat Treating
1. Foreman, R. W., Park Chemical Company, Detroit, Michigan, private
communication to R. R. Wilkinson, September 11, 1975.
2. Haga, L. J., "Principles of Heat Treating," in Heat Treating. 6(3):
13-14, March. 1974. •..."""
3. Focke, A. E., and F. E. Westermann, "The Effect of Heat Treating on
Metal Surfaces - A Review," in Proc. Internat. Conf. on Surface
Technol.. pp. 527-539, Society of Manufacturing Engineers, Dearborn,
Michigan (1973).
Photographic Processing
1. Roosen, R., G. Vanreusel, and R. G. L. Verbrugghe, "The Use of Bleach-
Fixing Baths in Color Motion-Picture Film Processing," JSMPTE, 132:
542 (1973).
2. Alletag, G. C., President, Alta Chemical Company, San Diego, California.
3. Cooley, A. C., "Regeneration and Disposal of Photographic Processing
Solutions Containing Hexacyanoferrate," SMPTE Meeting, Los Angeles,
California, September 28, 1975.
170
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Anti-Caking Agents
1. Wood, F., Technical Director, The Salt Institute, Alexandria, Virginia.
2. Code of Federal Regulations, Title 21, 121.1032CFR.
Agricultural and Pest Control Chemicals
1. Anonymous, Chemical Week, 117(9):34, August 27, 1975.
171
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CHAPTER X .. ' •
MATERIAL BALANCE AND ENERGY CONSUMPTION
In this section, the material and energy requirements for the pro-
duction of inorganic cyanides will be discussed. A material balance of
the industrial uses of cyanides is presented in detail. Also included
is a discussion on the waste produced in the manufacture and use of
inorganic cyanide. A final point will be the exposure of man and the
environment to cyanides.
RAW MATERIALS
Below are summarized the calculated raw material requirements for
various inorganic cyanides produced domestically in 1975 except where
noted.
1. Hydrogen cyanide produced as a by-product of acrylonitrile pro-
duction in the SOHIO process.
I/ 9
1974 acrylonitrile production- 1.36 x 10 Ib
hydrogen cyanide at 0.15 Ib/lb acrylonitrile 200 x 106 Ib
raw materials required at 85% yield:/ Q
propylene 1.8 x 10 Ib
ammonia 450 x 10$ Ib
2. Hydrogen cyanide produced by the Andrussow process.
6
hydrogen cyanide (MRI estimate) 275 x 10 Ib
raw materials required^/ ,
Q
methane 165 x 10 Ib
ammonia 170 x 106 Ib
3. Sodium cyanide produced by neutralization of hydrocyanic acid.
1975 sodium cyanide (MRI estimate)
raw materials required at 100% yield
1975 sodium cyanide (MRI estimate) 56.5 x 10 Ib
hydrogen cyanide 31 x 10fi Ib
sodium hydroxide 47 x 10 Ib
172
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4. Iron blue production.
1975 iron blue (estimate) 8.0 x 10 Ib
raw material^/ ,
ferrous sulfate 8.8 x 10 Ib
sodium ferrocyanide 1.4 x 10° Ib
sulfuric acid 2.6 x 106 Ib
ammonium sulfate 2.4 x 10° Ib
sodium chlorate 1.0 x 106 Ib
5. Sodium ferrocyanide production.
sodium ferrocyanide, decahydrate (estimate) 2.5 x 10 Ib
raw materials at 100% yield
calcium cyanide 1.3 x 10 Ib
ferrous sulfate 0.8 x 10J? Ib
sodium carbonate 1.1 x 10 Ib
6. Sodium ferricyanide production by chlorine oxidation of sodium
ferrocyanide.
sodium ferricyanide, monohydrate (estimate) 0.4 x 10 Ib
raw materials at 100% yield
sodium ferrocyanide, decahydrate 0.6 x 10 Ib
chlorine 0.05 x 106 Ib
ENERGY CONSUMPTION FOR PRODUCTION
Listed below are the energy consumptions for the production of in-
organic cyanides, differentiated by process where applicable. The figures
listed are average and specific process energy consumption may be higher
or lower depending on the reaction conditions used. This would be partic-
ularly true in the case in acrylonitrile processes where the reaction
temperatures and pressures may be different for different catalysts.
4/
1. By-product hydrogen cyanide from acrylonitrile production:—
Per 1.000 Ib acrvlonitrile*
Electricity 180 kwh
Steam (at 60 psig) 100 Ib
Fuel (other than for steam) None
Approximately 150 Ib of hydrogen cyanide would be produced.
173
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2. Hydrogen cyanide by the Andrussow process:
Per 1,000 Ib hydrogen cyanide
Electricity 420 kwh
Steam and fuel None
3. Sodium cyanide and potassium cyanide by neutralization:
Per 1,000 Ib sodium or potas-
sium, cyanide
Electricity 15 kwh
Steam 1,650 Ib
Fuel (other than for steam) None
WASTE MATERIAL PRODUCT
Waste produced in the manufacture of inorganic cyanides in most
cases is minimal with the exceptions of iron blue and ferrocyanide pro-
duction. Waste production can be in gaseous, liquid or solid form de-
pending on the cyanide produced.
By-Product Hydrogen Cyanide
Hydrogen cyanide is produced domestically as a by-product of acryl-
onitrile production by the SOHIO process. The reactants are all gaseous
and the process is at high temperature. Wastes produced are:
Solid waste; Insignificant amounts of silica catalyst result, pre-
senting no disposal problems •_!/
Liquid waste; Liquid wastes in acrylonitrile production are the.
most significant. Water used for absorption of the products, later dis-
tilled off, may contain several organic compounds as nitriles and cya-
nides including hydrogen cyanide which necessitates treatment. Liquid
wastes from these processes can be adequately treated by most of the
methods discussed in Chapter VIII.
Gaseous wastes; Several gaseous wastes are produced which may con-
tain hydrogen cyanide as an impurity. These gases are usually vented to
the air through a flare. The heat value of the gases is too low for use
in firing boilers, if the hydrogen cyanide is removed. The gases may be
suitable for combustion as boiler fuel, if the HCN is not recovered.
174
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Primary Hydrogen Cyanide
Hydrogen cyanide is produced directly in the Andrussow process.
Like the SOHIO acrylonitrile process, the reaction is between gaseous
reactants. Waste materials include:
Solid waste; Essentially none, since the catalyst is of the platinum
group metals and is recovered.
Liquid wastes; Liquid wastes result from water used in the process.
Cyanide contaminants are in the form of hydrogen cyanide and salts in-
cluding cyanide in association with ammonia. These wastes would lend
well to the treatment techniques presented in Chapter VIII.
Gaseous wastes; Wastes in the gas form are essentially the same
as those from acrylonitrile production.
Sodium Cyanide by Neutralization
In the production of sodium cyanide, hydrogen cyanide (hydrocyanic
acid) is neutralized with caustic soda in aqueous solutions. Waste ma-
terials include:
Solid and gaseous; Essentially no solid or gaseous wastes are pro-
duced since a balance between caustic and hydrocyanic acid is required.
Liquid wastes; Liquid wastes from sodium cyanide production are
water solutions containing sodium cyanide. Treatment is necessary before
discharge. These water wastes are ideally suited for alkaline chlorina-
tion.
Iron Blue
Production of iron blue pigments produces much waste material, see
Figure 12, Chapter VI.
Solid waste; Sulfuric acid is used in the production of iron blue,
which is neutralized with hydrated lime. This not only precipitates as
calcium sulfate, but also causes complex iron cyanides and hydrated iron
oxides to precipitate. The result is a large quantity of solid residue
which may contain free cyanide impurities.
The literature indicates that this solid waste is disposed in land-
fill, both on and off the production site^-
175
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Liquid waste; Water is used for washing the iron blue pigments
and for carrying the excess sulfuric acid and iron salts in iron blue
production. Ammonium salts are contained in the water. Solids are pre-
cipitated as above and removed from solution. The water likely still
contains cyanide impurities which should be treated before discharge.
Gaseous waste; Almost no gaseous wastes are produced in iron
blue manufacture.
Sodium Ferrocyanide
Manufacture of sodium ferrocyanide produces much solid waste and
potentially toxic aqueous waste.
Solid waste; In the production of sodium ferrocyanide, solid wastes
include calcium sulfates, carbonates and hydroxides as well as complex
iron cyanides and hydrated oxides. Residual process water in the solid
wastes may also contain dissolved cyanide salts.
Liquid waste; Liquid wastes include the water used in the reaction
and water for washing. The water probably contains sodium and calcium
cyanides not reacted and not precipitated. Part of the water is recycled
to the production stream.
Gaseous waste; Essentially no gaseous waste results from sodium
ferrocyanide production.
Sodium Ferricyanide
Sodium ferricyanide is manufactured by chlorine oxidation of sodium
ferrocyanide. Wastes are:
Solid waste; Essentially no solid waste is produced.
Liquid waste; Liquid waste consists of process and wash water.
This water could contain small amounts of the ferricyanides and ferro-
cyanides as well as residual chlorine.
Gaseous waste; Waste material in the gaseous form consists mainly
of chlorine gas which can be recycled to the process.
In conclusion, two questions arise;
1. How effective is a flare in destroying residual HCN in vent gases
from acrylonitrile and hydrogen cyanide production?
176
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2. What is the fate of ferrocyanide, ferricyanide, iron blue,
and other complex iron cyanides in essentially anaerobic landfill con-
ditions?
MATERIAL BALANCE OF CYANIDE BY INDUSTRIAL SECTOR
Figure 28 presents a detailed material balance for the production
of HCN and other cyanides as NaCN equivalent. Of the estimated 375 mil-
lion pounds of HCN produced in 1975, 41.2 million pounds of HCN or 75
million pounds as NaCN equivalent entered the inorganic industrial sec-
tor. Net imports of various cyanides accounted for 15 million pounds of
NaCN equivalent.
The merchant sales sector accounts for approximately 53 million
pounds of NaCN and 27 million pounds of NaCN equivalent as ferro- and
ferricyanides, iron blue, calcium cyanide, and heavy.metal cyanides
distributed over seven categories. Table 73 indicates the estimated
contribution of each sector as NaCN or NaCN equivalent.
Figure 28 also presents disposal methods with prominent choices
underlined for each sector. The highly toxic cyanide ion is primarily
treated by alkaline chlorination. Other less toxic cyanides such as
ferrocyanide and iron blue are either disposed of in municipal sewers,
landfilled, or occur in runoff water.
Note that regeneration is prominent only in the photographic proces-
sing chemicals sector. The economics are favorable but it is estimated
that perhaps only 15 to 20% of the ferrocyanide is now being regenerated.
EXPOSURE TO MAN AND THE ENVIRONMENT
The inorganic cyanides are generally end-products for industrial
use. These cyanides, with the exception of iron blue pigments and photo-
graphic chemicals, do not reach the consumer market as cyanides. Each
industrial sector is discussed to present the magnitude of exposure.
Electroplating
Approximately 50 million pounds of NaCN equivalent are consumed
annually in electroplating, principally as sodium cyanide. It is esti-
mated that one-half of the cyanide consumption is due to oxidation by
electrolysis in the plating bath*!'
177
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jjj.o/vi I-U.IN ~89% 375
v wiyuiill — .,_
Sector
(41. 2M HCN)
75. OM NaCN
i
M '
M By-Product
*
=,„*
Inorganic Sector
KCN 2.2M Captive Uses i° 01.,.,
Ca(CN)2 7 7M •
9.9M
KCN
Ferrocyanides
Ferricyanides
Heavy Metal Cyanides >
Acrylonitrile Process 100M HCN
Incinerated 100M HCN
Imports as NaCN , KCN, ~\ Net Imports
Ferro- and Ferricyanides, 1 15. 1 M as
Iron Blue. Ca(CN)2 j NaCN
Exports as NaCN J Equivalent
Merchant Uses 1 80M as NaCN Equivalent
•4 * * r * * • *
Min!n Photographic Metal Heat Metal Pigments • Agricultural . Anticaking
in'n9 Chemicals Treatment Finishing Pest Control Agents
r I
Disposal
Disposal -S/, Tailing Pond
Meth°* Recycle
NaOH, CI2
Amount
Disposed
Annually
as NaCN fi 5
Equivalent
Million
Pounds
I
. ,
Disposal
Municipal Sewers
NaOH, CI2
H202
KMNO4
Regeneration
Sodium Persulfate
Ozone, UV
Electrolysis
2.5
1
Disposal
NaOH, CI2
Electrolysis
H202
Municipal Sewer
Landfill
4.5
i
Disposal
NaOH. CI2
Electrolysis
Ozone, UV
H202
Municipal
Sewer
50
\
Disposal k/
Landfill
. Municipal
Incineration
Weathering
Municipal
Sewer
13.5
\ .
Disposal
Air
Weathering
0.5
1
Disposal
Weathering
Runoff
2.5
2/ Major methods of disposal are underlined.
-2/ Including disposal methods for consumer products. .
Figure 28. Material balance for the production of HCN and other cyanides
as NaCN equivalent (million Ib)
-------
Table 73. NaCN and NaCN EQUIVALENT BY INDUSTRIAL SECTOR
NaCN NaCN equivalent
Industrial sector (million Ib) (million Ib) Total
Metal finishing 50
Plating, stripping 43
Heavy metal cyanides 7
Pigment 13.5
Iron blue 13.5
Mining - flotation 6.5
and extraction 5.3 1«2
Metal heat treatment 4.4 . 0.2 4.6
Photographic chemicals 2.5 2.5
Anti-caking agents 2.5 2.5
Agriculture and pest
control 0.5 0.5
Total 53 27 80
Source: MRI estimate
179
-------
Nearly 25 million pounds of the cyanide consumed is dragged out of
the plating bath into the rinse waters. Cyanides in the rinse water re-
quire treatment prior to discharge. Of very minor consequence are spills
and deliberate dumping of concentrated plating solutions. Provisions are
usually made in those events to add the spills to the rinse waters for
treatment.
It has been estimated that nearly all of the cyanide released is
treated by some means, usually alkaline chlorination. It is possible
that some small plating shops in large cities may not treat wastes and
may discharge directly to municipal sewer systems. This figure is esti-
mated at < 17o of total cyanide consumption in metal finishing.
The exposure of cyanides from electroplating is minimal both to
man and the environment due to general treatment of the wastes.
Pigments
Approximately 13.5 million pounds .(NaCN equivalent) of iron blue
pigments are consumed annually in the U.S. These pigments are components
in printing inks, carbon paper, typewriter ribbons and, to a much .smaller
extent, paints.
Nearly all of these 13.5 million pounds of iron blue pigments are
exposed to man and the environment. This exposure is extremely wide-
spread and any immediate adverse impacts more likely would be due to
solid waste disposal of the medium carrying the pigments than due to
the pigments. Also the toxicity of the iron blue pigments is extremely
low.
Not known are the long-term effects of iron blue pigments exposed
to the environment, particularly those disposed to landfills. The great-
est part of these pigments are disposed of in this manner.
The mining industry currently consumes approximately 6.5 million
pounds as NaCN equivalent annually. The cyanides are sodium cyanide,
sodium ferrocyanide and calcium cyanide. All of the total annual con-
sumption of these cyanides enter the environment, generally by way of
tailing ponds. The consequences of this exposure is minimized with man-
agement of the tailing ponds.
180
-------
Management of the tailing ponds include:
• Vegetation of the dam to prevent failure;
* Control of runoff water;
• Storage of water seepage through the dam in retention ponds;
• Adequate size for lengthy retention times;
• Recycle of water to the mill; and
• Dams constructed on relatively impermeable soil.
The cyanides are also subjected to natural degradation by sunlight,
air and biological processes. Free cyanide may become attached to min-
eral and carbonaceous solids present and settle out. In more arid cli-
mates evaporation will consume all excess water with no discharge from
the tailing pond.
Preliminary data soon to be published by Calspan Corporation indi-
cate that cyanide in tailing pond effluents from lead and zinc milling
operations is less than 0.01 mg/liter. Effluents from copper and copper-
molybdenum should be comparable and in many cases essentially zero, as
these operations are predominantly located in arid climates where evap-
oration from tailing ponds consumes all excess water.
There has been no reported leakage from gold and silver plant tail-
ing pondsJi' However, one major gold producer is reported not to use
tailing ponds, but direct discharge of excess mill water. No data were
found to indicate the amount of cyanide lost to the environment from
this producer.
In conclusion, it is estimated that less than 10% of the cyanides
used in mining escaped to the environment uncontrolled. However, the
cyanide contained in tailing ponds may be a potential hazard, especially
to wildlife.
Heat Treating;
In the metal heat treating industry, 4.5 million pounds of sodium
cyanide' are consumed annually. This consumption results from the fol-
lowing: (a) drag-out to the quenching medium; (b) high temperature
air oxidation at the surface of the bath; and (c) reaction to produce
the hard case on the parts.
181
-------
Of environmental concern is the drag-out to the quenching medium.
Nearly all of the cyanides are treated prior to disposal much the same
as in electroplating. In fact many of the captive heat treaters are
operated in conjunction with electroplating operations. Treated waters
in most cases are discharged to municipal sewers.
In summary, very little exposure to man and the environment occurs
due to treatment of cyanides from the metal heat treating industry.
Photographic Chemicals
Approximately 2.5 million pounds of cyanides as NaCN equivalent
are used in the photography industry annually, principally as ferri-
cyanides and ferrocyanides.
All of the 2.5 million pounds consumed annually are lost from the
photographic processes. Most of these cyanides are discharged to munic-
ipal sewer systems by continuous discharge of rinse water. The rinse
waters contain low concentrations of these cyanides (i.e., < 1 ppm con-
centration). Only very occasionally would concentrated baths be dumped
and then probably with large quantities of water as diluent.
The ferrocyanide and ferricyanide subjected to primary treatment
in municipal sewage plants would likely be separated with the solid
matter. The cyanides could be absorbed on the organic constituents or
complexed with metallic compounds.
The sewage sludge may be disposed by spreading on land, both agri-
cultural and nonagricultural. Consequently, the ferro- and ferricyanides
from photographic processes may be not only exposed to man and the en-... -
vironment, but also introduced to the food chain.
Anti-Caking Ingredient in De-icing Salts
Sodium ferrocyanide and iron blue are used as an anti-caking in-
gredient in salt used for thawing ice, mainly on roads. Approximately
2.5 million pounds as NaCN equivalent are used in this manner yearly.
All of this 2.5 million pounds is exposed to the environment and
subject to runoff from the roads. Through storm sewers the ferrocyanide
will ultimately reach waterways. There the environmental effects may be
the greatest, as ferrocyanide can decompose in sunlight to cyanide which
is toxic. The ferrocyanides themselves are low in toxicity.
182
-------
Agricultural and Pest Control
No hard data are to be found on the consumption of inorganic cya-
nides used for agricultural pest control of rodents and predators. The
estimate is perhaps 0.5 million pounds each year. Hydrogen cyanide is
still used in small amounts in fumigation of grain and seed in storage.
Sodium and calcium cyanide are used against rodents and sodium cyanide
may be used for predator control.
All of the cyanides used for pest control enter the environment.
Hydrogen cyanide used for control of rodents would likely be used in
remote areas such as garbage dumps and grain storage areas. The use of
sodium cyanide for control of predators, namely coyotes, would be lim-
ited to sparsely populated rangelands.
Tables 74 through 78 present a summary of the estimated amounts
of inorganic cyanides that entered the environment in 1965, 1970, 1975,
1980, and 1985. The tables are self-explanatory and indicate release
and exposure to the environment of cyanide (as ferrocyanide and iron
blue) for the years indicated. Essentially all the ferrocyanide from
de-icers is released in runoff water, and under the action of sunlight
cyanide ion may be released and subsequently oxidized to cyanate, which
is much less toxic than cyanide (by a factor of "*• 1,000). Iron blue en-
ters the local treatment system as solid waste and approximately 10%
is incinerated and decomposed. The remaining 90% becomes part of a land-
fill.
The decomposition kinetics of ferrocyanide due to normal weathering
in ditches by the highway and iron blue in landfill (presumably anaerobic
decomposition) are unknown. Tables 74 through 78 assume a relatively
slow decomposition rate of 570/year.
Figure 29 presents the estimated total amount of ferrocyanide and
iron blue as environmental burden over the years 1950 to 1985 and was
developed from data similar to those presented in Tables 74 through 78.
Five sets of exposure data are presented assuming degradation rates of
5, 10, 20, 50 and 100%/year. At a degradation rate of 100%/year, the
amount of cyanide burden becomes approximately one half the annual
usage rate or about 8 million pounds in 1975. At a degradation rate of
50%/year, the amount of cyanide burden becomes approximately 1.5 times
the annual usage rate or 24 million pounds in 1975.
183
-------
00
Table 74. ESTIMATED AMOUNT OF CYANIDE AS NaCN EQUIVALENT IN USE
AND EXPOSED TO THE ENVIRONMENT AND MAN, 1965-1985
(million Ib)
Industrial
sector
Metal finishing
Pigment
Mining
Metal heat
treatment
Photographic
processing
Ant i -caking
agents
Annual
consumption
44.0
12.3
5.0
4.3
4.2
2.5
Inventory
3.7
1.0
0.4
0.4
0.4
1.2
Reservoir
in use
220.0
12.3
0.5
21.5
4.2
1.2
Release and
exposure to
local
treatment
plant
11.0
12.3
0
2.2
4.2
0
Amount of cyanide
Release and in environment by
exposure to sector as ferro- and
environment f erricyanides
in 1965 1970
0 0
11.1 8.3
1.5 0
0 0
3.8 2.8
2.5 1.9
1975
0
5.5
0
0
1.9
1.2
1980
0
2.8
0 .
0
1.0
0.6
1985
0
0
0
0
0
0
Agriculture and 2.0 0.2 2.0 0 2.0 0 0 0 0
pest control _
Total 74.3 7.3 261.7 29.7 20.9 13.0 8.6 4.4 0
-------
oo
Table 75. ESTIMATED AMOUNT OF CYANIDE AS NaCN EQUIVALENT IN USE
AND EXPOSED TO THE ENVIRONMENT AND MAN, 1970-1985
(million Ib)
Industrial
Annual
sector consumption
Metal finishing
Pigment
Mining
Metal heat
treatment
Photographic
processing
Ant i -caking
agents
Agriculture and
pest control
Total
55
12
6
4
5
2
1
87
.0
.9
.6
.9
.0
.5
.0
.9
Inventory
4.
1.
0.
0.
0.
1.
0.
8.
6
1
6
4
4
2
1
4
Reservoir
in use
275
12
0
24
5
1
1
320
.0
.9
.7
.5
.0
.2
.0
.3
Release and
exposure to
local
treatment
plant
14.0
12.9
0
2.4
5.0
0
0
34.3
Amount of cyanide
Release and in environment by
exposure to sector as ferro- and
environment f erricyanides
in 1970 1975
0 0
11.6 8.7
1.6 0
0 0
4.5 3.4
2.5 1.9
1.0 0
21.2 14.0
1980
0
5.8
0
0
2.2
1.2
0
9.2
1985
0
2.
0
0
1.
0.
0
4.
9
1
6
6
-------
oo
Table 76. ESTIMATED AMOUNT OF CYANIDE AS NaCN EQUIVALENT IN USE
AND EXPOSED TO THE ENVIRONMENT AND MAN, 1975-1985
(million Ib)
Industrial
Annual
sector consumption Inventory
Metal finishing
Pigment
Mining
Metal heat
treatment
Photographic
processing
Ant i -caking
agents
Agriculture and
pest control
Total
50
13
6
4
2
2
0
80
.0
.5
.5
.5
.5
.5
.5
.0
4
1
0
0
0
1
< 0
7
.2
.1
.5
.4
.2
.2
.1
.7
Reservoir
in use
250
13
0
22
2
1
0
290
.0
.5
.5
.5
.5
.2
.5
.7
Release and
exposure to
local
treatment
plant
0.5
13.5
0
< 0.1
2.5
0
0
16.6
Amount of cyanide
Release and in environment by
exposure to sector as ferro- and
environment f erricyanides
in 1975
0
12.1
1.5
0
2.2
2.5
0.5
18.8
1980
0
9.1
0
0
1.6
1.9
0
12.6
1985
0
6.
0
0
1.
1.
0
8.
0
1
2
3
-------
oo
Table 77. ESTIMATED AMOUNT OF CYANIDE AS NaCN EQUIVALENT IN USE
AND EXPOSED TO THE.ENVIRONMENT AND MAN, 1980-1985
(million Ib)
Industrial
sector
Metal finishing
P igment
Mining
Metal heat
treatment
Photographic
processing
Ant i -caking
agents
Agriculture and
pest control
Total
Annual
consumption
43.8
16.2
6.5
3.4
1.2
2.5
0.1
73.7
Inventory
3.6
1.4
0.5
0.3
0.1
1.2
< 0.1
7.2
Reservoir
in use
219.0
16.2
0.6
17.0
1.2
1.2
0.1
255.3
Release and
exposure to
local
treatment
plant
0.4
16.2
0
< 0.1
1.2
0
0
17.9
Release and
exposure to
environment
in 1980
0
14.6
1.5
0
1.1
2.5
0.1
19.8
Amount of cyanide
in environment by
sector as ferro- and
f erricyanides
1985
0
11.0
0
0
0.8
1.9
0
13.7
-------
oo
oo
Table 78. ESTIMATED AMOUNT OF CYANIDE AS NaCN EQUIVALENT IN USE
AND EXPOSED TO THE ENVIRONMENT AND MAN IN 1985
(million Ib)
Industrial
sector
Metal finishing
Pigment
Mining
Metal heat
treatment
Photographic
processing
Anti- caking
agents .
Agriculture and
pest control
Total
Annual
consumption
37.5
18.4
6.5
2.2
1.0
2.5
0
68.1
Inventory
3.1
1.5
0.5.
0.2
0.1
1.2
0
6.6
Reservoir
in use
188.0
18.4
0.6
11.0
1.0
1.2
0
. .
220.2
Release and
exposure to
local
treatment
plant
0.4
18.4
1.5
< 0.1
1.0
2.5
0
23.9
Amount of cyanide
in environment by
sector as ferro- and
f erricyanides
1985
0
16.6
1.5
0
0.9
2.5
0
21.5
-------
40-
20
Annual 5%
Degradation Rate
10% Degradation Rate
20%
50%
100%
1950 1955 1960 1965 1970 1975
Year
1980 1985
Figure 29. Estimated total amount of ferrocyanide and iron blue
as environmental burden, 1950-1985
189
-------
Four important points are to be made in connection with estimating
future ferrocyanide and iron blue burden on the environment:
* Degradation rates of ferrocyanide in roadside ditches exposed
to normal sunlight and weathering conditions require quantifi-
cation.
*. Degradation rates of iron blue under anaerobic landfill conditions
require quantification.
* Cyanide burden as ferrocyanide from de-icers depends on usage
rates of the de-icers and the amount added per ton of salt.
* Cyanide burden as iron blue depends on the extent to which iron
blue remains an important pigment.
Quantitative information on residual ferrocyanide and iron blue en-
vironmental burden is totally lacking. Figure 29 is best interpreted as
a range of possible environmental burdens over the last 25 years with a
projection of declining total cyanide usage to 1985. A more meaningful
interpretation must await quantification of degradation rates of ferro-
cyanide and iron blue under various environmental conditions.
190
-------
REFERENCES TO CHAPTER X
1. Anonymous, Chemical Marketing Reporter, 20J5(12):9, March 25, 1974.
2. Anonymous, Hydrocarbon Processing, 52j(ll):99, November 1973.
3. Anonymous, Assessment of Industrial Hazardous Waste Practices, In-
organic Chemicals Industry, U.S. Environmental Protection Agency,
EPA No. 68-01-2246, National Technical Information Service,
Springfield, Virginia (1975).
4. Caporali, G., Hydrocarbon Processing, 51(11):144-146, November 1972.
5. Lancy, L. E., Lancy Laboratories Division, Dart Industries, Zelienople,
Pennsylvania.
6. Potter, G. M., U.S. Bureau of Mines, Salt Lake City, Utah, Letter
of August 27, 1975.
191
-------
APPENDIX A
THERMALLY GENERATED CYANIDE SOURCES
193
-------
Thermally generated cyanides may be taken as cyanides resulting
from high temperature reaction of carbon and nitrogen compounds in a
reducing atmosphere. These conditions are met most favorably in coking
operations, blast furnace production of iron and ferroalloys, and op-
erations producing ferroalloys other than by blast furnaces. Each of
these operations is discussed briefly below, with estimated quantities
of cyanides generated where data were available.
COKE PRODUCTION
In the production of coke, coal is externally heated at about
1100°C, in the absence of air (pyrolysis) for approximately 18 hr. In
the process, materials volatile at 1100°C are driven from the coal.
Two types of ovens are used in the U.S. to make coke: (a) by-
product ovens and (b) beehive ovens. The main distinction.between the
two is that with by-product ovens the volatile matter can be collected
and processed for recovery of the different chemical constituents. The
volatile gases are not collected, but allowed to escape to the atmos-
phere in coke production from beehive ovens. Beehive oven operation is
minor domestically, with only 1% of total coke production in 1972*1'
Table A-l details the number of each type of oven in operation in 1974t
The reactions in the oven producing hydrogen cyanide can probably
be attributed to one or more of the following:—
C H + 2NH > 2HCN'+ 3H
HCN + H2
HCN + 3tT
£,
2HCN + 4H2
CO + NH L HCN 4- HO
The carbon compounds and the ammonia are produced by the breakdown of
the coal.
194
-------
2/
Table A-l. COKE OVENS OPERATED IN THE UNITED STATES AS OF JANUARY 1, 1974-
Number of coke ovens
Company
Alan Wood Steel Company
Armco Steel Corporation
Bethlehem Steel Corporation
CF&I Steel Corporation
Crucible, Inc.
Cyclops Corporation
Empire Detroit Steel Division
Donner-Hanna Coke Corporation^
Ford Motor Company
Industrial Products Group
Woodward Iron Division
Chattanooga Division
Total Industrial Products Group
Inland Steel Company
Interlake, Inc.
International Harvester Company
Wisconsin Steel Division
Jones & Laughlln Steel Corporation
Kaiser Steel Corporation
Lone Star Steel Corporation
National Steel Corporation
Granite City Steel Division
Great Lakes Steel Corporation
Weirton Steel Division
Total National Steel
Republic Steel Corporation
Sharon Steel Corporation
Carpentertown Coal and Coke Company
Total Sharon Steel
Shenango, Inc.
United States Pipe and Foundry Company
United States Steel Corporation
Eastern Steel Division
Central Steel Division
Western Steel Division
Southern Steel Division
Total U.S. Steel
Wheeling-Pittsburgh Steel Corporation
Youngstown Sheet and Tube Company
Grand Total
Beehive By-product
110
248
2,103
216
113
70 .
151
205
256
_J^ _44
300
579
215
112
586
315
78
137
233
^_ '381
751
897
60
266 -
266 60
105
240
1,962
804
. - 252
489
3,507
407
- 549
266 11,917
Total
110
248
2,103
216
113
70
151
205
256
44
300
579
215
112
586
315
78
137
233
381
751 '
897
60
266
326
105
240
1,962
804
252
489
3,507
407
_549
12,183
j/ Owned jointly by the Hanna Furnace Corporation and Republic Steel Corporation.
195
-------
The literature indicates that approximately 0.7 Ib of hydrogen
cyanide is produced for each ton of coal coked,»a' Table A-2 details
the coal consumption for coking and the estimated production of hydro-
gen cyanide for the years 1965, 1970, and 1974.
Table A-2. COAL CONSUMPTION FOR COKING AND CALCULATED HYDROGEN
CYANIDE PRODUCTION
Coal consumed Calculated hydrogen
for coking cyanide produced from
Year (tons) Reference coking (pounds)
1965 95.3 x 106 5 66 x 106
1970 96.5 x 106 6 68 x 10&
1974 89.4 x 106£/ 7 63 x 106
a/ Estimated coal consumed =
61.5 x 106 tons coke
0.69 tons coke b/
1 ton coal
b/ Reference 8.
The hydrogen cyanide produced in coking is ultimately lost or con-
sumed by the following: (a) burned as coke oven gas; (b) lost to waste-
water;—' or (c) lost to the air through cooling towers*!' The amount of
hydrogen cyanide burned as a constituent of coke oven gas may approach
80% of the hydrogen cyanide produced in by-product oven coking opera-
tions. The coke oven gas is burned not only to heat the coke ovens, but
also to preheat air consumed in blast furnaces.
80 x 106 ft3 oven gas x 800 ft-* HCN x. 27 g HCN x
7,500 tons of coal coked 1 x 106 ft3 oven gas 22.4 liters HCN
28.3 liters 1 Ib HCN n ... ., „ _ , ' , .
. f 3 x ' = 0.64 Ib HCN per ton of coal coked
a/ Calculated hydrogen cyanide production from coal coking Jt' Possi-
bly some (~ 10%) of the hydrogen cyanide may have been lost in
the process of recovering by-product chemicals (i.e., difference
between 0.7 and 0.64 Ib HCN per ton of coal coked).
196
-------
In a recent study by the EPA the water effluents from by-product
coke oven installations were analyzed for cyanides .is' The average water
effluent cyanide load was 0.128 Ib of hydrogen cyanide per ton of coke
produced. This would be equivalent to a total of about 8 million pounds
of hydrogen cyanide in water effluents annually for the coking industry,
assuming these ovens are typical. Based on the estimated total hydrogen
cyanide produced by coking operations in 1974, Table A-2, the hydrogen
cyanide in water effluents would constitute about 13% of the total hy-
drogen cyanide produced by coking.
In the past at least one coke producer, Pittsburgh Coke and Chemi-
cal, recovered hydrogen cyanide for sale»=/ No coke producer is now
known to recover hydrogen cyanide for sale, probably because of the
low value of hydrogen cyanide compared to the difficulties of handling
it.
BLAST FURNACE PRODUCTION OF IRON AND FERROALLOYS
Another source of thermally generated cyanides is blast furnace
production of pig iron from iron ores. Other metals and ferroalloys
can be produced in blast furnaces, but the blast furnace is most asso-
ciated with iron production. The processes are essentially the same
and discussion of pig iron production below can be assumed to apply
generally to the other metals and alloys produced in blast furnaces.
In the operation of a blast furnace producing pig iron, iron ore,
coke and limestone are charged to the furnace. Hot air is then forced
through the charge and the ore is reduced to iron metal by carbon mon-
oxide and hydrogen produced by the reaction of hot air with the coke.
Two essential materials in blast furnaces are coke and hot air.
The air can be heated using excess coke oven gas not consumed to heat
the coke ovens. For these reasons, most coking operations are located
adjacent to the blast furnaces and operated by the same company. Ap-
proximately 90% of the coke ovens operated in 1974 were integrated
furnace installationsJLJ
Some of the reactions involving coke in the blast furnace are:—
C + H20 ^ CO + H2
FeO + C ^ Fe + CO
197
-------
10/
Reactions producing iron metal from the ore include:—
Fe 0 + 3CO > 2Fe + 3CO
Fe00, + 4CO
34
FeO + CO
Fe 0 + 3H
^ J
Fe 0 + 4H > 3Fe + 4H 0
FeO + H -> Fe + HO
The reduction of the iron ore consumes about 50% of the carbon
monoxide and hydrogen produced. The remaining 50% can be used for
heating in other parts of the steel plant .i2' The blast furnace gases
may be burned to supply power for the air compressors supplying the
blast furnace or to heat this very same air.—
Hydrogen cyanide is produced by the high temperature reaction of
coke, nitrogen and water, the nitrogen being introduced in the air or
in the coke.
Water effluents from four blast furnaces producing pig iron were
sampled and analyzed.— The average effluent water load was 0.03 Ib
of hydrogen cyanide per ton of pig iron produced. The 1972 production
of pig iron was nearly 89 million tons.^ Assuming that the four blast
furnace installations sampled represent an average, the total hydrogen
cyanide in water effluents from blast furnace operation domestically
would be about 3 million pounds in 1972.
No data were found indicating the magnitude of total hydrogen cya-
nide produced in blast furnace operation.
The final disposal or loss of hydrogen cyanide from blast furnaces
may parallel that produced in coke ovens in that the greater portion of
hydrogen cyanide is probably burned. Losses of hydrogen cyanide occur
to effluent water and to air.
PRODUCTION OF FERROALLOYS OTHER THAN BY BLAST FURNACE
Production of ferroalloys by means other than by blast furnace
generally includes production with electric furnaces or exothermic
heat processes.— The differences are essentially the sources of heat.
In many of these processes, coke and air are used as the reducing ma-
terials, much the same as with the blast furnaces.
198
-------
Listed in Table A-3 are ferroalloy producers, locations, products
and types of furnaces• Listed in Table A-4 are selected ferroalloy pro-
duction for the years 1965, 1969, and 1972.
No data were found detailing the amount of hydrogen cyanide result-
ing from the ferroalloy industry.
Loss of hydrogen cyanide generated in ferroalloy production gener-
ally would be to (a) process water and to (b) air. In the electric fur-
naces operated with an open top, the gases evolved, including hydrogen
cyanide, may burn at the surface of the melt. The loss to process water
would be in operations where water is used to scrub the gases.
199
-------
Table A-3. PRODUCERS, LOCATIONS, PRODUCTS, AND FURNACE TYPE FOR FERROALLOY, 1972±!/
Product
Agrico Chemical Company
Atrco Alloys and Carbide
Alabama Metallurgical Corporation
Bethlehem Steel Corporation
Chromium Mining and Smelting Company
Climax Molybdenum Company
Diamond Shamrock Corporation
PMC Corporation
Foote Mineral Company
Kanna Furnace Corporation
Kanna Nickel Smelting Company
Hooker Chemical Corporation
Interlake Steel Corporation
Kawecki Chemical Company
Mobil Chemical Company
Molybdenum Corporation of America
Monsanto Chemical Company
N L Industries, Inc.
New Jersey Zinc Company
Ohio Ferro-Alloys Corporation
Reading Alloys
Shieldalloy Corporation
Stauffer Chemical Company
Tennessee Alloys Corporation
Tenn-Tex Alloy Chemical Corporation
of Houston
Union Carbide Corporation
U.S. Steel Corporation
Woodward Iron Company
Plant location
Pierce, Florida
Calvert City, Kentucky
Charleston, South Carolina
Mobile,. Alabama
Niagra Falls, New York
Selma, Alabama
Johnstown, Pennsylvania
Woodstock, Tennessee
Langeloth, Pennsylvania
Kingwood, West Virginia
Pocatello, Idaho
Cambridge, Ohio
Graham, West Virginia
Keokuk, Iowa
Vaneoram, Ohio
Wenatchee, Washington
Buffalo, New York
Riddle, Oregon
Columbia, Tennessee
Beverly, Ohio
Easton, Pennsylvania
Nichols, Florida
Washington, Pennsylvania
Columbia, Tennessee
Soda Springs, Idaho •
Niagra Falls, New York
Palmerton, Pennsylvania
Brilliant, Ohio
Philo, Ohio
Powhatan, Ohio
Tacoma, Washington
Robesonia, Pennsylvania
Newfield, New Jersey
Tarpon Springs, Florida
Mt. Pleasant, Tennessee
.Silver Bow, Montanta
Bridgeport, Alabama
Kimball, Tennessee
Houston, Texas
Alloy, West Virginia
Ashtabula, Ohio
Marietta, Ohio
Niagra Falls, New York
Portland, Oregon
Sheffield, Alabama
Clairton, Pennsylvania
McKeesport, Pennsylvania
Woodward, Alabama
Rockwood, Tennessee
Product^
FeP
FeCr, FeCrSi, FeMn, FeSi, SiMn
FeSi
FeMn
FeMn, SiMn, FeCr, FeSi, FeCrSi
FeMo
FeMn
FeP
FeB, FeCb, FeTi, FeV, FeCr,
FeCrSi, FeSi, silvery iron,
otherk/
Silvery iron
FeNi
FeP
FeCr, FeCrSi, FeSi, SiMn •
FeCb
FeP
FeMo, FeW, FeCb, FeB
FeP •
FeTi, otherk/
Spin
FeCr, FeSi, FeB, FeMn, SiMn,
otherk/
FeCb, FeV
FeV. FeTi, FeB, FeCb, NiCb,
CrMo, otherk'
FeP
FeSi
FeMn, SiMn
FeB, FeCr, FeCrSi, FeCb, FeSi,
FeMn, FeTi, FeW, FeV, SiMn,
otherk/
FeMn
FeSi, FeMn, SiMn
Type of furnace
Electric
Electric
Electric
Blast
Electric
Aluminothermic
Electric
Electric
Electric
• Blast
Electric
Electric
Electric
Aluminothermic
Electric
Electric and oluminothcrmic
Electric
Electric
Electric
Electric
Aluminothermic
Aluminothermic
Electric
Electric
Electric
Electric
Blast
Electric
CrMo.- Chromium molybdenum
FeMn - Ferromanganese
Spin - Splegeleisen
SiMn - Silicomanganese
FeSi - Ferrosilicon
FeP - Ferrophosphorus
FeCr - Ferrochromium
FeMo - Ferromolybdenum
FeNi - Ferronickel
FeTi - Ferrotitanium
FeW - Ferrotungsten
FeV - Ferrovanadium
FeB - Ferroboron
FeCb - Ferrocolumbium
NiCb - Nickel columbium
Si - Silicon metal
FeCrSi - Ferrochromiumsilicon
t>/ Includes Alsimer, Siraanal, zirconium alloys, ferrosilicon, boron, aluminum silicon alloys and miscellaneous ferroalloys.
200
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Table A-4. TOTAL FERROALLOY PRODUCTION (ALL TYPES)
Production
Year (tons) Reference
1965 2.8 x 106 16
1969 2.6 x 106 17
1972 2.5 x 106 15
201
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REFERENCES TO APPENDIX A
1. Sheridan, E. T., "Coke and Coal Chemicals," in Minerals Yearbook,
1972, Vol. I, Minerals, Metals and Fuels, Bureau of Mines, U.S.
Department of the Interior, U.S. Government Printing Office,
Washington, D.C. (1974).
2. Benzer, W. C., American Iron and Steel Institute, Private communi-
cation to R. R. Wilkinson (letter), October 1, 1975.
3. Kastens, M. L., and R. Barraclough, "Cyanides from the Coke Oven,"
in Industrial and Engineering Chemistry, 43J9):1882-1892,
September 1951.
4. Manka, D. P., "Coke Oven Gas Analysis . . . Monitoring Sulfur and
Cyanide," in Instrumentation Technology, 22(2):45-49, February
1975.
5. DeCarlo, J. A., and E. T. Sheridan, "Coke and Coal Chemicals," in
Minerals Yearbook, 1965. Vol. II, Mineral Fuels, Bureau of Mines,
U.S. Department of the Interior, U.S. Government Printing Office,
Washington, D.C., p. 202 (1967).
6. Sheridan, E. T., "Coke and Coal Chemicals," in Minerals Yearbook,
1970, Vol. I. Minerals. Metals and Fuels, Bureau of Mines, U.S.
Department of the Interior, U.S. Government Printing Office,
Washington, D.C. (1972).
7. Ferguson, J. P., American Coke and Coal Institute, Private communi-
cation to R. Clifford, Consultant (letter), September 26, 1975.
8. Sheridan, E. T., "Coke and Coal Chemicals," in Minerals Yearbook,
1972, Vol. I, Minerals, Metals and Fuels, Bureau of Mines, U.S.
Department of the Interior, U.S. Government Printing Office,
Washington, D.C., p. 437 (1974).
9. Monroe, S. G., A Study of the Characteristics of Liquid Wastes From
a By-Product Coke Plant May 14 to June 21, 1950, Federal Security
Agency, Public Health Service, Environmental Health Center,
Cincinnati, Ohio (1950).
202
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10. Knepper, W. A., "Iron," in Kirk-Othmer Encyclopedia of Chemical Tech-
nology, Vol. XII, 2nd completely revised edition, Interscience
Publishers, Division of John Wiley and Sons, Inc., New York, New
York, pp. 11-17 (1969).
11. Williams, R» E., "Iron and Steel Industry and Coke Manufacturing,"
in Waste Production and Disposal in Mining. Milling and Metallur-
gical Industries, Miller Freeman Publications, Inc., San Francisco,
California, pp. 178-235 (1975).
12. Dulaney, E» L», Development Document for Proposed Effluent Limita-
tions, Guidelines and New Source Performance Standards for the
Steel Making Segment of the Iron and Steel Manufacturing Point
Source Category.U.S. Environmental Protection Agency, EPA 440/ '
1-73/024, Washington, D.C. (1974).
13. Brantley, F. E., "Iron and Steel," in Minerals Yearbook. 1972, Min-
erals, Metals and Fuels, Bureau of Mines, U.S. Department of the
Interior, U.S. Government Printing Office, Washington, D.C. (1974).
14. Diercks, P. W., Development Document for Proposed Effluent Limita-
tions. Guidelines and New Source Performance Standards for the
Smelting and Slag Processing Segment of the Ferroalloy Manufac-
turing Point Source Category. U.S. Environmental Protection Ag-
ency, EPA 440/1-73/008, Washington, D.C. (1973).
15. Matthews, N. A., "Ferroalloys," in Minerals Yearbook. 1972, Vol.
I, Minerals, Metals and Fuels, Bureau of Mines, U.S. Department
of the Interior, U.S. Government Printing Office, Washington, D.C.,
pp. 525-533 (1974).
16. Thatcher, J. W., "Ferroalloys," in Minerals Yearbook, 1965, Vol.
I, Minerals and Metals, Bureau of Mines, U.S. Department of the
Interior, U.S. Government Printing Office, Washington, D.C. pp.
401-412 (1966).
17. Reno, H. T., "Ferroalloys," in Minerals Yearbook, 1969, Vol. I-II.
Minerals, Metals and Fuels, Bureau of Mines, U.S. Department of
the Interior, U.S. Government Printing Office, Washington, D.C.,
pp. 495-503 (1971).
203
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APPENDIX B
RESULTS OF THE WRITTEN QUESTIONNAIRE
204
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MRI developed a four-page questionnaire for use in gathering in-
formation from the seven producers of hydrogen cyanide. The question-
naire requested information on production, capacity, manufacturing and
waste treatment methodologies of cyanides in all physical forms and as
a constituent of any type of processed material. Copies of the ques-
tionnaire and an accompanying explanatory cover letter were sent to the
corporate offices of the following companies:
* American Cyanamid Company
* Dow Chemical Company
* E. I. du Pont de Nemours and Company, Inc.
* Hercules, Inc.
* Monsanto Company
* Rohm and Haas Chemical Company
* Vistron Corporation, Division of Standard Oil of Ohio
A sample copy of the entire questionnaire, including the cover
letter, follows.
205
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Midwest Research Institute is presently conducting a program for
the Office of Toxic Substances of the U.S. Environmental Protection
Agency under Contract No. 68-01-2687. The primary purpose of this pro-
gram is to compile information on the production, formulation, use,
and treatment of inorganic cyanides and to evaluate the extent that
they are released into the environment.
The following inorganic cyanides have been identified as being
pertinent to this study:
HCN, hydrogen cyanide Ferrocyanides
NaCN, sodium cyanide Ferricyanides
KCN, potassium cyanide Heavy metal cyanides
CaCCtOo, calcium cyanide Iron blue
The MRI study is based on information in the chemical literature
and private communications with industry personnel, via telephone,
letters, questionnaires and personal interviews. In order to obtain a
statistically reliable overview of the industrial situation on the
subject, it is important that we contact as many industries as possible.
We, therefore, respectfully solicit your cooperation in completing this
questionnaire; your early response (within 4 weeks) will be sincerely
appreciated.
In responding to this request, we do not seek information of a
proprietary nature. The results of the study will be developed in
terms of industrywide practices and trends.
If your department cannot supply the requested information, please
forward this questionnaire to other departments which can respond. If
any questions should arise concerning this questionnaire, please contact
Dr. Ralph Wilkinson at (816) 561-0202.
Please return the completed questionnaire to:
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
Attn: Ralph Wilkinson
Your cooperation in this matter will be appreciated.
206
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QUESTIONNAIRE PREPARED FOR OFFICE OF TOXIC SUBSTANCES
U.S. ENVIRONMENTAL PROTECTION AGENCY
(Please fill in the details and check the appropriate blanks.)
1. Parent Corporation Name:
Mailing Address:
2. Person to contact regarding information supplied in questionnaire.
Dr/Mr/Ms: •
Address:
Telephone:
3. If your company manufactures, or has manufactured within the past 10
years, any of the chemicals listed in the cover letter please com-
plete the following form:
Listed
Chemical Production Site: City or Town and State
a. •
b.
C. ;
d.
e.
f.
207
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4. What are the sources of each cyanide-material and the approximate
annual consumption?
Approx. Annual
Cyanide-Material Source Consumption
a. , .
b.
c.
d.
e.
f.
5. To the extent possible, within the constraints of proprietary consid-
erations for each product or formulation identified in Item 3, please
describe briefly the usage process.
Usage Process Description (e.g., Approximate
major reactions carried out or Annual Process
Cyanide-Material U.S. Patent Number) Usage
208
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6. Has any chemical analysis ever been made on any of your by-products
or waste material from the use-process(es) to determine the presence
of cyanides?
In by-products? Yes ' No
In process waste material? Yes No
7. For each "yes" answer to any category in Question 6, please identify
the cyandide(s) by name(s) and form(s) (i.e., solid, liquid or gas).
Also, please indicate the plant location(s) for each.*
Compound(s) Form(s) Plant Location(s)
* If additional space is required, please use the back of this sheet.
For each cyanide-material listed in Question 7, please indicate the
approximate concentration level of each compound(s) prior to and
after waste chemical treatment and where the material appears (i.e.,
by-product, or process waste material). If any compound appears in
two or more instances, please distinguish between the entries.
Concentration Concentration
Level Prior Level After
Compound(s) Where Material Occurs to Treatment Treatment
209
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9. Please provide a chronological description of your cyanide waste
disposal and treatment facilities during the last 10 years. This
should include liquid effluents, solid wastes and, if applicable,
contract disposal services.
210
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A discussion and summary.of the replies to this written inquiry
are presented in the following paragraphs.
1. American Cyanamid Company; Hydrogen cyanide and sodium fer-
rocyanide are produced at South Kenner, Louisiana. Hydrogen cyanide
was produced by the Andrussow process from 1954 to 1966. After 1966,
hydrogen cyanide was obtained as by-product from the SOHIO-acrylonitrile
process. Ferrocyanide has been produced since 1971 by reaction of so-
dium cyanide and ferrous chloride. Plant capacity was not given. Current
annual production of hydrogen cyanide is 22 million pounds and that of
sodium ferrocyanide is 10 million pounds. Both products are for captive
consumption.
Wastes include hydrogen cyanide in vent gases, salts of hydrogen
cyanide, metal cyanide complexes and organic cyanides (cyanohydrins)
as solutions or solids.
Waste treatment and handling methodologies include alkaline chlori-
nation in a recycle lagoon system, incineration, and an increasing re-
liance on disposal wells.
A second cyanide facility that American Cyanamid operates is lo-
cated at Willow Island, West Virginia, where iron blue has been manufac-
tured since 1964. Iron blue is prepared by combining sodium ferrocyanide,
ferrous sulfate, and ammonium sulfate under oxidizing conditions. Plant
capacity was not given. Production of iron blue averaged 8 million pounds
annually over the last 10 years.
The previous comments on cyanide wastes and treatment methodologies
also apply in the West Virginia location.
2. Dow Chemical Company; Hydrogen cyanide has been manufactured
at Freeport, Texas, since 1958 by the Andrussow process and is captively
consumed. Current capacity and production data were not given.
According to Dow Chemical Company, the hydrogen cyanide is produced
as a transitory intermediate and is present for only a few seconds. It
is neither processed, purified, nor sold. The primary use of hydrogen
cyanide appears to be in the synthesis of chelating agents, e.g., NTA
and EDTA.
No detailed discussion of cyanide wastes nor treatment methodologies
was given. In-process control results in an effluent that contains
< 0.2 mg/liter cyanide.
211
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3. E. I. du Pont de Nemours and Company, Inc.; Hydrogen cyanide
has been manufactured by the Andrussow process at Memphis, Tennessee,
since 1952. The material is used captively for the production of acetone
cyanohydrin and liquid HCN is available for merchant sales. Other pri-
mary and captive production facilities are located at LaPlace, Louisiana,
and Victoria, Texas, but details are lacking. Adiponitrile synthesis
appears to be the major use of hydrogen cyanide at these two locations.
Hydrogen cyanide has also been manufactured as by-product from
acrylonitrile at Beaumont, Texas, since 1970 and at Memphis, Tennessee.
Again, details are lacking as to capacity and production levels. Hydro-
gen cyanide is used to manufacture butyronitrile derivatives at the
Beaumont facility and sodium and potassium cyanide at the Memphis fa-
cility.
Waste cyanides occur in all manufacturing operations, principally
as rinse waters, gases and solutions. Various waste treatment techniques
reduce the cyanide level to < 0.2 mg/liter.
Liquid waste treatment methodologies include:
* Alkaline chlorination (1952 to date).
*• Incineration, including flaring for gaseous effluents
(1966 to date).
* Barging to the Gulf of Mexico (1969 to 1970).
* Alkaline hydrolysis (Kastone process) (1973 to date).
Solid waste treatment methdologies include:
* Landfill on site (some of the'waste receives alkaline
hydrolysis prior to land fill operation) (1955 to date).
* Burial of spent radioactive catalyst containing trace
cyanide residues at approved Atomic Energy Commission
site (1968 to 1973).
Du Pont also has facility at Niagara Falls, New York, where heavy
metal cyanides have been manufactured since 1912. The cyanides include
those of copper, zinc, and double-salts as sodium-copper cyanide and
potassium-copper cyanide. Capacity and production data are lacking.
These materials are generally made by simple replacement reactions
involving sodium or potassium cyanide and the appropriate metal salt
as chloride or sulfate.
212
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Wastes include solutions containing traces of soluble cyanides and
cyanogen gas. Some solid zinc cyanide may occur as waste material.
Cyanide wastes are currently and have historically been mixed in
the plant process sanitary sewer with large excesses of calcium hypo-
chlorite before discharge to the City of Niagara Falls Treatment Plant.
The Du Pont plant anticipates operation of a pretreatment facility to
handle all plant wastes by December 1976. When operational, the con-
centration of oxidizable cyanide in the total plant waste will be < 0.1
mg/liter prior to release to the City of Niagara Waste Treatment Plant.
4. Monsanto Company; Hydrogen cyanide is produced captively at
Texas City (primary) and Alvin, Texas (by-product). Both the Andrussow
and acrylonitrile processes are operational. The hydrogen cyanide is
produced for the manufacture of NTA, £-butylamine, and lactonitrile.
Capacity and production levels of all of these chemicals are lacking.
Hydrogen cyanide appears in waste streams, and after chlorination,
the cyanide level is reduced to < 0.1 mg/liter.
Waste treatment methodologies include alkaline chlorination with
chlorine gas (until 1974) and more recently, alkaline chlorination
using a sodium hypochlorite generator.
5. Vistron Corporation; Hydrogen cyanide has been produced for
merchant sales as by-product from the SOHIO-acrylonitrile process at
Lima, Ohio, since 1962. Annual production is about 29 million pounds.
Hydrogen cyanide, ferro-ferricyanides, and cyanohydrins are present
in waste gases and process water. Cyanide waste levels in process
effluents are < 0.02 mg/liter after treatment and before release to a
nearby river. Some liquid wastes are handled by deep well injection
and bio-oxidation systems. Gaseous effluents containing hydrogen cy-
anide are incinerated.
Hercules, Inc., of Glens Falls, New York, and Rohm and Haas of
Deer Park, Texas, declined to participate in the written questionnaire.
Each stated that technical and manufacturing information regarding
hydrogen cyanide and other cyanides had been released to the appropriate
EPA Regional Offices.
213
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BIBLIOGRAPHIC DATA
SHEET
1. Report No.
EPA 560/6-76-012
3. Recipient's Accession No.
I. Title and Subtitle
The Manufacture and Use of Selected Inorganic Cyanides
5. Report Date
April 2. 1976
6.
7. Auihor(s)
Ralph R. Wilkinson and Gary R. Cooper
8. Performing Organization Kept.
No.
9. Performing Organization Name and Address
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
10. Project/Task/Work Unit No.
Task III
11. Contract/Grant No.
Contract No. 68-01-2687
12. Sponsoring Organization Name and Address
Environmental Protection Agency
Office of Toxic Substances
Washington, D.C. 20460
13. Type of Report & Period
Covered
Final Report
14.
15. Supplementary Notes
16. Abstracts
The purposes of the study were to identify the production methods, importation,
exportation, use patterns, and exposure to man and the environment of selected inor-
ganic cyanides, including hydrogen cyanide, from 1965 to 1975. Data for the produc-
tion methods included the specific process, raw materials, annual production quanti-
ties, major manufacturers, waste products, environmental management of process wastes,
and other production data. Use patterns were identified and annual consumption data
were compiled for each compound in the respective area of utilization. Major con-
sumers in each use area were identified. Various possible methods for the exposure of
man and the environment to inorganic cyanides were discussed and evaluated. Future
production quantities and areas of usage were estimated to 1985.
17. Key Words and Document Analysis. 17a. Descriptors
Beneficiation
Cyanide hardening
Cyanides
Cyaniding (beneficiation)
Consumption
Deicers
17b. Identifiers/Open-Ended Terms
Environmental burden
Economic factors
Electroplating
Fumigation
Heat treatment
Metal finishing
Pest Control
Pigments
Photographic processing chemicals
Production methods
Utilization
Waste treatment
I7c. COSATI Field/Group Chemistry/Inorganic Cyanides
18. Availability Statement
Release Unlimited
19..Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This
Page
UNCLASSIFIED
21. No. of Pages
22. Price
FORM NTis-38 (REV. 10-73) ENDORSED BY ANSI AND UNESCO.
THIS FORM MAY BE REPRODUCED
USCOMM-DC S28S-P74
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