Environmental Protection Technology Series
REMOVAL OF HEAVY METALS
FROM INDUSTRIAL WASTEWATERS
USING INSOLUBLE STARCH XANTHATE
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-085
May 1978
REMOVAL OF HEAVY METALS FROM INDUSTRIAL WASTEWATERS
USING INSOLUBLE STARCH XANTHATE
by
Robert E. Wing, Leo L. Navickis,
Brian K. Jasberg, and Warren E. Rayford
Northern Regional Research Center
Agriculture Research Service
U.S. Department of Agriculture
Peoria, Illinois 61604
Interagency Agreement No. EPA-IAG-D5-0714
Project Officer
Hugh B. Durham
Industrial Pollution Control Division
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory-Cincinnati, U.S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection Agency,
nor does the mention of trade names or commercial products constitute en-
dorsement or recommendation for use.
11
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FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on our
health often require that new and increasingly more efficient pollution con-
trol methods be used. The Industrial Environmental Research Laboratory -
Cincinnati (lERL-Ci) assists in developing and demonstrating new and improved
methodologies that will meet these needs both efficiently and economically.
This report describes the preparation of an agriculturally based material
and its use in heavy metal cation removal from industrial wastewaters.
Insoluble starch xanthate (ISX) was prepared and evaluated in wastewaters from
printed circuit industries, lead battery companies, and a brass mill. Data
show that ISX offers most industries having heavy metal pollution problems a
material that effectively binds heavy metals and reduces their concentrations
to below strict discharge limits.
The Industrial Pollution Control Division should be contacted for further
information on this subject
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
111
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ABSTRACT
This report presents data that show insoluble starch xanthate (ISX) to
be an effective scavenger for heavy metal ions in selected industrial efflu-
ents. Experimental procedures are presented to show the ease of preparation
of ISX and its effectiveness in metal removal.
Results from bench-scale experiments utilizing ISX are given for (a)
copper removal from a brass mill wastewater, (b) lead removal from lead bat-
tery effluents, and (c) copper removal from circuit board copper etchant
rinse waters.
Two separate processes were developed for copper removal from electro-
less copper plating rinse waters and copper pyrophosphate electroplating
rinse waters. Evaluations of these processes are reported.
This report was submitted in fulfillment of Interagency Agreement
No. EPA-IAG-D5-0714 by Northern Regional Research Center under the sponsor-
ship of the U.S. Environmental Protection Agency. This report covers the
period July 1, 1975 to June 30, 1976, and work was completed October 1, 1976.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vii
Acknowledgment x
1. Introduction 1
Insoluble starch xanthate ................. 1
Brass mill wastewater 1
Lead battery effluents 2
Circuit board rinse waters 3
2. Conclusions 8
3. Recommendations 9
4. Experimental Procedures 10
Insoluble starch xanthate 10
Brass mill wastewater 13
Lead battery effluents 18
Circuit board rinse waters 20
5. Results and Discussion 23
Insoluble starch xanthate 23
Brass mill wastewater . 41
Lead battery effluents . 56
Circuit board rinse waters 70
References 101
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FIGURES
Number Page
1 Structures of electroless copper complexing agents 4
2 Brass mill treatment facility 16
3 %S vs CS~ charged in the xanthation of crosslinked starch 25
2+
4 Mount of magnesium ion (Mjg ) required for optimum ISX
filtration rate 27
5 ISX stability - copper removal 28
6 Particle size distribution of ISX 33
7 Treatment of synthetic copper solutions with ISX only 43
8 Treatment of synthetic copper solutions with ISX and Al + 45
9 Treatment of synthetic copper solutions with Al and ISX
(I copper removal) 46
10 Treatment of synthetic copper solutions with Al and ISX 47
11 Laboratory batch centrifuging of brass mill wastewater
with ISX only 49
12 Treatment of brass mill wastewater with ISX only 57
13 Treatment of brass mill wastewater with Al * only
(no pH readjustment) 58
14 Treatment of brass mill wastewater with Al only
(pH readjustment) 59
15 Treatment of brass mill wastewater with Fe only 60
16 Treatment of brass mill wastewater with Al^+ , TOV
and ISX 61
17 Treatment of brass mill wastewater with Al + and ISX
(no pH readjustment) 62
18 On site jar tests at brass mill 63
19 Copper removal from copper pyrophosphate with calcium ion vs
increasing orthophosphate concentration 96
20 Copper ammonia complex removal with ISX 100
VI
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TABLES
Number Page
1 Typical Copper Pyrophosphate Bath Composition 6
2 Synthetic Electroless Copper Bath Composition 21
3 Preparation and Analysis of Insoluble Starch Xanthate 26
4 ISX Preparations Using Additional Cake Wash Water 30
5 ISX Preparations Using Additional Magnesium Sulfate
in Cake Wash Water 30
6 Reuse of Mother Liquor in the Xanthation of Crosslinked
Starch 31
7 Solubility Product Constants for Metal Ethyl Xanthates 34
8 Removal of Heavy Metal Cations from Water with ISX 35
9 Removal of Metals from Dilute Solution with ISX 36
10 Heavy Metal Removal from 95 Liters of Water 37
11 Treatment of Industrial Effluents with ISX 38
12 Effect of Stirring Time on Copper Removal with ISX 39
13 Effect of Copper Removal with ISX in the Presence of
Sodium Chloride 39
14 Effect of Copper Concentration on Copper Removal with ISX 40
15 Copper-ISX Sludge Dewatering 40
16 Gold Removal with ISX 41
17 Nitric Acid (4N) Treatment of ISX Products 42
18 Copper Removal by Centrifugation from Synthetic Copper
Solutions Comparing Several Additives 48
Vll
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TABLES (cant.)
Number Page
19 Copper Removal from Brass Mill Wastewater Using Batch
Centrifugation 50
20 Copper Removal from Brass Mill Wastewater Using a
Continuous Centrifuge 51
21 Preliminary Jar Tests on Brass Mill Wastewater Comparing
Various Additives 52
22 Preliminary Jar Tests on Brass Mill Wastewater Comparing
Various Additives 53
23 Preliminary Jar Tests on Brass Mill Wastewater Comparing
Various Additives 54
24 Preliminary Jar Tests on Brass Mill Wastewater Comparing
Various Additives 55
25 Preliminary Jar Tests on Brass Mill Wastewater Comparing
Various Additives 56
26 Chemical Neutralization of Indiana Lead Battery Company
Effluent 64
27 Effect of Chemical Neutralization and Starch Xanthates
on Indiana Lead Battery Company Effluent 65
28 Chemical Neutralization and ISX Treatments for Indiana
Lead Battery Company Effluent 66
29 Barium Carbonate Treatment for Dissolved Solids Reduction
on Indiana Lead Battery Company Effluent 67
30 Standard Jar Test Treatments for Indiana Lead Battery
Company Effluent 68
31 Standard Jar Test Treatments for Indiana Lead Battery
Company Effluent 69
32 Standard Jar Test Treatments for Pennsylvania Lead
Battery Company Effluent 71
33 Standard Jar Test Treatments for Pennsylvania Lead
Battery Company Effluent 72
34 ISX Additions Before and After Flocculation of Pennsylvania
Lead Battery Company Effluent 73
35 Log Formation Constants for Complexes at pH 12 73
viii
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TABLES (cont.)
Number Page
36 Equilibrium Concentrations for Cu +-Ca -EDTA
System at pH 12 74
37 Copper Removal from Copper-EDTA Complex—Determination
of Mount of Calcium Ion Required and Effect of pH 75
38 Copper Removal from Copper-EDTA Complex—Effect of
Calcium Salt and Copper Concentration 76
39 .Copper Removal from Copper-NTA Complex 78
40 Copper Removal from Copper-HEDTA Complex 79
41 Copper Removal from Copper-NDA Complex 80
42 Copper Removal from Copper-Tartrate Complex 82
43 Copper Removal from Copper-Citrate Complex 83
44 Copper Removal from Copper-Gluconate Complex 84
45 Copper Removal from a Commercial Copper-EDTA-Type Complex 85
46 Copper Removal from Other Commerical Copper Complexes 86
47 Copper Removal from Copper-Quadrol Complex--Determination
of Amount of Ferrous Sulfate Required and Effect of Base .... 89
48 Effect of Final pH on Copper Removal from Copper-Quadrol
Complex 90
49 Copper Removal from Synthetic Copper Complexes with
Ferrous Sulfate Treatment 91
50 Copper Removal from Commerical Copper Complexes with
Ferrous Sulfate Treatment 92
51 Effect of pH on Copper and Pyrophosphate Removal 94
52 Copper Removal from Pure Copper Pyrophosphate Solutions 95
53 Actual Copper Pyrophosphate Bath Composition 95
54 Ca(OH)2 Treatment of Actual Copper Pyrophosphate
Electroplating Rinses 97
55 Ca(OH)2"CaC12 Treatment of Actual Copper Pyrophosphate
Electroplating Rinses 98
IX
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ACKNOWLEDGMENTS
We would like to acknowledge Clara E. Johnson and Lynne C. Copes for
product chemical analysis; C. L. Swanson for equilibrium concentration calcu-
lations; A. C. Stringfellow for the particle size distribution analysis;
W. L. Williams and L. D. Miller for Rotofeed operations; and numerous
chemical companies who supplied effluent and plating bath samples.
We acknowledge the kind assistance of Mr. John Ciancia who served as
the first EPA Project Officer.
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SECTION 1
INTRODUCTION
This is the final report on the Environmental Protection Agency (EPA)
Project No. IAG-D5-0714 activated July 1, 1975. The purpose of this study was
to develop an effective process to remove heavy metals from wastewaters of two
nonferrous metal industries and one metal finishing industry with insoluble
starch xanthate (ISX). More specifically, the study included the bench-scale
evaluation of effluents from a brass mill, two lead battery plants and a cir-
cuit board manufacturer.
INSOLUBLE STARCH XANTHATE
It has been previously shown that water-soluble starch xanthates in com-
bination with cationic polymers form polyelectrolyte complexes that effect-
ively remove heavy metal cations from water (1-3). Further studies revealed
that the cationic polymer could be eliminated by xanthating a highly cross-
linked starch to give a water-insoluble product (4-6). This product in the
sodium form, although effective in heavy metal removal, was difficult to
isolate in a room temperature stable form. It has been shown (4) that ISX
increased in room temperature stability if the product was converted to other
salt forms. The order of stability was Mg2+»Caz"l">Na+>NH4+. A detailed
description is given on how the addition of magnesium sulfate aids processing
of the product and yields a product with improved room temperature stability.
Data are also presented on ways to use ISX for optimum effectiveness in
treatment of industrial wastewaters.
BRASS MILL WASTEMTER
Recently numerous reports (7-12) have appeared on the use of cementation
with iron to remove dissolved copper from brass mill effluents. This method
is effective in removing 40-60% in most cases; however, this method is not
effective in reducing copper concentrations to low residual copper values.
The brass mill selected to work with is located in southwestern Illinois.
Their wastewater stream enters the waste treatment facility at pH 3.5-4.0
with an average copper content of 10 mg/1 and also contains zinc, nickel, and
chromium (III). After neutralization, equalization and initial sedimentation,
preflocculation, pH adjustment (lime trim), polyelectrolyte addition, floc-
culation, and final sedimentation and clarification, the wastewater is at
pH 9 with a copper concentration of 0.17-0.22 mg/1 (see Experimental Section
for more detailed discussion). The receiving stream of their discharge is a
low flow Illinois creek which provides little dilution of the treated waste-
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water. The Illinois Water Control Regulations require that the discharge to
such a creek shall meet the General Use Water Quality Standards. The copper
concentration permitted by these standards is 0.02 mg/1. A recent variance
to this company by the Illinois Pollution Control Board permits a discharge
copper concentration not to exceed 0.5 mg/1. All the other residual metal
concentrations in the treated wastewater were below discharge standards.
Much work was done with this company to evaluate ISX in conjunction with
coagulant aids while attempting to lower the copper concentration of their
final effluent to 0.02 mg/1 copper to meet the strict Illinois discharge
limit.
LEAD BATTERY EFFLUENTS
Recently several articles were published describing lead removal from
lead battery and picture tube manufacturing effluents using chemical treatment
(13-19). The most common treatment technique cited for removal of dissolved
lead is the reaction to form a highly insoluble lead precipitate followed by
sedimentation. Because lead carbonate and lead hydroxide are very insoluble,
lead is normally precipitated in these forms. The lead-containing effluents
are very acidic (pH 1-2) so neutralization with lime compounds, (calcium oxide
or calcium hydroxide), soda ash (sodium carbonate), or caustic soda (sodium
hydroxide) is required. Each of these neutralizing chemicals has advantages
and disadvantages (20).
Neutralization with Lime Compounds
The lime compounds are the lowest cost neutralizing chemicals and pro-
duce an effluent with a relatively low level of dissolved solids. Disadvan-
tages include equipment cost and operating problems with mixing and handling
the lime slurry and a potential hazard from the presence of lime dust. The
main disadvantages with lime are the slower reaction rates with acids which
leads to poor pH control due to lag time, and the disposal of the large
volumes of lead contaminated calcium sulfate sludge. Sometimes this sludge
is of suitable quality for lead reprocessing at a lead smelter.
Neutralization with Soda Ash
Soda ash costs 3 or 4 times as much as lime for an equivalent neutraliz-
ing value. There is some advantage because the equipment operation is
simpler and there is less sludge that requires disposal. The use of soda
ash, however, results in a high level of dissolved solids in the final
discharge water. The equipment cost for mixing and dissolving the soda ash
is high and the neutralization chamber must be ventilated because carbon
dioxide is released.
Neutralization with Caustic Soda
Caustic soda can be purchased at a 50% wt solution strength and only a
storage tank and feed pump are required for handling. The cost is 4 to 6
times that of lime for an equivalent neutralizing value. As with soda ash,
there is less sludge produced but the effluent is high in dissolved solids.
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After the effluent is neutralized and most of the lead precipitated, the
precipitate can be flocculated with ferric sulfate or polyelectrolytes fol-
lowed by sedimentation, centrifugation or filtration. For sedimentation, a
lagoon with at least a 48-hr retention time is recommended, with distribution
weirs for the inlet and outlet pipes. Periodic shutdown for sludge removal
is sometimes required.
Current methods of battery plant wastewater neutralization were reported
recently by the Illinois Institute of Technology Research Institute (21).
Eight battery plants ranging in production size from 250 to 12,000 batteries
per day were visited. From 42 to 290 liters of wastewater were discharged
for each battery produced and the lead concentration of the effluents was
0.04-23.9 mg/1. Seven plants used hydrated lime, caustic soda, or ammonia to
neutralize the effluent to between pH 7 to 8 before discharge. Some addition-
al treatment, normally settling in lagoons, was necessary before discharging.
It was concluded that the best process viewed was one that added a caustic
soda solution to two cascaded stirred tanks. The first tank pH was controlled
at 4.0 and the second tank at pH 8.0. The final effluent contained only
0.04 mg/1 lead; however, this process was the most expensive. The waste treat-
ment process using hydrated lime reduced the effluent lead concentration to
0.48 mg/1 with the aid of a lagoon. Major problems of this system are dis-
posal of lead contaminated calcium sulfate and lime precipitation in pipelines.
The plant that used ammonia had the highest effluent lead concentration with
1.9 mg/1 dissolved lead and 22.0 mg/1 suspended lead. The ammonia system was
the least expensive and the easiest to control; however, it was not effective
in reducing the amount of dissolved lead and it added water-soluble nitrogen
to the effluent.
It appears in some cases that chemical precipitation alone will reduce
lead concentrations to acceptable values to satisfy present EPA limitations
for discharge. The majority of companies, however, cannot meet the discharge
limits. The use of other techniques will be required to satisfy the limita-
tions on residual lead concentration and dissolved solids concentration.
Since some ion exchange materials offer an economical way to reduce pol-
lutants from lead battery wastewaters. the use of ISX as an ion exchange
material was evaluated in removing soluble lead from waters of two lead
battery manufacturers. Because of the acidic nature of the effluent a neu-
tralization pretreat was always utilized. Lime, caustic soda and soda ash
were all evaluated to see if there was any difference when used in combination
with ISX. The ISX was evaluated two ways, which included ISX addition to the
effluent before and after filtration of the sludge.
CIRCUIT BOARD RINSE WATERS
It will be costly to develop and design effective treatment processes for
the numerous different effluent streams of the printed circuit industry. Some
streams will have to be segregated for special treatment, while others can be
processed by conventional treatment. Counter flow rinsing, and other water
use reduction methods is a start to good water management. However, the use
of plating baths that contain unknown proprietary chemicals does add problems
to treatment design.
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Copper Removal from Electroless Copper Plating Rinse Waters
The electroless plating of copper on printed circuit boards and plastics
is usually an autocatalytic formaldehyde reduction of a complexed alkaline
copper (Figure 1) (22-26) . For concentrated plating baths (26) , treatments
such as (a) raising the temperature to 50-65°C, (b) adding excess formaldehyde
(1.5%) (27), (c) adding palladium activator (1-50 mg/1) (27), and (d) lowering
the pH, have all been used successfully in decomposing the copper complexes.
After plating is completed, it is necessary to rinse the plated articles.
These rinse waters contain complexed copper which must be removed to prevent
possible undesirable ecological effects as a result of introducing the copper
to receiving waters or biological sewage treatment systems. These rinses
with a pH around 10.9 usually contain 20-100 mg/1 of copper as complexed
copper. Since usual chemical treatment is not effective on these rinse
waters, special treatments are required and thus involve segregation of these
solutions from the main process waste waters. A simple calcium ion treatment
for removing copper from some of these rinse waters is presented. A similar
treatment was used by Linstrom et al. (28-30) for leaching copper oxide ores.
A more universal treatment was developed using ferrous sulfate and these
results are also presented.
Disodium Dihydrogen Ethylenediaminetetraacetate
(EDTA-Na7)
NaOOCCH2 ^CH2COOH
NO^O^N
COONa
XH
HOOCCH2 2
Trisodium Nitrilotriacetate
(NTA-Na3)
CH2COONa
CH2COONa
CH2COQNa
N-Hydroxyethylethylenediaminetriacetic Acid
(HEDTA)
u/wvu ru ns rsj
nuuiiUl.). ^.vjl^Lirl^Url
^\ / L L
NCH2CH2N
HOOC(H2 CH2COOH
Disodium Aminodiacetate
(NDA-Na2)
CH2COONa
HN/
CH2COONa
Figure 1. Structures of electroless copper complexing agents.
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Sodium Potassium Tartrate
(Rochelle Salt)
COQNa
HC-CH
HC-OH
COOK
Sodium Citrate
CH2COQNa
NaOOC-b-CH
CH2CCONa
Sodium Gluconate
CCONa
HC-CH
HO-CH
HC-OH
HC-CH
CH2CH
Triethanol Amine
N — CH2CH2CH
XCH2CH2CH
N,N,N'N' tetrakis (2-hydroxypropyl)-ethylaiediamine
OH CQuadrol) „
NCH2CH2N
CH3CHCH2 CH2CHCH3
OH CH
Figure 1 (continued). Structures of electroless copper complexing agents.
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Copper Removal from Copper Pyrophosphate Electroplating Rinse Waters
Copper plating in alkaline media with the copper pyrophosphate complex
anion has been known for over 125 years; however, it only gained commercial
importance about 35 years ago (31-32). Numerous articles have appeared dis-
closing bath formulations, operating conditions, and applications (33-37).
Most copper pyrophosphate baths utilize the components and operating condi- ,_
tions shown in Table 1. The predominant species in solution is the Cu(P20y)2
complex which requires for its formation a weight ratio of 5.48/1
(P^Oy^/Cu2*). Excess pyrophosphate ^Oy4") in the bath (7.0-8.5/1) is main-
tained to insure complete complexation, to keep precipitates from forming, and
to promote anode corrosion. Under normal operation of the bath pyrophosphate
hydrolyzes according to the following equation:
P9074" + H-O > 2HP0.2"
2 7 Z 4
TABLE 1. TYPICAL COPPER PYROPHOSPHATE BATH COMPOSITION
Constituent g/1 oz/gal
?+
Copper, Cu ,
Pyrophosphate, P207
Ammonia, NH3
Nitrate, N03"
22-38
150-250
1-3
5-10
3-5
20-33
0.12-0.37
0.67-1.33
Typical Operating Conditions
pH , „ 8.1-8.8
Ratio P2074-/Cu2"1" 7.0-8.5/1.0
Temperature 50-60°C , 7
Agitation Air, 1-1.5 ft /min-ft of
solution surface area
Cathode current density 10-80 amp/ft2
Anode current density 20-100 amp/ft2
Tank voltage 2-5 volts
This hydrolysis is increased by low pH (<8.0), high P2074"/Cu28.5/l), high temperature (>60°C), and local overheating due to insufficient
agitation. The presence of some orthophosphate (HP042~) anion is desired for
anode corrosion; however, when the HP04 concentration exceeds 97 to 112 g/1,
the bath is usually discarded or diluted and rebuilt because the conductivity
of the bath is lowered, the bright plating range is decreased, and banded
deposits are obtained. The bath contains ammonia which serves to increase
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conductivity and to aid anode corrosion. Nitrate is present to increase the
operating current density by reducing cathode polarization. Some baths con-
tain additives, i.e., oxalate or citrate to produce some brightening and
buffering action.
After the articles are plated, they are placed in a dragout or stagnant
rinse tank and are subsequently subjected to a series of flowing rinses. The
stagnant rinse usually is added back to the plating bath for makeup water.
The flowing rinse water containing Cu(P207)2"~, P^O? > and HPO^' has to be
treated before discharge to meet the ever increasingly stringent effluent
guidelines. Due to the EPA regulations governing the discharge of plating
effluents, treatment processes are needed to meet these limitiations. Since
very little information is available on the treatment of copper pyrophosphate
rinse waters (38-39), a treatment process was developed for these rinse waters.
Copper Removal £ rom Copper Etching Rinse Waters
Ammonium persulfate and alkaline [IsHaClrMfyCH or (Mfy^COsrlftyCH] etches
are very useful in the printed circuit industry to etch copper from circuit
boards. Several treatments for completely exhausted alkaline etch baths are
known: (a) treatment with aluminum (40) , (b) water dilution for copper car-
bonate precipitation (40), (c) caustic heat treatment (40-42), and (d) acid
sulfide treatment (43) . The "Caper1© (Continuous Ammonium Persulfate Etching
and Recovery) process (44-45) is effective in keeping the etching rate high
by continuously removing the dissolved copper. Rinse waters after treatment
contain the Cu(NH3)424' complex that must be removed before the rinse water
can be discharged.
The treatments mentioned for the concentrated baths are not effective to
lower the copper concentration consistently below 1 mg/1. A recent patent
(46) describes a chemical treatment for Cu(NH3)42+ rinse waters which lowers
the copper concentration to below 2 mg/1. Preliminary studies evaluating ISX
on Cu(NH3)42+ rinse waters indicates it to be an effective treatment for
lowering residual copper concentrations to below 0.1 mg/1.
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SECTION 2
CONCLUSIONS
Insoluble starch xanthate (ISX) is an effective heavy metal ion scavenger
by itself or in combination with other chemical treatments.
ISX is effective over a wide pH range (3-11) and in the presence of high
salt concentrations (0-10%).
ISX is applicable to batch-type or continuous flow systems, if available
engineering principles are properly applied.
ISX-metal sludge settles rapidly and dewaters to 25-50% solids after
filtration or centrifugation.
Metals can be recovered from the ISX-metal sludge by a 4N nitric acid
treatment or incineration.
The ISX is an inexpensive agriculturally-based product that leaves the
treated effluents essentially free of heavy metal contamination, which can
allow water reuse. Only sodium and magnesium ions are added to the water from
an ISX treatment.
Specifically this report shows bench scale studies with ISX: (a) in com-
bination with alum to lower residual copper levels to less than 0.02 mg/1 in
a brass mill wastewater without filtration, (b) to reduce residual lead con-
centrations to less than 0.05 mg/1 in lead battery effluents without
filtration, and (c) to remove copper ammonia complexes in circuit board
copper etchant rinse waters.
Two treatment processes were designed to remove copper from electroless
copper plating and copper pyrophosphate electroplating rinse waters.
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SECTION 3
RECOMMENDATIONS
Our experiments with insoluble starch xanthate (ISX) in this report were
limited to bench scale size by the scope of the project. However, the results
appear sufficiently promising to warrant larger scale experiments to reinforce
our laboratory findings and to realize the full potential of ISX as a
scavenger for heavy metal ions.
The use of 6-in settling column, for example, in testing the brass mill
wastewater with alum-ISX combinations is required to obtain copper removal
and settling data before on-site evaluation using a 11 X 10^ l/day wastewater
flow.
On-site testing at lead battery companies using ISX in lead removal in
batch-type and continuous flow systems is recommended.
On-site scaleup is also recommended at plating companies having uncom-
plexed metal rinses or copper ammonia rinses.
More information is also needed on how ISX is to be added in continuous
flow operations (ISX slurry) and batch-type systems (ISX solid). The possi-
bility of manufacturing on site is good.
We recommend also that a more extensive study be made to evaluate ISX as
a filter precoat by itself or mixed with various filter aids.
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SECTION 4
EXPERIMENTAL PROCEDURES
INSOLUBLE STARCH XANTHATE
General laboratory Preparation
A highly crosslinked starch (100 g, 101 H^) is slurried in water
(435 ml), and sodium hydroxide (45 g) in wate? (125 ml) is added. This mix-
ture is stirred 30 min. Carbon disulfide (30 ml) is added and the mixture is
stirred 1 hr in a covered beaker. Magnesium sulfate (19 g) in water (250 ml)
is added and the mixture is allowed to stir an additional 5 min. The slurry
is filtered through a Buchner funnel using Whatman No. 54 filter paper and the
solid is washed with water (1,000 ml). The solid (75$ H20) is then washed
with acetone then ether. After drying for 2 hr under vacuum at room temper-
ature, the product was analyzed. Yield 120 g; S, 9.62%; KfeQ, 8.92%; ash
12,89%.
Weights of reactants and analysis of products for several preparations
are found in Figure 3 and Table 3 (see pp. 25-26).
Preparations of ISX with Additional Water Washing
ISX was prepared as previously described; however, different amounts of
water (1-4 1) were used during washing. The wet cake was next solvent washed
with acetone then ether and then dried 4 hr under vacuum at 25°C, The pro-
ducts were then flash dried at 175°C and 305 m/min air velocity (1*5 sec
residence time). The analysis for these products is shown in Table 4 (see
P. 30).
Preparations of ISX Using Mditjonal Magnesium Sulfate in Wash Water
ISX was prepared as previously described (General Laboratory Prepara-
tion) ; however, various amounts of magnesium sulfate (0-30 g) in water
(500 ml) were used to wash the filtered product. The wet cakes were then
washed with water (1,OPO ml) and worked up as described in the previous sec-
tion. The analysis of the products is shown, in Table 5 (see p. 30).
Reuse of Mother Liquor in the Xanthation of Crosslinked Starch
ISX was prepared as previously described (General Laboratory Preparation);
however, the first 660 ml of mother liquor and wash water was saved for sub-
sequent xanthations. A 100-ml sample was titrated with acid (Q.97N HNOj) to
10
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pH 7.0 to determine the alkali content and make-up sodium hydroxide was
added to the remaining 560 ml for the next xanthation. The products were
worked up as previously described. The analysis of the products is shown in
Table 6 (see p. 31).
One-Step Crosslinking and Xanthation of Starch
Commercial corn starch (100 g, 101 H^O) is slurried in water (150 ml)
containing sodium chloride (1.5 g) and epichlorohydrin (7.0 ml). To this
slurry is added potassium hydroxide (6 g) in water (40 nil) slowly over 30 min
and the mixture is allowed to stir for 16 hr. The suspension now containing
the highly crosslinked starch can be xanthated as previously described (Gen-
eral Laboratory Preparation) after the addition of water (245 ml).
Pilot Plant--Rotofeed Preparation of ISX
Crosslinked starch (7.46 kg, d.b.) is slurried in water (29.84 kg) and
magnesium sulfate (1.34 kg) is added. The slurry is pumped into a Baker
Perkins Flowmaster Rotofeed (19.05 cm) at 890 g/min and 28°C. The sodium
hydroxide (4.66N, 24 1) is metered in at 470 ml/min and the carbon disulfide
(3.32 1) at 65 ml/min. The product is collected during the 50 min run and
after 30 min in a holding tank, water (37.8 1) is added for easier pumping
to the centrifuge. The mixture is centrifuged in a Tolhurst Centrifuge
(66 cm bowl, max. 2,400 rpm) at 650 rpm and then washed with water in the
machine (100 1). The cake is then dewatered to 27% solids at 1,500 rpm. The
cake is flash dried and gives the following analysis: S, 9.14%; ash, 14.06%;
H20, 3.16%.
Insoluble starch xanthate prepared commercially can be made in large
reactors as previously described or it can be made continuously via a high
shear mixer such as the Rotofeed, followed by centrifugation, washing, and
drying. Commercially prepared products might require minor changes in
reactant ratios to obtain maximum reaction efficiency.
A freeze-dried sample of the centrifuged cake gives the following
analysis: S, 9.82%; ash, 14.08%; 1^0, 1.86%; Na, 10.06 mg; Mg, 8.02 mg;
Na/Mg, 1.25; Capacity, 1.53 meq metal ion/g.
Flash Drying ISX
A Benco Bench Scale Vertical Pneumatic Dryer (flash drier) was used.
The unit (3 m high, 3.2 kg H20/hr drying capacity) was run at 175°C inlet
temperature and 305 m/min air velocity (1.5 sec residence time). The drier
was equipped with a 2.5 cm diameter variable speed horizontal screw feeder
with a vertical hopper. The wet cake of ISX (20% solids) was broken up and
fed into the screw feeder. After the 3rd pass, the inlet temperature was
reduced to 150°C and.the air,velocity to 245 m/min to minimize product de-
composition. Usually a total of 6 passes were required to dry the ISX
(<1% H20) in this small unit.
11
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Freeze Drying ISX
A VTKTIS Company Freeze Dryer, Model FFD-42 was used. The unit has five
trays with a total tray area of 1.52 m2. The washed cake of ISX (20% solids)
was slurried in water to give 5% solids (23.6 kg) and was poured into each of
the five trays to a depth of 1.3 cm. The slurry froze while its temperature
was reduced to -50°C. Then heat was supplied to the trays at a constant 38°C
and the vacuum applied to the chamber. The vacuum was maintained at 50-100
microns during the entire drying process. About 36 hr was needed to dry this
material to <1% water. The freeze drier condenser has a capacity of 22.7 kg
water and 1.2 kg of ISX (<1% H20) was obtained.
Spray Drying ISX
A NIRO portable spray drier (Copenhagen, Denmark) with a vaned atomizer
was used. The washed cake of ISX was slurried in water to give 5% solids and
the slurry was fed at a rate of 3 1/hr (spindle speed, 35,000 rpm; inlet temp-
erature, 260°C; and outlet temperature, 118°C). The recovered ISX from the
cyclone contained 2-3% H20.
Other Drying Methods
Several other drying methods (i.e., rotary vacuum, oven tray- and drum-
drying) were evaluated, all of which led to decomposition of the ISX due to
the longer exposure to heat.
ISX Particle Size Distribution
The particle size distribution of a freeze-dried ISX sample was deter-
mined using a Sharpies Micromerograph. The sample (0.03 g) was dispersed at
the top of the 2.28 m column to break up any agglomerates and to begin
settling in still air at the same moment. Figure 6 (see p. 33) shows the
results of this determination.
ISX Stability Study
A flash-dried ISX sample having the following analysis (S, 11.77%; ash,
21.20%; H20, 0.77%; Na, 13.0 mg; Mg, 7.7 mg; capacity, 1.84 meq metal ion/g)
was used to remove copper from standard copper solutions. The ISX samples
were stored at 0°C and 28°C. Every two weeks 0.0278 mg of each ISX sample
was added to separate beakers (50-ml samples) containing copper (31.77 mg/1)
at pH 4.0. After stirring 5 min, the solutions which ranged in pH from 8.5
to 8.9 were filtered and the residual copper was measured (Figure 5, see
p. 28).
Heavy Metal Removal with ISX
Synthetic solutions containing individual metal ions or mixtures of metal
ions were treated with ISX by adding calculated quantities of the dry solid.
The solutions were stirred for approximately 5 min at pH's 7 to 9. After
12
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filtration through Whatman 54 filter paper or medium porosity sintered glass
funnels, the residual metal concentrations were determined on a Varian
Techtron M 120 spectrophotometer (Tables 8 and 9, pp. 35-36).
Copper Removal, JJsing ISX as a Precoat on a Pressure Filter
A 3-plate stainless-steel horizontal pressure filter (Sparkler Manufac-
turing Company, Model 8-3) having a total filtration area of 929 cm2 was
used. The plates were covered with Sparkler filter media discs (Grade "M",
thin porous high wet-strength sheets, 21 cm in diameter with 2.5 cm center
hole). A gear pump having a maximum head of 4.2 kg/sq cm at 24.6 1 per min
was used to feed the filter. Two 95 1 tanks were used to supply the precoat
media and copper solution. A valving arrangement was used so that the flow
from either of the two tanks could be pumped without interruption to the
filter. The precoat slurry [ISX (200 g) and Hi-Flow or "Super-eel" filter
aid (200 g)] was suspended in water (83.3 1) and was recirculated at a rate
of 11.4 1/min through the filter until the water was clear. The filter cake
was approximately 1.25 cm thick and the inlet pressure was constant at
0.91 kg/cm2. The copper solution (38.0 g CuS04«5H20 in 83.3 1 of water) was
passed through the cake at a rate of 4 1/min. No change in head pressure was
noticed as the copper solution was recirculated through the cake. Several
other runs were made varying the ratios of ISX to "Hi-flo Super-eel".
Copper Recovery from Copper-ISX Sludge
A solution (95 1) containing copper (6,000 mg Cu/1) was treated with ISX
(1.89 meg metal ion/g, 100 g) by stirring for 10-12 min. After filtration
and drying, the sludge (105 g) was stirred with 4N HNC-3 (500 ml) for 30 min.
After filtration, the filtrate was analyzed and showed 5,994 mg Cu/1. The
resulting cake was dried and analyzed (Table 17, see p. 42).
Gold-Copper; Removal and Recovery from ISM Sludge
A solution (1,000 ml) containing Au (10.0 mg/1) and Cu (8.5 mg/1) was
treated with ISX (0.25 g) to a final pH 7.3. The residual gold (0.204 mg/1)
and copper (0.007 mg/1) were measured after filtration. The metal-ISX sludge
was slurried in 4N HNOs (20 ml) for 30 min, filtered, and water washed and
the filtrate diluted to 1 1. Metal analysis of the filtrate gave gold
(0.000 mg/1) and copper (8.6 mg/1). The sludge was then slurried in aqua
regia (20 ml) for 5 min, filtered, water washed, and the filtrate diluted to
1 1. Metal analysis of the filtrate gave gold (9.8 mg/1) and copper (0.000
mg/1).
BRASS MILL WASTEWATER
Equipment
Phipps-Bird six position ganged stirrer with voltage regulator.
Lourdes Beta-Fuge A2 centrifuge.
Sharpies Super Centrifuge; 10.5 cm diameter bowl.
13
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Sharpies Super Decanter P-600.
Gear Pump (24.6 1/min max) with rotameter.
Feed tank with with cone bottom (150 1) with air driven stirrer.
Materials
Inorganics Evaluated—
Powdered calcium hydroxide [Ca(OH)2; reagent grade] added as a solid.
Ferrous chloride (FeCl2, reagent grade) added as a 0.5 g/1 solution.
Ferric chloride (FeCls, reagent grade) added as a 0.5 g/1 solution.
Aluminum sulfate [Al2(S04)3'18H20 (alum), reagent grade] added as a
solid.
Sodium sulfide (Na2S, reagent grade) added as a 0.5 g/1 solution.
Sodium hydroxide (NaOH, 0.12N).
Hydrochloric acid (HC1, 5 wt %).
Bentonite (clay) added as a solid.
Polymers Evaluated—
Insoluble-starch xanthate (ISX, 1.5 meq metal ion/g) was prepared as
previously discussed and was added as a solid.
Soluble starch xanthate (SSX) was evaluated as an anionic flocculant and
was prepared as follows:
Commercial corn starch (324 g, 10.0% H20) is slurried with an axial flow
impeller in water (2,400 ml), and sodium hydroxide (40 g) in water (200 ml)
is added. This mixture is stirred 30 min. Carbon disulfide (24.3 ml) is
added and the mixture is stirred rapidly for 1 hr in a covered beaker. The
mixture (-vlOl solids, degree of substitution = 0.11) is stored at 5°C and
freshly diluted 5.07 g/1 for use.
Olin 5002 (Olin Corp.) added as a 0.5 g/1 freshly prepared solution.
Dearborn 420 (Dearborn Chemical Company) added as a 0.5 g/1 freshly pre-
pared solution.
Nalcolyte 676 (Nalco Chemical Company) added as a 0.5 g/1 freshly pre-
pared solution.
Analysis
Copper—
The initial and residual copper concentrations in unfiltered acidified
samples were determined on a Varian Techtron AA 120 Spectrophotometer.
Turbidity—
The clarity (or turbidity) was judged by visual observation.
14
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Brass mill wastewater
Samples were taken by treatment facility operators as the wastewater
leaves a 15-ft deep continuous flow clarifier, usually before chlorination.
The clear, pale yellow samples containing a few suspended solids were 24-36 hr
old when received. The pH range and total copper content of different 19 1
plastic containers were 8.6-9.5 and 0.088-0.210 rag/1, respectively. The con-
tainers were vigorously shaken before being sampled.
Present On-Site Treatment--
This brass mill is presently treating an average of 11 X 106 I/day but
can accommodate up to 17.4 X 10" I/day during rainfall (Figure 2).
Neutralization--The wastewaters received at the facility are acidic and
require neutralization to minimize corrosion of the treatment plant elements,
to enhance the effectiveness of the overall treatment process and to meet
state water quality criteria. Neutralization is accomplished by the addition
of a 2.5% w/v solution of lime during vigorous mixing by turbine agitators,
until the pH of the wastewaters reach a predetermined value (pH 5.5 to 6).
Equalization and initial sedipenta.tion--Following neutralization, the
wastewater flows by gravity into the equalization-sedimentation system. This
system accomplishes equalization by hydraulically controlling and attenuating
hydraulic surges and contaminant peak concentrations and provides for the
removal by sedimentation (settling) of a high percentage of settleable solids
material in the wastewaters. The settling of solids from the wastewaters
(^6 hr hold time) is accomplished through gravitational forces. The settled
materials are pumped to the sludge thickening unit for further treatment.
This basin is also equipped with mechanical surface skimming devices which
continuously remove scum and floating debris from the wastewaters before they
are passed to subsequent units. The basin is also equipped with magnetic
flow meters and control valves to provide hydraulic flow control. Emergency
overflow from this basin to an emergency holding lagoon is provided.
Pre-flocculation. pH adjustment ("lime trim")—This unit process is an
extension of the initial neutralization to insure pH control which is vital
to completing the precipitation of heavy metals and other contaminants by
chemical flocculation and coagulation. The optimum pH range for the "lime
trim" system is between pH 8 and pH 9, but the operating range is between pH 8
and pH 10.
Polyelectrolyte addition--In the "lime trim" system, the heavy metals are
converted to hydroxide forms, and exist as finely divided colloids. Anionic
polyelectrolytes (1.4 mg/1) cause these fine particles of metal hydroxides to
agglomerate in preparation for removal by flocculation and sedimentation.
Flocculation and final sedimentation--These unit processes occur in a
single basin designed to accomplish these two functions simultaneously.
Flocculation is an extension of the agglomeration process initiated by the
addition of the anionic polyelectrolyte. Mechanisms in the flocculator
15
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[Effluent to Creek
Flocculator
Clarifier
Pump
Room
Figure 2. Brass mill treatment facility.
-------
oscillate at a predetermined slow rate thus causing the agglomerated particles
to collide and increase in size. As these particles grow in size they enter
the sedimentation portion of the basin where they settle out.
Wastewaters at this stage have been separated into two fractions, a
clear supernatant and settled sludge. The clarified supernatant represents
the treated effluent to be discharged to a creek through a measuring device
(Parshall-flume) and is practically free of all dissolved metals and solids.
The settled sludge contains the heavy metals, lime, and other contaminants
removed by chemical coagulation.
ELocculator clarifier basins are equipped with surface skimmers to remove
floating material. This floating material is discharged to the sludge well
and mixed with the sludge. The sludge and scum (^5% solids) are now ready to
be transferred to the sludge thickening unit.
Exper^ntal.lagoon- -An experimental lagoon is available for tests to
provide additional data to the brass mill on the removal of soluble organic
material from the chemically treated effluent. This data will be available
for future design purposes should water quality criteria change drastically to
require further removal of soluble organic materials from the brass mill
effluent.
Emergency lagoon—An earthen lagoon acts as a surge tank for peak hy-
draulic flows due to storms. This lagoon is sealed with an asphaltic liner
and is equipped with an emergency overflow to the outfall facilities.
"Synthetic" Copper Solutions
For comparative jar testing, "synthetic" copper samples were prepared
OvO.20 mg/1) by dissolving 01804-5H20 in distilled water. The pH was raised
to the test value with calcium hydroxide. Any slight flucculations in pH were
controlled with dilute sodium hydroxide or hydrochloric acid.
Standard Jar Test Method
Samples Cbrass mill or synthetic copper, 950 ml) were placed in six 1-1
beakers, which were placed on squares of insulation material to minimize con-
vection currents. The paddles were lowered into the samples and the samples
were stirred at 100 rpm. The pH of all the samples was adjusted to the test
value (usually 9.0) with calcium hydroxide and samples (10 ml) were taken for
"initial copper." ISX was added and after 10 min the other additives were
added where desired. The pH was usually readjusted to the test value. The
stir speed was then decreased to 50 rpm for 5 min and then to 20 rpm for 60
min. Some tests were only stirred for 12 min as noted. During the 20-rpm
stir, the time for floe appearance was noted. The pH was constantly main-
tained at the desired value during the slow stir period. The pH of the brass
mill wastewater remained fairly constant apparently due to some buffer capa-
city, whereas the pH of the synthetic samples tended to decrease probably due
to carbon dioxide absorption and no buffering.
17
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At the end of the 60-min (or 12-min) stir, the paddles were removed to
allow unhindered settling. During the settling, the beakers were observed for
settling rate and clarity. After 10 and 30 min, samples (10 ml) were with-
drawn by pipette or by a manifold sampling arrangement at a point in the
center of the beaker 3.2 cm below the surface. Care was taken to avoid any
floating solids. The withdrawn samples were acidified, without filtering,
with two drops of copper-free concentrated hydrochloric acid and the copper
concentration determined by AA. A standard curve (0.01-0.50 mg/1 copper) was
made each day with 0.01 mg/1 copper as the lower limit of measurement.
Batch Centrifuging Test Method
Brass mill samples (1,000 ml) were sampled for initial copper and ISX
(28 mg) was added. After stirring (30 min), aliquots (20 ml) were placed in
centrifuge tubes. They were spun in the Beta-fuge for the times.and speeds
shown in Figure 11 (see p. 49). The temperature was maintained at 24 ± 2°C
by refrigeration. On all runs, the times shown were taken when the speed
was reached and then the brake was applied. At the end of each run, aliquots
(10 ml) were taken from the tubes and analyzed for total copper after acidi-
fication (2 drops of concentrated HC1). The results are shown as residual
copper vs spin time (min) at .the G's shown (Figure 11, Table 19).
Continuous Centrifuging Test Method
Brass mill samples or synthetic copper solutions were placed in the feed
tank where the pH was adjusted, and ISX or sulfide added. After a rapid stir
for 10-15 min, an aliquot (20 ml) was removed for copper analysis. Coagulant
aids (alum or polymers) were added where desired and the pH readjusted where
desired. After a slow stir (4-5 min) an aliquot (20 ml) was taken for initial
copper analysis. The slurry was pumped into the rotating "Super-Centrifuge"
bowl. Samples of the centrate were collected, acidified without filtering and
analyzed for total copper. The conditions of these runs and results are shown
in Tables 18 and 20 (see pp. 48, 51).
The same procedure was used with the P-600 Super-Decanter. This
machine has a scroll discharge which conveys the solids from the bowl. Since
only small quantities of sludge were formed by our treatments, the scroll was
disconnected and rotated with the bowl, so there was, presumably, no distur-
bance of the settled solids. In actual use, the scroll might resuspend some
of the finer particles (Table 20, see p. 51).
LEAD-BATTERY EFFLUENTS
Materials
Neutralization Agents Evaluated—
Sodium hydroxide (NaOH) was added as a 7N solution (280 g/1).
Sodium carbonate (Na2CC>3) was added as a 10% solution (100 g/1).
Calcium hydroxide [Ca(OH)2] was added as a solid.
Calcium carbonate (CaC03) was added as a solid.
18
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Polymers Evaluated—
Insoluble starch xanthate (ISX, 1.5 meq metal ion/g) was prepared as pre-
viously discussed and was added as a solid.
Soluble starch xanthate (SSX) was evaluated as an anionic £locculant and
was prepared as previously described.
Comnercial anionic polymers (Q > 5 g/1) * *
Dow A-23 (Dow Chemical Company).
Magnifloc 837A (American Cyanamid Company).
Nalcolyte 676 (Nalco Chemical Company).
Analysis
Metals--
Lead and iron concentrations were determined on a yarian Techtron AA 120
spectrdphotometer.
Suspended Solids--
Determined by filtration of 1-1 solutions through fine porosity predried
sintered glass funnels and redrying at 110°C.
Dissolved Solids—
Determined by evaporation of 1-1 solutions to dryness, and then drying
flasks at 110°C for an hour.
Lead Battery Effluent Sample (Indiana)
the sample (40 1) stored as received gave the following analysis: total
lead (4.05 mg/1), total iron (52.0 ing/1), pH (1,6), suspended solids
(39.3 mg/1), and dissolved solids (4.94 g/1).
Present On-Sjte Treatment (Indiana)
This company presently treats their raw Wastewater (75,700 I/day, 100
mg/1 total lead) by first settling the Suspended lead to lower the lead con-
centration to 5-20 mg/1. This is followed by adjusting the pH to 7.0 with
soda ash and allowing the sludge to settle for 2-7 days iil tanks. They have
evaluated on-site sodium borohydride-coke, peat and ISX to lower their lead
concentration to 0.05 mg/1 with some success. The company would like to go to
complete water recycle; however, their present dissolved solids concentration
is too high. They have considered passing their wastewater after settling
through a sand filter, charcoal filter* reverse osmosis unit, and a final
deionizer.
19
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Lead Battery Effluent Sample (Pennsylvania)
The sample (40 1) was stored as received and gave the following analysis:
total lead (1.03 mg/1) and pH (10.6).
Present Qn-Site Treatment (Pennsylvania)
This company presently treats 570,000-950,000 I/day (initial pH 1.0) with
hydrated lime to pH 6.0-9.0. After anionic polyelectrolyte addition, the
sludge is settled in clarifiers and settling basins. They have to lower their
total lead to 0.05 mg/1 and dissolved solids to 500 mg/1. Their suspended
solids concentration is presently below discharge limits.
Preliminary Experiments
Preliminary studies were conducted on the Indiana lead battery wastewater
to determine: (a) effectiveness of sodium hydroxide, sodium carbonate, cal-
cium hydroxide, and calcium carbonate as neutralization agents in metal
removal, floe settlability, and dissolved solids reduction, (b) effectiveness
of ISX for lead removal, (c) effectiveness of soluble starch xanthate for lead
removal and flocculating ability, (d) effectiveness of commercial anionic
polymers in flocculating ability, and (e) effectiveness of barium carbonate in
dissolved solids reduction.
Results of these studies are shown in Tables 26-29 (see pp. 64-67).
Standard Jar Tests
These tests were conducted using the preliminary testing data as a guide-
line. Results of these studies are found in Tables 30-31 (see pp. 68-69).
CIRCUIT BOARD RINSE WATERS
Copper Removal from Electroless Copper Plating Rinse Waters
Stock Copper Complex Baths--
Commercial baths were used as received or were prepared according to
supplier data sheets. Synthetic baths (51) were prepared as described in
Table 2.
Calcium Treatment of Rinse Solutions--
In most cases 1-1 solutions of 5-100 mg/1 copper in complex form were
treated at room temperature with either calcium hydroxide, calcium oxide,
calcium chloride, or calcium sulfate to pH 11.5-12.0 to precipitate the copper
as its hydroxide. The suspended copper hydroxide after a 5-min stirring time
was flocculated with 1.5 mg/1 anionic polyelectrolyte solutions (i.e., 0.5 g/1
solutions of either Nalcolyte 676 or Dow Purifloc A-23). After separation via
filtration through Whatman 54 filter paper, the residual copper was measured
via atomic absorption with a Varian Techtron AA 120 spectrophotometer.
20
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TABLE 2. SYNTHETIC ELECTROLESS COPPER BATH COMPOSITIONS (51)
Bath
EDTA*
NTAt
HEDTAt-*
NDAt
Tartrate§
Citrate!
Gluconatef
Triethanol
amine*
Quadrol*
Molecular
Components weight
CuS04-5H20
NaCN
NaOH
Formaldehyde (37%)
EDTA-Na2'2H20
NTA'Na'* «H20
HEDTA
NDA«Na2
CuS04-5H20
NaCN
NaOH
Formaldehyde (37%)
Tartrate-Na-K
CuS04'5H20
NaCN
NaOH
Formaldehyde (37%)
Citrate -Na3'2H20
Gluconate-Na
N(GH2GH2OH)3
Quadrol
249.69
49.01
39.99
30.03
372.25
275.00
278.26
195.08
249.69
49.01
39.99
30.33
282.25
249.69
49.01
39.99
30.33
294.11
218.16
149.00
292.00
Solution Cone.
moles/1
0.030
0.0004
0.125
0.08
0.036
0.0425
0.036
0.10
0.020
0.0002
0.125
0.47
0.0425
0.02
0.0002
0.125
0.40
0.051
0.05
0.05
0.026
g/1
7.49
0.0198
5.00
6.5 ml
13.40
11.69
10.02
19.50
5.00
0.0099
5.00
38.1 ml
12.00
5.00
0.0099
5.00
32.43 ml
15.00
10.90
7.60
7.60
Copper
Cone. ,
mg/1
1,910
1,730
1,890
1,790
1,082
1,122
1,551
1,120
1,282
* All reagents were dissolved individually in water. The copper solution was
added to the BETA solution. The sodium cyanide was added to the sodium
hydroxide solution. This mixture was then added to the complexed copper
and the volume adjusted to 1 1.
t All constituents and amounts as described in (*) were the same except
for the complexing agent.
+ The HEDTA solution was adjusted to pH 7 with sodium hydroxide before
addition of the copper solution.
§ Follow EDTA procedure (*).
# Use citrate bath concentrations and follow (*).
21
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Ferrous Sulfate Treatment of Rinse Solutions--
Solutions (1,000 ml) of 10-50 mg/1 copper in complex form were acidified
to pH 2.7-5.0 with IN H2SC>4 and ferrous sulfate (0.2-1.0 g) was added. After
stirring (5-60 min) the solutions were adjusted to a pH greater than 11.0 with
calcium hydroxide or sodium hydroxide and the precipitate was flocculated with
anionic polyelectrolyte (2.5-5.0 mg/1). After filtration, the residual copper
and iron concentrations were measured (see pp. 89-92, Tables 47-50).
Copper Removal from Copper Pyrophosphate Electroplating Rinse Waters
Rinse Waters --
Synthetic rinses were prepared according to supplier data sheets. Indus-
trial rinses were used as received.
Treatment of Rinse Waters --
Solutions (500 or 1,000 ml) containing various amounts of copper, pyro-
phosphate, and orthophosphate were treated with various combinations of
calcium hydroxide or calcium chloride and calcium hydroxide to a pH greater
than 9. After flocculation of the precipitate with an anionic polyelectrolyte,
the solution was filtered and the residual copper and phorphorus concentrations
were determined (see p.96, Tables 54-55).
Copper Removal from Copper Etching Rinse Waters
Solutions (1,000 ml) containing various concentrations of Cu(NH3)42+ from
synthetic and actual industrial rinses were treated with various amounts of
ISX. Residual copper concentrations were measured after a 5-min ISX contact
time followed by filtration (see p. 100, Figure 20).
22
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SECTION 5
RESULTS AND DISCUSSION
INSOLUBLE STARCH XANTHATE
Even though the main purpose of this project was to evaluate ISX for
heavy metal removal, a considerable amount of time was spent developing a way
to stabilize ISX to some degree so that its metal scavenging usefulness could
be utilized for industrial pollution control. The addition of magnesium sul-
fate during the preparation of ISX, gives this added stability, so the product
can be manufactured and have a reasonable shelf life before any degradation
occurs. The magnesium sulfate addition also affords (a) increased filtration
or centrifugation rates during workup, (b) increased flash drying feed rate,
and (c) increased settling rate in heavy metal cation removal.
The structure of ISX described in this report is a combination of the
sodium- and magnesium-form as shown below. When ISX removes heavy metals
Sodium form: Starch-0-C-£> wa
Magnesium form: Starch-O-C-S0^^ S-C-0-starch
from the solution, the usual mechanism of removal is shown using zinc as an
example.
2 Starch-0-C-S®%a + Zn2*
-2Na S
Cstarch-0-C)2Zn
(Starch-0-C>-S^2Mg2+ + Zn2+
However, when ISX removes copper (II) from solution, an oxidation-reduction
takes place as illustrated below. This mechanism has been shown previously
with soluble starch xanthates and alcohol xanthates (47-49).
4 Starch-0-C-SNa + 2Cu *N
S
2 starch-O-c'-SCu
Copper (I) starch xanthate
S S
+ starch-0-C-S-S-C-O-starch
starch xanthide
23
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Several preparations of ISX were made to evaluate reactant ratio effects
and the amount of magnesium sulfate required for product optimization (Figure
3 and Table 3). Figure 3 shows the %S incorporated in the product for
different volumes of carbon disulfide. Under the reaction conditions used,
30 ml of carbon disulfide would yield a product containing the most sulfur.
Due to the volatility of carbon disulfide a closed or covered reactor is
necessary for maximum xanthate formation. If carbon disulfide is used accord-
ing to manufacturer's brochures, it can be safely handled.
A preliminary study was made under constant reaction conditions (CS2,
15 ml) to determine the optimum amount of magnesium ion required to give the
most rapid dewatering rate of the product when filtered. Figure 4 shows the
inverse crack time required for the reaction slurry to be dewatered (product
cake to crack) vs the weight of magnesium ion used in the preparation which
would yield a product containing 5-6% sulfur. This means that for each % S in
the final product, 0.4 g magnesium ion (2.0 g MgSC>4) should be added for max-
imum filtration rate. Analysis of the filtrate showed all the magnesium to be
incorporated into the product. Magnesium chloride was also evaluated with
equal effectiveness in product workup, however, proportionately larger amounts
of a more expensive chemical would be required.
The addition of the magnesium sulfate solution caused the reaction slurry
to thicken initially; however, after 60 sec, the slurry became thin and was
easily filtered. The magnesium sulfate can also be added at the beginning of
the xanthation or added throughout the xanthation yielding equally effective
products.
Previously (4-6) it was shown that ISX in the sodium form was very
stable at 0°C; however, it only had a limited room temperature stability (1-
2 days). Treatment of the dry sodium form with physical mixtures of magnes-
ium oxide or magnesium sulfate showed no improvement in stability. The
magnesium ion treatment just described gives a product that is more stable at
room temperature which would allow the preparation, shipment, and use before
partial degradation occurred. If the product is stored below 10°C, the
stability increases significantly (2 mo) and at 0°C very little change is
observed after 1-yr storage.
The stability of ISX was determined by evaluating copper removal over a
period of 10 weeks with ISX samples stored at 0° and 28°C. Figure 5 shows
that the product stored at room temperature decomposes after 6 weeks, whereas
the product stored at 0° is still very effective in copper removal. Some
decomposition was noted after two weeks with the room temperature product as
the color started changing (pale yellow to gold) and slight color development
was noted when the sample was added to the copper solution; however, the
copper removal was good since the copper-ISX decomposition products precipi-
tated at a pH>8.5. After eight weeks, the product decomposed to such a degree
that the copper-decomposition products remained in solution (amber color) and
resulted in high residual copper values. The color and residual copper,
however, can be completely removed by adding a small amount of 30% hydrogen
peroxide above pH 8.
24
-------
0 5 10 15 20 25 30 35
Carbon Bisulfide, ml
Figure 3. ?« S vs CS2 charged in the xanthation of crosslinked starch.
25
-------
TABLE 3. PREPARATION AND ANALYSIS OF INSOLUBLE STARCH XANTHATE
Cross-
linked
starch*
A
A
A
A
A
A
B
Carbon
disulfide,
ml
IS
20
25
30
35
30
30
Magnesiumt
sulfate,
g
12.4
15
17
19
21.5
18+t
18tt
*
d.
5.
7.
8.
10.
8.
8.
9.
S t
b. IH2C*
76
44
70
12
86
05**
29**
2.19
1.34
1.40
0.85
1.74
1.33
0.86
% Ashi
10.72
16.52
19.20
24.08
18.15
13.31
16.32
Na,#
mg
8.5
10.6
12.1
14.2
13.2
11.4
12.8
Mg,#
mg
6.2
6.9
7.0
7.4
8.3
7.1
7.3
Capacity,"*
Na/Nfe meq/g
1.37
1.54
1.73
1.92
1.59
1.60
1.75
0.
1.
1.
1.
1.
1.
1.
88
14
20
56
36
24
44
* A. Epichlorohydrin crbsslinked starch (HPD-53-91E, The Hubinger Company, Keokulc,
Iowa). 9.09% H20; 100 g (0.56 mole, dry basis).
B. Vulca 90 (National Starch and Chemical Corp., Bridgewater, N.J.). 11.01 H20;
100 g (0.55 mole, dry basis). Additional water may be required to promote
easy stirring with Vulca 90.
t Approximately 2 g magnesium sulfate for each 1% S in the product is optimum.
* These products were only flash dried using a Benco Bench Scale Vertical
Pneumatic Dryer at 170°C and 305 m/min air velocity (1.5 sec residence
time) ; therefore, lower moisture values were obtained over solvent drying.
% % Ash includes sodium and magnesium of xanthate and bound alkali in product.
# A 0.25-g sample was treated with IN HNOj (45 ml) to remove all the sodium and
magnesium. The filtrates diluted to 1 1 and Na and Mg concentrations were
determined on a Varian Techtron AA 120 spectrophotometer.
~ • s
• -i — 1 »->•
where D.S. is the degree of substitution.
tt Magnesium sulfate (18 g) in water (180 ml) was added 45 sec after the carbon disulfide
and the reaction was allowed to proceed 1 hr.
** Lower sulfur values were due to the additional water used in the preparation.
26
-------
0.035
0.030
~ 0.015
+2
Figure 4. Amount of magnesium ion (Mg ) required for optimum
ISX filtration rate.
27
-------
10,000 -
1000 -
CO
10
Figure 5. ISX stability-copper removal.
28
-------
The moisture content of the stored ISX is very critical to product
stability. Samples having moisture contents of <2% can be stored for several
weeks at 28°C; however, samples having moisture contents >2% decompose faster.
ISX of any moisture content, however, can be stored without decomposition at
0°C. Samples of ISX which have decomposed have a pink-orange color and a
pungent odor.
Several additional things were tried to increase the stability of the ISX
further. The products described in Tables 4 and 5 did show some increase in
stability. The use of additional wash water only washes residual caustic from
the product (Table 4) and the first two liters of wash water contained 98% of
the caustic and salts from xanthation. In fact, 90% of the dissolved solids
were removed after 1 1 of wash. The removal of most of the excess caustic
should aid drying of the ISX, and also in storage and stability because of the
hygroscopic nature of sodium hydroxide.
Using additional amounts of magnesium sulfate in the wash water (Table 5)
was evaluated since a completely substituted magnesium starch xanthate was a
highly room temperature stable product (4). These washings wash out excess
caustic and also substitute magnesium for some of the sodium on the xanthate
forming magnesium starch xanthate. The magnesium starch xanthate portion is
only effective in metal removal at pH's above 7 because it dissociates easier
at that pH. This MgSCty wash treatment would, however, yield an effluent
higher in dissolved solids.
Since the mother liquor of the xanthation of starch contained a consider-
able quantity of base and since large volumes of water would be required in
the large-scale production of ISX, the reuse of the mother liquor was evalu-
ated. Product analysis (Table 6) shows very little difference in the products.
The increase in dissolved solids in the liquor had no effect on the subsequent
xanthation. The eventual discharge of this caustic process water could be
used to neutralize acidic process waters.
Evaluation of several drying procedures showed that ISX could be effect-
ively dried by flash-, spray-, or freeze-drying. Sodium ISX, without the
MgSfy treatment, could not be flash dried because it was slimy to feed. Drum
drying of ISX is a possible means of drying. Oven- and rotary vacuum-drying
led to considerable product decomposition in the few trials attempted.
Some additional observations about ISX are: (a) Some ISX samples ap-
peared to decompose faster in direct light (>3% moisture content). (b) If dry
ISX (1% moisture) is left in the open it will absorb water, and with time,
will decompose to lose all its sulfur, (c) The smaller the Na/Mg ratio, the
more stable the product; however, there appears to be some decrease in metal
removal ability at pH's less than 7.0 if the ratio is smaller.
The ISX can be made in large quantities by several methods. One method
would be to use a large, enclosed, stirred reactor in place of the covered
beaker which was described previously, followed by centrifugation, washing,
and drying. Another method which was evaluated successfully was to meter-in
a caustic solution and carbon disulfide separately into a high shear contin-
uous mixer, mixing these with a flowing stream of the crosslinked starch-
29
-------
TABLE 4. ISX PREPARATIONS USING ADDITIONAL CAKE NASH HATER*
Wash-water
volume,
ml
1000
1SOO
2000
3000
4000
Product
wt,
g
147.2
140.0
137.2
135.2
134.6
1 S.
solvent
10.90
10.31
9.70
9.27
9.08
d.b.
Hash
11.86
10.88
11.00
10.20
10.18
t
solvent
9.88
9.05
3.48
8.54
9.17
HjO
flash
0.80
0.69
0.86
0.90
0.82
t Ash.
solvent
22.72
19.74
17.98
17.11
15.02
d.b.
flash
14.80
16.93
18.12
16.32
16.57
Na,
mg
10.00
10.29
10.00
9.14
10.29
Mg,
mg
5.83
5.64
7.17
7.50
8.33
Na/Mg
1.71
1.82
1.39
1.22
1.23
Capacity
meq/g
1.85
1.70
1.72
1.59
1.59
ISX was prepared using General Laboratory Preparation except wet cake was washed with additional water.
See Table 3 for other notations.
TABLE 5. ISX PREPARATIONS USING ADDITIONAL MAGNESIUM SULFATE IN CAKE WASH WATER*
Weight MgSCvi
in wash
water, g
0
10
20
30
Product
wt, g
140.0
139.7
142.1
149.1
t S, d.b.
solvent flash
10.31
8.32
8.09
7.51
10.88
9.47
9.52
8.87
% H20
solvent
9.05
8.17
9.62
13.49
flash
0.69
0.19
2.18
2.02
% Ash,
solvent
19.74
16.42
14.94
6.08
d.b.
flash
16.93
14.15
14.64
5.20
Na,
mg
10.29
6.71
6.43
1.20
mg'
5.64
9.72
10.89
13.89
NVMg
1.82
0.69
0.59
0.09
Capacity,
neq/g
1.70
1.47
1.48
1.38
ISX was prepared using General Laboratory Procedure except wet cake was washed with indicated weight of
MgSC>4 in water (500 ml) and then with water (1,000 ml). See Table 3 for other notations.
-------
TABLE 6. REUSE OF MOTHER LIQUOR IN THE XANTHATION OF CROSSLINKED STARCH*
Wt NaOH
added, g
45
38.85
39.35
39.57
Product
wt, g
140.0
144.5
144.5
141.8
% S, d.b.
solvent
10.31
11.33
10.93
9.38
flash
10.88
12.07
11.42
10.07
% H?0
solvent
9.05
8.76
8.45
11.52
flash
0.69
0.72
0.49
0.49
% Ash,
solvent
19.74
23.29
18.58
16.73
d.b.
flash
16.93
20.53
17.51
15.35
Na,
rag
10.29
11.14
11.00
9.80
Mg, Capacity,
rag
5.64
6.61
6.86
7.25
Na/Hg
1.82
1.68
1.60 '
1.35
meq/g
1.70
1.88
1.78
1.57
ISX was prepared using the General Laboratory Preparation by adding the indicated amounts of NaOH to
560 ml of the mother liquor of the preceding xanthation. See Table 3 for other notations.
-------
magnesium sulfate slurry. This method shortens the xanthation time to about
30 min due to the excellent mixing; however, an additional hold time (30 min)
would be required to obtain maximum xanthation. After the addition of some
water to thin the thickened slurry, the product was centrifuged, washed, and
dried (flash and freeze). Using the described experimental procedure, pro-
ducts were obtained which corresponded to beaker-prepared products.
A particle size distribution was run on a freeze-dried ISX sample using
a Sharpies Micromerograph. Figure 6 shows the particle size (95%) to fall
between 5-40 microns. Even though ISX has a small particle size, the settling
rate of the metal-ISX precipitate is very efficient. Scanning electron micro-
scope photographs of ISX particles showed them to be of irregular shape and
non-porous similar to starch granules.
As a measure of the binding ability of ISX for metal ions, Table 7
shows the solubility product constants for several metal ethyl xanthates (50).
Values for the metal-ISX should correspond very closely with those listed.
The higher the sulfur content of the ISX, the greater its capacity for heavy
metal binding. The pH of the effluent to be treated should be pH 3 or higher
since ISX is unstable at lower pH's. The ISX used in all the metal removal
studies in this report still contained some sodium hydroxide, so when stoichio-
metric quantities were added to the unbuffered metal solutions a rise is pH to
above 7 was observed. If the pH does not rise above pH 7, caustic should be
added since maximum removal for most metals to below discharge limits (Tables
8-11) occurs above this pH.
The data in Tables 8 and 9 shows that ISX is effective in lowering metal
concentrations to below stringent discharge limits from synthetic solutions.
When ISX was compared (Table 10) with sodium hydroxide and calcium hydroxide,
the ISX treatments resulted in lower residual metal concentrations. ISX has
been shown effective in metal removal for many different industrial effluents
(Table 11).
The ISX can be added as a solid or as a slurry to either batch type or
continuous flow systems. Most heavy metal cations are removed instantaneously
so only a short contact time is required; however, up to 60 min contact
is not detrimental to removal (Table 12) and in most cases increases removal.
In some cases less than stoichiometic quantities of ISX give excellent removal.
This is probably caused by the pH increase with ISX. Salt concentrations of
0-10% in wastewaters have little influence on metal removal by ISX as shown by
copper removal in the presence of sodium chloride (Table 13). Metals of any
concentration can be removed with theoretical amounts of ISX (Table 14); how-
ever, concentrations over 100 mg/1 might not be economically favorable.
The effluent after an ISX treatment contains only sodium and magnesium
ions from the ISX. The BOD and COD of treated effluents are not increased due
to ISX treatment and in some cases are even lowered. Therefore, effluents
treated with ISX offer a possibility of water reuse. There is no detectable
sulfur byproduct in the treated effluent unless a decomposed ISX is used. The
use of an ISX which has decomposed slightly will sometimes turn the effluent
pink-amber, but at a pH above 8.5 these metal-bearing decomposition products
usually precipitate leaving a clear colorless effluent.
32
-------
40
o>
(N
GO
»20
10
co
0
0 20 40 60 80 100
Wt. % Less than Indicated Diam. of ISX Particles
Figure 6. Particle size distribution of ISX.
33
-------
TABLE 7. SOLUBILITY PRODUCT
CONSTANTS FOR METAL ETHYL
XANTHATES (50)
Ksp, metal ethyl
Metal xanthate
Agl+
Bi3+
Cd2+
Co2+
Fe2+
Hg2+
Ni
PH
5
6
^
2
5
5
8
1
>
1
1
x io-19
X 10-30
10" 3^
.6 X 10'14
.4 X 10'13
.2 X 10'20
X lO'8
.7 X 10'38
102+ ._
.4 X lO"1^
.7 X.IO"17
Sn?- _.
4.9 X 10'9
An effective way to use ISX is to precoat filters with ISX and filter
aids then pass metal containing effluents through them. This technique would
eliminate any gravity settling or centrifuging separations. The ISX alone can
be initially precoated on the filter or the metal-ISX sludge could be separ-
ated in this manner. Several runs were made using different combinations of
ISX and filter aid media. If care is taken, the cake will not crack and in
these cases excellent copper removal was observed (<0.1 mg/1 residual copper).
When the cake cracked the copper removal was less efficient (0.5-6.6 mg/1
residual copper). The cake was removed after all runs and observed. The top
layer was always a dark gold color of an ISX-copper sludge, whereas the
section next to the filter paper was the pale yellow color of unused ISX. One
run was made using the filter containing a 0.6 cm layer of filter aid only
and then passing through it a copper-ISX slurry. The residual copper on this
run was less than 0.02 mg/1 from an initial copper concentration of 82.8 mg/1.
In all the runs, the increase in pressure drop was negligible which would in-
dicate the metal-ISX is more filterable than gelatinous hydroxide precipitates.
More specific information on the use of ISX as a precoat is being gener-
ated by an industrial company. Data supplied by company officials agrees with
our findings. Another company has installed this technique in their plating
shop for heavy metal removal from plating rinse solutions. Three pressure
filters are precoated with ISX only every 2 weeks and the rinse waters from a
copper plating line, a nickel plating line and a tin-lead line are passed
through the three filters separately. Even though the rinses are passed
34
-------
TABLE 8. REMOVAL OF HEAVY METAL CATIONS FROM WATER WITH ISX*
Initial cone., ISX, Residual cone., Illinois discharge
Metal mg/1 g mg/1 limit, mg/1
Ag+
A>
(^2*
Co2+
Cro!
Cuf
Fe2+
Hg2+
Mn2+
Ni2+
Pb2+
Zn2+
53.94
30.00
56.20
29.48
26.00
31.77
27.92
100.00
27.47
29.35
103.60
32.69
0.32
0.50
0.64
0.64
0.64
0.32
0.32
0.64
0.64
0.64
0.64
0.32
0.016
<0.010
0.012
0.090
0.024
0.008
0.015
0.001
0.015
0.160
0.035
0.294
0.005
—
0.050
___
1.0
0.020
1.0
0.0005
1.0
1.0
0.100
1.0
* Synthetic solutions (1,000 ml) containing the individual metals at the
indicated concentration were treated with the indicated amount of ISX
(capacity =1.56 meq metal ion/g) at pH = 3.7. Solutions were stirred
for 5-60 min at a final pH of 8.9. After filtration, the residual
metals were determined by a Varian Techtron AA 120. The theoretical
weight of ISX for a divalent metal is 0.64 g. Value listed with less
than (<) was below detection limit.
through the cakes periodically, the average residual metal concentrations are
copper (0.06 mg/1), nickel (0.57 mg/1), and tin-lead (0.33 mg/1-0.09 mg/1).
This system has been in operation for 20 months with complete water recycle.
Complexed metals sometimes can be effectively removed with ISX; however,
this depends totally on the complexing agent. Copper complexes with EDTA,
NTA, citrate, tartrate, gluconate, and pyrophosphate are only partially removed
with ISX. If the pH of solutions of these complexes are lowered to a pH 2.5-
5.0, the complex dissociates and more effective copper removal is attainable.
The copper-ammonia complex [CufWj^2*) which is still positively charged is
effectively removed by ISX (see Copper Etchants under Circuit Board Effluents).
A consulting engineering firm has found that ISX effectively removes copper
from a copper-dye complex and has designed a 4.75 million I/day treatment
facility using ISX as a copper scavenger. Another company has found ISX
effective in removal of a copper-lignin complex (100 mg/1 copper) at 90°C and
pH 13-14. The presence of lime had no effect on the effectiveness of ISX in
this system.
The metal-ISX sludge settles fairly rapidly (95-98% settled in 10 min)
and the sludge can be removed by a clarifier, centrifuge, or filter. The
sludge obtained from a filter using small quantities of ISX is around 50%
35
-------
TABLE 9. REMOVAL OF METALS FROM DILUTE
SOLUTION WITH ISX*
Initial cone., Residual cone.,
Metal mg/1 mg/1
Cd2+
Co2*
Cr^+
Cu2+
Fe2+
Hg2+
\jtr\&''
i*J»»
Ni2+
Pb2+
Zn2+
5.62
2.95
2.60
3.18
2.79
100.00
2.75
2.93
10.36
3.27
0.001
<0.010
0.026
<0.005
0.001
0.0007
0.010
<0.050
<0.031
0.007
* A synthetic solution (1,000 ml) containing a
mixture of heavy metals of the indicated
concentrations at pH 3.5 was treated with ISX
(capacity =1.56 meq metal ion/g, 0.32 g) to
a final pH = 8.9. After filtration the residual
metals were determined by a Varian Techtron AA 120.
Values with less than (<) were below detection
limits.
solids which allows its handling ease. After 3 hr drying under ambient condi-
tions, the thin cakes increase to 90% solids. Thicker cakes would require
several days for drying (Table 15).
The metal-ISX can be landfilled or treated for metal recovery. If the
sludge is landfilled, the metal is bound fairly strongly and would have less
chance to be leached out than with a hydroxide sludge.
Recovery of the metal from ISX-metal sludge is possible by acid stripping
or incineration. The use of soluble complex eluting agents (EDTA, etc.) has
been totally ineffective in metal removal from a metal-ISX sludge. Several
acid stripping procedures were evaluated to recover a concentrated solution of
the metal ions and to recover the crosslinked starch for rexanthation. When a
copper-ISX sludge was treated with 6N HC1 or 18N ^804, ineffective copper
recovery was obtained (7% and 2.8%, respectively). However, when 4N HNO* was
evaluated, complete copper recovery was obtained (see p. 13). The same has
been found true for all metals evaluated except gold (0% stripped) and mercury
(3% stripped). Contacting the ISX-metal sludge with sodium or magnesium salts
showed no exchange with the copper.
36
-------
TABLE 10. HEAVY METAL REMOVAL FRCM 95 LITERS OF WATER*
Treatment
I
II
III
IV
V
Chemical
added
None
ISX*
None
NaCH§
NaOH
NaCH
NaOH
NaOH
None
Ca(OH)2#
Ca(OH)2
CaCCH)2
Ca(OH)2
Ca(CH)2
Ca(CH)2
None
NaCH
ISX
ISX
ISX
None
NaCH
NaOH
ISX
ISX
ISX
Concentration of metal
Illinois
Amount!-
added
103 g
190ml
2 ml
10 ml
6.5ml
23.5 ml
200 ml
13 ml
16 g
24 g
32 g
19 ml
1 ml
5.5 g
6.0 g
11 g
added
PH
6.5
7.0
2.3
6.5
7.0
7.5
8.0
9.0
6.7
6.5
7.0
7.5
8.0
9.0
10.0
6.5
7.0
7.5
8.0
8.5
3.3
6.5
7.0
7.5
8.0
8.5
Discharge Limit
Cd
Ug/1
5440
13
5260
5260
5100
4740
3610
1130
4740
4690
4460
3890
3140
330
9
5050
4720
3530
19
8
5930
5460
5300
4840
2010
6
5620
50
Cr
W5/1
2790
18
2930
1150
436
143
36
53
1040
36
18
14
14
14
14
7
125
0
0
0
2930
0
0
0
0
0
2600
1000
Cu
wg/1
3260
9
3350
1520
1450
630
108
76
1110
985
477
246
68
10
10
65
237
88
26
14
3230
72
14
4
3
0
3180
20
Fe
ug/1
3030
111
3040
47
486
139
14
72
1110
50
11
17
17
17
17
28
150
14
17
17
2670
17
17
0
1
17
2790
1000
Pb
WK/1
3670
0
4130
1740
2290
1100
46
183
2940
1650
275
46
46
23
23
826
826
183
46
23
6330
2940
692
0
0
0
10360
100
1*1
Mg/1
2740
2380
2670
2630
2630
2630
2420
1579
2780
2420
2320
2260
2100
990
0
2840
2840
2740
2630
1900
2950
2840
2740
2590
2020
0
2750
1000
Hg
Mg/1
9900
54
9960
>100
9800
>100
9900
9900
150
92
1.5
9850
140
93
29
10000
0.5
Ni
Mg/1
2960
23
2850
2830
2810
2790
2380
790
2920
2560
2460
2310
2270
1540
23
3000
2710
2100
115
23
2850
2770
2520
1770
15
6
2940
1000
Ag
wg/1
62
4
62
49
56
68
52
47
36
36
16
31
41
31
21
47
36
16
2
2
83
62
47
26
42
0
5390
5
Zn
Pg/1
2020
13
2900
2820
2590
1700
36
56
2510
2770
2200
1370
110
10
10
2310
1920
1100
51
10
2920
2350
2000
740
5
5
3270
1000
COD
mg/1
61
128
142
82
82
34
21
23
* Treatments I-IV were in 95 1 of tap water. Treatment V was in distilled water.
t The chemicals were added in the increments shown to reach the pH listed.
* ISX (!•! meq metal ion/g].
I NaCH (200 g/1).
» Ca(OH)2 (200 g/1).
37
-------
TABLE 11. TREATMENT OF INDUSTRIAL EFFLUENTS WITH ISX*
oo
Industrial effluent
sample
Steel pickling rinse
initial
treated
Nickel plating rinse
initial
treated
Zinc mine drainage
initial
treated
Aerospace plating rinse
initial
treated
Aerospace plating rinse
initial
treated
Aerospace plating rinse
initial
treated
Aerospace plating rinse
initial
treated
Aerospace plating rinse
initial
treated
Chemical plating rinse
initial
treated
Initial
PH
7.5
—
7.6
—
3.5
—
5.3
—
5.3
—
5.1
—
4.4
—
3.1
—
4.5
ISXt
wt, g
0.0612
—
0.9238
—
0.0315
—
0.1596
—
0.0416
—
0.2892
—
0.0302
__-
0.0510
—
0.2452
Final
PH
9.0
—
10.7
—
7.7
—
6.7
—
7.3
—
6.2
—
7.0
.__
7.5
—
7.1
Cd2+
87
5
150
4
333
13
147
0
833
17
4,197
15
Cr3+
250,000
216
19,444
13
3,611
744
2,833
222
20,000
17
Metal cone., vg/1
Cuz+ FeZ+ Pb2* Ni<+
34,640
120
923,000
34
150 3,045 555
16 0 0
105
9
1,340 47,180 267 6,640
16 3,227 0 55
105
0
217
0
141,000 13,111
100 166
a/*
4,836
16
* Sample (50-ml) of industrial effluent treated as received.
t ISX (1.1 meq metal ion/g).
-------
TABLE 12. EFFECT OF STIRRING TIME ON
COPPER REMOVAL WITH ISX*
Stirring time, Residual copper cone.,
min mg/1
1
5
30
60
120
240
480
0.02
<0.01
<0.01
0.02
0.06
0.08
0.08
* A solution (1000 ml) containing copper
C31.77 mg/1) at pH = 4.0 was treated with
ISX (0.653 g, 1.53 meq metal ion/g to pH = 8.9.
Aliquots (10 ml) were removed at the
indicated times and were filtered. The
residual copper concentration was determined
by a Varian Techtron AA 120 spectrophotometer.
TABLE 13. EFFECT OF COPPER REMOVAL WITH ISX IN THE PRESENCE
OF SODIUM CHLORIDE*
NaCl, Residual copper cone.,
g
0
1
2
5
10
mg/1
0.025
0.049
0.069
0.166
0.219
Sludge color
gold-brown
light gold
light gold
light gold
dark yellow
1 Copper removal
99.92
99.85
99.78
99.48
99.31
* Solutions (100 ml) containing copper (31.77 mg/1) and the
indicated weight of NaCl were treated with ISX (0.063 g, 1.53 meq
metal ion/g) at pH 3.7. Solutions were stirred 5 min to a final
pH of 8.6. After filtration, the residual copper concentration
was determined by a Varian Techtron AA 120.
39
-------
TABLE 14. EFFECT OF COPPER CONCENTRATION ON
COPPER REM3VAL WITH ISX*
Initial
copper cone.,
mg/1
0.5
1.0
5.0
10.0
50.0
100.0
ISX,
g
0.010
0.020
0.103
0.205
1.025
2.050
Final pH
8.0
8.1
8.7
8.8
9.2
9.2
Residual copper cone.,
mg/1
<0.01
0.05
<0.01
<0.01
0.04
0.03
* Solutions (1,000 ml) containing the indicated amounts of copper and
ISX (1-53 meq metal ion/g) were stirred 5 min and filtered. The
residual copper concentration was determined by a Varian Techtron
AA 120 spectrophotometer.
TABLE 15. COPPER-ISX
SLUDGE DEWATERING*
Weight of sludge,
Days g % Solids
0
1
2
3
6
779
668
553
418
220
25.7
30.0
36.2
47.8
90.0
1
* A copper solution (100 mg/1, 25 gal)
was treated at pH 4.0 with ISX (200 g,
1.5 meq metal ion/g) to a final pH of
8.8. After 5 min the, slurry was
filtered through a Buchner funnel
until no visible water remained. The
3 cm sludge cake was crumbled and
allowed to air dry at 22°C and 50%
relative humidity. Theoretical sludge
weight is 200 g.
40
-------
TABLE 16. GOLD
REMOVAL WITH ISX*
Final
pH
4
5
6
7
8
9.8
Residual gold,
mg/1
0.182
0.221
0.125
0.091
0.456
3.812
* Solutions (100 ml) containing
gold (30.0 mg/1) were treated
at the indicated pH's with ISX
(0.05 g, 1.53 meq metal ion/g).
After filtration, the residual
gold was determined by AA.
A study was made to determine the most effective pH for gold removal with
ISX. Table 16 shows that gold removal is best around pH 7 whereas for most
other metals higher pH's give better removal with ISX. As previously men-
tioned, 4N HN03 was ineffective in recovering gold from an ISX sludge. Aqua
regia (1 part HNOsrS parts HC1) was 100% effective in gold recovery and this
would allow its recovery in a pure state (see p. 13).
The crosslinked starch recovered after 4N HN03 treatment of a metal-ISX
sludge can be rexanthated for reuse. The acid treatment does destroy some of
the crosslinking but at least one regeneration still yields an effective metal
removal product. If a copper-ISX sludge is treated with 4N HN03, a product is
obtained that still contains 50% of its sulfur (Table 17) and this starch xan-
thide is still very effective in metal removal above pH 7.
BRASS MILL WASTEWATER
Our major objective in treating the brass mill wastewater we chose was to
lower the present total copper concentration from 0.2 mg/1 to 0.02 mg/1 so the
wastewater could be discharged to an Illinois creek having a 0.02 mg/1 copper
discharge limit. Preliminary bench scale experiments using ISX in combination
with filtration suggest that this objective may be achieved by a supplemental
process to conventional treatments. Since the brass mill has a high volume
flow (11.3 X 10^ I/day), we tried to adopt methods that would be economically
feasible for this industry.
41
-------
TABLE 17. NITRIC ACID (4N) TREATMENT OF ISX PRODUCTS*
Product analysis
«
Material
Crossliriked starch
ISX
Copper- ISX
Zinc-ISX
g
88
65
78
71
% S
0.05
0.07
8.14
0.27
* H20
6.84
6.88
5.08
7.60
% Ash
0.44
0.41
0.53
0.43
% N
0.10
0.06
0.11
0.05
The materials (100 g) were slurried in 4N HN03 (500 ml) for 30 min.
After filtration and a water wash, the cake was reslurried and adj listed
to pH 6.5 with IN NaOH. The slurry was filtered, water washed, acetone
dried, and air dried.
The results in this section were interpreted by making the following
assumptions: (a) The copper content is the total copper present in whatever
form it exists, i.e., as the unsettled copper-ISX complex, as Cu2* or Or-
ion, or as the hydroxide, carbonate, or oxide. The predominant species will
be governed primarily by the pH of the wastewater at the time of sampling.
(b) The jar tests are on a comparative basis only, comparing the amount of
total copper in suspension or solution at a fixed depth (3.2 cm), between
samples having different additives, pH's, etc. (c) The brass mill wastewater
samples evaluated were obtained at different times and some minor variations
in our data are representative of slightly different composition of wastewater
samples *
Preliminary jar test experiments were run on synthetic copper solutions
to obtain information and techniques which could be applied to an actual brass
mill wastewater. Since the brass mill wastewaters that we were working with
contained approximately 200 yg/1 copper at a pH of 9.0 to 9,5 after conven-
tional treatment, our studies with synthetic copper solutions were conducted
under these conditions. It is well known that at these pH's most of the cop-
per will precipitate as the hydroxide and will be present as small colloidal
particles. Sand filtration showed only limited removal (0-10%) starting with
200 yg/1 total copper at pH 9.0, while millipore filtration (0.45 y) showed
consistent copper removal (80%) on settled supernatants. Figure 7 shows data
which also corraborates the presence of colloidal copper hydroxide, since ISX
is ineffective in removing colloidal copper hydroxide. The increase in copper
concentration at the 25-mg ISX addition is probably due to additional copper-
ISX fines in suspension. All figures in this section include settling curves
at 10 and 30 min to show that longer settling times increase removal.
If the copper is present as colloidal copper hydroxide particles, coagu-
lant aids such as alum should aid in its settling. Several evaluations using
alum alone with synthetic copper solutions resulted in considerable copper
42
-------
160
140
^120
•
i 100
A—A 10 min Settling, pH = 9.0
A—A30 min Settling, pH = 8.4
^^
- A..7^*£>
-------
removal (20-80%) by settling of the colloidal copper hydroxide. Since alum
additions always lowered the pH, the pH was always readjusted to 9 unless
otherwise noted.
A combination treatment using ISX and alum at different concentrations
(Figures 8-10) shows that both soluble copper and colloidal copper hydroxide
can be lowered to very low residual copper concentrations. Figure 8 shows an
evaluation at constant A13+ (10 mg) and variable ISX (0-25 rag) at pH 9.0.
Figures 9 and 10 report data to show the effectiveness of variable amounts of
both ISX (5-15 mg) and Al3+ (0-25 mg). For these solutions ISX (15 mg) and
A13+ (10 mg) resulted in 95% copper removal in 10 min settling which is suffi-
cient to reach strict discharge limits (20 yg/1). The addition of increasing
amounts of alum gives greater copper removal, and even though there was some
turbidity at the 10-min sampling, excellent copper removal was obtained.
Several synthetic copper solutions were screened with ISX, coagulant
aids, and other additives using centrifugation as a means of separation.
Several industries use centrifuges as a means of separation of sludges so
copper solutions were evaluated over a broader concentration range. The data
in Table 18 show results that were very erratic, from which no definite con-
clusions can be drawn. Since the majority of the suspended solids formed was
copper hydroxide, it is assumed that the centrifugation techniques used in
these experiments were not optimum. The data do show that the pH is very
critical to obtain low residual copper concentrations. At the pH's we were
working at (7.3-9.3), alum was more effective in coagulating the colloidal
copper hydroxide, aiding its removal than the polymers evaluated. ISX showed
some improvement in soluble copper removal (Table 18).
The brass mill wastewater was also evaluated using centrifugation and ISX,
alum and other additives. Tables 19 and 20 show results that were more con-
sistent. Longer spin times using ISX in batch centrifugation studies gave
excellent results (Table 19 and Figure 11); however, this technique would not
be practical for industries having large water flows. The use of alum also
aided coagulation which resulted in more effective suspended particle removal.
Table 20 shows data from continuous centrifugation studies. Even though the
residual copper concentrations were still above desired concentrations, some
general trends were observed. The use of ISX, alum, and polymers, if properly
used, should aid in the removal of copper.
Preliminary jar test screening of ISX, coagulants, and other additives
on the brass mill wastewater was performed and the results are shown in Tables
21-25. If the pH is above 8.5, alum or ferric ion alone will reduce the resi-
dual copper to 20 yg/1 and/or remove greater than 90% of the total copper.
However, if the pH was below 8.0, ISX or sulfide ion was needed along with the
coagulant aid. Soluble starch xanthate alone compared to a commercial poly-
electrolyte (Olin 5002) was less effective considering the dosage required.
However, the addition of ISX to the soluble starch xanthate showed increased
copper removal. A commercial polymer (Dearborn 420) showed improvement in
copper removal with ISX and alum. In other studies, soluble starch xanthate
(4.2 mg/1) in the pH range of 9.8-11.7 was equally effective in copper removal
to commercial polymers (1.4 mg/1).
44
-------
tofl
160
4
140
120
4
•»
1 100
I 80
g 60
« 40
20
0
pH = 9.0
A—A 10 min. Settling
A—-A 30 min. Settling
Initial Copper Cone. 176-192//g/l
0 5 10 15 20 25
ISX(mg)/950 ml Synthetic Copper Solution
Figure 8. Treatment of synthetic copper solutions with ISX and Al .
45
-------
pH = 9.02-9.15
-a n
Initial Copper Cone.
162-210 m/\
Settling,
ISX, mg minutes
A
© © 10
0 5 10 15 20 25
AI3+ (mg]/950 ml Synthetic Copper Solution
Figure 9. Treatment of synthetic copper solutions with Al and ISX
(I copper removal).
46
-------
Settling,
ISX, mg minutes
A—A 5
A—A 5
©—0 10
©—© 10
D—a 15
a—a 15
10
30
10
30
10
30
pH = 9.02-9.15
Initial Copper Cone.
162-210 m/\
-n D
0 5 10 15 20 25
AI3+|mg]/950 ml Synthetic Copper Solution
Figure 10. Treatment of synthetic copper solutions with Al3* and ISX.
47
-------
TABLE 18. COPPER REMDVAL BY CENTRIFUGATION FROM SYNTHETIC COPPER
SOLUTIONS COMPARING SEVERAL ADDITIVES*
Feed
mg/1
ISX Al3* Na2S
26.4
6271
1,056§
20
20
12
12
10
10
21
20
20 10 ---
2.6
2.6
5.7
S.7
11.4
11.4
11.4 10 ---
9.8 --- O.S
0.5
10 —
10 15 ---
SSXt polymer
— —
— —
— —
4#
— —
4#
— —
4
— —
4#
4#
4#
4#
— —
4#
— —
1.5#
3.0#
— —
— —
3n#
™
— —
4n**
pH
9.6
8.1
8.0
8.0
8.0
7.8
—
—
—
8.5
9.0
9.0
9.0
9.1
9.1
—
—
8.6
8.6
9.3
9.0
9.0
9.0
9.0
9.3
9.3
9*c
.JO
9.0
8.45
Total Cu
mg/1
306
455
20,700
3,860
3,860
405
405
159
159
189
235
205
205
300
300
244
244
249
202
193
200
263
146
146
245
243
TJI-t
o41
280
140
Centrate
Total Cu
pH mg/1
9.6
—
—
—
—
7.9
—
8.4
8.4
8.8
—
—
—
—
—
7.3
7.8
—
—
—
—
—
—
—
—
—
...
140
370
3,620
870
260
265
240
150
140
160
100
66
40
60
160
244
244
115
110
10
110
115
78
70
10
0
1 QT
j.yj
180
85
*
Removal*
54.2
18.7
82.5
77.5
93.2
34.6
40.7
5.7
11.9
15.3
57.4
67.8
80.5
80.0
46.6
0
0
53.8
45.5
94.8
45.0
56.2
46.6
52.1
95.9
100.0
At A
43.4
35.7
39.3
* Synthetic copper solutions (95-150 1) were treated with additives as
indicated at a feed rate of 6.0 +_ 0.3 LPM and 26,600 X G in the Super
Centrifuge.
t Soluble starch xanthate (D.S. 0.11, freshly diluted).
* % Removal = Feed copper -centrate copper x 1QO>
ZoCQ COppGT
i Added in larger amounts to raise the pH.
# Dearborn 420.
** Nalcoyte 676.
48
-------
100.0
« 10.0
1.0
0.1
0
©
\
pH = 7.1
30 mg/l ISX
•- -• 3,200 x G
A—A 12,800 x
©—©28,500 x
Temp. 22-26°C
0
20 40 60 80
Residual Cu, i/g/l.
100
Figure 11. Laboratory batch centrifuging of brass mill wastewater
with ISX only.
49
-------
TABLE 19. COPPER REMOVAL FROM BRASS MILL WASTEWATER
USING BATCH CENTRIFUGATION*
Initial Final
ISX
30
30
30
30
30
30
30
30
30
mg/1
A13+ Polymert
— —
1.0
5
5
5
"""•"" — *""•*
Clay* pH
— 7.1
— 7.1
— 7.1
— 7.1
— 7.1
— 7.1
20 7.1
— 7.1
— 7.1
cu
yg/1 pH
202 —
202 —
202 7.1
202 ---
202 —
202 ---
202 —
202 —
202 —
Cu
Vg/1
112
104
33
15
46
29
31
22
49
MMMMBMMMMtMM
.Spin
MMWMMMUBBIlMlM
MMMMIMMIMMMM
time, %
min
0.66
1.0
20.0
60.0
60.0
60.0
60.0
60.0
60.0
X G
28M
28M
28M
28M
12. 8M
12. 8M
12. 8M
12. 8M
28M
Removal §
44.5
48.5
83.6
92.6
77.2
85.6
77.7
89.1
75.7
* Samples (20 ml) were treated with additives as indicated and centrifuged
in the Beta-fuge.
t Nalcolyte 676.
* Bentonite.
- *
A comprehensive series of jar tests were performed on the brass mill
effluent with ISX alone (0-25 mg) at various pH's (Figure 12). The reduction
in total copper was 26-55% of the initial concentrations after 10 min of
settling. The minimum residual copper values exhibited at 10 mg ISX were noted
previously (Figure 7) , however the theoretical amount of ISX to remove 200 yg
soluble copper is only 3.3 mg.
The use of alum as a coagulant aid to promote faster settling of copper
bearing solids was evaluated more completely on the brass mill wastewater.
This additive was chosen because it is commonly used in water clarification.
The addition of alum to brass mill wastewater samples resulted in a lowering
of pH (Figure 13). If the pH is not adjusted to above pH 8.0, very little
copper removal was observed and the solutions were all turbid. When samples
were readjusted to 9.1 and 10.0 after using various alum dosages, good copper
removal was obtained (Figure 14) . Up to approximately 4 mg A13+ the copper
removal was poor; however, above 5 mg A13+ copper removal increases to 90% at
pH 10.0. All supernatants were clear in 1-2 min; however, the settled solids
were voluminous and easily resuspended. Figure 15 shows that ferric ion as
50
-------
TABLE 20. COPPER REMOVAL FROM BRASS MILL WASTEWATER
USING A CONTINUOUS CENTRIFUGE*
Feed§ Centrate
mg/1 Total Cu Total Cu %
ISX A13+ Na2S SSXt Polymer* pH yg/1 pH yg/1 Removal
3.1
3.1
11.4
11.4
5.7
—
...
5.0
— — _„_
— —
— — —
...
— ... ...
10
10
...
4.0
—
2.0
3.0
...
...
...
8.1
8.1
8.6
8.8
8.6
7.6
7.1
6.95
224
224
224
242
200
219
346
243#
8.1
8.1
8.8
8.9
—
7.S
7.2
7.2
100
85
108
86
110
170
160
150**
55.4
62.1
55.3
64.4
45.0
22.4
53.7
38.3
* Samples (95 1) were treated with additives as indicated and
centrifuged in a P-600 centrifuge and super centrifuge.
t Soluble starch xanthate.
$ Dearborn 420.
§ Feed rate 6.0 = 0.3 LPM; 26,600 X G (Super Centrifuge).
f Feed rate 4.0-10.0 LPM; 5,300 X G (P-600).
** Average of 6 centrate samples.
ferric chloride was also an effective coagulant and even slightly better than
alum. The supernatants were all clear after 1-2 min of settling. Lime was
used to adjust the pH to 9.0.
A series of studies was made to determine whether ISX with a coagulant
aid would help to reduce the soluble copper concentration to below 20 yg/1.
Figure 16 shows some typical results using varying amounts of alum and ISX on
the brass mill wastewater. As little as 5 mg ISX and 5 mg A13+ lowered the
residual copper to below 10 yg/1. The samples having 10-20 mg A13+ were
slightly turbid with the turbidity increasing with alum content. The 10-min
settling samples were analyzed for residual aluminum concentration (3.0, 3.8,
7.7, 10.0 mg/1). Numerous other evaluations were run on the brass mill efflu-
ents which were received over a 6-month period. The results obtained were
very similar to the data of Figure 16. Figure 17 depicts data using ISX
(10 mg) and A13+ (0-10 mg) without pH adjustment back to 9.0. As the pH de-
creases with increasing A13+ amounts the residual copper concentration in-
creases but at 5 mg Al3+ it is still below the desired 20 yg/1.
51
-------
TABLE 21. PRELIMINARY JAR TESTS ON BRASS MILL WASTEWATER
COMPARING VARIOUS ADDITIVES*
mg/950 ml Wastewater
ISX
0
0
0
5
10
15
0
0
0
0
0
0
0
5
5
10
10
10
Soluble
starch
xanthatet
0
4
12
4
8
12
0
0
0
0
0
0
0
0
0
0
0
0
Polyelectrolytet
0
0
0
0
0
0
0
0.35
0.7
1.0
1.4
2.1
0
0
0
0
0
0
A13+
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5.2
0
5.2
10.4
Initial
Cu
wg/1
211
211
211
211
211
211
211
211
211
211
211
211
217
217
217
217
217
217
Final
Cu
yg/1
200
200
183
177
171
166
185
191
179
185
185
185
168
158
25
147
20
20
Final
PH
8.8
8.8
8.9
8.8
8.8
8.95
9.05
9.05
9.05
9.05
9.05
9.05
8.6
8.6
6.7
8.7
6.8
6.1
%
Reduction
5.2
5.2
13.2
16.1
18.9
21.3
12.3
9.5
15.1
12.2
12.3
12.3
22.6
27.2
88.5
32.2
90.8
90.8
Supernatant
at sampling
Slightly turbid
Slightly turbid
Slightly turbid
Slightly turbid
Slightly turbid
Slightly turbid
Very si. turbid
Very si. turbid
Very si. turbid
Very si. turbid
Very si. turbid
Very si. turbid
Clear
Clear
Slightly turbid
Clear
Slightly turbid
Slightly turbid
* Samples (950 ml) were treated with the indicated additives and evaluated using standard jar test
techniques. Samples were removed 3.2 cm below the surface after 10 min of settling.
t Soluble starch xanthate (D.S. 0.11, freshly diluted).
* Olin 5002.
-------
TABLE 22. PRELIMINARY JAR TESTS ON BRASS MILL WASTEWATER
COMPARING VARIOUS ADDITIVES*
(J*
ISX
0
0
0
0
0
0
0
10
10
10
0
0
0
10
10
10
0
0
A
0
0
5
10
0
10
0
0
0
7
0
10
0
0
0
7
0
10
L3+
.2
.4
.4
.8
.4
.8
.4
mg/1
Na2S
0
0
0
0
15
15
0
0
0
0
0
0
0
0
0
0
0
0
Fe2*
0
0
0
0
0
0
0
15
0
20
0
0
0
0
0
0
0
0
Fe3+
0
0
0
0
0
0
0
0
0
0
0
0
0
0
15
0
20
0
Initial
Cu
yg/1
224
224
224
224
224
224
211
240
200
211
257
231
213
197
165
206
197
219
Final
Cu
vg/l
174
182
56
61
167
5
159
114
108
20
50
105
135
97
13
10
15
7
Final
pH
8.3
9.2
6.6
6.0
8.8
6,2
8.4
8.5
8.4
7.8
8.2
8.2
9.1
9.1
8.8
8.9
8.8
8.5
% Supernatant
Reduction at sampling
22.3
18.7
75.0
72.5
25.4
99.0
24.6
52.5
46.0
90.5
80.5
54.5
36.6
50.7
92.4
95.1
92.4
96.8
Clear
Clear
Clear
Clear
Clear
Slightly turbid
—
—
Deep yellow
—
Deep yellow
:
Clear
Clear
Clear
Clear
Clear
Clear
color
color
* Samples (950 ml) were treated with the indicated additives and evaluated using standard jar test
techniques. Samples were removed 3.2 on below the surface after 10 min of settling.
-------
TABLE 23. PRELIMINARY JAR TESTS ON BRASS MILL WASTEWATER
COMPARING VARIOUS ADDITIVES*
mg/1
ISX
0
10
20
10
20
0
0
10
10
10
10
10
Initial
rsi
A13+ Polyelectrolytet yg/1
0
0
0
5.2
10.4
10.4
0
2.6
5.2
7.8
10.4
5.2
0
0
0
0
0
0
0
4
4
4
4
12
210
210
210
210
210
210
83
83
83
83
83
83
Final
fii
yg/1
59
38
30
16
3
19
40
2
7
2
2
2
PH
8.7
8.75
8.7
8.6
8.6
8.6
9.05
8.8
8.8
7.9
6.8
7.2
Reduction
71.9
81.0
85.7
92.4
98.7
90.9
51.8
97.6
91.4
97.6
97.6
97.6
* Samples (950 ml) were treated with the indicated additives and
evaluated using standard jar test techniques. Samples were removed
3.2 on below the surface after 10 min of settling.
t Dearborn 420.
Some of the information presented shows that the use of coagulants (alum
or ferric chloride) alone will lower copper concentrations to below the de-
sired 20 yg/1. Even though this was found to be true occasionally, the only
consistent copper removal to below 20 yg/1 was obtained with A13+ (>10 mg)
and ISX (>10 mg). To be certain of these evaluations on-site testing was
performed on fresh brass mill wastewaters. Figure 18 shows the results of
this testing. From the curves it is apparent that pH adjustment is required
and that ISX is required to reach 20 yg/1 residual copper.
Company representatives have worked closely with us on our evaluations
and the data generated from this study will be very useful to this type of
industry in reducing high residual copper concentrations in their effluent,
however considerably more work must be done to generage data using ISX in a
technically feasible and economically reasonable treatment process for waste-
waters containing heavy metals in a large volume, continuous flow facility.
Further scale-up of these techniques to a pilot plant size column (6-in
diameter) would be required to show its overall potential in large water flow
situations as an advanced stage of treatment following the conventional lime-
neutralization, flocculation, and sedimentation treatment process. Many in-
dustries which discharge wastewaters containing heavy metals have installed
or must install conventional lime-neutralization wastewater treatment
54
-------
TABLE 24. PRELIMINARY JAR TESTS ON BRASS MILL WASTEWATER
COMPARING VARIOUS ADDITIVES*
mg/1
ISX
0
10
10
10
0
0
0
10
0
0
0
0
0
10
0
0
0
0
0
10
0
0
0
0
0
0
0
0
0
0
0
10
10
10
10
10
10
A13+
0
10.4
26.0
52.0
52.0
104.0
0
0
2.6
5.2
7.8
10.4
0
0
2.6
5.2
7.8
10.4
0
0
2.6
5.2
7.8
10.4
0
0
0
10
10
10
10
0
0
10
10
10
10
Polymert
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1.4
1.4
1.4
0
1.4
0
1.4
1.4
1.4
0
1.4
0
Initial Final
Cu Cu
ug/1 ug/1
246
234
223
240
243
246
231
220
244
215
515
238
181
178
178
170
170
170
200
194
195
181
211
184
3,980
3,980
3,980
3,980
3,980
3,980
3,980
3,980
3,980
3,980
3,980
3,980
3,980
154
30
146
74
211
217
88
113
54
41
44
51
153
142
44
33
71
74
155
142
74
37
34
32
1,046
130
800
492
561
92
92
103
561
271
400
35
40
Final
PH
9.2
6.6
4.8
4.3
4.3
4.1
9.6
9.4
9.0
8.6
7.5
7.1
9.3
9.3
9.4
8.5
6.7
6.7
9.0
9.0
7.0
8.4
8.4
8.4
6.3
9.1
6.4
5.7
5.7
9.1
9.1
9.1
6.6
5.5
5.5
9.1
9.0
t
Reduction
37.4
87.2
34.5
69.2
13.1
11.8
61.9
48.6
77.9
80.9
91.4
78.5
15.5
20.2
75.3
80.6
54.7
56.5
22.5
26.8
62.4
79.5
83.9
82.9
73.7
96.7
79.9
87.6
85.9
97.8
97.8
97.4
85.9
93.2
89.9
99.1
99.0
Supernatant
at sampling
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Clear
Some floe
still
suspended
Some floe
still
suspended
Clear
Best floe
Worse floe
SI. turbid
SI. turbid
SI. turbid
SI. turbid
Clear
SI. turbid
Clear
SI. turbid
Clear
SI. turbid
* Samples (950 ml) were treated with the indicated additives and evaluated
using standard jar test techniques. Samples were removed 3.2 cm below the
surface after 10 min of settling.
t Olin 5002.
55
-------
TABLE 25. PRELIMINARY JAR TESTS ON BRASS MILL WASTEWATER
COMPARING VARIOUS ADDITIVES*
mg/1
ISX
0
0
5
5
0
5
0
5
0
10
5
10
0
0
0
0
5
15
A13+
0
10
2.5
5
5
10
0
5
10
5
10
15
0
5
10
20
10
10
Initial
Cu
yg/1
137
107
128
121
157
114
206
212
227
241
214
232
276
276
286
490
95
110
Final
Cu
yg/1
65
30
55
50
60
37
82
9
12
9
5
5
95
40
40
45
30
26
Final
PH
9.1
9.1
9.1
9.1
9.1
9.1
9.1
9.0
9.0
9.0
9.0
9.0
9.1
9.1
9.0
9.0
9.1
9.1
%
Reduction
52.5
72.0
57.0
41.3
61.7
67.5
60.2
95.7
94.7
96.3
98.1
97.8
65.6
85.5
86.0
90.8
68.4
76.3
Comments
Clear
Clear
Very si. turbid
Very si. turbid
Very si. turbid
Clear
Clear
Clear
SI. floe suspended
Clear
Very si. floe suspended
Very si. floe suspended
Best
Best
Next best
Few floes suspended
Few floes suspended
Few floes suspended
* Samples (950 ml) were treated with the indicated additives and
evaluated using standard jar test techniques. Samples were removed
3.2 cm below the surface after 10 min of settling.
facilities to comply with the U.S. EPA Best Practical Treatment (BPT) guide-
lines. The most effective use of ISX with or without coagulants as an
integral part of the conventional treatment process must be investigated fur-
ther to determine whether or not the additional equipment and processes for
advanced ISX treatment are necessary or economically reasonable.
LEAD BATTERY EFFLUENTS
Our major objective in treating the lead battery effluents we chose was
to lower the lead concentration to less than 0.05 mg/1. One lead battery
company (Indiana) wanted to reduce their residual lead concentration to less
than 0.05 mg/1 and also to reduce their dissolved solids concentration so the
water could be reused. During our bench-scale evaluations to reduce the lead
concentration with ISX, we also considered dissolved solids removal. The
other lead battery company (Pennsylvania) only desired lead removal to less
than 0.05 mg/1 .
56
-------
Initial Copper Cone. Settling,
x/g/l minutes
\\ Q—a 10.0
* \
0 5 10 15 20 25
ISX(mg)/950 ml Brass Mill Wastewater
Figure 12. Treatment of brass mill wastewater with ISX only.
57
-------
=c 100
80
» 60
120*x-(8.45)
*\
o»
sa.
a
o
_ 40
c
20
0
{ = pH Due To
Alum Addition
A A 10 min
A—A 30 min
Initial Copper Cone.
106-130 ni/\.
0 5 10 15 20 25
AI3+ (mgj/950 ml Brass Mill Wastewater
Figure 13. Treatment of brass mill wastewater with Al only
(no pH readjustment).
58
-------
pH 9.1 10 min
A—A pH 9.1 30 min
©—© pH 10.0 10 min
©--© pH 10.0 30 min
Initial Copper Cone.
107-133, fig/\
—0-
•-0 -5F-
0 5 10 15 20 25
AI3+(mgj/950 ml Brass Mill Wastewater
Figure 14. Treatment of brass mill wastewater with Al + only
(pH readjustment).
59
-------
pH = 9.0
A—A 10 min
A—A 30 min
Initial Copper Cone.
148-169
0 5 10 15 20 25
Fe3+ (mg)/950 ml Brass Mill Wastewater
Figure 15. Treatment of brass mill wastewater with Fe3* only
60
-------
100
pH = 9.0
Settling,
1SX (mg) minutes
A-
A-
0-
©..
-A 5
-A 5
-© 10
-© 10
-• 15
-• 15
10
30
10
30
10
30
Initial Copper Cone.
136-151
5 10 15
AI3+(mgj/950 ml Brass
20
Wastewater
Figure 16. Treatment of brass mill wastewater with Al and ISX.
61
-------
10 mg ISX
(pH After Adding Alum]
Initial Copper Cone. 169-180 //g/l
20
0 2 4 6 8 10 12
AI3+(mgj/950 ml Brass Mill Wastewater
Figure 17. Treatment of brass mill wastewater with A13+ and ISX
(no pH readjustment).
62
-------
(4.5)
(4.35)
L (pH at Sampling)
H: pH = 9.0, No ISX.
HI: pH = 9.0, 10 mg ISX.
0 5 10 15 20 25
AI3+(mg)/950 ml Brass Mill Wastewater
Figure 18. Qn-site jar tests at brass mill.
63
-------
TABLE 26. CHEMICAL NEUTRALIZATION OF INDIANA LEAD
BATTERY COMPANY EFFLUENT*
Neutralization
Agent
NaOH
Na,COT
L 3
CaCO-
Ca(OH)9
Final
PH
5.0
7.0
8.0
9.0
10.0
7.0
8.0
8.5
6.5t
7.0
8.0
Residual
Pb, mg/1
0.233
0.287
0.209
0.186
0.175
0.268
0.311
0.490
0.189
0.421
0.387
Residual
Fe, mg/1
1.04
0.934
0.625
0.625
0.166
0.487
0.068
0.050
5.89
0.536
0.216
Comments
2.7 g solid NaOH required
6.3 g solid Na7CO, required
8.0 g solid Ca(OH)7 required
* Initial [Pb] =4.05 mg/1; Initial [Fe] =52.0 mg/1; pH = 1.6.
t Maximum pH attainable.
The data obtained in the preliminary testing phase of the Indiana battery
company effluent was very erratic. However, from general observations and the
data shown in Tables 26-29 we were able to draw the following conclusions:
Ca) None of the neutralization agents by themselves gave any clear-cut advan-
tage in metal removal. The order of settlability was very pronounced [NaOH»
CaCOH)2>Na2C03] and the order of residual dissolved solids was as expected
Ca(OH)2<Na2C03] of the sludge over using no flocculating agent, (d) Commercial
anionic polyelectrolytes were very effective on increasing settling of the
sludge [NaOH»Ca(OH)2>Na2C03]. (e) Barium carbonate was slightly effective in
dissolved solids removal. Additional studies with barium hydroxide and cal-
cium carbonate gave similar results.
The results (Tables 30-31) from the standard jar tests show that ISX does
offer a way to reduce residual lead concentrations to below desired discharge
limits. Our chemical treatments to reduce dissolved solids were very in-
effective and ion-exhcange columns, reverse osmosis or distillation, would
have to be used. Table 30 shows a 54-651 removal of lead with ISX. However,
when sufficient ISX is incorporated as shown in Table 31, greater than 901
lead removal is noted with residual lead values below discharge limits.
64
-------
TABLE 27. EFFECT OF CHEMICAL NEUTRALIZATION AND STARCH XANTHATES
ON INDIANA LEAD BATTERY COMPANY EFFLUENT*
ON
Oi
Residual
Neutralization
agent
NaOH
NaOH
NaOH
Na,CO,
Lt O
NaOH to pH 7.5
then Ca(OH)7
Ca(OH)2
£j
Additional Final
treatment
Soluble starch xanthatet
(4 mg/1)
ISX* (0.05 g) then
soluble starch xanthate
(4 mg/1)
ISX (0.05 g) then Nalcolyte
676§ (4 mg/1)
Soluble starch xanthate
(8 mg/1)
Soluble starch xanthate
(5 mg/1)
Soluble starch xanthate
(5 mg/1)
pH
7.
7.
7.
7.
8.
8.
Pb
cone..
mg/1
5
5
5
0
1
1
0.
0.
0.
0.
0.
0.
344
122
311
588
250
250
Residual
Fe
cone.,
mg/1
0.
0.
0.
0.
0.
0.
045
021
026
688
063
103
Dissolved
solids g/1
Good
Good
Good
Slow
6.20 Good
Comments
fast
fast
fast
settling
settling
settling
floe
floe
floe
settling floe
fast
settling
floe
6.82 Medium settling floe
* Initial [Pb] = 4.05 mg/1; Initial [Fe] = 52.0 mg/1; pH = 1.6; dissolved solids
t Degree of substitution = 0.11 (5.07 g/1).
* 1.5 meq metal ion/g.
§ Commercial anionic polyelectrolyte.
4.94 g/1.
-------
TABLE 28. CHEMICAL NEUTRALIZATION AND ISX TREATMENTS
FOR INDIANA LEAD BATTERY COMPANY EFFLUENT*
Treatment
Residual Residual Dried Dissolved
Pb cone., Fe cone., sludge,g solids, g/1
mg/1 mg/1
Comments
1. NaOH to 01 = 4.0
2. Na2C03 to pH = 8.5
3. DowA-23t (2.5 mg/1)
1. NaOH to pH - 4.0
2. Ca(CH)2 to pH = 8.5
3. Dow A-23 C2.5 mg/1)
1. NaOH to pH = 4.0
2. Na2C03 to pH = 8.5
3. ISX* (O.lg)
4. Dow A-23 (2.5 mg/1)
1. NaOH to pH = 4.0
2. Ca(CH)2 to pH = 8.5
3. ISX (0.1 g)
4. Dow A-23 (2.5 mg/1)
0.158 <0.05
0.125
0.121
<0.05
<0.05
0.060 <0.05
0.283
0.271
Slow settling in
5 min - good
6.47 settling with
polymer
Medium settling in
5.97 5 min - good
settling with
polymer
* Initial [Pb] =4.05 mg/1; Initial [Fe] =52.0 mg/1; pH = 1.6.
t Commercial anionic polyelectrolyte.
$ 1.5 meq metal ion/g.
-------
TABLE 29. BARIUM CARBONATE TREATMENT FOR DISSOLVED SOLIDS
REDUCTION OF INDIANA LEAD BATTERY COMPANY EFFLUENT*
Neutralization
agent
NaOH
Na~CO_
M O
Ca(OH)2
Lt
NaOH
Na7CO,
M *?
Ca(OH)7
w
Additional
treatment
Soluble starch xanthatet
20 ml (10 mg/1)
Soluble starch xanthate
20 ml (10 mg/1)
Soluble starch xanthate
20 ml (10 mg/1)
0.3 g BaC03 then
soluble starch xanthate
20 ml (10 mg/1)
0.3 g BaCOs then
soluble starch xanthate
20 ml (10 mg/1)
0.3 g BaCOs then
soluble starch xanthate
20 ml (10 mg/1)
Final
pH
7.0
7.0
7.0
9.4
7.7
8.2
Residual Residual
Pb cone. , Fe cone. ,
mg/1 mg/1
» ~ _ — — —
— —
— —
0.100 0.050
0.200 0.085
0.04 0.050
Dissolved
solids
g/1
6.09
9.51
3.63
5.24
8.95
2.83
Comments
Tight fast
settling floe
Slow settling
floe
Loose medium
settling floe
* Initial dissolved solids - 4.94 g/1.
t Degree of substitution = 0.11 (5.07 g/1).
-------
TABLE 30. STANDARD JAR TEST TREATMENTS* FOR INDIANA LEAD BATTERY COMPANY EFFLUENT
OO
Experiment Number
Wastewatert, ml
Soluble starch
xanthate*, ml (mg/1)
Insoluble starch
xanthate §, g (mg/1)
Water, ml
Initial pH
NaOH (7N), ml
Na2C03 (10%), ml
Analysis after treatment
Residual [Pb], mg/1
Residual [Fe], mg/1
Suspended solids, mg/1
COD, mg/1
1
950
0
0
61.5
1.6
9.5
0
0.222
<0.05
39.3
104
2
950
8(4)
0
53.5
1.6
9.5
0
0.121
<0.05
42.6
— •• •_
3
950
8(4)
0.02 (20)
53.5
1.6
9.5
0
0.077
<0.05
19.5
80
4
950
0
0
8
1.6
0
63
0.310
<0.05
67.8
96
5
950
8(4)
0
0
1.6
0
63
0.211
<0.05
81.1
•m « *m
6
950
8(4)
0.02 (20)
0
1.6
0
63
0.144
<0.05
75.9
140
* Jar tests were run according to published methods.
t Initial [Pb] =4.05 mg/1, [Fe] =52.0 mg/1.
t NRRC product-Degree of Substitution = 0.11.
§ NRRC product-Degree of Substitution = 0.20.
-------
TABLE 31. STANDARD JAR TEST TREATMENTS* FOR INDIANA LEAD BATTERY COMPANY EFFLUENT
o\
vo
Sample Residual
Number Treatmentst Pb, mg/1*
1
2
3
4
5
6
NaOH (9.12 ml-2.55 g)
Ca(OH)2 (2.8 g)
NaoCOs C120 ml-12.0 g)
NaOH (8.6 ml-2.40 g) to
pH 5.0 then
Na2C03 (41.3 ml-4.13 g)
NaOH (8.6 ml-2.40 g) to
pH 5.0 then Ca(OH)7
(0.20 g) L
NaOH (8.85 ml-2.49 g) to
pH 6.0 then Na2C03
(37.7 ml-3.77 g)
0.28
0.31
0.22
0.18
0.22
0.17
Residual
Fe, mg/1*
0.12
0.11
0.14
0.18
0.13
0.16
Sludge §
Dried*
vol., ml sludge,
30
45
30
30
45
30
0.29
1.44
6.38
5.67
0.63
3.45
Dissolved** Residualtt Residualtt
solids, Pb, Fe,
g g/1
8.89
9.09
6.59
8.06
9.92
8.79
mg/1
0.04
0.03
0.02
0.02
0.02
0.03
mg/1
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
* Jar tests were run according to published methods.
t Neutralization agents were added to 880 ml wastewater to pH 9.0. Water was added to bring all
beakers to 1,000 ml. Magnifloc 837A (American Cyanamid) anionic polyelectrolyte (0.5 g/1, 2 ml)
was added to flocculate the sludge.
•t Residual metal concentrations were determined on a Varian Techtron AA 120 after filtration.
§ Apparent volume in bottom of 1-1 beakers.
# Weight of sludge after filtration and drying at 80°C for 24 hr.
** Dissolved solids in treated effluent.
tt The experiments were repeated incorporating 0.1 g/1 ISX before the flocculating agent.
-------
The use of sodium carbonate in our opinion is not a good choice as a
neutralization agent since it requires a large quantity to reach alkaline
pH's. This results in additional dissolved solids which makes the water not
recycleable unless treated further. The use of flocculating agents (anionic)
offers a way to enhance sludge settling. Usually after 2 min the solids were
completely settled. Soluble starch xanthate was evaluated to test its floccu-
lating and metal removal ability. It was not as effective as commercial
anionic polymers; however, its cost would be considerably less and it could
be made on-site. Soluble starch xanthate by itself did show a 30-40% removal
of lead.
Since the Pennsylvania battery effluent was already neutralized when
received, we only evaluated ISX for lead removal in the presence of various
anionic polyelectrolytes. The data in Tables 32-34 show that ISX does remove
lead from this wastewater. In Table 32, the ISX (0.02 g) was an insufficient
amount to do an effective job. This table also shows that a soluble starch
xanthate of a higher degree of substitution (D.S.) is not as effective as one
with a lower D.S. Commercial anionic polymers because of their higher molecu-
lar weight are superior flocculants. Table 33 shows that increasing the ISX
concentration does lower the lead concentration further. In this study, we
also evaluated a new insoluble carboxylated crosslinked starch and this
product also was found to be effective in lead removal. The data in Table 34
show ISX in sufficient amount will reduce the lead concentration to below the
desired 0.05 mg/1 limit when it is added before flocculation. Some lead re-
moval is observed after sludge removal; however, we feel that this residual
amount remaining could be as a colloidal lead hydroxide for which ISX would
have no affinity.
Battery companies have a choice of neutralization agents to adjust their
wastewater to alkaline pH's. We feel a combination of NaOH to pH 4-6 and
then Ca(XH)2 or Na2CC>3 to 8.5 offers some advantages in dissolved solids remov-
al, sludge amount, and flocculation ability. The use of ISX for lead removal
to below 0.05 mg/1 is a way to .meet their discharge limit. We also feel it is
advantageous to add the ISX before the anionic polymer.
CIRCUIT BOARD RINSE WATERS
We were contacted by several printed circuit board manufacturers to eval-
uate ISX in copper removal from several different rinse waters. During our
investigation, we found ISX was only partially effective when copper was in a
complexed form [very effective though for Cu(NH3)42+]. Therefore, we carried
out investigations further to develop simple, economical processes which were
effective in complexed copper removal. The rinse waters causing the most pro-
blems to these companies were from (a) electroless copper, (b) copper pyro-
phosphate, and (c) copper etching operations. The following discussion
presents our findings into the ways these copper complexes can be removed from
industrial effluents.
Copper Removal from Electroless Copper Plating Rinse Waters
The normal operating pH of electroless copper baths is in the range of 12-
13. In this pH range, the copper complex is soluble when calcium ion is not
70
-------
TABLE 32. STANDARD JAR TEST TREATMENTS* FOR
PENNSYLVANIA LEAD BATTERY COMPANY EFFLUENT
Experiment Number
Wastewater,t ml
Soluble starch xanthate,^
ml
ISX,# g
Nalco 676** (0.5 g/1) , ml
Water, ml
Analysis after treatment
Residual [Pb] , mg/1
Comments
1
960
0
0
0
40
1.03
slow
settling
2
960
8
0
0
32
0.87
good
settling
3
960
8
0.02
0
32
0.67
good
settling
4
960
8§
0
0
32
0.82
slow
settling
5'
960
8§
0.02
0
32
0.67
slow
settling
6
960
0
0
4
36
0.88
fast
settling
* Jar tests were run according to published methods.
t Initial [Pb] =1.03 mg/1, pH = 10.6,
* NRRC product - degree of substitution = 0.11 (5.07 g/1).
§ NRRC product - degree of substitution = 0.35 (5.07 g/1).
# NRRC product - 1.50 meq metal ion/g.
** Commercial anionic polyelectrolyte.
-------
ro
TABLE 33. STANDARD JAR TEST TREATMENTS* FOR
PENNSYLVANIA LEAD BATTERY COMPANY EFFLUENT
B
Experiment Number
Wastewater,t ml
Soluble starch xanthate,*
ml (mg/1)
ISX,§ g (mg/1)
Carboxylated starch,*
g (mg/1)
Water, ml
Analysis after treatment
Residual Pb, mg/1
1
960
0
0
0
40
1.05
2
960
20 CIO)
0
0
20
0.162
3
960
8(4)
0.05
0
32
0.108
4
960
0
(50) 0.05(50)
0
40
0.091
5
960
0
0
0.05(50)
40
0.076
6
960
0
0
0.10(100)
40
0.059
* Jar tests were run according to published methods.
t Initial [Pb] = 10.3 mg/1, pH = 10.6.
* NRRC product - degree of substitution = 0.11 (5.07 g/1).
§ NRRC product - 1.50 meq metal ion/g.
# NRRC product - 2.92 meq metal ion/g.
-------
TABLE 34. ISX ADDITIONS BEFORE AND AFTER FLOCCUIATION
OF PENNSYLVANIA LEAD BATTERY COMPANY EFFLUENT
Before
After
Sample*
size, ml
1,000
1,000
•MMMMMMMMlMll^H
ISX,t
g
0.1
0.1
Dow-A23,t
mg/1
2.5
2.5
••-•»• i mm*,**, ••••^•^•••i^
Residual
Pb, mg/1
0.045
0.112
(0.167)#
Driedi
sludge, g
6.33
7.76
* Initial [Pb] =1.03 mg/1, pH 10.6.
t NRRC product - 1.50 meq metal ion/g.
* Commercial anionic polyelectrolyte.
§ Sludge was filtered off and dried for 24 hr at 110 °C.
# Lead cone, after polyelectrolyte addition.
TABLE 35. LOG FORMATION CONSTANTS
FOR COMPLEXES AT pH 12 (52-55)
Ions
Caf
A log K Ca2+-Cu2H"
EDTA
10.7
15.7
5.0
Ligands
HEDTA
8.4
13.7
5.3
NTA
6.5
12.0
5.5
present. Treatment of copper complexes of the EDTA type with calcium hydroxide
at a pH greater than 11.5 yields a copper hydroxide precipitate. The forma-
tion of this precipitate might be unexpected since the copper-EDTA stability
constant at pH 11-12 is 105 tines greater than the constant for the calcium-
EDTA complex (52-55) (Table 35). However, if one considers the formation
constants and solubility product constants for the species involved [Cu^,
Ca2+, EDTA^-, and Cu(OH)2J one would expect to get copper removal (Table 36).
The removal of copper from several different types of complexes by calcium ion
over a limited pH range is an effective treatment for rinse waters of the
electroless plating of copper.
73
-------
TABLE 36. EQUILIBRIUM CONCENTRATIONS FOR Cu2+-Ca2+-EDTA4"
SYSTEM AT pH 12
Conditions
Species* Case It Case II* Case Illi Case IVf
Cu2+ ,
CuEDTA^"
EDTA4'
Ca2+
CaEDTA2"
Cu(OH)2
1.0 X 10"J5
6.0 X 10"T
1.2 X 10
— •> ••
___
__-
6.0 X 10" J6
5.4 X 10~l
1.8 X 10"*
— _ .
0.6 X 10"4 (101)
1.2 X 10"5
5.9 X 10 *
** _4
2575 X 10
1.3 X 10"4
~~ —
6.0 X 10"}^
1.7 X 10 •"
-&.
2570 X 10 *
7,2 X 10-4
6.0 X 10"4 (100%)
* Concentrations in moles/1.
2_
t Excess of EDTA with large formation constant for CuEDTA ignoring
possibility of Cu(OH)2.
f\
* Excess of EDTA with large formation constant for CuEDTA considering
precipitation of Cu(OH)2.
§ Concentrations of Cu , Ca , and EDTA ignoring solubility limit of
Cu(OH)2.
# Concentrations of Cu +, Ca +, and EDTA " considering solubility limit
of Cu(OH)2).
** Completely complexed due to excess metal ions.
Copper-EDTA Complex-
Several variables in the treatment process were evaluated to determine
what effect calcium ion had on the decomposition of the copper-EDTA complex.
Tables 37 and 38 present several treatments which show that excess calcium ion
C>150 mg/1) at a pH of 11.6 or greater will reduce copper levels to 0.2 mg/1
or less. Table 37 shows that effective copper removal can be achieved with
CaZH"/Cu2+ ratios greater than 2.5 above pH 11.7. Even though there was a
slight increase in pH over these various addition levels, it was actually the
increase in calcium ion which caused the decrease in the residual copper. At
a pH lower than 11.5 with sufficient calcium ion in solution (270 mg/1), no
precipitation was observed. As the pH was raised with the addition of more
calcium hydroxide or sodium hydroxide to a pH of 11.6 or greater, the copper
precipitates (99.61 removal) as the hydroxide. Good removal is obtained over
a pH range of 11.6 to 13.5; however, the optimum precipitation of copper hy-
droxide from a copper-EDTA complex is in the pH range of 11.6 to 12.5 (Table
37).
74
-------
TABLE 37. COPPER REMOVAL FROM COPPER-EDTA COMPLEX—DETERMINATION OF
AMOUNT OF CALCIUM ION REQUIRED* AND EFFECT OF pHt
Ca(OH)2 Added, 2+ 2+ Final Residual copper*
g Ca /Ctr pH cone., mg/1
Calcium ion required
0.05 0.54 11.7 28.67
0.10 1.08 11.8 5.17
0.15 1.62 11.9 2.01
0.20 2.16 12.0 1.05
0.25 2.70 12.1 0.82
0.50 5.41 12.2 0.23
Effect of pH
0.5
0.5
0.5
0.5
0.5
0.5
11.5
11.7
12.0
12.5
13.0
13.5
50.0
0.18
0.39
0.46
1.65
3.75
* Dilute 26.18 ml copper-EDTA stock solution to 1 1 (50 mg Cu/1) and then
adjust to pH 11.7 with sodium hydroxide (IN). Treat with calcium
hydroxide for 5 min, add Nalcolyte 676 (1.5 mg/1), and allow to settle
15 min before filtering.
t Follow * using initial pH 10.9 with 0.5 g calcium hydroxide. All pH
adjustments above 11.5 were made with sodium hydroxide.
$ Determined using Varian Techtron AA 120 spectrophotometer.
\ Rinse solutions containing 50 mg/1 complexed copper at temperatures of
20-60°C were treated with Ca(OH)2 (0.50 g/1) to a pH of 11.7. Dilute NaOH was
used to correct minor pH changes. Residual copper concentrations were in the
range of 0.29-0.50 mg/1.
Apparently most calcium compounds are effective as long as they are
soluble above pH 11.5. Calcium hydroxide (1.85 g/1, 0°C), calcium oxide
(1.31 g/1, 10*C), calcium chloride (5.95 g/1, 0*C), and calcium sulfate (2.09
g/1, 30 C) all are soluble to give good removal (Table 38). However, calcium
carbonate (0.0153 g/1, 25°C) is too insoluble to give effective copper removal.
Other calcium salts were not evaluated because they offered no economical or
ecological advantage.
75
-------
TABLE 38. COPPER REMOVAL FROM COPPER-EDTA COMPLEX—EFFECT OF CALCIUM SALT
AND COPPER CONCENTRATION*
Stock
solution,
.ml
26.18
26.18
26.18
26.18
26.18
26.18
26.18
26.18
2.62
52.36
250**
Initial
copper
cone. ,
mg/1
50
50
50
50
50
50
50
50
5
100
1,910
Initial
pH
10.9
10.9
11.7*
10.9
10.9
3.3§
10.9
10.9
10.3
11.1
11.7
Calcium
salt
CaO
CaCl-
CaCK
CaSOt
CaCO*
Ca(OH)2
Ca(OH)2
Ca(OH) 2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Weight
of salt,
g
0.50
0.75
0.75
0.92
0.68
0.69
0.50
0.50
0.50
1.00
1.29
Final
pH
11.6
11.6*
11.6
11.7*
11.6
11.7
11.7
11.7
11.6
11.6
12.0
Polymer
cone. ,
mg/1
1.5
1.5
1.5
1.5
1.5
1.5
1.5
—
1.5
1.5
1.5
Residualt
copper
cone.,
mg/1
0.14
0.22
0.20
0.44
36.00
0.05
0.18
1.21#
0.10
0.09
3.40
* One-liter solutions were prepared from the volume of stock indicated and were treated
accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IN).
§ pH adjusted with H2S04 (IN).
# Filtered after 16-hr settling.
** Used without dilution.
-------
When calcium chloride and calcium sulfate are used, a slight pH lowering
is observed due to copper hydroxide precipitation from solution. When calcium
oxide and calcium sulfate are used, an excess of calcium is noted in the
sludge due to their limited solubility at this pH. The described treatment is
effective on dilute rinses (5-100 mg/1) and even concentrated baths (1,910
mg/1) (Table 38).
The copper hydroxide floe which forms will gravity settle over a 4-16 hr
period. The supernatant of these treated rinses usually contained a concen-
tration in excess of 1 mg/1 residual copper (Table 38). These higher copper
values could result from a copper v. "• copper hydroxide equilibrium which
exists in these systems or from some small colloidal particles of copper
hydroxide which passed through the filter. However, if an anionic polyelectro-
lyte is added such as Nalcolyte 676 or Dow Purifloc A-23 (1.5 mg/1), the
copper hydroxide sludge settles quite rapidly and can be removed before an
equilibrium can develop. If the sludge is removed in less than 4 hr, no in-
crease in dissolved copper concentration is observed. Probably most anionic
polyelectrolytes would be effective flocculants for this treatment system.
Analysis of the blue sludge after dissolution in acid (51 HC1) and subse-
quent reprecipitation at pH 6-7 with sodium hydroxide indicated pure copper
hydroxide. A nitrogen analysis of the sludge was negative, which proved the
EDTA was in solution probably as the calcium complex. Evaporation of the
solution followed by nitrogen analysis of the resulting solid showed all the
EDTA to be here. Excess calcium ion could be removed from the treated water
by carbon dioxide treatment to form insoluble calcium carbonate.
Copper-NTA Complex--
Copper removal (99.9%) utilizing this calcium ion treatment from a copper-
NTA complex is very similar to that of EDTA (Table 39). The variables
discussed for EDTA also apply for the copper-NTA complex. Additional NTA'Na3
(0.0065 moles/1) had to be used over EDTA to form a stable complex.
Copper-HEDTA Complex—
When complexes are used containing hydroxyl groups in place of acetate,
the copper removal (97%) is somewhat less effective (Table 40). Since calcium
does not bind as effectively with hydroxyl groups as with acetate, copper re-
moval might be expected not to be as complete (53).
Copper-NDA Complex—
The calcium ion treatment is only 95% effective in the decomposition of
the copper-NDA complex. Even though the copper hydroxide precipitates from
solution, floe formation is poor under normal treatment conditions even with
an excess of anionic polyelectrolyte. However, at a pH of 12 with an excess
of calcium ion, a better floe is formed (Table 41).
77
-------
TABLE 39. COPPER REMOVAL FROM COPPER-NTA COMPLEX*
00
Stock
solution,
ml
28.60
28.60
28.60
28.60
2.86
57.20
2501
2501
250§
Initial
copper
cone. ,
mg/1
50
50
50
50
5
100
1,730
1,730
1,730
Initial
pH
11.0
11.0
11.0
11.0
10.1
11.1
11.8
11.8
11.8
Calcium
salt
CaO
CaCl2
CaS04
Ca(OH)2
Ca(CH)2
Ca(OH)2
Ca(OH)2
CaCl2
CaCl2
Weight
of salt,
g
0.50
0.75
0.92
0.50
0.34
0.40
1.00
1.27
1.82
Final
pH
11.6
11.7*
12.0*
11.7
11.7
11.7
12.0
11.7
11.7
Polymer
cone. ,
mg/1
1.5
1.5
1.5
1.5
1.5
1.5
2.0
2.0
2.0
Residualt
copper
cone. ,
mg/1
0.22
0.35
0.44
0.06
1.39
0.60
8.1
21.05
3.8
* One-liter solutions were prepared from the volume of stock solution indicated and were
treated accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IV).
•
§ Used without dilution.
-------
TABLE 40. COPPER REMOVAL FROM COPPER-HEDTA COMPLEX*
Stock
solution,
ml
26.5
26.5
26.5
26.5
2.65
53.0
250§
Initial
copper
cone.,
mg/1
50
50
50
50
5
100
1,890
Initial
PH
10.8
10.8
10.8
10.8
9.6
11.1
11.8
Calcium
salt
CaO
CaCl2
CaSCty
Ca(CH)2
Ca(CH)2
Ca(OH)2
Ca(OH)2
Weight
o£ salt,
g
0.50
0.75
0.92
0.50
0.50
0.50
2.00
Final
PH
11.7
11.8*
11.8*
11.8
11.8
11.8
12.0
Polymer
cone. ,
mg/1
1.5
1.5
1.5
1.5
1.5
1.5
2.0
Residualt
copper
cone. ,
mg/1
5.42
1.30
6.96
1.73
0.61
12.99
36.62
* One-liter solutions were prepared from the volume of stock solution indicated and were treated
accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IN).
§ Used without dilution.
-------
TABLE 41. COPPER REMOVAL FROM COPPER-NBA. COMPLEX*
oo
o
Stock
solution,
ml
27.93
27.93
27.93
2.79
55.86
250§
Initial
copper
cone. ,
mg/1
50
50
50
5
100
1,790
Initial
PH
11.0
11.0
11.0
10.4
11.5
11.8
Calcium
salt
CaO
CaCl2
Ca(CH)2
Ca(OH) 2
Ca(OH)2
CaCl2
Weight
of salt,
g
0.50
0.75
0.50
0.50
0.50
2.00
Final
pH
11.7
11.8*
11.7
11.8
11.8
11.7
Polymer
cone.,
mg/1
4.5
4.5
4.5
4.5
4.5
6.0
Residualt
copper
cone.,
mg/1
4.60
2.30
2.86
0.24
26.90
326
* One-liter solutions were prepared from the volume of stock solution indicated and were
treated accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IN).
§ Used without dilution.
-------
Copper-Tartrate Complex--
Treatment of dilute copper-tartrate complexes with calcium ion at pH 11.6
or greater is only 60-85% effective (Table 42). The use of excess calcium ion,
treatment to higher pH values (>12.0) and longer stirring times increase cop-
per removal. Since calcium tartrate is fairly insoluble (0.032 g/1, 0°C), a
considerable amount of the tartrate is also precipitated by the calcium ion
treatment. This fact has been proven by chemical analysis of the sludge.
Dissolution of the sludge in acid (5% HC1) and reprecipitation with sodium
hydroxide precipitates some copper hydroxide at pH 6-7; however, it takes a pH
of 10 to reprecipitate the rest of the copper and calcium tartrate. The
copper-tartrate complex is the only one tested where the complexing agent is
partially precipitated during calcium ion treatment.
Copper-Citrate Complex--
Treatment of dilute copper-citrate solutions with calcium ion gives simi-
lar results to tartrate (Table 43); however, the calcium-citrate complex is
more soluble (8.5 g/1, 18°C) and remains in solution. Excess calcium ion and
higher pH (>12.0) appear to aid in copper removal. However, when calcium
chloride is added at pH 11.2, a good copper hydroxide floe is formed. The
calcium ion treatment was totally ineffective in removal of copper from the
concentrated copper-citrate bath. The copper-citrate baths that were synthet-
ically prepared were only stable for a few hours, after which time pure copper
was autocatalytically deposited on the sides of the container.
Calcium-Gluconate Complex--
Even though gluconate forms a similar type of complex to citrate or
tartrate, two differences were noted. Treatment of the gluconate complexes
appear to give better copper removal at lower pH (10.9-11.6), and if very
dilute solutions (5 mg/1 copper) are treated there is no apparent removal
(Table 44). Calcium gluconate is very soluble (21.1 g/1, 15°C) and all the
gluconate remained in solution as the calcium salt.
Copper-Triethanol and Copper-Quadrol Complexes--
Treatment of these complexes at several pH's with different calcium salts
gave no copper removal.
Commercial Copper Complexes--
Table 45 shows the excellent removal (99.9%) from a commercial EDTA-type
bath (MacDermid A). This bath was received at a pH 2.5 to prevent any spon-
taneous autocatalytic decomposition during transit. The acid treatment did
not affect copper removal by calcium ion. Several other complexes of copper
were evaluated (Table 46). Shipley solution A, which is probably a citrate-
type complex, is only partially decomposed by calcium ion. Treatment of
Shipley A rinse solutions gave 50-80% copper removal; however, no removal is
observed when the stock solution is treated. Rinse solutions of MacDermid B
and Shipley B, C, and D are completely stable to calcium ion treatment at high
pH.
81
-------
TABLE 42. COPPER REMOVAL FROM COPPER-TARTRATE COMPLEX*
oo
Stock
solution,
ml
46.0
46.0
46.0
46.0
46.0
46.0
46.0
4.6
92
250**
250**
Initial
copper
cone.,
mg/1
50
50
50
50
50
50
50
5
100
1,082
1,082
Initial
pH
11.0
11.0
11.0
11.0
12.0*
3.3§
11.0
10.5
11.5
12.0
12.0
Calcium
salt
CaO
CaCl2
CaS04
Ca(QH)2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Ca(OH)2
CaCl2
Weight
of salt,
g
0.50
0.75
0.92
0.50
0.50
1.00
1.00#
0.50
1.00
2.00
2.00
Final
PH
11.7
12.3*
11.9*
11.9
12.3
11.5
11.6
12.0
12.3 ,
12.1
11.9
Polymer
cone. ,
mg/1
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
2.0
2.0
2.0
Residualt
copper
cone. ,
mg/1
19.38
7.17
20.27
21.00
13.48
10.70
6.39
0.88
8.45
6.05
19.20
* One-liter solutions were prepared from the volume of stock solution indicated and were
treated accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
j
* pH adjusted with NaOH (IN).
§ pH adjusted with H2S04 (IN).
# Used a 30-min stirring time.
** Used without dilution.
-------
TABLE 43. COPPER REMOVAL FROM COPPER-CITRATE COMPLEX*
oo
Stock
solution,
ml
44.56
44.56
44.56
44.56
44.56
44.56
4.46
89.12
Initial
copper
cone. ,
mg/1
50
50
50
50
50
50
5
100
Initial
PH
11.0
11.0
11.0
11.0
11.0
11.0
10.5
11.4
Calcium
salt
CaO
CaCl2
CaClo
Ca(OH)2
Ca(OH)2
Ca(OH)2
Ca(CH)2
CaCOH)*
Weight
of salt,
g
0.50
0.75
0.75
0.50
0.50
1.0
0.5
1.0
Final
PH
12.1
11.2
12.0*
11.8
12.1*
12.1
11.8
12.0
Polymer
cone.,
mg/1
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
Residualt
copper
cone. ,
mg/1
21.98
32.78
26.48
21.00
9.01
11.63
1.26
45.86
* One-liter solutions were prepared from the volume of stock solution indicated and were
treated accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IN).
-------
TABLE 44. COPPER REMOVAL FROM COPPER-GLUCONATE COMPLEX*
00
Stock
solution,
ml
32.23
32.23
32.23
32.23
32.23
3.22
64.46
250§
250§
Initial
copper
cone.,
mg/1
50
50
50
50
50
5
100
1,551
1,551
Initial
pH
10.9
11.0
11.0
10.9
11.0
10.4
11.2
11.9
11.8
Calcium
salt
CaO
CaCl2
CaS04
Ca(0rf)2
Ca(OH)2
Ca(OH)2
Ca(OH)2
CaCl2
CaCl2
Weight
of salt,
g
0.50
0.75
0.92
0.50
0.50
0.34
0.22
1.00
2.00
Final
pH
11.8
10.9
11.8*
11.5
12.1*
11.8
11.7
11.8
11.7
Polymer
cone.,
mg/1
1.5
1.5
1.5
1.5
1.5
1.5
1.5
2.0
2.0
Residualt
copper
cone. ,
mg/1
22.09
15.89
22.91
23.88
26.20
5.00
24.61
160.30
129.40
* One-liter solutions were prepared from the volume of stock solution indicated and were
treated accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IN).
§ Used without dilution.
-------
TABLE 45. COPPER REM3VAL FROM A COMMERCIAL COPPER-EDTA-TYPE COMPLEX*
oo
Cn
MacDermid
A
stock
solution,
ml
15
15
15
15
15
13.92
13.92
2
100
500**
Initial
copper
cone.,
mg/1
53.85
53.85
53.85
53.85
53.85
50
50
7.37
356.7
3,566
Initial
pH
3.5
3.5
3.5
3.5
3.5
10.9*
10.9*
4.1
2.9
2.5
Calcium
salt
CaO
CaCl2
Ca(OH)2
Ca(OH)2
Ca(OH}2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Ca(OH}2
Ca(OH)2
Weight
of salt,
g
0.67
0.75
0.42
1.00
1.00
0.46
0.46
1.00
1.20
3.68
Final
pH
11.8
11. 7t
11.6
11.6
11.6
11.7
11.7
11.7
11.6
11.6
Polymer
cone.,
mg/1
1.5
1.5
1.5
1.5
—
1.5
—
1.5
2.0
2.0
Residualt
copper
cone.,
mg/1
0.18
0.22
0.26
0.02
0.20§
0.32
1.20#
0.06
0.87
21.67
* One-liter solutions were prepared from the volume of stock solution indicated and were
treated accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IN).
§ Filtered without polymer treatment after 15-min settling.
# Filtered after 16-hr settling.
** Used without dilution.
-------
TABLE 46. COPPER REMOVAL FROM OTHER COMMERCIAL COPPER COMPLEXES*
oo
No.
Shipley
A
A
A
A
A
A
A
A
MacDermid
B
Shipley
B
C
D
Stock
solution,
ml
17.73
17.73
17.73
17.73
17.73
35.46
250§
250§
44
10.33
18.05
13.62
Initial
copper
cone.,
mg/1
50
50
50
50
50
100
2,820
2,820
50
50
50
50
Initial
pH
11.0
10.9
10.9
10.9
11.0
11.2
12.0
12.0
10.2
10.9
11.2
10.9
Calcium
salt
CaO
CaClo
CaCl2
CaS04
Ca(OH)2
Ca(OH)2
Ca(OH)2
CaCl2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Weight
of salt,
g
0.50
0.75
, 0.75
0.92
0.48
0.50
2.00
2.00
1.00
0.77
0.37
0.82
Final
pH
12.0
10.9
12.3*
11.9*
11.7
11.9
12.3
12.0
11.8
11.7
11.8
11.7
Polymer
cone.,
mg/1
1.5
1.5
1.5
1.5
1.5
1.5
—
—
—
—
—
•" " ~
Residualt
copper
cone.,
mg/1
23.07
24.08
9.00
1.62
12.00
50.50
2,820
2,820
50
50
50
50
* One-liter solutions were prepared from the volume of stock solution indicated and were
treated accordingly.
t Determined using a Varian Techtron AA 120 spectrophotometer.
* pH adjusted with NaOH (IN).
§ Used without dilution.
-------
The results show that treatment of electroless copper rinses or baths is
not always effective with calcium ion at high pH. The chemical structure of
the complexing agents in most cases determines which solutions will be decom-
posed. If the nitrogen in the complexing agents is completely substituted
with carboxyl groups, removal of copper by calcium ion is almost complete. In
most cases, copper removal is greatly reduced if complexing agents are used
which have some of the carboxyl groups replaced by hydrogen or hydroxyl groups.
Complexing agents containing no carboxyl groups and only hydroxyl groups show
no copper removal.
Some of the excess of calcium required for these treatments probably
precipitates as calcium carbonate, since carbonate is known to be present in
these types of rinse waters. This calcium ion treatment at high pH can be
conducted batchwise and probably could be operated continuously; however, only
batchwise treatment has been evaluated. Since the major product in the pro-
posed treatment is copper hydroxide (except when tartrate is the complexing
agent), the sludge could be reprocessed to recover copper in a reusable form
to help defray cost of treatment. Chemical cost of treatment for a 50 mg/1
copper-EDTA rinse with lime and polymer would be about $0.08/1,000 gal. The
supernatant after treatment would still contain a calcium complex but it would
have a much lower toxicity. Care should be taken in discharge of the calcium
complex effluent since the complexing agent will combine with other heavy met-
al ions when the pH is lowered. Several recent reports (56-58) do show that
copper in a complex form, i.e., with EDTA, NTA, or pyrophosphate, is signifi-
cantly less toxic than free copper ion. Formate, a byproduct of formaldehyde
catalyzed electroless copper baths, does not interfere with copper removal in
this proposed treatment and would remain soluble as calcium formate (16.2 g/1,
0°C). The addition of small amounts of sulf ide ion, ISX, or dithiocarbamates
after the calcium ion treatment aids in further copper removal.
An industrial electroless plating rinse was evaluated containing copper
(173 mg/1) and nickel (51.9 mg/1) as the tartrate complex. After treatment
with calcium ion, the residual copper was 0.3 mg/1 and the nickel was 0.1 mg/1.
These results were unexpected since treatment of standard copper tartrate com-
plexes only resulted in 60-801 copper removal. These results were reported to
the company and after similar success in their laboratory, the decision was
made to install hardware for this high pH-lime treatment process (January,
1977 start-up). They had evaluated at considerable expense RD, electrochemi-
cal, low pH-lime, 'sodium borohydride, and other techniques. They were using
sodium borohydride reduction until the more economical and more effective high
pH-lime treatment was installed. Presently they use a premised lime-calcium
chloride slurry to have a higher calcium ion concentration and they modify the
amounts daily depending on their copper-nickel concentrations. Their electro-
less copper rinse water (40,000 I/day) initially contains copper (50-300 mg/1)
and nickel (0-150 mg.l) and after high pH-lime treatment to pH 11.5-12.0, the
residual concentrations are 0.04-0.3 mg.l copper and 0.03-1.0 mg/1 nickel,
which satisfys the river discharge limit of 1.0 mg/1 for each metal. The
sludge is hauled away to an approved landfill.
ISX was evaluated for copper removal from these complexes; however, the
copper removal was not very effective unless the pH of the solution was low-
87
-------
ered to a pH of 3-5 to where the copper complex dissociates. Since the cal-
cium ion treatment offered a more economical approach, the use of ISX was not
evaluated further.
Since several commercial baths were untreatable by the calcium ion method,
we expanded our investigations to develop an effective treatment process for
these types of copper complexes. Chemical suppliers told us that the complex-
ing agent was Quadrol (Figure 1).
We discovered that if rinse waters containing this type of copper complex
were lowered to pH's where the complex dissociates, ferrous sulfate added and
the solution neutralized to a pH above 9, effective copper removal was ob-
tained. This treatment is effective because the ferrous ion reduces the (Xr
to Cu* and when the pH is raised, the copper will not recomplex. Acidifica-
tion was used in most of the studies because it assists in weakening or
dissociating the bonds in the copper complex and this is evidenced by a color
change in the solution from pale blue to colorless. The color change is a
useful guide to the amount of acid required for the pH adjustment and if com-
panies have rinses that turn colorless, acid would only have to be added to
that pH. In most of our studies we lowered the pH to 2.7. Even though the
data of Table 47 suggest the best treatment would be the addition of ferrous
sulfate to the rinse with no prior acidification, we found that some of the
commercial rinses known to be of the Quadrol-type gave better treatment by
lowering the pH to 2.7. These commercial rinses were the ones that did not
turn colorless at low pH's.
Table 47 also shows that as the copper concentration of the rinse in-
creases, the Fe2+/CuZ+ ratio can be lowered from 8.0 to 1.0 for effective
treatment. This fact is especially important from an economic point of view.
Since companies are going more to counterflow rinsing techniques for water use
reduction, the copper complex concentration will increase, so this more effec-
tive utilization of ferrous sulfate will be realized. The use of calcium
hydroxide and sodium hydroxide as neutralization agents (Table 47) were equal-
ly effective in copper and iron removal; however, the use of sodium hydroxide
gave lower dissolved solids and less sludge. The amount of ferrous sulfate
and the use of sodium hydroxide vs calcium hydroxide were also determined for
the MacDermid B rinse and the results were similar to those just discussed for
copper-Quadrol. The contact time at low pH with ferrous sulfate for 1 hr or a
stir at pH 11.2 for 2 hr after ferrous sulfate treatment showed no improvement
in metal removal and in fact at longer contact at 11.2 the residual copper and
iron increased. As long as the pH is raised above 9.0 (Table 48) the copper
removal is excellent, however, to lower the residual iron to low values the pH
had to be raised to 11.7.
Since we desired residual copper concentrations less than 0.05 mg/1 we
chose to use 1.0 g/1 ferrous sulfate for 50 mg/1 copper solutions and 0.4 g/1
ferrous sulfate for 10 mg/1 copper solutions. Companies could use considera-
bly less ferrous sulfate if these lower copper values were not required. The
ferrous sulfate treatment was evaluated on solutions containing different
synthetic copper complexes (Table 49). Whereas the previously discussed cal-
cium treatment was only very effective for the EDTA-type copper complexes, the
88
-------
TABLE 47. COPPER REM3VAL FRCM COPPER-QUADROL OM>LEX--DETERMINATION
OF AMDUNT OF FERROUS SULFATE REQUIRED AND EFFECT OF BASE*
Copper
cone.,
mg/1
50
50
SO
50
50
50
50
50
50
50
50
SO
10
10
10
10
1000
1000
1000
Adjusted
PH
2.7
2.7
2.7
2.7
2.7
2.7
2.7
2.7
9.5*
7.8
7.2
7.2§
2.7
2.7
2.7
5.4*
2.7
2.7
2.7
FeS04-7H20,
&
0.3
0.4
0.5
0.75
1.0
0.5
0.75
1.0
0.5
0.75
1.00
1.00
0.20
0.30
0.40
0.20
3.0
4.0
5.0
Fe2W+
1.2
1.6
2.0
3.0
4.0
2.0
3.0
4.0
2.0
3.0
4.0
4.0
4.0
6.0
8.0
4.0
0.6
0.8
1.0
Base
Ca(OHh
Ca(OH)2
S&i
Ca(CH)2
NaCH
NaCH
NaCH
Ca(OH)2
Ca(OH)2
Ca(OH)2
Ca(CH)2
Ca(CH)2
Ca(OH)2
Ca(OH)2
Ca(CH)2
Ca(OH)2
Ca(OH)2
Ca(OH)2
Residual
copper conc.,t
mg/1
33.0
15.5
0.58
0.16
0.01
1.25
0.22
0.05
0.44
0.01
0.01
0.09
6.60
1.42
0.07
1.00
421.0
147.0
0.36
Residual
iron cone. ,t
mg/1
4.74
8.70
9.46
5.68
2.68
8.42
4.54
5.16
6.38
6.70
7.41
3.06
0.49
1.52
1.00
1.48
27.5
85.0
12.5
* Copper-Quadrol solutions (1,000 ml) containing the indicated copper concentration at pH 10.6-11.9
were acidified with IN H2S04 to pH 2.7. Ferrous sulfate was added as a solid and after 5 min, the
pH was raised to 11.2 with the base listed. Nalcolyte 676 (2.5 mg/1) anionic pol/electrolyte was
added and the solutions were allowed to settle 5 min before filtering.
t Determined using a Varian Techtron AA 120 spectrophotometer.
t No acid added, pH lowering due to ferrous sulfate addition.
i Solution lowered to pH 2.7 after ferrous sulfate addition.
89
-------
TABLE 48. EFFECT OF FINAL pH* ON COPPER REMOVAL
FROM COPPER-QUADROL COMPLEX
Adjusted
PH
2.7
2.7
2.7
2.7
6.4*
6.4*
6.4*
6.4*
9.0§
9.0§
9.0§
Final
pH
7.0
9.0
11.0
11.7
7.0
9.0
11.0
11.7
9.0
11.0
11.7
Residual
copper conc.,t
mg/1
0.24
0.17
0.14
0.05
1.34
0.01
0.01
0.01
0.01
0.01
0.01
Residual
iron conc.,t
mg/1
25.4
10.5
4.5
0.31
48.6
13.8
1.4
0.23
14.1
1.9
0.17
* Dilute 39.0 ml copper-Quadrol stock solution to 1 1 (50 mg Cu/1)
and then adjust the solutions to the desired pH with IN 112804.
Treat solutions with ferrous sulfate (FeSO^Tt^O, 1.0 g) for
5 min, add calcium hydroxide to the indicated pH and add
Nalcolyte 676 (2.5 mg/1) for flocculation. After settling 5 min,
an aliquot (10 ml) was filtered through Whatman 54 filter paper
for analysis.
t Copper and iron concentrations were determined using a Varian
Techtron AA 120 spectrophotometer.
* Adjusted to pH 7.0 with acid, then to pH 6.4 with ferrous
sulfate.
§ Adjusted to pH 9.0 with ferrous sulfate.
ferrous sulfate treatment was effective on all the complexes evaluated.
Commercial rinses containing various copper complexes were treated with fer-
rous sulfate with excellent copper removal (Table 50).
The effluent after treatment in most cases was clear and colorless. When
the iron concentration was high in some experiments, the effluent was pale
yellow and sometimes hazy. This was overcome as previously mentioned by ad-
justment of the solution to a higher pH (11.7). The use of anionic polyelec-
trolytes (1.0-2.5 mg/1) was very effective in the flocculation and settling of
the sludge. Samples allowed to settle for 16 hr had residual copper concentra-
tions above 1 mg/1 whereas with the polyelectrolyte flocculated samples the
residual copper concentration was consistently below 0.1 mg/1 when the sludge
90
-------
TABLE 49. COPPER REMOVAL FROM SYNTHETIC COPPER COMPLEXES
WITH FERROUS SULFATE TREATMENT*
Initial
copper
cone.,
Complex mg/1
EDTA
NTA
Tartrate
Gluconate
Citrate
Triethanol
Amine
Quadrol
50
10
50
10
50
10
50
10
50
10
50
10
50
10
2N H2S04, pH for colorlesst FeS04»7H20, Ca(OH)2,
ml solution g g
3.8
0.8
2.2
0.7
8.0 4.5-4.8
2.0
2.5 4.5-4.7
0.7
4.8 4.0
1.8
6.0 5.5
1.5
5.9 3.0
1.3
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.16
0.94
1.26
0.44
1.54
0.64
0.88
0.53
0.76
0.45
1.04
0.64
0.73
0.51
Residual
copper cone. ,
mg/1
0.23
0.28
0.29
0.09
0.75
0.35
0.82
0.09
0.01
0.02
0.11
0.53
0.01
0.07
Residual
iron cone.,
mg/1
0.12
0.10
0.11
0.11
0.21
0.29
32.70
6.20
0.28
0.18
24.48
8.33
2.68
1.00
* Solutions (1»000 nil) containing the copper complexes at the indicated concentrations were acidified
with 2N H2S04 to pH 2.7. The indicated amount of ferrous sulfate was added and the solution stirred
for 5 min. Calcium hydroxide was added to raise the pH to 11.7 and the solutions were flocculated
with Nalcolyte 676 (2.5 mg/1) anionic polymer. After settling the solutions were filtered for
analysis.
t pH values listed is where copper complex dissociates. When no value is listed, the blue complex does
not dissociate above pH 1.8.
-------
TABLE 50. COPPER REMOVAL FROM COMMERCIAL COPPER COMPLEXES WITH FERROUS SULFATE TREATMENT*
to
Bath
Initial
copper
cone.,
mg/1
2NH2S04,
pH for
colorlesst
solution
FeS04'7H20,
g
Ca(OH)2
g
Residual
, copper cone.,
mg/1
Residual
iron cone. ,
mg/1
Dissolved*
solids ,
mg/1
MacDermid
A
A
B
B
C
C
Shipley
A
A
B
B
C
C
D
D
D
D
D
50
10
50
10
50
10
50
10
50
10
50
10
50
10
50
50
50
_-_
—
15.0
4.7
19.0
6.0
4.0
1.6
4.5
1.1
8.2
1.8
3.5
1.7
—
3.5
3.5
2.7-3.0
4.8
2.8
3.9
3.8
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
1.0
0.4
—
1.0
1.0
1.42
0.46
1.69
0.50
2.18
0.60
0.56
0.27
0.61
0.26
0.94
0.27
0.51
0.34
—
0.92
20.5
0.02
0.02
0.17
0.08
0.09
0.03
0.33
0.21
0,27
0.31
0.20
0.11
0.12
0.20
—
0.08
ml§ 0.16
7.1
2.3
17.8
6.3
21.0
5.9
0.53
0.47
24.86
2.78
14.17
2.72
6.94
1.47
—
6.85
8.88
—
—
—
—
—
—
—
—
-__
—
—
1,750
720
817
2,320
2,064
* Solutions (1,000 ml) containing the copper complexes at the indicated concentrations were acidified
with 2N H2S04 to pH 2.7. The indicated amount of ferrous sulfate was added and the solution stirred
for 5 min. Calcium hydroxide was added to raise the pH to 11.7 and the solutions were flocculated with
Nalcolyte 676 (2.5 mg/1) anionic polymer. After settling the solutions were filtered for analysis.
t pH values listed is where copper complex dissociates. When no value is listed, the blue complex
does not dissociate above pH 1.8.
* Filtered samples were evaporated to dryness, oven dried at 125°C, cooled, and weighed.
§ Sodium hydroxide (IN)•
-------
was removed within an hour. The same results were also observed with the
residual iron concentration. The sludge produced in this treatment was usual-
ly greenish-brown and very filterable. Several treatments using sodium hy-
droxide as the neutralization agent yielded a sludge that was very magnetic.
Even though we only evaluated the treatment batchwise, it could be operated
continuously metering in ferrous sulfate solutions. The chemical cost of
treatment for a 50 mg/1 copper-Quadrol type rinse with sulfuric acid, ferrous
sulfate, lime, and polymer would be about $0.36/1,000 gal.
Copper Removal From Copper Pyrophosphate Rinse Waters-
It is well known that cations such as Ca2+, Mg2+, Zn2+, A13+, and Fe3+
form insoluble precipitates with HP042~ and P2074" when an excess of cation is
present (59-67). Since calcium hydroxide, lime, and calcium chloride are eco-
nomical sources of Caz+, they were chosen for this study. As the Ca2+ is
added to the rinse, it complexes with the HP042' and the excess P20y4" precip-
itating them as their insoluble calcium salts. When the excess P2°7*~ is
removed, the copper precipitates probably as Cu2P207.
The copper pyrophosphate baths and rinses evaluated for the proposed
treatment process were from the printed circuit industry which uses these
baths for through-hole-plating of printed circuit boards. Since occasional
analysis (68-69) for copper, pyrophosphate, orthophosphate, and ammonia is
required for control purposes to keep the bath in good operating condition,
the plater knows the relative concentrations of pyrophosphate and orthophos-
phate in his rinses. Using this analytical information, we designed a treat-
ment process to lower the copper and phosphorus concentrations of synthetic
and actual rinse waters. The proposed treatment process can be modified as
the orthophosphate concentration builds up. New baths will contain very
little orthophosphate, and treatment of rinse waters from these baths with
calcium hydroxide or lime at pH's above 9 will give excellent copper and phos-
phorus removal. As the orthophosphate concentration builds up to >90 g/1, the
substitution of some calcium chloride for lime will be required to get more
Ca2+ into solution for excellent precipitation.
Synthetic solutions of known Cu2+, PzO?4", and HPC>42~ concentrations were
used to determine the optimum amounts of Ca2+ as Ca(OH)2, lime, or Ca(CH)2-
CaCl2 mixtures to be added to lower the total copper concentration to less
than 0.02 mg/1 and total phosphorus concentration to less than 1 mg/1. All
calcium compounds were added as solids. Table 51 shows that when an excess of
Ca2+ is present, a pH of 9-11.5 maximizes removal of copper. The pH's usually
fell in this range with the amount of lime or calcium hydroxide added. Calcu-
lations performed from the data presented in Table 52 and Figure 19 show that
2.7 mmoles Ca2+ are required to remove 0.9 mmoles ^2°7. and ?*° ^tao}es Ca
. .
are required to remove 1.0 mmoles HP042~. From this information it is possible
to calculate the amount of Caz required for any amount of P2C>74~ and HP04Z~
in actual rinse solutions.
Table 53 shows the composition of some actual baths. Even though the
p2°74"/Cu ratio is somewhat high and the HP042" concentration of Bath C is
well out of the preferred operation range, the above described Ca2* ratios were
used to treat diluted samples from these baths. The results in Tables 54 and
93
-------
TABLE 51. EFFECT OF pH ON COPPER AND
PYRQPHOSPHATE REMOVAL*
Final pH
5.6
7
8
9
10
11
11.5
Residual Cu,
mg/1
7.14
1.38
0.14
0.01
0.01
0.01
0.02
Residual P,
mg/1
4.3
2.2
1.6
0.2
0.2
0.2
0.2
* Copper pyrophosphate solutions (500 ml,
containing 22.87 mg total copper and
157.3 mg total pyrophosphate) were treated
with 525 mg calcium chloride (190 mg
calcium ion) to a pH of 5.6. Dilute
sodium hydroxide was used to adjust the
solutions to the indicated pH. After
stirring for 5 min, anionic polyelectrolyte
(Dow A-23, 5 mg/1) was added and the
residual copper and phosphorus concentrations
were determined after filtration.
55 show that the calculated Ca2+ ratio is applicable. Tables 54 and 55 also
show treatment results for some diluted dragout rinses from these baths.
Since Ca(OH)9 has a limited water solubility, a combined Ca(OH)2-CaCl7 treat-
ment was used for data in Table 55. The Ca(OH)o weight was calculated for the
total P2C>74~ present and the CaCl2 weight for the HP042" present in the rinse.
Since actual rinses may vary from 10 to 100 mg/1 Cu2* having corresponding
P2°7 and HP042~ concentrations, Ca2+ treatments were performed on rinses
with concentrations in this range and the data are shown in Table 54.
Since the actual composition of the sludge in precipitating the P20y4"
and HP042" was not determined and because of the low residual Ca2+ concentra-
tions in the treated rinses, an insoluble complex such as Gas (OH) ^4)3 (59,
60, 65) is possible. This would also account for the excess amount of Ca2+
required.
It is assumed that the copper precipitates as Cu2p207* This assumption
has been proven by varying the pH of precipitated pure copper pyrophosphate
solutions. In the pH range of 3-9, this precipitate is light blue in color;
however, above pH 10 the precipitate becomes royal blue. This coloring is
also true in treatment of actual rinses. If the copper precipitated as the
94
-------
TABLE 52. COPPER REMOVAL FROM PURE COPPER
PYROPHOSPHATE SOLUTIONS*
Sample
1
2
3
4
5
Ca(OH)2,
mg
150
175
200
250
300
Ca2*,
mg
81
95
108
135
162
Residual Cu,
mg/1
9.55
3.60
0.02
0.01
0.01
Residual P,
mg/1
___
0.2
0.2
0.2
* Copper pyrophosphate solutions (500 mi, containing
22.87 mg total copper and 157.3 mg total pyrophosphate)
at initial pH's of 9.1 were treated with various amounts
of calcium hydroxide to final pH's of 10.6-11.4. After
stirring for 5 min, anionic polyelectrolyte (Dow A-23,
5 mg/1) was added and the residual copper and phosphorus
concentrations were determined after filtration.
TABLE 53. ACTUAL COPPER PYROPHOSPHATE BATH COMPOSITION
Components
Bath A
oz/gal g/1
Bath B
oz/gal g/1
Bath C
oz/gal g/1
Cu2*
P2°74'
HP042-
NHs
Ratio P2074-/Cu2+
pH
2.
24.
1.
0.
9.
8.
6
3
5
28
3/1
95
19.
182.
11.
2.
49
17
25
10
2.
22.
11.
0.
9.
8.
5
9
6
48
2/1
Ib
18.
171.
84.
3.
74
67
96
60
2.
29.
22.
0.
10.
8.
9
8
3
68
3/1
15
21.74
223.40
167.17
5.10
hydroxide, this color change would not be observed and the Cu(OH)2 would
dissolve at pH's less than 5.
If desired, the residual Ca2+ in the treated rinse could be removed by
carbonation with carbon dioxide, which would give a concomitant lowering
of pH. If this carbonation is performed the pH of the effluent should not be
lowered below 9 if the phosphate sludge is still present. It is recommended,
if the rinse to be treated requires more than 1.3 g/1 Ca(OH)2, that some CaCl2
be used for greater Ca2+ solubility. Even though the descriBed treatment was
95
-------
100,000
10,000
1000
CJ
"555
o>
100 200 300
Orthophosphate, mg
500
Figure 19. Copper removal from copper pyrophosphate with calcium ion
vs increasing orthophosphate concentration.
Copper pyrophosphate solutions (500 ml, containing 22.87 mg total copper and
157.3 mg total pyrophosphate) containing the indicated amounts of orthophos-
phate were treated with calcium hydroxide (A, 350 mg-190 mg as Ca2+; B, 500 mg-
270 mg as Ca2+) to a final pH of 11.2-11.6. After stirring 5 min, anionic
polyelectrolyte (Dow A-23, 5 mg/1) was added and after filtration the residual
copper concentration was determined on a Varian Techtron M 120.
96
-------
to
--4
TABLE 54. Ca(OH)2 TREATMENT OF ACTUAL COPPER PYROPHOSPHATE ELECTROPLATING RINSES*
Initial
Cu cone.,
Rinse
A
B
C
A
B
C
A
B
A
B
A
mg/1
67.36
74.50
70.84
50
50
50
10
10
100
100
50
Initial
pH
8.9
8.1
7.7
8.6
8.0
7.7
8.4
8.1
8.7
8.1
8.6
Initial
P20y4" cone.,
mg/1
728.7
686.7
893.6
539
460
625
108
92
1,078
920
539
Initial
Residual
HP042" cone. , Ca(OH).,, Cuconc. ,
mg/1
45.0
347.8
668.7
33.4
233
468
6.7
47
67
466
33.4
mg
992
1,387
2,124
734
929
1,487
147
186
1,470
1,860
550 (as
lime)
mg/1
0.02
0.04
2.54
0.02
0.01
0.02
0.01
0.01
0.02
0.02
0.01
Residual
P cone.,
mg/1
0.2
0.6
3.1
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
Residual
Ca cone.
mg/1
30.2
14.3
3.6
27.4
19.7
44.7
» __
—
—
—
—
, Final
pH
11.4
11.5
11.4
11.1
11.2
11.3
10.6
10.8
11.6
11.6
11.1
* Copper pyrophosphate rinse solutions (1,000 ml) containing the indicated concentration were treated
with calcium hydroxide. After stirring for 5 min, anionic polyelectrolyte (Dow A-23, 5 mg/1) was
added and residual copper, calcium, and phosphorous were determined after filtration.
-------
oo
TABLE 55. Ca(OH)2-CaCl2 TREATMENT OF ACTUAL COPPER PYROPHOSPHATE ELECTROPLATING RINSES*
Rinse
A
B
C
A
B
C
Initial
Cu cone.,
mg/1
67.36
74.50
70.84
50
50
50
Initial
pH
8.9
8.1
7.7
8.6
8.0
7.7
Initial
P2074-
conc.,
mg/1
728.7
686.7
893.6
539
460
625
Initial
HP042-
conc.,
mg/1
45.0
347.8
668.7
33.4
233
468
Ca(OH)2,
mg
925
872
1,135
685
584
794
CaCl2
mg
97
751
1,444
72
503
1,011
Residual
Cu cone.,
mg/1
0.02
0.01
0.01
0.02
0.01
0.02
Residual
P cone.,
mg/1
0.3
0.2
0.2
0.2
0.2
0.2
Residual
Ca cone.,
mg/1
25.4
10.2
37.2
16.1
16.7
31.5
Final
pH
11.4
11.4
11.1
11.2
11.1
11.1
* Copper pyrophosphate rinse solutions (1,000 ml) containing the indicated concentration were treated
with calcium hydroxide and calcium chloride. After stirring for 5 min, anionic polyelectrolyte
(Dow A-23, 5 mg/1) was added and residual copper, calcium, and phosphorous were determined after
filtration.
-------
only evaluated batchwise, it could probably be operated continuously by using
a slurry or solution of the calcium compound. The precipitate settles fairly
rapidly; however, settling can be accelerated with the addition of 3-5 rag/1 of
an anionic polyelectrolyte. The chemical cost of treatment for a copper pyro-
phosphate rinse using lijne and polymer containing Cu2+ (54 mg/1), total P?074-
(500 mg/1) and HP042- (250 mg/1) would be about $0.16/1,000 gal.
Actual on-site treatments have been successful with Fe3+ substituted for
some of the Ca2+. During our investigation with concentrated copper pyrophos-
phate baths, preliminary results show that if large concentrations of copper
sulfate solutions are added to these baths the excess pyrophosphate complexes
with this copper to form a precipitate along with the copper pyrophosphate in
solution and some copper orthophosphate. The HPC^2" remaining in solution can
then be removed with excess Ca2+.
Copper Removal from Copper Etchant Rinse Waters--
Rinses from ammonium persulfate etching operations are acidic; however,
raising the pH with caustic does not remove all the Cu(NH3)42+ complex unless
steam is used to drive off the ammonia so copper hydroxide can precipitate.
The same is true of alkaline etch rinse waters. ISX was evaluated (Figure 20)
on several synthetic and industrial rinses and the copper concentration was
lowered from 28-54 mg/1 to less than 0.1 mg/1. Chemical analysis (%N) of the
sludge showed that the whole Cu(NH3)42+ complex is removed, which is an added
advantage (ammonia removal). A 1-hr ISX contact time aided the complex remov-
al in some cases. Several of the ammonium persulfate etches contain small
concentrations of mercuric chloride to increase the etch rate and ISX has
already been shown to be effective on this pollutant (Hg2+). Overall, it
appears the ISX treatment is effective for the Cu(NH3)4z+ complex in batch
treatments or in continuous flow operations using ISX as a filter precoat.
99
-------
100,000
10,000 -
5 iooo
O9
1.2
Figure 20. Copper ammonia complex removal with ISX.
Copper ammonia complex solutions (1»000 ml) were treated with increasing
amounts of ISX (capacity = 1.5 meq metal ion/g). Aliquots (10 ml) of the
supernatant were removed for copper analysis 5 min after each addition.
Theoretical weight required is 1.02 g for the 50 mg/1 copper ammonia solution.
Curve A. CuCNH-r^2"'" standard solution (50 mg/1 as Cu-initial);
theoretical weight ISX required is 1.02 g.
Curve B. Cu(NH3)42+ commercial rinse (53.63 mg/1 Cu-initial);
theoretical weight ISX required is 1.09 g.
Curve C. Cu(NH3)42+ commercial rinse (41.77 mg/1 Cu-initial);
theoretical weight ISX required is 0.85 g.
Curve D. Cu(NH3)42+ commercial rinse (28.35 mg/1 Cu-initial);
theoretical weight ISX required is 0.58 g.
100
-------
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105
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/2-78-085
3. RECIPIENT'S ACCESSIOI*NO.
4. TITLE AND SUBTITLE
5. REPORT DATE
May 1978 issuing date
REMOVAL OF HEAVY METALS FROM INDUSTRIAL WASTEWATERS
USING INSOLUBLE STARCH XANTHATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO,
Robert E. Wing, Leo L. Navickis, Brian K. Jasberg,
Warren V.. -Rayfo-rrl
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Northern Regional Research Center
Agricultural Research Service
U.S. Department of Agriculture
1815 North University Street
Peoria. Illinois
10. PROGRAM ELEMENT NO.
1BB61C
3610
NTRA
11. CONTRACT/GRANT NO.
EPA-IAG-D5-0711*
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab.
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio ^5268
- Gin. , OH
13. TYPE OF REPORT AND PERIOD COVERED
Final—July 75-June ?6
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The Northern Regional Research Center developed an effective process to remove heavy
metals from wastewaters of two nonferrous metal industries and insoluble starch
xanthate (ISX). The study included bench-scale evaluation of wastewaters from two
lead battery and one brass mill waste. The evaluation included: (l) Determination
of the metals and concentrations in the raw and treated wastewaters; (2) treatment
with ISX alone and in combination with selected coagulant aids; (3) recovery of
heavy metals from ISX sludge; and (U) determination of the potential reuse of the
treated effluent. Several other effective and economical treatment processes were
also developed for specific waste streams from printed circuit manufacturers. Based
on the evaluation of results in this study, recommendations were made as to the
desirability of constructing a prototype plant for actual on-site testing in selected
industries. This report contains an extensive bibliography of references dealing
with these industries.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COS AT I Field/Group
Control
Water Pollution
Toxic Metal Control
Industrial Wastes
Metal Finishing
Insoluble Starch Xanthate
Copper Removal from Rinse
Waters
Brass Mill Wastewaters
Lead Battery Effluents
68D
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
106
U. S. GOVERNMENT PRINTING OFFICE 1978-757-140/6836 Region No. 5m
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