EVALUATION OP AN ELECTRODIALYTIC
PROCESS FOR PURIFICATION OF HEXAVALENT
CHROMIUM SOLUTIONS
by
Dale W. Folsom, Jody A. Jones, and Robert F. Olfenbuttel
Battelle
Columbus, Ohio 43201
Contract No. 68-CO-0003
Work Assignment No. 3-36
Project Officer
Teresa Harten
Waste Minimization, Destruction, and Disposal
Research Division
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
) Printed on Recycled Paper
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NOTICE
This material has been funded wholly or in part by the U.S. Environmental Protection
Agency (EPA) under Contract No. 68-CO-0003 to Battelle. It has been subjected to the Agency's
peer and administrative review and approved for publication as an EPA document. Approval does not
signify that the contents necessarily reflect the views and policies of the U.S. Environmental
Protection Agency or Battelle; nor does mention of trade names or commercial products constitute
endorsement or recommendation for use. This document is intended only as advisory guidance to the
metal finishing and electronics industries in developing approaches to waste reduction. Compliance
with environmental and occupational safety and health laws is the responsibility of each individual
business and is not the focus of this document.
11
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FOREWORD
Today's rapidly developing and changing technologies and industrial products and practices
frequently carry with them the increased generation of materials that, if improperly dealt with, can
threaten both public health and the environment. The U.S. Environmental Protection Agency (EPA) is
charged by Congress with protecting the Nation's land, air, and water resources. Under a mandate of
national environmental laws, the agency strives to formulate and implement actions leading to a
compatible balance between human activities and the ability of natural systems to support and nurture life.
These laws direct the EPA to perform research to define our environmental problems, measure the
impacts, and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing, and
managing research, development, and demonstration programs to provide an authoritative, defensible
engineering basis in support of the policies, programs, and regulations of the EPA with respect to
drinking water, wastewater, pesticides, toxic substances, solid and hazardous wastes, Superfund-related
activities, and pollution prevention. This publication is one of the products of that research and provides
a vital communication link between the researcher and the user community.
Passage of the Pollution Prevention Act of 1990 marked a significant change in U.S. policies
concerning the generation of hazardous and nonhazardous wastes. This bill implements the national
objective of pollution prevention by establishing a source reduction program at the EPA and by assisting
states in providing information about and technical assistance for regarding source reduction. In support
of the emphasis on pollution prevention, the "Waste Reduction Innovative Technology Evaluation
(WRITE) Program" has been designed to identify, evaluate, and/or demonstrate new techniques and tech-
nologies that lead to waste reduction. The WRITE Program emphasizes source reduction and on-site
recycling. These methods reduce or eliminate transportation, handling, treatment, and disposal of hazard-
ous materials in the environment. The technology evaluation project discussed in this report describes
the use of an electrodialytic process to purify hexavalent chromium solutions. The electrodialytic process
reduces wastes by prolonging the use of the concentrated hexavalent chromium solution. The prolonged
use reduces the need for solution replacement, treatment, and disposal.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
in
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ABSTRACT
This evaluation addresses the waste reduction and economics of an electrodialytic process
that can be used to selectively remove impurities that build up in chromic acid solutions with use. The
removal of impurities extends the useful life of the chromic acid solution and avoids periodic replacement
of the solution. The electrodialytic units tested in this evaluation were manufactured by lonsep™. The
units were tested at SL Modern Hard Chrome in Camden, New Jersey, for a hard chromium plating
solution and at Paramax in St. Paul, Minnesota, for a chromic acid solution etching copper from printed
wire boards.
The electrodialytic process was found to effectively remove the impurities that build up in
chromic acid solutions. The rate of return on investment varied from being not cost effective to a
payback of less than 5 years. The payback is a function of the rate of contaminant buildup in the solution
— the more frequently a solution must be replaced when contaminants are not removed, the shorter the
payback after an electrolytic process is installed. There was a waste reduction of 68.4 kg (151 Ib)
annually in chromium reaching the environment from the chromium plating operation and a projected
reduction of 4,410 kg (9,700 Ib) in chromium reaching the environment from the copper etching
operation.
This report was submitted in partial fulfillment of Contract Number 68-CO-0003, Work
Assignment 3-36, under the sponsorship of the U.S. Environmental Protection Agency. The report
covers the period from May 1991 through January 1994 and work was completed as of January 24, 1994.
IV
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CONTENTS
Page
Notice „ ii
Foreword iii
Abstract iv
Figures vi
Tables vi
Acknowledgments vii
SECTION 1: Introduction 1
General Overview 1
Description of the Test Sites and Process 1
Test Sites 2
lonsep™ Electrodialytic Process 2
Literature Review 4
Statement of Project Objectives 5
SECTION 2: Conclusions and Recommendations 6
Chromium Plating Solution 6
Waste Reduction Potential 6
Economic Evaluation 7
Product Quality Evaluation 7
Chromic Acid Etching Solution 8
Waste Reduction Potential 8
Economic Evaluation 8
Product Quality Evaluation 8
SECTION 3: Materials and Methods 9
Site 1 — Chromium Plating 9
Waste Reduction Potential 9
Economic Evaluation ' 10
Product Quality Evaluation 10
Site 2 — Chromium Etching 11
Waste Reduction Potential 11
Economic Evaluation 12
Product Quality Evaluation 12
SECTION 4: Results and Discussion 14
Chromium Plating 14
Waste Reduction Potential . 14
Economic Evaluation 17
Product Quality Evaluation 18
Quality Assurance 19
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CONTENTS (Continued)
Pas
Chromium Etching 20
Waste Reduction Potential 20
Economic Evaluation 21
Product Quality Evaluation 23
Quality Assurance 23
SECTION 5: References 27
FIGURES
Number Page
1 lonsep™ electrodialytic process 3
2 lonsep™ electrodialytic process system diagram 3
3 lonsep™ system schematic 12
TABLES
Number Page
1 Samples collected for the hard chrome line testing 9
2 Samples collected from the etching line 11
3 Analytical results for the chromium plating line 15
4 Waste reduction of the chromium plating line 16
5 Economics of the chromium plating line 17
6 Accuracy of the chromium plating line analysis 19
7 Precision of the chromium plating line analysis 20
8 Waste reduction of the etching line 21
9 Economics of the etching line 22
10 Analytical results for the etching line at Paramax 24
11 Accuracy of the etching line analysis 25
12 Precision of the etching line analysis 26
VI
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ACKNOWLEDGMENTS
The U.S. Environmental Protection Agency and Battelle wish to acknowledge and thank the
companies that served as host test sites for this study. The two sites were SL Modern Hard Chrome of
Camden, New Jersey, and Paramax of St. Paul, Minnesota. The staff at each site provided assistance
and information during the study. In particular, we wish to thank Jeffrey Ballantyne at SL Modern Hard
Chrome and Mike Medina and Bob Haselman at Paramax.
vu
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SECTION 1
INTRODUCTION
GENERAL OVERVIEW
The objective of the U.S. Environmental Protection Agency's (U.S. EPA's) Waste
Reduction Innovative Technology Evaluation (WRITE) Program is to evaluate, in a typical workplace
environment, prototype or innovative commercial technologies that have potential for reducing wastes at
the source or for preventing pollution. In general, each technology is evaluated on three issues.
First, the impact of the new technology on waste generation is measured. The new
technology is compared to the existing technology (baseline) or the process that it replaces. The waste
generated from each technology is determined, and the values are compared.
Second, the economics of the new technology is quantified and compared with the economics
of the existing technology. It should be noted that improved economics is not the only criterion for using
a new technology. Justifications other than reduced costs would encourage implementing new approaches
or tedhnologies. Nevertheless, a measure of the economic impact of any potential change is useful.
Third, the effectiveness of the new technology is assessed. Waste reduction or pollution
prevention technologies typically recycle or reuse materials or use alternative materials or techniques.
Therefore, it is important to verify whether the quality of the feed materials and the quality of the product
are acceptable for the intended purpose.
This study evaluated an electrodialytic process that selectively removes impurities from
hexavalent chromium process solutions. The process uses a cation-selective membrane operated under
an electrolytic potential. Removal of the impurities makes possible extended use of the chromium
solution, thus reducing solution replacement and waste.
DESCRIPTION OF THE TEST SITES AND PROCESS
Metal finishing industries and printed wire board manufacturers use chromium process
solutions to plate chromium and to etch copper. The solutions contain hexavalent chromium, which is
1
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in an anionic form in solution. During plating or etching, cations build up in the solution, making it less
effective. The chromium solution must be .replaced when product quality drops or the etch rate falls
below an acceptable rate. This project estimated the increase in bath life by use of the lonsep™*
electrodialytic process for removal of contamination from both a chromium plating and a chromium
etching solution.
Test Sites
SL Modern Hard Chrome, located in Camden, New Jersey, was the site for testing the
electrodialytic process on a hard chromium plating solution. SL Modern Hard Chrome has specialized
in industrial hard chrome plating for over 35 years and plates a full spectrum of materials, ranging from
aluminum through the copper, ferrous, and nickel base alloys to zinc. The thickness varies from 0.0001
inch to 0.030 inch or more on parts ranging in size from a few ounces to several tons. The company,
which has 40 employees, had sales of up to $5 million in 1991.
Paramax (a Unisys company), located in St. Paul, Minnesota, was the site for testing the
electrodialytic process on a chromic acid etching solution. Paramax manufactures multilayer printed wire
boards at this facility. The boards have more than 10 layers and must meet military specifications.
Paramax Midwest Operations has 3,000 employees and had sales over $100 million in 1991.
lonsep™ Electrodialvtic Process
The aim of the technology is to reduce wastes by removing metals other than chromium
from the process solution. This improves plating and etching product quality and extends process solution
life. The lonsep™ electrodialytic process uses a voltage gradient to separate salt in a solution into cations
and anions. It also converts the anions to acids and cations to hydroxides using electricity and water.
Anions and cations react with water to form acids and bases, respectively. Chromium is present in the
anionic chromate form in the plating and etching solutions.
Figure 1 shows a two-compartment cell used for the purification of a chromium plating
solution. Metal contaminants (cations) migrate across a semipermeable membrane, under the influence
of the electric field. Conversion of the electroplatable metal cations to insoluble hydroxides occurs when
Mention of trade names or products does not constitute endorsement for use.
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ANODE
w MEMBRANE
CATHODE
+ SALTS CATIONS 4-
ANIONS Cu+* Cd+*
CrQj~ F~ ^
_j^. ^SO ^' **+ ^e
PO 1 ^ N' .
N°3 I **,. --~^"
H V Cri^CrO^
H+ PROCESS SOLUTION
>•
>• Co(OH) 2
>• Cd(OH) 2
>• Fe(OH) 3 BASES
>• AI(OH)3 ^^
>. Ni|OH)2 toHT)
IONSEP'MCATHOLYTE (^Hf)
Source: lonsep Corporation, 1989
Figure 1. lonsep™ electrodialytic process.
the cations migrate through the membrane, eliminating the buildup of metals on the cathode. Membranes
in the electrodialytic cells serve to physically separate the acidic, basic, and other process solutions.
Figure 2 shows the incorporation of the lonsep™ unit in a chromium process bath. The chromium anions
remain in the process solution and are returned to the process bath.
At SL Modern Hard Chrome, contamination builds up in the chromium plating solution.
The contaminants typically are in the form of cations, including iron, trivalent chromium, and lead. As
the contaminants build up, the plating solution fails to produce the required product quality and must be
PRODUCT
ITEMS TO BE
PLATED OR
ETCHED
I
CHROMIUM
PROCESS
BATH O
I
O SAMPLING POINT
lilONSEP
UNIT
CATHOLYTE
SOLUTION
Figure 2. lonsep™ electrodialytic process system diagram.
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replaced. At SL Modern Hard Chrome, it has been more than 3 years since a chromium plating bath was
replaced. The lonsep™ electrodialytic process is used to renibve the cations from the chromium plating
solution, allowing it to be used longer. The electrodialytic process was installed in 1988.
At Paramax, a chromic acid solution is used to etch copper from printed wire boards
(PWBs). As copper builds up in the etching solution, the etching rate becomes unacceptably slow.
Before lonsep™ was installed, the chromic acid solution was replaced with fresh solution from once a day
to once a week, at the operator's discretion. The lonsep™ electrodialytic process is used to remove
copper from the etching solution and to convert some of the trivalent chromium back to hexavalent
chromium electrolytically, extending the usefulness of the etching solution.
LITERATURE REVIEW
A literature review found two general articles and two papers specific to the electrodialytic
process. The two articles appeared in the July and August 1986 issues of Plating and Surface Finishing.
In these articles, Knill and Chessin discuss the contamination and purification of hexavalent chromium
plating baths. The first article, entitled "Contamination of Hexavalent Chromium Plating Baths,"
describes the sources of metal contaminants and their impact on the plating of chromium. It also
describes anions and organic contaminants. According to the authors, cleanliness and good work habits,
combined with standard filtration of the solution, can improve product quality more cost effectively than
any other quality control investment. The second article, entitled "Purification of Hexavalent Chromium
Plating Baths," details the methods that can be applied to remove contaminants from a hexavalent
chromium plating bath. The article discusses filtration, oxidation of trivalent chromium to hexavalent
by chemical and electrolytic means, ion exchange to remove contaminants, and electrolytic and
electrodialytic processes to purify hexavalent chromium plating baths. The authors assert that the most
valuable benefit from solution purification is the significant improvement in the quality of deposits and
the attendant reduction in rejects.
In "Removal of Metal Cations from Chromium Plating Solution," a paper presented at the
10th AESF/EPA Conference on Environmental Control for the Metal Finishing Industry, January 23-25,
1989, Cushnie and Anderson presented the results of a study that identified and tested technologies for
removing iron and copper from chromium plating solutions. The two technologies tested were an
electrodialytic membrane unit and an electrolytic porous pot. The results showed that the membrane
technology removed iron and copper better. In 16 days, the contaminant concentration dropped from
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10.4 g/L to 4.0 g/L with a membrane, and from 10.4 g/L to only 9.0 g/L with a porous pot under test
conditions. « .<.- - ,
Several papers and/or articles have been prepared by developers of the lonsep™
electrodialytic process. One of these, "Closed-Loop Processing of Chromic Acid Solutions," also
presented at the 10th AESF/EPA Conference, described how the electrodialytic process can be used to
remove contaminants from a chromium plating solution. It also described the use of the electrodialytic
process to recover regeneration solutions for ion exchange systems. The paper's authors found that the
electrodialytic technology can maintain closed-loop processing for most chromic acid solutions. They
also found that it was possible to maintain the rate of a metal-finishing operation and the quality of the
product over a long period without discarding or decanting part or all of the chromic acid finishing
solution.
STATEMENT OF PROJECT OBJECTIVES
The purpose of this project was to evaluate the applicability of the lonsep™ electrodialytic
process as a means of removing cations from both a chromium plating solution and a chromic acid etch-
ing solution. This project had the following objectives:
• Evaluate the ability of the lonsep™ electrodialytic process to remove
cations from chromium solutions.
• Evaluate the waste reduction potential of the technology.
» Evaluate the cost effectiveness of this technology compared to that of
current practice.
• Evaluate the effect of the lonsep™ electrodialytic process on product
quality.
The study compared the wastes generated and the life of the bath with and without use of the lonsep™
electrodialytic process. The comparison was performed at a hard chrome plater and at a printed wire
board manufacturer using a chromic acid etch bath, SL Modern Hard Chrome and Paramax, respectively.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
The conclusions and recommendations from this study are presented in two subsections.
The results of using the lonsep™ electrodialytic process to treat hexavalent chromium plating solutions
are discussed first, followed by the results of treating chromic acid etch solutions.
The tests conducted demonstrated that the lonsep™ system removes impurities from the
chromium plating and the chromic acid etch solutions. The rate of removal is 25 grams per day for a
250-amp unit, based on the buildup of metals in the catholyte solution.
CHROMIUM PLATING SOLUTION
Waste Reduction Potential
This study evaluated the waste reduction potential of the lonsep™ system used in a 1,400-gal
hard chromium plating bath. SL Modern Hard Chrome purchased the lonsep™ system as.part of its plan
to eliminate all industrial liquid waste discharges to the city. To achieve zero liquid discharge, SL Modern
Hard Chrome initially rinses parts over the bath and performs a final rinse that is totally collected in a
sump, filtered, and then returned to the bath to make up water lost to evaporation. Impurities build up
in the plating bath because all rinse water is returned to it; the lonsep™ system was purchased to reduce
this buildup. The only resulting waste discharge is the sludge from the lonsep™ catholyte solution. This
catholyte sludge contains levels of chromium at 2,000 to 3,200 mg/L total chromium and 760 to 1,050
mg/L hexavalent chromium and therefore must be handled as a hazardous waste.
The rate at which impurities are removed from the chromium plating bath and collected in
the catholyte solution leads to a projection that the plating bath would exceed permissible bath impurity
levels in 40 years. Thus, every 40 years the bath would have to be replaced if the lonsep™ unit were not
used. Using the lonsep™ system, SL Modern Hard Chrome generates one-third of a 55-gal drum of
catholyte sludge every month, or 220 gal per year, from the 1,400-gal bath. In 6.4 years, a volume equal
to that of the bath (1,400 gal) has been disposed of as sludge. Therefore, by volume alone, the lonsep™
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system generates more waste. Most of this sludge consists of metal hydroxides with a high concentration
of water because it is only decanted. However, there is a ngt reduction of 12 kg (26.6 Ib) annually in
chromium reaching the environment. If the bath is replaced every 40 years, the total annual discharge
is-calculated at 18.5 kg (40.8 Ib). With the catholyte solution replaced monthly (lonsep™ is.not used to
reclaim catholyte solution), the annual discharge of chromium is 6.5 kg (14.2 Ib).
Economic Evaluation
The operating cost associated to the chromium plating bath without the lonsep™ system is
$3,684 annually. The operating cost with the lonsep™ system is $3,578 annually. This is an annual sav-
ings of $106 in operating costs.
The cost savings from not having to strip and replate reject parts provides a major
motivation for using the lonsep™ system. This reduction in rejects resulted in annual cost savings of
$3,218 because the company did not have to strip the defective chromium plating and replate. Economic
data were not available for estimating cost savings resulting from not having to operate a wastewater
treatment system. However, management of SL Modern Hard Chrome believes that the ability to avoid
wastewater treatment plus the reduced reject rate more than offset the initial purchase cost. The savings
for the 1,400-gal bath is $106 annually. This results in a long payback without allowing credit for"
wastewater treatment cost avoidance.
In general, the payback of an lonsep™ unit is site specific and depends on how frequently
the plating bath is replaced and the associated disposal costs. The use of the lonsep™ system at other sites
requires sizing the unit to the rate of contaminant buildup in the chromium plating solution.
Product Quality Evaluation
*i
SL Modern Hard Chrome measured product quality by visual inspection for pits, blisters,
or any other plating deformity and thickness testing to ensure the desired chromium thickness and
uniformity over the plated item. The company found that use of the lonsep™ process resulted in a
5% decrease in rejected parts. Prior to introduction of the lonsep™ process, SL Modern Hard Chrome
employees waited for parts to be rejected before they performed a bath analysis to determine the reason
for defective plating. The reduction in rejects corresponded with the implementation of frequent bath
analysis and bath additions.
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CHROMIC ACID ETCHING SOLUTION
» tf. j< ff
Waste Reduction Potential
At a minimum, the etching solution at Paramax is replaced once a week, resulting in 200 gal
of chromium and copper waste solution for disposal. In the past, Paramax blended the waste with other
copper-containing wastestreams, and the copper was treated by electrowinning and sold for scrap. The
solution then had to be treated for chromium and other metals before discharge. The lonsep™ system at
Paramax removes the copper and makes possible reuse of the etching solution, thus eliminating the
discharge and replacement of the chromic acid etching solution. The sludge formed in the catholyte
solution is collected hi a filter press. The catholyte solution is reused, and the filter press is flushed with
waste acid to remove the sludge by resolubilizing it. The flushed liquid is then treated by electro winning
to recover copper. The projected waste reduction of chromium is 9,700 Ib per year.
Economic Evaluation
The installed cost of the unit was $563,000 and the annual savings is approximately
$126,000. The payback for the lonsep™ system at Paramax is projected to be 5 years. The savings are
the result of the reduced chromium disposal and chemical replacement costs provided by Paramax.
Product Quality Evaluation
The copper concentration in the etching solution must not exceed 25 g/L. The testing during
this evaluation reduced the copper concentration from 18.1 g/L to 10.8 g/L in the etching solution. The
etchant can then be reused. At present, environmental personnel at Paramax are trying to convince
production personnel that the lonsep™ system can effectively regenerate the etching solution and not affect
PWB quality. To do this, Paramax is collecting the etching solution when it is replaced and treating it
with the lonsep™ system. The regenerated/recovered etching solution then is used on test boards. The
testing results were not available at the time of this report. However, the chemical analysis of the
regenerated etching solution shows the solution to be within specifications.
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SECTION 3
MATERIALS AND METHODS
SITE 1 — CHROMIUM PLATING
Waste Reduction Potential
The catholyte solution was sampled over a 3-month period at SL Modern Hard Chrome, as
shown in Table 1. The lonsep™ system with sampling points at the first test site is shown hi Figure 2.
Any metals buildup in the catholyte solution represents what was removed from the plating bath by the
lonsep™ unit. Knowing the amount of metals in the catholyte solution and the duration of the solution
use made it possible to calculate the metals removal rate, which was assumed to correlate to the rate at
which metals would have built up in the plating bath had lonsep™ not been installed. Grab samples from
the catholyte tank were taken after the precipitated materials had been mixed well with the catholyte
solution. The solution was sampled immediately before disposal so that the amount of contaminants
removed from the chromium plating solution could be determined. The catholyte solutions usually were
TABLE 1. SAMPLES COLLECTED FOR THE HARD CHROME LINE TESTING
Description
Chromium Solution
Catholyte Solution
Catholyte Blank
Water Blanks
Sample I.D. No.
CSL-1
CSL-4
CSL-6
CSL-2
CSL-8
CSL-9
CSL-3
CSL-5
CSL-7
Type of Sample
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Date
4/6/92
4/7/92
4/7/92
4/6/92
3/6/92
2/6/92
4/6/92
4/7/92
4/7/92
Tune
12:35
9:15
13:45
12:45
9:15
10:30
13:15
10:00
14:15
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disposed of monthly. At SL Modern Hard Chrome, the first sampling of catholyte was from a catholyte
solution used for 2 months; the other two samples were both from catholyte solutions that were used
1 month. The samples were taken before disposal of the catholyte solution.
Metals analyses for chromium, iron, and lead were performed on the catholyte solution as
described under the product quality evaluation section for the plating solution. The purpose of the
analyses was to determine rate of rrietals buildup, which in turn was used to calculate the amount of use
that could be obtained from the chromium bath before disposal without the lonsep™ unit.
Blanks also were sampled and analyzed. One was taken of the fresh catholyte solution, and
two were taken of the tap water on site. The tap water was run several seconds before sampling.
Economic Evaluation
SL Modern Hard Chrome provided economic information on its operations. The
information provided included utility rates, chemical costs, disposal costs, and labor rates. A recent cost
analysis of the lonsep™ system was used. The savings were calculated on the difference between the
operating costs with and without the system. The payback period is then the cost of the system divided
by the annual savings.
Product Quality Evaluation
Chemical analyses of the chromium plating solution were used to verify that the solution
met their operational specifications for hard chromium plating solutions. These specifications are:
• Chromium oxide: 270 g/L (minimum)
• Chromium: 140 g/L (minimum)
• Total metals (cations): 52 g/L (maximum).
Over a 2-day period, three grab samples were taken from the well-mixed chromium plating
solution at SL Modern Hard Chrome. Total chromium, lead, and iron were analyzed by EPA Method
6010 (inductively coupled plasma spectrometry), and hexavalent chromium by EPA Method 7196 (colori-
metric method) by an outside contractor. Iron and lead were the only contaminant metals analyzed
because they are known to be the major contributors to contamination of the baths at the test site.
10
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Table 1 identifies the samples. SL Modern Hard Chrome also provided bath analysis data for total
chromium, hexavalent chromium, and sulfite* from December 3, 1991, through April 2, 1992.
The manufacturer routinely performed quality checks to determine product quality. Visual
inspections of the items for pitting, blisters, and any other coating deformities were performed. The
thickness of the chromium coating was checked, as was the uniformity of the coating thickness on the
plated item. The numbers of rejected parts both before and after installation of the lonsep™ system were
based on estimates of plating shop personnel because no records were available.
SITE 2 — CHROMIUM ETCHING
Waste Reduction Potential
The waste reduction potential was based on the difference between the amount of chromic
acid etch solution disposed without lonsep™ treatment and the amount of chromic acid etch that can be
reused after treatment with the lonsep™ unit. Samples of catholyte were collected as shown in Table 2.
TABLE 2. SAMPLES COLLECTED FROM THE ETCHING LINE
Description
Etchant
Catholyte
Catholyte Sludge
Water Blank (hot water makeup)
Sample I.D.
Date
5/19/92
5/19/92
5/20/92
5/21/92
5/21/92
5/19/92
5/19/92
5/19/92
5/20/92
5/21/92
5/21/92
5/20/92
5/21/92
5/21/92
No.
Time
12:35
15:30
10:00
10:45
16:00
11:45
13:18
15:20
10:45
10:45
16:00
13:00
16:30
16:00
Type of Sample
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
Grab
11
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The lonsep™ system schematic at Paramax is shown in Figure 3 with sampling points. Samples of the
sludge filtered from the catholyte tank also were collected The processing time of 3 days was used to
calculate the treatment rate of the lonsep™ unit. From the treatment rate, the amount of etchant for reuse
(per unit time) can be calculated.
Economic Evaluation
Paramax provided economic-information for its etching operations. The economic data
provided included utility rates, chemical costs, and installed equipment costs. The annual cost savings
is the difference in annual operating costs with and without the use of the lonsep™ system. The method
used to calculate the payback period is to divide the annual savings into the system installed cost.
Product Quality Evaluation
Chemical analyses of the spent chromic acid etching solution during treatment by the
lonsep™ unit at Paramax were used to verify that the solution met operational specifications for PWB
etching solutions. These specifications are as follows:
* Chromium oxide: 60 g/L (minimum)
• Chromium: 31 g/L (minimum)
" Total other metals (cations): 25 g/L (maximum)
" Copper: 0 to 25 g/L.
r
CHROMIC ACID
COLLECTION
TANK O
I
BANKS
OF
IONSEP
CELLS
1 ^
0 SAMPLING POINTS
-»
1
'
1
1
CATHOLYTE
TANK
\
"Y
L
0
^
>
o
FILTER PRESS
Figure 3. lonsep™ system schematic.
12
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Four grab samples were taken from the etching solution over a 3-day period. The final
sample represents the etching solution that wduld be reused if Paramax returned the Ionsep™-treated spent
etchant back to the etching line. Total chromium, copper, zinc, cadmium, lead, and iron were analyzed
by EPA Method 6010 (inductively coupled plasma spectrometry), and hexavalent chromium by EPA
Method 7196 (colorimetric method). Table 2 lists the samples taken at Paramax.
13
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SECTION 4
RESULTS AND DISCUSSION
Testing was done on the electrodialytic process applied to two different operations at two
distinct sites — a chromium plating solution at SL Modern Hard Chrome and a chromic acid etching
solution at Paramax. The results are discussed separately for each site because the bath process and the
lonsep™ process used at the two sites were very different. For each site, the discussion is divided into
the three project objectives: waste reduction potential, economic evaluation, and product quality
evaluation.
CHROMIUM PLATING
At SL Modern Hard Chrome, the chromium plating solution was recovered continuously
by placing the lonsep™ unit (cell) directly into the bath. The catholyte solution is contained in a plastic
55-gal drum outside the bath and is circulated through the lonsep™ cell.
Waste Reduction Potential
The waste reduction potential of the lonsep™ unit at SL Modern Hard Chrome is determined
from the extended bath life and the reduced number of rejects that require stripping and replating. The
actual contaminants are not broken out individually because the contaminants are disposed either with the
bath in the old practice or with the catholyte in the new process.
Table 3 shows analytical results for the catholyte solution and the chromium plating solution.
The catholyte solution was analyzed after the solution had been in use for 1 to 2 months and immediately
before disposal. Metals in the catholyte solution are metals that were removed from the plating bath.
Analysis indicates a removal rate of approximately 25 g total contaminant per day for a 250-amp lonsep™
unit. The rate is calculated by adding the mass of metals in the catholyte solution divided by the days
of catholyte solution use: CS1-8 (2,030 + 740 + 760 + 28 mg/L) x 3.785 L/gal x 55 gal/29 days/
1,000 mg/g = 25.5 g/day. If the contaminants were not removed, levels eventually would reach the limit
14
-------
TABLE 3. ANALYTICAL RESULTS FOR THE CHROMIUM PLATING BATH
Sample ID
Catholyte
CSL-9
CSL-8
CSL-2
Process Bath
CSL-1
CSL-4
CSL-6
Blanks
CSL-3
CSL-5
CSL-7
Cr
mg/L
3,230
2,030
2,500
153,000
151,000
155,000
0.07
0.03
0.05
Fe
mg/L
1,100
740
111
1,710
2,740
1,760
0.26
0.15
0.15
Cr6
mg/L
1,050
760
860
150,000
160,000
160,000
0.02
0.02
0.02
Pb
mg/L
48.6
27.5
27.6
7.71
89.8
70.4
0.034
< 0.03
< 0.03
Date Days Use
2/6/92
3/6/92
4/6/92
4/6/92
4/7/92
4/7/92
4/6/92
4/7/92
4/7/92
56
29
31
Time
12:35
9:15
13:45
13:15
10:00
14:15
of 52 g/L in the plating bath. The time estimated from these data for a 1,400-gal bath to reach that limit
is 52 g/L X 3.79 L/gal x 1,400 gal/25 g/day, or 11,036 days. Therefore, the use of lonsep™ extends
bath life beyond 40 years, which results in approximately 35 gal of solution saved per year (that would
otherwise go to the environment without lonsep™), based on an operation schedule of 250 days per year
(1,400-gal bath/40 year).
There is a significant reduction of chromium with the use of lonsep™ unit — from 165 Ib
to 14.2 Ib. The 14.2 Ib of chromium is the small amount lost to the catholyte solution. The reduction
is the result of not having to replace the bath periodically and of having all rinse water returned to the
plating bath to make up evaporative water losses.
Chromium is saved not only through reduced replacement of plating solution, but also
through the reduced number of rejects. For every reject, the company must strip and replate the part.
The reject data are based on estimates of plant personnel because no records were maintained. The reject
reduction also corresponds to the company's implementation of regular bath analysis and chemical
additions, which would also contribute to fewer rejects. The 5% decrease in rejects experienced by SL
Modern Hard Chrome corresponds to approximately 237 pounds of chromium per year that is not
disposed of with the stripper and that need not be purchased for addition to the plating solution. The
237 Ib of chromium oxide is calculated from the company's plating rate from this bath of 42,900 ft2 per
15
-------
year, at a plating amount of 1.77 oz CrO3 per ft2, and a 5% savings (0.05 x 42,900 ft2/yr x 1.77 oz/ft2
x l/16oz/lb). -
Table 4 summarizes the waste reduction potential of the new technology. The top part of
Table 4 ("without lonsep™") lists the wastes from infrequent bath replacement and the chromium stripped
from rejected parts. The bottom part of Table 4 ("with lonsep™") lists the chemicals used to make the
lonsep™ catholytic solution and the additional barium carbonate used to adjust the sulfate levels of the
chromium plating bath by precipitating the sulfate as barium sulfate. The use of barium carbonate
increased when lonsep™ was installed. The total waste without the use of lonsep™ amounts to 317 pounds
of CrO3 (165 Ib Cr). The total waste with the use of lonsep™ increases to 451 Ib. This increase is the
result of the catholyte salts and sludge and the increased use of barium carbonate to reduce sulfate in the
bath. The sulfate concentration builds up faster hi the bath because rinse water is reused in the bath when
the lonsep™ unit is used. In a 1-year period, 36 Ib of barium carbonate was used to form barium sulfate,
which precipitates out hi the bath. The precipitate is either filtered out or allowed to collect at the bottom
of the plating bath. The 36 Ib of barium carbonate would react to form 43 Ib of barium sulfate.
TABLE 4. WASTE REDUCTION OF THE CHROMIUM PLATING LINE
Waste Annual Generation
Without lonsep™
CrO3 hi bath solution 80 Ib (41.6 Ib Cr)
CrO3 due to rejects 237 Ib (123 Ib Cr)
Total Cr03 317 Ib (165 Ib Cr)
With lonsep™*
Catholyte solution
Sodium sulfate 120 Ib
Sodium carbonate 288 Ib
Additional barium sulfate from sulfate reduction w/BaCO3 43 Ib
Total* 451 Ib (14.2 Ib Cr+6)
* Sludge from lonsep™ not included because it should equal the amount of metal contaminants disposed
of with the chromium plating solution without lonsep™.
t The sludge for 1 year would contain 14.2 Ib Cr+6.
16
-------
Economic Evaluation
The annual operating costs with and without the lonsep™ unit are itemized in Table 5.
Without the lonsep™ system, the operation of a 1,400-gal bath costs $3,534 per year. The cost for the
same bath with an electrodialytic unit is $3,973 per year. According to SL Modern Hard Chrome
personnel, a major incentive for installing the equipment was to improve product quality. The reduction
in rejects results in economic savings (e.g., faster turnaround tune, decreased need for stripping solution,
and ease of operation). These costs were included in the operation without lonsep™.
The factors involved in the economic analysis are summarized in Table 5. Operating costs
include costs for labor, maintenance, chemicals, utilities (water and electricity), and waste treat-
ment/disposal.
TABLE 5. ECONOMICS OF THE CHROMIUM PLATING LINE
Description
Without lonsep™
Cr bath
Bath disposal
CrO3 due to rejects
Labor due to rejects
Strip solution replace-
ment and disposal
Total without lonsep™
With lonsep™
Catholyte solution
Sodium sulfate
Sodium carbonate
Water
Barium carbonate
Sludge disposal
Labor
Maintenance
Power
Total with lonsep™
Annual Usage
35 gal
35 gal
237 Ib
140 hr
100 gal
120 Ib
288 Ib
660 gal
36 Ib
4 drums
41 hr
—
8,100 kWh
Rate
$11.30/gal
$2/gal
$1.13/lb
$20/hr
$1.50/gal
$18/100 Ib
$18/100 Ib
$2.66/1000 gal
$1.22/lb
$205/drum
$20/hr
—
$.0902/kWh
Annual savings
Annual Cost
$396
70
268
2,800
150
$3,684
$22
52
2
44
820
•827
1,080
731
$3,578
$106
17
-------
• Labor for the lonsep™ unit is for a weekly check on the system of Va hour per week
and 2 hours per month to change the solution The labor rate is calculated at $20 per
hour.
5>
• Maintenance costs for the unit are for labor of 2 hours per month ($20/hr) to clean
lines and replace parts for each cell and materials costs of $300 for a pump that lasts
2 years and $450 annually to replace the lonsep™ membrane.
» Chemical costs for the unit are for the components of the catholyte solution as shown
in Table 5.
• The water cost is based on just the additional water that is used in lonsep™ catholyte
solution.
• The decrease in rejects results in savings-of the labor needed to reprocess the rejects
and the additional chromium that would be used to replate the part and replacement
and disposal of the strip solution. The replacement and disposal cost is estimated at
$1.SO/gal. The additional strip solution replacement due to rejects is estimated at 100
gal annually.
« Waste disposal costs are based on a waste disposal company's quote of $2/gal for
chromium bath disposal and an actual sludge disposal cost of $205 per drum.
The capital cost of a 250-amp lonsep™ unit in the fall of 1991 was $20,000. With the
.savings of $106 in annual costs using the lonsep™ unit, there is a payback on the unit of 189 years.
The firm is planning to add an lonsep™ unit to the caustic strip tanks to recover chromic acid
for recycle back to the plating baths and to recover the sodium hydroxide. This additional system, along
with the current practice of decanting the catholyte solution and adding the solution to the caustic strip
tanks, may eliminate the need for additional stripping solution and result in greater savings.
Although economic considerations are important, they are not the only justification for
installing waste reduction equipment. Because all rinsewater is returned to the plating baths, the
electrodialytic system allows SL Modern Hard Chrome to have zero discharge from its plating operations
to the city water treatment system. SL Modern Hard Chrome decided to purchase lonsep™ to avoid the
problems and costs of water discharge to the city.
Product Quality Evaluation
The products at SL Modern Hard Chrome are the chromium-plated parts. The parts are
inspected for pits, blisters, other deformities, and chromium thickness. The product quality is the plated
18
-------
part quality, which correlates with the plating bath quality (specifications). Based on discussions with
plant personnel, the number of rejects has decreased by about 5% since installation of the lonsep™ unit.
The fact that SL Modern Hard Chrome has experienced a drop in the number of rejects is a key factor
in its continued use of the lonsep™ unit. There are fewer rejects because the chromium plating quality
has improved, producing more uniform chromium deposit and fewer pits.
Analysis of the bath (Table 3) showed it was within specifications — the contaminant level
was below the maximum of 52 g/L and the chromium level was above the minimum of 140 g/L.
Quality Assurance
A Quality Assurance Project Plan (QAPP) (Battelle, 1992) was prepared at the outset of the
project to describe testing, sampling, and analysis procedures. Testing and sampling were carried out
at SL Modern Hard Chrome according to the QAPP. Tables 6 and 7 give the accuracy and precision,
respectively, of the analytical results.
Matrix spike recoveries (Table 6) were within 75% to 125% for all parameters except lead
in the process bath solution. Therefore, levels of lead measured hi the process bath should be considered
as minimum levels present because recovery from the spike is low. Precision (Table 7) was within
±25 % for all parameters except total chromium hi the catholyte, for which precision was measured close
TABLE 6. ACCURACY OF THE CHROMIUM PLATING LINE ANALYSIS
Parameter
Catholyte
Cr
Fe
Cr + 6
Pb
Process Bath
Cr
Fe
Cr + 6
Pb
Sample
No.
CSL-8
CSL-8
CSL-3
CSL-8
CSL-4
CSL-4
CSL-4
CSL-4
Regular
Sample
Mg/L
1,014
740
19
550
1,513
548
1,600
898
Matrix Spike
Level
MS
1,000
1,000
2,000
1,000
1,000
1,000
1,000
1,000
Matrix Spike
Measured
/tg/L
2,031
1,198
1,735
1,308
2,469
1,365
2,636
1,504
%
Recovery
102%
90%
86%
76%
96%
82%
104%
61%
Dilution
Factor
-
-
-
-
100,000
5,000
100,000
100
19
-------
TABLE 7. PRECISION OF THE CHROMIUM PLATING LINE ANALYSIS
Parameter
Catholyte
Cr
Fe
Cr + 6
Pb
Process
Cr
Fe
Cr + 6
Pb
Sample No.
CSL-5
CSL-5
CSL-3
CSL-5
CSL-4
CSL-4
CSL-4
CSL-4
Regular
Sample
mg/L
0.03
0.15
0.019
< 30
151,000
2,740
160,000
89,800
Duplicate
mg/L
0.04
0.17
0.021
< 30
156,000
3,110
161,000
77,900
Precision %
28.6
12.5
10
3.3
12.6
0.6
14.2
to the detection limit and fell slightly out of range. Completeness, accuracy, and precision data quality
objectives (DQOs) were met for this project.
CHROMIUM ETCHING
At Paramax, the etchant was recovered as a batch process in the following way for these
tests. Over a two-day period, etchant baths totalling 200 gal were removed from the process line to a
treatment tank and pumped through the lonsep™ unit. The unit ran continuously for 3 days. Paramax
has since established that the recovered etchant meets its stringent requirements for etching solutions.
Waste Reduction Potential
The waste reduction potential of the lonsep™ unit at Paramax was calculated based on how
many etchant bath disposals this, process can prevent. The number prevented depends on how fast
contaminants build up in the etchant bath and the extent of contaminant removal through the lonsep™ unit.
Experience at Paramax indicates that use of the lonsep™ unit prevents disposal of
approximately 7.5 baths per week. The facility currently disposes of 8.5 baths per week and estimates
that, with the lonsep™ unit, disposal will be reduced to 1 bath per week. The rate of contaminant buildup
in the etchant is slightly higher than the rate of removal by the lonsep™ system. Each bath contains
20
-------
110 gal (the lonsep™ unit can treat up to 500 gal, or about 4 baths in 4 days), which means that
41,250 gal of etchant bath solution would ntk be disposid of per year (7.5 bath/wk x 110 gal/bath x
50 wk/yr). The etchant concentrate is diluted 50% to make up the bath. Therefore, the lonsep™ unit
could reduce 20,625 gal of etchant concentrate per year going to the environment. This amount of
etchant contains approximately 7,154 pounds of chromium that would have otherwise gone to waste
(80 g/L CrO3 in etchant X 52 g Cr/100 g CrO3 x 20,625 gal x 3.785 L/gal). Table 8 summarizes the
items evaluated in the waste reduction analysis.
TABLE 8. WASTE REDUCTION OF THE ETCHING LINE
Amount Discarded
Per Year
Without lonsep™
Etchant 20,625 gal
Water 20,625 gal
Chromium 7,100 Ib
With lonsep™
Catholyte solution
Sodium chloride 10,000 Ib
Sodium sulfate 5,000 Ib
Soda ash 1,000 Ib
Water 25,000 gal
Chromium 42 Ib*
* estimated
Economic Evaluation
The lonsep™ unit at Paramax is still in the testing phase. Therefore, most of the cost analy-
-sis was based on Paramax estimates derived from economic information in plant records and experience
of the Paramax personnel. These estimates indicate that the unit can prevent the disposal of approx-
imately seven etchant baths per week, resulting in savings in disposal and replacement chemical costs.
Operating cost factors involved in the economic analysis for Paramax include labor,
maintenance, chemicals, utilities (water and electricity), and waste treatment/disposal.
21
-------
Labor for operating the lonsep™ unit is .based on an estimate of one full-time
technician at $20.00 per hour.
Paramax estimates maintenance for the unit will cost $30,000 per year. This figure
is mostly for replacement parts, including 4 membranes per year, and recoating the
anodes. Maintenance labor also is included hi Paramax's estimate.
Chemical costs for the unit are calculated from the estimated usage of catholyte
solution, the components of the solution, and their actual costs obtained from
Paramax.
The water cost is for the additional water that is used in the catholyte solution for the
lonsep™ unit and cost of water for Paramax.
The power cost for the unit is for the power actually used during the test run and the
unit cost of electricity for Paramax.
Waste disposal costs are for the actual costs at Paramax. Minimal disposal costs are
anticipated with the lonsep™, because most of the waste is recovered (i.e., both the
chromium bath and the copper are recovered).
Table 9 compares costs with and without the lonsep™ unit.
TABLE 9. ECONOMICS OF THE ETCHING LINE
Description
Without lonsep™
Etchant (concentrate)
Etchant disposal
Labor for disposal
Water*
Total
With lonsep™
Catholyte solution
Sodium chloride
Sodium sulfate
Soda ash
Water*
Labor
Maintenance
Power
Total
Annual Use
20,625 gal
41,250 gal
150 hr
20,625 gal
10,000 Ib
5,000 Ib
1,000 Ib
25,000 gal
2,000 hr
—
1,430 kWh
Rate $ Annual Cost $
4.85/gal
2.31/gal
20.00/hr
2.66/1000 gal
3.50/50 Ib
17.50/100 Ib
0.23/lb
2.66/1000 gal
20.00/hr
—
0.045/kWh
100,031
95,288
3,000
55
$198,374
700
875
230
66
40,000
30,000
65
$ 71,936
Water costs include sewage fee.
22
-------
Without the unit, costs of approximately $198,000 are incurred for replacement and disposal
of the etchant baths. Operating the unit costs approximately $72,000, mostly for added labor and main-
tenance on the unit. Thus, with the lonsep™ system, an approximate annual savings of $126,000 is
realized. The capital cost of the unit (specific to Paramax), including installation and modifications, was
$563,000. Dividing this by the annual savings results in a payback period of approximately 4.5 years.
Product Quality Evaluation
The lonsep™ unit at Paramax was in the initial testing phases. The etchant was sampled and
analyzed for both chromium and contaminants at the end of the 3-day treatment/recovery process. These
analyses were used to determine whether the renovated bath was within specifications, and bath quality
was an indication of product quality. The analytical results are shown in Table 10. Although total
chromium in the etchant remained constant, hexavalent chromium increased. The hexavalent chromium
started at approximately 74% of the total and increased to about 99%. It is believed that oxidation of
the trivalent chromium back to the hexavalent form caused the increase in hexavalent chromium
concentration. The resulting hexavalent chromium concentration of 30.3 g/L in the etchant over the 3-
day sampling period approached the minimum specification level of 31 g/L, as given in Section 3. This
could be increased further by longer treatment or by adding etchant concentrate. At the time this study
was conducted, the etchant had not been reused and the effect of recovered solution on in-house printed
wire board quality had not been evaluated.
As shown in Table 10, the cationic contaminants were within specification. The 10.8 g/L
(mostly copper) was below the maximum level of 25 g/L. Because the chromium and the contaminant
levels are both near specification levels, the etchant should be acceptable.
Quality Assurance
Testing and sampling at Paramax were carried out according to the QAPP with the following
exceptions. The initial plan for sample collection was for sampling at three locations: (1) chromium
etching bath, (2) lonsep™ return, and (3) catholyte solution. On site, it was realized that the lonsep™
return line was a continuous recirculation of the chromium process fluid at a flowrate of about 10 gpm.
Therefore, it was not necessary to sample both the process bath and the return line. The return line was
representative of the process bath and was sampled.
23
-------
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24
-------
Tables 11 and 12 give the analytical accuracy and precision, respectively, of the laboratory
testing. Matrix spike recoveries and precision for all parameters were within acceptable ranges except
for the precision of the iron results for the etchant samples which was slightly out of range. This implies
that the values for iron in the etchant samples (Table 10) are not significantly different from each other.
Completeness, accuracy, and precision data quality objectives in the QAPP were met.
TABLE 11. ACCURACY OF THE ETCHING LINE ANALYSIS
Parameter
Etchant
Cr, pg/L
Cu, pg/L
Fe, pg/L
Zn, ^tg/L
Cr+6, pg/L
Catholyte
Cd, pg/L
Cr, pg/L
Fe, /ig/L
Pb, pg/L
Zn, pg/L
(~"r+6 ,,o7T
V_*l , fA>Ł2/ •L-'
Sample
Date Time
5/21
it
"
5/21
it
5/19
5/21
5/21
5/19
5/21
5/21
16:00
16:00
15:20
16:00
16:00
15:20
16:00
16:00
Regular
Sample
1,515
646
1,168
1,340
300
14 ,
391
237
529
1,245
300
Matrix
Spike
Level
1,000
1,000
1,000
1,000
2,000
1,000
1,000
1,000
1,000
1,000
2,000
Matrix
Spike
Measured
2,542
1,714
1,939
2,207
2,416
987
1,445
968
1,532
2,141
2,416
Recovery
103
107
77
87
106
97
105
73
100
90
106
Dilution
Factors
20,000
20
5
10
100,000
-
-
-
-
-
-
25
26
-------
-------
Tables 11 and 12 give the analytical accuracy and precision, respectively, of the laboratory
testing. Matrix spike recoveries and precision for all parameters were within acceptable ranges except
for the precision of the iron results for the etchant samples which was slightly out of range. This implies
that the values for iron in the etchant samples (Table 10) are not significantly different from each other.
Completeness, accuracy, and precision data quality objectives in the QAPP were met.
TABLE 11. ACCURACY OF THE ETCHING LINE ANALYSIS
Parameter
Etchant
Cr, jttg/L
Cu, pg/L
Fe, ittg/L
Zn, jig/L
Cr+6, Mg/L
Catholyte
Cd, jig/L
Cr, jig/L
Fe, /ig/L
Pb, Mg/L
Zn, jug/L
Cr+6, jicg/L
Sample
Date Time
5/21
it
it
5/21
II
5/19
5/21
5/21
5/19
5/21
5/21
16:00
16:00
15:20
16:00
16:00
15:20
16:00
16:00
Regular
Sample
1,515
646
1,168
1,340
300
14 .
391
237
529
1,245
300
Matrix
Spike
Level
1,000
1,000
1,000
1,000
2,000
1,000
1,000
1,000
1,000
1,000
2,000
Matrix
Spike
Measured
2,542
1,714
1,939
2,207
2,416
987
1,445
968
1,532
2,141
2,416
%
Recovery
103
107
77
87
106
97
105
73
100
90
106
Dilution
Factors
20,000
20
5
10
100,000
-
-
-
-
-
-
25
-------
TABLE 12. PRECISION OF THE ETCHING LINE ANALYSIS
Parameter
Etchant
Cd, pg/L
Cr, mg/L
Cu, mg/L
Fe, mg/L
Pb, pg/1
Zn, mg/L
Cr+6, mg/L
Catholvte
Cd pg/L
Cr mg/L
Cu mg/L
Fe mg/L
Pb ^g/L
Zn mg/L
Cr+6 mg/L
Sample
Date Time
5/21
5/19
5/19
5/19
5/19
5/19
5/19
5/19
16:00
11
it
ll
n
ll
ll
11:45
15:20
15:20
15:20
15:20
15:20
13:18
Regular
Sample
*.
379
30,300
10,800
5.84
14,500
13,100
30,000
14
31.2
129.9
0.43
0.529
158
378
Duplicate Precision %
382
29,000
10,600
7.66
14,900
13,000
30,000
13
31.9
140.0
0.44
0.515
162
381
0.8
4.4
1.9
27
2.7
0.8
0.0
7.2
2.2
7.5
2.3
2.7
2.5
0.8
26
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SECTION 5
REFERENCES
Battelle. 1992. Quality Assurance Project Plan for the lonsep ™ Electrodialytic Process Evaluation,
February. Prepared for the U.S. Environmental Protection Agency, Risk Reduction Engineering
Laboratory, Cincinnati, OH.
Cushnie, G. C., Jr., and W. Anderson. 1989. "Removal of Metal Cations from Chromium Plating
Solution." Paper presented at the 10th AESF/EPA Conference on Environmental Control for the Metal
Finishing Industry, January 23-25, 1989.
lonsep Corporation, Inc. 1989. "Closed-Loop Processing of Chromic Acid Solutions." Paper presented
at the 10th AESF/EPA Conference on Environmental Control for the Metal Finishing Industry,
January 23-25, 1989.
Knill, E. C., and H. Chessin. 1986a. "Contamination of Hexavalent Chromium Plating Baths." Plating
and Surface Finishing, July.
Knill, E. C., and H. Chessin. 1986b. "Purification of Hexavalent Chromium Plating Baths." Plating
and Surface Finishing, August.
27
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