INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY # 174

1. Headline: An Experimental Project Using an Electrowinning

Cell and Ion Exchange Unit Minimizes Water Usage and

Hazardous Waste

2. Background: See below.

3. Cleaner Production Principle: New technology

4. Description of Cleaner production Application: This

experimental technology uses an electrowinning cell and

ion exchange system to recover copper and reduce water

usage.

Case Study Summary

Process and Waste Information: The line on which the

experiment was undertaken is composed of a bath for bright

acid copper plating, followed by a "dead" rinse and two

rinses in counterflow. Nothing about pretreatment is

mentioned in the source document. The dead rinse consists

of a tank of 1500 gallons used to replenish the volume

lost from the plating bath. The first running rinse, also

1500 gallons, overflowed to the waste treatment facility.

The second running of 3000 gallons, was fed with 4 gallons

of city water per minute.

In the first stage of the project, an electrowinning

system was introduced in a circulating loop with the dead

rinse resulting in reduction in the copper content and in

drag-out of copper into the running tanks. The

electrowinning cell design consisted of a tank using up to

50 square feet of cathode material and 48 square feet of

insoluble anode. A 300 Amp, six volt rectifier powered

the cell. Current densities could be varied throughout

the study. An air sparger was used to agitate the bath

liquid, although no heating was used. After successful

reduction of copper in the dead rinse, and thus in the

running rinses, an ion exchange unit was installed to

remove copper from the drag-out tank. The deionized water

was returned to the last rinse bath.

The ion exchange system consisted of a pump which supplied

four gallons of water per minute to the system. Two ion

exchange tanks containing 1.4 cubic feet of a strong acid

resin were used. The dual system allowed one tank to be

in service while the second tank automatically regenerated

or was in standby position. The technology resulted in

reduction of the copper concentration from 15 to 6 g/l in

the static rinse tank. In seven months of operation, 360

pounds of salvageable copper have been recovered by the

electrowinner. As a consequence, the concentration in the

first counterflow rinse dropped from over 200 to below 50

mg/l.

The water coming from the ion exchanger has copper levels

well below 0.01 mg/l and is reintroduced into the second

counterflow tank. It was necessary to change from city

water to softened water at the inlet. Regeneration is

necessary every second day and takes about 20 minutes.

The run-off water from the first counterflow rinse

contains 6 mg/l of copper. It is transformed into sludge

in the waste treatment system.

Stage of Development: Implemented, but tests are

continuing.

Material/Energy Balances and Substitutions:

Material Category Quantity Before

Quantity After

Waste Generation:

Sludge, 60% dry, 18.5

2.5 lbs/day

Feedstock Use: N/A

N/A

Water Use (gpm): 4

2

Energy Use: N/A current

density

See "Assumptions" for a discussion of sludge production

calculations.

5. Economics: Information not provided.

6. Advantages: Use of this technology was prompted by

tightening control on discharge limits and waste

production in the U.S. Sludge production and water usage

are reduced and salvageable copper are recovered.

7. Constraints: Copper at low concentrations in the

electrowinner burned while plating. Lowering current

densities also lowers plating to a rate at which the

cell cannot keep pace with the drag-out rate. The running

rinses had to be fed with demi-water.

8. Contacts and Citation

Citation: Reduce Water Consumption and Hazardous

Waste. Jerome Kovach, Kinetico Engineering Systems,

Inc., Newbury, Ohio, United States.

Industry/Program Contact and Address:

Jerome Kovach,

Kinetico Engineering Systems, Inc.,

Newbury, Ohio, United States.

9. Keywords: United States, USA, metal, electroplating, new

technology, plating, electrowinning, ion exchange, copper,

rinsing, sludge.

10. Reviewer's Comments:

Assumptions: No absolute figures on sludge production are

given. It is assumed all wastes of the company are sent

to the same facility.

As copper concentrations in the runoff water decreased by

over 75% (from over 200 to below 50 mg/l) and the runoff

was reduced from 4 to 2 gpm, it is assumed that the amount

of copper entering the waste treatment facility from the

experimental line decreased 87.5%. In the source

document, a 75% reduction was claimed. The sludge

production decreased by 16 lbs/day. From these figures,

the before and after sludge production were computed.

This case study was originally compiled by the UNEP IE

Working Group on Metal Finishing. It underwent a UNEP IE

funded technical review in 1994 for quality and

completeness. It was edited for the ICPIC diskette in

July 1995.

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