19    METAL RECOVERY WITH A NOVEL
ELECTROCHANGE™ PROCESS
C.-D. Zhou, Manager of Research
E. C. Stortz, Laboratory Manager
E. J. Taylor, President
R. P. Renz, Manager of Engineering
Faraday Technology, Inc.
Dayton, Ohio 45420
INTRODUCTION
Metals are widely used in various industrial processes. Due to the toxicity of heavy metals,
metal containing wastewater must be adequately treated. Currently, a precipitation method is
used to treat metal containing wastewater. Even though metals are removed from the water, undesirable sludges are generated as a by-product, which creates new waste disposal problems.
Therefore, recovery technologies are needed to recover and reuse metals, eliminating metal
sludges. There are several commercially available recovery technologies. They are: (1) elec-
trowinning, (2) ion-exchange, (3) reverse osmosis, (4) electrodialysis, and (5) evaporation.
Electrowinning and ion-exchange are widely used recovery technologies for treating wastewater contaminated with metals. The advantages of electrowinning include: (1) recovered pure
metal, (2) low capital cost, and (3) no chemical addition. However, due to the hydrogen evolution reaction, the current efficiency for electrowinning is low, resulting in high effluent concentration and high power consumption. The approach to improving the electrowinning process is to
increase the mass transfer rate and electrode surface area. Ion-exchange can effectively treat low
concentration wastewater and no chemicals are needed during the treatment. However, the cost is
extremely high when large volumes of wastewater with high initial concentrations are treated.
Another metal recovery approach couples electrowinning for high concentration metal removal
with an ion-exchange unit for "polishing" of the low concentration metal. A drawback of this approach is the high capital cost associated with the two metal recovery units.
In this study, we conducted experiments to recover copper from an ELECTROCHANGE™
system.1 The ELECTROCHANGE™ system integrates the electrowinning and ion-exchange
processes into a single unit. The system concentrates copper on ion-exchange resin followed by
plating onto electrode materials. Consequently, the advantages of the ELECTROCHANGE™
system include: (1) ion-exchange resin concentrates metal for efficient electrowinning onto electrode material, (2) ion-exchange resin is continuously regenerated in situ, (3) effective treatment
of wastewater from high concentration to low concentration, (4) low capital cost, and (5) no
chemical addition. Pulse current (PC) is used to enhance mass transfer rate during the ELECTROCHANGE™ metal recovery process.
Cost evaluations were conducted for the ELECTROCHANGE™ system and compared to the
other commercial metal recovery technologies. A technoeconomic map was obtained to show
how this technology is positioned to existing technologies over the treatment rate from 480 to
50,000 gpd and initial copper concentrations from 100 ppm to 1000 ppm.
'ELECTROCHANGE™ is a trademark of Faraday Technology. Inc.
51st Purdue Industrial Waste Conference Proceedings, 1996. Ann Arbor Press. Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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