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Pollution Prevention and Control Technologies for Plating Operations


Section 4 - Chemical Solution Maintenance

4.4 ION EXCHANGE

4.4.2 Development and Commercialization

The development and commercialization of the ion exchange process is reviewed in Section 3.4.2. The use of this technology for chromic acid bath maintenance is one of the oldest pollution prevention applications of ion exchange for the metal finishing industry. The first reported application was at the Rock Island Arsenal in 1952. The Arsenal's unit was designed to treat 1,000 gallons of contaminated chromium plating solution or 5,000 gallons of chromic acid anodizing solution. The purification process involved passing contaminated solution through a cation resin to remove trivalent chromium and tramp metals. The solutions were diluted prior to ion exchange treatment to avoid rapid oxidation of the resin and then reconcentrated using an evaporator. The general practice has not changed significantly since the first application, however today's resins are more chemically tolerant and selective and the equipment is much more sophisticated (e.g., automatic controls) (ref. 384). The first known commercial ion exchange product designed specifically for chromic acid bath maintenance was manufactured in 1975 (ref. 385).

Two of the respondents to the Vendors Survey (Eco-Tec Inc. and Kinetico Engineered Systems, Inc.) manufacture commercial units specifically for chromic acid bath treatment and a third company produces custom units. Kinetico Engineered Systems, Inc. also manufactures ion exchange equipment for trivalent chromium bath maintenance. Eighty-two percent of the ion exchange bath maintenance systems identified in the Users Survey were manufactured by either Eco-Tec Inc. or Kinetico Engineered Systems.


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