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Pollution Prevention and Control Technologies for Plating Operations


Section 3 - Chemical Recovery

3.5 ELECTROWINNING

3.5.2 Development and Commercialization

Electrowinning is presumed to be one of the earliest methods of metal recovery used in the plating industry, although no specific reference to its use prior to the 1960's was found (ref. 128). One of the reasons for its presumed early development and current widespread use is the fact that this process emulates the electroplating process. As such, it is readily accepted and understood by the plating industry. Further, for these same reasons, there are fewer system failures caused by misapplications or operational errors than with other recovery technologies such as ion exchange or membrane technologies. The electrowinning technology also has technical roots and contemporary applications in other industries, including electrorefining of copper, extraction of metallic aluminum from bauxite, and recovery of silver from photographic film manufacturing and developing operations.

Electrowinning can be performed using very simple equipment. As such, many plating shops have constructed units in-house. The effectiveness of these home-made units varies from shop to shop. Commercial units for plating applications are manufactured/sold by at least 40 companies (ref. 421). Many of these units, like the home-made models are also relatively simple in design. As discussed in Section 3.5.1, the efficiency of the electrowinning process is impacted by several electrochemical factors. Some commercial units, through the incorporation of more sophisticated design elements, minimize the impact of the electrochemical forces that reduce plating efficiency. Typically, these design elements are limited to the commercial units and are not found to any significant extent with the home-made versions.


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