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Pollution Prevention and Control Technologies for Plating Operations
Section 4 - Chemical Solution Maintenance
4.6 ION TRANSFER
4.6.8 Residuals Generation
Due to a lack of data, the true pollution prevention value of the ion transfer technology cannot be fully ascertained. Some evidence indicates that the porous pot technology is inefficient in the sense that a significant quantity of chromium waste is often generated relative to the volume of bath being maintained. This observation is especially evident for the large-scale porous pot units (i.e., Cosmos Minerals Corporation, Pfaudler, EP Technology). For example, a report prepared for the Air Force described an application where 16,830 gal. of hard chromium plating bath was maintained with two large porous pot systems (8 pots each). Annually, these systems generated 10,000 gallon of chromic acid waste. Also, equipment replacement (electrodes, pots) costs were $60,000 annually (ref. 372).
Similarly, one survey respondent indicated that use of a PPS1 generated 4,800 gpy of waste (combination of catholyte and wash-down water that is sent off-site for recycle) while maintaining a 3,000 gal. bath (PS 074).
For these applications, it appears that a "bleed and feed" strategy would be more efficient than use of a porous pot. However, some other survey respondents reported less waste generation and in some cases very small volumes (e.g., PS 194 and PS 118).
No data were located with respect to the waste generation rates of the polyfluorocarbon membrane technology.