Surface Treatment and Plating

The major source of hazardous metals from chromating and other chemical conversion processes, as well as from electro- and electroless plating, is generally the process baths themselves. Spent cleaners and etchants also can contain large quantities of metal removed from workpieces. 

Many waste streams are generated when process solutions are discarded due to impurities buildup. The waste generation rate can be lowered through lengthening solution life. This can be accomplished by impurity removal through filtration and ion exchange, as well as through reduction in the quantity of impurities introduced into the process solution. 

Many process and rinse solutions can be recycled in some way if operators and plant engineers fully understand the chemistry of their waste streams. Rinse solutions too contaminated for their original purpose can often be used as rinses elsewhere. Metals can be recovered from spent process solutions and wastewater using technologies such as reverse osmosis, ion exchange, electrolytic recovery, and evaporation. 

Treatment methodologies for process solution wastes include pH adjustment, flocculation, precipitation of metals, dewatering and sludge drying. Chelated metals require special treatment to break the complexes. Chromium, cyanide, electroless plating, and printed circuit board wastes often need to be segregated from other streams in order to reduce waste volumes and avoid the chance that some complexed metals may escape the treatment system. 

---

WASTE MANAGEMENT FOR SURFACE TREATMENT AND PLATING OPERATIONS... 

---