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Recovery of Chromium from Waste Solutions.
U S Pat 4 337 227 1982 Jun; :
Chromium is recovered from plating or etching wastewater by precipitation with benzoate. The chromium benzoate complex is separated, washed, and treated with alkali or h2so4 to recover benzoate and a chromium hydroxide product. Thus, waste etching solution was diluted with water to decrease the chromium concentration by 50 pct, heated, and 75 ml of ammonium benzoate was added at ph 4. The precipitate was filtered and washed, and 98.9 pct of the cr and 14.3 pct of the zn were recovered. The filter cake was reacted with na2co3 and naoh, filtered, and washed to give a product containing 51 pct cr(oh)3 and 6 pct zn(oh)2.
U.S. Pat. 4,337,227, June 29, 1982; Chem. Abst. 97:166,851F