Recovery of metal values from chrome etching solutions.
U S Pat 3 784 669 1974 Jan; :
Chromium and copper are recovered from spent etching solutions used for cu alloys. Thus, 25 g of a spent etching solution containing cu 30, cr6+ 30, and cr3+ 30 g/l was treated with 5 g sucrose and stirred at ambient temperature for 24 h. The ph was then adjusted from approximately 1.2 to 11.5 With naoh. Cu2o precipitated, was filtered, and contained <0.1 pct cr. The filtrate contained only 5 ppm cu. The cr in solution was then precipitated by heating to 60 deg. C for 10 min to destroy the complexing agent and by adjusting the ph to 7 with h2so4. The precipitate analyzed >99.9 pct hydrous chromium oxide, and the solution contained approximately 100 ppm cr3+.
U.S. Pat. 3,784,669; Jan. 8, 1974; Chem. Abstr. 80:85,955Q