Recovery of chromium from waste water - comprises adding base to waste water contg. trivalent chromium and organic solvent to ppte. chromium hydroxide

摘要

Process for recovering chromium from waste water comprises pptn. as chromium hydroxide. The process comprises forming a homogeneous soln. (A) from the waste water contg. Cr (III) salt and an organic solvent, so that (A) contg. 20-40 g/l Cr and 20-40% solvent; introducing (A) into a reaction vessel; adding base to give a pH of 8, to start the pptn.; adding base and waste water in parallel from separate positions to the stirred chromium hydroxide suspension at room temp. to a stationary work point with a solvent content of 15-30 vol. %, dissolved salts content of 2-5 Ma % and pH of 70-8.5; continuing the addition until the average grain size is 30-100 microns, and the suspension contains 200-600g/l; and filtering e.g, with a filter centrifuge. The ppte. is washed with water and dried. Pref. organic solvent is alcohol, ketone or acid amide. USE/ADVANTAGE - To reduce heavy metal content of waste water e.g, from chromate oxidn. processes, for steroids et