LEATHER WASTE DECHROMATION PROCESS Russian patent published in 2002 - IPC

FIELD: leather industry. SUBSTANCE: chrome chips are treated with oxidizing aqueous solution containing NaOH and H₂O₂, after which chips are squeezed, washed with water, squeezed, 4 times washed with water to pH 7.0-7.5, and finally squeezed. Treatment of chrome chips in subsequent stages is effected with exhausted oxidizing solution from the previous party, in which concentrations of NaOH and are preliminarily adjusted to initial values. Exhausted solution reused 5-7 times and containing Cr⁶ is filtered and combined with exhausted ash solution preliminarily filtered and containing sodium sulfide. Combined solution is acidified with sulfuric acid to reduce Cr(VI) into Cr(III) and to form chromium sulfate solution. The latter is separated and subjected to chromium recovery. EFFECT: accelerated process, avoided use of expensive reagents, and reduced waste water volume. 3 cl, 1 tbl, 9 ex