METHOD OF PURIFYING WASTE WATER FROM ARSENIC Russian patent published in 1997 - IPC

FIELD: waste water purification. SUBSTANCE: invention, in particular, relates to waste water produced at enterprises treating gallium and indium arsenides, etc. Waste water, prior to be subjected to electrocoagulation, is treated with ferrous sulfate in amount 1.0-1.2 g-eq per 1 g-eq of summary content of ferricyanide and arsenite. After precipitate is separated, calcium hydroxide is added to pH 9.5-10.0, followed by disodium phosphate to pH 6.5-7.5. Precipitate is separated, and solution is subjected to electrocoagulation with iron anode, current density 40-60 A/sq.m, and dwelling time of water in electrocoagulator 40-70 min. Waste water from chemical and mechanical polishing of gallium arsenide plates with solution containing, along with other, sodium aluminosilicates and hydrogen peroxide, prior to be treated with ferrous sulfate, is settled for 8-12 h to settle down aluminosilicates. In this case, ferrous sulfate is taken in amount 1.0-1.2 g-eq per 1 g-eq of summary content of ferricyanide, arsenate, and hydrogen peroxide. EFFECT: increased purification degree. 2 cl, 1 tbl