METHOD OF SYNTHESIS OF CHROME PHOSPHATE-CONTAINING PIGMENT Russian patent published in 2002 - IPC

FIELD: chemical technology. SUBSTANCE: invention relates to methods of synthesis of chrome phosphate-containing pigments used in paint and varnish industry. Method of synthesis of pigment involves interaction of the parent raw containing alkaline metal bichromates with phosphoric acid and sodium sulfite or thiosulfate as a reducing agent in the presence of sulfuric acid. Waste water from the process of utilization of solid waste of treatment of carbide acetylene is used as the parent raw containing the following components, wt. %: Cr⁶⁺ as measured for Na₂Cr₂O₇, 0.8-4.0; chrome phosphates, 2.5-3.5; chrome bisulfates, 15.0-16.0; sulfuric acid,1.5-2.0. Waste water has pH 3-3.5 and temperature 40-50 C. Phosphoric acid in mass concentration 85% is taken in amount 12.4-21.3 vol. % with respect to the parent waste water. Sodium sulfite is taken in amount 6.0-29.0 wt.% or sodium thiosulfate is taken in amount 2.0-10.0 wt.% with respect to the parent waste water as a reducing agent. Invention provides recuperation of valuable components from waste water, preparing an anticorrosive pigment. EFFECT: improved method of synthesis, decreased toxicity of waste water, decreased duration of process. 1 tbl