METHOD FOR PRODUCING MAGNESIUM SULPHATE AND IRON-OXIDE PIGMENTS FROM PRODUCTION WASTES Russian patent published in 2017 - IPC C01F5/40 C09C1/22 C09C1/24 C01G49/02 C01G49/06 

FIELD: chemistry.

SUBSTANCE: to produce magnesium sulphate and iron-oxide pigments from productions wastes, the fine-dispersed magnesium-containing raw material is reacted with the sulfuric acid spent etching solution containing iron sulfate. Dolomite dust formed upon calcination of dolomite at the temperature of 600-750°C is used as a magnesium-containing raw material. The ratio of sulfate-ions: dolomite dust in the etching solution is 1:1.1. Hydrothermal treatment of the produced suspension is carried out by blowing the solution with air, the oxygen of which oxidizes iron Fe⁺² to Fe⁺³. The precipitate is separated on a filter press and washed from water-soluble compounds. Thermal treatment of the precipitate is carried out to the iron-oxide pigment. Drying and grinding of the iron-oxide pigment are carried out simultaneously in a combined spray dryer. The filtrate separated from the filter press and wash water containing magnesium sulfate are fed to the reactor. The content of sulfate ions is increased in the solution to 35-40% by the addition of concentrated sulfuric acid and neutralized with dolomite dust at the temperature of 80-100°C to pH equal to 7.0-7.5. Crystallization of magnesium sulphate is carried out in a crystalliser.

EFFECT: invention allows to increase the yield of magnesium sulphate and iron+oxide pigments, to reduce energy consumption during the treatment of the sulfuric acid spent etching solution.

2 cl, 1 dwg, 2 tbl, 3 ex