METHOD OF PRODUCING IRON-CONTAINING COAGULANT FROM PRODUCTION WASTES Russian patent published in 2019 - IPC C01G49/10 C02F1/52 C23G1/36 C23F1/46 C01F11/46 C02F101/20 C02F103/16 

FIELD: chemistry.

SUBSTANCE: invention can be used in water treatment. Method of producing iron-containing coagulant involves oxidation of iron (II) to iron (III) by oxidation of spent etching solutions. In reactor equipped with agitator and air sprayer there supplied is waste sulphuric solution of metal etching, sulphuric acid and waste of calcium chloride. Obtained suspension is oxidised by air fed in amount of 1.5–2.0 g/(l⋅h) at temperature of 20–30 °C to pH 3.0–3.5. Then mixture is neutralized with waste calcium chloride at temperature 70–75 °C to pH 7.0–7.5. Iron (III) chloride and calcium sulphate are formed. Obtained suspension is directed to a filter press where precipitate is separated and cooled to temperature of 40–50 °C. Obtained gypsum, which is fed into drier of "boiling bed", where it is dried at temperature 150–180 °C and grinding to 4–6 mm. Separated filtrate is subjected to vacuum crystallisation at temperature of 80–90 °C. Obtained crystals are separated on a centrifuge, fed into a "fluidized bed" drier and dried at temperature of 100–110 °C, simultaneously crushing to 10–15 micron. Active iron-containing coagulant - crystalline iron (III) chloride is obtained. Filtrate is returned to reactor.

EFFECT: invention enables to obtain a coagulant which does not contain impurities from iron and calcium-containing wastes from production and improve the environment.

1 cl, 1 dwg, 1 tbl, 2 ex