METHOD OF PURIFYING WASTE WATER FROM FLUORINE Russian patent published in 2010 - IPC C02F1/58 C02F1/28 C02F101/14 

FIELD: chemistry.

SUBSTANCE: to realise the method, water is reacted with a cerium-containing reagent in form of cerium (III) sulphate or cerium (IV) sulphate in hydrolysis conditions while regulating pH in the range 4-7. The reagent is taken in ratio of 2.5-7.0 g-atom cerium per 1 g-atom of fluorine contained in the waste water being purified. In the said pH range, fluorine is bonded into a solid phase which forms during hydrolysis of cerium compounds, which is separated from the liquid phase. The fluorine-containing solid phase is treated with 80-95% sulphuric acid at 175-190°C to obtain hydrogen fluoride and regenerated cerium (IV) sulphate. The regenerated cerium (IV) sulphate can be dissolved in water and treated with hydrogen peroxide until bleached to obtain regenerated cerium (III) sulphate. The method provides deep purification of waste water from fluoride ions and fluorine-containing complexes with possibility of purifying large amounts of waste water. Degree of purification of waste water from fluorine of 1.25-1.5 mg/l is achieved, and residual content of the sulphate ion equals 165-340 mg/l, which is less than the maximum permissible concentration for drinking water reservoirs. Fluorine is extracted in form of commercial-grade compounds - fluorides of sodium or potassium.

EFFECT: proposed method is simple and can be realised in sediment ponds using standard equipment.

5 cl, 6 ex