METHOD OF PROCESSING PHOSPHOGYPSUM Russian patent published in 2013 - IPC C01F11/46 C01F17/00 

FIELD: chemistry.

SUBSTANCE: method of processing phosphogypsum involves leaching phosphogypsum which contains rare-earth elements and impurities, including phosphorus, fluorine and sodium, by passing sulphuric acid solution with concentration of 3-6 wt % at liquid-to-solid ratio of 1.5-2.0 through a layer of phosphogypsum to transfer the rare-earth elements and impurity components into the leaching solution. The leaching solution is separated in form of two consecutive portions, the volume of the first portion being smaller. The first portion is neutralised with a calcium-containing reagent to pH 6-8 and the precipitate which contains impurity components is separated. The calcium-containing reagent used is slaked or unslaked lime. The second portion of the leaching solution is taken for sorption extraction of rare-earth elements using a sulphoxide cationite to obtain a lean sulphuric acid solution. After leaching, the phosphogypsum is washed with water in amount of 0.4-0.5 l per kg of phosphogypsum to obtain washed phosphogypsum and washing sulphuric acid solution. That solution is mixed with the lean sulphuric acid solution, fortified with strong acid and taken for leaching phosphogypsum.

EFFECT: invention enables to remove phosphorus, fluorine and sodium impurities from phosphogypsum while ensuring a high degree of extraction of rare-earth elements, reduces consumption of sulphuric acid and calcium-containing reagent.

6 cl, 5 ex