METHOD OF PROCESSING PHOSPHOGYPSUM

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FIELD : chemistry.SUBSTANCE : method of processing phosphogypsum includes preliminary aqueous treatment thereof; leaching the phosphogypsum by passing a sulphuric acid solution with concentration of 3-6 wt % through a layer thereof with displacement and separation of the aqueous solution and transfer of rare-earth elements and impurity components, including thorium, into the leaching solution; neutralising the washed phosphogypsum to obtain a gypsum product; the rare-earth elements and thorium are extracted from the leaching solution by sorption using a sulphoxide cationite and forming a sulphuric acid solution with rare-earth elements and thorium which is recycled; desorbing the rare-earth elements and thorium from the saturated cationite to obtain a strippant, wherein desorption of rare-earth elements is carried out by treating the cationite with an ammonium salt solution followed by precipitation of rare-earth elements from the strippant with an ammonium-containing precipitant and separating the rare-earth element precipitate. Leaching of the phosphogypsum with sulphuric acid solution is carried out with liquid to solid ratio of not less than 1.4 : 1. Desorption of rare-earth elements and thorium from the saturated cationite is carried out in the following sequence : first, thorium by treating the cationite with sulphuric acid solution with concentration of 3-6 wt % to obtain a thorium-containing strippant, then rare-earth elements to obtain a strippant containing rare-earth elements.EFFECT : invention prevents formation of a radioactive thorium precipitate while ensuring high quality of the gypsum product, and improves extraction of rare-earth elements into a non-radioactive rare-earth concentrate.5 cl, 3 ex