I. R. Elizarova

On integrated processing of phosphogypsum

It is shown that phosphogypsums obtained from the Khibiny apatite concentrate can be purified by percolation leaching with low-concentration sulfuric acid solutions to remove admixtures of fluorides, phosphates, and water-soluble compounds of sodium, with simultaneous transfer of rare-earth element sulfides into solution. The achievable degree of impurity extraction enables use of the purified material as a gypsum raw material for manufacture of gypsum binders and cement. The method is applicable to processing of both currently produced phosphodihydrate, phosphohemihydrate, and mixtures of these and those long stored in dumps.

Recovery of rare earth elements from wet process extraction phosphoric acid

It is shown that an increase in the recovery of rare earth elements in fluorophosphate concentrates, which are obtained by treating the wet process phosphoric acid by ammonium fluoride, is achieved by prior partial neutralization of H3PO4 by ammonia. Therewith the consumption of ammonium fluoride is reduced that provides almost complete precipitation of rare earth elements.

Deposition of rare earth elements from a wet-process phosphoric acid by fluorine compounds

Effect of type and consumption of fluorine reagents (HF, NH4F·HF, NH4F and NaF) on the deposition of rare earth elements from the wet-process phosphoric acid of the dihydrate process was examined.

Treatment of fluorophosphate rare earth concentrate

Methods for primary processing of fluorophosphate rare earth concentrate precipitated from phosphoric acid of dihydrate process by introduction of fluoride ion were examined. Separation of rare earth cations from phosphorus, fluorine, and an appreciable part of the impurity cations by interaction of the concentrate with sulfonic cation resin in sulfuric acid was suggested. Further processing of sulfonic cation resin containing rare earth elements was possible by known methods.

Recovery of rare earth elements from the wet process phosphoric acid

The methods of producing non-radioactive rare earth concentrate from wet process phosphoric acid of dihydrate process of Khibiny apatite concentrate sulfuric acid treatment for fertilizer production have been proven. The features of their use in existing production were characterized.

Sorption conversion of phosphate concentrates of rare-earth metals

Treatment of phosphate concentrates of rare-earth elements with low-concentration nitric acid in the presence of a sulfocation exchanger (sorption conversion) enables effective separation of rare-earth elements from phosphorus and fluorine. The effect of the nitric acid concentration and temperature on the efficiency of the sorption conversion of rare-earth element phosphates and the behavior of cationic impurities in the course of the sorption conversion were studied. It was shown that no selective transfer of thorium into solution could be achieved in the course of conversion and subsequent desorption with solutions containing nitric acid or ammonium nitrate.

Hydrofluoride Synthesis of Fluorides of Some Rare-Earth Elements

Thermal gravimetric, X-ray phase, IR spectroscopic, and chemical analyses were applied to study the reaction of yttrium and neodymium oxides with NH4HF2.

Sorption of rare-earth elements from phosphogypsum sulfuric acid leaching solutions

Sorption technology for extracting rare-earth elements (REEs) from sulfuric acid solutions of phosphogypsum percolation leaching has been developed. Sorption conditions that enable to reach maximum REE content in the sorbent at minimum content of thorium and calcium have been found.

Isolation of rare earth elements from ammonium salts solutions

It has been shown that nonradioactive concentrate containing up to 97–99 wt % rare earth elements (REEs) oxides after calcinations might be isolated from the strippant based on concentrated aqueous solution (275–300 g/L) of ammonium sulfate or ammonium nitrate obtained during the REE extraction from phosphogypsum or phosphoric acid. A REE loss in thorium-containing precipitate does not exceed 0.1–0.5% in the hydrolytic precipitation of thorium.

Ruling out accumulation of thorium in sulfuric acid solutions for leaching of phosphogypsum

It is shown that introduction of fluoride ions into recycled sulfuric acid solutions used for leaching of rare-earth elements from phosphogypsum precludes accumulation of thorium in these solutions, thereby making it possible to develop a technology for obtaining concentrates of rare-earth elements that rules out formation of intermediate and waste radioactive products.