Rare Earth Metal Extraction from Apatite Ores

Resumo

Rare earth metals (REM) after sulfuric acid treatment of apatite ore are partly (15–20%) transferred into extraction phosphoric acid (EPA) solution. Solvent extraction of REM from model and industrial solutions of EPA is investigated. Di-(2-ethylhexyl)phosphoric acid (D2EHPA) diluted with kerosene is used as an extraction agent. The effect of impurity ions \( \left({\mathrm{Fe}}^{3+},{\mathrm{SO}}_4^{2\hbox{--}}\right) \) on REM extraction from industrial solutions is considered. Good separation coefficients of adjacent pairs of REM from EPA are obtained that may be used for effective separation the group of “light” from “heavy” rare earth metals from concentrated phosphoric acid solutions. Results of studies also show that an increase in the separation factor of erbium/ytterbium is possible by increasing the D2EHPA content in the organic phase. D2EHPA concentration, contact time, aqueous phase composition and the optimum conditions for the extraction of REM are determined. Using sulfuric acid concentration of 20 to 40% in the cleaning stage from iron provides additional purification from undesirable impurities. A production scheme is provided for REM separation during EPA treatment.