Extraction of rare earth elements from phosphogypsum and uranium in situ leaching solutions

The paper investigates the extraction of rare earth elements (REE) from technogenic sources – phosphogypsum and uranium in situ leaching (ISL) solutions. We found that mechanical activation significantly increases the degree of REE leaching from phosphogypsum. We also obtained data on sorption leaching of REEs from phosphogypsum. It has been shown that, depending on the ion exchanger used and its form, chemical activation can double the leaching degree of the target components. The paper presents the findings of the study on the sorption recovery of scandium from uranium in situ leaching solutions. We determined that Sc sorption from uranium ISL solutions on the Purolite S-957 cation exchanger is much more effective than on Lewatit TP-260, Purolite S-950, Tulsion CH-93 CH-93, and ECO-10 ampholites. However, it should be pointed out that none of the listed sorbents is highly selective towards scandium ions. The paper presents comparative data on Sc extraction from uranium ISL solutions using Lewatit VP OC-1026 and Axion 22 commercial solid extractants synthesized according to the method described in the paper. We determined the mechanism of scandium extraction from uranium ISL solutions using Axion-22 and proved that it shows high selectivity towards scandium ions. Studies on the desorption of scandium from the saturated solid extractant showed that the most effective desorption agent is an aqueous solution of hydrofluoric acid. Additionally, the paper investigates the sorption extraction of REEs from uranium ISL solutions on cation exchangers KU-2, KM-2P, and KF-11. We found that the best eluents for the desorption of REEs from the saturated cation exchanger are solutions of calcium chloride and ammonium nitrate. It has been shown that the concentration of REEs in the solution and the removal of major impurities (Fe and Al) are quite effective when REEs precipitate from the desorption solution by fractional hydrolysis. The paper describes the separation of La, Nd, and Sm by elution from the saturated impregnate containing phosphorylpodande and Di(2-ethylhexyl) phosphoric acid in its structure. It should also be noted that ionic liquids can be useful for the extraction of REEs from the solutions of various electrolytes. We presented one of the technological schemes illustrating REE extraction from phosphogypsum.