Environmentally sound technology development for processing of rare earth elements from waste permanent magnets synthetic leach solutions: recovery and separation perspectives

Abstract

Abstract An environmentally sound process was investigated as feasible to extract and separate rare earths from the synthetic leach liquors prepared based on waste permanent magnets composition analogs. Solvent extraction methods were used to screen different extractants to optimize and suggest the proper extraction system to recovery the different rare earth elements (REEs). Various experimental factors, equilibrium pH and impact of the extractant concentration were studied to select the optimum extraction system. Waste permanent magnets were treated in the initial stages with plating separation, sulfuric acid leaching and double salt precipitation. A second leaching process was implemented by hydrochloric acid; the leach liquor was treated by hydrometallurgy processes for the reprocessing and separation of rare earths present. Three phosphorous based commercial extractants Cyanex 272 (bis (2, 4, 4-trimethylpentyl) phosphinic acid), D2EHPA (bis (2, 4, 4-tri-methyl-pentyl) phosphinic acid) and PC 88A (2-ethyl-hexyl-phosphonic acid mono-2-ethyl-hexyl ester) were applied in the present study. Initial experiments suggested that Cyanex 272 is the best reagent for recovery and potential separation between REs, therefore the crowding studies were carried on. From this study appropriate experimental conditions for crowding were optimized to maximize the enrichment of rare earths while separating them.