Abstract
Chemical precipitation and solvent extraction have been widely used to transform rare earth (RE) sulfate into RE chloride in the field of hydrometallurgical process for monazite and bastnaesite, but there are some industrial challenges such as consuming a large amount of chemical reagents and producing wastewater. As for the transformation field of RE sulfate liquor, the development of sustainable and efficient transformation technology is an important industrial challenge. In this study, one step transformation and enrichment of RE sulfate into RE chloride using dibenzyl phosphate (DBP), diphenyl phosphate (DPP), triphenyl phosphate (TPP), diphenylphosphinic acid (DPPO) and 1,1′-binaphthyl-2,2′-diylhydrogenphosphate (DHGP) was studied. Unlike common solvent extraction, volatile organic solvents are not required in the extraction-precipitation processes. Different from the common chemical precipitation, the extraction-precipitants can be recycled. The investigation shows that DBP has a higher precipitation efficiency of RE than those of DPP, DPPO, TPP and DHGP. RE can be selectively separated from Mg and Ca by DBP. After stripping with concentrated hydrochloric acid, a high-concentration rare earth chloride solution of 187 g/L is obtained. This new method is easy to be implemented and has shown the potential of saving resources and protecting the environment.
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