Stripping and recovery of U and Th from EHEHPA in rare earth separation plant

Abstract

A circular process comprising of striping, acidification, precipitation and separation was proposed for stripping and recovery of U and Th from 2-ethylhexyl phosphoric acid mono-2-ethylexyl ester (EHEHPA) in rare earth separation plant. In this process, U and Th could be stripped by sodium carbonate in one step, and the stripping efficiencies reach to 98.04% and 97.50%, respectively. After stripping, the organic phase, which split into heavy and light phase, can be merged into one organic phase after acidified and regenerated by 3 mol/L H2SO4. The extraction ability test and FT-IR results show that the regeneration organic phase renews to the level of new EHEHPA. Finally, 98.8% of U and 99.3% of Th were precipitated and recovered from the stripped liquor after adjust the pH to 13 by NaOH. The pregnant liquor can be repeated used in the stripping process after adding the concentration of carbonate (CO32−) to 1.2 mol/L. This novel approach is both environmentally friendly and economically feasible. It has significantly contribution to the recovery of U and Th in rare earth separation processing.