Separation and purification of light rare earth elements from chloride media using P204 and Cyanex272 in sulfonated kerosene under non-saponification conditions

Abstract

The extraction of light rare earths (Pr and Nd) from chloride medium was investigated using a mixture of di(2-ethylhexyl) phosphoric acid (P204) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272) in sulfonated kerosene. The P204+Cyanex272 system exerted a synergistic effect on the separation of light rare earths, and the separation coefficient was higher than when P204 and Cyanex272 were used as extractants alone. The separation coefficient of Pr and Nd in the extraction system reached 1.75 when the pH of the aqueous phase material solution was approximately 2.5, and 1.5 mol/L hydrochloric acid as a stripping agent effectively eluted the rare earth ions in the loaded organic phase. Combining the slope method, infrared spectroscopy, and nuclear magnetic resonance spectroscopy, we explored the mechanism of the extracted Nd and Pr into the organic phase complex, and finally entered the organic phase with Re(HA₂)₂B. The P-O-H bond and P=O bond in the extractant P204 and Cyanex272 formed a coordination bond with Re³⁺. Therefore, this extraction method also provides a reference for a more environmentally friendly and efficient procedure for separation and purification of light rare earth elements Pr and Nd.