Extraction and separation of heavy rare earths from chloride medium by α-aminophosphonic acid HEHAPP

Abstract

The extraction and separation of heavy rare earths (REs) using newly synthesized α-aminophosphonic acid extractant 2-ethylhexyl-3-(2-ethylhexylamino)pentan-3-yl phosphonic acid (HEHAPP, HA) in n-heptane were investigated from chloride medium. The extraction stoichiometries of lanthanum, gadolinium, yttrium and lutetium are determined to be REA3 by the slope analysis method. The favorable separation factors of adjacent heavy REs(Ⅲ), i.e. βY/Ho, βEr/Y, βTm/Er, βYb/Tm and βLu/Yb, are determined to be 1.87, 1.36, 3.21, 3.22 and 1.93, respectively, when extracted from a binary system at proper condition. The loading capacities of HA for Ho, Er, Yb and Lu increase in the order Ho < Er < Yb < Lu with the values being 0.201, 0.205, 0.216 and 0.229 mol/L, respectively. So HA would be a potential extractant for the separation of heavy REs(Ⅲ). Among inorganic acids such as H2SO4, HNO3 and HCl, HCl is tested to be the most effective stripping agent.