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

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, H A ) in n-heptane were investigated from chloride medium. The extraction stoichiometries of lanthanum , gadolinium , yttrium and lutetium are determined to be RE A 3 by the slope analysis method. The favorable separation factors of adjacent heavy REs(Ⅲ), i.e. β Y/Ho , β Er/Y , β Tm/Er , β Yb/Tm and β Lu/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 H A 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 H A would be a potential extractant for the separation of heavy REs(Ⅲ). Among inorganic acids such as H 2 SO 4 , HNO 3 and HCl, HCl is tested to be the most effective stripping agent.