Separation of trivalent rare earths from nitrate medium using solvent extraction with a novel extractant 2-ethylhexyl ((2-ethylhexylamino)methyl) phosphonic acid

By introducing the amine group into the structure of P227, a novel extractant 2-ethylhexyl ((2-ethylhexylamino)methyl) phosphonic acid (EEAMPA, abbreviated as HA) was synthesized for the extraction and separation of trivalent rare earths (REs) from nitrate medium. The influence factors including extractant concentration, equilibrium time, HNO 3 concentration, separation factors, cycle regeneration, stripping acidity, and actual leach liquor of metal ions, were studied systematically. The results show that the extraction ability of EEAMPA for REs decreases with increasing acidity. A possible extraction mechanism is proposed and the extracted species as REHA 3 (NO 3 ) are confirmed by the slope analysis method. The extraction equilibrium can reach faster than P227. It shows good chemical stability and cycling regeneration. Stripping studies show that HCl is an excellent stripping agent and REs can be effectively stripped from the organic phase. A novel extractant EEAMPA can be applied to separate heavy rare earths from ion-adsorbed type rare earth ores. • EEAMPA was synthesized and its structure was characterized by 1 HNMR, MS, and IR. • The stoichiometry of the extracted species was determined. • The extractant can be used to separate adjacent heavy rare earths from nitrate medium. • The extractant has larger separation factors and lower stripping acid for heavy rare earths than HEHEHP.