Selective extraction and separation of Ce(IV) from thorium and trivalent rare earths in sulfate medium by an α-aminophosphonate extractant

- An α-aminophosphonate extractant was synthesized to extract and separate cerium(IV) from thorium and trivalent rare earths.
- The extractant can be used to selectively recover cerium in sulfate medium.
- The stoichiometry of the extracted species was determined.
- Thermodynamic functions were calculated for the extraction reaction.

A novel extractant, di (2-ethylhexyl) (2-((2-ethylhexyl) amino) propan-2-yl) phosphonate (DEHAPP, abbreviated as B), was synthesized for the selective extraction of Ce(IV) in sulfate medium. The effect of contact time, the H2SO4 concentration, the DEHAPP concentration and temperature on the Ce(IV) extraction were studied systematically. DEHAPP exhibits a good extraction ability towards Ce(IV) when compared with other neutral organophosphorus extractants such as Cyanex 923, Cyanex 925 and DEHEHP. The extraction equilibrium constants and thermodynamic parameters (ΔG, ΔH and ΔS) were calculated. The extraction reaction of Ce(IV) is an endothermic process. The extracted complexes were determined to be H2SO4·B(org) and Ce(HSO4)2SO4·2B(org). A extraction process to selectively recover Ce(IV) from bastnaesite leaching was proposed, by which the purity of cerium product reached 99.5% with a yield of 90.7%.