Selective separation of praseodymium(III) by di-(2-ethylhexyl) phosphoric acid using the complexing agent

摘要

It is a main problem that environment can be polluted by discharge of wastewater containing NH_4~+, Ca~(2+) and Na~+, when rare earths (REs) are extracted in a saponified system using di-(2-ethylhexyl) phosphoric acid (D2EHPA). Pointing to this problem, the selective separation of Pr(III) by liquid–liquid extraction using D2EHPA in the presence of a complexing agent of lactic acid (LA) has been studied. Results are shown that the maximum of separation factor (β) between Pr/Ce is 2.04 and extraction selectivity is also enhanced when compared with that of D2EHPA-HCl system. The thermodynamic function △H is determined as exothermically driven. The cation exchange mechanism is discussed by IR spectra. Thus, the results suggest that highly selective separation and extraction of Pr(III) from a Pr/Ce solution is possible, providing a simple and environment-friendly complexing method for extraction-separation rare earths, and promoting the sustainable development in rare earths practices.