Effect of complexing agent lactic acid on the extraction and separation of Pr(III)/Ce(III) with di-(2-ethylhexyl) phosphoric acid

The extraction of rare earths (REs) in a saponated system with di-(2-ethylhexyl) phosphoric acid (P204) as an extractant will produce a large amount of waste water, which contains NH4+, Ca2 + and Na+, and will seriously pollute the environment. The paper aims to develop a new system to eliminate the phenomena. The separation of Pr(III)/Ce(III) using P204 is investigated by adding a complexing agent lactic acid (LA) into the aqueous phase. The separation factor and extraction capacity are as high as 2.02 and 32.67 g/L with the increase of the lactic acid concentration, respectively, and both higher than those without the complexing agent. The cation-exchange mechanism is clarified by IR spectra and 1H NMR. The experimental results suggest that the complexing extraction method could be regarded as an effective strategy for separating REs.

► We developed a new unsaponified extraction system by adding a complexing agent.
► The cost of lactic acid is lower than those of EDTA and DTPA.
► Separation factor and extraction capacity were 2.02 and 32.67 g/L, respectively.
► The extraction mechanism was clarified by IR spectra and 1H NMR.