Ind. Eng. Chem. Res.

Neutral organophosphates have been used for the extraction and separation of rare earths, usually with the addition of an extra salting-out reagent to achieve the necessary high ionic strength. In this work, we propose a novel approach to extraction from rare earth solutions with fairly high concentrations without an extra salting-out reagent. The distribution behaviors of La, Pr, and Nd in a nitrate solution extracted with di-(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP) in kerosene under the action of a self-salting-out effect were investigated, including the extraction mechanism, extracted species, extraction isotherms, and effects of acidity and temperature. The obtained results show that the extraction species probably is RE(NO3)(3)center dot 1.5DEHEHP according to the slope analysis method and the saturation extraction method. Considering the other coexisting light rare earths, such as Ce and Sm, the separation factors were also examined through a comparison of the two commercial extractants P350 and TBP. The extraction selectivity for DEHEHP under the action of the self-salting-out effect is much higher than that of TBP but just slightly below that of P350. Finally, it can be concluded that the current system using DEHEHP as an extractant under the action of the self-salting-out effect shows good prospects for the purification of La from other light rare earths.Neutral organophosphates have been used for the extraction and separation of rare earths, usually with the addition of an extra salting-out reagent to achieve the necessary high ionic strength. In this work, we propose a novel approach to extraction from rare earth solutions with fairly high concentrations without an extra salting-out reagent. The distribution behaviors of La, Pr, and Nd in a nitrate solution extracted with di-(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP) in kerosene under the action of a self-salting-out effect were investigated, including the extraction mechanism, extracted species, extraction isotherms, and effects of acidity and temperature. The obtained results show that the extraction species probably is RE(NO3)(3)center dot 1.5DEHEHP according to the slope analysis method and the saturation extraction method. Considering the other coexisting light rare earths, such as Ce and Sm, the separation factors were also examined through a comparison of the two commercial extractants P350 and TBP. The extraction selectivity for DEHEHP under the action of the self-salting-out effect is much higher than that of TBP but just slightly below that of P350. Finally, it can be concluded that the current system using DEHEHP as an extractant under the action of the self-salting-out effect shows good prospects for the purification of La from other light rare earths