Regeneration of a binary mixture of Cyanex 272 and Alamine 336 for the solvent extraction of rare earths elements by treatment with sodium hydroxide solution

A binary mixture of Cyanex 272 and Alamine 336 has synergism on the solvent extraction of La, Pr and Nd from chloride solution. The binary mixture not only enhanced the extraction percentage of these metal ions but also improved the separation factors between Pr and Nd over La compared to Cyanex 272 alone. However, the stripped binary mixture could not extract the metals owing to the extraction of HCl by Alamine 336 during stripping as well as the interaction between Cyanex 272 and protonated Alamine 336. Although adding TBP to the binary mixture enhanced the stripping of metals from loaded organic, it hardly improved the regeneration of the binary mixture. The treatment of the stripped binary mixture with NaOH solution resulted in the regeneration of the mixture, which was verified by 6 cycles of extraction-stripping-regeneration. The interaction between the constituents in the binary mixture after extraction, stripping and regeneration was analyzed by employing the FT-IR spectra of the mixture.