Solvent extraction of Pr and Nd from chloride solution by the mixtures of Cyanex 272 and amine extractants

• Mixture of Cyanex 272 and Alamine 336 showed synergism on Pr and Nd extraction.
• The highest synergistic effect was obtained at Cyanex 272 mole fraction of 0.5.
• The solvent extraction reaction was identified by applying slope analysis method.
• The role of amine extractant was to extract hydrogen ions released from Cyanex 272.
• Chloride ion concentration has a profound effect on the extraction of hydrogen ion.

In the separation of rare earth elements by solvent extraction with organophosphorus extractants, bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) leads to lower extraction percentage but higher separation factor. In order to increase the extraction of Pr and Nd by Cyanex 272, its mixtures with amine extractants, such as tri-octyl/decyl amine (Alamine 336), trioctylamine (TOA) and tri-2-ethylhexyl amine (TEHA) have been employed from chloride solution. Among the studied extractant mixtures, the combination of Cyanex 272 and Alamine 336 showed that the best extraction ability and the maximum synergistic enhancement factors were 14.2 for Pr and 12.2 for Nd at Cyanex 272 mole fraction of 0.5. The role of Alamine 336 in this mixture was to extract hydrogen ions released from Cyanex 272. The overall solvent extraction reaction was identified by applying a slope analysis method to the experimental data. Moreover, it was found that the concentration ratio of Alamine 336 to chloride ion affected the enhancement in the extraction of the two metals. The quantitative stripping of both Pr and Nd was possible from the loaded mixture by using HCl or H2SO4 solution.