Studies on solvent extraction of Dy(III) and separation possibilities of rare earths using PC-88A from phosphoric acid solutions

Solvent extraction studies of Dy(III) from phosphoric acid medium has been investigated using PC-88A (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) alone and in combination with acidic, basic and neutral extractants. Systematic studies of Dy(III) using 0.04 mol/L PC-88A as a function of equilibrium pH, extractant concentration and metal concentration indicated the extracted organic complex stoichiometry as Dy·3(HA2). Extraction behaviour of other rare earths (REs) with 0.1 mol/L PC-88A suggested the possible separation of Lu + Yb from others in the acid range 0.6–1 mol/L. Based on this, effect of phase ratio was studied with a mixture of elements; three stages were needed for the separation of Lu + Yb from Dy + Tb at an A/O ratio of 2.5:1 and 1:1 at 0.6 mol/L and 1 mol/L acid, respectively. Studies on Dy(III) extraction using a mixture of extractants (PC-88A + other extractant) showed synergistic effect only with PC-88A + Cyanex 301 mixture. Stripping of metal from loaded organic with mineral acids showed that sulphuric acid as the best one.

► Dy(III) extraction reported using PC-88A and mixture of extractants from H3PO4.
► Separation possibilities of Dy(III) and other REs were studied using 0.1 M PC88-A.
► Among the examined mixture of extractants; PC88-A + Cyanex-301 showed synergism.
► Separation factors calculated for Dy(III) with other REs using PC-88A + Cyanex-301.