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 center dot 3(HA(2)). 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. (C) 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.