Solid–liquid extraction of heavy rare-earths from phosphoric acid solutions using Tulsion CH-96 and T-PAR resins

Abstract

Wet phosphoric acid produced industrially from natural rock phosphates generally contains uranium in appreciable amounts and rare-earths in trace concentrations. In this paper, the solid-phase extraction of mixture of seven heavy rare-earths (HREs) such as terbium (Tb), dysprosium (Dy), holmium (Ho), yttrium (Y), erbium (Er), ytterbium (Yb), and lutetium (Lu) from phosphoric acid solutions using Tulsion CH-96, a macroporous bifunctional phosphinic acid resin and T-PAR resin, a phosphoric acid resin has been investigated. The parameters studied include time, H 3PO 4 concentration, ratio of volume of aqueous phase to mass of resin, metal concentration, and temperature. Effect of H 3PO 4 concentration from 0.5 to 5 M in the aqueous phase containing 25 mg/L of each metal using Tulsion CH-96 indicated that the percent extraction of metals decreases with increase in acid concentration at any given mass of resin. Mechanism of metal transfer follows ion exchange type. The separation factors were evaluated based on the distribution coefficients in order to estimate the potential of the results for the separation of individual/pair of rare-earths from others.