Stabilization of solvent-impregnated resin capacities by different techniques

This paper reports the results obtained by studying stability characteristics and ion-exchange properties of solvent-impregnated resins (SIR) obtained by immobilization of different extractants such as, di-2-ethylhexylphosphoric acid (DEHPA), di-2-ethylhexyldithiophosphoric acid (DEHDTPA), and di-3-propylphenyldithiophosphoric acid (DPPDTPA) in granulated PS-DVB copolymer Amberlite XAD-2. It has been shown that different techniques such as, conventional conditioning (based on carrying out several sequential ion-exchange cycles), 'wet drying' (boiling of SIR sample in water), and post-impregnation encapsulation (coating of SIR beads with polysulfone layer) can be used to stabilize the capacity of freshly prepared SIR samples. The stabilizing efficiency of the last technique substantially exceeds that of two others. The equilibrium separation factors, alpha, determined for conventionally conditioned SIR samples towards Zn2+ and Cd2+ mixture has been found to equal alpha(Zn)(Cd) = 1.6 (for DEHPA-SIR), 96.9 (DEHDTPA-SIR), and 57.6 (DPPDTPA-SIR). The 'wet drying' procedure does not affect the selectivity of DEHPA-SIR while that of DEHDTPA- and DPPDTPA-SIR samples substantially changes after the heat treatment in water. (C) 1998 Elsevier Science B.V. AU rights reserved.