Solid-liquid extraction of terbium from phosphoric acid solutions using solvent-impregnated resin containing TOPS 99

BACKGROUND: In this work, the solid-liquid extraction of terbium from phosphoric acid solutions using solvent-impregnated resin containing TOPS 99, an equivalent of di-2-ethylhexyl phosphoric acid, has been investigated. The parameters studied include equilibration time, acid concentration, amount of resin, metal concentration, kinetics, temperature, loading, elution, regeneration and recycling. RESULTS: FT-IR results confirm the physical interaction of the extractant with the resin. The extraction of terbium with TOPS 99 impregnated Amberlite XAD 4 resin was acid dependent and transfer of metal follows a cation exchange mechanism. The loading capacity of TOPS 99-impregnated resin for terbium was calculated to be 23.8 mg g(-1) resin. Controlling mechanism of the adsorption was found to be a chemical reaction following pseudo-second-order kinetics. The endothermic nature of extraction was confirmed by temperature studies. Among the various eluants studied, H2SO4 was the best. Regeneration and recycling of the resin indicated the resin can be used for continuous cycles. CONCLUSIONS: Terbium was successfully extracted from phosphoric acid using TOPS 99 extractant impregnated into Amberlite XAD4 with amaximum loading of 23.8 mg g(-1) resin and fully recovered with 1 mol L-1 sulfuric acid. The resin was subjected to seven cycles of extraction and elution without any loss of performance. Further studies showed that terbium could be separated from lutetium. (C) 2010 Society of Chemical Industry