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 a maximum loading of 23.8 mg g⁻¹ resin and fully recovered with 1 mol L⁻¹sulfuric 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. Copyright