A Novel Weak Base Anion Exchange Resin Which Is Highly Selective for the Precious Metals Over Base Metals

The weak base anion exchange copolymer (P-SNTD) which is based on poly(styrene-co-divinylbenzene) with covalently bound 1,3,4-thiadiazole-2-amino-5-thiol (SNTD) groups shows selectivity for gold and the platinum-group-metals (PGMs) e.g. Pt(IV), Pd(II), Rh(III) and Ir(IV) in the presence of the base metals, e.g. Cu2+, Fe3+, Co2+ and Ni2+ in chloride media. The separation is particularly effective from 0.5 M to 3.0 M HCl as within this range the PGMs and gold are extracted as anionic species via an ion exchange mechanism. There was no loss of resin capacity in sorption-desorption cycles for gold recovery using acidic thiourea as eluent which gave quantitative elution.