Palladium and platinum binding on an imidazol containing resin

Platinum and palladium were efficiently recovered from HCl solutions (at concentrations as high as 1–2 M) using a vinylbenzyl chloride-divinylbenzene resin reacted with the sodium salt of diethylmalonate followed by reaction with 3-aminopropyl imidazol. Both palladium and platinum exhibit sorption capacities as high as 1 mmol metal g− 1 in 2 M HCl solutions (1.4–1.5 mmol metal g− 1 in 1 M HCl and 1.6–1.7 mmol metal g− 1 in 0.1 M HCl). The sorbent has a greater affinity for Pd at low HCl concentration, while Pt is preferred at higher HCl concentration, as shown by sorption performances in binary solutions. The sorption capacity is influenced by chloride concentration, while the presence of competitor ions (such as base metals) has little influence on binding performances: zinc shows the highest inhibiting effect (compared to copper and nickel). The sorption kinetics show that the agitation speed has a limited impact on sorption rate, while the kinetic rate decreases linearly with increasing metal concentration. Metals loaded on the resin can be recovered using 0.1 M thiourea solution as the eluent, with desorption efficiency exceeding 95% under selected experimental conditions. The recycling of the resin was effective for at least five sorption/desorption cycles.