Synthesised phosphine sulphide-type macroporous polymers for the preconcentration and separation of gold (III) and palladium (II) in a column system

Abstract

New macroporous polymers with an ionogenic group based on triisobutyl phosphine sulphide, with spacer arms containing O or S atoms, are evaluated in small-scale column adsorption processes. These resins are highly selective towards gold and palladium in hydrochloric acid media and they do not adsorb other Platinum Group Metals (PGM) such as Pt, Rh and Ir nor base metals such as Fe, Zn, Cu and Ni. The heteroatoms present in the spacer arm enhance the adsorption capacities of these polymers by coordinating the metal ions jointly with the functional group. The polymer that contains O atoms permits the direct separation of palladium and gold at linear flow rates lower than 80 mm min −1. The second polymer, which contains one S atom in the spacer arm, shows a higher breakthrough capacity for Pd ions and a decrease in the separation factor of gold and palladium. A temperature increase from 25 to 60°C produces a significant increase in gold adsorption resulting in a higher separation factor from palladium. Separate metal elution can be achieved by passing, firstly, a sodium nitrite 2 M solution at pH≈5, which can elute 75% of palladium without gold interference. A second elution with thiourea permits the total recovery of the remaining ions. This elution procedure has been applied to the preconcentration of both metal ions. Polymers were evaluated during 15 consecutive cycles without changes taking place in the adsorption and elution profiles of the metals.