Abstract
A new polymeric sorbent powder (MP-102) containing phosphine oxide groups was developed for the selective recovery of palladium by sorption from acidic effluents containing base metals such as nickel and copper. Experiments show an interesting affinity of MP-102 to palladium species with sorption capacity up to 1 mmol g−1 at pH 2, fast kinetics and up to 96% selectivity for Pd in presence of Cu and Ni at pH 1. It was found that 99% of the sorbed palladium can be stripped by elution with an acidified solution of thiourea. The influence of various operating parameters (pH, chloride concentrations and temperature) on Pd sorption equilibria was studied in presence of copper and nickel in order to investigate their influence on the sorption selectivity of the palladium species and to investigate the metal binding mechanisms. Experiments, supported by DFT calculations, suggest a coordination of Pd and Ni by the phosphine oxide groups, preferably in a bidentate mode (chelation), whereas Cu appears to bind to both amine and phosphine oxide groups. The sorption selectivity for palladium is likely due to the energy gain upon palladium coordination to MP-102 which is at least 40 kJ mol−1 higher than upon copper and nickel coordination.