Separation and recovery of platinum and rhodium by supported liquid membranes using bis(2-ethylhexyl)phosphoric acid (HDEHP) as a mobile carrier

Abstract

Transport of Pt and Rh ions from an aqueous 1 mol dm −3 HCl feed solution containing 20% stannous chloride into a stripping solution 8 mol dm −3 HCl through a supported liquid membrane (SLM) consisting of bis(2-ethylhexyl)phosphoric acid (HDEHP) in kerosene, supported on PVDF film, have been studied. Various parameters, such as concentration of HCl in feed and stripping solutions, concentration of HDEHP in the membrane, stirring time and concentration of SnCl 2 in 1 mol dm −3 HCl, have been investigated. Transport of Pt is independent whereas that of Rh increases with HDEHP concentration (0.003–2 mol dm −3) in the membrane phase. Mutual separation of Pt and Rh is achieved by preferential transport of Pt at low concentration of HDEHP (0.003 mol dm −3) and Rh left behind is recovered by transport at high concentration of HDEHP (2 mol dm −3) in membrane. Selective recovery of Pt and Rh have been achieved from other platinum group metal ions, gold and other metal ions. The methods have been demonstrated to recover Pt and demonstrated to recover Pt and Rh selectively from industrial waste samples such as catalyst, anode slime and artificial mixtures.