Extraction of gold(III) from hydrochloric acid solutions with a PVC-based polymer inclusion membrane (PIM) containing cyphos® IL 104

Abstract

Poly(vinyl chloride) (PVC) based polymer inclusion membranes (PIMs), with different concentrations of Cyphos® IL 104 asthe membrane extractant/carrier, were studied for their ability to extract Au(III) from hydrochloricacid solutions. Some of the PIMs also contained one of the following plasticizers or modifiers: 2-nitrophenyloctyl ether, dioctylphthalate, 1-dodecanol, 1-tetradecanol, or tri(2-ethylhexyl) phosphate. The best performance, in terms of extraction rate and amount of Au(III) extracted, was exhibited by a PIM consisting of 25 wt% Cyphos ® IL 104, 5 wt% 1-dodecanol, and 70 wt% PVC. An almost complete back-extraction ofthe Au(III) extracted from this membrane was achieved by using a 0.10 mol L −1 Na2SO3receiver solution at pH8. The stoichiometry of the extracted Au(III)/Cyphos® IL 104 adduct was determined as [P] + [AuCl4] − H + [PO2] − where [P] + and [PO2] − represent trihexyl(tetradecyl) phosphonium and bis(2,4,4-trimethylpentyl) phosphinate ions, respectively. Back-extraction of Au(III) is suggested to occur by reduction of Au(III) toAu(I), with the formation of the species [Au(SO3)2] 3− in the aqueous receiver solution. Loss of 1-dodecanol from the newly developed PIM to the aqueous solutions in contact with it was observed, which indicated that this membrane was suitable for single use in the efficient recovery of Au(III) from hydrochloric acid solutionsof electronic scrap orrecycled jewelry.