Abstract
: Poly(vinyl chloride) (PVC) based polymer inclusion membranes (PIMs), with different concentrations of Cyphos® IL 104 as the membrane extractant/carrier, were studied for their ability to extract Au(III) from hydrochloric acid 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 of the Au(III) extracted from this membrane was achieved by using a 0.10 mol L−1 Na2SO3 receiver solution at pH 8. 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) to Au(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 solutions of electronic scrap or recycled jewelry.
Highlights
During the past decade, there have been a number of studies of gold recovery from acid solutions using polymer inclusion membranes (PIMs) [1,2,3,4,5]
The present paper describes the use of a Poly(vinyl chloride) (PVC)-based PIM containing Cyphos® IL 104 as the carrier for the efficient extraction of Au(III) from hydrochloric acid solutions
Cyphos® IL 104, and so the equilibrium mole ratio of Au(III) to Cyphos® IL 104 in the PIM decreases. This result suggests that the stoichiometry of the adduct formed in the PIM between Cyphos® IL 104 and Au(III) is 1:1, and, together with a decrease in the pH of the receiver phase during back-extraction (see Section 2.4, Equation (2)), supports an extraction mechanism described by Equation (1)
Summary
There have been a number of studies of gold recovery from acid solutions using polymer inclusion membranes (PIMs) [1,2,3,4,5]. PIM was used mainly for Pd(II) separation), and thiacalix[4]arenes [3] These studies have shown successful extraction of Au(III) from hydrochloric acid solutions, with good selectivity over other base metal ions. Argiropoulos et al [1] have reported on the high selectivity of a PIM composed of PVC and Aliquat 336 as the carrier for Au(III) extraction from hydrochloric acid solutions, even in the presence of a 500-fold higher concentration of Cu(II). They encountered difficulties in stripping Au(III) in the receiving solution during transport experiments, and observed some instabilities of the membrane. The present paper describes the use of a PVC-based PIM containing Cyphos® IL 104 as the carrier for the efficient extraction of Au(III) from hydrochloric acid solutions
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