Recovery of gold from aqua regia digested electronic scrap using a poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) based polymer inclusion membrane (PIM) containing Cyphos® IL 104

• A polymer inclusion membrane (PIM) containing 30 wt% Cyphos® IL 104 is prepared.
• Poly(vinylidene fluoride-co-hexafluoropropylene) is used as the base-polymer.
• Au(III) is separated from an undiluted aqua regia digest of electronic scrap.
• Transport of other metal ions into the receiving solution is insignificant.
• The PIM shows excellent stability when exposed to undiluted aqua regia.

A PIM of composition 30 wt% Cyphos® IL 104 and 70 wt% poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) is described for the separation of Au(III) from its HCl solutions and from a solution obtained by the digestion of electronic scrap in aqua regia. This PIM has a high stability in acidic solutions such that no dilution of the digested aqua regia is necessary. Au(III) is back-extracted from the PIM using 0.50 mol L−1 Na2SO3. The stoichiometry of the extracted Au(III) ion-pair and the mechanism of back-extraction are discussed.Transport studies using the proposed PIM with an electronic scrap solution in aqua regia as the feed solution and 0.50 mol L−1 Na2SO3 solution as the receiving solution showed complete transport of Au(III) from the feed to the receiving solution even in the presence of a number of other metal ions at much higher concentrations than that of Au(III), including Cu(II) which was present at a concentration more than 1500-fold higher than that of Au(III).The proposed PIM-based technology is an attractive alternative to conventional solvent extraction methods since it eliminates the use of diluents which are often toxic, volatile and flammable. It successfully overcomes back-extraction issues associated with the use of other PIM-based systems and therefore it is expected to simplify and improve the efficiency of gold recovery from electronic scrap and jewellery.