Hydrophobic ionic liquids as novel extractants for gold(I) recovery from alkaline cyanide solutions

BACKGROUNDAlthough ionic liquids (ILs) as green solvents have become a focus of research in the field of metal ions separation, little attention has been paid to gold(I) recovery from alkaline cyanide solutions using ILs as extractants. Therefore, this work explores gold(I) extraction using hydrophobic imidazolium-based ionic liquids. RESULTSIt was found that an increase in the alkyl group chain substituted on the cation ring of the ionic liquid corresponded with an increase in gold(I) extraction. Almost all of the gold(I) (>98%) was extracted from the aqueous phase into the organic phase using pure [C(8)mim][PF6] as an extractant. With increased reaction temperature, the gold extraction efficiency also increased. The transfer mechanism of Au(CN)(2)(-) into the ionic liquid was proved to be an anion exchange reaction. Most of the gold(I) (>90%) in the [C(8)mim][PF6] phase could be directly deposited on a copper cathode through electrowinning. Energy dispersive spectrometry analysis and X-ray diffraction patterns suggested that the yellow deposits on the copper cathode were pure gold. Results of three recycling experiments indicated the excellent stability of the [C(8)mim][PF6]. CONCLUSIONIonic liquid extraction followed by direct electrodeposition from the organic phase is a feasible method for gold recovery from alkaline aurocyanide solutions. (c) 2014 Society of Chemical Industry