Solvent extraction and stripping of gold(I) cyanide in the tetradecyldimethylbenzylammonium chloride system

The solvent extraction of KAu(CN)2 from alkaline cyanide solutions by using quaternary ammonium tetradecyldimethylbenzylammonium chloride (TDMBAC) as extractant with the addition of tri-n-butylphosphate (TBP) has been investigated with the 198Au radioactive tracer method. The influence of several variables such as agitation time, volume percentage of TBP and the molar fraction of TDMBAC in the aqueous phase (xTDMBAC) were investigated. The results indicated that the organic phase has a high extraction capacity. Almost all of the Au(CN)2− (>95%) was transferred from the aqueous phase into the organic phase. Most of the Au(I) in the organic phase can be stripped with 2,2′-thiodiethanol, glycol or ammonium thiocyanate aqueous solutions, from which elemental gold could potentially be recovered by the addition of reducing agents, such as NaBH4 and zinc. The extraction mechanism can be explained based on a microemulsion mechanism while the mechanism of stripping by inorganic salts follows the perchlorate effect.