Thiocyanate hydrometallurgy for the recovery of gold. Part IV: Solvent extraction of gold with Alamine 336

Solvent extraction with amines has been evaluated as a possible method to purify and concentrate gold from thiocyanate solutions. No significant difference was observed in gold extraction with commercially available tertiary amines (Alamine 336, Alamine 308, and Alamine 304–1). The effects of Alamine 336 and thiocyanate concentrations were examined for gold extraction. Gold extraction isotherms were established at different thiocyanate concentrations. The extraction and stripping of gold showed satisfactory results at an organic/aqueous (O/A) ratio of 1:5 for extraction (~ 100%) and 5:1 for stripping (~ 92%), in the presence of decanol. Possible solvent extraction reactions and stripping reactions with thiourea are discussed in order to better understand the system chemistry. Sodium hydroxide/thiocyanate, ammonium hydroxide, and acidic thiourea were examined for the stripping of gold from the loaded organic phase. Acidic thiourea gave the best results (with complete stripping of gold) under the conditions studied.