Concentration and reduction of Au(I) thiosulfate to metallic gold

摘要

The recent developments on the concentration and recovery of gold from leached gold thiosulfate solutions by solvent extraction, reduction-precipitation, and electrochemical deposition are reviewed in this paper. Alkyl phosphorus esters have been found to extract gold only in alkaline thiosulfate solutions. The recovery of gold increases with thiosulfate concentrtion in the aqueous phase and with alkyl phosphorus esters concentration in the organic phase with aliphatic hydrocarbon diluents. The addition of ammonia improves the extraction. The extraction of gold with amines in either aliphatic or aromatic diluent decreased in the following order: primary>secondary>tertiary amines. Increase in the extractant concentration at high pH increased the extraction of gold. At pH<9, the primary amine, RR'CHNH_2 with 19-23 carbon atoms is the main extractant with TBP as the synergistic reagent and at pH>0, the primary amine shows a synergistic effect on the extraction of gold with TBP.