SYNERGISTIC EXTRACTION OF GOLD FROM SULFURIC-ACID-SOLUTION CONTAINING THIOUREA

As a part of the fundamental studies on the recovery of Au by solvent extraction, the synergistic effect of combined extractants on the extraction of Au from sulfuric acid solution containing thiourea was investigated. Extractants tested were di-(2-ethylhexyl) phosphoric acid (D2EHPA), tri-n-octylamine (TOA), tri-n-butyl phosphate (TBP) and trioctyl phosphine oxide (TOPO). Four kinds of extractant combinations, D2EHPA/TBP, D2EHPA/TOPO, TOA/TBP and TOA/TOPO, were tested to clarify the synergistic effect on the extraction of Au in terms of various concentration ratios, diluents, the concentration of sulfuric acid and the concentration of thiourea. The results obtained in this study were summarized as follows: (1) Combined extractants were superior to D2EHPA and TOA on the extraction of Au, the separation of Au and Fe (III) and the phase separation behavior. (2) D2EHPA/TOPO and TOA/TOPO were favorable to the extraction of Au and the separation of Au and Fe (III), respectively, compared with D2EHPA/TBP and TOA/TBP. (3) Benzene used as diluent was favorable to the extraction of Au and the separation of Au and Fe (III). (4) The extraction efficiency of Au and the separation efficiency of Au and Fe (III) were not dependent on the concentration of thiourea, but the concentration of sulfuric acid. (5) The mechanisms of the extraction of Au with the combined extractants were discussed.