Selective Extraction and Recovery of Gold from Complex Thiosulfate Pregnant Leach Liquor Using Cyphos IL 101

For the first time, an ionic liquid, Cyphos IL 101, has been evaluated for the selective gold recovery from thiosulfate leachate of sulfidic gold ore by solvent extraction. The pregnant leach solution at pH 9.5 contained 2.4 mg/L gold, 55.85 mg/L copper, and 0.26 mg/L silver in thiosulfate medium. The speciation of different metals was studied and selective gold extraction over copper and silver was achieved utilizing 0.1 mol/L Cyphos IL 101 at A/O = 5. Different ionic liquid carriers were tried to dilute Cyphos IL 101, and toluene was found the best choice. The number of extraction stages for gold was theoretically determined based on the McCabe Thiele diagram constructed for extraction and was confirmed at A/O = 4 and A/O = 5 followed by counter-current extraction. The different stripping agents were used and the gold stripping from the loaded organic solution was done using 5% thiourea in 1% HCl solution. The McCabe Thiele diagram for stripping was drawn and the number of theoretical stages needed to achieve an effective stripping was identified. A phase ratio of A/O = 1 needed three stripping stages, which were confirmed by the counter-current stripping experiment. Overall, the study showed attractive results and opens the area for further research in the future.