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

For thefirst time, an ionic liquid, Cyphos IL 101, hasbeen evaluated for the selective gold recovery from thiosulfateleachate of sulfidic gold ore by solvent extraction. The pregnant leachsolution at pH 9.5 contained 2.4 mg/L gold, 55.85 mg/L copper, and0.26 mg/L silver in thiosulfate medium. The speciation of differentmetals was studied and selective gold extraction over copper and silverwas achieved utilizing 0.1 mol/L Cyphos IL 101 at A/O = 5. Differentionic liquid carriers were tried to dilute Cyphos IL 101, and toluene was found the best choice. The number of extraction stages forgold was theoretically determined based on the McCabe Thiele diagram constructed for extraction and was confirmed at A/O = 4and A/O = 5 followed by counter-current extraction. The different stripping agents were used and the gold stripping from the loadedorganic solution was done using 5% thiourea in 1% HCl solution. The McCabe Thiele diagram for stripping was drawn and thenumber of theoretical stages needed to achieve an effective stripping was identified. A phase ratio of A/O = 1 needed three strippingstages, which were confirmed by the counter-current stripping experiment. Overall, the study showed attractive results and opens thearea for further research in the future.

Automated summary

For the first time, the application of an ionic liquid, Cyphos IL 101, for the selective recovery of gold from thiosulfate leachate of sulfidic gold ore by solvent extraction was evaluated. The study showed that Cyphos IL 101 achieved selective extraction of gold over copper and silver at A/O = 5, and toluene was the best choice as the diluent. Gold stripping from the loaded organic solution was done effectively using 5% thiourea in 1% HCl solution.