Thiocyanate (SCN–) is a promising alternative to cyanide as a lixiviant for gold extraction and is 1000 times less toxic than cyanide. In this study, the following leaching parameters were tested to optimize the gold recovery for the first time from an oxide ore using the response surface methodology: initial thiocyanate concentration (10–500 mM), initial Fe3+ concentration (10–500 mM), and pulp density (10–50% w/v). The maximum gold recovery (96%) was achieved with 500 mM thiocyanate, 100 mM Fe3+, and 50% pulp density at 25 °C and pH = 2 for 24 h. A kinetic study on the optimum leaching condition showed that it followed the shrinking core model, in which the rate-controlling mechanism was the diffusion process. These results are discussed in the context of the published literature.

No abstract

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.

No abstract

No abstract

No abstract

No abstract

No abstract