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.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.