Thiol functionalized activated carbon for gold thiosulfate recovery, an analysis of the interactions between gold and sulfur functions
(2023) Carbon — Vol. 204, p. 254-267 (2023)
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- Cyanide salts are currently used as leaching agents in gold extraction processes despite their toxicity. Thiosulfate is a greener choice, but its employment is constrained by the difficulty at recovering gold thiosulfate from the leachate using activated carbon, which in contrast, works well for gold-cyanide adsorption. Aiming to solve this problem, activated carbon has been covalently functionalized with thiol groups (-SH) through a peptide bond formation with cysteamine, as thiol-carrier molecule. The functionalized carbon accomplishes up to 100% Au recovery (with 2 and 25 ppm Au solution) in 8 h contact and its performance seems independent on the solution's pH. In-depth solid characterization techniques (XPS, TOF-SIMS, FTIR, PXRD, TEM, N₂ physisorption, elemental analysis) have been used to unravel the interactions between Au thiosulfate and thiol functions and two different gold adsorption mechanisms have been demonstrated: under acid conditions, the formation of Au1+- S chains has been proven. Under basic conditions, Au⁰ species have been detected in addition to Au1+- S chains. Elution of the gold loaded samples has been accomplished at a 71% level using Na₂S₂O₃ and NH₄OH as eluents.
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de la Torre-Miranda, N., Reilly, L., Eloy, P., Poleunis, C., & Hermans, S. (2023). Thiol functionalized activated carbon for gold thiosulfate recovery, an analysis of the interactions between gold and sulfur functions. Carbon, 204, 254-267. https://doi.org/10.1016/j.carbon.2022.12.061 (Original work published 2023)