Direct recovery of low-concentration Au(S₂O₃)₂³⁻ from pregnant leach solution using an activated carbon-coated titanium electrode

Abstract

Thiosulfate gold extraction technology has gained considerable interest owing to its environmental compatibility and broad applicability to diverse ore types. However, the lack of efficient methods to recover Au(S₂O₃)₂³⁻ from leaching solutions has hindered its industrial implementation. To address this challenge, this study used a thiosulfate leaching solution from quartz-type gold ores to design an activated carbon-coated titanium electrode (Ti@AC) with a porous surface structure. This electrode facilitated the direct reduction of low-concentration Au(S₂O₃)₂³⁻ to metallic gold (Au⁰) in solution, achieving a gold recovery of 99.58%, surpassing other recovery methods from the leaching solution by 30%–80%. After ten consecutive 200 L pilot-scale tests, the Ti@AC electrode demonstrated remarkable stability, consistently maintaining a recovery >98% and yielding 20.23 g of gold. The porous architecture of the activated carbon (AC) promoted the adsorption of low-concentration Au(S₂O₃)₂³⁻, while its low charge transfer resistance facilitated the efficient conversion of Au(S₂O₃)₂³⁻ to Au⁰. Moreover, the reduction reaction generated a concentration gradient near the cathode, promoting the diffusion of Au(S₂O₃)₂³⁻ toward the electrode and ensuring an efficient recovery process. This study provides a feasible strategy for the direct reduction of low-concentration precious metal ions to monomers with high recovery and low costs, which is promising for industrial applications.

Keywords

thiosulfate gold extraction / direct recovery / activated carbon electrode / low-concentration gold / pilot-scale test

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