Improved Gold Extraction from Double Refractory Ores through Surfactant Modification of Carbonaceous Matter

Various strategies have been explored to address the challenges posed by carbonaceous matter in double refractory gold ores (DRGOs), which hinder gold (Au) extraction during cyanidation. This study investigates surfactant-assisted surface modification to reduce the adsorption of the gold-cyanide complex (Au(CN)2−) onto carbonaceous matter. Anionic (2-naphthalenesulfonic acid sodium salt (NS), sodium dodecyl sulfate (SDS)), cationic (benzalkonium chloride (BC), dodecyltrimethylammonium chloride (DTAC)), and non-ionic surfactants (polyoxyethylene (10) octylphenyl ether (TX), dextrin (DX)) were evaluated. Activated carbon and five coals with varying graphiticities were used as carbonaceous matter models. Sorption isotherm studies revealed that the Langmuir model better described the adsorption behavior of NS, indicating monolayer sorption as the dominant mechanism. Linearized Langmuir analysis showed a generally positive correlation between surfactant adsorption and the Raman intensity ratio (ID/IG) of the carbonaceous matter. Zeta potential measurements confirmed the adsorption of surfactants onto the surface of treated DRGOs. Among all treatments, anionic surfactant-modified DRGOs exhibited the greatest reduction in Au(CN)2− adsorption, with optimized SDS treatment (0.5 mM) increasing normalized Au extraction from 53.1% to 80.4 ± 0.3%. The results suggest that electrostatic and π–π interactions are key mechanisms governing Au(CN)2− adsorption. This study provides practical insights into the application of surfactants for mitigating preg-robbing in DRGOs.