(Theme session) Academic exchange session in English

[1301-08-08] Enhancing Gold Extraction from Double Refractory Gold Ores through Surfactant-Assisted Carbonaceous Matter Modification

○Cindy -^{1[Student presentation: Doctoral course]}, Keiko Sasaki² (1. Kyushu University, 2. Waseda University)

司会：芳賀　一寿（秋田大学）

Keywords:Activated carbon, Carbonaceous matter, Coal, Double refractory gold ores, Surfactant

Many approaches have been explored to address the challenges posed by carbonaceous matter in double refractory gold ores (DRGOs), which significantly hinder gold (Au) extraction via cyanidation. This study investigates the use of surfactants to modify the surface properties of carbonaceous matter in order to reduce the undesirable adsorption of the gold–cyanide complex (Au(CN)₂⁻), a key contributor to “preg-robbing” and the consequent decline in Au extraction. Three types of surfactants—anionic, cationic, and non-ionic—were evaluated. Activated carbon and various coals with differing degrees of graphitic structure were employed to represent the carbonaceous matter found in DRGOs. Sorption isotherm studies revealed that the Langmuir model most accurately described the surfactant adsorption behavior, indicating the formation of a monolayer on the surface of the carbonaceous matter. A positive correlation was observed between the amount of surfactant adsorbed and the graphitization degree of the carbonaceous matter, as determined by Raman spectroscopy. Following kinetic studies and surfactant concentration optimization, the selected treatments were applied to pretreated DRGO samples. Zeta potential measurements confirmed the successful adsorption of surfactants to the surfaces of the treated samples. Among the surfactants tested, anionic surfactants demonstrated the most pronounced effect, reducing Au(CN)₂⁻ adsorption from approximately 32% to just 3%, while enhancing Au extraction from around 53% to over 72%. These findings suggest that electrostatic interactions and π–π stacking interactions play critical roles in the interaction between Au complexes and carbonaceous matter. Overall, this study provides valuable insights into the potential of using conventional surfactants to mitigate preg-robbing, offering a promising strategy for improving Au extraction from DRGOs.