Selective separation of chalcopyrite from talc using emodin as a green depressant: Experimental and DFT insights

Emodin (EM) was innovatively employed as a selective depressant for the flotation separation of chalcopyrite from talc. • EM exhibited significantly stronger adsorption on talc than on chalcopyrite. • EM selectively hindered PAX adsorption on talc while scarcely affecting chalcopyrite. • EM formed stronger Mg–O interactions on talc than Fe–O interactions on chalcopyrite. Talc and chalcopyrite both exhibit inherently high floatability, making their selective flotation separation particularly challenging. Therefore, the development of environmentally friendly depressants with high selectivity is essential for the efficient utilization of copper resources. In this study, the natural product emodin (EM) was employed as a novel green depressant for the flotation separation of chalcopyrite from talc. Under the optimum flotation conditions, EM effectively depressed talc flotation while exerting only limited influence on chalcopyrite, resulting in a recovery difference of 85.01 %age points between the two minerals. Artificial mixed-mineral flotation further confirmed the excellent separation performance, achieving a chalcopyrite recovery of 98.14% and a copper separation efficiency of 94.49%. Contact angle and zeta potential analyses demonstrated that EM effectively depressed talc flotation while exerting a limited influence on chalcopyrite flotation under potassium amyl xanthate (PAX) conditions. Microcalorimetry, XPS, and density functional theory (DFT) calculations further revealed that EM exhibited a much stronger affinity toward talc, preferentially forming stable Mg–O interactions with Mg active sites, whereas only relatively weaker Fe–O interactions were established on chalcopyrite. Collectively, these findings elucidate the molecular-level selective depression mechanism of EM toward talc, providing a theoretical basis for the efficient flotation separation of chalcopyrite from talc and the development of environmentally friendly flotation depressants. Download: Download high-res image (206KB) Download: Download full-size image