Heng Zhang, Hao Tang, Zhi Lei, Xu-Gang Zhang*, Peng-Fei Xu*
https://doi.org/10.1016/j.colsurfa.2026.141282
Separating chalcopyrite from naturally hydrophobic magnesium silicate gangue, especially talc, remains challenging in copper sulfide flotation. In this study, sodium phytate cross-linked starch (CL-S) was synthesized as an environmentally benign depressant for selective talc depression. Micro-flotation tests showed that CL-S strongly depressed talc over a wide pH range (pH 4–10), while exerting limited influence on chalcopyrite recovery. In artificial mixed-mineral flotation, CL-S produced a concentrate with a Cu grade of 26.32% and a Cu recovery of 91.19%, while reducing the MgO content to 5.23%. This performance was better than that obtained with conventional depressants such as carboxymethyl cellulose (CMC) and guar gum under the same conditions. Surface analyses indicated that phytate-derived hydroxyl and phosphate groups support preferential physical adsorption of CL-S on talc, mainly through hydrogen bonding, van der Waals forces, and hydration effects. This adsorption was consistent with increased surface hydrophilicity, as shown by the decrease in talc contact angle from 87.62° to 38.61°. In contrast, CL-S adsorption on chalcopyrite was limited, probably because of unfavorable electrostatic interactions and fewer oxygen-containing surface sites. These findings suggest that CL-S is a promising polysaccharide depressant for beneficiation of copper sulfide ores containing talc.