Study on the Flotation Behavior of CMS-Na for Talc with Different Particle Sizes: Based on the Hydrophobicity Difference of Fracture Surfaces

Talc, as a phyllosilicate mineral, is often associated with sulfides such as copper, molybdenum, and nickel, which severely impact the flotation of target minerals. Micro-flotation experiments combined with SEM, contact angle, FTIR, TOC, and AFM analyses were performed to explore the influence and mechanism of sodium carboxymethyl starch (CMS-Na) on the flotation behavior of talc with varying particle sizes in a butyl xanthate system. The flotation results indicate that when CMS-Na is used as a depressant, the recovery of coarse talc particles (−74 + 45 μm) is only about 1%, while fine talc particles (−23 μm) maintain a recovery rate of over 70%. FTIR analysis revealed that the interaction between CMS-Na and talc involves both chemical and physical adsorption mechanisms, with the most pronounced effect observed on fine-grained talc surfaces. TOC, AFM, and contact angle measurements further revealed that the proportion of exposed edge surfaces increases as the talc particle size decreases. These edge surfaces exhibited a higher affinity for CMS-Na, resulting in significant reagent adsorption. Consequently, at an equivalent reagent dosage, the adsorption of CMS-Na on the basal planes was reduced, leading to the retention of high surface hydrophobicity. This phenomenon is considered an important factor contributing to the poor depressive effect on fine-grained talc.