Synergistic depression of talc by sodium carboxymethyl starch and AlCl₃ in the selective separation of molybdenite and talc

In the field of mineral processing, the flotation separation of talc and molybdenite has long faced severe challenges, and the development of efficient flotation depressants is a crucial research direction to address this issue. Due to the complex pulp environment, the selective depression effect of a single flotation depressant is relatively poor and significantly influenced by pH levels. In contrast, combined depressants offer advantages such as synergistic depression mechanisms, multi-target action, and less sensitivity to pulp environment, making them the core technical for the flotation separation of talc and molybdenite. This study innovatively employs sodium carboxymethyl starch (CMS) and Aluminum chloride (AlCl₃) as combined depressants for the separation of talc and molybdenite and systematically compares the differences in adsorption behavior and mechanisms on different crystal surfaces of talc and molybdenite using various characterisation methods in conjunction with micro-flotation experiments. The results indicate that the unique structures and wettability differences of the various crystal surfaces of talc and molybdenite are the direct reasons affecting the depression effectiveness of the combined depressants. Further research shows that CMS and AlCl₃ first form a complex, which then adsorbs onto the surface of talc, with the combined adsorbent exhibiting stronger adsorption on the talc (100) surface than on the (001) surface. Flotation results indicate that when the concentration of CMS is 0.25 × 10⁻³ mol/L, the recovery rate of molybdenite reaches its highest at 92.51 %; conversely, when the concentration of CMS is 1.25 × 10⁻³ mol/L, the recovery rate of talc drops to its lowest at 13.01 %. This research offers a new technological avenue for the efficient selective separation of talc-containing molybdenite systems, showcasing significant industrial application value.