Heterogeneous adsorption of carboxymethyl starch on anisotropic molybdenite and talc surfaces and its effect on flotation

The effective recovery of talc-bearing molybdenum ores has been a research hotspot in the field of minerals processing, which is mainly attributed to the similarity of the physical and chemical properties of talc and molybdenite, especially floatability, which presents a challenge in the separation of the two during the beneficiation process. Herein, the coordination affinity, differentiated adsorption configurations, adsorption morphology, and bonding mechanisms of a polysaccharide-based depressant, carboxymethyl starch (CMS), on the layered hydrophobic minerals molybdenite and talc have been compared and its special use in flotation was investigated by various advanced techniques, including density functional theory (DFT) simulation, time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). The CMS adsorption on the talc surface was more affinitive than that of molybdenite and it is possible to achieve the selective separation of laminar hydrophobic minerals molybdenite and talc through the utilization of differential wettability. Flotation kinetics with 400 mg/L CMS as a depressant and 3*10⁻³ mol/L sodium diethyldithiocarbamate (DDTC) as a collector has highlighted the importance of the mineral particle sizes that the better depressant activity of CMS on the coarse-grained talc surface in comparison to that of molybdenite is attributed to the greater adsorption energy and more homogeneous adsorption morphology of CMS on the talc basal surface which is the dominant surface affecting the floatability.