New insight into effect of cation bridging on the differential bonding mechanism of sodium carboxymethyl starch in molybdenite-talc separation

The selective depression of talcose molybdenum ores has always been a pressing problem in the physical chemistry of flotation. Herein, aluminum ion was introduced to investigated its effect on the selective depression of sodium carboxymethyl starch (CMS) on molybdenite-talc separation. The micro-flotation experiments shows that the combination of CMS and aluminum ion exerts a synergistic depression in low alkaline environments and exhibits strong affinity on the talc. Fourier transform infrared spectroscopy (FTIR), adsorption isotherm, X-ray photoelectron spectroscopy (XPS) and Time-of-flight secondary ion mass spectrometry (TOF-SIMS) illustrate that aluminum ions act as a metal bridge to change the adsorption configuration as well as the adsorption strength of CMS. The primary factors influencing the adsorption of aluminum ion cross-linked with CMS (CMS-Al complex) on the molybdenite surface are electrostatic force, hydrophobic interaction and hydrogen bond, and sodium diethyldithiocarbamate (DDTC) can effectively accelerate its desorption. While CMS-Al complex has a stronger affinity on talc by hydrogen bonding and chemical interaction, which is not affected by DDTC. Differences in the adsorption affinities of DDTC and CMS-Al complex on the molybdenite and talc is another non-negligible factor in realizing the efficient molybdenite-talc separation.