Investigation into starch adsorption on hematite and quartz in flotation: Role of starch molecular structure

Various starches have been used as depressants in reverse flotation of iron ores. To date, the effect of molecular structures of starches on the depressing behavior is still not clear using simulation study. In this study, three starches with different ratios of amylose/amylopectin on the molecule (Normal Starch, Waxy Starch and Gelose 50) were used to study their depressing ability on the flotation of hematite and quartz. Microflotation, Zeta potential measurement, XPS analysis and AFM measurement were performed to investigate the interaction between the two minerals and the three starches. It was found that chemisorption occurred between hematite and the starches, while only hydrogen bonding was observed between quartz and the starches. In addition, it was obtained that the chemisorption strength between the starches and hematite under alkaline condition fell in the order: Waxy Starch > Normal Starch > Gelose 50, which was closely related to the ratios of amylose/amylopectin. The underlying mechanism for the different chemisorption strength was revealed via computational chemistry analysis. It is believed that the outcomes of this work could optimize the development of starch-based depressants in iron ore flotation.