XPS study on the mechanism of starch-hematite surface chemical complexation

Polysaccharides are some of the most widely employed flotation reagents in the mineral processing industry. Among several, starch is of particular importance for reverse flotation of iron ores. It is known to behave as an efficient depressant for hematite and, therefore, its interaction is of great relevance. In this paper, we investigate the surface chemistry of starch adsorbed onto hematite by means of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Our results indicate that starch undergoes an important oxidation process under industrial gelatinization conditions, which favors the binding of starch molecules. Meanwhile, the oxide surface is subjected to full hydroxylation, leading to strong polysaccharide-metal hydroxide interaction. Previously proposed starch interaction mechanisms are discussed, and the importance of acid-base interactions is underscored.