Adsorption and morphology of oxidized starches on graphite

Hydrophobic gangue minerals such as talc, graphite and mica cause selectivity problems during flotation separation because they can be floated together with valuable minerals. This issue becomes increasingly prominent as the higher quality resources are depleted quickly. Here, we demonstrate a promising and green approach which involves simple and oxidative modifications of starch structure features to inhibit graphite floatability. The primary focus was on comprehensively interrogating how systematically developed oxidized starch derivatives differentially and uniquely modify graphite surface hydrophobicity. Adsorption tests, AFM imaging and topographical characterisation were conducted and correlated with flotation responses in the absence (baseline case) and presence of the starch derivatives. At a low concentration (10 mg/L), the starch derivatives exhibited relatively similar surface adsorption in contrast to profound dissimilar flotation outcomes. However, attention to AFM morphological visualizations and resolving the adsorbed structural distributions at the nanoscale level revealed compelling evidence of disparate appearances on graphite surface. The oxidation-induced preferential conformations of starch structure features were judged as the overarching factors conferring surface hydrophobicity reductions, which is important if graphite flotation inhibition is to be successful.