The inhibition mechanism of esterified starch on flotation separation of fluorite and calcite

Herein, the flotation behavior of fluorite and calcite was examined before and after starch esterification through mineral flotation experiments. Moreover, the adsorption action mechanisms on minerals before and after starch esterification were investigated using methods such as solution surface tension measurement, infrared spectroscopy, and extended Derjaguin–Landau–Verwey–Overbeek theory. The results showed that after starch esterification (esterified starch), there was a greater difference in the mineral recovery rate compared to before starch esterification (ordinary starch), with a better inhibition effect on calcite. The interaction between mineral surfaces and ordinary starch was weaker than the interaction between minerals and esterified starch. In particular, after starch esterification, the surface tension increased, two minerals contact angle decreased, the surface potential became more negative, and the difference in the mineral recovery rate was greater than before starch esterification. After the interaction between minerals and esterified starch, calcite particles displayed good dispersibility, while the cohesion between calcite particles and sodium oleate particles decreased; notably, the effect on fluorite was opposite. Calcite and esterified starch exhibited chemical adsorption, impeding the adsorption of sodium oleate onto calcite and resulting in calcite inhibition. The interaction between fluorite surface and esterified starch involved electrostatic adsorption, with sodium oleate chemically adsorbed onto the fluorite surface. Chemical adsorption proved stronger than electrostatic adsorption, enabling sodium oleate to capture fluorite.