The selective adsorption mechanism of an amino acid surfactant in the flotation separation of fluorite from calcite

The mineral processing industry has faced challenges in separating fluorite/calcite using flotation because of the similarity of surface properties and the presence of surface transformations. In this paper, a novel dicarboxylic acid-based amino acid surfactant, 2-decanoylamino-pentanedioic acid (DPA), was used for the flotation separation of fluorite from calcite. The DPA adsorption behaviors on fluorite/calcite surfaces showed significant differences: the chemical reaction between the carboxyl group’s O atoms and Ca sites on the fluorite surface caused a significant DPA adsorption; in contrast, DPA formed a DPA-Ca precipitates with Ca²⁺ in the slurry in advance and then achieved weaker adsorption by interacting with O sites on calcite surface. In addition, thanks to its “double-headed” structure, there are more adsorption configurations of DPA on the mineral surface, providing different levels of hydrophobicity to further magnify fluorite/calcite floatability with different floatability. Consequently, DPA showed excellent collecting ability and selectivity for fluorite, and the recovery and grade of CaF₂ in the froth product of artificially mixed mineral flotation reached 85.85 % and 59.13 %, respectively, in a neutral pH and without adding frothers and inhibitors. Our study elucidates the adsorption mechanism of DPA on fluorite/calcite surfaces, which offers an innovative perspective on fluorite collector design and development, contributing to the effective and environmentally friendly exploitation of mineral resources.