Probing the role of hydrophobic groups on the performance of fatty acid surfactants for hematite flotation

Fatty acid surfactants, known for their cost-effectiveness and efficacy, are commonly used in the flotation process of hematite. An in-depth understanding of the role of hydrophobic groups on the performance of fatty acid surfactants can enhance and guide the utilization of surfactants for hematite flotation. Herein, four representative fatty acid surfactants with heterogeneous hydrophobic groups were selected and the influences of the hydrophobic group configuration on the adsorption behavior and flotation performance were systematically investigated by density functional theory (DFT) calculations, quantitative structure–activity relationship (QSAR) analyses, surface tension measurements, wettability tests and molecular simulations. The results of the DFT calculation and QSAR analysis reveal that logP is the primary parameter in determining the collective power of fatty acid surfactants for hematite. The results of the steric hindrance study suggest that the fatty acid with a cyclic hydrocarbon structure forms an L-shaped arrangement on mineral surface. This arrangement increases the intermolecular steric hindrance effects and reduces the coverage density. Compared to the l-shaped arrangement of fatty acids with straight hydrocarbon chains, the L-shaped arrangement possesses better selectivity towards hematite. The results of the flotation tests indicate that fatty acids with straight hydrocarbon chains possess a strong collection ability to hematite, while fatty acids with circular structures exhibit enhanced selectivity, providing experimental support for the adsorption model. This work provides a scientific approach to better understand the structure–activity relationship of surfactants in flotation, with implications for the development of effective surfactants for hematite.