A novel surfactant N-hydroxy-9,10-epoxy group-octadecanamide. Part Ⅰ. Application in the flotation separation of fluorite/calcite and adsorption selectivity on the mineral surfaces

Oleic acid plays a crucial role as the primary collector in fluorite flotation. N-hydroxy-9,10-epoxy group-octadecanamide (N-OH-9,10-O-ODA) is synthesized by modifying the structure of oleic acid. This modification involves converting the carboxyl group, a polar functional group of oleic acid, into N-hydroxy amide group and introducing an epoxy group. These modifications are aimed at enhancing the selectivity and collecting ability of oleic acid. Utilizing N-OH-9,10-O-ODA as the collector results in a significantly higher recovery rate of fluorite of approximately 95% compared to only about 20% for calcite. The fluorite surface treated with N-OH-9,10-O-ODA exhibits a more substantial negative shift in its zeta potential, approximately 73 mV, compared to the N-OH-9,10-O-ODA-treated calcite surface, which only displays an absolute value of approximately 41 mV. The greater discrepancy suggests a greater adsorption quantity of N-OH-9,10-O-ODA on fluorite surface, thereby enhancing its ability to collect fluorite particles more effectively. First-principles calculations reveal a higher adsorption energy of N-OH-9,10-O-ODA on fluorite surface compared to calcite. The disparity indicates a greater adsorption intensity of N-OH-9,10-O-ODA on fluorite surface, resulting in its higher adsorption amount on fluorite surface.