A novel anionic–nonionic mixed collector (SDBS/TOAM): synergistic effects and adsorption mechanism for the enhanced flotation of low-grade fluorapatite

Fatty acid collectors exhibit low efficiency in the flotation of low-grade fluorapatite (FAP). To address this problem, a novel mixed collector system composed of the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and the nonionic surfactant triolethanolamine oleate (TOAM) was developed. Flotation tests showed that the SDBS/TOAM mixture at a 1:1 M ratio improved the recovery by 4.8 % compared with SDBS alone. In artificially mixed ore flotation with starch as a hematite depressant, the recovery of the mixed system was still 6.5 % higher than that of SDBS alone, reaching 94.71 ± 0.17 % with a concentrate grade of 30.04 ± 0.35 %. Surface tension measurements indicated that the incorporation of TOAM generated a synergistic interaction with SDBS molecules, as evidenced by a significant reduction in the critical micelle concentration (CMC) of SDBS. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the mixed collector adsorbed onto the FAP surface mainly through chemical chelation with Ca 2+ and electrostatic interactions with O 2− sites, while atomic force microscopy measurements further confirmed that the surface became rougher after adsorption of the mixed collector. Molecular dynamics simulations further demonstrated that TOAM could intercalate between the sulfonate headgroups of SDBS, reduce the electrostatic repulsion among SDBS molecules, and promote aggregate formation through a bridging effect, thereby enabling more sulfonate groups to interact with the FAP surface and enhancing adsorption density. This study elucidates the synergistic adsorption mechanism of anionic–nonionic mixed collectors and provides important guidance for the rational design of efficient collectors for the flotation of low-grade phosphate ores. • Achieved 94.52 % fluorapatite recovery using a novel SDBS/TOAM mixed collector. • Revealed synergistic interfacial adsorption of SDBS/TOAM on fluorapatite surfaces. • TOAM intercalation between SDBS headgroups enhanced adsorption density on the fluorapatite surface. • Elucidated the synergistic adsorption mechanism of the mixed collector through FTIR, XPS, AFM, and molecular dynamics simulations.