The adsorption mechanism of synergic reagents and its effect on apatite flotation in oleamide-sodium dodecyl benzene sulfonate (SDBS) system

Abstract The usage of synergic reagents plays vital role in the effective flotation of phosphate ore. In this paper, the adsorption mechanism of synergic reagents and its effect on apatite flotation in oleamide-sodium dodecyl benzene sulfonate (SDBS) system were investigated via micro-flotation experiment, Zeta-potential determination, X-ray photo-electron spectroscopy (XPS), and Time-of-flight secondary ion mass spectrometry (ToF-SIMS). Experimental research represented that a highest recovery rate of 97.09% could be obtained when a mixed collector dosage of 4 × 10−4 mol/L was used with a molar ratio of oleamide to SDBS of 2:1 at pH = 9.0, and the recovery could be improved by ~4.87% comparing with the theoretical recovery rate of single collector. Results of Zeta potential and XPS indicated that the chemisorptions of C17H33CONH−, (C17H33CONH2)m and sulfonate species originated from the mixed collector onto apatite surfaces occurred. More importantly, the adsorption of amide could be reinforced in the presence of SDBS, and the N atomic concentration increased from 1.23% to 1.66%. The results of ToF-SIMS further confirmed that the normalized peak intensities of C4H5+ and C4H7+ for apatite-oleamide-SDBS sample showed a statistically increase comparing with corresponding results of apatite-oleamide sample, while the normalized peak intensities of C6H4+ presented an opposite trend comparing with that of apatite-SDBS sample. The whole thickness of the formed hydrophobic species on the apatite surfaces was approximately 40.29 nm. The synergistic effects of mixed collector were mainly attributed to the improvement of solubility and dispersion and the decrease in critical micelle concentration of oleamide in the presence of SDBS, which provided easy access to the interaction between C17H33CONH−, (C17H33CONH2)m and apatite surfaces. The results provided a new path for apatite flotation, and reinforced the theoretical basis for flotation technique of phosphate ore.