Synergistic mechanism of mixed cationic/anionic collectors on lepidolite flotation from the perspective of improving the performance of flotation foam

As important factors in the flotation process, the surface activities and self-aggregation behaviors of mixed cationic/anionic collectors represented by dodecylamine (DDA)/sodium oleate (NaOl) and DDA/sodium dodecyl benzene sulfonate (SDBS) at the gas/liquid interface were investigated using surface tension measurements and molecular dynamics simulations. Some parameters, such as the saturation adsorption values, the average minimum area per molecule, the micellar interaction parameter, as well as the polar group-water radial distribution function, were calculated. Molecular dynamics simulations showed that the mixtures aggregated more easily due to weakening of electrostatic polar group repulsions. Compared with the pure DDA system, the mixtures, especially DDA/SDBS, were oriented more perpendicularly at the gas/liquid interface and generated a thicker hydrophilic layer that exhibited reduced surface tension and improved hydrophobicity. Moreover, due to the strong polarity of the benzene ring and the sulfonic group, the DDA/SDBS system showed better hydration than the DDA/NaOl system, which indicated that the DDA/SDBS system has higher surface activity than the DDA/ NaOl system. The simulation results were in good agreement with the flotation and surface tension results from this work, which explains why DDA/SDBS demonstrated better flotation performance than DDA/NaOl in improving the performance of the flotation foam.