Effect of Metal Cations on the Kerosene/Water Interfacial Tension in Flotation Conditioning

In order to investigate the mechanism of metal cation diffusion at the kerosene/water interface and its effect on the oil/water interfacial tension, the migration patterns of Na⁺, Mg²⁺ and Al³⁺ with different concentrations and ionic valence states at the kerosene/water interface and the effect mechanism on the kerosene/water interfacial tension were investigated, using molecular dynamics simulation, interfacial static equilibrium analysis and high-speed camera dynamic acquisition test techniques. The results of the interfacial tension test showed that the interfacial tension between ionic solution and kerosene decreased with the increase of ionic valence state. Meanwhile, the results of molecular dynamics simulation and hydrostatic analysis showed that kerosene exhibited amphiphilicity at the oil/water interface, where the hydroxyl groups were directed toward the water molecules and the alkyl chains were directed toward the kerosene molecules. The number of water molecules entering the molecular gap of kerosene increased with the number of ions in water. The equivalent diameter of oil droplets increased with the increase of ionic valence, and oil droplets needed more internal energy to break through the surface energy of the oil/water interface, resulting in an increase of oil droplet volume, i.e. d_Al³⁺ > d_Mg²⁺ > d_Na⁺. The experimental results provide some theoretical support for the timely adjustment of metal cation types and concentrations in the flotation process, elimination of metal ions unfavorable to flotation performance, and improvement of flotation efficiency.