Synergistic adsorption of DDA/alcohol mixtures at the air/water interface: A molecular dynamics simulation

As one of the most important auxiliary collectors, alcohol is commonly used together with amine collectors in the flotation of oxide minerals to improve their grade and recovery. As important factors in the flotation process, the surface activity and self-aggregation behavior of DDA/alcohol mixtures at the water/air interface were investigated using molecular dynamics simulation and surface tension measurement. Four alcohol surfactants with different chain lengths, octanol (OCT), decanol (DEC), dodecanol (DOD), and tetradecanol (TER), were chosen to investigate the influence of the alkyl chain length on the surface activity and aggregation behavior. Molecular dynamics simulations show that DDA/alcohol mixtures exhibit strong synergism at the air/water interface and form compact packed hydrophobic films, compared to pure DDA at the same concentration. The mixtures appear to aggregate more easily due to the weakening of the electrostatic DDA headgroup repulsion. Among these four alcohols with different chain lengths, DDA/DOD and DDA/TER mixtures show good compatibility between surfactants tails, therefore, they can form the most tightly packed films at the air/water interface. Our simulation is in good agreement with previously reported data and surface tension results from this work. Therefore, this research on the molecular scale provides vital information on the surface behaviors of mixed surfactants at the air/water interface.