Synergetic adsorption of dodecane and dodecylamine on oxidized coal: Insights from molecular dynamics simulation

• We simulate the wettability of oxidized coal surface using MD simulation. • We investigate the synergetic adsorption of DDC and DDA on oxidized coal. • Adsorption of DDC can promote the effective adsorption of DDA cations on oxidized coal through dispersion interaction. • Synergistic adsorption of DDC and DDA is beneficial to the efficient separation and settlement of oxidized coal. In order to explore the synergetic adsorption mechanism of nonpolar hydrocarbon oil and cationic amine on OC (oxidized coal) surface, the MD (Molecular Dynamics) simulations were used to simulate the wettability of OC surface and the dynamic characteristics of DDC (Dodecane)/DDA (dodecylamine) adsorption on OC/water interface under different complex conditions. Water molecules in a nano water droplet have strong hydrogen bond adsorption with the OC surface, which is easy to be wetting and spread along the surface to occur strong hydration of OC surface. DDC can adsorb on OC surface well, while DDA cations can not. When DDC and DDA are co-adsorbed on OC surface, can have a synergistic adsorption effect. The synergistic adsorption mechanism is mainly that, after DDC adsorbed on OC surface, its carbon chain will adsorb partial DDA cations through dispersion interaction, thus promoting the effective adsorption of DDA cations on OC surface. Synergistic adsorption of DDC and DDA can not only improve the surface hydrophobicity of OC, but also reduce the surface negative electricity through the adsorption of DDA cations, to achieve the effect of effectively promoting the agglomeration of particles, which is very beneficial to the efficient separation and settlement of oxidized coal.