Adsorption and accumulation of N2 at the solid–liquid interface: The impact of hydration films

The adsorption and accumulation of gases at the solid–liquid interface facilitate the formation of nanobubbles, offering significant benefits to the separation of fine mineral particles in flotation processes. In this study, a synergy of experimental and molecular simulation (MD) simulations was employed to elucidate the effects of mineral surface hydration film characteristics on the behavior of gas adsorption and accumulation in aqueous environment. The research findings indicate that, in comparison to hydrophobic graphite, there is an improvement in both the thickness and stability of the surface hydration film subsequent to the oxidation of graphite. After graphite oxidation, the difficulty of gas adsorption, accumulation, and the formation of nanobubbles in aqueous environments increases, with only a limited number of nanobubbles tending to accumulate within the hydrophobic regions of the oxidized graphite surface. MD simulations reveal that, despite N2 molecules primarily experiencing Van der Waals forces on methylated-substrate and carboxylated-substrate, the difference in their adsorption strength is relatively minor. However, the substantial contrast in H2O molecule adsorption on methylated-substrate and carboxylated-substrate prevents N2 molecules from penetrating the hydrophilic carboxylated-substrate's pre-adsorbed water layer, whereas adsorption and accumulation of N2 molecules occur on the hydrophobic methylated-substrate surface.