Simulation of fatty acid adsorption at the magnesia surface

In this study, wet surface modification converted the hydrophilic magnesia (MgO) surface to a hydrophobic surface, which is crucial for magnesia additives in polymer fire retardants, inks, cosmetics and paint and paper materials and in the flotation of magnesia. For this reason, the adsorption of fatty acids at the magnesia surface in the wet surface modification process was examined by molecular dynamics simulations. The sessile drop contact angles at the magnesia surface with monolayer adsorption of lauric acid (C₁₂H₂₄O₂), oleic acid (C₁₈H₃₄O₂) and stearic acid (C₁₈H₃₆O₂) and the interfacial water structures at the magnesia surface with sub-monolayer, monolayer and bilayer fatty acid adsorption were analyzed and compared with the experimental results. The sessile drop contact angle at the magnesia surface increased as a function of the carbon (C) chain length with fatty acid adsorption and agreed with the experimental results. All the fatty acids were adsorbed at the magnesia surface, and the interaction energy results agreed with the adsorption phenomenon. A hydrophobic surface was established in monolayer stearic acid adsorption and was transformed into a hydrophilic surface in stearic acid bilayer adsorption.