Influence of ionic strength and surfactant concentration on the alkane contaminant desorption in solution: A molecular dynamics simulation

• The desorption of alkane molecules from solid surface in solution is investigated by molecular dynamics simulation. • The effects of ion concentration are discussed in detail. • The effects of surfactant concentration on the oil droplet desorption are investigated. • The equilibrium and non-equilibrium molecular dynamics simulations are performed to investigate three key factors. The cleaning of the optical and mechanical components in a high-power laser system is essential for the cleaning control of the high-power laser system. Many factors affect the cleaning efficiency of the solution cleaning. Ion concentration, surfactant concentration and molecular weight of organic molecules are three key factors. In this article, equilibrium and nonequilibrium molecular dynamics simulations are performed to investigate the interfacial interaction among fluid, substrate and oil droplets and the dynamic desorption process of the oil droplet. As the increase of ion concentration, the contact angle of the oil droplet decreases, and the height of the oil droplet decreases slightly. Higher ion concentrations make the oil droplet more hydrophobic because of the reduction in hydrogen bonds between oil droplets and water and the reduction in residual time. In water flow simulation, high ion concentration is not beneficial to the desorption of oil droplets. Pure water flooding is not effective as brine flooding, which is related to water flow velocity. High surfactant concentration is beneficial to the desorption of oil droplets without water flow. Alkane molecule with larger molecular weight is difficult to detach from the solid surface, since the higher interaction energy between alkane molecule and substrate.