In this work, the detachment mechanism of oil molecules from the hydrophobic solid surface in the aqueous surfactant solution is studied with lattice Monte Carlo simulations. Three different mechanisms for oil removal, including oil carrying microemulsion model, oil film stripping model, and surfactant-aided diffusion model are identified. The molecular mechanisms that agree with experimental observations are found to be dependent sensitively on surfactant structure. (C) 2015 Elsevier B.V. All rights reserved.