Oil droplet migration in the coupling of electric field and nano-confined shearing flow field: A molecular dynamics study

Electrocoagulation (EC) has become one of the main oily wastewater treatment method due to its low cost, high efficiency, and deep purification capability. In this study, the nano-oil droplet migration and deformation behaviors at different Reynolds numbers (Re), electrocapillary numbers (CaE), component types and SPAN (span-80) concentrations were investigated by molecular dynamics (MD) simulations. The weak interactions between SPAN&SiO2 (silicon dioxide) and ASP (asphaltene) molecules were mainly electrostatic interactions. The tendencies of oil droplet moving along the negative and positive x-axis were enhanced with respectively increasing CaE and Re, and the electric force (FE) was approximately equal to the shear force (FS) at CaE = 152.59 Re. The shearing flow field dominantly affected the tilt angle (θ), while the electric field mainly influenced the deformation ratio (D). ASP molecules were susceptible to FE, while RES (Resin) & HEX (n-hexane) molecules were susceptible to FS. In addition, the presence of both SPAN and SiO2 molecules can improve the oil droplet stability. The results can potentially provide theoretical guidance for the optimization of EC device.