Comparison of constant, pulsed, incremental and decremental direct current applications on solid-liquid phase separation in oil sediments

[Display omitted] •Electrokinetic treatment of oil sediments used for water, soils and oil seperation.•Four different electrical regimes was applied to evaluate phase separation.•Conductive liquid and solids moved to the opposite direction.•Higher light hydrocarbon separation was obtained using IDC and DDC.•DDC and IDC were the most effective in inducing phase separation. Phase separation of oil wastes can mitigate the effects on the environment, by decreasing the volume of hazardous materials and regenerate energy. This study focused on the advanced electrokinetic method as a treatment technology to treat oil sediments from oil refineries and separate them into their individual phase components. The effects of four types of electrical field on the phase separation of oil sediments from an oil refinery were investigated namely constant direct current (CDC), pulsed direct current (PDC), incremental direct current (IDC) and decremental direct current (DDC). The results showed that the extent and quality of phase separation differed based on the type of electrical current applied, and indicated that different mechanisms such as electroosmosis, electrophoresis, electro-demulsification, and electro-sedimentation might have been involved in the separation process depending on the type of electrical supply. The application of DDC and IDC was found to cause a significant separation of solids by electrophoresis with the movement of almost 70% of solids to the anode of the reactors. The DDC and IDC regimes resulted in the most efficient phase separation of the oil sediments, and even incurred a highly resolved separation of light hydrocarbons at the top anode.