Abstract: The oily wastewater produced by petrochemical enterprises is generated in large quantities and contains complex components, making the removal of emulsified oil a key and challenging aspect of the treatment process. Electrocoalescence demulsification technology has been increasingly attracted attention due to its advantages of high separation efficiency and no secondary pollution, but certain technical limitations are also faced. First, the demulsification mechanisms of oil-in-water (O/W) type emulsions under electric fields are systematically reviewed, and the influence of electric field parameters and the addition of demulsifiers on demulsification efficiency is analyzed. It is pointed out that long hydraulic retention time and low demulsification efficiency under flow conditions are considered the main constraints for industrial application. Then, the synergistic mechanism of electrocoalescence enhanced by materials is discussed from the aspects of increasing coalescence sites and shortening the migration distance required for oil droplet accumulation, and the influence of electric field parameters and material properties on demulsification performance is systematically summarized. Finally, in view of current research shortcomings, suggestions are proposed for future development, including that further in-depth studies be conducted on oil droplet motion and coalescence behavior, optimization of material properties and bed structure be pursued, and the design and integration of three-dimensional electrodes be explored.

Key words: oily wastewater, oil removal, emulsion, demulsification, electric field, coalescence materials, synergistic coalescence