Demulsification and oil recovery from oil-in-water cutting fluid wastewater using electrochemical micromembrane technology

A novel electrochemical micromembrane technology coupling membrane and electric method was developed to demulsify oily wastewater and recover oil. The diameter of the oil droplets increased to 55.0 μm from the initial 7.0 μm after treating the emulsion with the electrochemical micromembrane technology. Chemical oxygen demand removal rate and oil recovery reached 87.89% and 5173 mg/L, respectively, after cycling for 90 min at 10.0 V voltage with a 10.0 mm electrode distance, a 5.0 μm micromembrane pore size and a 0.5 L/min flow rate. Micromembrane pore sizes of 1.0 and 5.0 μm were both effective for decreasing chemical oxygen demand and recovering oil. The recovered oil was the mixture of mineral oil and ester according to the Raman infrared spectroscopy analysis. Surface charge redistribution and electrogenerated destruction for hydrophilic groups of surfactant molecules are responsible for oil coalescence. The electrochemical micromembrane technology used in this study offer an attractive treatment option to demulsify oily wastewater.