Systematic Design of a Flow-Through Titanium Electrode-Based Device with Strong Oil Droplet Rejection Property for Superior Oil-in-Water Emulsion Separation Performance.

ABSTRACT

Oily wastewater treatment has been restricted by the existence of stable oil-in-water (O/W) emulsions containing micrometer-sized oil droplets. However, the strong adhesion and stacking of emulsified oil droplets on the surface of current separation media cause serious fouling of the treatment unit and the rapid decline of treatment efficiency. Herein, a novel flow-through titanium (Ti) electrode-based filtration device with remarkable oil droplet rejection property was well designed for the continuously separating O/W emulsion. In contrast to the pristine Ti foam, the permeance of the TiO2 nanoarray-coated Ti foam (NATF) increased from 2538 to 4364 L m-2 h-1 bar-1 through gravity-driven flow. Further, more than ∼70% permeability can be maintained after 6 h of O/W emulsion filtration using the current device, the value of which was markedly higher than that of conventional oil/water separation filters (less than 5%). According to the results of wettability test, the super-oil-repellent surface endowed by this nanoarray structure primarily avoided the formation of a compact oil fouling layer. When the voltage was applied, accompanied by the electrophoresis effect, redistribution of surfactant molecules on the surface of oil droplets induced by an electric field made them readily captured by the microbubbles continuously generated from the electrode, thereby rapidly migrating these bubble-adhered oil droplets far from the filtration medium.