Photoswitchable and reusable superhydrophobic/hydrophilic TiO2-coated stainless-steel mesh as oil–water separator

This study fabricated a superhydrophobic/hydrophilic stainless-steel mesh with a TiO2-coated surface for efficient oil–water separation. The mesh manifested both hydrophobic and hydrophilic properties upon incorporating fluorine- and amine-containing silanes, respectively. The photoswitching speed and recovery of surface properties were evaluated by adjusting the UV irradiation period. Additionally, the mesh was subjected to ultrasonic treatment to enhance the photoswitching speed. After alternating UV irradiation and ultrasonification treatments, the variations in contact angle confirmed the feasibility of reversible surface conversion: 158° → 15° → 149.4° → 9.1° → 146.8° → 8.4° → 147.3°. Furthermore, the oil–water separation efficiency of the fluorine-modified mesh was assessed using water and n-hexane solutions. Over eight cycles, the hydrophobic/hydrophilic mesh achieved an average separation efficiency of 95.3% and 96.7%, respectively. The separation process occurred within approximately 5 s. Thus, this study proposed a comprehensive approach for developing a single superhydrophobic mesh capable of facile and rapid photoswitching between hydrophilic and hydrophobic properties. The developed mesh offers precise filtration, durability, and reusability, contributing to sustainable oil–water separation processes.