Fabrication of superhydrophilic and underwater superoleophobic CuxO/TiO2 mesh for oil–water separation

Abstract

Superhydrophilic and underwater superoleophobic meshes were fabricated for oil–water separation applications. High purity copper (Cu) meshes were anodized to produce a mixed-phase copper oxide (CuxO) layer. Titanium dioxide (TiO2) films were grown on the CuxO meshes via reactive sputter deposition in an admixture of argon and oxygen plasma followed by heat treatment. The CuxO/TiO2 meshes exhibited superhydrophilicity through the complete wetting of water in air. When the meshes were submerged underwater, the superoleophobic property was revealed using a mineral oil droplet with a contact angle of up to 151°. Separation of mineral oil from water (1:1 v/v) using the CuxO/TiO2 meshes was demonstrated using a custom-built separator. Chemical oxygen demand (COD) concentration measurement of the filtrates showed a decrease from 350 mg O2/L using a Cu mesh only to 84 mg O2/L using the CuxO/TiO2 mesh. Visible-light sensitivity was realized with the coupling of CuxO with TiO2. When the meshes were exposed to simulated solar light, self-cleaning property of the composite was activated. The visible-light irradiation of the used mesh exposed for at least 30 min degraded the residual oil thereby restoring the superhydrophilic property of the surface. The restoration would allow reusability of the CuxO/TiO2 meshes. After visible-light-induced cleaning of the mesh and reusing the mesh with a fresh oil–water sample, the COD of the filtrate was 86 mg O2/L.

Keywords

• Copper oxide
• Titanium dioxide
• Sputter deposition
• Anodization
• Oil–water separation