Nanostructured TiO₂/CuO dual-coated copper meshes with superhydrophilic, underwater superoleophobic and self-cleaning properties for highly efficient oil/water separation

Oil-contaminated water caused by either oil spill disasters or industrial disposal has posed a global risk to environmental sustainability and human health. To address the ever-growing need for highly efficient separation of oil/water mixtures, nanostructured TiO₂/CuO dual coatings were fabricated on the copper mesh by a combination of electrochemical anodization and layer-by-layer self-assembly deposition to render its surface with superhydrophilic, underwater superoleophobic and self-cleaning functionality. Cu(OH)₂ nanoneedle arrays (NNA) were vertically grown from the copper mesh surfaces by electrochemical anodization processes, followed by the deposition of TiO₂ multilayer on the Cu(OH)₂ NNA via layer-by-layer assembly prior to being calcinated to form TiO₂/CuO dual coatings. The nanostructured TiO₂/CuO NNA dual-coated copper meshes were demonstrated to exhibit a high separation efficiency (oil residue content less than 20 ppm), excellent water flux (more than 80 kL·h⁻¹·m⁻²), and desirable self-cleaning ability under ultraviolet (UV) illumination. The photo-catalytic ability of the deposited TiO₂ layers enabled the facile and rapid removal of the oil contaminants on the mesh surface under UV illumination to recover oil/water separation ability of the as-fabricated mesh for recycle use. With the adherent features of superhydrophilicity, underwater superoleophobicity and self-cleaning ability, the proposed TiO₂/CuO NNA dual-coated meshes are potentially useful in practical oil/water separation applications.