Fabrication of Photo-Responsive Mesh Membrane with Surface-Engineered Wettability for Oil–Water Separation and Photocatalytic Degradation of Organic Pollutants

Abstract

A photo-responsive TiO2-coated stainless-steel mesh membrane (TiO2@SSM), possessing unique surface wettability, was fabricated. This TiO2@SSM membrane is found to be capable of separating oil and water from oily water and has the potential to carry out photocatalytic self-cleaning and/or the degradation of organic pollutants present in water. The fabrication of TiO2@SSM is quite simple: titanium dioxide (TiO2) nanoparticles were spray-coated onto stainless steel microporous mesh (SSM) substrates and annealed at the temperature of 500 °C. The fabricated TiO2@SSM membrane was structurally and morphologically characterized by XRD, FE-SEM, EDX, and elemental mapping. The contact angle measurements using a goniometer showed that the fabricated TiO2@SSM membrane surface is superhydrophilic and superoleophilic in air and superoleophobic under water. This is a favorable wetting condition for the water passing oil–water separation membrane, and this water passing property of the membrane eased the common problem of the fast clogging of the membrane by oil. An oil–water separation efficiency of about 99% was achieved, when the TiO2@SSM membrane was used as the separating medium in the gravity-driven oil–water separation system, unlike the uncoated stainless steel mesh membrane, which allowed both oil and water to pass together. This confirmed that the oil–water separating functionality of the membrane is attributed to TiO2 coating on the stainless steel mesh. The photocatalytic degradation property of the TiO2@SSM membrane is an added advantage, where the membrane can be potentially used for self-cleaning of the membrane’s surface and/or for water purification.