Photo-responsive Mn-doped TiO2-based superhydrophobic/ underwater superoleophobicity membrane for efficient oil-water separation and photothermal decontamination

Abstract

In recent years, oily wastewater has become an important factor in environmental pollution. As a transition metal element, manganese is able to introduce new impurity band gaps using d-orbital hybridization to extend the photoresponse range of TiO2, thus enabling TiO2 to be self-cleaned under UV irradiation more easily. Therefore, we synthesized superhydrophobic/submerged superoleophobic Mn@TiO2-modified membranes which possess a self-cleaning property under UV light using manganese element-doped titanium dioxide and cotton fabric as the substrate by hydrothermal method and then investigated the relevance between the doping concentration of Mn and super-hydrophobicity. The results showed that water contact angles of prepared membranes with the Mn ions doping concentrations of 0.5 mol/L, 1.0 mol/L, and 1.5 mol/L were 147.89°, 150.43°, and 153.37°, respectively. The membrane with 1.5 mol/L was effective for the separation of the dichloromethane-water mixture. Under Xenon lamp irradiation, three membranes with different concentrations showed a significant temperature increase with the maximum rising to 53.1 ℃ within 2 min, reflecting an excellent photothermal conversion capability. In addition, the decontamination ability of the Mn@TiO2 membrane was tested under UV light. The Mn@TiO2 membrane was able to degrade the oil-red solution dripping on the surface, showing that the membrane had a good self-cleaning performance, which was significant for industrial applications.