Reversible conversion superwetting coatings with TiO₂-based heterojunction materials for enhancing efficient oily...

Oily wastewater, such as from oil spills, chemical leaks, and organic pollutants, has become a serious environmental pollution problem. Superhydrophobic cotton fabric has attracted extensive research interest as an ideal material for handling oily wastewater, but this solution is difficult to balance efficient oil-water separation and removal of organic pollutants in complex oily wastewater. Therefore, the combination of superwetting and photocatalysis is expected to provide an efficient and simple solution. Firstly, heterojunction g-C₃N₄/TiO₂ (CNTi) was synthesized via thermal polymerization; vinyl-terminated dimethylpolysiloxane (V-PDMS) and acrylic acid (AA) were polymerized using free radical polymerization, and then superwetting coating cotton fabric (V-PDMS/AA/CNTi/CF) was co-constructed by a facile dip coating method. The as-prepared superwetting coating strategy was considered suitable for a wide range of substrates, providing new perspectives for the practical application of constructing bifunctional materials with reversible conversion wettability and photocatalytic degradation. Through a pH-responsive reversible conversion wettability mechanism, for different types of oil/water mixtures, the separation efficiency reached more than 99 % for heavy-density oil/water mixtures and more than 96 % for light-density oil/water mixtures, with excellent recoverability and stability. In addition, it demonstrated highly selective degradation of organic pollutants such as Rhodamine B, methylene blue, methyl orange, tetracycline hydrochloride, and levofloxacin hydrochloride. The main active species for photocatalytic degradation were identified as the superoxide radical anion (·O₂¯) and the hydroxyl radical (·OH) through quenching experiments. This work combined highly efficient oil-water separation and photocatalytic degradation technologies to provide a new approach and solution for the design of multifunctional water purification materials.