Surface engineering for anti-wetting and antibacterial membrane for enhanced and fouling resistant membrane distillation performance

With the emergence of membrane fouling as a prominent issue in long-term MD performance, it has become imperative to manufacture superhydrophobic membranes with antibacterial properties. In this study, a novel superhydrophobic and antibacterial membrane is fabricated using trichloro(1H,1H,2H,2H-perfluorooctyl)silane (TPFOS) and titanium dioxide nanoparticles (TiO2-NPs) as chemical modifiers. The virgin PVDF membrane was pre-treated using PEG-co-PMAA, followed by plasma treatment, to enhance the COOH and OH groups on the top layer and promote formation of coordinate bonds on the membrane surface to TiO2. TPFOS was used to impart a superhydrophobic behavior to the titanium-enriched membrane surface. Membrane characteristics were investigated using SEM-EDS, FT-IR, AFM, XPS, porosimetry, and tensile strength analysis. The PVDF/PP-PT/Ti/Si (polyvinylidene difluoride/ coated PEG-co-PMAA-plasma treated/titanium nanoparticles/perfluorooctyl silane) composite membrane showed a superior contact angle of ~152° and a better self-cleaning ability than that of the pristine PVDF membrane. Plasma treatment of the membrane results in increasing the porosity of the membrane by the mechanism of polymer ablation. Furthermore, the superhydrophobic membrane displayed superior performance due to enhanced water flux and improved salt rejection over long-term DCMD operation. It also possessed excellent antibacterial properties, exhibiting a bacterial reduction of ~99% when tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This investigation demonstrates a simple approach to design multifunctional membranes showing anti-wetting, anti-bio-fouling, self-cleaning, and robust characteristics in MD desalination operations.