Combined Dip‐Coating and Spray Coating Techniques for Modifying PVDF Membranes With PDMS and TiO₂ for Photocatalytic Membrane Distillation

Membrane modification or functionalization techniques are widely studied to develop membranes with tailored properties for specific applications. This work investigates the combination of two methods—dip‐coating and spray coating—to impart photocatalytic properties to PVDF membranes for application in vacuum membrane distillation (VMD). Hydrophilic PVDF membrane samples are first immersed in PDMS solutions at concentrations of 5%, 7.5%, or 10% (wt/vol), followed by thermal curing in an oven. The membranes are then re‐immersed in the PDMS solution and spray‐coated with a mixture of water and ethanol at a ratio of 1:4 (vol/vol), and TiO 2 at concentrations of 1%, 1.25%, or 1.5% (wt/vol). Increasing the PDMS concentration does not lead to significant variations in membrane hydrophobicity, with contact angles consistently exceeding 124°. However, in the photocatalytic degradation of methylene blue (MB), PDMS concentration influences the degradation rate, while TiO 2 concentration enhances MB degradation, achieving over 85% efficiency. In VMD performance, salt rejection exceeds 90%, with TiO 2 showing no significant impact on membrane flux. Conversely, increasing PDMS concentration reduces membrane pore size, consequently affecting flux.