Fabrication and optimization of superhydrophobic ZnO-SA/PVC/PVP nanocomposite membrane distillation for highly saline RO brine recovery

The induced phase separation method was used to fabricate polyvinyl chloride (PVC) flat sheets for membrane distillation (MD) of RO brine feed by using dimethylformamide (DMF) and water as solvent and nonsolvent, respectively. Polyvinylpyrrolidone (PVP) and zinc oxide (ZnO) nanoparticles were utilized to improve the membrane structure and modify pore surfaces. The Taguchi experimental design approach was employed to investigate the impacts of concentrations of PVP and ZnO nanoparticles on the membrane's structural characteristics and performance. SEM, XRD, and FT-IR were used to characterize the surface and cross-sectional morphology, as well as the presence of crystalline phases and cross-linked organic groups, respectively. The water contact angle was measured to determine the wettability of the surface membrane and the impact of ZnO nanoparticles on its hydrophobicity. The membrane synthesis and MD process parameters were optimized for a Persian Gulf feed brine to obtain a maximum contact angle of 148°, under 80 °C and 12 L.min-1 circulating feed water, and resulted in high salt rejection (96.4%) and proper permeability water flux (4.2 L.m-2h-1).