Enhancing membrane performance in removal of hazardous VOCs from water by modified fluorinated PVDF porous material

Fluorinated membranes have significant importance in separation due to their inertness, fouling resistance. A novel modification methodology of poly(vinylidene fluoride) (PVDF) membranes was developed employing piranha reagent to activate the fluorinated surface followed by consecutive grafting with 1H,1H,2H, 2H-Perfluorooctyltriethoxysilane (FC6). Membranes were implemented in membrane distillation for the removal of hazardous volatile organic compounds (ethyl acetate - EtAc) from water. Octyl group functionalized membranes were also tested for comparison. Membranes were characterized using AFM, ATR-FTIR, SEM, DSC, XRD, goniometric and porometry techniques. Results showed a significant improvement in the membrane performance. Flux of EtAc and PSI changed in the following way between pristine (J(EtAc) = 1.8 kg h(-1) m(-2), PSI = 33 kg h(-1) m(-2)) and 1-min activated membrane (J(EtAc) = 3.0 kg h(-1) m(-2), PSI = 72 kg h(-1) m(-2)). Furthermore, for functionalized sample with FC6 the performance was following JEtAc = 5.2 kg h(-1) m(-2) and PSI = 227 kg h(-1) m(-2). The activation and functionalization influenced significantly material properties. Higher roughness, contact angle and more open structure were noticed after 1-min activation (RMS = 182 nm, CA = 122 degrees, 0.797 mu m) in comparison to pristine one (RMS = 142 nm, CA = 116 degrees, 0.551 mu m). An improvement of mechanical features was also observed comparing pristine (F-adh = 25.2 nN, H = 0.13 GPa, E = 2.10 GPa) and the membrane functionalized by FC6 (F-adh = 19.3 nN, H = 0.27 GPa, E = 2.38 GPa).