Fabrication and VMD Performance of TiO2 Nanocomposite PVDF Membranes and PVDF-PTFE Composite Membranes

Abstract

In this study, two different strategies were carried out to modify the polyvinylidene fluoride (PVDF) distillation membrane for desalination. The first strategy was the addition of TiO2 nanoparticles into the target membranes and a synergistic effect of hydrophilic and hydrophobic nanoparticles was found for the first time in this work. And the other strategy was the introduction of another polymer material, polytetrafluoroethylene (PTFE), to the PVDF membranes to fabricate a flat sheet PVDF-PTFE composite membrane and this is the first attempt that such a membrane to be made. Two types of membranes were characterized by scanning electron microscopy (SEM) detection, porosity measurement, energy dispersive X-ray spectroscopy (EDX), Attenuated total reflectance (ATR)-Fourier transformed infrared spectroscopy (FTIR), contact angle (CA) measurement, atomic force spectroscopy (AFM) detection and liquid entry pressure of water (LEPw) measurement. Their performance was evaluated by vacuum membrane distillation (VMD) experiments. And the best VMD pure water permeate flux of the membranes fabricated under these two modify strategies could achieve 4.26 kg/m2h (M-L5-B2) and 5.61 kg/m2h (M-40), respectively, when that of pure PVDF membrane is only 0.71 kg/m2h. The salt rejection of the prepared composite membranes are all stably higher than 99.5% which demonstrate their capacity for desalination.