Fabrication and characterization of moderately hydrophobic membrane with enhanced permeability using a phase-inversion method in membrane distillation

Although membrane distillation (MD) is considered to be a potentially useful alternative desalination process, it presents challenges including membrane fouling and potential risk of wetting. In this study, a novel approach was adopted in an attempt to address these issues. MD membranes were prepared based on the phase-inversion technique to increase their hydrophilicity (to reduce fouling) and by adjusting the polymer concentration to decrease their pore size (to reduce wetting). MD membranes were fabricated by a non-solvent induced phase separation method using solutions containing polyvinylidene fluoride (PVDF), N,N-Dimethylformamide, and LiCl. The conditions for the preparation of membranes were optimized through a series of experiments. The results showed that the optimum concentration of PVDF was 14 wt.%. Membranes prepared under the optimum conditions had a low contact angle (75.67° ± 1.44°) and a small pore size (0.11 μm), leading to sufficient liquid entry pressure (2.93 ± 0.06 bar) for MD operation. In addition, the porosity of membranes was found to be high (84% ± 0.008%), resulting in a higher flux (average flux 20.2 ± 0.11 L/m2 h) than commercially available PVDF membrane. The membrane also showed a stable rejection (>99.9%) during long-term operation.