Preparation and characterization of PVDF/nonwoven fabric flat-sheet composite membranes for desalination through direct contact membrane distillation

The polyvinylidene fluoride (PVDF) flat-sheet composite membranes were prepared for membrane distillation using hydrophilic polyester nonwoven fabric as a support through coating and wet phase inversion process. The influence of non-solvent additive on membrane morphology, porosity, pore size and pore size distribution, hydrophobicity and permeability were evaluated. It was found that the membrane with a mixture of acetone and H3PO4 as non-solvent additive had a thinner top skin and a more porous network sponge-like layer from the morphology study. This membrane also exhibited a narrow pore size distribution and its mean pore size was about 0.22 mu m in diameter. The rough membrane surface with smaller nodules produced a higher contact angle of 82.6 +/- 0.7 degrees with water according to atomic force microscope images analysis. During the direct contact membrane distillation (DCMD) process of 35 g/L sodium chloride solution, the maximum transmembrane permeate flux about 47.6 kg/m(2) h was obtained with the feed solution at 80.5 degrees C and the cold distillate water at 20.0 degrees C. Furthermore, the membrane showed satisfying performance stability in the 240 h continuous desalination experiment, indicating that the prepared PVDF/nonwoven fabric flat-sheet composite membrane may be of great potential to be utilized in DCMD process for desalination. (c) 2012 Elsevier B.V. All rights reserved.