Preparation, characterisation and performance of polyvinylidene fluoride membrane for sodium chloride rejection in direct contact membrane distillation

In this study, two types of hydrophobic polyvinylidene fluoride hollow fibre membranes were fabricated by the wet/dry phase inversion method with N,N-dimethylacetamide and N-1-methyl- 2-pyrrolidone as solvents, respectively. The effects of solvent on the membrane characteristics were investigated based on the results of gravitational method and scanning electron microscope. The gravitational test revealed that the membrane porosity and pore size could be improved with the use of N-1-methyl-2-pyrrolidone solvent. The scanning electron microscope images of membrane cross-section demonstrated a similar finger-like layer structure in both membranes, extending from inner to outer surface. Lastly, the performance test of sodium chloride removal by direct contact membrane distillation indicated that the polyvinylidene fluoride membrane with N-1-methyl-2-pyrrolidone solvent had a better performance in relative to that with N,N-dimethylacetamide solvent. This finding implied that the polyvinylidene fluoride membrane with N-1-methyl-2-pyrrolidone as solvent had the greater potential to be utilised in water and wastewater treatment.