Preparation and characterization of polyvinylidene fluoride membranes for membrane distillation

Polyvinylidene fluoride (PVDF) flat-sheet membranes were prepared for membrane distillation (MD). Pure water was used as a pore-forming additive in the casting solution. Dimethylacetamide (DMAC) was used as the solvent. The polymer solutions were cast over a glass plate or over a nonwoven polyester backing material. The prepared supported and unsupported PVDF membranes were characterized in terms of their nonwettability, pore size and porosity. MD experiments were carried out using a vacuum membrane distillation (VMD) configuration and employing pure water or chloroform/water binary mixtures as the feed. The influence of some relevant parameters, such as the feed temperature, stirring rate, or downstream pressure on the MD flux was studied. The effect of water in the casting solution on the geometrical properties of the membrane is discussed and evaluated. The dependence of the MD flux and separation factor on the geometrical properties of the supported and unsupported membranes was also studied.