Hyflon/PVDF membranes prepared by NIPS and TIPS: Comparison in MD performance

Membrane distillation (MD) is a promising technology for the treatment of highly saline waters. However, there are few microporous hydrophobic membranes, available as hollow fibers and flat sheets, properly manufactured for MD. In the present paper, highly hydrophobic Hyflon/PVDF composite hollow fiber membranes were prepared by coating three kinds of Hyflon AD on poly(vinylidene fluoride) (PVDF) membranes. The PVDF hollow fiber membranes were prepared via two different techniques (i.e. NIPS and TIPS). The six different Hyflon AD/PVDF composite membranes were characterized and tested in MD, both in direct contact (DCMD) and vacuum (VMD) configuration. The testing of the membranes in VMD showed that the performance of the different membranes was, as expected, strongly dependent on pore size, porosity, liquid entry pressure (LEP) and contact angle (Phi). DCMD experiments revealed that another parameter influencing the membrane performance is the thickness because it allows reducing the heat loss due to conduction through the membrane.