CF4 plasma modified highly interconnective porous polysulfone membranes for direct contact membrane distillation (DCMD)

Preparation of MD membranes with a low tortuosity and high DCMD flux is reported. Hydrophilic flat sheet polysulfone (PSf), blended with polyvinylpyrrolidone (PVP) membranes were prepared by dual-bath coagulation phase inversion, where N-methylpyrrolidone (NMP)/water mixtures were used as the first coagulant before immersion into a water bath. CF4 plasma modification was utilized to render the originally hydrophilic membranes hydrophobic. The membranes were characterized by scanning electron microscopy (SEM), water contact angle, X-ray photoelectron spectroscopy (XPS), liquid entry pressure (LEPw), and gas permeability. Results demonstrated that the first coagulation bath acted as a dense skin layer remover in comparison to a PSf membrane prepared in a single water bath. CF4 plasma modified porous PSf membranes using pure NMP as the first coagulant showed a contact angle of 144 degrees and a DCMD flux of 5333 kg/m(2) . h (T-f = 70.3 degrees C), which was 80% higher than a commercial PVDF membrane with comparable performance stability. Heat and mass simulation modeling results demonstrated that the tortuosity of the PSf membranes is close to 1 in contrast to 2.5 for the commercial PVDF membranes. This result provides some theoretical understanding of the origin of the high performance of PSf MD membranes. (C) 2015 Elsevier B.V. All rights reserved.