(485g) Tri-Bore PVDF Hollow Fibers with a Super-Hydrophobic Coating for Membrane Distillation

Membranes with good mechanical strength, high vapor flux and outstanding anti-wetting properties are essential for membrane distillation (MD) applications. In this work, porous polyvinylidene fluoride (PVDF) tri-bore hollow fiber membranes with super-hydrophobicity are developed to achieve these desired properties. The tri-bore hollow fiber offers better mechanical strength than the conventional single-bore fiber. To improve its anti-wetting properties, Teflon^® AF 2400 is coated on the membrane surface. The effects of coating on membrane morphology, performance and anti-wetting properties have been thoroughly investigated. With an optimal coating condition (0.025 wt% of Teflon^® AF 2400, 30 s), a super-hydrophobic surface with a contact angle of 151^o is achieved. The resultant membrane shows an increase of 109% in liquid entry pressure (LEP) with a slight sacrifice of 21% in flux. Long term direct contact MD tests have confirmed that the Teflon^® AF 2400 coated membrane has enhanced stability with an average flux of 21 kg m^-2 h^-1 and rejection of 99.99% at 60 C for desalination application.