Tri-bore PVDF hollow fibers with a super-hydrophobic coating for membrane distillation

•Tri-bore hollow fiber to improve mechanical strength.•Teflon® AF 2400 coating to form super-hydrophobic surface with a contact angle of 151°.

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° 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.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (143 K)Download as PowerPoint slide