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Development of a composite membrane with underwater-oleophobic fibrous surface for robust anti-oil-fouling membrane distillation

Wang, Kunpeng, Hou, Deyin, Qi, Peng, Li, Kuiling, Yuan, Ziyi, Wang, Jun
Journal of colloid and interface science 2019 v.537 pp. 375-383
adhesion, asymmetric membranes, coatings, crosslinking, distillation, fouling, hydrophilicity, hydrophobicity, nanofibers, oils, petroleum, sodium chloride, spectroscopy, thermal stability, thermoplastics, wastewater, wettability, zeta potential
Membrane fouling caused by non-polar foulants is a challenging problem for hydrophobic membranes, which hinders the industrial implementation of membrane distillation (MD). The hydrophilic coating can create a hydration layer at solid-water interface, thereby the hydrophilic surfaces are expected to supply a barrier inhibiting adhesion of hydrophobic foulants. Hence, it should be possible to develop anti-fouling composite membranes through constructing a hydrophilic skin layer onto hydrophobic MD membranes. Herein, we fabricated a novel composite membrane for excellent anti-oil-fouling performance in MD process by electrospinning polyetherimide (PEI) nanofibers on the hydrophobic polyvinylidene fluoride (PVDF) membrane surface, followed by cross-linking with ethanediamine (EDA). The membrane morphology and structure properties, surface zeta potential and wettability, thermal stability were all systematically characterized, and force spectroscopy was used to quasi-quantitatively evaluate oil-membrane adhesion force. Compared with the PVDF membrane, the PVDF/PEI-EDA composite membrane exhibited strong resistance to crude oil with underwater oil contact angle of about 145° and low oil-membrane adhesion force, which contributed to the stable performance during MD desalinating an oily and saline solution. The fabricated composite membrane with underwater-oleophobic fibrous surface can effectively mitigate oil-fouling in MD and promote MD to treat highly saline wastewater with high concentration of hydrophobic foulants.