Preparation and characterization of electro-spun nanofiber membranes and their possible applications in water treatment

Nano-scale materials can be designed to exhibit novel and significantly improved physical and chemical properties. Polymer nanofibers, an important class of nano-materials, have attracted increasing attention in the last 10 years because of their high surface-to-mass (or volume) ratio and special characteristics attractive for advanced applications. In particular, electro-spun nanofiber membranes (ENMs) have high porosity, interconnected open pore structure and tailorable membrane thickness. Moreover, their high surface hydrophobicity makes them suitable for membrane distillation (MD). In this paper, recent progresses are reviewed on the preparation of different types of nanofibers with different secondary nanostructures, including hollow nanofibers. Applications of hollow nanofibers for membrane separation processes are then discussed based on an imaginary design of hollow nanofiber module. Application of ENMs in MD is, on the other hand, not a product of imagination but experiments have already been conducted in various laboratories, as reviewed in this paper. In particular, the experimental results obtained in our laboratory for desalination of saline water and gases stripping of VOCs are highlighted. By using an electrospun PVDF nanofiber membrane, saline water with NaCl content of 6% was successfully desalinated for more than 20 days with no indication of membrane wetting. The PVDF ENM could also be successfully used in gas-stripping of chloroform, representing VOCs, with mass transfer coefficients higher than hollow fiber membranes. It is expected that MD by ENMs can be applied for many other purposes such as waste water treatment, food processing, and treatment of pharmaceutical products. (C) 2012 Elsevier B.V. All rights reserved.