Development of highly efficient composite hollow fiber membrane used for membrane distillation_fabrication of single layer hollow fiber membrane

• Main Author: Li, Guo Liang.
• Other Authors: Wang Rong
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Environmental engineering::Water treatment
• Online Access: http://hdl.handle.net/10356/39566
• Institution: Nanyang Technological University

In this era of water shortage, converting sea water into fresh water becomes more and more important. As an alternative approach for desalination, membrane distillation process with hollow fiber membranes attracts much attention. However, MD process has not been widely applied to industrial use yet. One of the main barriers is due to its relatively low permeate flux. This project aims at preparing various polyvinylidene fluoride (PVDF) hydrophobic hollow fiber membranes with different structures and water permeations properties, which are intended for use in the MD process. PVDF hollow fibers were prepared with different dope formulas and spinning conditions through the dry jet wet-spinning process. Dimethyl acetamide (DMAc) was used as solvent; Polyethylene glycol (PEG)200 and Pluronic F127 were used as an additive to the solution respectively. It is found that higher polymer concentration and smaller air gap distance would reduce the quantity and size of the voids formed in the hollow fibers. Solutions containing PEG200 and Pluronics F127 formed different membrane structures. Pluronic F127 appeared to form more porous fiber structure than PEG200, while PEG200 would dissolve out of the membranes faster. DI water and 20wt. % methanol were used as the internal coagulants respectively. Methanol, as a weak non-solvent, formed fibers with only outer skins, eliminating the inner skins. Sponge-like interconnected structures were present as the inner wall of the fibers. A better understanding on the membrane formation was attained through this study, which would provide useful experiences for the further development of MD hollow fiber membranes.