PhD Oral Qualifying Examination : Development of Hollow Fiber Membranes for Air Filtration Applications

Speaker Wang Liang-Yi (Supervisor(s): Prof Chung Tai-Shung, Neal and A/Prof Yu Liya)

Host Department of Chemical and Biomolecular Engineering

Date/Time 30 May - 30 May, 2.00pm

Venue E5-02-32 , Faculty of Engineering, National University of Singapore


In order to minimize the growing concerns of adverse air pollutions, many efforts have been devoted to develop filters for airborne particles removal. Compared with conventional fibers filter media, hollow fibers feature of self-supported properties with tunable pore sizes, which makes hollow fibers a good candidate for filtration processes. This study reveals as the first attempt to apply hollow fibers for air filtration of ultrafine particles. The most challenging part to make hollow fiber air filters is to lower membrane resistance while maintaining a high filtration efficiency. Therefore, different approaches were applied to fabricate high gas permeance hollow fibers. Firstly, different molecular weights of polyethylene glycols (PEGs) were added into spinning dopes. The formation of loosely connected cross-section and porous outer skin enhanced the gas permeance of polyvinylidene fluoride (PVDF) hollow fibers. Secondly, a dilute PVDF dope with SiO2 additives was used to prepare hollow fibers. After etching out SiO2 by KOH, the hollow fibers displayed a N2 permeance of 8.1 x 105 GPU. All the developed hollow fibers showed excellent filtration efficiency of > 99.999% against polydispersed sodium chloride (NaCl) and bis(2-ethylhexyl) sebacate (DEHS) particles with a geometric mean size of ~30 nm and ~50 nm. Moreover, the filtration efficiency remained at > 99.999% over 36 hour continuous filtration experiments under a highly polluted situation with a very small increment in pressure drop of 100 Pa. In the future, the hollow fiber with higher mechanical properties will be developed to make fibers easier to be handled and scale-up. Moreover, to increase the reusability of hollow fibers, different cleaning strategies will be studied.