Electrospun nanofibrous polysulfone membrane for microfiltration

Abstract

Electrospinning creates sub-micron to nano-scale fibers through an electrically charged jet of polymer solution/melt. Through this process, non-woven membranes for separation technology can be developed. These electrospun nanofibrous membranes (ENMs) possess desirable attributes such as high porosity (>80%), pore sizes ranging from tens of nanometer to several micrometers, interconnected open pore structure and large surface area per unit volume, highly attractive as barrier materials for separation technology as well as biotechnology. This paper explores the viability of developing a fibrous membrane via electrospun nanofibrous web for separation technology and demonstrates its applicability in particulate removal. Polysulfone nanofibers were electrospun into membranes and characterized to relate its structural properties to membrane properties and performance. Membranes of different fiber morphologies and diameter were electrospun by varying the polymer concentration from 15, 18 and 20 %wt/vol. Beaded nanofibers (280 nm) were obtained from 15% solution and nanofibers of 350nm and 500nm from 18% and 20% solution respectively. Presence of beaded fibers and the thickness of the ENMs were observed to have a significant influence on the pore-size distribution, mean flow pore-size and bubble point. The presence of beads, if numerous, will lead to much reduced pore-sizes as well as porosity. Likewise, as the thickness of the ENM increased, the pore-size also reduced but this is due to more layers of nanofibers deposited that give rise to many more hindrance to flow path. It was shown that the ENMs can be successfully employed as filters for the removal of micro-particles above their bubble point. When the micro-particles are larger than the pores within the ENM, the membrane acts as screen filter and no fouling was observed. The ENM was most severely and irreversibly fouled when separating 2 and 1 um particles. However, to fully understand this phenomenon, more tests are required. When sub-micron particles were separated, they tend to get attracted to the surface of the nanofibers and thus the ENM acts a depth filter. The above findings highlight the potential of ENMs as barrier materials separation technology. There are immense potential applications both in biotechnology as well as water treatment. These membranes can be used as pre-filters prior to ultrafiltration or nanofiltration to minimize the possibility of fouling and contamination from micro-organisms or micro-particles. © 2007 American Water Works Association Membrane Technology Conference All Rights Reserved.