Development of Novel Porous Substrates for Ultrafiltration, Desalination and Water Reclamation: Part III

摘要

The objective of this overall project was to develop novel porous supports which can be used to fabricate composite membranes for desalination and water reclamation by reverse osmosis. Two commercially-available polymers were integrated: poly (phenylene oxide) and ethyl cellulose. The former (PPO), chemically-modified to the desired porous support via common water coagulating techniques, was described previously. The development of the ethyl cellulose (ET) support is currently reported. Several attempts to prepare the asymmetric (salt-rejecting) membrane from ET had limited success, and was discontinued due to inferior performance and particulate contamination in the commercial grade ET polymer. The attractiveness of ET over cellulose acetate resides in its pendent ester linkages (stable over a wide pH range), much lower surface energy and hydrophilicity, and, hence, the fine porous matrix prepared from ET via phase inversion by water coagulation does not collapse on drying. A variety of porous substrates were developed and studied. Further, hollow fibers and composite desalination membranes were prepared; the latter providing information for the preparation of conventional composite membranes using the ET substrate. Membranes developed from commercial ET were macrovoid-free, having a morphology corresponding to the ultimate structure needed from such porous supports. Membrane morphologies were studied using scanning electron microscopy.