The Development of Chlorine Resistant Ultrathin Film Composite Membranes from Soluble Aromatic Polyimide Thin Films on Polybutylene Terephthalate Supports

摘要

Disclosure of the first asymmetric cellulose acetate reverse osmosis (RO) membrane stimulated considerable interest in synthetic polymeric membranes. Commercial diaminophenylindane (DAPI) polyimides had specified properties indicative that they could be modified and converted into chlorine-resistant RO membranes of both integrally skinned (asymmetric) and ultrathin film composite types, but DAPI-based polyimides showed a lack of resistance to degradation by both chlorine and chlorosulfonic acid. New support membranes of poly(butylene terephthalate), PBT, were shown to be resistant to chlorine and most organic solvents, and more wettable than polysulfone membranes. Membranes of PBT may prove an attractive alternative to polysulfone supports, especially if a replacement for the expensive hexafluoroisopropanol solvent can be found. PBT membrane pore size could be controlled by air velocity adjustment above the nascent membrane. Further, it was concluded that sulfonation was generally unsuited for increasing hydrophobic membrane polymer hydrophilicity, and that anionic-exchange type ionogenic RO membrane polymers were superior to cationic tupes in both processing and end-use characteristics. Thus, future work will focus on polymers bearing quaternary ammonium groups, rather than sulfonate groups.