Preparation, Characterization and Performance Study of New Polysulfone Based Nanofiltration Membranes for Water Filtration

Abstract

Nanofiltration (NF) is a membrane based liquid separation technology which displays separation characteristics in the intermediate range between Reverse Osmosis (RO) and Ultrafiltratiom (UF). RO is capable of producing very clean water and high concentrate rejection. UF may be used for removal of suspended solids and large organic molecules. Most of the membranes were prepared from organic polymers. Inorganic polymers tend to be expensive. Cellulose derivatives, polysulfone, polyamides polyvinyldifloride are presently available polymers which are being extensively used for membrane preparation. For membranes to be competitive with conventional technology, a membrane process needs to operate with a high rate of flux, high degree of selectivity and high resistance to fouling. There are three main areas of interest when it comes to improving membrane performance: the synthesis process, post-synthesis modification and application process. These three processes were focused and discussed in present work. Synthesis of polymers, chemical modification of polymers and surface modification of the membranes were performed and discussed in this thesis. Polysulfonylaminobenzamide (PSAB), methylated polysulfonylaminobenzamide (mPSAB), poly[(4-aminophenyl)sulfonyl]butanediamide (PASB) and methylated poly[(4-aminopheonyl)sulfonyl]butanediamide (mPASB) were synthesized. Chitosan (CS) was modified into N-Phthaloyl chitosan (NCS) and polysulfone (PSf) was modified into sulfonated polysulfone (sPSf). These polymers were blend with polysulfone for the preparation of NF membranes. Surface modification was mainly carried out by chemical modification, physical vapor deposition and beam irradiation. The general properties of prepared membranes fall in UF and NF regime. The properties varied depending on the nature of the polymer, the functional group present in the polymer and manufacturing process. It was shown that the novel polymers and polymer modification enhanced the performance of the membrane.