Nano-Enhanced Composite Membranes for Water Desalination

This project presents a potential alternative desalination technique that utilizes the ion rejection properties of single walled carbon nanotubes dispersed in a lyotropic liquid crystal (LLC) matrix. Previous research has pointed to the polymerizable surfactant methacryloxy ethyl hexadecyl dimethyl ammonium bromide (C16MA) having capabilities of filtering molecular components smaller than a nanometer, when oriented in cylindrical micelles. SWCNTs were dispersed in deionized water by probe sonication and addition of surfactant cetyltrimethylammonium bromide (CTAB) due to SWCNTs’ hydrophobic properties. Membranes were produced containing 55wt% C16MA, 37wt% DI water, 0.1wt% with respect to the monomer (WRM) SWCNTs, 1.9 wt% WRM 2,2-dimethoxy-2-phenylacetophenone (photointiator), 3 wt% WRM CTAB, 3.8 wt% WRM N,N-methylenebisacrylamide (water soluble crosslinker), and 5.3wt% WRM tetraethylene glycol diacrylate (water insoluble crosslinker). The resulting photopolymerizable gel was pressed between two glass slides onto a polyethersulfone membrane to produce a defect free membrane. When UV-polymerized, the crosslinked surfactant forms an LLC which theoretically contains SCWNTs in highly ordered interstitial sites. Pressure driven filtration of tap water through the membranes was conducted. Flux rates were compared between samples with SWCNTs, without SWCNTs, and a polyethersulfone membrane. The SWCNT membrane demonstrated no defects when undergoing filtration. Further investigation of the membranes produced through the gel press method must be conducted to confirm the efficacy of desalination with these membranes.