TiO₂ Composite Membranes And Its Water Filtration Property

The problems existed widely in membrane separation are the high cost of the membrane and membrane fouling, which directly affects the efficiency and economy of membrane separation. The purpose of this dissertation is to eliminate irreversible membrane fouling and reduce the cost of membrane separation. The nano-TiO₂ coating/casting solution was prepared by a sol-gel method and/or mixing with the dissolved organic polymer in solvents. The nano-TiO₂ inorganic/organic composite membranes were prepared by coating a layer of casting solution on the cheap industrial fabric followed by phase inversion treatment. The structures and characteristics of nano-TiO₂ inorganic/organic composite membranes are studied. A new nano-TiO₂ inorganic/organic composite membrane which is hydrophilic, antifouling and low-cost was obtained.(1) The nano-TiO₂ coating/casting solution was prepared by a sol-gel method and/or mixing with the dissolved polysulfone polymer in organic solvents (DMAC, NMP) . The nano-TiO₂ inorganic/organic composite membranes were prepared by coating a layer of casting solution on the cheap terylene (polyester) fabric or polypropylene non-woven cloth, followed by phase inversion treatment. The results showed that the composite membranes have uniform thick surface layer and loose reticulate cross structure. The nano-TiO₂ has good compatibility in composite membranes. The composite membranes show property of high flux, good rejection (The average rejection rate of kaoline minerals and yeast solution are more than 95%) , as well as antifouling and endurable features, which promises a wide application in water treatment.(2) To develop antifouling, low-cost MF/UF membranes, composite membranes are prepared by coating solution mixture containing highly hydrophilic chitosan, hydrophilic polyethylene glycol (PEG) and TiO₂ on the cheap terylene fabric or PP non-woven base membranes. The experimental results proved that increasing the concentration of chitosan in coating solution increased the rejection rate of turbidity minerals in solutions, reduced pure water flux of the composite membrane. Under the same preparative conditions, pure water fluxes of the produced composite terylene membranes are bigger than that of non-woven composite membranes, but rejection rates are lower than that of non-woven composite membranes. Chitosan composite membranes demonstrate good characteristics of anti-fouling. When the mass fraction of chitosan ,CH₃COOH, PEG,TiO₂ species are 1%, 2%, 4% and 1% in the coating solution, composite membranes had the best filtration performance. Addition of TiO₂ can improve the anti-fouling performance but shorten the filtration cycle period. By simple washing or immersion in the cleaning solution, the restoration percentage of flux ,as well as the flux decline rate of composite membrane are both better than that of the un-coated base membranes.