Study On Surface Modified TiO₂-SiO₂/PSF Composite Membrane And Its Properties

The treatment and reuse of the waste water especially waste water containing oilfrom industry and household have great significances, in terms of solving the problemof shortage of water resources, protecting environment and maintaining sustainabledevelopment of human beings. Membrane processes have received significantattention as a promising technology for separation of liquid mixtures and waterpurification processes because of their simple operation, low operating costs andeffective removement of the emulsified and soluble oil in wastewater. However,practical applications of PSF membranes for treating wastewater containing oil arelimited because of its poor anti-fouling and mechanical properties. Consequently,enhancing the hydrophilic property, anti-fouling capability and mechanical propertyof PSF membrane by adding material is now the focus of many researchers.It can be explained by the model of Tanabe that the TiO₂-SiO₂composite particleshows super-hydrophilic property because there are abundant Br nsted acid sites onthe surface of the TiO₂-SiO₂material. In this study, the surface modified TiO₂-SiO₂particle （SM-TS particle） with low surface energy and strong hydrophilicity wasprepared by modifying TiO₂-SiO₂particle with silanization and phosphorylation.Then the particle was added into the polysulfone （PSF） membrane and thenSM-TS/PSF composite membrane was prepared by phase inversion method. Theoptimum preparation conditions of SM-TS/PSF composite membrane were: theconcentration of PSF is15wt.%, the concentration of porogen （PEG400） is4wt.%, theratio of SM-TS/PSF is10wt.%.SEM micrographs of cross section of SM-TS/PSF composite membrane showthat SM-TS particles uniformly dispersed inside the composite membrane; experimentresults indicate that the SM-TS particles effectively improved the hydrophilicity,tensile strength and permeation flux of the composite membrane.The SM-TS/PSF composite membrane was used to treat with waste watercontaining oil （oil concentration46mg/L）, the result show that the permeation flux ofthe composite membrane reaches to127L/m²h, oil concentration and rejection rate ofthe treated water is3.7mg/L and92%respectively, which meet the requirement forwater reinjection （oil concentration≤5.0mg/L）. The composite membrane was washed by physical and chemical cleaning after a period time operation, and itshowed a high flux recovery rate.Analyses were performed on the structure of SM-TS particle and transfer processof water through the membrane, which can theoretically explain the goodhydrophilicity, tensile strength and anti-fouling capability of SM-TS/PSF compositemembrane.