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Composite sol-gel process for photocatalytic titanium dioxide Keshmiri, Mehrdad

Abstract

Photocatalytic TiO₂ decomposes organic and inorganic pollutants upon irradiation with UV light. TiO₂ thin films and powder suspensions are used for purification treatments, but small surface area of TiO₂ films, and difficult filtration of powders are the two major drawbacks in application of photocatalytic TiO₂. The major objective of this work was to develop a novel process to combine the thin film coatings and the fine (sub-micron) powder anatase TiO₂ to provide high photocatalytic efficiency thick films and self-supported membranes. The microstructural properties and photocatalytic efficiency of the developed materials were characterized and compared with that of the conventional TiO₂ coatings and powders. Photocatalytic activity of CSG TiO₂ was measured through the ability to decompose organic compounds (trichloroethane, dioxane, toluene), as well as to destroy bacteria. The major achievement of this work is the development of a process wherein structurally sound, thick films and membranes of CSG anatase photocatalytic TiO₂ can be produced in reproducible way. A novel method for the synthesis of monodispersed anatase TiO₂ microspheres through colloidal precipitation has also been established. The microspheres were used as filler TiO₂ in the composite microstructure, bonded with sol-gel derived TiO₂, to produce the composite sol-gel (CSG) TiO₂. A sol-gel-assisted sintering model for the CSG thick films and self-supported membranes was established and validated by experimental data. The model has the ability to predict the sintering behavior of the CSG- TiO₂, in terms of the reduction of specific surface area versus the time of heating, particularly at the initial and intermediate stages of the sintering.

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