Preparation of fine particulate composites having magnetism as photocatalytic materials for waste water treating

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1 Preparation of silica-based composites covered with titaniaTTIP-hexane solution was poured into the reaction system, in which silica particles were prepared by suspending acetic acid aqueous solution in TEOS-hexane solution. Three methods for adding TTIP solution was attempted : (method 1) all the solution was added at a time of 24 or 36 h ; (method 2) the solution was divided into two parts, and each half was added at times of 24 and 36 h ; (method 3) the solution was divided into four parts, and each quarter was added at times of 24, 28, 32, and 36 h. Results obtained were summarized as follows.(1) Titania content increased with increasing TTIP concentration. Addition methods did not affect it.(2) By method 1, titania agglomerates of 10 μm in diameter adhered onto the surface of the composites.(3) The agglomerates decreased by the dividing addition. By method 3, covering was uniform.(4) The effects of calcining temperature on the specific surface area or the crystalline phase were discussed.2 Photocatalytic degradation of an organic compound in waste water with compositesPhotocatalytic degradation of dye solution was examined. Results obtained were summarized as follows.(1) With using the composite calcined at 1073 K, the concentration decreased without UV irradiation. It decreased moreover with radiation.(2) The degradation was more notably with using the composite calcined at 773 K.(3) Overall degradation with the composites was much larger than titania ultrafine particles, owing to the effect of adsorption in addition to photocatalytic activity.(4) Dye adsorbed was eliminated by firing, and the composites could be reused for waste water treating.(5) It was very easy to separate the photocatalysis from water treated.