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

1二氧化钛包覆二氧化硅基复合材料的制备将乙酸水溶液悬浮于TEOS-正己烷溶液中制备二氧化硅颗粒，将TTIP-正己烷溶液倒入反应体系中。尝试了三种添加TTIP溶液的方法：（方法1）在24或36 h时添加所有溶液;（方法2）将溶液分为两部分，在24和36 h时添加每一半;（方法3）将溶液分为四部分，在24、28、32和36 h时添加每四分之一。所得结果总结如下。(1)二氧化钛含量随着TTIP浓度的增加而增加。添加方法对其无影响。(2)方法1制备的复合材料表面附着有粒径为10 μm的二氧化钛团聚体。(3)通过分次添加，团聚体减少。采用方法3，覆盖均匀。(4)讨论了煅烧温度对复合材料比表面积和晶相的影响。2复合材料光催化降解废水中有机物的研究考察了复合材料对染料溶液的光催化降解作用。所得结果总结如下。(1)使用在1073 K下煅烧的复合物，在没有UV照射的情况下，浓度降低。而且随着辐射的减少。(2)在773 K下煅烧的复合材料降解效果更明显。(3)复合材料的整体降解比二氧化钛超微粒子大得多，这是由于除了光催化活性之外的吸附作用。(4)通过焙烧去除了吸附的染料，该复合材料可重复用于废水处理。(5)处理后的水很容易分离出杂质。

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.