| Photocatalytic technology was a new environmental-friendly technology, which has been showed a vast and tempting prospect in the field of environmental protection and management. Especially in recent years, the photocatalytic technology governance environment has been pushed to a new climax because of the haze phenomena. Titanium dioxide is the most widely used semiconductor photocatalyst, which has many advantages, including earth abundance, chemical stability, high photocatalytic activity, nontoxicity, non-pollution, and so on. Naturally, Photocatalytic technology becomes the first choice for improving the environment. However, there are some drawbacks such as easy to reunion, easy-loss, difficult-recycling in the process of practical application of nano-TiO2 powers. The photocatalytic materials coated with TiO2 can effectively compensate for these shortcomings, and can improve the catalytic activity to a certain extent.Nano titanium dioxide powder was prepared by sol-gel method, with sulfuric acid, hydrochloric acid and citric acid monohydrate as acid catalyst. The effects of the acid type and dosage and calcination temperature on the structures and properties were studied by a single variable method. The preparation conditions are determined as follows:acid catalyst is 1.5mL H2SO4 or hydrochloric acid, calcination temperature is 500℃ and calcination time two hours. Results as follow:the samples prepared by H2SO4 have uniform particle size distribution, small particle size, and their catalytic activities are generally high. The sample remains anatase when calcined at 700℃ for two hours. Monohydrate citric acid as acid catalyst, which is beneficial to the formation of TiO2 rutile phase, is suitable for the preparation of mixed crystal type at lower temperatures. The amount of hydrochloric acid has a great influence on the crystalline form of TiO2. While a relatively small amount of hydrochloric acid used, samples are pure anatase titanium dioxide. When the amount of hydrochloric acid is greater than 1.0 mL, the crystal type of the samples are mixed crystal with anatase and rutile. With the increase of amount of hydrochloric acid, the content of rutile phase and the particle size are increased. TiO2 prepared with 1.5mL of hydrochloric acid has the strongest photocatalytic activity.Cenosphere composite photocatalyst coated by titanium dioxide was prepared. The influence of carrier type, loading, preparation method on supported catalysts photocatalytic properties was studied, and the best preparation conditions are determined as followed:the carrier is floating beads, load capacity is 1g floating beads for per 5mL titanium source and preparation method is sol-gel. Hollow microsphere, as a carrier, can effectively improve the catalytic activity of TiO2 and reduce the use amount of TiO2. The photocatalytic activity of the load type catalyst is stable, repeatedly used four times, photocatalytic activity with little change.In order to study the effects of elements doping modification on the properties of the load type catalyst, the elements of Fe and Ba were used as dopent in this article. Results show that the catalytic activity of the load type catalyst can’t be improved by doped Fe3+ in the UV area. The probable cause is that the irons in the cenosphere matrix move into the lattice of TiO2 after calcining process, which becomes the doping elements. So too much iron doped into TiO2 may become recombination centers of electrons and holes. Therefore the catalytic activity is reduced in the UV area. But it can make its catalytic activity in the visible area increased. The incorporation of Ba2+ cannot increase the catalytic activity of catalyst, on the contrary suppressed the catalytic activity.In addition, the supported catalyst has a strong photocatalytic activity in the visible region when cooperated with H2O2. After recycled many times, the synergistic effect of H2O2 still exists. |
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