| Semiconductor TiO2photocatalysts have the excellent properties that can be usedin purification, degradation of organic pollutants, and many other fields. Since thepowder TiO2is difficult recovered after the use, and can not be recycled easily, so theuse of TiO2faces to certain limitations. To solve this problem, the preparation of aconvenient recycling and high photocatalytic active photocatalyst is concerned about. Inthis article two hierarchical porous ceramic photocatalysts was prepared byfreeze-drying at room temperature, and it can be obtained the outstanding organicpollutants removal efficiencies by using them.First, the porous crystalline TiO2ceramic photocatalysts are prepared by theroom-temperature freeze-drying process with the high thermal stability mesoporousTiO2powders. The results are showed that the TiO2photocatalysts are anatase at800℃of calcination temperature, and are with hierarchical porous structure. Through thecatalyst porosity and the compressive strength test, it can be showed that with thecalcination temperature increasing from700℃to900℃, the porosity are97.1%,92.5%,and87%, respectively, and the compressive strength is from0.28MPa to1.38MPa. Inthe photocatalytic degradation test, with the porous crystalline TiO2photocatalystprepared at800℃ofcalcination temperature,10mg/L of the initial rhodamine Bconcentration,11of pH,20W of UV-A irradiation, and5h of the reaction time,95%ofthe rhodamine B degradation efficiency can be obtained. And the degradation efficiencyof the rhodamine B can still reach95%after six recycling.Second, based on the above experimental studies and in order to further improvethe ceramic photocatalytic properties, the SiO2/TiO2composite powders are used toprepare the porous ceramic photocatalyst by the room-temperature freeze-dryingprocess. The experimental results are showed that the TiO2are still anatase at900℃ofcalcination temperature. By the N2adsorption-desorption, the pressure mercury analyzer and the scanning electron microscope test, it can be concluded that amacroporous/mesoporous ceramic structure is the presence. Through the ceramiccatalyst porosity and compressive strength test, it is showed that with the calcinationtemperature increasing from800℃to1000℃, the porosity are91%,86.7%, and80.1%,respectively, and the compressive strength are from0.43MPa to1.92MPa. In thephotocatalytic degradation test, with the SiO2/TiO2photocatalyst prepared at900℃ofcalcination temperature,10.0mg/L of the initial rhodamine B concentration,11of pH,20W of UV-A irradiation, and3h of the reaction time,99%of the rhodamine Bdegradation efficiency can be obtained. And the degradation efficiency of the rhodamineB can still reach99%after six recycling.In order to study the degradation mechanism of photocatalytic reaction process, thedifferent radical scavengers are added in the photocatalytic reaction. The effect of freeradicals on the pollutants for the two kind of floating hierarchical porous ceramicphotocatalytic system all are as: O2-> h+> OH.Third, the two kinds of hierarchical porous ceramic are applied in the continuousstream shallow pool photocatalytic reactor. When HRT is1h, with10mg/L ofRhodamine B,11of pH, the degradation efficiencies of two kinds of ceramic are81.7%and85.1%, respectively.Two floating hierarchical porous ceramic photocatalysts are applied in continuousstream shallow pool photocatalytic reactor for the simulated real dye wastewaterdegradation. It can be showed when the HRT is1h,71.7%and79.5%of the simulatedreal dye wastewater decolorization efficiencies and74.9%and82.1%of COD removalefficiencies can be obtained, respectively. |
