| At present, titanium dioxide(TiO2) photocatalytic technology is an emerging of environmental technology with broad development prospect, especially in the study of water treatment by the attention of many researchers. This technology is non-toxic, safe, good stability, high catalytic activity, short cycle, low energy consumption. In addition, pollutants can be mineralized and decomposed into water, carbon dioxide, or non-toxic small molecules at room temperature by this technology. But in the actual application process there are some deficiencies leading to the TiO2 deactivation, such as adsorption of reaction product, surface hydroxyl groups lost, aggregation of particles, or the influence of carrier and so on. The activity of catalyst and its life are the key factors which can affect photocatalytic technology can be applied to practice. So the deactivation mechanism of TiO2 and regeneration method is the precondition of TiO2 photocatalytic technology application to environment. This paper aimed to investigate the activity, deactivation and regeneration of the TiO2 photocatalyst using Congo red as the reactant. The main results are as follows:(1) In the experiments of TiO2 photocatalytic degradation simulation wastewater of Congo red, the decolorization rate of Congo red were 86%,83.4%,79.1%,65.1%,46%, and 18.8% respectively after 1,2,3,4,6, and 8 times reaction by TiO2.The activity of TiO2 remained about the same at the first three times, then the activity gradually reduced after the fourth using, fresh TiO2 was inactivated after 8-time usage. At the same time, the quality of adsorbate on the surface of TiO2 increase with the increase of number of catalysts used until adsorption gradually into balance on the surface of TiO2 after 6-times usage, the quality of the adsorbate no longer having significantly increased.(2) SEM, EDS, XRD, UV-vis diffuse reflectance spectra and FTIR spectra were used afterwards to determine the changing properties of the photocatalysts, including surface morphology, crystal structure, optical property and surface materials. The results showed that there were two main reasons for the deactivation of TiO2, one of which was the strong agglomeration of TiO2 particles; the other reason was caused by the intermediate products of Congo red, such as sulphate, nitrate and carbon-containing compound. These intermediate products accumulated in the surface of TiO2, occupied the active sites, and obstructed photons and substrates from reaching the catalyst surface. TiO2 thus lost its photocatalytic activity gradually.(3) Regeneration TiO2 on the decolorization rate of Congo red were 27.4%,41.8% and 47.3% respectively by UV irradiation, ultrasonic cleaning, H2O2 cleaning. The deactivation TiO2 didn’t get high efficiency regeneration. UV+ H2O2+ ultrasonic cleaning regeneration is a method of joint regeneration with the advantages of single method, and synergy with each other at the same time. After the method of regeneration, the deactivation of TiO2 is almost completely regenerated with the decolorization rate of 82.7%. Roasting regeneration also had good regeneration effect. And the deactivation of TiO2 got the similar efficient regeneration with the decolorization rate of 81.4%. |
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