| Nanostructured Zn-TiO2films were dip coated on slide glass substrates (75×25×1mm) by sol-gel route, and the photocatalytic activity of coated glass was evaluated by themethod of degrading methylene blue solution. Through orthogonal analysis, the factors ofzinc content, pulling rate, heat-treatment temperature and holding time were investigated.Also, the most important factor influencing photochemical performance and thetheoretical optimum combination were obtained and validated. The structure, surfacemorphology and phase transformation of Zn-TiO2films were studied by X-ray diffraction,field emission scanning electron microscope and differential scanning calorimetry.The results reveal that the sol can produce anatase after400℃heattreament, andonly anatase exists until the temperature reaches650℃. When surpasses700℃, theamount of anatase decreases sharply and rutile become the main phase. With500℃,1hheat-treatment, there is no change in XRD spectrum of low zinc content (below1wt%)Zn-TiO2samples versus pure TiO2, but reaches1wt%, new phase of ZnTiO3(Ecandrewsite) appeares. With1wt%,2wt%and3wt%zinc doping, the TiO2transformation temperature from anatase to rutile are532.5℃,636.3℃and651.7℃respectively. In general, the doping of zinc lowers transformation temperature and thenpromotes the formation of rutile. Furthermore, the lower concentration of zinc element is,the more significant the promoting effect will be.Compared with pure TiO2film, better photocatalytic degradation of methylene bluesolution (MB) are observed in Zn-TiO2samples. To degrade80%MB, TiO2film needs23min while9#Zn-TiO2only need18min. The orthogonal analysis indicates that theoptimum combination is A1B3C2D1, and the order of influencing degradation rate is D＞B＞C＞A, that is, holding time is the most important factor. With the increase of holdingtime, the degradation efficiency decreases. After validation, the degradation rate ofA1B3C2D1really improves versus pure TiO2film and the highest increases by17.6%. |
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