AbstractThe photocatalytic mixed crystal nano-TiO2 particles were incorporated with concrete by means of the internal doping method (IDM) and spraying method (SPM) in this paper. To evaluate the photocatalytic degradation efficiency of mixed crystal nano-TiO2 concrete, the methyl orange (MO) was chosen to simulate pollutants. The physicochemical characteristics and photocatalytic performance of mixed crystal nano-TiO2 concrete prepared by above two different methods were experimentally investigated under UV irradiation and solar irradiation. Furthermore, the effects of two key influential factors including pollutant concentration and irradiation condition were also analyzed and discussed. Experimental results indicate that the nano-TiO2 concrete prepared by the spraying method (SPM) exhibits maximum photocatalytic degradation efficiency of 73.82% when the sprayed nano-TiO2 slurry concentration is 10mg/L. The photocatalytic degradation efficiency of unpolished nano-TiO2 concrete is much higher than that of polished nano-TiO2 concrete under the same exposure time of UV irradiation. Moreover, the photocatalytic degradation efficiency of nano-TiO2 concrete decreases with the increase of pollutant concentration. The irradiation condition has an obvious influence on the photocatalytic degradation efficiency of nano-TiO2 concrete. In the aspect of applications, the practical recommendations for the nano-TiO2 concrete with self-cleaning capacity were presented according to the experimental results.

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AbstractCdS/TiO2 composite photocatalysts were made by the method of secondary ball milling at different ball milling speeds, milling time, and material ratios. After the secondary ball milling process, parts of the samples were calcined at high temperatures. X-ray diffraction (XRD) and UV-Vis diffuse reflectance spectroscopy (DRS) were used to observe the powder particle size, structural defect, bandgap, and absorption spectrum of the samples. Combined with the observation results, the effects of ball milling speed, time, material ratio, and high-temperature calcination on the photocatalytic performance of CdS/TiO2 composite samples were analyzed. Furthermore, the methyl orange (MO) was chosen to simulate pollutants, and the photocatalytic degradation rate of CdS/TiO2 composite photocatalysts for MO was evaluated under sunlight and UV irradiation conditions. The photocatalytic degradation efficiency of CdS/TiO2 photocatalyst under UV irradiation is much higher than that under sunlight irradiation. The experimental results reveal that secondary ball milling can effectively promote the formation of CdS/TiO2 composite nanostructure and the high-temperature calcination can reduce the bandgap width, which makes the samples easier to be excited. When the ball milling speed, time, and material ratio were respectively 400 rpm, 10 h, 25:75, and then calcined at high temperature, after 2 h of irradiation under UV light, CdS/TiO2 composite photocatalysts exhibited maximum photocatalytic degradation efficiency of 57.84%.

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