Heterojunction photocatalytic materials show excellent performance in degrading toxic pollutants. This study investigates the influence of calcination temperature on the performances of floral Bi2O3/TiO2composite photocatalyst crystal, which was prepared with glycerol, bismuth nitrate, and titanium tetrachloride as the major raw materials via the solvothermal method. XRD, SEM/TEM, BET, Uv-vis, and XPS were employed to analyze the crystal structure, morphology, specific surface area, band gap, and surface chemical structure of the calcined temperature catalysts. The calcination temperature influence on the catalytic performance of composite photocatalysis was tested with rhodamine B (RhB) as the degradation object. The results revealed the high catalytic activity and higher photocatalytic performance of the Bi2O3/TiO2catalyst. The degradation efficiency of the Bi2O3/TiO2catalyst to RhB was 97%, 100%, and 91% at 400 °C, 450 °C, and 500 °C calcination temperatures, respectively, in which the peak degradation activity appeared at 450 °C. The characterization results show that the appropriate calcination temperature promoted the crystallization of the Bi2O3/TiO2catalyst, increased its specific surface area and the active sites of catalytic reaction, and improved the separation efficiency of electrons and holes.Keywords:calcination temperature;Bi2O3/TiO2compound;visible light;photodegradation
Nan Wang,Xing Li,Yanling Yang,Zhiwei Zhou,Yi Shang,Xiaoxuan Zhuang,Tingting Zhang
In a previous study, we used a sol-hydrothermal method with a one-stage calcination in an air atmosphere at 400 °C to prepare composites of Bi 2 O 3 -TiO 2 supported on powdered activated carbon (Bi-Ti/PAC-1). However, the photocatalytic efficiency of those composites was relatively low due to their high band gap and the single crystal phase of their TiO 2 . To improve the photocatalytic efficiency, we developed a two-stage calcination method with a first calcination in air at 300 °C followed by a second calcination in a N 2 atmosphere (at 500, 600, or 700 °C) to form the Bi 2 O 3 -TiO 2 composites (Bi-Ti/PAC-2). Compared with Bi-Ti/PAC-1, the photocatalytic degradation efficiency of sulfamethazine (SMT) by Bi-Ti/PAC-2-700 increased by 32 % under solar light irradiation. Bi-Ti/PAC-2-700 contained two TiO 2 crystal phases, rutile and anatase, and its band gap was 2.58 eV, far less than that of Bi-Ti/PAC-1. Electron paramagnetic resonance measurements and trapping experiments showed that the superoxide radical, hole, and hydroxyl radical each played an important role in the degradation of SMT, among which the superoxide radical predominated. The degradation pathway of SMT included four processes: oxidation of hydroxyl radical, SO 2 extrusion, N C and S N bond cleavage. We also determined that solution pH, humic acid, and inorganic ions had varying effects on the photocatalytic degradation capability of Bi-Ti/PAC-2-700. We measured the efficiency of Bi-Ti/PAC-2-700 for SMT degradation in natural river and lake water and found it to be >85 %, sufficient for practical applications. This study provides a green and efficient photocatalyst that can be applied to water treatment processes.
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