Zeng Li, Sun Hongjuan, Peng Tongjiang, Lv Xia
Key Laboratory of Solid Waste Treatment and Resource Recycle, Southwest University of Science and Technology, Ministry of Education, Mianyang, China.
School of Architecture and Civil Engineering, Chengdu University, Chengdu, China.
Front Chem. 2019 Aug 6;7:538. doi: 10.3389/fchem.2019.00538. eCollection 2019.
Nano-TiO (T), TiO/montmorillonite mixture (Mix), and TiO/montmorillonite composite (Com) were prepared by using TiOSO•2HO as the precursor of TiO and montmorillonite as the matrix. The phase transition process of TiO and the degradation of methylene blue (MB) in T, Mix, and Com were studied by x-ray diffraction (XRD), infrared spectrum (IR), scanning electron microscopy with energy spectrum (SEM-EDS), and other methods. The results show that, except for the fact that the heating temperature has a great influence on the phase transition and grain growth of TiO, the introduction of montmorillonite has an obvious inhibition effect on the phase transition and grain growth of TiO, and the inhibition effect of the Com is obviously stronger than Mix. In Com, Ti-O-Si chemical bond was formed between TiO and oxygen atoms with negative charge on the bottom of the structure layer of montmorillonite, which is the main reason for inhibition effect. However, in Mix, TiO only covers the surface of montmorillonite without breaking the degree of order of montmorillonite and forming no chemical bond with montmorillonite, so the inhibition effect is small. From degradation of MB, it was found that before the structure of montmorillonite was destroyed (400-600°C), the total degradation percentage in Mix (85.3-99.5%) was higher than T and Com. At high temperature (above 700°C), because of the inhibition effect, the total degradation percentage of MB in Com is much larger than T and Mix, even above 1,100°C, the total degradation percentage can still reach at 47%. Therefore, in industrial applications, Mix and Com can be selected to degradation MB, according to the actual application temperature range.
以TiOSO₄•2H₂O为TiO₂的前驱体，蒙脱石为基体，制备了纳米TiO₂（T）、TiO₂/蒙脱石混合物（Mix）和TiO₂/蒙脱石复合材料（Com）。采用X射线衍射（XRD）、红外光谱（IR）、能谱扫描电子显微镜（SEM-EDS）等方法研究了TiO₂的相变过程以及T、Mix和Com中甲基蓝（MB）的降解情况。结果表明，除加热温度对TiO₂的相变和晶粒生长有很大影响外，蒙脱石的引入对TiO₂的相变和晶粒生长有明显的抑制作用，且Com的抑制作用明显强于Mix。在Com中，TiO₂与蒙脱石结构层底部带负电荷的氧原子之间形成了Ti-O-Si化学键，这是产生抑制作用的主要原因。然而，在Mix中，TiO₂仅覆盖在蒙脱石表面，未破坏蒙脱石的有序度，也未与蒙脱石形成化学键，因此抑制作用较小。从MB的降解情况来看，发现在蒙脱石结构被破坏之前（400-600°C），Mix中的总降解率（85.3-99.5%）高于T和Com。在高温（700°C以上）下，由于抑制作用，Com中MB的总降解率远高于T和Mix，甚至在1100°C以上，总降解率仍可达到47%。因此，在工业应用中，可根据实际应用温度范围选择Mix和Com来降解MB。
