Preparation Of Metal Oxide Heterojunction Photocatalysts And Study On Photocatalytic Degradation Performances For Tetracycline Hydrochloride

Tetracycline hydrochloride(TCH)is one of the most widely used antibiotics in veterinary medicine because of its low cost,wide adaptability,and high antibacterial activity.Because of its large use,the water environment problem is getting worse and worse,which seriously destroys the ecological balance.Semiconductor photocatalytic technology is widely used in the degradation of TCH due to its easy operation,low energy consumption and no secondary pollution.However,the rapid recombination of electrons and holes in semiconductors is a key factor limiting the photocatalytic efficiency.In this study,HNbWO6 nanosheets and montmorillonite nanosheets were used as substrate materials to construct heterojunctions by loading CuO and MnO2 to form built-in electric field to improve the photocatalytic degradation efficiency for TCH.The degradation mechanism of TCH on heterojunction photocatalysts was analyzed and verified by spectral characterization and free radical capture experiments.The specific research contents are as follows:CuO@HNbWO6-NS and MnO2@HNbWO6-NS composite photocatalysts are synthesized by exfoliating-assembled method.The phase structure and photoelectric properties of the as-prepared photocatalysts were analyzed in detail by a variety of physicochemical characterization techniques.The characterization results showed that there was an obvious interaction between the supported oxide and HNbWO6-NS.The composite photocatalyst was applied to the photocatalytic degradation of TCH.The results showed that CuO@HNbWO6-NS had the best degradation effect on TCH under simulated sunlight,and the degradation rate was 74.7%after 2 hours.The possible photocatalytic mechanism was proposed by electrochemical impedance spectroscopy and free radical quenching experiments.The contribution rate of free radicals in this photocatalytic system from large to small was:·O2->h+>·OH.Due to the formation of heterojunction,the migration of photogenerated carriers is accelerated and the life of free electrons is prolonged,thereby enhancing the photocatalytic performance of the composites.Montmorillonite(MMT)nano-materials,which are cheaper and easier to be obtained,were used as the substrate to prepare the CuO@MMT and CuO/MnO2@MMT via easy impregnation method.Laser Raman spectroscopy(LRS)and X-ray photoelectron spectroscopy(XPS)showed the interaction between oxide and MMT,The characterizations of UV-vis-DRS and EIS proved the effect of this interaction on the band gap structure and electron-hole transfer efficiency of the catalyst.The application of composite catalyst in photocatalytic degradation of TCH can obtain obvious improvement effect.The degradation effect of composite catalyst is more than that of single component oxide and MMT.The degradation effect of two component composite catalyst(CuO/MnO2@MMT)is more than that of single component composite catalyst.The degradation rate of TCH can reach 82.4%after 2 hours.Through the free radical quenching experiment,the contribution rate of photocatalytic degradation system is:-O2->h+>·OH.The results show that the structure of semiconductor heterojunction can effectively improve the space separation efficiency of electrons and holes and enhance the photocatalytic efficiency of semiconductor.Figure 36 Table 4 Reference 89...