Photocatalytic Degradation Of Rhodamine B And Bright Green By N-doped Zn₂GeO₄ And Its Catalytic Degradation Of Dye

With the continuous development of industry in the world,dyestuff is discharged into the water environment along with the waste water,which poses a threat to human health and water quality.Therefore,in consideration of resource conservation and health protection,the degradation of dye wastewater research has far-reaching significance.Photocatalytic technology is a promising method for the degradation of dyes in water environment because of its green,environmental protection,high efficiency and low cost.Zn₂GeO₄has strong redox ability and good photostability,so it is a potential photocatalyst.In this paper,Zn₂GeO₄was selected as the main material,and N doping was used to improve the photocatalytic activity of the catalyst,which was applied to the degradation of different dyes.The main contents and results are as follows:（1）N-doped Zn₂GeO₄was studied by solvothermal method,and a series of characterization tests were carried out on the morphology,structure and composition of the obtained materials.The doped Zn₂GeO₄nanorods in SEM and TEM images lengthen and reduce agglomeration.X-ray photoelectron spectroscopy（XPS）showed that the N content on the catalyst surface increased and the N was doped successfully.Ultraviolet-visible diffuse reflectivity（UV-Vis）spectra show that the doping level in the band structure of Zn₂GeO₄narrates the band gap width and makes the electron transition easier.Fourier transform infrared spectroscopy（FT-IR）confirmed that the vibration intensity of the doped catalyst O-H increased significantly,indicating that the number of hydroxyl groups on the surface of the catalyst increased.The hydroxyl groups on the surface reacted with the light-generated holes to generate active hydroxyl radicals,which further enhanced the catalytic activity of the catalyst.The catalytic performance of N-Zn₂GeO₄material obtained by N-doping was improved,but the lattice and specific surface area of the catalyst did not change significantly before and after doping,which proved that the catalyst maintained the same stability compared with the undoped material.（2）The catalytic activity of the catalyst was evaluated by the degradation of Rhodamine B and brilliant green solution,and the degradation mechanism was explored.The results showed that the photocatalytic degradation of rhodamine B and bright green complied with the first order kinetics.The degradation rate of rhodamine B reached 94%in14 min at the catalyst dosage of 166.7 mg/L and 33.3 mg/L at the catalyst dosage of 50μM and the doping ratio of 1.The degradation rate of brilliant green reached 96%within 10 min and was almost completely removed.The degradation rate of the two dyes decreased with the increase of initial substrate concentration.In the process of photocatalytic experiments,the width of the band gap was narrowed due to N doping,and the amount of hydroxyl radicals on the surface of the catalyst increased,which enhanced the catalytic activity.According to the experiment of free radical capture,superoxide free radical,hydroxyl free radical and hole free radical all participate in the degradation of dye,and play different roles in the process.The degradation pathway of brilliant green mainly involves four reactions,namely hydroxylation,demethylation,direct oxidation and benzene ring opening reaction,and produces nine intermediate products.