Study On Degradation Of Rhodamine B In Dye Wastewater By SnO₂ Composite Photocatalyst

During the textile printing and dyeing process,a large amount of wastewater containing harmful additives such as Rhodamine B（Rh B）will be generated,which will inevitably cause water pollution.Rhodamine B in dye wastewater can be degraded by a photocatalytic process,and this research area has been studied domestic and abroad.Metal oxide nanomaterials have become important catalytic materials because of their excellent properties.Tin dioxide（SnO₂）is one of them.Due to its large forbidden band width（3.6e V）,SnO₂ can only absorb and use light energy in the ultraviolet range.In order to improve the photocatalytic performance of SnO₂ materials in the visible light field,not only can it be performed with other metals or non-metal oxides.Recombination to prepare binary or multiple composite photocatalysts,and layer structures of different sizes can be constructed to achieve good light capture.Therefore,based on SnO₂,a variety of composite photocatalysts with a certain UV/visible light response have been prepared.First,SnO₂/Zn O composites with photocatalytic activity under ultraviolet light were prepared by microwave-assisted hydrothermal method.SEM and XRD characterization were used to analyze its structure and composition.XRD results showed that Zn and Sn existed as Zn O and SnO₂.Due to the addition of chloroplatinic acid during the preparation,metal platinum（Pt）was also found;SEM results show that Zn O particles are attached to the SnO₂ sheet structure,and a heterojunction is formed between them.The degradation of 37%Rh B（within 210 min）under UV light may be due to the synergy between Zn O and SnO₂.In this paper,Sn₃O₄/Sn₂O₃/SnO₂ flower-shaped photocatalyst was also prepared by the same method,and the composite materials were analyzed by SEM and XRD characterization.XRD results showed that Sn coexisted in three forms:Sn₃O₄,Sn₂O₃,and SnO₂;SEM results showed that the material was a flower-like structure assembled from sheets with a large specific surface area.The degradation efficiency of Rh B under UV light reached more than 40%.Improved photocatalytic performance.Secondly,SnO₂/g-C₃N₄（PSG）composite photocatalyst was synthesized in one step by microwave-assisted hydrothermal method.The photocatalyst synthesized in one step can improve the photocatalytic performance,and the degradation efficiency of Rh B can reach more than 90%in 240min.Similarly,a g-C₃N₄/SnO₂ composite photocatalyst was synthesized by a two-step method.Unlike the（PSG）composite photocatalyst,SnO₂ and g-C₃N₄ were synthesized separately in the process.SEM,TEM,XPS,XRD,TG,BET,FT-IR,UV-vis,DRS,PC,and PL were used to analyze the specific surface area,composition,morphology,absorbance of the composite material.The addition of g-C₃N₄ enhances the light absorption performance of the raw materials,increases the specific surface area and the photocurrent intensity.The heterojunction formed between the two promotes the separation of photogenerated electrons and holes.The degradation efficiency of Rh B is more than 98%（within 240 min）.Finally,a GS-CQDs composite material doped with carbon quantum dots（CQDs）was prepared by a two-step method,in which CQDs were prepared by ordinary hydrothermal methods.The composition,absorbance,morphology,and photocatalytic performance of the above-mentioned partial characterization methods were analyzed.The maximum photocatalytic effect was achieved when the CQDs doping amount was 7%,and the degradation efficiency of Rh B was more than 97%within 3 hours.It can be seen that the photocatalytic activity of g-C₃N₄/SnO₂composites is improved after doping with CQDs,indicating that the addition of CQDs inhibits the recombination of photogenerated electrons and holes,and promotes the separation of photogenerated carriers.