The Preparation Of Heterojunction P Hotocatalysts And A Study Of Its Degradation Performance On Printing And Dyeing Wastewater

Semiconductor photocatalytic oxidation technology has developed rapidly in recent years,and has shown remarkable ability to degrade pollutants in various fields.The specific operation method of this technology in sewage treatment is generally to fully mix the semiconductor photocatalytic materials with the sewage to be treated,and then expose it under visible light irradiation;at this time,under the irradiation of light,the photocatalyst can produce substances with strong ability of oxidation and reduction,which is capable of degrading pollutants into harmless substances,so as to achieve the purpose of purifying the water environment.Since most photocatalytic materials can only respond to ultraviolet light,resulting in unsatisfactory catalytic activity of the photocatalytic materials under visible light,and some characteristics of the semiconductor material itself are closely related to photocatalytic activity,so the focus of research in this field is to perform a series of modifications on semiconductor photocatalytic materials to widen their response to visible light,thereby improving activity of semiconductor photocatalytic materials to degrade pollutants.In this paper,the visible light-responsive photocatalytic materials based on In VO₄and Ti O₂are studied.The surface of the material is modified by means of semiconductor composite to broaden the optical response range of the material itself and improve the photocatalytic performance.Three kinds of different composite photocatalyst materials including In VO₄/Cd S,Ti O₂/HCCN and Ti O₂/Zn S were mainly synthesized,and the microstructure,morphology,optical properties and chemical composition of the composite were characterized by XRD,SEM,TEM,FT-IR,UV-vis and XPS.Finally,rhodamine B was used as the target pollutant to test the photocatalytic activity of In VO₄/Cd S,Ti O₂/HCCN and Ti O₂/Zn S composite materials respectively.The results showed that the photocatalytic activity of the three composite materials was stronger than that of the single material.The main research contents are as follows:1.In VO₄nanospheres with regular morphology were prepared by hydrothermal method,and then the In VO₄nanospheres were compounded on the surface of Cd S microspheres by hydrothermal method,and thereby the In VO₄/Cd S composite photocatalytic materials with different mass ratios were prepared.XRD detected the existence of In VO₄and Cd S in the composite material,and the XPS analysis results also confirmed the elemental composition of the two-phase composite.The UV-vis analysis results show that the two-phase compound broadens the absorption range of the material and makes its visible light utilization rate higher.At the same time,the two-phase recombination is conducive to generating more photo-generated electron-holes,thereby improving the photocatalytic efficiency.Taking Rh B as the target pollutant,the degradation performance of photocatalyst on Rh B wastewater was investigated under the simulated light source of xenon lamp,and the photocatalytic reaction mechanism was discussed.The results showed that the photocatalytic activity of the composite is stronger than that of pure In VO₄and Cd S,and 40%In/Cd composite has the highest degradation efficiency.2.HCCN nanocrystalline sheets were prepared by thermal polycondensation method,and Ti O₂nanoparticles were loaded onto the surface of HCCN nanocrystalline sheets by hydrothermal method to prepare composite photocatalytic materials with different mass ratios of Ti O₂/HCCN.SEM and TEM showed that the addition of Ti O₂nanoparticles can change the dense stacking mode of HCCN nanocrystalline sheets,making them more dispersed and exposed to more pollutants.Uv-vis analysis showed that the absorption edge of the two-phase composite was significantly redshifted,which enhanced the utilization of visible light.At the same time,the formation of heterojunction of the composite material also makes the photogenerated electrons of Ti O₂/HCCN-holes live longer,thus improving the photocatalytic activity of the material.The photocatalytic activity of Ti O₂/HCCN composite was studied with Rh B as the degradation object,and its photocatalytic mechanism was discussed.The results showed that the photocatalytic activity of the composite was stronger than that of pure Ti O₂and HCCN,among which 50%Ti/CN composite had the highest degradation efficiency.3.Ti O₂nanowires were prepared by sol-gel and template method,and then Ti O₂nanowires were supported on the Zn S microspheres by solid phase method,so that Ti O₂nanowires formed a uniform film covering Zn S microspheres,and composite photocatalytic materials with different mass ratios of Ti O₂/Zn S were prepared.SEM and TEM showed that the nano film formed by the stacking of Ti O₂nanowires uniformly covered the surface of Zn S microspheres,which changed the surface morphology of Zn S microspheres with the original lamellar structure.Uv-vis showed that the absorption spectrum of the two-phase composite was redshifted,increasing the visible light utilization range.At the same time,the photoelectron-hole separation efficiency was improved by the two-phase recombination.Rh B was used as the degradation pollutant to test the photocatalytic activity of Ti O₂/Zn S composite material,and the photocatalytic principle of the composite material with nano-film-coated microsphere structure was discussed.The results showed that the photocatalytic activity of the composite was stronger than that of pure Ti O₂and Zn S,among which 60%Ti/Zn composite had the highest degradation efficiency.