The Construction Of Novel Z-scheme Catalytic System ?NiGa₂O₄-Bi₂O₃ And NiGa₂O₄-BiVO₄? And The Applied Research On Sonocatalytic Degradation Of Organic Pollutants

As an Advanced Oxidation Technology?AOPs?,ultrasonic catalytic degradation technology has been widely applied in the field of pollutant management in recent years.Compared with light,ultrasonic irradiation has many advantages,such as strong penetrability,special transmission mode,high efficiency and simple operation.It can replace light and become an effective method to deal with non-transparent and low transparency organics.However,in the actual degradation process,the effect of a single ultrasonic irradiation deal with organic pollutants is not very good.Recently,the method of combining semiconductor materials with ultrasonic waves to process organic pollutants has attracted the attention of many scholars.The sonocatalytic degradation process is similar to the photocatalytic reaction,that is,ultrasonic can instead light to excite the catalyst.As a semiconductor catalytic material,TiO₂ has high chemical stability,excellent catalytic activity and low cost,which is widely used in the field of catalysis.However,TiO₂ has a wide band-gap?3.2 eV?which can be only excited by UV light below 380 nm and has a low utilization rate of light.In recent years,bismuth series photocatalysts show good catalytic performance under visible light and have been widely applied in environmental pollution treatment.A large number of experimental studies have shown that Bi₂O₃ and BiVO₄ as advanced semiconductor materials have a wide range of application in photovoltaic materials and high temperature superconducting materials due to their stable chemical properties,good oxygen mobility,and excellent dielectric properties.However,photogenerated electrons and holes generated are easy to recombine because of the narrow band-gap of Bi₂O₃ and BiVO₄,which will affect the catalytic performance.In order to further broaden the light response range of the catalyst and to restrain the combination of the electron and hole,the catalyst can be improved from two aspects.On the one hand,Er³⁺:Y₃Al₅O₁₂ as up-conversion luminescence agent?from visible-light to ultraviolet-light?provides enough ultraviolet-light for satisfying the energy demand of wide band-gap semiconductors in sonoluminescence.On the other hand,a semiconductor material with a relatively wide band-gap is selected in combination with Bi₂O₃ or BiVO₄ to broaden the light response range of the catalyst.In the first part of the study,a novel three-component nanocomposite,Au/NiGa₂O₄-Au-Bi₂O₃,was successfully prepared using hydrothermal and calcination methods.XRD,SEM,DRS and EDX were used to characterize the crystal morphology,surface morphology,band-gap and chemical composition.The activity of the sonocatalyst was investigated by degrading RhB under ultrasonic irradiation.The degradation degree of organic dyes was evaluated by TOC and UV-vis spectrophotometers.Meanwhile,some main influence factors,such as mass ratio of NiGa₂O₄ and Bi₂O₃ in Au/NiGa₂O₄-Au-Bi₂O₃ nanocomposite,ultrasonic irradiation time and used times,on the sonocatalytic degradation of some organic pollutants were investigated.The wide-adaptability of Au/NiGa₂O₄-Au-Bi₂O₃ nanocomposite could also further be studied by decomposing several representative organic dyes.In the second part of the study,a novel Z-scheme structure catalyst Er³⁺:Y₃Al₅O₁₂@Ni(Fe_0.05Ga_0.95)₂O₄-Au-BiVO₄ was synthesized via sol-hydrothermal and calcination methods.X-ray powder diffraction?XRD?,energy dispersive X-ray spectroscopy?EDX?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FT?-IR,UV-vis DRS,Raman spectroscopy and photoluminescence?PL?were used to characterize the crystal morphology,chemical composition,structure,band-gap and surface morphology,respectively.The novel Z-scheme Er³⁺:Y₃Al₅O₁₂@Ni(Fe_0.05Ga_0.95)₂O₄-Au-BiVO₄ nanocomposite was applied to the sonocatalytic degradation of sulfanilamide solution to investigate the activity.To explore the process of sonocatalysis,the effects of hydroxyl radicals?·OH?and hole scavengers were also investigated.In addition,the effect of ultrasonic irradiation time on the sonocatalytic degradation efficiency and cycle number are investigated by using TOC and UV-vis spectroscopy and the degradation rule of sonocatalysis is also explored by building a first-order kinetic reaction.It can be found that the sonocatalytic degradation rate decreases only slightly in five times recycle use.The resultsindicatethatthesonocatalyticactivityof Er³⁺:Y₃Al₅O₁₂@Ni(Fe_0.05Ga_0.95)₂O₄-Au-BiVO₄ nanocomposite is rather stable.The researchesprovethatthepreparedZ-scheme Er³⁺:Y₃Al₅O₁₂@Ni(Fe_0.05Ga_0.95)₂O₄-Au-BiVO₄ nanocomposite displays an excellent sonocatalytic activity in degradation of sulfonamides under ultrasonic irradiation.