Preparation Of Modified Bi₄O₅Br₂ Photocatalyst And Its Degradation Of Recirculated Leachate Under Visible Light

In view of the poor biochemical properties of leachate produced in the later stage of the operation of the bioreactor landfill technology and the poor treatment effect of the leachate ex situ aerobic biological treatment system,it was proposed to replace the ex situ aerobic biological treatment with photocatalytic oxidation technology in the late stage of operation to further degrade refractory organic matters in leachate.In order to improve the utilization rate of visible light,the visible light-responsive photocatalyst Bi₄O₅Br₂ was selected as the basic material,and its photocatalytic performance was further improved through composite modification.To achieve the purpose of reducing the concentration of refractory organic matter in the recirculated leachate and improving the leachate biochemical property,this study was carry out,which will provide a reference for the treatment of recirculated leachate by using photocatalytic oxidation technology and bioreactor.The main research results are as follows:First,the visible light-responsive photocatalyst Bi₄O₅Br₂ was prepared by in-situ precipitation method at room temperature and hydrothermal method.Experiments on photocatalytic degradation of Rhodamine B（Rh B）solution showed that the Bi₄O₅Br₂（BOB）prepared by in-situ precipitation method at room temperature has better degradation performance.Under visible light irradiation for 30 min,the removal rate of 20 mg/L RhB solution was 95.85%with 0.5 g/L catalyst.The XRD,SEM and XPS characterization methods proved the successful preparation of the catalyst BOB.Based on the above preparation method,by using the in-situ precipitation method at room temperature and adding zeolite ZSM-5 in the preparation process,the best composite ratio of1%composite catalyst 1ZSM/BOB was successfully prepared.By using ultrasonic-assisted in-situ precipitation method at room temperature and adding biochar（BC）in the preparation process,a composite catalyst 1.5BC/BOB with an optimal composite ratio of 1.5%was successfully prepared.The structure and morphology of the composite catalyst were analyzed by XRD,SEM,XPS and other basic characterization methods;UV-vis diffuse reflectance spectroscopy showed that the light absorption capacity after compounding was enhanced;photocurrent response,fluorescence spectrum and other performance test results showed the photocatalyst separation efficiency of the composite catalyst has been significantly improved,thereby improving the photocatalytic performance.The experiments of photocatalytic degradation of RhB,bisphenol A,and tetracycline hydrochloride under visible light showed that the compounded catalyst has significantly improved in adsorption and photocatalysis.Free radical trapping experiments showed that superoxide radicals and holes are the main active groups during the photocatalytic reaction.Finally,based on the preparation and characterization analysis of the above catalyst,the catalyst 1.5BC/BOB was selected to study the photocatalytic degradation of the recirculated leachate.The changes of basic water quality and organic matter before and after photocatalytic treatment were analyzed by TOC,A₂₅₄,ultraviolet-visible spectrum,three-dimensional fluorescence spectrum and so on.The experimental results show that about 90%of the fluorescent substances in the recirculated leachate belong to humus,and the degradation effect of 1 g/L 1.5BC/BOB photocatalytic system is limited.By adding persulfate with a mass ratio of 1:2 to photocatalytic system,the treatment effect of recirculated leachate can be improved.