Preparation Of Bi-based Composite Catalyst Materials And Their Photocatalytic Degradation Of Organic Pollutants

Bismuth-based compounds provide researchers with a promising new family of photocatalysts due to their variety,controllable structure and good photocatalytic activity.Among them,BiNbO₄ is a material with a mixed layered Aurvillius phase structure.It has physical and chemical characteristics such as electricity,light and thermoelectricity,which makes it widely used in microwave media,ferroelectricity,photodegradation pollutants and photocatalytic hydrogen production.BiOX?X=Cl,Br and I?is a layered nanostructured material consisting of two lone pairs of ions and?Bi O?₂²⁺.Its characteristics such as high dipole,indirect band gap,high hole redox potential and easy formation of oxygen vacancies?OVs?provide structural support for BiOX to become a good photocatalytic material.Nevertheless,this kind of materials have a relatively narrow light absorption range or the electrons?e^-?and holes?h⁺?generated by materials are easily recombined under the condition of light irradiation.Therefore,a method of constructing heterojunction composite material can be used to improve the photogenerated charge transfer and photocatalytic activity.In this paper,Ag₃PO₄/BiNbO₄,BiOCl/Mn₃O₄ and Bi/BiOCl/BiOI composites were prepared by co-precipitation method,solvothermal method and acidification reduction method,respectively.And the structure and photoelectric properties of the prepared materials were characterized.Taking Rhodamine B?Rh B?and Bisphenol A?BPA?as target pollutants for photocatalytic degradation,investigate the photocatalytic performance of materials and external factors?contaminant concentration,solution p H and salinity?affecting photocatalytic degradation.And the mechanism of photocatalytic reaction was discussed.The research content mainly includes:1.BiNbO₄ in the prepared Ag₃PO₄/BiNbO₄ material is relatively uniformly deposited on the surface of the Ag₃PO₄ material.When the BiNbO₄ content in composite was 10%and the Rh B solution was exposed to light for 30 min,the degradation rate of Rh B with a concentration of 20 mg/L and p H 6 at a dosage of 0.5g/L with composite material could reach 98.83%.Based on the kinetic study,the photodegradation process of Rh B follows the pseudo-first-order kinetic equation.The elementary silver particles on the surface of Ag₃PO₄ after irradiation provide a good channel for electron transport.2.BiOCl/Mn₃O₄ composites prepared have the flower-like structure with lamellar accumulation.When the mass fraction of Mn₃O₄ was 10%,at 40 min of light exposure,the Rh B solution with initial concentration of 20 mg/L was catalyzed by 0.5 g/L composite material,and its degradation rate was 95.17%.The improvement of the catalytic performance is mainly due to the ability of the flower structure of the composite material to trap pollutants and reflect light and to broaden the light absorption range.The photodegradation process of Rh B conforms to the pseudo-first-order reaction kinetic model,and the dominant active species is h⁺.3.Bi/BiOCl/BiOI composite material prepared by the three-step method was a ternary material combining amorphous and crystalline material,and it was applied to the photocatalytic degradation of BPA.The BPA degradation rate with p H 6 and initial concentration of 10 mg/L in 0.5 g/L Bi/BiOCl/BiOI composite reached 98.42%for 60min in the light.The ternary composite material has good stability.After four cycles,the catalytic degradation efficiency of BPA does not apparent decline.This is basically because of the modification of the material structure by the acid reduction method and surface plasmon resonance?SPR?effect and oxygen vacancies generated by the reduction of Na BH₄,which hinder the composite of electrons and holes in the material and improve the catalytic degradation performance of the Bi/BiOCl/BiOI ternary material.