Degradation And Mechanism Of Organic Contaminants With Bismuth-contained Composites Under Visible Light

Dye wastewater is complex and difficult to be degradated,leading to water eutrophication and the death of plants and animals.Antibiotics easily remains in the water environment and causes a serious threat to the ecosystem.The traditional methods of treating wastewater are difficult to remove pollutants.However,the photocatalytic technology is considered as a promising method for effectively removal of environmental pollutants.It has some advantages,such as good stability,high catalytic activity,fast reaction rate and so on.To increase the catalyst's utilization of light,degrade dye wastewater and antibiotics more efficiently and environmentally and improve the water environment,this study synthetized m-Bi₂O₄/Bi₂O₂CO₃ photocatalyst by a facil one-step hydrothermal method.Moreover,the research also synthetized a novel heterostructure photocatalyst m-Bi₂O₄/BiOCl through the facile ion-etching method.The physical,chemical and optical properties of photocatalysts were obtained by various characterization methods,including X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,scanning electron microscopy?SEM?,high resolution transmission electron microscopy?TEM?,selected area electron diffraction pattern?SAED?,X-ray photoelectron spectroscopy?XPS?,UV-vis diffuse reflectance spectrum?UV-vis DRS?,Raman,Specific surface area analyzer?BET?and fluorescence spectroscopy?PL?.Meanwhile,the m-Bi₂O₄/Bi₂O₂CO₃ subject has comprehensively evaluated the degradation performance of Rhodamine B?RhB?,methyl orange?MO?and mixed dyes under visible light.In the research,the effects of the initial concentration of dye and the amount of catalyst were investigated and the kinetic fit was used to characterize the rate of degradation.The MO,malachite green?MG?and tetracycline were selected as the target pollutants to evaluate the m-Bi₂O₄/BiOCl photocatalytic performance.The free radical trapping experiments was conducted to explore the respective roles of hydroxyl radicals?·OH?,holes?h⁺?and superoxide free radicals(·O^2-)during the photocatalytic degradation.Combining with the photocurrent response experiments,the mechanism of m-Bi₂O₄/Bi₂O₂CO₃ photocatalytic degradation of dyes and m-Bi₂O₄/BiOCl degradation contaminants were proposed.The research results of m-Bi₂O₄/Bi₂O₂CO₃ photocatalytic degradation of dyes are as follows:The experiment successfully prepared m-Bi₂O₄/Bi₂O₂CO₃ photocatalyst.Compared with the blank experiment and single catalyst degradation,the dyes of RhB and MO could be degraded under visible light and the best photocatalyst was 6-B/BOC.It could degraded93.4%of RhB within 50 min and the removal rate was up to 95.3%for MO in 10 min.When the concentration of RhB was 5 mg/L,the photocatalytic activity was best.Adding 75 mg of6-B/BOC samples,the degradation rate was the fastest.In addition,the catalyst also degraded mixed dyes of RhB,MO and methylene blue?MB?.The h⁺and·O^2-played a major role during the process of catalytic degradation.It could oxidate organic matters directly or indirectly.The 6-B/BOC composite had the lowest PL intensity and the electrons and holes are less likely to be recombined internally.At the same time,the strongest photocurrent signal was indicated that the carrier was transferred effectively.This research results of m-Bi₂O₄/BiOCl degrading organic pollutants are as follows:The heterostructured m-Bi₂O₄/BiOCl photocatalyst was successfully synthetized.Comparing with the photolysis of pollutants and the single of catalyst degradation,the optimal ratio of photocatalyst BCl-1 degraded 95%of MO in 10 min,85.5%of tetracycline within 150 min and the degradation rate of MG within 70 min was 87.1%.In the process of degradation,the h⁺was the most vital free radical and·O^2-was important,but the role of·OH was non-essential.Compared with the BiOCl,the composite increased the threshold of absorbed light,decreased the bandgap energy and improved the utilization of photons.The BCl-1 photocatalyst exhibited the strongest photoelectric signal and the highest separated rate of electrons and holes,resulting in the enhancement of photocatalytic activity.