Preparation Of Cobalt-based Composite Bimetal Oxide Catalyst And Its Activation Of Peroxymonosulfate Degradation Of Rhodamine B

Due to the development of printing and dyeing industry,a large number of dye wastewater goes into the water,which is harmful to the environment and human health.Rhodamine B（RhB）is a common pollutant in printing and dyeing wastewater.Advanced oxidation technology based on sulfate radical(SO₄^·-)is a widely studied water treatment method in recent years.Due to its advantages of strong oxidation capacity,high degree of mineralization and good stability of oxidizing agent,SO₄^·-has a good application prospect in the degradation of organic pollutants.The key to the application of SO₄^·-advanced oxidation techniques is to find methods and catalysts to activate persulphates.Thermal activation,ultraviolet activation and other applications are difficult because of the need for additional energy.With Co as a typical transition metal oxide to activate hydrogen persulfate to produce sulfate radical,not only has a good effect,but also can solve the shortcomings of homogeneous catalytic system with poor stability and not easy recovery,so it has become a research hotspot in the field of environmental catalysis.This paper takes rhodamine B as the target pollutant,uses Co₃O₄-Bi₂O₃,LaCoO₃,MnCo₂O_4.5to activate bisulfate to produce sulfate radical,uses a variety of methods to characterize the catalyst,and studies the influencing factors of the reaction system,reaction mechanism,etc.,expects to provide technical support for the treatment of printing and dyeing wastewater.Main research contents include:（1）Three Co₃O₄-Bi₂O₃catalysts were prepared by coprecipitation with different precipitators,and it was found that ammonia water was a better precipitator than Na OH and Na HCO₃.The three catalysts were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）and X-ray photoelectron spectroscopy（XPS）,and it was found that Bi and Co had a strong interaction in Co₃O₄-Bi₂O₃.The catalyst Co₃O₄-Bi₂O₃prepared by the three precipitants all had good catalytic effect.At 30°C,when the amount of PMS was 1.0 g/L and the amount of catalyst was 0.1 g/L,50 mg/L RhB could be completely degraded within 30 min.At the same time,the influencing factors of Co₃O₄-Bi₂O₃/PMS system were studied.At 30°C,the PMS was1.0 g/L,the catalyst was 0.1 g/L,and the concentration of RhB was 50 mg/L.The types of free radicals in CBO/PMS system were studied.^·OH and SO₄^·-were the main free radicals in the system.The reaction mechanism is that the surface activation of Co₃O₄-Bi₂O₃catalyst,PMS,produces SO₄^·-,which contacts with RhB to oxidize it to obtain small inorganic molecules such as CO₂and H₂O,so as to achieve the purpose of degrading pollutants.The reusability and stability of Co₃O₄-Bi₂O₃were studied.（2）Three perovskites,including LaCoO₃,LaMnO₃ and LaFeO₃,were successfully prepared by sol-gel method,and the three catalysts were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）and X-ray photoelectron spectroscopy（XPS）.It was found that LaCoO₃had the best catalytic effect and less cobalt ions were dissolved.At 30°C,when the amount of PMS is 0.5 g/L and the amount of catalyst is 0.1 g/L,50 mg/L RhB can be completely degraded within 30min.The influence factors of LaCoO₃/PMS system were studied.At 30°C,the quantity of PMS was 0.5 g/L,the quantity of catalyst was 0.1 g/L,and the concentration of RhB was 50 mg/L.The effects of common anions on the system were investigated.Among them,Cl^-,H₂PO₄^-,SO₄^2-and HCO₃^-had promoting effects on the system,while NO₃^-had less influence,and CO₃^2-had double effects.The types of free radicals in LaCoO₃/PMS were studied.^·OH and SO₄^·-were the main free radicals in the system.The reaction mechanism is that the surface activation of LaCoO₃catalyst PMS produces SO₄^·-,which contacts with RhB to oxidize it to obtain small inorganic molecules such as CO₂and H₂O,so as to achieve the purpose of degrading pollutants.The reusability and stability of LaCoO₃were studied.After four reusability,the catalyst still maintained good structure and catalytic performance.（3）MnCo₂O_4.5 spinel was successfully prepared by means of soluble heat calcining,and the performance of the three catalysts was compared.It was found that the catalyst prepared at 400°C had the best catalytic effect compared with 300°C and500°C,and the Co ion was less dissolved.The three catalysts were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）and X-ray photoelectron spectroscopy（XPS）.At 25°C,when the amount of PMS is 0.5 g/L and the amount of catalyst is 0.05 g/L,100 mg/L RhB can be completely degraded within20 min.The influence factors of MnCo₂O_4.5/PMS system were studied.At 25°C,the quantity of PMS was 0.5 g/L,the quantity of catalyst was 0.05 g/L,and the concentration of RhB was 100 mg/L.The effects of common anions on the system were investigated.Among them,H₂PO₄^-had a promoting effect on the system,HCO₃^-had an inhibiting effect,and Cl^-had a dual effect.The types of free radicals in MnCo₂O_4.5/PMS were studied.^·OH and SO₄^·-were the main free radicals in the system.The reaction mechanism is that surface activation of MnCo₂O_4.5catalyst PMS produces SO₄^·-,which contacts with RhB to oxidize it to obtain small inorganic molecules such as CO₂and H₂O,so as to achieve the purpose of degrading pollutants.The reuse performance and stability of MnCo₂O_4.5were studied.After four times of reuse,the catalyst still maintained good structure and catalytic performance.