Mesoporous Carbon-Anchored Cobalt Ferrite Nanoparticles As An Activator Of Peroxymonosulfate For Efficient Degradation Of Congo Red

With the rapid development of society and the increase of people’s material needs,the utilization rate of printing and dyeing wastewater in industry and daily life has increased significantly,and the resulting wastewater discharge has brought serious harm to aquatic organisms,ecosystems and human health.In all kinds of organic dyes,Congo red（CR）is widely used in cotton fiber color,in other industries used as acid-base indicator,in the manufacturing and use process of high loss rate of a typical azo organic dye pollutants.It is difficult to remove in the natural environment due to benzene rings and other structures that are difficult to degrade,causing some annoyance to the natural ecological environment.Therefore,the research on effective removal of CR in wastewater has become one of the hot spots of researchers at home and abroad.In this study,CR in water was used as the target pollutant,nano-CoFe₂O₄ and mesoporous carbon-supported nano-cobalt ferrite（nano-CoFe₂O₄@MC）were used as catalysts.Various analytical techniques were used to characterize the catalysts prepared under the optimal conditions,and an activated peroxymonosulfate（PMS）advanced oxidation system was established.The degradation effect and influencing factors of the oxidation system on CR were discussed,and the degradation mechanism of CR by the catalyst activated PMS system was revealed.The specific analysis results are as follows:（1）Nano-CoFe₂O₄ was prepared by coprecipitation method.The uniform arrangement of spherical nano-CoFe₂O₄ was clearly observed by SEM images,and a little aggregation occurred after the reaction.XRD results prove that the catalyst is composed of Co,Fe,O and other elements;FTIR results show that nano-CoFe₂O₄ has abundant surface functional groups,and the catalyst has no obvious change after reaction,indicating that the catalyst has good catalytic stability.XPS analysis showed that the catalyst was composed of Co,Fe and O elements.TGA and VSM analysis catalysts have excellent thermal stability and magnetic properties.The results of the above determination method prove the successful preparation of nano-CoFe₂O₄.It is found that the degradation efficiency of nano-CoFe₂O₄/PMS system is better than that of nano-CoFe₂O₄ and PMS.In the nano-CoFe₂O₄/PMS system,when the dosage of nano-CoFe₂O₄ is 0.1 g/L,the concentration of PMS is 0.5 mmol/L and p H is 6.0,the degradation rate of CR at 0.02 g/L reaches the highest 89.75%in 60 min.Anions in water inhibit CR degradation to different degrees in this system.After 5 cycles,the removal rate of nano-CoFe₂O₄ for CR is still above 83%.Studies on the activation mechanism showed that reactive oxygen species（ROS）such as^·O₂^-,¹O₂,^·OH and SO₄^-·all participated in the degradation reaction.（2）Nano-CoFe₂O₄@MC was prepared by hydrothermal method.SEM and TEM images showed that the spherical nanoparticles were uniformly arranged together,and the loading of MC solved the aggregation site defect of nano-CoFe₂O₄.The results of XRD and FTIR analysis showed that the catalyst was successfully prepared and contained carboxyl group（COOH）,hydroxyl group（OH）,carbonyl group（C=O and C-O）and other rich functional groups.BET analysis results indicate that the catalyst possess a large specific surface area.XPS analysis results show that the catalyst is composed of Fe,Co,O,C and other elements.VSM results show that the catalyst has excellent magnetic properties.The results of TGA and Raman test show that the catalyst has unexceptionable thermal stability and defect degree.The experimental results show that the degradation effect of nano-CoFe₂O₄@MC/PMS system is better than that of nano-CoFe₂O₄/PMS,MC/PMS,nano-CoFe₂O₄,PMS and MC systems.In nano-CoFe₂O₄@MC/PMS system,when nano-CoFe₂O₄@MC dosage was 0.01 g/L,PMS concentration was 0.3 mmol/L and p H was 6.0,the degradation rate of CR 0.02 g/L reached the highest 91.25%within 60 min.Anion and humic acid in water have different effects on the degradation of CR.It was found that the removal rate of CR was still as high as88.35%after 5 cycles,indicating that the catalyst had excellent stability.The mechanism of activation of PMS showed that ROS contributed to the degradation of CR in different degrees,and the contribution rate was^·O₂^->¹O₂>^·OH>SO₄^-·.Twelve intermediate products were identified by LC-MS analysis,and three possible CR degradation pathways were proposed.In summary,nano-CoFe₂O₄@MC catalyst has the advantages of higher surface energy,strong catalytic stability and high recyclability,which provides reference for the application and development of advanced oxidation technology of persulfate.