Study On Preparation Of MXene-based Iron Complex Materials And Their Catalytic Degradation Of Organic Dyes

With the changes of the times,the problem of environmental pollution is becoming more and more serious.As the source of life,water pollution cannot be ignored.Industrial wastewater represented by organic dyes has attracted widespread attention due to its complex composition and high chromaticity.As a type of wastewater that is difficult to treat,it is not easy to be removed by ordinary sewage treatment methods.Fenton oxidation technology has emerged in the field of organic dye wastewater treatment due to its strong oxidizing property and good degradation effect on organic dyes.For the Fenton oxidation technology,the performance of the catalyst plays a decisive role.As a new type of material,MXene has the characteristics of large specific surface area,easy surface modification,good structural stability and so on,which can be used for the preparation of catalyst materials.Based on this,in this study,MXene-based iron complex catalysts were prepared and the efficient degradation of organic dyes was achieved.The main research contents and results are as follows:（1）Due to the electronegativity of the MXene,the cationic surfactant,chitosan,containing amino groups can be modified onto the MXene,and then it can react with pyridine-4-carboxaldehyde to form Schiff base.A synthetic route for the MXene-based Schiff base pyridine iron complex catalyst was designed and successfully prepared,because that Fe can form coordination bonds with the C=N in Schiff bases and the N in pyridine rings.The samples at key steps in the preparation process were characterized by SEM+EDS,TEM,XPS and FT-IR,and the status of each sample was analyzed,which demonstrated that MXene-Bpy@Fe contains Fe²⁺and Fe³⁺required for the Fenton reaction,providing a theoretical basis for the subsequent catalytic degradation of organic dyes.（2）The catalytic performance of MXene-Bpy@Fe was tested in terms of catalyst concentration,H₂O₂ concentration,p H,temperature,cycling stability and degradation of different organic dyes.The results show that the increase of the catalyst concentration or the decrease of the H₂O₂ concentration is beneficial to increase the degradation rate of methylene blue（MB）,and the increase of the temperature can also accelerate the degradation of MB.Furthermore,the cycle stability of MXene-Bpy@Fe is good,and it also shows good degradation effect on different organic dyes.（3）Since Fe can form coordination bonds with-COOH in trimesic acid to form complexes,the diazotized 5-aminoisophthalic acid was used as a bridge between MXene and the complexes so that the Fe complexes could be modified onto MXene,and then the catalyst named MXene-H3BTC@Fe was prepared.Characterization analysis demonstrates the successful preparation of the catalyst and the MXene-H3BTC@Fe after the high temperature treatment has contained a large amount of Fe²⁺and Fe³⁺,which is conducive to the rapid Fenton reaction and can achieve the efficient degradation of organic dyes.（4）The catalytic performances of MXene-H3BTC@Fe including catalyst concentration,H₂O₂ concentration,p H,temperature,cycling stability and degradation of different organic dyes were tested.The results show that the optimal combination of Fenton reagent is 0.2 g/L of MXene-H3BTC@Fe with 18 mmol/L of H₂O₂,and it can be used under acidic,neutral or weak alkaline conditions.What’s more,MXene-H3BTC@Fe has shown excellent cyclic stability and good degradation effect on different organic dyes.（5）By analyzing the kinetics of the catalytic degradation of organic dyes using MXene-Bpy@Fe or MXene-H3BTC@Fe as the catalyst,it is found that the catalytic kinetics of the two are more closely related to the pseudo-first-order and pseudo-second-order reaction kinetics.The free radical experiments corroborated that·OH and·O₂^-play the key roles in the degradation of the organic dyes and that the yield of·OH is greater than that of·O₂^-.ESR tests show that·OH and·O₂^-are generated by the catalyst catalyzing H₂O₂,and both of them are present throughout the catalytic degradation process.