Preparation Of Catalyst Based On The Structure Of MIL-53(Fe) And Its Application In Advanced Oxidation Treatment Of Printing And Dyeing Wastewater

High water consumption and high waste water discharge of Printing and dyeing is the biggest problem to impede the sustainable development of the printing and dyeing industry.Advanced Oxidation Processes(AOPs)can produce a large number of free radicals,which can oxidize and destroy wastewater pollutants efficiently and mineralize wastewater pollutants,and then realize the reuse of treated water.Therefore,AOPs is one of the most promising technologies to solve the above problems in the printing and dyeing industry.Metal-Organic Frameworks(MOFs),as a new type of porous material,has attracted much attention in the application of AOPs.However,in the heterogeneous Fenton and other AOPs,there are still problems such as excessive amount of oxygen source and low efficiency,which affect its wide application.In this paper,by designing and adjusting the internal node structure of a typical Fe-MOFs catalyst-MIL-53(Fe),a new type of catalyst Fe?-MIL-53(Fe)is developed.While improving its mass transfer performance,Increase the number of active centers to promote the efficient cycle conversion of Fe(?)/Fe(?),thereby enhancing the Fenton-like activity of Fe-MOFs.On this basis,aiming at the problem that H2O2 with a highly symmetrical structure is difficult to be activated thermodynamically,the performance of the prepared catalyst to activate non-symmetrical structure of peroxyacetic acid(PAA)was explored,so as to obtain a more efficient advanced oxidation and degradation system for printing and dyeing wastewater.In addition,the one-step calcination method is used to develop the MIL-53(Fe)carbon-based derivative,and the high electron transport ability of inorganic carbon is used to promote the high-efficiency cycle conversion of Fe(?)/Fe(?)to strengthen the catalytic activation of PAA.The specific research content and results are as follows:Part 1:Study on preparation of Fe(?)/Fe(?)Multivalent MIL-53(Fe)and its Fenton-like Activity.In order to improve the Fenton activity of Fe-MOFs,a multivalent MIL-53(Fe)(Fe?-MIL-53(Fe)was developed in this chapter by using Fe(?)substitution method to regulate the structure of iron-oxo nodes in MIL-53(Fe).The effect and mechanism of its synergistic Fenton reaction on the degradation of 4-NP model pollutant were studied.The results show that the ferrous ion doping strategy can increase Fe(?)coordination unsaturation sites and increase the redox potential of Fe(?)/Fe(?)in MIL-53(Fe),thereby achieving Fe(?)/Fe(?)cycle is accelerated to enhance the Fenton-like catalytic reaction performance of MIL-53(Fe).When Fe(?)doping amount is 30%,Fe?-MIL-53(Fe)shows excellent catalytic performance,and the degradation rate and kinetic degradation rate constants of Fe?-MIL-53(Fe)are 1.39 and 9.48 times of that of MIL-53(Fe),respectively.The synergistic catalysis mechanism of ferrous ion doping strategy was found:The substitution of Fe(?)can act as a stronger H2O2 catalytic active site than Fe(?),and promote the occurrence of Fe(?)?Fe(?)oxidation half reaction;in addition,Fe(?)substitution can induce the generation of more unsaturated coordination Fe(?)centers,enhance the Lewis acid site density,promote the occurrence of Fe(?)4Fe(?)reduction half reaction,improve the cycle conversion efficiency of Fe(?)/Fe(?)active centers,and thus activate H2O2 decomposition to produce more·OH,at last enhanced removal of typical organic pollutants from printing and dyeing wastewater.Part 2:Study on the catalytic activation performance of Fe?-MIL-53(Fe)for Peroxyacetic Acid.In order to further improve the catalytic oxidation efficiency of advanced oxidation system using Fe-MOFs as catalyst,this chapter selects peroxyacetic acid(PAA),which is more easily activated thermodynamically as the oxygen source of advanced oxidation systems,and heterogeneous catalysis based on Fe-MOFs was developped.The effect and mechanism of PAA on the degradation of typical organic pollutants 4-nitrophenol(4-NP)in printing and dyeing wastewater were studied.The results show that the kinetic degradation rate constant of 4-NP in the Fe?-MIL-53(Fe)catalytically activated PAA system is 2.23 times that of the original Fe?-MIL-53(Fe)catalytically activated H2O2 system,up to 0.052 min-1.It was found that the high-efficiency oxidative degradation effect of 4-NP in the Fe?-MIL-53(Fe)catalytically activated PAA system depends on the chemical behavior of peroxyacetic acid on the surface of the catalyst:On the one hand,compared with H2O2,the structure of asymmetric PAA was more easily activated by the O-OH and OO-H bonds,and further decomposed into·OH;on the other hand,the Fe(?)/Fe(?)cyclic conversion continuously decomposes PAA to produce more abundant·OH and RO·,and multi-path oxidation degrades wastewater organic pollutants of printing and dyeing.Part 3:Preparation of calcined MIL-53(Fe)material and its catalytic activation performance for Peroxyacetic Acid.In order to further strengthen the catalytic activation efficiency of MIL-53(Fe)PAA,in this chapter,a carbon-based derivative of MIL-53(Fe)was developed by a one-step calcination method.The carbonization effect of inorganic carbon with high electron transport ability was used to improve the electron transfer ability of PAA catalytic activation surface interface reaction,so as to strengthen the catalytic activation effect of PAA.The results show that a kind of mesoporous iron/carbon composite hybrid material(MIL-53(Fe)carb-based derivative)can be prepared by heating MIL-53(Fe)in nitrogen atmosphere at 500?for 3 h.The 4-NP kinetic degradation rate constant of the PAA system catalyzed by MIL-53(Fe)carbon-based derivatives is 7.78 times that of the PAA system catalyzed by MIL-53(Fe),up to 0.28 min-1.It was found that the mechanism of synergistic catalytic activation of MIL-53(Fe)carbon-based derivatives on PAA was as follows:The carbonization effect induced a more efficient transfer of electrons between the two substrates of iron and carbon in the material,which improved the catalytic activation effect on PAA,thus promoting the system to produce more reactive oxygen species to degrade organic pollutants in printing and dyeing wastewater.The research in this paper found that based on the controllability of the iron-oxygen cluster structure in MIL-53(Fe)and combined with the characteristics of Fenton reaction rate-limiting steps of Fe-MOFs,the strategies of Fe(II)doping to increase the unsaturated site of Fe(III)coordination and to increase the redox potential of Fe(III)/Fe(II)in MIL-53(Fe)to accelerate the performance of cyclic synergistic Fenton catalytic reactions were proposed;based on Fe-MOFs+H2O2 Fenton-like raction,a novel Fe-MOFs+PAA catalytic activation system with higher catalytic oxidation efficiency was proposed by taking advantage of the easy catalytic activation of the asymmetric molecular structure of peracetic acid;based on the high electron transport capacity of carbonization effect of Fe-MOFs carbon derivatives and the internal relationship between OH generated by the breaking of O-O bond of peroxyacetic acid and electron transport,an innovative strategy was proposed to prepare iron/carbon hybrid material with high composite conductivity by one-step calcination to enhance the catalytic activation of PAA by Fe-MOFs,as a heterogeneous catalyst for PAA catalytic activation,iron/carbon hybrid material has a better catalytic performance than MIL-53(Fe),achieving a more rapid and efficient degradation of target organic pollutants.In conclusion,this study provides a good theoretical basis and methodical guidance for the development and practical application of advanced oxidation catalysts in the field of advanced treatment of printing and dyeing wastewater.