Study On Defective Fe(Ⅱ)-MOFs And Its Derivatives Activate Persulfate For Targeted Degradation Of Emerging Contaminants In Water

With the rapid development of industry and the improvement of environmental analysis technology,the types of emerging contaminants（ECs）detected in water bodies are increasing,and the concentration of ECs in water bodies is low（ng/L-μg L）.However,it is highly toxic and difficult to biodegrade,which seriously threatens the sustainable development of the ecological environment and human health.The advanced oxidation technology based on persulfate（PS）has attracted the attention of researchers because of its strong oxidative degradation ability,broad p H application range,and efficient removal of ECs in water.However,the existing PS activation method has the problems that excessive free radicals quench side reactions and easily cause secondary pollution.Metal-organic frameworks（MOFs）with large specific surface area,open metal sites,and adjustable pore structure have attracted widespread attention in the field of heterogeneous catalysis.However,there are few catalytic active sites in the framework of existing iron-based MOFs,low degradation efficiency for low-concentration emerging pollutants,and increased yield of toxic oxidation by-products.Therefore,designing an environmentally friendly heterogeneous catalyst with high-density catalytic active sites is of great research significance for the efficient degradation of ECs.Based on the fact that fewer active sites exposed in the framework of existing iron-based MOFs limit their catalytic activation efficiency,this thesis adopts the regulator-induced method to prepare iron-based MOFs with high density coordination unsaturated metal active sites for catalytic activation of PS to treat typical emerging contaminants TBBPA,to investigate the effect of the regulator chain length structure on the crystal structure,surface morphology,specific surface area and pore structure of the catalyst,the valence state of the metal center,and the catalytic activation of PS oxidation of TBBPA.The study found that Fe（BDC）（DMF,F）-OA-30 prepared with OA octanoic acid（OA）as the and molar equivalent concentration of 30 has the most complete surface morphology and crystal structure,the largest specific surface area of 76.3 m2/g,and pore 0.725 cm3/g,the maximum density of coordinated unsaturated metal active sites,that is,the maximum relative content of Fe^II/Fe^IIIis 2.35,and the removal rate of TBBPA reaches 90.13%within 120 minutes.Using Fe（BDC）（DMF,F）-OA-30 as a catalyst,the effects of reaction conditions such as the amount of catalyst added,the amount of PS,the initial concentration of TBBPA and the initial p H of the reaction solution on its catalytic reaction were investigated.It was found in[TBBPA]=0.018 m M,the catalyst dosage is 1.0 g/L and[TBBPA:PS]=1:200,under the optimal process conditions,the degradation efficiency of TBBPA reached 97.55%after 120minutes of reaction,and the first-order reaction rate constant was 3.22 min^-1.At the same time,it was confirmed that the octanoic acid（OA）competes with the original terephthalic acid ligand for the coordination construction defect Fe（BDC）（DMF,F）-OA-30,which generates more coordinated unsaturated metal active sites to promote the reaction system.The electron transfer rate and the formation of a good redox cycle reaction generate free radicals,from which the possible reaction mechanism of the catalytic reaction is derived.Based on the existing iron-based MOFs catalytically activating PS systems,a large number of free radicals are generated in a short period of time,which is prone to quenching reactions,resulting in low free radical utilization efficiency,low degradation efficiency for low-concentration emerging pollutants,and increased yields of toxic oxidation by-products.In this study,Fe（BDC）（DMF,F）-OA-30 derivative（C-Fe-Nx）is used as the catalytic active center to prepare a dual-function catalyst MIPs@C-Fe-Nx with targeted recognition adsorption center and catalytic active center-Nx,the study found that MIP-3@C-Fe-Nx can remove up to 104.6 mg?g^-1 of TBBPA through the synergistic effect of catalysis and adsorption.Competitive adsorption experiments show that MIP-3@C-Fe-Nx the imprinting factors of TBBPA and its debrominated products are all higher than 3.80.The combination of DFT theoretical calculations and LC-MS experimental results indicate that the degradation pathways of TBBPA mainly include the debromination of the benzene ring,the cleavage of the carbon atom of the isopropyl center,that is,the?-bond cleavage and the debromination hydroxylation process on the benzene ring.Study on defective Fe（II）-MOFs and its derivatives activate persulfate for targeted degradation of emerging contaminants in water...