Effect And Mechanism Of Madnetic Nano MnFe₂O₄/CNT Activated Persulfate On Catalytic Degradation Of Tetracycline

Tetracycline（TC）is widely used in the prevention and treatment of human and animal infections because of its excellent antibacterial properties and low price.However,it contains many benzene rings,high molecular weight,and its chemical properties are stable and not easily degraded.Sulfate radical（SO₄^-·）-based advanced oxidation technology has attracted the attention of researchers due to its long half-life,a wide range of suitable p H values,high selectivity to pollutants,and not easily affected by inorganic ions in water.Sulfate radical（SO₄^-·）-based advanced oxidation technology is mainly divided into homogeneous reaction systems and heterogeneous reaction systems.Mn Fe₂O₄is widely used as a heterogeneous catalyst because it contains two transition metals（Mn,Fe）,it can theoretically enhance the catalytic oxidation effect of heterogeneous advanced oxidation system,and strong magnetic properties.However,it is easy to cause agglomeration during use,which affects the activation performance of the catalyst,and many metal ions are precipitated,which can cause secondary pollution.How to solve these problems and improve the catalytic oxidation of the system is the key.In this study,four kinds of Mn Fe₂O₄/CNT（CNT as carbon nanotubes）nanocomposites with different mass ratios were made.As we all know,CNT has the inherent nature of carbon materials,has a high specific surface area and graphite cavity structure,and has the conductivity and heat conductivity of metal materials.It can be used as the carrier of catalysts to improve the dispersion of catalysts and eliminate the adverse effects of toxic metal leaching.Mn Fe₂O₄/CNT was applied to the catalytic oxidation system and three-dimensional electrode system.TC was used as the target pollutant to explore the effect and mechanism of catalyst in activating persulfate oxidation and degradation of TC.The main contents of the paper include the following parts:（1）The effect and mechanism of Mn Fe₂O₄/CNT activated persulfate oxidation to degradation of TC.The most active catalysts,80 wt%Mn Fe₂O₄/CNT,were selected by the difference between the catalytic removal rate and the adsorption removal rate.XRD results show that 80wt.%Mn Fe₂O₄/CNT materials are successfully fabricated;SEM images clearly show that the Mn Fe₂O₄grows evenly on carbon nanotubes;VSM test results show that the80wt.%Mn Fe₂O₄/CNT has strong magnetic properties and significant solid-liquid separation;BET analysis shows that the 80wt.%Mn Fe₂O₄/CNT has a large specific surface area and the pores are mainly distributed between 2-50 nm.The effects of catalyst dosage,oxidant dosage,initial concentration of TC,temperature,and initial p H on the degradation efficiency of TC were investigated.The results showed that the removal efficiency of TC was 80wt.%.Under the conditions（80wt.%Mn Fe₂O₄/CNT dosage,PDS concentration,reaction time,initial p H,initial concentration of TC,and the reaction temperature were 0.5 g/L,4 m M,90 min,5.9,40mg/L,and 30℃,respectively）,the removal efficiency of TC and TOC reached 78.85%and51.97%,respectively.The results of XRD and the contribution of metal ions to the system before and after the reaction proved that the material has good stability;the reusability of80wt.%Mn Fe₂O₄/CNT is evaluated,and the catalyst remains high activity after three times of repetition;this proves that 80wt.%Mn Fe₂O₄/CNT catalyst has better stability and reusability.According to the free radical capture experiment and EPR characterization test,the active species of the system were determined.The system contained SO₄^-·,·OH,·O₂^-,and the possible reaction mechanism was inferred by XPS analysis of the catalyst before and after the reaction.The intermediate products of TC were detected by liquid chromatography-mass spectrometry（UPLC-MS）,and the degradation pathway was inferred.（2）The effect and mechanism of electro Mn Fe₂O₄/CNT on the oxidation and degradation of tetracycline by persulfate.A new activation method,which is introduced into Mn Fe₂O₄/CNT/PMS system,is used to form a three-dimensional electrode system,and the removal efficiency of TC is investigated.The most active catalyst,20wt.%Mn Fe₂O₄/CNT was selected by the difference between the electric CO removal rate and the catalytic removal rate.XRD results show that 20wt.%Mn Fe₂O₄/CNT materials are successfully fabricated;SEM images clearly show that the Mn Fe₂O₄grows evenly on CNT;VSM test results show that 20wt.%Mn Fe₂O₄/CNT has strong magnetic properties and significant solid-liquid separation;BET analysis shows that the material has a large specific surface area.The effects of catalyst dosage,oxidant dosage,current density,and initial p H of TC on the removal efficiency of TC were investigated.The TC removal efficiency reached 87.7%under the conditions（20wt.%Mn Fe₂O₄/CNT dosage,PMS concentration,current density,initial p H,initial concentration of TC,and the reaction time were 0.1 g/L,6 m M,10 m A/cm²,5.9,40mg/L,and 120 min,respectively）.Moreover,the type of free radicals in the system was determined by the free radical capture experiment,and the internal reaction mechanism was inferred by XPS analysis of the catalyst before and after the reaction.The intermediate products of the system were detected by UPLC H-CLASS+QTOF G2-XS and their reaction paths were inferred.