| Chloramphenicol is a broad-spectrum antibiotic with good antibacterial properties and low production cost.It is widely used in the treatment of human or animal diseases.However,the residual chloramphenicol in the environment is harmful to the human body and the ecological environment.Chloramphenicol is frequently detected in the water body,and most of the detection concentrations are low.The sewage plant has a low degradation effect on antibiotics.SO4-produced by the activation of persulfate has the advantages of high oxidation-reduction potential,long existence time and wide applicable pH range.It has been applied in the research of antibiotic removal.In this paper,Fe3O4-MnO2 magnetic nanomaterials were synthesized by a simple one-pot heat method.The prepared materials have the advantages of low cost and environmental friendliness,The magnetic properties can meet the requirements of magnetic separation,which can effectively activate PMS to degrade chloramphenicol in water.In this paper,Fe3O4,MnO2 and Fe3O4-MnO2 magnetic nanomaterials were synthesized separately.During the preparation of Fe3O4-MnO2,the reaction speed was adjusted to obtain three different materials(slow,medium and fast)of Fe3O4-MnO2;Increase the amount of Fe to get Fe3O4-MnO2 with different Fe/Mn ratios(6,5,4,3.3,2.7);Various characterizations of the synthesized materials were made,analyze the basic morphology,composition elements,magnetic size,etc.of the materials were systematically studed;results SEM and TEM images show that Fe3O4 is uniform spherical particles,with the MnO2 coating on the surface of the material,The composite material has a core-shell structure;the slow-synthesized Fe3O4MnO2 has incomplete MnO2 coating on the surface,and the morphology is similar to Fe3O4.The surface morphologies of medium-speed and fast-synthetic materials are similar;EDS diagrams showed that Fe and Mn are the main elements in the composite materials,with the ratio of the two being about 4;element mapping of different elements is similar,indicating that the composite elements are evenly distributed;The standard card confirms that the synthesized material is containing Fe3O4 and ?-MnO2;the measurement of the VSM of the material shows that the magnetization of Fe3O4-MnO2 is up to 24.7 emu g-1,which can achieve magnetic separation during the experiment;BET analysis results show that the pore volume,the average pore diameter and the specific surface area of Fe3O4-MnO2 are 0.54 cm3 g-1,26.77 nm,and 70.73 m2 g-1 respectively Compared with the standard spectrum,the XPS spectrum shows that three typical peaks of O1 s,Mn2p,and Fe2p appear at the binding energy of 529 eV,653 eV,and 724 eV,respectively.After the preparation of materials,the adsorption and catalytic effects of different materials were studied.The activation effects of different rotation speeds and different Fe/Mn synthetic materials were compared;Fe3O4-MnO2 activations effects towards PMS,PS and H2O2 were compared.The effect of dosage of Fe3O4-MnO2,dosage of PMS,and the initial pH on the degradation were investigated.The removal of TOC in the reaction was studied.The results show that the degradation effects of medium-and slow-speed synthetic materials are similar,and the removal rate of chloramphenicol is above 90%.For slow-speed synthetic materials,because MnO2 is not well coated the activation effect is limited;The catalytic degradation showed the best performance when Fe/Mn is 4,mainly due to the difference in shell thickness;Fe3O4-MnO2 has the most significant activation effect towards PMS,and its effects for PS and H2O2 are not obvious.This is due to the difference in bond energy caused by the difference in the structure of three oxidants.While PMS has an asymmetric structure;the results show that the removal rate of chloramphenicol is different with the adding amount of Fe3O4-MnO2 and PMS.The activation effect is poor under alkaline conditions.NOM and several common anions inhibit the removal effect of chloramphenicol to a certain extent;With the final removal rate of TOC being 46.6%;The XPS pattern and the XRD pattern of the material before and after the reaction did not change significantly,indicating that the material is relatively stable.The quenching experiment combined with EPR technology was used to verify the types of free radicals and dominant free radicals present in the system;XPS technology was used to analyze the changes in element valence and content before and after the material reaction,and FTIR technology was used to analyze the functional groups present on the surface of the material.Intermediates generated during the degradation process by liquid-mass spectrometry technology to infer the possible degradation path of chloramphenicol;The dissolution of Fe and Mn ions in the system after the reaction is investigated with ICP,The prepared materials were used for five times to evaluate its recycling use.The results show that:Fe3O4-MnO2/PMS system produces SO4·-and·OH,and SO4·-plays a major role in the degradation of chloramphenicol During the activation process,Mn plays a catalytic role,and there is an electronic exchange between Fe and Mn,which promotes the conversion between Fe2+/Fe3+ and Mn3+/Mn4+.This synergistic effect between Fe and Mn improves the activation effect of the prepared material The product produced during the degradation process is analyzed by liquid-mass spectrometry and chlorineamycin is mainly removed by denitrification,hydroxyl structure,oxidation of amino groups and side chain breakage;the dissolution of Fe and Mn ions is lower than the national emission standard,and Fe3O4-MnO2 can still guarantee a certain degree of recycling after five uses Removal rate. |
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