Construction Of Iron-Based Wide-pH Electro-Fenton-Like System And Its Efficient Degradation Of Antibiotic Wastewater

The electro-Fenton reaction is a low-cost,high-efficiency,and environmentally friendly advanced oxidation technology and has attracted much attention in the treatment of water pollution.However,it is limited by the low Fe（III）/Fe（II）cycle reaction efficiency,the limited in-situ generation ability of H₂O₂and restricted p H application range.The electro-Fenton-like technology can overcome the above shortcomings to a certain extent and has been extensively researched.This paper focuses on the construction of iron-based wide-p H electro-Fenton-like system and its research on the efficient degradation of antibiotic wastewater.The main research contents includes the following three parts:（1）The electro-Fenton reaction is limited by the low in-situ generation capacity of H₂O₂and the slow redox cycle of Fe（III）/Fe（II）.In this chapter,Fe₃O₄-CaO₂was used as the cathode,and a self-circulating electro-Fenton-like system was constructed under the promotion of peroxomonosulfate（PMS）,which realized the efficient degradation of refractory organic wastewater.The degradation efficiency of the system for levofloxacin（LEV）reached 92.1%,and the removal rate of COD was as high as 89.8%.The power consumption was only 0.76 k Wh m^-3,which was about 5.0%of the traditional electro-Fenton method.The main reason for the outstanding performance of this system is partially related to the structure of the Fe₃O₄-CaO₂catalyst.Since CaO₂is wrapped by Fe₃O₄,the structure of Fe₃O₄-CaO₂catalyst is relatively stable.Mechanistic analysis showed that CaO₂could not only replace H₂O₂to promote the oxidation of Fe（II）to Fe（III）,but also form a complex with Fe（III）and PMS to transfer electrons from the ligand to the metal,thereby enhancing the reducing reaction from Fe（III）to Fe（II）and lowering the energy consumption of the whole degradation reaction.At the same time,the hydrolysis product Ca（OH）₂reacts with Fe（III）in the presence of H₂O₂,and is continuously converted into CaO₂.As a result,an efficient continuous cycle of CaO₂/Ca（OH）₂and Fe（III）/Fe（II）simultaneously occurs on the CaO₂@Fe₃O₄surface,resulting in more active species.Quenching experiments and electron paramagnetic resonance（EPR）showed that ¹O₂was the main active species for degrading LEV.This work innovatively proposes a self-circulating electro-Fenton-like system,and broadens the potential application of CaO₂@Fe₃O₄in the degradation of organic pollutant wastewater.（2）Using tannic acid（TA）as the organic ligand and Fe and Ce as the metal sources,Fe-Ce-TA MPNs with the metal polyphenol network structure were prepared.Then porous carbon supported Fe-Ce oxide（Fe₂O₃-Ce O₂/PC）were synthesized by calcining the above metal-phenol network structure materials.Using this material as the cathode,an electro-Fenton-like system was constructed.Under the optimal conditions of natural p H,20 mg L^-1TC and the current density of 20 m A cm^-2,the degradation rate of TC reached 93.6%,and the removal rate of COD also reached 93.7%after electrolysis for120 min.The main reasons for the remarkable performance of the electro-Fenton-like system are as follows.Firstly,the porous network structure derived from MOF templates can expose more active sites,ensuring the full contact between pollutants and active sites.In addition,the introduction of tannic acid can effectively broaden the applicable p H range.The cycle of Fe（III）/Fe（II）and Ce（IV）/Ce（III）and the regeneration of Fe（II）and Ce（IV）is obviously enhanced under the wide p H conditions,which is conducive to the generation of ROS and achieving the effective removal of pollutants under the neutral p H conditions.Therefore,the heterogeneous electro-Fenton-like system based on Fe₂O₃-Ce O₂/PC derived from Fe-Ce-TA MPNs can overcome the p H limitation to some extent and effectively remove organic pollutants in wastewater under neutral p H conditions.（3）NiFeCe LDH/NF cathode was prepared by hydrothermal method,and the results of SEM,XPS,EDS and XRD confirmed the successful preparation of the material.In addition,the electrocatalytic performance of the Ni Fe Ce LDH/NF cathode was deeply analyzed by combining CV,EIS,and LSV.Under the optimal conditions of p H 5.8,initial CFX concentration of 20 mg L^-1and current density of 30 m A cm^-2,the degradation rate and removal rate of COD reached 93.6%and 88.9%within 120 min,respectively.Combined with the experimental results,it is speculated that the improved degradation efficiency of CFX by this system is mainly attributed to the synergistic effect among the three metals of Fe,Ni,and Ce.The presence of NTA promotes the redox cycles of Fe（Ⅲ）/Fe（Ⅱ）,Ni（Ⅲ）/Ni（Ⅱ）and Ce（Ⅳ）/Ce（Ⅲ）in a wide p H range,which enhances the generation efficiency of H₂O₂and active species,and effectively promote the oxidative decomposition of CFX.Lastly,according to the results of GC-MS and UV-vis,the possible electro-Fenton degradation pathways of CFX was deduced.