Efficacy Of Fe₃O₄/GO/Nickel Foam Cathodic Electro-fenton Method For The Degradation Of Antibiotic Wastewater

A pharmaceutical company has added a market-oriented quinolone production line,while the original workshop production process has changed,the water quality and quantity has changed significantly,the pretreatment section needs to explore the process and complete the biochemical section process transformation at the same time.Electro-fenton as a highly efficient and green pretreatment means has attracted the attention of researchers.The choice of cathode material greatly affects the efficiency of electro-fenton treatment,so it is necessary to develop cathode materials that can collect current efficiently and have low impedance.In this paper,Fe₃O₄/GO/nickel foam composite electrode was prepared with the starting point of increasing the active sites on the surface of the cathode material and effective current collection,and the electrode was characterised by scanning electron microscopy,transmission electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,and the results showed that Fe₃O₄/GO formed a core-shell structure and was successfully loaded on the surface of nickel foam,and the doping of GO formed new chemical bonds,and the cathode The doping of GO resulted in the formation of new chemical bonds and the increase of oxygen-containing functional groups on the surface of the material,which increased the active sites of chemical reactions.The optimum conditions for the degradation of norfloxacin by Fe₃O₄/GO/nickel foam electro-Fenton method were pH 3,reaction current 0.3A,electrolyte concentration 0.05 mol/L and aeration 200 m L/min.The COD removal rate was 78.9%under the optimum conditions.The COD removal rate decreased from 78.9%to 42.1%after the cathode material was reused five times,and the leaching and depletion of Fe and O elements were demonstrated by SEM-MAPPING.The mechanism of electro-fenton degradation of norfloxacin was further explored.Firstly,the TOC mineralisation rate was measured and could reach 56%within 2h.The UV full scan spectrogram proved that the absorption peak of norfloxacin gradually decreased at 278 nm,and the 3D fluorescence spectrogram could indirectly determine that the intermediate products of norfloxacin were located in the fulvic acid-like and humic acid-like regions.From the detection of LC-MS,the possible intermediate products were deduced。The structural formulae of the intermediates and the four possible degradation pathways of norfloxacin were deduced from the LC-MS detection,and the ESR was used to demonstrate that·OH was the main degradation agent.The results of the study on the effect of inorganic ions in wastewater on electro-fenton showed that the presence of Cl^-contributed to the removal of COD,with COD removal increasing from 78.9%to 86.7%,while CO₃^2-burst hydroxyl radicals,with COD removal decreasing from 78.9%to 38.9%,and NO₃^-had a weak inhibitory effect on hydroxyl radicals,with COD removal decreasing by 7%from 78.9%.The actual wastewater used in electro-fenton,the COD removal rate was 35.7%,so the application of electro-fenton to the actual wastewater needs to consider the real wastewater water quality conditions such as control ion concentration.The COD removal rates of 86.8%and 78.9%were achieved by conventional and electro-fenton methods respectively,and it is clear that electro-fenton is more advantageous when the COD removal rates are close.Finally the wastewater upgrading project of this pharmaceutical company was carried out,the original process primary A/O was transformed into secondary A/O and a new sedimentation tank was added.In response to the collapse of the system’s denitrogenation capacity,a controlled dilution method with low load operation was adopted,and after half a month of commissioning,the wastewater was completed to meet the discharge standards.