Study On Iron Oxychloride/Graphite Felt Based Composite Cathode In Electro-Fenton System For The Degradation Of Ciprofloxacin Wastewater

The overuse of antibiotics and their continuous release into the environment have caused serious environmental pollution problems,endangering ecological safety and human health.Ciprofloxacin（CIP）is a typical quinolone antibiotic,it is difficult to remove it from the environment using traditional biochemical methods.Electro-Fenton technology has been proven to be an effective electrochemical advanced oxidation technology for the removal of refractory organic pollutants from water.However,the conventional electro-Fenton technology has problems such as narrow pH application range,generation of iron sludge,and unrecyclable catalyst.Based on this,the iron oxychloride/graphite felt（FeOCl/GF）based composite cathode electro-Fenton system is proposed in this paper.An integrated composite cathode was prepared by using graphite felt with large specific surface area and oxygen reduction catalytic performance as the cathode substrate and loaded with FeOCl Fenton-like catalyst.By immobilizing the active electro-Fenton catalyst component on the cathode,the in situ electroproduction and activation of H₂O₂ are achieved at the cathode,thus reducing the mass transfer resistance and catalyst recovery cost.The oxidative degradation efficiency of electro-Fenton catalysis was strengthened in a wide pH range through composite means,a heterogeneous cathodic electro-Fenton system was constructed and the research on the degradation of antibiotic CIP wastewater was carried out.GF@PANI@FeOCl composite cathode was synthesized by a two-step method of in situ electrodeposition and low-temperature calcination for the removal of CIP from water by three-electrode electro-Fenton,and the catalytic activity of electro-Fenton was enhanced by introducing the conductive polymer PANI.The study of CIP degradation performance under different operating conditions revealed that 100%of CIP was removed by electrolysis for 40min at an applied voltage of-0.6 V under near-neutral conditions,and the quenching experiment and fluorescence detection confirmed that·OH was the main radical in the electro-Fenton system.The presence of PANI enhanced the conductivity of FeOCl and accelerated the reduction of Fe（Ⅲ）,which in turn generated more·OH for more efficient CIP degradation.GF@MoS₂@FeOCl composite cathodes were fabricated by a two-step method of in situ hydrothermal method and low-temperature calcination.The electrocatalytic activity was enhanced by the introduction of inorganic metal sulfide MoS₂.The removal of CIP reached 100%and the mineralization reached 74.4%at 90 min of electrolysis in a three-electrode electro-Fenton system with-0.6 V applied under near-neutral conditions.After 6 cycles of treatment,the removal of CIP was maintained above 90%,showing a high stability of electro-Fenton degradation.Fluorescence detection and XPS analysis showed that MoS₂ accelerated the regeneration of Fe（II）during the electro-Fenton process and promoted the decomposition of H₂O₂ to produce·OH.According to the degradation products detected by LC-MS,a degradation pathway was proposed in which the piperazine ring of CIP were destroyed by·OH attack.To eliminate the aeration energy consumption of aeration and improve oxygen utilization of cathode,an OCNTs/FeOCl NADE composite cathode was prepared to achieve the simultaneous natural diffusion of oxygen,in situ electro-generation and activation of H₂O₂processes in liquid-gas-solid three phase interfaces on cathode.In the two-electrode electro-Fenton system,the OCNTs/FeOCl NADE composite cathode obtained efficient removal of CIP（100%）within 90 min in a wide pH range of 3～9 with a current of 75 m A current.The radical quenching experiments and EPR detection showed that ¹O₂ played a major role in the electro-Fenton system.Five degradation pathways of CIP were proposed based on the degradation products detected by LC-MS combined with the calculation of the Fukui function.The OCNTs/FeOCl NADE composite cathode with good CIP removal performance and economic benefits was applied to the pilot-scale study of the electro-Fenton degradation of CIP wastewater.Without any catalyst addition,aeration or pH adjustment,the removal of 10 mg/L CIP wastewater was 100%within 6 h with 17.1 V applied and the volumetric liquid flow set to18 L/h.And 1 mg/L CIP wastewater was completely removed within only 1h,which has good application value and economic benefits.In conclusion,three economical electro-Fenton composite cathodes were developed and applied to the efficient removal of ciprofloxacin wastewater in the electro-Fenton system in this study,providing a theoretical basis and technical reference for the development and application of electro-Fenton technology.