Preparation Of Flow-through Functionalized Carbon Fiber Electrodes And Its Heterogeneous Electro-fenton Performance

Heterogeneous electro-Fenton process is an emerging electrochemical advanced oxidation technology that can utilize solid catalysts to activate H₂O₂ produced by oxygen reduction reaction（ORR）into·OH with strong oxidizing ability,possessing great potential in the field of organic wastewater treatment.But the electrocatalytic O₂ reduction with the multi-products characteristic suffers from a poor controllability for·OH generation.The external addition of H₂O₂ after efficient production provides a new way for the electro-Fenton reaction.It is significant for improving the catalytic performance of heterogeneous electro-Fenton to preparing electrode materials with high H₂O₂ yield and high H₂O₂ activation utilization,respectively.Compared with the traditional batch or flow-by mode of electro-Fenton reaction,the flow-through mode can shorten the diffusion distance of reactant molecules to electrode and increase the exposed area of the active site in electrode.In addition,the preparation of conventional heterogeneous electro-Fenton electrodes is mainly based on coating,which suffers from poor electrode stability that the active species are easy to fall off and agglomerate.The flow-through electrode prepared by hot pressing process can effectively prevent the catalyst from falling off and enhance the diffusion of reactant molecules,thereby improving the catalytic activity of heterogeneous electro-Fenton reaction.In this work,the operating parameters of hot pressing process for preparing carbon fiber electrodes were optimized,a flow-through electrochemical H₂O₂synthesis system with carbon black（CB）and polytetrafluoroethylene（PTFE）modified carbon fiber cathode and a flow-through electrochemical H₂O₂ activation system with FeOCl-modified carbon fiber cathode were constructed.The heterogeneous electro-Fenton performance of electrodes was improved by adjusting the ratio of CB,PTFE,and the iron loadings,thereby achieving efficient removal of organic pollutants.The research contents and results are shown as follows:（1）The carbon black（CB）and polytetrafluoroethylene（PTFE）modified carbon fiber（CF） electrodes were prepared,and the operating parameters of hot pressing process were optimized to 100°C,1.0 MPa and 30 min by measuring performance of electrochemical H₂O₂synthesis.CF electrode with 1:5 of CB and PTFE ratio exhibited 0.47 m M H₂O₂ production at7 m A current with current efficiency of 59.19%.The stable H₂O₂ yield（0.47 m M）within 600min demonstrated the stability of CF electrodes prepared by hot pressing process,providing a new perspective for the preparation of flow-through electrodes.（2）The FeOCl-modified CF cathode（CF-10Fe）was prepared by the optimized hot pressing process,and a flow-through electrochemical H₂O₂ activation system was designed for high-efficiency·OH production.The·OH yield of flow-through electrode reached up to 0.99mmol L^-1 with a remarkable H₂O₂ utilization rate of 9.94%.The phenol removal of CF-10Fe electrode by electrochemical H₂O₂activation was 99.0%at hydraulic retention time（HRT）of2.4 min,10 m M H₂O₂,10 m A and p H 7,and the corresponding TOC removal reached 67.4%.The stable phenol removal performance in the duration of 900 min demonstrated the long-term stability of flow-through electrode.The chemical oxygen demand（COD）value of secondary effluent of actual petrochemical wastewater was successfu1ly reduced from 77.6mg L^-1 to 42.3 mg L^-1,which was lower than the national wastewater discharge standard of China(GB 18918-2002,I-A:COD<50 mg L^-1).