Research Of Methyl Orange Wastewater Treatment By Using Bioelectric Fenton System With Graphene-based Cathode Materials

The bioelectric Fenton system was constructed with graphene composite cathode material with high electrical conductivity,which effectively removed the refractory organic matter in wastewater.The degradation mechanism of typical pollutant methyl orange（MO）were analyzed in this paper.The graphene composite cathode material,modified by Fe²⁺and graphene,was prepared by chemical coprecipitation method.The production of·OH could be strengthened by the two-electron redox process in the cathode range.The start-up period of the bioelectric Fenton system can be accelerated using the river sediment as the source of electrogenic bacteria,whose succession process of dominant species was analyzed in the anodic sediments.The mechanism of electro-microorganisms in this system to degrade organic pollutants provides a theoretical basis for the practical application of bio-electric Fenton system in the treatment of refractory organic wastewater.In the preparation process of the cathode materials,Fe²⁺as a reduction agent of graphene oxide（GO）,could trigger ammonia to form graphitic N in graphene sheets,obtaining the graphite N modified reduced GO with Fe₃O₄ nanoparticles（N-rGO/Fe₃O₄）cathode materials.In the bioelectric Fenton system,the maximum output voltage and the maximum power density was 0.528 V and 178.17 m W/m³,respectively.The degradation of MO was up to 68.91%within 25 h,which could be contributed to the graphitic N in the graphene sheets,producing H₂O₂.·OH,with a strong oxidizing ability can be formed in-situ in the cathode materials between H₂O₂ and Fe²⁺released from N-rGO/Fe₃O₄ to degrade MO,in which no additional H₂O₂ and Fe²⁺were added with a low operation cost.The river sediment has good conductivity and abundant active microorganisms,and it has excellent performance in the removal of refractory organic matter with a good biodegradable electricity performance.The stabilized output voltage of bioelectric Fenton system was 0.55 V after 350 h of operation,and the degradation ability of organic matter in the anode deposit was 16.1%,reflecting the increasing activity of microorganisms in the anode sediment.High-throughput sequencing of the anode electrode material showed that the microbial colonies became the dominant species with the start of the system,accounting for 71.24%,among which Geobacter and Shewanella,becoming the two major bacteria to produce electricity with a large number of extracellular electrons for the bioelectric Fenton system.