Efficient degradation of 2,4,6-trichlorophenol using microbial fuel cell with MnFe2O4/PTFE@CF cathode

Abstract

Chlorophenol contamination in groundwater is considered a significant environmental issue. The remediation of groundwater pollution using electrochemical catalytic technology is regarding as an economical and environmentally friendly method. This study developed a novel MnFe₂O₄/PTFE@CF electrode as a bioelectro-Fenton cathode for the degradation of 2,4,6-TCP. PTFE modification created a gas diffusion layer on the surface of the carbon felt current collector, enhancing the oxygen utilization rate and the performance of the two-electron reduction to generate H₂O₂ at the bioelectro-Fenton cathode. Additionally, the MnFe₂O₄ material, adhered to the carbon felt surface by PTFE, formed a bimetallic heterogeneous Fenton catalyst. Comparing the new MnFe₂O₄/PTFE@CF electrode with an unmodified CF electrode as the bioelectro-Fenton cathode for degrading 2,4,6-TCP, the heterogeneous system exhibited superior performance in terms of aeration rate, pH, and pollutant initial concentration. The MnFe₂O₄/PTFE@CF electrode showed degradation rates that were 27.81 % and 46.5 % higher than those of the individual iron and manganese oxide catalysts, respectively. After 70 h, the TOC mineralization rate reached 58.08 %. Among the coexisting ions, Cl^- promotes the degradation of pollutants, while SO₄^2-、HCO₃^-和NO₃^- inhibit the degradation as their concentrations increase. Radical quenching experiments indicated that ·OH radicals produced from H₂O₂ playing a dominant role for the the degradation of 2,4,6-TCP. Specific degradation products were identified through GC–MS, and a reasonable degradation pathway was proposed based on these findings. After five cycles in the heterogeneous bioelectro-Fenton system, the degradation rate of 2,4,6-TCP remained over 70 %, and less than 1 % of iron and manganese ions leaching from the cathode was detected. In addition, the Microbial Fuel Cell with MnFe2O4/PTFE@CF Cathode was coupled with groundwater circulation well, and the remediation efficiency of 58.42 % to 93.34 % was achieved for 2,4,6-TCP in sandbox after 120 h.