| Dyeing wastewater refers to emissions in the pretreating of dyeing, printing and finishing process for cotton, wool, chemical fiber and other textile products, with characters of large discharge, complex composition, biodegradable resistance, and belongs to a kind of industrial wastewater difficult to be treated. Methods for printing and dyeing wastewater treatment mainly include chemical coagulation, biological method, adsorption method(such as activated carbon), advanced oxidation process(Fenton reagent, ozone oxidation, etc.), electrochemical method, photocatalytic oxidation, etc. Microbial fuel cell(MFC) as a green energy system can employ microbial attached to the surface of the electrode to oxidize all types of the organic pollutants, which has obtained attention from researchers for its simultaneous removal of organic pollutants and electricity generation. In recent years, MFC using oxygen as electron acceptor achevied attention for the reduction of oxygen to H2O2 produced by a two-electron transfer. The H2O2 produced in cathode chamber can oxidize the wastewater, which is called bioelectrical Fenton reaction in some articles. Its application in MFC not only achieved high removal efficiency of dyeing wastewater but also solved the high cost caused by the use of H2O2.Activated carbon(AC)/ PTFE electrode has many advantages including low cost, good conductivity and generation of Fenton reaction intermediaries H2O2 and so on. In this paper, AC/PTFE and AC/MnO2/PTFE cathodes were prepared by pressure, and used to constitute a two-chambered MFC with carbon felt anode. The microorganisms in the anode chamber were inoculated to another MFC, had been operated for a year with sewage as nutrients by batch mode. The simultaneous removal of RhB and electricity generation of MFC, equipped with AC/PTFE and AC/MnO2/PTFE cathode, were studied. The simultaneous removal of RhB and electricity generation of MFC by an electron-Fenton process were also studied with 0.2 g/L Fe2+ in cathodic catholyte.Firstly, the simultaneous removal of RhB and electricity generation of MFC, with carbon felt anode and AC/PTFE cathode of mass ratios 6:1, 5:1, 3:1, were studied. The external resistor is 200 Ω, and open-circuit MFC was set for control for all experiments. The result showed that the RhB removal efficiency and maximum power density of MFC decreased with the increase in the amount of PTFE under open-and close-circuit conditions for MFC. Under close-circuit conditions, the efficiency was 96.3 %,75.8 %,39.0 %, and the maximum power density of MFC was 105.6 mW· m-2,102.0 mW· m-2,80.7 mW·m-2 respectively. The internal resistance changed from 300Ω to 400Ω when the mass ratios of AC/PTFE cathode changed from 6 to 3 based on the polarization curves. The influence of electrolyte concentration, the initial concentration of Rhodamine B on RhB removal and electricity generation were studied with AC/PTFE cathode of mass ration 6, and the influence of pH with 0.2 g/L Fe2+ in cathodic catholyte on on RhB removal and electricity generation was also studied. The result showed that RhB removal efficiency increased with the increase of electrolyte concentration but not its relationship did not showed strongly in a certain range, and decreased with the increase of initial concentration of RhB, the maximum power density of MFC increased with the increase of electrolyte concentration and the initial concentration of RhB. The removal efficiency and maximum power density reached 98.9 %, 210 mW ? m-2 in 36 hours when pH=3, the efficiency and maximum power density improved significantly.Manganese dioxide was prepared by the reduction of KMnO4 by MnSO4 to modified AC/PTFE electrode, and was characterized by FTIR and XRD. AC/MnO2/PTFE cathode with AC/MnO2 mass ration of 90:10, 95:5, 80:20 were prepared to simultaneous removal of RhB and improvement of power output. The result showed that the best RhB removal efficiency was 83.3 % for initial concentration of 50 mg/L when the AC/MnO2 mass ration is 90:10, maximum power density was 223 mW·m-2, twice higher than the AC/PTFE electrode. The influence of electrolyte concentration, the initial concentration of Rhodamine B on RhB removal and electricity generation were studied with AC/ MnO2/PTFE cathode of mass ration 90:10, and the influence of pH with 0.2 g/L Fe2+ in cathodic catholyte on on RhB removal and electricity generation was also studied. The situations were consistent with the trend got by AC/PTFE electrode.Finally, MFC with AC/MnO2/PTFE of mass ration 90:10 and AC/PTFE cathode of mass ration 6, was constructed to treat real printing and dyeing wastewater with catholyte pH= 3. The result showed that the removal efficiency reached 77.0 % in 36 h for AC/PTFE cathode, and 74.5 % for AC/MnO2/PTFE cathode. |
PDF Full Text Request