Study Of Microbial Fuel Cells Using Persulfate Activation Technology

The energy crisis and environmental crisis become more and more serious for human being.It is important to develop renewable energy environment instead of oli and coal today. As anew renewable energy, microbial fuel cell is the production of microbiology technology andbattery technology. It is the device which uses microorganism as catalyzer to catalyse fuel intoelectricity energy. Microbial fuel cell is an emerging technology that can treat wastewater andharvest electricity simultaneously. MFC has obtained a great attention attributable to its abilityin treating wastewaters and harvesting electricity simultaneously. However, the researchershad difficult in improving the power generation and removing biorefractory organics.Cathodic activation loss is an important problem which limited power generation of MFC.Many soluble electron acceptors with high reduction rate on carbon electrodes have beenadopted in MFCs to improve the power generation. The azo dye wastewater is characterizedwith high value of CODcr, complication of organic components, more difficult remediation,and high colority. In present study, ferrous ion activated potassium persulfate as the cathodesolutions were proposed. The reaction can produce free radical with strong oxidizing couldimprove the power generation and degrade organic contaminants.This paper investigated a two-chamber MFC （built in a traditional "H" shape） using ferrousion activated potassium persulfate as the cathode solution for the first time. The performanceof the MFC with K₂S₂O₈-Fe²⁺system was discussed and compared with that of K₂S₂O₈andH₂O₂-Fe²⁺ system, respectively. These results demonstrated that the introduced ferrous ioncould improve the power generation significantly. The MFC with K₂S₂O₈-Fe²⁺was morestable than that with Fenton. Additionally, the performance of MFC with a continuous flowMFC in anode chamber was also investigated. The initial K₂S₂O₈/Fe²⁺molar ratios and theinitial pH, which can affect the performance of MFC, were discussed in this study. IncreasingFe²⁺ concentration can produce more sulfate free radicals that would increase power output.However, excess Fe²⁺could possibly lead to the destruction of sulfate free radical and thereduction of sulfate free radical made the power generation decreased in MFC. The resultsstated that the MFC acquired a maximum power density of401mW m^-2with K₂S₂O₈-Fe²⁺atthe molar ratios of2:1. The result showed that the MFC using K₂S₂O₈-Fe²⁺was lessinfluenced by pH. Voltage output was decreased with pH increased.This study also constructed a microbial fuel cell using Fe （II）-EDTA catalyzed persulfate asthe cathode solutions to decolorize Orange G and recover electricity simultaneously. ChelatedFe²⁺could activate persulfate to generate sulfate free radicals which with high oxidation potential （E0=2.6V.） can degrade azo dyes Minimization of free Fe²⁺by EDTA, and theresulting slow generation of SO₄^-·, can be beneficial in reducing peroxide consumption andcan increase contaminant degradation efficiency. The authors investigated the influences ofsome important operating parameters such as pH value of cathode solutions, dosages ofK₂S₂O₈, Fe²⁺and EDTA on the OG degradation and power generation in aqueous solution.Furthermore, the kinetics of OG degradation by Fe（II）-EDTA activated persulfate waselucidated based on the experimental data. To obtain more OG degradation, less persulfateconsumption and higher power generation, a suitable operating condition was selected as:[OG]=0.1mmol L^-1,[K₂S₂O₈]=4.0mmol L^-1,[Fe²⁺]=1.0mmol L^-1,[EDTA]=1.0mmolL^-1, pH=3.0. Under an optimal condition, the maximum power density achieved91mW m^-2,the OG removal rate was97.4%and the K₂S₂O₈remaining rate was47.3%after12hours. TheUV–visible absorption spectra data revealed that with the color removed from the cathodesolution.The kinetics study indicated that the decolorization kinetics of OG followed thesecond-order kinetics well. The apparent kinetic rate constants （k₂） of the decolorization ofOG was found to be543.1M^-1min^-1 and the regression coefficient （R²） was0.9827at anoptimal condition.