Microbial Electrochemical Coupled System For Enhancemnet Of Azo Dye Decolorization From Wastewater

Azo dye wastewater is toxic and highly persistent to biodegradation, raising attention for environmental concerns. Microbial electrochemical systems (MES) have shown potentials for azo dye wastewater remediation, however, they are still facing with several challenges, such as low removal rate, high energy consumption and low mineralization efficiency. In this article, two MES coupled systems were developed to enhance azo dye removal from wastewater, which would further broaden the application of MES technology. The main contents of our research work and the results are summarized as the follows:1. A MFC (microbial fuel cell)-MEC (microbial electrolysis cell) coupled system was established and demonstrated to be able to enhance azo dye decolorization in this study. The decolourization rate in the coupled system had a 36.52% to 75.28% improvement compared to the single MFC. Anodic acetate concentration of both the MFC and the MEC showed a positive effect on azo dye decolourization, while the cathodic pH of both MEC and MFC in the range of 7.0-10.3 had an insignificant impact on reactor performance in the coupled system. Moreover, a theoretical analysis was conducted to find the essential preconditions for successfully develop this MFC-MEC coupled system. The theoretical analysis reveals that the MFC should have higher short-circuit electricity generation than the MEC before connecting together for a successful coupled system.2. Bicarbonate-activation peroxide (BAP) system was coupled into a MES for azo dye removal under alkaline condition to expand the application of eloctro-Fenton from acidic to alkaline range. Firstly, the effects of several factors on BAP were evaluated, it was found that H2O2 and CO32- positively affect BAP at pH 13, while, the effect of H2O2 and CO32- was insignificant at pH 8.6. Then the feasibility of the coupled system for azo dye removal was explored and decolorization efficiency was observed to be 21.13% higher than pure electrochemical reduction. Finally, oxidation mechanism was studied by radical quenching experiments and electron paramagnetic resonance (EPR). Additionally, degradation products were identified and degradation pathway was proposed through high resolution mass spectrum.