Bin Hou

Explore various co-substrates for simultaneous electricity generation and Congo red degradation in air-cathode single-chamber microbial fuel cell

Microbial fuel cell (MFC) holds a great promise to harvest electricity directly from a wide range of ready degradable organic matters and enhance degradation of some recalcitrant contaminants. Glucose, acetate sodium and ethanol were separately examined as co-substrates for simultaneous bioelectricity generation and Congo red degradation in a proton exchange membrane (PEM) air-cathode single-chamber MFC. The batch test results showed that more than 98% decolorization at the dye concentration of 300 mg/L were achieved within 36 h for all tested co-substrates during electricity generation. The decolorization rate was different with the co-substrates used. The fastest decolorization rate was achieved with glucose followed by ethanol and sodium acetate. Accumulated intermediates were observed during Congo red degradation which was demonstrated by UV-Visible spectra and high performance liquid chromatography (HPLC). Electricity generation was sustained and not significantly affected by the Congo red degradation. Glucose, acetate sodium and ethanol produced maximum power densities of 103 mW/m(2), 85.9 mW/m(2) and 63.2 mW/m(2), respectively, and the maximum voltage output decreased by only 7% to 15%. Our results demonstrated the feasibility of using various co-substrates for simultaneous decolorization of Congo red and bioelectricity generation in the MFC and showed that glucose was the preferred co-substrate.

Further treatment of decolorization liquid of azo dye coupled with increased power production using microbial fuel cell equipped with an aerobic biocathode

A microbial fuel cell (MFC) incorporating a recently developed aerobic biocathode is designed and demonstrated. The aerobic biocathode MFC is able to further treat the liquid containing decolorization products of active brilliant red X-3B (ABRX3), a respective azo dye, and also provides increased power production. Batch test results showed that 24.8% of COD was removed from the decolorization liquid of ABRX3 (DL) by the biocathode within 12 h. Metabolism-dependent biodegradation of aniline-like compound might be mainly responsible for the decrease of overall COD. Glucose is not necessary in this process and contributes little to the COD removal of the DL. The similar COD removal rate observed under closed circuit condition (500 Ω) and opened circuit condition indicated that the current had an insignificant effect on the degradation of the DL. Addition of the DL to the biocathode resulted in an almost 150% increase in open cycle potential (OCP) of the cathode accompanied by a 73% increase in stable voltage output from 0.33 V to 0.57 V and a 300% increase in maximum power density from 50.74 mW/m(2) to 213.93 mW/m(2). Cyclic voltammetry indicated that the decolorization products of the ABRX3 contained in the DL play a role as redox mediator for facilitating electron transfer from the cathode to the oxygen. This study demonstrated for the first time that MFC equipped with an aerobic biocathode can be successfully applied to further treatment of effluent from an anaerobic system used to decolorize azo dye, providing both cost savings and high power output.

Performance and microbial diversity of microbial fuel cells coupled with different cathode types during simultaneous azo dye decolorization and electricity generation

To study the effect of cathode type on performance and microbial diversity of the MFC, aerobic biocathode and air-cathode were incorporated into microbial fuel cells (MFCs) which were explored for simultaneous azo dye decolorization and electricity generation. The electrochemical impedance spectroscopy (EIS) results demonstrated that the catalytic activity of the microorganisms on the biocathode surface was comparable with that of the platinum coated on the air-cathode. The power density achieved by using biocathode was lower than air-cathode, but the biocathode could greatly improve the Congo red decolorization rate. By using the biocathode, 96.4% decolorization of Congo red was obtained within 29 h, whereas, about 107 h was required to achieve the same decolorization efficiency with the air-cathode. 16S rRNA sequencing analysis demonstrated a phylogenetic diversity in the communities of the anode biofilm and showed clear differences between the anode-attached populations in the MFCs with a different cathode type.

Effect of Congo Red on Electrochemical Characteristics of the Bioanode of Microbial Fuel Cell Explored for Simultaneous Azo Dye-containing Wastewater Treatment and Electricity Generation

To exploit the outstanding ability of microbial fuel cell (MFC) for simultaneous treatment of azo dye - polluted wastewater and bioelectricity generation, the effect of a representative azo dye - Congo red on the electrochemical characteristics of the bioanode of an air-cathode single chambered MFC was investigated in detail. The electrochemical impedance spectroscopy (EIS) showed that decolorization of different concentration of the Congo red had a negligible effect on the Ohmic resistance (Rohm) of the anode, but the charge-transfer resistance (Rc) and the diffusion resistance (Rd) were significantly influenced. The Rc and Rd firstly decreased then increased with increasing Congo red concentration, possibly due to the fact that Congo red can be served as electron shuttle for conveniently electrons transfer from bacteria to the anode at low concentration, but results in accelerated consumption of electrons at high concentration. The cathode impedance was totally not affected by the Congo red addition. cyclic voltammetry (CV) indicated that long-term decolorization of Congo red resulted in the change in the catalytic active site of the anode biofilm.

Enhanced Power Density and Decolorization of Air-cathode Single-chamber Microbial Fuel Cells with Microfiltration Membranes

In order to increase the power output and reduce the cost of MFCs, micro filtration membrane (MFM) air-cathode MFC (MFM-MFC) and proton exchange membrane (PEM) air-cathode MFC (PEM-MFC) were compared in the performance of the simultaneous decolorization of azo dye and power generation. Batch test results showed that the PEM-MFC produced a maximum power density of 272 mW/m2. The using the MFM in stead of the PEM increased the maximum power density to 310 mW/m2. The coulombic efficiencies were 7.25% and 19.9% in the MFM-MFC and PEM-MFC, respectively. An accelerated decolorization of Congo red was observed in the MFM-MFC which was due to its lower internal resistance. The HPLC chromatogram of anode solution indicated that the decolorization of Congo red can be achieved and the do colorization products were accumulated and could not be further degraded in the MFC. This study suggests that it is feasible for the MFC using MFM in place of PEM in the operation of the simultaneous decolorization of azo dye and power generation.

Effect of Anodic Biofilm Growth on the Performance of the Microbial Fuel Cell (MFC)

Electrochemical impedance spectroscopy (EIS) and Cyclic Voltammetry (CV) were used to explore the mechanism of the effect of anodic biofilm growth on power output of the microbial fuel cell (MFC) at different operational conditions. These operational conditions included MFC systems with and without the bacterial catalyst and at different periods of biofilm growth. Power density increased with the development of biofilm on the anodic surface. Higher power density of 594 mW/m² was observed on day 30 (a maturate bioflim) compared with the power density of 33.4 mW/m² on day 5 (an immature biofilm). The MFC without biofilm catalyst generated unnoticeable power density of 8.6 mW/m². These results showed that biofilm growth greatly reduced the anode polarization impedance and facilitated the kinetics of the electrochemical reactions so as to enhance extracellular electron transfer from bacteria to anode electrode and increase the power generation.