Abstract
The bio-electron-Fenton system integrates microbial fuel cell and Fenton process into a single system to destroy the organic and bio-refractory contaminants in wastewater. Its performance is closely dependent on the sufficient electron supplement by the oxidation process in anode chamber and the reduction process in cathode chamber. This article presents a novel cathode of a bio-electron-Fenton system which can simultaneously achieve good electron supplement and the wastewater treatment in cathode chamber. The cathode consists of indium-tin-oxide conductive glass on which layers of graphene-poly(vinyl alcohol) composite are sprayed by electrospinning. The material characterization is verified by Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The voltage, current, and power density of the system are verified by cyclic voltammetry. The wastewater treatment is verified by dye decolorization. With the addition ratio of 4 wt% graphene, the system achieves the optimal power density of 74.1 mW/m2, open-circuit voltage of 0.42 V, and the decolorization of reactive black 5 of 60.25%. By constant-resistance discharge testing within three-cycle, the system can stably supply a maximum voltage of 0.41 V or above. Hence, the proposed electrospun graphene-poly(vinyl alcohol) composite cathode electrode can not only improve the power-supply efficiency but also enhance the efficiency of wastewater treatment.
Highlights
A microbial fuel cell (MFC) operates on the following principle: When organic substances are decomposed by the bacteria in an anolyte, hydrogen ions and electrons form, which are transferred to the cathode of the MFC system for use in the reduction reaction,[1,2] as shown in Figure 1.3 The hydrogen ions reach the cathode chamber through the proton exchange membrane, while the electrons move via the external circuit
An Reduced graphene oxide (r-GO)-poly(vinyl alcohol) (PVA) composite was deposited onto an ITO electrode by electrospinning, and the composite ITO electrode was applied to the bio-electro-Fenton MFC (BEFMFC)
We can draw the following conclusions: 1. Observing the nanofiber morphology by SEM after the r-GO was conjugated to the PVA: The average fiber diameter of electrospun PVA nanofibers was 123.73 nm; the fiber diameter of PVA nanofibers decreased gradually on increasing the addition amount of r-GO, eventually reaching the minimum level of 103.74 nm when the addition weight percentage of r-GO was 8 wt%
Summary
A microbial fuel cell (MFC) operates on the following principle: When organic substances are decomposed by the bacteria in an anolyte, hydrogen ions and electrons form, which are transferred to the cathode of the MFC system for use in the reduction reaction,[1,2] as shown in Figure 1.3 The hydrogen ions reach the cathode chamber through the proton exchange membrane, while the electrons move via the external circuit. Apart from electricity generation, the cathode chamber can simultaneously degrade wastewater during the cell reaction. An electro-Fenton (EF) system is capable of initiating an electrochemical Fenton reaction in an acidic environment. It involves continuous electro-generation of H2O2 at the Department of Mechanical and Electro-Mechanical Engineering, National Ilan University, Yilan, Taiwan. Nanomaterials and Nanotechnology cathode supplied with O2, using an iron catalyst to produce hydroxyl radicals (ÁOH) by Fenton reaction. Note that the continuous electro-generation of H2O2 requires an external electric source.[4] During the EF reaction, the oxygen gas present in the electrolyte is reduced electrochemically, generating H2O2 in the cathode. As long as oxygen gas and iron sources are available in the system, the Fenton reaction will proceed
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