ABSTRACT
Microbial reduction of insoluble iron minerals by dissimilatory iron reducing bacteria (DIRB) is an important environment process in the iron biogeochemical cycle. We reported that the bio-current generated from oxidation of organic matter by these bacteria in the presence of iron oxides can be used as an indicator for microbial dissolution of insoluble iron oxides. Bioelectrochemical experiments were conducted to investigate the effects of the specific bacteria and the phase identity of iron oxides on bio-current generation by recording the current response as a result of a poised constant potential. Experimental results indicated that the bio-current generation can be greatly enhanced by iron oxide addition under all the conditions varying in the type of pure culture or iron oxide. The increase in the bio-current was linearly correlated with the increased concentration of biogenic Fe(II) detected either by chemical analysis or cyclic voltammetry (CV) tests. This can be understood based on the proposed mechanism that the Fe(II)/Fe(III) couple functions as the electron mediator shuttling electrons from the microbes to the electrodes.
Subject(s)
Aeromonas hydrophila/metabolism , Biosensing Techniques/methods , Ferric Compounds/metabolism , Ferrous Compounds/analysis , Ferrous Compounds/metabolism , Shewanella/metabolism , Electrochemical Techniques/methods , Oxidation-Reduction , Sensitivity and SpecificityABSTRACT
A unique one-step method for fabrication of a membraneless microbial fuel cell (MFC) cathode was developed by coating a conductive polymer onto stainless steel mesh. The resulting polypyrrole/anthraquinone-2-sulfonate (PPy/AQS) film was synthesized via electropolymerization using AQS as the dopants. The scanning electron microscopy results indicated that the PPy/AQS film was uniformly formed on the metal mesh electrode without cracks on its surface and featuring a globular structure. Being equipped with such a cathode that was able to catalyze oxygen reduction and prevent water leakage, the membraneless MFC allowed power generation over 250 h and exhibited a maximum power density of 575 mW m(-2). Increasing film thickness seemed to result in a reduction in power performance due to the increased ohmic resistance of the cathode material and the enhanced difficulty for oxygen diffusion inside the cathode.
Subject(s)
Bioelectric Energy Sources , Biosensing Techniques , Polymers/chemistry , Pyrroles/chemistry , Anthraquinones/chemistry , Microscopy, Electron, Scanning , Stainless Steel/chemistryABSTRACT
The Fe(III)/Fe(II) couple can play a significant role in the abiotic reduction of 2-nitrophenol (2-NP) at the cathode chamber of a microbial fuel cell (MFC). Experimental results demonstrate that Fe(II) addition to the cathode chamber contributes to a significant increase in the reaction rate of 2-NP removal and the power performance of MFC. Observed pseudo first-order rate constants and power densities are heavily dependent on the identity of the Fe(II)-complexing ligands. The Fe(II) complex coordinated with citrate results in the highest rate constant up to 0.12 h(-1) as compared to other organically complexed iron species including Fe(II)-EDTA, Fe(II)-acetate and Fe(II)-oxalate, and iron species uncomplexed with any organic ligands. In addition, the presence of Fe(II)-citrate species leads to a maximum volumetric power density of 1.0 W m(-3), which is the highest value among those obtained with other iron species for the similar MFC system.
