Tian-Shun Song

Effects of sediment pretreatment on the performance of sediment microbial fuel cells

In the present study, the effects of different pretreatment methods for sediments on the performance of sediment microbial fuel cells (SMFCs) were evaluated. Autoclaved (30 and 60 min), and heated (150 °C, 3 h) sediments demonstrated high power density, compared with control and heated (60 °C, 3 h) sediments. An SMFC with heated (60 °C, 3 h) sediment was found to easily form a biocathode. The power density of an SMFC with heated (150 °C, 3 h) sediment was 214 mW m(-2) on day 24. Furthermore, autoclaved (30 and 60 min) and heated (3 h, 60 and 150 °C) sediments accelerated the production of dissolved organic matter (DOM). The DOM in heated (60 °C, 3 h) sediments had larger molecular sizes. The present study demonstrates that SMFCs can have high power density and high loss on ignition removal efficiencies when produced from sediments by suitable pretreatment methods.

Construction and operation of freshwater sediment microbial fuel cell for electricity generation.

In this work, sediment microbial fuel cell (SMFC) with granule activated carbon (GAC) cathode and stainless steel anode was constructed in laboratory tests and various factors on SMFC power output were investigated. The maximum power densities for the SMFC with GAC cathode was 3.5xa0mW m−2, it was much higher than SMFC with round stainless steel cathode. Addition of cellulose reduced the output power from SMFC at the beginning of experiments, while the output power was found to increase after adding cellulose to sediments on day 90 of operation. On 160xa0day, maximum power density from the SMFC with adding 0.2% cellulose reached to 11.2xa0mW m−2. In addition, the surface morphology of stainless steel anode on day 90 was analyzed by scanning electron microscope. It was found that the protection layer of the stainless steel as electrode in SMFCs was destroyed to some extent.

Various voltage productions by microbial fuel cells with sedimentary inocula taken from different sites in one freshwater lake.

In this study, single-chamber microbial fuel cells (MFCs) were inoculated with sedimentary samples taken from one freshwater shallow lake. After 98 days of operation, it was found that sedimentary inocula had strong effect on MFC performances, and Fe(III) contents in sediments were significantly related to voltage values produced from MFCs. Inoculation of the sedimentary sample from the site with the highest Fe(III) content led to the production of the highest voltage with a value of 580 mV, while voltage from the MFC inoculated with sediments from the site with the lowest Fe(III) concentration was less than 30 mV at the end of the experiments. In addition, microbial communities of anode biofilms from the MFCs with the highest and lowest voltages showed significant difference. This study will help enable scientific decisions to be made regarding the selection of freshwater sediments as MFC inoculum, and survey exoelectrogenic microorganisms within sediments.

Comparison of the

Iron oxide nanoparticle, named synthetic magnetite, as contrast agent has been widely used in clinical MRI. Recently, a new magnetite nanocrystal, called magnetosome, has been found in magnetotactic bacteria. Physicochemical and magnetorelaxo-metric characterization of bacteria magnetosomes and iron oxide nanoparticles are investigated. Bacterial magnetosomes have the larger mean aggregate size, better dispersion and obviously stronger ferromagnetism compared to synthetic magnetites. The samples of several concentrations of magnetic nanoparticles were analyzed using a clinical 3.0 T MR-scanner. The signal decay in the Magnetic Resonance images is found to change proportionally to the nanoparticles concentration. Two kinds of nanoparticles can be though as a negative contrast agent and show slight effects on T1, but strong effects on T2 weighted images. Notice that at the same concentration the signal attenuation of bacterial magnetite samples is more obvious than that of synthetic magnetite samples.

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This paper introduces the design of a high magnetic field permanent magnet for Magnetic Birefringence of Vacuum-Q&A Experiment. The magnet is required to have 2.2T maximum magnetic-flux density on the axis of the columnar air-gap (diameter: 27 mm, length: 600 mm) and not more than 0.00001 T magnetic flux leakage at 10 mm away from the round surface of the magnet. Also the magnet should rotate at 10 Hz driven by a motor. All of these requirements have been satisfied. Furthermore, a maximum 2.3 T on the axis of columnar air-gap is reached. The higher magnetic field is reached in two aspects, material and structure. High performance materials, 1J22 and N42M, were adopted and a special structure is designed to shield the leakage flux. Further improvement on this magnet can be achieved with the adoption of more advanced materials.

NMR Relaxation Enhancement Produced by Bacterial Magnetosomes and Synthetic Iron Oxide Nanoparticles for Potential Use as MR Molecular Probes

Microbial electrosynthesis (MES) is a biocathode-driven process, producing high-value chemicals from CO2. Here, an in situ self-assembled graphene oxide (rGO)/biofilm was constructed, in MES, for high efficient acetate production. GO has been successfully reduced by electroautotrophic bacteria for the first time. An increase, of 1.5 times, in the volumetric acetate production rate, was obtained by self-assembling rGO/biofilm, as compared to the control group. In MES with rGO/biofilm, a volumetric acetate production rate of 0.17gl-1d-1 has been achieved, 77% of the electrons consumed, were recovered and the final acetate concentration reached 7.1gl-1, within 40days. A three-dimensional rGO/biofilm was constructed enabling highly efficient electron transfer rates within biofilms, and between biofilm and electrode, demonstrating that the development of 3D electroactive biofilms, with higher extracellular electron transfer rates, is an effective approach to improving MES efficiency.

Design of a 2.3 T rotating permanent dipole magnet

Halbach cylinder magnet has been widely used as field source due to its great features. However, the existence of the magnetic moment in the Halbach cylinder magnet limits its application in some fields. To eliminate the dipole moment of the whole magnet system, a method is presented here that incorporates permanent magnets to provide an opposite dipole moment. Both the FEM simulation and the experimental results demonstrate that this method is effective.

High efficiency microbial electrosynthesis of acetate from carbon dioxide by a self-assembled electroactive biofilm

BackgroundThe conversion of CO2 into high value-added products has a very important environmental and economic significance. Microbial electrosynthesis (MES) is a promising technology, which adopts a bioelectrochemical system to transform CO2 into organic chemicals.ResultsIn this study, Clostridium scatologenes ATCC 25775T, an anaerobic acetogenic bacterium, demonstrated its utility as a biocatalyst in a MES system, for the first time. With the cathodic potential of the MES system decreased from −xa00.6 to −xa01.2xa0V (vs. Ag/AgCl), the current density of the MES, and the production of organic chemicals, increased. Combining the genetic analysis and the results of the wet lab experiments, we believe C. scatologenes may accept electrons directly from the cathode to reduce CO2 into organic compounds at a potential of −xa00.6xa0V. The acetic and butyric acid reached a maximum value of 0.03 and 0.01xa0g/L, respectively, and the maximum value of total coulombic efficiency was about 84%, at the potential of −xa00.6xa0V. With the decrease in cathodic potentials, both direct electron transfer and exogenous electron shuttle, H2 might be adopted for the C. scatologenes MES system. At a potential of −xa01.2xa0V, acetic acid, butyric acid and ethanol were detected in the cathodic chamber, with their maximum values increasing to 0.44, 0.085 and 0.015xa0g/L, respectively. However, due to the low H2 utilization rate by the C. scatologenes planktonic cell, the total coulombic efficiency of the MES system dropped to 37.8%.ConclusionClostridium scatologenes is an acetogenic bacterium which may fix CO2 through the Wood–Ljungdahl pathway. Under H2 fermentation, C. scatologenes may reduce CO2 to acetic acid, butyric acid and ethanol. It can also be used as the biocatalyst in MES systems.

A Method on Decreasing Magnetic Moment of Halbach Cylinder Magnets

The electricity-driven bioreduction of carbon dioxide to multi-carbon organic compounds, particularly acetate, has been achieved in microbial electrosynthesis (MES). MES performance can be limited by the amount of cathode surface area available for biofilm formation and slow substrate mass transfer. Here, a fluidized three-dimensional electrode, containing granular activated carbon (GAC) particles, was constructed via MES. The volumetric acetate production rate increased by 2.8 times through MES with 16u202fgu202fL-1 GAC (0.14u202fgu202fL-1u202fd-1) compared with that of the control (no GAC), and the final acetate concentration reached 3.92u202fgu202fL-1 within 24u202fdays. Electrochemical, scanning electron microscopy, and microbial community analyses suggested that GAC might improve the performance of MES by accelerating direct and indirect (via H2) electron transfer because GAC could provide a high electrode surface and a favorable mass transport. This study attempted to improve the efficiency of MES and presented promising opportunities for MES scale-up.