[show abstract][hide abstract] ABSTRACT: Given few in-depth studies available on the application of nitrogen-doped carbon powders (NDCP) to air-cathode microbial fuel cells (ACMFCs), a low-cost and durable catalyst of NDCP was prepared and used as cathodic catalyst of ACMFCs. Compared to the untreated carbon powders, the N-doped treatment significantly increased the maximum power density (MPD) of ACMFC. A two-step pretreatment of heat treatment and hydrochloric acid immersion can further obviously increase the MPD. With a reasonably large loading of catalyst, the MPD of NDCP based ACMFC was comparable to that of carbon-supported platinum (Pt/C) based ACMFC, while the cost was dramatically reduced. The pretreatment increased the key nitrogen functional groups, pyridinic-like and pyrrolic-like nitrogen. A third new key nitrogen functional group, nitrogen oxide, was discovered and the mechanism of its contribution was explained. Compared to the inherent deterioration problem of Pt/C, NDCP exhibited high stability and was superior for long-term operation of ACMFCs.
[show abstract][hide abstract] ABSTRACT: The cost of electrode materials is one of the most important factors limiting the scale of microbial fuel cells (MFCs). In this study, a novel double-sided cloth (DC) without diffusion layer is using as air-cathode, which decreases the cost and simplifies electrode production process. Using Pt as catalyst, the maximum power density of MFC using DC cathode is 0.70±0.02Wm−2, which is similar to that obtained using carbon cloth (CC) cathodes (0.66±0.01Wm−2). After running in stable status, the Coulombic efficiencies (CEs) (18±1%) and COD removal rates (75±3%) are almost the same as those of CC cathode with diffusion layers. Using carbon powder as catalyst on the DC cathode, the maximum powder density is 0.41±0.01Wm−2, with a COD removal rate of 66±2% and a CE of 13.9±0.5%. The total cost of cathode based on power output decreases as follows: CC with Pt (CC-Pt, 2652$W−1), DC with Pt (DC-Pt, 1007$W−1) and DC with carbon powder (DC-C, 22$W−1), showing that DC is an inexpensive and promising cathode material for future applications.
[show abstract][hide abstract] ABSTRACT: Because of the advantages of low cost, good electrical conductivity and high oxidation resistance, nitrogen-doped carbon (NDC) materials have a potential to replace noble metals in microbial fuel cells (MFCs) for wastewater treatment. In spite of a large volume of studies on NDC materials as catalysts for oxygen reduction reaction, the influence of sulfide on NDC materials has not yet been explicitly reported so far. In this communication, nitrogen-doped carbon powders (NDCP) were prepared by treating carbon powders in nitric acid under reflux condition. Sodium sulfide (Na(2)S) was added to the cathodic electrolyte to compare its effects on platinum (Pt) and NDCP cathodes. Cell voltages, power density and cathodic potentials were monitored without and with Na(2)S and after Na(2)S was removed. The maximum cell voltage of the MFCs with Pt cathode decreased by 10% in the presence of Na(2)S that did not change the performance of the MFC with NDCP cathode, and the maximum power density of the MFC with NDCP cathode was even 11.3% higher than that with Pt cathode (222.5 ± 8 mW m(-2) vs. 199.7 ± 4 mW m(-2)).
[show abstract][hide abstract] ABSTRACT: Biodiesel production through transesterification of lipids generates large quantity of biodiesel waste (BW) containing mainly glycerin. BW can be treated in various ways including distillation to produce glycerin, use as substrate for fermentative propanediol production and discharge as wastes. This study examined microbial fuel cells (MFCs) to treat BW with simultaneous electricity generation. The maximum power density using BW was 487 ± 28 mW/m(2) cathode (1.5A/m(2) cathode) with 50mM phosphate buffer solution (PBS) as the electrolyte, which was comparable with 533 ± 14 mW/m(2) cathode obtained from MFCs fed with glycerin medium (COD 1400 mg/L). The power density increased from 778 ± 67 mW/m(2) cathode using carbon cloth to 1310 ± 15 mW/m(2) cathode using carbon brush as anode in 200 mM PBS electrolyte. The power density was further increased to 2110 ± 68 mW/m(2) cathode using the heat-treated carbon brush anode. Coulombic efficiencies (CEs) increased from 8.8 ± 0.6% with carbon cloth anode to 10.4 ± 0.9% and 18.7 ± 0.9% with carbon brush anode and heat-treated carbon brush anode, respectively.
[show abstract][hide abstract] ABSTRACT: Nafion, poly(tetrafluoroethylene) (PTFE) and polymers made of Nafion-PTFE mixture (Nafion and PTFE ratios of 1:2 and 2:1) were examined as catalyst binders in air-cathode microbial fuel cells (MFCs). MFC tests showed that the maximum power density (from 549 to 1060 mW/m2) increased with the increase of Nafion percentage in binders (from 0% to 100%). Multi-cycle tests (25 cycles) showed that the maximum voltages decreased by 4-6% with simultaneous increase in Coulombic efficiency in all MFCs using various binders (from 20% to 29% with Nafion binder; from 17% to 26% with other binders), indicating that adjustable Nafion/PTFE mixed polymers were applicable in MFCs as catalyst binders when considering both cost and performance of cathodes.
[show abstract][hide abstract] ABSTRACT: Due to increased discharge of CO(2) is incurring problems, CO(2) sequestration technologies require substantial development. By introducing anodic off gas into an algae grown cathode (Chlorella vulgaris), new microbial carbon capture cells (MCCs) were constructed and demonstrated here to be an effective technology for CO(2) emission reduction with simultaneous voltage output without aeration (610+/-50 mV, 1000 Omega). Maximum power densities increased from 4.1 to 5.6 W/m(3) when the optical density (OD) of cathodic algae suspension increased from 0.21 to 0.85 (658 nm). Compared to a stable voltage of 706+/-21 mV (1000 Omega) obtained with cathodic dissolved oxygen (DO) of 6.6+/-1.0 mg/L in MCC, voltage outputs decreased from 654 to 189 mV over 70 h in the control reactor (no algae) accompanied with a decrease in DO from 7.6 to 0.9 mg/L, indicating that cathode electron acceptor was oxygen. Gas analysis showed that all the CO(2) generated from anode was completely eliminated by catholyte, and the soluble inorganic carbon was further converted into algal biomass. These results showed the possibility of a new method for simultaneous carbon fixing, power generation and biodiesel production during wastewater treatment without aeration.
[show abstract][hide abstract] ABSTRACT: A baffled air-cathode microbial fuel cell (BAFMFC) was designed and operated under continuous flow. With glucose fed as substrate, an average voltage of 652 mV was obtained under the external resistance of 1000 Omega (30 degrees C). The maximum power density was 15.2 W/m(3) with the chemical oxygen demand (COD) removal rate of 88.0%. The overall resistance was 13.7 Omega while ohmic internal resistance was 10.8 Omega. Average COD removal rate was 69.7-88.0%, when COD loading varied from 4.11 kg COD/(m(3)NACd) to 16.0 kg COD/(m(3)NACd). The liquid from corn stover steam explosion process (COD=7160+/-50mg/L) was treated by BAFMFC, and the maximum power density was 10.7 W/m(3) with the average COD removal rate was 89.1%. The present study indicated BAFMFC can be comparable to the traditional anaerobic baffled reactor in COD removal rate for high-concentration wastewater and have an advantage in energy harvest from wastewater.
[show abstract][hide abstract] ABSTRACT: Corn stover is usually treated by an energy-intensive or expensive process to extract sugars for bioenergy production. However, it is possible to directly generate electricity from corn stover in microbial fuel cells (MFCs) through the addition of microbial consortia specifically acclimated for biomass breakdown. A mixed culture that was developed to have a high saccharification rate with corn stover was added to single-chamber, air-cathode MFCs acclimated for power production using glucose. The MFC produced a maximum power of 331 mW/m2 with the bioaugmented mixed culture and corn stover, compared to 510 mW/m2 using glucose. Denaturing gradient gel electrophoresis (DGGE) showed the communities continued to evolve on both the anode and corn stover biomass over 60 days, with several bacteria identified including Rhodopseudomonas palustris. The use of residual solids from the steam exploded corn stover produced 8% more power (406 mW/m2) than the raw corn stover. These results show that it is possible to directly generate electricity from waste corn stover in MFCs through bioaugmentation using naturally occurring bacteria.
Environmental Science and Technology 09/2009; 43(15):6088-93. · 5.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: Microbial fuel cell (MFC) is a novel device using biomass and microorganism to produce electricity. Three groups of cube-shaped microbial fuel cells were constructed and operated in fed batch at 30degC, 20degC and 15degC, respectively. The Bacteria present in domestic wastewater were inoculated as the biocatalyst, and 1 g/L glucose was fed as substrate during set-up. While the system was stable, the substrate was replaced with domestic wastewater (320mg COD/L) as sole carbon source. Voltage was affected by temperature obviously: compared to that operated at 30degC (434.3mV), the voltage reduced to 382.8mV at 20degC, and 297.0 mV at 15degC, which was tested under the external resistance of 1000Omega. Power density was decreased 54.9% from 30degC to 15degC (Pmax=367.7mW/m<sup>2</sup> at 30degC). The coulombic efficiency of 42.2% at 30degC was over two times higher than that in 15degC (CE=18.4%). However, the COD removal rate was only a slight reduction, decreased from 71.4% (30degC) to 66.2% (15degC). The efficient reactors at different temperature were selected and the biofilm attached on the anode was separated with roll tube method under the facultative anaerobic condition. The same configuration of MFCs was used to evaluate the electrochemical activity of electrogenic bacteria with nutrient broth as substrate. 41 strains were totally separated, whose voltage and power density were measured. Two excellent isolates were obtained, FLL2 and FLL3. The voltage of FLL2 and FLL3 were about 210mV, of which the maximum power density were over 65mW/m<sup>2</sup>. The colony characteristic of excellent electrogenic bacteria were generally smooth, flat, round, yellow and opaque. All obtained strains were brevibacteria with pilus, with the topographic height of several microns, observed under scanning electron microscope (SEM).
Power and Energy Engineering Conference, 2009. APPEEC 2009. Asia-Pacific; 05/2009
[show abstract][hide abstract] ABSTRACT: The acclimation of anode-respiring bacteria (ARB) played a key role in starting up a microbial fuel cell (MFC). Conventionally, spontaneous colonization was employed in this process. Descript here is an investigation of decreasing the start-up time by applying an anodic positive poised potential. During start-up period, the maximal current output increased from 0.42 to 3 mA since the anode potential was poised at +200 mV versus Ag/AgCl, which was due to the increase of driving force of substrate oxidation. A higher voltage output and a lower charge transfer resistance analyzed by electrochemical impedance spectroscopy (EIS) were observed, showing that applied potential could increase the electrochemical activity of anodic microbiota during start-up period. The MFC with anodic positive poised potential need 35 days to obtain a similar current output in two consecutive circles, which was 24 days faster than that of the control MFC operated under 1000 Ω. When both MFCs were started up, no difference on performance was observed.
[show abstract][hide abstract] ABSTRACT: Effective wastewater treatment using microbial fuel cells (MFCs) will require a better understanding of how operational parameters and solution chemistry affect treatment efficiency, but few studies have examined power generation using actual wastewaters. The efficiency of wastewater treatment of a beer brewery wastewater was examined here in terms of maximum power densities, Coulombic efficiencies (CEs), and chemical oxygen demand (COD) removal as a function of temperature and wastewater strength. Decreasing the temperature from 30 degrees C to 20 degrees C reduced the maximum power density from 205 mW/m2 (5.1 W/m3, 0.76 A/m2; 30 degrees C) to 170 mW/m2 (20 degrees C). COD removals (R COD) and CEs decreased only slightly with temperature. The buffering capacity strongly affected reactor performance. The addition of a 50-mM phosphate buffer increased power output by 136% to 438 mW/m2, and 200 mM buffer increased power by 158% to 528 mW/m2. In the absence of salts (NaCl), maximum power output varied linearly with wastewater strength (84 to 2,240 mg COD/L) from 29 to 205 mW/m2. When NaCl was added to increase conductivity, power output followed a Monod-like relationship with wastewater strength. The maximum power (P max) increased in proportion to the solution conductivity, but the half-saturation constant was relatively unaffected and showed no correlation to solution conductivity. These results show that brewery wastewater can be effectively treated using MFCs, but that achievable power densities will depend on wastewater strength, solution conductivity, and buffering capacity.
Applied Microbiology and Biotechnology 05/2008; 78(5):873-80. · 3.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: Eight kinds of amino acids including L-Serine (Ser), L-Asparagine (Asn), L-Asparticacid (Asp), L-Glutamicacid (Glu), DL-Alanine (Ala), L-lysine (Lys), L-Histidine (His) and L-Arginine (Arg) are tested as substrates of single-chambered air–cathode microbial fuel cells (MFCs) with domestic wastewater as inoculation. Their total organic carbon (TOC) concentrations in solution are standardized as 720 mg L−1. Ser produces the highest power density of 768 mW m−2 and Ala produces the lowest of 556 mW m−2. The Coulombic efficiencies (CEs) vary from 13 ± 3% (obtained with Arg) to 30 ± 1% (obtained with Ala). The removal efficiencies of total nitrogen (TN) are from 55 ± 5% (Asn) to 94 ± 4% (Asp), which may be associated with CEs. Maximum voltage outputs and TOC concentrations of the substrates appear to satisfy the empirical Monod-type equation when the external resistance is 150 Ω. The performances of MFCs are considered to relate to the molecular weights and structures of eight amino acids.