He Lee

Electricity production from beer brewery wastewater using single chamber microbial fuel cell

The performance of electricity production from beer brewery wastewater in a single chamber membrane-free microbial fuel cell (MFC) was investigated. Experimental results showed that the MFCs could generate electricity from full-strength wastewater (2,239 mg-COD/L, 50 mM PBS added) with the maximum power density of 483 mW/m2 (12 W/m3) at 30 degrees C and 435 mW/m2 (11 W/m3) at 20 degrees C, respectively. Temperature was found to have bigger impact on cathode potential than anode potential. Results suggested that it is feasible to generate electricity with the treatment of beer brewery wastewater.

Sequestration of CO2 discharged from anode by algal cathode in microbial carbon capture cells (MCCs).

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.

Continuous electricity generation by a graphite granule baffled air–cathode microbial fuel cell

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.

Application of nitrogen-doped carbon powders as low-cost and durable cathodic catalyst to air-cathode microbial fuel cells

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.

Treatment of biodiesel production wastes with simultaneous electricity generation using a single-chamber microbial fuel cell

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.

Effects of sulfide on microbial fuel cells with platinum and nitrogen-doped carbon powder cathodes

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)).

Power generation using adjustable Nafion/PTFE mixed binders in air-cathode microbial fuel cells.

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.

Electricity Generation in Microbial Fuel Cells at Different Temperature and Isolation of Electrogenic Bacteria

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 2 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 2 . 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).