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RISS 인기검색어
- 검색키워드
- 저자 : Sokhee P. Jung (검색결과 76 건)
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Effects of brush-anode configurations on performance and electrochemistry of microbial fuel cells
Kang, Heunggu,Jeong, Jaesik,Gupta, Prabuddha L.,Jung, Sokhee P. Elsevier 2017 International journal of hydrogen energy Vol.42 No.45
<P><B>Abstract</B></P> <P>For practical implementation of MFC, increasing power generation is important because it is closely related with energy production rate and wastewater treatability. However, it is not known which relative arrangement of anode and cathode gives the best performance, and it is necessary to know electrochemical reference point of the brush anode for this. Five different brush-anode configurations were tested in a single-chambered cubic MFC. By merely changing a brush anode configuration, power and current densities were increased by 20% and 30%, respectively. The horizontally-positioned anode configuration (H1) with the closest anode-cathode distance produced the highest power and current. EIS showed that anode impedance and full-cell impedance were decreased by 60% and 49%, respectively. CE and EE were not significantly affected by the anode-cathode distance, but the horizontal type cells showed relatively higher CE, EE and COD removal rate and shorter batch time. The center of a titanium current collector and the center of carbon fibers of a brush-anode were found to be statistically-significant reference points for MFC electrochemistry.</P> <P><B>Highlights</B></P> <P> <UL> <LI> By merely changing anode configuration, P<SUB>max</SUB> increased by 20%. </LI> <LI> By merely changing anode configuration, I<SUB>opt</SUB> increased by 30%. </LI> <LI> Anode impedance and full-cell impedance decreased by 60% and 49%, respectively. </LI> <LI> The horizontal anode with closest electrode distance produced the highest power and current. </LI> <LI> The center of a titanium current collector and the center of carbon fibers were statistically-significant reference points. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Kang, Heunggu,Kim, Eojin,Jung, Sokhee P. Elsevier 2017 International journal of hydrogen energy Vol.42 No.45
<P><B>Abstract</B></P> <P>An MRC is a bioelectrochemical system combining a microbial fuel cell (MFC) with a RED stack to generate electricity from salinity gradient and organic wastewater with simultaneous treatment. Operating an MRC at an optimum flowrate to RED is important because it is closely related with energy production rate and economic feasibility. However, influence of RED flowrates on MRC electrochemistry and power production have not been investigated. For this purpose, four different flowrates of high concentration and low concentration solutions were tested. Maximum power density was highest in 10 mL/min (3.71 W/m<SUP>2</SUP>) and optimum current density was highest in 7.5 mL/min (5.36 A/m<SUP>2</SUP>). By mere increasing the flowrate to MRC, maximum power and optimum current densities increased by 17.7% and 16.2%. EIS showed that impedances of anode, cathode and full-cell were decreased by 51%, 31% and 19%, respectively. Anode CV showed that peak current density was increased by 25.7%. COD removal and CE were not affected by RED flowrate. Power generation at 7.5 mL/min and 10 mL/min were not so different, but current production was better at 7.5 mL/min. Therefore, considering energy production, the RED flowrate of 7.5 mL/min is a reasonable choice for MRC operation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> By increasing RED flowrate, P<SUB>max</SUB> increased by 17.7%. </LI> <LI> By increasing RED flowrate, I<SUB>opt</SUB> increased by 16.2%. </LI> <LI> P<SUB>max</SUB> were similar in 7.7 mL/min and 10 mL/min (∼3.7 W/m<SUP>2</SUP>). </LI> <LI> I<SUB>opt</SUB> was highest in 7.5 mL/min (∼5.4 A/m<SUP>2</SUP>). </LI> <LI> 7.5 mL/min was the best flowrate in the tested MRC. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Jung, Sokhee P.,Kim, Eojin,Koo, Bonyoung Elsevier 2018 CHEMOSPHERE - Vol.209 No.-
<P><B>Abstract</B></P> <P>Carbon-based material is commonly used for anodes in MFCs, but its low conductivity often limits anodic performance. Application of corrosion-resistive current collector to carbon-based anode can be a promising strategy for increasing the anodic performance. In this study, it was hypothesized increasing metal current collector improved anodic performance. Two different carbon-felt anodes with titanium wires (CF-W) or stainless steel mesh (CF-M) as a current collector were tested in a single chamber MFC. In the short-term tests such as polarization and impedance tests, CF-M with the larger current collector area (21.7 cm<SUP>2</SUP>) had 33% higher maximum power (2311 mW/m<SUP>2</SUP>), 81% lower anodic resistance (3 Ω), and 92% lower anodic impedance (1.1 Ω). However, in the long-term tests, CF-W with the smaller current collector area (0.6 cm<SUP>2</SUP>) showed higher performance in power and current generation, COD removal, and CE (51%, 10%, 11%, and 5% higher, respectively) and produced 41% higher net current in cyclic voltagramm (20.0 mA vs. 14.2 mA). This result shows that larger current collector is advantageous in short-term performance and disadvantageous in long-term performance, because the larger current collector is good for current collection, but interferes with mass transfer and microbial growth.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two types of anodes differing in area and material of current collectors were tested. </LI> <LI> Tested carbon felt anodes with titanium wires (CF-W) or stainless steel mesh (CF-M). </LI> <LI> In short-term tests, CF-M with larger current collector showed higher performances. </LI> <LI> In the long-term tests, CF-W with smaller current collector showed higher performance. </LI> <LI> CF-M is good for current collection, but mass transfer and microbial growth inhibited. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Nam, Taehui,Son, Sunghoon,Koo, Bonyoung,Hoa Tran, Huong Viet,Kim, Jung Rae,Choi, Yonghoon,Jung, Sokhee P. Elsevier 2017 International journal of hydrogen energy Vol.42 No.45
<P><B>Abstract</B></P> <P>Various materials and anode structures have been applied to enhance MFC performance. However, their comparative evaluation of performance and electrochemistry has not yet been investigated in detail under a same condition. In this study, a carbon-cloth anode, an anode-cathode assembly, and a brush anode with two different orientations were tested under a same condition for comparative analyses on their performance and electrochemistry, in order to reveal their unique electrochemical characteristics. The brush anode cells exhibited better performance than the carbon cloth cells. The brush anodes showed 41–72% higher maximum power densities, 18–75% higher maximum current density and 24–32% higher optimum current densities than the carbon cloth anodes. The brush anodes showed 25–43 Ω lower anodic polarization resistance than the carbon cloth anodes. The brush anodes showed 1.6–21.2 Ω lower ohmic impedance, 7.7–10.6 Ω lower charge transfer impedance and 9.3–31.8 Ω lower anodic impedance than the carbon cloth anodes. Anodic ohmic impedance was greatest in the carbon-cloth-anode MFC (21.9 Ω), where loose contact between a carbon cloth and a current collector might cause the high ohmic resistance, and large solution resistance in the cell could diminish anode performance due to slow ion transport. In order to improve MFC performance by modifying anode structures, we suggest the followings: 1) an anode should have large surface area, 2) anodic carbon material and a metal current collector must be tightly connected, 3) locating a brush anode closer to a cathode can be important.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The brush anodes produced up to 72% higher power densities than the carbon cloth anodes. </LI> <LI> The brush anodes produced up to 32% higher current densities than the carbon cloth anodes. </LI> <LI> The brush anodes had up to 43 Ω lower anode resistance than the carbon cloth anodes. </LI> <LI> The brush anodes had up to 31.8 Ω lower anode impedance than the carbon cloth anodes. </LI> <LI> Loose electrical contact and slow ion transport might increase anodic ohmic resistance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Koo, Bonyoung,Lee, Seung-Mok,Oh, Sang-Eun,Kim, Eun Jung,Hwang, Yuhoon,Seo, Dongjune,Kim, Jin Young,Kahng, Yung Ho,Lee, Yong Woon,Chung, Seon-Yong,Kim, Seong-Jun,Park, Jeong Hun,Jung, Sokhee P. Elsevier 2019 ELECTROCHIMICA ACTA Vol.297 No.-
<P><B>Abstract</B></P> <P>Activated carbon (AC) is an inexpensive catalyst for oxygen reduction in an air cathode of microbial fuel cells (MFCs). In the AC-based cathode, carbon black (CB) is used as a conductive supporting material. In this study, it was hypothesized cathodic performance would increase if reduced graphene oxide (rGO) replaces CB in an optimum ratio. rGO replaced CB in the four different weight ratios of rGO toCB: 0:30 (rGO0); 5:25 (rGO5); 15:15 (rGO15); 30:0 (rGO30). Maximum power density was the best in rGO15 (2642 mW/m<SUP>2</SUP>) followed by rGO5 (2142 mW/m<SUP>2</SUP>). In the optimum external resistance operation, rGO5 and rGO15 showed similar power (∼1060 mW/m<SUP>2</SUP>), higher than the others. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy also showed that the optimal rGO additions improved cathodic performance and reduced cathodic internal resistance. Due to the flatter and wider shape of rGO and 5 times higher electrical conductivity than CB, the rGO addition improved the cathodic performance, but the complete replacement of CB with rGO decreased the cathodic performance due to the increased thickness and the morphological crack. The optimum rGO addition is a simple and effective method for improving cathodic performance.</P>
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( Bonyoung Koo ),( Sokhee P. Jung ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
Characterizations of the electrochemistry of a microbial fuel cell (MFC) is very important in developing bioelectrochemical energy producing wastewater treatment process. Compared to the development of MFC technology, however, understanding of its electrochemical characterization is still insufficient. The main reason is that its electrochemical analysis is very difficult due to the complex nature of the anode biofilm, which is a key to generating electricity. In this experiment, the influence of the measurement potential of impedance and the scanning rate for polarization curve on the MFC electrochemistry was investigated. The experiment was performed after stabilizing the system for accurate measurement. Unlike the previous batch tests showing the lowest anodic impedance at -400 mV vs. Ag/AgCl, the anodic impedance decreased and the current production increased as the anode potential increased up to +5.7 mV vs. Ag/AgCl in the continuous flow MFC. However, the cathodic impedance was very little affected by the measuring potential because the activated carbon catalyst is abiotic and much less sensitive to electrical stimulation than the anode biofilm. The polarization curves were produced at two scanning rates (1 and 0.1 mV/s) in a continuous mode, and those electrochemical data were comparatively analyzed. When it is difficult to maintain a steady state for a long time in an MFC, it will be possible to produce polarization curves in a short time with a faster scanning rate. When performance analysis is needed, the comparative analysis would be possible among the data at different conditions through extrapolation.
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( Bonyoung Koo ),( Sokhee P. Jung ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
Although MFC has many applications, the most promising application is in wastewater treatment. MFC can be grafted into a sewage treatment plant to remove the remaining organic matter and generate energy for the operation of the sewage treatment plant. Many studies have been carried out to improve the performance of these MFCs, and they have shown the potential for commercialization of MFCs, such as showing results of grafting them with actual sewage treatment plants. The current research trend of MFC scale-up is as follows. i) development of electrodes and membranes with high economy and performance to reduce high cost, ii) development of materials resistant to contamination, corrosion and clogging for long-term operation, iii) connection of multiple modules to minimize losses Scale up in the form of a stack. However, there are still a number of obstacles that prevent scale-up. The main obstacles are high cost, low power generation due to internal losses, durability and removal of contaminants. Therefore, it is important to develop efficient electrodes and ion membranes and increase the actual wastewater treatment efficiency in order to reduce the high cost and internal losses. Looking at the results of MFC scale-up studies so far, it has been shown that stack configuration can achieve high performance by reducing internal losses, is cheaper than scaling up a single reactor, and has high pollutant handling capacity. Suggested research strategies for scale-up for future practical use are as follows. First, by using a stack type reactor, secondly by using a reactor without an ion film to reduce internal resistance and cost, thirdly by using a microbial anode as the ultimate catalyst for durability and sustainability, and finally by increasing the processing efficiency. It is to achieve high treatment efficiency through pre-treatment and post-treatment by grafting other sewage treatment processes to increase it.
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Recent Trends of Oxygen Reduction Catalysts in Microbial Fuel Cells
( Bonyoung Koo ),( Sokhee P. Jung ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
Microbial fuel cell (MFC) is a system being developed for a next-generation energy-producing wastewater treatment process that treats wastewater and recovers energy. Because an MFC cathode performing oxygen reduction is a bottleneck in performance enhancement, significant improvement of the cathode performance is necessary for the practical implementation of MFC system. The most ideal oxygen reduction catalyst is known as platinum. However, platinum is expensive and not long-lasting, making it difficult to apply to a real application. For this reason, a lot of research has been conducted on development of cathode catalysts in the MFC field. One of the important goals of MFC technology is an energy-independent or energy-supplied wastewater treatment process. Considering the size of the wastewater treatment plant and the characteristics of the wastewater, the ideal cathode catalyst for this should have high durability and high economic efficiency in long-term operation. Summarizing the research results so far, the activated carbon-based catalyst is considered to be the most promising ORR catalyst for the practical use of MFC. The 1,210 mW/$ achieved by the activated carbon catalyst mixed with CB is the highest cost-performance ratio in the studies reported to date. It is necessary to study electrochemical mechanisms and materials to improve the performance and durability of activated carbon catalysts, and research for mass production of electrodes is needed.
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Trends of microbial electrochemical technologies for nitrogen removal in wastewater treatment
( Bonyoung Koo ),( Sokhee P. Jung ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
The removal of organic carbon and nutrients (i.e. N and P) from wastewater is essential for the protection of the water environment. Especially, nitrogen compounds cause eutrophication in the water environment, resulting in bad water quality. Conventional nitrogen removal systems require high aeration costs and additional organic carbon. Microbial electrochemical system (MES) is a sustainable environmental system that treats wastewater and produces energy or valuable chemicals by using microbial electrochemical reaction. Innovative and cost-effective nitrogen removal is feasible by using MESs and increasing attention has been given to the MES development. In MEC, nitrogen removal technology through external applied voltage electrochemically oxidizes ammonium under perfect anaerobic conditions and achieves denitrification without additional carbon source. The nitrogen removal efficiency can be increased by improving the adhesion of electroactive microorganisms of the oxidation electrode and the reduction electrode catalyst of the MEC, the activity of the biofilm catalyst, and the electrode electron transfer efficiency. However, in terms of practical use, it is necessary to develop an effective electrode structure to solve the electrode clogging problem caused by various contaminants and suspended matter in wastewater.
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