Microbial fuel cell research and application of the latest developments

Microbial fuel cell (MFC) is a kind of micro-organisms as the anode catalyst, the chemical energy directly into electricity biological device. The use of MFC can not only directly in the water or sludge in the organic matter degradation, but also in microbial metabolism of organic compounds can be generated in the process transformed into an electronic current, to gain power [lj. Since Fes 10-reducing bacteria has been reported that the electrochemical activity, the study found no medium for the microbial fuel cell can be used to operate the bacteria sony pcga-bp2r laptop battery, as a renewable alternative energy sources and new sewage treatment methods, microbial fuel cell has given rise to of particular concern. I will focus on research and microbial fuel cell related internal parameters and to explore better ways of improvement, to improve the performance of microbial fuel cells.
A microbial fuel cell to obtain the power density
Due to the presence of a high resistance limits the maximum power density, therefore, from the microbial fuel cell to obtain the upper limit of the power levels still remain unknown. Several groups of studies have shown that microbial flora and fuel with similar microbial fuel cell can produce 10 times the difference between the number of maximum power density. Can be seen that the performance of microbial fuel cells and reactors from the configuration of factors related to the decision, such as the super-potential and resistance. Chemical fuel cells, microbial fuel cells with a higher number of 10 times the power density [lv〕. This is because the micro-device within the various system parameters to increase its resistance, such as water and organic nitrogen demand, anode catalyst and reactor configuration and so on. Therefore, the reactor must be optimized geometry and the electrolyte, thereby reducing the resistance and to the catalytic potential of microorganisms to maximize.
Two rate-limiting factor in microbial fuel cells
Like other fuel cells, micro fuel cell performance is by the current, power density and fuel oxidation rate decision. The factors that affect the fuel oxidation rate more, including the catalytic activity of the anode, fuel-proliferation, the spread of electrons and protons, and consumption.
2.1 The choice of anode catalyst micro-organisms
From the view of the composition of microbial fuel cell anode can be attached to micro-organisms and transmission of electronic, is to determine the microbial fuel cell produced electricity generation capacity is an important factor, is to study micro-organisms producing electrical and electronic transfer mechanism rationale an important supportive tool, so the microbial fuel cell anode study has very important significance.
Learned person in microbial fuel cells, activated sludge or anaerobic sludge digestion device, you can generate 0.6V open-circuit potential, closed-circuit when the current can be ignored. To the anode chamber to repeat the supply of fuel, 2 ~ 3 weeks, current can gradually reach a stable value. Analysis of the small ribosomal (165rDNA) showed that bacteria on the anode is different from the use of sludge as inoculum of the bacterial flora Qing〕. Concentrated microbial groups in terms of performance is determined by its dell inspiron 1525 laptop battery, concentrated the most suitable poly-microbial can improve fuel efficiency provided by and used under the given conditions to promote microbial fuel cells run successfully.
In the enrichment process, using pure culture of the microbial fuel cell electrode surface covered with biofilm. Forming microbial biofilm between cells and electrodes of electronic, you can through insoluble Fe3 10 as the electron acceptor to restore direct contact between the electronic transfer of Qing〕, or to pass through special pili. Some data indicate that some bacteria can produce a natural body of electronic flow, but flow of microbial fuel cell within the e-produce biological importance has attracted suspicion.
2.2 Proton mass transfer
Like with the chemical fuel cells, micro fuel cells are also used cation-exchange membrane, in microbial fuel cells proton mass will not be restricted, if the operation in similar conditions, microbial fuel cell anode catalytic activity than the activity of chemical fuel cells low. In general, the chemical fuel cells, microbial fuel cells can produce more than one nursing a height of about a few times the current density. Microbial fuel cell cathode proton consumption rate than the rate of transport through the membrane faster-ching〕, this difference may be caused by microbial fuel cells and fuel cells, the intrinsic chemical differences. Microbial fuel cell using a variety of inorganic compounds, in addition to things, as a fuel for the maintenance of microbial metabolism, while chemical fuel cell is a simple as fuel. Microbial fuel cell used in the chemical substances in the aqueous phase decomposition of cation, the concentration ratio of these cations under neutral pH, the proton concentration was significantly higher than a nursing-fold [2s mouth, they can interfere with transmembrane proton transport. Microbial fuel cells proton mass Another limiting factor is the water quality as the electrolyte solution of choice.
Rozendal, etc. verify the cathode chamber by a layer of the Nafion 117 membrane transport cation transport effect and the effect of microbial fuel cell performance honk〕. In the two-bedroom with a yin and yang of the microbial fuel cell, transported to the cathode from the anode chamber room to remove the proton (K +, Na +, NH death, Mg, +, Ca "+) cations outside the positive charge carried by the quantity and through Circuit transferred the same number of electrons. Analysis of microbial fuel cell from the film shows, K + and Na + membrane sulfonate residues account for about 74%. cation transport does not depend on the concentration gradient to complete, but an electrodialysis process. In fact, this means that there is no microbial fuel cell proton transport, mainly through the neutral cation transport, rather than proton transport to sustain. This phenomenon raises a range of electrochemical and microbiological the problem, which affected the efficient operation of microbial fuel cells. acidification in the anode chamber of the increase in anode potential while reducing the activity of microbial catalytic anode reaction, while the cathode chamber reduced the anodic potential is alkaline. you can go to film or containing low concentrations of cations with the electrolyte to avoid this cation a priority, rather than proton transfer.
Usually close-fitting manner microbial fuel cell to avoid the two electrodes short-circuit, this time to film the performance of microbial fuel cell to maximize Tian〕. As the cathode current room will salt or acid solution into the increase. This shows that the proliferation of protons in the aqueous phase is a slow process, with a high salt concentration in the electrolyte to the membrane microbial fuel cell in the proton diffusion rate of speed. As mentioned above, salts inhibit transmembrane proton transport, but the promotion of protons in the aqueous phase of the effective diffusion. In the microbial fuel cell with a membrane, using a reduced proton diffusion depth of the reactor and low-salt electrolyte can increase the anode proton transfer. Miniature microbial fuel cell performance increase may be caused by the diffusion caused by the depth of the reduction [28〕. As the cathode surface of the alkali, with limited buffering capacity of the cathode-electrolyte salt concentration in the low-value can lead to lower cathode potential. Using potassium permanganate as an electron acceptor, due to increases in the cation exchange membrane and cathode, casing-type microbial fuel cell power density can be as high 3987mw/mZ, two-room type than the 34.5 times higher than the microbial fuel cell. Permanganate used the double-pipe microbial fuel cell resistance to 51.Zn, while the two-room-type microbial fuel cells and 1623n.
From the above results can be seen that the proton mass is a microbial fuel cell of the main limiting factors, it is by increasing the battery's internal resistance to influence the microbial hp pavilion zd8000 series laptop battery cell performance.
2.3 The oxygen reduction on the cathode
Oxygen is usually as a microbial fuel cell cathode reaction of the electron acceptor. Have confirmed that the oxygen reduction reaction is a weak microbial fuel cell optimum operating constraints. Commonly used electrode material is graphite, but for the oxygen reduction reaction is weak in terms of catalyst, because it has more than 6.69 / L of dissolved oxygen saturation value. This value is approximately saturated water vapor in the dissolved oxygen concentration of 80%. In order to improve the catalytic activity, usually platinum-modified graphite electrodes, this could make the saturation level of dissolved oxygen increased to 2.0mg / L, the resultant current is the maximum to do more than simply using graphite electrodes 3 to 4 times higher, but its large-scale applications are limited by cost constraints.
Usually cathode regulator - to increase the oxygen ferrocyanide is also the driving force. In the chemical fuel cells, researchers have examined a variety of materials and their mixtures to replace the expensive platinum cathode kiss〕. These materials include copper, gold, put / drill, key, tungsten and manganese, they use the redox properties of their respective cathode and oxygen in the electron transfer between the indirect. Also studied a 3-valent iron, complex drilling, magnesia coffee〕, etc., as microbial fuel cell cathode materials performance. However, as a microbial fuel cell cathode catalyst, most of them are not as good as platinum and high efficiency. Its effectiveness as a cathode catalyst for the most critical criteria is their affinity for oxygen, which show affinity for the cathodic reaction of dissolved oxygen saturation concentration or K. Value, because the resulting current intensity and the concentration of dissolved oxygen showed a dynamic relationship between horses 3 '1 2:.
In the enzyme fuel cell [sa〕〕 coffee and microbial fuel cells has been used oxygen reductase - catalase and peroxidase as a cathode catalyst. Aerobic respiratory electron transport system, the end of the oxidase on the molecular oxygen affinity than any known chemical catalyst for the high. Therefore, the aerobic bacteria in the 0.1mg / L of low dissolved oxygen concentrations have the greatest ability to breathe. To this end, the study focus on that as a cathode catalyst on the aerobic bacteria. Cathode biofilm development on improving the overall performance of microbial fuel cells have a significant role.
Closed-loop conditions, the bacteria formed on the cathode is different from the open-loop conditions, the bacteria on the cathode. In seawater and freshwater sediment microbial fuel cell [3s · 36〕 and man-made water-bed-type microbial fuel cell foot〕 also conducted the same monitoring. Bergel, etc. found in sea water corrosion in the formation of biofilm coated stainless steel cathodes, hydrogen fuel cells do get 0.32w / m, the power density [3s ".
2.4 electron acceptor other than oxygen
In addition to the aforementioned ferrocyanide, the permanganate can be used as an electron acceptor. Cathode with potassium permanganate as an electron acceptor (oxidizer) and two-bedroom-type microbial fuel cell can generate a maximum of 115.6mw / m "of the power density, than with ferrocyanide (power density of 25.6 mw / mZ) and oxygen (power density 10.2mw/mZ) as electron acceptor resulting from the high power density, respectively 4.5 times and 11.3 times. This is due to microbial fuel cells permanganate provides a higher open-circuit potential. These results indicate that the cathode reaction also affect the microbial fuel cell applications, an important factor.
3 microbial fuel cell applications in wastewater treatment
In wastewater treatment, microbial fuel cell with the existing methods do not possess several advantages. In the wastewater treatment process, the microbial fuel cell can be used as an energy power restoration, addition, in more stable conditions than in aerobic treatment can also produce less sludge.
The microbes in the aerobic treatment of organic pollutants carried by the use of all the energy, while the microbial fuel cell in the growth of microorganisms in these energy consuming only a small part of most of the conversion to electricity. Assuming a redox potential of 0.32V under the electrons from the contaminants passed to adjoin Sa nucleotide, using oxygen as an electron acceptor end, then the energy of pollutants carried by approximately 1 / 3 is the use of micro-organisms, and the rest 2 / 3 into electricity. This proves that micro-organisms in wastewater treatment sludge from the fuel cell can be substantial savings to address the capital. In different operating conditions, glucose and water half-saturation constant (K,), respectively 79 a 103mg / L and 461 ~ 719mg / L vary. Note these values in order to achieve the required effluent standards, microbial fuel cell to be the most suitable operating conditions of fuel concentrations. Because of this, optimization of microbial fuel cell can not only enhance output power, but also by detecting the quality of effluents to deal effectively with waste water.
4 Conclusion
Microbial fuel cell is a kind of repair to use the energy from sewage novel method of sewage treatment. The performance of microbial fuel cells by its resistance to impact, such resistance is the proton mass and the weak cathode caused by the oxygen reduction reaction. Protons in the aqueous phase of the transport rate is very slow, in the hollow fiber reactor to improve the proton transfer between two poles of yin and yang can minimize the depth of the proton transfer, thereby reducing the resistance.
Cathodic oxygen reduction reaction and the concentration of dissolved oxygen into a unipolar response relationship. Used with a cathode can improve the aerobic performance of fuel cells. Appropriate aggregation of concentrated cathode micro-organisms can be further enhanced oxygen reduction kinetics.
As the microbial fuel cell operating conditions with a moderate resource-efficient and pollution-free, etc., has given rise to energy, environment, space and other concerns, the current micro-device has been applied to biochemical oxygen demand sensor cafe '. 〕. Through this improvement, greatly enhanced the performance of microbial fuel cells. With further in-depth study, which in sewage treatment as well as other aspects of the application will become an apple 15-inch powerbook g4 laptop battery.