CN101409355B - A photosynthetic microbial fuel cell - Google Patents

Abstract

A photosynthetic microbial fuel cell belongs to the technical field of microbial fuel cells. The photosynthetic microbial fuel cell consists of two electrode chambers, the cathode and the anode, which are connected by a proton exchange membrane. Each electrode chamber is filled with a certain amount of solution in the anode chamber and the cathode chamber. Photosynthetic microorganisms are adsorbed on the surface of the anode to degrade organic waste and heavy metal wastewater. Photosynthesis, releasing electrons and protons. Photosynthetic microorganisms transfer electrons to the anode, protons enter the cathode through the proton exchange membrane, and combine with oxygen in the air to form water. The transfer of electrons between the electrodes generates a voltage between the electrodes, which powers the external circuit. Its advantages are: no need to add electron transfer mediators, no need to increase the oxygen content on the surface of the cathode through external power, no need to add additional nutrients to the anode to generate electricity while cultivating photosynthetic microorganisms (algae, photosynthetic bacteria), and the battery structure is simple. Adding wastewater to the anode not only increases the electric energy, but also benefits the growth and reproduction of photosynthetic microorganisms, saves costs, and can solve some pollution and produce hydrogen and methane.

Description

A photosynthetic microbial fuel cell

technical field

The invention belongs to the technical field of microbial fuel cells, and relates to a device capable of processing heavy metal/organic complex pollutant wastewater while obtaining electric energy, cultivating and harvesting photosynthetic microorganisms (algae, photosynthetic bacteria), and generating methane and hydrogen.

Background technique

Microbial Fuel Cell is a device that uses microorganisms (Microbe) as a catalyst to convert the chemical energy of fuels such as sugar and organic acids into electrical energy. This device has dual functions, that is, on the one hand, it can treat sewage, and on the other hand, it can also use the harmful waste in the sewage as a raw material to generate electricity.

Due to the potential advantages of microbial fuel cells, people are very optimistic about its development prospects, but it is still far away to be used as a power source for actual production and life. The main reason is that the output power density is far from meeting the actual requirements. At present, the power density of the proton exchange membrane fuel cell can reach 3W/cm ² , while the power density of the biofuel cell has not yet reached 1mW/cm ² , which shows the huge gap between the two. The biggest factor restricting the output power density of biofuel cells is the electron transfer process. Since the reducing substances produced by metabolism are isolated from the outside world by the membrane of microorganisms, the electron transfer channel between microorganisms and electrodes is blocked. Although the microbes in the battery can transfer electrons directly to the electrodes, the amount and rate of electron transfer is low. This is because microbial cells contain non-conductive substances, so it is difficult for electrons to pass through the cell membrane from the normal microbial electron transport chain to the electrode. The main method to solve this problem is to add redox molecules to the cathode chamber as electron transfer mediators, but These mediators are usually toxic compounds and are expensive, such that it is not economical to apply such fuel cells to actual wastewater treatment.

Kim Byung-hong and others from the Korea Institute of Science and Technology applied for a patent "A biofuel cell using wastewater and activated sludge for wastewater treatment" (ZL00810805.6), which uses the electrochemical activity in wastewater and activated sludge Microorganisms oxidize organic matter contained in wastewater. A biofuel cell includes a cathode compartment and an anode compartment respectively containing a conductive mediator next to the interior of the biofuel cell; an anode placed in the anode compartment; a cathode placed in the cathode compartment; and an intervening cathode compartment An ion exchange membrane used to separate the anode compartment and the cathode compartment between the anode compartment containing organic wastewater and activated sludge and maintaining anaerobic conditions during the operation of the biofuel cell. Although the fuel cell does not need to add any electron transfer mediator, in order to maintain the anaerobic state of the anode cell and the high dissolved oxygen state of the cathode cell, it is necessary to continuously feed nitrogen into the anode cell and oxygen into the cathode cell, increasing the The running cost of the battery.

Liu Yisheng of Zhejiang University and others applied for the invention patent "Microbial Fuel Cell" (200410066753.9),

The cabinet of this microbial fuel cell is divided into an anode cavity and a cathode separator. There are holes on the separator, and a hydrogen ion selective membrane is arranged on the hole. There are glucose, sodium dihydrogen phosphate and methylene blue (mediator) in the anode cavity. The configured solution, the anode cavity is covered with a sealing cover, and the anode graphite rod is fixed on the sealing cover. One end of the anode graphite rod extends into the anode cavity and is immersed in the solution. Beer yeast and its culture medium are placed, and the cathode cavity is filled with a solution composed of potassium ferricyanide and ferrous fumarate. The cathode cavity is covered with an end cover, and the cathode graphite rod is fixed on the end cover. One end extends into the cathode cavity and is immersed in the solution in the cavity.

The microbial fuel cells of the above two patents are composed of a cathode chamber and an anode chamber, and the anodes all use mediators to transfer electrons. The mediator is very expensive and needs to be replenished frequently. Compared with the power provided by the biofuel cell, the cost of adding the mediator is extremely high. And many redox mediators are toxic, making them unusable in open environments where energy is obtained from organic matter. Therefore, microbial fuel cells with redox mediators are not suitable for use as a simple long-term energy source. And the culture medium of yeast used in the patent of Zhejiang University needs to take out the anode and add it regularly, which is inconvenient to operate and has a small application range.

In addition, there are other forms of microbial fuel cell reports, but the microorganisms adopted generally use organic matter to transfer electrons as substrates, and cannot directly utilize the convenient and easy-to-obtain and abundantly supplied solar energy.

Contents of the invention

The purpose of the present invention is to solve the problem that the microorganisms used in the existing microbial fuel cells all use organic substances as substrates to transfer electrons, and cannot directly use convenient, readily available and adequately supplied solar energy. The use of light energy microbial fuel cells can cultivate algae and collect electrical energy; using this device, photosynthetic microorganisms can grow and reproduce while processing domestic and industrial organic waste and heavy metal wastewater, and the output power can be increased, which is conducive to the growth and reproduction of algae, and can also produce biogas and hydrogen . This photosynthetic microbial fuel cell not only adds an energy direction for human beings, but also solves the pollution problems of organic matter and heavy metals, and at the same time harvests algae to produce biogas and hydrogen.

A photosynthetic microbial fuel cell, comprising a cathode chamber 10 and an anode chamber 9, the cathode chamber 10 and the anode chamber 9 are connected by a proton exchange membrane 6, and a vacuum pad 5 is sandwiched between the proton exchange membrane and the bipolar chambers to keep sealing. The cathode and anode chambers are equipped with a ventilation port 2, a feed port 7 and a sampling port 8, and the upper parts are all open and exposed to the air to form an aerobic state. The anode chamber has a gas intake port 1 for collecting H ₂ and CH ₄ . The graphite electrode 11 in the anode chamber and the graphite electrode 12 in the cathode chamber are connected to the external load resistor 3 through wires. The anode and cathode compartments are filled with cathode buffer, and the anode compartment is filled with anode buffer and culture medium. Graphite electrodes are pre-placed in a petri dish for enrichment of photosynthetic microorganisms. After forming a mature biofilm, the anode that absorbs photosynthetic microorganisms 4 and forms a mature biofilm is inserted into the anode chamber. Organic waste and heavy metal wastewater can be added through the feed port of the anode chamber, and potassium ferricyanide can be fed through the cathode feed port.

In the photosynthetic microbial fuel cell without an electron transfer mediator provided by the invention, the photosynthetic microorganisms are adsorbed on the surface of the anode, carry out photosynthetic growth and reproduction, degrade organic waste and heavy metal wastewater at the same time, and release electrons and protons. Photosynthetic microorganisms transfer electrons to the anode, and then transfer them to the cathode through an external circuit. The protons enter the cathode through the proton exchange membrane, and the electrons and protons combine with oxygen in the air to form water. The transfer of electrons between the electrodes generates a voltage between the electrodes, which powers the external circuit. The anode produces hydrogen and methane when photosynthetic microorganisms degrade organic waste and heavy metal wastewater, which can be collected and used. And algae can be harvested regularly.

The anode chamber is connected with microorganisms 4 capable of photosynthesis, such as Chlorella, Spirulina, Anabaena, and photosynthetic bacteria. When this kind of microorganism is connected to the anode, it can maintain a certain battery voltage without adding additional nutrients. The voltage of this device is 0.09-0.2V. With the amount of potassium ferricyanide added to the cathode, the area and quantity of the anode plate will increase. Different, the voltage value is different.

Photosynthetic microorganisms carry out photosynthetic reproduction and growth in the anode chamber, and photosynthetic microorganisms, such as chlorella, spirulina, anabaena, etc., can be harvested regularly.

While the photosynthetic microorganisms in the anode carry out photosynthesis and growth and reproduction, they can treat organic waste and heavy metal wastewater, increase the output of electric energy, and benefit the growth and reproduction of algae.

Photosynthetic microorganisms can produce biogas and hydrogen while degrading organic wastewater, and improve the utilization rate of solar energy.

Before use, the proton exchange membrane needs to be boiled in 30% H ₂ O ₂ , 0.5mol/L H ₂ SO ₄ and deionized water for 1 hour, and then stored in deionized water for later use. The electrodes are all unpolished high-purity graphite electrodes. Before use, soak them in 1.0mol/L HCl to remove impurity ions, and then soak them in 1.0mol/L NaOH to remove cells adsorbed on their surfaces. After the graphite electrode is treated, it is placed in a chlorella culture vessel for algae enrichment for future use.

The anode buffer, cathode buffer, and photosynthetic microorganism culture medium need to be sterilized at 121°C for 15 minutes and set aside.

The growth temperature of photosynthetic microorganisms is between 0-80°C, and the best temperature is 25-30°C, which can directly use sunlight. The light intensity of the external light source is 0-10 ⁶ lux, and the best light intensity is 4.5×10 ³ -5×10 ³ lux. The load resistance is 0-10MΩ. As the load resistance increases, the battery voltage gradually increases, but the growth rate gradually slows down. However, the battery power first increases and then decreases, and the battery output power is the largest near the optimum load resistance. The optimum load resistance of this device is 500-530Ω, as shown in Figure 2.

Photosynthetic microbial fuel cells undergo the following reactions:

Photosynthesis:

anode:

Cathode: O ₂ +4H ⁺ +4e ^- →H ₂ O (4)

The voltage generated by the photosynthetic microbial fuel cell is composed of two parts: one part is photosynthetic microorganisms (microalgae, photosynthetic bacteria) for photosynthetic photolysis of H ₂ O, and the electrons and protons generated in this process are transferred to the cathode (formula (2)) The other part is the process of exogenous cell metabolism of carbohydrates produced by photosynthesis, the cytochrome accumulated outside the cell membrane loses electrons to the anode (formula (3)), and the electrons reach the cathode through the external circuit. The protons are transferred to the cathode through the proton exchange membrane, and the electrons are transferred to the cathode by the external circuit, and form water with the oxygen in the water (formula (4)). The addition of potassium ferricyanide accelerates the transfer of electrons, which is beneficial to increase the voltage.

The advantages of the photosynthetic microbial fuel cell are: no need to add electron transfer mediators, no need to use external power to increase the fuel concentration of the anode surface microorganisms, and the oxygen content on the surface of the cathode, and the anode does not need to add additional nutrients to maintain the battery voltage, the battery structure is simple . Microorganisms can be used to degrade organic waste and heavy metal wastewater by using the energy of photosynthetic growth and reproduction process, and can produce biogas and hydrogen while increasing electric energy. While using light energy to cultivate photosynthetic microorganisms, it can also process organic waste and heavy metal waste, obtain electricity, and produce biogas and hydrogen.

Description of drawings

Figure 1 is a schematic diagram of the structure of a photosynthetic microbial fuel cell.

1. Air intake (H ₂ , CH ₄ ); 2. Vent (air/O ₂ ); 3. Load resistance; 4. Photosynthetic microorganisms; 5. Vacuum pad; 6. Proton exchange membrane; 7. Feed port; 8. Feed port; 9. Anode chamber; 10. Cathode chamber; 11. Anode graphite electrode; 12. Cathode graphite electrode

Figure 2 is the resistance-output power and resistance-voltage diagram of the battery

Figure 3 is the voltage-time curve of the chlorella microbial fuel cell

Figure 4 is the voltage-time curve of the photosynthetic bacteria microbial fuel cell (the anode is added to domestic wastewater)

Figure 5 is the voltage-time curve of the spirulina microbial fuel cell (the anode is added to a mine organic waste-heavy metal composite wastewater)

Detailed ways

Embodiment one:

The microorganisms are Chlorella vulgaris, cultured from water samples obtained from the river, and separated by the water droplet separation method. The medium composition (1L) is as follows:

Table 1 Medium formula table (1L)

Table 2 Medium trace element formula table (1L)

The photosynthetic microbial fuel cell consists of two electrode chambers, the cathode and the anode, which are connected by a proton exchange membrane (Nation-117, Dupont). 1000ml solution, the physical surface area of the anode plate is 75cm ² , add the anode buffer solution (Table 3) and the above-mentioned culture medium to the anode chamber, and add the cathode buffer solution (Table 4) and potassium ferricyanide solution to the cathode chamber. All devices were placed in a light incubator for experiments. The growth temperature is 25-30°C, the light intensity is 4.5×10 ³ lx, and the load resistance is determined to be 510Ω.

Table 3 Anode chamber buffer composition (/L)

basal medium KCl 0.1g, NH4Cl 0.2g, NaH2PO4 0.6g Wolfe Vitamin Solution 10ml, see ATCC medium 2433 Wolfe Mineral Solution 10ml, see ATCC medium 2433 NaCl 2.9g Buffer NaHCO3 2.5g

Table 4 Cathode chamber buffer composition (/L)

basal medium KCl 0.1g, NH4Cl 0.2g, NaH2PO4 0.6g Buffers and electrolytes Tric-HCl (final pH 7.0), NaCl 2.9g

The electrode is pre-placed in a petri dish for enrichment of chlorella. After forming a mature biofilm, when the anode is inserted into the electrode chamber, the voltage rises rapidly to about 0.2V, as shown in Figure 3. When the potassium ferricyanide is consumed, the battery voltage drops to 0.12V, and it operates stably. When the electrode is replaced with an electrode that is not connected to chlorella, the voltage immediately drops to the background voltage, and when the original electrode is replaced again, the voltage rises rapidly to about 0.12V. Show that the output of electrical energy Chlorella, both photosynthetic microorganisms play a decisive role. Then add 50mmol/L potassium ferricyanide solution to the cathode, and the voltage value rises rapidly to 0.2V. This is because the reduction rate of Fe ³⁺ in potassium ferricyanide is faster than the oxidation rate of Fe ²⁺ oxidized by O ₂ , which can accelerate the transfer rate of electrons and increase the output of electric energy. After a period of reaction, the potassium ferricyanide is consumed, and the battery voltage drops and tends to be stable. At this time, inject 50mmol/L potassium ferricyanide solution, and the voltage value rises rapidly. After 7 days, 5.1 grams of Chlorella can be harvested from the anode.

Example 2:

Photosynthetic bacteria (photosynthetic bacteria referred to as PSB) were isolated in Xiaoyuehe, Beijing. The medium used for isolation was: organic matter 1.5-2g, (NH ₄ ) ₂ SO ₄ 1g, NaCl 2g, NaCO ₃ 5g, K ₂ HPO ₄ 0.5g, MgSO ₄ ·7H ₂ O0.2g, distilled water 1000mL, pH 7.0, culture at 25-30℃ under light. The isolated PSB has a Gram-negative reaction and is single-cell egg garden and spherical. The colony is rose red, moist and smooth, and the liquid culture of the bacteria is dark red. The bacterial suspension after liquid culture contains 2.6- 280 million/mL, identified as Rhodobacter sphaeroides, Rhodobacter palustri s, Rhodobacter Capsulatus, Rhodospirillum rubrum and other strains.

The photosynthetic microbial fuel cell consists of two electrode chambers, the cathode and the anode, which are connected by a proton exchange membrane (Nation-117, Dupont). A vacuum pad is sandwiched between the proton exchange membrane and the bipolar chambers to keep it sealed. Each electrode chamber is filled with 1000ml solution. The physical surface area of the anode plate is 90cm ² , two pieces are used in series. Anode buffer (Table 3) and Zarrouk's medium were added to the anode chamber, and cathode buffer (Table 4) was added to the cathode chamber. All devices were placed in a light incubator for experiments. The growth temperature is 25-30°C, the light intensity is 4.9×10 ³ lx, and the load resistance is determined to be 530Ω.

The electrode is placed in a petri dish in advance for PSB enrichment. After the mature biofilm is formed, when the anode is inserted into the electrode chamber, the voltage rises rapidly to about 0.25V, as shown in Figure 4. Add 30ml of sewage, COD=321.2mg/L, from the sedimentation tank of Beijing Gaobeidian Sewage Treatment Plant to the anode. The voltage rises rapidly to around 0.31V, and as the sewage degrades, the voltage continues to drop, so does the COD. When the voltage drops to 0.25V, the above-mentioned sewage is added again, and the voltage rises rapidly to 0.31V, and the above process is repeated. The COD of sewage treated for 5 days can be reduced from 321.2mg/L to 122.6mg/L, the removal rate reaches 61.8%, and 1.6 liters of hydrogen is produced.

Example 3:

The photosynthetic microorganism is Spirulina, using Zarrouk's medium, adding 150mL of culture medium into a 250mL Erlenmeyer flask, and inoculating Spirulina in the logarithmic growth phase. To 10 or so, THZ-82 type constant temperature shaker shaker 30 ℃, 24h · d ^-1 light shake flask culture.

The photosynthetic microbial fuel cell consists of two electrode chambers, the cathode and the anode, which are connected by a proton exchange membrane (Nation-117, Dupont). A vacuum pad is sandwiched between the proton exchange membrane and the bipolar chambers to keep it sealed. Each electrode chamber is filled with 1000ml solution. The physical surface area of the anode plate is 120 cm ² , the anode chamber is filled with anode buffer (Table 3) and Zarrouk's medium, and the cathode chamber is filled with cathode buffer (Table 4). All devices were placed in a light incubator for experiments. The growth temperature is 25-30°C, the light intensity is 4.7×10 ³ lx, and the load resistance is determined to be 520Ω.

The electrodes are pre-placed in a Petri dish for enrichment of spirulina. After forming a mature biofilm, when the anode is inserted into the electrode chamber, the voltage rises rapidly to about 0.18V, as shown in Figure 5. The composition of metal-organic composite wastewater from a certain mine is shown in Table 5. Take 20ml and add it to the anode, and the voltage quickly rises to about 0.26V. As the degradation voltage of sewage continues to decrease, the COD also decreases. When the voltage drops to 0.18V, the above sewage is added again, and the voltage rises rapidly to 0.26V, and the above process is repeated. The COD of sewage treated for 8 days can be reduced from 820mg/L to 125.8mg/L, and the removal rate reaches 84.8%. After 8 days, 6.2 grams of Spirulina can be harvested from the anode, and 1 liter of biogas can be produced.

Table 5 Treatment results of metal-organic compound pollution

serial number Pollutants Index after flocculation purification Indicators after 8 days of photosynthetic microbial fuel cell treatment 1 COD(mg/L) 820 125.8 2 BOD(mg/L) 156 90 3 Chromaticity (times) 260 90 4 SS(mg/L) 90 - 5 Anilines (mg/L) 4.5 - 6 Sulfide (mg/L) 0.8 - 7 Total N (mg/L) 122 45 8 Total P (mg/L) 4.3 1.9

serial number Pollutants Index after flocculation purification Indicators after 8 days of photosynthetic microbial fuel cell treatment 9 pH 7.12 7.9 10 Mn(mg/L) 81 twenty four 11 Cu(mg/L) 69 12 12 Ni(mg/L) 85 14

Claims (6)

1. A photosynthetic microbial fuel cell is characterized in that it comprises cathode chamber (10) and anode chamber (9), cathode chamber (10) and anode chamber (9) are connected by proton exchange membrane (6), and proton exchange membrane and bipolar chamber A vacuum pad (5) is sandwiched between them to keep the seal; the cathode and anode chambers are equipped with vents (2), feed ports (7) and sampling ports (8), and the upper parts of the cathode and anode chambers are exposed to the air to form a good Oxygen state; the anode chamber has a gas intake port (1) to collect H ₂ and CH ₄ ; the graphite electrode (11) in the anode chamber and the graphite electrode (12) in the cathode chamber are connected to the external load resistor (3) through wires; the cathode and anode chambers Load the cathode buffer, and the anode chamber is filled with the anode buffer and culture medium; the graphite electrode is pre-placed in a petri dish for enrichment of photosynthetic microorganisms, and after the formation of a mature biofilm, the photosynthetic microorganisms (4) will be adsorbed to form a mature biofilm. The anode is inserted into the anode chamber; organic waste and heavy metal wastewater are added from the feed port of the anode chamber, and potassium ferricyanide is added from the cathode feed port; photosynthetic microorganisms (4) refer to chlorella, spirulina, anabaena and photosynthetic microorganisms (4) One or a combination of bacteria; the photosynthetic bacteria are Rhodobactersphaeroides, Rhodobacter palustris, Rhodobacter Capsulatus, Rhodospirillum rubrum. 2. A kind of photosynthetic microorganism fuel cell as claimed in claim 1, it is characterized in that photosynthetic microorganism is adsorbed on the anode surface, carries out photosynthetic growth and reproduction, degrades organic waste and heavy metal waste water simultaneously, releases electron and proton; Photosynthetic microorganism transfers electron to the anode, and then transferred to the cathode through the external circuit, the protons enter the cathode through the proton exchange membrane, and the electrons and protons combine with the oxygen in the air to form water; the electron transfer between the electrodes generates a voltage between the electrodes, which supplies energy for the external circuit; the anode is in When photosynthetic microorganisms degrade organic waste and heavy metal wastewater, they produce hydrogen and methane, which can be collected and used; and algae can be harvested regularly. 3. A kind of photosynthetic microbial fuel cell as claimed in claim 1 or 2, it is characterized in that the photosynthetic microorganisms that anode chamber accesses, need not add nutrient in addition; Photosynthetic microorganisms carry out photosynthetic reproduction and growth in anode chamber, can harvest photosynthetic microorganisms regularly; Photosynthetic microorganisms in the anode can process organic waste and heavy metal wastewater while performing photosynthesis, growth and reproduction, increase the output of electric energy, and benefit the growth and reproduction of algae; photosynthetic microorganisms can produce biogas and hydrogen while degrading organic wastewater, and improve solar energy utilization Rate. 4. A photosynthetic microbial fuel cell as claimed in claim 1, characterized in that the proton exchange membrane needs to be boiled in 30% H ₂ O ₂ , 0.5mol/L H ₂ SO ₄ and deionized water for 1 hour before use, and then stored in Standby in deionized water; the electrodes are all unpolished high-purity graphite electrodes, soaked in 1.0mol/L HCl before use to remove impurity ions, and then soaked in 1.0mol/L NaOH to remove cells adsorbed on its surface; After the electrode is treated, it is placed in a chlorella culture vessel for algae enrichment for future use. 5. A photosynthetic microbial fuel cell as claimed in claim 1 or 2, characterized in that the growth temperature of photosynthetic microorganisms is between 0-80°C, sunlight is directly used, the light intensity of the external light source is 0-10 ⁶ lux, and the load resistance is 0-10MΩ. 6. A photosynthetic microbial fuel cell as claimed in claim 5, characterized in that the growth temperature of photosynthetic microorganisms is 25-30°C, the light intensity of the external light source is 4.5×10 ³ -5×10 ³ lux, and the load resistance is 500-530Ω.

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