CN102400169B - Method for producing hydrogen by alkalescent microbe electrolysis - Google Patents

Abstract

The invention belongs to the technical field of microbe electrochemistry and aims to provide a method for producing hydrogen by alkalescent microbe electrolysis. The method comprises steps of: (1) starting an electrolytic bath under a microbiological fuel cell mode: accessing a resistor in a closed-loop of a system and replacing a solution in the electrolytic bath when a voltage is low; continuing to replace until voltages at two ends of the resistor are higher than 500mV to finish anode starting; (2) producing hydrogen under a microbe electrolytic bath mode: replacing a cathode in the started electrolytic bath with stainless steel net or foamed nickel, keeping solution in the whole electrolytic bath in a anaerobic state and applying 0.4-0.8 V voltage at two ends of the cathode and the anode by using direct-current power supply and realizing hydrogen production of the electrolytic bath at 20-35 DEG C. The invention can effectively inhibit generation of methane, realize long time continuous operation or multiple batch operation and generate gas with low methane content; the method has a low cost and can obtain high hydrogen generation rate; utilization rate of organic matter under an alkalescent environment is increased, and hydrogen generation stability of the system is increased.

Description

A method for hydrogen production by alkaline microbial electrolysis

technical field

The invention belongs to the technical field of microbial electrochemistry, and in particular relates to a hydrogen production method by alkaline microbial electrolysis.

Background technique

Hydrogen energy is a clean energy. The development of hydrogen energy is of great significance to future energy and the environment. At present, the production of hydrogen mainly comes from non-renewable materials such as petroleum and natural gas, and hydrogen is prepared by chemical means such as catalytic cracking and gasification. However, the hydrogen of the future must be obtained from renewable resources. Hydrogen production by electrolysis of water, hydrogen production by solar photolysis of water and hydrogen production by biological fermentation are sustainable hydrogen production methods. The electrolysis of water consumes a lot of energy and costs a lot. Solar photolysis of water has low efficiency and stability problems. The biological fermentation method has the advantages of cleanness, low energy consumption, and pollution control at the same time. It is considered to be an important method and approach for hydrogen production in the future, but this method still has the problem of low utilization of biomass raw materials. Utilizing the characteristics of microbial electricity production, combined with electrolysis water technology, a microbial electrolysis cell hydrogen production system has been developed, which can use any biodegradable substance to produce hydrogen, with high energy efficiency, and can use organic wastewater to achieve energy recovery and purification at the same time The environmental and energy win-win effect of sewage.

The hydrogen production system of the microbial electrolysis cell uses microorganisms to oxidize organic matter at the anode to generate electrons and protons, and the electrons and protons are combined at the cathode to generate hydrogen with the help of a small external voltage. It can be designed as double room and single room. The dual-chamber microbial electrolysis cell uses an ion-exchange membrane to separate the battery into a cathode chamber and an anode chamber, such as the Chinese patent "Bioelectrochemical method for producing hydrogen" (publication number CN1856706A). The dual-chamber battery has complex structure, high manufacturing and operating costs, and low hydrogen production rate. Long-term operation has the problem of a decrease in the pH value of the anode and an increase in the pH value of the cathode. On the contrary, the single-chamber microbial electrolytic cell removes the ion exchange membrane, makes the battery compact and simple, reduces the manufacturing cost, reduces the internal resistance of the battery, and doubles the hydrogen production rate, which is the best structure for practical applications. However, at present, the single-chamber microbial electrolytic cell only obtains a high hydrogen production rate in short-term operation, and the hydrogen production rate gradually decreases in long-term operation. The reason is that methanogenic bacteria grow rapidly in the neutral reaction solution and use hydrogen to reduce carbon dioxide into methane. Reduces hydrogen yield [Rader, G.K. and B.E. Logan.. Int. J. Hydrogen Energy. 2010; 35(17): 8848-8854). Methanogens can also directly receive electrons from the cathode to reduce carbon dioxide to methane, thereby reducing the electrical efficiency of the system for hydrogen production [Cheng, S., et al., Environ.Sci.Technol.2009; 43(10): 3953- 3958]. Inhibiting the growth of methanogens is a key problem that must be solved in single-chamber microbial electrolysis hydrogen production technology.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the problem of low hydrogen production efficiency due to methane produced by single-chamber microbial electrolytic hydrogen production, and provide an alkaline microbial electrolytic hydrogen production method that can effectively inhibit the growth of methanogenic bacteria without affecting the hydrogen production efficiency . The microorganisms used in this method come from urban domestic sewage, anaerobic activated sludge, brewery wastewater, etc., are domesticated and cultivated in alkaline media and organic substrates, and are directly domesticated and grown on the anode under the closed-circuit condition of the battery to form a film.

In order to solve technical problems, the hydrogen production method of alkaline microbial electrolytic cell provided by the invention comprises steps:

(1) Start the electrolytic cell in microbial fuel cell mode:

First, uniformly mix the organic waste water and the nutrient solution A at a volume ratio of 1:1, then adjust the pH of the mixed solution to 9-12 with an alkaline solution, and add an organic substrate at a ratio of 1 g/liter to obtain a mixed solution B; Add the mixed solution B into the electrolytic cell, and connect a 1000 ohm resistor in the closed circuit of the system. When the voltage across the resistor is lower than 20mV, replace the solution in the electrolytic cell with the new mixed solution B; continue to replace the reactor solution until When the voltage across the resistor is greater than 500mV, the anode start is complete;

(2) Hydrogen production in microbial electrolytic cell mode:

Replace the cathode in the activated electrolytic cell with stainless steel mesh or nickel foam, isolate the electrolytic cell from the air with a cover plate, and keep the entire electrolytic cell solution in an anaerobic state; use alkaline solution to adjust the pH value of nutrient solution A to 9-12 , and add the organic substrate at a ratio of 0.5 to 8 g/liter, and then add the mixed solution into the electrolytic cell as the electrolyte; use a DC power supply to apply a voltage of 0.4 to 0.8 V at the cathode and anode ends of the electrolytic cell to make the electrolytic cell at 20 Operate at ~35°C to realize hydrogen production;

The composition of the nutrient solution A is: each liter of the nutrient solution includes 8.4g NaHCO ₃ , 0.31g NH ₄ Cl, 0.13g KCl, 2ml trace element solution, and the balance is distilled water;

The trace element solution uses water as a solvent, and includes the following solutes per liter of solution: 2mg biotin, 2mg vitamin B, 10mg vitamin B6, 5mg riboflavin, 5mg thiamine, 5mg niacin, 5mg vitamin B3, 0.1mg B -12, 5mg p-aminobenzoic acid, 5mg lipoic acid, 1.5g NTA, 3.0g MgSO ₄ , 0.5g MnSO ₄ ·H ₂ O, 1.0g NaCl, 0.1g FeSO ₄ ·7H ₂ O, 0.1g CaCl ₂ ·2H ₂ O, 0.1g CoCl ₂ 6H ₂ O, 0.13g ZnCl ₂ , 0.01g CuSO ₄ 5H ₂ O, 0.01g AlK(SO ₄ ) ₂ 12H ₂ O, 0.01g H ₃ BO ₃ , 0.025g Na ₂ MoO ₄ , 0.024g NiCl ₂ ·6H ₂ O, 0.025g _{Na 2} WO ₄ ·2H ₂ O;

The electrolytic cell used is a single-chamber electrolytic cell composed of a battery case, an anode and an air cathode. The anode is an activated carbon brush made of titanium wire and activated carbon fiber, and the air cathode is coated with a diffusion layer and granular activated carbon on both sides. The carbon cloth of the catalytic layer, with the diffusion layer facing the air and the activated carbon catalytic layer facing the electrolyte.

In the present invention, the organic matrix is any one of sodium acetate, acetic acid, glucose, ethanol or formic acid.

In the present invention, the organic wastewater is any one of urban domestic sewage, beer wastewater, food processing wastewater or animal husbandry wastewater.

In the present invention, the alkaline solution is NaOH or KOH solution with a concentration of 1M.

Compared with prior art, the beneficial effect of the present invention is:

(1) It can effectively suppress the generation of methane, long-term continuous operation or multi-batch operation, the methane content of the output gas is less than 1%, and the hydrogen production rate is 0.1-2.5m ³ H ₂ /m ³ ·day.

(2) Nickel foam and stainless steel mesh are used as the cathode catalyst to replace the noble metal Pt. Although the cost is reduced, a higher hydrogen production rate can still be obtained.

(3) In an alkaline environment, the utilization rate of organic matter is improved, and the stability of hydrogen production in the system is improved.

Description of drawings

Fig. 1 is a schematic structural diagram of the microbial fuel cell described in Example 1 of the present invention (startup of the electrolytic cell).

Fig. 2 is a schematic structural diagram of the microbial fuel cell described in Example 1 of the present invention (hydrogen production by an electrolytic cell).

Numbers in Fig. 2: 1 battery shell, 2 carbon fiber brush anode, 3 air cathode, 4 gas collection tube, 5 resistor, 6 DC power supply, 7 electrolytic cell cathode.

Fig. 3 shows the variation of hydrogen production and current of 6 batches with time when the applied voltage of Example 1 is 0.6V.

Fig. 4 shows the variation of hydrogen production and current with time when the applied voltage is 0.6V and the matrix concentration is 4 g/L in Example 6.

Detailed ways

The implementation of the present invention will be described in detail below through specific embodiments.

Alkaline microbial electrolytic cell hydrogen production method among the present invention, comprises steps:

(1) Start the electrolytic cell in microbial fuel cell mode:

First, uniformly mix the organic waste water and the nutrient solution A at a volume ratio of 1:1, then adjust the pH of the mixed solution to 9-12 with an alkaline solution, and add an organic substrate at a ratio of 1 g/liter to obtain a mixed solution B; Add the mixed solution B into the electrolytic cell, and connect a 1000 ohm resistor in the closed circuit of the system. When the voltage across the resistor is lower than 20mV, replace the solution in the electrolytic cell with the new mixed solution B; continue to replace the reactor solution until When the voltage across the resistor is greater than 500mV, the anode start is complete;

(2) Hydrogen production in microbial electrolytic cell mode:

Replace the cathode in the activated electrolytic cell with stainless steel mesh or nickel foam, isolate the electrolytic cell from the air with a cover plate, and keep the entire electrolytic cell solution in an anaerobic state; use alkaline solution to adjust the pH value of nutrient solution A to 9-12 , and add the organic substrate at a ratio of 0.5 to 8 g/liter, and then add the mixed solution into the electrolytic cell as the electrolyte; use a DC power supply to apply a voltage of 0.4 to 0.8 V at the cathode and anode ends of the electrolytic cell to make the electrolytic cell at 20 Operation at ~35°C achieves hydrogen production.

The composition of the nutrient solution A is: each liter of the nutrient solution includes 8.4g NaHCO ₃ , 0.31g NH ₄ Cl, 0.13g KCl, 2ml trace element solution, and the balance is distilled water; the trace element solution uses water as a solvent, and each One liter of solution includes the following solutes: 2 mg biotin, 2 mg vitamin B, 10 mg vitamin B6, 5 mg riboflavin, 5 mg thiamin, 5 mg niacin, 5 mg vitamin B3, 0.1 mg B-12, 5 mg p-aminobenzoic acid, 5 mg sulfur Caprylic acid, 1.5g NTA, 3.0g MgSO ₄ , 0.5g MnSO ₄ ·H ₂ O, 1.0g NaCl, 0.1g FeSO ₄ ·7H ₂ O, 0.1g CaCl ₂ ·2H ₂ O, 0.1g CoCl ₂ ·6H ₂ O , 0.13g ZnCl ₂ , 0.01g CuSO ₄ ·5H ₂ O, 0.01g AlK(SO ₄ ) ₂ ·12H ₂ O, 0.01g H ₃ BO ₃ , 0.025g Na ₂ MoO ₄ , 0.024g NiCl ₂ ·6H ₂ O , 0.025g Na ₂ WO ₄ ·2H ₂ O;

The electrolytic cell used is a single-chamber electrolytic cell composed of a battery case, an anode and an air cathode. The anode is an activated carbon brush made of titanium wire and activated carbon fiber, and the air cathode is coated with a diffusion layer and granular activated carbon on both sides. The carbon cloth of the catalytic layer, with the diffusion layer facing the air and the activated carbon catalytic layer facing the electrolyte.

The data of each embodiment when producing hydrogen under the microbial electrolytic cell mode are shown in the table below.

Specific embodiment serial number 1 2 3 4 5 6 1M sodium hydroxide √ √ √ √ √ 1M potassium hydroxide √ pH 10 10 9 12 10 10 domestic sewage √ √ Beer wastewater √ √ Food processing wastewater √ Livestock wastewater √ Sodium acetate 2 g/L 8 g/L 4 g/L Acetic acid 0.5 g/L Glucose 1 g/L ethanol 1 g/L Formic acid 4 g/L 2mL trace element solution √ √ √ √ √ √ Cathode material for hydrogen production electrolysis cell stainless steel mesh stainless steel mesh stainless steel mesh stainless steel mesh stainless steel mesh nickel foam Applied voltage (volts) 0.6 0.6 0.8 0.4 0.7 0.6 Test temperature (℃) 30 30 20 35 30 30

Claims (4)

1. a method for producing hydrogen by alkalescent microbe electrolysis, is characterized in that, comprises the following steps:

(1) under microbiological fuel cell pattern, start electrolyzer:

First by the volume ratio of 1: 1, organic waste water is evenly mixed with nutritive medium A, then with basic solution, adjusting pH of mixed value is 9～12, and adds organism matrix in the ratio of 1 grams per liter, obtains mixed liquid B; Mixed liquid B is added in electrolyzer, in the loop line of system, access 1000 ohmic resistances, when resistance both end voltage is during lower than 20mV, by new mixed liquid B, change the solution in electrolyzer; Continue to change reactor solution until resistance both end voltage is greater than 500mV, anode starts complete;

(2) hydrogen manufacturing under microorganism electrolysis cell pattern:

With stainless (steel) wire or nickel foam, change and started the negative electrode in electrolyzer, with cover plate, by electrolyzer and air insulated, make whole electrolytic solution cell in anaerobic state; The pH value of using basic solution to adjust nutritive medium A is 9～12, and adds organism matrix in the ratio of 0.5～8 grams per liter, then in mixing solutions joins electrolyzer as electrolytic solution; Utilize direct supply at the additional 0.4～0.8V voltage in electrolyzer anode and cathode two ends, make electrolyzer move and realize hydrogen manufacturing at 20～35 ℃;

Described nutritive medium A consists of: every liter of nutritive medium comprises 8.4g NaHCO ₃, 0.31g NH ₄cl, 0.13gKCl, 2ml trace element solution, surplus is distilled water;

Described trace element solution be take water as solvent, and every liter of solution comprises following solute: 2mg vitamin H, 2mg vitamins B, 10mg vitamin B6,5mg riboflavin, 5mg thiamines, 5mg nicotinic acid, 5mg vitamin B3,0.1mg B-12,5mg para-amino benzoic acid, 5mg Thioctic Acid, 1.5g NTA, 3.0g MgSO ₄, 0.5g MnSO ₄h ₂o, 1.0g NaCl, 0.1g FeSO ₄7H ₂o, 0.1g CaCl ₂2H ₂o, 0.1g CoCl ₂6H ₂o, 0.13g ZnCl ₂, 0.01g CuSO ₄5H ₂o, 0.01g AlK (SO ₄) ₂12H ₂o, 0.01g H ₃bO ₃, 0.025g Na ₂moO ₄, 0.024g NiCl ₂6H ₂o, 0.025gNa ₂wO ₄2H ₂o;

The electrolyzer using is the single compartment electrolytic cell consisting of battery container, anode and air cathode; its anode is the active carbon brush of being made by titanium silk and activated carbon fiber; air cathode is the carbon cloth that two sides applies respectively diffusion layer and granulated active carbon Catalytic Layer, and with diffusion layer towards air, activated carbon catalysis layer towards electrolytic solution.

2. method for producing hydrogen by alkalescent microbe electrolysis according to claim 1, is characterized in that, described organism matrix is any one in sodium acetate, acetic acid, glucose, ethanol or formic acid.

3. method for producing hydrogen by alkalescent microbe electrolysis according to claim 1, is characterized in that, described organic waste water is any one in city domestic sewage, beer waste water, food processing wastewater or livestock industry waste water.

4. method for producing hydrogen by alkalescent microbe electrolysis according to claim 1, is characterized in that, described basic solution is NaOH or KOH solution, and its concentration is 1M.

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