Alkali-modified bagasse biochar as well as preparation method and application thereof

Abstract

The invention discloses alkali-modified bagasse biochar as well as a preparation method and application thereof. The method comprises the following steps: uniformly mixing bagasse with an alkaline solution, reacting under mild conditions, carrying out solid-liquid separation, drying the solid, and pyrolyzing to obtain the alkali-modified bagasse biochar. The alkali-modified bagasse biochar has higher specific surface area and porosity, the structure also becomes loose and porous, and the buffer capacity to an acid environment becomes stronger. When the alkali-modified biochar is applied to a lignocellulose dark fermentation biological hydrogen production system, more microorganisms can be adsorbed, and the inhibition effect of too low pH on hydrogen production can be effectively relieved, so that the system can stably operate under higher substrate concentration, and the yield of hydrogen is greatly increased. When the strain is applied to a semi-continuous fermentation system, the fermentation time is effectively shortened, so that the system stably and efficiently performs biological hydrogen production, and a foundation is laid for subsequent industrial production of biological hydrogen production through lignocellulose dark fermentation.

Description

Technical Field

[0001] The present invention belongs to the field of preparing biochar from lignocellulose and biohydrogen production, and specifically relates to an alkali-modified bagasse biochar and a preparation method and application thereof. Background Art

[0002] Hydrogen, a fuel with high calorific value and a combustion byproduct consisting solely of water, is considered a promising alternative to fossil fuels. Currently, the main sources of hydrogen are steam methane reforming and coal gasification, which are energy-intensive and environmentally unfriendly. Biohydrogen production, however, has attracted widespread attention due to its sustainability and eco-friendliness. Lignocellulose, as the most abundant, inexpensive, and renewable raw material on Earth, is widely used in dark fermentation biohydrogen production.

[0003] Biochar is produced by the thermal decomposition or pyrolysis of carbonaceous biomass (such as lignocellulose and sewage sludge) at temperatures between 300 and 900°C. Its porous structure, large surface area, abundant surface functional groups, strong adsorption capacity, and excellent electrochemical properties make it a popular enhancer for dark fermentation biohydrogen production. While biochar can effectively enhance dark fermentation biohydrogen production, its effectiveness in boosting hydrogen production in dark fermentation systems remains to be seen. Summary of the Invention

[0004] The primary purpose of the present invention is to provide a method for preparing alkali-modified bagasse biochar.

[0005] Another object of the present invention is to provide alkali-modified bagasse biochar obtained by the above preparation method.

[0006] Another object of the present invention is to provide the use of the above-mentioned alkali-modified sugarcane bagasse biochar in dark fermentation biological hydrogen production.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing alkali-modified bagasse biochar comprises the following steps:

[0009] (1) placing bagasse powder in an alkaline solution for alkaline treatment;

[0010] (2) subjecting the product obtained by alkali treatment in step (1) to solid-liquid separation to obtain a solid;

[0011] (3) drying the solid obtained in step (2) and then crushing it;

[0012] (4) The product obtained by pulverizing in step (3) is heat-connected to obtain alkali-modified sugarcane bagasse biochar.

[0013] The bagasse described in step (1) is dried bagasse.

[0014] The bagasse powder described in step (1) is a powder that can pass through a 50-mesh sieve; preferably, it is a powder that can pass through a 100-mesh sieve.

[0015] The base described in step (1) is an inorganic base; preferably at least one of sodium bicarbonate, sodium carbonate and sodium hydroxide.

[0016] The concentration of the alkaline solution in step (1) is preferably 20-50 g / L; more preferably 20-30 g / L.

[0017] The amount of the alkaline solution in step (1) is preferably 10 to 30 mL of alkaline solution per gram of bagasse; more preferably 20 mL of alkaline solution per gram of bagasse.

[0018] The alkali treatment in step (1) is preferably performed by heating in a water bath.

[0019] The temperature of the alkali treatment in step (1) is preferably 40-80°C; more preferably 40-60°C.

[0020] The time of the alkali treatment in step (1) is preferably 1-4 hours.

[0021] The solid-liquid separation method in step (2) is preferably suction filtration; more preferably, vacuum filtration.

[0022] The drying method described in step (3) is preferably air drying.

[0023] The drying temperature in step (3) is preferably 50-60°C; more preferably 55°C.

[0024] The specific operation of the pyrolysis in step (4) is preferably as follows: the product obtained by pulverizing in step (3) is placed in an alumina crucible, sealed with tin foil, and then pyrolyzed in a muffle furnace.

[0025] The pyrolysis conditions are preferably a heating rate of 5-15°C / min, heating to 300-900°C and keeping warm for 1-4 hours; more preferably a heating rate of 5-10°C / min, heating to 300-600°C and keeping warm for 2-4 hours; most preferably a heating rate of 10°C / min, heating to 600°C and keeping warm for 2 hours.

[0026] Alkali-modified bagasse biochar is obtained by the above preparation method.

[0027] The application of the alkali-modified bagasse biochar in dark fermentation biohydrogen production preferably includes the following steps: adding the alkali-modified bagasse biochar to a dark fermentation medium to obtain a dark fermentation reaction system; then inoculating bacteria for dark fermentation to obtain hydrogen.

[0028] The particle size of the alkali-modified bagasse biochar is preferably able to pass through a 40-mesh sieve.

[0029] The composition of the dark fermentation medium is preferably as follows: 1.30 g / L (NH4)2SO4, 0.13 g / L CaCl2·2H2O, 2.60 g / L MgCl2·6H2O, 1.43 g / L KH2PO4, 6.00 g / L sodium glycerophosphate, 0.0011 g / L FeSO4·7H2O, 0.25 g / L reduced glutathione, 4.50 g / L yeast powder, 0.001 g / L resazurin, 15 g / L bagasse powder, and the pH is adjusted to 6.5-7.5.

[0030] The bagasse powder is obtained by crushing dried bagasse and passing it through a 100-mesh sieve.

[0031] The pH is preferably 7.0.

[0032] The amount of the alkali-modified bagasse biochar is preferably calculated based on a concentration of 1-10 g / L in a dark fermentation reaction system; more preferably, it is calculated based on a concentration of 3-7 g / L in a dark fermentation reaction system.

[0033] The bacterial species is preferably a biohydrogen-producing bacterium; more preferably a thermophilic anaerobic hydrogen-producing bacterium; most preferably a thermophilic anaerobic bacillus or a thermophilic anaerobic vibrio; further preferably at least one of Acetivibrio thermocellus DSM 1313 and Thermoanaerobacterium thermosaccharolyticum MJ1.

[0034] The dark fermentation is anaerobic dark fermentation.

[0035] The temperature of the dark fermentation is preferably 45-60°C; more preferably 50-55°C.

[0036] The dark fermentation method is batch dark fermentation or semi-continuous dark fermentation.

[0037] The semi-continuous dark fermentation refers to replacing part of the dark fermentation reaction system in each fermentation cycle and continuing the dark fermentation.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] The present invention first mixes the sugarcane bagasse with an alkaline solution evenly and reacts them under mild conditions. After solid-liquid separation, the solid is dried and then pyrolyzed to obtain alkali-modified sugarcane bagasse biochar. By soaking the sugarcane bagasse in an alkaline solution and then pyrolyzing it, the stubborn cross-linked structure in the sugarcane bagasse is broken, so that the alkali-modified biochar has a higher specific surface area and porosity, and the structure becomes loose and porous, and the buffering capacity for acidic environments becomes stronger. Applying the alkali-modified sugarcane bagasse biochar to a dark fermentation biohydrogen production system of lignocellulose can adsorb more microorganisms and effectively alleviate the inhibitory effect of too low pH on hydrogen production, so that the system can operate stably at a higher substrate concentration, greatly increasing the hydrogen production. Applying it to a semi-continuous fermentation system effectively shortens the fermentation time, allowing the system to stably and efficiently produce biohydrogen, laying the foundation for the subsequent industrial production of biohydrogen from dark fermentation of lignocellulose. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a scanning electron microscope image of the microscopic morphology of ordinary biochar in comparative example 3.

[0041] Figure 2 This is a scanning electron microscope image of the microscopic morphology of the AB-10 alkali-modified biochar of Example 2.

[0042] Figure 3 This figure shows the effect of different alkali-modified biochars on the hydrogen production of the dark fermentation biohydrogen production system.

[0043] Figure 4 This is a graph showing the effect of different concentrations of AB-10 alkali-modified biochar on the hydrogen production of the dark fermentation biohydrogen production system.

[0044] Figure 5 This is a diagram showing the effect of adding AB-10 biochar on the semi-continuous dark fermentation biohydrogen production system in Example 2. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

[0046] Example 1 Preparation of AB-1 to AB-9 Alkali-Modified Biochars and Their Application in Dark Fermentation Biohydrogen Production

[0047] (1) crushing the dried bagasse at room temperature and passing it through a 100-mesh sieve to obtain bagasse powder;

[0048] (2) Add bagasse powder to 20-40 g / L sodium bicarbonate, sodium hydroxide, and sodium carbonate solutions at a ratio of 1:20 (w / v, g / mL), stir evenly, and place in a constant temperature water bath heated to 40-80°C for 1-4 hours;

[0049] (3) After the water bath, solid-liquid separation was performed using a vacuum filtration device, and the solid was placed in an electric heated blast drying oven at 55°C for drying;

[0050] (4) The dried solid was crushed and placed in an alumina crucible, sealed with tin foil, and pyrolyzed in a muffle furnace at 600°C with a heating rate of 10°C / min for 2 h. After cooling, the solid was ground and passed through a 40-mesh sieve to obtain AB-1 to AB-9 alkali-modified biochars;

[0051] (5) AB-1 to AB-9 alkali-modified biochars were added to the dark fermentation biohydrogen production system using sugarcane bagasse as the substrate. The specific hydrogen production is shown in Table 1;

[0052] Among them, the fermentation medium composition used in the dark fermentation reaction system is: 1.30g / L (NH4)2SO4, 0.13g / L CaCl2·2H2O, 2.60g / L MgCl2·6H2O, 1.43g / L KH2PO4, 6.00g / L sodium glycerophosphate, 0.0011g / LFeSO4·7H2O, 0.25g / L reduced glutathione, 4.50g / L yeast powder, 0.001g / L resazurin, 15g / L substrate (dried sugarcane bagasse passed through 100 mesh), and the pH is adjusted to 7.0.

[0053] The strains used in the dark fermentation reaction system are Acetivibrio thermocellus DSM 1313 and Thermoanaerobacterium thermosaccharolyticum MJ1. DSM 1313 was purchased from the German Collection of Microorganisms and Cell Cultures (DSMZ) of the Leibniz Institute, and MJ1 was isolated from papermaking sludge by our laboratory with the accession number GDMCC No: 60096. It is deposited in the Guangdong Provincial Microbial Culture Collection of the Guangdong Provincial Institute of Microbiology and has been disclosed in the patent application "CN201611020566.6-A Thermoanaerobacterium thermosaccharolyticum and its application in biohydrogen production".

[0054] Add seed culture medium to a vial, then inoculate DSM 1313 and MJ1, respectively. Cultivate at 55°C, 150 rpm, and shake for 18 hours to obtain DSM 1313 and MJ1 seed solutions. The composition of the seed culture medium is essentially the same as that of the fermentation medium in the dark fermentation reaction system, except that DSM 1313 uses 10 g / L microcrystalline cellulose as the carbon source, while MJ1 uses 10 g / L cellobiose. The composition of the seed culture medium is (excluding carbon source): 1.30g / L (NH4)2SO4, 0.13g / L CaCl2·2H2O, 2.60g / L MgCl2·6H2O, 1.43g / L KH2PO4, 6.00g / L sodium glycerolphosphate, 0.0011g / L FeSO4·7H2O, 0.25g / L reduced glutathione, 4.50g / L yeast powder, and 0.001g / L resazurin.

[0055] Dark fermentation medium was added to the vial, and 3 g / L of alkali-modified biochar was added to obtain a dark fermentation reaction system (here, batch fermentation was carried out in a sealed vial without an air bag; hydrogen production was calculated by using gas chromatography to determine the percentage of hydrogen and carbon dioxide in the vial gas, and then calculated using the formula H is the hydrogen yield (mL / L), V1 is the headspace volume (L), V2 is the fermentation medium volume (L), H2% is the hydrogen percentage (%), CO2% is the carbon dioxide percentage (%), T is room temperature, which is 298.15K, R is the gas constant, which is 8.314 (J / (mol·K)), 0.14 represents 0.14 MPa, the nitrogen pressure in a sealed serum bottle, and 22.4 is the volume of 1 mol of gas at standard temperature and pressure (L / mol). DSM 1313 seed solution and MJ1 seed solution were mixed in a volume ratio of 2:1 to obtain a mixed bacterial solution; the mixed bacterial solution was inoculated into a dark fermentation reaction system at 10% v / v of the dark fermentation reaction system and cultured under anaerobic conditions at 55°C for 32 hours.

[0056] (6) The results in Table 1 were subjected to a range analysis, and it was found that the factor that had the greatest impact on the performance of dark fermentation biohydrogen production by alkali-modified biochar was temperature, followed by time, concentration, and alkali solution. The optimal combination was that the alkali solution was sodium hydroxide, the concentration was 20 g / L, the temperature was 60 °C, and the time was 4 h.

[0057] Table 1 Dark fermentation biohydrogen production performance of AB-1 to AB-9 alkali-modified biochars

[0058]

[0059] Example 2 Preparation of AB-10 Alkali-Modified Biochar and Its Application in Dark Fermentation Biohydrogen Production

[0060] Alkali-modified bagasse biochar AB-10 was prepared using the optimal combination obtained in Example 1 (alkali solution was sodium hydroxide, concentration was 20 g / L, temperature was 60° C., and time was 4 h). The specific steps were as follows:

[0061] (1) crushing the dried bagasse at room temperature and passing it through a 100-mesh sieve to obtain bagasse powder;

[0062] (2) Add sugarcane bagasse powder to 20 g / L sodium hydroxide solution at a ratio of 1:20 (w / v), stir evenly, and place in a constant temperature water bath heated to 60 °C for 4 h;

[0063] (3) After the water bath, solid-liquid separation was performed using a vacuum filtration device, and the solid was placed in an electric heated blast drying oven at 55°C for drying;

[0064] (4) The dried solid was crushed and placed in an alumina crucible, sealed with tin foil, and pyrolyzed in a muffle furnace at 600°C and a heating rate of 10°C / min for 2 h to obtain AB-10 alkali-modified biochar;

[0065] (5) When AB-10 alkali-modified biochar was added to the dark fermentation biohydrogen production system using sugarcane bagasse as the substrate (same as Example 1, the pH of the system was 8.0), the hydrogen production was as high as 3769 mL / L, indicating that AB-10 biochar had the best promoting effect on the hydrogen production system.

[0066] Comparative Example 1: Dark fermentation for biohydrogen production without adding biochar

[0067] Without adding biochar, dark fermentation biohydrogen production was carried out directly with sugarcane bagasse as the substrate. That is, the mixed bacterial solution of Example 1 was inoculated into the culture medium used in the dark fermentation reaction system at 10% v / v, which was set as the control group. The hydrogen production was 2076 mL / L.

[0068] Comparative Example 2: Adjusting the pH of the fermentation system to produce hydrogen by dark fermentation

[0069] Without adding biochar, the pH of the culture medium used in the dark fermentation reaction system was adjusted to 8.0 to simulate the pH of the fermentation system after adding alkaline biochar; dark fermentation biohydrogen production was carried out using sugarcane bagasse as the substrate, which was set as the pH adjustment control group, and the hydrogen production was 2194mL / L.

[0070] Comparative Example 3 Preparation of Ordinary Biochar and Its Application in Dark Fermentation Biohydrogen Production

[0071] (1) crushing the dried bagasse at room temperature and passing it through a 100-mesh sieve to obtain bagasse powder;

[0072] (2) The sugarcane bagasse powder was placed in an alumina crucible, sealed with tin foil, and pyrolyzed in a muffle furnace at 600 °C and a heating rate of 10 °C / min for 2 h to obtain ordinary biochar;

[0073] (3) Ordinary biochar (3 g / L, the same as in Example 1) was added to the dark fermentation biohydrogen production system with sugarcane bagasse as the substrate. After mixing, the pH was 7.3. This was set as the control biochar group, and the hydrogen production was 2498 mL / L.

[0074] Comparative Example 4 Preparation of Ordinary Biochar and Its Application in Dark Fermentation Biohydrogen Production with pH Adjustment

[0075] (1) crushing the dried bagasse at room temperature and passing it through a 100-mesh sieve to obtain bagasse powder;

[0076] (2) The sugarcane bagasse powder was placed in an alumina crucible, sealed with tin foil, and pyrolyzed in a muffle furnace at 600 °C and a heating rate of 10 °C / min for 2 h to obtain ordinary biochar;

[0077] (3) Adding ordinary biochar (3 g / L, the same as in Example 1) to a dark fermentation biohydrogen production system using bagasse as a substrate;

[0078] (4) The pH of the fermentation system was adjusted to 8.0 to simulate the pH of the fermentation system after adding alkaline biochar. This was set as the control biochar pH adjustment group, and the hydrogen production was 2510 mL / L.

[0079] Effect comparison ratio

[0080] (1) Comparison of the microstructure of alkali-modified AB-10 biochar and conventional biochar (see Figure 1 、 Figure 2 Compared with ordinary biochar, AB-10 biochar is smaller in size, has a rougher surface and more pores, and these pores are not only on the surface of the biochar, but also deep into the interior of the biochar.

[0081] (2) The pore characteristics and pH of alkali-modified AB-10 biochar and ordinary biochar were measured using a fully automatic specific surface area and porosity analyzer and a PB-10 pH meter. The pH was measured by dispersing the biochar in 50 times the volume of deionized water and mixing it evenly before measuring the pH value. The results are shown in Table 2. It can be seen that compared with ordinary biochar, the BET surface area and micropore area of ​​AB-10 biochar increased by 2.13 times and 2.50 times, respectively, and the total pore volume and micropore volume also increased by 1.67 times and 3.00 times, respectively. This shows that AB-10 biochar has a higher specific surface area and porosity, and the pore size has become smaller, with more micropores. In addition, the pH of AB-10 biochar is also much higher than that of ordinary biochar, indicating that it has a stronger buffering capacity for acidic environments.

[0082] Table 2 Porosity characteristics of biochar

[0083]

[0084] (3) The dark fermentation biohydrogen production performance of AB-1 to AB-10 alkali-modified biochar was compared with that of ordinary biochar. The reaction system, conditions and time were the same as in Example 1, except that the biochar was different. Figure 3 The results show that the addition of biochar can increase hydrogen production during dark fermentation biohydrogen production, and the promoting effect is more obvious after the biochar is modified with alkali, especially AB-10 biochar, which increased hydrogen production by 81.55% and 50.94% compared with the control group and the ordinary biochar group, respectively. In addition, the hydrogen production of the control group and the control biochar group did not change significantly after adjusting the pH during dark fermentation biohydrogen production, indicating that the effect of alkaline biochar in promoting hydrogen production cannot be achieved by simply adjusting the pH. The increase in hydrogen production of AB-10 biochar may be more dependent on its pore structure, which is more conducive to the growth and metabolism of microorganisms.

[0085] (4) 1-10 g / L AB-10 alkali-modified biochar was added to the dark fermentation biohydrogen production system with sugarcane bagasse as substrate. The results were as follows: Figure 4 When the addition concentration of AB-10 alkali-modified biochar is 3 g / L, the promoting effect on the hydrogen production system is the best, and the hydrogen production is 3680 mL / L.

[0086] (5) AB-10 alkali-modified biochar was added to the semi-continuous dark fermentation biohydrogen production system. The system was carried out in a 500mL reaction bottle with an operating volume of 300mL. The inoculation amount of the mixed bacterial liquid was 20%, the addition amount of AB-10 alkali-modified biochar was 3g / L, the culture medium and culture temperature were consistent with the normal dark fermentation biohydrogen production system, and the sampling time was 12-48h (depending on the degree of inflation of the air bag, and the sampling was counted as one fermentation cycle); at the end of each fermentation cycle, 80% of the fresh culture medium (pH = 9), modified biochar and substrate were replaced; at the same time, after each cycle of fermentation liquid was centrifuged at 8000rpm, the solid was added back to the fermentation system (calculation of hydrogen production: first determine the total volume of the gas in the air bag, and then calculate the percentage of hydrogen in the gas according to gas chromatography to obtain the hydrogen production). The results obtained are as follows. Figure 5 As shown, the cumulative hydrogen production in the AB-10 biochar group was significantly higher than that in the control group (culture conditions and sampling procedures were consistent with those of the semi-continuous dark fermentation system for hydrogen production using AB-10 alkali-modified biochar, except that no AB-10 alkali-modified biochar was added, and the sampling time was 48-72 hours). This was a 2.82-fold increase compared to the control group. Furthermore, AB-10 biochar significantly improved the hydrogen production efficiency of the system, shortened the fermentation time, and enabled stable and efficient hydrogen production.

[0087] The above description is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing alkali-modified bagasse biochar, characterized in that The steps include: (1) placing bagasse powder in an alkaline solution for alkaline treatment; (2) subjecting the product obtained by alkali treatment in step (1) to solid-liquid separation to obtain a solid; (3) drying the solid obtained in step (2) and then crushing it; (4) pyrolyzing the product obtained by pulverizing in step (3) to obtain alkali-modified sugarcane bagasse biochar; The base described in step (1) is an inorganic base.

2. The method for preparing alkali-modified bagasse biochar according to claim 1, wherein: The bagasse powder in step (1) is a powder that can pass through a 50-mesh sieve; The alkali described in step (1) is at least one of sodium bicarbonate, sodium carbonate and sodium hydroxide.

3. The method for preparing alkali-modified bagasse biochar according to claim 1, wherein: The concentration of the alkaline solution in step (1) is 20-50 g / L; The amount of the alkaline solution in step (1) is 10 to 30 mL per gram of bagasse; The temperature of the alkali treatment in step (1) is 40-80°C; The time of the alkali treatment in step (1) is 1-4 hours.

4. The method for preparing alkali-modified bagasse biochar according to claim 1, wherein: The alkali treatment in step (1) is carried out by heating in a water bath; The solid-liquid separation method in step (2) is suction filtration; The drying method in step (3) is air drying; The specific operation of the pyrolysis described in step (3) is as follows: the product obtained by crushing in step (3) is placed in an alumina crucible, sealed with tin foil, and then pyrolyzed in a muffle furnace.

5. The method for preparing alkali-modified bagasse biochar according to claim 4, characterized in that: The drying temperature in step (3) is 50-60°C; The pyrolysis conditions are as follows: a heating rate of 5-15°C / min, heating to 300-900°C and keeping the temperature for 1-4h.

6. An alkali-modified bagasse biochar, characterized by: The method is obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the alkali-modified bagasse biochar according to claim 6 in dark fermentation biohydrogen production.

8. The use according to claim 7, characterized in that The method comprises the following steps: adding the alkali-modified bagasse biochar according to claim 6 into a dark fermentation culture medium to obtain a dark fermentation reaction system; and then inoculating bacteria to carry out dark fermentation to obtain hydrogen.

9. The use according to claim 8, characterized in that: The dark fermentation medium is composed of: 1.30 g / L (NH4)2SO4, 0.13 g / L CaCl2·2H2O, 2.60 g / L MgCl2·6H2O, 1.43 g / L KH2PO4, 6.00 g / L sodium glycerophosphate, 0.0011 g / L FeSO4·7H2O, 0.25 g / L reduced glutathione, 4.50 g / L yeast powder, 0.001 g / L resazurin, 15 g / L bagasse powder, and the pH is adjusted to 6.5-7.5; The amount of the alkali-modified bagasse biochar is calculated based on its concentration in the dark fermentation reaction system of 1-10 g / L; The bacterial species is biological hydrogen-producing bacteria.

10. The use according to claim 9, characterized in that: The particle size of the alkali-modified bagasse biochar is such that it can pass through a 40-mesh sieve; The bacterial species is thermophilic anaerobic hydrogen-producing bacteria; The dark fermentation is anaerobic dark fermentation; The temperature of the dark fermentation is 45-60°C.

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