Modified biochar, soil conditioner and preparation method

Abstract

The invention relates to the technical field of saline-alkali soil improvement, in particular to modified charcoal, a soil conditioner and a preparation method. The invention provides modified biochar. The modified biochar comprises pretreated biochar as well as lactic acid groups and ascorbic acid groups which are loaded on the surface of the pretreated biochar. The invention also provides a preparation method of the modified biochar, a soil conditioner obtained by compounding the modified biochar with a specific microbial flora, and a preparation method of the soil conditioner. The modified biochar provided by the invention has excellent adsorption capacity on sodium ions in saline-alkali soil, and the soil conditioner prepared from the modified biochar and specific microorganisms not only has stronger sodium ion adsorption capacity, but also can improve the germination rate of crops and promote healthy growth of the crops; the method has an obvious effect on improvement of saline-alkali soil, especially saline-alkali soil stressed by sodium ions.

Description

Technical Field

[0001] The present invention relates to the technical field of saline-alkali land improvement, and in particular to a modified biochar, a soil conditioner and a preparation method thereof. Background Art

[0002] Land resources are the foundation of human survival. In recent years, with the increasing human activities and global climate change, the problem of soil salinization in my country has become increasingly serious, resulting in a gradual reduction in the area of ​​arable land. Sodium ions are the main stress ions in saline-alkali land. Excessive sodium ions will cause soil compaction, reduce soil aeration and water retention capacity, and thus make the crop growth environment worse, affecting crop fertility absorption and growth. High concentrations of sodium ions will also affect the growth and metabolism of the plant itself. Plant roots are prone to physiological dehydration in a high-salt environment, causing the plant to wilt or even die. Therefore, it is of great significance to seek a method for improving saline-alkali land.

[0003] At present, the improvement methods for saline-alkali land mainly include physical improvement, chemical improvement and biological improvement. Among them, biochar is a porous carbon with a high comparative area and strong adsorption capacity. Its pore structure is conducive to the fixation and transmission of various substances in the soil, and has a positive effect on the reproduction of many microorganisms. It can reasonably improve the soil environment, reduce soil nutrient loss, and ensure the benign changes in the physical and chemical properties of the soil. However, due to the influence of the firing process, it is alkaline and has more base ions. If it is directly applied to saline-alkali soil, the degree of salinization will increase. Therefore, it is necessary to acid-modify biochar. At present, the acid modification of biochar is mainly carried out with inorganic acids. However, based on the principles of green chemistry, the equipment erosion, toxicology and environmental problems caused by the application of inorganic acids have attracted more and more attention, while organic acids can be used as green and sustainable materials due to their biological sources. Therefore, this patent uses organic acids to modify biochar, and in order to further improve the improvement effect of biochar on saline-alkali soil, further compounding of acid-modified biochar and salt-tolerant growth-promoting microorganisms is carried out to provide microbial improvement agents for the green and sustainable improvement of saline-alkali soil. Summary of the invention

[0004] In view of this, the present invention provides a modified biochar, a soil conditioner and a preparation method for repairing saline-alkali land under sodium ion stress. The modified biochar does not require the use of mineral acid modification, and has a larger specific surface area and a larger number of surface functional groups. The adsorption effect of sodium ions is significantly enhanced, which is of great significance for the improvement of saline-alkali land under sodium ion stress.

[0005] In order to solve the above technical problems, the present invention provides a modified biochar, comprising pretreated biochar and lactic acid groups and ascorbic acid groups loaded on the surface of the pretreated biochar.

[0006] The present invention utilizes lactic acid and ascorbic acid to modify the pretreated biochar, and the hydroxyl group and carboxyl group in the lactic acid molecule and the hydroxyl group in the ascorbic acid molecule react chemically or generate electrostatic adsorption with the abundant carboxyl group, hydroxyl group, amino group and amide group on the surface of the pretreated biochar, so that the surface of the original biochar is acidic, and the specific surface area and the number of surface functional groups are greatly increased. When applied to saline-alkali land, it can not only continuously reduce the alkalinity of the saline-alkali soil, but also show a strong adsorption capacity for sodium ions in the saline-alkali soil, thereby providing a guarantee for the growth of crop roots; in addition, the lactic acid and ascorbic acid loaded on the surface of the biochar can form a three-dimensional "network" structure, thereby increasing the permeability of the soil, facilitating the migration of sodium ions in the saline-alkali land, and making it easier to be adsorbed by the modified biochar.

[0007] In combination with the first aspect, the average particle size of the modified biochar is 20 to 60 μm.

[0008] In combination with the first aspect, the method for preparing the pretreated biochar is: cleaning the original biochar, immersing it in a magnesium chloride solution, and drying it after cleaning.

[0009] The original biochar is immersed in magnesium chloride solution, so that more magnesium ions can be loaded on the surface of biochar, thereby providing more active sites and further improving the adsorption capacity of sodium ions in saline-alkali land.

[0010] Preferably, the concentration of the magnesium chloride solution is 1-2 mol / L.

[0011] Preferably, the raw biochar can be obtained by burning biomass such as corn stalks, rice husks, reeds and hemp stalks.

[0012] The second aspect of the present invention provides a method for preparing the modified biochar, which comprises: dissolving the lactic acid and ascorbic acid in water to obtain an acidic solution, adding the pretreated biochar thereto and stirring for 3 to 4 hours, separating the solid and the liquid, drying and grinding to obtain the modified biochar.

[0013] The present invention immerses and stirs the pretreated biochar in an aqueous solution of lactic acid and ascorbic acid for 3 to 4 hours, so that the hydroxyl and carboxyl ions in the lactic acid and ascorbic acid are exchanged with the surface groups of the biochar, thereby improving the adsorption capacity of sodium ions.

[0014] In combination with the second aspect, the concentration of lactic acid in each liter of water is 200-300 g / L, the concentration of ascorbic acid in each liter of water is 150-200 g / L, and 0.5-1 kg of pretreated biochar is added to each liter of acidic solution.

[0015] The third aspect of the present invention provides a soil conditioner, comprising the modified biochar and a mixed bacterial community formed by immobilizing and culturing bacterial liquid of Bacillus sp. and / or Bacillus sp. on the modified biochar carrier.

[0016] The present invention loads yellow sea bacillus and / or Velez bacillus on the surface of modified biochar through fixed culture. Both yellow sea bacillus and Velez bacillus can grow and reproduce in saline-alkali land under high concentration sodium ion stress. The plant hormones secreted during their growth process can promote the germination and growth of crops, and the volatile compounds can effectively improve the compaction of saline-alkali land, increase the air permeability of the soil, and help the healthy development and growth of the root system of crops. At the same time, the modified biochar can provide a nutrient source for the growth and reproduction of microorganisms. The sodium ions adsorbed by the modified biochar can prompt the microbial flora to accelerate the secretion of plant hormones and volatile compounds, thereby further promoting the germination and growth of crops and the development of the root system. The volatile organic matter secreted by the microbial flora will increase the permeability of the soil, making the sodium ions more easily adsorbed by the modified biochar, and then continue to promote the secretion of the microbial flora, forming a positive cycle with a mutually promoting effect.

[0017] In conjunction with the third aspect, the deposit number of the yellow sea Bacillus is CGMCC No.32788, and the deposit number of the Velez Bacillus is CGMCC No.24438.

[0018] Combined with the third aspect, the effective viable count is 10 8 ~10 10 Pieces / g.

[0019] The fourth aspect of the present invention provides a method for preparing the above-mentioned soil conditioner, comprising the steps of: mixing the modified biochar with the activated bacterial solution of Bacillus subtilis and / or Bacillus velezii at a ratio of 50 to 100 g / L, shaking for 1 to 2 hours, filtering by plate and frame or centrifuging, and drying the obtained solid to obtain the soil conditioner.

[0020] A fifth aspect of the present invention provides a use of the above-mentioned soil conditioner in repairing saline-alkali land under sodium ion stress.

[0021] Beneficial effects obtained by the present invention: The modified biochar provided by the present invention has excellent adsorption capacity for sodium ions in saline-alkali land. The soil improver prepared by combining it with specific microorganisms not only has a stronger ability to adsorb sodium ions, but also can improve the germination rate of crops and promote the healthy growth of crops. It has obvious effects on the improvement of saline-alkali land, especially saline-alkali land under sodium ion stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a SEM photo of the original biochar before pretreatment in Example 1;

[0023] Figure 2 This is the SEM photo of the modified biochar in Example 1. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] At present, mineral acids are mostly used for the modification of biochar. However, the application of mineral acids will lead to new toxicological and environmental problems, which is not in line with the development concept of green chemistry. Although the overall modification effect of organic acids such as oxalic acid, citric acid or tartaric acid is more obvious than that of mineral acids, the improvement effect on saline-alkali land under the stress of higher concentrations of sodium ions still needs to be further improved. In view of this, the present invention provides a modified biochar and a soil conditioner containing the same. The biochar is modified by lactic acid and ascorbic acid and loaded with a specific microbial flora. The obtained soil conditioner significantly improves the improvement effect of saline-alkali land under the stress of higher concentrations of sodium ions, and can also promote the growth and development of crop roots.

[0026] In the following examples and comparative examples, the yellow sea Bacillus and Velez Bacillus used were obtained by the following method:

[0027] The dilution plating method was used to separate microorganisms from saline-alkali soil samples with LB culture medium containing 5% salt. Strains with large colony diameters were selected for culture in LB liquid culture medium. The seed soaking method was used to determine the effects of the strains on the germination and growth of wheat seeds in 1% salt-containing plates. Strains with good salt tolerance and growth-promoting effects were obtained and molecular biological identification was carried out.

[0028] Among them, Bacillus marisflavi BM-C55 was deposited in the General Microbiology Center of China Culture Collection on November 25, 2024, with the deposit number CGMCC No.32788, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing; Bacillus velezensis YQ-1-8 was deposited in the General Microbiology Center of China Culture Collection on February 28, 2022, with the deposit address being No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, and the deposit number is CGMCC No.24438.

[0029] Example 1

[0030] The embodiment of the present invention provides a modified biochar, which is prepared according to the following method:

[0031] (1) Preparation of pretreated biochar: corn stalks were cut into 3-4 cm pieces, cleaned and dried, and then loaded into a tubular furnace and fired at 400°C to obtain fired pieces as raw biochar; the raw biochar was cooled and immersed in a magnesium chloride solution for 20 h, followed by solid-liquid separation, and the solid biochar was dried, ground and passed through a 60-mesh sieve to obtain pretreated biochar.

[0032] (2) Preparation of modified biochar: 700 g of pretreated biochar was weighed and added to 1 L of a mixed acid solution of lactic acid and ascorbic acid and immersed and stirred for 3.5 h, wherein the concentration of lactic acid was 250 g / L and the concentration of ascorbic acid was 160 g / L. After the immersion, the solid and liquid were separated, and the obtained solid was ground to obtain a modified biochar with an average particle size of 35 μm.

[0033] Among them, the SEM photos of biochar before pretreatment are as follows Figure 1 The SEM images of the modified biochar are shown in Figure 2 shown.

[0034] contrast Figure 1 and Figure 2 It can be seen that the pore density on the surface of biochar modified with lactic acid and ascorbic acid increases, indicating that the specific surface area of ​​the modified biochar is larger.

[0035] Example 2

[0036] The embodiment of the present invention provides a modified biochar, which is prepared according to the following method:

[0037] (1) Preparation of pretreated biochar: Reeds were cut into 3-4 cm pieces, cleaned and dried, and then placed in a tubular furnace and fired at 350°C to obtain fired pieces as raw biochar; the raw biochar was cooled and immersed in a magnesium chloride solution for 20 h, followed by solid-liquid separation, and the solid biochar was dried, ground and passed through a 60-mesh sieve to obtain pretreated biochar.

[0038] (2) Preparation of modified biochar: 500 g of pretreated biochar was weighed and added to 1 L of a mixed acid solution of lactic acid and ascorbic acid and stirred for 3 h, wherein the concentration of lactic acid was 200 g / L and the concentration of ascorbic acid was 150 g / L. After the immersion, the solid and liquid were separated, and the obtained solid was ground to obtain modified biochar with an average particle size of 25 μm.

[0039] Example 3

[0040] The embodiment of the present invention provides a modified biochar, which is prepared according to the following method:

[0041] (1) Preparation of pretreated biochar: The rice husk is cleaned and dried, and then placed in a tubular furnace and fired at 450°C to obtain fired fragments as raw biochar; the raw biochar is cooled and immersed in a magnesium chloride solution for 22 hours, followed by solid-liquid separation, and the solid biochar is dried, ground and passed through a 60-mesh sieve to obtain pretreated biochar.

[0042] (2) Preparation of modified biochar: 1000 g of pretreated biochar was weighed and added to 1 L of a mixed acid solution of lactic acid and ascorbic acid and immersed and stirred for 4 h, wherein the concentration of lactic acid was 300 g / L and the concentration of ascorbic acid was 200 g / L. After the immersion, the solid and liquid were separated, and the obtained solid was ground to obtain a modified biochar with an average particle size of 58 μm.

[0043] Example 4

[0044] The present invention provides a soil conditioner, which is prepared according to the following method:

[0045] The modified biochar prepared in Example 1 was added to the activated bacterial solution of Bacillus subtilis at a ratio of 75 g / L, and cultured with shaking at 28° C. for 1.5 h, followed by centrifugation. The obtained solid was the modified biochar with Bacillus subtilis loaded on the surface, which was dried at 65° C. for 10 h to obtain a soil conditioner.

[0046] After testing, the number of effective live bacteria in the obtained soil conditioner is 10 9 Pieces / g.

[0047] Example 5

[0048] The present invention provides a soil conditioner, which is prepared according to the following method:

[0049] The modified biochar prepared in Example 2 was added to the activated bacterial solution of Bacillus subtilis at a ratio of 50 g / L, and cultured with shaking at 30°C for 1 h. Then, the solid obtained was modified biochar with Bacillus subtilis loaded on the surface. The solid was dried at 60°C for 10 h to obtain a soil conditioner.

[0050] After testing, the number of effective live bacteria in the obtained soil conditioner is 10 10 Pieces / g.

[0051] Example 6

[0052] The present invention provides a soil conditioner, which is prepared according to the following method:

[0053] The modified biochar prepared in Example 3 was added to the activated bacterial solution of Bacillus Velezii at a ratio of 100 g / L, and cultured with shaking at 26°C for 2 h, followed by solid-liquid separation. The obtained solid was the modified biochar with Bacillus velesiensis loaded on the surface, which was dried at 62°C for 12 h to obtain a soil conditioner.

[0054] After testing, the number of effective live bacteria in the obtained soil conditioner is 10 10 Pieces / g.

[0055] Comparative Example 1

[0056] This comparative example provides a modified biochar, and the preparation method thereof is as follows:

[0057] (1) Preparation of pretreated biochar: corn stalks were cut into 3-4 cm pieces, cleaned and dried, and then placed in a tubular furnace for sintering at 400°C to obtain sintered pieces as raw biochar; after the raw biochar was cooled, it was ground and passed through a 60-mesh sieve to obtain pretreated biochar.

[0058] (2) Preparation of modified biochar: The steps are the same as step (2) in Example 1.

[0059] Comparative Example 2

[0060] This comparative example provides a modified biochar, and the preparation method thereof is as follows:

[0061] (1) Preparation of pretreated biochar: The steps are the same as step (1) in Example 1

[0062] (2) Preparation of modified biochar: 700 g of pretreated biochar was weighed and added to 1 L of oxalic acid solution for immersion and stirring for 3.5 h, wherein the concentration of oxalic acid was 80 g / L. After the immersion, the solid and liquid were separated, and the obtained solid was ground to obtain modified biochar with an average particle size of 40 μm.

[0063] Comparative Example 3

[0064] This comparative example provides a modified biochar, and the preparation method thereof is as follows:

[0065] (1) Preparation of pretreated biochar: The steps are the same as step (1) in Example 1

[0066] (2) Preparation of modified biochar: 700 g of pretreated biochar was weighed and added to 1 L of a mixed acid solution of oxalic acid and ascorbic acid and immersed and stirred for 3.5 h, wherein the concentration of oxalic acid was 80 g / L and the concentration of ascorbic acid was 160 g / L. After the immersion, the solid and liquid were separated, and the obtained solid was ground to obtain a modified biochar with an average particle size of 53 μm.

[0067] Comparative Example 4

[0068] This comparative example provides a soil conditioner, and its preparation method is similar to that of Example 4, except that the modified biochar prepared in Comparative Example 1 is used.

[0069] Comparative Example 5

[0070] This comparative example provides a soil conditioner, and its preparation method is similar to that of Example 4, except that the modified biochar prepared in Comparative Example 2 is used.

[0071] Comparative Example 6

[0072] This comparative example provides a soil conditioner, and its preparation method is similar to that of Example 4, except that the modified biochar prepared in Comparative Example 3 is used.

[0073] Test Example 1

[0074] The specific surface area and pore volume of the modified biochars obtained in Examples 1 to 3 and Comparative Examples 1 to 3 and the corresponding original biochars were measured by nitrogen adsorption method, and the results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As can be seen from Table 1, the specific surface area, pore volume and pore diameter of the modified biochar obtained in Examples 1 to 3 are all improved, indicating that the modified biochar provided by the present invention has better adsorption capacity. As can be seen from Comparative Example 1, when the biochar is pretreated without impregnation with a magnesium chloride solution, the specific surface area, pore volume and pore diameter of the modified biochar obtained are all reduced compared with Example 1, indicating that the use of a magnesium chloride solution for impregnation during pretreatment is helpful to increase the specific surface area, pore volume and pore diameter; and as can be seen from Comparative Examples 2 to 3, when the mixed acid solution of lactic acid and ascorbic acid is completely replaced by an oxalic acid solution or a mixed acid solution of oxalic acid and ascorbic acid, the specific surface area, pore volume and pore diameter of the modified biochar obtained are increased compared with the unmodified biochar, but the increase is significantly lower than that of Example 1, indicating that the method of modifying biochar using a mixed solution of lactic acid and ascorbic acid provided by the present invention can greatly increase the specific surface area of ​​the biochar, thereby improving its adsorption capacity.

[0078] Test Example 2

[0079] Prepare 5g / L Na 2 CO 3 The solution simulates the leachate of saline-alkali soil under sodium ion stress, and the improvement effects of the corresponding unmodified biochar, the soil conditioners obtained in Examples 4 to 6 and Comparative Examples 4 to 6 are tested respectively. Specifically, 5 g / L of Na 2 CO 3Put 200 mL of the solution into a 500 mL conical flask, add 0.5 g of the corresponding soil conditioner respectively, seal the bottle mouth with a sealing film, place it in a constant temperature oscillator and shake for 24 h at a rotation speed of 120 rpm. Take the supernatant, measure its sodium ion concentration with an atomic absorption spectrometer, and calculate the sodium ion adsorption performance (calculated as sodium carbonate) of the soil conditioner according to the following formula.

[0080] ,

[0081] Among them, C 0 , C e respectively represent the initial concentration of the Na 2 CO 3 solution and the concentration at adsorption equilibrium. V represents the volume of the solution, and m is the mass of the added soil conditioner. The calculation results are shown in Table 2.

[0082] Table 2

[0083]

[0084] It can be seen from the test results in Table 2 that the soil conditioner provided by the present invention has a much higher sodium ion adsorption capacity than that of the biochar without any modification. And when lactic acid is replaced by oxalic acid or only oxalic acid is used for modification completely, the sodium ion adsorption capacity of the obtained soil conditioner is significantly lower than that of the soil conditioner prepared from the biochar modified by lactic acid and ascorbic acid.

[0085] Test Example 3

[0086] Add the modified biochars obtained in Examples 1 to 3, Comparative Examples 4 to 6 and the soil conditioners obtained in Examples 4 to 6 to the saline-alkali land to be repaired at a dosage of 120 kg / mu respectively. After rotary tillage, plant wheat 30 days later. At the same time, use the saline-alkali land without using any biochar or conditioner as a blank control. After 1 month of germination and growth, count the emergence rate and plant height of wheat. The results are shown in Table 3. Among them, the saline-alkali land used for testing is medium sodium soil.

[0087] Table 3

[0088]

[0089] Based on Table 2 and Table 3 comprehensively, it can be known that the soil conditioner provided by the present invention, by loading specific microbial flora on the surface of the modified biochar, the obtained soil conditioner can not only adsorb sodium ions with high efficiency, but also improve the crop germination rate and promote crop growth, which is of great significance for improving the saline-alkali land mainly stressed by sodium ions in China.

[0090] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A modified biochar, characterized in that: The invention comprises pretreated biochar and lactic acid groups and ascorbic acid groups loaded on the surface of the pretreated biochar.

2. The modified biochar according to claim 1, characterized in that The average particle size of the modified biochar is 20 to 60 μm.

3. The modified biochar according to claim 1, characterized in that The preparation method of the pretreated biochar is as follows: the original biochar is cleaned, immersed in a magnesium chloride solution, and then dried after cleaning.

4. The method for preparing modified biochar according to claim 1, characterized in that: The lactic acid and ascorbic acid are dissolved in water to obtain an acidic solution, the pretreated biochar is added thereto and stirred for 3 to 4 hours, the solid-liquid is separated, and the solution is dried and then ground to obtain the modified biochar.

5. The method for preparing modified biochar according to claim 4, characterized in that: The concentration of lactic acid in each liter of water is 200-300 g / L, the concentration of ascorbic acid in each liter of water is 150-200 g / L, and 0.5-1 kg of pretreated biochar is added to each liter of acidic solution.

6. A soil conditioner, characterized in that: The modified biochar comprises the modified biochar according to any one of claims 1 to 3, and a mixed bacterial community formed by immobilizing and culturing bacterial liquid of Bacillus flavus and / or Bacillus velez on the modified biochar carrier.

7. The soil conditioner according to claim 6, characterized in that The deposit number of the yellow sea bacillus is CGMCC No.32788, and the deposit number of the Velez bacillus is CGMCC No.24438.

8. The soil conditioner according to claim 6, characterized in that The effective viable count is 10 8 ~10 10 cfu / g.

9. The method for preparing the soil conditioner according to any one of claims 6 to 8, characterized in that the steps include: The modified biochar is mixed with activated bacterial solution of Bacillus flavus and / or Bacillus velezii at a ratio of 50-100 g / L, shaken for 1-2 hours, filtered through a plate and frame or centrifuged, and the obtained solid is dried to obtain the soil conditioner.

10. Use of the soil conditioner according to any one of claims 6 to 8 in repairing saline-alkali land under sodium ion stress.

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