A composite saline-alkali soil conditioner and its preparation method

Abstract

The present invention discloses a composite saline-alkali soil conditioner, which, by weight fraction, comprises 30-40 parts of iron ion-modified biochar, 10-20 parts of inorganic waste residue, 5-10 parts of humic acid, 10-15 parts of modified polyacrylamide, and 1-3 parts of auxiliary bacterial agent; the modified polyacrylamide has a structure shown in Formula A below, wherein x:y:z = (10-15):(3-5):(2-3), and the molecular weight is 50,000-120,000. The composite saline-alkali soil conditioner provided by the present invention is prepared by compounding iron ion-modified biochar, inorganic waste residue, humic acid, modified polyacrylamide, and auxiliary bacterial agent, has excellent salt reduction and carbon fixation capabilities, and reduces resource waste and environmental pollution by reusing agricultural and forestry waste and waste residue, and can be widely applied to the field of saline-alkali soil improvement.

Description

Technical Field

[0001] The present invention relates to the technical field of farmland additives, and particularly relates to a composite saline-alkali soil conditioner and a preparation method thereof. Background Art

[0002] The harms of saline-alkali land to plants are mainly in the following aspects: First, it causes physiological drought in plants. Excessive soluble salts can increase the osmotic pressure of the soil solution, causing physiological drought in plants, so that the roots and seeds cannot absorb enough water from the soil during germination, and even cause water to exude from the root cells, making the plants wilt and even die; Second, it harms plant tissues. In the dry season, excessive accumulation of salts in the surface soil layer is likely to damage the hypocotyl. At high pH values, it will also cause direct poisoning of plants by hydroxyl groups. Excessive accumulation of salts in plant tissues will damage the protoplasm, hinder protein synthesis, and accumulate nitrogen-containing intermediate metabolites, causing cell poisoning; Third, it affects the normal nutrient absorption of plants. Due to the competition of exchangeable sodium ions, the absorption of potassium, phosphorus and other nutrient elements by plants is reduced, and the transfer of phosphorus is also inhibited, thus affecting the nutritional status of plants; Fourth, it affects the stomatal opening and closing of plants. Under the action of high-depth salts, the starch synthesis in the guard cells of stomata is hindered, so that the cells cannot close, and the plants are prone to drought and withering.

[0003] At present, the methods and technologies for improving and utilizing saline-alkali land in China can be roughly summarized into four types: physical improvement, water conservancy improvement, chemical improvement and biological improvement.

[0004] And the carbon element in the soil is an important element on which plant growth depends. In addition to CO2 in the air, the carbon element required by plants during growth also includes organic carbon and inorganic carbon in the soil. And the soil releases a large amount of carbon dioxide into the atmosphere every year. The amount of carbon dioxide released from the soil every year far exceeds the amount of carbon dioxide emitted into the atmosphere by the combustion of fossil fuels every year. Therefore, carbon sequestration in agricultural soil will be beneficial to crop production and at the same time can relieve the pressure brought by high-concentration carbon dioxide in the atmosphere.

[0005] Therefore, there is an urgent need for a composite saline-alkali soil conditioner that can recycle agricultural and forestry waste and waste residues and has excellent salt reduction and carbon sequestration capabilities. Summary of the Invention

[0006] Object of the Invention: Aiming at the defects of the prior art, the object of the present invention is to provide a composite saline-alkali soil conditioner that can recycle agricultural and forestry waste and waste residues and has excellent salt reduction and carbon sequestration capabilities and a preparation method thereof.

[0007] Technical Solution:

[0008] On the one hand, the present invention provides a composite saline-alkali soil conditioner, which, by weight fraction, comprises 30-40 parts of iron ion-modified biochar, 10-20 parts of inorganic waste residue, 5-10 parts of humic acid, 10-15 parts of modified polyacrylamide, and 1-3 parts of auxiliary bacterial agent;

[0009] The modified polyacrylamide has the structure shown in Formula A below:

[0010]

[0011] where x:y:z = (10-15):(3-5):(2-3), and the molecular weight is 50,000-120,000.

[0012] In the present invention, adding humic acid can, on the one hand, reduce the pH of saline-alkali soil and improve the alkaline environment of saline-alkali soil, and on the other hand, displace sodium ions in the soil, improve the adsorption effect of the conditioner on salts, and make the salts easy to elute, thereby enhancing the salt reduction ability of the conditioner.

[0013] Furthermore, the iron ion-modified biochar is prepared by the following steps:

[0014] (1) Wash the agricultural and forestry waste with distilled water to remove impurities, pyrolyze it in a closed environment at 450-500 °C for 2-3 hours, and then grind it to a particle size < 1.5 mm to obtain biochar;

[0015] (2) Add the biochar to a ferric chloride solution, ultrasonicate for 30-50 minutes, then adjust the pH to 2-3, stir for 2-4 hours, filter, wash, dry, and then calcine at 300-350 °C for 1-2 hours, and grind to a particle size < 1.5 mm to obtain the iron ion-modified biochar.

[0016] In the present invention, the iron ion-modified biochar is prepared by treating agricultural and forestry waste and loading iron ions. After being soaked in ferric chloride, the biochar can not only load iron ions, improve the adsorption ability of the biochar to ions in the soil, but also increase the number of pores in the biochar, improve the specific surface area of the biochar, and thereby enhance the adsorption rate and adsorption capacity of the biochar for salts; at the same time, the large pore structure of the iron ion-modified biochar can also increase the content of organic matter in the soil and improve the carbon capture ability of the soil, achieving the carbon sequestration effect of the soil.

[0017] Furthermore, in step (1), the agricultural and forestry waste is selected from at least one of corn straw, rice husk, tree bark, or tree leaves; in step (2), the mass ratio of the biochar to ferric chloride is 1:1.5-2; the concentration of the ferric chloride solution is 0.5-0.8 mol / L.

[0018] Further, the inorganic waste residue is selected from at least one of slag, desulfurization waste or fly ash; the auxiliary bactericide is selected from at least one of nitrogen-fixing bacteria, Bacillus subtilis, Brevibacillus laterosporus or Streptomyces fradiae.

[0019] Further, the modified polyacrylamide is prepared by the following steps:

[0020] (1) An acryloyl quaternary ammonium salt is prepared by reacting dimethylamino triethylsilane with allyl bromide;

[0021] (2) The modified polyacrylamide is prepared by polymerizing acrylamide, acryloyl quaternary ammonium salt and vinyl benzoic acid.

[0022] In the present invention, the acrylamide structure of the modified polyacrylamide enables the polymer to have excellent stability and certain adsorption capacity, which can combine with fine soil particles to form a stable structure, thereby optimizing the soil structure and improving soil stability, and can improve the water retention capacity and salt elution capacity of the soil; the benzoic acid structure can further improve the molecular stability and can adjust the soil pH to improve the saline-alkali soil environment; the quaternary ammonium salt structure can improve the dispersibility of the modified polyacrylamide. On the one hand, during the preparation of the modifier, it can increase the pore volume of biochar, improve the adsorption rate and adsorption capacity of biochar, thereby enhancing the salt reduction and carbon sequestration capabilities, and can be evenly dispersed between iron ion-modified biochar and inorganic waste residue to form a uniform and stable structure; on the other hand, it can improve the evenness of the distribution of the modifier in the soil and can improve the salt reduction and carbon sequestration efficiency of the modifier.

[0023] Further, the specific method of step (1) is: in a reactor, add dimethylamino triethylsilane and an alcohol solvent, stir and mix evenly, under nitrogen protection, heat up to 35-45 °C, slowly dropwise add allyl bromide, the dropping time is 2-3 hours, after the dropping is completed, heat up to 60-65 °C, keep warm and react for 6-8 hours, then remove the alcohol solvent, and obtain the acryloyl quaternary ammonium salt after recrystallization.

[0024] The acryloyl quaternary ammonium salt has the structure shown in formula B below:

[0025]

[0026] Further, the molar ratio of dimethylamino triethylsilane to allyl bromide is 1:1.2-1.4.

[0027] Further, the specific method of step (2) is: in a reactor, add acrylamide, acryloyl quaternary ammonium salt and vinyl benzoic acid to deionized water in proportion, stir evenly, then introduce nitrogen for 20-30 minutes, add an initiator, seal the reactor, heat up to 85-95 °C, keep warm and react for 6-8 hours, then cool to room temperature, filter and wash to obtain the modified polyacrylamide.

[0028] In the present invention, the modified polyacrylamide is prepared by polymerizing acrylamide, acryloyl quaternary ammonium salt and vinyl benzoic acid. Through the interaction between the structures of the three, the formed polymer has excellent dispersibility and stability, and can effectively combine iron ion-modified biochar and inorganic waste residue to form a uniformly dispersed particulate structure with a large number of pores, having excellent salt reduction and carbon sequestration capabilities.

[0029] Furthermore, the initiator is selected from one of ammonium persulfate, sodium persulfate or potassium persulfate; the molar ratio of acrylamide, acryloyl quaternary ammonium salt and vinyl benzoic acid is (10 - 15):(3 - 5):(2 - 3).

[0030] On the other hand, the present invention provides a preparation method of the above-mentioned composite saline-alkali soil conditioner, including the following steps: uniformly mixing iron ion-modified biochar, inorganic waste residue, humic acid and modified polyacrylamide in proportion, adding them to a granulator for granulation, and continuously spraying an auxiliary bacterium agent. After granulation, sieving is carried out, and the particles with a particle size of 2 - 3 mm are retained as the composite saline-alkali soil conditioner.

[0031] Beneficial effects:

[0032] (1) The composite saline-alkali soil conditioner provided by the present invention is prepared by compounding iron ion-modified biochar, inorganic waste residue, humic acid, modified polyacrylamide and an auxiliary bacterium agent, has excellent salt reduction and carbon sequestration capabilities, and through the reuse of agricultural and forestry waste and waste residue, reduces resource waste and environmental pollution, and can be widely applied to the field of saline-alkali soil improvement.

[0033] (2) In the composite saline-alkali soil conditioner provided by the present invention, the iron ion-modified biochar is prepared by loading iron ions after treating agricultural and forestry waste. After the biochar is soaked in ferric chloride, it can not only load iron ions, improve the adsorption capacity of the biochar for ions in the soil, but also increase the number of pores in the biochar, improve the specific surface area of the biochar, and thus enhance the adsorption rate and adsorption capacity of the biochar for salts; at the same time, the large number of pore structures of the iron ion-modified biochar can also increase the content of organic matter in the soil and improve the carbon capture capacity of the soil, realizing the carbon sequestration effect of the soil.

[0034] (3) In the composite saline-alkali soil conditioner provided by the present invention, adding humic acid can, on the one hand, reduce the pH of saline-alkali soil and improve the alkaline environment of saline-alkali soil, and on the other hand, displace sodium ions in the soil, improve the adsorption effect of the conditioner on salts, and make the salts easy to elute, thereby enhancing the salt reduction ability of the conditioner.

[0035] (4) In the composite saline-alkali soil conditioner provided by the present invention, the modified polyacrylamide is prepared by polymerization of acrylamide, propylene quaternary ammonium salt and vinyl benzoic acid. Through the interaction between the three structures, the formed polymer has excellent dispersibility and stability, and can effectively combine iron ion-modified biochar and inorganic waste residue to form a uniformly dispersed particle structure containing a large number of pores, and has excellent salt reduction and carbon fixation capabilities.

[0036] (5) In the composite saline-alkali soil conditioner provided by the present invention, the acrylamide structure of the modified polyacrylamide makes the polymer have excellent stability and certain adsorption capacity, and can combine with fine soil particles to form a stable structure, thereby optimizing the soil structure, improving soil stability, and improving the soil's water retention capacity and salt elution capacity; the benzoic acid structure can further improve the molecular stability, and can adjust the soil pH and improve the saline-alkali soil environment; the quaternary ammonium salt structure can improve the dispersibility of the modified polyacrylamide. On the one hand, during the preparation process of the conditioner, it can increase the pore volume of biochar, improve the adsorption rate and adsorption capacity of biochar, and thus enhance the salt reduction and carbon fixation capabilities, and can be evenly dispersed between the iron ion modified biochar and the inorganic waste residue to form a uniform and stable structure; on the other hand, it can improve the uniformity of the distribution of the conditioner in the soil, and can improve the salt reduction and carbon fixation efficiency of the conditioner. DETAILED DESCRIPTION

[0037] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0038] The commercially available saline-alkali soil conditioner is Hanliu soil conditioner purchased from Qingdao Leiwo Biotechnology Co., Ltd.; the commercially available biochar is 300-mesh plant straw charcoal purchased from Henan Li Ze Environmental Protection Technology Co., Ltd.; the commercially available polyacrylamide is P434411 purchased from Aladdin; the remaining reagents and equipment are conventional reagents and equipment in this technical field.

[0039] Preparation of iron ion modified biochar

[0040] The iron ion modified biochar was prepared by the following steps:

[0041] (1) After washing the corn stalks with distilled water to remove impurities, the corn stalks were pyrolyzed in a closed environment at 500° C. for 3 hours, and then ground into a particle size of less than 1.5 mm to obtain biochar;

[0042] (2) Add 5 g of biochar to 100 mL of a ferric chloride solution with a concentration of 0.6 mol / L, ultrasonicate for 50 minutes, adjust the pH to 2 using hydrochloric acid, stir for 4 hours, filter, wash, dry, and then calcine at 350 °C for 2 hours, and grind to a particle size < 1.5 mm to obtain the iron ion-modified biochar.

[0043] Preparation of Modified Polyacrylamide-1

[0044] Modified polyacrylamide-1 is prepared through the following steps:

[0045] (1) In a reactor, add 0.1 mol of dimethylaminotriethylsilane and 100 mL of absolute ethanol, stir and mix evenly, under nitrogen protection, heat up to 40 °C, slowly dropwise add 0.13 mol of allyl bromide over 3 hours, after the dropping is completed, heat up to 60 °C, keep the temperature for reaction for 8 hours, remove the absolute ethanol, and obtain the allyl quaternary ammonium salt after recrystallization;

[0046] (2) In a reactor, add 0.15 mol of acrylamide, 0.05 mol of allyl quaternary ammonium salt, and 0.03 mol of vinyl benzoic acid to deionized water, stir evenly, introduce nitrogen for 30 minutes, add 0.5 g of ammonium persulfate, seal the reactor, heat up to 90 °C, keep the temperature for reaction for 6 hours, then cool to room temperature, filter and wash to obtain the modified polyacrylamide-1;

[0047] The average molecular weight of modified polyacrylamide-1 is 80,000;

[0048] Mass spectrometry data of allyl quaternary ammonium salt: Analyze the product by LC-MS, and the m / z of the product is 739.32 (100.0%), 740.38 (47.4%), 741.36 (18.0%), 742.37 (4.6%).

[0049] Preparation of Modified Polyacrylamide-2

[0050] It is basically the same as the preparation of modified polyacrylamide-1, the difference is that step (1) is not carried out, and the allyl quaternary ammonium salt in step (2) is changed to an equal amount of acrylamide.

[0051] Preparation of Modified Polyacrylamide-3

[0052] It is basically the same as the preparation of modified polyacrylamide-1, the difference is that vinyl benzoic acid in step (2) is changed to an equal amount of acrylamide.

[0053] Example 1

[0054] A composite saline-alkali soil conditioner is prepared through the following steps:

[0055] By weight, 30 parts of iron ion-modified biochar, 20 parts of inorganic waste residue, 10 parts of humic acid, and 10 parts of modified polyacrylamide-1 are mixed evenly in proportion and then added to a granulator for granulation. Meanwhile, 0.5 parts of nitrogen-fixing bacteria and 0.5 parts of Bacillus subtilis are continuously sprayed. After granulation, it is sieved, and the particles with a particle size of 2-3 mm are retained, which are the composite saline-alkali soil conditioner.

[0056] Example 2

[0057] Basically the same as Example 1, except that the components are changed to 35 parts of iron ion-modified biochar, 15 parts of inorganic waste residue, 7 parts of humic acid, 12 parts of modified polyacrylamide, 1 part of nitrogen-fixing bacteria, and 1 part of Bacillus subtilis.

[0058] Example 3

[0059] Basically the same as Example 1, except that the components are changed to 40 parts of iron ion-modified biochar, 10 parts of inorganic waste residue, 5 parts of humic acid, 15 parts of modified polyacrylamide, 1 part of nitrogen-fixing bacteria, and 1 part of Bacillus subtilis.

[0060] Comparative Example 1

[0061] Commercially available saline-alkali soil conditioner.

[0062] Comparative Example 2

[0063] Basically the same as Example 1, except that the iron ion-modified biochar is replaced with an equal amount of commercially available biochar.

[0064] Comparative Example 3

[0065] Basically the same as Example 1, except that the modified polyacrylamide-1 is replaced with an equal amount of commercially available polyacrylamide.

[0066] Comparative Example 4

[0067] Basically the same as Example 1, except that the modified polyacrylamide-1 is replaced with an equal amount of modified polyacrylamide-2.

[0068] Comparative Example 5

[0069] Basically the same as Example 1, except that the modified polyacrylamide-1 is replaced with an equal amount of modified polyacrylamide-3.

[0070] Performance Test

[0071] A tomato planting experiment was carried out on the saline-alkali land along the coast of Jiangsu: Tomato fields with an area of 1 mu each were selected. In the experimental groups, the products of Examples 1-3 and Comparative Examples 1-5 were applied at 40 kg / 667 m 2 during tomato sowing, while the control group was not added. The same water and fertilizer management was adopted. After the tomato harvest, statistics were carried out, and parallel tests were set up. At the same time, the carbon sequestration amount, crop yield, total soil salt content, and average soil pH of different test fields were detected.

[0072] The test results are shown in the following table:

[0073] <![CDATA[Carbon sequestration amount (t·hm -2 ·a -1 )]]> <![CDATA[Yield (kg·667m -2 )]]> Total salt content (g / kg) pH Example 1 19 5680 5.7 8.21 Example 2 20 5700 5.5 8.21 Example 3 20 5710 5.4 8.23 Comparative Example 1 7 5150 8.9 8.54 Comparative Example 2 11 5270 7.6 8.26 Comparative Example 3 12 5310 7.3 8.32 Comparative Example 4 15 5420 6.7 8.25 Comparative Example 5 17 5580 6.2 8.28 Control Group 2 4100 13.2 8.67

[0074] From the comparison of the test results of Examples 1-3 and Comparative Example 1, it can be seen that the composite saline-alkali soil conditioner provided by the present invention has more excellent carbon sequestration and salt reduction capabilities than the saline-alkali soil conditioner in the prior art, and can adjust the pH of saline-alkali soil, thereby increasing the yield of crops in saline-alkali soil, and is applicable to the field of improving saline-alkali soil.

[0075] From the comparison of the test results of Examples 1-3 and Comparative Example 2, it can be seen that adding iron ion-modified biochar to the composite saline-alkali soil conditioner provided by the present invention can effectively improve the carbon sequestration and salt reduction capabilities of the conditioner.

[0076] From the comparison of the test results of Examples 1-3 and Comparative Examples 3-5, it can be seen that adding modified polyacrylamide to the composite saline-alkali soil conditioner provided by the present invention can significantly improve the carbon sequestration and salt resistance capabilities of the conditioner through its amide structure, quaternary ammonium salt structure and benzoic acid structure, and can adjust the soil pH and increase the yield of crops in saline-alkali soil.

[0077] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it. It cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A composite saline-alkali soil conditioner, characterized in that: By weight, it comprises 30-40 parts of iron ion modified biochar, 10-20 parts of inorganic waste residue, 5-10 parts of humic acid, 10-15 parts of modified polyacrylamide and 1-3 parts of auxiliary bacterial agent; The modified polyacrylamide has a structure shown in the following formula A: ， Where x: y:z=(10-15):(3-5):(2-3), molecular weight 50000-120000; The iron ion modified biochar is prepared by the following steps: (1) The agricultural and forestry waste is washed with distilled water to remove impurities, pyrolyzed in a closed environment at 450-500°C for 2-3 hours, and then ground to a particle size of less than 1.5 mm to produce biochar; (2) adding the biochar to a ferric chloride solution and ultrasonicating it for 30-50 minutes, adjusting the pH to 2-3, stirring it for 2-4 hours, filtering, washing, and drying it, calcining it at 300-350° C. for 1-2 hours, and grinding it to a particle size of less than 1.5 mm to obtain the iron ion modified biochar.

2. The composite saline-alkali soil conditioner according to claim 1, characterized in that: In step (1), the agricultural and forestry waste is selected from at least one of corn stalks, rice husks, barks or leaves; in step (2), the mass ratio of biochar to ferric chloride is 1:1.5-2; and the concentration of the ferric chloride solution is 0.5-0.8 mol / L.

3. The composite saline-alkali soil conditioner according to claim 1, characterized in that: The inorganic waste residue is selected from at least one of slag, desulfurization waste or fly ash; the auxiliary bacterial agent is selected from at least one of nitrogen-fixing bacteria, Bacillus subtilis, Brevibacillus laterosporus or Streptomyces freundii.

4. The composite saline-alkali soil conditioner according to claim 1, characterized in that: The modified polyacrylamide is prepared by the following steps: (1) Propylene quaternary ammonium salt is prepared by reacting dimethylaminotriethylsilane with propylene bromide; (2) The modified polyacrylamide is prepared by polymerizing acrylamide, propylene quaternary ammonium salt and vinyl benzoic acid.

5. The composite saline-alkali soil conditioner according to claim 4, characterized in that: The specific method of step (1) is as follows: add dimethylaminotriethylsilane and an alcohol solvent into a reactor, stir and mix them evenly, raise the temperature to 35-45°C under nitrogen protection, slowly drop allyl bromide for 2-3 hours, raise the temperature to 60-65°C after the dropwise addition, keep the temperature for reaction for 6-8 hours, remove the alcohol solvent, and obtain the propylene quaternary ammonium salt after recrystallization.

6. The composite saline-alkali soil conditioner according to claim 5, characterized in that: The molar ratio of dimethylaminotriethylsilane to propylene bromide is 1:1.2-1.

4.

7. The composite saline-alkali soil conditioner according to claim 4, characterized in that: The specific method of step (2) is as follows: in a reactor, acrylamide, quaternary ammonium salt of propylene and vinyl benzoic acid are added to deionized water in proportion, stirred evenly and then nitrogen is introduced for 20-30 minutes, an initiator is added, the reactor is sealed, the temperature is raised to 85-95°C and the reaction is kept warm for 6-8 hours, then the reactor is cooled to room temperature, filtered and washed to obtain the modified polyacrylamide.

8. The composite saline-alkali soil conditioner according to claim 7, characterized in that: The initiator is selected from one of ammonium persulfate, sodium persulfate or potassium persulfate; the molar ratio of acrylamide, propylene quaternary ammonium salt and vinyl benzoic acid is (10-15): (3-5): (2-3).

9. The method for preparing the composite saline-alkali soil conditioner according to any one of claims 1 to 8, characterized in that: The following steps are involved: The iron ion modified biochar, inorganic waste residue, humic acid and modified polyacrylamide are mixed evenly in proportion and added to a granulator for granulation, and auxiliary bacterial agents are continuously sprayed. After granulation, the particles are sieved and the particles with a particle size of 2-3 mm are retained, which is a composite saline-alkali soil conditioner.

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