Composite saline-alkali soil conditioner and preparation method thereof

Abstract

The invention discloses a composite saline alkali soil conditioner, which is prepared from the following ingredients in parts by weight: 30 to 40 parts of iron ion modified charcoal, 10 to 20 parts of inorganic waste residues, 5 to 10 parts of humic acid, 10 to 15 parts of modified polyacrylamide and 1 to 3 parts of auxiliary microbial agents. The modified polyacrylamide has a structure as shown in a formula A, the ratio of x to y to z is (10-15): (3-5): (2-3), and the molecular weight is 50000-120000. The composite saline-alkali soil conditioner provided by the invention is prepared by compounding the iron ion modified biochar, the inorganic waste residue, the humic acid, the modified polyacrylamide and the auxiliary microbial agent, has excellent salt reduction and carbon sequestration capabilities, reduces resource waste and environmental pollution by reusing agricultural and forestry wastes and the waste residue, and has a good application prospect. The method can be widely applied to the field of improvement of saline-alkali soil. # imgabs0 #

Description

Technical Field

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

[0002] The harm of saline-alkali land to plants mainly includes the following aspects: First, it causes physiological drought of plants. Excessive soluble salts can increase the osmotic pressure of soil solution, causing physiological drought of plants, making it impossible for roots and seeds to absorb enough water from the soil when germinating, and even causing water to seep out of root cells, causing plants to wilt or even die; second, it harms plant tissues. Excessive accumulation of salt in the topsoil during the dry season can easily damage the hypocotyl. Under high pH values, it can also cause direct hydroxyl poisoning of plants. Excessive accumulation of salt in plant tissues can damage 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 nutrients by plants is reduced, and the transfer of phosphorus will also be inhibited, thus affecting the nutritional status of plants; fourth, it affects the opening and closing of plant stomata. Under the action of high-depth salts, the synthesis of starch in stomatal guard cells is hindered, so that the cells cannot be closed, and plants are prone to drought and withering.

[0003] At present, there are roughly four methods and technologies for improving and utilizing saline-alkali land in China: physical improvement, hydraulic improvement, chemical improvement and biological improvement.

[0004] The carbon element in the soil is an important element that plants rely on for growth. In addition to CO2 in the air, the carbon elements required for plant growth also include 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 each year far exceeds the carbon dioxide emitted into the atmosphere by the burning of fossil fuels each year. Therefore, carbon sequestration in agricultural soils will be beneficial to crop production and can also alleviate the pressure caused by high concentrations of 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 wastes and residues and has excellent salt reduction and carbon fixation capabilities. Summary of the invention

[0006] Purpose of the invention: In view of the defects of the prior art, the purpose of the present invention is to provide a composite saline-alkali soil conditioner and a preparation method thereof, which can recycle agricultural and forestry wastes and waste residues and has excellent salt reduction and carbon fixation capabilities.

[0007] Technical solution:

[0008] On the one hand, the present invention provides a composite saline-alkali soil conditioner, which comprises, by weight, 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 a structure shown in the following formula A:

[0010]

[0011] Wherein x:y:z=(10-15):(3-5):(2-3), and the molecular weight is 50000-120000.

[0012] The addition of humic acid in the present invention can reduce the pH of saline-alkali soil and improve the alkaline environment of saline-alkali soil on the one hand, and can replace sodium ions in the soil on the other hand, improve the adsorption effect of the improver on salt, and make the salt easier to wash off, thereby enhancing the salt-reducing ability of the improver.

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

[0014] (1) washing the agricultural and forestry waste with distilled water to remove impurities, pyrolyzing it in a closed environment at 450-500° C. for 2-3 hours, and grinding it to a particle size of less than 1.5 mm to obtain biochar;

[0015] (2) adding the biochar to a ferric chloride solution and ultrasonicating for 30-50 minutes, adjusting the pH to 2-3, stirring for 2-4 hours, filtering, washing, and drying, calcining at 300-350° C. for 1-2 hours, and grinding to a particle size of less than 1.5 mm to obtain the iron ion modified biochar.

[0016] The iron ion modified biochar in the present invention is prepared by loading iron ions after treating agricultural and forestry wastes. After being soaked in ferric chloride, the biochar can not only load iron ions and improve the biochar's adsorption capacity for ions in the soil, but also increase the number of pores in the biochar, increase the specific surface area of ​​the biochar, and thus enhance the biochar's adsorption rate and adsorption capacity for salt; 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 soil's carbon capture capacity, thereby achieving the soil carbon fixation effect.

[0017] Furthermore, 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.

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

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

[0020] (1) preparing propylene quaternary ammonium salt by reacting dimethylaminotriethylsilane with propylene bromide;

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

[0022] The acrylamide structure of the modified polyacrylamide in the present invention enables the polymer to have excellent stability and certain adsorption capacity, and can be combined with fine soil particles to form a stable structure, thereby optimizing the soil structure, improving the soil stability, and improving 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, and improve the saline-alkali soil environment; the quaternary ammonium salt structure can improve the dispersibility of the modified polyacrylamide, on the one hand, in the process of preparing the improver, the pore volume of the biochar can be increased, the adsorption rate and adsorption capacity of the biochar can be improved, and the salt reduction and carbon fixation capabilities can be enhanced, and the improver 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, the uniformity of the distribution of the improver in the soil can be improved, and the salt reduction and carbon fixation efficiency of the improver can be improved.

[0023] Furthermore, the specific method of step (1) is as follows: in a reactor, dimethylaminotriethylsilane and an alcohol solvent are added, stirred and mixed evenly, heated to 35-45° C. under nitrogen protection, and allyl bromide is slowly added dropwise for 2-3 hours. After the addition is completed, the temperature is raised to 60-65° C., and the reaction is kept warm for 6-8 hours, and the alcohol solvent is removed. The propylene quaternary ammonium salt is obtained after recrystallization.

[0024] The propylene quaternary ammonium salt has a structure shown in the following formula B:

[0025]

[0026] Furthermore, the molar ratio of dimethylaminotriethylsilane to propylene bromide is 1:1.2-1.4.

[0027] Furthermore, the specific method of step (2) is as follows: in a reactor, acrylamide, propylene quaternary ammonium salt and vinyl benzoic acid are added to deionized water in proportion, stirred evenly and 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 cooled to room temperature, filtered and washed to obtain the modified polyacrylamide.

[0028] The modified polyacrylamide in the present invention 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, 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.

[0029] Furthermore, 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).

[0030] On the other hand, the present invention provides a method for preparing the composite saline-alkali soil conditioner, comprising the following steps: mixing iron ion modified biochar, inorganic waste residue, humic acid and modified polyacrylamide in proportion, adding the mixture to a granulator for granulation, and continuously spraying auxiliary bacterial agents. After granulation, the mixture is sieved to retain particles with a particle size of 2-3 mm, which are 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 auxiliary bacterial agent, and has excellent salt reduction and carbon fixation capabilities. It can also reduce resource waste and environmental pollution by recycling agricultural and forestry wastes and waste residues, and can be widely used in 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 on agricultural and forestry waste after treatment. After being soaked in ferric chloride, the biochar can not only load iron ions and improve the biochar's adsorption capacity for ions in the soil, but also increase the number of pores in the biochar, increase the specific surface area of ​​the biochar, and thus enhance the biochar's adsorption rate and adsorption capacity for salt; 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 soil's carbon capture capacity, thereby achieving the soil carbon fixation effect.

[0034] (3) In the composite saline-alkali soil conditioner provided by the present invention, the addition of humic acid can, on the one hand, reduce the pH value of the saline-alkali soil and improve the alkaline environment of the saline-alkali soil; on the other hand, it can replace the sodium ions in the soil, thereby improving the adsorption effect of the conditioner on salt and making the salt easier to wash off, thereby enhancing the salt-reducing 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) 5 g of biochar was added to 100 mL of 0.6 mol / L ferric chloride solution and ultrasonicated for 50 minutes, and then the pH was adjusted to 2 using hydrochloric acid. After stirring for 4 hours, the solution was filtered, washed, and dried, and then calcined at 350° C. for 2 hours and ground to a particle size of <1.5 mm to obtain the iron ion modified biochar.

[0043] Preparation of modified polyacrylamide-1

[0044] Modified polyacrylamide-1 was prepared by the following steps:

[0045] (1) In a reactor, 0.1 mol of dimethylaminotriethylsilane and 100 mL of anhydrous ethanol were added, stirred and mixed evenly, and the temperature was raised to 40° C. under nitrogen protection, and 0.13 mol of propylene bromide was slowly added dropwise for 3 hours. After the addition was completed, the temperature was raised to 60° C., and the reaction was kept warm for 8 hours, and the anhydrous ethanol was removed. The propylene quaternary ammonium salt was obtained after recrystallization;

[0046] (2) In a reactor, 0.15 mol of acrylamide, 0.05 mol of propylene quaternary ammonium salt and 0.03 mol of vinyl benzoic acid were added to deionized water, stirred evenly and nitrogen was introduced for 30 minutes, 0.5 g of ammonium persulfate was added, the reactor was sealed, the temperature was raised to 90° C. and the reaction was maintained for 6 hours, then cooled to room temperature, filtered and washed to obtain the modified polyacrylamide-1;

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

[0048] Mass spectrum data of propylene quaternary ammonium salt: The product was analyzed by LC-MS, and the m / z of the product was 739.32 (100.0%), 740.38 (47.4%), 741.36 (18.0%), and 742.37 (4.6%).

[0049] Preparation of modified polyacrylamide-2

[0050] The preparation method is basically the same as that of modified polyacrylamide-1, except that step (1) is not performed and the propylene quaternary ammonium salt in step (2) is replaced with an equal amount of acrylamide.

[0051] Preparation of modified polyacrylamide-3

[0052] The preparation method is basically the same as modified polyacrylamide-1, except that in step (2), ethylene benzoic acid is replaced by an equal amount of acrylamide.

[0053] Example 1

[0054] The composite saline-alkali soil conditioner is prepared by 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 added to a granulator for granulation, and 0.5 parts of nitrogen-fixing bacteria and 0.5 parts of Bacillus subtilis are continuously sprayed. After granulation, the particles are sieved and the particles with a particle size of 2-3 mm are retained, which is the composite saline-alkali soil conditioner.

[0056] Example 2

[0057] The method is 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] The method is 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] The method is basically the same as Example 1, except that the iron ion modified biochar is replaced by an equal amount of commercially available biochar.

[0064] Comparative Example 3

[0065] The method is basically the same as Example 1, except that the modified polyacrylamide-1 is replaced by an equal amount of commercially available polyacrylamide.

[0066] Comparative Example 4

[0067] The method is basically the same as Example 1, except that the modified polyacrylamide-1 is replaced by an equal amount of modified polyacrylamide-2.

[0068] Comparative Example 5

[0069] The method is basically the same as Example 1, except that the modified polyacrylamide-1 is replaced by an equal amount of modified polyacrylamide-3.

[0070] Performance Testing

[0071] A tomato planting experiment was conducted in saline-alkali land along the Jiangsu coast: a tomato field with an area of ​​1 mu was selected, and the experimental group applied 40kg / 667m 2 The products of Examples 1-3 and Comparative Examples 1-5 were not added to the control group. The same water and fertilizer management was adopted, and statistics were taken after the tomato harvest. Parallel experiments were set up, and the carbon fixation, crop yield, soil total salt content and soil average pH of different test fields were tested at the same time.

[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] According to the comparison of the test results of Examples 1-3 with those of Comparative Example 1, the composite saline-alkali soil conditioner provided by the present invention has better carbon fixation 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 suitable for the field of saline-alkali soil improvement.

[0075] According to 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 fixation and salt reduction capabilities of the conditioner.

[0076] According to the comparison of the test results of Examples 1-3 and Comparative Examples 3-5, it can be seen that the addition of modified polyacrylamide to the composite saline-alkali soil conditioner provided by the present invention can significantly improve the carbon fixation and salt barrier 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 implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite saline-alkali soil conditioner, characterized in that: By weight, it contains 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: Wherein x:y:z=(10-15):(3-5):(2-3), and the molecular weight is 50000-120000.

2. The composite saline-alkali soil conditioner according to claim 1, characterized in that: The iron ion modified biochar is prepared by the following steps: (1) washing the agricultural and forestry waste with distilled water to remove impurities, pyrolyzing it in a closed environment at 450-500° C. for 2-3 hours, and grinding it to a particle size of less than 1.5 mm to obtain biochar; (2) adding the biochar to a ferric chloride solution and ultrasonicating for 30-50 minutes, adjusting the pH to 2-3, stirring for 2-4 hours, filtering, washing, and drying, calcining at 300-350° C. for 1-2 hours, and grinding to a particle size of less than 1.5 mm to obtain the iron ion modified biochar.

3. The composite saline-alkali soil conditioner according to claim 2, 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.

4. 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.

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

6. The composite saline-alkali soil conditioner according to claim 5, characterized in that: The specific method of step (1) is as follows: in a reactor, dimethylaminotriethylsilane and an alcohol solvent are added, stirred and mixed evenly, heated to 35-45° C. under nitrogen protection, and allyl bromide is slowly added dropwise for 2-3 hours. After the addition is completed, the temperature is raised to 60-65° C., and the reaction is kept warm for 6-8 hours, and the alcohol solvent is removed. The propylene quaternary ammonium salt is obtained after recrystallization.

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

4.

8. The composite saline-alkali soil conditioner according to claim 5, characterized in that: The specific method of step (2) is as follows: in a reactor, acrylamide, propylene quaternary ammonium salt and vinyl benzoic acid are added to deionized water in proportion, stirred evenly and 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 cooled to room temperature, filtered and washed to obtain the modified polyacrylamide.

9. The composite saline-alkali soil conditioner according to claim 8, 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).

10. The method for preparing the composite saline-alkali soil conditioner according to any one of claims 1 to 9, 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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