Saline-alkali soil repairing agent and preparation method thereof

Abstract

The invention relates to a saline-alkali soil remediation agent and a preparation method thereof.The remediation agent is composed of a biochar-nano-silicon dioxide composite carrier, magnetized humic acid and intelligent salt-control slow-release microspheres, the biochar-nano-silicon dioxide composite carrier is composed of rice hull biochar, nano-silicon dioxide, a silane coupling agent and a salt-tolerant bacterium agent, and the stock cycle of the salt-tolerant bacterium agent is larger than or equal to 120 days; organic acid is continuously secreted to reduce the pH; the adsorption capacity of ions is enhanced by a magnetized humic acid modification process, and residues of a nano material are avoided; the intelligent salt-control slow-release microspheres regulate and control salt migration, release humic acid at low temperature and expand at high temperature to block upward movement of salt, salt directional adsorption, salt return resistance and soil structure long-acting improvement are achieved, and efficient remediation and long-acting salt return resistance of the saline-alkali soil are achieved. The remediation agent can reduce the pH value of soil to a neutral range, the sodium adsorption ratio is reduced by 70% or above, the crop yield is increased by 2-3 times, and the remediation agent does not contain harmful substances such as strong acid, strong alkali and formaldehyde, is environmentally friendly and is suitable for treating moderate and severe saline-alkali soil.

Description

Technical Field

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

[0002] Saline-alkali land refers to soils with salt content that affects the growth of crops. According to incomplete statistics from UNESCO and the Food and Agriculture Organization, the global area of ​​saline-alkali land is 954.38 million hectares, of which 99.13 million hectares are in my country. The formation of alkaline and alkali-rich soils in my country is largely related to the accumulation of carbonates in the soil, resulting in a generally high degree of alkalinity. Plants in areas with severe saline-alkali soils are virtually unable to survive.

[0003] In order to meet the needs of planting, saline-alkali land needs to be improved and repaired. The existing saline-alkali land repair technology has the following problems: Traditional humic acid modification relies on chemical reagents, which can easily cause secondary pollution; The survival rate of biochar-loaded bacterial agents is low and cannot inhibit the upward movement of salt for a long time; The slow-release structure is single and cannot dynamically respond to changes in soil temperature and humidity; The adsorption capacity for chloride ions (Cl⁻) is insufficient, and the salt return phenomenon is serious. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems and propose a saline-alkali land remediation agent and a preparation method thereof. Through the synergistic modification of biochar-nanosilica composite carrier materials, magnetized humic acid activation, intelligent salt-controlling slow-release microspheres and salt-tolerant bacteria directional domestication technology, directional salt adsorption, anti-salt return and long-term improvement of soil structure are achieved.

[0005] To achieve the above objectives, the present invention provides the following technical solutions: a saline-alkali land remediation agent and a preparation method thereof, comprising a biochar-nanosilica composite carrier, magnetized humic acid, and intelligent salt-controlling slow-release microspheres, wherein the biochar-nanosilica composite carrier is composed of rice husk biochar, nanosilica, a silane coupling agent, and a salt-tolerant bacterial agent; The intelligent salt-controlling sustained-release microspheres have a multi-level design, a thermosensitive gel core and an outer coating. The thermosensitive gel core is composed of thermosensitive material PNIPAM (poly N-isopropylacrylamide) and potassium silicate; the outer coating is a sodium alginate-humic acid composite film.

[0006] A method for preparing a saline-alkali land repair agent, wherein the preparation process of the biocarbon-nanosilica composite carrier is as follows: (1) Rice husk biochar was crushed to 200 mesh and immersed in an ethanol solution containing 5% KH-560 silane coupling agent; (2) Add nanosilica with a ratio of rice husk biochar to silica of 10:1 and ultrasonicate for 1 h; (3) Vacuum sintering was performed at 200°C for 2 hours. After cooling, the mixture was immersed in a suspension of salt-tolerant bacteria and adsorbed by shaking for 4 hours, and then centrifuged and dried.

[0007] The modification of the magnetized humic acid comprises the following steps: (1) Straw pretreatment: corn straw was crushed to 0.5 mm, mixed with cellulase and laccase, and enzymatically hydrolyzed at 45°C for 48 hours, and the crude humic acid solution was filtered; (2) Magnetization modification: Add humic acid crude solution Nanoparticles, humic acid and The ratio was 10:1, stirred at 50°C for 2 hours, separated by a magnetic field and then dried; Construction of intelligent salt-controlled sustained-release microspheres: The thermosensitive gel core is made of PNIPAM and potassium silicate. Potassium silicate and PNIPAM are dissolved in deionized water at a mass ratio of 2:1 and cross-linked at 50°C to form a thermosensitive gel. The outer coating is a sodium alginate-humic acid composite membrane, which is copolymerized with sodium alginate and 3-sulfopropyl methacrylate (SPMA) to introduce sulfonic acid groups, use magnetized humic acid as the cross-linking point, and then adopt gradient The solution solidifies to form double-layer microspheres.

[0008] Furthermore: the rice husk biochar is pyrolyzed at 600°C, has a specific surface area of ​​≥400 m² / g, and a nano-silicon dioxide particle size of 50 nm.

[0009] Furthermore: biochar-nanosilica composite carrier, magnetized humic acid, and intelligent salt-controlled slow-release microspheres are mixed in a mass ratio of 5:3:2, and a 0.5T magnetic field is applied for directional compaction to form porous particles with a particle size of 2~4mm and a porosity ≥60%.

[0010] Furthermore, the intelligent salt-controlling slow-release microspheres release humic acid when the soil is moist, and expand when water in the soil evaporates strongly to block the upward movement of salt.

[0011] Furthermore: the salt-tolerant bacterial agent is a composite bacterial community of Halomonas and Bacillus gelatinosa acclimated in a 0.5%-8% NaCl gradient.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses a biochar-nanosilica composite carrier to load a salt-tolerant bacterial agent. The salt-tolerant bacteria have a storage period of ≥120 days and continuously secrete organic acids to lower the pH. Magnetized humic acid activation enhances the adsorption capacity of ions. Magnetized humic acid can be quickly recovered through a magnetic field with a recovery rate of ≥90%, avoiding the residue of nanomaterials. Intelligent salt-controlling slow-release microspheres regulate salt migration, releasing humic acid at low temperatures and expanding at high temperatures to block salt upward migration, achieving directional salt adsorption, anti-salt return, and long-term improvement of soil structure, thus achieving efficient restoration and long-term anti-salt return of saline-alkali land. This repair agent contains a salt-tolerant bacterial agent that can lower the soil pH to a neutral range, reduce the sodium adsorption ratio by more than 70%, and increase crop yields by 2-3 times. In addition, this repair agent does not contain harmful substances such as strong acids, strong bases, and formaldehyde. The heavy metal content of smoking wastewater is lower than the national standard. It is environmentally friendly and suitable for the treatment of medium and heavy saline-alkali land. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only for more clearly illustrating the embodiments of the present invention or the technical solutions in the prior art. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 Schematic diagram of the structure of the repair agent of the present invention; Figure 2 Schematic diagram of the response mechanism of the intelligent salt-controlling sustained-release microspheres of the present invention, namely, release at low temperature and blocking at high temperature; Figure 3 This is a diagram showing the growth status of soil corn without using the repair agent of the present invention; Figure 4 This is a diagram showing the growth status of corn after using the repair agent of the present invention; Figure 5 This is a comparison chart of crop growth in the test field using the repair agent of the present invention and the control group where no repair agent was used. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments. However, the embodiments are only intended to illustrate the present invention and not to limit the present invention.

[0016] A saline-alkali land restoration agent is composed of a biochar-nanosilica composite carrier, magnetized humic acid, and intelligent salt-controlling slow-release microspheres.

[0017] The biochar-nanosilica composite carrier is composed of rice husk biochar, nanosilica, a silane coupling agent and a salt-tolerant bacteria agent, specifically: (1) Rice husk biochar was crushed to 200 mesh and immersed in an ethanol solution containing 5% KH-560 silane coupling agent; (2) Add nanosilica with a ratio of rice husk biochar to silica of 10:1 and ultrasonicate for 1 h; (3) Vacuum sintering was performed at 200°C for 2 hours. After cooling, the mixture was immersed in a suspension of salt-tolerant bacteria and adsorbed by shaking for 4 hours, and then centrifuged and dried.

[0018] Magnetized humic acid modification: (1) Straw pretreatment: corn straw was crushed to 0.5 mm, mixed with cellulase and laccase, and enzymatically hydrolyzed at 45°C for 48 hours, and the crude humic acid solution was filtered; (2) Magnetization modification: Add humic acid crude solution Nanoparticles, humic acid and The ratio was 10:1, stirred at 50°C for 2 hours, separated by a magnetic field and then dried; The carboxyl content of the modified magnetized humic acid increased to 2.8 mmol / g, while that of the unmodified humic acid was ≤1.5 mmol.

[0019] Construction of intelligent salt-controlled sustained-release microspheres Thermosensitive gel core: The thermosensitive material is PNIPAM poly(N-isopropylacrylamide), whose lower critical solution temperature is set at 35°C, matching the surface temperature of saline-alkali land in summer. When the soil temperature is greater than 35°C, the PNIPAM chains dehydrate and shrink, and the gel expansion rate is ≥150%, physically blocking the upward migration of salt ions. Potassium silicate (K2O·SiO2) is added to form an interpenetrating network (IPN) with PNIPAM, with potassium silicate comprising 40% by weight. This improves the mechanical strength of the gel (compressive strength ≥ 5 MPa) and prevents cracking during field mechanical compaction. Potassium silicate and PNIPAM are dissolved in deionized water at a mass ratio of 2:1 and cross-linked at 50°C to form a thermosensitive gel.

[0020] Outer membrane: Sodium alginate-humic acid composite membrane: Sulfonic acid group grafting: Sodium alginate is copolymerized with 3-sulfopropyl methacrylate potassium (SPMA) to introduce sulfonic acid groups (- ), enhance the targeted adsorption of Cl⁻ (selectivity coefficient K=5.2); Magnetized humic acid doping: Magnetized humic acid ( The loading rate is 10%) as cross-linking points to improve the stability of the membrane (the swelling rate is reduced by 30%) and impart magnetic responsiveness.

[0021] Calcium cross-linking optimization: using a gradient Concentration cross-linking (0.5%→2.0%) forms a non-uniform structure with a dense outer layer and a loose inner layer, which can achieve the staged release of humic acid. Specifically, the thermosensitive gel is immersed in a mixture of 3% sodium alginate and 5% magnetized humic acid, and then dripped The solution solidifies to form double-layer microspheres.

[0022] Slow-release mechanism: Humic acid is released at low temperatures (when the soil is moist), and expansion at high temperatures (when evaporation is strong) blocks the upward movement of salt.

[0023] The biochar-nanosilica composite carrier, magnetized humic acid, and intelligent salt-controlled slow-release microspheres are mixed in a mass ratio of 5:3:2, and a 0.5T magnetic field is applied for directional compaction to form porous particles, which are the repair agent of the present invention, with a particle size of 2-4mm and a porosity of ≥60%. Example

[0024] Preparation of repair agent Preparation of biochar-nanosilica composite carrier: 10 kg of rice husk biochar was crushed to 200 mesh and immersed in an ethanol solution containing 5% KH-560 silane coupling agent. Add 1 kg of nano-silica and ultrasonicate for 1 hour; The samples were vacuum sintered at 200℃ for 2 hours and then immersed in 2kg of salt-tolerant bacteria suspension (viable bacteria count 5× CFU / g) were adsorbed by shaking for 4 hours and then centrifuged to dry; 10 kg of biochar-nanosilica composite carrier, 6 kg of magnetized humic acid, and 4 kg of intelligent salt-controlled slow-release microspheres were weighed and mixed, and a 0.5 T magnetic field was applied for directional compaction to form porous particles, i.e., the repair agent.

[0025] The above-obtained repair agent was used in saline-alkali land repair test and applied to the moderate and severe saline-alkali land in the Yellow River Delta. The repair agent was spread at a rate of 300 kg / mu and tilled to a 20 cm soil layer. The repair effect was tested after 90 days. The soil indicators were as follows:

[0026] Field corn was planted in the control field and the experimental field. The experimental data are as follows: Growth index data are shown in Table 1

[0027] The yield index data are shown in Table 2

[0028]

[0029] Soil index numbers are shown in Table 3

[0030] The present invention can achieve the following performances: 1. Directed adsorption and recovery Magnetized humic acid can be quickly recovered through the magnetic field, with a recovery rate of ≥90%, avoiding the residue of nanomaterials; 2. Intelligent salt control The thermosensitive gel dynamically responds to the soil environment, expanding at high temperatures to block the upward migration of salt; 3. Long-term repair The salt-tolerant bacteria have a storage period of ≥120 days and continuously secrete organic acids to lower the pH; 4. Environmentally friendly There are no strong acids, strong alkalis, formaldehyde and other harmful substances throughout the process, and the heavy metal content in salt washing wastewater is lower than the national standard (GB 5084-2021).

[0031] The contents not described in detail in the present invention are all prior art.

[0032] The above description is only a preferred embodiment of the present invention and is not limited to the description in the specification and implementation mode. Therefore, any equivalent changes or modifications made according to the structure, features and principles described in the scope of the patent application of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A saline-alkali land repair agent, characterized in that: Including biochar-nanosilica composite carrier, magnetized humic acid, intelligent salt control slow-release microspheres, The biochar-nanosilica composite carrier is composed of rice husk biochar, nanosilica, a silane coupling agent and a salt-tolerant bacteria agent; The intelligent salt-controlling sustained-release microspheres have a multi-level design, a thermosensitive gel core and an outer coating. The thermosensitive gel core is composed of thermosensitive material PNIPAM (poly N-isopropylacrylamide) and potassium silicate; the outer coating is a sodium alginate-humic acid composite film.

2. The method for preparing a saline-alkali land repair agent according to claim 1, wherein: The preparation process of the biocarbon-nanosilica composite carrier is as follows: (1) Rice husk biochar was crushed to 200 mesh and immersed in an ethanol solution containing 5% KH-560 silane coupling agent; (2) Add nanosilica with a ratio of rice husk biochar to silica of 10:1 and ultrasonicate for 1 h; (3) vacuum sintering at 200°C for 2 hours, cooling, immersing in a suspension of salt-tolerant bacteria for 4 hours of oscillation adsorption, and then centrifugation drying; The modification of the magnetized humic acid comprises the following steps: (1) Straw pretreatment: corn straw was crushed to 0.5 mm, mixed with cellulase and laccase, and enzymatically hydrolyzed at 45°C for 48 hours, and the crude humic acid solution was filtered; (2) Magnetization modification: nanoparticles were added to the crude humic acid solution at a ratio of 10:1, stirred at 50 °C for 2 h, separated by magnetic field, and then dried; Construction of intelligent salt-controlled sustained-release microspheres: The thermosensitive gel core is made of PNIPAM and potassium silicate. Potassium silicate and PNIPAM are dissolved in deionized water at a mass ratio of 2:1 and cross-linked at 50°C to form a thermosensitive gel. The outer coating is a sodium alginate-humic acid composite membrane. Sulfonic acid groups are introduced by copolymerizing sodium alginate with 3-sulfopropyl methacrylate potassium (SPMA). Magnetized humic acid is used as the cross-linking point, and then a gradient solution is used for solidification to form double-layer microspheres.

3. The method for preparing a saline-alkali land repair agent according to claim 2, wherein: The rice husk biochar is pyrolyzed at 600°C, has a specific surface area of ​​≥400 m² / g, and has a nano-silicon dioxide particle size of 50 nm.

4. The method for preparing a saline-alkali land repair agent according to any one of claims 1 to 2, characterized in that: Biochar-nanosilica composite carrier, magnetized humic acid, and intelligent salt-controlled slow-release microspheres were mixed in a mass ratio of 5:3:2 and compacted under a 0.5T magnetic field to form porous particles with a particle size of 2-4mm and a porosity of ≥60%.

5. The saline-alkali land repair agent according to claim 1, characterized in that: The intelligent salt-controlling slow-release microspheres release humic acid when the soil is moist, and expand when water in the soil evaporates strongly to block the upward movement of salt.

6. A saline-alkali land repair agent according to claim 1, wherein the salt-tolerant bacteria agent is a composite bacterial community of Halomonas and Bacillus gelatinosa acclimated in a 0.5%-8% NaCl gradient.

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