Preparation process of soil conditioner and application of soil conditioner in soil improvement

Abstract

The invention discloses a preparation process of a soil conditioner and application of the soil conditioner in soil improvement, and the preparation process comprises the following steps: S1, preparation of pretreated biomass; s2, preparation of composite biochar; s3, preparation of sulfhydrylated biochar; s4, preparing the modified composite biochar; and S5, uniformly mixing the modified composite charcoal, kaolin, humic acid, fly ash, slaked lime and vermiculite to obtain the soil conditioner. According to the soil conditioner, modified composite biochar prepared through specific functionalization is blended with kaolin, humic acid, fly ash, slaked lime and vermiculite according to a certain proportion, and the prepared soil conditioner has unique advantages in the aspects of improving soil organic matter, fixing carbon, providing microelements and especially regulating and controlling the activity of soil microorganisms; advanced complementation and synergistic interaction of all the components are achieved, and the comprehensive treatment requirement of complex degraded soil can be better met.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil improvement, and in particular relates to a preparation process of a soil conditioner and its application in soil improvement. Background Art

[0002] Soil provides fertility and a living environment for crop growth. As a complex ecosystem, soil has been severely degraded by excessive agricultural development, construction projects, and natural disasters, leading to the destruction of soil structure and deterioration of its physical and chemical properties. This degradation not only reduces soil fertility but also diminishes its water retention capacity and biodiversity. In particular, soil acidification, compaction, and a decrease in organic matter content adversely impact the normal growth of crops. Soil acidification, in particular, exacerbates soil acidity, causing a decrease in the content of numerous soil nutrients and a decline in soil fertility, severely impacting crop yield and quality.

[0003] To address the problem of soil degradation, various soil improvement measures can be taken, such as applying organic or inorganic fertilizers, using lime to adjust soil pH, and introducing probiotic microorganisms. Although these methods can improve soil quality, most of them have problems such as high cost, short-term effects, or easy negative impacts on the environment. Soil conditioners can improve soil structure, improve soil physical and chemical properties, enrich soil nutrients, enhance soil water and fertilizer retention capacity, increase soil biological activity, and maintain soil ecological balance. Currently used soil conditioners include organic, inorganic chemical, and biological types. However, most current soil conditioners are single-type components, so the effect of soil improvement is not ideal.

[0004] In the prior art, Chinese patent application CN114507531A discloses a tea garden acidic soil conditioner and improvement process. The soil conditioner is made of the following raw materials by weight: 10-20 parts of dolomite powder, 40-60 parts of modified biochar, 5-10 parts of humic acid, 5-10 parts of earthworm castings, 5-10 parts of organic fertilizer, 6-12 parts of composite bacterial agent, 3-8 parts of nitrification inhibitor, and 10-15 parts of lignin super absorbent resin. This soil conditioner can effectively improve the fertility of the soil and solve the problem of insufficient soil water retention capacity, and inhibit the reduction of soil base saturation; at the same time, the soil improvement process provided by the present invention can further alleviate soil acidification, improve the root micro-zone soil microenvironment, and thus improve the quality of tea. However, this patent only targets acidic soil in tea gardens, and it solves the problems of soil pH and water retention capacity, and cannot adjust the activity of microorganisms in the soil. Chinese patent application CN108409488A discloses an acidifying soil conditioner comprising the following raw materials by weight: 10-20 parts soybean meal, 15-30 parts humic acid, 8-15 parts manure, 5-17 parts crop straw, 3-10 parts corn flour, 3-5 parts polyacrylamide, 3-8 parts wheat bran, 5-25 parts rapeseed cake, 10-30 parts bentonite, 8-25 parts wood ash, 1.3-2.3 parts biological agent, 3-9 parts mushroom residue, and 3-15 parts tea-processing waste. However, with the increasing problem of soil acidification, this acidifying soil conditioner still fails to meet demand, leaving room for further improvement. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a preparation process of a soil conditioner and its application in soil improvement. The soil conditioner can adjust the pH value of acidic soil, effectively improve soil porosity, and prevent soil compaction; increase the organic matter content in the soil and enhance the activity of microorganisms in the soil, while also having the effect of carbon sequestration, thereby significantly improving the physical and chemical properties of the soil.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A preparation process of a soil conditioner comprises the following steps:

[0008] S1. Add biomass powder to a sodium hydroxide solution, adjust the pH to 4-6 after soaking, then add tannic acid and stir. After stirring, filter, dry, and grind. Then, soak in a glutaraldehyde solution for 5 minutes, filter, and heat-treat to obtain pretreated biomass.

[0009] S2. Add the pretreated biomass in step S1 to deionized water, then add manganese nitrate and ferric nitrate, stir evenly, then add ammonia water to carry out a hydrothermal reaction, and after the reaction is completed, filter, wash, dry, and calcine to obtain composite biochar;

[0010] S3, adding the composite biochar prepared in step S2 to an ethanol aqueous solution, and then adding γ-mercaptopropyltrimethoxysilane, stirring and reacting, and filtering, washing, and drying after the reaction is completed to obtain thiolated biochar;

[0011] S4, adding the thiolated biochar prepared in step S3 to toluene, followed by adding methyl 5-allyl-3-methoxysalicylate and azobisisobutyronitrile, and reacting at a constant temperature. After the reaction is completed, filtering, washing, and drying to obtain a modified composite biochar;

[0012] S5. Evenly mix the modified composite biochar, kaolin, humic acid, fly ash, slaked lime, and vermiculite to obtain the soil conditioner.

[0013] Preferably, the biomass powder in step S1 is one or more of rice straw, corn straw, wheat straw or sorghum straw, the mass concentration of the sodium hydroxide solution is 3-4%, the mass concentration of the hydrochloric acid is 5%, the temperature of the immersion treatment is 30-40°C, and the time is 2-3h.

[0014] Preferably, in step S1, the mass ratio of the biomass powder, sodium hydroxide, and tannic acid is 80-90:1000-1200:15-20, the stirring temperature is 40-50°C, the speed is 100-150r / min, the time is 3-4h, the mass concentration of the glutaraldehyde solution is 5%, the heat treatment temperature is 100-120°C, and the time is 30-40min.

[0015] In the present invention, the biomass powder is treated with alkali solution immersion, which effectively destroys the dense structure of the plant fiber, increases the specific surface area and exposes more active functional groups. Tannic acid is then added and adsorbed onto the surface of the activated biomass. The biomass is then immersed in a glutaraldehyde solution. After heat treatment, a certain degree of cross-linking occurs between the biomass and the tannic acid molecules, which greatly enhances the adhesion of the tannic acid to the biomass and prevents the tannic acid from being separated from the biomass during the subsequent hydrothermal reaction. On the one hand, tannic acid contains a large number of phenolic hydroxyl groups and multiple benzene rings. The phenolic hydroxyl groups have the ability to complex metal ions, which helps to load minerals in the subsequent steps. At the same time, tannic acid also promotes the formation of aromatic carbon structures during the pyrolysis process, which can improve the long-term stability, carbon fixation capacity, structural improvement durability, water and nutrient retention capacity and pollutant adsorption and fixation capacity of the modified composite biochar in the soil conditioner.

[0016] Preferably, the mass fraction of the ammonia water in step S2 is 5-8%, the mass ratio of the pretreated biomass, deionized water, manganese nitrate, iron nitrate, and ammonia water is 90-100:1200-1500:20-25:15-20:50-60, the temperature of the hydrothermal reaction is 120-140°C, and the time is 2-4h.

[0017] Preferably, the calcination process in step S2 is: under a nitrogen atmosphere, the temperature is raised to 400-500°C at a heating rate of 5-8°C, kept warm for 1-2 hours, and then the temperature is raised to 600-700°C at a heating rate of 2-3°C, kept warm for 3-4 hours.

[0018] In the present invention, pretreated biomass is co-precipitated with manganese nitrate and ferric nitrate under the condition of adjusting the pH value with ammonia water. Through hydrothermal treatment and step-by-step calcination, the in-situ, uniform loading and high dispersion of manganese and iron oxide nanoparticles in the biochar matrix are achieved. The prepared composite biochar not only has a porous structure and the characteristics of biochar itself, but also has good soil structure improvement and carbon sequestration capabilities. Moreover, the loaded iron and manganese oxides may play a certain catalytic or auxiliary adsorption role in the transformation or degradation of certain soil pollutants, thereby improving the comprehensive function of the improver.

[0019] Preferably, in step S3, the mass ratio of the composite biochar to γ-mercaptopropyltrimethoxysilane is 60-70:5-8, the temperature of the stirring reaction is 60-70° C., and the time is 1-2 h.

[0020] In the present invention, γ-mercaptopropyltrimethoxysilane is used to perform surface functionalization on the composite biochar, so that thiol functional groups are introduced into the composite biochar, providing reactive sites for subsequent chemical reactions.

[0021] Preferably, in step S4, the mass ratio of the thiolated biochar, 5-allyl-3-methoxysalicylic acid methyl ester, and azobisisobutyronitrile is 60-70:6-9:0.2-0.3; the temperature of the isothermal reaction is 80-90° C., and the time is 2-3 h.

[0022] In the present invention, azobisisobutyronitrile is used as an initiator, and a "thiol-ene" click chemistry reaction is used to covalently link the 5-allyl-3-methoxysalicylic acid methyl ester molecule with the composite biochar, thereby stably fixing the compound on the biochar. After the soil conditioner is applied to the soil, it can continuously and long-term stimulate the growth and activity of beneficial microbial communities in the soil, increase the number and diversity of beneficial microorganisms, and further promote the decomposition of soil organic matter, the circulation and effectiveness of nutrients, and the absorption of nutrients by plants, ultimately helping to improve soil health and crop productivity.

[0023] Preferably, the mass ratio of the modified composite biochar, kaolin, humic acid, fly ash, slaked lime and vermiculite in step S5 is 40-50:20-30:15-25:5-10:3-5:25-35.

[0024] In the present invention, modified composite biochar prepared with specific functionalization is physically blended with traditional soil improvement materials such as kaolin, humic acid, fly ash, slaked lime, vermiculite, etc. in a certain proportion, so that the prepared soil improver has unique advantages in increasing soil organic matter, fixing carbon, providing trace elements, and especially regulating soil microbial activity. At the same time, it also has the functions of increasing soil porosity, preventing compaction, regulating pH, and enhancing water and fertilizer retention capacity, etc., realizing the complementary advantages and synergistic effect between the components, making the improvement effect of the obtained soil improver more comprehensive and more significant, and better meeting the comprehensive management needs of complex degraded soils.

[0025] The present invention also protects a soil conditioner prepared by the above-mentioned preparation process.

[0026] The present invention also protects the use of the soil conditioner as described above in improving soil.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The preparation process of the soil conditioner provided by the present invention is as follows: first, the biomass powder is soaked in alkali solution, then tannic acid is added, and then immersed in glutaraldehyde solution. After heat treatment, a certain degree of cross-linking occurs between the biomass and the tannic acid molecules, which greatly enhances the adhesion of tannic acid on the biomass, not only laying a foundation for the subsequent uniform loading of metal ions and the regulation of the pore structure of biochar, but also the introduction of tannic acid is conducive to improving the aromatization degree and chemical stability of the composite biochar, improving the surface chemical properties of the composite biochar material, thereby enhancing the utilization value of the biomass raw materials and the modified composite biochar. The performance potential of biochar was investigated. The pretreated biomass was then co-precipitated with manganese nitrate and ferric nitrate under the condition of adjusting the pH with ammonia water. Hydrothermal treatment and step-by-step calcination were used to achieve in situ, uniform loading and high dispersion of manganese and iron oxide nanoparticles in the biochar matrix. The obtained composite biochar not only has a porous structure, but also has good soil structure improvement and carbon fixation capabilities. The presence of iron and manganese oxides may locally change the soil pH, ionic strength or redox conditions, thereby indirectly affecting the abundance and activity of specific microbial populations, significantly improving the overall effectiveness of the soil conditioner.

[0029] (2) The preparation process of the soil conditioner provided by the present invention is to modify the composite biochar using γ-mercaptopropyltrimethoxysilane, and then introduce 5-allyl-3-methoxysalicylic acid methyl ester into the composite biochar by chemical grafting. Compared with the traditional method of adding free microbial agents or simply mixing organic matter, this method of immobilizing signal molecules enables the modified biochar to continuously and fixedly display these chemical signals on its surface and surrounding microenvironment after being applied to the soil, and to serve as a long-term signal source to attract, screen or stimulate the colonization and metabolic activity of specific beneficial microorganisms in the soil. It not only overcomes the problems of low survival rate of exogenous agents and easy loss and degradation of signal molecules, but also can more sustainably and effectively improve the microecological flora in the soil, promote the biological effectiveness of nutrients, and fundamentally improve the biological fertility and health level of the soil.

[0030] (3) The preparation process of the soil conditioner provided by the present invention is to physically blend the modified composite biochar that has undergone multi-step functional modification with traditional soil improvement materials such as kaolin, humic acid, fly ash, slaked lime, and vermiculite in a certain proportion. The soil conditioner fully exerts the synergistic effect. The modified composite biochar has its unique core functions of increasing organic matter, long-term carbon fixation, pollutant fixation, and continuous regulation of soil microbial communities through grafting signal molecules. It synergizes with kaolin, humic acid, fly ash, slaked lime, vermiculite and other components to improve the physical structure of the soil, regulate the soil pH, and enhance the water and fertilizer retention capacity, so that the final soil conditioner is significantly improved in terms of the comprehensiveness, efficiency and durability of the improvement effect, and can more effectively deal with complex soil degradation problems. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from commercially purchased raw materials.

[0033] Example 1

[0034] A preparation process of a soil conditioner comprises the following steps:

[0035] S1. Add 850 g of rice straw powder to 11 L of 3.5% sodium hydroxide solution, soak at 35° C. for 2.5 h, add 5% hydrochloric acid to adjust the pH to 5, then add 180 g of tannic acid, stir at 45° C. and 130 rpm for 3.5 h, filter, dry, and grind. Then, soak in 5% glutaraldehyde solution for 5 min, filter, and heat-treat at 110° C. for 35 min to obtain pretreated biomass.

[0036] S2. Add 950 g of the pretreated biomass in step S1 to 14 kg of deionized water, then add 230 g of manganese nitrate and 180 g of ferric nitrate, stir evenly, add 550 g of 7% ammonia water, and hydrothermally react at 130 ° C for 3 hours. After the reaction is completed, filter, wash, dry, and calcine. The calcination process is as follows: under a nitrogen atmosphere, increase the temperature to 450 ° C at a heating rate of 6 ° C, keep warm for 1.5 hours, then increase the temperature to 650 ° C at a heating rate of 2.5 ° C, and keep warm for 3.5 hours to obtain composite biochar;

[0037] S3, adding 650g of the composite biochar prepared in step S2 to 10L of ethanol aqueous solution (the volume ratio of ethanol to water is 3:1), then adding 70g of γ-mercaptopropyltrimethoxysilane, stirring and reacting at 65°C for 1.5h. After the reaction is completed, filtering, washing, and drying to obtain thiolated biochar;

[0038] S4. Add 650 g of the thiolated biochar in step S3 to 10 L of toluene, followed by adding 75 g of methyl 5-allyl-3-methoxysalicylate and 2.5 g of azobisisobutyronitrile. The mixture is reacted at 85 °C in a nitrogen atmosphere for 2.5 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain a modified composite biochar.

[0039] S5. By weight, 45 parts of the modified composite biochar in step S4, 25 parts of kaolin, 20 parts of humic acid, 8 parts of fly ash, 4 parts of slaked lime, and 30 parts of vermiculite are mixed evenly to obtain the soil conditioner.

[0040] Example 2

[0041] A preparation process of a soil conditioner comprises the following steps:

[0042] S1. 800 g corn straw powder was added to 10 L of 3% sodium hydroxide solution, and the mixture was immersed at 30° C. for 3 h. Then, 5% hydrochloric acid was added to adjust the pH to 6. Then, 150 g of tannic acid was added, and the mixture was stirred at 40° C. and 100 rpm for 4 h. The mixture was filtered, dried, and ground. The mixture was then immersed in 5% glutaraldehyde solution for 5 min, filtered, and heat-treated at 100° C. for 40 min to obtain pretreated biomass.

[0043] S2. Add 900 g of the pretreated biomass in step S1 to 12 kg of deionized water, then add 200 g of manganese nitrate and 150 g of ferric nitrate, stir evenly, add 500 g of 5% ammonia water, and hydrothermally react at 120 ° C for 4 h. After the reaction is completed, filter, wash, dry, and calcine. The calcination process is as follows: under a nitrogen atmosphere, increase the temperature to 400 ° C at a heating rate of 5 ° C, keep warm for 2 h, then increase the temperature to 600 ° C at a heating rate of 2 ° C, and keep warm for 4 h to obtain composite biochar;

[0044] S3, adding 600g of the composite biochar prepared in step S2 to 10L of ethanol aqueous solution (the volume ratio of ethanol to water is 3:1), then adding 50g of γ-mercaptopropyltrimethoxysilane, stirring and reacting at 60°C for 2h, filtering, washing, and drying after the reaction is completed to obtain thiolated biochar;

[0045] S4. Add 600 g of thiolated biochar from step S3 to 10 L of toluene, followed by 60 g of methyl 5-allyl-3-methoxysalicylate and 2 g of azobisisobutyronitrile. The mixture is reacted at 80° C. under a nitrogen atmosphere for 3 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain a modified composite biochar.

[0046] S5. By weight, 40 parts of the modified composite biochar in step S4, 20 parts of kaolin, 15 parts of humic acid, 5 parts of fly ash, 3 parts of slaked lime, and 25 parts of vermiculite are mixed evenly to obtain the soil conditioner.

[0047] Example 3

[0048] A preparation process of a soil conditioner comprises the following steps:

[0049] S1. 900 g of wheat straw powder was added to 12 L of 4% sodium hydroxide solution, and the mixture was immersed at 40° C. for 2 h. Then, 5% hydrochloric acid was added to adjust the pH to 4. 200 g of tannic acid was then added, and the mixture was stirred at 50° C. and 150 rpm for 3 h. The mixture was filtered, dried, and ground. The mixture was then immersed in 5% glutaraldehyde solution for 5 min, filtered, and heat-treated at 120° C. for 30 min to obtain pretreated biomass.

[0050] S2. Add 1000 g of the pretreated biomass in step S1 to 15 kg of deionized water, then add 250 g of manganese nitrate and 200 g of ferric nitrate, stir evenly, add 600 g of 8% ammonia water, and hydrothermally react at 140° C. for 2 h. After the reaction is completed, filter, wash, dry, and calcine. The calcination process is as follows: under a nitrogen atmosphere, increase the temperature to 500° C. at a heating rate of 8° C., keep warm for 1 h, then increase the temperature to 700° C. at a heating rate of 3° C., and keep warm for 3 h to obtain composite biochar;

[0051] S3, adding 700g of the composite biochar prepared in step S2 to 10L of ethanol aqueous solution (the volume ratio of ethanol to water is 3:1), then adding 80g of γ-mercaptopropyltrimethoxysilane, stirring and reacting at 70°C for 1h. After the reaction is completed, filtering, washing, and drying to obtain thiolated biochar;

[0052] S4. Add 700 g of the thiolated biochar in step S3 to 10 L of toluene, followed by adding 90 g of methyl 5-allyl-3-methoxysalicylate and 3 g of azobisisobutyronitrile. The mixture is reacted at 90 °C in a nitrogen atmosphere for 2 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain a modified composite biochar.

[0053] S5. By weight, 50 parts of the modified composite biochar in step S4, 30 parts of kaolin, 25 parts of humic acid, 10 parts of fly ash, 5 parts of slaked lime, and 35 parts of vermiculite are mixed evenly to obtain the soil conditioner.

[0054] Comparative Example 1

[0055] A preparation process of a soil conditioner comprises the following steps:

[0056] S1. Add 850 g of rice straw powder to 11 L of 3.5% sodium hydroxide solution, soak at 35° C. for 2.5 h, add 5% hydrochloric acid to adjust the pH to 5, then filter, wash, and dry to obtain pretreated biomass;

[0057] S2. Add 950 g of the pretreated biomass in step S1 to 14 kg of deionized water, then add 230 g of manganese nitrate and 180 g of ferric nitrate, stir evenly, add 550 g of 7% ammonia water, and hydrothermally react at 130 ° C for 3 hours. After the reaction is completed, filter, wash, dry, and calcine. The calcination process is as follows: under a nitrogen atmosphere, increase the temperature to 450 ° C at a heating rate of 6 ° C, keep warm for 1.5 hours, then increase the temperature to 650 ° C at a heating rate of 2.5 ° C, and keep warm for 3.5 hours to obtain composite biochar;

[0058] S3, adding 650g of the composite biochar prepared in step S2 to 10L of ethanol aqueous solution (the volume ratio of ethanol to water is 3:1), then adding 70g of γ-mercaptopropyltrimethoxysilane, stirring and reacting at 65°C for 1.5h. After the reaction is completed, filtering, washing, and drying to obtain thiolated biochar;

[0059] S4. Add 650 g of the thiolated biochar in step S3 to 10 L of toluene, followed by adding 75 g of methyl 5-allyl-3-methoxysalicylate and 2.5 g of azobisisobutyronitrile. The mixture is reacted at 85 °C in a nitrogen atmosphere for 2.5 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain a modified composite biochar.

[0060] S5. By weight, 45 parts of the modified composite biochar in step S4, 25 parts of kaolin, 20 parts of humic acid, 8 parts of fly ash, 4 parts of slaked lime, and 30 parts of vermiculite are mixed evenly to obtain the soil conditioner.

[0061] Compared with Example 1, tannic acid was not introduced into the biomass in step S1 of this comparative example.

[0062] Comparative Example 2

[0063] A preparation process of a soil conditioner comprises the following steps:

[0064] S1. Add 850 g of rice straw powder to 11 L of 3.5% sodium hydroxide solution, soak at 35° C. for 2.5 h, add 5% hydrochloric acid to adjust the pH to 5, then add 180 g of tannic acid, stir at 45° C. and 130 rpm for 3.5 h, filter, dry, and grind. Then, soak in 5% glutaraldehyde solution for 5 min, filter, and heat-treat at 110° C. for 35 min to obtain pretreated biomass.

[0065] S2. calcining 950 g of the pretreated biomass in step S1. The calcination process is as follows: under a nitrogen atmosphere, raising the temperature to 450° C. at a heating rate of 6° C., holding the temperature for 1.5 h, then raising the temperature to 650° C. at a heating rate of 2.5° C., holding the temperature for 3.5 h, to obtain composite biochar;

[0066] S3, adding 650g of the composite biochar prepared in step S2 to 10L of ethanol aqueous solution (the volume ratio of ethanol to water is 3:1), then adding 70g of γ-mercaptopropyltrimethoxysilane, stirring and reacting at 65°C for 1.5h. After the reaction is completed, filtering, washing, and drying to obtain thiolated biochar;

[0067] S4. Add 650 g of the thiolated biochar in step S3 to 10 L of toluene, followed by adding 75 g of methyl 5-allyl-3-methoxysalicylate and 2.5 g of azobisisobutyronitrile. The mixture is reacted at 85 °C in a nitrogen atmosphere for 2.5 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain a modified composite biochar.

[0068] S5. By weight, 45 parts of the modified composite biochar in step S4, 25 parts of kaolin, 20 parts of humic acid, 8 parts of fly ash, 4 parts of slaked lime, and 30 parts of vermiculite are mixed evenly to obtain the soil conditioner.

[0069] Compared with Example 1, this comparative example did not introduce iron and manganese oxides onto the biochar.

[0070] Comparative Example 3

[0071] A preparation process of a soil conditioner comprises the following steps:

[0072] S1. Add 850 g of rice straw powder to 11 L of 3.5% sodium hydroxide solution, soak at 35° C. for 2.5 h, add 5% hydrochloric acid to adjust the pH to 5, then add 180 g of tannic acid, stir at 45° C. and 130 rpm for 3.5 h, filter, dry, and grind. Then, soak in 5% glutaraldehyde solution for 5 min, filter, and heat-treat at 110° C. for 35 min to obtain pretreated biomass.

[0073] S2. Add 950 g of the pretreated biomass in step S1 to 14 kg of deionized water, then add 230 g of manganese nitrate and 180 g of ferric nitrate, stir evenly, add 550 g of 7% ammonia water, and hydrothermally react at 130 ° C for 3 hours. After the reaction is completed, filter, wash, dry, and calcine. The calcination process is as follows: under a nitrogen atmosphere, increase the temperature to 450 ° C at a heating rate of 6 ° C, keep warm for 1.5 hours, then increase the temperature to 650 ° C at a heating rate of 2.5 ° C, and keep warm for 3.5 hours to obtain composite biochar;

[0074] S3, adding 650g of the composite biochar prepared in step S2 to 10L of ethanol-water solution (the volume ratio of ethanol to water is 3:1), then adding 70g of γ-mercaptopropyltrimethoxysilane, stirring and reacting at 65°C for 1.5h. After the reaction is completed, filtering, washing, and drying to obtain modified composite biochar;

[0075] S4. By weight, 45 parts of the modified composite biochar in step S3, 25 parts of kaolin, 20 parts of humic acid, 8 parts of fly ash, 4 parts of slaked lime, and 30 parts of vermiculite are mixed evenly to obtain the soil conditioner.

[0076] Compared with Example 1, in this comparative example, 5-allyl-3-methoxysalicylic acid methyl ester was not introduced into the composite biochar.

[0077] The soil conditioner prepared in Examples 1-3 and Comparative Examples 1-3 was applied to improve acidified soil. The physical and chemical properties of the soil are shown in Table 1 below. A total of 7 groups were set up, the blank group was not applied with soil conditioner, and the remaining 6 groups were applied with the soil conditioner prepared in Examples 1-3 and Comparative Examples 1-3, respectively. Specifically, the soil was deep plowed and loosened to break the soil to a depth of 20 cm, and then the soil conditioner was applied at a dosage of 50 kg per mu. The soil and the soil conditioner were mixed evenly by plowing and stirring, and then field management was carried out in a conventional manner. After three months of improvement, soil in the 10 cm tillage layer was randomly collected from five sampling points in each group. The following indicators of the cultivated soil before and after soil improvement were measured to evaluate the composite amendments of each group. The total porosity of the soil before and after improvement was determined by the ring knife method; soil dehydrogenase was determined by the triphenyltetrazolium chloride (TTC) method: expressed as the mass (μg) of triphenylformamide (TPF) formed in 1 g of soil after 24 hours; soil neutral phosphatase was determined by the disodium phenyl phosphate colorimetric method: expressed as the mass (μg) of triphenylformamide (TPF) formed in 1 g of soil after 24 hours; and soil neutral phosphatase was determined by the disodium phenyl phosphate colorimetric method: expressed as the mass (μg) of triphenylformamide (TPF) formed in 1 g of soil after 24 hours. The mass (mg) of phenol released and converted into phosphorus (P) is expressed; soil carbon sequestration (SOCS) is the difference between the soil carbon pool before and after improvement, SOCS = SOCP2-SOCP1, that is: where SOCP2 is the soil carbon pool after improvement, kg; SOCP1 is the soil carbon pool before improvement, kg; soil carbon pool (SOCP) is calculated according to the following formula: SOCP = SOC×BD×A×H, where SOCP is the soil carbon pool, kg; SOC is the soil organic carbon content, g·kg -1 BD is soil bulk density, g·cm -3 ; A is the soil area, m 2 ; H is the tillage depth, which is 0.2m in the present invention. The test results are shown in Table 2 below.

[0078] Table 1 Physical and chemical properties of soil

[0079]

[0080] Table 2

[0081]

[0082] As can be seen from Table 2 above, the soil conditioner prepared by the present invention has a good improvement effect, can adjust the pH value of acidic soil, effectively improve soil porosity, and prevent soil compaction; increase the organic matter content in the soil and enhance the activity of microorganisms in the soil, while also having a carbon sequestration effect, thereby significantly improving the physical and chemical properties of the soil.

[0083] The above content is a further detailed description of the present invention in combination with specific implementation examples. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

[0084] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A preparation process of a soil conditioner, characterized in that: The following steps are involved: S1. Add biomass powder to a sodium hydroxide solution, adjust the pH to 4-6 after soaking, then add tannic acid and stir. After stirring, filter, dry, and grind. Then, soak in a glutaraldehyde solution for 5 minutes, filter, and heat-treat to obtain pretreated biomass. S2. Add the pretreated biomass to deionized water, then add manganese nitrate and ferric nitrate, stir evenly, then add ammonia water to carry out a hydrothermal reaction. After the reaction is completed, filter, wash, dry, and calcine to obtain composite biochar; S3, adding the composite biochar to an ethanol aqueous solution, and then adding γ-mercaptopropyltrimethoxysilane, stirring and reacting to obtain thiol-modified biochar; S4, adding the thiol-modified biochar to toluene, and then adding methyl 5-allyl-3-methoxysalicylate and azobisisobutyronitrile, and reacting at a constant temperature to obtain a modified composite biochar; S5. Evenly mix the modified composite biochar, kaolin, humic acid, fly ash, slaked lime, and vermiculite to obtain the soil conditioner.

2. The preparation process according to claim 1, characterized in that In step S1, the biomass powder is one or more of rice straw, corn straw, wheat straw or sorghum straw, the mass concentration of the sodium hydroxide solution is 3-4%, the temperature of the immersion treatment is 30-40° C., and the time is 2-3 hours.

3. The preparation process according to claim 1, characterized in that In step S1, the mass ratio of the biomass powder, sodium hydroxide, and tannic acid is 80-90:1000-1200:15-20, the stirring temperature is 40-50°C, the rotation speed is 100-150r / min, the time is 3-4h, the mass concentration of the glutaraldehyde solution is 5%, the heat treatment temperature is 100-120°C, and the time is 30-40min.

4. The preparation process according to claim 1, characterized in that The mass fraction of the ammonia water in step S2 is 5-8%, the mass ratio of the pretreated biomass, deionized water, manganese nitrate, iron nitrate and ammonia water is 90-100:1200-1500:20-25:15-20:50-60, the temperature of the hydrothermal reaction is 120-140° C., and the time is 2-4 hours.

5. The preparation process according to claim 1, characterized in that: The calcination process in step S2 is as follows: in a nitrogen atmosphere, the temperature is raised to 400-500° C. at a heating rate of 5-8° C., kept at this temperature for 1-2 hours, and then the temperature is raised to 600-700° C. at a heating rate of 2-3° C., kept at this temperature for 3-4 hours.

6. The preparation process according to claim 1, characterized in that In step S3, the mass ratio of the composite biochar to γ-mercaptopropyltrimethoxysilane is 60-70:5-8, the stirring reaction temperature is 60-70° C., and the time is 1-2 hours.

7. The preparation process according to claim 1, characterized in that In step S4, the mass ratio of the thiolated biochar, 5-allyl-3-methoxysalicylic acid methyl ester, and azobisisobutyronitrile is 60-70:6-9:0.2-0.3; the temperature of the isothermal reaction is 80-90° C., and the time is 2-3 hours.

8. The preparation process according to claim 1, characterized in that The mass ratio of the modified composite biochar, kaolin, humic acid, fly ash, slaked lime and vermiculite in step S5 is 40-50:20-30:15-25:5-10:3-5:25-35.

9. A soil conditioner prepared by the preparation process according to any one of claims 1 to 8.

10. Use of the soil conditioner according to claim 9 in improving soil.

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