Preparation process of soil conditioner and application thereof in soil improvement

Abstract

The application 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 mercapto biochar; S4, preparation of modified composite biochar; and S5, mixing of the modified composite biochar, kaolin, humic acid, fly ash, slaked lime and vermiculite to obtain the soil conditioner. The soil conditioner is prepared by blending the modified composite biochar with specific functions, the kaolin, the humic acid, the fly ash, the slaked lime and the vermiculite in a certain proportion, and the soil conditioner has unique advantages in improving soil organic matter, fixing carbon, providing trace elements and especially regulating soil microbial activity, realizes complementary advantages and synergistic effects among the components, and can better meet the comprehensive management requirements of complex degraded soil.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil improvement, and particularly relates to a preparation process of a soil improver and application of the soil improver in soil improvement. BACKGROUND

[0002] Soil provides fertility and living environment for crop growth. As a complex ecological system, soil structure is destroyed and physicochemical properties are deteriorated due to excessive agricultural development, engineering construction and natural disasters, resulting in serious soil degradation. Soil degradation not only reduces soil fertility, but also reduces the water retention capacity and biodiversity of soil, especially soil acidification, soil hardening and decrease of organic matter content, thereby adversely affecting the normal growth of crops. Among them, soil acidification aggravates the increase of soil acidity, causes the decrease of the content of a large number of soil nutrient elements, and reduces soil fertility, which seriously affects the yield and quality of crops.

[0003] In order to solve 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 effect or easy to have negative impact on the environment. Soil improver can improve soil structure, improve soil physicochemical properties, enrich soil nutrition, improve soil water and fertilizer retention capacity, improve soil biological activity and maintain soil ecological balance. At present, the types of soil improver include organic, inorganic chemical and biological. However, most of the current soil improvers are single component, so the effect of improving soil is not ideal.

[0004] In the prior art, Chinese patent application CN114507531A discloses a tea garden acidic soil conditioner and an improvement process. The soil conditioner is made of the following raw materials in parts 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 manure, 5-10 parts of organic fertilizer, 6-12 parts of compound microbial agent, 3-8 parts of nitrification inhibitor, and 10-15 parts of lignin superabsorbent resin. The soil conditioner can effectively improve the fertility of the soil and solve the problem of insufficient water retention capacity of the soil, and inhibit the reduction of soil base saturation. At the same time, through the soil improvement process provided by the application, the soil acidification can be further alleviated, the soil microenvironment of the root part can be improved, and the quality of tea leaves can be improved. However, the patent is only directed to the acidic soil of tea garden, and it solves the problem of soil pH and water retention capacity, and cannot adjust the activity of microorganisms in the soil. Chinese patent application CN108409488A discloses an acidified soil conditioner, which comprises the following raw materials in parts by weight: 10-20 parts of soybean meal, 15-30 parts of humic acid, 8-15 parts of manure, 5-17 parts of crop straw, 3-10 parts of corn flour, 3-5 parts of polyacrylamide, 3-8 parts of wheat bran, 5-25 parts of rapeseed cake, 10-30 parts of bentonite, 8-25 parts of wood ash, 1.3-2.3 parts of biological bacterial agent, 3-9 parts of mushroom residue, and 3-15 parts of tea making waste. However, with the increasingly prominent problem of soil acidification, the acidified soil conditioner still cannot meet the use requirements, and there is still room for further improvement. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application 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 the soil porosity, prevent soil compaction, increase the organic matter content in the soil, and improve the activity of microorganisms in the soil, while also having the effect of carbon sequestration, thereby significantly improving the physicochemical properties of the soil.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

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

[0008] S1, adding biomass powder into sodium hydroxide solution, adjusting the pH to 4-6 after immersion treatment, then adding tannic acid, stirring, filtering, drying, grinding, then filtering after immersion in glutaraldehyde solution for 5 min, and heat treating to obtain pretreated biomass;

[0009] S2, adding the pretreated biomass in step S1 into deionized water, then adding manganese nitrate and iron nitrate, stirring uniformly, adding ammonia water, and performing hydrothermal reaction, then filtering, washing, drying, and calcining to obtain composite biochar;

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

[0011] S4, adding the mercapto-modified biochar in step S3 into toluene, then adding 5-allyl-3-methoxysalicylic acid methyl ester and azobisisobutyronitrile, constant-temperature reacting, filtering, washing and drying after the reaction is completed to obtain modified composite biochar;

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

[0013] Preferably, 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 mass concentration of the hydrochloric acid is 5%, the temperature of the impregnation 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 temperature of the stirring is 40-50°C, the rotating speed is 100-150r / min, the time is 3-4h, the mass concentration of the glutaraldehyde solution is 5%, and the temperature of the heat treatment is 100-120°C, and the time is 30-40min.

[0015] In the present application, the biomass powder is subjected to alkali liquid impregnation treatment, which effectively destroys the dense structure of plant fibers, increases the specific surface area and exposes more active functional groups, then tannic acid is added to be adsorbed to the surface of the activated biomass, and then the biomass is immersed in a glutaraldehyde solution, and after heat treatment, a certain degree of cross-linking occurs between the biomass and tannic acid molecules, which greatly enhances the adhesion of tannic acid on the biomass, preventing tannic acid from separating from the biomass during the subsequent hydrothermal reaction process. On the one hand, tannic acid contains a large amount of phenolic hydroxyl groups and multiple benzene rings, and the phenolic hydroxyl groups have the ability to complex metal ions, which helps to load minerals in the subsequent step, and at the same time, tannic acid also promotes the formation of aromatic carbon structures during pyrolysis, which can improve the long-term stability, carbon sequestration capacity, structure 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, ferric nitrate and ammonia water is 90-100:1200-1500:20-25:15-20:50-60, and the temperature of the hydrothermal reaction is 120-140℃ and the time is 2-4h.

[0017] Preferably, the calcination process in step S2 is as follows: under a nitrogen atmosphere, the temperature is raised to 400-500℃ at a heating rate of 5-8℃, and then the temperature is raised to 600-700℃ at a heating rate of 2-3℃, and the temperature is maintained for 3-4h.

[0018] In the present application, the pretreated biomass is co-precipitated with manganese nitrate and ferric nitrate under the condition of ammonia water adjusting pH, and through hydrothermal treatment and step-by-step calcination, the in-situ and uniform loading and high dispersion of manganese and iron oxide nanoparticles in the biochar matrix are realized. 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 capacity. 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 soil amendment.

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

[0020] In the present application, the surface of the composite biochar is functionalized by γ-mercaptopropyltrimethoxysilane, so that mercapto functional groups are introduced onto the composite biochar, thereby providing reactive sites for subsequent chemical reactions.

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

[0022] In the present application, azobisisobutyronitrile is used as an initiator to covalently link 5-allyl-3-methoxysalicylic acid methyl ester molecules to the composite biochar through "thiol-ene" click chemistry, thereby stably fixing the compound on the biochar. After the soil amendment is applied to the soil, it can continuously stimulate the growth and activity of beneficial microbial communities in the soil for a long time, thereby increasing the number and diversity of beneficial microorganisms, and further promoting the decomposition of soil organic matter, the circulation and availability of nutrients, and the absorption of nutrients by plants, thereby ultimately helping to improve the soil health level 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 application, the modified composite biochar prepared by specific functionalization is physically blended with traditional soil improvement materials such as kaolin, humic acid, fly ash, slaked lime and vermiculite in a certain proportion, so that the prepared soil conditioner has unique advantages in improving soil organic matter, carbon sequestration, providing trace elements and especially regulating soil microbial activity, and also has the advantages of improving soil porosity, preventing compaction, adjusting pH, enhancing water and fertilizer retention capacity, etc., realizing the complementary advantages and synergistic effect of each component, so that the improvement effect of the obtained soil conditioner is more comprehensive and more significant, and can better meet the comprehensive management needs of complex degraded soil.

[0025] The present application also protects a soil conditioner prepared by the preparation process as described above.

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

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

[0028] (1) The preparation process of the soil conditioner provided by the present application first impregnates biomass powder with alkaline solution, then adds tannic acid, and then immerses it in glutaraldehyde solution. After heat treatment, a certain degree of crosslinking occurs between the biomass and the tannic acid molecules, greatly enhancing the adhesion strength of the tannic acid on the biomass. Not only does it lay the foundation for the uniform loading of metal ions and the regulation of the pore structure of the biochar, but also the introduction of tannic acid helps to improve the degree of aromaticity and chemical stability of the composite biochar, and improves the surface chemical properties of the composite biochar material, thereby enhancing the utilization value of the biomass raw material and the performance potential of the modified composite biochar. Subsequently, the pretreated biomass is co-precipitated with manganese nitrate and iron nitrate under the condition of ammonia water adjusted pH, and is subjected to hydrothermal treatment and step-by-step calcination, realizing the 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 sequestration capacity. 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 comprehensive performance of the soil conditioner.

[0029] (2) The preparation process of the soil conditioner provided by the application, then the composite biochar is modified by using γ-mercaptopropyl trimethoxysilane, and 5-allyl-3-methoxysalicylic acid methyl ester is introduced onto the composite biochar by chemical grafting. Compared with the traditional method of adding free microbial inoculants or simply mixing organic matter, this method of immobilizing signal molecules enables the modified biochar to continuously and specifically display these chemical signals on its surface and in the surrounding microenvironment after being applied to the soil, thereby serving as a long-acting signal source to attract, screen or stimulate the colonization and metabolic activity of specific beneficial microorganisms in the soil. This method not only overcomes the problems of low survival rate of exogenous inoculants and easy loss and degradation of signal molecules, but also more effectively and durably improves the microecological flora in the soil and promotes the biological effectiveness of nutrients, thereby fundamentally improving the biological fertility and health level of the soil.

[0030] (3) The preparation process of the soil conditioner provided by the application, finally the modified composite biochar modified by multi-step functionalization is physically blended with kaolin, humic acid, fly ash, slaked lime, vermiculite and other traditional soil improvement materials in a certain proportion. The soil conditioner fully exhibits a synergistic effect. The modified composite biochar has the core functions of increasing organic matter, long-acting carbon sequestration, fixing pollutants and especially continuously regulating the soil microbial community by grafting signal molecules. The kaolin, humic acid, fly ash, slaked lime, vermiculite and other components synergistically improve the soil physical structure, regulate the soil pH, and enhance the water and fertilizer retention capacity, so that the final soil conditioner is significantly improved in comprehensiveness, efficiency and durability of the improvement effect, and can more effectively cope with complex soil degradation problems. DETAILED DESCRIPTION

[0031] The technical solutions of the application will be described below in detail with reference to the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0032] Unless otherwise specified, the chemical reagents and materials in the application are purchased through market channels or synthesized from raw materials purchased through market channels.

[0033] Example 1

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

[0035] S1, 850 g of rice straw powder was added to 11 L of 3.5% by mass sodium hydroxide solution, and after immersion treatment at 35℃ for 2.5 h, 5% by mass hydrochloric acid was added to adjust the pH to 5, then 180 tannic acid was added, and stirred at 45℃ and 130 r / min for 3.5 h, filtered, dried, ground, then filtered after immersion in 5% by mass glutaraldehyde solution for 5 min, and heat treated at 110℃ for 35 min to obtain pretreated biomass;

[0036] S2, 950 g of pretreated biomass in step S1 was added to 14 kg of deionized water, then 230 g of manganese nitrate, 180 g of ferric nitrate was added, stirred uniformly, then 550 g of 7% by mass ammonia water was added, and hydrothermal reaction was carried out at 130℃ for 3 h, after the reaction was completed, filtration, washing, drying and calcination were carried out, the calcination process was as follows: under nitrogen atmosphere, the temperature was raised to 450℃ at a heating rate of 6℃, and kept for 1.5 h, then the temperature was raised to 650℃ at a heating rate of 2.5℃, and kept for 3.5 h, to obtain composite biochar;

[0037] S3, 650 g of composite biochar in step S2 was added to 10 L of ethanol aqueous solution (volume ratio of ethanol to water was 3:1), then 70 g of γ-mercaptopropyl trimethoxysilane was added, and stirred at 65℃ for 1.5 h, after the reaction was completed, filtration, washing and drying were carried out to obtain mercaptanized biochar;

[0038] S4, 650 g of mercaptanized biochar in step S3 was added to 10 L of toluene, then 75 g of 5-allyl-3-methoxysalicylic acid methyl ester, 2.5 g of azobisisobutyronitrile was added, and constant temperature reaction was carried out at 85℃ for 2.5 h under nitrogen atmosphere, after the reaction was completed, filtration, washing and drying were carried out to obtain modified composite biochar;

[0039] S5, 45 parts of 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, 30 parts of vermiculite were mixed uniformly, to obtain the soil conditioner.

[0040] Example 2

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

[0042] S1, 800 g of corn straw powder was added to 10 L of 3% by mass sodium hydroxide solution, and after immersion treatment at 30℃ for 3 h, 5% by mass hydrochloric acid was added to adjust the pH to 6, then 150 tannic acid was added, and stirred at 40℃ and 100 r / min for 4 h, filtered, dried, ground, then filtered after immersion in 5% by mass glutaraldehyde solution for 5 min, and heat treated at 100℃ for 40 min to obtain pretreated biomass;

[0043] S2, 900g of the pretreated biomass in step S1 was added to 12kg of deionized water, then 200g of manganese nitrate, 150g of ferric nitrate was added, after stirring uniformly, 500g of 5% mass fraction of ammonia water was added, and hydrothermal reaction was carried out at 120℃ for 4h, after the reaction was completed, filtration, washing, drying and calcination were carried out, the calcination process was as follows: under the atmosphere of nitrogen, the temperature was increased to 400℃ at the rate of 5℃, and the temperature was kept for 2h, then the temperature was increased to 600℃ at the rate of 2℃, and the temperature was kept for 4h, to obtain the composite biochar;

[0044] S3, 600g of the composite biochar in step S2 was added to 10L of ethanol aqueous solution (the volume ratio of ethanol to water was 3:1), then 50g of γ-mercaptopropyl trimethoxysilane was added, and stirring reaction was carried out at 60℃ for 2h, after the reaction was completed, filtration, washing and drying were carried out, to obtain the mercapto-modified biochar;

[0045] S4, 600g of the mercapto-modified biochar in step S3 was added to 10L of toluene, then 60g of 5-allyl-3-methoxysalicylic acid methyl ester, 2g of azobisisobutyronitrile was added, and constant temperature reaction was carried out at 80℃ under the atmosphere of nitrogen for 3h, after the reaction was completed, filtration, washing and drying were carried out, to obtain the modified composite biochar;

[0046] S5, 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, 25 parts of vermiculite were mixed uniformly, to obtain the soil conditioner.

[0047] Example 3

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

[0049] S1, 900g of wheat straw powder was added to 12L of 4% mass concentration of sodium hydroxide solution, after immersion treatment at 40℃ for 2h, 5% mass concentration of hydrochloric acid was added to adjust the pH to 4, then 200g of tannic acid was added, stirring was carried out at 50℃ and 150r / min for 3h, then filtration, drying and grinding were carried out, then after immersion in 5% mass concentration of glutaraldehyde solution for 5min, filtration was carried out, and heat treatment was carried out at 120℃ for 30min, to obtain pretreated biomass;

[0050] S2, 1000g of the pretreated biomass in step S1 was added to 15kg of deionized water, then 250g of manganese nitrate, 200g of ferric nitrate was added, after stirring uniformly, 600g of 8% mass fraction of ammonia water was added, and hydrothermal reaction was carried out at 140℃ for 2h, after the reaction was completed, filtration, washing, drying and calcination were carried out, the calcination process was as follows: under the atmosphere of nitrogen, the temperature was increased to 500℃ at the rate of 8℃, and the temperature was kept for 1h, then the temperature was increased to 700℃ at the rate of 3℃, and the temperature was kept for 3h, to obtain the composite biochar.

[0051] S3, 700 g of the composite biochar in step S2 was added into 10 L of an ethanol aqueous solution (the volume ratio of ethanol to water was 3:1), then 80 g of γ-mercaptopropyltrimethoxysilane was added, and the reaction was stirred at 70°C for 1 h. After the reaction was completed, filtration, washing, and drying were performed to obtain mercaptide biochar;

[0052] S4, 700 g of the mercaptide biochar in step S3 was added into 10 L of toluene, then 90 g of 5-allyl-3-methoxysalicylic acid methyl ester and 3 g of azobisisobutyronitrile were added, and the reaction was performed at 90°C for 2 h under a nitrogen atmosphere. After the reaction was completed, filtration, washing, and drying were performed to obtain modified composite biochar;

[0053] S5, 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 were uniformly mixed to obtain the soil conditioner.

[0054] Comparative Example 1

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

[0056] S1, 850 g of rice straw powder was added into 11 L of a sodium hydroxide solution with a mass concentration of 3.5%, and the mixture was immersed and treated at 35°C for 2.5 h. Then, hydrochloric acid with a mass concentration of 5% was added to adjust the pH to 5. Subsequently, filtration, washing, and drying were performed to obtain pretreated biomass.

[0057] S2, 950 g of the pretreated biomass in step S1 was added into 14 kg of deionized water, then 230 g of manganese nitrate and 180 g of iron nitrate were added, and the mixture was stirred uniformly. Then, 550 g of ammonia water with a mass fraction of 7% was added, and the mixture was hydrothermally reacted at 130°C for 3 h. After the reaction was completed, filtration, washing, and drying were performed, and the calcination process was as follows: under a nitrogen atmosphere, the temperature was increased to 450°C at a heating rate of 6°C, and the temperature was maintained for 1.5 h. Then, the temperature was increased to 650°C at a heating rate of 2.5°C, and the temperature was maintained for 3.5 h to obtain composite biochar.

[0058] S3, 650 g of the composite biochar in step S2 was added into 10 L of an ethanol aqueous solution (the volume ratio of ethanol to water was 3:1), then 70 g of γ-mercaptopropyltrimethoxysilane was added, and the reaction was stirred at 65°C for 1.5 h. After the reaction was completed, filtration, washing, and drying were performed to obtain mercaptide biochar.

[0059] S4, 650 g of the thiolated biochar in step S3 was added into 10 L of toluene, then 75 g of 5-allyl-3-methoxysalicylic acid methyl ester and 2.5 g of azobisisobutyronitrile were added, and the reaction was carried out at 85°C under a nitrogen atmosphere for 2.5 h. After the reaction was completed, filtration, washing and drying were performed to obtain the modified composite biochar;

[0060] S5, 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 were uniformly mixed to obtain the soil conditioner.

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

[0062] Comparative Example 2

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

[0064] S1, 850 g of rice straw powder was added into 11 L of a sodium hydroxide solution with a mass concentration of 3.5%, and was immersed and treated at 35°C for 2.5 h. Then, the pH was adjusted to 5 by adding a hydrochloric acid solution with a mass concentration of 5%. Then, 180 g of tannic acid was added, and stirring was carried out at 45°C and 130 r / min for 3.5 h. Filtration, drying and grinding were performed, then the pretreated biomass was obtained by filtering after being immersed in a glutaraldehyde solution with a mass concentration of 5% for 5 min and being heat-treated at 110°C for 35 min.

[0065] S2, 950 g of the pretreated biomass in step S1 was calcined. The calcination process was as follows: the temperature was increased to 450°C at a heating rate of 6°C under a nitrogen atmosphere, and was kept for 1.5 h. Then, the temperature was increased to 650°C at a heating rate of 2.5°C, and was kept for 3.5 h to obtain the composite biochar.

[0066] S3, 650 g of the composite biochar in step S2 was added into 10 L of an ethanol aqueous solution (the volume ratio of ethanol to water was 3:1), then 70 g of γ-mercaptopropyltrimethoxysilane was added, and the reaction was carried out at 65°C for 1.5 h. After the reaction was completed, filtration, washing and drying were performed to obtain the thiolated biochar.

[0067] S4, 650 g of the thiolated biochar in step S3 was added into 10 L of toluene, then 75 g of 5-allyl-3-methoxysalicylic acid methyl ester and 2.5 g of azobisisobutyronitrile were added, and the reaction was carried out at 85°C under a nitrogen atmosphere for 2.5 h. After the reaction was completed, filtration, washing and drying were performed to obtain the modified composite biochar.

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

[0069] Compared with Example 1, the present comparative example does not introduce iron and manganese oxides on the biochar.

[0070] Comparative Example 3

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

[0072] S1, 850g of rice straw powder is added to 11L of 3.5% mass concentration sodium hydroxide solution, and after immersion treatment at 35℃ for 2.5h, 5% mass concentration hydrochloric acid is added to adjust the pH to 5, then 180 tannic acid is added, and stirred at 45℃ and 130r / min for 3.5h, filtered, dried, ground, then filtered after immersion in 5% mass concentration glutaraldehyde solution for 5min, and heat treated at 110℃ for 35min to obtain pretreated biomass;

[0073] S2, 950g of the pretreated biomass in step S1 is added to 14kg of deionized water, then 230g of manganese nitrate and 180g of iron nitrate are added, stirred uniformly, then 550g of 7% mass fraction ammonia water is added, and hydrothermally reacted at 130℃ for 3h, and after the reaction is completed, filtered, washed, dried and calcined, the calcination process is as follows: under nitrogen atmosphere, the temperature is raised to 450℃ at a heating rate of 6℃, and kept for 1.5h, then the temperature is raised to 650℃ at a heating rate of 2.5℃, and kept for 3.5h, to obtain composite biochar;

[0074] S3, 650g of the composite biochar in step S2 is added to 10L of ethanol aqueous solution (volume ratio of ethanol to water is 3:1), then 70g of γ-mercaptopropyltrimethoxysilane is added, and stirred at 65℃ for 1.5h, and after the reaction is completed, filtered, washed and dried to obtain modified composite biochar;

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

[0076] Compared with Example 1, the present comparative example does not introduce 5-allyl-3-methoxysalicylic acid methyl ester on the composite biochar.

[0077] The soil improver prepared from Examples 1-3 and Comparative Examples 1-3 is applied to acidification soil improvement, and the soil physical and chemical properties are as shown in Table 1, a total of 7 groups are set, the blank group is not applied with the soil improver, and the remaining 6 groups are respectively applied with the soil improver prepared from Examples 1-3 and Comparative Examples 1-3, specifically as follows: the soil is treated by deep ploughing and deep scarifying, the soil breaking depth is 20 cm, then the soil improver is applied, the use amount is 50 kg per mu, the soil and the soil improver are mixed uniformly by ploughing and stirring, and then the field management is carried out in a conventional manner. After 3 months of improvement, 10 cm plough layer soil is randomly taken from 5 collection points in each group, the following indexes of the plough layer soil before and after the improvement are determined, and the composite improver of each group is evaluated; wherein the total porosity of the soil before and after the improvement is determined by the cutting ring method; the soil dehydrogenase is determined by the method of chlorinated triphenyl tetrazolium (TTC), and is expressed by the mass (μg) of triphenylformazan (TPF) formed in 1 g of soil after 24 h; the soil neutral phosphatase is determined by the method of benzenedipotassium phosphate colorimetry, and is expressed by the mass (mg) of phenol released and converted into phosphorus (P) in 1 g of soil after 24 h; the soil carbon sequestration (SOCS) is the difference between the soil carbon pool before and after the improvement, SOCS = SOCP2-SOCP1, that is: in the formula, SOCP2 is the soil carbon pool after the improvement, kg; SOCP1 is the soil carbon pool before the improvement, kg; the soil carbon pool (SOCP) is calculated according to the following formula: SOCP = SOC x BD x A x H, in the formula, SOCP is the soil carbon pool, kg; SOC is the soil organic carbon content, g·kg -1 ; BD is the soil bulk density, g·cm -3 ; A is the soil area, m 2 ; H is the plough layer depth, and the present application takes 0.2 m. The test results are as shown in Table 2.

[0078] Table 1 Soil physical and chemical properties

[0079]

[0080] Table 2

[0081]

[0082] As can be seen from Table 2, the soil improver prepared by the present application has good improvement effect, can adjust the pH value of the acid soil, effectively improve the soil porosity, prevent the soil from being hardened, increase the organic matter content in the soil and improve the activity of the microorganisms in the soil, and also has the effect of carbon sequestration, thereby significantly improving the physical and chemical properties of the soil.

[0083] The above is a further detailed description of the present application in combination with specific implementation examples, and cannot be deemed to limit the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field of the present application, some simple deductions or replacements can be made without departing from the concept of the present application, and all of them shall be deemed to fall within the protection scope of the present application.

[0084] Those skilled in the art will easily understand that the above is only a preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A preparation process for a soil conditioner, characterized in that, Includes the following steps: S1. Add biomass powder to sodium hydroxide solution, impregnate and adjust pH to 4-6, then add tannic acid and stir. After stirring, filter, dry and grind, then impregnate in glutaraldehyde solution for 5 minutes and filter. Perform heat treatment 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. Add the composite biochar to an ethanol aqueous solution, then add γ-mercaptopropyltrimethoxysilane, and stir to react to obtain thiolized biochar. S4. Add mercapto-modified biochar to toluene, then add methyl 5-allyl-3-methoxysalicylate and azobisisobutyronitrile, and carry out a constant temperature reaction to obtain modified composite biochar. S5. Mix the modified composite biochar, kaolin, humic acid, fly ash, quicklime, and vermiculite evenly to obtain the soil conditioner. In step S1, the mass ratio of biomass powder, sodium hydroxide, and tannic acid is 80-90:1000-1200:15-20. The stirring temperature is 40-50℃, the stirring speed is 100-150 r / min, and the time is 3-4 h. The mass concentration of the glutaraldehyde solution is 5%. The heat treatment temperature is 100-120℃, and the time is 30-40 min.

2. The preparation process according to claim 1, characterized in that, The biomass powder mentioned 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 temperature of the impregnation treatment is 30-40℃, and the time is 2-3h.

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

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

5. 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, and the stirring reaction temperature is 60-70℃ for 1-2 hours.

6. The preparation process according to claim 1, characterized in that, In step S4, the mass ratio of thiolated biochar, methyl 5-allyl-3-methoxysalicylate, and azobisisobutyronitrile is 60-70:6-9:0.2-0.3; the isothermal reaction is carried out at a temperature of 80-90℃ for 2-3 hours.

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

8. A soil conditioner prepared by the preparation process according to any one of claims 1-7.

9. The application of the soil conditioner as described in claim 8 in soil improvement.

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