A soil conditioner for saline-alkali soil improvement and a method for preparing the same

Abstract

The application discloses a soil conditioner for saline-alkali soil improvement and a preparation method thereof, and belongs to the technical field of saline-alkali soil improvement. The soil conditioner is prepared by taking a light / biological double-degradation foaming carrier as a base body, filling the base body with microcapsules with a core-shell structure, filling the microcapsules with organic matter fulvic acid and humic acid, and covering the surface of the light / biological double-degradation foaming carrier with a microgel film. The structure has good slow-release effect on organic matter. The hydroxyl group of a biological-based polyurethane monomer castor oil polyether polyol is bonded with the silicon hydroxyl group of modified nano titanium dioxide obtained by treatment of gamma-aminopropyl triethoxysilane, so that the nano titanium dioxide is loaded in the biological-based polyurethane foaming material. The light / biological double-degradation foaming carrier can be decomposed by light degradation and biological degradation. The chitosan and potassium alginate of the shell body of the microcapsule are natural materials, and the soil conditioner has good degradability when applied in soil.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of saline-alkali soil improvement, and particularly relates to a soil conditioner for saline-alkali soil improvement and a preparation method thereof. BACKGROUND

[0002] The saline-alkali soil has the characteristics of high salt content, easy compaction, poor structure, low organic matter content, and weak water and fertilizer storage capacity, which determines that it is extremely difficult to use in agriculture during the process from reclamation to desalination to normal soil. Meanwhile, improper agricultural utilization methods make the soil salinization have a recurrence. The saline-alkali soil is a widely existing form of land degradation in the world, especially in arid and semi-arid regions. The formation of the saline-alkali soil is mainly due to the accumulation of salt in the soil, which can seriously affect the soil structure, reduce the soil fertility, limit the growth of plants, and eventually lead to the decrease of agricultural yield. The treatment of the saline-alkali soil is a complex and challenging task, which involves the improvement of soil physical properties, the reduction of salt content, and the enhancement of soil biological activity.

[0003] At present, the biological method is considered to be the most effective and safe method in the saline-alkali soil improvement technology. By introducing salt-tolerant plants or microorganisms, the accumulation of soil organic matter and the diversity of microorganisms are promoted. This method is environmentally friendly and sustainable, but the existing biological conditioner has a slow action speed, an unobvious effect, and a large limitation under environmental conditions.

[0004] A saline-alkali soil conditioner and a special microcapsule type organic acid slow-release preparation thereof are disclosed in Chinese Patent No. CN105001876B. The slow-release preparation is prepared by taking an acrylic polymer as a capsule wall and taking an organic acid as a capsule core to form a microcapsule type. However, the acrylic polymer in the scheme is usually a synthetic macromolecular material, and the degradation speed thereof in the natural environment is relatively slow. Due to the stability of the molecular structure and the lack of effective microbial enzymes in the natural environment, the acrylic polymer is easy to remain in the soil for a long time, which changes the soil structure and has a potential negative impact on the soil ecosystem. SUMMARY

[0005] The application aims to provide a soil conditioner for saline-alkali soil improvement and a preparation method thereof, which is based on a light / biological double-degradation foaming carrier, filled with microcapsules with a core-shell structure, filled with organic yellow humic acid and humic acid in the microcapsules, and covered with a microgel film on the surface of the light / biological double-degradation foaming carrier, which has a good slow-release effect on organic matter; the modified nano-titanium dioxide obtained by treatment with gamma-aminopropyl triethoxysilane contains silicon hydroxyl groups, which are bonded with the hydroxyl groups of the bio-based castor oil polyether polyol monomer, so that the nano-titanium dioxide is loaded in the bio-based polyurethane foaming material; the light / biological double-degradation foaming carrier can be promoted to decompose through light degradation and biological degradation, and the chitosan and potassium alginate of the microcapsule shell are natural materials, so that the soil conditioner has good degradability when applied in soil.

[0006] The application can be achieved by the following technical scheme: a preparation method of a soil conditioner for saline-alkali soil improvement, comprising the following steps:

[0007] Step one: add the microcapsule compound, light / biological double-degradation foaming carrier and deionized water into a reaction kettle, ultrasonic dispersion for 40-60 min, stirring at 20-25 DEG C and 400-500 r / min for 2-3 h, then add potassium alginate and 1-2 wt.% glutaraldehyde solution, continue to stir and crosslink for 20-30 min, filter, wash the filter cake with ionized water and anhydrous ethanol for 2-3 times respectively, and vacuum dry at 60-80 DEG C for 1-2 h to obtain a double-assembled microcapsule carrier compound.

[0008] Step two: add N-isopropyl acrylamide and N,N'-methylene bispropylamide into a reaction kettle, stirring at 20-25 DEG C and 400-500 r / min for 20-30 min, then add sodium dodecyl sulfate and deionized water, heat to 40-50 DEG C, continue to stir for 20-30 min, pass in ammonia gas at a flow rate of 10-12 min / L for 30-40 min, heat to 70-80 DEG C, add ammonium persulfate, continue to stir under nitrogen atmosphere for 6-7 h, then add the double-assembled microcapsule carrier compound into the reaction kettle, continue to stir for 20-30 min, filter, wash the filter cake with petroleum ether and ionized water for 2-3 times respectively, and vacuum dry at 60-80 DEG C for 1-2 h to obtain a soil conditioner for saline-alkali soil improvement.

[0009] Further, the amount ratio of the microcapsule compound, light / biological double-degradation foaming carrier, deionized water, potassium alginate and glutaraldehyde solution in step one is 2-2.5 kg: 2-3 kg: 3-4 L: 2-2.5 kg: 0.4-0.5 L.

[0010] Further, the use amount ratio of N-isopropyl acrylamide, N,N'-methylene bispropylamide, sodium dodecyl sulfate, deionized water, ammonium persulfate and double-assembly microcapsule carrier complex in step two is 3-4 kg: 1.2-1.5 kg: 0.1-0.2 kg: 3-4 L: 0.4-0.5 L: 2-3 kg.

[0011] Further, the microcapsule complex in step one is prepared by the following steps:

[0012] The magnetized modified zeolite powder, fulvic acid, humic acid and deionized water are added into the reaction kettle, ultrasonic dispersion is carried out for 40-60 min, vacuum impregnation is carried out at 20-25 ℃ and 400-500 r / min for 20-30 min, then the chitosan solution is added into the reaction kettle, ultrasonic dispersion is carried out at 40-45 ℃ for 40-60 min, the potassium chloride solution with a concentration of 0.5-0.6 mol / L is added to adjust the pH value to 5.5-6, and centrifugation is carried out at 1000-1200 r / min for 5-6 min to obtain the first assembly coated microcapsule complex.

[0013] Further, the chitosan solution is obtained by stirring and mixing chitosan and 1-2% glacial acetic acid solution according to a use amount ratio of 4-5 kg: 7.5-8.5 L.

[0014] Further, the use amount ratio of magnetized modified zeolite powder, fulvic acid, humic acid, deionized water, chitosan solution and potassium chloride solution is 3-4 kg: 0.5-0.7 kg: 0.3-0.5 kg: 3-4 L: 8-9 L: 0.5-0.6 L.

[0015] Further, the magnetized modified zeolite powder is prepared by the following steps:

[0016] The zeolite powder, citric acid and deionized water are added into the reaction kettle, stirring is carried out at 50-55 ℃ and 400-500 r / min for 20-30 min, then the nano-ferroferric oxide particles are added, vacuum impregnation is carried out at 50-55 ℃ and 400-500 r / min for 2-3 h, filtration is carried out, the filter cake is washed with deionized water until the last washing liquid is neutral, and the magnetized modified zeolite powder is obtained.

[0017] Further, the use amount ratio of zeolite powder, citric acid, deionized water and nano-ferroferric oxide particles is 4-5 kg: 1-2 kg: 8-9 L: 0.8-1 kg.

[0018] Further, the light / biological double-degradation foaming carrier in step one is prepared by the following steps:

[0019] The castor oil polyether polyol, modified nano-titanium dioxide and deionized water are added into a reaction kettle, stirred at 20-25 DEG C and 400-500 r / min for 40-60 min, then triethylene diamine, dibutyl tin dilaurate, 1,4 butanediol as a chain extender and isocyanate are added, continue to stir for 40-60 min, inject into a mold, heated to 120-130 DEG C and stirred at 80-90 r / min for 10-12 min, mature, demould, naturally cooled to room temperature, vacuum dried at 60-80 DEG C for 1-2 h, crushed, the light / biological double-degradable foaming carrier with a particle size of 0.5-0.7 mm is obtained.

[0020] Further, the use amount ratio of the castor oil polyether polyol, modified nano-titanium dioxide, deionized water, triethylene diamine, dibutyl tin dilaurate, 1,4 butanediol and isocyanate is 14-15 L: 5-6 kg: 20-25 L: 0.1-0.2 kg: 0.2-0.3 L: 0.1-0.2 L: 0.3-0.4 L.

[0021] Further, the modified nano-titanium dioxide powder is prepared by the following steps:

[0022] The nano-titanium dioxide powder with a particle size of 40-50 nm and anhydrous ethanol are added into a reaction kettle, ultrasonic dispersion is carried out for 10-20 min, stirred at 80-85 DEG C and 400-500 r / min for 1-2 h, gamma-aminopropyl triethoxysilane is added, continue to stir for 1-2 h, filtration, the filter cake is washed with ion water and anhydrous ethanol for 2-3 times respectively, vacuum dried at 60-80 DEG C for 1-2 h, the modified nano-titanium dioxide powder treated by silane coupling agent is obtained.

[0023] Further, the use amount ratio of the nano-titanium dioxide powder, anhydrous ethanol and gamma-aminopropyl triethoxysilane is 3-4 kg: 8-9 L: 800-900 mL.

[0024] The beneficial effects of the application are:

[0025] 1, the soil conditioner for saline-alkali soil improvement prepared by the application takes the light / biological double-degradable foaming carrier as a matrix, fills the double-assembled microcapsules with core-shell structure in the inside, fills the organic matter fulvic acid and humic acid in the double-assembled microcapsules, and covers a layer of microgel film on the surface of the light / biological double-degradable foaming carrier, the structure has good slow-release effect on the organic matter and has good water-retention capacity. The foaming carrier and the microgel film show water absorption and swelling, after water absorption and swelling, a porous structure is formed in the soil, the PH, air permeability and water permeability of the soil are reduced, the hardening phenomenon is alleviated, the porous structure can provide a good parasitic environment for soil microorganisms, and the porous structure has rich pores and large specific surface area, can provide more adsorption sites, and thus the adsorption capacity of nano-magnetic iron oxide on heavy metals is improved.

[0026] 2、The double-assembly microcapsule carrier complex of the present application, after the magnetized modified zeolite powder is treated by citric acid etching, the surface is rough and porous and carries negative carboxyl groups, which crosslink with the positive amino groups in the chitosan molecular chain to assemble, after the first assembly is completed, the microcapsule complex is dispersed in the potassium alginate aqueous solution, and the carboxyl groups in the potassium alginate molecular chain complete the second crosslinking assembly, forming a core-shell microcapsule with a polyelectrolyte film on the surface of the modified zeolite, the shell is potassium alginate, has a large number of carboxyl groups, and the light / biological double-degradation foaming carrier is loaded with modified nano titanium dioxide treated by a silane coupling agent, which can fix the microcapsule by using the amino groups on the surface of the nano titanium dioxide, realizing the stable and long-acting release of organic matter.

[0027] 3、The microcapsule complex of the present application, by filling nano magnetite particles into the internal pores of the zeolite, the nano magnetite particles are positively charged under acidic conditions, the magnetized modified zeolite powder, fulvic acid and humic acid are dispersed in deionized water, the specific adsorption of the positive charge of the nano magnetite particles to the negative charge of the fulvic acid and humic acid is realized, so as to fix the fulvic acid and humic acid in the internal voids, and then crosslink with the positive amino groups in the chitosan molecular chain to assemble, the porous nature can improve the adsorption of nano magnetite to heavy metals in soil.

[0028] 4、The light / biological double-degradation foaming carrier of the present application, by mixing castor oil polyether polyol, nano titanium dioxide and deionized water, the prepolymer formed is polymerized and foamed under the action of initiator, catalyst and chain extender, to obtain a light / biological double-degradation foaming carrier; the hydroxyl groups of the bio-based polyurethane monomer castor oil polyether polyol are bonded with the silicon hydroxyl groups of the modified nano titanium dioxide obtained by treating with γ-aminopropyl triethoxysilane, so that the nano titanium dioxide is loaded in the bio-based polyurethane foaming material; the light / biological double-degradation foaming carrier can be decomposed by promoting decomposition through photodegradation and biodegradation, and has good degradability when applied in soil as a soil conditioner. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] Embodiment 1: A preparation method of a soil conditioner for saline-alkali soil improvement, comprising the following steps:

[0031] S1: 3 kg of nano-titanium dioxide powder with a particle size of 40-50 nm and 8 L of anhydrous ethanol were added to a reaction kettle, ultrasonic dispersion was performed for 10 min, stirring was performed at 80 °C and 400 r / min for 1 h, 800 mL of γ-aminopropyl triethoxysilane was added, and stirring was continued for 1 h, filtration was performed, the filter cake was washed with ionized water and anhydrous ethanol for 2 times respectively, and vacuum drying was performed at 60 °C for 1 h to obtain modified nano-titanium dioxide powder treated by silane coupling agent.

[0032] S2: 14 L of castor oil polyether polyol, 5 kg of modified nano-titanium dioxide and 20 L of deionized water were added to a reaction kettle, stirring was performed at 20 °C and 400 r / min for 40 min, then 0.1 kg of triethylene diamine, 0.2 L of dibutyl tin dilaurate, 0.1 L of 1,4-butanediol as a chain extender and 0.3 L of isocyanate were added, stirring was continued for 40 min, injection was performed, heating was performed to 120 °C and stirring was performed at 80 r / min for 10 min, curing was performed, demolding was performed, natural cooling was performed to room temperature, vacuum drying was performed at 60 °C for 1 h, and crushing was performed to obtain a light / biological double-degradable foaming carrier with a particle size of 0.5-0.7 mm.

[0033] The castor oil polyether polyol, nano-titanium dioxide and deionized water are mixed to form a prepolymer, which is polymerized and foamed under the action of an initiator, a catalyst and a chain extender to obtain a light / biological double-degradable foaming carrier; the hydroxyl groups of the bio-based polyurethane monomer castor oil polyether polyol are bonded with the silicon hydroxyl groups of the modified nano-titanium dioxide obtained by treatment with γ-aminopropyl triethoxysilane, so that the nano-titanium dioxide is loaded in the bio-based polyurethane foaming material; the light / biological double-degradable foaming carrier can promote decomposition through photodegradation and biodegradation, and has good degradability when applied in soil as a soil conditioner.

[0034] S3: 4 kg of zeolite powder, 1 kg of citric acid and 8 L of deionized water were added to a reaction kettle, stirring was performed at 50 °C and 400 r / min for 20 min, then 0.8 kg of nano-magnetite particles were added, vacuum impregnation was performed at 50 °C and 400 r / min for 2 h, and filtration was performed, the filter cake was washed with deionized water until the last washing liquid was neutral, and a magnetized modified zeolite powder was obtained.

[0035] The zeolite powder and nano-magnetite particles are dispersed in deionized water for impregnation, and the nano-magnetite particles are filled into the internal pores of the zeolite through physical adsorption.

[0036] S4: 3 kg of modified zeolite powder, 0.5 kg of fulvic acid, 0.3 kg of humic acid and 3 L of deionized water were added to the reaction kettle, ultrasonic dispersion for 40 min, vacuum immersion at 20℃ and 400 r / min for 20 min, then 8 L of chitosan solution was added to the reaction kettle, ultrasonic dispersion at 40℃ for 40 min, then 0.5 L of 0.5 mol / L potassium chloride solution was added to adjust the pH value to 5.5, and centrifugation was carried out at 1000 r / min for 5 min to obtain the first assembled coated microcapsule composite.

[0037] S5: 2 kg of microcapsule composite, 2 kg of light / biological double-degradable foaming carrier and 3 L of deionized water were added to the reaction kettle, ultrasonic dispersion for 40 min, stirring at 20℃ and 400 r / min for 2 h, then 2 kg of potassium alginate and 0.4 L of 1% glutaraldehyde solution were added, and crosslinking was continued for 20 min, then filtration was carried out, the filter cake was washed with ionized water and anhydrous ethanol for 2 times respectively, and vacuum drying was carried out at 60℃ for 1 h to obtain the double-assembled microcapsule carrier composite.

[0038] After the magnetized modified zeolite powder is treated by citric acid etching, the surface is rough and porous and carries negative carboxyl groups, which are crosslinked and assembled with the positively charged amino groups in the chitosan molecular chain. After the first assembly is completed, it is dispersed in a potassium alginate aqueous solution, and the second crosslinking assembly is completed with the carboxyl groups in the potassium alginate molecular chain to form a core-shell type microcapsule with a polyelectrolyte film on the surface of the modified zeolite.

[0039] The negatively charged fulvic acid and humic acid in the assembly process can be combined with the positively charged amino groups in the chitosan molecular chain, which is not conducive to the formation of the core-shell structure. By filling the nano-magnetite particles into the internal pores of the zeolite, the nano-magnetite particles are positively charged under acidic conditions. The magnetized modified zeolite powder, fulvic acid and humic acid are dispersed in deionized water, and the specific adsorption of the positively charged nano-magnetite particles to the negative charges of the fulvic acid and humic acid is used to fix the fulvic acid and humic acid in the internal voids, thereby avoiding affecting the formation of the core-shell structure and avoiding the shedding of the fulvic acid and humic acid due to physical adsorption.

[0040] The shell of the double-assembled microcapsule carrier composite is potassium alginate, which has a large number of carboxyl groups, and the light / biological double-degradable foaming carrier has a modified nano-titanium dioxide treated by a silane coupling agent on the surface, which can be used to fix the microcapsule by using the amino groups on the surface of the nano-titanium dioxide.

[0041] S6: 3 kg of N-isopropyl acrylamide, 1.2 kg of N,N'-methylene bispropylamide were added into a reaction kettle, stirred at 20℃ and 400 r / min for 20 min, then 0.1 kg of sodium dodecyl sulfate and 3 L of deionized water were added, heated to 40℃, and stirred for 20 min, ammonia gas was introduced at a flow rate of 10 min / L for 30 min, heated to 70℃, and 0.4 L of ammonium persulfate was added, and the reaction was continued under a nitrogen atmosphere for 6 h, then 2 kg of double-assembly microcapsule carrier complex was added into the reaction kettle, and stirred for 20 min, filtered, and the filter cake was washed with petroleum ether and ionized water for 2 times respectively, and vacuum dried at 60℃ for 1 h, to obtain a soil conditioner for saline-alkali soil improvement.

[0042] A mixture of poly-N-isopropyl acrylamide microgel and hydrogel was prepared by emulsion polymerization using N-isopropyl acrylamide, and a microgel film was obtained.

[0043] A soil conditioner for saline-alkali soil improvement has a light / biological double-degradable foaming carrier as a matrix, is filled with microcapsules with a core-shell structure inside, the microcapsules are filled with organic matter fulvic acid and humic acid, and a microgel film is covered on the surface of the light / biological double-degradable foaming carrier. The structure has good water retention capacity, the foaming carrier and the microgel film show water absorption and swelling, and after water absorption and swelling, a porous structure is formed in the soil, the air permeability and water permeability of the soil are increased, the hardening phenomenon is alleviated, and when the porous structure is used with microbial agents, a good parasitic environment is provided for soil microorganisms, and the porous structure can improve the adsorption capacity of nano-ferroferric oxide for heavy metals.

[0044] Example 2: A preparation method of a soil conditioner for saline-alkali soil improvement, comprising the following steps:

[0045] S1: 3.5 kg of nano-titanium dioxide powder with a particle size of 40-50 nm and 8.5 L of anhydrous ethanol were added into a reaction kettle, ultrasonic dispersion was performed for 15 min, stirring was performed at 82.5℃ and 450 r / min for 1.5 h, 850 mL of γ-aminopropyl triethoxysilane was added, and stirring was continued for 1.5 h, the filter cake was washed with ionized water and anhydrous ethanol for 2 times respectively, and vacuum drying was performed at 70℃ for 1.5 h, to obtain a modified nano-titanium dioxide powder treated with a silane coupling agent.

[0046] S2: 14.5 L castor oil polyether polyol, 5.5 kg modified nano titanium dioxide and 22.5 L deionized water were added into the reaction kettle, stirred at 22.5 ℃ and 450 r / min for 50 min, then 0.15 kg triethylene diamine, 0.25 L dibutyl tin dilaurate, 0.15 L 1,4-butanediol as chain extender and 0.35 L isocyanate were added, continued to stir for 50 min, injected into the mold, heated to 125 ℃ and stirred at 85 r / min for 11 min, cured, demolded, naturally cooled to room temperature, vacuum dried at 70 ℃ for 1.5 h, crushed, to obtain a light / biologically double-degradable foaming carrier with a particle size of 0.5-0.7 mm.

[0047] S3: 4.5 kg zeolite powder, 1.5 kg citric acid and 8.5 L deionized water were added into the reaction kettle, stirred at 52.5 ℃ and 450 r / min for 25 min, then 0.9 kg nano-magnetic iron oxide particles were added, vacuum impregnated at 52.5 ℃ and 450 r / min for 2.5 h, filtered, and the filter cake was washed with deionized water until the last washing liquid was neutral, to obtain a magnetically modified zeolite powder.

[0048] S4: 3.5 kg of magnetically modified zeolite powder, 0.6 kg of fulvic acid, 0.4 kg of humic acid and 3.5 L of deionized water were added into the reaction kettle, ultrasonic dispersed for 50 min, vacuum impregnated at 22.5 ℃ and 450 r / min for 25 min, then 8.5 L of chitosan solution was added into the reaction kettle, ultrasonic dispersed for 50 min at 42.5 ℃, then 0.55 L of potassium chloride solution with a concentration of 0.55 mol / L was added to adjust the pH value to 5.75, centrifuged at 1100 r / min for 5.5 min, to obtain a first assembled coated microcapsule composite.

[0049] S5: 2.25 kg of microcapsule composite, 2.5 kg of light / biologically double-degradable foaming carrier and 3.5 L of deionized water were added into the reaction kettle, ultrasonic dispersed for 50 min, stirred at 22.5 ℃ and 450 r / min for 2.5 h, then 2.25 kg of potassium alginate and 0.45 L of glutaraldehyde solution with a mass fraction of 1.5% were added, continued to stir for crosslinking for 25 min, filtered, the filter cake was washed with ionized water and anhydrous ethanol for 2 times respectively, vacuum dried at 70 ℃ for 1.5 h, to obtain a double-assembled microcapsule carrier composite.

[0050] S6: 3.5 kg of N-isopropyl acrylamide, 1.35 kg of N,N'-methylene bispropylamide were added into a reaction kettle, stirred at 22.5 ℃ and 450 r / min for 25 min, then 0.15 kg of sodium dodecyl sulfate and 3.5 L of deionized water were added, heated to 45 ℃, and stirred for another 25 min, 35 min of ammonia gas was introduced at a flow rate of 11 min / L, heated to 75 ℃, 0.45 L of ammonium persulfate was added, and the reaction was continued to stir for 6.5 h under a nitrogen atmosphere, then 2.5 kg of double-assembly microcapsule carrier complex was added into the reaction kettle, and stirred for another 25 min, filtered, the filter cake was washed with petroleum ether and ionized water for 2 times respectively, and vacuum dried at 70 ℃ for 1.5 h to obtain a soil conditioner for saline-alkali soil improvement.

[0051] Example 3: A preparation method of a soil conditioner for saline-alkali soil improvement, comprising the following steps:

[0052] S1: 4 kg of nano-titanium dioxide powder with a particle size of 40-50 nm and 9 L of anhydrous ethanol were added into a reaction kettle, ultrasonic dispersion was performed for 20 min, stirring was performed at 85 ℃ and 500 r / min for 2 h, 900 mL of γ-aminopropyl triethoxysilane was added, and stirring was continued for 2 h, the filter cake was washed with ionized water and anhydrous ethanol for 3 times respectively, and vacuum drying was performed at 80 ℃ for 2 h to obtain modified nano-titanium dioxide powder treated by silane coupling agent.

[0053] S2: 15 L of castor oil polyether polyol, 6 kg of modified nano-titanium dioxide and 25 L of deionized water were added into a reaction kettle, stirring was performed at 25 ℃ and 500 r / min for 60 min, then 0.2 kg of triethylene diamine, 0.3 L of dibutyl tin dilaurate, 0.2 L of 1,4-butanediol as a chain extender and 0.4 L of isocyanate were added, stirring was continued for 60 min, injection was performed, heating was performed to 130 ℃ and stirring was performed at 90 r / min for 12 min, curing was performed, demolding was performed, natural cooling was performed to room temperature, vacuum drying was performed at 80 ℃ for 2 h, and crushing was performed to obtain a light / biological double-degradable foaming carrier with a particle size of 0.5-0.7 mm.

[0054] S3: 5 kg of zeolite powder, 2 kg of citric acid and 9 L of deionized water were added into a reaction kettle, stirring was performed at 55 ℃ and 500 r / min for 30 min, then 1 kg of nano-magnetite particles were added, vacuum impregnation was performed at 55 ℃ and 500 r / min for 3 h, the filter cake was washed with deionized water until the last washing liquid was neutral, and a magnetized modified zeolite powder was obtained.

[0055] S4: 4 kg of magnetization modified zeolite powder, 0.7 kg of fulvic acid, 0.5 kg of humic acid and 4 L of deionized water were added to the reaction kettle, ultrasonic dispersion for 60 min, vacuum immersion at 25℃ and 500 r / min for 30 min, then 9 L of chitosan solution was added to the reaction kettle, ultrasonic dispersion at 45℃ for 60 min, then 0.6 L of 0.6 mol / L potassium chloride solution was added to adjust the pH value to 6, and centrifugation was carried out at 1200 r / min for 6 min to obtain the first assembled coated microcapsule composite.

[0056] S5: 2.5 kg of microcapsule composite, 3 kg of light / biological double-degradation foaming carrier and 4 L of deionized water were added to the reaction kettle, ultrasonic dispersion for 60 min, stirring at 25℃ and 500 r / min for 3 h, then 2.5 kg of potassium alginate and 0.5 L of 2% glutaraldehyde solution were added, and the crosslinking was continued for 30 min, filtration, and the filter cake was washed with ionized water and anhydrous ethanol for 3 times respectively, and vacuum drying at 80℃ for 2 h to obtain the double-assembled microcapsule carrier composite.

[0057] S6: 4 kg of N-isopropyl acrylamide and 1.5 kg of N,N'-methylene bispropylamide were added to the reaction kettle, stirring at 25℃ and 500 r / min for 30 min, then 0.2 kg of sodium dodecyl sulfate and 4 L of deionized water were added, heated to 50℃, and continued to stir for 30 min, then ammonia gas was introduced at a flow rate of 12 min / L for 40 min, heated to 80℃, and 0.5 L of ammonium persulfate was added, and the stirring was continued for 7 h under nitrogen atmosphere, then 3 kg of double-assembled microcapsule carrier composite was added to the reaction kettle, and the stirring was continued for 30 min, filtration, and the filter cake was washed with petroleum ether and ionized water for 3 times respectively, and vacuum drying at 80℃ for 2 h to obtain the soil conditioner for saline-alkali soil improvement.

[0058] Comparative Example 1: On the basis of Example 3, the modified nano-titanium dioxide in step S2 was replaced by the same amount of nano-titanium dioxide powder with a particle size of 40-50 nm in step S1, and the remaining steps were unchanged, to prepare the soil conditioner for saline-alkali soil improvement.

[0059] Comparative Example 2: On the basis of Example 3, no light / biological double-degradation foaming carrier was added in step S5, and the remaining steps were unchanged, to prepare the soil conditioner for saline-alkali soil improvement.

[0060] Comparative Example 3: On the basis of Example 3, the magnetization modified zeolite powder in step S4 was replaced by the same amount of zeolite powder in step S3, and the remaining steps were unchanged, to prepare the soil conditioner for saline-alkali soil improvement.

[0061] Comparative Example 4: On the basis of Example 3, the double-assembled microcapsule carrier complex in step S5 is directly used as a soil conditioner for saline-alkali soil improvement.

[0062] The soil conditioners for saline-alkali soil improvement prepared in Examples 1-3 and Comparative Examples 1-4 are subjected to performance testing in a saline-alkali area in the northeast of Suzhou City, Anhui Province. Two weeks before corn planting, the surface layer of the planting area is subjected to deep tillage treatment using deep tillage machinery. The surface layer of the deep tillage treatment has a depth of 23 cm, and the treatment is repeated 3 times. The soil conditioner is applied at a rate of 2 kg / mu, and reclamation is performed once after application, with a reclamation depth of 30 cm. The physicochemical properties of the soil before corn planting and at corn harvest are tested, 20 samples are taken from each test field, the average values of the physicochemical properties are calculated, and the content of heavy metal (cadmium) in the soil is measured. The results are shown in Table 1.

[0063] Table 1 Performance test table of soil conditioner for saline-alkali soil improvement

[0064]

[0065]

[0066] As can be seen from Table 1, the soil conditioners prepared in Examples 1-3 have significantly better organic matter, soil porosity and water absorption than the comparative examples after being applied to the soil, and have significantly lower water-soluble total salt, soil pH and cadmium content than the comparative examples. This shows that the soil conditioner prepared in the present application has a good slow-release effect on organic matter, excellent water absorption, can improve the pH of the soil and the porosity of the soil, and can remove heavy metals from the soil.

[0067] In Comparative Example 1, modified nano-titanium dioxide is replaced by nano-titanium dioxide powder, which is treated with a silane coupling agent. The nano-titanium dioxide can be loaded on the light / biological dual-degradable foaming carrier. The nano-titanium dioxide can promote the degradation of the light / biological dual-degradable foaming carrier, and the modified nano-titanium dioxide has a large number of amino groups on its surface that can bond with the carboxyl groups on the surface of the microcapsules, thereby fixing the microcapsules and achieving long-term slow release.

[0068] In Comparative Example 2, no light / biological dual-degradable foaming carrier is added. The light / biological dual-degradable foaming carrier has excellent water absorption capacity and large pores, and can load more microcapsules. The amino groups on the surface of the light / biological dual-degradable foaming carrier can bond with the carboxyl groups on the surface of the microcapsules, thereby fixing the microcapsules and achieving long-term slow release.

[0069] In the comparative example 3, the magnetization modified zeolite powder is replaced by zeolite powder, the surface of the magnetization modified zeolite powder is rough and porous and carries negative carboxyl groups after etching treatment by citric acid, the nano-Fe3O4 particles are filled into the internal pores of the zeolite, the nano-Fe3O4 particles are positively charged under acidic conditions, the magnetization modified zeolite powder, fulvic acid and humic acid are dispersed in deionized water, the specific adsorption of the positive charge of the nano-Fe3O4 particles to the negative charge of the fulvic acid and humic acid is used to realize the fixation of the fulvic acid and humic acid in the internal voids, so as to avoid affecting the formation of the core-shell structure.

[0070] In the comparative example 4, the double-assembly microcapsule carrier complex is directly used as a soil conditioner for saline-alkali soil improvement, a mixture of poly-N-isopropyl acrylamide microgel and hydrogel is prepared by emulsion polymerization using N-isopropyl acrylamide, a microgel film is obtained, the microgel film covers the surface of the photo / biological double-degradable foaming carrier, the pores of the microgel film are smaller than the pores of the foaming carrier, forming a layer of barrier to further improve the slow release of organic matter and the absorption of water.

[0071] It should be noted that, in this document, the terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0072] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a soil conditioner for improving saline-alkali soil, characterized in that: Includes the following steps Step 1: Add the microcapsule complex, the photo / biological dual-degradable foaming carrier and deionized water into a reactor, ultrasonically disperse for 40-60 minutes, stir at 20-25°C and 400-500 r / min for 2-3 hours, then add potassium alginate and 1-2wt% glutaraldehyde solution, continue stirring and cross-linking for 20-30 minutes, filter, wash the filter cake with deionized water and anhydrous ethanol for 2-3 times respectively, and vacuum dry to obtain a dual-assembled microcapsule carrier complex; Step 2: Add N-isopropylacrylamide and N,N'-methylenebispropylamide to a reactor, stir at 20-25°C and 400-500 r / min for 20-30 minutes, then add sodium lauryl sulfate and deionized water, heat to 40-50°C, continue stirring for 20-30 minutes, introduce ammonia gas at a flow rate of 10-12 min / L for 30-40 minutes, heat to 70-80°C, add ammonium persulfate, continue stirring and reacting under a nitrogen atmosphere for 6-7 hours, then add the double-assembled microcapsule carrier complex to the reactor, continue stirring for 20-30 minutes, filter, wash the filter cake with petroleum ether and deionized water for 2-3 times, respectively, and vacuum dry to obtain a soil conditioner for saline-alkali soil improvement; The microcapsule complex in step 1 is prepared by the following steps: The magnetized modified zeolite powder, fulvic acid, humic acid and deionized water were added to a reactor, ultrasonically dispersed for 40-60 minutes, and vacuum impregnated at 20-25°C and 400-500 r / min for 20-30 minutes. The chitosan solution was then added to the reactor, ultrasonically dispersed at 40-45°C for 40-60 minutes, and then a potassium chloride solution with a concentration of 0.5-0.6 mol / L was added to adjust the pH value to 5.5-6. The mixture was centrifuged at 1000-1200 r / min for 5-6 minutes to obtain a first assembled and coated microcapsule complex. The magnetized modified zeolite powder is prepared by the following steps: Add zeolite powder, citric acid and deionized water into a reactor, stir at 50-55°C and 400-500 rpm for 20-30 minutes, then add nano-ferroferric oxide particles, vacuum impregnate for 2-3 hours, filter, and wash the filter cake with deionized water until the last washing liquid is neutral to obtain magnetized modified zeolite powder; The photo / biologically degradable foaming carrier in step 1 is prepared by the following steps: Castor oil polyether polyol, modified nano titanium dioxide and deionized water are added to a reactor, stirred at 20-25°C and 400-500 r / min for 40-60 minutes, then triethylenediamine, dibutyltin dilaurate, 1,4-butanediol and isocyanate are added, and stirring is continued for 40-60 minutes. The mixture is injected into a mold, heated to 120-130°C and stirred at 80-90 r / min for 10-12 minutes, aged, demoulded, naturally cooled to room temperature, vacuum dried, and crushed to obtain a photo / biological dual-degradable foaming carrier with a particle size of 0.5-0.7 mm. The modified nano titanium dioxide powder is prepared by the following steps: Nano-titanium dioxide powder with a particle size of 40-50 nm and anhydrous ethanol are added to a reactor, ultrasonically dispersed for 10-20 minutes, stirred at 80-85°C and 400-500 r / min for 1-2 hours, γ-aminopropyltriethoxysilane is added, stirring is continued for 1-2 hours, filtered, and the filter cake is washed with deionized water and anhydrous ethanol for 2-3 times respectively, and vacuum dried to obtain modified nano-titanium dioxide powder treated with a silane coupling agent.

2. The method for preparing a soil conditioner for improving saline-alkali soil according to claim 1, wherein: The usage ratio of the microcapsule complex, the light / biological dual-degradable foaming carrier, deionized water, potassium alginate and glutaraldehyde solution in step 1 is 2-2.5 kg: 2-3 kg: 3-4 L: 2-2.5 kg: 0.4-0.5 L.

3. The method for preparing a soil conditioner for improving saline-alkali soil according to claim 1, wherein: The dosage ratio of N-isopropylacrylamide, N,N'-methylenebispropylamide, sodium lauryl sulfate, deionized water, ammonium persulfate and the double-assembled microcapsule carrier complex in step 2 is 3-4 kg: 1.2-1.5kg: 0.1-0.2kg: 3-4L: 0.4-0.5L: 2-3kg.

4. The method for preparing a soil conditioner for improving saline-alkali soil according to claim 1, wherein: The chitosan solution is obtained by stirring and mixing chitosan and 1-2 wt% glacial acetic acid solution in a dosage ratio of 4-5 kg:7.5-8.5 L.

5. The method for preparing a soil conditioner for improving saline-alkali soil according to claim 1, characterized in that: The usage ratio of the magnetized modified zeolite powder, fulvic acid, humic acid, deionized water, chitosan solution and potassium chloride solution is 3-4 kg: 0.5-0.7 kg: 0.3-0.5 kg: 3-4 L: 8-9 L: 0.5-0.6 L.

6. The method for preparing a soil conditioner for improving saline-alkali soil according to claim 1, characterized in that: The magnetized modified zeolite powder is prepared by the following steps: Add zeolite powder, citric acid and deionized water into a reactor, stir at 50-55°C and 400-500 rpm for 20-30 minutes, then add nano-ferroferric oxide particles, vacuum impregnate for 2-3 hours, filter, and wash the filter cake with deionized water until the last washing liquid is neutral to obtain magnetized modified zeolite powder; The usage ratio of the zeolite powder, citric acid, deionized water and nano-ferroferric oxide particles is 4-5 kg: 1-2 kg: 8-9 L: 0.8-1 kg.

7. The method for preparing a soil conditioner for improving saline-alkali soil according to claim 1, characterized in that: The usage ratio of the castor oil polyether polyol, modified nano titanium dioxide, deionized water, triethylenediamine, dibutyltin dilaurate, 1,4-butanediol and isocyanate is 14-15L: 5-6kg: 20-25L: 0.1-0.2kg: 0.2-0.3L: 0.1-0.2L: 0.3-0.4L.

8. The method for preparing a soil conditioner for improving saline-alkali soil according to claim 1, characterized in that: The usage ratio of the nano titanium dioxide powder, anhydrous ethanol and gamma-aminopropyltriethoxysilane is 3-4 kg: 8-9 L: 800-900 mL.

9. A soil conditioner for improving saline-alkali soil, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

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