PH response type nano soil conditioner, preparation method thereof and method for preventing and treating soil re-acidification

Abstract

The invention provides a pH response type nano soil conditioner, a preparation method thereof and a method for preventing and treating soil re-acidification, and relates to the technical field of soil conditioning and re-acidification prevention and treatment. According to the pH response type nano soil conditioner, macroporous silicon dioxide serves as a carrier, the surface of the macroporous silicon dioxide is modified with ketone groups, carboxyl modified nano carbon black and sodium tripolyphosphate are loaded on the macroporous silicon dioxide, the macroporous silicon dioxide further has acylhydrazone bonds connected with pore channels, the acylhydrazone bonds can respond to and break when the pH of soil is lower than 5.5, and therefore opening of the pore channels is controlled, and the pH response type nano soil conditioner is obtained. The loaded carboxyl modified nano carbon black and sodium tripolyphosphate are slowly released. The released carboxyl modified nano carbon black adsorbs and fixes acidic substances in the soil, so that the pH value of the soil can be increased to a certain extent, and the acid-resistant buffer capacity of the soil can be improved; the released sodium tripolyphosphate can neutralize H < + > in the soil, so that the pH value of the soil is increased; the pH response type nano soil conditioner provided by the invention can effectively prevent and treat a re-acidification phenomenon after acidified soil treatment.

Description

Technical Field

[0001] The invention relates to the technical field of soil conditioning and re-acidification prevention and control, and in particular to a pH-responsive nano soil conditioner and a method for preparing the same and preventing and controlling soil acidification. Background Art

[0002] The area of ​​red and yellow soil in southern my country is increasing year by year. Among them, red soil is highly acidic, with a pH value of about 4.5 to 6.0, while yellow soil is more acidic, with a pH value of generally 4.0 to 5.5; the stronger the soil acidity, the faster the increase in acidification area, and the development of acidified arable land is becoming more and more severe. However, the pH value of soil is crucial to plant growth, and most crops thrive in neutral or slightly acidic soil. Therefore, soil acidification will affect the normal growth of crops, induce plant diseases and insect pests, and cause crop yield reduction; it will also cause excessive heavy metals in agricultural products, thereby threatening human food safety and health.

[0003] However, the treatment and restoration of acidified soils require a long period of time. At the same time, due to various reasons such as excessive application of fertilizers, atmospheric acid deposition, and improper farming methods, the acidified soil after treatment is prone to re-acidification. At present, my country has carried out a lot of research on soil acidification improvement, but most of them use traditional products such as lime, dolomite, fly ash, biochar and other industrial by-products to directly improve soil acidification, and there is little research on soil re-acidification.

[0004] Existing Chinese patent document CN115724698A discloses an acidic soil conditioner and a preparation method thereof, wherein the acidic soil conditioner comprises the following raw materials in parts by weight: 10-20 parts of sepiolite powder, 5-10 parts of hydroxy calcium phosphate, 10-15 parts of chitosan, 5-10 parts of polyacrylic acid hydrogel, 20-30 parts of humic acid, 10-20 parts of biochar powder and 20-30 parts of soybean meal. The conditioner can improve the pH of acidic soil, effectively adsorb fertilizers, retain fertilizers and water well, and maintain slow release, providing sufficient nutrients and water for crops, and will not cause soil compaction and "re-acidification" phenomenon after long-term use.

[0005] Existing Chinese patent document CN 107033910A discloses a composition for regulating soil acidity, which is composed of straw biochar, alkali residue and organic fertilizer, wherein the ratio of straw biochar, alkali residue and organic fertilizer is (80-100): (6-15): 50. The combination of the three materials can significantly improve soil acidity, increase soil fertility, and thus increase crop yields, while also improving soil acidification resistance, prolonging the improvement effect time, and slowing down the re-acidification process.

[0006] The soil conditioners provided in the above schemes can slow down the process of soil "re-acidification" to a certain extent, but they cannot fundamentally solve the re-acidification problem after acidified soil treatment.

[0007] The present invention aims to solve the problem of soil re-acidification and provides a slow-release pH-responsive soil conditioner to prevent and control the re-acidification phenomenon after acidified soil treatment. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a pH-responsive nano-soil conditioner and a method for preparing and controlling soil acidification. The purpose is to release carboxyl-modified nano-carbon black and sodium tripolyphosphate loaded on a macroporous silica carrier by responding to the acidification of the soil environment pH (pH below 5.5), thereby solving the problem of re-acidification after the existing acidified soil treatment.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a pH-responsive nano soil conditioner, which uses macroporous silica nanoparticles as a carrier, wherein the surface of the macroporous silica is modified with ketone groups and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate, and the macroporous silica also has an acylhydrazone bond connecting the pores, wherein the acylhydrazone bond can respond and break when the soil pH is lower than 5.5, thereby controlling the opening of the pores and slowly releasing the loaded carboxyl-modified nano carbon black and sodium tripolyphosphate.

[0011] In a second aspect, the present invention provides a method for preparing the pH-responsive nano soil conditioner, comprising the following steps:

[0012] S1. Using macroporous silica nanoparticles as raw materials, macroporous silica with keto groups modified on the surface (expressed as MPS-K) is prepared;

[0013] S2, based on the macroporous silica with keto groups modified on the surface prepared in S1, further preparing macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate (STPP) (represented by MPS-K-CB@STPP);

[0014] S3, catalyzing the reaction of the macroporous silica with keto group modified on the surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate prepared in S2 with a polymer with hydrazide groups at the end, so as to obtain the pH-responsive nano soil conditioner.

[0015] Furthermore, the method for preparing the macroporous silica with keto groups modified on the surface in step S1 is as follows:

[0016] S101, adding macroporous silica nanoparticles, water and ethanol into a reaction container, dispersing them by ultrasonic treatment, controlling the reaction temperature, dropping an aminosilane coupling agent, and after the reaction is complete, centrifuging to remove the supernatant, washing the obtained solid, and obtaining amino-modified macroporous silica;

[0017] S102, dispersing the amino-modified macroporous silica obtained in step S101 in the first organic solvent, stirring at room temperature, adding a ketone-containing compound, controlling the temperature for reflux reaction, centrifuging to remove the supernatant, washing the obtained solid, and obtaining a macroporous silica with surface modified ketone groups (denoted as MPS-K).

[0018] Furthermore, in step S101, the mass ratio of the macroporous silica nanoparticles to the aminosilane coupling agent is 10-20:1-2.

[0019] Preferably, in step S101, the pore size of the macroporous silica nanoparticles is 50-100 nm.

[0020] Furthermore, in step S101, the ultrasonic dispersion time is 0.5 to 1 hour.

[0021] Furthermore, in step S101, the reaction temperature is 50-70°C; and the reaction time is 12-24h.

[0022] Furthermore, in step S101, the aminosilane coupling agent is any one of KH550 (γ-aminopropyltriethoxysilane), KH792 (N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane) and KH602 (N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane). Preferably, KH550 is used.

[0023] Furthermore, in step S102, the mass ratio of amino-modified macroporous silica to the ketone-containing compound is 35-40:60-65.

[0024] Furthermore, in step S102, the ketone group-containing compound is any one of pyruvic acid and acetoacetic acid.

[0025] Furthermore, in step S102, the first organic solvent is any one of ethanol, methanol, and isopropanol.

[0026] Furthermore, in step S102, the temperature of the reflux reaction is 60-0°C and the time is 8-10 hours.

[0027] Furthermore, in step S102, the entire reflux reaction process needs to be protected by an inert gas, and the inert gas is preferably nitrogen.

[0028] Furthermore, the solid is generally washed three times after removing the supernatant in steps S101 and S102.

[0029] Furthermore, the method for preparing macroporous silica with keto-modified surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate in step S2 is as follows:

[0030] S201, mixing carboxyl-modified nano carbon black, water, and a second organic solvent, stirring them sufficiently, and then treating them with ultrasound to fully disperse them to obtain a suspension;

[0031] S202, adding the surface-modified keto-group macroporous silica obtained in step S1 to the suspension in S201, stirring thoroughly and then subjecting to ultrasonic treatment to allow the carboxyl-modified nano-carbon black to fully enter the pores of the macroporous silica and be loaded;

[0032] S203, adding sodium tripolyphosphate aqueous solution to the solution after the reaction in S202, stirring thoroughly, and then subjecting to ultrasonic treatment to allow the sodium tripolyphosphate to fully enter the pores of the macroporous silica and be loaded;

[0033] S204, subjecting the mixed liquid after the reaction in S203 to solid-liquid separation treatment, repeatedly washing the separated powder to remove unloaded carboxyl-modified nano-carbon black, sodium tripolyphosphate and solvent, and obtaining macroporous silica (MPS-K-CB@STPP) with keto group modified on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate after drying.

[0034] Furthermore, in step S201, the mass ratio of the carboxyl-modified nano carbon black, the second organic solvent and water is 1-2:1-2:6-8.

[0035] Furthermore, the carboxyl-modified nano-carbon black is prepared by the following method: the carboxyl-modified nano-carbon black is obtained by mixing and modifying the nano-carbon black with concentrated nitric acid; the mass ratio of the nano-carbon black to the concentrated nitric acid is 1-4:4-8; the modification temperature is 50-80°C, and the time is 2-4h.

[0036] Preferably, the particle size of the nano carbon black is 20 to 30 nm.

[0037] Preferably, the second organic solvent is ethanol.

[0038] Furthermore, in step S201, the ultrasonic treatment time is 1 to 2 hours.

[0039] Furthermore, in step S202, the ultrasonic treatment time is 10 to 12 hours.

[0040] Furthermore, in step S202, the mass ratio of the macroporous silica with surface modified keto groups to the suspension of S201 is 1:50-100.

[0041] Furthermore, in step S203, the mass ratio of the sodium tripolyphosphate aqueous solution to the solution after the reaction in S202 is 5 to 10:1.

[0042] Furthermore, in step S203, the concentration of the sodium tripolyphosphate aqueous solution is 5 to 10 g / L, preferably 10 g / L.

[0043] Furthermore, in step S203, the ultrasonic treatment time is 10 to 12 hours.

[0044] Furthermore, the preparation process of step S3 is specifically as follows:

[0045] The macroporous silica with keto-modified surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate prepared by S2 is dispersed in water, activated by adding a catalyst, and then a polymer with a hydrazide group at the end is added, reacted at room temperature, separated from the solid and the liquid, washed with water, and dried to obtain a pH-responsive soil conditioner.

[0046] Furthermore, in step S3, the polymer having a hydrazide group at the end is methoxy polyethylene glycol hydrazide.

[0047] Furthermore, in step S3, the catalyst is one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride or N-hydroxysuccinimide, preferably N-hydroxysuccinimide.

[0048] Preferably, the reaction time of step S3 is 24 to 48 hours.

[0049] Preferably, the mass ratio of the macroporous silica with keto group modified on the surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate to the polymer with hydrazide group at the end is 5-6:2-3.

[0050] Preferably, in steps S201, S202 and S203, the ultrasonic treatment temperature is 30-50°C, and the ultrasonic frequency is 600-800 kHz.

[0051] In a third aspect, the present invention also provides a method for preventing and controlling soil re-acidification, wherein the method uses the above-mentioned pH-responsive nano soil conditioner or the pH-responsive nano soil conditioner prepared by the above-mentioned preparation method to treat the soil.

[0052] Furthermore, the method specifically comprises spreading the pH-responsive nano-soil conditioner evenly on the soil surface at a rate of 50 to 100 kg / mu 10 to 15 days before crop planting, and tilling and mixing the soil evenly.

[0053] Preferably, the application is performed one year after treating acidified soil.

[0054] Preferably, application is made on acidic paddy soil.

[0055] The present invention has the following beneficial effects:

[0056] The pH-responsive nano soil conditioner provided by the present invention uses macroporous silica nanoparticles as carriers, the surface of the macroporous silica is modified with ketone groups and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate, and it also has an acylhydrazone bond connecting the pores. The acylhydrazone bond connecting the pores will respond and break when the soil pH is lower than 5.5, thereby controlling the opening of the pores and slowly releasing the carboxyl-modified nano carbon black and sodium tripolyphosphate loaded on the macroporous silica. Since the released carboxyl-modified nano carbon black can adsorb and fix acidic substances in the soil, it can increase the soil pH value to a certain extent, and at the same time increase the soil's acid-resistant buffering capacity. The released sodium tripolyphosphate can neutralize H in the soil. + , thereby raising the pH value of the soil.

[0057] Therefore, the pH-responsive nano soil conditioner provided by the present invention can effectively prevent and control the re-acidification phenomenon after acidified soil treatment.

[0058] At the same time, the macroporous silica nanoparticle carrier has good biocompatibility and stability. The pH-responsive soil conditioner prepared with it will not have a negative impact on the soil if the acidified soil after treatment does not undergo re-acidification. At the same time, it can be slowly decomposed by the organic acids secreted by the rice roots, thereby providing a long-term effective silicon source for rice.

[0059] In summary, the pH-responsive nano soil conditioner of the present invention can provide a special solution to the problem of re-acidification of acidified soil after treatment. DETAILED DESCRIPTION

[0060] As used herein:

[0061] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0062] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0063] When each parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0064] In these examples, parts and percentages are by mass unless otherwise indicated.

[0065] "Weight parts" / "mass parts" refers to the basic measurement unit that indicates the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g, 2g, etc. If we say that the mass parts of component A are a parts and the mass parts of component B are b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Or, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0067] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments.

[0068] The raw materials and their sources used in the following examples are as follows:

[0069] Macroporous silica nanoparticles: Hangzhou Jikang New Materials Co., Ltd.; pore size is 50-100nm, particle size is 150-200nm.

[0070] Aminosilane coupling agent: Yunsheng Chemical (Shandong) Co., Ltd.

[0071] Pyruvic acid: Hubei Kewode Chemical Co., Ltd.

[0072] Sodium tripolyphosphate: Shandong Lida Chemical Co., Ltd.

[0073] Methoxypolyethylene glycol hydrazide: Shanghai Denuo Chemical Co., Ltd.

[0074] N-Hydroxysuccinimide sulfonate: Jiangsu Bosite Chemical Co., Ltd.

[0075] KH550 (γ-aminopropyltriethoxysilane): Jinan Yunuo Chemical Co., Ltd.

[0076] The carboxyl-modified nano-carbon black in the following examples was prepared by the following method: carboxyl-modified nano-carbon black was obtained by mixing and modifying nano-carbon black with concentrated nitric acid (3 mol / L); the mass ratio of nano-carbon black to concentrated nitric acid was 1:4; the modification temperature was 50°C and the time was 4 hours. Nano-carbon black: purchased from Jinan Tiancheng Carbon Black Factory, with a particle size of 20 to 30 nm.

[0077] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0078] Example 1

[0079] This embodiment provides a method for preparing a pH-responsive nano soil conditioner, comprising the following steps:

[0080] S1. Using macroporous silica nanoparticles as raw materials, macroporous silica with keto groups modified on the surface is prepared as follows:

[0081] S101. Add macroporous silica nanoparticles, water and ethanol into a reactor, and use ultrasonic dispersion for 1 hour to fully disperse the macroporous silica nanoparticles in water and ethanol; control the reaction temperature at 60°C, and add KH550 (γ-aminopropyltriethoxysilane) dropwise at a mass ratio of macroporous silica nanoparticles to aminosilane coupling agent of 10:1. After reacting for 24 hours, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain amino-modified macroporous silica.

[0082] S102, dispersing the amino-modified macroporous silica obtained in step S101 in methanol, stirring at room temperature, adding acetone in a mass ratio of 40:60 of amino-modified macroporous silica and acetone, controlling the temperature to 70°C for reflux reaction for 10 hours, and passing nitrogen gas throughout the process for protection. After the reaction is completed, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain macroporous silica with surface modified with keto groups (denoted as MPS-K).

[0083] S2. Based on the macroporous silica with keto groups modified on the surface prepared in S1, macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate is further prepared, as follows:

[0084] S201. Carboxyl-modified nano carbon black, water and ethanol are mixed in a mass ratio of 1:1:8, stirred sufficiently, and then subjected to ultrasonic treatment at an ultra-frequency of 800 kHz at 50° C. for 2 h to fully disperse the nano carbon black to obtain a suspension.

[0085] S202, adding the MPS-K prepared in S102 into the suspension of step S201 at a mass ratio of 1:80, stirring sufficiently, and then treating with ultrasound at an ultra-frequency of 800 kHz at 50°C for 10 hours to allow the carboxyl-modified nano-carbon black to fully enter the pores of the macroporous silica and be loaded.

[0086] S203. Add 10 g / L sodium tripolyphosphate solution into the solution after the reaction in S202 at a mass ratio of 5:1. After sufficient stirring, use ultrasonic treatment with an ultra-frequency of 800 kHz at 50°C for 10 hours to allow the sodium tripolyphosphate to fully enter the pores of the macroporous silica and be loaded.

[0087] S204. The mixed liquid after the reaction in S203 is subjected to solid-liquid separation treatment, and the separated powder is washed with water for multiple times to remove unloaded carboxyl-modified nano-carbon black, sodium tripolyphosphate and solvent, and after drying, macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate (denoted as MPS-K-CB@STPP) is obtained.

[0088] S3. Disperse the MPS-K-CB@STPP prepared in S2 in water, add N-hydroxysuccinimide for activation, then add methoxypolyethylene glycol hydrazide in a mass ratio of 5:3, react at room temperature for 48 hours, separate the solid and liquid, wash with water, and dry to obtain the pH-responsive soil conditioner.

[0089] Example 2

[0090] This embodiment provides a method for preparing a pH-responsive nano soil conditioner, comprising the following steps:

[0091] S1. Using macroporous silica nanoparticles as raw materials, macroporous silica with keto groups modified on the surface is prepared as follows:

[0092] S101. Add macroporous silica nanoparticles, water and ethanol into a reactor, and use ultrasonic dispersion for 1 hour to fully disperse the macroporous silica nanoparticles in water and ethanol; control the reaction temperature at 50°C, and add KH550 dropwise at a mass ratio of macroporous silica nanoparticles to aminosilane coupling agent of 10:2. After reacting for 20 hours, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain amino-modified macroporous silica.

[0093] S102, dispersing the amino-modified macroporous silica obtained in step S101 in isopropanol, stirring at room temperature, adding acetone in a mass ratio of 35:65 between the amino-modified macroporous silica and acetone, controlling the temperature to 60°C for reflux reaction for 10 hours, and passing nitrogen gas throughout the process for protection. After the reaction is completed, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain macroporous silica with surface modified with keto groups (denoted as MPS-K).

[0094] S2. Based on the macroporous silica with keto groups modified on the surface prepared in S1, macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate is further prepared, as follows:

[0095] S201. Carboxyl-modified nano carbon black, water and ethanol are mixed in a mass ratio of 2:2:8, stirred sufficiently, and then subjected to ultrasonic treatment at an ultra-frequency of 700 kHz at 40° C. for 2 h to fully disperse the nano carbon black to obtain a suspension.

[0096] S202, adding the MPS-K prepared in S102 into the suspension of step S201 at a mass ratio of 1:100, stirring sufficiently, and then treating with ultrasound at an ultra-frequency of 700 kHz at 40°C for 11 hours, so that the carboxyl-modified nano-carbon black can fully enter the pores of the macroporous silica and be loaded.

[0097] S203. Add 10 g / L sodium tripolyphosphate solution into the solution after the reaction in S202 at a mass ratio of 10:1. After sufficient stirring, use ultrasonic treatment with an ultra-frequency of 700 kHz at 40°C for 11 hours to allow the sodium tripolyphosphate to fully enter the pores of the macroporous silica and be loaded.

[0098] S204. The mixed liquid after the reaction in S203 is subjected to solid-liquid separation treatment, and the separated powder is washed with water for multiple times to remove unloaded carboxyl-modified nano-carbon black, sodium tripolyphosphate and solvent, and after drying, macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate (denoted as MPS-K-CB@STPP) is obtained.

[0099] S3. Disperse the MPS-K-CB@STPP prepared in S2 in water, add N-hydroxysuccinimide for activation, then add methoxypolyethylene glycol hydrazide at a mass ratio of 6:2, react at room temperature for 36 hours, separate the solid and liquid, wash with water, and dry to obtain the pH-responsive soil conditioner.

[0100] Example 3

[0101] This embodiment provides a method for preparing a pH-responsive nano soil conditioner, comprising the following steps:

[0102] S1. Using macroporous silica as a raw material, macroporous silica with keto groups modified on the surface is prepared as follows:

[0103] S101. Add macroporous silica nanoparticles, water and ethanol into a reactor, and use ultrasonic dispersion for 0.5 h to fully disperse the macroporous silica nanoparticles in water and ethanol; control the reaction temperature at 70°C, and add KH602 dropwise at a mass ratio of macroporous silica nanoparticles to aminosilane coupling agent of 20:1. After reacting for 12 h, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain amino-modified macroporous silica.

[0104] S102, dispersing the amino-modified macroporous silica obtained in step S101 in ethanol, stirring at room temperature, adding acetone in a mass ratio of 40:65 between the amino-modified macroporous silica and acetone, controlling the temperature to 80°C for reflux reaction for 8 hours, and passing nitrogen gas throughout the process for protection. After the reaction is completed, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain macroporous silica with surface modified with keto groups (denoted as MPS-K).

[0105] S2. Based on the macroporous silica with keto groups modified on the surface prepared in S1, macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate is further prepared, as follows:

[0106] S201. Carboxyl-modified nano carbon black, water and ethanol are mixed in a mass ratio of 1:1:6, stirred sufficiently, and then subjected to ultrasonic treatment at an ultra-frequency of 600 kHz at 30° C. for 1 h to fully disperse the nano carbon black to obtain a suspension.

[0107] S202, adding the MPS-K prepared in S102 into the suspension of step S201 at a mass ratio of 1:50, stirring sufficiently, and then treating with ultrasound at an ultra-frequency of 600 kHz at 30°C for 12 hours to allow the carboxyl-modified nano-carbon black to fully enter the pores of the macroporous silica and be loaded.

[0108] S203. Add 10 g / L sodium tripolyphosphate solution into the solution after the reaction in S202 at a mass ratio of 8:1. After sufficient stirring, use ultrasonic treatment with an ultra-frequency of 600 kHz at 30°C for 12 hours to allow the sodium tripolyphosphate to fully enter the pores of the macroporous silica and be loaded.

[0109] S204. The mixed liquid after the reaction in S203 is subjected to solid-liquid separation treatment, and the separated powder is washed with water for multiple times to remove unloaded carboxyl-modified nano-carbon black, sodium tripolyphosphate and solvent, and after drying, macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate (denoted as MPS-K-CB@STPP) is obtained.

[0110] S3. Disperse the MPS-K-CB@STPP prepared in S2 in water, add N-hydroxysuccinimide for activation, then add methoxypolyethylene glycol hydrazide at a mass ratio of 5:2, react at room temperature for 24 hours, separate the solid and liquid, wash with water, and dry to obtain the pH-responsive soil conditioner.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing a nano soil conditioner, which is mainly different from Example 1 in that the macroporous silica is not loaded with sodium tripolyphosphate, and specifically comprises the following steps:

[0113] (1) Add macroporous silica nanoparticles, water and ethanol into a reactor, and use ultrasonic dispersion for 1 hour to fully disperse the macroporous silica nanoparticles in water and ethanol; control the reaction temperature at 60°C, and add KH550 (γ-aminopropyltriethoxysilane) dropwise according to the mass ratio of macroporous silica to aminosilane coupling agent of 10:1. After reacting for 24 hours, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain amino-modified macroporous silica.

[0114] (2) The amino-modified macroporous silica obtained in step (1) is dispersed in methanol, stirred at room temperature, acetone is added in a ratio of 40:60 by mass of the amino-modified macroporous silica and acetone, the temperature is controlled to 70° C. and refluxed for 10 h, nitrogen is passed throughout the process for protection, and after the reaction is completed, the supernatant is removed by centrifugation, and the obtained solid is washed, and the process is repeated three times to obtain a macroporous silica with a surface modified with keto groups (denoted as MPS-K).

[0115] (3) Carboxyl-modified nano-carbon black, water, and ethanol were mixed in a mass ratio of 1:1:8, stirred thoroughly, and then treated with ultrasound at an ultra-frequency of 800 kHz at 50° C. for 2 h to fully disperse the mixture.

[0116] (4) MPS-K is added to the suspension of step (3) at a mass ratio of 1:80, and after sufficient stirring, it is treated with ultrasound at an ultra-frequency of 800 kHz at 50° C. for 10 h to allow the carboxyl-modified nano-carbon black to fully enter the pores of the macroporous silica and be fully loaded.

[0117] (5) subjecting the mixed solution loaded in step (4) to solid-liquid separation, washing the separated powder with water for multiple times to remove unloaded carboxyl-modified nano-carbon black and solvent, and obtaining macroporous silica (MPS-K-CB) with keto-modified surface and loaded with carboxyl-modified nano-carbon black after drying.

[0118] (6) The MPS-K-CB prepared in step (5) is dispersed in water, N-hydroxysuccinimide is added for activation, and then methoxypolyethylene glycol hydrazide is added in a mass ratio of 5:3, reacted at room temperature for 48 hours, and then the solid-liquid separation is performed, washed with water, and dried to obtain the product.

[0119] Comparative Example 2

[0120] This comparative example provides a method for preparing a nano soil conditioner, which is mainly different from Example 1 in that the macroporous silica is not loaded with carboxyl-modified nano carbon black, and specifically comprises the following steps:

[0121] (1) Add macroporous silica nanoparticles, water and ethanol into a reactor, and use ultrasonic dispersion for 1 hour to fully disperse the macroporous silica nanoparticles in water and ethanol; control the reaction temperature at 60°C, and add KH550 (γ-aminopropyltriethoxysilane) dropwise according to the mass ratio of macroporous silica nanoparticles to aminosilane coupling agent of 10:1. After reacting for 24 hours, centrifuge to remove the supernatant, wash the obtained solid, and repeat three times to obtain amino-modified macroporous silica.

[0122] (2) The amino-modified macroporous silica obtained in step (1) is dispersed in methanol, stirred at room temperature, acetone is added in a ratio of 40:60 by mass of the amino-modified macroporous silica and acetone, the temperature is controlled to 70° C. and refluxed for 10 h, nitrogen is passed throughout the process for protection, and after the reaction is completed, the supernatant is removed by centrifugation, and the obtained solid is washed, and the process is repeated three times to obtain a macroporous silica with a surface modified with keto groups (denoted as MPS-K).

[0123] (3) MPS-K was added to water at a treatment ratio of 1:80, and then 10 g / L sodium tripolyphosphate solution was added at a mass ratio of 5:1. After sufficient stirring, the mixture was treated with an ultrasonic wave at an ultra-frequency of 600-800 kHz at 30-50°C for 10 h to allow the sodium tripolyphosphate to fully enter the pores of the macroporous silica and be fully loaded.

[0124] (4) subjecting the mixed solution loaded in step (3) to solid-liquid separation, washing the separated powder with water for multiple times to remove unloaded sodium tripolyphosphate and solvent, and drying to obtain macroporous silica (MPS-K-STPP) with keto group modified on the surface and loaded with sodium tripolyphosphate.

[0125] (5) The MPS-K-STPP prepared in step (4) is dispersed in water, N-hydroxysuccinimide is added for activation, and then methoxypolyethylene glycol hydrazide is added in a mass ratio of 5:3, reacted at room temperature for 48 hours, and then the solid-liquid separation is performed, washed with water, and dried to obtain the product.

[0126] In order to verify the feasibility and effect of the scheme of the present invention, the present invention carried out the following soil cultivation test.

[0127] Application Example 1

[0128] Soil from a paddy field in Ningxiang, Hunan was selected, naturally air-dried and passed through a 10-mesh sieve, and then packaged into plastic barrels at 2 kg / barrel.

[0129] The experiment set up 11 treatments:

[0130] Treatment 1: pH-responsive nano soil conditioner prepared in Example 1, added in an amount of 0.3 g / kg;

[0131] Treatment 2: pH-responsive nano soil conditioner prepared in Example 1, added at 0.6 g / kg;

[0132] Treatment 3: pH-responsive nano soil conditioner prepared in Example 2, added at 0.3 g / kg;

[0133] Treatment 4: pH-responsive nano soil conditioner prepared in Example 2, added in an amount of 0.6 g / kg;

[0134] Treatment 5: pH-responsive nano soil conditioner prepared in Example 3, added in an amount of 0.3 g / kg;

[0135] Treatment 6: pH-responsive nano soil conditioner prepared in Example 3, added in an amount of 0.6 g / kg;

[0136] Treatment 7: the nano soil conditioner prepared in Comparative Example 1, with an addition amount of 0.3 g / kg;

[0137] Treatment 8: the nano soil conditioner prepared in Comparative Example 1, with an addition amount of 0.6 g / kg;

[0138] Treatment 9: the nano soil conditioner prepared in Comparative Example 2, with an addition amount of 0.3 g / kg;

[0139] Treatment 10: the nano soil conditioner prepared in Comparative Example 2, with an addition amount of 0.6 g / kg;

[0140] Treatment 11: Blank control.

[0141] After each treatment is mixed evenly, add appropriate amount of water until 60% of the field water capacity. Place the plastic bucket in a constant temperature and humidity incubator (HWS-150b) and culture for 30 days. During this period, water is regularly added to maintain soil moisture content. Then add 10mL of 1mol / L hydrochloric acid solution to each treatment soil, continue to regularly add water to maintain soil moisture content, and culture for 30 days.

[0142] Afterwards, soil samples from each treatment part were taken to measure soil pH (electrode method) to evaluate the control effect of the pH-responsive nano soil conditioner prepared in each example on soil re-acidification. Specific results are shown in Table 1.

[0143] Table 1 The control effect of different treatments on soil re-acidification in Application Example 1

[0144] Group Soil pH Process 1 5.31 Process 2 5.87 Process 3 5.27 Process 4 5.71 Process 5 5.36 Process 6 5.92 Process 7 4.95 Process 8 5.32 Process 9 5.12 Processing 10 5.45 Process 11 4.47

[0145] It can be seen from Table 1 that the pH-responsive nano soil conditioner provided by the present invention has an obvious control effect on soil re-acidification. Single loading of carboxyl-modified nano carbon black or sodium tripolyphosphate on the macroporous silica carrier will affect the control effect of the final soil conditioner on soil re-acidification.

[0146] Application Example 2

[0147] A flat field was selected in a certain acidification control project area in Teng County, Guangxi, for the verification test of the pH-responsive nano-soil conditioner of the present invention for the prevention and control of soil re-acidification. A 2.5-meter-wide protection row was set around the test area, and each plot was 3*10m 2 At the same time, a ridge (20 cm in width and 30 cm in height) was set between every two plots, and plastic film was covered on the ridge to prevent water and fertilizer from flowing into different plots, and the plots were arranged in random groups.

[0148] Treatment 1: Blank (CK), conventional fertilization (application of 51% (26-10-15) compound fertilizer 225kg / hm 2 As base fertilizer), without applying the pH-responsive nano soil conditioner of the present invention;

[0149] Treatment 2: Conventional fertilization (application of 51% (26-10-15) compound fertilizer 225kg / hm 2 As base fertilizer + 50 kg / mu of pH-responsive nano soil conditioner prepared in Example 1 of the present invention;

[0150] Treatment 3: Conventional fertilization (application of 51% (26-10-15) compound fertilizer 225kg / hm 2 As base fertilizer + 100 kg / mu of pH-responsive nano soil conditioner prepared in Example 1 of the present invention;

[0151] 60 days before rice planting, after spreading fertilizer, evenly spread soil conditioner on the field surface, then mix the soil conditioner with the soil by plowing, and pour in appropriate amount of water to mature for 30 days. Pour 1 kg of 98% concentrated sulfuric acid into 100 kg of water to prepare 1% concentration of sulfuric acid water. 30 days before rice planting, evenly spray it on each plot, and pour in appropriate amount of water to continue to mature for 30 days. Later, transplant the Yexiangyou No. 9 rice variety uniformly, with a transplanting row spacing of 20 cm × 25 cm, and the field water management and fertilization conditions are consistent with the local management conditions.

[0152] After the experiment, mixed samples from 5-6 sampling points in each plot were collected and sent to Zhejiang Zhenong Testing and Certification Technology Co., Ltd. to measure the soil pH index (in accordance with the relevant methods in standard NY / T 1973-2021). When the rice was harvested, it was harvested, dried and weighed separately in each plot to calculate the yield.

[0153] Table 2 The control effect of different treatments on soil re-acidification in Application Example 2

[0154]

[0155] From the data in Table 2, it can be seen that the soil pH of treatment 2 and treatment 3 increased by 9.3% and 17.6% respectively compared with treatment 1 (CK). This indicates that the pH-responsive nano soil conditioner provided by the present invention can effectively prevent and control the re-acidification problem after acidic soil treatment.

[0156] Table 3 Effects of different treatments on rice yield in Application Example 2

[0157]

[0158] As shown in Table 3, the rice yields of treatment 2 and treatment 3 increased by 3.2% and 5.4% respectively compared with treatment 1 (CK). This indicates that the pH-responsive nano-soil conditioner prepared by the present invention not only solves the problem of re-acidification after acidic soil treatment, but also has a certain yield-increasing effect on rice yield.

[0159] The above descriptions are only some preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A pH-responsive nano soil conditioner, characterized in that: The pH-responsive nano soil conditioner uses macroporous silica nanoparticles as carriers, the surface of the macroporous silica is modified with ketone groups and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate, and it also has acylhydrazone bonds connecting pores, and the acylhydrazone bonds can respond and break when the soil pH is lower than 5.5, thereby controlling the opening of the pores and slowly releasing the loaded carboxyl-modified nano carbon black and sodium tripolyphosphate.

2. A method for preparing the pH-responsive nano soil conditioner according to claim 1, characterized in that: The steps include: S1. Using macroporous silica as a raw material to prepare macroporous silica with keto groups modified on the surface; S2, based on the macroporous silica with keto groups modified on the surface prepared in S1, preparing macroporous silica with keto groups modified on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate; S3, catalyzing the reaction of the macroporous silica with keto group modified on the surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate prepared in S2 with a polymer with hydrazide groups at the end, so as to obtain the pH-responsive nano soil conditioner.

3. The method for preparing the pH-responsive nano soil conditioner according to claim 2, characterized in that: Step S1 The method for preparing macroporous silica with surface modified with keto groups is as follows: S101, adding macroporous silica nanoparticles, water and ethanol into a reaction container, dispersing by ultrasonic for 0.5 to 1 hour, controlling the reaction temperature to be 50 to 70° C., the reaction time to be 12 to 24 hours, dropping an aminosilane coupling agent, and after the reaction is complete, centrifuging to remove the supernatant, washing the obtained solid, and obtaining amino-modified macroporous silica; the mass ratio of the macroporous silica nanoparticles to the aminosilane coupling agent is 10 to 20:1 to 2; S102, dispersing the amino-modified macroporous silica obtained in step S101 in a first organic solvent, stirring at room temperature, adding a ketone-containing compound, wherein the mass ratio of the amino-modified macroporous silica to the ketone-containing compound is 35-40:60-65; under the protection of an inert atmosphere, controlling the temperature to 60-90° C. to perform a reflux reaction for 8-10 hours, centrifuging to remove the supernatant, washing the obtained solid, and obtaining a macroporous silica with a surface modified with ketone groups.

4. The method for preparing the pH-responsive nano soil conditioner according to claim 3, characterized in that: In step S101, the aminosilane coupling agent is any one of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

5. The method for preparing the pH-responsive nano soil conditioner according to claim 3, characterized in that: In step S102, the ketone group-containing compound is any one of pyruvic acid and acetoacetic acid; and the first organic solvent is any one of ethanol, methanol, and isopropanol.

6. The method for preparing the pH-responsive nano soil conditioner according to claim 2, characterized in that: Step S2: The method for preparing macroporous silica with keto-modified surface and loaded with carboxyl-modified nano carbon black and sodium tripolyphosphate is as follows: S201, mixing carboxyl-modified nano-carbon black, water, and a second organic solvent, wherein the mass ratio of the carboxyl-modified nano-carbon black, the second solvent, and water is 1-2:1-2:6-8; after fully stirring, using ultrasonic treatment for 1-2 hours to fully disperse the mixture to obtain a suspension; S202, adding the surface-modified keto-group macroporous silica obtained in step S1 to the suspension of S201, wherein the mass ratio of the surface-modified keto-group macroporous silica to the suspension of S201 is 1:50-100; after sufficient stirring, subjecting the suspension to ultrasonic treatment for 10-12 hours to allow the carboxyl-modified nano-carbon black to fully enter the pores of the macroporous silica and be loaded; S203, adding sodium tripolyphosphate aqueous solution to the solution after the reaction of S202, the mass ratio of sodium tripolyphosphate aqueous solution to the solution after the reaction of S202 is 5-10:1; after sufficient stirring, ultrasonic treatment is performed for 10-12 hours to allow sodium tripolyphosphate to fully enter the pores of macroporous silica and be loaded; S204, subjecting the mixed liquid after the reaction in S203 to solid-liquid separation treatment, repeatedly washing the separated powder to remove unloaded carboxyl-modified nano-carbon black, sodium tripolyphosphate and solvent, and obtaining macroporous silica with keto group modified surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate after drying.

7. The method for preparing the pH-responsive nano soil conditioner according to claim 6, characterized in that: In steps S201, S202 and S203, the ultrasonic treatment temperature is 30-50°C and the ultrasonic frequency is 600-800 kHz.

8. The method for preparing the pH-responsive nano soil conditioner according to claim 1, characterized in that: The preparation process of step S3 is as follows: The macroporous silica with keto group modification on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate prepared by S2 is dispersed in water, a catalyst is added for activation, and then a polymer with hydrazide groups at the end is added, wherein the mass ratio of the macroporous silica with keto group modification on the surface and loaded with carboxyl-modified nano-carbon black and sodium tripolyphosphate to the polymer with hydrazide groups at the end is 5-6:2-3; the reaction is carried out at room temperature for 24-48 hours, the solid-liquid is separated, the mixture is washed with water, and the pH-responsive soil conditioner is obtained.

9. The method for preparing the pH-responsive nano soil conditioner according to claim 8, characterized in that: The polymer with hydrazide groups at the end is methoxy polyethylene glycol hydrazide; the catalyst is one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.

10. A method for preventing and controlling soil acidification, characterized in that: The method uses the pH-responsive nano soil conditioner described in claim 1 or the pH-responsive nano soil conditioner prepared by any preparation method described in claims 2 to 9 to treat the soil; specifically, 10 to 15 days before crop planting, the pH-responsive nano soil conditioner is evenly spread on the soil surface at 50 to 100 kg / mu, and the soil is tilled and evenly mixed.

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