Temperature / pH dual-responsive biochar-based phosphate fertilizer, preparation method and application thereof

Abstract

The application provides a temperature / pH dual-response biochar-based phosphate fertilizer, a preparation method and application thereof, and belongs to the technical field of agricultural fertilizers.The temperature-sensitive chitosan derivative is prepared by sequentially performing acylation reaction, mercapto reaction and temperature-sensitive monomer reaction on chitosan; the amino-modified acylhydrazone type biochar-based phosphate carrier material is prepared by sequentially performing oxidation, adsorption of phosphorus and acylhydrazone reaction on biochar; and finally, the amino-modified acylhydrazone type biochar-based phosphate carrier material and the temperature-sensitive chitosan derivative are polymerized by using atom transfer radical polymerization reaction sites. The biochar-based phosphate fertilizer obtained by the application can realize dual response to temperature and pH. Under high-temperature conditions, the biochar-based phosphate fertilizer can be dehydrated and polycondensed to reduce release, and under acidic conditions, the biochar-based phosphate fertilizer can release phosphate by breaking acylhydrazone bonds, so as to meet the precise absorption of crops and increase the utilization efficiency of phosphate fertilizer.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer technology, and in particular to a temperature / pH dual-responsive biochar-based phosphate fertilizer, its preparation method, and its application. Background Technology

[0002] Applying the same amount of fertilizer during hot weather, especially when moisture is scarce, can easily lead to excessively high concentrations of fertilizer in localized soil solutions. This is because high temperatures cause rapid evaporation, and if watering is not timely, the high fertilizer concentration can cause excessive pressure at the application site, resulting in seedling or root burn. Applying fertilizer too close to the roots can easily cause plant dehydration, leading to reduced yield. Therefore, fertilizer application should be reduced or the concentration of fertilizer in the soil solution should be decreased during hot weather or at midday.

[0003] 74% of China's arable land is phosphorus deficient. However, in some areas, the long-term and excessive application of phosphate fertilizers has led to the accumulation of phosphorus in the soil, resulting in a reduced utilization rate of phosphate fertilizers during the current season, typically only 15% to 25%, and a cumulative utilization rate of less than 50%. In addition, the availability of phosphorus in the soil is significantly affected by pH. When the pH value is above 7.5 or below 6, phosphate forms a delayed-release form with calcium or iron and aluminum, further reducing its availability.

[0004] Therefore, there is an urgent need for a phosphate fertilizer that can be applied at high temperatures and whose effective utilization rate can be guaranteed even in acidic environments. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a temperature / pH dual-responsive biochar-based phosphate fertilizer, its preparation method and application. The biochar-based phosphate fertilizer provided by this invention can be applied in high temperature and acidic environments and can improve fertilizer utilization efficiency.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a temperature / pH dual-responsive biochar-based phosphate fertilizer includes the following steps:

[0008] S1. Preparation of temperature-sensitive chitosan derivatives: These derivatives are prepared by sequentially performing acylation, thiolation, and reaction with temperature-sensitive comonomers on chitosan.

[0009] S2. Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supporting material: prepared by sequentially oxidizing, adsorbing phosphorus, and acylhydrazoneizing biochar.

[0010] S3. Atom transfer radical polymerization reaction sites are introduced into the amino-modified acylhydrazone-based biochar-based phosphorus-supporting material. Water, temperature-sensitive chitosan derivative and pentamethyldiethylenetriamine are added, ultrasonically dispersed, and copper bromide is added under a nitrogen atmosphere. After reacting at room temperature for 25 min to 35 min, the material is dried to obtain the temperature-sensitive modified acylhydrazone-based phosphorus-supporting material. The material is then extruded and granulated to obtain a temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0011] Preferably, the preparation of the temperature-sensitive chitosan derivative in step S1 specifically includes the following steps:

[0012] With a molecular weight of 2×10 4 ~3.5×10 4 Chitosan is dissolved in 1%–3% acetic acid solution or 2%–5% methanesulfonic acid solution to obtain chitosan acetic acid / methanesulfonic acid solution. The chitosan acetic acid / methanesulfonic acid solution is then graft copolymerized in a homogeneous phase to obtain acylated chitosan derivatives with an acylation degree ≥1.8.

[0013] A mercaptochitosan derivative was prepared by adding dimercaprol to an acylated chitosan derivative and carrying out an amidation reaction at 50°C for 4 hours under the presence of an activator and a condensing agent. The amounts of the activator and the condensing agent added were both 0.15% to 0.5% of the weight of the chitosan acetic acid / methanesulfonic acid solution.

[0014] Add the first phase transfer agent to the thiol chitosan derivative, mix well, and obtain the first suspension;

[0015] The temperature-sensitive comonomer material is dissolved in an organic solvent, mixed well, and then a first suspension and a first activator are added. The mixture is reacted at 65°C for 8 to 10 hours to obtain the temperature-sensitive chitosan derivative.

[0016] Preferably, the amount of acetic acid solution used is 20 mL to 30 mL of acetic acid solution with a volume concentration of 1% to 3% per gram of chitosan; the amount of dimercaprol added is 10 mL to 30 mL of dimercaprol added per 2 g to 6 g of acylated chitosan derivative; the thermosensitive comonomer material is N-isopropylacrylamide, and the amount added is 1 g of thermosensitive comonomer material added per 1 mL to 3.5 mL of the first suspension; the amount of organic solvent added is 1.67 mL to 3 mL of organic solvent added per gram of thermosensitive comonomer material.

[0017] Preferably, the preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supported material in step S2 specifically includes the following steps:

[0018] Biochar was soaked in hydrogen peroxide solution for 12-24 hours, filtered, washed, and dried at 85-95°C for 4-8 hours to obtain oxidized biochar material.

[0019] Oxidized biochar material was impregnated in potassium dihydrogen phosphate solution, stirred evenly, sealed and allowed to stand for 18h to 36h, and then dried at 35℃ to 45℃ for 1h to 2h to obtain biochar-based phosphorus-supported material.

[0020] A second phase transfer agent was added to the biochar-based phosphorus-loaded material, and after stirring evenly, hydrazine hydrate and a second activator were added sequentially. N2 was introduced under stirring for 30-60 minutes, and the temperature was raised to 70°C for 12-15 hours. After the reaction was completed, the reactants were added dropwise to diethyl ether, and the precipitate was obtained by filtration. The precipitate was dried at 35-45°C for 1.5-2.5 hours to obtain the acylhydrazone-type biochar-based phosphorus-loaded material.

[0021] An acylhydrazone-type biochar-based phosphorus-supported material was dissolved in anhydrous ethanol, and triethanolamine, 3-aminopropyltriethoxysilane, and 10% ammonia water were added sequentially. The reaction was carried out with N2 under stirring for 4 to 8 hours to obtain an amino-modified acylhydrazone-type biochar-based phosphorus-supported material.

[0022] Preferably, the first phase transfer agent and the second phase transfer agent are one or more of the following: chain polyethylene glycol dialkyl ether, cyclodextrin, tetradecyltrimethylammonium chloride, benzyltriethylammonium chloride, pyridine, and tributylamine; the amount of the first phase transfer agent added is 0.025 mL to 0.03 mL or 0.025 g to 0.03 g per mL of mercaptochitosan derivative; the amount of the second phase transfer agent added is 0.0075 mL to 0.015 mL or 0.0075 g to 0.015 g per g of biochar-based phosphorus-supported material; the first activator and the second activator are one or more of the following: styrenephosphine, trialkylphosphine, cinchona bark, and 2-hydroxy-2-methyl-1-phenylpropanone.

[0023] Preferably, the biochar is one or more of pineapple leaf biochar, banana stalk biochar, and jackfruit peel residue biochar, and the pH of the biochar is 9.10 to 10.35; the concentration of the hydrogen peroxide solution is 10 wt% to 30 wt%; and the potassium dihydrogen phosphate solution is a saturated potassium dihydrogen phosphate solution, added in an amount of 20 mL to 50 mL of saturated potassium dihydrogen phosphate solution per gram of oxidized biochar.

[0024] Preferably, the weight ratio of amino-modified hydrazone-type biochar-based phosphorus-supported material and temperature-sensitive chitosan derivative in S3 is (4-10):(1-3); the amount of pentamethyldiethylenetriamine added is 0.5 mL to 1 mL of pentamethyldiethylenetriamine per 4 g to 10 g of amino-modified hydrazone-type biochar-based phosphorus-supported material.

[0025] Preferably, the method for introducing atom transfer radical polymerization reaction sites on the amino-modified hydrazone-type biochar-based phosphorus-supported material in step S3 is as follows: introducing atom transfer radical polymerization reaction sites on the biochar material in toluene through the action of triethylamine and 2-bromoisobutyryl bromide.

[0026] The present invention also provides a method for preparing a temperature / pH dual-responsive biochar-based phosphate fertilizer as described in the above-mentioned scheme, resulting in a temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0027] The present invention also provides an application of the temperature / pH dual-responsive biochar-based phosphate fertilizer described in the above-mentioned scheme in agriculture.

[0028] Beneficial Technical Effects: This invention provides a temperature / pH dual-responsive biochar-based phosphate fertilizer, its preparation method, and its application. The invention prepares a temperature-sensitive chitosan derivative by sequentially performing acylation, thiolation, and reaction with a temperature-sensitive comonomer on chitosan. An amino-modified acylhydrazone-based biochar-based phosphorus-carrying material is prepared by sequentially oxidizing, adsorbing phosphorus, and acylhydrazone-modifying biochar. Finally, the amino-modified acylhydrazone-based biochar-based phosphorus-carrying material and the temperature-sensitive chitosan derivative are polymerized using atom transfer radical polymerization. The biochar-based phosphate fertilizer obtained by this invention exhibits dual response to temperature and pH. Under high-temperature conditions, it can dehydrate and condense, reducing release, and under acidic conditions, it releases phosphate ions through the cleavage of acylhydrazone bonds, thus meeting the needs of precise crop absorption and increasing the utilization efficiency of phosphate fertilizer. Attached Figure Description

[0029] Figure 1 A preparation route diagram for a temperature / pH dual-responsive biochar-based phosphate fertilizer;

[0030] Figure 2 A schematic diagram of the structure of a temperature / pH dual-responsive biochar-based phosphate fertilizer;

[0031] Figure 3 The stability of the temperature / pH dual-responsive biochar-based phosphate fertilizers prepared in Examples 1-5 in aqueous solution;

[0032] Figure 4 The infrared spectra of temperature / pH dual-responsive biochar-based phosphate fertilizers prepared in Examples 1 to 5 are shown, where a corresponds to Example 1, b corresponds to Example 2, c corresponds to Example 3, d corresponds to Example 4, and e corresponds to Example 5.

[0033] Figure 5 SEM images of temperature / pH dual-responsive biochar-based phosphate fertilizers prepared in Examples 1-5, where A corresponds to Example 1, B corresponds to Example 2, C corresponds to Example 3, D corresponds to Example 4, and E corresponds to Example 5;

[0034] Figure 6 The growth status of maize plants after applying Examples 1-5 and Comparative Examples 1-2. Detailed Implementation

[0035] This invention provides a method for preparing a temperature / pH dual-responsive biochar-based phosphate fertilizer, comprising the following steps:

[0036] S1. Preparation of temperature-sensitive chitosan derivatives: These derivatives are prepared by sequentially performing acylation, thiolation, and reaction with temperature-sensitive comonomers on chitosan.

[0037] S2. Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supporting material: prepared by sequentially oxidizing, adsorbing phosphorus, and acylhydrazoneizing biochar.

[0038] S3. Atom transfer radical polymerization reaction sites are introduced into the amino-modified acylhydrazone-based biochar-based phosphorus-supporting material. Water, temperature-sensitive chitosan derivative and pentamethyldiethylenetriamine are added, ultrasonically dispersed, and copper bromide is added under a nitrogen atmosphere. After reacting at room temperature for 25 min to 35 min, the material is dried to obtain the temperature-sensitive modified acylhydrazone-based phosphorus-supporting material. The material is further extruded and granulated to obtain a temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0039] The preparation route of the temperature / pH dual-responsive biochar-based phosphate fertilizer of this invention is as follows: Figure 1 As shown.

[0040] The present invention first prepares temperature-sensitive chitosan derivatives by sequentially performing acylation, thiolation and reaction with temperature-sensitive comonomers on chitosan.

[0041] In this invention, the preparation of temperature-sensitive chitosan derivatives preferably includes the following steps: [The text abruptly ends here, so the translation stops.] 4 ~3.5×10 4 Chitosan is dissolved in a 1%–3% acetic acid solution or a 2%–5% methanesulfonic acid solution to obtain a chitosan-acetic acid / methanesulfonic acid solution. This solution is then graft copolymerized in a homogeneous phase to obtain an acylated chitosan derivative with an acylation degree ≥1.8. Dimercaptopropanol is added to the acylated chitosan derivative, and an amidation reaction is carried out at 50°C for 4 hours under the presence of an activator and a condensing agent to obtain a mercapto chitosan derivative. The amount of activator and condensing agent added is 0.15%–0.5% of the weight of the chitosan-acetic acid solution. A first phase transfer agent is added to the mercapto chitosan derivative and mixed to obtain a first suspension. The temperature-sensitive comonomer material is dissolved in an organic solvent, mixed, and then the first suspension and a first activator are added. The mixture is reacted at 65°C for 8–10 hours to obtain a temperature-sensitive chitosan derivative.

[0042] In this invention, the activator is preferably 1-hydroxy-benzotriazole, and the amount of the activator used is preferably 0.15% of the chitosan acetic acid / methanesulfonic acid solution; the condensing agent is preferably diisopropylcarbodiimide, and the amount of the condensing agent used is preferably 0.3% of the chitosan acetic acid / methanesulfonic acid solution; the activator of this invention can enable acylated chitosan to retain more amino active sites, which facilitates the introduction of thiol groups; the condensing agent can enable thiol groups to undergo polymerization reactions at the amino active sites.

[0043] In this invention, the preferred amount of acetic acid solution used is 20 mL to 30 mL of acetic acid solution with a volume concentration of 1% to 3% per gram of chitosan; the preferred amount of dimercaprol added is 10 mL to 30 mL of dimercaprol added per 2 g to 6 g of acylated chitosan derivative; the preferred amount of thermosensitive comonomer is N-isopropylacrylamide, added at 1 g of thermosensitive comonomer material per 1 mL to 3.5 mL of the first suspension; the preferred amount of organic solvent added is 1.67 mL to 3 mL of organic solvent added per gram of thermosensitive comonomer material; the preferred organic solvent is one or more of isopropanol, methyl ethyl ketone, hexane, cyclohexanone, and ethylene glycol ethyl ether; an organic acid is also preferably added before graft copolymerization, and the preferred organic acid in the homogeneous phase is anhydride (CH3CO)2O, acyl halide SOCl2, or (COCl)2, and the preferred amount of organic acid added is 0.2 mL to 1 mL per gram of chitosan. This invention selects N-isopropylacrylamide (NIPAM) as a temperature-sensitive material to be added, which can dehydrate and condense at high temperatures, increasing material stability and reducing release.

[0044] In this invention, the first phase transfer agent is preferably one or more of chain polyethylene glycol dialkyl ether, cyclodextrin, tetradecyltrimethylammonium chloride, benzyltriethylammonium chloride, pyridine, and tributylamine; the amount of the first phase transfer agent added is preferably 0.025 mL to 0.03 mL or 0.025 g to 0.03 g per mL of mercaptochitosan derivative; the first activator is preferably one or more of tricresylphosphine, trialkylphosphine, cinchona bark, and 2-hydroxy-2-methyl-1-phenylpropanone.

[0045] This invention further prepares amino-modified acylhydrazone-type biochar-based phosphorus-supported materials by sequentially oxidizing, adsorbing phosphorus, and acylhydrazoneizing biochar.

[0046] In this invention, the preparation of amino-modified acylhydrazone-type biochar-based phosphorus-loaded material specifically includes the following steps: soaking biochar in hydrogen peroxide solution for 12-24 hours, filtering, washing, and drying at 85-95°C for 4-8 hours to obtain oxidized biochar material; impregnating the oxidized biochar material in potassium dihydrogen phosphate solution, stirring evenly, sealing and standing for 18-36 hours, and drying at 35-45°C for 1-2 hours to obtain biochar-based phosphorus-loaded material; adding a second phase transfer agent to the biochar-based phosphorus-loaded material, stirring evenly, and then sequentially adding hydrazine hydrate and a second activator. The agent was treated with N2 under stirring for 30-60 minutes, and the temperature was raised to 70℃ for 12-15 hours. After the reaction was completed, the reactants were added dropwise to diethyl ether, filtered to obtain precipitate, and dried at 35℃-45℃ for 1.5-2.5 hours to obtain acylhydrazone-type biochar-based phosphorus-supported material. The acylhydrazone-type biochar-based phosphorus-supported material was dissolved in anhydrous ethanol, and triethanolamine, 3-aminopropyltriethoxysilane, and 10% ammonia water were added in sequence. The reaction was treated with N2 under stirring for 4-8 hours to obtain amino-modified acylhydrazone-type biochar-based phosphorus-supported material.

[0047] In this invention, the second phase transfer agent is preferably one or more of the following: chain-like polyethylene glycol dialkyl ether, cyclodextrin, tetradecyltrimethylammonium chloride, benzyltriethylammonium chloride, pyridine, and tributylamine; the amount of the second phase transfer agent added is 0.0075 mL to 0.015 mL or 0.0075 g to 0.015 g per g of biochar-based phosphorus-supported material; the second activator is one or more of the following: tricresylphosphine, trialkylphosphine, cinchona bark, and 2-hydroxy-2-methyl-1-phenylpropanone; the weight ratio of the second phase transfer agent to the second activator is 1:(0.8 to 2.5). This invention uses a phase transfer agent to uniformly disperse the raw materials in the system, making the reaction easier to carry out.

[0048] In this invention, the biochar is preferably one or more of pineapple leaf biochar, banana stalk biochar, and jackfruit peel residue biochar, and the pH of the biochar is 9.10 to 10.35. The biochar used in this invention has an alkaline pH, which can neutralize the acidity of potassium dihydrogen phosphate, increase the adsorption efficiency of biochar materials for phosphate, and help control the aggravation of soil acidification when applied to acidic soils.

[0049] In this invention, the concentration of the hydrogen peroxide solution is preferably 10wt% to 30wt%, more preferably 20wt%, and the amount of hydrogen peroxide solution added is preferably 1:(30-50) of biochar to hydrogen peroxide (w / v); the potassium dihydrogen phosphate solution is a saturated potassium dihydrogen phosphate solution, and the amount added is preferably 20mL to 50mL of saturated potassium dihydrogen phosphate solution per gram of oxidized biochar; the amount of triethanolamine added is preferably 0.3mL of triethanolamine per 100mL of ethanol; the amount of 3-aminopropyltriethoxysilane added is preferably 0.5mL per 100mL of ethanol; the concentration of the ammonia water is preferably 10wt%, and the amount added is preferably 4mL per 100mL of ethanol.

[0050] Finally, this invention introduces atom transfer radical polymerization reaction sites into an amino-modified acylhydrazone-based biochar-supported phosphorus material, adds water, a temperature-sensitive chitosan derivative, and pentamethyldiethylenetriamine, ultrasonically disperses the mixture, adds copper bromide under a nitrogen atmosphere, reacts at room temperature for 25-35 minutes, and then dries it to obtain a temperature-sensitive modified acylhydrazone-based biochar-supported phosphorus material (i.e., NIPAM-modified acylhydrazone-based biochar-supported phosphorus material), which is then extruded and granulated to obtain a temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0051] In this invention, the preferred weight ratio of the amino-modified acylhydrazone-based biochar phosphorus-supporting material to the temperature-sensitive chitosan derivative is (4-10):(1-3); the amount of pentamethyldiethylenetriamine added is 0.5 mL-1 mL of pentamethyldiethylenetriamine per 4 g-10 g of amino-modified acylhydrazone-based biochar phosphorus-supporting material; the preferred amount of water added is 40 mL-60 mL of water per 1 g-4 g of amino-modified acylhydrazone-based biochar phosphorus-supporting material; and the preferred amount of copper bromide added is 0.1 g of copper bromide per 8 g-20 g of amino-modified acylhydrazone-based biochar phosphorus-supporting material. By rationally controlling the addition ratio of the amino-modified acylhydrazone-based biochar phosphorus-supporting material, the temperature-sensitive chitosan derivative, and pentamethyldiethylenetriamine, this invention can ensure the formation of the temperature-sensitive modified acylhydrazone-based biochar phosphorus-supporting material.

[0052] In this invention, the preferred method for introducing atom transfer radical polymerization reaction sites onto amino-modified acylhydrazone-based biochar-supported phosphorus material is as follows: atom transfer radical polymerization reaction sites are introduced onto the biochar material in toluene via the action of triethylamine and 2-bromoisobutyryl bromide. The amount of toluene added is 2.5 mL to 12.5 mL per 1 g to 2.5 g of amino-modified acylhydrazone-based biochar-supported phosphorus material; the amount of triethylamine added is 1.5 mL to 4 mL per 1 g to 2.5 g of amino-modified acylhydrazone-based biochar-supported phosphorus material; and the amount of 2-bromoisobutyryl bromide added is 0.2 mL to 0.8 mL per 1 g to 2.5 g of amino-modified acylhydrazone-based biochar-supported phosphorus material. Atom transfer radical polymerization is a novel living polymerization reaction. In atom transfer radical polymerization, different catalytic methods can form carbon-carbon, carbon-sulfur, and carbon-nitrogen bonds. This invention polymerizes an amino-modified acylhydrazone-based biochar phosphorus-supporting material and a temperature-sensitive chitosan derivative together via atom transfer radical polymerization. The resulting temperature-sensitive modified acylhydrazone-based biochar phosphorus-supporting material possesses both a temperature-sensitive component that enables its use in high-temperature environments and acylhydrazone bonds that help it stably release phosphate groups in acidic environments. The molecular structure of the temperature-sensitive modified acylhydrazone-based biochar phosphorus-supporting material is as follows: Figure 2 As shown.

[0053] In this invention, the drying temperature is preferably 65℃~75℃, more preferably 70℃, and the drying time is preferably 5h~7h, more preferably 6h; the extrusion granulation is preferably carried out using a commonly used extrusion granulation method in the art.

[0054] The present invention also provides a method for preparing a temperature / pH dual-responsive biochar-based phosphate fertilizer as described in the above-mentioned scheme, resulting in a temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0055] In this invention, biochar-based phosphate fertilizer can be dehydrated and condensed under high temperature conditions to reduce release, and release phosphate ions through the cleavage of acylhydrazone bonds under acidic conditions to meet the precise absorption of crops and increase the utilization efficiency of phosphate fertilizer.

[0056] The present invention also provides an application of the temperature / pH dual-responsive biochar-based phosphate fertilizer described in the above-mentioned scheme in agriculture.

[0057] In this invention, there are no special limitations on the type or method of application. Any application type or method acceptable in agriculture using biochar-based phosphate fertilizer is acceptable. There are also no special limitations on the amount used, which can be adjusted according to the actual situation.

[0058] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0059] Unless otherwise specified, the experimental methods used in this invention are all conventional methods, and the materials and reagents used are all commercially available unless otherwise specified.

[0060] Example 1

[0061] (1) Preparation of temperature-sensitive chitosan derivatives:

[0062] 2g chitosan (molecular weight 2×10) 4 Add 50 mL of 1% acetic acid solution to the mixture, mix well, and then add 1 mL of acid anhydride graft copolymerization under nitrogen protection for 24 h. Wash with water, filter, and dry to obtain 2.3 g of acylated chitosan derivative.

[0063] 2g of acylated chitosan derivative was added to 10mL of 7% dimercaprol solution and mixed evenly. Then, 0.075mL of 1-hydroxy-benzotriazole and 0.15mL of diisopropylcarbodiimide were added, and the amidation reaction was carried out at 50℃ for 4h to obtain 12mL of solution containing mercapto-chitosan derivative.

[0064] Add 0.2 g of cyclodextrin to 8 mL of thiol chitosan derivative, mix well, and obtain the first suspension;

[0065] 1 g of N-isopropylacrylamide was dissolved in 3 mL of isopropanol, mixed well, and then 3.5 mL of the first suspension and 0.2 mL of trialkylphosphine were added. The mixture was reacted at 65 °C for 8 h and filtered to obtain 6 g of temperature-sensitive chitosan derivative.

[0066] (2) Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supporting materials:

[0067] 20g of pineapple leaf biochar (pH: 9.94) was soaked in 200mL of 30wt% hydrogen peroxide solution for 12h, then filtered. The filter residue was washed with distilled water, ultrasonically cleaned for 30min, and dried at 90℃ for 4h to obtain 18g of oxidized biochar material.

[0068] 18g of oxidized biochar material was impregnated with 900mL of saturated potassium dihydrogen phosphate solution, stirred evenly, sealed and allowed to stand for 24h, the biochar was washed with distilled water 2-3 times, and dried at 40℃ for 2h to obtain 26g of biochar-based phosphorus-supported material; each gram of oxidized biochar can adsorb 450mg of phosphate.

[0069] 0.2 g of cyclodextrin was added to 20 g of biochar-based phosphorus-supported material and stirred evenly. Then, 0.1 mL of hydrazine hydrate and 0.2 mL of trialkylphosphine were added sequentially. N2 was introduced under stirring for 30 min, and the temperature was raised to 70 °C for 12 h. After the reaction was completed, the reactants were slowly added to a large amount of diethyl ether, and the precipitate was filtered to obtain the precipitate. The precipitate was dried at 40 °C for 2 h to obtain 21 g of acylhydrazone-type biochar-based phosphorus-supported material.

[0070] 20g of acylhydrazone-type biochar-based phosphorus-supported material was dissolved in 200mL of anhydrous ethanol, and 0.6mL of triethanolamine, 1mL of 3-aminopropyltriethoxysilane, and 8mL of 10% ammonia water were added sequentially. The reaction was carried out with N2 under stirring for 4h to obtain 21g of amino-modified acylhydrazone-type biochar-based phosphorus-supported material.

[0071] (3) Add 50 mL of toluene to 20 g of amino-modified acylhydrazone-based biochar-based phosphorus-supporting material, stir evenly, add 30 mL of triethylamine and 1.6 mL of 2-bromoisobutyryl bromide, add 50 mL of water, 6 g of temperature-sensitive chitosan derivative and 2 mL of pentamethyldiethylenetriamine, disperse ultrasonically, add 0.1 g of copper bromide under nitrogen atmosphere, and perform atom transfer radical polymerization reaction at room temperature for 30 min, and then dry in a drying oven at 70 ℃ for 6 h to obtain temperature-sensitive modified acylhydrazone-based biochar-based phosphorus-supporting material. Further extrusion granulation is performed to obtain temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0072] Example 2

[0073] (1) Preparation of temperature-sensitive chitosan derivatives:

[0074] 8g chitosan (molecular weight 3.5×10⁻⁶) 4 Add 160 mL of 3% acetic acid solution to the mixture, mix well, add 4 mL of acid anhydride graft copolymerization under nitrogen protection, wash with water, filter, and obtain 9.5 g of acylated chitosan derivative.

[0075] 6g of acylated chitosan derivative was added to 30mL of 7% dimercaprol solution, mixed evenly, and then 0.24mL of 1-hydroxy-benzotriazole and 0.48mL of diisopropylcarbodiimide were added. The amidation reaction was carried out at 50℃ for 4h to obtain 36mL of mercapto-chitosan derivative solution.

[0076] Add 0.2 mL of chain-like polyethylene glycol dialkyl ether to 8 mL of mercapto-chitosan derivative, mix well, and obtain the first suspension;

[0077] 2g of N-isopropylacrylamide was added to 3.54mL of methyl methyl ketone and mixed well. Then, 3.54mL of the first suspension and 0.4mL of tricresylphosphine were added. The mixture was reacted at 65℃ for 9h and filtered to obtain 3.5g of temperature-sensitive chitosan derivative.

[0078] (2) Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supporting materials:

[0079] 20g of banana stalk biochar (pH: 10.26) was soaked in 100mL of 10wt% hydrogen peroxide solution for 24h and then filtered. The filter residue was washed with distilled water, ultrasonically cleaned for 30min, and dried at 85℃ for 4h to obtain 18g of oxidized biochar material.

[0080] 10g of oxidized biochar material was impregnated in 200mL of saturated potassium dihydrogen phosphate solution, stirred evenly, sealed and allowed to stand for 36h, the biochar was washed 2-3 times with distilled water, and dried at 45℃ for 2h to obtain 14g of biochar-based phosphorus-supported material.

[0081] 0.15 mL of chain-like polyethylene glycol dialkyl ether was added to 10 g of biochar-based phosphorus-supported material. After stirring evenly, 0.1 mL of hydrazine hydrate and 0.2 mL of 2-hydroxy-2-methyl-1-phenylpropanone were added sequentially. N2 was introduced under stirring for 60 min, and the temperature was raised to 70 °C for 15 h. After the reaction was completed, the reactants were slowly added to a large amount of diethyl ether. The precipitate was filtered to obtain the sediment, which was dried at 45 °C for 1.5 h to obtain 10.5 g of acylhydrazone-type biochar-based phosphorus-supported material.

[0082] 10g of acylhydrazone-type biochar-based phosphorus-supported material was dissolved in 100mL of anhydrous ethanol, and then 0.3mL of triethanolamine, 0.5mL of 3-aminopropyltriethoxysilane, and 4mL of 10% ammonia water were added sequentially. The mixture was stirred and then treated with N2 for 8h to obtain 12g of amino-modified acylhydrazone-type biochar-based phosphorus-supported material.

[0083] (3) Add 20 mL of toluene to 8 g of amino-modified acylhydrazone-based biochar-based phosphorus-supporting material, stir evenly, add 12 mL of triethylamine and 1.6 mL of 2-bromoisobutyryl bromide, add 50 mL of water, 2 g of temperature-sensitive chitosan derivative and 1 mL of pentamethyldiethylenetriamine, disperse by ultrasonication, add 0.1 g of copper bromide under nitrogen atmosphere, and perform atom transfer radical polymerization reaction at room temperature for 25 min, and then dry in a drying oven at 70 °C for 6 h to obtain temperature-sensitive modified acylhydrazone-based biochar-supporting material. Further extrusion granulation is then performed to obtain temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0084] Example 3

[0085] (1) Preparation of temperature-sensitive chitosan derivatives:

[0086] 4g chitosan (molecular weight 2.5×10⁻⁶) 4 Add 120 mL of 2% methanesulfonic acid solution to the mixture, mix well, add 1 mL of acid anhydride graft copolymerization under nitrogen protection, wash with water, filter, and obtain 4.5 g of acylated chitosan derivative.

[0087] 4g of acylated chitosan derivative was added to 20mL of 7% dimercaprol solution, mixed evenly, and then 0.18mL of 1-hydroxy-benzotriazole and 0.36mL of diisopropylcarbodiimide were added. The amidation reaction was carried out at 50℃ for 4h to obtain 25mL of mercapto-chitosan derivative solution.

[0088] Add 0.2 mL of tetradecyltrimethylammonium chloride to 8 mL of mercapto-chitosan derivative, mix well, and obtain the first suspension;

[0089] 1 g of N-isopropylacrylamide was added to 2 mL of cyclohexanone, mixed well, and then 1.5 mL of the first suspension and 0.16 mL of tricresylphosphine were added. The mixture was reacted at 65 °C for 10 h and filtered to obtain 3.5 g of temperature-sensitive chitosan derivative.

[0090] (2) Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supporting materials:

[0091] 20g of jackfruit peel residue biochar (pH: 10.35) was soaked in 200mL of 20wt% hydrogen peroxide solution for 18h, then filtered. The filter residue was washed with distilled water, ultrasonically cleaned for 30min, and dried at 95℃ for 4h to obtain 18g of oxidized biochar material.

[0092] 15g of oxidized biochar material was impregnated in 675mL of saturated potassium dihydrogen phosphate solution, stirred evenly, sealed and allowed to stand for 30h, and dried at 35℃ for 2h to obtain 17g of biochar-based phosphorus-supported material.

[0093] 0.15 mL of tetradecyltrimethylammonium chloride was added to 15 g of biochar-based phosphorus-supported material and stirred evenly. Then, 0.1 mL of hydrazine hydrate and 0.2 mL of tricresylphosphine were added sequentially. N2 was introduced under stirring for 40 min, and the temperature was raised to 70 °C for 15 h. After the reaction was completed, the reactants were slowly added to a large amount of diethyl ether, filtered to obtain the precipitate, and dried at 35 °C for 2.5 h to obtain 16 g of acylhydrazone-type biochar-based phosphorus-supported material.

[0094] 15g of acylhydrazone-type biochar-based phosphorus-supported material was dissolved in 100mL of ethanol, and then 0.3mL of triethanolamine, 0.5mL of 3-aminopropyltriethoxysilane, and 4mL of 10% ammonia water were added sequentially. The mixture was stirred and then treated with N2 for 8 hours to obtain 17g of amino-modified acylhydrazone-type biochar-based phosphorus-supported material.

[0095] (3) Add 20 mL of toluene to 15 g of amino-modified acylhydrazone-based biochar-based phosphorus-supporting material, stir evenly, then add 13.5 mL of triethylamine and 3 mL of 2-bromoisobutyryl bromide, 50 mL of water, 4 g of temperature-sensitive chitosan derivative and 1.5 mL of pentamethyldiethylenetriamine, ultrasonically disperse, add 0.1 g of copper bromide under nitrogen atmosphere, and perform atom transfer radical polymerization reaction at room temperature for 35 min, then dry in a drying oven at 70 °C for 6 h to obtain temperature-sensitive modified acylhydrazone-based biochar-supporting material, further extruded and granulated to obtain temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0096] Example 4

[0097] (1) Preparation of temperature-sensitive chitosan derivatives:

[0098] 6g chitosan (molecular weight 3.0×10⁻⁶) 4 Add 150 mL of 2% acetic acid solution to the mixture, mix well, and then add 1.2 g of (COCl)2 graft copolymer under nitrogen protection. Wash with water, filter, and obtain 6.5 g of acylated chitosan derivative.

[0099] Add 30 mL of 7% dimercaprol solution to 5 g of acylated chitosan derivative, mix well, then add 0.225 mL of 1-hydroxy-benzotriazole and 0.45 mL of diisopropylcarbodiimide, and carry out amidation reaction at 50 °C for 4 h to obtain 35 mL of mercapto-chitosan derivative solution.

[0100] Add 0.3 mL of benzyltriethylammonium chloride to 10 mL of mercaptochitosan derivative, mix well, and obtain the first suspension;

[0101] 6g of N-isopropylacrylamide was mixed with 10mL of ethylene glycol ethyl ether, 12.5mL of the first suspension and 0.54g of cinchona alkali were added, and the mixture was reacted at 65℃ for 8.5h. After filtration, 7g of temperature-sensitive chitosan derivative was obtained.

[0102] (2) Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supporting materials:

[0103] 20g of jackfruit peel residue biochar (pH: 9.10) was soaked in 500mL of 20wt% hydrogen peroxide solution for 16h, then filtered. The filter residue was washed with distilled water, ultrasonically cleaned for 30min, and dried at 90℃ for 4h to obtain 18g of oxidized biochar material.

[0104] 18g of oxidized biochar material was impregnated in 540mL of saturated potassium dihydrogen phosphate solution, stirred evenly, sealed and allowed to stand for 32h, and then dried at 40℃ for 1.5h to obtain 20.5g of biochar-based phosphorus-supported material.

[0105] 0.15 mL of phase transfer agent tributylamine was added to 20 g of biochar-based phosphorus-supported material. After stirring evenly, 0.1 mL of hydrazine hydrate, 0.1 mL of tricresylphosphine, and 0.1 g of cinchona alkaloid were added sequentially. N2 was introduced under stirring for 50 min, and the temperature was raised to 70 °C for 14 h. After the reaction was completed, the reactants were slowly added to a large amount of diethyl ether. The precipitate was filtered to obtain the sediment, which was dried at 40 °C for 2 h to obtain 23.5 g of acylhydrazone-type biochar-based phosphorus-supported material.

[0106] 20g of acylhydrazone-type biochar-based phosphorus-supported material was dissolved in 100mL of ethanol, and then 0.3mL of triethanolamine, 0.5mL of 3-aminopropyltriethoxysilane, and 4mL of 10% ammonia water were added sequentially. The reaction was carried out with N2 under stirring for 6h to obtain 21g of amino-modified acylhydrazone-type biochar-based phosphorus-supported material.

[0107] (3) Add 50 mL of toluene to 20 g of amino-modified acylhydrazone-based biochar-based phosphorus-supporting material, stir evenly, then add 30 mL of triethylamine and 4 mL of 2-bromoisobutyryl bromide, add 50 mL of water, 6 g of temperature-sensitive chitosan derivative and 2 mL of pentamethyldiethylenetriamine, disperse by ultrasonication, add 0.1 g of copper bromide under nitrogen atmosphere, and perform atom transfer radical polymerization reaction at room temperature for 30 min, then dry in a drying oven at 70 ℃ for 6 h to obtain temperature-sensitive modified acylhydrazone-based biochar-supporting material, further extruded and granulated to obtain temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0108] Example 5

[0109] (1) Preparation of temperature-sensitive chitosan derivatives:

[0110] 6g of chitosan (molecular weight 3.0×104) was added to 150mL of 5% methanesulfonic acid solution. After mixing evenly, 1.6mL of SOCl2 was added under nitrogen protection for graft copolymerization. The mixture was washed with water and filtered to obtain about 6.5g of acylated chitosan derivative.

[0111] Add 30 mL of 7% dimercaprol solution to 5 g of acylated chitosan derivative, mix well, then add 0.225 mL of 1-hydroxy-benzotriazole and 0.45 mL of diisopropylcarbodiimide, and carry out amidation reaction at 50 °C for 4 h to obtain 32 mL of mercapto-chitosan derivative solution.

[0112] Add 0.6 mL of tributylamine to 20 mL of thiol chitosan derivative, mix well, and obtain the first suspension;

[0113] 6g of N-isopropylacrylamide was added to 10mL of cyclohexanone, mixed well, and then 0.54g of cinchona alkaloid was added to the first suspension at a ratio of 12mL. The mixture was reacted at 65℃ for 9.5h and filtered to obtain 8.5g of temperature-sensitive chitosan derivative.

[0114] (2) Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-supporting materials:

[0115] 20g of pineapple leaf biochar (pH: 9.94) was soaked in 500mL of 20wt% hydrogen peroxide solution for 24h, then filtered. The filter residue was washed with distilled water, ultrasonically cleaned for 30min, and dried at 90℃ for 6h to obtain 18g of oxidized biochar material.

[0116] Add 540 mL of saturated potassium dihydrogen phosphate solution to 18 g of oxidized biochar material, impregnate, stir evenly, seal and let stand for 24 h, and dry at 40 °C for 2 h to obtain 20.5 g of biochar-based phosphorus-supported material.

[0117] 0.15 mL of tributylamine was added to 20 g of biochar-based phosphorus-supported material and stirred evenly. Then, 0.1 mL of hydrazine hydrate, 0.1 mL of trialkylphosphine, and 0.1 g of cinchona alkaloid were added sequentially. N2 was introduced under stirring for 45 min, and the temperature was raised to 70 °C for 14 h. After the reaction was completed, the reactants were slowly added dropwise to a large amount of diethyl ether. The precipitate was filtered to obtain the sediment, which was dried at 40 °C for 2 h to obtain 23.5 g of acylhydrazone-type biochar-based phosphorus-supported material.

[0118] 20g of acylhydrazone-type biochar-based phosphorus-supported material was dissolved in 100mL of ethanol, and then 0.3mL of triethanolamine, 0.5mL of 3-aminopropyltriethoxysilane, and 4mL of 10% ammonia water were added sequentially. The mixture was stirred and then treated with N2 for 5h to obtain 21g of amino-modified acylhydrazone-type biochar-based phosphorus-supported material.

[0119] (3) Add 100 mL of toluene to 20 g of amino-modified acylhydrazone-based biochar-based phosphorus-supporting material, stir evenly, add 30 mL of triethylamine and 4 mL of 2-bromoisobutyryl bromide, add 50 mL of water, 6 g of temperature-sensitive chitosan derivative and 2 mL of pentamethyldiethylenetriamine, disperse by ultrasonication, add 0.1 g of copper bromide under nitrogen atmosphere, and perform atom transfer radical polymerization reaction at room temperature for 30 min, and then dry in a drying oven at 70 ℃ for 6 h to obtain temperature-sensitive modified acylhydrazone-based biochar-supporting material. Further extrusion granulation is performed to obtain temperature / pH dual-responsive biochar-based phosphate fertilizer.

[0120] Comparative Example 1

[0121] Compared with Example 1, in this comparative example, the first suspension was added at a ratio of 1 mL of the first suspension for every 3 g of N-isopropylacrylamide, and no activator was used when preparing the temperature-sensitive chitosan derivative, that is, the temperature-sensitive chitosan derivative preparation reaction was not carried out and the preparation was unsuccessful; the rest of the operations were the same as in Example 1.

[0122] Comparative Example 2

[0123] Compared with Example 1, in this comparative example, the ratio of amino-modified acylhydrazone-based biochar-supported phosphorus material to temperature-sensitive chitosan derivative is 1:3; the amount of pentamethyldiethylenetriamine added is 5 mL of pentamethyldiethylenetriamine per gram of amino-modified acylhydrazone-based biochar-supported phosphorus material, and no triethylamine, 2-bromoisobutyryl bromide and copper bromide are added, that is, no temperature-sensitive chitosan derivative grafting sites are introduced on the amino-modified acylhydrazone-based biochar-supported phosphorus material; the rest of the operation is the same as in Example 1.

[0124] Experimental Example 1

[0125] 2g of the temperature / pH dual-responsive biochar-based phosphate fertilizer obtained in Examples 1-5 was dissolved in 50mL of water, and the stability of the biochar-based phosphate fertilizer aqueous solution was observed. The results are as follows: Figure 3 As shown.

[0126] The temperature / pH dual-responsive biochar-based phosphate fertilizers obtained in Examples 1-5 were subjected to infrared spectroscopy and SEM analysis, respectively. The infrared spectra are shown below. Figure 4 As shown, the SEM results are as follows: Figure 5 As shown.

[0127] Experimental Example 2

[0128] 250g of soil samples with pH=5.5 and pH=7.5 were weighed into plastic cups, and the moisture content was adjusted to 60% of the maximum field capacity. 20g of fertilizer samples prepared in Examples 1-5 and Comparative Examples 1-2 were added to each cup, respectively. The cups were placed in constant temperature incubators at 16℃, 20℃, 24℃, 30℃, 35℃, and 40℃. The moisture content was adjusted every two days. After 7 days of incubation, the soil samples were ground and passed through a 2mm sieve. The available phosphorus content was determined using the hydrochloric acid-ammonium fluoride extraction method, and the phosphorus release rate of the fertilizer samples was calculated. The phosphorus release rate (%) in the fertilizer sample = (available phosphorus content in the soil after 7 days of incubation - available phosphorus content in the original soil) * 100 / phosphorus content of the fertilizer sample. The experimental results are shown in Table 1. It can be seen that the biochar-based phosphate fertilizers prepared in Comparative Examples 1 and 2 did not show a significant response to temperature.

[0129] Table 1. Phosphorus release rate in temperature / pH dual-responsive biochar-based phosphate fertilizer

[0130]

[0131]

[0132] Experimental Example 3

[0133] Weigh 20g of fertilizer samples prepared in Examples 1-5 and Comparative Examples 1-2, and 500g of soil samples into pots respectively. Add 0.45g of urea, 2.20g of potassium chloride, and 80g of commercially available organic fertilizer, and mix thoroughly. Add 250ml of water and activate the mixture in the dark at room temperature for 7 days. Then, transplant 3 pre-germinated corn seedlings with 3-4 leaves into each pot. Adjust the water content every 3 days. After 15 days of cultivation, the growth status of the corn plants is as follows. Figure 6 As shown in Table 2, maize plants were harvested after 35 days of cultivation. The fresh weight, plant height, stem diameter, and phosphorus content of the maize plants were measured. The results were calculated using the following formula:

[0134] Phosphate fertilizer utilization efficiency (%) = Phosphate accumulation in plants × 100 / Phosphate content of fertilizer in the example.

[0135] Table 2. Effects of temperature / pH dual-responsive biochar-based phosphate fertilizer on maize plant growth.

[0136]

[0137]

[0138] As shown in Tables 1 and 2, the temperature / pH dual-responsive biochar-based phosphate fertilizer prepared by this invention releases phosphorus slowly at low temperatures. The release rate can reach over 30% between 24℃ and 30℃. At higher temperatures (35℃ to 40℃), dehydration and condensation occur, reducing phosphorus release. The phosphorus release rate is higher at lower pH (pH=5.5) and lower at pH=7.5, indicating that the biochar-based phosphate fertilizer prepared by this invention can achieve a dual response to temperature and pH. In contrast, the comparative example shows an irregular response to temperature and pH, with a high release rate, easily released in one step, and then fixed in the soil, reducing its bioavailability. Furthermore, the temperature / pH dual-responsive biochar-based phosphate fertilizer prepared by this invention has a significant promoting effect on the growth of maize plants, significantly increasing the phosphorus content in maize plants, increasing fertilizer utilization efficiency, and reducing phosphorus loss.

[0139] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a temperature / pH dual-responsive biochar-based phosphate fertilizer, characterized in that, Includes the following steps: S1. Preparation of temperature-sensitive chitosan derivatives: This is achieved by sequentially performing acylation, thiolation, and reaction with a temperature-sensitive comonomer on chitosan. Specifically, S1 includes the following steps: [The text then abruptly shifts to a different topic:] ...a mixture with a molecular weight of 2×10... 4 ~3.5×10 4 Chitosan is dissolved in a 1%–3% acetic acid solution or a 2%–5% methanesulfonic acid solution to obtain a chitosan-acetic acid / methanesulfonic acid solution. This solution is then graft copolymerized in a homogeneous phase to obtain an acylated chitosan derivative with an acylation degree ≥1.

8. Dimercaptopropanol is added to the acylated chitosan derivative, and an amidation reaction is carried out at 50°C for 4 hours under the presence of an activator and a condensing agent to obtain a mercapto chitosan derivative. The amounts of the activator and condensing agent added are both 0.15%–0.5% of the weight of the chitosan-acetic acid / methanesulfonic acid solution. A first phase transfer agent is added to the mercapto chitosan derivative, and the mixture is stirred to obtain a first suspension. A temperature-sensitive comonomer material is dissolved in an organic solvent, stirred, and then the first suspension and a first activator are added. The mixture is stirred at 65°C. The reaction is carried out at ℃ for 8-10 hours to obtain a temperature-sensitive chitosan derivative; the activator is preferably 1-hydroxy-benzotriazole; the condensing agent is preferably diisopropylcarbodiimide; the amount of acetic acid solution used is 20-30 mL of 1%-3% acetic acid solution per gram of chitosan; the amount of dimercaprol added is 10-30 mL of dimercaprol per 2-6 g of acylated chitosan derivative; the temperature-sensitive comonomer is N-isopropylacrylamide, and the amount added is 1 g of temperature-sensitive comonomer per 1-3.5 mL of the first suspension; the amount of organic solvent added is 1.67-3 mL of organic solvent per gram of temperature-sensitive comonomer. S2. Preparation of amino-modified acylhydrazone-type biochar-based phosphorus-carrying material: This is prepared by sequentially oxidizing, adsorbing phosphorus, and acylhydrazone-modifying biochar. Specifically, S2 includes the following steps: immersing biochar in hydrogen peroxide solution for 12-24 hours, filtering, washing, and drying at 85-95°C for 4-8 hours to obtain oxidized biochar material; immersing the oxidized biochar material in potassium dihydrogen phosphate solution, stirring evenly, sealing and standing for 18-36 hours, and drying at 35-45°C for 1-2 hours to obtain biochar-based phosphorus-carrying material; adding a second... A phase transfer agent was stirred until homogeneous, and then hydrazine hydrate and a second activator were added sequentially. N2 was bubbled through the mixture while stirring for 30-60 minutes, and the temperature was raised to 70°C for 12-15 hours. After the reaction was complete, the reactants were added dropwise to diethyl ether, and the precipitate was filtered and dried at 35-45°C for 1.5-2.5 hours to obtain an acylhydrazone-type biochar-based phosphorus-loaded material. The acylhydrazone-type biochar-based phosphorus-loaded material was dissolved in anhydrous ethanol, and triethanolamine, 3-aminopropyltriethoxysilane, and 10% ammonia solution were added sequentially. N2 was bubbled through the mixture while stirring for 4-8 hours to obtain an amino-modified acylhydrazone-type biochar-based phosphorus-loaded material. The first phase transfer agent and the second phase transfer agent are both selected from one or more of the following: chain-like polyethylene glycol dialkyl ether, cyclodextrin, tetradecyltrimethylammonium chloride, benzyltriethylammonium chloride, pyridine, and tributylamine; the amount of the first phase transfer agent added is 0.025 mL to 0.03 mL or 0.025 g to 0.03 g per mL of mercapto-chitosan derivative; the amount of the second phase transfer agent added is 0.0075 mL to 0.015 mL or 0.0075 g to 0.015 g per g of biochar-based phosphorus-supported material; the first activator and the second activator are both selected from one or more of the following: styrenephosphine, trialkylphosphine, cinchona bark, and 2-hydroxy-2-methyl-1-phenylpropanone; S3. Introducing atom transfer radical polymerization reaction sites onto the amino-modified acylhydrazone-based biochar-based phosphorus-supporting material, adding water, temperature-sensitive chitosan derivatives, and pentamethyldiethylenetriamine, ultrasonically dispersing, adding copper bromide under a nitrogen atmosphere, reacting at room temperature for 20-50 minutes, and then drying to obtain a temperature-sensitive modified acylhydrazone-based biochar-supporting material, which is then extruded and granulated to obtain a temperature / pH dual-responsive biochar-based phosphate fertilizer; the introduction of atom transfer radical polymerization reaction sites onto the amino-modified acylhydrazone-based biochar-supporting material... The method for introducing atom transfer radical polymerization reaction sites is as follows: atom transfer radical polymerization reaction sites are introduced into the biochar material in toluene through the action of triethylamine and 2-bromoisobutyryl bromide; the weight ratio of amino-modified acylhydrazone-based biochar-based phosphorus-supported material and temperature-sensitive chitosan derivative in S3 is (4-10):(1-3); the amount of pentamethyldiethylenetriamine added is 0.5 mL to 1 mL of pentamethyldiethylenetriamine per 4 g to 10 g of amino-modified acylhydrazone-based biochar-based phosphorus-supported material.

2. The preparation method of the temperature / pH dual-responsive biochar-based phosphate fertilizer according to claim 1, characterized in that, The biochar is one or more of pineapple leaf biochar, banana stalk biochar, and jackfruit peel residue biochar, and the pH of the biochar is 9.10 to 10.35; the concentration of the hydrogen peroxide solution is 10 wt% to 30 wt%; the potassium dihydrogen phosphate solution is a saturated potassium dihydrogen phosphate solution, and the amount added is 20 mL to 50 mL of saturated potassium dihydrogen phosphate solution per gram of oxidized biochar.

3. A method for preparing a temperature / pH dual-responsive biochar-based phosphate fertilizer according to claim 1 or 2.

4. The application of the temperature / pH dual-responsive biochar-based phosphate fertilizer of claim 3 in agriculture.

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