A carbon-based soil conditioner and its preparation method

Abstract

The present invention relates to the technical field of soil improvement, and discloses a carbon-based soil conditioner and a preparation method thereof. In the present invention, biochar, humic acid-based modified hydrogel, diatomite, hydroxyapatite, Bacillus licheniformis, and Bacillus coagulans are stirred and mixed, and then a polyvinyl alcohol solution is sprayed into the mixture, granulated and dried to obtain the carbon-based soil conditioner. Imidazoline quaternary ammonium salts and quaternary phosphonium salts can adsorb on the negatively charged cell surface of bacteria through their positive charges, and the hydrophobic groups are inserted into the lipid layer, causing the leakage of intracellular substances and leading to the death of bacteria; guanidine groups destroy the cell membrane of bacteria through strong positive charge adsorption, bind and coagulate nucleic acids and enzymes, playing an antibacterial role; the nitrogen atoms in the imidazole group and triazine group act as hydrogen bond acceptors, enhancing the hydrogen bond interaction with the hydrogel molecular chain and improving the water retention performance of the conditioner; the benzene ring hydrophobic groups form reversible cross-linking points through hydrophobic association, constituting a dynamic three-dimensional network and improving the water retention performance of the conditioner.

Description

Technical Field

[0001] The present invention relates to the technical field of soil improvement, and particularly to a carbon-based soil conditioner and a preparation method thereof. Background Art

[0002] Soil conditioners are important functional materials in the fields of agricultural production and ecological restoration. They improve soil fertility and promote plant growth by regulating the physical structure, chemical properties, and microbial environment of the soil. Traditional soil conditioners mainly focus on improving soil air permeability, adjusting the pH value, or supplementing organic matter, such as using materials like straw, humic acid, and bentonite. However, with the intensification of global climate change and land degradation problems, single-functional conditioners can no longer meet the requirements of modern agriculture for improving the comprehensive performance of the soil. Especially in scenarios such as insufficient water retention in arid regions and the accumulation of pathogenic microorganisms in continuous cropping soils, the existing technologies have limitations in water retention performance and antibacterial performance. Patent CN109456131B discloses a wood vinegar liquid carbon-based soil conditioner with the effects of reducing soil salinity and alkalinity and increasing crop yield and efficiency, but its water retention effect and antibacterial effect on the soil still need to be improved. Summary of the Invention

[0003] (I) Technical Problems to be Solved

[0004] Aiming at the deficiencies of the prior art, the present invention provides a carbon-based soil conditioner and a preparation method thereof. The soil conditioner prepared by the present invention has good water retention and antibacterial properties for the soil.

[0005] (II) Technical Solutions

[0006] To achieve the above object, the present invention provides the following technical solutions: A carbon-based soil conditioner, comprising the following weight components: 25 - 30 parts by weight of biochar, 2 - 4 parts by weight of humic acid-based modified hydrogel, 1.5 - 2.5 parts by weight of diatomite, 3 - 4 parts by weight of hydroxyapatite, 1.6 - 2 parts by weight of Bacillus licheniformis, 0.8 - 1.2 parts by weight of Bacillus coagulans, 3.2 - 5 parts by weight of 5% polyvinyl alcohol solution.

[0007] Preferably, the preparation method of the humic acid-based modified hydrogel includes the following steps:

[0008] (1) Add 6 - 9 g of succinic acid, 13 - 19.5 mL of diethylenetriamine, and 60 - 90 mL of a water-carrying agent to a reactor, stir and mix, react at 162 - 170 °C for 3.5 - 4 h, then continue to heat up to 180 - 190 °C and react for 4 - 6 h. After the reaction is completed, rotary evaporate to remove the water-carrying agent to obtain an imidazoline intermediate;

[0009] (2) Add 7.4 - 8 g of imidazoline intermediate and 10.6 - 12.4 g of 1 - allyl - 3 - chlorobenzene to 70 - 100 mL of anhydrous ethanol solvent, stir and mix, heat up to 52 - 58 °C and react for 9 - 12 h. After the reaction is completed, rotary evaporate to remove anhydrous ethanol, recrystallize with 50 - 80 mL of a 1:1 ethanol - acetone mixed solution under ice bath, and vacuum dry to obtain the imidazoline quaternary ammonium salt modified cross - linker;

[0010] (3) Dissolve 2.2 - 2.5 g of chitosan in 80 - 120 mL of acetic acid solution with a mass fraction of 1.6% - 2%, stir to dissolve, add 0.02 - 0.04 g of 1 - hydroxybenzotriazole initiator and react for 20 - 30 min, then add 4.5 - 5 g of (3 - carboxypropyl) triphenylphosphonium bromide, introduce nitrogen for protection, heat up to the reaction temperature and react for 15 - 19 h. After the reaction is completed, dialyze and then freeze - dry to obtain the phosphonium salt modified chitosan;

[0011] (4) Add 3.6 - 4.2 g of cyanuric chloride to 30 - 40 mL of acetonitrile solvent at 0 - 4 °C, stir to dissolve. Then dissolve 7.6 - 8 g of polyhexamethylene biguanide in 45 - 50 mL of deionized water, and drop it into the cyanuric chloride solution. Add 0.03 - 0.07 g of acid - binding agent to adjust the pH to neutral, and react at a constant temperature for 8.5 - 10 h to obtain Solution 1. Dissolve 2.4 - 2.8 g of phosphonium salt modified chitosan in 100 - 140 mL of deionized water, add Solution 1 to the phosphonium salt modified chitosan solution, and react at 42 - 45 °C for 12 - 15 h. After the reaction is completed, dialyze and then freeze - dry to obtain the guanidine - containing phosphonium salt modified chitosan;

[0012] (5) Add 1 - 1.2 g of humic acid and 10 - 12 mL of sodium hydroxide solution to the reactor, then add 50 - 60 mL of deionized water, stir to dissolve. Then add 1.2 - 1.4 g of guanidine - containing phosphonium salt modified chitosan, stir and heat up to 40 - 48 °C, introduce nitrogen for 10 - 15 min to remove oxygen, add 0.12 - 0.14 g of potassium persulfate initiator, 14 - 18 g of acrylic acid solution with a neutralization degree of 50% - 60%, and 0.03 - 0.04 g of imidazoline quaternary ammonium salt modified cross - linker, heat up to 65 - 75 °C and react for 2.5 - 3.5 h. After the reaction is completed, wash with deionized water, dry at 55 - 60 °C and then pulverize to obtain the humic acid - based modified hydrogel.

[0013] Preferably, the water - carrying agent in step (1) is toluene.

[0014] Preferably, the reaction temperature after adding (3 - carboxypropyl) triphenylphosphonium bromide in step (3) is 78 - 84 °C.

[0015] Preferably, in the step (4), the acid-binding agent is triethylamine.

[0016] Preferably, in the step (5), the mass fraction of the sodium hydroxide solution is 18% - 24%.

[0017] Preferably, the preparation method of the acrylic acid solution with a neutralization degree of 50% - 60% in the step (5) is as follows: Add 34.3 mL of acrylic acid to 500 mL of deionized water, stir to dissolve, add 10 - 12 g of sodium hydroxide thereto at 0 - 10°C, and react for 40 - 50 min to obtain an acrylic acid solution with a neutralization degree of 50% - 60%.

[0018] Preferably, the preparation method of the carbon-based soil conditioner is as follows: Add biochar, humic acid-based modified hydrogel, diatomite, hydroxyapatite, Bacillus licheniformis, and Bacillus coagulans to a mixer, stir and mix, then spray 5% polyvinyl alcohol solution into it as a binder, extrude and granulate in a granulator, and dry at 40 - 50°C until the water content is 4% - 8% to obtain the carbon-based soil conditioner.

[0019] (III) Beneficial technical effects

[0020] In the present invention, biochar, humic acid-based modified hydrogel, diatomite, hydroxyapatite, Bacillus licheniformis, and Bacillus coagulans are added to a mixer, stirred and mixed, then 5% polyvinyl alcohol solution is sprayed into it as a binder, extruded and granulated in a granulator, and dried to obtain the carbon-based soil conditioner.

[0021] Imidazoline quaternary ammonium salts and quaternary phosphonium salts can be adsorbed on the negatively charged cell surface of bacteria through their positive charges, and the hydrophobic groups are inserted into the lipid layer, changing the cell membrane permeability, destroying the membrane structure, causing the leakage of intracellular substances, and leading to the death of bacteria; guanidine groups adsorb and destroy the cell membrane of bacteria through strong positive charges, combine and coagulate nucleic acids and enzymes, resulting in the leakage of intracellular substances and the loss of metabolic functions, thus playing an antibacterial role; the nitrogen atoms in the imidazole group and triazine group act as hydrogen bond acceptors, enhancing the hydrogen bond interaction with the hydrogel molecular chain, forming a stable physical cross-linked network structure, improving the water retention performance of the conditioner; the benzene ring hydrophobic groups form reversible cross-linking points through hydrophobic association, constituting a dynamic three-dimensional network, and the hydrophobic interaction enhances the elastic modulus and compressive resistance of the hydrogel, enabling it to maintain the structural integrity under external pressure, reducing the passive extrusion of water, and improving the water retention performance of the conditioner. Description of the drawings

[0022] Figure 1 is the synthesis reaction formula of the imidazoline quaternary ammonium salt modified cross-linking agent.

[0023] Figure 2 is the synthesis reaction formula of the guanidine group-containing quaternary phosphonium salt modified chitosan. Detailed implementation manners Example 1

[0024] (1) Add 6 g of succinic acid, 13 mL of diethylenetriamine, and 60 mL of toluene as a water-carrying agent to the reactor, stir and mix. After reacting at 162 °C for 3.5 h, continue to heat up to 180 °C and react for 4 h. After the reaction is completed, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate;

[0025] (2) Add 7.4 g of the imidazoline intermediate and 10.6 g of 1-allyl-3-chlorobenzene to 70 mL of anhydrous ethanol solvent, stir and mix, heat up to 52 °C and react for 9 h. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, and recrystallize with a 50 mL mixed solution of ethanol-acetone with a volume ratio of 1:1 under ice bath, and dry in vacuum to obtain an imidazoline quaternary ammonium salt modified crosslinking agent;

[0026] (3) Dissolve 2.2 g of chitosan in 80 mL of acetic acid solution with a mass fraction of 1.6%, stir to dissolve, add 0.02 g of 1-hydroxybenzotriazole initiator and react for 20 min, then add 4.5 g of (3-carboxypropyl) triphenylphosphonium bromide, pass in nitrogen for protection, heat up to 78 °C and react for 15 h. After the reaction is completed, dialyze and then freeze-dry to obtain a phosphonium salt modified chitosan;

[0027] (4) Add 3.6 g of cyanuric chloride to 30 mL of acetonitrile solvent at 0 °C, stir to dissolve, dissolve 7.6 g of polyhexamethylene biguanide in 45 mL of deionized water, and then drop it into the cyanuric chloride solution. Add 0.03 g of triethylamine as an acid-binding agent to adjust the pH to neutral, and react at a constant temperature for 8.5 h to obtain Solution 1. Dissolve 2.4 g of the phosphonium salt modified chitosan in 100 mL of deionized water, add Solution 1 to the phosphonium salt modified chitosan solution, and react at 42 °C for 12 h. After the reaction is completed, dialyze and then freeze-dry to obtain a guanidine group-containing phosphonium salt modified chitosan;

[0028] (5) Add 34.3 mL of acrylic acid to 500 mL of deionized water, stir to dissolve, add 10 g of sodium hydroxide at 0 °C, and react for 40 min to obtain an acrylic acid solution with a neutralization degree of 50%. Add 1 g of humic acid, 10 mL of sodium hydroxide solution with a mass fraction of 18% to the reactor, then add 50 mL of deionized water, stir to dissolve, add 1.2 g of the guanidine group-containing phosphonium salt modified chitosan, stir and heat up to 40 °C, pass in nitrogen for 10 min to remove oxygen, add 0.12 g of potassium persulfate initiator, 14 g of acrylic acid solution with a neutralization degree of 50%, and 0.03 g of imidazoline quaternary ammonium salt modified crosslinking agent, heat up to 65 °C and react for 2.5 h. After the reaction is completed, wash with deionized water, dry at 55 °C and then pulverize to obtain a humic acid-based modified hydrogel;

[0029] (6) Add 25 parts by weight of biochar, 2 parts by weight of humic acid-based modified hydrogel, 1.5 parts by weight of diatomite, 3 parts by weight of hydroxyapatite, 1.6 parts by weight of Bacillus licheniformis, and 0.8 parts by weight of Bacillus coagulans to the mixer, stir and mix, then spray 3.2 parts by weight of 5% polyvinyl alcohol solution as a binder into it, extrude and granulate in a granulator, and dry at 40 °C until the water content is 4% to obtain a carbon-based soil conditioner. Example 2

[0030] (1) Add 9 g of succinic acid, 19.5 mL of diethylenetriamine, and 90 mL of toluene as a water-carrying agent to the reactor, stir and mix, react at 170 °C for 4 h, then continue to heat up to 190 °C and react for 6 h. After the reaction is completed, rotary evaporate to remove the toluene water-carrying agent to obtain an imidazoline intermediate;

[0031] (2) Add 8 g of the imidazoline intermediate and 12.4 g of 1-allyl-3-chlorobenzene to 100 mL of anhydrous ethanol solvent, stir and mix, heat up to 58 °C and react for 12 h. After the reaction is completed, rotary evaporate to remove anhydrous ethanol, recrystallize with 80 mL of a mixed solution of ethanol-acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinking agent;

[0032] (3) Dissolve 2.5 g of chitosan in 120 mL of 2% acetic acid solution by mass, stir and dissolve, add 0.04 g of 1-hydroxybenzotriazole initiator and react for 30 min, then add 5 g of (3-carboxypropyl) triphenylphosphonium bromide to it, introduce nitrogen protection, heat up to 84 °C and react for 19 h. After the reaction is completed, dialyze and then freeze-dry to obtain quaternary phosphonium salt modified chitosan;

[0033] (4) Add 4.2 g of cyanuric chloride to 40 mL of acetonitrile solvent at 4 °C, stir and dissolve, then dissolve 8 g of polyhexamethylene biguanide in 50 mL of deionized water, and drop it into the cyanuric chloride solution. Add 0.07 g of triethylamine as an acid-binding agent to adjust the pH to neutral, and react at a constant temperature for 10 h to obtain Solution 1. Dissolve 2.8 g of quaternary phosphonium salt modified chitosan in 140 mL of deionized water, add Solution 1 to the quaternary phosphonium salt modified chitosan solution, and react at 45 °C for 15 h. After the reaction is completed, dialyze and then freeze-dry to obtain guanidine group-containing quaternary phosphonium salt modified chitosan;

[0034] (5) Add 34.3 mL of acrylic acid to 500 mL of deionized water, stir to dissolve, add 12 g of sodium hydroxide thereto at 10 °C, react for 50 min to obtain an acrylic acid solution with a neutralization degree of 60%. Add 1.2 g of humic acid and 12 mL of a sodium hydroxide solution with a mass fraction of 24% to the reactor, then add 60 mL of deionized water, stir to dissolve, add 1.4 g of guanidine group-containing quaternary phosphonium salt-modified chitosan thereto, stir and heat up to 48 °C, introduce nitrogen for 15 min to remove oxygen, add 0.14 g of potassium persulfate initiator, 18 g of the acrylic acid solution with a neutralization degree of 60%, and 0.04 g of imidazoline quaternary ammonium salt-modified crosslinking agent, heat up to 75 °C and react for 3.5 h. After the reaction is completed, wash with deionized water, dry at 60 °C and then pulverize to obtain humic acid-based modified hydrogel;

[0035] (6) Add 30 parts by weight of biochar, 4 parts by weight of humic acid-based modified hydrogel, 2.5 parts by weight of diatomite, 4 parts by weight of hydroxyapatite, 2 parts by weight of Bacillus licheniformis, and 1.2 parts by weight of Bacillus coagulans to a mixer, stir and mix, then spray 5 parts by weight of a 5% polyvinyl alcohol solution as a binder thereto, extrude and granulate in a granulator, and dry at 50 °C until the water content is 8% to obtain a carbon-based soil conditioner. Example 3

[0036] (1) Add 7.5 g of succinic acid, 16.2 mL of diethylenetriamine, and 75 mL of toluene as a water-carrying agent to a reactor, stir and mix, react at 166 °C for 3.8 h, then continue to heat up to 185 °C and react for 5 h. After the reaction is completed, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate;

[0037] (2) Add 7.7 g of the imidazoline intermediate and 11.5 g of 1-allyl-3-chlorobenzene to 85 mL of an anhydrous ethanol solvent, stir and mix, heat up to 55 °C and react for 10.5 h. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, recrystallize with a 65 mL ethanol-acetone mixed solution with a volume ratio of 1:1 under ice bath, and dry in vacuum to obtain an imidazoline quaternary ammonium salt-modified crosslinking agent;

[0038] (3) Dissolve 2.4 g of chitosan in 100 mL of an acetic acid solution with a mass fraction of 1.8%, stir to dissolve, add 0.03 g of 1-hydroxybenzotriazole initiator and react for 25 min, then add 4.7 g of (3-carboxypropyl) triphenylphosphonium bromide thereto, protect with nitrogen, heat up to 81 °C and react for 17 h. After the reaction is completed, dialyze and then freeze-dry to obtain quaternary phosphonium salt-modified chitosan;

[0039] (4) Add 3.9 g of cyanuric chloride to 35 mL of acetonitrile solvent at 2 °C. After stirring and dissolving, dissolve 7.8 g of polyhexamethylene biguanide in 48 mL of deionized water, then drop it into the cyanuric chloride solution. Add 0.05 g of triethylamine as an acid-binding agent to adjust the pH to neutral, and react at a constant temperature for 9.2 h to obtain Solution 1. Dissolve 2.6 g of quaternary phosphonium salt modified chitosan in 120 mL of deionized water, add Solution 1 to the quaternary phosphonium salt modified chitosan solution, and react at 43 °C for 13.5 h. After the reaction, dialyze and then freeze-dry to obtain guanidine group quaternary phosphonium salt modified chitosan;

[0040] (5) Add 34.3 mL of acrylic acid to 500 mL of deionized water, stir and dissolve. Add 11 g of sodium hydroxide to it at 5 °C and react for 45 min to obtain an acrylic acid solution with a neutralization degree of 55%. Add 1.1 g of humic acid, 11 mL of sodium hydroxide solution with a mass fraction of 21% to the reactor, then add 55 mL of deionized water, stir and dissolve. Then add 1.3 g of guanidine group quaternary phosphonium salt modified chitosan to it, stir and heat up to 44 °C, introduce nitrogen for 12 min to remove oxygen, add 0.13 g of potassium persulfate initiator, 16 g of acrylic acid solution with a neutralization degree of 55%, and 0.035 g of imidazoline quaternary ammonium salt modified crosslinking agent, heat up to 70 °C and react for 3 h. After the reaction, wash with deionized water, dry at 58 °C and then pulverize to obtain humic acid-based modified hydrogel;

[0041] (6) Add 28 parts by weight of biochar, 3 parts by weight of humic acid-based modified hydrogel, 2 parts by weight of diatomite, 3.5 parts by weight of hydroxyapatite, 1.8 parts by weight of Bacillus licheniformis, and 1 part by weight of Bacillus coagulans to a mixer, stir and mix. Then spray 4.1 parts by weight of 5% polyvinyl alcohol solution as a binder into it, extrude and granulate in a granulator, and dry at 45 °C until the water content is 6% to obtain a carbon-based soil conditioner. Example 4

[0042] (1) Add 6 g of succinic acid, 13 mL of diethylenetriamine, and 60 mL of toluene as a water-carrying agent to a reactor, stir and mix. After reacting at 162 °C for 3.5 h, continue to heat up to 180 °C and react for 4 h. After the reaction, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate;

[0043] (2) Add 7.4 g of the imidazoline intermediate and 10.6 g of 1-allyl-3-chlorobenzene to 70 mL of anhydrous ethanol solvent, stir and mix, heat up to 52 °C and react for 9 h. After the reaction, remove anhydrous ethanol by rotary evaporation, recrystallize with a 50 mL mixed solution of ethanol-acetone with a volume ratio of 1:1 under ice bath, and dry in vacuum to obtain an imidazoline quaternary ammonium salt modified crosslinking agent;

[0044] (3) Dissolve 2.5 g of chitosan in 120 mL of 2% acetic acid solution, stir to dissolve, add 0.04 g of 1-hydroxybenzotriazole initiator and react for 30 min, then add 5 g of (3-carboxypropyl) triphenylphosphonium bromide, pass nitrogen for protection, heat up to 84 °C and react for 19 h. After the reaction is completed, dialyze and then freeze-dry to obtain quaternary phosphonium salt modified chitosan;

[0045] (4) Add 4.2 g of cyanuric chloride to 40 mL of acetonitrile solvent at 4 °C, stir to dissolve. Then dissolve 8 g of polyhexamethylene biguanide in 50 mL of deionized water, and drop it into the cyanuric chloride solution. Add 0.07 g of triethylamine acid-binding agent to adjust the pH to neutral, and react at a constant temperature for 10 h to obtain Solution 1. Dissolve 2.8 g of quaternary phosphonium salt modified chitosan in 140 mL of deionized water, add Solution 1 to the quaternary phosphonium salt modified chitosan solution, and react at 45 °C for 15 h. After the reaction is completed, dialyze and then freeze-dry to obtain guanidine group-containing quaternary phosphonium salt modified chitosan;

[0046] (5) Add 34.3 mL of acrylic acid to 500 mL of deionized water, stir to dissolve, add 11 g of sodium hydroxide at 5 °C, and react for 45 min to obtain an acrylic acid solution with a neutralization degree of 55%. Add 1.1 g of humic acid, 11 mL of 21% sodium hydroxide solution to the reactor, then add 55 mL of deionized water, stir to dissolve, and then add 1.3 g of guanidine group-containing quaternary phosphonium salt modified chitosan. Stir and heat up to 44 °C, pass nitrogen for 12 min to remove oxygen, add 0.13 g of potassium persulfate initiator, 16 g of acrylic acid solution with a neutralization degree of 55%, and 0.035 g of imidazoline quaternary ammonium salt modified crosslinking agent, heat up to 70 °C and react for 3 h. After the reaction is completed, wash with deionized water, dry at 58 °C and then pulverize to obtain humic acid-based modified hydrogel;

[0047] (6) Add 28 parts by weight of biochar, 3 parts by weight of humic acid-based modified hydrogel, 2 parts by weight of diatomite, 3.5 parts by weight of hydroxyapatite, 1.8 parts by weight of Bacillus licheniformis, and 1 part by weight of Bacillus coagulans to the mixer, stir and mix, then spray 4.1 parts by weight of 5% polyvinyl alcohol solution as a binder, extrude and granulate in a granulator, and dry at 45 °C until the water content is 6% to obtain a carbon-based soil conditioner. Example 5

[0048] (1) Add 7.5 g of succinic acid, 16.2 mL of diethylenetriamine, and 75 mL of toluene water-carrying agent to the reactor, stir and mix. After reacting at 166 °C for 3.8 h, continue to heat up to 185 °C and react for 5 h. After the reaction is completed, rotary evaporate to remove the toluene water-carrying agent to obtain an imidazoline intermediate;

[0049] (2) Add 7.7 g of imidazoline intermediate and 11.5 g of 1-allyl-3-chlorobenzene to 85 mL of anhydrous ethanol solvent, stir and mix, heat up to 55 °C and react for 10.5 h. After the reaction is completed, rotary evaporate to remove anhydrous ethanol, recrystallize with 65 mL of a mixed solution of ethanol-acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinking agent;

[0050] (3) Dissolve 2.2 g of chitosan in 80 mL of acetic acid solution with a mass fraction of 1.6%, stir to dissolve, add 0.02 g of 1-hydroxybenzotriazole initiator and react for 20 min, then add 4.5 g of (3-carboxypropyl) triphenylphosphonium bromide, introduce nitrogen protection, heat up to 78 °C and react for 15 h. After the reaction is completed, dialyze and then freeze-dry to obtain a phosphonium salt modified chitosan;

[0051] (4) Add 3.6 g of cyanuric chloride to 30 mL of acetonitrile solvent at 0 °C, stir to dissolve, dissolve 7.6 g of polyhexamethylene biguanide in 45 mL of deionized water, then drop it into the cyanuric chloride solution, add 0.03 g of triethylamine acid-binding agent to adjust the pH to neutral, and react at a constant temperature for 8.5 h to obtain Solution 1. Dissolve 2.4 g of phosphonium salt modified chitosan in 100 mL of deionized water, add Solution 1 to the phosphonium salt modified chitosan solution, and react at 42 °C for 12 h. After the reaction is completed, dialyze and then freeze-dry to obtain a guanidine group-containing phosphonium salt modified chitosan;

[0052] (5) Add 34.3 mL of acrylic acid to 500 mL of deionized water, stir to dissolve, add 12 g of sodium hydroxide at 10 °C, and react for 50 min to obtain an acrylic acid solution with a neutralization degree of 60%. Add 1.2 g of humic acid, 12 mL of sodium hydroxide solution with a mass fraction of 24% to the reactor, then add 60 mL of deionized water, stir to dissolve, add 1.4 g of guanidine group-containing phosphonium salt modified chitosan, stir and heat up to 48 °C, introduce nitrogen for 15 min to remove oxygen, add 0.14 g of potassium persulfate initiator, 18 g of acrylic acid solution with a neutralization degree of 60%, and 0.04 g of imidazoline quaternary ammonium salt modified crosslinking agent, heat up to 75 °C and react for 3.5 h. After the reaction is completed, wash with deionized water, dry at 60 °C and then pulverize to obtain a humic acid-based modified hydrogel;

[0053] (6) Add 30 parts by weight of biochar, 4 parts by weight of humic acid-based modified hydrogel, 2.5 parts by weight of diatomite, 4 parts by weight of hydroxyapatite, 2 parts by weight of Bacillus licheniformis, and 1.2 parts by weight of Bacillus coagulans to the mixer, stir and mix, then spray 5 parts by weight of 5% polyvinyl alcohol solution as a binder into it, extrude and granulate in a granulator, and dry at 50 °C until the water content is 8% to obtain a carbon-based soil conditioner.

[0054] Comparative Example 1

[0055] Compared with Example 5, the difference in this comparative example is that in step (5), carboxymethyl chitosan is used instead of guanidine group-containing quaternary phosphonium salt-modified chitosan.

[0056] Comparative Example 2

[0057] Compared with Example 5, the difference in this comparative example is that in step (5), N,N'-methylenebisacrylamide crosslinker is used instead of imidazoline quaternary ammonium salt-modified crosslinker.

[0058] The antibacterial experiment was set with 8 treatments. For 7 treatment groups, 2.0 kg of sterilized soil was taken, and the carbon-based soil conditioners in Examples 1-5 and Comparative Examples 1-2 were respectively added to the sterilized soil at 40 g. Sterile water was added to make the soil water content reach 60%. 20 mL of a bacterial suspension containing Ralstonia solanacearum, Rhizoctonia solani, Fusarium oxysporum, and Sclerotinia sclerotiorum (10 8 CFU / mL) was evenly sprayed onto the soil, and cultured in the dark at 25 °C for 14 days; the control group was without adding a soil conditioner, and the others were the same as the treatment groups. Calculate the antibacterial rate, antibacterial rate = (number of bacteria in the control group - number of bacteria in the treatment group) / number of bacteria in the control group × 100%. The experimental soil was taken from the research base farm of South China Agricultural University. The test results are shown in Table 1.

[0059] Table 1: Antibacterial performance test.

[0060] Item Bacteriostasis Rate (%) Example 1 95.3 Example 2 94.6 Example 3 95.5 Example 4 96.1 Example 5 94.8 Comparative Example 1 70.6 Comparative Example 2 79.2

[0061] As can be seen from Table 1, the carbon-based soil conditioners in Examples 1-5 of the present invention have a better antibacterial effect on the soil compared with the carbon-based soil conditioners in Comparative Examples 1-2.

[0062] Mix the carbon-based soil conditioners in Examples 1-5 and Comparative Examples 1-2 with dry soil at a ratio of 0.5 wt%, place them in a PVC pipe with a diameter of 4.5 cm and a length of 15 cm, seal the bottom of the pipe with a nylon mesh (300 mesh) and weigh it. Then suspend the PVC pipe in deionized water for 12 h. Take out the pipe and hang it vertically on a rack to let the water flow out freely. End when no more water seeps out within 10 min, and weigh the pipe. Calculate the maximum water holding rate. The maximum water holding rate = (total weight of the entire pipe when no more water seeps out after wetting - weight of dry soil and PVC pipe before wetting) / (weight of dry soil and PVC pipe before wetting - weight of PVC pipe) × 100%. The experimental soil was taken from the research base farm of South China Agricultural University. The test results are shown in Table 2.

[0063] Table 2: Water retention performance test.

[0064] Item Maximum Water Holding Rate (%) Example 1 46.8 Example 2 47.4 Example 3 47.0 Example 4 46.5 Example 5 47.2 Comparative Example 1 39.2 Comparative Example 2 36.3

[0065] As can be seen from Table 2, compared with the carbon-based soil conditioners in Comparative Examples 1-2, the carbon-based soil conditioners in Examples 1-5 of the present invention have a better water retention effect on the soil.

[0066] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art in the relevant technical field can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A carbon-based soil conditioner, characterized in that, It comprises the following weight components: 25-30 parts by weight of biochar, 2-4 parts by weight of humic acid-based modified hydrogel, 1.5-2.5 parts by weight of diatomite, 3-4 parts by weight of hydroxyapatite, 1.6-2 parts by weight of Bacillus licheniformis, 0.8-1.2 parts by weight of Bacillus coagulans, 3.2-5 parts by weight of 5% polyvinyl alcohol solution; The preparation method of the humic acid-based modified hydrogel, which comprises the following steps: (1) Add 6-9 g of succinic acid, 13-19.5 mL of diethylenetriamine, and 60-90 mL of a water-carrying agent into a reactor, stir and mix, react at 162-170 °C for 3.5-4 h, then continue to heat up to 180-190 °C and react for 4-6 h. After the reaction is completed, rotary evaporate to remove the water-carrying agent to obtain an imidazoline intermediate; (2) Add 7.4-8 g of the imidazoline intermediate and 10.6-12.4 g of 1-allyl-3-chlorobenzene into 70-100 mL of an anhydrous ethanol solvent, stir and mix, heat up to 52-58 °C and react for 9-12 h. After the reaction is completed, rotary evaporate to remove the anhydrous ethanol, recrystallize with 50-80 mL of a mixed solution of ethanol-acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinking agent; (3) Dissolve 2.2-2.5 g of chitosan in 80-120 mL of an acetic acid solution with a mass fraction of 1.6%-2%, stir to dissolve, add 0.02-0.04 g of 1-hydroxybenzotriazole initiator and react for 20-30 min, then add 4.5-5 g of (3-carboxypropyl) triphenylphosphonium bromide, introduce nitrogen protection, heat up to the reaction temperature and react for 15-19 h. After the reaction is completed, dialyze and then freeze-dry to obtain a quaternary phosphonium salt modified chitosan; (4) Add 3.6-4.2 g of cyanuric chloride into 30-40 mL of an acetonitrile solvent at 0-4 °C, stir to dissolve, dissolve 7.6-8 g of polyhexamethylene biguanide in 45-50 mL of deionized water, then drop it into the cyanuric chloride solution, add 0.03-0.07 g of an acid-binding agent to adjust the pH to neutral, and react at a constant temperature for 8.5-10 h to obtain Solution 1. Dissolve 2.4-2.8 g of the quaternary phosphonium salt modified chitosan in 100-140 mL of deionized water, add Solution 1 to the quaternary phosphonium salt modified chitosan solution, and react at 42-45 °C for 12-15 h. After the reaction is completed, dialyze and then freeze-dry to obtain a guanidine group-containing quaternary phosphonium salt modified chitosan; (5) Add 1 - 1.2 g of humic acid and 10 - 12 mL of sodium hydroxide solution to the reactor, then add 50 - 60 mL of deionized water. After stirring and dissolving, add 1.2 - 1.4 g of guanidine - containing quaternary phosphonium salt - modified chitosan. Stir and heat up to 40 - 48 °C, introduce nitrogen for 10 - 15 min to remove oxygen. Add 0.12 - 0.14 g of potassium persulfate initiator, 14 - 18 g of acrylic acid solution with a neutralization degree of 50% - 60%, and 0.03 - 0.04 g of imidazoline quaternary ammonium salt - modified cross - linker. Heat up to 65 - 75 °C and react for 2.5 - 3.5 h. After the reaction is completed, wash with deionized water, dry at 55 - 60 °C and then pulverize to obtain humic - acid - based modified hydrogel.

2. The carbon-based soil conditioner according to claim 1, wherein In the step (1), the water - carrying agent is toluene.

3. The carbon-based soil conditioner according to claim 1, wherein In the step (3), the reaction temperature after adding (3 - carboxypropyl) triphenylphosphonium bromide is 78 - 84 °C.

4. The carbon-based soil conditioner according to claim 1, characterized in that, In the step (4), the acid - binding agent is triethylamine.

5. The carbon-based soil conditioner according to claim 1, characterized in that, In the step (5), the mass fraction of the sodium hydroxide solution is 18% - 24%.

6. The carbon-based soil conditioner according to claim 1, wherein The preparation method of the acrylic acid solution with a neutralization degree of 50% - 60% in the step (5) is as follows: Add 34.3 mL of acrylic acid to 500 mL of deionized water, stir and dissolve. Add 10 - 12 g of sodium hydroxide at 0 - 10 °C and react for 40 - 50 min to obtain an acrylic acid solution with a neutralization degree of 50% - 60%.

7. A preparation method of the carbon-based soil conditioner according to any one of claims 1-6, characterized in that, The preparation method of the carbon - based soil conditioner is as follows: Add bio - carbon, humic - acid - based modified hydrogel, diatomite, hydroxyapatite, Bacillus licheniformis, and Bacillus coagulans to a mixer, stir and mix. Then spray 5% polyvinyl alcohol solution as a binder and extrude and granulate in a granulator. Dry at 40 - 50 °C until the water content is 4% - 8% to obtain the carbon - based soil conditioner.

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