Carbon-based soil conditioner and preparation method thereof

Abstract

The invention relates to the technical field of soil improvement, and discloses a carbon-based soil conditioner and a preparation method thereof. The preparation method comprises the following steps: stirring and mixing biochar, humic acid-based modified hydrogel, diatomite, hydroxyapatite, bacillus licheniformis and bacillus coagulans, spraying a polyvinyl alcohol solution into the mixture, granulating, and drying to obtain the carbon-based soil conditioner. The imidazoline quaternary ammonium salt and the quaternary phosphonium salt can be adsorbed on the surfaces of negatively charged thalli through positive charges, and hydrophobic groups are inserted into a lipoid layer, so that intracellular substances leak, and bacteria die; guanidyl adsorbs and destroys cell membranes of thalli through strong electropositivity, combines and solidifies nucleic acid and enzyme, and plays a role in bacteriostasis; nitrogen atoms in an imidazole group and a triazine group are used as hydrogen bond receptors, so that the hydrogen bond interaction with a hydrogel molecular chain is enhanced, and the water retention capacity of the modifier is improved; a benzene ring hydrophobic group forms reversible crosslinking points through hydrophobic association, a dynamic three-dimensional network is formed, and the water retention performance of the modifier is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil improvement, and in particular 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 focus on improving soil permeability, adjusting pH or supplementing organic matter, such as using materials such as straw, humic acid, and bentonite. However, with the intensification of global climate change and land degradation problems, single-function conditioners can no longer meet the needs of modern agriculture for improving the comprehensive performance of soil, especially in arid areas where soil water retention is insufficient and continuous soil pathogenic microorganisms accumulate. The existing technology has the limitations of poor water retention and antibacterial properties. Patent CN109456131B discloses a wood vinegar carbon-based soil conditioner that has the effects of reducing soil salt and alkali, increasing crop yield and efficiency, but its water retention and antibacterial effects on soil need to be improved. Summary of the invention

[0003] 1. Technical issues to be resolved In view of the shortcomings 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 soil.

[0004] (II) Technical solution To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a carbon-based soil conditioner, comprising the following components by weight: 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 diatomaceous earth, 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, and 3.2-5 parts by weight of 5% polyvinyl alcohol solution.

[0005] Preferably, the method for preparing the humic acid-modified hydrogel 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 to a reactor, stir and mix, react at 162-170° C. for 3.5-4 h, then continue to heat to 180-190° C. for 4-6 h. After the reaction is completed, remove the water-carrying agent by rotary evaporation 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 to 70-100 mL of anhydrous ethanol solvent, stir and mix, heat to 52-58° C. and react for 9-12 hours. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, and recrystallize with 50-80 mL of a mixed solution of ethanol and 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 1.6%-2% acetic acid solution, stir to dissolve, add 0.02-0.04 g of 1-hydroxybenzotriazole initiator to react for 20-30 min, then add 4.5-5 g of (3-carboxypropyl)triphenylphosphonium bromide, pass nitrogen protection, heat to reaction temperature for 15-19 h, after the reaction is completed, dialyze and freeze-dry to obtain quaternary phosphonium salt modified chitosan; (4) Add 3.6-4.2 g of cyanuric chloride to 30-40 mL of acetonitrile solvent at 0-4°C, stir to dissolve, dissolve 7.6-8 g of polyhexamethylene biguanide in 45-50 mL of deionized water, and then dropwise add the polyhexamethylene biguanide to 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 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 freeze-dry to obtain guanidine-containing quaternary phosphonium salt-modified chitosan; (5) Add 1-1.2 g of humic acid, 10-12 mL of sodium hydroxide solution, and then add 50-60 mL of deionized water into the reactor, stir to dissolve, add 1.2-1.4 g of guanidine-containing quaternary phosphonium salt-modified chitosan, stir and heat to 40-48 ° C, introduce nitrogen for 10-15 min to deoxygenate, 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-linking agent, heat 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 crush to obtain humic acid-modified hydrogel.

[0006] Preferably, the water-carrying agent in step (1) is toluene.

[0007] Preferably, the reaction temperature after adding (3-carboxypropyl)triphenylphosphonium bromide in step (3) is 78-84°C.

[0008] Preferably, the acid binding agent in step (4) is triethylamine.

[0009] Preferably, the mass fraction of the sodium hydroxide solution in step (5) is 18%-24%.

[0010] Preferably, the preparation method of the acrylic acid solution with a neutralization degree of 50%-60% in step (5) is: add 34.3 mL of acrylic acid to 500 mL of deionized water, stir to dissolve, add 10-12 g of sodium hydroxide at 0-10° C., react for 40-50 minutes, and obtain an acrylic acid solution with a neutralization degree of 50%-60%.

[0011] Preferably, the preparation method of the carbon-based soil conditioner is: adding biochar, humic acid-modified hydrogel, diatomaceous earth, hydroxyapatite, Bacillus licheniformis, and Bacillus coagulans into a mixer, stirring and mixing, and then spraying 5% polyvinyl alcohol solution as a binder therein, extruding and granulating in a granulator, and drying at 40-50°C to a moisture content of 4%-8% to obtain a carbon-based soil conditioner.

[0012] 3. Beneficial technical effects The present invention prepares a carbon-based soil conditioner by stirring and mixing biochar, humic acid-modified hydrogel, diatomaceous earth, hydroxyapatite, Bacillus licheniformis and Bacillus coagulans, spraying a polyvinyl alcohol solution as a binder therein, extruding and granulating the mixture in a granulator, and then drying the mixture.

[0013] Imidazoline quaternary ammonium salts and quaternary phosphonium salts can be adsorbed on the negatively charged bacterial surface through their positive charge, and the hydrophobic group is inserted into the lipid layer, which changes the permeability of the cell membrane, destroys the membrane structure, causes the leakage of intracellular substances, and leads to bacterial death; the guanidine group destroys the bacterial cell membrane through strong positive adsorption, combines and coagulates nucleic acids and enzymes, causes the leakage of intracellular substances and the loss of metabolic function, thereby playing an antibacterial role; the nitrogen atoms in the imidazole group and the triazine group act as hydrogen bond receptors, enhance the hydrogen bonding effect with the hydrogel molecular chain, form a stable physical cross-linked network structure, and improve the water retention performance of the improver; the benzene ring hydrophobic group forms a reversible cross-linking point through hydrophobic association to form a dynamic three-dimensional network, and the hydrophobic interaction enhances the elastic modulus and compressive resistance of the hydrogel, so that it can still maintain structural integrity under external pressure, reduce passive water extrusion, and improve the water retention performance of the improver. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the synthetic reaction formula of imidazoline quaternary ammonium salt modified cross-linking agent.

[0015] Figure 2 It is a synthetic reaction formula for chitosan modified with guanidine-containing quaternary phosphonium salt. DETAILED DESCRIPTION Example 1

[0016] (1) Add 6 g of succinic acid, 13 mL of diethylenetriamine, and 60 mL of toluene water-carrying agent into a reactor, stir and mix, react at 162° C. for 3.5 h, then continue to heat to 180° C. for 4 h. After the reaction is completed, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate; (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 to 52° C. and react for 9 h. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, and recrystallize with 50 mL of a mixed solution of ethanol and acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinker; (3) Dissolve 2.2 g of chitosan in 80 mL of 1.6% acetic acid solution, stir to dissolve, add 0.02 g of 1-hydroxybenzotriazole initiator to react for 20 min, then add 4.5 g of (3-carboxypropyl)triphenylphosphonium bromide, pass nitrogen protection, heat to 78 °C to react for 15 h, after the reaction is completed, dialyze and freeze-dry to obtain quaternary phosphonium salt modified chitosan; (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 add it dropwise to the cyanuric chloride solution, add 0.03 g of triethylamine acid binding agent to adjust the pH to neutral, react at constant temperature for 8.5 h to obtain solution 1, dissolve 2.4 g of quaternary phosphonium salt-modified chitosan in 100 mL of deionized water, add solution 1 to the quaternary phosphonium salt-modified chitosan solution, react at 42°C for 12 h, and after the reaction is completed, dialyze and freeze-dry to obtain guanidine-containing quaternary phosphonium salt-modified chitosan; (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, react for 40 min to obtain an acrylic acid solution with a neutralization degree of 50%, add 1 g of humic acid and 10 mL of a sodium hydroxide solution with a mass fraction of 18% to the reactor, add 50 mL of deionized water, stir to dissolve, add 1.2 g of guanidine-containing quaternary phosphonium salt-modified chitosan, stir and heat to 40 ° C, introduce nitrogen for 10 min to deoxygenate, 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 to 65 ° C to react for 2.5 h, after the reaction is completed, wash with deionized water, dry at 55 ° C and crush to obtain a humic acid-modified hydrogel; (6) Add 25 parts by weight of biochar, 2 parts by weight of humic acid-modified hydrogel, 1.5 parts by weight of diatomaceous earth, 3 parts by weight of hydroxyapatite, 1.6 parts by weight of Bacillus licheniformis, and 0.8 parts by weight of Bacillus coagulans into a mixer, stir and mix, spray 3.2 parts by weight of 5% polyvinyl alcohol solution as a binder, extrude and granulate in a granulator, and dry at 40°C to a moisture content of 4% to obtain a carbon-based soil conditioner. Example 2

[0017] (1) Add 9 g of succinic acid, 19.5 mL of diethylenetriamine, and 90 mL of toluene water-carrying agent into a reactor, stir and mix, react at 170° C. for 4 h, then continue to heat to 190° C. for 6 h. After the reaction is completed, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate; (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 to 58° C. and react for 12 h. After the reaction, remove the anhydrous ethanol by rotary evaporation, recrystallize with 80 mL of a mixed solution of ethanol and acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinker; (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 to react for 30 min, then add 5 g of (3-carboxypropyl)triphenylphosphonium bromide, pass nitrogen protection, heat to 84 °C to react for 19 h, after the reaction is completed, dialyze and freeze-dry to obtain quaternary phosphonium salt modified chitosan; (4) Add 4.2 g of cyanuric chloride to 40 mL of acetonitrile solvent at 4°C, stir to dissolve, dissolve 8 g of polyhexamethylene biguanide in 50 mL of deionized water, then add it dropwise to the cyanuric chloride solution, add 0.07 g of triethylamine acid binding agent to adjust the pH to neutral, react at 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, react at 45°C for 15 h, and after the reaction is completed, dialyze and freeze-dry to obtain guanidine-containing quaternary phosphonium salt-modified chitosan; (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, react for 50 min, and obtain an acrylic acid solution with a neutralization degree of 60%. Add 1.2 g of humic acid and 12 mL of a 24% sodium hydroxide solution to the reactor, then add 60 mL of deionized water, stir to dissolve, add 1.4 g of guanidine-containing quaternary phosphonium salt-modified chitosan, stir and heat to 48°C, introduce nitrogen for 15 min to deoxygenate, add 0.14 g of potassium persulfate initiator, 18 g of an acrylic acid solution with a neutralization degree of 60%, and 0.04 g of an imidazoline quaternary ammonium salt-modified crosslinker, heat to 75°C and react for 3.5 h. After the reaction, wash with deionized water, dry at 60°C and crush to obtain a humic acid-modified hydrogel. (6) Add 30 parts by weight of biochar, 4 parts by weight of humic acid-modified hydrogel, 2.5 parts by weight of diatomaceous earth, 4 parts by weight of hydroxyapatite, 2 parts by weight of Bacillus licheniformis, and 1.2 parts by weight of Bacillus coagulans into a mixer, stir and mix, spray 5 parts by weight of a 5% polyvinyl alcohol solution as a binder, extrude and granulate in a granulator, and dry at 50°C to a moisture content of 8% to obtain a carbon-based soil conditioner. Example 3

[0018] (1) Add 7.5 g of succinic acid, 16.2 mL of diethylenetriamine, and 75 mL of toluene water-carrying agent into a reactor, stir and mix, react at 166° C. for 3.8 h, then continue to heat to 185° C. for 5 h. After the reaction is completed, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate; (2) Add 7.7 g of the imidazoline intermediate and 11.5 g of 1-allyl-3-chlorobenzene to 85 mL of anhydrous ethanol solvent, stir and mix, heat to 55° C. and react for 10.5 h. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, recrystallize with 65 mL of a mixed solution of ethanol and acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinker; (3) Dissolve 2.4 g of chitosan in 100 mL of 1.8% acetic acid solution, stir to dissolve, add 0.03 g of 1-hydroxybenzotriazole initiator to react for 25 min, then add 4.7 g of (3-carboxypropyl)triphenylphosphonium bromide, pass nitrogen protection, heat to 81 °C to react for 17 h, after the reaction is completed, dialyze and freeze-dry to obtain quaternary phosphonium salt modified chitosan; (4) Add 3.9 g of cyanuric chloride to 35 mL of acetonitrile solvent at 2°C, stir to dissolve, dissolve 7.8 g of polyhexamethylene biguanide in 48 mL of deionized water, then add it dropwise to the cyanuric chloride solution, add 0.05 g of triethylamine acid binding agent to adjust the pH to neutral, react at 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, react at 43°C for 13.5 h, and after the reaction is completed, dialyze and freeze-dry to obtain guanidine-containing quaternary phosphonium salt-modified chitosan; (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, react for 45 min, and obtain an acrylic acid solution with a neutralization degree of 55%. Add 1.1 g of humic acid and 11 mL of a 21% sodium hydroxide solution to the reactor, then add 55 mL of deionized water, stir to dissolve, add 1.3 g of guanidine-containing quaternary phosphonium salt-modified chitosan, stir and heat to 44 ° C, introduce nitrogen for 12 min to deoxygenate, add 0.13 g of potassium persulfate initiator, 16 g of an acrylic acid solution with a neutralization degree of 55%, and 0.035 g of an imidazoline quaternary ammonium salt-modified crosslinker, heat to 70 ° C and react for 3 h. After the reaction, wash with deionized water, dry at 58 ° C and crush to obtain a humic acid-modified hydrogel; (6) Add 28 parts by weight of biochar, 3 parts by weight of humic acid-modified hydrogel, 2 parts by weight of diatomaceous earth, 3.5 parts by weight of hydroxyapatite, 1.8 parts by weight of Bacillus licheniformis, and 1 part by weight of Bacillus coagulans into a mixer, stir and mix, spray 4.1 parts by weight of a 5% polyvinyl alcohol solution as a binder, extrude and granulate in a granulator, and dry at 45°C to a moisture content of 6% to obtain a carbon-based soil conditioner. Example 4

[0019] (1) Add 6 g of succinic acid, 13 mL of diethylenetriamine, and 60 mL of toluene water-carrying agent into a reactor, stir and mix, react at 162° C. for 3.5 h, then continue to heat to 180° C. for 4 h. After the reaction is completed, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate; (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 to 52° C. and react for 9 h. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, and recrystallize with 50 mL of a mixed solution of ethanol and acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinker; (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 to react for 30 min, then add 5 g of (3-carboxypropyl)triphenylphosphonium bromide, pass nitrogen protection, heat to 84 °C to react for 19 h, after the reaction is completed, dialyze and freeze-dry to obtain quaternary phosphonium salt modified chitosan; (4) Add 4.2 g of cyanuric chloride to 40 mL of acetonitrile solvent at 4°C, stir to dissolve, dissolve 8 g of polyhexamethylene biguanide in 50 mL of deionized water, then add it dropwise to the cyanuric chloride solution, add 0.07 g of triethylamine acid binding agent to adjust the pH to neutral, react at 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, react at 45°C for 15 h, and after the reaction is completed, dialyze and freeze-dry to obtain guanidine-containing quaternary phosphonium salt-modified chitosan; (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, react for 45 min, and obtain an acrylic acid solution with a neutralization degree of 55%. Add 1.1 g of humic acid and 11 mL of a 21% sodium hydroxide solution to the reactor, then add 55 mL of deionized water, stir to dissolve, add 1.3 g of guanidine-containing quaternary phosphonium salt-modified chitosan, stir and heat to 44 ° C, introduce nitrogen for 12 min to deoxygenate, add 0.13 g of potassium persulfate initiator, 16 g of an acrylic acid solution with a neutralization degree of 55%, and 0.035 g of an imidazoline quaternary ammonium salt-modified crosslinker, heat to 70 ° C and react for 3 h. After the reaction, wash with deionized water, dry at 58 ° C and crush to obtain a humic acid-modified hydrogel; (6) Add 28 parts by weight of biochar, 3 parts by weight of humic acid-modified hydrogel, 2 parts by weight of diatomaceous earth, 3.5 parts by weight of hydroxyapatite, 1.8 parts by weight of Bacillus licheniformis, and 1 part by weight of Bacillus coagulans into a mixer, stir and mix, spray 4.1 parts by weight of a 5% polyvinyl alcohol solution as a binder, extrude and granulate in a granulator, and dry at 45°C to a moisture content of 6% to obtain a carbon-based soil conditioner. Example 5

[0020] (1) Add 7.5 g of succinic acid, 16.2 mL of diethylenetriamine, and 75 mL of toluene water-carrying agent into a reactor, stir and mix, react at 166° C. for 3.8 h, then continue to heat to 185° C. for 5 h. After the reaction is completed, remove the toluene water-carrying agent by rotary evaporation to obtain an imidazoline intermediate; (2) Add 7.7 g of the imidazoline intermediate and 11.5 g of 1-allyl-3-chlorobenzene to 85 mL of anhydrous ethanol solvent, stir and mix, heat to 55° C. and react for 10.5 h. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, recrystallize with 65 mL of a mixed solution of ethanol and acetone with a volume ratio of 1:1 under ice bath, and vacuum dry to obtain an imidazoline quaternary ammonium salt modified crosslinker; (3) Dissolve 2.2 g of chitosan in 80 mL of 1.6% acetic acid solution, stir to dissolve, add 0.02 g of 1-hydroxybenzotriazole initiator to react for 20 min, then add 4.5 g of (3-carboxypropyl)triphenylphosphonium bromide, pass nitrogen protection, heat to 78 °C to react for 15 h, after the reaction is completed, dialyze and freeze-dry to obtain quaternary phosphonium salt modified chitosan; (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 add it dropwise to the cyanuric chloride solution, add 0.03 g of triethylamine acid binding agent to adjust the pH to neutral, react at constant temperature for 8.5 h to obtain solution 1, dissolve 2.4 g of quaternary phosphonium salt-modified chitosan in 100 mL of deionized water, add solution 1 to the quaternary phosphonium salt-modified chitosan solution, react at 42°C for 12 h, and after the reaction is completed, dialyze and freeze-dry to obtain guanidine-containing quaternary phosphonium salt-modified chitosan; (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, react for 50 min, and obtain an acrylic acid solution with a neutralization degree of 60%. Add 1.2 g of humic acid and 12 mL of a 24% sodium hydroxide solution to the reactor, then add 60 mL of deionized water, stir to dissolve, add 1.4 g of guanidine-containing quaternary phosphonium salt-modified chitosan, stir and heat to 48°C, introduce nitrogen for 15 min to deoxygenate, add 0.14 g of potassium persulfate initiator, 18 g of an acrylic acid solution with a neutralization degree of 60%, and 0.04 g of an imidazoline quaternary ammonium salt-modified crosslinker, heat to 75°C and react for 3.5 h. After the reaction, wash with deionized water, dry at 60°C and crush to obtain a humic acid-modified hydrogel. (6) Add 30 parts by weight of biochar, 4 parts by weight of humic acid-modified hydrogel, 2.5 parts by weight of diatomaceous earth, 4 parts by weight of hydroxyapatite, 2 parts by weight of Bacillus licheniformis, and 1.2 parts by weight of Bacillus coagulans into a mixer, stir and mix, spray 5 parts by weight of a 5% polyvinyl alcohol solution as a binder, extrude and granulate in a granulator, and dry at 50°C to a moisture content of 8% to obtain a carbon-based soil conditioner.

[0021] Comparative Example 1 The difference between this comparative example and Example 5 is that in step (5), carboxymethyl chitosan is used instead of the chitosan modified with guanidine-containing quaternary phosphonium salt.

[0022] Comparative Example 2 The difference between this comparative example and Example 5 is that in step (5), N,N'-methylenebisacrylamide cross-linking agent is used instead of imidazoline quaternary ammonium salt modified cross-linking agent.

[0023] The antibacterial experiment was conducted in 8 treatments. 2.0 kg of sterilized soil was taken from 7 treatment groups. 40 g of the carbon-based soil conditioner in Examples 1-5 and Comparative Examples 1-2 was added to the sterilized soil. Sterile water was added to make the soil moisture content reach 60%. 20 mL of bacterial suspension (10 8 CFU / mL) was evenly sprayed into the soil and cultured at 25℃ in the dark for 14 days; the control group did not add soil amendments, and the rest was the same as the treatment group. Calculate the antibacterial rate, antibacterial rate = (control group bacteria number - treatment group bacteria number) / control group bacteria number × 100%. The experimental soil was taken from the farm of the scientific research base of South China Agricultural University. The test results are shown in Table 1.

[0024] Table 1: Antibacterial performance test.

[0025] project Antibacterial 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 It can be seen from Table 1 that the carbon-based soil conditioner in Examples 1-5 of the present invention has a better antibacterial effect on the soil than the carbon-based soil conditioner in Comparative Examples 1-2.

[0026] The carbon-based soil conditioner in Examples 1-5 and Comparative Examples 1-2 was mixed with dry soil at a ratio of 0.5wt%, placed in a PVC tube with a diameter of 4.5cm and a length of 15cm, sealed with a nylon mesh (300 mesh) at the bottom of the tube and weighed, then the PVC tube was suspended and soaked in deionized water for 12h, the tube was taken out and vertically hung on a rack to allow water to flow out freely, and the end point was no more water seepage within 10min, and the weight of the tube was weighed. Calculate the maximum water holding rate, the maximum water holding rate = (total weight of the entire tube after wetting without water seepage - weight of dry soil and PVC tube before wetting) / (weight of dry soil and PVC tube before wetting - weight of PVC tube) × 100%. The experimental soil was taken from the farm of the scientific research base of South China Agricultural University. The test results are shown in Table 2.

[0027] Table 2: Water retention performance test.

[0028] project Maximum water holding capacity (%) 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 It can be seen from Table 2 that the carbon-based soil conditioner in Examples 1-5 of the present invention has a better water retention effect on the soil than the carbon-based soil conditioner in Comparative Examples 1-2.

[0029] 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 do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A carbon-based soil conditioner, characterized in that: The invention comprises the following components by weight: 25-30 parts by weight of biochar, 2-4 parts by weight of humic acid-modified hydrogel, 1.5-2.5 parts by weight of diatomaceous earth, 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, and 3.2-5 parts by weight of 5% polyvinyl alcohol solution.

2. The carbon-based soil conditioner according to claim 1, characterized in that The preparation method of the humic acid-modified hydrogel 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 to a reactor, stir and mix, react at 162-170° C. for 3.5-4 h, then continue to heat to 180-190° C. for 4-6 h. After the reaction is completed, remove the water-carrying agent by rotary evaporation 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 to 70-100 mL of anhydrous ethanol solvent, stir and mix, heat to 52-58° C. and react for 9-12 hours. After the reaction is completed, remove the anhydrous ethanol by rotary evaporation, and recrystallize with 50-80 mL of a mixed solution of ethanol and 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 1.6%-2% acetic acid solution, stir to dissolve, add 0.02-0.04 g of 1-hydroxybenzotriazole initiator to react for 20-30 min, then add 4.5-5 g of (3-carboxypropyl)triphenylphosphonium bromide, pass nitrogen protection, heat to reaction temperature for 15-19 h, after the reaction is completed, dialyze and freeze-dry to obtain quaternary phosphonium salt modified chitosan; (4) Add 3.6-4.2 g of cyanuric chloride to 30-40 mL of acetonitrile solvent at 0-4°C, stir to dissolve, dissolve 7.6-8 g of polyhexamethylene biguanide in 45-50 mL of deionized water, and then dropwise add the polyhexamethylene biguanide to 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 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 freeze-dry to obtain guanidine-containing quaternary phosphonium salt-modified chitosan; (5) Add 1-1.2 g of humic acid, 10-12 mL of sodium hydroxide solution, and then add 50-60 mL of deionized water into the reactor, stir to dissolve, add 1.2-1.4 g of guanidine-containing quaternary phosphonium salt-modified chitosan, stir and heat to 40-48 ° C, introduce nitrogen for 10-15 min to deoxygenate, 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-linking agent, heat 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 crush to obtain humic acid-modified hydrogel.

3. The carbon-based soil conditioner according to claim 2, characterized in that The water-carrying agent in step (1) is toluene.

4. The carbon-based soil conditioner according to claim 2, characterized in that The reaction temperature after adding (3-carboxypropyl)triphenylphosphonium bromide in step (3) is 78-84°C.

5. The carbon-based soil conditioner according to claim 2, characterized in that In the step (4), the acid binding agent is triethylamine.

6. The carbon-based soil conditioner according to claim 2, characterized in that The mass fraction of the sodium hydroxide solution in step (5) is 18%-24%.

7. The carbon-based soil conditioner according to claim 2, characterized in that The preparation method of the acrylic acid solution with a neutralization degree of 50%-60% in the step (5) is as follows: 34.3 mL of acrylic acid is added to 500 mL of deionized water, stirred to dissolve, 10-12 g of sodium hydroxide is added thereto at 0-10° C., and reacted for 40-50 minutes to obtain an acrylic acid solution with a neutralization degree of 50%-60%.

8. A method for preparing the carbon-based soil conditioner according to any one of claims 1 to 7, characterized in that: The preparation method of the carbon-based soil conditioner is as follows: biochar, humic acid-modified hydrogel, diatomaceous earth, hydroxyapatite, Bacillus licheniformis and Bacillus coagulans are added into a mixer, stirred and mixed, and then 5% polyvinyl alcohol solution is sprayed therein as a binder, extruded and granulated in a granulator, and dried at 40-50° C. to a water content of 4%-8%, so as to obtain the carbon-based soil conditioner.

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