Woody peat source soil conditioner and preparation process thereof

Abstract

The invention relates to the technical field of soil conditioner treatment, and discloses a woody peat source soil conditioner and a preparation process thereof. The preparation method comprises the following steps: introducing acrylamide into carboxymethyl chitosan under the action of ultraviolet curing, and introducing acetylcysteine and humate into carboxymethyl chitosan under the action of a cross-linking agent to prepare the composite bio-based chelating agent. The flocculant is prepared by modifying polyacrylamide with formaldehyde and mercaptoacetic acid in sequence. Alkaline woody peat is selected as a raw material, and is calcined in a nitrogen atmosphere to prepare woody peat biochar; carboxymethyl-beta-cyclodextrin is grafted after the sustained-release microspheres are subjected to amination treatment, so that the surfaces of the sustained-release microspheres contain functional groups such as hydroxyl and carboxyl. The woody peat charcoal is used as a basic carrier, polyacrylamide, modified polyacrylamide and polyaluminum chloride are used as cross-linking agents, and a flocculating agent and sustained-release microspheres are successfully loaded on the surface of the woody peat charcoal, so that the woody peat source soil conditioner is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of soil conditioner treatment, in particular to a woody peat-source soil conditioner and a preparation process thereof. Background Art

[0002] Rice fields are located in a special growing environment where rice will experience alternating periods of wetness and drought. This growing environment causes heavy metal elements in rice fields to be highly active, exposing rice to a serious risk of excessive heavy metals.

[0003] In rice fields, the complex pollution of heavy metals is serious, which not only affects the normal growth of rice and leads to reduced yields, but also enters the food chain through soil and rice, posing a direct threat to human life and health.

[0004] Therefore, it is very important to control the heavy metal pollution in paddy soil to ensure the safety of rice. This measure is not only related to ecological and environmental safety, but also closely related to food safety, which cannot be ignored. Taking measures to reduce the level of heavy metal pollution, protect the quality of agricultural products and food safety in the food chain is essential to maintain ecological balance and protect people's health.

[0005] Therefore, it is of great significance to invent a woody peat-derived soil conditioner and a preparation process thereof. Summary of the invention

[0006] The object of the present invention is to provide a woody peat-derived soil conditioner and a preparation process thereof, so as to solve the problems raised in the above-mentioned background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] A preparation process of a woody peat-derived soil conditioner comprises the following steps:

[0009] S1: placing the sustained-release microsphere emulsion in an environment of 20-50°C, adding fuming nitric acid under high-speed stirring to react for 10-20 minutes, washing until the pH is neutral, and obtaining a nitro sustained-release microsphere emulsion; placing the nitro sustained-release microsphere emulsion in an environment of 70-90°C, adjusting the pH to 8-10, adding sodium dithionite to react for 3-4 hours, washing until the pH is neutral, filtering, and drying to obtain amino sustained-release microspheres; dissolving carboxymethyl-β-cyclodextrin in anhydrous ethanol, adding amino sustained-release microspheres to react for 24 hours, washing, and drying to obtain cyclodextrin-modified sustained-release microspheres;

[0010] S2: Pretreat the woody peat and set it aside; place the pretreated woody peat in a nitrogen atmosphere, heat it to 600-620°C and keep it warm for 2-2.5 hours to obtain woody peat biochar; add the woody peat biochar and cyclodextrin modified slow-release microspheres into anhydrous ethanol and stir evenly, add polyaluminum chloride, polyacrylamide, and modified polyacrylamide and stir evenly, shake the reaction for 12-14 hours, let it stand and precipitate, filter, wash, and dry to obtain a woody peat source soil conditioner.

[0011] Furthermore, the method for preparing the sustained-release microsphere emulsion comprises the following steps:

[0012] Add acrylamide, 2-methyl-2-propionamidopropanesulfonic acid and a bio-based chelating agent into deionized water, add ammonium persulfate and N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix Span 80 and Tween 60 evenly, add white oil and stir evenly to obtain oil phase A; stir aqueous phase A and oil phase A evenly, add styrene and stir evenly, add sodium sulfite under a nitrogen atmosphere, heat to 30-35°C, react for 30-45 minutes, precipitate, and obtain a sustained-release microsphere emulsion.

[0013] Furthermore, the proportions of the components in the aqueous phase A, by weight, are 15-20 parts of acrylamide, 3-5 parts of 2-methyl-2-propionamidopropanesulfonic acid, 10-15 parts of bio-based chelating agent, 4-8 parts of ammonium persulfate, and 0.1-0.5 parts of N,N'-methylenebisacryloyl; the proportions of the components in the oil phase, by weight, are 12-20 parts of Span 80, 4-8 parts of Tween 60, and 48-60 parts of white oil; the proportions of the components in the sustained-release microsphere emulsion, by weight, are 10-20 parts of aqueous phase A, 25-40 parts of oil phase A, 20-35 parts of styrene, and 0.05-0.1 parts of ammonium sulfite.

[0014] Furthermore, the preparation method of the bio-based chelating agent comprises the following steps:

[0015] The carboxymethyl chitosan is dissolved in deionized water, acrylamide is added, the pH is adjusted to 7-7.5, a photoinitiator is added under a nitrogen atmosphere, photocuring is performed, washing, purification, drying, grinding, and polymer powder is obtained; the polymer powder is dissolved in deionized water, acetylcysteine, humate, and a cross-linking agent are added, the pH is adjusted to 5-5.5, heated to 40-45° C. for reaction for 2-2.5 hours, washed, dried, and ground to obtain a bio-based chelating agent.

[0016] Furthermore, the mass ratio of the carboxymethyl chitosan: acrylamide is (1-2): (3.5-7); the mass ratio of the polymer powder: acetylcysteine: humate: cross-linking agent is 1: (1-2): (1-2): 0.03; the photoinitiator is azobisisobutyramidine hydrochloride; and the cross-linking agent is 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride.

[0017] Furthermore, the preparation method of the modified polyacrylamide comprises the following steps:

[0018] Dissolve acrylamide, sodium formate and ammonium persulfate in deionized water, heat to 85-90°C and react for 2-2.5 hours to obtain polyacrylamide; add polyacrylamide to formaldehyde, adjust the pH to 11-11.5, heat to 50-55°C and react for 2-2.5 hours to obtain hydroxymethyl polyacrylamide; add hydroxymethyl polyacrylamide to thioglycolic acid, adjust the pH to 4.75-5, heat to 25-30°C and react for 2 hours to obtain modified polyacrylamide.

[0019] Furthermore, the proportions of the components in the polyacrylamide are, by mass, 24-30 parts of acrylamide, 0.03-0.05 parts of sodium formate, and 0.5-0.8 parts of ammonium persulfate; the molar ratio of the polyacrylamide:formaldehyde is 1:1; and the molar ratio of the hydroxymethyl polyacrylamide:thioglycolic acid is 1:(3.2-3.5).

[0020] Furthermore, the mass ratio of the sustained-release microsphere emulsion: fuming nitric acid is (2-3):(2-3); the mass ratio of the nitro sustained-release microsphere emulsion: sodium dithionite is (10-15):(3-4); and the mass ratio of the carboxymethyl-β-cyclodextrin: amino sustained-release microspheres is 5:(1.5-2).

[0021] Furthermore, the proportions of the components in the woody peat source soil conditioner are, by weight, 90-100 parts of woody peat biochar, 3.2-6.4 parts of cyclodextrin modified slow-release microspheres, 20-25 parts of polyaluminium chloride, 2-4 parts of polyacrylamide, and 2-4 parts of modified polyacrylamide.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0023] The invention firstly reacts with the hydroxyl group in carboxymethyl chitosan through ultraviolet curing to introduce acrylamide into the carboxymethyl chitosan, and then reacts with the amino group in the carboxymethyl chitosan structure under the action of 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride crosslinking agent to introduce acetylcysteine ​​and humate into the carboxymethyl chitosan to prepare a composite bio-based chelating agent; however, the bio-based chelating agent generally has the disadvantage of being affected by different pH values, making its own efficiency of removing cadmium ions unstable, and at the same time, the complex and numerous fungi in the soil have a great influence on the service life of the bio-based chelating agent. In order to meet the specified effective cadmium ion content in the soil within a certain period of time, it needs to be repeatedly applied, resulting in the destruction of the soil structure and increased toxicity to plant growth. In order to solve this problem, the present invention uses acrylamide, bio-based chelating agent, ammonium persulfate and other substances as water phase, and uses Span 80, Tween 60 and white oil as oil phase. Styrene is added during the microemulsion polymerization process formed by mixing the water phase and the oil phase to prepare a core-shell microsphere to coat the bio-based chelating agent. The prepared sustained-release microsphere expands by absorbing water. Under the action of the ammonium persulfate degumming agent, the internally coated bio-based chelating agent is slowly released. The microsphere has pH buffering, reduces the pH to affect the cadmium ion removal rate, reduces the damage of fungi in the soil to the bio-chelating agent, and improves the life of the bio-based chelating agent.

[0024] With the help of slow-release microspheres, the efficiency of bio-based chelating agents in removing cadmium ions is stable and the service life is improved; however, due to the slow release of the early application process, the removal rate of cadmium ions in the soil is slow; for this reason, the present invention intends to prepare a substance that can remove cadmium ions in large quantities and efficiently in the early stage, first roughly remove the cadmium ions in the soil, and then further chelate and remove the subsequent cadmium ions with the cooperation of slow-release microspheres. Therefore, the present invention prepares a flocculant by modifying polyacrylamide by formaldehyde and thioglycolic acid; selects alkaline woody peat as a raw material, and calcines it in a nitrogen atmosphere to prepare woody peat biochar; by aminating the slow-release microspheres and grafting carboxymethyl-β-cyclodextrin, the surface of the slow-release microspheres contains functional groups such as hydroxyl and carboxyl. With woody peat biochar as the basic carrier, polyacrylamide, modified polyacrylamide, and polyaluminum chloride as cross-linking agents, the flocculant and slow-release microspheres are successfully loaded on the surface of woody peat biochar. The rough and irregular surface and heterogeneous pore structure of woody peat biochar are used in conjunction with the flocculant system to adsorb cadmium ions in the soil under alkaline conditions, achieving the effect of long-term removal of cadmium ions throughout the entire process, reducing the number of applications of soil conditioners, and also having the effect of regulating and increasing the pH value of the soil, maintaining the alkalinity of the soil pH, and improving the cadmium ion removal rate efficiency and stability of the bio-based chelating agent. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the following examples, carboxymethyl chitosan was purchased from Shanghai Yuanye Biotechnology Co., Ltd., with a carboxylation degree of ≥80%; acrylamide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; acetylcysteine ​​was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; humate was purchased from Beijing Bowei Shennong Technology Co., Ltd.; ammonium persulfate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; carboxymethyl-β-cyclodextrin was purchased from Shanghai McLean Biochemical Technology Co., Ltd.; polyaluminum chloride was purchased from polyaluminum chloride, with a purity of ≥99%; woody peat was purchased from Nanjing Baore Chemical Co., Ltd., with a pH of 8.97 and an organic matter content of ≥35.0%; the remaining raw materials were all commercially available.

[0027] Example 1: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 35 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, and grind to obtain a bio-based chelating agent;

[0028] S2: Add 15g acrylamide, 3g 2-methyl-2-propionamidopropanesulfonic acid, and 10g bio-based chelating agent to 200mL deionized water, add 4g ammonium persulfate and 0.1g N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix 12g Span 80 and 4g Tween 60 evenly, add 48g white oil and stir evenly to obtain oil phase A; stir 10g aqueous phase A and 25g oil phase A evenly, add 20g styrene and stir evenly, add 0.05g sodium sulfite under nitrogen atmosphere, heat to 30°C for reaction for 30min, precipitate, and obtain a sustained-release microsphere emulsion;

[0029] S3: 20g of the sustained-release microsphere emulsion was placed in an environment of 20-50°C, 20g of fuming nitric acid was added under high-speed stirring to react for 10min, and the solution was washed until the pH was neutral to obtain a nitro sustained-release microsphere emulsion; 10g of the nitro sustained-release microsphere emulsion was placed in an environment of 70°C, the pH was adjusted to 9, 3g of sodium dithionite was added to react for 3h, the solution was washed until the pH was neutral, suction filtered, and dried to obtain amino sustained-release microspheres; 5g of carboxymethyl-β-cyclodextrin was dissolved in anhydrous ethanol, 1.5g of amino sustained-release microspheres was added to react for 24h, the solution was washed, and dried to obtain β-cyclodextrin modified sustained-release microspheres;

[0030] S4: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.2, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0031] S5: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm sieve, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 3.2 g of cyclodextrin-modified sustained-release microspheres are added to anhydrous ethanol and stirred evenly, 20 g of polyaluminum chloride, 2 g of polyacrylamide, and 2 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0032] Example 2: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 35 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, grind,

[0033] Obtaining a bio-based chelating agent;

[0034] S2: Add 20g acrylamide, 3g 2-methyl-2-propionamidopropanesulfonic acid, and 15g bio-based chelating agent to 200mL deionized water, add 4g ammonium persulfate and 0.1g N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix 12g Span 80 and 4g Tween 60 evenly, add 48g white oil and stir evenly to obtain oil phase A; stir 10g aqueous phase A and 25g oil phase A evenly, add 20g styrene and stir evenly, add 0.05g sodium sulfite under nitrogen atmosphere, heat to 30°C for reaction for 30min, precipitate, and obtain a sustained-release microsphere emulsion;

[0035] S3: 20g of the sustained-release microsphere emulsion was placed in an environment of 20-50°C, 20g of fuming nitric acid was added under high-speed stirring to react for 10min, and the solution was washed until the pH was neutral to obtain a nitro sustained-release microsphere emulsion; 10g of the nitro sustained-release microsphere emulsion was placed in an environment of 70°C, the pH was adjusted to 9, 3g of sodium dithionite was added to react for 3h, the solution was washed until the pH was neutral, suction filtered, and dried to obtain amino sustained-release microspheres; 5g of carboxymethyl-β-cyclodextrin was dissolved in anhydrous ethanol, 1.5g of amino sustained-release microspheres was added to react for 24h, the solution was washed, and dried to obtain β-cyclodextrin modified sustained-release microspheres;

[0036] S4: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.5, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0037] S5: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm sieve, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 3.2 g of cyclodextrin-modified sustained-release microspheres are added to anhydrous ethanol and stirred evenly, 20 g of polyaluminum chloride, 2 g of polyacrylamide, and 2 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0038] Example 3: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 35 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, grind,

[0039] Obtaining a bio-based chelating agent;

[0040] S2: Add 20g acrylamide, 3g 2-methyl-2-propionamidopropanesulfonic acid, and 15g bio-based chelating agent to 200mL deionized water, add 4g ammonium persulfate and 0.1g N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix 12g Span 80 and 4g Tween 60 evenly, add 48g white oil and stir evenly to obtain oil phase A; stir 10g aqueous phase A and 25g oil phase A evenly, add 20g styrene and stir evenly, add 0.05g sodium sulfite under nitrogen atmosphere, heat to 30°C for reaction for 30min, precipitate, and obtain a sustained-release microsphere emulsion;

[0041] S3: 20g of the sustained-release microsphere emulsion was placed in an environment of 20-50°C, 20g of fuming nitric acid was added under high-speed stirring to react for 10min, and the solution was washed until the pH was neutral to obtain a nitro sustained-release microsphere emulsion; 10g of the nitro sustained-release microsphere emulsion was placed in an environment of 70°C, the pH was adjusted to 9, 3g of sodium dithionite was added to react for 3h, the solution was washed until the pH was neutral, suction filtered, and dried to obtain amino sustained-release microspheres; 5g of carboxymethyl-β-cyclodextrin was dissolved in anhydrous ethanol, 1.5g of amino sustained-release microspheres was added to react for 24h, the solution was washed, and dried to obtain β-cyclodextrin modified sustained-release microspheres;

[0042] S4: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.5, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0043] S5: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm sieve, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 4.8 g of cyclodextrin-modified sustained-release microspheres are added to anhydrous ethanol and stirred evenly, 25 g of polyaluminum chloride, 3 g of polyacrylamide, and 3 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0044] Example 4: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 35 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, grind,

[0045] Obtaining a bio-based chelating agent;

[0046] S2: Add 20g acrylamide, 3g 2-methyl-2-propionamidopropanesulfonic acid, and 15g bio-based chelating agent to 200mL deionized water, add 4g ammonium persulfate and 0.1g N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix 12g Span 80 and 4g Tween 60 evenly, add 48g white oil and stir evenly to obtain oil phase A; stir 10g aqueous phase A and 25g oil phase A evenly, add 20g styrene and stir evenly, add 0.05g sodium sulfite under nitrogen atmosphere, heat to 30°C for reaction for 30min, precipitate, and obtain a sustained-release microsphere emulsion;

[0047] S3: 20g of the sustained-release microsphere emulsion was placed in an environment of 20-50°C, 20g of fuming nitric acid was added under high-speed stirring to react for 10min, and the solution was washed until the pH was neutral to obtain a nitro sustained-release microsphere emulsion; 10g of the nitro sustained-release microsphere emulsion was placed in an environment of 70°C, the pH was adjusted to 9, 3g of sodium dithionite was added to react for 3h, the solution was washed until the pH was neutral, suction filtered, and dried to obtain amino sustained-release microspheres; 5g of carboxymethyl-β-cyclodextrin was dissolved in anhydrous ethanol, 1.5g of amino sustained-release microspheres was added to react for 24h, the solution was washed, and dried to obtain β-cyclodextrin modified sustained-release microspheres;

[0048] S4: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.5, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0049] S5: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm screen, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 6.4 g of cyclodextrin-modified sustained-release microspheres are added to anhydrous ethanol and stirred evenly, 25 g of polyaluminum chloride, 4 g of polyacrylamide, and 4 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0050] Comparative Example 1: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 35 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, grind,

[0051] Obtaining a bio-based chelating agent;

[0052] S2: Add 15g acrylamide, 3g 2-methyl-2-propionamidopropanesulfonic acid, and 5g bio-based chelating agent to 200mL deionized water, add 4g ammonium persulfate and 0.1g N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix 12g Span 80 and 4g Tween 60 evenly, add 48g white oil and stir evenly to obtain oil phase A; stir 10g aqueous phase A and 25g oil phase A evenly, add 20g styrene and stir evenly, add 0.05g sodium sulfite under nitrogen atmosphere, heat to 30°C for reaction for 30min, precipitate, and obtain a sustained-release microsphere emulsion;

[0053] S3: 20g of the sustained-release microsphere emulsion was placed in an environment of 20-50°C, 20g of fuming nitric acid was added under high-speed stirring to react for 10min, and the solution was washed until the pH was neutral to obtain a nitro sustained-release microsphere emulsion; 10g of the nitro sustained-release microsphere emulsion was placed in an environment of 70°C, the pH was adjusted to 9, 3g of sodium dithionite was added to react for 3h, the solution was washed until the pH was neutral, suction filtered, and dried to obtain amino sustained-release microspheres; 5g of carboxymethyl-β-cyclodextrin was dissolved in anhydrous ethanol, 1.5g of amino sustained-release microspheres was added to react for 24h, the solution was washed, and dried to obtain β-cyclodextrin modified sustained-release microspheres;

[0054] S4: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.2, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0055] S5: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm screen, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 3.2 g of cyclodextrin-modified sustained-release microspheres are added to anhydrous ethanol and stirred evenly, 20 g of polyaluminum chloride, 2 g of polyacrylamide, and 1 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0056] Comparative Example 2: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 35 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, grind,

[0057] Obtaining a bio-based chelating agent;

[0058] S2: 15 g acrylamide, 3 g 2-methyl-2-propionamidopropanesulfonic acid, and 20 g bio-based chelating agent were added to 200 mL deionized water, and 4 g ammonium persulfate and 0.1 g N, N'-methylenebisacrylamide were added and stirred to obtain aqueous phase A; 12 g Span 80 and 4 g Tween 60 were mixed and stirred to obtain oil phase A; 10 g aqueous phase A and 25 g oil phase A were stirred and stirred, 20 g styrene was added and stirred to obtain a sustained-release microsphere emulsion; 0.05 g sodium sulfite was added under a nitrogen atmosphere, heated to 30 ° C for reaction for 30 min, and precipitated to obtain a sustained-release microsphere emulsion;

[0059] S3: 20g of the sustained-release microsphere emulsion was placed in an environment of 20-50°C, 20g of fuming nitric acid was added under high-speed stirring to react for 10min, and the solution was washed until the pH was neutral to obtain a nitro sustained-release microsphere emulsion; 10g of the nitro sustained-release microsphere emulsion was placed in an environment of 70°C, the pH was adjusted to 9, 3g of sodium dithionite was added to react for 3h, the solution was washed until the pH was neutral, suction filtered, and dried to obtain amino sustained-release microspheres; 5g of carboxymethyl-β-cyclodextrin was dissolved in anhydrous ethanol, 1.5g of amino sustained-release microspheres was added to react for 24h, the solution was washed, and dried to obtain β-cyclodextrin modified sustained-release microspheres;

[0060] S4: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.2, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0061] S5: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm screen, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 3.2 g of cyclodextrin-modified sustained-release microspheres are added to anhydrous ethanol and stirred evenly, 20 g of polyaluminum chloride, 2 g of polyacrylamide, and 6 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0062] Comparative Example 3: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 35 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, grind,

[0063] Obtaining a bio-based chelating agent;

[0064] S2: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.2, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0065] S3: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm screen, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 3.2 g of bio-based chelating agent are added to anhydrous ethanol and stirred evenly, 20 g of polyaluminum chloride, 2 g of polyacrylamide, and 2 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0066] Comparative Example 4: A method for preparing a woody peat-derived soil conditioner: S1: Dissolve 10 g of carboxymethyl chitosan in 150 mL of deionized water, add 70 g of acrylamide, adjust the pH to 7, add 1 g of azobisisobutylamidine hydrochloride under a nitrogen atmosphere, UV-curing, washing, purification, drying, grinding, and obtaining a polymer powder; Dissolve 10 g of the polymer powder in 200 mL of deionized water, add 10 g of acetylcysteine, 10 g of humate, and 0.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, adjust the pH to 5, heat to 40°C for reaction for 2 h, wash, dry, grind,

[0067] Obtaining a bio-based chelating agent;

[0068] S2: Add 15g acrylamide, 3g 2-methyl-2-propionamidopropanesulfonic acid, and 10g bio-based chelating agent to 200mL deionized water, add 4g ammonium persulfate and 0.1g N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix 12g Span 80 and 4g Tween 60 evenly, add 48g white oil and stir evenly to obtain oil phase A; stir 10g aqueous phase A and 25g oil phase A evenly, add 20g styrene and stir evenly, add 0.05g sodium sulfite under nitrogen atmosphere, heat to 30°C for reaction for 30min, precipitate, and obtain a sustained-release microsphere emulsion;

[0069] S3: 20g of the sustained-release microsphere emulsion was placed in an environment of 20-50°C, 20g of fuming nitric acid was added under high-speed stirring to react for 10min, and the solution was washed until the pH was neutral to obtain a nitro sustained-release microsphere emulsion; 10g of the nitro sustained-release microsphere emulsion was placed in an environment of 70°C, the pH was adjusted to 9, 3g of sodium dithionite was added to react for 3h, the solution was washed until the pH was neutral, suction filtered, and dried to obtain amino sustained-release microspheres; 5g of carboxymethyl-β-cyclodextrin was dissolved in anhydrous ethanol, 1.5g of amino sustained-release microspheres was added to react for 24h, the solution was washed, and dried to obtain β-cyclodextrin modified sustained-release microspheres;

[0070] S4: 24 g acrylamide, 0.03 g sodium formate, and 0.5 g ammonium persulfate were dissolved in deionized water, heated to 85-90°C for reaction for 2-2.5 hours to obtain polyacrylamide; polyacrylamide was added to formaldehyde solution at a molar ratio of 1:1, the pH was adjusted to 11, and the solution was heated to 50°C for reaction for 2 hours to obtain hydroxymethyl polyacrylamide; hydroxymethyl polyacrylamide was added to thioglycolic acid at a molar ratio of 1:3.2, the pH was adjusted to 4.75, and the solution was heated to 25°C for reaction for 2 hours to obtain modified polyacrylamide;

[0071] S5: The woody peat is naturally air-dried, crushed, and sieved through a 0.9 mm sieve, then washed with deionized water, filtered, dried, and set aside; the pretreated woody peat is placed in a nitrogen atmosphere, heated to 600°C for 2 hours to obtain woody peat biochar; 100 g of woody peat biochar and 3.2 g of cyclodextrin-modified sustained-release microspheres are added to anhydrous ethanol and stirred evenly, 20 g of polyaluminum chloride, 2 g of polyacrylamide, and 2 g of modified polyacrylamide are added and stirred evenly, and the reaction is shaken for 12 hours, allowed to stand for precipitation, filtered, washed, and dried to obtain a woody peat-derived soil conditioner.

[0072] Test: A cadmium-contaminated farmland in a certain area was selected as the test field. The basic physical and chemical properties of the soil were: pH 6.24, organic matter content 32.8g / kg, total Cd content 0.898mg / kg, and effective Cd content 0.588mg / kg. The effective Cd content exceeded the medium-risk screening value of 0.3mg / kg (5.5<pH≤6.5) specified in GB15618-2018;

[0073] The woody peat source soil conditioner prepared in the examples and comparative examples was set at a conventional recommended dosage of 2500 kg / hm 2 Application, select 3 randomly arranged areas, the area is 5m×5m, each treatment is repeated 3 times, 20cm tillage coating is manually plowed in May, plowed 3 times; transplant the seedlings in June, keep the daily water management and fertilization consistent, and harvest the rice in mid-November.

[0074] After the maturity period, 5 portions of cultivated soil layer and plants with similar growth were collected using the "five-point method" and mixed evenly; the mixed soil samples were naturally air-dried and sieved at 2 mm to obtain the soil samples to be tested; the mixed plants were washed, withered at 105°C for 30 minutes, dried at 70°C, shelled, ground, and sieved at 0.15 mm to obtain the brown rice to be tested.

[0075] Soil pH was measured according to HJ962-2018; soil available Cd was determined according to GB / T23739-2009; brown rice Cd was determined according to GB5009.15-2014.

[0076] Table 2. Soil and brown rice test data

[0077]

[0078]

[0079] Conclusion: The soil conditioners prepared in Examples 1-4 have excellent cadmium ion removal effects.

[0080] In Comparative Example 1, the amount of biological chelating agent added to the slow-release microsphere emulsion is small, and the amount of modified polyacrylamide added to the woody peat source soil conditioner is small, resulting in insufficient chelating groups such as thiol and carboxyl groups to react with cadmium ions, resulting in a low cadmium ion removal rate;

[0081] In Comparative Example 2, a large amount of biological chelating agent was added to the slow-release microsphere emulsion, and a large amount of modified polyacrylamide was added to the woody peat-derived soil conditioner, which resulted in the dissociation of unreacted chelating groups such as thiol and carboxyl groups on the excess molecular chain, which existed in the form of negative ions, resulting in a large amount of negative charge on the surface. Due to the electrostatic repulsion, repulsion was generated, resulting in a decrease in the removal rate of cadmium ions.

[0082] In Comparative Example 3, the biochelating agent is not introduced into the biochar in the form of slow-release microspheres, the loading rate is low, the lack of buffer is easily affected by pH, the cadmium ion removal effect is unstable, long-term removal is not possible, and the cadmium ion removal rate is low;

[0083] In the comparative example 4, excessive acrylamide was added in the process of preparing the polymer powder in the biochelating agent, resulting in excessively long molecular chains of the polymer powder structure, which easily generated entanglement between chains, and was not conducive to the subsequent grafting with acetylcysteine ​​and humate, resulting in a lower grafting rate and a reduction in the number of active groups that reacted with cadmium ions, resulting in a lower cadmium ion removal rate.

[0084] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation process of a woody peat-derived soil conditioner, characterized in that: The following steps are involved: S1: placing the sustained-release microsphere emulsion in an environment of 20-50°C, adding fuming nitric acid under high-speed stirring to react for 10-20 minutes, washing until the pH is neutral, and obtaining a nitro sustained-release microsphere emulsion; placing the nitro sustained-release microsphere emulsion in an environment of 70-90°C, adjusting the pH to 8-10, adding sodium dithionite to react for 3-4 hours, washing until the pH is neutral, filtering, and drying to obtain amino sustained-release microspheres; dissolving carboxymethyl-β-cyclodextrin in anhydrous ethanol, adding amino sustained-release microspheres to react for 24 hours, washing, and drying to obtain cyclodextrin-modified sustained-release microspheres; S2: Pretreat the woody peat and set it aside; place the pretreated woody peat in a nitrogen atmosphere, heat it to 600-620°C and keep it warm for 2-2.5 hours to obtain woody peat biochar; add the woody peat biochar and cyclodextrin modified slow-release microspheres into anhydrous ethanol and stir evenly, add polyaluminum chloride, polyacrylamide, and modified polyacrylamide and stir evenly, shake the reaction for 12-14 hours, let it stand and precipitate, filter, wash, and dry to obtain a woody peat source soil conditioner.

2. The preparation process of a woody peat-derived soil conditioner according to claim 1, characterized in that: The method for preparing the sustained-release microsphere emulsion comprises the following steps: Add acrylamide, 2-methyl-2-propionamidopropanesulfonic acid and a bio-based chelating agent into deionized water, add ammonium persulfate and N,N'-methylenebisacrylamide and stir evenly to obtain aqueous phase A; mix Span 80 and Tween 60 evenly, add white oil and stir evenly to obtain oil phase A; stir aqueous phase A and oil phase A evenly, add styrene and stir evenly, add sodium sulfite under a nitrogen atmosphere, heat to 30-35°C, react for 30-45 minutes, precipitate, and obtain a sustained-release microsphere emulsion.

3. The preparation process of a woody peat-derived soil conditioner according to claim 2, characterized in that: The proportions of the components in the aqueous phase A by weight are 15-20 parts of acrylamide, 3-5 parts of 2-methyl-2-propionamidopropanesulfonic acid, 10-15 parts of bio-based chelating agent, 4-8 parts of ammonium persulfate, and 0.1-0.5 parts of N,N'-methylenebisacrylamide; the proportions of the components in the oil phase by weight are 12-20 parts of Span 80, 4-8 parts of Tween 60, and 48-60 parts of white oil; The components in the sustained-release microsphere emulsion are calculated by weight: 10-20 parts of water phase A, 25-40 parts of oil phase A, 20-35 parts of styrene, and 0.05-0.1 parts of ammonium sulfite.

4. The preparation process of a woody peat-derived soil conditioner according to claim 2, characterized in that: The preparation method of the bio-based chelating agent comprises the following steps: The carboxymethyl chitosan is dissolved in deionized water, acrylamide is added, the pH is adjusted to 7-7.5, a photoinitiator is added under a nitrogen atmosphere, photocuring is performed, washing, purification, drying, grinding, and polymer powder is obtained; the polymer powder is dissolved in deionized water, acetylcysteine, humate, and a cross-linking agent are added, the pH is adjusted to 5-5.5, heated to 40-45° C. for reaction for 2-2.5 hours, washed, dried, and ground to obtain a bio-based chelating agent.

5. The preparation process of a woody peat-derived soil conditioner according to claim 4, characterized in that: The mass ratio of the carboxymethyl chitosan: acrylamide is (1-2): (3.5-7); the mass ratio of the polymer powder: acetylcysteine: humate: cross-linking agent is 1: (1-2): (1-2): 0.03; the photoinitiator is azobisisobutyramidine hydrochloride; and the cross-linking agent is 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride.

6. The preparation process of a woody peat-derived soil conditioner according to claim 1, characterized in that: The preparation method of the modified polyacrylamide comprises the following steps: Dissolve acrylamide, sodium formate and ammonium persulfate in deionized water, heat to 85-90°C and react for 2-2.5 hours to obtain polyacrylamide; add polyacrylamide to formaldehyde, adjust the pH to 11-11.5, heat to 50-55°C and react for 2-2.5 hours to obtain hydroxymethyl polyacrylamide; add hydroxymethyl polyacrylamide to thioglycolic acid, adjust the pH to 4.75-5, heat to 25-30°C and react for 2 hours to obtain modified polyacrylamide.

7. The preparation process of a woody peat-derived soil conditioner according to claim 6, characterized in that: The proportions of the components in the polyacrylamide are calculated by mass: 24-30 parts of acrylamide, 0.03-0.05 parts of sodium formate, and 0.5-0.8 parts of ammonium persulfate; the molar ratio of the polyacrylamide: formaldehyde is 1:1; the molar ratio of the hydroxymethyl polyacrylamide: thioglycolic acid is 1:(3.2-3.5).

8. The preparation process of a woody peat-derived soil conditioner according to claim 1, characterized in that: The mass ratio of the sustained-release microsphere emulsion: fuming nitric acid is (2-3):(2-3); the mass ratio of the nitro sustained-release microsphere emulsion: sodium dithionite is (10-15):(3-4); the mass ratio of the carboxymethyl-β-cyclodextrin: amino sustained-release microsphere is 5:(1.5-2).

9. The preparation process of a woody peat-derived soil conditioner according to claim 1, characterized in that: The proportions of the components in the woody peat source soil conditioner are calculated by weight: 90-100 parts of woody peat biochar, 3.2-6.4 parts of cyclodextrin modified slow-release microspheres, 20-25 parts of polyaluminium chloride, 2-4 parts of polyacrylamide, and 2-4 parts of modified polyacrylamide.

10. A soil conditioner prepared according to the preparation process of a woody peat-derived soil conditioner according to any one of claims 1 to 9.

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