Soil stabilizer and application thereof in soil remediation
By combining biochar with hydrogel to form a three-dimensional network structure, the problem of low fixation efficiency of biochar under dynamic changes in soil moisture is solved, and efficient and stable adsorption and fixation of heavy metals are achieved.
Patent Information
- Application Number
- CN202511489890.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-17
- Publication Date
- 2026-01-27
AI Technical Summary
Existing soil stabilizers, such as biochar, do not have a stable adsorption effect on heavy metals and have low fixation efficiency when soil moisture changes dynamically.
By combining biochar with hydrogel, the water absorption and retention properties of hydrogel are used to prolong the contact time between biochar and heavy metals, and a three-dimensional network structure is formed through Schiff base reaction to enhance the fixation effect of heavy metals.
It improves the adsorption stability and fixation efficiency of heavy metals, adapts to complex soil environments, and enhances the stabilization effect on heavy metals.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of soil remediation technology, specifically relating to a soil stabilizer and its application in soil remediation. Background Technology
[0002] Soil, as a fundamental resource for human survival and development, directly impacts ecological security and agricultural product quality. However, with rapid industrialization and urbanization, soil pollution has become increasingly severe. Heavy metal pollution, in particular, has become a major global environmental and public health issue due to its high toxicity, difficulty in degradation, and tendency to accumulate and amplify through the food chain.
[0003] To address these issues, various soil remediation technologies have been developed and applied, primarily including physical engineering (such as topsoil replacement and leaching), chemical (such as passivation / stabilization), biological (such as phytoremediation and microbial remediation), and agroecological regulation (such as pH adjustment and water management). Among these, chemical passivation / stabilization technology has been widely used in engineering practice due to its wide applicability to various soil types, large treatment capacity, relatively short remediation cycle, relatively simple operation, superior cost-effectiveness, and typically significant remediation effects.
[0004] Currently, commonly used materials as soil stabilizers for heavy metals mainly fall into several categories: natural clay minerals (such as bentonite, zeolite, and attapulgite), phosphorus-containing substances (such as phosphates and phosphate rock powder), alkaline substances (such as lime and limestone powder), iron and aluminum oxides (such as red mud and iron oxides), and organic matter (such as biochar, humic acid, and organic compost). These materials mainly alter the occurrence form of heavy metals in soil through physicochemical mechanisms such as adsorption, precipitation, ion exchange, and complexation / chelation, thereby reducing their mobility, bioavailability, and ecotoxicity. However, each of these individual materials has its limitations. Taking biochar as an example, biochar is used as an environmental remediation or agricultural improvement material primarily due to its low cost, easy availability, and multifunctionality. However, the adsorption capacity of biochar for heavy metals often fails to meet the remediation needs of highly polluted soils. Its limited surface active sites lead to insufficient adsorption stability, and its surface functional groups have relatively low activity. When interacting with heavy metals, the adsorption effect is not stable enough, resulting in the re-release of adsorbed heavy metals. Therefore, its stability needs to be improved. In addition, the hydrophobicity of biochar makes it less dispersible in soil, which affects its full contact with heavy metals and thus limits its stabilization efficiency. Summary of the Invention
[0005] The purpose of this invention is to provide a soil stabilizer and its application in soil remediation, so as to solve the problem of poor adsorption effect of soil stabilizers.
[0006] The objective of this invention can be achieved through the following technical solutions: A soil stabilizer comprising a hydrogel and biochar is prepared by the following steps: grafting a hydrophilic monomer onto carboxymethyl chitosan to obtain carboxymethyl chitosan / acrylic acid / acrylamide, adding biochar and mixing thoroughly, and then adding an aldehyde crosslinking agent for room temperature crosslinking to obtain the soil stabilizer. The aldehyde crosslinking agent is sodium alginate oxide. This soil stabilizer belongs to the category of hydrogel-biochar composites.
[0007] Biochar adsorbs heavy metals primarily through ion exchange and surface adsorption. Its mechanisms include reducing the release of heavy metals from the soil and converting them into stable forms with low mobility and low toxicity, thereby effectively inhibiting the migration and diffusion of heavy metals in the soil. However, both mechanisms are limited by the contact time between biochar and heavy metals. Since the water loss rate varies significantly among different soils, rapid water loss shortens the effective contact time between biochar and heavy metals, leading to a decrease in fixation efficiency. Therefore, dynamic changes in soil moisture are one of the key factors affecting the heavy metal fixation effect of biochar. This invention combines biochar with hydrogel, utilizing the water absorption and retention properties of the hydrogel to increase the contact time between biochar and heavy metals, thereby improving the fixation effect. In this invention, the biochar is added before the aldehyde-based crosslinking agent; the biochar can be uniformly dispersed in the hydrogel crosslinking system, resulting in an organic-inorganic composite soil stabilizer that improves the treatment effect.
[0008] To further improve the treatment effect of heavy metals, sodium alginate oxide is selected as the aldehyde crosslinking agent in this invention. In this soil stabilizer, sodium alginate oxide not only acts as a crosslinking agent, increasing the number of hydrophilic groups in the soil stabilizer and improving water absorption efficiency, but also forms a Schiff base with the amino groups in carboxymethyl chitosan / acrylic acid / acrylamide, which can chelate heavy metal ions and improve the stabilization effect of heavy metals. More importantly, the chelates formed by Schiff bases are generally more stable than simple amino chelates and are more suitable for complex soil environments.
[0009] In some possible implementations, the hydrophilic monomers include acrylic acid and acrylamide, with the mass ratio of acrylic acid to acrylamide being 1:1-2.
[0010] In some possible embodiments, the mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:8-10. The biochar has a mesh size of 200.
[0011] In some possible implementations, the degree of oxidation of sodium alginate is 50%; the mass ratio of hydrophilic monomer to sodium alginate is 10:2-3.
[0012] Sodium oxidized alginate, as a crosslinking agent, increases the number of hydrophilic groups in soil stabilizers and strengthens the hydrogen bonds between them and water molecules, thereby improving water absorption efficiency. However, further increasing the dosage will lead to excessively strong hydrogen bonding between hydrophilic groups, causing the polymer network to shrink, which in turn leads to a decrease in water absorption rate and indirectly affects the fixation effect of metal ions.
[0013] In some possible implementations, the soil stabilizer is prepared by the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate initiator was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers were added, and the mixture was stirred and reacted for 50-60 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 40-50 minutes. After crosslinking was completed, the mixture was dried, washed with ethanol and water, and then vacuum dried to constant weight to obtain a soil stabilizer.
[0014] Carboxymethyl chitosan has good water solubility. Under the action of an initiator, the active sites (such as hydroxyl and carboxymethyl groups) in carboxymethyl chitosan form macromolecular free radicals. These macromolecular free radicals combine with the double bonds (C=C) of hydrophilic monomers (such as acrylic acid and acrylamide), initiating the formation of new free radicals from the hydrophilic monomers. The hydrophilic monomers continuously add to the active chain, forming a grafted structure to obtain carboxymethyl chitosan / acrylic acid / acrylamide.
[0015] Among hydrophilic monomers, acrylic acid has a high water absorption rate and strong water retention capacity, but poor salt resistance. By introducing acrylamide, the salt resistance of soil stabilizers can be improved. Acrylamide also has a certain water absorption capacity, which can ensure salt resistance while also having good water absorption and retention effects.
[0016] In some possible implementations, the mass ratio of hydrophilic monomer to initiator is 10:0.08.
[0017] In some possible embodiments, the oxidized sodium alginate is prepared by the following steps: Sodium alginate and water were mixed to prepare a 2.5% solution. Sodium periodate was added, and the reaction was carried out in the dark for 24 hours. The reaction was terminated by adding ethylene glycol in an equimolar amount of sodium periodate. Sodium chloride and anhydrous ethanol were added to precipitate the precipitate. The ratio of anhydrous ethanol to sodium chloride was 5 g: 100 mL to promote precipitation. The precipitate was filtered and dissolved in deionized water. The precipitate was precipitated again with ethanol. This process was repeated three times. The precipitate was then dried under vacuum at 40 °C to obtain oxidized sodium alginate.
[0018] The oxidation degree of sodium alginate increases with the amount of sodium periodate added. When 0.4-0.6 mol of sodium periodate is added for every 1 mol of sodium alginate monomer unit, the oxidation degree of sodium alginate is in the range of 35% to 55%.
[0019] In some possible embodiments, the biochar is polydopamine-coated biochar. Polydopamine coating introduces functional groups such as catechol, amino, and quinone groups onto the surface of the biochar, enhancing its chelating ability for multivalent heavy metals and improving the soil stabilizer's selectivity and adsorption performance for heavy metal ions. The catechol and amino functional groups introduced onto the biochar surface can form hydrogen bonds with carboxyl and hydroxyl groups in the hydrogel, thereby increasing the interfacial bonding strength between the polydopamine-coated biochar and the hydrogel through chemical cross-linking and physical anchoring, thus improving the stability of the soil stabilizer.
[0020] In some possible implementations, polydopamine-coated biochar is formed by the self-polymerization of dopamine on the surface of biochar under alkaline conditions.
[0021] The specific steps are as follows: Dopamine hydrochloride was added to a 10 mmol / L pH 8.5 tris(hydroxymethyl)aminomethane hydrochloride buffer solution, and biochar material was added. The mixture was stirred and reacted at 25-30℃ for 24 h. After filtration, washing and drying, polydopamine-coated biochar was obtained.
[0022] Application of a soil stabilizer in soil remediation.
[0023] The beneficial effects of this invention are: This invention provides a soil stabilizer comprising a hydrogel and biochar. The soil stabilizer is prepared through the following steps: grafting a hydrophilic monomer onto carboxymethyl chitosan to obtain carboxymethyl chitosan / acrylic acid / acrylamide; adding biochar and mixing thoroughly; and then adding an aldehyde-based crosslinking agent for room temperature crosslinking to obtain the soil stabilizer. The aldehyde-based crosslinking agent is sodium alginate oxide. A three-dimensional network structure of the hydrogel-biochar composite is formed through a Schiff base reaction. Utilizing the synergistic effect between different materials, the limitations of single materials are overcome, and multiple synergistic effects are generated through material composites: the addition of biochar before crosslinking ensures its uniform dispersion in the gel network, forming an organic-inorganic hybrid structure; the three-dimensional network of the hydrogel provides ultra-high water absorption and retention capacity, significantly prolonging the interfacial contact time between biochar and heavy metals; and the abundant oxygen-containing functional groups and porous structure on the surface of the biochar enhance the density of heavy metal anchoring points. In particular, sodium alginate oxide has a dual function as a green crosslinking agent: its aldehyde group forms a pH-stable Schiff base bond with the polymer amino group, ensuring the structural integrity in acidic soil environments; at the same time, the carboxyl group provided by the sodium alginate chain segment can synergistically chelate heavy metal ions. Detailed Implementation
[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0025] The following is a detailed description of a soil stabilizer and its application in soil remediation according to an embodiment of this application.
[0026] Example 1
[0027] This embodiment provides a soil stabilizer, comprising hydrogel and biochar, which is prepared through the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate, an initiator, was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers, including acrylic acid and acrylamide, were added. The mixture was stirred and reacted for 55 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 45 minutes. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried at 40°C to constant weight to obtain a soil stabilizer.
[0028] Sodium alginate oxide is prepared through the following steps: Sodium alginate and water were mixed to prepare a 2.5% solution. Sodium periodate was added, and the reaction was carried out in the dark for 24 hours. The reaction was terminated by adding ethylene glycol in an equimolar amount of sodium periodate. Sodium chloride and anhydrous ethanol were added to precipitate the precipitate. The ratio of anhydrous ethanol to sodium chloride was 5 g: 100 mL to promote precipitation. The precipitate was filtered and dissolved in deionized water. It was then precipitated again with ethanol. This process was repeated three times. The precipitate was then dried under vacuum at 40 °C to obtain oxidized sodium alginate. The oxidation degree of the obtained oxidized sodium alginate was 50%.
[0029] The mass ratio of acrylic acid to acrylamide is 1:1. The mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:8. The mass ratio of hydrophilic monomer to sodium alginate is 10:2. The mass ratio of hydrophilic monomer to initiator is 10:0.08.
[0030] Example 2
[0031] This embodiment provides a soil stabilizer, comprising hydrogel and biochar, which is prepared through the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate, an initiator, was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers, including acrylic acid and acrylamide, were added. The mixture was stirred and reacted for 55 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 45 minutes. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried at 40°C to constant weight to obtain a soil stabilizer.
[0032] Sodium oxidized alginate is the same as in Example 1.
[0033] The mass ratio of acrylic acid to acrylamide is 1:1.5. The mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:8. The mass ratio of hydrophilic monomer to sodium alginate is 10:2. The mass ratio of hydrophilic monomer to initiator is 10:0.08.
[0034] Example 3
[0035] This embodiment provides a soil stabilizer, comprising hydrogel and biochar, which is prepared through the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate, an initiator, was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers, including acrylic acid and acrylamide, were added. The mixture was stirred and reacted for 55 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 45 minutes. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried at 40°C to constant weight to obtain a soil stabilizer.
[0036] Sodium oxidized alginate is the same as in Example 1.
[0037] The mass ratio of acrylic acid to acrylamide is 1:2. The mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:8. The mass ratio of hydrophilic monomer to sodium alginate is 10:2. The mass ratio of hydrophilic monomer to initiator is 10:0.08.
[0038] Example 4
[0039] This embodiment provides a soil stabilizer, comprising hydrogel and biochar, which is prepared through the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate, an initiator, was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers, including acrylic acid and acrylamide, were added. The mixture was stirred and reacted for 55 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 45 minutes. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried at 40°C to constant weight to obtain a soil stabilizer.
[0040] Sodium oxidized alginate is the same as in Example 1.
[0041] The mass ratio of acrylic acid to acrylamide is 1:1. The mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:8. The mass ratio of hydrophilic monomer to sodium alginate is 10:2.5. The mass ratio of hydrophilic monomer to initiator is 10:0.08.
[0042] Example 5
[0043] This embodiment provides a soil stabilizer, comprising hydrogel and biochar, which is prepared through the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate, an initiator, was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers, including acrylic acid and acrylamide, were added. The mixture was stirred and reacted for 55 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 45 minutes. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried at 40°C to constant weight to obtain a soil stabilizer.
[0044] Sodium oxidized alginate is the same as in Example 1.
[0045] The mass ratio of acrylic acid to acrylamide is 1:1. The mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:8. The mass ratio of hydrophilic monomer to sodium alginate is 10:3. The mass ratio of hydrophilic monomer to initiator is 10:0.08.
[0046] Example 6
[0047] This embodiment provides a soil stabilizer, comprising hydrogel and biochar, which is prepared through the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate, an initiator, was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers, including acrylic acid and acrylamide, were added. The mixture was stirred and reacted for 55 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 45 minutes. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried at 40°C to constant weight to obtain a soil stabilizer.
[0048] Sodium oxidized alginate is the same as in Example 1.
[0049] The mass ratio of acrylic acid to acrylamide is 1:1. The mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:10. The mass ratio of hydrophilic monomer to sodium alginate is 10:2. The mass ratio of hydrophilic monomer to initiator is 10:0.08.
[0050] Example 7
[0051] This embodiment provides a soil stabilizer. The difference between this embodiment and Embodiment 1 is that the biochar is polydopamine-coated biochar. Polydopamine-coated biochar is formed by the self-polymerization of dopamine on the surface of biochar under alkaline conditions. The specific steps are as follows: Dopamine hydrochloride was added to a 10 mmol / L pH 8.5 tris(hydroxymethyl)aminomethane hydrochloride buffer solution, and biochar material was added. The mixture was stirred and reacted at 25°C for 24 h. After filtration, washing and drying, polydopamine-coated biochar was obtained.
[0052] The remaining raw materials and preparation process are the same as in Example 1.
[0053] Example 8
[0054] This embodiment provides a soil stabilizer. The difference between this embodiment and Embodiment 2 is that the biochar is polydopamine-coated biochar. Polydopamine-coated biochar is formed by the self-polymerization of dopamine on the surface of biochar under alkaline conditions. The specific steps are as follows: Dopamine hydrochloride was added to a 10 mmol / L pH 8.5 tris(hydroxymethyl)aminomethane hydrochloride buffer solution, and biochar material was added. The mixture was stirred and reacted at 25°C for 24 h. After filtration, washing and drying, polydopamine-coated biochar was obtained.
[0055] The remaining raw materials and preparation process are the same as in Example 2.
[0056] Comparative Example 1
[0057] Compared with Example 1, this comparative example replaces acrylamide with acrylic acid, while the remaining raw materials and preparation process remain the same as in Example 1.
[0058] Comparative Example 2
[0059] Compared with Example 1, this comparative example provides the same aldehyde group, but replaces sodium alginate with 50% oxidation degree with glutaraldehyde.
[0060] Comparative Example 3
[0061] The difference between this comparative example and Example 1 is that biochar was not added during the preparation process.
[0062] Carboxymethyl chitosan was dissolved in water, and potassium persulfate, an initiator, was added under nitrogen protection. After stirring and dispersing, hydrophilic monomers, including acrylic acid and acrylamide, were added. The mixture was stirred and reacted for 55 min to obtain carboxymethyl chitosan / acrylic acid / acrylamide. An aldehyde crosslinking agent was added, and the mixture was stirred and crosslinked for 45 min. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried at 40°C to constant weight to obtain a hydrogel. The obtained hydrogel was mixed with biochar. The amount of raw materials used was the same as in Example 1.
[0063] Performance tests were conducted on Examples 1-8 and Comparative Examples 1-3: Simulated contaminated soil: Soil from the topsoil layer (0-20cm depth) of a farmland was collected. After natural air drying, impurities such as stones, plant roots, and fallen leaves were removed by sieving. The soil was then ground through a 2mm sieve and contaminated with lead nitrate and cadmium nitrate tetrahydrate solutions. Contaminated soil with a lead concentration of 846.36 mg / kg and a cadmium concentration of 855.62 mg / kg was prepared. Stabilizers from Examples 1-8 (3% by weight of the contaminated soil) were added to the contaminated soil. The soil was sprayed daily with deionized water to maintain a moisture content of approximately 50%, with continuous stirring. The soil was aged for one week before use.
[0064] Simulated water sample: Simulated acid rain components, pH value 5, with 2.2 mg of magnesium chloride, 2.3 mg of potassium nitrate, 18.3 mg of calcium sulfate, and 9.3 mg of ammonium sulfate added per liter of water.
[0065] The columns are made of PVC, 50cm high and 10cm in diameter. The soil sample is about 40cm high. 1.5cm thick glass wool is placed at both ends of each column to prevent water from clogging the outlet. The simulated water flow rate is 25mL / h.
[0066] The stabilizing effect of the stabilizer was tested using a soil column experiment. After 30 days, the distance from the top of the soil column was recorded at 0 cm, 18 cm, and 29 cm, designated as the upper, middle, and lower parts. Leaching experiments were conducted on soil contaminated with heavy metals according to the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The average concentration of heavy metals was recorded, and the retention rates for lead and chromium were calculated. Retention rate W (%) = C S / C0×100%, where C S C0: Average concentration of a certain heavy metal in the soil after the above experiment (mg / kg); C0: Concentration of the heavy metal in the soil before the experiment (mg / kg). The results are shown in Table 1. Table 1
[0067] In this invention, the stabilization efficiency of the composite stabilizer for heavy metals is evaluated based on the degree of reduction in the concentration of heavy metals in the leaching solution. According to Table 1, and in conjunction with Examples 7-8, it can be seen that, under otherwise unchanged conditions, replacing biochar with polydopamine-coated biochar enhances the selectivity and adsorption performance of the soil stabilizer for heavy metal ions, and also helps to improve the stability of the soil stabilizer in use.
[0068] As can be seen from Example 1 and Comparative Example 1, when all hydrophilic monomers are acrylic acid, the soil stabilizer has a low retention rate of heavy metals. This is because acrylic acid has poor salt resistance. Under the simulated acid rain conditions in this application, the presence of inorganic salts and other components also results in poor water absorption and retention of the soil stabilizer. Moreover, the hydrophilic monomers do not contain acrylamide, which reduces the number of crosslinking sites with the crosslinking agent, making it impossible to form a more stable water absorption and retention system, thus directly or indirectly reducing the retention rate of metals.
[0069] As can be seen from Example 1 and Comparative Example 2, replacing the crosslinking agent with a conventional aldehyde crosslinking agent reduces the number of hydrophilic groups in the soil stabilizer, which is not conducive to improving the water absorption and water retention rate of the soil stabilizer. Rapid water loss will shorten the effective contact time between biochar and heavy metals, indirectly affecting the retention rate of heavy metals.
[0070] As can be seen from Example 1 and Comparative Example 3, in this invention, biochar can be uniformly dispersed in the hydrogel crosslinking system, which can improve the treatment effect of the stabilizer. Heavy metal ions are more likely to diffuse to the active sites of the material (including activated carbon and hydrogel), undergo adsorption and adsorption exchange, and inhibit the diffusion and transfer of heavy metals. Hydrogel has good water absorption and water retention, but low mechanical strength. Although biochar has a certain adsorption capacity, its selectivity and fixation are poor. Although the separate addition in Comparative Example 3 has a certain ability to retain heavy metals, its stability in the rinsing system makes it difficult to fully exert the retention effect.
[0071] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A soil stabilizer, characterized in that, The soil stabilizer is prepared by grafting carboxymethyl chitosan with hydrophilic monomers to obtain carboxymethyl chitosan / acrylic acid / acrylamide, adding biochar and mixing evenly, and then adding an aldehyde crosslinking agent for room temperature crosslinking to obtain a soil stabilizer. The hydrophilic monomers include acrylic acid and acrylamide, and the aldehyde crosslinking agent is sodium alginate oxide.
2. The soil stabilizer according to claim 1, characterized in that, The mass ratio of acrylic acid to acrylamide is 1:1-2.
3. The soil stabilizer according to claim 1, characterized in that, The mass ratio of carboxymethyl chitosan, hydrophilic monomer, and biochar is 1:10:8-10.
4. A soil stabilizer according to claim 1, characterized in that, The degree of oxidation of the oxidized sodium alginate is 50%; the mass ratio of the hydrophilic monomer to the oxidized sodium alginate is 10:2-3.
5. A soil stabilizer according to claim 1, characterized in that, The soil stabilizer is prepared through the following steps: Carboxymethyl chitosan was dissolved in water, and potassium persulfate was added under nitrogen protection. After stirring and dispersing, a hydrophilic monomer was added, and the mixture was stirred and reacted for 50-60 minutes to obtain carboxymethyl chitosan / acrylic acid / acrylamide. A dispersion of biochar and water was added, and after stirring and dispersing, an aldehyde crosslinking agent was added. The mixture was stirred and crosslinked for 40-50 minutes. After crosslinking, the mixture was dried, washed with ethanol and water, and then vacuum dried to constant weight to obtain a soil stabilizer.
6. A soil stabilizer according to claim 5, characterized in that, The mass ratio of hydrophilic monomer to potassium persulfate is 10:0.
08.
7. A soil stabilizer according to claim 4, characterized in that, The oxidized sodium alginate is prepared by the following steps: Sodium alginate and water were mixed to prepare a solution. Sodium periodate was added, and the reaction was carried out in the dark. Ethylene glycol was added to terminate the reaction. Sodium chloride and anhydrous ethanol were added to precipitate the precipitate. The precipitate was filtered and dissolved in deionized water. The precipitate was precipitated again with ethanol. The process was repeated three times. The precipitate was then dried under vacuum to obtain oxidized sodium alginate.
8. A soil stabilizer according to claim 1, characterized in that, The biochar is polydopamine-coated biochar.
9. A soil stabilizer according to claim 1, characterized in that, Polydopamine-coated biochar is formed by the self-polymerization of dopamine on the surface of biochar under alkaline conditions.
10. The application of a soil stabilizer as described in any one of claims 1-9 in soil remediation.