Abandoned biomass-based arable soil remediation modifier and preparation method thereof

Abstract

The invention relates to the technical field of soil remediation, in particular to a cultivated land soil remediation modifier based on waste biomass and a preparation method thereof.The cultivated land soil remediation modifier comprises, by mass, 5-10% of modified biomass, 5-10% of waste biomass and the balance water. 1-5% of a microbial agent; 1-5% of a gel material; 10 to 20% of bentonite; the balance of organic fertilizer; the preparation method comprises the following steps: S1, preparing the rigid matrix; s2, preparing flexible slurry; s3, preparing a cultivated land soil remediation modifier; according to the arable soil remediation modifier, the modified biomass and the bentonite are used as rigid matrixes, the gel material, the microbial agent and the organic fertilizer are used as flexible slurry, and the rigid matrixes are beneficial for breaking hardening and increasing pores; the flexible slurry improves the water retention capacity, can prevent particles from loosening and collapsing in soil when encountering water, and prolongs the action time of the cultivated land soil remediation modifier.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, specifically to a farmland soil remediation and amendment based on waste biomass and its preparation method. Background Technology

[0002] Arable land soil is the foundational resource for agricultural production, and its health directly impacts food security and ecological sustainability. However, with rapid industrial and agricultural development, arable land faces multiple risks, including soil acidification, salinization, declining organic matter, and heavy metal pollution. For example, soil acidification (pH below 5.5) is a prominent issue in southern farmland, leading to increased heavy metal activity and a higher risk of crop absorption. Simultaneously, excessive use of chemical fertilizers and pesticides causes soil compaction and microbial community decline, resulting in the degradation of arable land's ecological functions. While commonly used remediation technologies (such as chemical passivation and soil replacement) can provide short-term benefits, they suffer from high costs (up to several thousand yuan per mu), a significant risk of secondary pollution, and unsustainable effects. Furthermore, single technologies are insufficient to address complex pollution, and long-term use of some mineral amendments (such as lime) can damage soil aggregate structure, further exacerbating soil fertility decline.

[0003] Waste biomass (such as straw, rice husks, and garden pruning waste) offers unique advantages as a remediation raw material, being green, low-cost, and resource-efficient. Its resource utilization represents a win-win solution to both environmental pollution and soil remediation needs. For example, biomass power plant ash is rich in silicates and elements such as calcium and potassium, which can be used to make passivating agents. Through ion exchange, these agents adsorb heavy metals, reducing cadmium content in rice by 69-93% while increasing yield by 24-79%. Secondly, waste biomass can be converted into biochar through carbonization technology. Its porous structure enhances soil water and fertilizer retention capacity and immobilizes pollutants. Furthermore, the organic fertilizer produced through fermentation replenishes soil organic matter and rebuilds the microbial community. Data shows that in Xiuyan County, Liaoning Province, soil organic matter increased and crop yields increased by over 20% after improvement with straw-based biochar fertilizer. Compared to traditional soil conditioners, biomass materials are derived from nature, biodegradable, and residue-free, aligning with the concept of "nature-based remediation."

[0004] Therefore, this invention aims to design a farmland soil remediation and amendment based on waste biomass and its preparation method to improve the above-mentioned problems. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a farmland soil remediation and amendment agent based on waste biomass and its preparation method.

[0006] A farmland soil remediation and amendment agent based on waste biomass, comprising the following components by mass ratio: Modified biomass: 5-10%; Microbial inoculant: 1-5%; Gel material: 1~5%; Bentonite: 10~20%; Organic fertilizer: remaining amount; The method for preparing the modified biomass is as follows: Waste biomass is ground and dried to obtain powder with a particle size of 0.1~0.2mm. The powder is then modified by microwave irradiation with a power of 500~600W for 30~40min to obtain modified powder. The modified powder was mixed with a phosphoric acid solution with a mass fraction of 45-55% at a solid-liquid ratio of 1g:50-80mL, and refluxed at 85-90℃ for 1-2h. After the reflux extraction was completed, the mixture was filtered to obtain the extract. First, add 1-2% hexadecyltrimethylammonium bromide aqueous solution at a volume ratio of 10-15:1 to the extract. Mix at 0.5-1 MPa for 15-20 min to obtain a first mixture. Then, adjust the pH of the first mixture to 7-9. After pH adjustment, add 5-10 wt% humic acid (based on the modified powder) to the first mixture and adjust the pressure to 0.1-0.2 MPa. Continue mixing for 30-40 min to obtain a second mixture. The second mixture was heated to 600-650°C at 5-10°C / min under inert gas and kept at that temperature for 2-3 hours to obtain modified biomass.

[0007] Furthermore, the waste biomass is one or more of corn stalks, apple branches, and Sichuan pepper branches.

[0008] Note: Corn stalks, apple branches, and Sichuan pepper branches are agricultural wastes with large output and local characteristics in Northwest my country. Utilizing these wastes locally can reduce raw material costs and transportation expenses. Corn stalks are loose and porous, and when returned to the field, they can increase soil porosity, effectively break up soil compaction, improve soil aeration, enhance water retention, and provide nutrients for microorganisms, promoting soil microbial activity. Apple branches and Sichuan pepper branches have a high degree of lignification and tough fibers; after being crushed, they also help improve soil aggregate structure and enhance soil stability.

[0009] In one embodiment of the present invention, the gel material is a modified fiber composite aerogel material, and the preparation method of the modified fiber composite aerogel material is as follows: The surface of mulberry bark fiber is alkalized to obtain alkalized mulberry bark fiber. Polyglutamic acid and tetraethylenepentamine are dissolved in HEPES buffer at a solid-liquid ratio of 1g:100ml:15~20ml, and the pH value is adjusted to 8~9 to obtain a modified solution. The alkalized mulberry bark fiber is then immersed in the modified solution at a solid-liquid ratio of 1g:20~30ml for 5~7h to obtain pre-modified mulberry bark fiber, which is then washed and dried. The pre-modified mulberry bark fiber is then immersed in a hydrolysate of silane coupling agent with a volume fraction of 20-25% at a solid-liquid ratio of 1g:15-20ml for 1-2 hours to obtain modified mulberry bark fiber. After washing the modified mulberry bark fiber, it is heat-treated at 105-115℃ for 30-40 minutes to obtain heat-treated mulberry bark fiber. Iron oxide nanoparticles with a particle size of 20-30 nm were dispersed in an ethanol solution with a mass fraction of 50-55% at a solid-liquid ratio of 1 g: 80-90 ml to obtain a dispersion of organic magnetized particles. The dispersion of heat-treated mulberry bark fiber, ethylene oxide, and organic magnetized particles was mixed at a solid-liquid ratio of 1 g: 10 ml: 60-80 ml for 60-90 min, and then the product was filtered and dried to obtain a composite material. The composite material was vacuum impregnated in a silica sol with a pH of 6-7 at a solid-liquid ratio of 1g:40-50ml, at a temperature of 25-35℃, a vacuum degree of 0.08-0.09MPa, and an impregnation time of 30-40min to obtain an impregnated product. Then, fumed silica was introduced into the impregnated product at a rate of 0.5-0.8L / min, and the reaction was carried out at 50-60℃ for 2-4h. Finally, the modified fiber composite aerogel material was obtained by supercritical drying.

[0010] Note: Mulberry bark fiber is a natural rigid skeleton. Alkali treatment removes impurities such as hemicellulose and lignin, exposing more hydroxyl groups and significantly improving its surface activity and reaction sites, laying the foundation for subsequent chemical grafting. Furthermore, mulberry bark fiber has a high pectin content, making it more easily degraded by soil microorganisms, gradually releasing organic matter and improving soil fertility. Its degradation process may contribute to the formation of substances beneficial to soil aggregate structure. It also has a certain complexing ability for heavy metal ions (such as cadmium and lead). Polyglutamic acid is an excellent natural polyelectrolyte containing a large number of carboxyl groups, while tetraglutamic acid... Ethylenepentamine, rich in amino groups, can be grafted onto mulberry bark fibers through chemical bonding under alkaline conditions. This introduces a large number of functional groups that can fix heavy metals in the soil through ion exchange or complexation, while also enhancing the hydrophilicity and water retention of the material. The hydrolytic group at one end of the silane coupling agent reacts with the hydroxyl groups on the fiber surface, while the organic functional group at the other end can combine with the subsequent silica sol, enhancing the interfacial compatibility and bonding force between the mulberry bark fiber and the inorganic silica sol, improving the durability of the material. This treatment also helps to complete the hydrolysis and condensation reaction of the coupling agent, forming a stable chemical bond. The surface of nano-iron oxide particles has abundant active sites (such as hydroxyl groups and iron ions), which can strongly adsorb heavy metal ions such as cadmium, lead, arsenic and chromium in the soil through mechanisms such as complexation, ion exchange and redox. Vacuum impregnation ensures that the silica sol fully fills all the pores of the fiber skeleton. The subsequently introduced fumed silica will continue to react and deposit on the existing skeleton, significantly strengthening the mechanical strength of the entire aerogel network and giving it a certain degree of compressive strength in the soil.

[0011] Furthermore, the supercritical drying process involves a pressure of 10-15 MPa, a temperature of 30-50°C, a drying time of 10-12 h, and a pressure release rate of 150-200 kPa / min after drying.

[0012] Note: In supercritical drying, temperature and pressure need to be matched; too low a temperature may require higher pressure to compensate for the fluid density.

[0013] Furthermore, the method for alkalizing the surface of the mulberry bark fiber is as follows: the mulberry bark fiber is reacted with a NaOH solution with a mass fraction of 10-20% at a solid-liquid ratio of 1g:50-60ml, the reaction temperature is 80-100°C, and the reaction time is 2-4h.

[0014] Note: In the alkalization process, concentration, temperature and time are interdependent. Excessive concentration or temperature may cause excessive damage to the fibers. If the alkalization treatment of the fiber surface is insufficient, the bonding force between the fiber and the aerogel matrix will be weak. During the drying process, the fiber-aerogel interface may become a weak point and is prone to cracking under stress.

[0015] As another aspect of the present invention, the gel material is one or more of cellulose hydrogel, polyacrylic acid hydrogel, and carboxymethyl chitosan gel.

[0016] Note: Cellulose hydrogels can physically absorb and retain water through their three-dimensional network structure, and can increase soil organic matter after degradation; polyacrylic acid hydrogels can achieve ultra-high water absorption and repeated swelling through the hydrophilic groups on the polymer chain, have strong water retention, and have a certain ion exchange capacity; carboxymethyl chitosan gels can fix heavy metal ions through complexation with functional groups such as amino and carboxyl groups.

[0017] Furthermore, the concentration of the microbial agent is 1×10⁻⁶. 8 ~1×10 10 The microbial agent comprises Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth in a volume ratio of 1:1:0.8~1, wherein the bacterial concentrations of the Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth are the same.

[0018] Note: The above-mentioned microbial strains work synergistically to fix nitrogen, solubilize phosphorus, promote growth, improve soil microecology, increase fertilizer utilization, and reduce soil diseases.

[0019] Furthermore, the organic fertilizer is one or more of manure, soybean residue, and fruit peel.

[0020] Description: Manure can be used to improve soil fertility in the long term. It has a high humus content and is effective in regulating soil pH. It is rich in minerals and can repair soil nutrient imbalances. Soybean residue can quickly replenish nitrogen and alleviate nitrogen deficiency symptoms in crops. The amino acids and polypeptides produced during the decomposition of soybean residue can be directly absorbed by crops to promote growth. It activates microorganisms quickly and is suitable for fields with continuous cropping obstacles. Fruit peels can quickly replenish carbon sources and promote microbial reproduction. It is rich in potassium and enhances crop stress resistance. The organic acids in fruit peels can dissolve insoluble phosphorus and potassium in the soil, making it suitable for soils with severe nutrient fixation.

[0021] A method for preparing a farmland soil remediation and amendment agent based on waste biomass as described in any of the above includes the following steps: S1. Preparation of rigid matrix The modified biomass is mixed with bentonite for 30-40 minutes to obtain a mixture. The mixture is then extruded and granulated to obtain a rigid matrix with a particle size of 3-5 mm. S2. Preparation of flexible slurry Add the microbial agent to the organic fertilizer and stir at 100-200 rpm for 15-20 minutes to obtain a premix. Add the gelling material to the premix and continue stirring and mixing at 200-300 rpm for 20-30 minutes to obtain a flexible slurry; S3, Preparation of arable land soil remediation and amendment agents In a vacuum environment of -0.06 ~ -0.09 MPa, the flexible slurry prepared by S2 is combined with the rigid matrix prepared by S1 by a low-pressure injection method. The pressure of the low-pressure injection is 0.1~0.3 MPa to obtain the composite matrix. The composite matrix is ​​then dried at 30-35°C until the moisture content is <15%, thus obtaining a farmland soil remediation and amendment agent.

[0022] Compared with existing farmland soil remediation and amendment agents, the beneficial effects of this invention are: (1) In this invention, waste biomass is crushed to increase the specific surface area of ​​the raw material, providing a sufficient reaction interface for subsequent chemical modification. Then, microwave irradiation modification is carried out to destroy the dense structure of biomass, initially activate the biomass, and generate more active sites on its surface to enhance the reaction activity with modifiers such as phosphoric acid. Then, phosphoric acid is refluxed for extraction, which can remove some impurities such as hemicellulose and introduce phosphorus-containing functional groups and acidic sites into the material. This plays an important role in adjusting soil pH and fixing heavy metals. Quaternary ammonium salt is added first to introduce cation sites. Quaternary ammonium salt provides positive charge and can electrostatically adsorb negatively charged anionic pollutants in the soil. After adjusting the alkali, humic acid is added. Humic acid is an excellent natural soil conditioner that can improve the aggregate structure, retain water and fertilizer and integrate metal ions. Gradient pressure treatment can promote the deep loading of functional molecules onto the waste biomass. Finally, pyrolysis carbonizes the functional groups and biomass introduced in the previous steps to generate a porous biochar-based material. The modified biomass obtained has a stable structure and is not easily decomposed after being applied to the soil. It can achieve carbon sequestration and play a long-term role in adsorbing pollutants.

[0023] (2) This invention designs a soil remediation and amendment agent with a rigid-flexible structure. Modified biomass and bentonite are used as rigid matrices to form a strong and porous skeleton. Gel materials, microbial agents and organic fertilizers are used as flexible slurries to fill and bind the rigid matrices. The rigid particles help to break up the compaction and increase the porosity. The flexible gel improves the water retention capacity and can prevent the particles from loosening and disintegrating when they come into contact with water in the soil, prolonging the action time and avoiding short-term failure. Among them, the gel material forms a hydration protective layer in the pores of the rigid matrix, creating a buffer microenvironment for microorganisms, which can significantly improve the survival rate of the microbial agents, enabling them to colonize and work continuously, improving the stability of the microbial agents. The gel network physically adsorbs nutrients, improves the utilization rate of organic fertilizers, reduces loss, and continuously provides fertilizer for crops and microorganisms, avoiding root burn or nutrient deficiency. The rigid-flexible structure simultaneously improves the soil aggregate structure, aeration and water retention, creating an environment conducive to root growth.

[0024] (3) The modified fiber composite aerogel material prepared in this invention uses mulberry bark fiber as a rigid skeleton. After alkalization treatment, impurities such as hemicellulose and lignin in the fiber can be removed, exposing more hydroxyl groups, which significantly improves its surface activity and reaction sites, laying the foundation for subsequent chemical grafting. Polyglutamic acid is an excellent natural polyelectrolyte containing a large number of carboxyl groups, while tetraethylenepentamine is rich in amino groups. Under alkaline conditions, they can be grafted onto mulberry bark fiber through chemical bonding, introducing a large number of functional groups that can fix soil heavy metals through ion exchange or complexation, while enhancing the hydrophilicity and water retention of the material. The hydrolytic group at one end of the silane coupling agent The reaction with hydroxyl groups on the fiber surface and the organic functional groups at the other end can combine with the subsequent silica sol, enhancing the interfacial compatibility and bonding force between mulberry bark fiber and inorganic silica sol, improving the durability of the material. The treatment also helps to complete the hydrolysis and condensation reaction of the coupling agent, forming a stable chemical bond. The surface of the nano iron oxide particles has abundant active sites, which can strongly adsorb heavy metal ions such as cadmium, lead, arsenic, and chromium in the soil through mechanisms such as complexation. Vacuum impregnation ensures that the silica sol fully fills all the pores of the fiber skeleton, and the subsequently introduced fumed silica will continue to react and deposit on the existing skeleton, significantly strengthening the mechanical strength of the entire aerogel network. Attached Figure Description

[0025] Figure 1 This is a graph showing the increase or decrease in soil organic carbon content in Experiment Example 1 of this invention; Figure 2 This is a graph showing the cadmium conversion rate results of Experimental Example 1 of the present invention; Figure 3 This is a graph showing the increase or decrease in soil organic carbon content in Experiment Example 2 of this invention; Figure 4 This is a graph showing the cadmium conversion rate results of Experimental Example 2 of the present invention; Figure 5 This is a graph showing the increase or decrease in soil organic carbon content in Experiment Example 3 of this invention; Figure 6 This is a graph showing the cadmium conversion rate results of Experimental Example 3 of the present invention; Figure 7 This is a graph showing the increase or decrease in soil organic carbon content in Experiment Example 4 of this invention. Figure 8 This is a graph showing the cadmium conversion rate results of Experimental Example 4 of the present invention; Detailed Implementation

[0026] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0027] Example 1: A farmland soil remediation and amendment agent based on waste biomass, comprising the following components by mass ratio: Modified biomass: 8%; Microbial inoculant: 3%; Gel material: 3%; Bentonite: 15%; Organic fertilizer: remaining amount; The method for preparing the modified biomass is as follows: Waste biomass was ground and dried at 60°C for 2 hours. The waste biomass was corn stalks. Powder with a particle size of 0.1~0.2 mm was obtained. The powder was then modified by microwave irradiation with a power of 550 W for 35 min to obtain modified powder. The modified powder was mixed with a 50% phosphoric acid solution at a solid-liquid ratio of 1g:65mL, and refluxed at 88℃ for 1.5h. After the reflux extraction was completed, the mixture was filtered to obtain the extract. First, add 1.5% hexadecyltrimethylammonium bromide aqueous solution at a volume ratio of 12:1 to the extract. Mix at 0.8 MPa for 18 min to obtain the first mixture. Then, adjust the pH of the first mixture to 8. After pH adjustment, add 8 wt% humic acid of modified powder to the first mixture and adjust the pressure to 0.15 MPa. Continue mixing for 35 min to obtain the second mixture. The second mixture was heated to 630°C at 8°C / min under an inert gas (helium) and held for 2.5 h to obtain modified biomass. The gel material is a cellulose hydrogel, and the concentration of the microbial agent is 1×10⁻⁶. 9 The microbial agent comprises Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth in a volume ratio of 1:1:0.9, wherein the bacterial strain concentrations of the Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth are the same; the organic fertilizer is chicken manure. The preparation method of the microbial inoculant is as follows: Bacillus (CGMCC 1.2416), nitrogen-fixing bacteria (CGMCC 1.5796), and phosphate-solubilizing bacteria (CGMCC No.33054) are activated separately, streaked on plates, and incubated at 30℃ for 48h. The cultured strains are then inoculated into LB liquid medium and cultured at 30℃ and 180r / min for 24h with shaking to obtain seed liquid. The seed liquids of the three strains are then inoculated into TSB liquid medium and cultured at 30℃ and 200r / min with shaking for 72h to obtain fermentation broth. The three fermentation broths are then mixed to obtain the compound microbial inoculant.

[0028] Example 2: A method for preparing a farmland soil remediation and amendment agent based on waste biomass as described in Example 1, comprising the following steps: S1. Preparation of rigid matrix Modified biomass was mixed with bentonite for 35 minutes to obtain a mixture, which was then extruded and granulated to obtain a rigid matrix with a particle size of 3.5~4.5 mm. S2. Preparation of flexible slurry Add the microbial agent to the organic fertilizer and stir at 150 rpm for 18 minutes to obtain a premix. Add the gel material to the premix and continue stirring and mixing at 250 rpm for 25 min to obtain a flexible slurry; S3, Preparation of arable land soil remediation and amendment agents In a vacuum environment of -0.08 MPa, the flexible slurry prepared by S2 was combined with the rigid matrix prepared by S1 by a low-pressure injection method. The pressure of the low-pressure injection was 0.2 MPa, and a composite matrix was obtained. The composite matrix is ​​then dried at 32°C until the moisture content is 10%, thus obtaining a farmland soil remediation and amendment agent.

[0029] Example 3: This example differs from Example 1 in that, by mass ratio, it includes the following components: Modified biomass: 5%; Microbial inoculant: 1%; Gel material (polyacrylic acid-based hydrogel): 1%; Bentonite: 10%; Organic fertilizer (soybean residue): remaining amount; The concentration of the microbial agent is 1×10⁻⁶. 8 The microbial agent comprises Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth in a volume ratio of 1:1:0.8, wherein the bacterial concentrations of the Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth are the same.

[0030] Example 4: This example differs from Example 1 in that it includes the following components by mass ratio: Modified biomass: 10%; Microbial inoculant: 5%; Gel material (carboxymethyl chitosan gel): 5%; Bentonite: 20%; Organic fertilizer (kiwi peel): Balance; The concentration of the microbial agent is 1×10⁻⁶. 10 The microbial agent comprises Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth in a volume ratio of 1:1:1, wherein the bacterial concentrations of the Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth are the same.

[0031] Example 5: The difference between this example and Example 1 is that the waste biomass (apple branches) is ground and dried to obtain powder with a particle size of 0.1~0.2mm. The powder is then modified by microwave irradiation with a power of 500W for 30min to obtain modified powder.

[0032] Example 6: This example differs from Example 1 in that waste biomass (corn stalks and pepper branches in a mass ratio of 1:1) is ground and dried to obtain powder with a particle size of 0.1~0.2mm. The powder is then modified by microwave irradiation with a power of 600W for 40min to obtain modified powder.

[0033] Example 7: The difference between this example and Example 1 is that the modified powder was mixed with a 45% phosphoric acid solution at a solid-liquid ratio of 1g:50mL, and refluxed at 85°C for 1h. After the reflux extraction was completed, the mixture was filtered to obtain the extract.

[0034] Example 8: The difference between this example and Example 1 is that the modified powder was mixed with a 55% phosphoric acid solution at a solid-liquid ratio of 1g:80mL, and refluxed at 90°C for 2 hours. After the reflux extraction was completed, the mixture was filtered to obtain the extract.

[0035] Example 9: The difference between this example and Example 1 is that a 1% hexadecyltrimethylammonium bromide aqueous solution is first added to the extract at a volume ratio of 10:1, and the mixture is first mixed at 0.5 MPa for 15 min to obtain the first mixture.

[0036] Example 10: This example differs from Example 1 in that a 2% hexadecyltrimethylammonium bromide aqueous solution is first added to the extract at a volume ratio of 15:1, and the mixture is first mixed at 1 MPa for 20 min to obtain the first mixture.

[0037] Example 11: The difference between this example and Example 1 is that the pH of the first mixture is adjusted to 7. After the pH adjustment is completed, humic acid accounting for 5 wt% of the modified powder is added to the first mixture, and the pressure is adjusted to 0.1 MPa. Mixing is continued for 30 minutes to obtain the second mixture.

[0038] Example 12: The difference between this example and Example 1 is that the pH of the first mixture is adjusted to 9. After the pH adjustment is completed, humic acid accounting for 10 wt% of the modified powder is added to the first mixture, and the pressure is adjusted to 0.2 MPa. Mixing is continued for 40 min to obtain the second mixture.

[0039] Example 13: The difference between this example and Example 1 is that the second mixture is heated to 600°C at 5°C / min under an inert gas and kept at that temperature for 2 hours to obtain modified biomass.

[0040] Example 14: The difference between this example and Example 1 is that the second mixture is heated to 650°C at 10°C / min under an inert gas and kept at that temperature for 3 hours to obtain modified biomass.

[0041] Example 15: This example differs from Example 1 in that the gel material is a modified fiber composite aerogel material, and the preparation method of the modified fiber composite aerogel material is as follows: The mulberry bark fiber was subjected to surface alkalization treatment by reacting it with a 15% NaOH solution at a solid-liquid ratio of 1g:55ml at a reaction temperature of 90°C for 3 hours to obtain alkalized mulberry bark fiber. Polyglutamic acid and tetraethylenepentamine were dissolved in HEPES buffer at a solid-liquid ratio of 1g:100ml:18ml, and the pH was adjusted to 8.5 to obtain a modified solution. The alkalized mulberry bark fiber was then immersed in the modified solution at a solid-liquid ratio of 1g:25ml for 3 hours to obtain pre-modified mulberry bark fiber. The fiber was then washed with deionized water and dried at 80°C for 2 hours. The pre-modified mulberry bark fiber was then immersed in a hydrolysate of 23% silane coupling agent at a solid-liquid ratio of 1g:18ml for 1.2h to obtain modified mulberry bark fiber. The modified mulberry bark fiber was then taken out, washed with deionized water, and heat-treated at 110℃ for 30~40min to obtain heat-treated mulberry bark fiber. Iron oxide nanoparticles with a particle size of 24-26 nm were dispersed in a 52% ethanol solution at a solid-liquid ratio of 1 g: 85 ml to obtain a dispersion of organic magnetized particles. The dispersion of heat-treated mulberry bark fiber, ethylene oxide, and organic magnetized particles was mixed at a solid-liquid ratio of 1 g: 10 ml: 70 ml for 75 min. The product was then filtered and dried at 100 °C to constant weight to obtain a composite material. The composite material was vacuum impregnated in silica sol with a pH of 6.5 at a solid-liquid ratio of 1g:45ml at a temperature of 30℃ and a vacuum degree of 0.08MPa for 35min to obtain an impregnated product. Then, fumed silica was introduced into the impregnated product at a rate of 0.7L / min and reacted at 55℃ for 3h. Then, it was supercritically dried at a pressure of 12MPa, a temperature of 40℃, and a drying time of 11h. After drying, the pressure was released at a rate of 180kPa / min to obtain the modified fiber composite aerogel material.

[0042] Example 16: This example differs from Example 15 in that the mulberry bark fiber is reacted with a 10% NaOH solution at a solid-liquid ratio of 1g:50ml, the reaction temperature is 80°C, and the reaction time is 2h to obtain alkalized mulberry bark fiber.

[0043] Example 17: This example differs from Example 15 in that the mulberry bark fiber is reacted with a 20% NaOH solution at a solid-liquid ratio of 1g:60ml, the reaction temperature is 100°C, and the reaction time is 4h to obtain alkalized mulberry bark fiber.

[0044] Example 18: This example differs from Example 15 in that polyglutamic acid and tetraethylenepentamine are dissolved in HEPES buffer at a solid-liquid ratio of 1g:100ml:15ml, and the pH is adjusted to 8 to obtain a modified solution. Then, alkalized mulberry bark fiber is immersed in the modified solution at a solid-liquid ratio of 1g:20ml for 5 hours to obtain pre-modified mulberry bark fiber.

[0045] Example 19: This example differs from Example 15 in that polyglutamic acid and tetraethylenepentamine are dissolved in HEPES buffer at a solid-liquid ratio of 1g:100ml:20ml, and the pH is adjusted to 9 to obtain a modified solution. Then, alkalized mulberry bark fiber is immersed in the modified solution at a solid-liquid ratio of 1g:30ml for 7 hours to obtain pre-modified mulberry bark fiber.

[0046] Example 20: The difference between this example and Example 15 is that the pre-modified mulberry bark fiber was immersed in a hydrolysate of 20% silane coupling agent at a solid-liquid ratio of 1g:15ml for 1 hour to obtain modified mulberry bark fiber. After washing the modified mulberry bark fiber, it was heat-treated at 105℃ for 30 minutes to obtain heat-treated mulberry bark fiber.

[0047] Example 21: The difference between this example and Example 15 is that the pre-modified mulberry bark fiber was immersed in a hydrolysate of 25% silane coupling agent at a solid-liquid ratio of 1g:20ml for 2 hours to obtain modified mulberry bark fiber. After washing the modified mulberry bark fiber, it was heat-treated at 115℃ for 40 minutes to obtain heat-treated mulberry bark fiber.

[0048] Example 22: This example differs from Example 15 in that iron oxide nanoparticles with a particle size of 20-24 nm are dispersed in a 50% ethanol solution at a solid-liquid ratio of 1 g: 80 ml to obtain a dispersion of organic magnetized particles; the dispersion of heat-treated mulberry bark fiber, ethylene oxide, and organic magnetized particles is mixed at a solid-liquid ratio of 1 g: 10 ml: 60 ml for 60 min, and then the product is filtered and dried to obtain a composite material.

[0049] Example 23: This example differs from Example 15 in that iron oxide nanoparticles with a particle size of 26-30 nm are dispersed in a 55% ethanol solution at a solid-liquid ratio of 1 g: 90 ml to obtain a dispersion of organic magnetized particles; the dispersion of heat-treated mulberry bark fiber, ethylene oxide, and organic magnetized particles is mixed at a solid-liquid ratio of 1 g: 10 ml: 80 ml for 90 min, and then the product is filtered and dried to obtain a composite material.

[0050] Example 24: This example differs from Example 15 in that the composite material is vacuum impregnated in a silica sol with a pH of 6 at a solid-liquid ratio of 1g:40ml, at a temperature of 25°C, a vacuum degree of 0.08MPa, and an impregnation time of 30min to obtain an impregnated product. Then, fumed silica is introduced into the impregnated product at a rate of 0.5L / min, and the reaction is carried out at 50°C for 2h.

[0051] Example 25: This example differs from Example 15 in that the composite material is vacuum impregnated in a silica sol with a pH of 7 at a solid-liquid ratio of 1g:50ml, at a temperature of 35°C, a vacuum degree of 0.09MPa, and an impregnation time of 40min to obtain an impregnated product. Then, fumed silica is introduced into the impregnated product at a rate of 0.8L / min, and the reaction is carried out at 60°C for 4h.

[0052] Example 26: This example differs from Example 15 in that the supercritical drying pressure is 10 MPa, the temperature is 30°C, the drying time is 10 h, and the pressure is released at a rate of 150 kPa / min after drying is completed.

[0053] Example 27: This example differs from Example 15 in that the supercritical drying pressure is 15 MPa, the temperature is 50°C, the drying time is 12 h, and the pressure is released at a rate of 200 kPa / min after drying is completed.

[0054] Example 28: The difference between this example and Example 2 is that the modified biomass and bentonite are mixed for 30 minutes to obtain a mixture, and then the mixture is extruded and granulated to obtain a rigid matrix with a particle size of 3~3.5mm.

[0055] Example 29: The difference between this example and Example 2 is that the modified biomass and bentonite are mixed for 40 minutes to obtain a mixture, and then the mixture is extruded and granulated to obtain a rigid matrix with a particle size of 4.5~5mm.

[0056] Example 30: The difference between this example and Example 2 is that the microbial agent is added to the organic fertilizer and stirred at 100 rpm for 15 minutes to obtain a premix. Then add the gel material to the premix and continue stirring and mixing at 200 rpm for 20 minutes to obtain a flexible slurry.

[0057] Example 31: The difference between this example and Example 2 is that the microbial agent is added to the organic fertilizer and stirred at 200 rpm for 20 minutes to obtain a premix. Then add the gel material to the premix and continue stirring and mixing at 300 rpm for 30 min to obtain a flexible slurry.

[0058] Example 32: This example differs from Example 2 in that, in a vacuum environment of -0.06 MPa, the flexible slurry prepared by S2 is composited with the rigid matrix prepared by S1 by a low-pressure injection method. The pressure of the low-pressure injection is 0.1 MPa, resulting in a composite matrix. The composite matrix is ​​then dried at 30°C until the moisture content is 5%, thus obtaining a soil remediation and amendment agent for arable land.

[0059] Example 33: This example differs from Example 2 in that, in a vacuum environment of -0.09 MPa, the flexible slurry prepared by S2 is composited with the rigid matrix prepared by S1 by a low-pressure injection method. The pressure of the low-pressure injection is 0.3 MPa, resulting in a composite matrix. The composite matrix is ​​then dried at 35°C until the moisture content is 14%, thus obtaining a soil remediation and amendment agent for arable land.

[0060] Experimental Example: The description of this experimental example is based on the scheme described in Example 2, and aims to illustrate the practical application effect of the present invention.

[0061] Experiment 1: The soil remediation and amendment agents prepared in each example were added to saline-alkali soil from the Guanzhong Plain that had passed through a 2mm sieve at an addition ratio of 0.5wt%, and stored in 180mL plastic cups and stirred thoroughly. Deionized water was added to the soil weekly to fill 60% of the pore volume, and each plastic cup was wrapped with a layer of aluminum foil (with 6 holes of 0.5 cm in diameter). After 400 days of cultivation, soil samples were taken, and the increase or decrease in soil organic carbon content before and after the addition of the soil remediation and amendment agents was measured using the potassium dichromate oxidation-external heating method.

[0062] Experiment 2: Based on Experiment 1, the water-stable aggregate components of Example 1 were determined using the wet sieving method: Soil was spread evenly on a 0.25 mm sieve surface, soaked in water for 5 minutes, and then vibrated in water at a vibration frequency of 25 times / min with an amplitude of 3 cm. The soil was then passed through 0.25 mm and 0.053 mm sieves sequentially. The content of large aggregates, micro-aggregates, and soil clay content was detected.

[0063] Experiment 3: Add 1.5wt% of arable land soil remediation and amendment to chromium-contaminated soil with a chromium content of 15mg / kg, mix thoroughly for 3 hours, and test the cadmium conversion rate before and after addition.

[0064] 1. The study investigated the increase or decrease in soil organic carbon content, the content of large and micro aggregates in the soil, the content of soil clay particles, and the conversion rate of cadmium in Example 1. The results are shown in Table 1.

[0065] Table 1 Performance data for Example 1

[0066] As shown in Table 1, the soil remediation and amendment agent provided by this invention can effectively increase the organic carbon content of the soil. Furthermore, regarding the proportion of soil particle size distribution, it significantly increases the proportion of large and micro aggregates in the soil and reduces the proportion of clay particles. This indicates that the invention can improve soil aggregate structure, reduce soil compaction, and improve soil physical properties. Simultaneously, it can bind with heavy metal ions in the soil, reducing the bioavailability of heavy metals and mitigating heavy metal pollution of soil and crops.

[0067] 2. To investigate the effects of component proportions on the increase or decrease of soil organic carbon content and cadmium conversion rate.

[0068] The difference between Comparative Example 1 and Example 1 is that the modified biomass was changed to waste biomass heated to 630°C at 8°C / min under inert gas and kept at that temperature for 2.5h to obtain biochar. from Figure 1 and Figure 2 The results analysis shows that the pore structure of the biochar obtained by direct pyrolysis in Example 1 is not optimized, the specific surface area is usually low, and its surface lacks targeted functional groups (such as phosphate and quaternary ammonium groups). This will result in a significant decrease in the adsorption and anchoring capacity of the material for specific pollutants in the soil (such as phosphate ions and heavy metal ions) compared with Examples 1 and 3-4. Comparing Examples 1 and 3-4, it can be seen that both too small and too large a proportion of modified biomass will reduce the increase or decrease in soil organic carbon content and cadmium conversion rate. Therefore, from a comprehensive perspective, the parameters of Example 1 are relatively better.

[0069] 3. To investigate the effects of modified biomass preparation on the increase or decrease of soil organic carbon content and cadmium conversion rate.

[0070] The difference between Comparative Example 2 and Example 1 is that the waste biomass is not modified by microwave irradiation. from Figure 3 and Figure 4The results analysis showed that, due to the lack of microwave irradiation modification in Control Example 2, the microstructure of the biomass raw material was not sufficiently destroyed, and the reactive sites were not adequately exposed. This directly affects the efficiency of subsequent chemical modification (such as reflux extraction with phosphoric acid solution), making it difficult for the modifier to be effectively loaded onto the biomass framework. Therefore, the effect of the modifier was significantly reduced compared to Examples 1 and 5-14. Comparing Examples 1 and 5-14, it can be seen that excessively small or large microwave irradiation modification parameters, excessively small or large extraction solution preparation parameters, excessively small or large first mixed solution preparation parameters, and excessively small or large second mixed solution preparation parameters will reduce the increase or decrease of soil organic carbon content and cadmium conversion rate. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

[0071] 4. To investigate the effects of the preparation of modified fiber composite aerogel materials on the increase or decrease of soil organic carbon content and cadmium conversion rate.

[0072] Table 2 Performance data for Example 15

[0073] The difference between Comparative Example 3 and Example 15 is that no pre-modification of the mulberry bark fiber is performed; The difference between Comparative Example 4 and Example 15 is that no organic magnetized particles were added to the dispersion. As can be seen from the results in Table 2, the modified fiber composite aerogel material provided in Example 15 has a highly stable organic carbon form, and its decomposition rate in the soil is very slow. Moreover, the three-dimensional porous structure of the modified fiber composite aerogel material can not only retain water and nutrients, but also protect organic carbon, thereby resisting the rapid decomposition of organic carbon by microorganisms, thus greatly extending the residence time of organic carbon in the soil and achieving true carbon fixation. Therefore, the performance of Example 15 is significantly improved compared with Example 1. from Figure 5 and Figure 6 The results analysis showed that, since Control Example 3 lacked pre-modification of mulberry bark fibers, its bonding with the gel material mainly relied on weak physical entanglement. After being applied to the soil, when subjected to environmental stresses such as wet-dry cycles and freeze-thaw changes, the interface was prone to become a weak point and cracked and separated, resulting in the destruction of the rigid-flexible structure, rapid loss of gel components, and a significant shortening of the material's service life. Control Example 4 lacked magnetic responsiveness, lost its ability to migrate and transform charged pollutants in the soil, and its adsorption capacity for heavy metal ions was greatly reduced. Therefore, the performance of Control Examples 3 and 4 was significantly lower than that of Examples 15 to 27. Comparing Examples 15 to 27, it can be seen that excessively small or large alkalization parameters, excessively small or large pre-modification parameters, excessively small modified heat treatment parameters, excessively small or large composite material preparation parameters, excessively small or large impregnation parameters, and excessively small or large supercritical drying parameters will all reduce the increase or decrease in soil organic carbon content and cadmium conversion rate. In Example 21, the larger heat treatment parameters resulted in the same increase or decrease in soil organic carbon content as in Example 15, but the cadmium conversion rate decreased relatively. Therefore, from an economic point of view, the parameters in Example 15 are relatively more effective.

[0074] 5. To investigate the effects of the preparation method of arable land soil remediation and amendment on the increase or decrease of soil organic carbon content and cadmium conversion rate.

[0075] The difference between Comparative Example 5 and Example 2 is that all raw materials were mixed uniformly in one step; from Figure 7 and Figure 8 The results analysis shows that, compared with Example 5, when all raw materials are mixed at once, the components will be disordered and mixed together. On the one hand, rigid particles cannot form an effective supporting skeleton, resulting in poor material mechanical strength and easy disintegration in the soil. On the other hand, the active ingredients such as microbial agents are directly exposed to the complex mixing and processing environment, and their survival rate will drop sharply. At the same time, the gel network cannot uniformly and effectively encapsulate and fix the functional components, resulting in the failure of nutrient slow release and microbial slow control functions. Therefore, the effect is significantly lower than that of Example 2 and Examples 28 to 33. Comparing Examples 2 and 28 to 33, it can be seen that if the preparation parameters of the rigid aggregate are too small or too large, the preparation parameters of the flexible sauce are too small or too large, and the parameters of low-pressure injection under vacuum are too small or too large, the increase or decrease of soil organic carbon content and cadmium conversion rate will be reduced. Therefore, from a comprehensive perspective, the parameter effect of Example 2 is relatively better.

Claims

1. A farmland soil remediation and amendment agent based on waste biomass, characterized in that, By mass ratio, it includes the following components: Modified biomass: 5-10%; Microbial inoculant: 1-5%; Gel material: 1~5%; Bentonite: 10~20%; Organic fertilizer: remaining amount; The method for preparing the modified biomass is as follows: Waste biomass is ground and dried to obtain powder with a particle size of 0.1~0.2mm. The powder is then modified by microwave irradiation with a power of 500~600W for 30~40min to obtain modified powder. The modified powder was mixed with a phosphoric acid solution with a mass fraction of 45-55% at a solid-liquid ratio of 1g:50-80mL, and refluxed at 85-90℃ for 1-2h. After the reflux extraction was completed, the mixture was filtered to obtain the extract. First, add 1-2% hexadecyltrimethylammonium bromide aqueous solution at a volume ratio of 10-15:1 to the extract. Mix at 0.5-1 MPa for 15-20 min to obtain a first mixture. Then, adjust the pH of the first mixture to 7-9. After pH adjustment, add 5-10 wt% humic acid (based on the modified powder) to the first mixture and adjust the pressure to 0.1-0.2 MPa. Continue mixing for 30-40 min to obtain a second mixture. The second mixture was heated to 600-650°C at 5-10°C / min under inert gas and kept at that temperature for 2-3 hours to obtain modified biomass.

2. The farmland soil remediation and amendment agent based on waste biomass as described in claim 1, characterized in that, The waste biomass is one or more of corn stalks, apple branches, and pepper branches.

3. A farmland soil remediation and amendment agent based on waste biomass as described in claim 1, characterized in that, The gel material is a modified fiber composite aerogel material, and the preparation method of the modified fiber composite aerogel material is as follows: The surface of mulberry bark fiber is alkalized to obtain alkalized mulberry bark fiber. Polyglutamic acid and tetraethylenepentamine are dissolved in HEPES buffer at a solid-liquid ratio of 1g:100ml:15~20ml, and the pH value is adjusted to 8~9 to obtain a modified solution. The alkalized mulberry bark fiber is then immersed in the modified solution at a solid-liquid ratio of 1g:20~30ml for 5~7h to obtain pre-modified mulberry bark fiber, which is then washed and dried. The pre-modified mulberry bark fiber is then immersed in a hydrolysate of silane coupling agent with a volume fraction of 20-25% at a solid-liquid ratio of 1g:15-20ml for 1-2 hours to obtain modified mulberry bark fiber. After washing the modified mulberry bark fiber, it is heat-treated at 105-115℃ for 30-40 minutes to obtain heat-treated mulberry bark fiber. Iron oxide nanoparticles with a particle size of 20-30 nm were dispersed in an ethanol solution with a mass fraction of 50-55% at a solid-liquid ratio of 1 g: 80-90 ml to obtain a dispersion of organic magnetized particles. The dispersion of heat-treated mulberry bark fiber, ethylene oxide, and organic magnetized particles was mixed at a solid-liquid ratio of 1 g: 10 ml: 60-80 ml for 60-90 min, and then the product was filtered and dried to obtain a composite material. The composite material was vacuum impregnated in a silica sol with a pH of 6-7 at a solid-liquid ratio of 1g:40-50ml, at a temperature of 25-35℃, a vacuum degree of 0.08-0.09MPa, and an impregnation time of 30-40min to obtain an impregnated product. Then, fumed silica was introduced into the impregnated product at a rate of 0.5-0.8L / min, and the reaction was carried out at 50-60℃ for 2-4h. Finally, the modified fiber composite aerogel material was obtained by supercritical drying.

4. A farmland soil remediation and amendment agent based on waste biomass as described in claim 3, characterized in that, The supercritical drying process involves a pressure of 10-15 MPa, a temperature of 30-50°C, and a drying time of 10-12 hours. After drying, the pressure is released at a rate of 150-200 kPa / min.

5. A farmland soil remediation and amendment agent based on waste biomass as described in claim 1, characterized in that, The method for alkalizing the surface of the mulberry bark fiber is as follows: the mulberry bark fiber is reacted with a NaOH solution with a mass fraction of 10-20% at a solid-liquid ratio of 1g:50-60ml, the reaction temperature is 80-100°C, and the reaction time is 2-4h.

6. A farmland soil remediation and amendment agent based on waste biomass as described in claim 1, characterized in that, The gel material is one or more of cellulose hydrogel, polyacrylic acid hydrogel, and carboxymethyl chitosan gel.

7. A farmland soil remediation and amendment agent based on waste biomass as described in claim 1, characterized in that, The concentration of the microbial agent is 1×10⁻⁶. 8 ~1×10 10 The microbial agent comprises Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth in a volume ratio of 1:1:0.8~1, wherein the bacterial concentrations of the Bacillus fermentation broth, nitrogen-fixing bacteria fermentation broth, and phosphate-solubilizing bacteria fermentation broth are the same.

8. A farmland soil remediation and amendment agent based on waste biomass as described in claim 1, characterized in that, The organic fertilizer is one or more of manure, soybean residue, and fruit peel.

9. A method for preparing a farmland soil remediation and amendment agent based on waste biomass as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Preparation of rigid matrix The modified biomass is mixed with bentonite for 30-40 minutes to obtain a mixture. The mixture is then extruded and granulated to obtain a rigid matrix with a particle size of 3-5 mm. S2. Preparation of flexible slurry Add the microbial agent to the organic fertilizer and stir at 100-200 rpm for 15-20 minutes to obtain a premix. Add the gelling material to the premix and continue stirring and mixing at 200-300 rpm for 20-30 minutes to obtain a flexible slurry; S3, Preparation of arable land soil remediation and amendment agents In a vacuum environment of -0.06 ~ -0.09 MPa, the flexible slurry prepared by S2 is composited with the rigid matrix prepared by S1 by a low-pressure injection method. The pressure of the low-pressure injection is 0.1 ~ 0.3 MPa, and a composite matrix is ​​obtained. The composite matrix is ​​then dried at 30-35°C until the moisture content is <15%, thus obtaining a farmland soil remediation and amendment agent.

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