Soil remediation and crop yield improvement composite material and preparation method and application thereof

Abstract

The application discloses a soil remediation and crop yield improvement composite material and a preparation method and application thereof, and belongs to the technical field of soil and fertilizer. The composite material comprises magnesium and aluminum, and the mass fraction of the magnesium and aluminum is 93-99.2%, and trace components, and the mass fractions of the trace components are as follows: 0.5%-1.5% of calcium, 0%-1.0% of iron, 0.05%-0.5% of copper, 0%-1.0% of zinc, 0.05%-0.4% of boron, 0.05%-0.5% of lanthanum, 0.05%-0.1% of molybdenum, 0%-1.0% of manganese and 0.1%-1.0% of silicon. The composite material of the application generates magnesium-aluminum intercalated two-dimensional nanometer functional materials in situ by hydrolysis in soil, regulates the oxidation-reduction potential of the soil, supplements trace elements, inhibits soil acidification and salinization, enriches microbial diversity, enhances the stress resistance, drought resistance and disease and pest resistance of plants, realizes the super-stable mineralization of heavy metals, the degradation of agricultural chemical residues and the yield improvement of crops.

Description

Technical Field

[0001] This invention relates to the field of soil and fertilizer technology, and in particular to composite materials for soil remediation and crop quality improvement and yield enhancement, as well as their preparation methods and applications. Background Technology

[0002] Currently, soil pollution and degradation are intensifying. Heavy metals, due to their non-degradability, bioaccumulation, and ecophysiological toxicity, have become one of the most serious environmental and health problems facing the world. Globally, approximately 14%-17% of farmland is contaminated with heavy metals, with cadmium pollution being particularly prominent.

[0003] Soil physicochemical properties (such as pH, redox potential, micronutrients, and toxic and harmful heavy metals and their forms) and microbial community structure are important indicators of soil health and productivity. Soil contamination with heavy metals and agricultural chemicals (herbicides, pesticide residues) severely inhibits microbial diversity and their activity, leading to heavy metal accumulation and reduced crop yields. In particular, under arid and high-temperature conditions, excessive cadmium pollution in rice is frequent, posing a threat to food security due to heavy metal pollution in paddy field soils.

[0004] Applying chemical agents, microbial agents, or remediation materials, along with foliar spraying of inhibitors, to heavy metal-contaminated soils is the most economical and feasible method for large-scale in-situ remediation of agricultural soils. Currently commonly used solidification and stabilization remediation materials / agents include chemical agents such as sulfides and phosphates, microbial agents such as Pseudomonas and Bacillus, and remediation materials such as lime, biochar, and clay minerals, as well as foliar inhibitors such as silicon-based and selenium-based agents. However, these materials have significant drawbacks in practical applications. Chemical agents easily lead to soil compaction and are associated with the risk of secondary pollution; microbial agents have poor environmental adaptability and long remediation cycles; among traditional passivation materials, lime-based passivators can cause soil compaction and disrupt the soil's microecological balance, while biochar and clay minerals have the problem of heavy metal reactivation after adsorption saturation; the effectiveness of foliar inhibition is constrained by multiple factors such as formulation characteristics, application method, and environmental conditions, and the cadmium control effect is extremely unstable. In general, current remediation materials generally suffer from low solidification and stabilization efficiency, poor durability, disruption of soil electrolyte balance, damage to microbial community structure, and high risks of desorption and secondary pollution.

[0005] Patent publications CN119702675A and CN119683667A disclose a co-precipitation method for preparing magnesium-based hydrotalcite for soil heavy metal pollution remediation. While exhibiting some solidification and stabilization effects on heavy metals in soil, these methods suffer from complex preparation processes, difficulty in controlling the process, and a lack of effective regulation of soil redox potential. Patent publication CN112915962A discloses a liquid-phase reduction method for loading nano-zero-valent iron onto magnesium-aluminum hydrotalcite to prepare a composite material. Although this method introduces redox functionality, it faces technical challenges such as the easy deactivation and poor stability and long-term effectiveness of the active component, nano-zero-valent iron. Furthermore, current soil heavy metal pollution remediation materials have significant shortcomings in improving crop quality and yield. Their mechanisms of action focus solely on pollution control, failing to fully consider crop growth needs. Not only do they fail to improve soil fertility, but some materials also alter soil physicochemical properties, hindering nutrient absorption and utilization by crop roots, making it difficult to achieve the synergistic goal of soil remediation and crop yield increase. "Overall, my country's soil remediation research is in the follow-up stage, with low original innovation and applicability. Patented technologies are mainly concentrated in solidification / stabilization agents, microbial remediation agents, and thermal desorption equipment, which are relatively simple in type, and site applications are mainly for single pollution" (Wu Fengchang et al., Department of Earth Sciences, National Natural Science Foundation of China, 2021, p. 182).

[0006] Therefore, developing novel soil conditioning and remediation materials with multiple synergistic mechanisms, including in-situ ultra-stable mineralization of soil heavy metal and agricultural chemical residues, conditioning of soil physicochemical properties, improvement of soil structure, promotion of soil microorganisms and biodiversity, and enhancement of plant stress resistance, drought resistance and pest and disease resistance, has become an urgent need to ensure food security under the current situation of non-point source pollution of soil heavy metals. Summary of the Invention

[0007] The purpose of this invention is to provide a composite material for soil remediation and crop quality improvement and yield enhancement, and its preparation method, in order to solve the above-mentioned problems.

[0008] This invention provides a composite material for soil remediation and crop quality improvement and yield enhancement, comprising magnesium and aluminum as well as trace components. The mass fraction of magnesium (Mg) and aluminum (Al) is 93-99.2%, wherein the mass ratio between magnesium and aluminum is 1:1-6:1. The mass fraction of the trace components is 0.8-7%, and the trace components include one or more of calcium (Ca), iron (Fe), copper (Cu), zinc (Zn), boron (B), lanthanum (La), molybdenum (Mo), manganese (Mn), and silicon (Si).

[0009] Preferably, in the above-mentioned soil remediation and crop quality improvement and yield enhancement composite material, the mass fractions of the trace components are as follows: calcium 0.5%-1.5%, iron 0%-1.0%, copper 0.05%-0.5%, zinc 0%-1.0%, boron 0.05%-0.4%, lanthanum 0.05%-0.5%, molybdenum 0.05%-0.1%, manganese 0%-1.0%, and silicon 0.1%-1.0%.

[0010] Preferably, in the above-mentioned soil remediation and crop quality improvement and yield enhancement composite material, the magnesium is derived from magnesium ingots or magnesium powder with a purity of not less than 99.95%, the aluminum is derived from aluminum ingots or aluminum powder with a purity of not less than 99.95%, and the trace components calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese, and silicon are derived from calcium powder, iron powder, copper powder, zinc powder, boron powder, lanthanum powder, molybdenum powder, manganese powder, and silicon powder with a purity of not less than 99.9%, respectively.

[0011] A method for preparing the soil remediation and crop quality improvement / yield enhancement composite material as described above is provided. Magnesium and aluminum, along with trace components, are mixed in a specific mass ratio. The composite material is prepared using a melt atomization method, a mechanical ball milling method, or a combination of both. The alloy prepared by melt atomization exhibits regular spherical shapes with a smooth and dense surface and a particle size of 0.01-2 mm. The composite material prepared by mechanical ball milling consists of irregular flake-like or blocky particles with a rough surface and a particle size of 0.05-2 mm. The composite material prepared by melt atomization followed by mechanical ball milling has a spherical matrix with nano-sized fine particles attached to it, also with a particle size of 0.01-2 mm. The alloy phase of the composite material obtained by the above preparation methods is β-Mg17Al12.

[0012] Preferably, in the above-mentioned method for preparing a soil remediation and crop quality improvement and yield enhancement composite material, the preparation method is carried out by first melting and atomizing followed by mechanical ball milling, including the following steps:

[0013] S1. Mix magnesium ingots and aluminum ingots in a mass ratio, load them into a vacuum induction melting furnace under argon protection, heat them to 780-820℃ at a gradient of 3-8℃ per minute, melt for 40-90 minutes, then cool them down to 720-780℃ at a gradient of 1-3℃ per minute and hold at that temperature, during which a pulsed magnetic field with a frequency of 30-40Hz and an intensity of 0.05-0.2T is applied for stirring.

[0014] S2. A specially designed double-layer atomizing disk with an upper diameter of 150-180mm and a lower diameter of 200-220mm is used for atomization under the protection of a nitrogen-argon mixed atmosphere. The rotation speed of the upper layer is controlled at 18000-20000r / min, the rotation speed of the lower layer is 12000-15000r / min, and the atomization pressure is 0.4-0.6MPa to obtain matrix particles with a particle size of 0.2-1.5mm. The volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere is 1:3.

[0015] S3. Mix the atomized particles with calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese or silicon powder in a mass ratio and load them into a ball mill jar with temperature control function. The particle size of the calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese or silicon powder is 30-80nm.

[0016] S4. A two-stage ball milling process is adopted: In the first stage, 3mm alumina ceramic beads and 6mm tungsten carbide beads are used at a mass ratio of 2:1 and a ball-to-material ratio of 8:1. The balls are milled at a speed of 280-320r / min for 0.5-1 hours, and the temperature is controlled at 15-25℃. In the second stage, 5mm zirconia ceramic beads are used at a ball-to-material ratio of 5:1. The balls are milled at a speed of 180-220r / min for 2-3 hours, and the temperature is controlled at 30-40℃.

[0017] S5. After ball milling, air classification and vibrating sieving are combined to precisely control the particle size distribution of the final product within the range of 0.01-2mm, of which 0.01-0.1mm accounts for 8-12%; 0.1-1mm accounts for 65-75%; and 1-2mm accounts for 15-25%.

[0018] Preferably, in the above-mentioned method for preparing a soil remediation and crop quality improvement and yield enhancement composite material, the preparation method is melt atomization, which includes the following steps:

[0019] S1. Mix magnesium ingots and aluminum ingots, calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese or silicon powder in a mass ratio, and load them into a vacuum induction melting furnace under argon protection. Heat the mixture to 800°C at a rate of 5-10°C per minute and melt it for 25-110 minutes. Then, cool the mixture to 750°C at a rate of 2-5°C per minute and hold it at that temperature. At the same time, apply an alternating magnetic field with a frequency of 50Hz and an intensity of 0.1-0.3T and stir for 10 minutes. The particle size of the calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese or silicon powder is 50-100nm.

[0020] S2. Atomization is carried out using an atomizing device with an atomizing disc diameter of 190-200mm and a rotation speed of 15000-18000r / min under argon atmosphere protection. The particle size distribution is controlled by adjusting the atomization pressure and gas flow rate. The atomizing tank of the atomizing device needs to be controlled at a temperature below 30℃ through an ammonia refrigeration system to obtain spherical magnesium-aluminum alloy composite particles with a particle size of 0.01-2mm.

[0021] S3. The obtained particulate material is surface activated by treating it in microwave plasma for 5-10 minutes, wherein the microwave plasma is an Ar / H2 mixture and the treatment power is 1kW.

[0022] Preferably, in the above-mentioned method for preparing a soil remediation and crop quality improvement and yield enhancement composite material, mechanical ball milling is used, including the following steps:

[0023] S1. Mix magnesium, aluminum, calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese or silicon powder in a mass ratio and load it into a vacuum ball mill jar; wherein the particle size of magnesium, aluminum, calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese or silicon powder is 50-100nm.

[0024] S2. Use 10mm zirconia ceramic beads and 15mm cemented carbide beads as the ball milling media, with a mass ratio of 1:1 and a ball-to-material ratio of 8:1. Inert gas is introduced for protection, and 0.5-1wt% stearic acid is added as a process control agent.

[0025] S3. A two-stage ball milling process is adopted: the first stage is ball milling at 400r / min for 2 hours for coarse crushing, and the second stage is ball milling at 200r / min for 4 hours for fine alloying, finally obtaining composite particles with a particle size of 0.05-2mm.

[0026] An application of a soil remediation and crop quality improvement composite material as described above, wherein the composite material is used for soil pollution remediation and improvement, wherein the composite material is applied to the soil by rotary tillage at a rate of 20-200 kg / mu and a tillage depth of 10-30 cm. After the composite material is applied to the soil, it forms a magnesium-aluminum intercalated two-dimensional nanomaterial in situ, which anchors heavy metals in the crystal lattice to achieve ultra-stable mineralization, and changes the dominant bacteria in the soil from Arthrobacter to heavy metal-tolerant growth-promoting bacteria such as Spirulina neonicotinae and Massériale, thereby improving the soil microbial community structure, fixing heavy metals, and improving the quality and yield of planted crops.

[0027] Preferably, in the application of the aforementioned soil remediation and crop quality improvement and yield enhancement composite material, the composite material is also used in combination with an inorganic alkaline conditioner. The inorganic alkaline conditioner may be selected from calcium cyanamide, sodium silicate, etc., wherein the mass ratio of the composite material to the inorganic alkaline conditioner is 1:0.5-1. The application method is as follows: dig a 20-30cm trench 20-30cm away from the crop, apply the composite material, cover with 5-10cm of soil, and then apply a certain amount of the inorganic alkaline conditioner. Through the slow release of magnesium and aluminum elements in the composite material and the synergistic effect of the inorganic alkaline conditioner, the soil pH is raised to the range of 6.5-7.5, inhibiting soil acidification and further improving the cadmium fixation efficiency.

[0028] Preferably, in the application of the above-mentioned soil remediation and crop quality improvement and yield enhancement composite material, the composite material is also used in combination with organic amendments such as humic acid, amino acids, and lignin, and in combination with nitrogen-fixing / phosphorus-solubilizing bacterial agents.

[0029] When the composite material is used in combination with humic acid-based organic amendments, the mass ratio of the composite material to the humic acid-based organic amendments is 1:0.3-1.5. The application method is as follows: dig a 20-30cm trench 20-30cm away from the crop, apply the composite material, cover with 5-10cm of soil, and then apply a certain amount of organic amendment. Through the synergistic effect of the ion exchange of the magnesium-aluminum intercalated two-dimensional nanomaterials formed by the composite material and the chelation effect of the carboxyl / phenolic hydroxyl functional groups in the organic amendment, the cadmium fixation efficiency is further improved, resulting in increased crop yield.

[0030] When the composite material is used in combination with nitrogen-fixing / phosphate-solubilizing microbial agents, the application method is as follows: the composite material is applied by rotary tillage to a depth of 10-30 cm at a rate of 20-200 kg / mu. After the microbial agent has been cultured, it is applied by irrigation at an inoculum rate of 1-3 × 10⁻⁶. 8 CFU / g promotes microbial colonization by releasing H2 and nutrients in trace amounts through composite materials, and utilizes the biological nitrogen fixation / phosphorus solubility properties of functional microbial agents to form a micro-ecological regulation system, thereby increasing the number of beneficial microorganisms in the soil and further improving the absorption and utilization rate of nitrogen, phosphorus and potassium elements by crops.

[0031] Therefore, by employing the aforementioned composite material for soil remediation and crop quality improvement and yield enhancement, and its preparation method, the present invention achieves the following beneficial effects:

[0032] (1) After the composite material is applied to the soil, its magnesium-aluminum alloy hydrolyzes in situ to generate magnesium-aluminum intercalated two-dimensional nanomaterials. Soil aggregates can also serve as heterogeneous carriers for the nucleation and growth of magnesium-aluminum intercalated two-dimensional nanomaterials, achieving ultra-stable mineralization of heavy metals such as cadmium and lead. The soil after applying the composite material has long-term stable performance. Simulating the soil aging process within 100 years, cadmium still exists in a stable form with a leaching concentration of 0, and there is no risk of secondary pollution. It shows significant cadmium fixation effect in soils with a wide pH range, breaking through the bottleneck problem of traditional remediation materials being limited by soil pH. Even under arid extreme climate conditions, it can maintain a low redox potential for a long time, allowing the root Fe 2+ and Mn 2+ Increased concentration induces the formation of a dense iron film, inhibiting the absorption of cadmium by crop roots, significantly reducing the cadmium content in rice, which meets the requirements of the National Food Safety Standard for Limits of Contaminants in Food.

[0033] (2) It regulates the physical and chemical properties and redox potential of soil, releases magnesium, silicon and trace elements, and enhances crop photosynthesis. It slowly releases trace amounts of hydrogen, improves soil structure, permeability, water retention and looseness, and inhibits soil acidification; it enhances plant stress resistance, regulates plant growth and development, and improves drought resistance and disease and pest resistance. It can achieve long-term reduction of soil redox potential, which can be reduced from 522mV to -98mV, promote soil Fe-Mn-S cycle, and accelerate soil self-repair process.

[0034] (3) Composite materials can achieve microbial community optimization and ecological function enhancement: improve microbial α diversity and optimize soil ecological function. Promote the abundance of Proteobacteria from 20% to 55%-65%, and change the dominant genera from Arthrobacter to cadmium-resistant Spirulina and Masseybacter, thereby enhancing the heavy metal fixation capacity.

[0035] (4) The composite material is prepared by melt atomization, mechanical ball milling or melt atomization followed by mechanical ball milling. The particle size is controllable, the sphericity is high, the composition is uniform, and it is suitable for large-scale production. When applying, the composite material is added when rotary tilling the land, and crops can be planted. The repair method is simple, the repair efficiency is high, and no additional equipment is required.

[0036] (5) Composite materials significantly improve crop yield and quality. By releasing trace elements such as magnesium and silicon, they provide sufficient nutrition for crop growth, promote root development and leaf photosynthesis of crops such as rice, regulate soil redox potential, effectively block the absorption of heavy metals, ensure the healthy growth of crops, and significantly improve the safety and quality of agricultural products. This results in a 20.6% increase in rice yield, a 14.9% increase in thousand-grain weight, an 8.1% increase in protein content, and an 11.6% increase in folic acid content. This indicates that composite materials can meet the dual needs of agricultural production for soil remediation and crop quality improvement and yield increase.

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0038] Figure 1 The image shows the XRD patterns of the composite material before and after remediation in Example 6 of the present invention, which describes a soil remediation and crop quality improvement and yield enhancement composite material and its preparation method.

[0039] Figure 2 The image shows an SEM image of the composite material in Example 6 of the present invention, which is a soil remediation and crop quality improvement and yield enhancement composite material and its preparation method. (a) is the original composite material, (b) is the composite material after remediation, (c) is a magnified image of the composite material after remediation, and (d) is soil aggregate.

[0040] Figure 3 Example 6 of the present invention provides a composite material for soil remediation and crop quality improvement and yield enhancement, and its preparation method, showing the cadmium leaching concentration during a simulated soil aging process over 100 years.

[0041] Figure 4 Example 7 of this invention, a composite material for soil remediation and crop quality improvement and yield enhancement, and its preparation method, illustrates the effect of the composite material on soil physicochemical properties, wherein (a) is a schematic diagram of the effect on pH, and (b) is a schematic diagram of the effect on Eh.

[0042] Figure 5 Example 8 of this invention describes the effect of a composite material (phylum level) on the microbial community structure of cadmium-contaminated soil on soil remediation and crop quality improvement and yield enhancement.

[0043] Figure 6 Example 8 of this invention describes the effect (at the genus level) of a composite material for soil remediation and crop quality improvement and yield enhancement, and its preparation method, on the microbial community structure of cadmium-contaminated soil. Detailed Implementation

[0044] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0046] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0047] Examples 1-5 use different element ratios to prepare composite materials, the specific element ratios are shown in Table 1, and the preparation method is to first melt and atomize and then mechanically ball mill.

[0048] Table 1 Element ratios in Examples 1-5

[0049] ;

[0050] The composite materials prepared in Examples 1-5 were applied to contaminated soil with a cadmium concentration of 5.38 mg / kg by rotary tillage. The cadmium content and quality of the rice are shown in Table 2.

[0051] Table 2. Cadmium content and quality of rice in Examples 1-5

[0052] ;

[0053] As shown in Table 2, Example 3, with a magnesium-aluminum mass ratio of 3:1 and containing appropriate trace elements, performed best in cadmium pollution remediation and crop quality improvement. Its rice cadmium content was controlled at 0.09 mg / kg, yield reached 762 kg / mu, and the thousand-grain weight was 28.9 g. This was mainly due to the efficient fixation of cadmium ions by the magnesium-aluminum intercalated two-dimensional nanostructure formed by magnesium-aluminum hydrolysis, while calcium inhibited crop absorption of cadmium through ion competition. Iron and manganese, among other elements, promoted the conversion of cadmium into insoluble CdS / CdCO3 by participating in soil redox reactions, further improving the fixation rate. Silicon guided the formation of a silicon-cadmium co-precipitate layer and an iron-manganese film in the crop roots, blocking the absorption of cadmium by rice. Zinc, copper, and molybdenum reduced cadmium toxicity by activating the antioxidant enzyme system, while zinc and boron synergistically promoted auxin synthesis and improved photosynthetic efficiency. Lanthanum reduced cadmium transport by altering cell membrane permeability, while manganese and molybdenum jointly regulated nitrogen metabolism. Through the synergistic effect between the main components magnesium-aluminum and trace elements, crop yield and quality were improved while cadmium was fixed. Example 1, with its excessively low trace element content, will affect crop yield; Example 3, with its excessively high trace element content, will affect cadmium fixation. Furthermore, both excessively high and low magnesium-aluminum ratios will affect cadmium fixation. Therefore, limiting the magnesium-aluminum ratio to 1:1-6:1 and the trace element ratio to 0.5%-1.5% calcium, 0%-1.0% iron, 0.05%-0.5% copper, 0%-1.0% zinc, 0.05%-0.4% boron, 0.05%-0.5% lanthanum, 0.05%-0.1% molybdenum, 0%-1.0% manganese, and 0.1%-1.0% silicon yields the best results.

[0054] Example 6

[0055] Verification of the Ultra-Stable Mineralization Performance of Magnesium-Aluminum Alloy Materials

[0056] Magnesium and aluminum ingots in a mass ratio of 3:1 were selected as the main components, supplemented with 1.5% calcium, 1.0% iron, 0.5% copper, 0.5% zinc, 0.1% boron, 0.4% lanthanum, 0.1% molybdenum and 1.0% silicon. The process employed was molten atomization: high-purity magnesium ingots, aluminum ingots, and trace components were mixed in a specific ratio and added to a vacuum induction melting furnace under argon protection. The temperature was increased to 800°C at a rate of 5°C per minute and melted for 60 minutes. The temperature was then decreased to 750°C at a rate of 3°C per minute, followed by heat treatment. During this period, an alternating magnetic field with a frequency of 50Hz and an intensity of 0.1T was applied and stirred for 10 minutes. Atomization was performed using an atomizing device with an atomizing disc diameter of 200mm and a rotation speed of 1600r / min under argon protection. The particle size distribution was controlled by adjusting the atomization pressure and gas flow rate. The atomizing tank of the atomizing device needed to be kept below 30°C using an ammonia refrigeration system to obtain spherical magnesium-aluminum alloy composite particles with a particle size of 0.01-2mm. The obtained particle material was then surface activated by treating it in microwave plasma for 10 minutes to obtain a smooth, regular spherical alloy with a particle size of 0.01-2mm.

[0057] The material was added to contaminated soil containing 25 mg / kg cadmium at mass ratios of 0.1%, 0.5%, and 1.0%, and then incubated under moist conditions for 130 days. Available cadmium in the soil was extracted using a diethylenetriaminepentaacetic acid (DTPA) extract at a solid-liquid ratio of 1:2 and pH 7.3, and its content was determined by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the available cadmium concentration decreased from 14.52 mg / kg in the original soil to 2.39, 1.44, and 0.88 mg / kg, respectively, with fixation rates reaching 83.5%, 90.1%, and 93.9%, respectively. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) characterization of the soil after composite material remediation revealed the in-situ formation of layered magnesium-aluminum intercalated two-dimensional nanomaterials on the material surface. XRD showed a typical characteristic peak for magnesium-aluminum intercalated two-dimensional nanomaterials at 2θ = 11.14°, while SEM revealed a 50-100 nm plate-like crystal structure. (See appendix.) Figure 1-2 As shown. Further simulation experiments with acid rain leaching were conducted. At pH 5.6, after 100 cycles, the cadmium leaching concentration was 0, verifying the material's ultra-stable mineralization and long-term stability against heavy metals. (See appendix.) Figure 3 As shown.

[0058] Example 7

[0059] Verification of the effect of soil physicochemical properties and redox potential regulation

[0060] The main raw materials are magnesium powder and aluminum powder in a mass ratio of 2:1, combined with 0.5% calcium, 0.5% copper, 0.5% zinc, 0.2% boron, 0.3% lanthanum, 0.1% molybdenum, 0.5% manganese, and 1.0% silicon powder. The mixture is prepared by mechanical ball milling: magnesium, aluminum, and trace components are mixed in the mass ratio and placed in a vacuum ball mill jar. A mixture of 10mm zirconia ceramic beads and 15mm cemented carbide beads is used as the milling media at a mass ratio of 1:1 and a ball-to-material ratio of 8:1. An inert gas is introduced for protection, and 0.5-1wt% stearic acid is added as a process control agent. A two-stage ball milling process is employed: the first stage involves ball milling at 400 rpm for 2 hours for coarse crushing, and the second stage involves ball milling at 200 rpm for 4 hours for fine alloying, ultimately obtaining composite particles with a particle size of 0.05-2mm.

[0061] The material was applied at a rate of 200 kg / mu to soil with a pH of 7.29 and a cadmium content of 25 mg / kg. After rotary tillage to a depth of 20 cm, samples were taken periodically. Soil pH was measured using a pH meter, and an oxidation-reduction potential (Eh) meter was inserted 2-3 cm into the soil and allowed to stand for 30 minutes before reading. The available content of trace elements such as magnesium, molybdenum, nickel, and manganese was determined using DTPA extraction combined with inductively coupled plasma atomic emission spectrometry (ICP-AES). The experiment showed that as soil pH increased from 7.29 to 9.44, Eh decreased from a low of 522 mV to a low of -98 mV, then slowly increased, remaining below the initial state after 35 days. The available content of trace elements magnesium, molybdenum, nickel, and manganese initially increased and then decreased, with increases of up to 1.4 times, 3.9 times, 1.9 times, and 3.9 times, respectively. (See Appendix). Figure 4 As shown in Table 3.

[0062] Table 3. Changes in available trace element content in soil after adding remediation materials.

[0063] ;

[0064] Example 8

[0065] Validation of Microbial Community Optimization and Ecological Function Enhancement

[0066] A composite material with a particle size of 0.01-2 mm was prepared by melt atomization using magnesium and aluminum ingots in a 1:1 mass ratio as the main components, with the addition of 0.5% calcium, 0.1% iron, 0.5% copper, 1.0% zinc, 0.1% boron, 0.2% lanthanum, 0.05% molybdenum, 1.0% manganese, and 1.0% silicon. The material was applied to soil with a pH of 6.52 and a cadmium content of 33.8 mg / kg. After 35 days of cultivation, samples were taken for analysis, and a blank control group (soil without the composite material) was included.

[0067] Total DNA was extracted from soil microorganisms, and PCR amplification of the 16S rRNA gene V3-V4 region was performed using primers 338F / 806R. High-throughput sequencing was performed using the Illumina Nextseq 2000 platform, and community diversity and structure were analyzed using the Meiji Bio Cloud Platform. Results showed that microbial α-diversity increased after the addition of remediation materials (see Table 4). The abundance of Proteobacteria increased from 20% to 65%, and the dominant genera changed from *Arthrobacter* to *Noviherbaspirillum* (abundance 14.9%) and *Massilia* (abundance 18.8%) (see Appendix). Figure 5-6 As shown. Further screening using linear discriminant analysis revealed that the material treatment group was enriched with microbial communities associated with heavy metal tolerance, and the expression level of cadmium tolerance genes in the soil increased by 2.1 times, confirming the enhanced cadmium fixation capacity of the microbial community.

[0068] Table 4. Changes in microbial diversity index after adding remediation materials.

[0069] ;

[0070] Example 9

[0071] The composite material is prepared by a method of melt atomization followed by mechanical ball milling, specifically including the following steps:

[0072] (1) Mix magnesium ingots and aluminum ingots with a purity of ≥99.95% at a mass ratio of 3:1, load them into a vacuum induction melting furnace under argon protection, heat them to 800°C at a heating rate of 5°C / min, hold them at that temperature for 60 minutes, and then cool them down to 750°C at a rate of 2°C / min and hold them at that temperature. During this period, apply a pulsed magnetic field with a frequency of 35Hz and an intensity of 0.1T to stir.

[0073] (2) A double-layer atomizing disk with an upper diameter of 160 mm and a lower diameter of 210 mm was used for atomization in a nitrogen-argon mixed atmosphere. The rotation speed of the upper layer was controlled at 19000 r / min, the rotation speed of the lower layer was controlled at 13000 r / min, and the atomization pressure was 0.5 MPa to obtain matrix particles with a particle size of 0.2-1.5 mm. The volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere was 1:3.

[0074] (3) Mix the atomized particles with trace element powder (1.5% calcium, 1.0% iron, 0.3% copper, 0.5% zinc, 0.2% boron, 0.2% lanthanum, 0.1% molybdenum, 0.2% manganese and 1.0% silicon) in proportion and load them into a temperature-controlled ball mill jar.

[0075] (4) In the first stage, 3mm alumina ceramic beads and 6mm tungsten carbide beads with a mass ratio of 2:1 and a ball-to-material ratio of 8:1 were used. The balls were ball-milled at 300r / min for 45 minutes and the temperature was controlled at 20℃.

[0076] (5) In the second stage, 5mm zirconia ceramic beads were used with a ball-to-material ratio of 5:1. The balls were ball-milled at 200r / min for 2.5 hours, and the temperature was controlled at 35℃.

[0077] (6) After air classification and vibrating sieving, a composite material with a particle size distribution of 10% for 0.01-0.1mm, 70% for 0.1-1mm, and 20% for 1-2mm is obtained.

[0078] Example 10

[0079] The composite material is prepared by melt atomization, which specifically includes the following steps:

[0080] (1) Magnesium ingots and aluminum ingots with a purity ≥99.95% (mass ratio 3:1) are mixed with trace element powders (1.5% calcium, 1.0% iron, 0.3% copper, 0.5% zinc, 0.2% boron, 0.2% lanthanum, 0.1% molybdenum, 0.2% manganese and 1.0% silicon), and loaded into a vacuum induction melting furnace under argon protection. The temperature is raised to 800℃ at 7℃ / min and melted for 60 minutes. Then the temperature is lowered to 750℃ at 3℃ / min and held at the same time. An alternating magnetic field with a frequency of 50Hz and an intensity of 0.2T is applied and stirred for 10 minutes.

[0081] (2) Atomization was carried out in an argon atmosphere using an atomizing disc with a diameter of 195 mm and a rotation speed of 16000 r / min. The temperature of the atomizing tank was controlled to be ≤30℃ to obtain spherical composite particles with a particle size of 0.05-2 mm.

[0082] (3) The particles were treated in a microwave plasma of Ar / H2 mixed gas at a power of 1kW for 8 minutes to activate the surface.

[0083] Example 11

[0084] The preparation of composite materials using mechanical ball milling includes the following steps:

[0085] (1) Mix magnesium powder and aluminum powder (mass ratio 3:1) with purity ≥99.95% with trace element powder (1.5% calcium, 1.0% iron, 0.3% copper, 0.5% zinc, 0.2% boron, 0.2% lanthanum, 0.1% molybdenum, 0.2% manganese and 1.0% silicon) and load them into a vacuum ball mill jar;

[0086] (2) Use 10mm zirconia ceramic beads and 15mm cemented carbide beads with a mass ratio of 1:1, with a ball-to-material ratio of 8:1, purged with argon gas for protection and 0.8wt% stearic acid added;

[0087] (3) The first stage is coarse crushing by ball milling at 400 r / min for 2 hours;

[0088] (4) The second stage involves fine alloying by ball milling at 200 r / min for 4 hours;

[0089] (5) The composite material with a thickness of 0.05-2 mm was obtained by vibrating sieve.

[0090] The materials prepared in Examples 9-11 were added at a mass ratio of 0.5% to soil with a pH of 7.29, a cadmium concentration of 25 mg / kg, and an available cadmium concentration of 14.52 mg / kg. After 35 days of moist cultivation, the effects on the soil cadmium fixation performance and soil physicochemical properties are shown in Table 5.

[0091] Table 5. Effects of repair materials on cadmium curing performance and physicochemical properties.

[0092] ;

[0093] Example 12

[0094] The composite material prepared in Example 9 was applied to cadmium-contaminated soil at a concentration of 5.23 mg / kg. During the rice grain-filling stage, the field water holding capacity was maintained at 40% as a drought treatment, while the soil was kept submerged at a depth of 1-2 cm during the remaining growing season.

[0095] Example 13

[0096] Magnesium and aluminum ingots with a purity ≥99.95% were mixed at a mass ratio of 3:1 and then combined with trace element powders (1.5% calcium, 1.0% iron, 0.5% copper, 0.5% zinc, 0.2% boron, 0.2% lanthanum, 0.1% molybdenum, 0.5% manganese, and 1.0% silicon) and loaded into a vacuum induction melting furnace. Under argon protection, the mixture was heated to 800℃ at a heating rate of 8℃ / min and held for 60 minutes. The temperature was then lowered to 750℃ at a cooling rate of 3℃ / min and held. Simultaneously, an alternating magnetic field with a frequency of 50Hz and an intensity of 0.2T was applied and stirred for 10 minutes to fully homogenize the alloy melt. A 195mm diameter atomizing disc was used for atomization under argon atmosphere protection, with the rotation speed controlled at 16500r / min. By adjusting the atomization pressure and gas flow rate, and with the aid of an ammonia refrigeration system, the temperature of the atomizing tank was maintained at 25-28℃ to obtain spherical composite particles with a particle size of 0.01-2mm. The obtained particulate material was surface activated by treating it in microwave plasma for 5 minutes to prepare the target material. The material was applied at a rate of 150 kg / mu to soil contaminated with 5.23 mg / kg cadmium, and the soil was rotary tilled to a depth of 20 cm. Dryland rice, variety Hanxiang No. 1, was planted.

[0097] Example 14

[0098] A composite material was prepared by mixing magnesium and aluminum ingots (purity ≥99.95%, mass ratio 3:1) with 1.5% calcium, 1.0% iron, 0.3% copper, 0.5% zinc, 0.2% boron, 0.2% lanthanum, 0.1% molybdenum, 0.2% manganese, and 1.0% silicon powder, using a method of first melting and atomizing followed by mechanical ball milling. The composite material was then applied in combination with calcium cyanamide. A 30cm trench was dug 30cm away from the crop, the composite material was applied, covered with 10cm of soil, and then a certain amount of alkaline calcium cyanamide was applied. The application rate of the composite material and calcium cyanamide was 100kg / mu. Through the slow release of magnesium and aluminum elements in the composite material and the synergistic effect of calcium cyanamide, the pH increased from 4.58 to 6.5-7.5, and the cadmium curing efficiency was increased by 8.71-11.7% compared to applying the composite material or calcium cyanamide alone.

[0099] Example 15

[0100] A composite material was prepared by mixing magnesium and aluminum powders in a 1:1 mass ratio, along with 1.5% calcium, 1.0% iron, 0.5% copper, 0.1% zinc, 0.4% boron, 0.2% lanthanum, 0.1% molybdenum, 0.2% manganese, and 1.0% silicon powder, using a mechanical ball milling method. The composite material was then applied in combination with potassium humate. A 20cm trench was dug 25cm away from the crop, the composite material was applied, covered with 5cm of soil, and then a certain amount of potassium humate was applied. The application rates of the composite material and potassium humate were 100kg / mu and 50kg / mu, respectively. Through the synergistic effect of the ion exchange of the magnesium-aluminum intercalated two-dimensional nanomaterials in the composite material and the chelation effect of the carboxyl / phenolic hydroxyl functional groups in humic substances, the cadmium solidification efficiency was increased by 8.77%-19.1%, and crop yield increased by 10.2%-22.9%.

[0101] Example 16

[0102] A composite material was prepared by mixing magnesium ingots and aluminum ingots (purity ≥99.95%, mass ratio 6:1) with 1.0% calcium, 1.0% iron, 0.1% copper, 0.5% zinc, 0.1% boron, 0.5% lanthanum, 0.1% molybdenum, 0.2% manganese, and 1.0% silicon powder, using a melt atomization method. The composite material was then applied in combination with Bacillus subtilis. The composite material was applied by rotary tillage to a depth of 20 cm at a rate of 150 kg / mu, while the Bacillus subtilis was applied by irrigation at an inoculum rate of 2 × 10⁻⁶. 8 CFU / g promotes microbial colonization through the slow release of H2 and nutrients from composite materials, and utilizes the biological nitrogen fixation / phosphorus solubilization characteristics of functional microbial agents to form a micro-ecological regulation system, increasing the number of beneficial microorganisms in the soil by 3-5 times, while improving the absorption and utilization rate of nitrogen, phosphorus and potassium elements by crops by 15-30%.

[0103] Comparative Example 1

[0104] Compared to Example 8, the soil was sterilized by placing it in steam at 80-100°C for 30-60 minutes before adding the remediation material.

[0105] Example 8 compared and analyzed the effects of remediation materials on the available cadmium content in soil under conditions of natural presence of indigenous microorganisms and absence of microorganisms. The results are shown in Table 6.

[0106] Table 6. Effects of remediation materials on available cadmium in soil under different microbial conditions.

[0107] ;

[0108] As shown in Table 6, in natural soil containing indigenous microorganisms, the cadmium fixation rate of the added remediation material reached 82.8%; however, after sterilization treatment, the cadmium fixation rate of the remediation material decreased to 53.0%, indicating that indigenous microorganisms played a key role in the cadmium fixation process, contributing 29.8%. The composite material of Example 8 can improve the soil microbial community to achieve a better cadmium fixation effect.

[0109] Comparative Example 2

[0110] Compared to Example 9, the melting temperature is 900°C.

[0111] Comparative Example 3

[0112] Compared with Example 9, a single-layer atomizing disc is used, with a diameter of 200 mm and a rotation speed of 15000 r / min.

[0113] Comparative Example 4

[0114] Compared with Example 9, a single-stage ball milling process was used, with ball milling at 300 r / min for 3 hours.

[0115] Comparative Example 5

[0116] Compared to Example 10, the melting temperature is 900°C.

[0117] Comparative Example 6

[0118] Compared to Example 10, no surface activation treatment was performed.

[0119] Comparative Example 7

[0120] Compared with Example 11, a single-stage ball milling process was used, with ball milling at 400 r / min for 4 hours.

[0121] Comparative Examples 2-7 were prepared using different preparation methods and parameters to produce composite materials with different particle sizes. They were added at a mass ratio of 0.5% to soil with a pH of 7.29, a cadmium concentration of 25 mg / kg, and an available cadmium concentration of 14.52 mg / kg. After 35 days of moist cultivation, the effects on the soil cadmium fixation performance and soil physicochemical properties are shown in Table 7.

[0122] Table 7. Effects of repair materials on cadmium curing performance and physicochemical properties.

[0123] ;

[0124] The preparation method and key parameters significantly affect the effectiveness of the composite material in remediating cadmium-contaminated soil. Referring to Tables 5 and 7, it can be seen that, compared to Comparative Examples 2-4, Example 9, using a melting temperature of 800℃, avoids the uneven composition caused by element volatilization at 900℃. The double-layer atomizing disc produces more uniform matrix particles, and the two-stage ball milling process achieves particle refinement and thorough mixing of trace elements. The final cadmium solidification rate of the material is 90.5%, significantly higher than the 66.3% solidification rate of Comparative Example 2, 77.8% of Comparative Example 3, and 70.5% of Comparative Example 4. It also more effectively increases soil pH, reduces Eh, and optimizes the solidification environment. Example 10, compared to… Compared with Comparative Examples 5-6, the melting temperature of 800℃ is better than 900℃ to reduce element loss, and the microwave plasma surface activation treatment significantly improves the particle reactivity. Its solidification rate of 70.2% is much higher than that of Comparative Example 5 (53.0%) and Comparative Example 6 (38.2%), and its effect on regulating soil pH and Eh is also better. Compared with Comparative Example 7, Example 11 uses a two-stage ball milling process to ensure particle fineness and composition uniformity better than a single-stage ball milling. The solidification rate of 84.4% is higher than that of Comparative Example 7 (72.5%), and its effect on regulating soil physicochemical properties is more conducive to the stable solidification of cadmium.

[0125] Comparative Example 8

[0126] Compared to Example 12, no remediation materials were added to the soil as a control treatment.

[0127] Comparative Example 9

[0128] Compared to Example 12, the composite material, when applied to the soil, kept the rice submerged in 1-2 cm of water throughout its entire growth cycle.

[0129] Comparative Example 10

[0130] Compared with Comparative Example 8, the rice was kept submerged in 1-2 cm of water throughout its entire growth cycle.

[0131] Comparative Example 11

[0132] Compared to Comparative Example 8, commercially available biochar passivation material was added to the soil.

[0133] Comparative Example 12

[0134] Compared with Comparative Example 8, the application of commercially available foliar barrier agents during the rice grain-filling stage was more effective.

[0135] Table 8 shows the cadmium content of grains grown in soils with different water management and different remediation materials compared to Examples 12 and Comparative Examples 10-12.

[0136] Table 8. Cadmium content in rice grains

[0137] ;

[0138] Experimental results show that the magnesium-aluminum alloy composite material prepared in Example 12 has a significant remediation effect on cadmium-contaminated soil with a concentration of 5.23 mg / kg. Compared with Comparative Example 8 without the addition of remediation materials, the cadmium content in rice grains decreased from 0.86 mg / kg to 0.08 mg / kg. In Example 12, which was subjected to drought treatment during the rice grain filling stage after the addition of magnesium-aluminum alloy composite material, there was no significant difference in cadmium content compared with Comparative Example 9, which was flooded throughout the entire process. This indicates that the magnesium-aluminum alloy composite material can maintain a good remediation effect under both drought and flood conditions. Comparative Example 10 did not add any remediation materials, but it still reduced the cadmium content in rice grains during the entire process of flooding, indicating that it can promote the soil self-remediation process under flood conditions. At the same time, the remediation effect of this composite material is significantly better than that of Comparative Example 11, which added commercially available biochar passivation material, and Comparative Example 12, which was sprayed with commercially available foliar barrier agent. Its mechanism of action is chemical solidification-microbial synergy. Specifically: (1) In-situ formation of magnesium-aluminum intercalated two-dimensional nanomaterials to achieve ultra-stable mineralization of cadmium; (2) By maintaining a low Eh environment in the soil, promoting the Fe-Mn-S cycle in the soil, accelerating soil self-repair, and forming an iron film in the rhizosphere to inhibit the absorption of cadmium by rice; (3) Improving the structure of the soil microbial community and promoting the growth of microorganisms that fix cadmium.

[0139] Comparative Example 13

[0140] Compared to Example 13, no materials were added to the soil as a control treatment.

[0141] Comparative Example 14

[0142] Compared to Example 13, no trace elements were added during the material preparation process.

[0143] Comparative Example 15

[0144] Compared with Comparative Example 13, a commercially available soil conditioner was added to the soil, which contained ≥10% calcium and magnesium, ≥0.2% zinc, ≥0.1% iron, ≥0.05% copper, ≥10% sulfur, ≥0.2% boron, ≥0.05% manganese, and ≥0.001% molybdenum.

[0145] Example 13 and Comparative Examples 13-15 compared the effects of the presence or absence of trace elements and trace element conditioners alone on the yield and quality of upland rice. The results are shown in Table 9.

[0146] Table 9. Grain yield and quality of dryland rice

[0147] ;

[0148] As shown in Table 9, the magnesium-aluminum based composite material of the present invention exhibits significant technical advantages in the remediation of heavy metal contaminated soil and the improvement of crop quality and yield. As shown in Example 13, after adding a magnesium-aluminum alloy material containing a specific combination of trace elements, the cadmium content of the rice grains decreased to 0.08 mg / kg, which is 89.7% lower than that of Comparative Example 13 without any added materials, and significantly better than the 0.89 mg / kg of the commercially available conditioner in Comparative Example 15. It is worth noting that although the magnesium-aluminum alloy in Comparative Example 14 without trace elements could also reduce the cadmium content to 0.12 mg / kg, its effect on increasing yield and quality was limited. The yield per unit area of ​​655 kg / mu and the protein content of 18.9% were only 5.3% and 1.6% higher than those of Comparative Example 13 without any added materials, respectively. Example 13 showed a 20.6% increase in yield per unit area and an 8.1% increase in protein content compared to Comparative Example 13. While the commercially available conditioner in Comparative Example 15 showed good yield-increasing effects and quality indicators, it resulted in cadmium accumulation in the grains that was even higher than in Comparative Example 13, where no materials were added to the soil. This phenomenon reveals a technical contradiction between "yield increase" and "cadmium reduction" in traditional conditioners. In contrast, this invention achieves a dual breakthrough in cadmium fixation efficiency and crop quality improvement through the synergistic effect of a magnesium-aluminum intercalated two-dimensional nanomaterial matrix and a specific trace element system. This technical effect exceeds the reasonable expectations of those skilled in the art.

[0149] Therefore, this invention employs the aforementioned composite material for the remediation of heavy metal contaminated soil, its preparation method, and its application. After the composite material is applied to the soil, its magnesium-aluminum alloy undergoes in-situ hydrolysis to generate magnesium-aluminum intercalated two-dimensional nanomaterials. Soil aggregates can also serve as heterogeneous carriers for the nucleation and growth of these magnesium-aluminum intercalated two-dimensional nanomaterials, achieving ultra-stable mineralization of heavy metals such as cadmium and lead. The soil after applying the composite material exhibits long-term stability. Simulating a 100-year soil aging process, cadmium remains in a stable form with a leaching concentration of 0, posing no risk of secondary pollution. It demonstrates significant cadmium fixation effects in soils across a wide pH range, overcoming the bottleneck problem of traditional remediation materials being limited by soil pH. Even under arid extreme climatic conditions, it can maintain a low redox potential for a long period, allowing root Fe... 2+ and Mn 2+ Increased concentration induces the formation of a dense iron film, inhibiting the absorption of cadmium by crop roots, significantly reducing the cadmium content in rice, which meets the requirements of the National Food Safety Standard for Limits of Contaminants in Food.

[0150] It regulates soil physicochemical properties and redox potential, releases magnesium, silicon, and trace elements, and enhances crop photosynthesis. It slowly releases trace amounts of hydrogen, improving soil structure, aeration, water retention, and looseness, and inhibiting soil acidification; it also enhances plant stress resistance, regulates plant growth and development, and improves drought and pest resistance. It can achieve long-term reduction of soil redox potential, decreasing it from 522mV to -98mV, promoting soil Fe-Mn-S cycling, and accelerating soil self-repair processes.

[0151] Composite materials can optimize microbial communities and enhance ecological functions: increase microbial α-diversity, optimize soil ecological functions, promote the increase of Proteobacterium abundance from 20% to 55%-65%, shift the dominant genera from Arthrobacter to cadmium-resistant Spirulina and Massey's bacterium, and enhance the ability to fix heavy metals.

[0152] The composite material is prepared by melt atomization, mechanical ball milling, or a combination of melt atomization and mechanical ball milling. It has controllable particle size, high sphericity, and uniform composition, making it suitable for large-scale production. When applying it, the composite material is added during rotary tillage, and crops can be planted immediately. The repair method is simple, the repair efficiency is high, and no additional equipment is required.

[0153] Composite materials significantly improve crop yield and quality. By releasing trace elements such as magnesium and silicon, they provide sufficient nutrition for crop growth, promote root development and leaf photosynthesis in crops such as rice, regulate soil redox potential, effectively block the absorption of heavy metals, and ensure healthy crop growth. At the same time, they significantly improve the safety and quality of agricultural products, increasing rice yield by 20.6%, thousand-grain weight by 14.9%, protein content by 8.1%, and folic acid content by 11.6%. This shows that composite materials can meet the dual needs of agricultural production for soil remediation and crop quality improvement and yield enhancement.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A composite material for soil remediation and crop quality improvement and yield enhancement, characterized in that, It includes magnesium and aluminum as well as trace elements, wherein the mass fraction of magnesium and aluminum is 93-99.2%, and the mass ratio between magnesium and aluminum is 1:1-6:1; the mass fraction of trace elements is 0.8-7%, and the trace elements include one or more of calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese, and silicon; the alloy phase of the composite material is β-Mg17Al12.

2. The soil remediation and crop quality improvement and yield enhancement composite material according to claim 1, characterized in that, The mass fractions of the trace components are as follows: calcium 0.5%-1.5%, iron 0%-1.0%, copper 0.05%-0.5%, zinc 0%-1.0%, boron 0.05%-0.4%, lanthanum 0.05%-0.5%, molybdenum 0.05%-0.1%, manganese 0%-1.0%, and silicon 0.1%-1.0%.

3. The soil remediation and crop quality improvement and yield enhancement composite material according to claim 1, characterized in that, The magnesium is derived from magnesium ingots or magnesium powder with a purity of not less than 99.95%, the aluminum is derived from aluminum ingots or aluminum powder with a purity of not less than 99.95%, and the trace components calcium, iron, copper, zinc, boron, lanthanum, molybdenum, manganese, and silicon are derived from calcium powder, iron powder, copper powder, zinc powder, boron powder, lanthanum powder, molybdenum powder, manganese powder, and silicon powder with a purity of not less than 99.9%, respectively.

4. A method for preparing a soil remediation and crop quality improvement and yield-increasing composite material as described in any one of claims 1-3, characterized in that, Composite materials are prepared by mixing magnesium and aluminum, along with trace components, in a specific mass ratio, using either melt atomization, mechanical ball milling, or a combination of both. The resulting composite material has an alloy phase of β-Mg17Al12. The alloy prepared by melt atomization exhibits regular spherical shapes with a smooth and dense surface and a particle size of 0.01-2 mm. The composite material prepared by mechanical ball milling consists of irregular flake or block-shaped particles with a rough surface and a particle size of 0.05-2 mm. The composite material prepared by melt atomization followed by mechanical ball milling has a spherical matrix with nano-sized fine particles attached to it, and a particle size of 0.01-2 mm.

5. The method for preparing the soil remediation and crop quality improvement and yield enhancement composite material according to claim 4, characterized in that, The preparation method employs a process of first melting and atomizing followed by mechanical ball milling, and includes the following steps: S1. Mix magnesium ingots and aluminum ingots in a mass ratio, load them into a vacuum induction melting furnace under argon protection, heat them to 780-820℃ at a gradient of 3-8℃ per minute, melt for 40-90 minutes, then cool them down to 720-780℃ at a gradient of 1-3℃ per minute, and then hold them at that temperature. During this time, apply a pulsed magnetic field with a frequency of 30-40Hz and an intensity of 0.05-0.2T to stir. S2. A double-layer atomizing disk with an upper diameter of 150-180 mm and a lower diameter of 200-220 mm is used for atomization under the protection of a nitrogen-argon mixed atmosphere. The rotation speed of the upper layer is controlled at 18000-20000 r / min, the rotation speed of the lower layer is controlled at 12000-15000 r / min, and the atomization pressure is 0.4-0.6 MPa to obtain matrix particles with a particle size of 0.2-1.5 mm. The volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere is 1:

3. S3. Mix the atomized particles and trace component powder according to the mass ratio and load them into a ball mill jar with temperature control function; S4. A two-stage ball milling process is adopted: In the first stage, 3mm alumina ceramic beads and 6mm tungsten carbide beads are used at a mass ratio of 2:1 and a ball-to-material ratio of 8:

1. The balls are milled at a speed of 280-320r / min for 0.5-1 hours, and the temperature is controlled at 15-25℃. In the second stage, 5mm zirconia ceramic beads are used at a ball-to-material ratio of 5:

1. The balls are milled at a speed of 180-220r / min for 2-3 hours, and the temperature is controlled at 30-40℃. S5. After ball milling, air classification and vibrating sieving are combined to precisely control the particle size distribution of the final product within the range of 0.01-2mm, of which 0.01-0.1mm accounts for 8-12%; 0.1-1mm accounts for 65-75%; and 1-2mm accounts for 15-25%.

6. The method for preparing the soil remediation and crop quality improvement and yield enhancement composite material according to claim 4, characterized in that, The preparation method is melt atomization, and includes the following steps: S1. Mix magnesium ingots, aluminum ingots, and trace component powders in a mass ratio, and load them into a vacuum induction melting furnace under argon protection. Heat the mixture to 800°C at a rate of 5-10°C per minute, and melt it for 25-110 minutes. Then, cool the mixture to 750°C at a rate of 2-5°C per minute and hold it at that temperature. At the same time, apply an alternating magnetic field with a frequency of 50Hz and an intensity of 0.1-0.3T and stir for 10 minutes. S2. Atomization is carried out using an atomizing device with an atomizing disc diameter of 190-200mm and a rotation speed of 15000-18000r / min under argon atmosphere protection. The particle size distribution is controlled by adjusting the atomization pressure and gas flow rate. The atomizing tank of the atomizing device needs to be controlled at a temperature below 30℃ through an ammonia refrigeration system to obtain spherical magnesium-aluminum alloy composite particles with a particle size of 0.01-2mm. S3. The obtained particulate material is treated in microwave plasma for 5-10 minutes to activate its surface.

7. The method for preparing the soil remediation and crop quality improvement and yield enhancement composite material according to claim 4, characterized in that, The preparation method, which employs mechanical ball milling, includes the following steps: S1. Mix magnesium powder, aluminum powder, and trace component powder according to the mass ratio and load them into a vacuum ball mill jar; S2. Use 10mm zirconia ceramic beads and 15mm cemented carbide beads as the ball milling media, with a mass ratio of 1:1 and a ball-to-material ratio of 8:

1. Inert gas is introduced for protection, and 0.5-1wt% stearic acid is added as a process control agent. S3. A two-stage ball milling process is adopted: the first stage is ball milling at 400r / min for 2 hours for coarse crushing, and the second stage is ball milling at 200r / min for 4 hours for fine alloying, finally obtaining composite particles with a particle size of 0.05-2mm.

8. The application of a soil remediation and crop quality improvement and yield enhancement composite material as described in any one of claims 1-3, characterized in that, The composite material is used for soil pollution remediation and improvement. It is applied to the soil by rotary tillage at a rate of 20-200 kg / mu and a tillage depth of 10-30 cm. After application, the composite material forms a magnesium-aluminum intercalated two-dimensional nanomaterial in situ, which anchors heavy metals in the crystal lattice to achieve ultra-stable mineralization. It also changes the dominant bacteria in the soil from Arthrobacter to heavy metal-tolerant growth-promoting bacteria such as Spirulina and Massey's bacterium, thereby improving the soil microbial community structure, fixing heavy metals, and improving the quality and yield of crops.

9. The application of the soil remediation and crop quality improvement and yield enhancement composite material according to claim 8, characterized in that, The composite material is used in combination with an inorganic alkaline conditioner, wherein the mass ratio of the composite material to the inorganic alkaline conditioner is 1:0.5-1. The application method is as follows: dig a 20-30cm trench at a distance of 20-30cm from the crop, apply the composite material, cover it with 5-10cm of soil, and then apply a certain amount of inorganic alkaline conditioner. Through the slow release of magnesium and aluminum elements in the composite material and the synergistic effect of the inorganic alkaline conditioner, the soil pH is raised to the range of 6.5-7.5, soil acidification is inhibited, and the cadmium fixation efficiency is further improved.

10. The application of the soil remediation and crop quality improvement and yield enhancement composite material according to claim 8, characterized in that, The composite material may be used in combination with one or more organic modifiers such as humic acid, amino acids, and lignin, or the composite material may be used in combination with nitrogen-fixing / phosphate-solubilizing bacteria. When the composite material is used in combination with the organic amendment, the mass ratio of the composite material to the organic amendment is 1:0.3-1. The application method is as follows: dig a 20-30cm trench at a distance of 20-30cm from the crop, apply the composite material, cover it with 5-10cm of soil, and then apply a certain amount of organic amendment. The synergistic effect of the ion exchange of the magnesium-aluminum intercalated two-dimensional nano-functional material formed by the composite material and the chelation effect of the carboxyl / phenolic hydroxyl functional groups in the organic amendment further enhances the cadmium fixation efficiency and increases crop yield. When the composite material is used in combination with nitrogen-fixing / phosphate-solubilizing microbial agents, the application method is as follows: the composite material is applied by rotary tillage to a depth of 10-30 cm at a rate of 20-200 kg / mu. After the microbial agent has been cultured, it is applied by irrigation at an inoculum rate of 1-3 × 10⁻⁶. 8 CFU / g promotes microbial colonization by releasing H2 and nutrients in trace amounts through composite materials, and utilizes the biological nitrogen fixation / phosphorus solubility properties of functional microbial agents to form a micro-ecological regulation system, thereby increasing the number of beneficial microorganisms in the soil and further improving the absorption and utilization rate of nitrogen, phosphorus and potassium elements by crops.

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