Acid-activated tailings sand-based vegetation composite material for soil remodeling and its preparation method

Abstract

This invention discloses an acid-activated tailings sand-based vegetated composite material for soil remediation and its preparation method, belonging to the field of soil remediation technology. The composite material comprises the following raw materials in parts by weight: 67-85 parts tailings powder, 2-10 parts acid activator, 15-30 parts phosphogypsum, 7-12 parts limestone powder, 15-25 parts cement, 65-90 parts soil, 25-40 parts organic nutrients, and 0.5-5 parts amendment. The acid activator is a mixture of acid and salt components in a mass ratio of 3:1 to 5:1, and is prepared as an aqueous solution with an acid component mass fraction of 10%-50% and a pH of 2.3-4.5. This invention directly incorporates soil into the cementing system, forming dotted or network-like cementation between soil particles, possessing both engineering strength and a loose, porous structure. This invention achieves the synergistic utilization of tailings sand and phosphogypsum, and is suitable for ecological restoration of mine slopes, spoil heaps, etc.

Description

Technical Field

[0001] This invention relates to the field of soil remediation and land reclamation technology, specifically to a composite material prepared from industrial solid waste such as tailings sand, used to reconstruct damaged mine soil and construct a plant growth medium layer, and its preparation method. Background Technology

[0002] With the green transformation of my country's mining industry, the resource utilization, reduction, and harmless treatment of tailings have become urgent technological challenges. From a chemical composition perspective, most tailings sand is rich in elements such as silicon, aluminum, and calcium, possessing the potential to prepare auxiliary cementitious materials. However, its original activity is low, limiting its direct strength. Its reactivity can be improved through chemical activation.

[0003] Currently, alkali-activated geopolymer technology is a common method for improving the activity of tailings sand. For example, CN121369181A discloses a wide-ratio ecological nutrient soil based on iron tailings modified with geopolymers and its preparation method. This nutrient soil uses sodium hydroxide and water glass as alkali activators to improve tailings activity, and then adds organic nutrients and functional regulators. CN121225902A discloses a copper-molybdenum tailings-based alkali-activated cementitious material and its preparation method. The 3-day compressive strength of this cementitious material can reach over 20 MPa, and it also possesses certain freeze-thaw resistance. CN121405405A discloses a high-volume iron tailings-based ultra-early-strength cementitious material for underground mining and its preparation method and application. This cementitious material also uses alkali activation, achieving ultra-short setting time and ultra-high early strength even with high solid waste content. However, in the field of mine ecological restoration, whether plants can grow normally in the restoration area is the core indicator for evaluating the restoration effect. The activators used in the above-mentioned alkaline activation technology, such as sodium hydroxide and water glass, are usually highly alkaline (pH can reach above 13). When applied to mine restoration projects, they can easily create a strongly alkaline environment, which can severely inhibit or even poison vegetation growth.

[0004] In recent years, scholars have begun to explore the use of acidic solutions to activate tailings sand. Acid activation technology can effectively dissolve the silica-alumina glass in tailings sand, generating a gelling substance and significantly improving its activity. CN121225897A discloses an organic acid-activated solid waste-based gelling material, using citric acid, oxalic acid, and polyacrylic acid as composite organic acid activators, achieving a 28-day compressive strength exceeding 40 MPa. CN120829272A discloses an acid-activated gelling material for coal-based solid waste and its preparation method, using phosphoric acid as the main activator to activate coal-based solid waste. The above studies indicate that acid activation of tailings for preparing gelling materials has certain technical feasibility. CN121063866A discloses a moss ecological brick and its preparation method, using phosphorus tailings and iron tailings to provide necessary phosphorus and other trace elements for moss growth. However, for the engineering needs of large-scale mine soil improvement and the reconstruction of loose and fertile plant growth media layers, existing technologies have not yet provided effective solutions.

[0005] In current mine ecological restoration projects, cement is commonly used as a binding material in shotcrete applications. However, the high carbon emissions from cement production contradict the green and environmentally friendly concept of mine restoration, and the dense structure of cement-based materials is not conducive to the extension of plant roots. Therefore, developing a vegetated composite material that uses tailings sand as the main raw material, employs mild acid activation, can be integrated with the soil for reconstruction, and balances engineering stability and ecological adaptability is of significant practical importance. Summary of the Invention

[0006] To address the technical problems of existing alkaline activation technologies, such as their high alkalinity which is detrimental to plant growth; the prevalence of existing acid-activated materials as rigid carriers rather than soil amendments; and the poor ecological adaptability of traditional cement-based materials, this invention aims to provide an acid-activated tailings sand-based vegetation composite material for soil remediation and its preparation method. This material can be uniformly mixed with the soil to be remediated, forming moderate cementation between soil particles to construct a plant growth medium layer that possesses both erosion resistance and a loose, porous structure.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On the one hand, an acid-activated tailings sand-based vegetation composite material for soil reconstruction is provided, comprising the following raw material components by weight: 67-85 parts tailings sand, 2-10 parts acid activator, 15-30 parts phosphogypsum, 7-12 parts limestone powder, 15-25 parts cement, 65-90 parts soil, 25-40 parts organic nutrient components, and 0.5-5 parts amendment; wherein the acid activator is composed of acid components and salt components in a mass ratio of 3:1 to 5:1.

[0008] Furthermore, the tailings sand is at least one of iron tailings, gold tailings, and copper tailings, and its chemical composition includes CaO, SiO2, Al2O3, and Fe2O3, wherein the SiO2 content is greater than 40%, and the sum of the SiO2 and Al2O3 contents is ≥60%; the tailings sand is ground to a specific surface area of ​​350–450 m². 2 / kg.

[0009] Furthermore, the acid component is at least one of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, propionic acid, and oxalic acid, and the salt component is a soluble fluoride or sulfate.

[0010] Furthermore, the salt component is sodium fluoride or aluminum sulfate.

[0011] Furthermore, the acid activator is prepared as an aqueous solution during use, wherein the mass fraction of the acid component in the aqueous solution is 10-50%, and the pH value of the aqueous solution is 2.3-4.5.

[0012] Furthermore, the phosphogypsum is a by-product of phosphate chemical industry, pretreated by water washing or neutralization; the specific surface area of ​​the limestone powder is not less than 300 m². 2 / kg; the cement is ordinary silicate cement or composite silicate cement.

[0013] Furthermore, the soil includes at least one of the following: in-situ mine soil, engineering waste soil, imported soil, sandy soil, clay, heavy metal contaminated soil, or artificially prepared substrate; the organic nutrient components include at least one of the following: decomposed livestock and poultry manure, rice husks, sawdust, and humus.

[0014] Furthermore, the amendment is composed of compound fertilizer and water-retaining agent mixed in a mass ratio of 3:1 to 1:1. The compound fertilizer is a nitrogen-phosphorus-potassium compound fertilizer, and the water-retaining agent is an agricultural and forestry polyacrylamide water-retaining agent.

[0015] On the other hand, a method for preparing the above-mentioned acid-activated tailings sand-based vegetation composite material is provided, comprising the following steps: S1. Dry the tailings sand to a moisture content ≤1%, and grind it in a ball mill to a specific surface area of ​​350-450 m². 2 / kg; S2. Weigh out the phosphogypsum, limestone powder, cement and tailings powder ground in S1 by weight, mix them evenly to obtain a mixed dry material; S3. Weigh the acid component and salt component according to the mass ratio, mix them evenly to obtain a solid composite acid activator; then dissolve the solid composite acid activator in water, stir evenly, and prepare an aqueous solution of acid activator with an acid component mass fraction of 10-50% and a pH value of 2.3-4.5; S4. Add the acid activator to the mixed dry material in S2 and stir to form a uniform slurry; S5. Add soil, organic nutrients and amendment to the slurry in S4 in proportion, continue stirring for 1-2 minutes until evenly mixed, and you will get acid-activated tailings sand-based vegetation composite material.

[0016] Furthermore, in S4, a planetary cement mortar mixer is used for mixing, with a mixing speed of 140±5 r / min and a mixing time of 3 to 5 min.

[0017] The mechanism of action of this invention is as follows: First, mechanical grinding increases the specific surface area of ​​the tailings sand, disrupting its stable glassy structure and increasing reactive sites. Subsequently, the acidic component in the acidic activator further erodes the tailings particles, causing the breakage of silicon-oxygen bonds (Si-O) and aluminum-oxygen bonds (Al-O), initially releasing active silicon and aluminum species. Simultaneously, salt components (such as fluorides) form soluble complexes with silicon and aluminum ions on the tailings surface through complexation, accelerating the dissociation of the silicon-aluminum framework and synergistically enhancing the efficiency of tailings activity with the acidic component.

[0018] The active silica-alumina species released under the above-mentioned acid activation react with calcium ions (Ca) produced during cement hydration. 2+ ) and sulfate ions (SO4) provided by phosphogypsum 2- The soil undergoes a hydration reaction, producing cementitious products such as ettringite (AFt) and hydrated calcium silicate (CSH) gel. Cement, as an early source of strength, ensures the initial molding stability of the material. These cementitious products form dot-like or network-like bonds between soil particles, providing appropriate strength support for the material while preserving the original loose and porous structure of the soil, creating space for plant root growth.

[0019] Meanwhile, the various functional components work synergistically: phosphogypsum, after pretreatment, reduces the content of soluble phosphorus and fluorine, eliminating the risk of toxicity to plants; the calcium sulfate it provides not only participates in the hydration reaction to form ettringite, but also provides medium-level nutrients such as sulfur and calcium for plant growth. Limestone powder, as micro-aggregate, fills the voids in the framework, optimizing the particle size distribution of the material, reducing drying shrinkage, and improving the overall density and volume stability of the material. Organic nutrient components (composted livestock and poultry manure, rice husks, sawdust, etc.) give the material a good porous structure, significantly enhancing its water-holding and fertilizer-retaining capacity, and continuously providing organic matter and nutrients for plant growth. The compound fertilizer in the amendment provides readily available nutrients such as nitrogen, phosphorus, and potassium, while the water-retaining agent (polyacrylamide) greatly improves the water retention performance of the material, enhancing the plant's drought resistance. In addition, phosphogypsum and limestone powder also help chemically seal heavy metal ions, reducing ecological risks. Ultimately, through the synergistic effect of the above components, a vegetation composite material integrating engineering strength, ecological function, and environmental safety is formed, which can effectively reconstruct damaged soil and promote rapid vegetation recovery.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. Unlike existing technologies that process materials into independent bricks or rigid carriers (such as the moss ecological bricks in CN121063866A), this invention directly incorporates the soil to be restored into the cementitious system. The resulting composite material is itself a modified "artificial soil" that can be directly used in ecological restoration projects. This achieves seamless integration of the restoration material with the native soil and significantly simplifies the construction process.

[0021] 2. This invention, by controlling the amount and degree of reaction of the cementing material, forms a moderate dotted or network-like cementation between soil particles, which not only improves the material's resistance to water and wind erosion, but also preserves the soil's original aeration, permeability, and root penetration. The material's porosity can be controlled between 25% and 35%, providing an ideal space for plant root extension and microbial activity.

[0022] 3. The total amount of industrial solid waste such as tailings sand and phosphogypsum incorporated into this invention can reach over 80%, significantly reducing material costs and mitigating environmental impact, which aligns with the concept of a circular economy. Simultaneously, it solves two major environmental challenges: mine tailings storage and comprehensive utilization of phosphogypsum, resulting in significant economic and environmental benefits.

[0023] 4. This invention uses acid activation instead of traditional alkali activation or high-temperature activation, resulting in mild reaction conditions, low energy consumption, and avoiding the inhibitory effect of a strongly alkaline environment on plant growth. The final pH value of the material can be adjusted to the neutral range (6.2–7.1), and the seed germination index can reach 78%–92%, creating a favorable chemical environment for vegetation restoration.

[0024] 5. The material prepared by this invention has an unconfined compressive strength of 0.4 to 1.0 MPa after 28 days, which meets the engineering requirements for slope stability and erosion resistance. At the same time, the organic nutrient components optimize the pore structure of the material, the water-retaining agent in the modifier greatly improves the water holding capacity, and the compound fertilizer provides fast-acting nutrients, thus achieving a balance between engineering stability and ecological adaptability.

[0025] 6. The alkaline environment of sulfate and limestone powder in the phosphogypsum of this invention helps to convert heavy metal ions into insoluble precipitates (such as heavy metal sulfides, carbonates or hydroxides), while the physical solidification effect of the gelling products further reduces the mobility and bioavailability of heavy metals, effectively controlling ecological risks.

[0026] 7. The phosphogypsum of this invention provides sulfate ions for the gelation reaction, while also releasing medium-level nutrients such as sulfur and calcium for plant growth; the organic nutrient components continuously supply nitrogen, phosphorus, potassium and trace elements; the compound fertilizer in the amendment supplements the fast-acting nutrients, forming a "fast-acting + long-acting" nutrient supply system.

[0027] 8. The raw material ratio of this invention can be optimized within a set range according to the needs of the remediation scenario. For example, increasing the proportion of cementitious components (cement, acid activator) can enhance early strength, making it suitable for shotcreting construction on steep slopes; increasing the proportion of organic nutrient components and amendments can improve water and fertilizer retention capacity, making it suitable for reconstructing barren soils; increasing the content of phosphogypsum and limestone powder can enhance the stabilization effect of heavy metals, making it suitable for remediation of contaminated sites. At the same time, the prepared material has good construction adaptability and can be formed by various methods such as spraying, pouring, and paving to meet the engineering needs of different terrains and construction conditions.

[0028] 9. This invention replaces high-performance cementitious materials such as cement with industrial solid waste, significantly reducing carbon emissions; the acid activation process is carried out at room temperature and pressure, with energy consumption far lower than that of high-temperature activation processes; the final product of the material is environmentally friendly and does not produce secondary pollution. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] Example 1, as a preferred embodiment of the present invention, the raw material components of the acid-activated tailings sand-based vegetation composite material in this example include: 75 parts of tailings sand, 4 parts of acid activator, 20 parts of phosphogypsum, 10 parts of limestone powder, 20 parts of cement, 80 parts of soil, 30 parts of organic nutrient components, and 2 parts of conditioner. The acid activator is composed of sulfuric acid and sodium fluoride in a mass ratio of 4:1.

[0031] The preparation method of acid-activated tailings sand-based vegetation composite material in this embodiment includes the following steps: S1. Tailings sand pretreatment: Dry the tailings sand to a moisture content ≤1%, and grind it in a ball mill to a specific surface area of ​​400 m². 2 / kg; S2. Dry material mixing: Weigh the phosphogypsum, limestone powder, cement and tailings powder ground in S1 according to the above weight proportions, put them in the mixer and mix for 15 minutes to obtain the mixed dry material; S3. Preparation of acid activator: Weigh sulfuric acid and sodium fluoride according to the above mass ratio, mix them evenly to obtain a solid composite acid activator; then dissolve the solid composite acid activator in water, stir evenly, and prepare an aqueous solution of acid activator with a sulfuric acid mass fraction of 20% and a pH value of 3.0. S4. Slurry preparation: Add the acid activator to the mixed dry materials of S2 and stir to form a uniform slurry; the stirring is carried out by a planetary cement mortar mixer with a stirring speed of 140 r / min and a stirring time of 4 min; S5. Add soil, organic nutrients and amendment to the slurry in S4 in the above proportion, continue stirring for 1 minute, mix evenly, and you will get acid-activated tailings sand-based vegetation composite material.

[0032] Example 2, as a preferred embodiment of the present invention, the raw material components of the acid-activated tailings sand-based vegetation composite material in this example include: 67 parts of tailings sand, 6 parts of acid activator, 25 parts of phosphogypsum, 7 parts of limestone powder, 15 parts of cement, 80 parts of soil, 35 parts of organic nutrient components, and 4 parts of conditioner. The acid activator is composed of phosphoric acid and aluminum sulfate in a mass ratio of 5:1.

[0033] The preparation method of the acid-activated tailings sand-based vegetation composite material in this embodiment is the same as that in Example 1, except that: S3. Preparation of acid activator: Weigh phosphoric acid and aluminum sulfate according to the above mass ratio, mix them evenly to obtain a solid composite acid activator; then dissolve the solid composite acid activator in water, stir evenly, and prepare an aqueous solution of acid activator with a phosphoric acid mass fraction of 30% and a pH value of 2.5.

[0034] Example 3, as a preferred embodiment of the present invention, the raw material components of the acid-activated tailings sand-based vegetation composite material in this example include: 80 parts of tailings sand, 3 parts of acid activator, 15 parts of phosphogypsum, 12 parts of limestone powder, 25 parts of cement, 80 parts of soil, 25 parts of organic nutrient components, and 1 part of conditioner. The acid activator is composed of oxalic acid and sodium fluoride in a mass ratio of 3:1.

[0035] The preparation method of the acid-activated tailings sand-based vegetation composite material in this embodiment is the same as that in Example 1, except that: S3. Preparation of acid activator: weigh oxalic acid and sodium fluoride according to the above mass ratio, mix them evenly to obtain a solid composite acid activator; then dissolve the solid composite acid activator in water, stir evenly, and prepare an aqueous solution of acid activator with an oxalic acid mass fraction of 15% and a pH value of 3.8.

[0036] Comparative Example 1 (without acid activator): This comparative example differs from Example 1 in that no acid activator is added, and the liquid volume reduced due to the lack of acid activator is made up with an equal mass of water to ensure that the total liquid-solid ratio of the system remains consistent with that of Example 1. The composition of other raw materials and preparation methods are the same as those in Example 1.

[0037] Comparative Example 2 (without added organic nutrients) differs from Example 1 in that no organic nutrients are added, and an equal mass of soil is used to compensate for the reduction in the total amount of solid raw materials due to the lack of organic nutrients, so as to ensure that the total mass of raw materials remains consistent with that of Example 1. The composition of other raw materials and the preparation method are the same as those in Example 1.

[0038] Comparative Example 3 (Alkali Activation): This comparative example differs from Example 1 in that an alkaline activator is used instead of an acidic activator. The alkaline activator is a compound of sodium hydroxide and water glass (modulus 1.2, NaOH concentration 2 mol / L), and its dosage is the same as that of the acidic activator in Example 1. Water is added to adjust to the same liquid-solid ratio. The pH value of the alkaline activator aqueous solution is 13.0. The composition of other raw materials and the preparation method are the same as in Example 1.

[0039] The plant-based composite materials prepared in each embodiment and comparative example were subjected to the following tests, and the results are shown in Table 1.

[0040] 1. Unconfined compressive strength test: The test was conducted according to the "Specification for Cement-Soil Mix Design" (JGJ / T 233-2011). The prepared composite material was placed into a 100mm×100mm×100mm mold and cured under standard conditions (temperature 20±2℃, humidity ≥95%) for 28 days. The unconfined compressive strength was then tested using a universal testing machine with a loading rate controlled at 1mm / min. Three specimens were tested in each group, and the average value was taken.

[0041] 2. Porosity test: The saturated weighing method was used for determination. The specimens cured for 28 days were dried to constant weight (60℃) and the dry weight m1 was recorded; then the specimens were vacuum saturated with water for 24 hours and the dry weight of the saturated surface m2 was recorded; finally, the specimens were suspended in water and the weight in the water m3 was recorded.

[0042] Porosity P is calculated using the following formula: P = (m2 - m1) / m2 -m3) × 100%.

[0043] 3. pH test: The test was conducted in accordance with the "Determination of Soil pH" (NY / T 1377-2007). A composite material sample cured for 28 days was taken, air-dried, and passed through a 2mm sieve. Deionized water was added at a solid-liquid ratio of 1:5 (mass-volume ratio). The sample was shaken for 30 minutes, allowed to stand for 1 hour, and then the pH of the supernatant was measured using a pH meter.

[0044] 4. Seed germination index test: The test was conducted according to the "Test Method for Seed Germination in Solid Waste" (GB / T 27851-2011). Composite material samples that had been cultured for 28 days were mixed with deionized water at a solid-liquid ratio of 1:5, shaken for 2 hours, and then filtered to obtain the extract. Filter paper was placed in a petri dish, and 20 ryegrass seeds were evenly placed on top. The treatment group received 5 mL of the extract, while the control group received 5 mL of deionized water. After culturing at 25℃ in the dark for 5 days, the germination rate was recorded, and root length was measured.

[0045] The seed germination index (GI) is calculated using the following formula: GI = (germination rate of treatment group × average root length of treatment group) / (germination rate of control group × average root length of control group) × 100%.

[0046] Table 1. Test results of the examples and comparative examples

[0047] As can be seen from the test results in Table 1: Comparing Example 1 and Comparative Example 1, it can be seen that without the addition of acid activator, the 28-day compressive strength of the material increased to 0.55 MPa, but the porosity decreased to 22.5%, and the seed germination index decreased to 65%. This indicates that although the acid activator slightly reduces the strength of the material, it can effectively adjust the pH of the material to the neutral range, improve the pore structure, and significantly enhance the ecological adaptability of the material.

[0048] Comparing Example 1 and Comparative Example 2, it can be seen that without the addition of organic nutrients, the 28-day compressive strength of the material increased to 0.56 MPa, but the porosity decreased to 21.0%, and the seed germination index plummeted to 42%. This indicates that although organic nutrients may reduce the strength of the material to some extent, they can significantly improve the pore structure of the material and enhance its water and fertilizer retention capacity, making them a key component in ensuring the ecological function of the material.

[0049] Comparing Example 1 and Comparative Example 3, it can be seen that when an alkali activator is used, the 28-day compressive strength of the material is significantly increased to 1.35 MPa, but the porosity decreases to 15.0%, and the seed germination index also drops sharply to 15%. This indicates that alkali activation can enhance the strength of the material and increase the density of the matrix, but a highly alkaline environment and a dense structure will seriously affect seed germination and growth, making it unsuitable for soil remediation.

[0050] Comparing Examples 1-3, it can be seen that composite materials with adjustable properties can be obtained by using different acid activator systems. Among them, the phosphoric acid system (Example 2) is more acidic (pH=2.5), with the lowest pH (6.2) and the highest porosity (32.1%) after activation, and the best seed germination index (92%), making it suitable for scenarios with high requirements for porosity and ecological function; the oxalic acid system (Example 3) is less acidic (pH=3.8), but has the highest strength (0.60MPa) and the lowest porosity (25.3%), making it suitable for slope restoration scenarios with high strength requirements; the sulfuric acid system (Example 1) has a balanced overall performance, taking into account both strength (0.45MPa) and ecological function (85%), making it suitable for general ecological restoration scenarios.

[0051] In summary, this invention, through the rational proportioning of acid activators, gelling components, and ecological components, can provide a good plant growth environment while ensuring a certain level of engineering strength, achieving a balance between engineering stability and ecological adaptability. The formula can be optimized according to the needs of different remediation scenarios, and it has broad application prospects.

[0052] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. Acid-activated tailings-based geocomposite for soil reconstruction, characterized in that it comprises: It includes the following raw material components by weight: 67-85 parts tailings sand, 2-10 parts acid activator, 15-30 parts phosphogypsum, 7-12 parts limestone powder, 15-25 parts cement, 65-90 parts soil, 25-40 parts organic nutrient components, and 0.5-5 parts amendment; wherein, the acid activator is a compound of acid components and salt components in a mass ratio of 3:1 to 5:

1.

2. The acid-activated tailings sand-based vegetation composite material according to claim 1, characterized in that, The tailings sand is at least one of iron tailings, gold tailings and copper tailings, and the chemical composition thereof includes CaO, SiO2, Al2O3 and Fe2O3, wherein the content of SiO2 is greater than 40%, and the sum of the contents of SiO2 and Al2O3 is ≥60%; the tailings sand is ground to have a specific surface area of 350-450 m 2 / kg.

3. The acid-activated tailings sand-based vegetation composite material according to claim 1, characterized in that, The acid component is at least one of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, propionic acid, and oxalic acid, and the salt component is a soluble fluoride or sulfate.

4. The acid-activated tailings sand-based vegetation composite material according to claim 3, characterized in that, The salt components are sodium fluoride or aluminum sulfate.

5. The acid-activated tailings-based geoccomposite of claim 1, wherein, When using the acid activator, it is prepared as an aqueous solution with an acid component mass fraction of 10-50% and a pH value of 2.3-4.

5.

6. The acid-activated tailings-based geoccomposite of claim 1, wherein, Phosphogypsum is a by-product of phosphorus chemical industry, which is pretreated by washing or neutralization; the specific surface area of limestone powder is not less than 300 m 2 / kg; The cement is ordinary silicate cement or composite silicate cement.

7. The acid-activated tailings-based geoccomposite of claim 1, wherein, The soil includes at least one of the following: in-situ mine soil, engineering waste soil, imported soil, sandy soil, clay, heavy metal contaminated soil, or artificially prepared substrate; the organic nutrient components include at least one of the following: well-rotted livestock and poultry manure, rice husks, sawdust, and humus.

8. The acid-activated tailings-based geoccomposite of claim 1, wherein, The amendment is composed of compound fertilizer and water-retaining agent mixed in a mass ratio of 3:1 to 1:

1. The compound fertilizer is a nitrogen-phosphorus-potassium compound fertilizer, and the water-retaining agent is an agricultural and forestry polyacrylamide water-retaining agent.

9. A method of preparing an acid-activated tailings-based geocomposite according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Dry the tailings sand to a moisture content of <1%, and grind in a ball mill to a specific surface area of 350-450 m2 / kg; 2 / kg; S2. Weigh out the phosphogypsum, limestone powder, cement and tailings powder ground in S1 by weight, mix them evenly to obtain a mixed dry material; S3. Weigh the acid component and salt component according to the mass ratio, mix them evenly to obtain a solid composite acid activator; then dissolve the solid composite acid activator in water, stir evenly, and prepare an aqueous solution of acid activator with an acid component mass fraction of 10-50% and a pH value of 2.3-4.5; S4. Add the acid activator to the mixed dry material in S2 and stir to form a uniform slurry; S5. Add soil, organic nutrients and amendment to the slurry in S4 in proportion, continue stirring for 1-2 minutes until evenly mixed, and you will get acid-activated tailings sand-based vegetation composite material.

10. The method of claim 9, wherein, In S4, a planetary cement mortar mixer is used for mixing, with a mixing speed of 140±5 r / min and a mixing time of 3 to 5 min.

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