Lithium slag-based artificial soil based on different soil layer functions and preparation method thereof

Abstract

The invention relates to lithium slag-based artificial soil based on different soil layer functions and a preparation method of the lithium slag-based artificial soil. The lithium slag-based artificial soil comprises a surface soil layer, a leaching layer, a deposition layer and a parent material layer according to soil profile layers. Compared with an existing technology for preparing artificial soil from solid waste materials such as lithium slag, red mud and coal gangue, the preparation process is simple, the cost is low, and the prepared soil is free of secondary pollution risk and is environmentally friendly; the preparation of the artificial soil of soil layers with different ecological functions in a soil profile configuration can be realized, so that the artificial soil meets the requirements of mine land reclamation and mine ecological restoration on the artificial soil with a stable soil body structure, the green restoration concept that lithium slag comes from a mine and then returns to the mine is embodied, and precious natural soil resources are not consumed; and a plurality of solid waste materials which are difficult to dispose can be recycled, the recovery and treatment cost of the mine ecological environment after mining is reduced, the pollution caused by solid waste stockpiling is reduced, and the ecological environment of a mining area and the surrounding of the mining area is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization and soil reconstruction, and relates to a lithium slag-based artificial soil based on different soil layer functions and a preparation method thereof. Background Art

[0002] Lithium smelting slag is an industrial solid waste generated during the production of lithium carbonate from lithium-containing ores (such as spodumene or lepidolite) through processes such as batching, high-temperature roasting, and leaching. Typically, 10-30 tons of lithium smelting slag are produced for every ton of lithium carbonate produced. In recent years, with the rapid development of the new energy industry, lithium smelting slag production has increased annually. However, the comprehensive utilization rate of lithium smelting slag is very low, which has become a bottleneck and pain point hindering the sustainable development of the lithium-ion new energy industry. Lithium smelting slag is a lightweight, light-colored, porous aluminosilicate mineral material. Its main components include SiO2, Al2O3, and CaO. Currently, its main application is in the building materials industry, such as cement, concrete, and sintered bricks. However, due to the presence of harmful metallic elements such as beryllium and thallium in lithium smelting slag, the building materials industry struggles to meet the demand for large-scale lithium smelting slag utilization. Achieving efficient, green, and economical large-scale processing and utilization of lithium smelting slag has become a major scientific and technological challenge that urgently needs to be solved in the development of the lithium battery industry.

[0003] Artificial soil is a new type of soil created from organic and inorganic solid waste. It can be used to grow plants and boasts large waste disposal capacity, pollution reduction, carbon sequestration, and scalable production. It effectively addresses the challenges of disposing of large amounts of multi-source solid waste and addressing soil resource shortages. Industrial waste, construction waste, and composted agricultural and forestry waste can all serve as components of artificial soil. Reports have already been published on the use of solid waste materials such as coal gangue, tailings, and red mud to create artificial soil.

[0004] In the patent application "A Method for Preparing Artificial Soil Based on Coal Gangue" (CN 117281010A), artificial soil is prepared by heat treatment at 450-550°C to remove coal gangue and diatomaceous earth crystallization water, which increases production costs and hinders widespread application. In the patent application "An Artificial Soil Modified by Copper Tailings and Its Preparation Method" (CN 113173763A), the potential secondary pollution risk to the ecological environment caused by the harmful heavy metal content in copper tailings is not considered. In the patent application "A Method for Preparing Artificial Planting Soil Using Red Mud and Its Application" (CN 119631850A), the preparation steps are numerous and complex, making large-scale production difficult. In the patent application "Lithium Slag-Based Artificial Soil and Its Preparation Method" (CN 118872567A), artificial soil suitable for plant growth is prepared using microwave-assisted acid leaching to remove trace amounts of beryllium and thallium, and high-temperature anaerobic fermentation for soil composting. The preparation methods involved in the above-mentioned patents all focus on the selection of topsoil materials, composition ratios and production processes, and do not consider the preparation methods of artificial soils with different ecological functions in natural soil profiles with stable soil structures. They are unable to meet the demand for artificial soils with stable soil structures in mining area land reclamation and mine ecological restoration.

[0005] Mining often damages the original natural soil structure, causing the loss of the original functions of the natural soil strata, thereby affecting plant growth and exacerbating soil erosion and water loss. Land reclamation and ecological restoration in mining areas require vertically stacking individual soil units within a few meters of the surface, taking into account the land use being reclaimed and simulating naturally developed soils to construct a rational soil profile configuration, ensuring optimal productivity. Each layer in a natural soil profile has distinct ecological functions. The topsoil plays a vital role during plant germination and seedling growth. Rich in organic matter and nutrients, it serves as the primary activity zone for plant roots. The eluvial layer lies beneath the topsoil layer, where water leaches downward from the surface, reducing its organic matter content and fertility. The alluvial layer, beneath the eluvial layer, precipitates and accumulates materials leached from the upper soil layers. This layer has a heavy, compact texture, high mineral content, and low organic matter content. The parent material layer, which is not fully matured into soil, has larger particles and a high mineral content. Located at the bottom of the soil layer, it supports the overall soil structure.

[0006] Therefore, developing an artificial soil with a stable soil structure is very important to meet the needs of land reclamation and mine ecological restoration in mining areas. Summary of the Invention

[0007] To address the lack of a method for preparing lithium slag-based artificial soil with different soil layer functions in stable soil required for land reclamation and mine ecological restoration in mining areas, the present invention aims to provide a lithium slag-based artificial soil with different soil layer functions that is simple to operate, economical, and safe, and a preparation method thereof. The method utilizes lithium slag-based artificial soil, which is produced in large quantities but difficult to dispose of on a large scale, as the main raw material, based on the soil pH changing from low to high, the organic matter content changing from high to low, the bulk density changing from low to high, and the texture changing from loose to compact, in the natural soil profile. The method modifies the lithium slag by adding other solid waste materials to the soil, using lithium slag, which is produced in large quantities but difficult to dispose of on a large scale, as the main raw material. This method improves the scale utilization rate of lithium slag, effectively solving the practical problem of difficult disposal of large amounts of multi-source solid wastes such as lithium slag, construction waste, domestic sludge, crop straw, fly ash, and steel slag, while meeting the requirements of artificial soil with stable structure and excellent performance for land reclamation and mine ecological restoration in mining areas.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a lithium slag-based artificial soil based on the functions of different soil layers. The lithium slag-based artificial soil includes a topsoil layer, a leaching layer, a sedimentation layer, and a parent material layer according to the soil profile.

[0010] The raw materials for preparing the topsoil layer include lithium slag, construction waste soil, organic materials, granulation promoter, water retention agent, microbial agent, and heavy metal stabilizer;

[0011] The raw materials for preparing the leaching layer include lithium slag, construction waste soil, organic materials, granulation promoter, microbial agent, and heavy metal stabilizer;

[0012] The raw materials for preparing the deposition layer include lithium slag, construction waste soil, organic materials, heavy metal stabilizers, and structural stabilizers;

[0013] The raw materials for preparing the parent material layer include lithium slag, heavy metal stabilizer and structural stabilizer.

[0014] Based on the ecological concept of lithium slag returning to and from mining areas, transforming "abandoned mining areas" into "fertile farmland," this invention aims to reconstruct artificial soil lacking distinct soil layers for land reclamation and mine ecological restoration in mining areas. Using clay-like lithium smelting slag as the primary material, supplemented with organic materials rich in organic matter and nitrogen and phosphorus nutrients, heavy metal stabilizers, and structural stabilizers, this method produces lithium slag-based artificial soil with different ecological functions. The topsoil layer features high organic matter content, sufficient nutrients, loose soil texture, and low available heavy metal content, making it suitable for plant growth. The eluvial layer features a relatively compact texture and moderate organic matter content, providing sufficient nutrients for plant roots. The sedimentation layer features a compact and heavy texture, high mineral content, and low organic matter content. The parent material layer features a compact texture, stable structure, and high mineral content. This overcomes the technical bottleneck of existing artificial soils, which are limited to the topsoil layer and lack other functional soil layers. This lithium slag-based artificial soil is low-cost, poses no secondary pollution risk, and is environmentally friendly. It "turns waste into treasure," reduces the cost of post-mining ecological restoration and management of the mine environment, reduces pollution from solid waste storage, and improves the ecological environment in and around the mining area. This achieves the multiple goals of efficient solid waste utilization, land resource expansion, and environmental green restoration.

[0015] Preferably, the raw materials for preparing the topsoil layer include, by mass percentage on a dry basis, 100 parts of lithium slag, 10-40 parts of construction waste soil, 15-50 parts of organic material, 0.6-3 parts of agglomeration promoter, 0.05-0.3 parts of a water retaining agent, 0.03-0.45 parts of a microbial agent, and 0.7-6.5 parts of a heavy metal stabilizer.

[0016] Taking the mass of lithium slag as 100 parts, the mass of construction waste soil can be selected as 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 40 parts, etc.; the mass of organic material can be selected as 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, etc.; the mass of granulation promoter can be selected as 0.6 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, etc.; the mass of water retaining agent can be selected as 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, The mass fractions of the microbial agent can be selected from 0.03 parts, 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, etc.; the mass fractions of the heavy metal stabilizer can be selected from 0.7 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, etc.; other specific point values within the above numerical ranges can be selected, and they will not be repeated here.

[0017] Preferably, the raw materials for preparing the leaching layer include, by mass parts on a dry basis, 100 parts of lithium slag, 5-15 parts of construction waste soil, 7-20 parts of organic materials, 1-3 parts of agglomeration promoter, 0.03-0.2 parts of microbial agent, and 1-5.5 parts of heavy metal stabilizer.

[0018] Taking the mass of lithium slag as 100 parts, the mass of construction waste soil can be selected as 5 parts, 7 parts, 8 parts, 10 parts, 12 parts, 15 parts, etc.; the mass of organic material can be selected as 7 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, etc.; the mass of granulation promoter can be selected as 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, etc.; the mass of microbial agent can be selected as 0.03 parts, 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, etc.; the mass of heavy metal stabilizer can be selected as 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, etc.; other specific point values within the above numerical ranges can be selected, and they will not be repeated here.

[0019] Preferably, the raw materials for preparing the deposition layer include, by mass parts on a dry basis, 100 parts of lithium slag, 5-15 parts of construction waste soil, 2-11 parts of organic materials, 0.6-5 parts of heavy metal stabilizer, and 3.5-25 parts of structural stabilizer.

[0020] Taking the mass of lithium slag as 100 parts, the mass shares of construction waste soil can be selected as 5 parts, 7 parts, 8 parts, 10 parts, 12 parts, 15 parts, etc.; the mass shares of organic materials can be selected as 2 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 10 parts, 11 parts, etc.; the mass shares of heavy metal stabilizers can be selected as 0.6 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.; the mass shares of structural stabilizers can be selected as 3.5 parts, 5 parts, 7 parts, 8 parts, 10 parts, 12 parts, 15 parts, 20 parts, 22 parts, 25 parts, etc.; other specific point values within the above numerical ranges can be selected, and they will not be repeated here.

[0021] Preferably, the raw materials for preparing the parent material layer include 100 parts of lithium slag, 0.6-7 parts of heavy metal stabilizer, and 10-33 parts of structural stabilizer in terms of mass parts on a dry basis.

[0022] Taking the mass of lithium slag as 100 parts, the mass parts of heavy metal stabilizer can be selected as 0.6 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 6 parts, 7 parts, etc.; the mass parts of structural stabilizer can be selected as 10 parts, 12 parts, 13 parts, 15 parts, 18 parts, 20 parts, 25 parts, 28 parts, 30 parts, 33 parts, etc.; other specific point values within the above numerical ranges can be selected, and they will not be repeated here.

[0023] Preferably, the organic material includes any one of domestic sludge, crop straw or chicken manure organic fertilizer, or a combination of at least two of them.

[0024] Preferably, the domestic sludge is activated sludge from municipal sewage treatment plants and meets the organic material standards specified in NY / T3034-2016, "General Requirements for Soil Conditioners." The domestic sludge has a moisture content of no more than 60%, an organic matter content of over 30%, and a nutrient content (N+P2O5+K2O) of approximately 5%. It is primarily used to increase the organic matter content and nutrients of the artificial soil.

[0025] Preferably, the crop straw includes any one of rice straw, corn straw, wheat straw, cotton straw, rape straw, and sugarcane straw, or a combination of at least two thereof; and is used to increase the organic matter content of the artificial soil, while improving the pore structure of the artificial soil and enhancing its air and water permeability.

[0026] Preferably, the chicken manure organic fertilizer is fermented and decomposed chicken manure organic fertilizer that meets the requirements of GB / T 19610-2019, "Organic Fertilizer: Chicken Manure Organic Fertilizer." The chicken manure organic fertilizer has a total organic matter content of no less than 25% on a dry basis and is used to increase the organic matter content of the artificial soil, provide nutrients for plant growth, and improve the aggregate structure of the artificial soil.

[0027] Preferably, the heavy metal stabilizer comprises calcium phosphate and / or fly ash.

[0028] Calcium phosphate is a white crystal or amorphous powder, slightly soluble in water, with a chemical formula of Ca3(PO4)2. It is often used as an acidity regulator and heavy metal stabilizer. The calcium phosphate in the artificial soil of the present invention reduces the precipitation and mobility of harmful metal ions such as beryllium, thallium, chromium, and cadmium in the artificial soil by increasing the pH or forming insoluble metal phosphate substances with harmful metal ions such as beryllium, thallium, chromium, and cadmium, thereby reducing the risk of secondary pollution.

[0029] Fly ash is a solid waste generated by coal-fired power plants. Its main oxide components are SiO2 and Al2O3, accounting for about 50% of the total mass. It has high surface activity and can reduce the mobility of metal ions by adsorbing them, thereby improving the environmental safety of artificial soil applications.

[0030] Preferably, the structural stabilizer comprises low-alkali cement and / or steel slag.

[0031] Preferably, the low-alkali cement is sulphoaluminate cement.

[0032] The free expansion rate of sulphoaluminate cement is usually between 0-0.1%, the strength grade is 42.5, the pH value is ≤10.5, the Al2O3 content in the cement clinker is not less than 30%, the SiO2 content is not more than 10.5%, and CaO is about 15-35% of the cement mass.

[0033] In the artificial soil of the present invention, the role of low-alkali cement is mainly reflected in two aspects: first, it solidifies metal ions such as beryllium, thallium, and chromium in lithium slag through physical encapsulation, adsorption, chemical precipitation, and isomorphous substitution, thereby reducing the precipitation of harmful metal elements; second, it cements solid particles such as lithium slag, fly ash, and steel slag together through hydration reaction, thereby improving the strength of the artificial soil and enhancing the artificial soil's ability to resist erosion and scour.

[0034] Preferably, the steel slag is industrial solid waste generated during the steelmaking process, and contains 2-8% iron, 40-60% calcium oxide, 3-10% magnesium oxide, and 1-8% manganese oxide.

[0035] In the artificial soil of the present invention, the steel slag plays the following roles: first, it increases the mineral content of the lithium slag-based artificial soil, increases the bulk density of the artificial soil, and enhances the supporting effect of the bottom artificial soil on the upper soil layer; second, the minerals in the steel slag can solidify and stabilize highly mobile harmful metal ions such as beryllium, thallium, and chromium in the artificial soil through adsorption and cation exchange, thereby reducing the risk of precipitation of harmful metal elements in the artificial soil.

[0036] Preferably, the lithium slag is a powdered solid material produced by high-temperature smelting of spodumene or lepidolite ore, containing 45-65% SiO2, 19-25% Al2O3, 3-29% CaO, and 3.4-13.2% SO3;

[0037] Preferably, the construction waste soil is soil excavated from a construction site, which has been dried, crushed, and screened to remove debris with a particle size exceeding 5 mm, and is used to increase the aggregate content of the artificial soil and accelerate the maturation of the artificial soil.

[0038] Preferably, the agglomeration promoter comprises anionic polyacrylamide.

[0039] Anionic polyacrylamide is a water-soluble high molecular polymer with the appearance of white powder or translucent particles. It can bind together solid particles such as lithium slag, activated sludge, chicken manure, fly ash, etc. in materials through physical and chemical reactions, accelerating the formation of water-stable aggregates similar to natural soil in artificial soil, playing a role in regulating factors such as water, fertilizer, air, and heat in artificial soil, and promoting the growth of plant roots.

[0040] Preferably, the water-retaining agent comprises sodium polyacrylate water-absorbing resin.

[0041] Sodium polyacrylate water-absorbing resin is a functional polymer material containing strong hydrophilic groups and a certain degree of cross-linking. It appears as white particles and can absorb hundreds or even thousands of times its own weight in water. It has a strong water-retention capacity and is non-toxic and harmless. It can also retain fertilizer and moisture in artificial soil.

[0042] Preferably, the microbial agent comprises EM agent.

[0043] EM microbial agent is mainly composed of a variety of beneficial bacteria such as spore bacteria, lactic acid bacteria, yeast bacteria, photosynthetic bacteria, actinomycetes, etc., which plays a role in accelerating the decomposition of straw and improving the biological characteristics of artificial soil.

[0044] As a more preferred technical solution of the present invention, the lithium slag-based artificial soil comprises a topsoil layer, a leaching layer, a sedimentation layer and a parent material layer according to the soil profile layer;

[0045] The raw materials for preparing the topsoil layer include, by weight of dry basis, 100 parts of lithium slag, 10-40 parts of construction waste, 12-26 parts of domestic sludge, 3-8.5 parts of crop straw, 1.5-8.5 parts of chicken manure organic fertilizer, 0.6-3 parts of pelletizing promoter, 0.05-0.3 parts of water retaining agent, 0.03-0.45 parts of microbial agent, 0.7-5.5 parts of calcium phosphate, and 0-1 parts of fly ash;

[0046] The raw materials for preparing the leaching layer include, by weight of dry basis, 100 parts of lithium slag, 5-15 parts of construction waste soil, 5-13 parts of domestic sludge, 1.6-3 parts of crop straw, 1.2-3 parts of chicken manure organic fertilizer, 1-3 parts of pelletizing promoter, 0.03-0.2 parts of microbial agent, 1-4 parts of calcium phosphate, and 0-1.5 parts of fly ash;

[0047] The raw materials for preparing the deposition layer include, by weight of dry basis, 100 parts of lithium slag, 5-15 parts of construction waste soil, 2-11 parts of domestic sludge, 0.6-4 parts of calcium phosphate, 0-1 part of fly ash, 3.5-14 parts of low-alkali cement, and 0-11 parts of steel slag;

[0048] The raw materials for preparing the parent material layer include, by weight of dry basis, 100 parts of lithium slag, 0.6-6 parts of calcium phosphate, 0-1 part of fly ash, 10-20 parts of low-alkali cement, and 0-13 parts of steel slag.

[0049] In a second aspect, the present invention provides a method for preparing the lithium slag-based artificial soil based on different soil layer functions according to the first aspect, the preparation method comprising the following steps:

[0050] The raw materials for preparing the topsoil layer, the eluvial layer, the sedimentation layer and the parent material layer are mixed separately and then mixed with water to prepare a water-containing material; the water-containing material is piled up for natural curing, and after the material is matured, each layer of lithium slag-based artificial soil is prepared.

[0051] The artificial soils of different soil layers obtained after the above-mentioned maturation were evaluated for their applicability and environmental risks by measuring physical and chemical indicators such as pH, organic matter content, bulk density, porosity, and the content of harmful metal elements such as beryllium, thallium, and chromium and their effective content.

[0052] Preferably, the mass ratio of the preparation raw materials to water is (3-5):1, for example, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.7:1, 4.8:1, 5:1, etc.

[0053] Preferably, the natural curing is carried out at 10-40°C (e.g., 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc.) for 30-90 days (e.g., 30 days, 35 days, 40 days, 45 days, 50 days, 55 days, 60 days, 65 days, 70 days, 80 days, 90 days, etc.).

[0054] Other specific point values within the above numerical ranges can be selected and will not be described in detail here.

[0055] Preferably, water is added every 3-5 days during the natural curing process to keep the material moist.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] (1) Compared with existing artificial soil technologies prepared from solid waste materials such as lithium smelting slag, red mud, and coal gangue, the artificial soil based on lithium smelting slag of the present invention has a simple preparation process, low cost, and no secondary pollution risk, and is environmentally friendly.

[0058] (2) The artificial soil mainly composed of lithium smelting slag according to the present invention can realize the preparation of artificial soil with different ecological functional soil layers in the soil profile configuration, breaking through the technical bottleneck of the existing artificial soil preparation method being limited to the surface soil but lacking other functional soil layers. It can meet the demand for artificial soil with a stable soil structure for land reclamation and mine ecological restoration in mining areas, embodying the green restoration concept of lithium slag coming from the mining area and returning to the mining area, without consuming precious natural soil resources;

[0059] (3) The artificial soil mainly composed of lithium smelting slag involved in the present invention can recycle other difficult-to-dispose solid waste materials such as domestic sludge, crop straw, fly ash, steel slag, etc., realizing "turning waste into treasure", reducing the cost of post-mining mine ecological environment restoration and management, reducing the pollution caused by solid waste storage, and improving the ecological environment of the mining area and its surrounding areas. DETAILED DESCRIPTION

[0060] In order to further illustrate the technical means and effects adopted by the present invention, the technical solutions of the present invention are further described below in conjunction with the preferred embodiments of the present invention, but the present invention is not limited to the scope of the embodiments.

[0061] The lithium slag used in the following examples is selected from the smelting slag of spodumene or lepidolite that meets the "General Industrial Solid Waste Storage and Landfill Pollution Control Standard" (GB 18599-2020), and the particle size of the lithium slag particles is required to be no more than 2 mm; the construction waste soil used is the soil excavated from the construction site after drying, crushing and screening out the debris with a particle size of more than 5 mm; the domestic sludge and chicken manure used are crushed into 2-5 mm granular products after air-drying, and the crop straw is crushed into 5-10 mm length fiber material after air-drying; the EM bacterial agent used is a product of EM decomposing fungi purchased from Henan Wobao Biotechnology Co., Ltd.; the granulation promoter used is purchased from Zhengzhou The anionic polyacrylamide with a molecular weight of 6 million is produced by Daqian Environmental Protection Technology Co., Ltd.; the water-retaining agent used is sodium polyacrylate water-absorbing resin model KL-SAP purchased from Zhejiang Satellite New Materials Technology Co., Ltd.; the fly ash used is solid waste from coal-fired power generation in thermal power plants, and its main oxide components are SiO2 and A12O3, accounting for about 50% of the total mass; the low-alkali cement used is L.SAC42.5 grade sulphoaluminate cement purchased from Yudengdian Group Cement Co., Ltd.; the steel slag used has a particle size of no more than 5mm and a pH value of no more than 10.

[0062] Example 1

[0063] Spodumene slag was used as the main raw material, and the materials in the dry basis ratio shown in Table 1 were added. After uniform mixing, the mixture was mixed with 20% water and naturally aged (20-30° C.) for 3 months to produce artificial soil with different soil layer functions that can be used for mining area ecological restoration. The physical and chemical indicators of the finished artificial soil are shown in Table 2, and the content of harmful metal elements and their effective content are shown in Table 3.

[0064] Table 1

[0065]

[0066] Table 2

[0067]

[0068]

[0069] As shown in Table 2, the artificial soil of the topsoil layer and the leached layer made of spodumene slag as the main raw material of the present invention has a physical and chemical index of pH 6-8.5 as specified in the "Greening Planting Soil" (CJ / T340-2016) after 3 months of maturation, an organic matter content of no more than 30%, and a bulk density of <1.35 g / cm 3 The technical requirement of porosity ≥ 15% is met. The water-stable aggregate content in the topsoil layer exceeds 40%, making it suitable for plant growth. Compared with the topsoil layer and eluvial layer, the sedimentation layer and parent material layer have a higher pH, lower organic matter content, increased bulk density, and lower porosity. This indicates that the sedimentation layer and parent material layer are more compact and less permeable than the upper two layers. This can prevent the precipitation and migration of harmful metal elements in the artificial soil, reducing the risk of secondary contamination of the artificial soil.

[0070] Table 3

[0071]

[0072] As shown in Table 3, the total amount and available content of the harmful metal elements beryllium and thallium in the artificial soils of different soil layers, made primarily from spodumene slag, are lower than those in the spodumene slag raw material. Although the chromium content in the artificial soils of different soil layers is slightly higher than that in the spodumene raw material, it still meets the technical requirements for total chromium content specified in the "Greening Planting Soil" (CJ / T 340-2016). After 90 days of natural curing, the available content of beryllium, thallium, and chromium in each layer of the artificial soil decreased by 23.5%-94.1%, 46.3%-96.5%, and 22.6%-40.6%, respectively, compared to the day 0 content. This indicates that the formation of the artificial soil aggregate structure makes it more difficult for harmful metal elements in the soil to precipitate and migrate, reducing the risk of pollution to plants and the surrounding ecological environment.

[0073] Example 2

[0074] Lepidolite slag was used as the main raw material, and the materials in the dry basis ratio shown in Table 4 were added, mixed evenly, and mixed with 30% water. After natural aging (20-30° C.) for 3 months, artificial soil with different soil layer functions that can be used for mining area ecological restoration was produced. The physical and chemical indicators of the finished artificial soil are shown in Table 5, and the content of harmful metal elements and their effective content are shown in Table 6.

[0075] Table 4

[0076]

[0077] Table 5

[0078]

[0079]

[0080] As shown in Table 5, the artificial soil of the topsoil layer and the eluvial layer made of lepidolite slag as the main raw material of the present invention has a physical and chemical index of pH 6-8.5 as specified in the "Greening Planting Soil" (CJ / T340-2016) after 3 months of maturation, an organic matter content of no more than 30%, and a bulk density of <1.35 g / cm 3 The technical requirement of a porosity of ≥15% is met. The water-stable aggregate content in the topsoil exceeds 70%, making it suitable for plant growth. Compared to the topsoil and eluvial layers, the sedimentation layer and parent material layer have a higher pH, lower organic matter content, increased bulk density, and lower porosity. This indicates that the sedimentation layer and parent material layer are more compact and less permeable to water and air than the upper two layers. This effectively prevents the precipitation and migration of harmful metal elements in the artificial soil, reducing the risk of secondary contamination of the artificial soil.

[0081] Table 6

[0082]

[0083]

[0084] The data in Table 6 show that the total amount and available content of the harmful metallic elements beryllium and thallium in the artificial soils of different soil layers, made primarily from lepidolite slag, are lower than those in the lepidolite slag raw material. Although the chromium content in the artificial soils of different soil layers is slightly higher than that in the spodumene raw material, it still meets the technical requirements for total chromium content specified in the "Greening Planting Soil" (CJ / T 340-2016). After 90 days of natural curing, the available beryllium content in the artificial soils of the topsoil and eluvial layers decreased by 13.6%-51.9%, respectively, compared to the 0-day results. While the available beryllium content in the artificial soils of the sedimentary and parent material layers increased slightly compared to the 0-day results, the levels were still significantly below the 20 μg / kg beryllium leaching limit specified in the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB 5085.3-2007), indicating that beryllium in the artificial soil leachate poses no risk of contamination to surrounding water bodies. The effective contents of thallium and chromium in each layer of artificial soil after 90 days of curing were reduced by 53.9%-69.6% and 38.3%-53.7% respectively compared with those at day 0, indicating that with the formation of the aggregate structure of the artificial soil, the harmful metal elements in the artificial soil are more difficult to dissolve and migrate, reducing their pollution risks to plants and the surrounding ecological environment.

[0085] The applicant declares that the present invention is illustrated by the above-described embodiments, but the present invention is not limited to the above-described embodiments. This does not mean that the present invention must rely on the above-described embodiments in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for raw materials in the present invention, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

[0086] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0087] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A lithium slag-based artificial soil based on different soil layer functions, characterized in that: The lithium slag-based artificial soil comprises a topsoil layer, a leaching layer, a sedimentation layer and a parent material layer according to the soil profile layer; The raw materials for preparing the topsoil layer include lithium slag, construction waste soil, organic materials, granulation promoter, water retention agent, microbial agent, and heavy metal stabilizer; The raw materials for preparing the leaching layer include lithium slag, construction waste soil, organic materials, granulation promoter, microbial agent, and heavy metal stabilizer; The raw materials for preparing the deposition layer include lithium slag, construction waste soil, organic materials, heavy metal stabilizers, and structural stabilizers; The raw materials for preparing the parent material layer include lithium slag, heavy metal stabilizer and structural stabilizer.

2. The lithium slag-based artificial soil based on different soil layer functions according to claim 1, characterized in that: The raw materials for preparing the topsoil layer include, by weight of dry basis, 100 parts of lithium slag, 10-40 parts of construction waste soil, 15-50 parts of organic materials, 0.6-3 parts of agglomeration promoter, 0.05-0.3 parts of a water retaining agent, 0.03-0.45 parts of a microbial agent, and 0.7-6.5 parts of a heavy metal stabilizer. The raw materials for preparing the leaching layer include, by weight of dry basis, 100 parts of lithium slag, 5-15 parts of construction waste soil, 7-20 parts of organic materials, 1-3 parts of agglomeration promoter, 0.03-0.2 parts of microbial agent, and 1-5.5 parts of heavy metal stabilizer; The raw materials for preparing the deposition layer include, by weight of dry basis, 100 parts of lithium slag, 5-15 parts of construction waste soil, 2-11 parts of organic materials, 0.6-5 parts of heavy metal stabilizer, and 3.5-25 parts of structural stabilizer; The raw materials for preparing the parent material layer include 100 parts of lithium slag, 0.6-7 parts of heavy metal stabilizer, and 10-33 parts of structural stabilizer in terms of mass parts on a dry basis.

3. The lithium slag-based artificial soil based on different soil layer functions according to claim 1 or 2, characterized in that: The organic material includes any one of domestic sludge, crop straw or chicken manure organic fertilizer, or a combination of at least two of them.

4. The lithium slag-based artificial soil based on different soil layer functions according to claim 3, characterized in that: The domestic sludge is activated sludge from urban domestic sewage treatment plants and meets the organic material standards specified in NY / T 3034-2016 "General Requirements for Soil Conditioners"; Preferably, the crop straw includes any one of rice straw, corn straw, wheat straw, cotton straw, rape straw, and sugarcane straw, or a combination of at least two thereof; Preferably, the chicken manure organic fertilizer is fermented and decomposed chicken manure organic fertilizer, which meets the requirements of GB / T 19610-2019 "Organic Fertilizer Chicken Manure Organic Fertilizer".

5. The lithium slag-based artificial soil with different soil layer functions according to any one of claims 1 to 4, characterized in that: The heavy metal stabilizer includes calcium phosphate and / or fly ash; Preferably, the structural stabilizer comprises low-alkali cement and / or steel slag.

6. The lithium slag-based artificial soil based on different soil layer functions according to claim 5, characterized in that: The low-alkali cement is sulphoaluminate cement; Preferably, the steel slag is industrial solid waste generated during the steelmaking process, and contains 2-8% iron, 40-60% calcium oxide, 3-10% magnesium oxide, and 1-8% manganese oxide.

7. The lithium slag-based artificial soil with different soil layer functions according to any one of claims 1 to 6, characterized in that: The lithium slag is a powdery solid material produced by high-temperature smelting of spodumene or lepidolite ore, containing 45-65% SiO2, 19-25% Al2O3, 3-29% CaO, and 3.4-13.2% SO3; Preferably, the construction waste soil is soil excavated from a construction site, which has been dried, crushed, and screened to remove debris with a particle size exceeding 5 mm.

8. The lithium slag-based artificial soil with different soil layer functions according to any one of claims 1 to 7, characterized in that: The agglomeration promoter includes anionic polyacrylamide; Preferably, the water-retaining agent comprises sodium polyacrylate water-absorbing resin; Preferably, the microbial agent comprises EM agent.

9. The method for preparing lithium slag-based artificial soil based on different soil layer functions according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: The raw materials for preparing the topsoil layer, the eluvial layer, the sedimentation layer and the parent material layer are mixed separately and then mixed with water to prepare a water-containing material; the water-containing material is piled up for natural curing, and after the material is matured, each layer of lithium slag-based artificial soil is prepared.

10. The preparation method according to claim 9, characterized in that The mass ratio of the preparation raw materials to water is (3-5):1; Preferably, the natural curing is carried out at 10-40°C for 30-90 days; Preferably, water is added every 3-5 days during the natural curing process to keep the material moist.

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