High-consumption ecological nutrient soil based on geopolymer modified lithium tailings and preparation method of high-consumption ecological nutrient soil

Abstract

The invention discloses high-absorption-amount ecological nutrient soil based on geopolymer modified lithium tailings and a preparation method of the high-absorption-amount ecological nutrient soil, relates to the technical field of waste resource utilization and ecological restoration, and aims to solve the technical problems that the land is occupied by accumulation of the lithium tailings, the environment is polluted by soluble salt and heavy metal, and the resource utilization rate is extremely low. Lithium tailings are used as a core raw material (70-90%), a geopolymer gel system is matched to construct a stable framework and solidify pollutants, organic nutrient components and a function regulator are compounded to optimize physicochemical properties and nutrient supply, and the ecological nutrient soil is prepared through the processes of raw material pretreatment, synergistic excitation, gradient maintenance and the like. The nutrient soil realizes super-large-scale absorption of the lithium tailings, has a pore structure suitable for plant growth, has water and fertilizer retention capabilities, and has heavy metal and soluble salt leaching amounts in line with Soil Environmental Quality Agricultural Land Soil Pollution Risk Management and Control Standards. The plant growth requirements of scenes such as mine regreening, landscaping, side slope ecological protection and saline-alkali soil improvement can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste resource utilization and ecological restoration, more specifically, to a high-consumption ecological nutrient soil based on geopolymer modified lithium tailings and a preparation method thereof. BACKGROUND

[0002] Lithium tailings are the main solid waste generated in the process of lithium mining and beneficiation. With the rapid development of the new energy industry, the demand for lithium has surged, and the annual discharge of lithium tailings in China has exceeded 10 million tons, with a cumulative accumulation of hundreds of millions of tons. This type of solid waste not only occupies a large amount of land resources, but also contains soluble lithium salts, sulfates, and heavy metals such as lead, cadmium, and arsenic, which can pollute the surrounding soil and water through leaching and weathering processes, leading to soil salinization and vegetation wilting. In addition, the fine structure and loose structure of the tailings particles can easily cause dust and landslides, which have become a key bottleneck restricting the green development of the lithium industry.

[0003] Currently, the resource utilization of lithium tailings is extremely limited, mainly concentrated in the fields of low-value road base fillers and brick-making raw materials, with a utilization rate of less than 15%. Moreover, the pollution risk of soluble salts and heavy metals has not been addressed. In existing technologies for preparing nutrient soil from solid waste, the proportion of solid waste is generally less than 60%, which cannot achieve large-scale consumption of lithium tailings. At the same time, there are problems such as poor stabilization of pollutants, insufficient structural stability of nutrient soil, weak water and fertilizer retention capacity, and difficulty in meeting the plant growth requirements of ecological restoration scenarios.

[0004] Geopolymer, as a new type of inorganic cementitious material, is formed by alkali activation of aluminosilicate raw materials to form a three-dimensional network structure. It not only has high strength and stability, but also can simultaneously immobilize heavy metals and soluble salts through physical encapsulation, chemical adsorption, and chemical bonding. In addition, it can produce good interfacial bonding and synergistic reaction with the aluminosilicate components in lithium tailings. Based on this, the present application innovatively uses 70-90 parts by weight of lithium tailings as the core raw material, combined with geopolymer technology to achieve the stabilization of pollutants and the large-scale consumption of solid waste. At the same time, the nutrient components and preparation process are optimized to prepare an ecologically safe and excellent performance ecological nutrient soil, providing a new technical path for the resource utilization and ecological restoration of lithium tailings. SUMMARY

[0005] In view of the serious pollution and low utilization rate of lithium tailings, as well as the low consumption of existing solid waste nutrient soil and high pollution risk, one of the purposes of the present application is to provide a high-consumption ecological nutrient soil based on geopolymer modified lithium tailings, to achieve the large-scale consumption and harmless disposal of lithium tailings, and at the same time obtain high-quality ecological nutrient soil suitable for ecological restoration scenarios.

[0006] To solve the above technical problems, the present application provides the following technical solutions: A high-consumption ecological nutrient soil based on geopolymer modified lithium tailings, comprising the following raw materials by weight: lithium tailings (lithium mine exploitation / mining by-products) 70-90 parts, geopolymer cementing system 6-15 parts, organic nutrient component 3-10 parts, functional regulator 2-5 parts, water 4-8 parts.

[0007] Preferably, the particle size of the lithium tailings is 100-200 mesh, wherein the SiO2 content is ≥55%, the Al2O3 content is ≥8%, the water content is ≤5%, the pH value is 6.5-9.0, and the leaching amount of heavy metals (lithium, lead, cadmium, arsenic, etc.) and the soluble salt content after pretreatment meet the GB 15618-2018 standard.

[0008] Preferably, the geopolymer cementing system is compounded by an alkali activator and an aluminosilicate precursor at a mass ratio of 1:2.5-1:5; the alkali activator is a mixed system of sodium hydroxide and water glass, wherein the mass ratio of sodium hydroxide to water glass is 1:3-1:6, and the modulus of the water glass is 2.0-2.8; the aluminosilicate precursor is a mixture of one or more of fly ash, slag, and metakaolin, and the active SiO2+Al2O3 content in the aluminosilicate precursor is ≥75%.

[0009] Preferably, the organic nutrient component is a mixture of one or more of decomposed straw, humus soil, biochar, and decomposed livestock and poultry manure, and the organic matter content is ≥45% and the particle size is ≤3mm.

[0010] Preferably, the functional regulator is compounded by a water-retaining agent, slow-release fertilizer, pollutant stabilizer, and pH regulator at a mass ratio of 1:1:1:1-2:1:1:1; the water-retaining agent is a polyacrylamide water-retaining agent; the slow-release fertilizer is a urea-formaldehyde resin coated compound fertilizer; the pollutant stabilizer is humic acid or zeolite powder; and the pH regulator is wood ash or potassium dihydrogen phosphate.

[0011] The core innovation of the present application is to break through the dual bottleneck of consumption and pollution control of traditional solid waste nutrient soil, take 70-90 parts by weight of lithium tailings as the core raw material, and utilize the triple action of the geopolymer cementing system: first, build a stable nutrient soil skeleton through a three-dimensional network structure and optimize the pore structure; second, solidify soluble salts through physical wrapping and chemical adsorption, reducing the risk of soil salinization; third, stabilize heavy metals through chemical bonding, blocking the migration path of pollution; then, combine the nutrient supply function of the organic nutrient component and the performance optimization of the functional regulator, and through scientific proportioning and process control, prepare an ecological nutrient soil that has ultra-large-scale consumption, pollutant co-stabilization, and plant growth adaptability.

[0012] As the core raw material, lithium tailings are rich in SiO2 and Al2O3, which can have a synergistic alkali-activation reaction with the geopolymer cementitious system, ensuring the structural stability of the nutrient soil and maximizing the consumption of solid waste (70-90 parts); the geopolymer cementitious system selects industrial solid waste precursors, further improving the comprehensive utilization efficiency of solid waste and realizing "waste treatment with waste". The organic nutrient component provides organic matter, nitrogen, phosphorus, potassium and other nutrients required for plant growth, while improving soil aggregation; the functional regulator optimizes water retention, slow-release of fertilizer efficiency and pH value, while strengthening the stabilization effect of pollutants, ensuring the ecological safety and scene adaptability of the nutrient soil.

[0013] The second object of the present application is to provide a preparation method of high-consumption ecological nutrient soil based on lithium tailings modified by geopolymer, comprising the following steps: (1) The raw materials are treated by a combined process of "water washing and desalting + chemical stabilization": the lithium tailings are dried to a moisture content of ≤5%, crushed and sieved through a 100-200 mesh sieve, and then washed with water for 30-60 min with a liquid-solid ratio of 2:1. After filtration, the soluble salts are removed by drying. Then, 1-3% of the lithium tailings are added to the mixture as a pollutant stabilizer, and the mixture is stirred uniformly and then left to stand for 24-48 h to reduce the activity of heavy metals. The organic nutrient component is crushed to a particle size of ≤3 mm and reserved for use; (2) Geopolymer cementitious system preparation: mix the alkali activator and the aluminosilicate precursor in proportion, stir uniformly, and then leave to stand for 15-30 min to ensure that the alkali activation activity is fully released, and then reserve for use; (3) Mixing and stirring: first, add the pretreated lithium tailings and the organic nutrient component to the mixer and dry mix for 8-15 min until they are uniformly mixed. Then, add the geopolymer cementitious system and water, and wet mix for 20-30 min until the material is loose and free of lumps, with a stirring speed of 350-500 r / min; (4) Activation and curing: spread the mixed material on the curing site, control the environmental temperature at 22-32℃ and the humidity at 65-85%, and cure for 5-10 days. For the first 3 days, the curing is done in a closed environment, and for the next 7 days, the material is turned over once a day and gradually ventilated to reduce the humidity, ensuring uniform curing and stable structure; (5) Product processing: after curing, the material is crushed and sieved through an 8-10 mesh sieve to remove a small amount of lumps and impurities, and the ecological nutrient soil product is obtained.

[0014] Further, in step (1), the water washing and desalting process is adjusted according to the soluble salt content of the lithium tailings: when the salt content is ≥3%, the water washing and desalting process is repeated 1-2 times to ensure that the soluble salt content of the finished product is ≤0.5%.

[0015] Further, in step (1), the chemical stabilization process is adjusted according to the type of pollutants in the lithium tailings: when the lithium and arsenic content is high, humic acid is preferred; when the lead and cadmium content is high, zeolite powder is preferred.

[0016] Further, 0.5-1.2 parts by weight of biological bacteria are added in the wet mixing process in step (3) to improve the nutrient soil nutrient conversion efficiency and salt tolerance.

[0017] Further, the combination of natural airing and ventilation is adopted in the later curing period of step (4) for 7-10 days to control the moisture content of the finished product at 15-20%, so as to facilitate storage and transportation.

[0018] In the preparation process, the combined pretreatment process of "water washing desalination + chemical stabilization" effectively removes soluble salt and reduces the activity of heavy metals; the geopolymer activation step ensures sufficient alkali activation reaction; and the mixed stirring and gradient curing process controls the structural stability and performance consistency of the nutrient soil, and the overall process is simple and easy to operate, suitable for large-scale production.

[0019] Compared with the prior art, the beneficial effects of the present application are: 1. High solid waste disposal capacity: the proportion of lithium tailings is 70-90 parts by weight, and the single batch disposal capacity is much higher than that of the prior art, which can quickly digest the stock lithium tailings and solve the problem of solid waste accumulation pollution in the mining industry; the geopolymer cementing system selects industrial solid waste precursors, and the comprehensive utilization rate of solid waste is more than 90%; 2. Significant pollution stabilization effect: through the triple synergistic effect of "water washing + geopolymer wrapping + functional regulator solidification", the soluble salt content is ≤0.5%, the heavy metal leaching amount meets the GB 15618-2018 standard, there is no secondary pollution risk, and the ecological safety is high; 3. Strong physicochemical property adaptability: the pore structure formed by the cooperation of geopolymer and lithium tailings has a porosity of 32-48% and a water retention rate of ≥62%, and the pH value is stably in the suitable range of 6.0-7.8, which can meet the growth needs of ecological restoration pioneer plants such as alfalfa, sea buckthorn, alkali bush, and rye grass, and green plants; 4. Low cost and wide application: the raw material is mainly lithium tailings, which is easy to obtain and low in price, and the preparation process is simple, so the cost is only 40-65% of that of traditional ecological restoration soil after large-scale production; it can be widely used in mine re-greening, slope ecological protection, landscaping, saline-alkali land improvement and other scenes, and has significant environmental, economic and social benefits. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0021] The test materials and reagents used in the following examples, and the like, can be obtained commercially unless otherwise specified, and the specific techniques or conditions not noted in the examples can be performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Example

[0022] The present example provides a high-consumption ecological nutrient soil based on geopolymer modified lithium tailings.

[0023] 1. Raw material ratio (weight parts): lithium tailings 70 parts (150 mesh, SiO2 content 60%, Al2O3 content 10%, water content 4%, pH value 8.2), geopolymer cementitious system 15 parts (alkali activator: sodium hydroxide + water glass = 1:4, modulus 2.2; precursor: fly ash + slag = 1:1, active SiO2 + Al2O3 content 78%), organic nutrient component 10 parts (matured straw + biochar = 1:1, organic matter content 48%), functional regulator 3 parts (water retention agent + slow-release fertilizer + humic acid + wood ash = 1:1:1:1), water 6 parts; 2. Preparation steps: (1) The lithium tailings were dried to a water content of 4%, crushed to pass through a 150 mesh sieve, washed and stirred with water at a liquid to solid ratio of 2:1 for 40 min, filtered and dried, then 1.5% humic acid was added, stirred uniformly, and left to stand for 36 h; the matured straw and biochar were crushed to a particle size of ≤2 mm; (2) The mixed alkali activator and precursor were activated for 20 min; (3) The tailings and organic nutrient component were dry mixed for 10 min, then the geopolymer cementitious system, water and 1.0 part of bio-inoculant were added, and wet mixing was performed at 400 r / min for 25 min; (4) Curing at 28°C and 75% humidity for 7 d, sealed for the first 3 d, and then turned over once a day and ventilated for the next 4 d; (5) Crushed to pass through a 10 mesh sieve to obtain the finished product.

[0024] 3. Performance testing: The ecological nutrient soil prepared in the present example has a porosity of 42%, a water retention rate of 68%, a pH value of 7.2, an organic matter content of 8.5%, a soluble salt content of 0.3%, a heavy metal (lithium, lead, arsenic) leaching amount lower than the detection limit, and a germination rate of 96% for planting alfalfa, with the root length increased by 28% compared to ordinary green soil. Example

[0025] The present example provides a high-consumption ecological nutrient soil based on geopolymer modified lithium tailings.

[0026] 1. Raw material ratio (weight parts): lithium tailings 80 parts (180 mesh, SiO2 content 58%, Al2O3 content 9%, water content 3%, pH value 8.5), geopolymer cementitious system 10 parts (alkali activator: sodium hydroxide + water glass = 1:5, modulus 2.5; precursor: metakaolin + fly ash = 1:2, active SiO2+Al2O3 content 82%), organic nutrient component 6 parts (humus + livestock and poultry manure compost = 2:1, organic matter content 46%), functional regulator 4 parts (water-retaining agent + slow-release fertilizer + zeolite powder + potassium dihydrogen phosphate = 2:1:1:1), water 5 parts; 2. Preparation steps: same as example 1, water washing and stirring for 50 min (salt content 3.2%, repeated water washing 1 time), 2% zeolite powder is added for pretreatment, and the curing time is 8d; 3. Performance detection: through detection, the pore porosity of the ecological nutrient soil prepared in this example is 40%, the water retention rate is 70%, the pH value is 7.5, the organic matter content is 7.2%, the soluble salt content is 0.25%, the heavy metal leaching amount meets the standard, and the survival rate is 94% when used for planting sea buckthorn in mine greening, and the growth cycle is shortened by 12d compared with ordinary greening soil. Example

[0027] This example provides a high-consumption ecological nutrient soil based on lithium tailings modified by geopolymer.

[0028] 1. Raw material ratio (weight parts): lithium tailings 90 parts (200 mesh, SiO2 content 55%, Al2O3 content 8%, water content 5%, pH value 8.8), geopolymer cementitious system 6 parts (alkali activator: sodium hydroxide + water glass = 1:6, modulus 2.8; precursor: slag + metakaolin = 3:1, active SiO2+Al2O3 content 76%), organic nutrient component 3 parts (biochar + composted straw = 1:1, organic matter content 45%), functional regulator 5 parts (water-retaining agent + slow-release fertilizer + zeolite powder + wood ash = 2:1:1:1), water 8 parts; 2. Preparation steps: same as example 1, water washing and stirring for 60 min (salt content 4.0%, repeated water washing 2 times), 3% zeolite powder is added for pretreatment, and the curing time is 10d; 3. Performance detection: through detection, the pore porosity of the ecological nutrient soil prepared in this example is 35%, the water retention rate is 62%, the pH value is 7.8, the organic matter content is 6.1%, the soluble salt content is 0.4%, the heavy metal leaching amount meets the standard, and the coverage rate is 92% when used for planting alkali bush in saline-alkali land improvement, and the salt resistance is improved by 35% compared with ordinary soil.

[0029] The core innovation of the present application is to break through the dual bottleneck of traditional solid waste nutrient soil in terms of consumption capacity and pollution control, using 70-90 parts by weight of lithium tailings as the core raw material, and using the triple action of the geopolymer gel system: first, constructing a stable nutrient soil skeleton through a three-dimensional network structure and optimizing the pore structure; second, solidifying soluble salt through physical wrapping and chemical adsorption, reducing the risk of soil salinization; third, stabilizing heavy metals through chemical bonding, blocking the pollution migration path; combined with the nutrient supply function of the organic nutrient component and the performance optimization of the functional regulator, through scientific proportioning and process control, an ecological nutrient soil with ultra-large scale consumption, pollution co-stabilization and plant growth adaptability is prepared.

[0030] The lithium tailings, as the core raw material, are rich in SiO2 and Al2O3, which can have a synergistic alkali activation reaction with the geopolymer gel system, ensuring the stability of the nutrient soil structure and maximizing the solid waste consumption capacity (70-90 parts); the geopolymer gel system selects industrial solid waste precursors, further improving the comprehensive utilization efficiency of solid waste and realizing "waste treatment with waste". The organic nutrient component provides organic matter, nitrogen, phosphorus, potassium and other nutrients required for plant growth, and improves soil aggregation; the functional regulator optimizes the water retention, fertilizer release and pH value, and at the same time, strengthens the pollution stabilization effect, ensuring the ecological safety and scene adaptability of the nutrient soil.

[0031] During the preparation process, the "water washing desalination + chemical stabilization" combined pretreatment process is used to effectively remove soluble salt and reduce heavy metal activity; the geopolymer activation step ensures sufficient alkali activation reaction; the mixing, stirring and gradient curing process control ensures the structural stability and performance consistency of the nutrient soil, and the overall process is simple and easy to operate, suitable for large-scale production.

[0032] The present application discloses preferred embodiments, but is not limited thereto, and those skilled in the art can easily understand the spirit of the present application and make different inferences and changes based on the above embodiments, as long as they do not deviate from the spirit of the present application, and are within the protection scope of the present application.

Claims

1. A high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings, characterized in that, The raw materials include the following parts by weight: 70-90 parts lithium tailings, 6-15 parts geological polymer cementing system, 3-10 parts organic nutrient components, 2-5 parts functional regulator, and 4-8 parts water.

2. The high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 1, characterized in that: The lithium tailings have a particle size of 100-200 mesh, with SiO2 content ≥55%, Al2O3 content ≥8%, moisture content ≤5%, and pH value of 6.5-9.

0.

3. The high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 1, characterized in that: The geopolymer gelling system is composed of an alkali activator and an aluminosilicate precursor in a mass ratio of 1:2.5-1:

5. The alkaline activator is a mixture of sodium hydroxide and water glass, wherein the mass ratio of sodium hydroxide to water glass is 1:3-1:6, and the modulus of water glass is 2.0-2.

8. The aluminosilicate precursor is one or more of fly ash, slag, and metakaolin, and the active SiO2+Al2O3 content in the aluminosilicate precursor is ≥75%.

4. The high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 1, characterized in that: The organic nutrient components are one or more of the following: decomposed straw, humus, biochar, and decomposed livestock and poultry manure, with an organic matter content ≥45% and a particle size ≤3mm.

5. The high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 1, characterized in that: The functional regulator is a compound of water-retaining agent, slow-release fertilizer, pollutant stabilizer and pH adjuster in a mass ratio of 1:1:1:1-2:1:1:1 by mass. The water-retaining agent is a polyacrylamide-based water-retaining agent; The slow-release fertilizer is a urea-formaldehyde resin coated compound fertilizer; The pollutant stabilizer is humic acid or zeolite powder. The pH adjuster is wood ash or potassium dihydrogen phosphate.

6. A method for preparing high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) The raw materials are treated by a combination of "water washing and desalination + chemical stabilization": the lithium tailings are dried to a moisture content of ≤5%, crushed and passed through a 100-200 mesh sieve, and washed with water and stirred for 30-60 minutes according to a liquid-solid ratio of 2:

1. After filtration, the soluble salts are removed by drying. Then, 1-3% of the mass of the lithium tailings as a pollutant stabilizer is added, stirred evenly and left to stand for 24-48 hours to reduce the activity of heavy metals. The organic nutrient components are crushed to a particle size of ≤3mm and set aside. (2) Preparation of geopolymer gelation system: Mix alkali activator and aluminosilicate precursor in proportion, stir evenly and let stand for 15-30 min to ensure that the alkali activation activity is fully released, and set aside for later use; (3) Mixing and stirring: First, add the pretreated lithium tailings and organic nutrients to the mixer and dry mix for 8-15 minutes until the mixture is uniform; then add the geopolymer gelling system and water and wet mix for 20-30 minutes until the material is loose and free of lumps. The stirring speed is controlled at 350-500 r / min. (4) Stimulation and curing: Spread the mixture evenly on the curing site, control the ambient temperature at 22-32℃ and humidity at 65-85%, and cure for 5-10 days; keep the site sealed for the first 3 days, and turn it over once a day from the 4th to the 10th day and gradually ventilate to reduce humidity, so as to ensure uniform curing and structural stability. (5) Finished product processing: After the curing is completed, the material is crushed and passed through an 8-10 mesh sieve to remove a small amount of lumpy impurities, and then the finished ecological nutrient soil is obtained.

7. The method for preparing high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 6, characterized in that, In step (1), the water washing and desalination process is adjusted according to the soluble salt content of lithium tailings: when the salt content is ≥3%, the water washing is repeated 1-2 times to ensure that the soluble salt content of the finished product is ≤0.5%.

8. The method for preparing high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 6, characterized in that: In step (1), the chemical stabilization process is adjusted according to the type of pollutants in lithium tailings: humic acid is preferred when the lithium and arsenic content is high, and zeolite powder is preferred when the lead and cadmium content is high.

9. The method for preparing high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 6, characterized in that, In step (3), 0.5-1.2 parts by weight of biological agent are added during the wet mixing process to improve the nutrient conversion efficiency and salt tolerance of the nutrient soil.

10. The method for preparing high-capacity ecological nutrient soil based on geopolymer-modified lithium tailings according to claim 6, characterized in that: In step (4), during the later stages of curing (7-10 days), natural air drying and ventilation are combined to control the moisture content of the finished product at 15-20%, which facilitates storage and transportation.