Lithium slag lightweight aggregate as well as preparation method and application thereof

Abstract

The invention relates to a lithium slag lightweight aggregate as well as a preparation method and application thereof. The lithium slag lightweight aggregate is prepared from the following raw materials: lithium slag, silica fume, fly ash, a phosphate curing agent and a fluxing agent. According to the lithium slag lightweight aggregate, the phosphate curing agent is added, thallium in the lithium slag is promoted to form insoluble minerals, the thallium element in the lepidolite slag is subjected to harmless curing treatment, leaching of toxic substances in the lithium slag is reduced, the pollution problem is solved, and meanwhile the problem that a large amount of lithium slag occupies a stacking site in the industrial production process is solved.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology of lithium mica smelting slag, and in particular to a lithium slag lightweight aggregate, its preparation method and uses. Background Technology

[0002] Lithium methane slag is a major hazardous solid waste in the lithium battery industry. Traditional disposal methods (landfill or high-temperature sintering) result in excessive thallium leaching. Furthermore, lithium slag contains large amounts of elements such as silicon, aluminum, and calcium, and landfilling would lead to significant resource waste. Therefore, how to harmlessly and recycle lithium slag is of great significance to the healthy development of the lithium battery industry.

[0003] Traditional lightweight aggregates are mainly composed of SiO2, Al2O3, Fe2O3, and CaO, and are typically made from natural minerals such as clay, shale, fly ash, coal mine overburden, loess, or sludge, through high-temperature firing with the addition of expanding materials. However, the extraction of these traditional raw materials easily leads to soil erosion and ecological damage, making the search for sustainable alternative raw materials an urgent need for the industry.

[0004] Thiol-containing lithium slag produced in the lithium battery industry has the potential to serve as a substitute for lightweight aggregates due to its high content of SiO2 and Al2O3. However, its resource utilization faces severe challenges. Currently, the large-scale stockpiling of lithium slag not only occupies land, but the thallium in it may also migrate and spread, polluting the surrounding soil and water bodies and causing serious environmental risks.

[0005] Although there has been some research on the application of lithium slag in cement, foam ceramics and other fields, 85% of the thallium element is released in the form of flue gas during the traditional preparation of lightweight aggregates. The resource utilization process and the final products formed by lithium slag containing thallium involve the release and re-pollution of thallium ions.

[0006] Therefore, how to effectively solidify thallium and prevent its re-release during sintering or use, thus preventing further pollution, is a technical problem that urgently needs to be solved in the harmless treatment of thallium-containing lithium slag solid waste and the resource utilization of lithium slag. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a lithium slag lightweight aggregate, its preparation method, and its applications. The lithium slag lightweight aggregate of the present invention has a high lithium slag content and good thallium fixation effect, achieving high-content resource utilization and harmless treatment of lithium slag. The bulk density of the lightweight aggregate is 700 kg / m³. 3 -1200kg / m 3 The cylinder compressive strength is 12MPa-18MPa.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a lithium slag lightweight aggregate, wherein the raw materials for preparing the lithium slag lightweight aggregate include lithium slag, silica fume, fly ash, phosphate curing agent and flux.

[0010] The lithium slag lightweight aggregate provided by this invention promotes the formation of insoluble minerals from thallium in the lithium slag by adding a phosphate solidifying agent. This solidifies the thallium in the lepidolite slag, rendering it harmless and reducing the leaching of toxic substances from the lithium slag, thus solving the pollution problem. It also addresses the issue of large amounts of lithium slag occupying storage space during industrial production. The lightweight aggregate has a bulk density of 700 kg / m³. 3 -1200kg / m 3 The compressive strength of the cylinder is 12MPa-18MPa. This invention achieves matrix densification by introducing active micro-aggregates such as silica fume and utilizes phosphates to synergistically enhance the cementitious structure, constructing high-strength, denser pore walls. This results in an increase in compressive strength within an acceptable density range. Compared to existing porous lightweight aggregate technologies, this invention offers higher strength and achieves a good balance between high strength and lightweight, making it more suitable for structural engineering applications.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0012] Preferably, based on the total mass of the raw materials for preparing the lithium slag lightweight aggregate being 100 wt.%, the lithium slag accounts for 50 wt.% to 70 wt.%, for example, it can be 50 wt.%, 52 wt.%, 55 wt.%, 58 wt.%, 60 wt.%, 62 wt.%, 65 wt.%, 68 wt.%, or 70 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] Preferably, the silica fume accounts for 5wt.%-10wt.%, for example, it can be 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.% or 10wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, the fly ash accounts for 10wt.%-20wt.%, for example, it can be 10wt.%, 11wt.%, 12wt.%, 13wt.%, 14wt.%, 15wt.%, 16wt.%, 17wt.%, 18wt.%, 18wt.% or 20wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the phosphate curing agent accounts for 1wt.%-5wt.%, for example, it can be 1wt.%, 2wt.%, 3wt.%, 4wt.% or 5wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] This invention further controls the addition amount of phosphate curing agent to 1wt.%-5wt.%, as the amount of phosphate curing agent affects the reaction path and microstructure formation of the gelation system. If the addition amount is too high, the excess phosphate ions will competitively consume the active aluminum source in the system and may reduce the alkalinity of the reaction system, thereby inhibiting the normal formation and development of the aluminosilicate geopolymer network. At the same time, the excessively fast reaction rate and excessive crystalline phase formation will introduce internal stress, destroy the uniformity and integrity of the matrix structure, and lead to an increase in micro-defects, which is macroscopically manifested as a deterioration in cylinder compressive strength. If the addition amount is too low, it is insufficient to form a continuous and sufficient amount of aluminum phosphate-based bonding bridges, which cannot effectively bind the raw material particles such as lithium slag and fly ash into a whole, resulting in weak interparticle interface bonding, loose and porous microstructure, and the matrix failing to achieve the expected structural strength.

[0017] Preferably, the flux accounts for 1 wt.% to 5 wt.%, for example, it can be 1 wt.%, 2 wt.%, 2.5 wt.%, 3 wt.%, 3.5 wt.%, 4 wt.% or 5 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the lithium slag includes lepidolite slag.

[0019] Preferably, the phosphate curing agent comprises any one or a combination of at least two of sodium dihydrogen phosphate, calcium dihydrogen phosphate, trisodium phosphate, calcium phosphate, or disodium hydrogen phosphate. Typical but non-limiting combinations include combinations of sodium dihydrogen phosphate and calcium dihydrogen phosphate, combinations of calcium dihydrogen phosphate and trisodium phosphate, combinations of calcium phosphate and disodium hydrogen phosphate, combinations of sodium dihydrogen phosphate, calcium dihydrogen phosphate, and trisodium phosphate, combinations of trisodium phosphate, calcium phosphate, and disodium hydrogen phosphate, or combinations of sodium dihydrogen phosphate, trisodium phosphate, and disodium hydrogen phosphate.

[0020] This invention utilizes the preferred phosphate as a curing agent, where the phosphate ions can react with the dissolved thallium ions. Tl3PO4 promotes the formation of insoluble thallium phosphate precipitates with low solubility and stable chemical properties in lithium slag, thereby solidifying the thallium element in lithium mica slag to render it harmless and reducing the leaching of toxic substances from lithium slag, thus solving the pollution problem.

[0021] In addition, compared with the conventional use of fluorinated minerals to solidify thallium in the prior art, the present invention has the following advantages: by forming a thermodynamically stable thallium phosphate chemical precipitate, a fundamental transformation from physical encapsulation to chemical bonding is achieved. This not only has better wide pH stability and environmental safety, avoiding the risk of fluorine pollution, but also significantly improves the material strength while achieving efficient thallium solidification by constructing a "phosphate-geopolymer" synergistic gelation structure.

[0022] Preferably, the flux comprises sodium tetraborate.

[0023] In this invention, the role of the flux is to lower the melting point.

[0024] In a second aspect, the present invention provides a method for preparing lithium slag lightweight aggregate as described in the first aspect, the method comprising the following steps:

[0025] (1) Mix lithium slag, silica fume, fly ash, flux, and phosphate curing agent to obtain mixed raw materials;

[0026] (2) The mixed raw materials are granulated, dried and sintered to obtain the lithium slag lightweight aggregate.

[0027] This invention achieves thallium solidification by reacting a phosphate curing agent with thallium in lithium slag. The thallium reacts with the phosphate and enters the hydroxyphosphate lattice and the interatomic spaces of the molecules. The addition of a flux reduces the temperature required for subsequent sintering. Granulation is used to transform the designed powder composition into a precursor that is suitable for high-quality, controllable sintering in terms of both physical morphology and chemical composition. The preparation method of this invention is simple and suitable for large-scale promotion.

[0028] Preferably, the mixing method in step (1) includes ball milling.

[0029] Preferably, the rotational speed of the ball mill is 800rpm-1200rpm, for example, it can be 800rpm, 850rpm, 900rpm, 950rpm, 1000rpm, 1050rpm, 1100rpm, 1150rpm or 1200rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] Preferably, the specific mixing method includes first mixing lithium slag, silica fume and fly ash and ball milling for 30 min-60 min, and then adding flux and phosphate curing agent and continuing ball milling for 20 min-40 min.

[0031] Preferably, the drying temperature in step (2) is 100℃-120℃, for example, it can be 100℃, 105℃, 110℃, 115℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the drying time is 0.5h-2h, for example, it can be 0.5h, 1h, 1.5h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the granulation is carried out in a disc granulator.

[0034] Preferably, the average particle size obtained by granulation is 6mm-18mm, for example, it can be 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm or 18mm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0035] Preferably, the sintering includes a first-stage sintering and a second-stage sintering.

[0036] Preferably, the heating rate of the sintering is 5℃ / min-8℃ / min, for example, it can be 5℃ / min, 6℃ / min, 7℃ / min or 8℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the sintering temperature in the first stage is 400℃-500℃, for example, it can be 400℃, 420℃, 450℃, 480℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, the sintering time of the first stage is 50 min to 70 min, for example, it can be 50 min, 55 min, 60 min, 65 min or 70 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the sintering temperature in the second stage is 1000℃-1200℃, for example, it can be 1000℃, 1050℃, 1100℃, 1150℃ or 1200℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] This invention further optimizes the second-stage sintering temperature to be 1000℃-1200℃. The second-stage sintering temperature affects the amount of liquid phase generated, the viscosity, and the formation of the final material's microstructure during the sintering process. If the second-stage sintering temperature is too high, it will lead to an excessive amount of liquid phase and excessively low viscosity, resulting in gas escape, coarsening of pores, and thinning of pore walls, which in turn causes a significant decrease in material strength and the risk of overheating and deformation. If the second-stage sintering temperature is too low, it will result in insufficient liquid phase generation, inadequate bonding between particles, underdeveloped pore structure, and defects in the pore walls, thereby leading to lower material strength and insufficient thallium consolidation effect.

[0041] Preferably, the sintering time in the second stage is 15 min to 45 min, for example, it can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min or 45 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0043] (1) Lithium slag, silica fume and fly ash are ball-milled at a speed of 800 rpm-1200 rpm for 30 min-60 min according to the mass ratio. Then, flux and phosphate curing agent are added, and ball milling is continued at a speed of 800 rpm-1200 rpm for 20 min-40 min to obtain mixed raw materials.

[0044] (2) The mixed raw materials are placed in a disc granulator for granulation to obtain pellets with an average particle size of 6mm-18mm. The pellets are dried at 100℃-120℃ for 0.5h-2h. The pellets are then sintered at 400℃-500℃ for 50min-70min in the first stage. After that, the temperature is increased to 1000℃-1200℃ at a heating rate of 5℃ / min-8℃ / min. The second stage of sintering is carried out for 15min-45min to obtain the lithium slag light aggregate.

[0045] Thirdly, the present invention provides an application of the lithium slag lightweight aggregate as described in the first aspect, wherein the lithium slag lightweight aggregate is used in the construction field.

[0046] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] (1) The lithium slag lightweight aggregate provided by this invention promotes the formation of insoluble minerals from thallium in lithium slag by adding a phosphate solidifying agent, thereby solidifying the thallium element in the lithium mica slag to render it harmless. This reduces the leaching of toxic substances from the lithium slag, solving the pollution problem, and also addresses the issue of large amounts of lithium slag occupying storage space during industrial production. The bulk density of the lightweight aggregate is 700 kg / m³. 3 -1200kg / m 3 The cylinder compressive strength is 12MPa-18MPa.

[0049] (2) The present invention achieves thallium solidification by reacting the phosphate solidifying agent with thallium in lithium slag, and the thallium element reacts with the phosphate and enters the hydroxyphosphate lattice and molecular atomic gaps; the addition of flux reduces the temperature required for subsequent sintering; granulation is to transform the designed powder composition into a precursor that is suitable for high-quality and controllable sintering in terms of physical morphology and chemical composition; the preparation method of the present invention is simple and suitable for large-scale promotion. Detailed Implementation

[0050] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0051] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0052] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0053] The silica fume and fly ash used in the embodiments of this invention are both products of Henan Yixiang New Materials Co., Ltd.

[0054] The lithium mica residue used in this embodiment of the invention is all from Fengxin County, Jiangxi Province. The chemical composition of the lithium mica residue is shown in Table 1. The moisture content of the lithium mica residue is 15%-20%.

[0055] Table 1

[0056]

[0057] Example 1

[0058] This embodiment provides a lithium slag lightweight aggregate, the raw materials for which the lithium slag lightweight aggregate is prepared include 65 wt.% lithium slag, 8 wt.% silica fume, 18 wt.% fly ash, 4 wt.% sodium dihydrogen phosphate and 5 wt.% sodium tetraborate;

[0059] The method for preparing lithium slag lightweight aggregate provided in this embodiment includes the following steps:

[0060] (1) Lithium mica slag, silica fume and fly ash were ball-milled at 1000 rpm for 45 min according to the above mass ratio. Then sodium tetraborate and sodium dihydrogen phosphate were added and ball-milled for another 25 min at 1000 rpm to obtain the mixed raw materials.

[0061] (2) The mixed raw materials are placed in a disc granulator for granulation. The disc granulator rotates at 25 r / min and tilts at 60° to obtain pellets with an average particle size of 11 mm. The pellets are dried at 110°C for 1.5 h and then sintered at 450°C for 60 min in the first stage. After that, the temperature is increased to 1100°C at a heating rate of 5°C / min for 30 min in the second stage to obtain the lithium slag light aggregate.

[0062] Example 2

[0063] This embodiment provides a lithium slag lightweight aggregate, the raw materials for which include 62 wt.% lithium slag, 9 wt.% silica fume, 19 wt.% fly ash, 5 wt.% calcium dihydrogen phosphate and 5 wt.% sodium tetraborate.

[0064] The method for preparing lithium slag lightweight aggregate provided in this embodiment includes the following steps:

[0065] (1) Lithium mica slag, silica fume and fly ash were ball-milled at 800 rpm for 60 min according to the above mass ratio. Then sodium tetraborate and calcium dihydrogen phosphate were added, and the mixture was ball-milled at 800 rpm for another 40 min to obtain the mixed raw materials.

[0066] (2) The mixed raw materials are placed in a disc granulator for granulation. The disc granulator rotates at 25 r / min and tilts at 60° to obtain pellets with an average particle size of 8 mm. The pellets are dried at 100°C for 2 h and then sintered at 400°C for 70 min in the first stage. After that, the temperature is increased to 1000°C at a heating rate of 6°C / min and sintered in the second stage for 15 min to obtain the lithium slag light aggregate.

[0067] Example 3

[0068] This embodiment provides a lithium slag lightweight aggregate, the raw materials for which the lithium slag lightweight aggregate is prepared include 68 wt.% lithium slag, 6 wt.% silica fume, 18 wt.% fly ash, 4 wt.% calcium phosphate and 4 wt.% sodium tetraborate;

[0069] The method for preparing lithium slag lightweight aggregate provided in this embodiment includes the following steps:

[0070] (1) Lithium mica slag, silica fume and fly ash were ball-milled at 1200 rpm for 30 min according to the above mass ratio. Then sodium tetraborate and calcium phosphate were added and ball-milled for another 20 min at 1200 rpm to obtain the mixed raw materials.

[0071] (2) The mixed raw materials are placed in a disc granulator for granulation. The disc granulator rotates at 25 r / min and tilts at 60° to obtain pellets with an average particle size of 18 mm. The pellets are dried at 120°C for 0.5 h and then sintered at 500°C for 50 min in the first stage. After that, the temperature is increased to 1200°C at a heating rate of 8°C / min and sintered in the second stage for 15 min to obtain the lithium slag light aggregate.

[0072] Example 4

[0073] This embodiment provides a lithium slag lightweight aggregate. The only difference from Embodiment 1 is that, in preparing this lithium slag lightweight aggregate, the mass fraction of sodium dihydrogen phosphate curing agent in step (1) is 0.5 wt.%, and the excess mass fraction is distributed to lithium mica slag, silica fume, fly ash and curing agent according to the mass ratio. The other preparation steps remain unchanged.

[0074] Example 5

[0075] This embodiment provides a lithium slag lightweight aggregate. The only difference from Embodiment 1 is that, in preparing this lithium slag lightweight aggregate, the mass fraction of sodium dihydrogen phosphate curing agent in step (1) is 10 wt.%, and the excess mass fraction is reduced from lithium mica slag, silica fume, fly ash and curing agent according to the mass ratio. The other preparation steps remain unchanged.

[0076] Example 6

[0077] This embodiment provides a lithium slag lightweight aggregate. The only difference from Embodiment 1 is that the sintering temperature in the second stage of step (2) is 930°C when preparing the lithium slag lightweight aggregate.

[0078] Example 7

[0079] This embodiment provides a lithium slag lightweight aggregate. The only difference from Embodiment 1 is that the sintering temperature in the second stage of step (2) is 1300℃ when preparing the lithium slag lightweight aggregate.

[0080] Comparative Example 1

[0081] This comparative example provides a lithium slag lightweight aggregate. The only difference from Example 1 is that, in preparing this lithium slag lightweight aggregate, phosphate curing agent is not added in step (1). The excess mass fraction is distributed to lithium mica slag, silica fume, fly ash and curing agent according to the mass ratio. The other preparation steps remain unchanged.

[0082] Comparative Example 2

[0083] This comparative example provides a lithium slag lightweight aggregate. The only difference from Example 1 is that, in preparing this lithium slag lightweight aggregate, step (1) replaces the phosphate curing agent with an equal mass fraction of calcium fluoride, while the other preparation steps remain unchanged.

[0084] Testing: The lithium slag lightweight aggregates prepared in the examples and comparative examples were tested:

[0085] (1) Thallium leaching concentration: According to the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid Nitric Acid Method" (HJ / T 299-2007) or the corresponding standard, the sample was leached under specific acidic conditions (such as pH=3.21), and then the thallium content in the leachate was determined by precision instruments such as inductively coupled plasma mass spectrometry (ICP-MS).

[0086] (2) Bulk density of lithium slag lightweight aggregate: It is calculated by measuring the mass of the dry aggregate after filling a container of known volume in a natural stacking state, in accordance with the "Lightweight Aggregates and Their Test Methods" (GB / T 17431.2) or the corresponding standard.

[0087] (3) Compressive strength of lithium slag lightweight aggregate: According to "Lightweight aggregate and its test methods" (GB / T 17431.2) or the corresponding standard, the single-stage granular aggregate is loaded into the pressure cylinder and the ultimate pressure value when it is pressed into a depth of 20mm is determined by a press.

[0088] The test results are shown in Table 2 below.

[0089] Table 2

[0090]

[0091] The test results show that:

[0092] (1) As can be seen from Examples 1-3, this invention promotes the formation of insoluble minerals from thallium in lithium slag by adding a phosphate solidifying agent, thereby solidifying the thallium element in the lithium mica slag to render it harmless. This reduces the leaching of toxic substances from the lithium slag, solving the pollution problem and also addressing the issue of large amounts of lithium slag occupying storage space during industrial production. The bulk density of the lightweight aggregate is 700 kg / m³. 3 -1200kg / m 3The cylinder compressive strength is 12MPa-18MPa.

[0093] (2) By comparing Example 1 with Examples 4-5, it can be seen that by further controlling the amount of phosphate curing agent added to 1wt.%-5wt.%, the amount of phosphate curing agent added affects the reaction path and microstructure formation of the gelation system. If the amount added is too much, the excess phosphate ions will competitively consume the active aluminum source in the system and may reduce the alkalinity of the reaction system, thereby inhibiting the normal formation and development of the aluminosilicate geopolymer network. At the same time, the excessively fast reaction rate and the excessive crystal phase formation will introduce internal stress, destroy the uniformity and integrity of the matrix structure, and lead to an increase in micro defects, which is macroscopically manifested as the deterioration of the cylinder compressive strength. If the amount added is too little, it is not enough to form a continuous and sufficient amount of aluminum phosphate-based bonding bridge, and it is not possible to effectively bond the raw material particles such as lithium slag and fly ash into a whole, resulting in weak interfacial bonding between particles, loose and porous microstructure, and the matrix cannot achieve the expected structural strength.

[0094] (3) By comparing Example 1 with Examples 6-7, it can be seen that the present invention further controls the sintering temperature of the second stage to 1000℃-1200℃. The sintering temperature of the second stage affects the amount of liquid phase generated, viscosity and the formation of the final material microstructure during the sintering process. If the sintering temperature of the second stage is too high, it will lead to excessive liquid phase and low viscosity, resulting in gas escape, coarsening of pores and thinning of pore walls, which will cause a significant decrease in material strength and the risk of overheating and deformation. If the sintering temperature of the second stage is too low, it will result in insufficient liquid phase generation, insufficient bonding between particles, underdeveloped pore structure and defects in pore walls, which will lead to low material strength and failure to fully achieve the thallium solidification effect.

[0095] (4) As can be seen from Example 1 and Comparative Examples 1-2, the present invention promotes the formation of insoluble minerals of thallium in lithium slag by adding phosphate solidifying agent, so that the thallium element in lithium mica slag is solidified in a harmless manner, reducing the leaching of toxic substances in lithium slag and solving the pollution problem. At the same time, it solves the problem of a large amount of lithium slag occupying the storage space during industrial production. However, when phosphate solidifying agent is not added or other substances such as fluoride are added, it is impossible to achieve the technical effect of thallium ion leaching concentration being lower than 0.1 μg / L.

[0096] In summary, this invention promotes the formation of insoluble minerals from thallium in lithium slag by adding a phosphate solidifying agent, thereby solidifying the thallium in lithium mica slag to render it harmless. This reduces the leaching of toxic substances from the lithium slag, thus solving the pollution problem. At the same time, it also solves the problem of large amounts of lithium slag occupying storage space during industrial production.

[0097] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A lightweight lithium slag aggregate, characterized in that, The raw materials for preparing the lithium slag lightweight aggregate include lithium slag, silica fume, fly ash, phosphate curing agent, and flux.

2. The lithium slag lightweight aggregate according to claim 1, characterized in that, Based on a total mass of 100 wt.% of the raw materials used in the preparation of the lithium slag lightweight aggregate, the lithium slag accounts for 50 wt.%-70 wt.%. Preferably, the silica fume accounts for 5 wt.%-10 wt.%; Preferably, the fly ash accounts for 10 wt.%-20 wt.%; Preferably, the phosphate curing agent accounts for 1 wt.%-5 wt.%; Preferably, the flux accounts for 1 wt.%-5 wt.%.

3. The lithium slag lightweight aggregate according to claim 1 or 2, characterized in that, The lithium slag includes lepidolite slag; Preferably, the phosphate curing agent includes any one or a combination of at least two of sodium dihydrogen phosphate, calcium dihydrogen phosphate, trisodium phosphate, calcium phosphate, or disodium hydrogen phosphate; Preferably, the flux comprises sodium tetraborate.

4. A method for preparing lithium slag lightweight aggregate as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Mix lithium slag, silica fume, fly ash, flux, and phosphate curing agent to obtain mixed raw materials; (2) The mixed raw materials are granulated, dried and sintered to obtain the lithium slag lightweight aggregate.

5. The preparation method according to claim 4, characterized in that, The mixing method in step (1) includes ball milling; Preferably, the rotational speed of the ball mill is 800 rpm to 1200 rpm; Preferably, the specific mixing method includes first ball milling lithium slag, silica fume and fly ash for 30 min-60 min, and then adding flux and phosphate curing agent to continue ball milling for 20 min-40 min.

6. The preparation method according to claim 4 or 5, characterized in that, The granulation is carried out in a disc granulator; Preferably, the average particle size obtained by granulation is 6mm-18mm.

7. The preparation method according to any one of claims 4-6, characterized in that, The drying temperature in step (2) is 100℃-120℃; Preferably, the drying time is 0.5h-2h.

8. The preparation method according to any one of claims 4-7, characterized in that, The sintering includes a first-stage sintering and a second-stage sintering; Preferably, the sintering heating rate is 5℃ / min-8℃ / min; Preferably, the sintering temperature in the first stage is 400℃-500℃; Preferably, the sintering time in the first stage is 50-70 minutes; Preferably, the sintering temperature in the second stage is 1000℃-1200℃; Preferably, the sintering time in the second stage is 15 min to 45 min.

9. The preparation method according to any one of claims 4-8, characterized in that, The preparation method includes the following steps: (1) Lithium slag, silica fume and fly ash are ball-milled at a speed of 800 rpm-1200 rpm for 30 min-60 min according to the mass ratio. Then, flux and phosphate curing agent are added, and ball milling is continued at a speed of 800 rpm-1200 rpm for 20 min-40 min to obtain mixed raw materials. (2) The mixed raw materials are placed in a disc granulator for granulation to obtain pellets with an average particle size of 6mm-18mm. The pellets are dried at 100℃-120℃ for 0.5h-2h. The pellets are then sintered at 400℃-500℃ for 50min-70min in the first stage. After that, the temperature is increased to 1000℃-1200℃ at a heating rate of 5℃ / min-8℃ / min. The second stage of sintering is carried out for 15min-45min to obtain the lithium slag light aggregate.

10. The use of the lithium slag lightweight aggregate as described in any one of claims 1-3, characterized in that, The lithium slag lightweight aggregate is used in the construction industry.

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