Porous ceramic material based on lithium slag and high-carbon fly ash and preparation method thereof

Abstract

The invention discloses a porous ceramic material based on lithium slag and high-carbon fly ash and a preparation method thereof.The preparation method comprises the following steps that spodumene lithium extraction slag is washed and dried, and pretreated spodumene lithium extraction slag is obtained; carrying out dry mixing on the pretreated spodumene lithium extraction slag, salt chemical industry high-carbon low-activity fly ash and a binder to obtain a dry mixture; adding water into the dry mixture, and uniformly mixing to obtain plastic ceramic slurry; carrying out pressure forming on the plastic ceramic slurry in a mold to obtain a ceramic green body; and sintering the green body in an air atmosphere, and then cooling to obtain the porous ceramic material, the final temperature of sintering ranges from 1200 DEG C to 1300 DEG C; the content of unburned carbon in the pre-spodumene lithium extraction slag is 1-5 wt%, and the content of unburned carbon in the salt chemical industry high-carbon low-activity fly ash is 5-30 wt%.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials and solid waste resource utilization technology, and in particular to a porous ceramic material based on lithium slag and high-carbon fly ash and its preparation method. Background Technology

[0002] Lithium smelting slag is the residue produced after extracting lithium salts from lithium ore. It contains abundant oxides of silicon, aluminum, and calcium, as well as residual lithium. Currently, a large amount of spodumene lithium extraction slag is mainly disposed of through stockpiling, posing a potential environmental pollution hazard. Although it contains fluxing components such as Li₂O and possesses sintering activity, high-value-added utilization methods are scarce. Meanwhile, high-carbon, low-activity fly ash generated by industries such as salt chemical industry, with an unburned carbon content exceeding 15%, is severely limited in its application in traditional building materials and is generally considered unusable solid waste. The large-scale stockpiling of these two types of industrial solid waste creates a dual dilemma of resource waste and environmental pressure.

[0003] Porous ceramics have important applications in filtration, catalysis, and other fields due to their unique structural characteristics, but traditional preparation techniques face inherent contradictions. On the one hand, to achieve sufficient sintering densification and strength development, high sintering temperatures (typically >1300℃) are required. This not only increases energy consumption, but more importantly, the added pore-forming agent often decomposes prematurely or burns away excessively at high temperatures, making it difficult to precisely match the sintering process with the matrix, resulting in poor pore structure stability. On the other hand, while relatively low-temperature sintering is beneficial for the retention of pore-forming agents and pore formation, it is difficult to ensure sufficient sintering and strength development of the matrix. This contradiction of "high temperature damages pores, low temperature weakens the matrix" makes it difficult for traditional processes to simultaneously achieve high porosity and high strength. In addition, existing solid waste utilization methods mostly rely on single raw materials, resulting in limited space for composition control; and for high-carbon fly ash, conventional technologies often regard residual carbon as a harmful component that needs to be removed beforehand, which increases treatment costs and energy consumption.

[0004] Therefore, it is essential to develop a new method that can synergistically process two types of solid waste, avoid the use of exogenous pore-forming agents, and achieve pore structure and ceramic strength at lower temperatures. Summary of the Invention

[0005] In view of this, this application provides a porous ceramic material based on lithium slag and high-carbon fly ash and its preparation method, which is used to solve the problem of how to simultaneously improve pore structure and strength.

[0006] To achieve the above technical objectives, this application adopts the following technical solution: In a first aspect, this application provides a method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash, comprising the following steps: After iron removal treatment, the lithium extraction slag from spodumene is washed with water and dried to obtain pretreated lithium extraction spodumene slag. Pretreated lithium spodumene lithium extraction slag, high-carbon and low-activity fly ash from salt chemical industry, and binder are dry-mixed to obtain dry-mix material. Add water to the dry mixture and mix well to obtain a plastic ceramic slurry; Plastic ceramic slurry is pressed into a mold to form a ceramic green body; In an air atmosphere, green bodies are sintered and then cooled to produce porous ceramic materials. The final sintering temperature is 1200-1300℃; the unburned carbon content in spodumene lithium extraction slag is 1-5wt%, and the unburned carbon content in high-carbon, low-activity fly ash from salt chemical industry is 5-30wt%.

[0007] Preferably, the lithium extraction slag from spodumene comprises the following components in parts by mass: 8-40 parts Al2O3, 30-75 parts SiO2, 0.1-5 parts MgO, 0.1-10 parts Fe2O3, 0.1-10.0 parts alkaline oxides, and 1-10 parts unburned carbon; the alkaline oxides include Na2O and K2O.

[0008] Preferably, the pretreated spodumene lithium extraction slag comprises the following components in parts by mass: 10-30 parts Al2O3, 40-80 parts SiO2, 0.1-3 parts MgO, 0.1-2 parts Fe2O3, 0.1-10 parts alkaline oxides, and 1-5 parts unburned carbon; the alkaline oxides include Na2O and K2O.

[0009] Preferably, the high-carbon, low-activity fly ash for salt chemical industry comprises the following components in parts by weight: 10-50 parts Al2O3, 30-70 parts SiO2, 0.1-10 parts MgO, 0.1-15 parts Fe2O3, 0.1-10.0 parts alkaline oxides, and 5-30 parts unburned carbon; the alkaline oxides include Na2O and K2O.

[0010] Preferably, based on the total mass of lithium spodumene extraction slag and salt chemical high-carbon low-activity fly ash as 100%, the proportion of salt chemical high-carbon low-activity fly ash is 20-30%.

[0011] Preferably, the adhesive includes one or more of glycerin, carboxymethyl cellulose, epoxy resin, acrylate adhesive, and phosphate inorganic adhesive; and the amount of adhesive used is 0.1-10% of the dry mix.

[0012] Preferably, the amount of water used is 10-30% of the dry mix.

[0013] Preferably, the sintering procedure is as follows: heat up to 1000℃ at 10℃ / min, then heat up to 1200-1300℃ at 2-5℃ / min, and hold for 6-8 hours.

[0014] Preferably, the cooling procedure is as follows: the temperature is reduced to 500°C at a rate of 2-5°C / min, and then allowed to cool naturally to room temperature.

[0015] Preferably, the pressure for pressurization is 20-60 MPa and the pressurization time is 60-90 s.

[0016] Secondly, this application provides a porous ceramic material.

[0017] The beneficial effects of this application are as follows: To address the issue of adding exogenous pore-forming agents, this invention utilizes the incompletely burned carbon in high-carbon, low-activity fly ash as an endogenous pore-forming agent. During the sintering process, pores are formed in situ through the oxidation reaction of carbon, eliminating the need for expensive external pore-forming agents. This simplifies the process, reduces costs and energy consumption, and enables high-value-added synergistic utilization of spodumene lithium extraction slag and high-carbon, low-activity fly ash solid waste.

[0018] To address the issue of high sintering temperatures, this invention achieves low-temperature sintering (1100-1300℃) by synergistically regulating material composition (mineral phase adjustment) and microstructure (pore structure). Abundant unburned carbon can serve as fuel to provide calorific value, thereby reducing the liquid phase formation temperature and matching it with the pore stabilization process. This results in high-performance porous ceramics.

[0019] To address the limited performance control of single solid waste, this invention utilizes elements such as Si and Al in high-carbon, low-activity fly ash as silicon and aluminum sources to regulate and optimize the mineral phase composition and pore distribution of porous ceramics. This improves the mass and heat transfer and thermodynamic field during the calcination process of lithium extraction spodumene slag and high-carbon, low-activity fly ash, accelerating the formation of stable crystalline phases such as mullite, thereby achieving a synergistic multiplication of high strength and high porosity in porous ceramics. Attached Figure Description

[0020] Figure 1 The ceramic XRD pattern is shown in Comparative Example 1. Figure 2 The ceramic XRD pattern is shown in Comparative Example 2. Figure 3 The ceramic XRD pattern of Example 1; Figure 4 Here is the ceramic XRD pattern of Example 3; Figure 5 Macroscopic images of different ceramics; Figure 6 Comparative Example 1: SEM image of ceramics; Figure 7 Comparative Example 2: SEM image of ceramics; Figure 8 Example 1: SEM image of ceramic; Figure 9 Example 3: SEM image of ceramics; Figure 10 Comparative Example 1: Ceramic EDS plot; Figure 11 Comparative Example 2: Ceramic EDS plot; Figure 12 Example 1: Ceramic EDS diagram; Figure 13 Example 3: Ceramic EDS diagram. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] This application provides a method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash, including the following steps: The lithium extraction slag from spodumene is washed and dried to obtain pretreated lithium extraction spodumene slag. At the same time, the high-carbon, low-activity fly ash from the salt chemical industry is dried to a certain weight. The drying temperature is 100-120℃. Pretreated spodumene lithium extraction slag, high-carbon and low-activity fly ash from salt chemical industry, and binder are dry-mixed to obtain a dry mixture; specifically, the mixture is placed in a mixing mortar and dry-mixed for 10 minutes. Water is added to the dry mix for wet mixing to obtain a plastic ceramic slurry. This step aims to improve the molding properties of the powder and prevent dust and delamination during subsequent pressing. Plastic ceramic slurry is placed in a mold and unidirectionally pressurized under a hydraulic press or other pressure equipment to obtain a ceramic green body; The dried green body is placed in a muffle furnace or box furnace and sintered in air atmosphere, and then cooled to obtain a porous ceramic material. The final sintering temperature is 1200-1300℃; the unburned carbon content in spodumene lithium extraction slag is 1-10wt%, and the unburned carbon content in high-carbon, low-activity fly ash from salt chemical industry is 5-30wt%.

[0023] This application successfully prepared porous ceramic materials with both high porosity and high strength in the low-temperature range of 1100-1300℃ through the synergistic effect of lithium spodumene extraction slag and high-carbon, low-activity fly ash. The reason for this is: The alkali metal components such as lithium and sodium contained in spodumene lithium extraction slag act as natural fluxes during sintering, lowering the eutectic temperature of the system and providing a chemical basis for the formation of a low-temperature liquid phase. Simultaneously, the unburned carbon components in high-carbon, low-activity fly ash oxidize and release heat during sintering, providing internal heat energy to the system. This internal heating effect optimizes the heat transfer process and promotes the sintering kinetics at low temperatures. Therefore, this application utilizes spodumene lithium extraction slag to lower the liquid phase formation temperature from a chemical composition perspective, and high-carbon fly ash to promote sintering from an energy supply perspective, jointly achieving the firing of ceramic powder materials at low temperatures. One of the functions of high-carbon fly ash is as an endogenous pore-forming agent. The carbon particles in high-carbon fly ash are uniformly distributed in the matrix. Under low-temperature conditions, after oxidation and burn-off, they form a porous structure in situ. This endogenous pore-forming method ensures the uniformity of pore distribution and porosity. At the same time, the low-temperature liquid phase promoted by spodumene lithium extraction slag can timely encapsulate and stabilize the newly formed pores, effectively preventing the collapse of the pore structure. Furthermore, by using elements such as Si and Al in high-carbon, low-activity fly ash as supplementary raw materials, they work synergistically with spodumene lithium extraction slag to participate in the reaction in the low-temperature liquid phase environment. Through the synergistic regulation of material composition and microstructure, the mineral phase composition and pore distribution of porous ceramics are optimized, promoting the formation of stable crystalline phases such as mullite, and thus forming a robust framework structure at the pore walls. This synergistic effect allows pore formation and framework strengthening to be completed simultaneously within the same low-temperature range, achieving a synergistic improvement in porosity and strength.

[0024] In some embodiments, the lithium extraction slag from spodumene comprises the following components in parts by weight: 8-40 parts Al2O3, 30-75 parts SiO2, 0.1-5 parts MgO, 0.1-10 parts Fe2O3, 0.1-10.0 parts alkaline oxides, and 1-10 parts unburned carbon; the alkaline oxides include Na2O and K2O.

[0025] In this embodiment, the spodumene lithium extraction slag is washed and dried to remove some soluble salts (such as sulfates and chlorides) and free iron, thereby reducing their adverse effects on the sintering process and the performance of the final product. After treatment, a pretreated spodumene lithium extraction slag is obtained, comprising the following components in parts by mass: 10-30 parts Al2O3, 40-80 parts SiO2, 0.1-3 parts MgO, 0.1-2 parts Fe2O3, 0.1-10 parts alkaline oxides, and 1-5 parts unburned carbon. The alkaline oxides include Na2O and K2O.

[0026] In some embodiments, the high-carbon, low-activity fly ash for salt chemical industry comprises the following components in parts by weight: 10-50 parts Al2O3, 30-70 parts SiO2, 0.1-10 parts MgO, 0.1-15 parts Fe2O3, 0.1-10.0 parts alkaline oxides, and 5-30 parts unburned carbon; the alkaline oxides include Na2O and K2O.

[0027] In this embodiment, the high-carbon, low-activity fly ash from the salt chemical industry is a mixture of high-carbon, low-activity fly ash from different sources. The high-carbon, low-activity fly ash has three functions in this application: unburned carbon components create pores in situ through oxidation during sintering, forming a uniformly distributed pore structure; the exothermic oxidation of carbon provides endogenous heat energy to the system, optimizing the heat transfer process; and the components participate in the construction of the ceramic crystal phase.

[0028] In some embodiments, based on the total mass of lithium spodumene extraction slag and salt chemical high-carbon low-activity fly ash as 100%, the proportion of salt chemical high-carbon low-activity fly ash is 20-30%.

[0029] In this embodiment, if too much high-carbon, low-activity fly ash from the salt chemical plant is used, it will lead to an excessively high content of unburned carbon in the system. During sintering, the intense oxidation of carbon will generate excessive gas, resulting in excessively large pores, thin pore walls, and even structural collapse. Simultaneously, excessive residual carbon may hinder the uniform distribution of the liquid phase and the development of crystal phases, reducing the overall strength and stability of the ceramic. If the amount used is too small, there will be insufficient endogenous pore-forming agent, making it difficult to form a sufficient and uniform pore structure, resulting in low porosity. Furthermore, the supplementary role of fly ash as a silicon and aluminum source will be weakened, which is not conducive to the formation of reinforcing crystal phases such as mullite, thus affecting the overall performance of the material. In some embodiments, the adhesive includes one or more of glycerol, carboxymethyl cellulose, epoxy resin, acrylate adhesive, and phosphate inorganic adhesive; and the amount of adhesive used is 0.1-10% of the dry mix.

[0030] In some embodiments, the amount of water used is 10-30% of the dry mix.

[0031] In some embodiments, the sintering process is as follows: the temperature is increased to 1000°C at 10°C / min, and then increased to 1200-1300°C at 2-5°C / min, and held for 6-8 hours.

[0032] In this embodiment, after reaching the target temperature, isothermal sintering is carried out for 6-8 hours to ensure sufficient phase formation and densification.

[0033] In some embodiments, the cooling procedure is as follows: after sintering, the temperature is reduced from 1200-1300°C to 500°C at a rate of 2-5°C / min, then the power is cut off, and the temperature is allowed to cool naturally to room temperature (20-25°C).

[0034] In some embodiments, the pressure for press molding is 20-60 MPa, and after press molding, the pressure is held for 60-90 seconds before slowly releasing the pressure to prevent stress concentration from causing cracking of the green body.

[0035] This application provides a porous ceramic material whose phase composition mainly includes quartz and mullite, with an apparent porosity of 20%-70%, a compressive strength of 2MPa-8MPa, and a thermal conductivity of 0.1-0.3.

[0036] The following specific embodiments further illustrate this solution.

[0037] Sources of raw materials for the embodiments and comparative examples of this application The lithium extraction slag from spodumene comprises the following components in parts by mass: 8.64 parts Al2O3, 74.46 parts SiO2, 1.88 parts MgO, 5.33 parts Fe2O3, 2.63 parts alkaline oxides, and 7.06 parts unburned carbon; the alkaline oxides include Na2O and K2O.

[0038] The high-carbon, low-activity fly ash for salt chemical industry comprises the following components by mass: 24.92 parts Al2O3, 45.07 parts SiO2, 1.06 parts MgO, 4.30 parts Fe2O3, 2.53 parts alkaline oxides, and 22.12 parts unburned carbon; the alkaline oxides include Na2O and K2O.

[0039] Example 1 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash includes the following steps: After washing the spodumene lithium extraction residue five times with water, it was dried at 100℃ to constant weight to obtain pretreated spodumene lithium extraction residue. The pretreated spodumene lithium extraction residue includes the following components by mass: 22.05 parts Al2O3, 70.43 parts SiO2, 1.08 parts MgO, 1.56 parts Fe2O3, 1.69 parts alkaline oxides, and 3.19 parts unburned carbon; the alkaline oxides include Na2O and K2O; and the high-carbon, low-activity fly ash from the salt chemical industry was dried at 100℃ to constant weight. 16g of pretreated spodumene lithium extraction slag, 4g of high-carbon, low-activity fly ash from salt chemical industry, and binder were placed in a mixing mortar and dry-mixed for 10 minutes to achieve initial uniformity, resulting in a dry mixture. The amount of binder used was 1% of the dry mixture. Water is added to the dry mixture at a rate of 15% of the total mass of the dry mixture, and wet mixing is performed to obtain a plastic ceramic slurry. Plastic ceramic slurry is placed in a mold and unidirectionally pressurized under a hydraulic press or other pressure equipment. The pressure is slowly applied to 40 MPa and held at this pressure for 60 seconds. Then the pressure is slowly released to obtain a ceramic green body. The dried green body is placed in a muffle furnace or box furnace and sintered in air. The sintering procedure is as follows: Heating stage: The temperature is increased from room temperature to 1000℃ at a constant rate of 10℃ / min; then the heating rate is reduced to 5℃ / min, and heating continues until the target sintering temperature of 1250℃ is reached. Holding stage: After reaching the target temperature, isothermal sintering is carried out for 6 hours to ensure sufficient phase formation and densification. Cooling stage: After sintering, the furnace temperature is reduced from the target temperature to 500℃ at a controlled rate of 5℃ / min; then the power is cut off, and the sample is allowed to cool naturally with the furnace to room temperature of 25℃, thus obtaining the porous ceramic material. Example 2 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is the same as in Example 1, except that the amount of pretreated spodumene lithium slag is 14g and the amount of high-carbon, low-activity fly ash from salt chemical industry is 6g.

[0040] Example 3 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is the same as in Example 1, except that the sintering temperature is 1300℃.

[0041] Example 4 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is the same as in Example 2, except that the sintering temperature is 1300℃.

[0042] Comparative Example 1 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is the same as in Example 1, except that the high-carbon, low-activity fly ash from salt chemical industry is replaced with an equal amount of pretreated spodumene lithium extraction slag.

[0043] Comparative Example 2 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is the same as in Example 3, except that the high-carbon, low-activity fly ash from salt chemical industry is replaced with an equal amount of pretreated spodumene lithium extraction slag.

[0044] Comparative Example 3 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is described. The other contents are the same as those in Example 1, except that the pretreated spodumene lithium extraction slag is replaced with an equal amount of high-carbon, low-activity fly ash from salt chemical industry.

[0045] Comparative Example 4 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is the same as in Example 1, except that the sintering temperature is 1400℃.

[0046] Comparative Example 5 A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash is the same as in Example 3, except that the high-carbon, low-activity fly ash from salt chemical industry is replaced with exogenous pore-forming agent graphite.

[0047] Testing and Evaluation (1) Phase composition analysis Figures 1 to 4 The XRD patterns are for Comparative Example 1, Comparative Example 2, Example 1, and Example 3, respectively. The main diffraction peaks of Comparative Example 1 (pure spodumene lithium extraction slag, sintered at 1250℃) and Comparative Example 2 (pure spodumene lithium extraction slag, sintered at 1300℃) correspond to the quartz (SiO2) phase, indicating that without the addition of high-carbon, low-activity fly ash, the spodumene lithium extraction slag itself mainly forms a quartz crystal structure during sintering, with a single mineral phase.

[0048] In contrast, both Example 1 (80% spodumene lithium-extracting slag + 20% high-carbon, low-activity fly ash, 1250℃) and Example 3 (80% spodumene lithium-extracting slag + 20% high-carbon, low-activity fly ash, 1300℃) showed obvious mullite characteristic diffraction peaks in their XRD patterns. Furthermore, as the sintering temperature increased from 1250℃ to 1300℃ (Example 3), the intensity of the mullite peaks increased, while the quartz peaks relatively weakened. This phenomenon confirms that the introduction of high-carbon, low-activity fly ash provided additional Al2O3 and SiO2 sources, which reacted with the components in the lithium slag during sintering to generate the mullite crystalline phase. Mullite, as a high-strength, high-stability ceramic phase, effectively enhances the skeletal structure of porous ceramics.

[0049] (2) Microstructure and porosity characteristics Figures 6 to 9 The SEM images clearly show the microstructure of different samples. Comparative Example 1 shows a relatively dense microstructure with fewer and smaller pores, which is related to the lack of endogenous pore-forming agents in pure spodumene lithium extraction slag. Comparative Example 2 shows signs of local overburning, with a more compact structure and further reduced porosity.

[0050] Both Examples 1 and 3 exhibit a distinct porous structure with uniformly distributed pores, most of which are interconnected. Example 3, at a higher sintering temperature, shows a more developed pore structure and clearer pore walls, indicating that increased sintering temperature promotes liquid-phase sintering and pore structure stabilization.

[0051] Based on the pore structure data in Table 2: the specific surface area of ​​Example 1 is 0.1700 m². 2 / g, pore volume 0.000186 cm³ 3 / g, with an average pore size of 17.2363 nm. The specific surface area of ​​Example 3 was increased to 0.2433 m². 2 / g, but the pore volume decreased slightly to 0.000026 cm³.3 The average pore size increased slightly to 17.7448 nm / g. This change indicates that with the increase of sintering temperature, the carbon oxidation pore-forming process is more complete, forming more abundant micropores and mesopores, leading to an increase in specific surface area; however, at the same time, the high temperature also promotes the closure of some pores and the densification of the framework, resulting in a slight decrease in the total pore volume. This shows that by controlling the sintering temperature, the pore size distribution and specific surface area of ​​the material can be precisely optimized to meet the needs of water treatment.

[0052] EDS analysis ( Figures 10-13 This further verified the elemental distribution and mineral phase formation. Comparative Example 1 mainly consisted of Si and O elements, corresponding to the quartz phase; while Comparative Example 2 had a similar elemental distribution, but showed local enrichment of Ca and Fe, possibly originating from impurities in spodumene lithium extraction slag. In Examples 1 and 3, uniformly distributed Al, Si, and O elements were detected, and the Al / Si ratio was consistent with the theoretical composition of mullite, confirming the successful formation of the mullite phase.

[0053] (3) Macroscopic performance and dimensional changes The diameters of different samples were tested, as shown in Table 1. Comparative Example 1 had a diameter of 4.8 cm; Comparative Example 2's diameter increased to 5.3 cm, possibly due to slight expansion caused by the melting of low-melting-point components in the spodumene lithium extraction slag at high temperatures; Example 1 had a diameter of 4.6 cm; and Example 3's diameter returned to 4.8 cm. The diameter changes reflect the shrinkage and expansion behavior during sintering. The addition of high-carbon, low-activity fly ash introduced gases generated by carbon oxidation, forming pores in the molded body and inhibiting sintering shrinkage to some extent; while the formation of the liquid phase at high temperatures promoted densification. The combined effect of these two factors led to diameter fluctuations under different conditions. Figure 5 The macroscopic physical images intuitively show that the sample of the embodiment has a uniform color and obvious porous structure, with no obvious cracks or deformation, indicating that the molding and sintering process is stable and reliable.

[0054] The specific surface area was determined according to GB / T 19587-2017, the average pore size was determined according to GB / T 21650.1-2008, and the compressive strength was determined according to GB / T 1964-1996. The specific surface area of ​​Example 1 was 0.17 m². 2 / g, pore volume is 0.000186cm³ 3 / g, with an average pore size of 17.2363nm; the specific surface area of ​​Example 3 is 0.2433m². 2 / g, pore volume is 0.000026cm³ 3 / g, with an average pore size of 17.7448nm.

[0055] Table 1 Test Results

[0056] The core of this invention lies in the innovative use of incompletely burned carbon in high-carbon, low-activity fly ash as an endogenous pore-forming agent, replacing the traditional method of adding an external pore-forming agent, thereby simplifying the preparation process and reducing energy consumption and costs. Simultaneously, other components in the fly ash (such as Si and Al) can serve as silicon and aluminum sources, participating in the regulation of the mineral phase composition of porous ceramics. Using spodumene lithium extraction slag as a matrix, the high-carbon, low-activity fly ash functions as both a pore-forming agent and a supplementary raw material. During high-temperature sintering, the carbon in the fly ash generates pores in situ through oxidation, forming porous ceramics with a stable framework structure and good connectivity. Furthermore, the lithium and other components contained in the spodumene lithium extraction slag can act as fluxes, effectively reducing the sintering temperature of the system and achieving low-temperature sintering in the range of 1100–1300℃. In addition, by synergistically regulating the dosage of high-carbon, low-activity fly ash, its carbon content, and the sintering temperature, the porosity and compressive strength of the resulting porous ceramics can be precisely adjusted, achieving synergistic optimization of high strength and high porosity. This method not only expands the limitations of performance regulation of single solid waste raw materials, but also significantly improves the flexibility and controllability of material design.

[0057] This invention synergistically utilizes the high-value-added spodumene lithium extraction slag with high-carbon, low-activity fly ash, practicing the concept of "treating waste with waste". Compared with using fly ash or lithium slag alone, the composite system is significantly improved in terms of mineral phase composition, pore structure distribution, mass and heat transfer efficiency, and thermal field uniformity, which is conducive to accelerating the formation of stable crystalline phases such as mullite.

[0058] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash, characterized in that, Includes the following steps: The lithium extraction slag from spodumene is washed with water and dried to obtain pretreated lithium extraction spodumene slag. The pretreated spodumene lithium extraction slag, salt chemical high-carbon low-activity fly ash and binder are dry-mixed to obtain a dry mixture. Water is added to the dry mixture and mixed evenly to obtain a plastic ceramic slurry; The plastic ceramic slurry is pressed into a mold to obtain a ceramic green body; The green body is sintered in air and then cooled to obtain the porous ceramic material. The final sintering temperature is 1200-1300℃; the unburned carbon content in the pre-spodumene lithium extraction slag is 1-5wt%, and the unburned carbon content in the high-carbon, low-activity fly ash from the salt chemical industry is 5-30wt%.

2. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, The pretreated spodumene lithium extraction slag comprises the following components in parts by weight: 10-30 parts Al2O3, 40-80 parts SiO2, 0.1-3 parts MgO, 0.1-2 parts Fe2O3, 0.1-10 parts alkaline oxides, and 1-5 parts unburned carbon; the alkaline oxides include Na2O and K2O.

3. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, The high-carbon, low-activity fly ash for salt chemical industry comprises the following components in parts by weight: 10-50 parts Al2O3, 30-70 parts SiO2, 0.1-10 parts MgO, 0.1-15 parts Fe2O3, 0.1-10.0 parts alkaline oxides, and 5-30 parts unburned carbon; the alkaline oxides include Na2O and K2O.

4. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, Based on the total mass of lithium spodumene extraction slag and salt chemical high-carbon low-activity fly ash as 100%, the proportion of salt chemical high-carbon low-activity fly ash is 20-30%.

5. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, The adhesive includes one or more of glycerin, carboxymethyl cellulose, epoxy resin, acrylate adhesive, and phosphate inorganic adhesive; and the amount of the adhesive used is 0.1-10% of the dry mix.

6. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, The amount of water used is 10-30% of the dry mixture.

7. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, The sintering process is as follows: the temperature is increased to 1000℃ at 10℃ / min, and then increased to 1200-1300℃ at 2-5℃ / min, and held for 6-8 hours.

8. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, The cooling procedure is as follows: the temperature is reduced to 500°C at a rate of 2-5°C / min, and then allowed to cool naturally to room temperature.

9. The method for preparing porous ceramic materials based on lithium slag and high-carbon fly ash according to claim 1, characterized in that, The pressure for the pressure molding process is 20-60 MPa, and the pressing time is 60-90 seconds.

10. A porous ceramic material obtained by the preparation method according to any one of claims 1-9.

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