Preparation method of high-porosity foamed ceramic with high doping amount of lithium slag

Abstract

The invention provides a preparation method of high-porosity foamed ceramic with high doping amount of lithium slag, and relates to the technical field of solid waste recycling, the preparation method comprises the following steps: levigating and drying lepidolite tailings and lithium slag to obtain lithium-containing powder; mixing the lithium-containing powder, fly ash, calcium carbonate, albite, kaolin and a foaming agent SiC, and performing ball milling to obtain dry milled powder; adding water into the dry ground powder, and uniformly mixing to obtain mixed pug; putting the mixed pug into a metal mold, carrying out pressure forming by using a powder tablet press, and drying to obtain a foamed ceramic green body; and firing and molding the ceramic green body at 1200-1250 DEG C to obtain the foamed ceramic. According to the method, the adding amount of the lithium slag is high, and the technical problems that the lithium slag is difficult to utilize and pollutes the environment can be effectively solved. Calcium carbonate and SiC are used as a mixed pore-forming agent, so that the uniformity of a ceramic pore structure can be ensured, and the prepared porous ceramic is high in porosity and good in mechanical strength.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste recycling, and specifically relates to a preparation method of a high-porosity foam ceramic with a high lithium slag content. Background Art

[0002] Lithium mica smelting slag is a solid waste (abbreviated as lithium slag) produced after lithium mica is treated for lithium extraction. Due to the complex and diverse ore components and low grade, a large amount of waste slag is produced during the production process of lithium smelting. According to the grade of the original ore for lithium extraction, but with the rapid consumption of spodumene resources, the raw materials for extracting lithium salts will mainly be lithium mica with a low lithium content. It is expected that the output of lithium slag will increase explosively in the future. The amount of lithium slag produced per ton of lithium carbonate production ranges from 20 to 55 tons. Therefore, it is of great practical importance to realize the effective utilization of tailings resources as soon as possible. SiO2 and Al2O3 in the composition of lithium mica smelting slag have many similarities with the basic composition of ceramics, which also means that lithium mica smelting slag has the practical feasibility of making foam ceramics.

[0003] Foam ceramics is a novel material with a high specific surface area, high porosity, low density and thermal conductivity. It has good selectivity for liquid and gaseous media, and also exhibits excellent energy absorption and damping effects. As an innovative porous material, it has significant applications in various fields such as molten metal, gas and liquid filtration, clean separation, chemical catalytic materials, sound absorption and shock absorption, high-quality thermal insulation materials, biological materials, specific wall materials, and sensing materials. Therefore, it has a wide range of uses in industries such as environmental protection, energy, chemical engineering, and biology. In the prior art, the porous ceramics prepared from lithium slag have low porosity and poor mechanical strength. Summary of the Invention

[0004] The present invention provides a preparation method of a high-porosity foam ceramic with a high lithium slag content, which solves the technical problems of low porosity and poor mechanical strength of the porous ceramics prepared from lithium slag in the prior art.

[0005] To achieve the above-mentioned invention purpose, the technical solution provided by the present invention is as follows:

[0006] A preparation method of a high-porosity foam ceramic with a high lithium slag content, comprising the following steps:

[0007] S1. Grinding and drying lithium mica tailings and lithium slag to obtain lithium-containing powder;

[0008] S2. Mixing the lithium-containing powder, fly ash, calcium carbonate, albite, kaolin and foaming agent SiC and then ball-milling to obtain dry-milled powder;

[0009] S3. Adding water to the dry-milled powder and mixing evenly to obtain a mixed mud material;

[0010] S4. Place the mixed mud into a metal mold and perform pressure forming using a powder press. After drying, a green body of foam ceramics is obtained. The content of Al2O3 in the green body of foam ceramics is 10-30 wt%, the content of SiO2 is 50-70 wt%, and the total content of CaO and MgO is greater than 1.5 wt%.

[0011] S5. Fire and form the green body of ceramics at 1200-1250 °C to obtain foam ceramics.

[0012] Preferably, by mass, the lithium slag is 28-44 parts, the lithium mica tailings are 41-57 parts, the fly ash is 10 parts, the calcium carbonate is 1-9 parts, the albite is 5 parts, the kaolin is 5 parts, and the foaming agent SiC is 0.25-0.55 parts.

[0013] Preferably, the rotation speed of the ball milling in S2 is 380 r / min, and the ball milling time is 120 min.

[0014] Preferably, the average particle size of the dry-milled powder in S2 is less than 75 microns.

[0015] Preferably, the mass of water in S3 is 10-12% of the total mass of the dry-milled powder.

[0016] Preferably, the size of the metal mold in S4 is 6×2×2 cm, and the pressure of the pressure forming is 20 MPa.

[0017] Preferably, the drying temperature in S4 is 105-110 °C, and the drying time is 10-12 h.

[0018] Preferably, the heating-up system for the firing and forming in S5 is as follows: heat at a heating rate of 9 °C / min to 900-950 °C, hold for 30 min at 900-950 °C, and then heat at a heating rate of 5 °C / min to 1200-1250 °C and hold for 20-60 min.

[0019] The lithium mica tailings contain a large amount of mineral components such as quartz and feldspar. These minerals can play a good role in skeleton support during the sintering process of foam ceramics. During high-temperature sintering, quartz particles are intertwined with each other to form a stable skeleton structure, enhancing the overall strength of the foam ceramics. At the same time, some chemical components will undergo chemical reactions during the sintering process to promote the formation of crystal phases beneficial to strength. The main components of the lithium slag are silicon and aluminum oxides, and their role in promoting the formation of high-strength crystal phases is relatively weak.

[0020] In the present invention, by adding calcium carbonate, preliminary pore structures can be formed in the green body at an early stage, improving the overall foaming performance, thereby increasing the porosity. The free Ca formed after decomposition enables the formation of calcium silicate phase in the system, thus enhancing the compressive strength. At the same time, it prevents the quartz phase from turning into cristobalite in the molten state and reduces the content of the quartz phase. This change helps to reduce the viscosity of the molten liquid system at high temperatures, facilitating the formation of pores and reducing the apparent density of the foam ceramic. The pore-forming agent in the present invention is a mixture of calcium carbonate and SiC. Calcium carbonate and SiC act together to form pores. Calcium carbonate (CaCO₃) decomposes at high temperatures (about 900 °C for complete decomposition) to generate CO₂ gas, forming the early pore structure of the green body. The decomposition process is as shown in Equation (I).

[0021]

[0022] Silicon carbide (SiC) reacts with oxygen at high temperatures to generate CO₂ and SiO₂, while producing gas to form pores. The decomposition process is as shown in Equation (II).

[0023] SiC + 2O₂ → SiO₂ + CO₂↑ (II)

[0024] The decomposition temperatures of the two foaming agents are different (calcium carbonate is lower and SiC is higher), and gas can be generated at different temperature stages to form a more uniform pore structure. In addition, the combined action of calcium carbonate and SiC can produce pores of different sizes, forming a gradient pore structure. This structure is beneficial to improving the mechanical properties and thermal insulation properties of the foam ceramic. At the same time, the CaO generated by the decomposition of calcium carbonate can react with SiO₂, Al₂O₃, etc. in the raw materials to form silicates or aluminosilicates, enhancing the strength of the ceramic. A single foaming agent may lead to uneven pore distribution due to too fast or too slow reaction. The high-temperature foaming effect of SiC can make up for the deficiency that calcium carbonate decomposes completely at high temperatures, ensuring that gas is still generated at high temperature stages.

[0025] In addition, albite is added in the present invention. Albite has a relatively low melting point, and the binding ability of sodium to oxygen is greater than that of silicon to oxygen, enabling the raw materials to reach the eutectic effect at a lower temperature and reducing the viscosity of the eutectic phase. During the sintering process, albite will form a liquid phase at a lower temperature. These liquid phases can promote the rearrangement and mass transfer process of the raw material particles, thereby reducing the sintering temperature of the foam ceramic. For a raw material system that originally requires a higher temperature to be sintered densely, after adding an appropriate amount of albite, a good sintering effect may be achieved at a lower temperature. This is beneficial to reducing production energy consumption and costs, and at the same time can also reduce some adverse effects that may be brought about by high-temperature sintering. An appropriate amount of albite can broaden the sintering temperature range, making the sintering process easier to control. However, if the addition amount is too much, the green body may collapse due to excessive liquid phase at high temperatures, affecting the forming and properties of the foam ceramic.

[0026] The amount of lithium slag used is relatively large, because the impurities contained in the lithium slag, some metal oxides, will interfere with the normal reaction of the foaming agent. Taking silicon carbide as a foaming agent as an example, at high temperature, silicon carbide reacts with oxygen to produce gas to form pores. Impurities in lithium slag may react with the foaming agent, consume the foaming agent, and cause the gas generation to be unstable, and a uniform pore structure cannot be formed. The activity of lithium slag is relatively low, and it is difficult to fully react with other components in the ceramic system to form a high-strength network structure. When the amount of lithium slag used is large, the proportion of other effective ingredients will be diluted, resulting in a decrease in the strength of the ceramic matrix. At the same time, due to the differences in the particle morphology and surface properties of lithium slag and other raw materials, the addition of a large amount of lithium slag will destroy the structural continuity of the ceramic interior, and it is easy to produce stress concentration points when stressed, reducing the flexural strength and compressive strength of the material. The present invention uses a composite pore-forming agent, and simultaneously compounding lithium mica tailings with lithium slag to solve the technical problem of poor strength of the ceramic matrix during the use of lithium slag alone. When calcium carbonate and silicon carbide are used in combination, the gas production process of the two complements each other. Calcium carbonate begins to decompose and produce gas at a relatively low temperature, providing the initial gas source and driving force for the formation of early pores; while silicon carbide continues to oxidize and produce gas at a higher temperature, maintaining the growth and development of pores at the high temperature stage. This synergistic effect makes the entire foaming process more stable and continuous, which is conducive to the formation of more and evenly distributed pores, and solves the problem that adding a large amount of lithium slag will destroy the continuity of the internal structure of the ceramic, thereby improving the porosity of the foamed ceramic.

[0027] The technical solution of the present invention has at least the following beneficial effects compared with the prior art:

[0028] The invention uses a high amount of lithium slag, which can effectively solve the technical problem that lithium slag is difficult to use and pollutes the environment. The invention uses calcium carbonate and SiC as mixed pore-forming agents, continuously forms pores at different temperatures, can ensure the uniformity of the ceramic pore structure, and is beneficial to improving the mechanical strength of the ceramic. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the XRD pattern of the foam ceramic prepared in Example 1;

[0030] Figure 2 This is a physical picture of the foam ceramic prepared in Example 1;

[0031] Figure 3 is a SEM microstructure image of the foam ceramic prepared in Example 1;

[0032] Figure 4 This is a physical picture of the foam ceramic prepared in Example 2;

[0033] Figure 5 is a SEM microstructure image of the foam ceramic prepared in Example 2;

[0034] Figure 6 The physical diagram of the foam ceramic prepared in Example 3;

[0035] Figure 7 The SEM microstructural diagram of the foam ceramic prepared in Example 3;

[0036] Figure 8 The physical diagram of the foam ceramic prepared in Comparative Example 1;

[0037] Figure 9 The SEM microstructural diagram of the foam ceramic prepared in Comparative Example 1;

[0038] Figure 10 The physical diagram of the foam ceramic prepared in Comparative Example 2;

[0039] Figure 11 The SEM microstructural diagram of the foam ceramic prepared in Comparative Example 2;

[0040] Figure 12 The physical diagram of the foam ceramic prepared in Comparative Example 3;

[0041] Figure 13 The SEM microstructural diagram of the foam ceramic prepared in Comparative Example 3;

[0042] Figure 14 The physical diagram of the foam ceramic prepared in Comparative Example 4;

[0043] Figure 15 The SEM microstructural diagram of the foam ceramic prepared in Comparative Example 4. Detailed implementation manners

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] Example 1

[0046] This example provides a method for preparing a high-porosity foam ceramic with a high lithium slag content, including the following steps:

[0047] S1. Grind and dry 41 parts of lithium mica tailings and 28 parts of lithium slag to obtain a lithium-containing powder. The components of the lithium mica tailings and the lithium slag are shown in Table 1;

[0048] Table 1 Components of lithium mica tailings and lithium slag

[0049] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> CaO MgO LOI Lithium slag 26.79 12.46 0.14 0.09 3.39 3.39 20.25 0.77 0.27 Lepidolite tailings 75.23 14.81 0.14 - 2.08 5.86 0.36 - 1.23

[0050] S2. Mix all the lithium-containing powder materials, 10 parts of fly ash, 1 part of calcium carbonate, 5 parts of albite, 5 parts of kaolin, and 0.25 part of foaming agent SiC, and then ball mill for 120 min at a rotation speed of 380 r / min to obtain dry-milled powder materials. The average particle size of the dry-milled powder materials is less than 75 microns.

[0051] S3. Add 10% of the total mass of water to the dry-milled powder materials, and mix evenly to obtain mixed mud materials.

[0052] S4. Place the mixed mud materials into a metal mold with a size of 6×2×2 cm, and use a powder press for pressure forming at a pressure of 20 MPa. Dry at 105 °C for 10 h to obtain a green body of foam ceramics. The content of Al2O3 in the green body of foam ceramics is 10 wt%, the content of SiO2 is 70 wt%, and the total content of CaO and MgO is greater than 1.5 wt%.

[0053] S5. Heat the green body of ceramics at a heating rate of 9 °C / min to 900 °C, hold for 30 min at 900 °C, and then heat to 1200 °C at a heating rate of 5 °C / min and hold for 60 min to obtain foam ceramics. Its XRD pattern is as Figure 1 shown.

[0054] In this example, the porosity of the prepared foam ceramics is 74.49%, the compressive strength is 7.1 MPa, and the apparent density is 0.673 g / cm 3 . The physical diagram of the foam ceramics prepared in this example is as Figure 2 , and its SEM microstructural diagram is as Figure 3 . It can be seen that the pore sizes of the foam ceramics prepared in this example are similar and the pore distribution is uniform.

[0055] Example 2

[0056] This example provides a preparation method of high-porosity foam ceramics with high lithium slag content, including the following steps:

[0057] S1. Grind and dry 57 parts of lithium mica tailings and 44 parts of lithium slag to obtain lithium-containing powder materials.

[0058] S2. Mix all the lithium-containing powder materials, 10 parts of fly ash, 9 parts of calcium carbonate, 5 parts of albite, 5 parts of kaolin, and 0.55 part of foaming agent SiC, and then ball mill for 120 min at a rotation speed of 380 r / min to obtain dry-milled powder materials. The average particle size of the dry-milled powder materials is less than 75 microns.

[0059] S3. Add 12% of the total mass of water to the dry-milled powder materials, and mix evenly to obtain mixed mud materials.

[0060] S4. Place the mixed mud into a metal mold with dimensions of 6×2×2 cm, and use a powder press for pressure forming at a pressure of 20 MPa. Dry it at 110 °C for 12 h to obtain a green foam ceramic body. The content of Al2O3 in the green foam ceramic body is 30 wt%, the content of SiO2 is 50 wt%, and the total content of CaO and MgO is greater than 1.5 wt%.

[0061] S5. Heat the green ceramic body at a heating rate of 9 °C / min to 950 °C, hold it at 950 °C for 30 min, then heat it at a heating rate of 5 °C / min to 1250 °C and hold it for 20 min to obtain the foam ceramic.

[0062] In this example, the porosity of the prepared foam ceramic is 87.94%, the compressive strength is 2.87 MPa, and the apparent density is 0.332 g / cm 3 . The physical picture of the foam ceramic prepared in this example is as shown in Figure 4 , and its SEM microstructural diagram is as shown in Figure 5 . It can be seen that the pore sizes of the foam ceramic prepared in this example are similar in size and the pore distribution is uniform.

[0063] Example 3

[0064] This example provides a preparation method of a high-porosity foam ceramic with a high lithium slag content, including the following steps:

[0065] S1. Grind and dry 45 parts of lithium mica tailings and 35 parts of lithium slag to obtain a lithium-containing powder.

[0066] S2. Mix all the lithium-containing powder, 10 parts of fly ash, 5 parts of calcium carbonate, 5 parts of albite, 5 parts of kaolin, and 0.3 parts of foaming agent SiC, and ball mill them at a rotation speed of 380 r / min for 120 min to obtain a dry-milled powder. The average particle size of the dry-milled powder is less than 75 microns.

[0067] S3. Add 11% of the total mass of water to the dry-milled powder, and mix them evenly to obtain a mixed mud.

[0068] S4. Place the mixed mud into a metal mold with dimensions of 6×2×2 cm, and use a powder press for pressure forming at a pressure of 20 MPa. Dry it at 108 °C for 11 h to obtain a green foam ceramic body. The content of Al2O3 in the green foam ceramic body is 20 wt%, the content of SiO2 is 60 wt%, and the total content of CaO and MgO is greater than 1.5 wt%.

[0069] S5. Heat the green ceramic blank at a heating rate of 9 °C / min to 920 °C, hold for 30 min at 920 °C, then heat to 1230 °C at a heating rate of 5 °C / min and hold for 40 min to obtain the porous ceramic.

[0070] The porosity of the porous ceramic prepared in this example is 82.37%, the compressive strength is 5.2 MPa, and the apparent density is 0.528 g / cm 3 . The physical picture of the porous ceramic prepared in this example is as Figure 6 , and its SEM microstructural diagram is as Figure 7 . It can be seen that the cavity shape of the porous ceramic prepared in this example is regular and the pore distribution is relatively uniform.

[0071] Comparative Example 1

[0072] This comparative example is the same as Example 1, except that in this comparative example, calcium carbonate is replaced with an equal amount of foaming agent SiC. The porosity of the porous ceramic prepared in this comparative example is 86.4%, the compressive strength is 1.5 MPa, and the apparent density is 0.363 g / cm 3 .

[0073] The physical picture of the porous ceramic prepared in this comparative example is as Figure 8 , and its SEM microstructural diagram is as Figure 9 . It can be seen that the pore size of the porous ceramic prepared in this comparative example is larger. The role of SiC in the foaming system is more significant and the influence on the foaming process is more complex. As the amount of SiC increases, the pore walls will gradually become thinner and darker, the connectivity between pores is enhanced, and some interconnected channels are formed. At the same time, the surface and internal structures of the sample look relatively loose, resulting in a decrease in the compressive strength of the sample.

[0074] Comparative Example 2

[0075] This comparative example is the same as Example 1, except that in this comparative example, the foaming agent SiC is replaced with an equal amount of calcium carbonate. The porosity of the ceramic prepared in this comparative example is 72.66%, the compressive strength is 9.4 MPa, and the apparent density is 0.730 g / cm 3 . The physical picture of the porous ceramic prepared in this comparative example is as Figure 10 , and its SEM microstructural diagram is as Figure 11 . It can be seen that the pore sizes of the porous ceramic prepared in this comparative example are different, and the pore structure and pore distribution are very uneven. Some regions have good compactness, and obvious larger pores can be seen in some regions. The amount of foaming agent calcium carbonate added is too small, the amount of gas generated by the foaming agent is small, and the distribution in the melt is uneven, which will cause large differences in the sizes of the formed pores, resulting in a low porosity and incomplete foaming of some pores.

[0076] Comparative Example 3

[0077] This comparative example is the same as Example 1, except that the amount of lithium slag in this comparative example is 50 parts. The porosity of the ceramic prepared in this comparative example is 79.59%, the compressive strength is 1.2 MPa, and the apparent density is 0.545 g / cm 3 . The physical diagram of the foamed ceramic prepared in this comparative example is as shown in Figure 12 , and its SEM microstructural diagram is as shown in Figure 13 . It can be seen that the pore sizes of the foamed ceramic prepared in this comparative example vary greatly, and many pores with smaller sizes are distributed around the pore walls of the large pores. Therefore, the mechanical strength of the ceramic in this comparative example is poor. It can be seen that too much amount of lithium slag will cause the pore environment of the prepared ceramic to deteriorate and the mechanical strength to decrease significantly.

[0078] Comparative Example 4

[0079] This comparative example is the same as Example 1, except that the amount of albite in this comparative example is 10 parts. The porosity of the ceramic prepared in this comparative example is 84.57%, the compressive strength is 1.4 MPa, and the apparent density is 0.397 g / cm 3 . The physical diagram of the foamed ceramic prepared in this comparative example is as shown in Figure 14 , and its SEM microstructural diagram is as shown in Figure 15 . It can be seen that the pore sizes of the foamed ceramic prepared in this comparative example vary greatly, and many pores with smaller sizes are distributed around the pore walls of the large pores. However, too much amount of albite will cause the pore environment of the prepared ceramic to deteriorate and the mechanical strength to decrease.

[0080] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a high-porosity foam ceramic with high lithium slag content, characterized in that: The following steps are involved: S1, grinding and drying the lithium mica tailings and lithium slag to obtain lithium-containing powder; S2, mixing the lithium-containing powder, fly ash, calcium carbonate, albite, kaolin and foaming agent SiC and then ball-milling to obtain dry-milled powder; S3, adding water to the dry-milled powder, mixing evenly to obtain a mixed mud material; S4, placing the mixed mud into a metal mold, and using a powder tablet press to perform pressure molding, and obtaining a foam ceramic green body after drying, wherein the content of Al2O3 in the foam ceramic green body is 10-30wt%, the content of SiO2 is 50-70wt%, and the total content of CaO and MgO is greater than 1.5wt%; S5, sintering the ceramic green body at 1200-1250° C. to obtain foamed ceramic.

2. The method for preparing a high-porosity foam ceramic with high lithium slag content according to claim 1, characterized in that: In the dry-milled powder described in S2, the lithium slag is 28-44 parts, the lithium mica tailings is 41-57 parts, the fly ash is 10 parts, the calcium carbonate is 1-9 parts, the albite is 5 parts, the kaolin is 5 parts and the foaming agent SiC is 0.25-0.55 parts by mass.

3. The method for preparing a high-porosity foam ceramic with high lithium slag content according to claim 1, characterized in that: The ball milling speed in S2 is 380 r / min, and the ball milling time is 120 min.

4. The method for preparing a high-porosity foam ceramic with high lithium slag content according to claim 1, characterized in that: The average particle size of the dry-ground powder in S2 is less than 75 microns.

5. The method for preparing a high-porosity foam ceramic with high lithium slag content according to claim 1, characterized in that: The mass of the water in S3 is 10-12% of the total mass of the dry-ground powder.

6. The method for preparing a high-porosity foam ceramic with high lithium slag content according to claim 1, characterized in that: The size of the metal mold in S4 is 6×2×2 cm, and the pressure of the pressure molding is 20 MPa.

7. The method for preparing a high-porosity foam ceramic with high lithium slag according to claim 1, characterized in that: The drying temperature in S4 is 105-110° C., and the drying time is 10-12 h.

8. The method for preparing a high-porosity foam ceramic with high lithium slag content according to claim 1, characterized in that: The heating system for sintering and molding described in S5 is: heating to 900-950°C at a heating rate of 9°C / min, keeping at 900-950°C for 30 minutes, and then heating to 1200-1250°C at a heating rate of 5°C / min and keeping for 20-60 minutes.

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