Layered bimetal hydroxide composite gel flame-retardant material based on coal gangue as well as preparation method and application of layered bimetal hydroxide composite gel flame-retardant material
By preparing a layered bimetallic hydroxide composite gel material based on coal gangue, the problems of LDHs sheet aggregation and insufficient thermal stability were solved, achieving efficient flame retardancy and spontaneous combustion inhibition of coal gangue, with significant environmental protection and sustainability.
Patent Information
- Application Number
- CN202511525838.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-24
- Publication Date
- 2026-02-13
AI Technical Summary
Existing coal gangue-based base layer bimetallic hydroxides (LDHs) are prone to lamellar aggregation during preparation, resulting in limited flame retardant properties and insufficient thermal stability, leading to poor spontaneous combustion inhibition effects on coal gangue.
By pretreating coal gangue, preparing an acid leaching solution using a eutectic solvent system, and adding metal salts to form a bimetallic ion system, a three-dimensional network structure is constructed by combining guar gum/bentonite composite gel, thus forming a layered bimetallic hydroxide composite gel material based on coal gangue.
It significantly improves the dispersibility and structural stability of LDHs, enhances the thermal stability and flame retardant properties of the material, forms a dense residue layer at high temperatures, effectively blocks oxygen diffusion, increases the ignition point by more than 20°C, reduces the preparation cost, and realizes the resource utilization of solid waste.
Smart Images
Figure CN121518147A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of comprehensive utilization of coal gangue resources, and particularly relates to a layered double hydroxide composite gel flame-retardant material based on coal gangue, a preparation method and application thereof. By extracting divalent and trivalent metal ions from coal gangue and compounding them with natural polymer gel (such as guar gum) and bentonite in a eutectic system, high value-added conversion of coal gangue is achieved. The obtained composite material can be further used in the field of flame-retardant and functional materials, thereby realizing resource utilization and environmental protection of solid industrial waste. BACKGROUND
[0002] Coal gangue is a large amount of solid waste generated in the process of coal mining and washing, mainly composed of sulfides, aluminosilicates and a small amount of organic matter. The annual discharge of coal gangue in China is about 280 million tons, accounting for 10%-15% of the raw coal output, and the comprehensive utilization rate is less than 30%. Long-term stacking not only occupies land resources, but also is easy to cause spontaneous combustion due to air, water and heat accumulation, producing harmful gases such as CO, CO2 and SO2, and may lead to migration of heavy metals to the environment, causing air, soil and water pollution, accompanied by secondary disasters such as explosion and collapse, posing significant ecological and safety risks. Therefore, it is of great social, environmental and economic significance to develop efficient and sustainable coal gangue flame-retardant and spontaneous combustion suppression technologies.
[0003] Layered double hydroxides (LDHs) as a kind of environmentally friendly, non-toxic and structure-tunable functional material show good application prospect in the field of flame retardation and spontaneous combustion suppression. LDHs are composed of positively charged metal hydroxide layers and interlayer exchangeable anions, forming a two-dimensional layered structure, and its thermal response and interface function can be optimized by composition and interlayer control. Typical magnesium-aluminum carbonate type LDHs can delay heat conduction through dehydration endothermic at less than 200°C, and the high-temperature decomposition product forms a dense inorganic residue layer, blocking the contact of oxygen and combustible groups, thereby effectively interrupting the spontaneous combustion reaction chain, showing significant flame retardant performance.
[0004] However, traditional coal gangue-based LDHs are prone to layer aggregation during preparation, resulting in a decrease in specific surface area and limited flame retardant efficiency. In order to improve the dispersibility and structural stability of LDHs, the traditional coal gangue-based LDHs material needs to be improved to enhance the thermal stability, flame retardant performance and environmental adaptability of coal gangue-based LDHs, providing an innovative solution for the application of coal gangue spontaneous combustion suppression and functional materials. SUMMARY
[0005] The present application aims to solve the problems of layer aggregation during preparation, limited flame retardant performance and insufficient thermal stability of existing coal gangue-based LDHs, and to realize the synergistic enhancement of coal gangue resource utilization and efficient flame retardant function.
[0006] To solve the above technical problems, the technical scheme adopted by the present application is: a preparation method of a layered double hydroxide composite gel flame retardant material based on coal gangue, comprising the following steps: pretreating the coal gangue to expose the silicon and aluminum components therein; preparing an acid leaching solution in a eutectic solvent system using the coal gangue as a silicon and aluminum source, adding metal salts to the acid leaching solution to provide the divalent and trivalent metal ions required by the double metal system; and then mixing the acid leaching solution with a guar gum / bentonite composite gel to form a composite gel flame retardant material with a gel support structure.
[0007] The preparation method of the layered double hydroxide composite gel flame retardant material based on coal gangue comprises the following steps: Step 1: pretreating the coal gangue to obtain coal gangue powder; Step 2: dispersing the coal gangue powder in water, adding hydrochloric acid to adjust the pH value, and stirring in a water bath at 60-90°C for 1-2 hours to obtain an acid leaching solution, then adding metal salts to the acid leaching solution to provide the divalent and trivalent metal ions required by the double metal system; Step 3: adjusting the acid leaching solution to pH=6, mixing with a deep eutectic solvent, slowly adding a composite gel formed by a high molecular gel and bentonite, stirring uniformly, then adding an alkaline substance to alkalinize the mixture, stirring and then transferring to a constant temperature oven for drying; Step 4: washing the dried product until it is neutral, then drying the washed product in a vacuum oven to obtain the product.
[0008] In step 1, the pretreatment method of the coal gangue is: placing the coal gangue in a muffle furnace for calcination at 900°C for 3 hours, ball milling the calcined coal gangue for 1 hour, and sieving through a 100 mesh screen to obtain coal gangue powder with uniform particle size; In step 2, the ratio of coal gangue powder to water is 1:5, and hydrochloric acid is added to adjust the pH value to 1; the metal salts added are magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) and aluminum nitrate nonahydrate (Al(NO3)3·9H2O), with a molar ratio of 2:1, and the total metal ion concentration is controlled at 0.1 mol / L.
[0009] In step 3, the composite gel added is formed by guar gum and bentonite, and the preparation method is: preparing a 0.5-1 wt% guar gum aqueous solution, stirring uniformly at room temperature, then adding 1-3 wt% bentonite to the guar gum aqueous solution, continuing to stir to form a composite gel, and the mass ratio of guar gum to bentonite is 1:0.2-10.
[0010] In the third step, the deep eutectic solvent is obtained by mixing choline chloride and urea at a molar ratio of 1:2, and the basic substance added is KOH.
[0011] In the third step, the temperature is kept at 100°C for 48 hours after being transferred to the constant temperature oven.
[0012] In the fourth step, the product after drying is repeatedly washed with deionized water and ethanol until it is neutral, and the temperature of the vacuum oven is 50°C.
[0013] In addition, the present application provides a coal gangue-based layered double hydroxide composite gel flame-retardant material prepared according to the preparation method of the coal gangue-based layered double hydroxide composite gel.
[0014] In addition, the present application also provides the application of the coal gangue-based layered double hydroxide composite gel flame-retardant material, specifically the application in the natural inhibition of coal gangue.
[0015] The present application provides a coal gangue-based layered double hydroxide composite gel flame-retardant material, a preparation method and application thereof. By introducing a natural polymer / bentonite composite gel as a support and dispersion medium for the precursor of LDHs, the three-dimensional network structure and lamellar arrangement are adjusted, which not only significantly improves the dispersibility and structural stability of the LDHs lamella based on coal gangue, but also enables the uniform distribution and stable arrangement of the LDHs lamella. In addition, the prepared material can be partially carbonized to form a heat-insulating carbon layer at high temperature, thereby enhancing the thermal stability and flame-retardant performance of the material. Moreover, the presence of the gel helps to uniformly distribute the interlayer water and anions, thereby strengthening the low-temperature heat absorption capacity and high-temperature residue barrier effect, and achieving synergistic enhancement of the flame-retardant performance. At the same time, the present application can also make full use of the metal elements in coal gangue to realize the high-value conversion of solid waste, reduce the preparation cost, and has environmental protection and sustainability.
[0016] Compared with the prior art, the present application has the following beneficial effects: Solid waste resource utilization: The coal gangue is used as a silicon-aluminum source to prepare layered double hydroxide, which avoids the high cost and high pollution problems of traditional chemical reagents, and realizes the high-value utilization of bulk solid waste.
[0017] Green preparation process: The mild reaction is carried out through the deep eutectic solvent (DES) system, which simplifies the process steps and reduces the energy consumption and environmental load.
[0018] Composite gel enhancement: The introduction of guar gum / bentonite composite gel to construct a three-dimensional network structure not only improves the dispersibility and stability of the layered double hydroxide, but also enhances the film-forming property and adhesion of the flame-retardant material.
[0019] The flame-retardant performance is significantly improved: the flame-retardant material shows stronger endothermic effect in the low-temperature stage and can form a stable and dense residual barrier layer in the high-temperature stage, effectively blocking the diffusion of oxygen. Test results show that the ignition point is increased by more than 20℃ than that of the original coal gangue, and the thermal stability and flame-retardant performance are obviously better than those of traditional materials.
[0020] In summary, the present application not only realizes the resource utilization of the bulk solid waste of coal gangue, but also obtains the C-LDH / complex gel flame-retardant material which has a green low-consumption process and excellent flame-retardant performance, and can be widely applied to the flame-retardant of coal gangue storage, the spontaneous combustion inhibition in the coal storage and transportation process, and the field of polymer composite materials, building materials and flame-retardant coating as an environmental-friendly flame-retardant agent, showing excellent thermal adaptability and flame-retardant effect, and having significant industrial promotion and industrialization value. BRIEF DESCRIPTION OF DRAWINGS
[0021] Figure 1 Fig. 1 is an AFM graph of a layered double hydroxide composite gel material based on coal gangue obtained by the embodiment one of the present application; Figure 2 Fig. 2 is a TG / DSC curve graph of the original coal gangue; Figure 3 Fig. 3 is a TG / DSC graph of a layered double hydroxide composite gel material based on coal gangue obtained by the embodiment one of the present application. DETAILED DESCRIPTION
[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.
[0023] Embodiment one The embodiment one of the present application provides a preparation method of a layered double hydroxide based on coal gangue and guar gum / bentonite composite gel. The silicon aluminum components in the coal gangue are exposed by pretreatment. The coal gangue is used as a silicon aluminum source to prepare an acid leaching solution in a eutectic solvent system. Metal salts are added to the acid leaching solution to provide divalent and trivalent metal ions required by the double metal system. Then, the acid leaching solution is mixed with the guar gum / bentonite composite gel to form a composite gel flame-retardant material with a gel support structure. Specifically, the following steps are included: Step one: the coal gangue is pretreated to expose the silicon aluminum components therein, and coal gangue powder is obtained.
[0024] In the step one, the pretreatment method of the coal gangue is as follows: The coal gangue was placed in a muffle furnace for calcination at a high temperature of 900°C for 3 hours. The calcined coal gangue was ball milled for 1 hour and sieved through a 100 mesh screen to obtain coal gangue powder with uniform particle size.
[0025] In this embodiment, 100 g of coal gangue taken from the Shijiazhuang Coal Mine of Lu'an Group was placed in a muffle furnace for calcination at a high temperature of 900°C for 3 hours. The calcined coal gangue was ball milled for 1 hour and sieved through a 100 mesh screen to obtain coal gangue powder with uniform particle size.
[0026] Step two: The coal gangue powder was dispersed in ultrapure water, hydrochloric acid was added to adjust the pH value, and stirring was performed in a 60-90°C water bath for 1-2 hours. After the reaction was completed, filtration was performed to obtain an acid leaching solution. Subsequently, metal salts were added to the acid leaching solution to provide the divalent and trivalent metal ions required for the bimetallic system. The metal salts were magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) and aluminum nitrate nonahydrate (Al(NO3)3·9H2O), and the molar ratio was 2:1, with the total metal ion concentration controlled at 0.1 mol / L.
[0027] In the step two, the ratio of coal gangue powder to water was 1:5, and hydrochloric acid was added to adjust the pH value to 1.
[0028] Specifically, in this embodiment, 10 g of coal gangue powder was dispersed in 50 mL of ultrapure water (solid-liquid ratio of 1:5), hydrochloric acid was added dropwise to adjust the solution pH to 1, stirring was performed in a 60-90°C water bath for 1-2 hours, and filtration was performed to obtain an acid leaching solution. Subsequently, 0.85 g of Mg(NO3)2·6H2O and 0.63 g of Al(NO3)3·9H2O were added, so that the total metal ion concentration in the system was 0.1 mol / L, and the molar ratio of Mg 2+ / Al 3+ was 2:1. Stirring was continued for 30-60 min to ensure that the metal ions were fully dissolved and uniformly distributed. The concentrations of Mg 2+ and Al 3+ were determined by atomic absorption spectrophotometry to confirm that the metal ion ratio in the system met the design requirements.
[0029] Step three: The acid leaching solution was adjusted to pH=6, mixed with the deep eutectic solvent, slowly added with guar gum / bentonite composite gel while stirring uniformly, then an alkaline substance was added to the mixture to make it alkaline, and after stirring, it was transferred to a constant temperature oven for drying.
[0030] In step three, the acid leaching solution obtained in step two is mixed with guar gum / bentonite composite gel, and layered bimetallic hydroxide is generated in situ during the alkalization reaction, which combines with the gel network to form a composite material with a supporting structure.
[0031] In step three, the added composite gel is formed from guar gum and bentonite, and its preparation method is as follows: Prepare a 0.5–1 wt% guar gum aqueous solution and stir it at room temperature until homogeneous. Then add 1–3 wt% bentonite to the guar gum aqueous solution and continue stirring to form a composite gel. The mass ratio of guar gum to bentonite is 1:0.2~10.
[0032] Furthermore, in step three, the eutectic solvent used is a mixture of choline chloride and urea at a molar ratio of 1:2, and the added alkaline substance is KOH. After being transferred to a constant temperature oven, it is kept at 100°C for 48 hours.
[0033] Specifically, in this embodiment, the acid leaching solution was adjusted to pH=6 and then mixed with 50 mL of deep eutectic solvent. The composite gel was slowly added while stirring until homogeneous. Then, 1.69 g of KOH (equivalent to a system concentration of approximately 0.3 mol / L) was added to the mixture and stirred for 30 min. The reaction system was transferred to a constant temperature oven and kept at 100°C for 48 hours to obtain a layered bimetallic hydroxide (C-LDH) guar gum-bentonite composite gel material based on coal gangue.
[0034] Step 4: Wash the dried product until it is neutral, and then place the washed product in a vacuum oven to dry it, thus obtaining the final product.
[0035] After the reaction was complete, the product was washed repeatedly with deionized water and ethanol until neutral. The washed product was then dried overnight in a vacuum oven at 50°C to obtain the final C-LDH / guar gum-bentonite composite gel material.
[0036] like Figure 1 As shown, the material observed through AFM testing revealed that the LDH sheets were uniformly dispersed and ultra-thin, with low surface roughness, and the composite gel network was uniformly distributed. From... Figure 3 The TG / DSC test results show that, compared to Figure 2The ignition point of the obtained composite coal gangue is increased from 497.99 DEG C of the original coal gangue to 521.27 DEG C. Moreover, the obtained composite can significantly absorb heat in the low-temperature stage, delay the temperature rising rate of the system; and can form a dense and stable inorganic residue layer in the high-temperature stage, effectively block the contact between oxygen and combustible groups, and exhibit excellent thermal stability and flame retardant performance. Compared with the original coal gangue, the composite exhibits higher thermal stability and more excellent flame retardant performance. The prepared composite can be applied to the fields of coal, stone storage flame retardation, coal spontaneous combustion inhibition, polymer or wood composite flame retardant treatment and the like.
[0037] Example Two The application of the layered double hydroxide composite gel in coal gangue spontaneous combustion inhibition is provided in the second embodiment of the application. The layered double hydroxide composite gel based on coal gangue prepared in Example One is made into a slurry, and is uniformly coated on the surface of the coal gangue pile body in a spraying manner, with a coating thickness of about 2-5 mm. After spraying, the slurry is naturally dried for 12 hours to form a continuous and dense barrier layer.
[0038] In the simulated coal gangue storage environment, the spontaneous combustion tendency of the coated and uncoated samples is compared and tested. The results show that: the uncoated sample starts to show signs of accelerated oxidation at about 220-250 DEG C, and obvious combustion occurs at about 495 DEG C; the sample coated with the composite material exhibits stronger heat absorption capacity in the low-temperature stage, effectively delaying the temperature rise of the coal gangue; the ignition point is increased to 520 DEG C, and the residue layer formed after combustion is dense, which can effectively block the further diffusion of oxygen. The results show that the composite material prepared by the application can significantly inhibit the spontaneous combustion reaction during the storage of coal gangue, delay the temperature rising rate, and increase the ignition point, and has good flame retardant and safety protection effect, and can be widely applied to the spontaneous combustion inhibition engineering of coal gangue storage yard, coal mine underground fire prevention and other solid waste storage places.
[0039] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.
Claims
1. A method for preparing a layered bimetallic hydroxide composite gel flame retardant material based on coal gangue, characterized in that, Includes the following steps: Coal gangue is pretreated to expose its silica-alumina components; in a eutectic solvent system, an acid leaching solution is prepared using coal gangue as the silica-alumina source, and metal salts are added to the acid leaching solution to provide the divalent and trivalent metal ions required for the bimetallic system; then the acid leaching solution is mixed with guar gum / bentonite composite gel to form a composite gel flame retardant material with a gel-supported structure.
2. The method for preparing a layered bimetallic hydroxide composite gel flame retardant material based on coal gangue according to claim 1, characterized in that, Includes the following steps: Step 1: Pre-treat the coal gangue to obtain coal gangue powder; Step 2: Disperse coal gangue powder in water, add hydrochloric acid to adjust the pH value, and stir in a 60–90°C water bath for 1–2 hours. Filter to obtain acid leaching solution, and then add metal salts to the acid leaching solution to provide the divalent and trivalent metal ions required for the bimetallic system. Step 3: Adjust the pH of the acid leaching solution to 6, mix it with the deep eutectic solvent, slowly add the composite gel formed by the polymer gel and bentonite, and stir evenly. Then add an alkaline substance to the mixture to alkalize it, stir, and transfer it to a constant temperature oven to dry. Step 4: Wash the dried product until it is neutral, and then place the washed product in a vacuum oven to dry it, thus obtaining the final product.
3. The method for preparing a layered bimetallic hydroxide composite gel flame retardant material based on coal gangue according to claim 2, characterized in that, In step one, the pretreatment method for coal gangue is as follows: The coal gangue was placed in a muffle furnace and calcined at 900°C for 3 hours. The calcined coal gangue was then ball-milled for 1 hour and sieved through a 100-mesh sieve to obtain coal gangue powder with uniform particle size. In step two, the ratio of coal gangue powder to water is 1:5, and hydrochloric acid is added to adjust the pH value to 1; the added metal salts are magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) and aluminum nitrate nonahydrate (Al(NO3)3·9H2O), with a molar ratio of 2:1, and the total metal ion concentration is controlled at 0.1 mol / L.
4. The method for preparing a layered bimetallic hydroxide composite gel flame retardant material based on coal gangue according to claim 2, characterized in that, In step three, the added composite gel is formed from guar gum and bentonite, and its preparation method is as follows: Prepare a 0.5–1 wt% guar gum aqueous solution and stir it at room temperature until homogeneous. Then add 1–3 wt% bentonite to the guar gum aqueous solution and continue stirring to form a composite gel. The mass ratio of guar gum to bentonite is 1:0.2~10.
5. The method for preparing a layered bimetallic hydroxide composite gel flame retardant material based on coal gangue according to claim 2, characterized in that, In step three, the eutectic solvent used is a mixture of choline chloride and urea in a molar ratio of 1:2, and the added alkaline substance is KOH.
6. The method for preparing a layered bimetallic hydroxide composite gel flame retardant material based on coal gangue according to claim 2, characterized in that, In step three, the food is transferred to a constant temperature oven and kept at 100°C for 48 hours.
7. The method for preparing a layered bimetallic hydroxide composite gel flame retardant material based on coal gangue according to claim 2, characterized in that, In step four, the dried product is repeatedly washed with deionized water and ethanol until it is neutral, and the temperature of the vacuum oven is 50°C.
8. A layered bimetallic hydroxide composite gel flame retardant material based on coal gangue, characterized in that, The layered bimetallic hydroxide composite gel based on coal gangue was prepared according to any one of claims 1 to 7.
9. The application of the layered bimetallic hydroxide composite gel flame retardant material based on coal gangue according to claim 8, characterized in that, This includes its application in suppressing spontaneous combustion of coal gangue.