Coal gangue activating treatment method, prepared calcined coal gangue and application

Abstract

The invention relates to the field of building materials, and particularly discloses a coal gangue activation treatment method, prepared calcined coal gangue and application, the treatment method comprises the following steps: pretreatment: crushing and screening coal gangue to obtain coal gangue particles; the coal gangue particles are treated in a eutectic solvent, ultrasonic-assisted treatment is carried out for 2-3 h, pretreated coal gangue is obtained after water washing, the eutectic solvent comprises an HBA component and an HBD component, the HBA component is a mixture of choline chloride and an amide compound, and the HBD component is a mixture of a carboxylic acid mixture and polyhydric alcohol; calcining: calcining the pretreated coal gangue at 400-450 DEG C to obtain calcined coal gangue, the invention also discloses the calcined coal gangue prepared by the method, and the method has the characteristic of realizing coal gangue activation treatment under lower energy consumption.

Description

Technical Field

[0001] The present application relates to the field of building materials, and more specifically, to a method for activating and treating coal gangue, the obtained calcined coal gangue and its application. Background Art

[0002] As one of the most important structural materials, the performance of concrete has a significant impact on building structures. The main technical approach to improving the durability of concrete is to use chemical admixtures and mineral admixtures. Mineral admixtures can participate in hydration, act as cementitious materials, improve the microstructure of the interface, block the internal pores of concrete, and improve the durability of concrete. The main mineral admixtures currently used are slag, fly ash, silica fume, etc.

[0003] As a solid waste generated during coal mining and washing, coal gangue not only occupies land but also pollutes the environment when it is piled up in large quantities. At present, the resource utilization of coal gangue has become a hot issue in the coal industry. However, since coal gangue contains a large amount of inorganic minerals and organic matter, its activity is low and it is difficult to use directly. Therefore, processing and activating coal gangue is expected to replace traditional mineral admixtures, solve the problem of resource utilization of coal gangue, and improve the various properties of concrete, especially durability, so as to realize the recycling of solid waste from the coal industry in construction projects.

[0004] At present, the activation methods of coal gangue mainly include physical activation and chemical activation. Physical activation mainly changes the pore structure and specific surface area of ​​coal gangue through high-temperature calcination, ball milling and other methods to improve its activity. Chemical activation treats coal gangue by adding chemical reagents such as acid or alkali to promote the improvement of activity. However, the physical method is used to calcine coal gangue, the calcination temperature is high, and the energy consumption is high. The chemical activation method has high concentration of acid and alkali treatment, which has high equipment requirements and low activation efficiency. These all restrict the large-scale industrial application of coal gangue activation. Summary of the invention

[0005] In order to solve the existing high energy consumption and realize the activation treatment of coal gangue, the present application provides a method for activating the treatment of coal gangue, the prepared calcined coal gangue and its application.

[0006] In the first aspect, the present application provides a method for activating coal gangue, which adopts the following technical solution: A method for activating coal gangue comprises the following steps: Pretreatment: crushing and screening the coal gangue to obtain coal gangue particles; Pretreatment: treating the gangue particles in a low eutectic solvent and performing an ultrasonic-assisted treatment for 2-3 hours, and washing with water to obtain pretreated gangue, wherein the low eutectic solvent includes an HBA component and an HBD component, wherein the HBA component is a mixture of choline chloride and amide compounds, and the HBD component is a mixture of a carboxylic acid mixture and a polyol; Calcination: Calcine the pretreated gangue at 400-450°C to obtain calcined gangue.

[0007] By adopting the above technical scheme, the coal gangue is mainly composed of polymeric minerals with high stability and complete crystal form such as quartz and kaolinite. These minerals are difficult to react with other substances at room temperature. When the coal gangue is activated by high-temperature calcination, the kinetic energy of each microscopic particle in the coal gangue increases at high temperature, causing the bridge bonds between the silicon-oxygen tetrahedron and the aluminum-oxygen triangle to break, destroying the thermodynamically stable glass phase structure generated by the orderly arrangement of the material molecules, so that the calcined coal gangue contains a large amount of active aluminum oxide and silicon oxide, thereby achieving activation.

[0008] In the present application, the gangue is first crushed and screened, and then treated in a low eutectic solvent under ultrasonic-assisted conditions. The amide compounds in the HBA component act as hydrogen bond acceptors. The nitrogen atom in the amide molecule and the oxygen atom on the carbonyl group have lone electron pairs. These lone electron pairs form coordination bonds and hydrogen bonds with metal ions such as silicon and aluminum in the gangue, changing the structure and charge distribution of silicates, thereby increasing the activity of the gangue. The HBD component uses carboxylic acids and polyols. Carboxylic acids react with carbonates in the gangue to form soluble metal carboxylates, which are helpful for the release of metal ions. The hydroxyl polarity rich in the polyol interacts with the polar region on the surface of the gangue, weakens the original chemical bonds, makes the metal ions more easily dissolved, and realizes the activation of the gangue. The addition of choline chloride forms a more stable low eutectic system with other components. The addition of low eutectic solvents changes the internal chemical structure and charge distribution of coal gangue. The chemical reaction between the low eutectic solvents and coal gangue helps to destroy the original strong crystal structure of coal gangue, reduce the reaction temperature and activation energy, and increase the reactivity of coal gangue, so that coal gangue can be calcined at a lower temperature to achieve a good activation effect and reduce energy consumption.

[0009] Ultrasonic treatment is used in conjunction with low eutectic solvent treatment. Ultrasonic treatment will promote the activation effect of the above-mentioned low eutectic solvent on coal gangue, and will also destroy the mineral crystal structure in the coal gangue, promote the transformation and activity improvement of mineral components, and then carry out subsequent calcination treatment to further reduce the calcination temperature, so that the coal gangue can be calcined at a lower temperature, which can achieve the activation of coal gangue, and the activation effect is more excellent.

[0010] Optionally, in the calcination step, the pretreated coal gangue and calcium fluoride are added together before calcination, and the mass of the added calcium fluoride is 0.05-0.1wt% of the pretreated coal gangue.

[0011] By adopting the above technical solution, the addition of calcium fluoride can reduce the melting point during the calcination process, help to better decompose the mineral components in the coal gangue, promote the transformation of the structure in the coal gangue, further reduce the calcination temperature and improve the activation effect of the coal gangue.

[0012] Optionally, in the pretreatment step, the low eutectic solvent is dissolved in 4-6 volume times of water to obtain a low eutectic solvent solution for use, and the added amount of the low eutectic solvent is 8-10wt% of the coal gangue particles.

[0013] By adopting the above technical solution, the low eutectic solvent is dissolved in water and diluted before use, which can play a better activation role and change the structure of coal gangue, which is beneficial to the ultimate improvement of the activity of coal gangue.

[0014] Optionally, in the pretreatment step, the amide compound is one or more of formamide and acetamide; The carboxylic acid mixture is a mixture of glycolic acid and one of citric acid, malic acid and levulinic acid in a mass ratio of 1: (0.5-0.8); The polyol is selected from one or more of ethylene glycol, glycerol and xylitol.

[0015] By adopting the above technical scheme, the carboxylic acid mixture includes at least hydroxyacetic acid, which contains both hydroxyl group and carboxylic acid. The chemical reaction between hydroxyacetic acid and the components of coal gangue particles helps to destroy the original crystal structure of coal gangue, increase disorder, and improve the activity of coal gangue. Moreover, the addition of carboxyacetic acid helps to transform the crystal structure of coal gangue, so that the coal gangue can be calcined at a lower temperature to achieve a better activation effect.

[0016] Optionally, the mass ratio of choline chloride, amide compound, carboxylic acid mixture and polyol is 1:(1.2-1.5):(1.2-1.5):(0.6-0.8).

[0017] By adopting the above technical solution and controlling the addition ratio of raw materials in the low eutectic solvent, a stable low eutectic solvent system is obtained, and a better activation effect is achieved on the basis of lowering the calcination temperature.

[0018] Optionally, the coal gangue in the pre-treatment step is clay rock coal gangue.

[0019] By adopting the above technical scheme, clay rock-type coal gangue is selected as coal gangue, which has higher volcanic ash activity. Volcanic ash activity refers to the reaction of active components in volcanic ash with water at high temperature to generate water-hardening products such as calcium silicate, calcium aluminosilicate, etc. These products have higher strength and stability. The use of clay rock-type coal gangue with higher volcanic ash activity in concrete can better improve the strength and durability of concrete.

[0020] Optionally, the particle size of the coal gangue particles in the pre-treatment step is 50 μm-1 mm.

[0021] By adopting the above technical solution, the coal gangue is processed into the above particle size range in the pre-treatment step, which is more conducive to the subsequent activation operation.

[0022] Optionally, in the calcination step, the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcination, and the amount of sodium thiosulfate added is 3-5wt% of the pretreated coal gangue.

[0023] By adopting the above technical scheme, silicon and aluminum in the coal gangue exist in a stable form, and the addition of sodium thiosulfate can react with the hydroxyl groups or oxygen atoms on its surface to change its surface properties, which helps to increase the activity of aluminum oxide and silicon oxide, thereby increasing the content of active aluminum oxide and silicon oxide. Moreover, the addition of sodium thiosulfate plays a catalytic role in the activation process of coal gangue, accelerates the reaction of coal gangue with other activators, and improves the activation efficiency. Moreover, sodium thiosulfate can also react with organic components in coal gangue to destroy the stable chemical structure, thereby destroying the stable crystal structure in coal gangue, which helps to improve the activity of coal gangue.

[0024] In a second aspect, the present application provides a method for calcining coal gangue, using the following technical solution: A calcined coal gangue is prepared by the above method.

[0025] By adopting the above technical solution and the chemical-physical combined activation method for coal gangue in the present application, the activity of coal gangue can be significantly improved under relatively low calcination temperature conditions.

[0026] In a third aspect, the present application provides an application of calcined coal gangue, using the following technical solution: As described the application of calcined coal gangue in concrete.

[0027] By adopting the above technical scheme, the calcined coal gangue prepared in the present application has higher activity, and the calcined coal gangue can react with alkaline materials such as lime to generate a hydraulic substance, which can be used as an admixture for concrete to improve the strength, wear resistance, impermeability and durability of concrete, and improve the comprehensive performance of concrete.

[0028] In summary, this application has the following beneficial effects: 1. The addition of the low eutectic solvent in the present application changes the internal chemical structure and charge distribution of the coal gangue, and the chemical reaction between the low eutectic solvent and the low eutectic solvent helps to destroy the original strong crystal structure of the coal gangue, reduce the reaction temperature and activation energy, and improve the reaction activity of the coal gangue, so that the coal gangue can be calcined at a lower temperature to achieve a good activation effect and reduce energy consumption; 2. Ultrasonic treatment is used in conjunction with the low eutectic solvent treatment. Ultrasonic treatment will promote the activation effect of the above-mentioned low eutectic solvent on coal gangue, and will also destroy the mineral crystal structure in the coal gangue, promote the transformation and activity improvement of the mineral components, and then carry out subsequent calcination treatment to further reduce the calcination temperature, so that the coal gangue can be calcined at a lower temperature, which can achieve the activation of the coal gangue; 3. The addition of calcium fluoride in the present application can reduce the melting point during the calcination process, help the mineral components in the coal gangue to melt and decompose better, promote the transformation of the structure in the coal gangue, further reduce the calcination temperature and improve the activation effect of the coal gangue; 4. The carboxylic acid mixture in the low eutectic solvent of the present application at least includes glycolic acid, which contains both hydroxyl groups and carboxylic acids. Its chemical reaction with the components of the coal gangue particles helps to destroy the original crystal structure of the coal gangue, increase disorder, and improve the activity of the coal gangue. Moreover, more importantly, the addition of carboxylic acid may also affect the melting behavior of the coal gangue, help the mineral components in the coal gangue to melt and decompose better, and help the transformation of the crystal structure of the coal gangue, so that the coal gangue can be calcined at a lower temperature to achieve a better activation effect. DETAILED DESCRIPTION

[0029] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0030] The method provided in the present application crushes and screens the gangue to obtain the ore material. The crushing degree in the step is adjusted according to the adaptability of the gangue use. The calcined and activated gangue can be used as an admixture, coarse aggregate or fine aggregate in concrete. When the calcined gangue is used as coarse aggregate, the processing size is greater than 5 mm, and when it is used as fine aggregate, the size of the gangue after crushing and screening is less than 5 mm, which is used to improve the performance of concrete.

[0031] Example 1 A method for activating coal gangue comprises the following steps: S1. Pretreatment: Using 1kg of coal gangue as the treatment standard, the clay rock coal gangue is crushed and sieved to obtain coal gangue particles with a particle size of 50μm-1mm; S2, pretreatment: taking a low eutectic solvent of 9 wt% of the mass of the gangue particles in step S1 and dissolving it in 5 volume times of water to obtain a low eutectic solvent solution, then immersing the gangue particles obtained after the pretreatment in step S1 in the low eutectic solvent solution, and performing ultrasonic-assisted treatment for 2.5 h, the ultrasonic treatment frequency is 25 KHz, the ultrasonic power is 30 W, and then washing with water to obtain pretreated gangue; The low eutectic solvent is a liquid formed by heating and stirring an HBA component and an HBD component at 90° C. The HBA component is a mixture of choline chloride and an amide compound, the HBD component is a mixture of a carboxylic acid mixture and a polyol, and the mass ratio of choline chloride, the amide compound, the carboxylic acid mixture and the polyol is 1:1.3:1.3:0.7, the amide compound is formamide, the carboxylic acid mixture is a mixture of glycolic acid and citric acid in a mass ratio of 1:0.6, and the polyol is ethylene glycol; S3. Calcination: calcine the pretreated coal gangue at 430° C. for 1 h to obtain calcined coal gangue.

[0032] Example 2 A method for activating coal gangue comprises the following steps: S1. Pretreatment: Using 1kg of coal gangue as the treatment standard, the clay rock coal gangue is crushed and sieved to obtain coal gangue particles with a particle size of 50μm-1mm; S2, pretreatment: taking 8wt% of the low eutectic solvent of the mass of the gangue particles in step S1 and dissolving it in 4 volume times of water to obtain a low eutectic solvent solution, then immersing the gangue particles obtained after the pretreatment in step S1 in the low eutectic solvent solution, and performing ultrasonic-assisted treatment for 2h, the ultrasonic treatment frequency is 22KHz, the ultrasonic power is 28W, and then washing with water to obtain pretreated gangue; The low eutectic solvent is a liquid formed by heating and stirring an HBA component and an HBD component at 90° C. The HBA component is a mixture of choline chloride and an amide compound, the HBD component is a mixture of a carboxylic acid mixture and a polyol, and the mass ratio of choline chloride, the amide compound, the carboxylic acid mixture and the polyol is 1:1.2:1.2:0.6, the amide compound is acetamide, the carboxylic acid mixture is a mixture of glycolic acid and levulinic acid in a mass ratio of 1:0.5, and the polyol is glycerol; S3. Calcination: calcining the pretreated coal gangue at 400° C. for 40 min to obtain calcined coal gangue.

[0033] Example 3 A method for activating coal gangue comprises the following steps: S1. Pretreatment: Using 1kg of coal gangue as the treatment standard, the clay rock coal gangue is crushed and sieved to obtain coal gangue particles with a particle size of 50μm-1mm; S2, pretreatment: taking a low eutectic solvent of 10 wt% of the mass of the gangue particles in step S1 and dissolving it in 6 volume times of water to obtain a low eutectic solvent solution, then immersing the gangue particles obtained after the pretreatment in step S1 in the low eutectic solvent solution, and performing ultrasonic-assisted treatment for 3 h, the ultrasonic treatment frequency is 26 KHz, the ultrasonic power is 32 W, and then washing with water to obtain pretreated gangue; The low eutectic solvent is a liquid formed by heating and stirring an HBA component and an HBD component at 90° C. The HBA component is a mixture of choline chloride and an amide compound, the HBD component is a mixture of a carboxylic acid mixture and a polyol, and the mass ratio of choline chloride, the amide compound, the carboxylic acid mixture and the polyol is 1:1.5:1.5:0.8, the amide compound is formamide, the carboxylic acid mixture is a mixture of glycolic acid and malic acid in a mass ratio of 1:0.8, and the polyol is xylitol; S3. Calcination: calcining the pretreated coal gangue at 450° C. for 80 min to obtain calcined coal gangue.

[0034] Example 4 A method for activating gangue is carried out according to the method in Example 1, except that during calcination in step S3, pretreated gangue and calcium fluoride are added together before calcination, and the mass of added calcium fluoride is 0.08wt% of the pretreated gangue.

[0035] Example 5 A method for activating gangue is carried out according to the method in Example 1, except that during calcination in step S3, pretreated gangue and calcium fluoride are added together before calcination, and the mass of added calcium fluoride is 0.05wt% of the pretreated gangue.

[0036] Example 6 A method for activating gangue is carried out according to the method in Example 1, except that during calcination in step S3, pretreated gangue and calcium fluoride are added together before calcination, and the mass of added calcium fluoride is 0.1wt% of the pretreated gangue.

[0037] Example 7 A method for activating coal gangue is carried out according to the method in Example 1, except that the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcining, and the amount of sodium thiosulfate added is 4wt% of the pretreated coal gangue.

[0038] Example 8 A method for activating coal gangue is carried out according to the method in Example 1, except that the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcining, and the amount of sodium thiosulfate added is 3wt% of the pretreated coal gangue.

[0039] Example 9 A method for activating coal gangue is carried out according to the method in Example 1, except that the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcining, and the amount of sodium thiosulfate added is 5wt% of the pretreated coal gangue.

[0040] Comparative Example 1 A method for activating coal gangue is carried out according to the method in Example 1, except that the pretreatment in step S2 is not performed.

[0041] Comparative Example 2 A method for activating gangue is carried out according to the method in Example 1, except that the pretreatment in step S2 is not carried out, and the calcination temperature in step S3 is 650° C. and the calcination time is 2 hours.

[0042] Comparative Example 3 A method for activating gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, the HBA component is formamide and the HBD component is ethylene glycol, and the added mass ratio of formamide to ethylene glycol is 1.3:0.7.

[0043] Comparative Example 4 A method for activating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, ethylene glycol is used as the HBD component, no carboxylic acid mixture is added, and the mass ratio of choline chloride, formamide and ethylene glycol added is 1:1.3:0.7.

[0044] Comparative Example 5 A method for activating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, formamide is used as the HBA component, choline chloride is not added, and the mass ratio of formamide, carboxylic acid mixture and polyol is 1.3:1.3:0.7.

[0045] Comparative Example 6 A method for activating and treating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, the low eutectic solvent is directly replaced with citric acid in an equal amount.

[0046] Comparative Example 7 A method for activating and treating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, the low eutectic solvent liquid is directly replaced with citric acid in an equal amount.

[0047] Performance Testing The gangue prepared in the above examples and comparative examples was tested for volcanic ash activity to characterize the effect of improving the activity of the gangue. Specifically, the calcium hydroxide consumption method was used, which is mainly based on the fact that clay rock gangue generates amorphous silicon oxide and aluminum oxide after high-temperature calcination. Amorphous silicon oxide and aluminum oxide can react with calcium hydroxide to generate hydrated silicate, aluminate, etc. The reaction process will consume calcium hydroxide. The specific detection method is: The gangue prepared in the embodiment and the comparative example were mixed with calcium oxide in a mass ratio of 8:2, 10 g of the sample was accurately weighed, added into 500 mL of water, stirred thoroughly, and sealed in a test tube with a rubber stopper. The mixture was cured at room temperature, and 1 g of the hydrated sample after curing for 28 days was taken, dried at 60 ° C, and ground to a specific surface area of ​​400 m 2 / kg, sealed and stored, the glycerol-anhydrous ethanol method was used to determine the remaining calcium hydroxide in the gangue-calcium hydroxide-water system, the difference between the amount of calcium hydroxide in the initial sample and the remaining amount was the calcium hydroxide reaction amount, the reaction amount reflected the activity of the gangue, the percentage of the calcium hydroxide reaction amount to the initial calcium hydroxide mass was the gangue activity, and the statistical results were shown in Table 1 below.

[0048] Table 1: Referring to the test results of Table 1 above, it can be seen that the coal gangue prepared in the present application has excellent volcanic ash activity. Referring to the test results of Example 1 and Examples 4-6, it can be seen that when calcium fluoride is used to calcine the pretreated coal gangue together, the activity of the obtained coal gangue is significantly improved at the same calcination temperature. Referring to the test results of Example 1 and Examples 7-9, it can be seen that the addition of sodium thiosulfate can further improve the activity of the coal gangue. Referring to the test results of Example 1 and Comparative Example 1, when the coal gangue is not pretreated and directly calcined at 430°C, its activity is low. Combined with the test results of Comparative Example 2, it can be seen that after the present application is processed by step S2, the activity is close to or even better than the current high-temperature 650°C calcination activity. The method provided by the present application can achieve activation of coal gangue by calcination at a lower temperature, which is similar to the existing high-temperature calcination effect, or even better, and greatly reduces energy consumption.

[0049] Referring to the test results of Example 1 and Comparative Examples 3-5, it can be seen that when choline chloride and carboxylic acid compounds are not added to the low eutectic solvent in Comparative Example 3, the activity effect on coal gangue is significantly reduced, and when the carboxylic acid compound is not added in Comparative Example 4, its effect is also significantly reduced. Referring to Comparative Example 5 in which choline chloride is not added, it is improved compared with Comparative Examples 3 and 4, but is significantly lower than Comparative Example 1. The main reason is that the addition of choline chloride helps to form a stable low eutectic system, thereby playing a role. Referring to the test results of Comparative Examples 6 and 7, without being treated with a low eutectic solvent, at a lower temperature and with a weak acid treatment, the activity effect on coal gangue is still poor.

[0050] Application Examples The gangue prepared in the embodiments and comparative examples of the present application is used as an admixture in concrete. Specifically, 100 kg of gangue, 200 kg of cement, 90 kg of water, 30 kg of fly ash and 5 kg of water reducer are stirred for 15 minutes, and then 450 kg of coarse aggregate and 550 kg of fine aggregate are added and stirred for 25 minutes to obtain test concrete, wherein the gangue is the calcined gangue prepared in the above embodiments and comparative examples of the present application, the fine aggregate is calcined gangue (prepared in the embodiments and comparative examples of the present application) and sand in a mass ratio of 1:0.3, the sand is fine sand with a coefficient modulus of 1.8-2.0, the coarse aggregate is crushed stone, and the crushed stone is 5-15 mm continuous graded crushed stone, the fly ash is F Class I fly ash, the water reducer is polycarboxylic acid water reducer (can be purchased from Jinan Hongtai Chemical Co., Ltd., model 0007), and the cement is ordinary Portland cement with PO42.5. The concrete prepared by using the calcined coal gangue prepared in the examples and comparative examples of the present application was tested for 28d compressive strength (Mpa) in accordance with GB / T50081-2016 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete", and the test results are shown in Table 2 below.

[0051] Comparative Application Examples The method in the application example is followed, except that the gangue admixture is replaced by fly ash in equal amounts, and sand is used as fine aggregate. Control concrete is prepared according to the method in the application example, and the control concrete is tested for 28d compressive strength (Mpa) in accordance with GB / T50081-2016 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete". The test results are shown in Table 2 below.

[0052] Table 2: Referring to the test results in Table 1 above, combined with the test results of the comparative application examples, it can be seen that the calcined coal gangue obtained by the treatment method in this application, when applied to concrete, helps to improve the strength of the concrete.

[0053] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for activating coal gangue, characterized in that: The following steps are involved: Pretreatment: crushing and screening the coal gangue to obtain coal gangue particles; Pretreatment: treating the gangue particles in a low eutectic solvent, and performing ultrasound-assisted treatment, and washing with water to obtain pretreated gangue, wherein the low eutectic solvent includes an HBA component and an HBD component, wherein the HBA component is a mixture of choline chloride and amide compounds, and the HBD component is a mixture of a carboxylic acid mixture and a polyol; Calcination: Calcine the pretreated gangue at 400-450°C to obtain calcined gangue.

2. The method for activating coal gangue according to claim 1, characterized in that: In the calcination step, the pretreated coal gangue and calcium fluoride are added together and then calcined, and the added mass of calcium fluoride is 0.05-0.1wt% of the pretreated coal gangue.

3. The method for activating coal gangue according to claim 1, characterized in that: In the pretreatment step, the low eutectic solvent is dissolved in 4-6 volume times of water to obtain a low eutectic solvent solution for use, and the addition amount of the low eutectic solvent is 8-10wt% of the coal gangue particles.

4. The method for activating coal gangue according to claim 1, characterized in that: In the pretreatment step, the amide compound is selected from one or more of formamide and acetamide; The carboxylic acid mixture is a mixture obtained by mixing glycolic acid with one of citric acid, malic acid and levulinic acid in a mass ratio of 1: (0.5-0.8); The polyol is selected from one or more of ethylene glycol, glycerol and xylitol.

5. The method for activating coal gangue according to claim 1, characterized in that: The mass ratio of choline chloride, amide compound, carboxylic acid mixture and polyol is 1:(1.2-1.5):(1.2-1.5):(0.6-0.8).

6. The method for activating coal gangue according to claim 1, characterized in that: The coal gangue in the pre-treatment step is selected from clay rock type coal gangue.

7. The method for activating coal gangue according to claim 1, characterized in that: The particle size of the coal gangue particles in the pre-treatment step is 50 μm-1 mm.

8. The method for activating coal gangue according to claim 1, characterized in that: In the calcination step, the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcination, and the amount of sodium thiosulfate added is 3-5wt% of the pretreated coal gangue.

9. Calcined coal gangue obtained by the method according to any one of claims 1 to 8.

10. Use of the calcined coal gangue as claimed in claim 9 in concrete.

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