Modified coal gangue and application thereof in soil remediation

Abstract

The invention discloses a preparation method of modified coal gangue, and the preparation method comprises the following steps: S1, carrying out acid pickling and water washing on coal gangue, then carrying out high-temperature calcination, after calcination is finished, crushing, and sieving with a 80-200-mesh sieve to obtain coal gangue powder; s2, dissolving lignin in an alkaline reagent to obtain an alkaline solution of lignin, dispersing the obtained coal gangue powder in the alkaline solution of lignin, performing ultrasonic treatment, adding ethylene glycol diglycerol ether and a coupling agent after ultrasonic treatment, and stirring to obtain a coal gangue / lignin solution; s3, hydroxypropyl-beta-cyclodextrin, tetracarboxylic acid and an initiator are sequentially added into the obtained coal gangue / lignin solution, stirring reaction is conducted, then standing and filtering are conducted, an obtained solid product is washed and freeze-dried, and the modified coal gangue is obtained. According to the method, backfill reclamation of the coal gangue can be realized through modification treatment of the coal gangue.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and in particular, relates to modified coal gangue and application thereof in soil remediation. Background Art

[0002] Coal gangue is solid waste generated and discharged during coal mining and beneficiation, accounting for 10-15% of raw coal production.

[0003] Gangue backfill refers to the use of gangue to replace soil, sand, stone and other production materials to fill underground voids, surface excavation areas of open-pit mining, borrow pits, underground mining subsidence areas and natural pits for the purpose of land reclamation in projects such as filling and reclamation, ecological landscape restoration, construction land and agricultural land leveling, and landform protection to prevent surface collapse. Since there are a variety of heavy metal elements in gangue, when it is directly used for backfilling, the gangue will inevitably lead to the migration of heavy metal elements it contains under the influence of external environments such as weathering, erosion, and rainwater leaching. For example, heavy metal elements enter the atmosphere along with harmful gases, which will deteriorate the air environment and affect human health. Therefore, at present, the above phenomenon can be prevented by pre-treating the gangue before backfilling.

[0004] At present, cement, lime, thermoplastic / thermosetting microencapsulation and agent stabilization / solidification technology are commonly used to treat coal gangue to control the migration, diffusion and dissolution of heavy metal elements in coal gangue. However, the existing modified materials / methods still have shortcomings. Summary of the invention

[0005] The purpose of the present invention is to provide a modified coal gangue and its application in soil remediation, so as to realize the backfilling and reclamation of the coal gangue by modifying the coal gangue.

[0006] To this end, the present invention provides the following technical solutions.

[0007] One aspect of the present invention provides a method for preparing modified coal gangue, the preparation method comprising the following steps:

[0008] S1: After acid washing and water washing, the coal gangue is calcined at high temperature, and after calcination, it is crushed through a 80-200 mesh sieve to obtain coal gangue powder;

[0009] S2: dissolving lignin in an alkaline reagent and adjusting the pH to 8-12, heating to 80-100° C. to obtain an alkaline solution of lignin, dispersing the obtained coal gangue powder in the obtained alkaline solution of lignin in an amount of 1 g:20-50 ml by mass volume ratio and ultrasonically treating, adding ethylene glycol diglycerol ether and a coupling agent after the ultrasonic treatment and stirring for 1-2 hours to obtain a coal gangue / lignin solution;

[0010] S3: Add hydroxypropyl-β-cyclodextrin, tetracarboxylic acid and initiator to the obtained gangue / lignin solution in the volume mass ratio of 100 ml gangue / lignin solution: 3-10 g hydroxypropyl-β-cyclodextrin: 0.01-0.05 g tetracarboxylic acid: 0.003-0.007 g initiator in sequence, stir the reaction at 50-100°C for 2-4 hours, then let it stand for 30-50 minutes, and then filter. Wash and freeze-dry the obtained solid product to obtain modified gangue.

[0011] As a preferred embodiment of the present invention, in step S1, the high temperature calcination conditions are: temperature 200-400° C., time 4-6 hours.

[0012] As a preferred embodiment of the present invention, in step S2, the alkaline reagent is selected from one or more of sodium hydroxide and potassium hydroxide.

[0013] As a preferred embodiment of the present invention, in step S2, the ultrasonic treatment conditions are: power 600-1000W, time 20-40min.

[0014] As a preferred embodiment of the present invention, in step S2, the amount of ethylene glycol diglycerol ether added is 1 to 3 times the mass of the coal gangue powder.

[0015] As a preferred embodiment of the present invention, in step S2, the coupling agent is selected from one or more of methylsiloxane and ethylsiloxane.

[0016] As a preferred embodiment of the present invention, in step S2, the amount of the coupling agent added is 0.3-0.5% of the mass of ethylene glycol diglycerol ether.

[0017] As a preference of the present invention, in step S3, the tetracarboxylic acid is selected from one or more of 3,3',5,5'-sulfinyl diisophthalic acid, 3,3',5,5'-sulfonyl diisophthalic acid, 3,3',5,5'-azadiisophthalic acid, 3,3',5,5'-oxydiisophthalic acid, 3,3',5,5'-carbonyl diisophthalic acid or 3,3',5,5'-methylene diisophthalic acid.

[0018]

[0019]

[0020] As a preferred embodiment of the present invention, in step S3, the initiator is selected from one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0021] Another aspect of the present invention also provides a use of modified coal gangue prepared according to the preparation method of modified coal gangue as described above in soil remediation.

[0022] By means of the above technical solution, the present invention has at least the following advantages:

[0023] 1. The present invention can prevent the migration, diffusion and dissolution of heavy metal elements contained in the coal gangue by modifying the coal gangue. On the other hand, the surface of the modified coal gangue contains a large amount of negative charges, which can also achieve the adsorption and combination of heavy metals, thereby reducing the heavy metal content in the surrounding environment during the backfilling and reclamation of coal gangue.

[0024] 2. The present invention uses lignin, which is widely available, as one of the raw materials. The lignin is compounded with the gangue under the action of ethylene glycol diglycerol and a coupling agent. The coupling agent plays a bridging role and can "connect" the lignin and the gangue to obtain surface-modified gangue. Subsequently, hydroxypropyl-β-cyclodextrin is used to coat the surface-modified gangue of ethylene glycol diglycerol. At the same time, a polymerization reaction is carried out under the action of an initiator to introduce polycarboxyl anions. The obtained modified gangue not only contains rich organic matter, but also prevents the dissolution of heavy metals in the gangue through the coating effect of lignin and hydroxypropyl-β-cyclodextrin.

[0025] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the percentage content involved in the present invention refers to mass percentage for solid-liquid mixing and solid-solid mixing, and refers to volume percentage for liquid-liquid mixing.

[0028] Unless otherwise specified, the percentage concentrations referred to in the present invention all refer to final concentrations, which refer to the percentage of the added component in the system after the addition of the component.

[0029] The temperature parameters in the present invention, if not specifically limited, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument.

[0030] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0031] Unless otherwise specified, the coal gangue used in the following examples was sourced from the Bulianta gangue dump in Shendong Mining Area, ethylene glycol diglycerol was purchased from Shandong Jinshengtai Chemical Co., Ltd., and other materials, reagents, etc. were all available from commercial sources.

[0032] Embodiment 1:

[0033] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0034] S1: After acid washing and water washing, the coal gangue is calcined at 300°C for 5 hours. After calcination, it is crushed through a 100-mesh sieve to obtain coal gangue powder.

[0035] S2: dissolving lignin in a 4 mol / L sodium hydroxide solution and adjusting the pH to 10, heating to 90°C, stirring the solution until the lignin is dissolved, and obtaining an alkaline solution of lignin; dispersing the obtained coal gangue powder in the obtained alkaline solution of lignin according to a mass volume ratio of 1 g:35 ml and ultrasonically treating it at a power of 800 W for 30 min, adding ethylene glycol diglycerol ether (the amount added is 2 times the mass of the coal gangue powder) and methylsiloxane (the amount added is 0.4% of the mass of ethylene glycol diglycerol ether) after the ultrasonic treatment, stirring for 1.5 h, and obtaining a coal gangue / lignin solution;

[0036] S3: Add hydroxypropyl-β-cyclodextrin, 3,3',5,5'-sulfinyl diisophthalic acid and ammonium persulfate to the obtained gangue / lignin solution in the volume mass ratio of 100 ml: 6.5 g: 0.03 g: 0.005 g in sequence, stir the reaction at 75°C for 3 hours, then let it stand for 40 minutes, and then filter. Wash the obtained solid product three times with deionized water and freeze-dry it at -20°C to obtain modified gangue.

[0037] Embodiment 2:

[0038] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0039] S1: After acid washing and water washing, the coal gangue is calcined at 200°C for 6 hours. After calcination, it is crushed through an 80-mesh sieve to obtain coal gangue powder.

[0040] S2: dissolving lignin in a 5 mol / L sodium hydroxide solution and adjusting the pH to 12, heating to 80°C, stirring the solution until the lignin is dissolved, and obtaining an alkaline solution of lignin; dispersing the obtained coal gangue powder in the obtained alkaline solution of lignin according to a mass volume ratio of 1 g:50 ml and ultrasonically treating it at a power of 600 W for 40 min, adding ethylene glycol diglycerol ether (the amount added is 1 times the mass of the coal gangue powder) and coupling agent ethyl siloxane (the amount added is 0.3% of the mass of ethylene glycol diglycerol ether) after the ultrasonic treatment, stirring for 1 hour, and obtaining a coal gangue / lignin solution;

[0041] S3: Add hydroxypropyl-β-cyclodextrin, 3,3',5,5'-sulfonyl diisophthalic acid and sodium persulfate to the obtained gangue / lignin solution in the volume mass ratio of 100 ml: 10 g: 0.01 g: 0.007 g, stir the reaction at 50°C for 4 hours, then let it stand for 30 minutes, and then filter. Wash the obtained solid product three times with deionized water and freeze-dry it at -20°C to obtain modified gangue.

[0042] Embodiment 3:

[0043] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0044] S1: After acid washing and water washing, the coal gangue is calcined at 400°C for 4 hours. After calcination, it is crushed through a 200-mesh sieve to obtain coal gangue powder.

[0045] S2: dissolving lignin in a 3 mol / L sodium hydroxide solution and adjusting the pH to 8, heating to 100°C, stirring the solution until the lignin is dissolved, and obtaining an alkaline solution of lignin; dispersing the obtained coal gangue powder in the obtained alkaline solution of lignin according to a mass volume ratio of 1 g:20 ml and ultrasonically treating it at a power of 1000 W for 20 min, adding ethylene glycol diglycerol ether (the amount added is 3 times the mass of the coal gangue powder) and methylsiloxane (the amount added is 0.5% of the mass of ethylene glycol diglycerol ether) after the ultrasonic treatment, stirring for 2 h, and obtaining a coal gangue / lignin solution;

[0046] S3: Add hydroxypropyl-β-cyclodextrin, 3,3',5,5'-azadiisophthalic acid and ammonium persulfate to the obtained gangue / lignin solution in the volume mass ratio of 100 ml: 3 g: 0.05 g: 0.003 g in sequence, stir the reaction at 100°C for 2 hours, then let it stand for 50 minutes, and then filter. Wash the obtained solid product three times with deionized water and freeze-dry it at -20°C to obtain modified gangue.

[0047] Comparative Example 1:

[0048] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0049] S1: After acid washing and water washing, the coal gangue is calcined at 300°C for 5 hours. After calcination, it is crushed through a 100-mesh sieve to obtain coal gangue powder.

[0050] S2: Disperse the obtained coal gangue powder in water at a mass volume ratio of 1g:35ml and perform ultrasonic treatment for 30min at a power of 800W. After the ultrasonic treatment, add ethylene glycol diglycerol ether (the amount added is 2 times the mass of the coal gangue powder) and methylsiloxane (the amount added is 0.4% of the mass of ethylene glycol diglycerol ether) and stir for 1.5h to obtain a coal gangue solution;

[0051] S3: Add hydroxypropyl-β-cyclodextrin, 3,3',5,5'-sulfinyl diisophthalic acid and ammonium persulfate to the obtained gangue solution in the volume mass ratio of 100 ml: 6.5 g: 0.03 g: 0.005 g in sequence, stir the reaction at 75°C for 3 hours, then let it stand for 40 minutes, and then filter. Wash the obtained solid product three times with deionized water and freeze-dry it at -20°C to obtain modified gangue.

[0052] Comparative Example 2:

[0053] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0054] S1: After acid washing and water washing, the coal gangue is calcined at 300°C for 5 hours. After calcination, it is crushed through a 100-mesh sieve to obtain coal gangue powder.

[0055] S2: dissolving lignin in a 4 mol / L sodium hydroxide solution and adjusting the pH to 10, heating to 90°C, stirring the solution until the lignin is dissolved, and obtaining an alkaline solution of lignin; dispersing the obtained coal gangue powder in the obtained alkaline solution of lignin in an amount of 1 g:35 ml by mass volume ratio, and ultrasonically treating the mixture at a power of 800 W for 30 min to obtain a coal gangue / lignin solution;

[0056] S3: Add hydroxypropyl-β-cyclodextrin, 3,3',5,5'-sulfinyl diisophthalic acid and ammonium persulfate to the obtained gangue / lignin solution in the volume mass ratio of 100 ml: 6.5 g: 0.03 g: 0.005 g in sequence, stir the reaction at 75°C for 3 hours, then let it stand for 40 minutes, and then filter. Wash the obtained solid product three times with deionized water and freeze-dry it at -20°C to obtain modified gangue.

[0057] Comparative Example 3:

[0058] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0059] S1: After acid washing and water washing, the coal gangue is calcined at 300°C for 5 hours. After calcination, it is crushed through a 100-mesh sieve to obtain coal gangue powder.

[0060] S2: dissolving lignin in a 4 mol / L sodium hydroxide solution and adjusting the pH to 10, heating to 90°C, stirring the solution until the lignin is dissolved, and obtaining an alkaline solution of lignin; dispersing the obtained coal gangue powder in the obtained alkaline solution of lignin according to a mass volume ratio of 1 g:35 ml and ultrasonically treating it at a power of 800 W for 30 min, adding ethylene glycol diglycerol ether (the amount added is 2 times the mass of the coal gangue powder) and methylsiloxane (the amount added is 0.4% of the mass of ethylene glycol diglycerol ether) after the ultrasonic treatment, stirring for 1.5 h, and obtaining a coal gangue / lignin solution;

[0061] S3: Add hydroxypropyl-β-cyclodextrin to the obtained gangue / lignin solution in a volume mass ratio of 100 ml:6.5 g, stir the reaction at 75°C for 3 hours, then let it stand for 40 minutes, and then filter. Wash the obtained solid product three times with deionized water and freeze-dry it at -20°C to obtain modified gangue.

[0062] Comparative Example 4:

[0063] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0064] S1: After acid washing and water washing, the coal gangue is calcined at 300°C for 5 hours. After calcination, it is crushed through a 100-mesh sieve to obtain coal gangue powder.

[0065] S2: dispersing the obtained coal gangue powder in water at a mass volume ratio of 1 g:35 ml to obtain a coal gangue solution;

[0066] S3: Add hydroxypropyl-β-cyclodextrin, 3,3',5,5'-sulfinyl diisophthalic acid and ammonium persulfate to the obtained gangue solution in the volume mass ratio of 100 ml: 6.5 g: 0.03 g: 0.005 g in sequence, stir the reaction at 75°C for 3 hours, then let it stand for 40 minutes, and then filter. Wash the obtained solid product three times with deionized water and freeze-dry it at -20°C to obtain modified gangue.

[0067] Comparative Example 5:

[0068] A method for preparing modified coal gangue, the preparation method comprising the following steps:

[0069] S1: After acid washing and water washing, the coal gangue is calcined at 300°C for 5 hours. After calcination, it is crushed through a 100-mesh sieve to obtain coal gangue powder.

[0070] S2: Dissolve lignin in 4 mol / L sodium hydroxide solution and adjust the pH to 10, heat to 90°C, stir the solution until the lignin is dissolved, and obtain an alkaline solution of lignin; disperse the obtained coal gangue powder in the obtained alkaline solution of lignin according to a mass volume ratio of 1g:35ml and ultrasonically treat it at a power of 800W for 30min. After the ultrasonic treatment, add ethylene glycol diglycerol ether (the amount added is 2 times the mass of coal gangue powder) and methylsiloxane (the amount added is 0.4% of the mass of ethylene glycol diglycerol ether) and stir for 1.5h, then filter, wash the obtained solid product with deionized water 3 times, and then freeze-dry it at -20°C to obtain modified coal gangue.

[0071] Comparative Example 6:

[0072] Coal gangue without any treatment.

[0073] Experiment 1: Heavy metal leaching experiment of coal gangue

[0074] The heavy metal leaching experiment of coal gangue was completed according to the basis of immersion test and the requirements of the industry standards "HJ / T 299-2007 Solid Waste Leaching Toxicity Method Sulfuric Acid Nitric Acid Method" and "HJ 557-2010 Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method". The concentrations of Cd, As, Pb, Cu, Cr, Zn and Ni in the soil leachate were determined by inductively coupled plasma mass spectrometry (ICP-MS, PerkinElmer Nexlon 300X). The specific operations are as follows:

[0075] The modified gangue / gangue of Examples 1-3 and Comparative Examples 1-6 were respectively soaked in a barrel containing 1L of leaching solution at a fixed solid-liquid ratio of 1:10 (i.e., 1g:10ml) using a mixed nitric acid / sulfuric acid solution of pH=2, deionized water of pH=7, and sodium hydroxide solution of pH=12 as leaching solutions. The barrel mouth was sealed. The sampling time was set to 1h, 6h, 12h, 1d, 5d, 15d, and 30d, respectively. About 5mL of the leaching solution was taken with a syringe each time, and filtered into a 10mL centrifuge tube using a 0.45μm filter membrane to obtain the leaching solution to be tested. During the test, the same variable part was tested 3 times to calibrate the experimental error. After sampling, the immersion solution was filled to a constant volume of 1L. The results are shown in Tables 1-7.

[0076] Table 1 Determination of Cd (μg / L) concentration of different modified coal gangue

[0077]

[0078]

[0079] Table 2 Determination of As (μg / L) concentration of different modified coal gangue

[0080]

[0081] Table 3 Pb (μg / L) concentration determination of different modified coal gangue

[0082]

[0083] Table 4 Ni (μg / L) concentration determination of different modified coal gangue

[0084]

[0085]

[0086] Table 5 Determination of Cu (μg / L) concentration of different modified coal gangue

[0087]

[0088]

[0089] Table 6 Determination of Cr (μg / L) concentration of different modified coal gangue

[0090]

[0091]

[0092] Table 7 Determination of Zn (μg / L) concentration of different modified coal gangue

[0093]

[0094]

[0095] From the results of Tables 1 to 7, it can be seen that the solidification effect of each metal element of the coal gangue after certain modification treatment (corresponding to Examples 1-3 and Comparative Examples 1-5) is significantly better than that of the coal gangue without any treatment (corresponding to Example 6). And compared with the modified coal gangue of Comparative Examples 1-6, the metal leaching content of the coal gangue of Examples 1-3 of the present invention is significantly lower. The above results show that the method of the present invention can effectively prevent the migration and dissolution of heavy metals in coal gangue.

[0096] Experiment 2: Application of different modified coal gangue in soil remediation

[0097] In order to further explore the application of modified coal gangue in soil remediation, this experiment conducted a soil column test, collected soil leaching solution and further determined nitrogen leaching data.

[0098] The diameter of the PVC column used was 56 cm and the height was 25 cm. A layer of 100 mesh nylon mesh was placed at the bottom of the soil column to prevent soil loss. In each soil column, acid-washed quartz sand was evenly spread at the bottom of the column, about 1 cm.

[0099] The soil (from the dumping ground of the open-pit coal mine in Shendong Mining Area) was naturally air-dried, ground and passed through a 2mm sieve to remove animal and plant residues as spare soil. The coal gangue of Example 1 and Comparative Examples 1-6 were mixed with soil in a mass ratio of 1:1 to obtain different groups of soil mixtures. Then each group of soil mixtures was placed in a soil column until the soil column was covered, and finally covered with quartz sand, about 1 cm. All columns were stabilized for 1 day before the test. After equilibrium, the leaching test was started, and the steps were as follows: 200 ml of deionized water was added to each group for rapid leaching; the leaching solution was collected in a 50 ml centrifuge tube; and stored in a dark refrigerator at 4°C before analysis. Afterwards, the ammonium nitrogen and nitrate nitrogen in the leaching solution were determined respectively according to the "Determination of Ammonia Nitrogen in Water Quality Salicylic Acid Spectrophotometry" (HJ 536-2009) and the "Determination of Nitrate Nitrogen in Water Quality Ultraviolet Spectrophotometry" (HJ / T 346-2007). The test conditions were: temperature 25°C, relative humidity 65%. The results are shown in Table 8.

[0100] Table 8 Nitrogen leaching data of different repaired soils

[0101]

[0102]

[0103] It can be seen from the results in Table 8 that the modified coal gangue of Example 1 of the present invention can significantly reduce the leaching amount of ammonium nitrogen and nitrate nitrogen when used in soil remediation.

[0104] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing modified coal gangue, characterized in that: The preparation method comprises the following steps: S1: After acid washing and water washing, the coal gangue is calcined at high temperature, and after calcination, it is crushed through a 80-200 mesh sieve to obtain coal gangue powder; S2: dissolving lignin in an alkaline reagent and adjusting the pH to 8-12, heating to 80-100° C. to obtain an alkaline solution of lignin, dispersing the obtained coal gangue powder in the obtained alkaline solution of lignin in an amount of 1 g:20-50 ml by mass volume ratio and ultrasonically treating, adding ethylene glycol diglycerol ether and a coupling agent after the ultrasonic treatment and stirring for 1-2 hours to obtain a coal gangue / lignin solution; S3: Add hydroxypropyl-β-cyclodextrin, tetracarboxylic acid and initiator to the obtained gangue / lignin solution in the volume mass ratio of 100 ml gangue / lignin solution: 3-10 g hydroxypropyl-β-cyclodextrin: 0.01-0.05 g tetracarboxylic acid: 0.003-0.007 g initiator in sequence, stir the reaction at 50-100°C for 2-4 hours, then let it stand for 30-50 minutes, and then filter. Wash and freeze-dry the obtained solid product to obtain modified gangue.

2. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S1, the high temperature calcination conditions are: temperature 200-400°C, time 4-6h.

3. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S2, the alkaline reagent is selected from one or more of sodium hydroxide and potassium hydroxide.

4. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S2, the ultrasonic treatment conditions are: power 600-1000W, time 20-40min.

5. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S2, the amount of ethylene glycol diglycerol added is 1 to 3 times the mass of the coal gangue powder.

6. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S2, the coupling agent is selected from one or more of methylsiloxane and ethylsiloxane.

7. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S2, the coupling agent is added in an amount of 0.3-0.5% of the mass of ethylene glycol diglycerol ether.

8. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S3, the tetracarboxylic acid is selected from one or more of 3,3',5,5'-sulfinyl diisophthalic acid, 3,3',5,5'-sulfonyl diisophthalic acid, 3,3',5,5'-azadiisophthalic acid, 3,3',5,5'-oxydiisophthalic acid, 3,3',5,5'-carbonyl diisophthalic acid or 3,3',5,5'-methylene diisophthalic acid.

9. The method for preparing modified coal gangue according to claim 1, characterized in that: In step S3, the initiator is selected from one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

10. Use of the modified coal gangue prepared by the method according to any one of claims 1 to 9 in soil remediation.

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