Modified bentonite, its preparation method, bentonite-based seepage prevention materials and their applications

Abstract

This invention provides a method for preparing modified bentonite, comprising: step S1, mixing bentonite, an intercalating agent, and water to obtain a mixed slurry, wherein the intercalating agent includes sodium hexafluorosilicate; step S2, freezing the mixed slurry to obtain a frozen mixed slurry; and step S3, thawing and drying the frozen mixed slurry to obtain modified bentonite. This invention uses sodium hexafluorosilicate as one of the intercalating agent components to modify bentonite, and through freezing and thawing steps, it prepares sodium-based bentonite while simultaneously increasing the interlayer spacing and improving its impermeability.

Description

Technical Field

[0001] This invention relates to the field of bentonite-based seepage-proof materials, and more specifically, to a modified bentonite, its preparation method, bentonite-based seepage-proof materials, and their applications. Background Technology

[0002] Bentonite was first discovered in ancient strata in Wyoming, USA. Due to its high swelling capacity when exposed to water, strong cation exchange capacity, and low permeability, it is widely used in sewage treatment and seepage prevention work in landfills, coal gangue landfills, etc.

[0003] As mentioned above, bentonite possesses excellent swelling properties; its expansion coefficient decreases after swelling upon contact with water, making it a highly effective seepage-proof material. Specifically, when bentonite comes into contact with water, up to four layers of water molecules enter the interlayer regions of the bentonite molecules, accumulating there and increasing the interlayer spacing. The H2O molecules between the layers then undergo cationic bonding with interlayer cations to generate H3O. + It can also adsorb some foreign cations, thereby balancing the Si content in bentonite. 4+ Al 3+ The excess negative charge resulting from the replacement of low-valent cations causes bentonite to crystallize and swell, expanding its volume to 4 to 20 times its original size. This, in turn, blocks the interlayer voids of bentonite, reducing its permeability coefficient and thus giving it excellent anti-permeability properties.

[0004] However, bentonite in its pure form has poor expansion and mechanical properties, making it difficult for bentonite-based geomembranes prepared from it to meet the performance requirements of relevant applications. Therefore, providing a method for modifying bentonite to improve its expansion and mechanical properties, thereby enhancing the expansion and mechanical properties of the bentonite-based geomembranes prepared from it, is one of the important problems that need to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a modified bentonite, its preparation method, bentonite-based seepage-proof materials and their applications, in order to solve the problem of poor expansion performance and mechanical properties of existing bentonite-based seepage-proof materials.

[0006] To achieve the above objectives, the first aspect of this application provides a method for preparing modified bentonite, the method comprising: step S1, mixing bentonite, an intercalating agent and water to obtain a mixed slurry, wherein the intercalating agent includes sodium hexafluorosilicate; step S2, freezing the mixed slurry to obtain a frozen mixed slurry; and step S3, thawing and drying the frozen mixed slurry to obtain modified bentonite.

[0007] Furthermore, in step S2, the freezing temperature is -5 to -15°C, and the freezing time is 30 to 60 minutes.

[0008] Furthermore, after thawing and before drying in step S3, the thawed frozen mixture is maintained at 3-5°C for 10-20 minutes.

[0009] Further, the intercalating agent is a mixture of sodium hexafluorosilicate and sodium dodecyl sulfate; preferably, the weight ratio of sodium hexafluorosilicate to sodium dodecyl sulfate in the intercalating agent is 1:(1-5).

[0010] Further, in step S1, the weight ratio of bentonite to intercalating agent is 1:(0.1 to 0.3); and / or, the weight ratio of bentonite to water is 1:(3 to 6).

[0011] Furthermore, before step S2, the mixed slurry is subjected to ultrasonic treatment; preferably, the ultrasonic treatment power is 20-60 kHz and the time is 20-40 min / L.

[0012] Furthermore, the mixing process in step S1 is carried out at a temperature of 70–90°C for 20–40 minutes.

[0013] A second aspect of the present invention provides modified bentonite prepared by the above-described method for preparing modified bentonite.

[0014] A third aspect of the present invention provides a bentonite-based impermeable material comprising 95-105 parts of the above-mentioned modified bentonite, 1-6 parts of coal gasification slag, and 0.1-0.5 parts of sodium hydroxide; preferably, the bentonite-based impermeable material comprises 95-105 parts of the above-mentioned modified bentonite, 2-4 parts of coal gasification slag, and 0.2-0.3 parts of sodium hydroxide; preferably, the particle size of the coal gasification slag is 5-25 μm.

[0015] A fourth aspect of the present invention provides an application of the above-mentioned bentonite-based impermeable material in the field of impermeable, waterproof and barrier materials.

[0016] By applying the technical solution of this invention, sodium hexafluorosilicate is used as one of the intercalating agents to modify bentonite. Through freezing and thawing steps, it is prepared into sodium-based bentonite, while the interlayer spacing is expanded and the seepage prevention performance is improved. The modified bentonite is further compounded with coal gasification slag, sodium hydroxide, etc. to obtain bentonite-based seepage prevention materials. The obtained bentonite-based seepage prevention materials have good seepage prevention performance and mechanical properties, and can be widely used in multiple material fields such as seepage prevention, waterproofing and barrier. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] As described in the background section, existing bentonite-based impermeable materials suffer from poor expansion and mechanical properties. To address these issues, the first aspect of this invention provides a method for preparing modified bentonite, comprising: step S1, mixing bentonite, an intercalating agent, and water to obtain a mixed slurry, wherein the intercalating agent includes sodium hexafluorosilicate; step S2, freezing the mixed slurry to obtain a frozen mixed slurry; and step S3, thawing and drying the frozen mixed slurry to obtain modified bentonite.

[0019] This invention modifies bentonite using a simple preparation method, effectively improving its impermeability. Specifically, in step S1, the invention first uses a special intercalating agent containing sodium hexafluorosilicate to modify bentonite, preparing it into hydrated sodium-based bentonite. In step S2, a freezing step is used to cause the water adsorbed within the sodium-based bentonite to crystallize and expand, thereby increasing the interlayer spacing of the sodium-based bentonite. More importantly, because sodium hexafluorosilicate in the composite intercalating agent has high solubility in high-temperature water but is not easily soluble in water at low temperatures, some of the sodium hexafluorosilicate adsorbed within the sodium-based bentonite will also crystallize out during the freezing step, further increasing the interlayer spacing of the sodium-based bentonite and thus further improving the impermeability of the resulting modified bentonite.

[0020] It is worth mentioning that, compared with other sodium-based reagents such as sodium carbonate, sodium chloride, sodium fluoride, sodium hexametaphosphate, and sodium pyrophosphate, the sodium hexafluorosilicate used in this invention contains silicate ions (SiF6) with an octahedral structure. 2- This unique molecular composition and structure endows sodium hexafluorosilicate with hygroscopic properties not found in other sodium-based reagents mentioned above. Therefore, as described above, during the preparation process, a freezing step can introduce water of crystallization into the sodium-based bentonite, thereby expanding the interlayer spacing. Furthermore, the precipitation phenomenon caused by the freezing and thawing steps further expands the interlayer spacing, thereby enhancing the bentonite's impermeability and mechanical properties.

[0021] Specifically, the bentonite used in this invention contains ≥85wt% montmorillonite. Commonly used bentonite can be used in its preparation; commercially available products are readily available.

[0022] In a preferred embodiment, the freezing temperature in step S2 is -5 to -15°C, and the freezing time is 30 to 60 minutes. Freezing at this temperature allows the adsorbed water from sodium hexafluorosilicate to be more completely converted into crystal water, and also allows the sodium hexafluorosilicate solute to be more dispersed and crystallize together with the adsorbed water as a solvent. Selecting a freezing time of 30 to 60 minutes allows for more complete crystallization, which can further expand the interlayer spacing and improve the seepage prevention performance of the modified bentonite.

[0023] Furthermore, after thawing and before drying in step S3, the thawed frozen mixture is maintained at 3–5°C for 10–20 minutes. As mentioned above, sodium hexafluorosilicate and water molecules adsorbed between bentonite layers inevitably exhibit kinetic differences during crystallization. Therefore, uneven dispersion of sodium hexafluorosilicate and water molecules is unavoidable during freezing and thawing. Based on this, maintaining the frozen mixture at 3–5°C for 10–20 minutes after thawing promotes diffusion kinetically, which helps achieve relative solute uniformity. This ensures that sodium hexafluorosilicate is more evenly dispersed between bentonite layers, thus minimizing the aforementioned issues. This allows for a more effective increase in the interlayer spacing of bentonite and maintains the uniformity of the bentonite structure, thereby improving its mechanical and impermeability properties.

[0024] In a typical embodiment, the intercalating agent is a mixture of sodium hexafluorosilicate and sodium dodecyl sulfate. While sodium dodecyl sulfate is a common bentonite modifier in the art, the inventors have discovered through extensive experimentation that when used in combination with sodium hexafluorosilicate as an intercalating agent, it exhibits a more pronounced synergistic effect, significantly enhancing its impermeability. The underlying principle may be attributed to the close-packed structure and high symmetry of both the octahedral silicate ions in sodium hexafluorosilicate and the tetrahedral sulfate ions in sodium dodecyl sulfate in terms of crystal field. This similarity in crystal field allows for better synergistic interaction, resulting in a superior intercalation effect and imparting higher impermeability to the modified bentonite. Furthermore, a preferred weight ratio of sodium hexafluorosilicate to sodium dodecyl sulfate in the intercalating agent is 1:(1-5). This ratio allows for better synergistic compatibility, further improving the impermeability of the resulting modified bentonite.

[0025] In the process of bentonite modification experiments, in order to obtain better modification effect and thus more effectively improve the impermeability of bentonite after modification, in a preferred embodiment, the weight ratio of bentonite to intercalating agent in step S1 is 1:(0.1~0.3); and / or, the weight ratio of bentonite to water is 1:(3~6).

[0026] To ensure the intercalating agent, especially sodium hexafluorosilicate, is more fully dispersed within the bentonite interlayers and achieves a superior intercalation effect, in a preferred embodiment, the mixed slurry is ultrasonically treated before step S2. This ultrasonic treatment allows for more thorough contact between the bentonite particles and the solute molecules of the intercalating agent, thereby enabling more sodium hexafluorosilicate and adsorbed water molecules to enter the interlayers of the bentonite particles. This results in a more significant intercalation effect during subsequent freezing and thawing processes, enhancing the impermeability of the modified bentonite. Preferably, the ultrasonic treatment power is 20–60 kHz, and the time is 20–40 min / L to achieve a better intercalation effect.

[0027] In a typical embodiment, the mixing process in step S1 is carried out at a temperature of 70–90°C for 20–40 minutes. Mixing at this temperature and time allows the bentonite, water, and intercalating agent to be mixed more thoroughly and uniformly, and allows the sodium hexafluorosilicate and sodium dodecyl sulfate, which are used as intercalating agents, to be more completely dissolved in water. This facilitates the intercalation effect of the two agents, increases the interlayer spacing of the bentonite, and thus improves its impermeability.

[0028] A second aspect of the present invention provides a modified bentonite prepared by the above-described method. Because the obtained bentonite contains sodium hexafluorosilicate, which effectively increases its interlayer spacing, both its impermeability and mechanical properties are significantly improved.

[0029] A third aspect of the present invention provides a bentonite-based impermeable material comprising 95-105 parts of the aforementioned modified bentonite, 1-6 parts of coal gasification slag, and 0.1-0.5 parts of sodium hydroxide; in a preferred embodiment, the particle size of the coal gasification slag is 5-25 μm. Specifically, the bentonite-based impermeable material can be obtained by simply mixing the aforementioned modified bentonite, sodium hydroxide, and coal gasification slag in a specific ratio; the coal gasification slag is from the Ordos Coal-to-Oil Plant.

[0030] In the aforementioned components of the bentonite-based seepage-proof material, coal gasification slag is a solid residue formed from inorganic minerals and residual carbonaceous particles during the coal gasification reaction. It can be classified into coarse and fine slag based on particle size. Its main component is SiO2, and it also contains inorganic substances such as CaO, MgO, TiO2, and Al2O3. The main mineral phase is amorphous aluminosilicate, interspersed with crystalline phases such as quartz and calcite. As one of the industrial wastes with large emissions, it lacks effective utilization methods. Based on this, the bentonite-based seepage-proof material of this invention utilizes the coal gasification slag as a resource, which is beneficial for reducing environmental pollution and lowering the production costs and waste disposal costs of related industries. When used, the modified bentonite containing sodium hexafluorosilicate, sodium hydroxide, and coal gasification slag reacts further with water under the action of alkali. Inorganic oxides in the coal gasification slag, such as CaO, SiO2, and Al2O3, undergo hydration reactions to form cement, thereby improving the basic mechanical properties of the bentonite. Simultaneously, sodium hexafluorosilicate reacts with alkali to generate silica gel containing many active groups. These active groups can further react with substances (Ca, Si, Al, etc.) in the fine coal gasification slag, dehydrating to form silicon oxide bonds, thereby further enhancing the bonding force between bentonite-based impermeable materials, enabling them to meet the mechanical performance requirements of impermeable layers in coal gangue landfills. Finally, the addition of fine coal gasification slag with a particle size of 5–25 μm can also reduce the shrinkage of bentonite-based impermeable materials, preventing the formation of drying cracks and maintaining their stability during application.

[0031] Based on this, selecting the proportions of modified bentonite, coal gasification slag, and sodium hydroxide within the aforementioned range allows these three components to better coordinate and combine, forming a more uniform bentonite-based impermeable material, thereby further improving its mechanical and impermeability properties. In a more preferred embodiment, the bentonite-based impermeable material comprises 95–105 parts of the aforementioned modified bentonite, 2–4 parts of coal gasification slag, and 0.2–0.3 parts of sodium hydroxide. Extensive experiments by the inventors have shown that selecting the proportions of these three components within the aforementioned range results in a bentonite-based impermeable material with better compressive strength and impermeability.

[0032] A fourth aspect of the present invention provides an application of the aforementioned bentonite-based seepage-proof material in the field of seepage prevention, waterproofing, and barrier materials. Specifically, the prepared bentonite-based seepage-proof material can be used in the application scenario of harmless backfilling and reclamation of coal gangue to set a seepage-proof layer at the bottom and around the backfill site; it can also be prepared as a seepage-proof layer with a fixed sodium-based bentonite waterproof blanket; or it can be laid directly, such as laying the aforementioned bentonite-based seepage-proof material on a compacted and leveled foundation, while simultaneously laying a flexible waterproof geomembrane or other conventional seepage-proof layer laying methods.

[0033] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0034] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0035] Example 1

[0036] A method for preparing bentonite-based impermeable materials:

[0037] (1) Prepare the following raw materials in parts by weight: 100 parts modified bentonite, 4 parts coal gasification slag (coal gasification slag from the Ordos Coal-to-Oil Plant, with a particle size range of 5μm to 25μm), and 0.3 parts sodium hydroxide.

[0038] (2) Bentonite, intercalating agent (sodium hexafluorosilicate and sodium dodecyl sulfate, with a mass ratio of sodium hexafluorosilicate to sodium dodecyl sulfate of 1:3) and water were mixed and ultrasonically treated at 40 kHz for 30 min. Then, the mixture was frozen, thawed, and dried to obtain modified bentonite. The mass ratio of bentonite to intercalating agent was 1:0.2; the mass ratio of bentonite to water was 1:4; the mixing temperature was 90 ℃; the mixing time was 22 min; the freezing temperature was -10 ℃; the freezing time was 40 min; and after thawing, the temperature of the system was maintained at 4 ℃ for 15 min.

[0039] Example 2

[0040] A method for preparing bentonite-based impermeable materials:

[0041] (1) Prepare the following raw materials in parts by weight: 100 parts modified bentonite, 2 parts coal gasification fine slag (coal gasification slag from the Ordos Coal-to-Oil Plant, with a particle size range of 5μm to 25μm), and 0.2 parts sodium hydroxide.

[0042] (2) Bentonite, intercalating agent (sodium hexafluorosilicate and sodium dodecyl sulfate, with a mass ratio of sodium hexafluorosilicate to sodium dodecyl sulfate of 1:4) and water were mixed and ultrasonically treated at 40 kHz for 30 min. Then, the mixture was frozen, thawed, and dried to obtain modified bentonite. The mass ratio of bentonite to intercalating agent was 1:0.3; the mass ratio of bentonite to water was 1:5; the mixing temperature was 80 ℃; the mixing time was 35 min; the freezing temperature was -15 ℃; the freezing time was 35 min; and after thawing, the temperature of the system was maintained at 5 ℃ for 15 min.

[0043] (3) The modified bentonite, sodium hydroxide and coal gasification slag are mixed evenly in the above proportions to obtain bentonite-based seepage-proof material.

[0044] Example 3

[0045] A method for preparing bentonite-based impermeable materials:

[0046] (1) Prepare the following raw materials in parts by weight: 100 parts modified bentonite, 1 part coal gasification fine slag (coal gasification slag from the Ordos Coal-to-Oil Plant, with a particle size range of 5μm to 25μm), and 0.1 parts sodium hydroxide.

[0047] (2) Bentonite, intercalating agent (sodium hexafluorosilicate and sodium dodecyl sulfate, with a mass ratio of sodium hexafluorosilicate to sodium dodecyl sulfate of 1:2) and water were mixed and ultrasonically treated at 40 kHz for 30 min. Then, the mixture was frozen, thawed, and dried to obtain modified bentonite. The mass ratio of bentonite to intercalating agent was 1:0.3; the mass ratio of bentonite to water was 1:6; the mixing temperature was 70 ℃; the mixing time was 40 min; the freezing temperature was -5 ℃; the freezing time was 50 min; and after thawing, the temperature of the system was maintained at 3 ℃ for 20 min.

[0048] (3) The modified bentonite, sodium hydroxide and coal gasification slag are mixed evenly in the above proportions to obtain bentonite-based seepage-proof material.

[0049] Example 4

[0050] A method for preparing bentonite-based impermeable materials:

[0051] (1) Prepare the following raw materials in parts by weight: 100 parts modified bentonite, 6 parts coal gasification fine slag (coal gasification slag from the Ordos Coal-to-Oil Plant, with a particle size range of 5μm to 25μm), and 0.5 parts sodium hydroxide.

[0052] (2) Bentonite, intercalating agent (sodium hexafluorosilicate and sodium dodecyl sulfate, with a mass ratio of sodium hexafluorosilicate to sodium dodecyl sulfate of 1:3) and water were mixed and ultrasonically treated at 40 kHz for 30 min. Then, the mixture was frozen, thawed, and dried to obtain modified bentonite. The mass ratio of bentonite to intercalating agent was 1:0.3; the mass ratio of bentonite to water was 1:4; the mixing temperature was 85 ℃; the mixing time was 25 min; the freezing temperature was -13 ℃; the freezing time was 50 min; and the temperature of the system was maintained at 3 ℃ after thawing for 16 min.

[0053] (3) The modified bentonite, sodium hydroxide and coal gasification slag are mixed evenly in the above proportions to obtain bentonite-based seepage-proof material.

[0054] Example 5

[0055] A method for preparing bentonite-based impermeable materials:

[0056] The only difference between this embodiment and Example 1 is that sodium dodecyl sulfate is not added, but is replaced with an equal weight of sodium hexafluorosilicate.

[0057] Example 6

[0058] A method for preparing bentonite-based impermeable materials:

[0059] The only difference between this embodiment and Embodiment 1 is that the freezing temperature is -2°C and the freezing time is 20 minutes.

[0060] Example 7

[0061] A method for preparing bentonite-based impermeable materials:

[0062] The only difference between this embodiment and Embodiment 1 is that there is no step of maintaining the system at 4°C after thawing and before drying.

[0063] Comparative Example 1

[0064] A method for preparing bentonite-based impermeable materials:

[0065] The only difference between this embodiment and Embodiment 1 is that no coal gasification slag is added.

[0066] Comparative Example 2

[0067] A method for preparing bentonite-based impermeable materials:

[0068] The only difference between this embodiment and Example 1 is that sodium hydroxide is not added.

[0069] Comparative Example 3

[0070] A method for preparing bentonite-based impermeable materials:

[0071] The only difference between this embodiment and Embodiment 1 is that the freezing and thawing steps are not performed.

[0072] Comparative Example 4

[0073] A method for preparing bentonite-based impermeable materials:

[0074] The only difference between this embodiment and Example 1 is that sodium hexafluorosilicate is not added, but replaced with an equal weight of sodium dodecyl sulfate.

[0075] Test method:

[0076] (1) Test of permeability coefficient

[0077] The permeability coefficient of the sample was tested using a modified filtration loss test. A slurry was prepared by mixing bentonite (a type of geotextile material) with 350 ml of deionized water and stirring at 800 r / min in a JJ-1 electric mixer for 2 hours. The mixture was then poured into the filtration loss meter at the 300 mL mark. After sealing, a pressure of 100 kPa was applied to the filtration loss meter for the test. The volume of the filtrate was compressed every 5 minutes. After the filtration was completed, the total filtration loss V within time t was recorded. The suspension in the cup was then extracted, the surface slurry of the bentonite cake was scraped off, and the bentonite-based geotextile cake was weighed and dried to calculate the water mass fraction w. w The permeability coefficient of bentonite cake is calculated using the following formula:

[0078]

[0079] In the formula: γ w Where is the specific gravity of deionized water; V is the volume of free water filtered out; P0 is the initial air pressure; A is the filter cake area of ​​the bentonite-based impermeable material; t is the filter pressing time; Θ is the slope of the P0t / VV relationship curve; β is the proportionality coefficient of V to A, calculated as follows:

[0080]

[0081] Where w m ρ represents the mass fraction of bentonite-based impermeable material in the mud. w ρ is the density of deionized water. s is the maximum dry density of the clay cake; e is the average void ratio of the bentonite clay cake, calculated using the following formula:

[0082]

[0083] d s The density of bentonite-based waterproofing material; S r Saturation of bentonite-based waterproofing materials.

[0084] (2) Test of unconfined compressive strength

[0085] The sample was prepared into a slurry and placed in a 50mm×50mm mold. The hydration reaction was carried out in a constant temperature and humidity chamber for 28 days. The unconfined compressive strength of the specimen after 28 days of hydration reaction was tested using a YAD-600 fully automatic pressure testing machine. By adjusting the center position of the pressure clamp, pressure was applied uniformly at a speed of 1mm / s until the specimen ruptured. The unconfined compressive strength value of the specimen was then recorded.

[0086] The performance test results of the bentonite-based impermeable materials prepared in the above embodiments and comparative examples, including their unconfined compressive strength and permeability coefficient, are shown in Table 1.

[0087] Table 1

[0088] Sample Permeability coefficient (cm / s) Unconfined compressive strength (kPa) Example 1 <![CDATA[1.7×10 -12 ]]> 860 Example 2 <![CDATA[8.9×10 -12 ]]> 845 Example 3 <![CDATA[3.7×10 -11 ]]> 834 Example 4 <![CDATA[7.9×10 -11 ]]> 856 Example 5 <![CDATA[9.1×10 -10 ]]> 807 Example 6 <![CDATA[8.4×10 -10 ]]> 832 Example 7 <![CDATA[7.9×10 -11 ]]> 841 Comparative Example 1 <![CDATA[4.5×10 -10 ]]> 709 Comparative Example 2 <![CDATA[6.8×10 -9 ]]> 652 Comparative Example 3 <![CDATA[5.2×10 -7 ]]> 783 Comparative Example 4 <![CDATA[4.6×10 -8 ]]> 741

[0089] As can be seen from the above description, the embodiments of the present invention use sodium hexafluorosilicate as one of the intercalating agents to modify bentonite, and through freezing and thawing steps, it is prepared into sodium-based bentonite while expanding the interlayer spacing and improving the seepage prevention performance. The modified bentonite is further compounded with coal gasification slag, sodium hydroxide, etc. to obtain bentonite-based seepage prevention materials. The obtained bentonite-based seepage prevention materials have good seepage prevention performance and mechanical properties, and can be widely used in multiple material fields such as seepage prevention, waterproofing and barrier.

[0090] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing modified bentonite, characterized in that, The preparation method includes: Step S1: Mix bentonite, intercalating agent and water to obtain a mixed slurry, wherein the intercalating agent includes sodium hexafluorosilicate; Step S2: Freeze the mixed slurry to obtain a frozen mixed slurry; the freezing temperature is -5~-15℃ and the time is 30~60min; Step S3: Thaw and dry the frozen mixed slurry to obtain the modified bentonite.

2. The method for preparing modified bentonite according to claim 1, characterized in that, After thawing and before drying in step S3, the thawed frozen mixture is maintained at 3-5°C for 10-20 minutes.

3. The method for preparing modified bentonite according to claim 1 or 2, characterized in that, The intercalating agent is a mixture of sodium hexafluorosilicate and sodium dodecyl sulfate.

4. The method for preparing modified bentonite according to claim 3, characterized in that, The weight ratio of sodium hexafluorosilicate and sodium dodecyl sulfate in the intercalating agent is 1:(1~5).

5. The method for preparing modified bentonite according to claim 1 or 2, characterized in that, In step S1, The weight ratio of the bentonite to the intercalating agent is 1:(0.1~0.3). And / or, the weight ratio of the bentonite to water is 1:(3~6).

6. The method for preparing modified bentonite according to claim 1 or 2, characterized in that, Before step S2, the mixture is subjected to ultrasonic treatment.

7. The method for preparing modified bentonite according to claim 6, characterized in that, The ultrasonic treatment power is 20~60kHz, and the time is 20~40min / L.

8. The method for preparing modified bentonite according to claim 1 or 2, characterized in that, The mixing process in step S1 is carried out at a temperature of 70~90℃ for 20~40 minutes.

9. A modified bentonite prepared by the method of any one of claims 1 to 8.

10. A bentonite-based impermeable material, characterized in that, The bentonite-based seepage-proof material comprises 95-105 parts of the modified bentonite as described in claim 9, 1-6 parts of coal gasification slag, and 0.1-0.5 parts of sodium hydroxide.

11. The bentonite-based waterproofing material according to claim 10, characterized in that, The bentonite-based seepage-proof material comprises 95-105 parts of the modified bentonite, 2-4 parts of coal gasification slag, and 0.2-0.3 parts of sodium hydroxide.

12. The bentonite-based waterproofing material according to claim 10, characterized in that, The particle size of the coal gasification slag is 5~25μm.

13. The application of any one of the bentonite-based impermeable materials according to claims 10 to 12 in the field of impermeable, waterproof and barrier materials.

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