Bentonite Compositions and Their Applications

Abstract

This invention provides a bentonite composition and its applications. The bentonite composition comprises polyethyleneimine-modified fly ash and polymer-modified bentonite with sulfonic acid anions; and the weight ratio of polyethyleneimine-modified fly ash to polymer-modified bentonite with sulfonic acid anions is 1:6–12. The interaction of polymer ions with different charges on the surfaces of the polyethyleneimine-modified fly ash and the modified bentonite reduces the permeability coefficient of the bentonite composition, significantly improving the suitability of bentonite as a seepage barrier material.

Description

Technical Field

[0001] This invention relates to the field of coal solid waste treatment technology, and more specifically, to a bentonite composition and its application. Background Technology

[0002] Current disposal technologies are mostly focused on the application of harmless backfilling and reclamation of coal gangue, including several scenarios. The first involves setting up an impermeable layer at the bottom and around the perimeter, followed by a coal gangue layer, a compacted layer, another coal gangue layer, and another compacted layer, topped with reclaimed soil. The second involves setting an impermeable layer at the bottom and around the perimeter, filling with a mixture of slurry material and coal gangue, and then topped with reclaimed soil. In most cases, the impermeable layer is a crucial structural layer. A good impermeable layer requires a low permeability coefficient.

[0003] For example, Chinese invention application CN105672365A discloses a GCL vertical seepage barrier wall and its preparation method. The GCL vertical seepage barrier wall includes a vertical seepage barrier wall body, with a sodium-based bentonite waterproofing blanket fixed to the outside of the body. The sodium-based bentonite waterproofing blanket includes a vertical seepage barrier structure and a top fixing structure. This invention's seepage barrier wall has a low permeability coefficient, good bonding with the soil, and good seepage prevention effect. Chinese invention application CN107459291A discloses an environmentally friendly seepage-proof bentonite and its preparation method. Its raw materials mainly include the following components by weight: 8-13 parts of acrylamide copolymer, 1.5-4 parts of a first crosslinking agent, 2-4 parts of a second crosslinking agent, 0.15-0.35 parts of thiourea, and 91-107 parts of bentonite. The acrylamide copolymer has flocculating, thickening, and binding effects. The first crosslinking agent transforms it into a three-dimensional network structure polymer through an ionic crosslinking mechanism. The second crosslinking agent improves the strength and elasticity of the linear molecules. The cross-linked products of the network structure interpenetrate and embed into the bentonite, increasing the permeability of the bentonite. The dense network structure forms a dense filter cake with the bentonite. In addition, the cross-linked products form a thin film on the surface of the bentonite, making it difficult for water or metal ions to seep out.

[0004] However, when the above-mentioned materials are used as impermeable layers, their permeability coefficient is still relatively high. It is necessary to provide a new impermeable layer material with a lower permeability coefficient. Summary of the Invention

[0005] The main objective of this invention is to provide a bentonite composition and its application to solve the problem of high permeability coefficient in existing anti-seepage layer materials.

[0006] To achieve the above objectives, according to one aspect of the present invention, a bentonite composition is provided, comprising polyethyleneimine-modified fly ash and polymer-modified bentonite having sulfonic acid anions; wherein the weight ratio of polyethyleneimine-modified fly ash to polymer-modified bentonite having sulfonic acid anions is 1:6 to 12.

[0007] Furthermore, polyethyleneimine-modified fly ash is prepared by the following method: first, fly ash and polyethyleneimine undergo a first-stage reaction, and then glutaraldehyde is added to the system to continue the second-stage reaction, so as to obtain polyethyleneimine-modified fly ash.

[0008] Furthermore, the polymer-modified bentonite with sulfonic acid anions is prepared by the following method: a mixture containing sodium bentonite, N,N-methylenebisacrylamide, acrylic acid monomer, 2-acrylamido-2-methylpropanesulfonic acid and an initiator is subjected to a polymerization reaction to obtain the polymer-modified bentonite with sulfonic acid anions.

[0009] Furthermore, the reaction time of the first stage is 12-48 hours; preferably, the reaction time of the second stage is 1-5 hours; preferably, the temperature of the first stage reaction and the temperature of the second stage reaction are each independently 30-50°C.

[0010] Furthermore, the polymerization temperature is 60~80℃; preferably, the polymerization time is 1~3h.

[0011] Furthermore, the amount of glutaraldehyde used is 2-8% of the weight of fly ash; preferably, the weight ratio of fly ash to polyethyleneimine is 1-3:1.

[0012] Furthermore, the weight-average molecular weight M of polyethyleneimine w The concentration is 20,000 to 100,000 Daltons; preferably, the preparation method further includes a step of activating the fly ash with sodium hydroxide at a temperature of 500 to 600°C before reacting the fly ash with polyethyleneimine.

[0013] Further, the solid content of the mixture is 30~50wt%; preferably, the weight ratio of sodium bentonite, N,N-methylenebisacrylamide, acrylic acid monomer and 2-acrylamido-2-methylpropanesulfonic acid is 400~600:1~5:100:20~40.

[0014] Furthermore, the degree of neutralization of the acrylic monomer is 50-70%.

[0015] To achieve the above objectives, according to one aspect of the present invention, the application of the aforementioned bentonite composition as an impermeable layer material is provided.

[0016] By applying the technical solution of this invention, the interaction of polymer ions with different charges on the surfaces of polyethyleneimine-modified fly ash and modified bentonite reduces the permeability coefficient of the bentonite composition and significantly improves the adaptability of bentonite as a seepage barrier material. Detailed Implementation

[0017] The terms “comprising,” “including,” “having,” and similar expressions used in this invention are not intended to exclude the presence of any optional components, steps, or procedures, whether or not any optional components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all methods claimed by using the term “comprising” may include one or more additional steps, equipment parts or components, and / or substances. In contrast, the term “consisting of” excludes any components, steps, or procedures not specifically described or enumerated. Unless otherwise stated, the term “or” refers to members listed individually and in any combination.

[0018] 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.

[0019] As described in the background section of this application, existing geomembrane materials suffer from high permeability coefficients. To address this issue, this application provides a bentonite composition comprising polyethyleneimine-modified fly ash and polymer-modified bentonite with sulfonic acid anions; wherein the weight ratio of the polyethyleneimine-modified fly ash to the polymer-modified bentonite with sulfonic acid anions is 1:6 to 12, for example, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, or 1:12. The interaction of polymer ions with different charges on the surfaces of the polyethyleneimine-modified fly ash and the polymer-modified bentonite with sulfonic acid anions reduces the permeability coefficient of the bentonite composition, significantly improving the suitability of bentonite as a geomembrane material.

[0020] To further reduce the permeability coefficient of the bentonite composition and improve its suitability as a seepage barrier material, in a preferred embodiment, the weight ratio of polyethyleneimine-modified fly ash to polymer-modified bentonite with sulfonic acid anions is 1:8 to 10, for example, 1:8, 1:9 or 1:10.

[0021] In a preferred embodiment, polyethyleneimine-modified fly ash is prepared by the following method: first, fly ash is reacted with polyethyleneimine in a first-stage reaction, and then glutaraldehyde is added to the system to continue the second-stage reaction, thereby obtaining polyethyleneimine-modified fly ash. Specifically, in a preferred embodiment, fly ash is mixed with sodium hydroxide and activated at 500-600°C. After activation, the mixture is cooled to room temperature and then mixed with 3-8 times its weight of water and stirred for 20-26 hours. The mixture is then filtered, washed alternately with dilute acid solution (e.g., a 12.8% hydrochloric acid aqueous solution) and water until neutral, and vacuum dried to obtain activated fly ash. The activated fly ash is then added to an ethanol solution of polyethyleneimine (PEI) for a first-stage reaction. Subsequently, glutaraldehyde in aqueous solution is added for a second-stage reaction. After the reaction is complete, the mixture is filtered, washed with water, and vacuum dried to obtain polyethyleneimine-modified fly ash.

[0022] It should be further noted that this application does not specifically limit the fly ash used; conventional fly ash in the art is acceptable. For example, in one optional embodiment, the fly ash comprises 35.0–37.0 wt% CaO, 24.0–26.0 wt% SiO2, 16.0–18.0 wt% SO3, 9.0–10.5 wt% Al2O3, 4.0–5.0 wt% Fe2O3, 1.5–2.0 wt% Na2O, 0.8–1.2 wt% MgO, 0.6–0.8 wt% K2O, 0.4–0.6 wt% TiO2, 0.1–0.3 wt% SrO, 0.01–0.02 wt% MnO, and the balance being unavoidable impurities.

[0023] In a preferred embodiment, polymer-modified bentonite with sulfonic acid anions is prepared by the following method: a mixture containing sodium bentonite, N,N-methylenebisacrylamide, acrylic acid monomer, 2-acrylamido-2-methylpropanesulfonic acid, and an initiator (no particular limitation, such as potassium persulfate or other commonly used initiators in the art) is subjected to a polymerization reaction to obtain polymer-modified bentonite with sulfonic acid anions. Specifically, in a preferred embodiment, under stirring conditions, sodium bentonite and N,N-methylenebisacrylamide are first dispersed in water by weight and kept at 60-80°C for 0.1-0.8 h to obtain a sodium bentonite mixture. Then, an aqueous solution of acrylic acid monomer and 2-acrylamido-2-methylpropanesulfonic acid are added to the above sodium bentonite mixture, and an initiator is added to adjust the solid content of the mixture to 30-50 wt%. The mixture is reacted at 60-80°C for 1-3 hours. After the reaction is complete, it is filtered, washed with water, and vacuum dried to obtain polymer-modified bentonite with sulfonic acid anions. It is further noted that this application does not specifically limit the use of sodium-based bentonite, which can be purchased from companies such as Wuhan Kanos Technology Co., Ltd. To further improve the uniformity of the properties of the polymer-modified bentonite with sulfonic acid anions, in a preferred embodiment, the polymerization temperature is 60-80°C, for example, 60°C, 65°C, 70°C, 75°C, or 80°C; the polymerization time is 1-3 hours, for example, 1 hour, 2 hours, or 3 hours. In a preferred embodiment, the solid content of the mixture is 30-50 wt%, for example, 30 wt%, 40 wt%, or 50 wt%. In a preferred embodiment, the degree of neutralization of the acrylic acid monomer is 50-70%, for example, 50%, 60%, or 70%.

[0024] To further improve the performance uniformity of polyethyleneimine-modified fly ash, in a preferred embodiment, the first stage reaction time is 12-48 hours, for example, 12 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, or 48 hours; the second stage reaction time is 1-5 hours, for example, 1 hour, 3 hours, or 5 hours; the temperatures of the first and second stage reactions are independently 30-50°C, for example, 30°C, 40°C, or 50°C. In a preferred embodiment, the amount of glutaraldehyde is 2-8% of the weight of fly ash, for example, 2%, 4%, 6%, or 8%. In a preferred embodiment, the weight ratio of fly ash to polyethyleneimine is 1-3:1, for example, 1:1, 2:1, or 3:1. In a preferred embodiment, the weight-average molecular weight M of polyethyleneimine is... wThe capacitance is 20,000 to 100,000 Daltons, for example, 20,000 Daltons, 40,000 Daltons, 60,000 Daltons, 80,000 Daltons, or 100,000 Daltons. Preferably, before reacting the fly ash with polyethyleneimine, the preparation method further includes a step of activating the fly ash with sodium hydroxide at a temperature of 500 to 600°C.

[0025] To further balance the performance uniformity of the polymer-modified bentonite with sulfonic acid anions, in a preferred embodiment, the weight ratio of sodium bentonite, N,N-methylenebisacrylamide, acrylic acid monomer, and 2-acrylamido-2-methylpropanesulfonic acid is 400~600:1~5:100:20~40, for example, 400:1:100:20, 500:2.5:100:30, or 600:5:100:40.

[0026] This application also provides an application of the aforementioned bentonite composition as a seepage barrier material. For the reasons stated above, when the bentonite composition is used as a seepage barrier material, it exhibits a low permeability coefficient and good adaptability.

[0027] 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.

[0028] Example 1

[0029] Under stirring conditions, 500 parts by weight of sodium-based bentonite (purchased from Wuhan Kanos Technology Co., Ltd.) and 3 parts by weight of N,N-methylenebisacrylamide were dispersed in water and kept at 70°C for 0.5 h to obtain a sodium-based bentonite mixture. 100 parts by weight of an aqueous solution of acrylic monomer (neutralization degree of 60%) and 30 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid were added to the above sodium-based bentonite mixture, along with 2 parts by weight of potassium persulfate, to adjust the solid content of the mixture to 40 wt%. The mixture was reacted at 70°C for 2 h. After the reaction was complete, the mixture was filtered, washed with water, and vacuum dried to obtain polymer-modified bentonite with sulfonic acid anions.

[0030] IR testing: Modified sodium-based bentonite at 30-42 cm⁻¹ -1 2985cm -1 1720cm -1 1672cm -1 1614cm -1 1458cm -1 1414cm -1 1368cm -1 1090cm -1 980cm -1 and 512cm-1 The presence of characteristic absorption peaks at certain positions indicates successful modification.

[0031] Example 2

[0032] Fly ash comprises the following components: 35.84 wt% CaO, 26.69 wt% SiO2, 17.68 wt% SO3, 10.32 wt% Al2O3, 4.88 wt% Fe2O3, 1.87 wt% Na2O, 1.14 wt% MgO, 0.76 wt% K2O, 0.55 wt% TiO2, 0.25 wt% SrO, 0.01 wt% MnO, and the balance being unavoidable impurities.

[0033] Fly ash was mixed with sodium hydroxide at a 1:1 weight ratio and activated at 550°C for 3 hours. The mixture was then cooled to room temperature and stirred with 5 times its weight of water for 24 hours. The mixture was then filtered, washed alternately with dilute acid (12.8% hydrochloric acid) and water until neutral, and vacuum dried to obtain activated fly ash.

[0034] Activated fly ash was added to 10 wt% polyethyleneimine (weight average molecular weight M). w In a 60,000 Dalton ethanol solution, activated fly ash and PEI were mixed at a weight ratio of 2:1. The mixture was stirred at 40°C for 24 hours. Then, 5% (by weight) of glutaraldehyde (present as an aqueous solution of the activated fly ash) was added, and the reaction was continued at 40°C for another 2 hours. After the reaction was complete, the mixture was filtered, washed with water, and vacuum dried to obtain polyethyleneimine-modified fly ash.

[0035] IR test: PEI modified fly ash at 2938 cm⁻¹ -1 1657cm -1 and 1468cm -1 The presence of characteristic absorption peaks at certain positions indicates successful modification.

[0036] Example 3

[0037] The polymer-modified bentonite with sulfonic acid anions from Example 1 and the PEI-modified fly ash from Example 2 were added to water at a weight ratio of 9:1 and wet-mixed. The mixture was then filtered, washed with water, and vacuum-dried to obtain the bentonite composition.

[0038] Performance testing

[0039] The permeability coefficient of fly ash-modified bentonite was determined using a TST-55 permeameter manufactured by Nanjing Zhongyan Instrument Equipment Manufacturing Co., Ltd. Wet sample preparation was used to prevent stratification. Samples were prepared using a 70mm × 52mm ring cutter and then cured at 21℃ and 98% relative humidity. After 7 days, the samples were cut using a 62mm × 40mm ring cutter. The cut samples were placed between two porous stones in a permeameter coated with Vaseline, and the permeability coefficients (m / s) of Example 3, Example 1, and sodium-based bentonite raw materials in high-purity water were measured. The latter two served as control groups. The results are shown in Table 1.

[0040] Table 1

[0041] Sample Permeability coefficient Bentonite composition in Example 3 <![CDATA[1.2×10 -13 ]]> In Example 1, the polymer-modified bentonite with sulfonic acid anions <![CDATA[4.9×10 -11 ]]> Sodium-based bentonite (purchased from Wuhan Kanos Technology Co., Ltd.) <![CDATA[2.6×10 -10 ]]>

[0042] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 bentonite composition used as a seepage barrier material, characterized in that, The bentonite composition used as the impermeable layer material includes polyethyleneimine-modified fly ash and polymer-modified bentonite with sulfonic acid anions; and the weight ratio of the polyethyleneimine-modified fly ash to the polymer-modified bentonite with sulfonic acid anions is 1:6~12. The polyethyleneimine-modified fly ash is prepared by the following method: first, fly ash and polyethyleneimine undergo a first-stage reaction, and then glutaraldehyde is added to the system to continue the second-stage reaction, so as to obtain the polyethyleneimine-modified fly ash. The polymer-modified bentonite with sulfonic acid anions is prepared by the following method: a mixture containing sodium bentonite, N,N-methylenebisacrylamide, acrylic acid monomer, 2-acrylamido-2-methylpropanesulfonic acid and an initiator is subjected to a polymerization reaction to obtain the polymer-modified bentonite with sulfonic acid anions.

2. The bentonite composition as a seepage barrier material according to claim 1, characterized in that, The reaction time in the first stage is 12-48 hours.

3. The bentonite composition as a seepage barrier material according to claim 2, characterized in that, The second stage of the reaction takes 1 to 5 hours.

4. The bentonite composition as a seepage barrier material according to claim 2, characterized in that, The temperature of the first stage reaction and the temperature of the second stage reaction are each independently 30~50℃.

5. The bentonite composition as a seepage barrier material according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 60~80℃.

6. The bentonite composition as a seepage barrier material according to claim 5, characterized in that, The polymerization reaction takes 1 to 3 hours.

7. The bentonite composition as a seepage barrier material according to claim 1, characterized in that, The amount of glutaraldehyde used is 2 to 8% of the weight of the fly ash.

8. The bentonite composition as a seepage barrier material according to claim 7, characterized in that, The weight ratio of fly ash to polyethyleneimine is 1~3:

1.

9. The bentonite composition as a seepage barrier material according to claim 1, characterized in that, The weight-average molecular weight M of the polyethyleneimine w The range is 20,000 to 100,000 Daltons.

10. The bentonite composition as a seepage barrier material according to claim 9, characterized in that, Before reacting the fly ash with the polyethyleneimine, the preparation method further includes the step of activating the fly ash with sodium hydroxide at a temperature of 500-600°C.

11. The bentonite composition as a seepage barrier material according to claim 1, characterized in that, The solid content of the mixture is 30-50 wt%.

12. The bentonite composition as a seepage barrier material according to claim 11, characterized in that, The weight ratio of the sodium bentonite, the N,N-methylenebisacrylamide, the acrylic acid monomer, and the 2-acrylamido-2-methylpropanesulfonic acid is 400~600:1~5:100:20~40.

13. The bentonite composition as a seepage barrier material according to claim 1, characterized in that, The degree of neutralization of the acrylic monomer is 50-70%.

14. The use of a bentonite composition as a seepage barrier material according to any one of claims 1 to 13.