Preparation method of fly ash-organobentonite barrier wall with barrier property on chlorobenzene compounds in water

Abstract

The invention relates to the technical field of application of environmental chemistry technology in environmental protection, and particularly discloses a preparation method of a fly ash-organobentonite barrier wall with barrier performance on chlorobenzene compounds in water, which comprises the following steps: preparation of organobentonite: mixing powdery sodium bentonite with deionized water, stirring, adding a tetraethylammonium bromide modifier, stirring, adding an initiator, stirring, adding an initiator, and stirring to obtain the organobentonite; stirring, centrifugally separating, washing, sieving and storing for later use; hydrating the bentonite; the preparation method comprises the following steps: putting bentonite into a beaker, adding water, stirring with a glass rod, and stirring on a stirrer for 24 hours to complete the hydration process of the bentonite; the preparation method is suitable for preparation of the barrier wall for the underground water polluted by the chlorobenzene compounds, migration and diffusion paths of the chlorobenzene compounds in the underground water environment are effectively blocked, pollutants are isolated outside the surrounding environment, pollution to the environment is reduced, and human health is guaranteed. The method has the advantages of wide field application range, high interception efficiency, high speed and the like, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental chemical technology in environmental protection application, and specifically relates to a method for preparing a fly ash-organic bentonite barrier wall having barrier properties for chlorobenzene compounds in water. Background Art

[0002] Chlorobenzene compounds (CBs) are a class of monocyclic aromatic hydrocarbon compounds containing only hydrogen and chlorine atoms. According to the substitution position and number of chlorine atoms, they can be divided into 12 types: monochlorobenzene (MCB), dichlorobenzene (1,2-DCB, 1,3DCB and 1,4-DCB), trichlorobenzene (1,2,3-TCB, 1,2,4-TCB and 1,3,5-TCB), tetrachlorobenzene (1,2,3,4-tetraCB, 1,2,3,5-tetraCB and 1,2,4,5-tetraCB), pentachlorobenzene (penta CB) and hexachlorobenzene (HCB). The physical and chemical properties of chlorobenzene compounds are relatively stable, not easy to decompose, and can remain in the environment for a long time. They are typical organic pollutants that are difficult to degrade and easy to enrich. In addition, the hydrophobic characteristics of chlorobenzene compounds make it easy to bioaccumulate. When articles or sites contaminated by chlorobenzene compounds come into contact with the human body, chlorobenzene compounds will be enriched in the neutral fats such as the nervous tissue, liver, and kidney of the human body. Excessive intake can also induce three-cause effects (carcinogenicity, teratogenicity, and mutagenicity). Therefore, chlorobenzene compounds are a class of compounds with varying degrees of toxicity, bioaccumulation, and persistence, and their discharge and use may cause potential harm to the environment. At present, chlorobenzene compounds have been listed in the priority control pollutant category by many countries. In 1989, my country has already listed chlorobenzene, o-dichlorobenzene, p-dichlorobenzene and hexachlorobenzene in the blacklist of key controlled pollutants in water. Because chlorobenzene compounds have a potential threat to human health and life safety, it is extremely important to repair the contaminated plots of chlorobenzene compounds and prevent and control the spread of their pollutants.

[0003] Chlorobenzene compounds are produced and used in the fields of chemical industry, agriculture, medicine, etc. The impact of chlorobenzene organic matter in groundwater on the surrounding water environment is an issue that cannot be ignored. Chlorobenzene organic matter will form a pollution plume in the aquifer, will spontaneously diffuse at a certain diffusion rate, and will further migrate under the action of hydraulic gradient, thus posing a risk to the surrounding water environment. Chlorobenzene organic matter can form adsorption phase, dissolved phase and non-aqueous phase in groundwater, has a long half-life and is easy to migrate. Therefore, blocking or even cutting off the migration of pollutants can control the risk of chlorobenzene organic matter inside the contaminated site.

[0004] In the control of pollution spread, the barrier wall method is a relatively economical and effective method. The barrier wall is to build a vertical wall in situ to separate two areas. It blocks the path of pollution spread and limits the migration of pollutants to achieve the purpose of pollution control. It is one of the important technical means of risk control. At present, the United States, Europe and other countries have conducted in-depth research on the development of barrier wall materials. By modifying natural barrier materials, the permeability of barrier materials and the effective diffusion coefficient of pollutant migration can be reduced, and the barrier material's ability to adsorb pollutants can be enhanced. At present, there is little research in this area in my country. In order to block pollution, the U.S. Environmental Protection Agency document stipulates that barrier walls must have very low permeability, and it is recommended that the wall permeability coefficient should not exceed 10 -9 m / s. The smaller the permeability coefficient, the better the anti-seepage effect on pollutants, but it cannot be too low to avoid blocking the normal flow of water. The barrier barrier mainly blocks pollutants through adsorption. The current research on barrier performance mainly includes adsorption performance research, mechanical performance research, environmental resistance research, etc.

[0005] According to the different materials, barrier walls can be divided into soil-bentonite barrier walls, cement-bentonite barrier walls, geomembrane-bentonite barrier walls, etc. Soil-bentonite barrier walls are widely used in the remediation of contaminated sites. Their main components are on-site soil and bentonite slurry, which have the advantages of low cost and good barrier performance.

[0006] Bentonite is a clay rock with montmorillonite as the main mineral. Bentonite has a large specific surface area, cation exchange capacity and excellent adsorption characteristics. As an efficient, multi-purpose and easy-to-operate adsorption material, it is widely used in water pollution prevention and control. Organic bentonite has a greatly enhanced ability to adsorb organic pollutants compared to bentonite. Fly ash is the main solid waste discharged from coal-fired power plants. It is a loose and porous solid particle with a large specific surface area. Its main component is SiO 2 、Al 2 O 3 , Fe 2 O 3 , CaO, MgO and unburned carbon, etc., contain a large number of active points such as Al and Si, which can undergo chemical adsorption and physical adsorption with the adsorbate, and can be used as adsorbents or coagulants in wastewater treatment. They have the advantage of low price. Using fly ash to treat pollutants can achieve the effect of "treating waste with waste".

[0007] At present, there are two main measures to control groundwater pollution in my country. One is remediation technology and the other is interception technology. The former can effectively eliminate environmental pollution, but due to the differences in the conditions of contaminated sites and the complex behavior of pollutants in the environment, the cost of remediation or removal is high and the effect is poor. The latter is efficient and fast, and can intercept and seal pollutants in the environment in a relatively short time. Therefore, the application of pollutant barrier wall technology in the risk control of groundwater contaminated sites is becoming more and more widespread. Summary of the invention

[0008] The object of the present invention is to provide a method for preparing a fly ash-organobentonite barrier wall having barrier properties for chlorobenzene compounds in water, so as to solve the problems raised in the above-mentioned background technology.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for preparing a fly ash-organobentonite barrier wall having barrier properties for chlorobenzene compounds in water comprises the following steps:

[0011] S1. Preparation of organic bentonite:

[0012] Mix powdered sodium bentonite with deionized water, stir with a magnetic stirrer at 60°C, add tetraethylammonium bromide modifier, stir for 2 h, let stand at room temperature for 24 h, centrifuge, and wash with deionized water until there is no white precipitate in the supernatant (Br) detected by silver nitrate indicator. - ), dried at 120°C for 2h, passed through a 0.178mm sieve and stored for later use;

[0013] S2. Bentonite hydration;

[0014] Put bentonite in a beaker, add water, stir with a glass rod, and then place on a stirrer and stir for 24 hours to complete the hydration process of bentonite;

[0015] S3. Determination of fly ash-organic bentonite barrier wall material ratio:

[0016] The barrier wall materials are sodium bentonite, soil, organic bentonite, fly ash and CaCO 3 , sodium bentonite, fly ash and CaCO in the materials 3 The mass proportions of the organic bentonite are 10%, 10%, and 2% respectively, and then organic bentonite is added respectively, the mass proportions of the organic bentonite include but are not limited to 0%, 2%, 4%, 6%, 8%, and 10% of organic bentonite, and the mass proportions of soil added to the organic bentonite include but are not limited to 78%, 76%, 74%, 72%, 70%, and 68%;

[0017] S4. Preparation method of fly ash-organic bentonite barrier wall:

[0018] Soil, fly ash, CaCO 3 , stir the sodium bentonite mixture with a glass rod, slowly add the bentonite that has been hydrated for 24 hours, stirring with a glass rod while adding, until the mixture and the hydrated bentonite are completely mixed, fill the ring knife with the barrier wall material slurry, level it, and put it in a curing box at 21°C and 98% relative humidity for 7 days.

[0019] Preferably, the fly ash-organic bentonite barrier wall material ratio is: sodium bentonite, fly ash and CaCO 3 The mass proportions of organic bentonite were 10%, 10% and 2% respectively, and then 0% (S1), 2% (S2), 4% (S3), 6% (S4), 8% (S5) and 10% (S6) were added respectively. The mass proportions of soil added in the corresponding materials numbered S1 to S6 were 78% (S1), 76% (S2), 74% (S3), 72% (S4), 70% (S5) and 68% (S6).

[0020] Preferably, the engineering mechanical properties and chemical compatibility tests of six groups of material samples are as follows.

[0021] ① Determination of permeability coefficient of barrier wall: Place the cutter ring with the sample after consolidation into the infiltration chamber of the rigid infiltmeter, install the upper and lower permeable stones and tighten them with nuts; open the water inlet valve, wait for water to flow into the infiltration chamber, open the exhaust / water valve to exhaust the air in the infiltration chamber, and close the exhaust / water valve and the water inlet valve after there are no bubbles. Pour water into the measuring tube to raise the water to the preset height. After it stabilizes, open the water inlet valve between the measuring tube and the infiltmeter to allow water to flow through the sample. When water drops flow out of the outlet, record the water head height and time at this moment as the starting height and starting time. Then, measure the change in water head height at fixed time intervals. After the measurement is completed, use the formula The permeability coefficient can be calculated. The permeability coefficient of the barrier wall should be controlled within 10 -10 m / s≤k≤10 -9 m / s, and the permeability coefficient of the wall samples numbered S2, S3, S4 and S5 in the six groups of materials is 1.246×10 -10 ~8.404×10 -10 m / s, meets the requirements.

[0022] ② Determination of compressive strength: Place the cured barrier wall samples in a room temperature environment and use a microcomputer-controlled electronic universal testing machine to measure the compressive strength of the barrier wall samples after drying. The test wall sample area is 2998.1mm 2, with a height of 40mm. The compressive strength required to meet the strength requirements of the groundwater barrier wall must be greater than 103.4kPa. The compressive strength of the six groups of wall samples ranged from 1.63 to 3.82MPa, all meeting the requirements.

[0023] ③ Determination of adsorption amount: Weigh 0.5g of wall material into a 50mL centrifuge tube, add 30mL of 10mg / L monochlorobenzene, o-dichlorobenzene, and p-dichlorobenzene mixed chlorobenzene solution, seal with a polytetrafluoroethylene cap, and place in a constant temperature oscillating box at 298.15K and 150r / min for oscillation. Take samples after 12h. Centrifuge the sample in a centrifuge at 4000r / min for 8min, take 10mL of supernatant into a headspace injection bottle, add 2g of solid NaCl at the same time, seal and shake until completely dissolved, and enter the headspace-gas chromatography-mass spectrometry (HS-GCMS) for testing. Parallel groups and blank groups are set during the experiment. Within the appropriate permeability coefficient range, the adsorption of chlorobenzene compounds by wall materials shows a trend of increasing with the increase of organic bentonite addition.

[0024] Preferably, according to ①②③, the mass ratio of fly ash-organic bentonite barrier wall material that meets the barrier performance for chlorobenzene compounds in water is: sodium bentonite: organic modified bentonite: fly ash: soil: CaCO 3 It is 10:8:10:70:2.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Preparation of organic bentonite

[0027] This method uses bentonite as raw material. Since the silicon-oxygen structure on the surface of bentonite is highly hydrophilic and the interlayer cations are easily hydrolyzed, a thin water film is usually formed on the surface of bentonite, which makes it difficult to effectively adsorb hydrophobic organic pollutants. In order to solve this problem, organic ionic compounds are used to replace interlayer exchangeable ions or water molecules to prepare organic modified bentonite. Organic bentonite has a larger interlayer spacing than bentonite, and its ability to adsorb organic pollutants is greatly enhanced. Using organic bentonite to treat organic pollutants in wastewater has significant economic value and ecological environmental advantages.

[0028] (2) Establishment of a method for preparing a fly ash-organic bentonite barrier wall with barrier properties for chlorobenzene compounds in water

[0029] This method uses sodium bentonite, organic modified bentonite, fly ash, soil and CaCO 3As raw materials, the barrier performance of the barrier wall to chlorobenzene compounds was comprehensively investigated from the engineering mechanical properties and chemical compatibility of the wall samples through the determination of material permeability coefficient, compressive strength and adsorption capacity. The mass ratio of fly ash-organic bentonite barrier wall materials that meet the barrier performance for chlorobenzene compounds in water is sodium bentonite: organic modified bentonite: fly ash: soil: CaCO 3 It is 10:8:10:70:2.

[0030] (3) Economic and environmental protection

[0031] The method of the present invention mainly achieves the purpose of intercepting and sealing pollutants in the environment, restricting their migration, and reducing the impact of pollutants on the environment through two procedures: material preparation and barrier wall preparation. It has the characteristics of short repair cycle, high efficiency, and fast speed. For some sites with strong pollutant diffusion, imperfect repair technology, large site area, and high economic cost, it can achieve efficient and easy pollution control effect.

[0032] In addition, in the method of the present invention, various waste liquids are collected and subjected to environmental protection treatment such as pH value detection or adjustment before being discharged in compliance with the standards, thus reflecting the purpose of being environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the preparation method of the present invention;

[0034] Figure 2 This is a graph showing the measurement results of sodium bentonite before modification of the present invention;

[0035] Figure 3 This is a diagram showing the measurement results of the modified organic bentonite of the present invention;

[0036] Figure 4 1 is the XRD spectrum of bentonite before and after modification according to the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0038] Embodiment 1:

[0039] See also Figure 1-Figure 4 As shown, a method for preparing a fly ash-organobentonite barrier wall having barrier properties for chlorobenzene compounds in water comprises the following steps:

[0040] S1. Preparation of organic bentonite:

[0041] Mix powdered sodium bentonite with deionized water, stir with a magnetic stirrer at 60°C, add tetraethylammonium bromide modifier, stir for 2 h, let stand at room temperature for 24 h, centrifuge, and wash with deionized water until there is no white precipitate in the supernatant (Br) detected by silver nitrate indicator. - ), dried at 120°C for 2h, passed through a 0.178mm sieve and stored for later use;

[0042] S2. Bentonite hydration;

[0043] Put bentonite in a beaker, add water, stir with a glass rod, and then place on a stirrer and stir for 24 hours to complete the hydration process of bentonite;

[0044] S3. Determination of fly ash-organic bentonite barrier wall material ratio:

[0045] The barrier wall materials are sodium bentonite: organic modified bentonite: fly ash: soil: CaCO 3 The mass ratio is 10:8:10:70:2;

[0046] S4. Preparation method of fly ash-organic bentonite barrier wall:

[0047] Soil, fly ash, CaCO 3 , stir the sodium bentonite mixture with a glass rod, slowly add the bentonite that has been hydrated for 24 hours, stirring with a glass rod while adding, until the mixture and the hydrated bentonite are completely mixed, fill the ring knife with the barrier wall material slurry, level it, and put it in a curing box at 21°C and 98% relative humidity for 7 days.

[0048] The method for determining the proportion of fly ash-organic bentonite barrier wall materials is as follows:

[0049] Sodium bentonite, fly ash and CaCO in the material 3 The mass proportions of the materials were 10%, 10%, and 2%, respectively, and then 0% (S1), 2% (S2), 4% (S3), 6% (S4), 8% (S5), and 10% (S6) of organic bentonite were added. The corresponding materials numbered S1 to S6 had soil mass proportions of 78% (S1), 76% (S2), 74% (S3), 72% (S4), 70% (S5), and 68% (S6). The engineering mechanical properties and chemical compatibility tests of the six groups of material samples are as follows.

[0050] ① Determination of permeability coefficient of barrier wall: Place the cutter ring with the sample after consolidation into the infiltration chamber of the rigid infiltmeter, install the upper and lower permeable stones and tighten them with nuts; open the water inlet valve, wait for water to flow into the infiltration chamber, open the exhaust / water valve to exhaust the air in the infiltration chamber, and close the exhaust / water valve and the water inlet valve after there are no bubbles. Pour water into the measuring tube to raise the water to the preset height. After it stabilizes, open the water inlet valve between the measuring tube and the infiltmeter to allow water to flow through the sample. When water drops flow out of the outlet, record the water head height and time at this moment as the starting height and starting time. Then, measure the change in water head height at fixed time intervals. After the measurement is completed, use the formula The permeability coefficient can be calculated. The permeability coefficient of the barrier wall should be controlled within 10 -10 m / s≤k≤10 -9 m / s, and the permeability coefficient of the wall samples numbered S2, S3, S4 and S5 in the six groups of materials is 1.246×10 -10 ~8.404×10 -10 m / s, meets the requirements.

[0051] ② Determination of compressive strength: Place the cured barrier wall samples in a room temperature environment and use a microcomputer-controlled electronic universal testing machine to measure the compressive strength of the barrier wall samples after drying. The test wall sample area is 2998.1mm 2 , with a height of 40mm. The compressive strength required to meet the strength requirements of the groundwater barrier wall must be greater than 103.4kPa. The compressive strength of the six groups of wall samples ranged from 1.63 to 3.82MPa, all meeting the requirements.

[0052] ③ Determination of adsorption amount: Weigh 0.5g of wall material into a 50mL centrifuge tube, add 30mL of 10mg / L monochlorobenzene, o-dichlorobenzene, p-dichlorobenzene mixed chlorobenzene solution, seal with a polytetrafluoroethylene cap, place in a constant temperature oscillating box at 298.15K, 150r / min, and take samples after 12h. Centrifuge the sample in a centrifuge at 4000r / min for 8min, take 10mL of supernatant into a headspace injection bottle, add 2g of solid NaCl at the same time, seal and shake until completely dissolved, enter the headspace-gas chromatography-mass spectrometry (HS-GCMS) test, and set parallel groups and blank groups during the experiment. Within the appropriate permeability coefficient range, the adsorption of chlorobenzene compounds by wall materials shows a trend of increasing with the increase of organic bentonite addition.

[0053] According to ①②③, the mass ratio of fly ash-organic bentonite barrier wall materials that meet the barrier properties for chlorobenzene compounds in water is as follows: sodium bentonite: organic modified bentonite: fly ash: soil: CaCO 3 It is 10:8:10:70:2.

[0054] Table 1 summarizes six barrier wall material ratio schemes of the present invention.

[0055] Chlorobenzene compound detection method: headspace-gas chromatography-mass spectrometry (HS-GCMS) was used to determine the content of chlorobenzene compounds. The headspace sampler sample chamber was 70°C, the valve box was 90°C, and the pipeline was 100°C; the gas chromatography column was an HP-5ms capillary column, the program temperature was 50°C (maintained for 5 minutes), increased to 100°C at a rate of 20°C / min, and then increased to 140°C at a rate of 8°C / min (maintained for 1 minute), the injection port was 250°C, and the injection was not split. The ion source temperature was 200°C, the interface temperature was 250°C, the full scan mode, and the external standard method was used for quantification.

[0056] Table 1 Fly ash-organic bentonite barrier wall material ratio scheme

[0057]

[0058] The bentonite of the present invention is also called bentonite, which is a clay rock with montmorillonite as the main mineral. As an efficient, multi-purpose, easy-to-operate adsorption material, bentonite has a large specific surface area, cation exchange capacity and excellent adsorption characteristics, and is therefore widely used in water pollution prevention and control. The silicon-oxygen structure on the surface of bentonite has a strong hydrophilicity, and the interlayer cations are easily hydrolyzed, so a thin water film is usually formed on the surface of bentonite, which makes it difficult to effectively adsorb hydrophobic organic pollutants.

[0059] Fly ash is the main solid waste discharged from coal-fired power plants. It is a loose and porous solid particle with a large specific surface area. Its main component is SiO 2 、Al 2 O 3 , Fe 2 O 3 There are a lot of active points such as Al and Si in fly ash, CaO, MgO and unburned carbon, which can chemically and physically adsorb with adsorbents to adsorb heavy metals and organic matter in water. It is used as an adsorbent or coagulant in wastewater treatment, and has the advantage of low price. Therefore, using fly ash to treat pollutants can achieve the effect of "treating waste with waste".

[0060] The scanning electron microscope of the present invention obtains a high-resolution image by scanning the sample surface and measuring the reflected electronic signal. The measurement results of the sodium bentonite before modification are as follows: Figure 2

[0061] The test results of modified organic bentonite are as follows: Figure 3

[0062] Comparing the electron photos of bentonite before and after organic modification, compared with the original sodium-based bentonite, the structure of the organic-modified bentonite is looser, with more pores, significantly reduced large-area agglomeration, and significantly more flaky structures. It can be inferred that the larger surface area of ​​the organic bentonite is conducive to the physical adsorption of CBs by the wall material, and also provides a larger contact area for chemical adsorption.

[0063] XRD analysis:

[0064] XRD is an experimental method to study the structure of materials through the diffraction effect between X-rays and crystals. The spectrum of bentonite before and after modification is as follows: Figure 4 .

[0065] According to the experimental results, the interlayer spacing of sodium bentonite is 0.4074nm, and the interlayer spacing of organobentonite is 1.4336nm, indicating that tetraethylammonium bromide has successfully modified sodium bentonite. The interlayer spacing of the modified organobentonite is increased, which is conducive to enhancing the adsorption effect of CBs.

[0066] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0067] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a fly ash-organobentonite barrier wall having barrier properties for chlorobenzene compounds in water, characterized in that: The following steps are involved: S1. Preparation of organic bentonite: Mix powdered sodium bentonite with deionized water, stir with a magnetic stirrer at 60°C, add tetraethylammonium bromide modifier, stir for 2 h, let stand at room temperature for 24 h, centrifuge, and wash with deionized water until there is no white precipitate in the supernatant (Br) detected by silver nitrate indicator. - ), dried at 120°C for 2h, passed through a 0.178mm sieve and stored for later use; S2. Bentonite hydration; Put bentonite in a beaker, add water, stir with a glass rod, and then place on a stirrer and stir for 24 hours to complete the hydration process of bentonite; S3. Determine the material ratio of fly ash-organobentonite barrier wall; The barrier wall materials are sodium bentonite, soil, organic bentonite, fly ash and CaCO3, the mass proportions of sodium bentonite, fly ash and CaCO3 in the materials are 10%, 10% and 2% respectively, and then organic bentonite is added respectively, the mass proportions of the organic bentonite include but are not limited to 0%, 2%, 4%, 6%, 8% and 10% of organic bentonite, and the mass proportions of soil added to the organic bentonite include but are not limited to 78%, 76%, 74%, 72%, 70% and 68%; S4. Preparation method of fly ash-organic bentonite barrier wall: Mix the sodium bentonite, soil, fly ash and CaCO3 with a glass rod, slowly add the bentonite that has been hydrated for 24 hours, stirring with a glass rod while adding until the mixture is completely mixed with the hydrated bentonite, fill the ring cutter with the barrier wall material slurry, level it, and put it in a curing box at 21°C and 98% relative humidity for 7 days.

2. The method for preparing a fly ash-organobentonite barrier wall having barrier properties for chlorobenzene compounds in water according to claim 1, characterized in that: The mass ratio of the sodium bentonite: organic modified bentonite: fly ash: soil: CaCO3 is 10:8:10:70:2.

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