Ternary nano-composite modified bentonite-based vertical barrier material for antibiotic-polluted underground water as well as preparation method and application of ternary nano-composite modified bentonite-based vertical barrier material

Abstract

The invention provides a ternary nano-composite modified bentonite-based vertical barrier material for underground water polluted by antibiotics, which comprises sodium modified calcium bentonite, an Mg-Al LDH (layered double hydroxide) / g-C3N4 / ZIF-8 ternary nano-composite and sandy soil, the ternary nano-composite is prepared by the following steps: reacting magnesium nitrate hexahydrate, aluminum nitrate nonahydrate and urea at high pressure and high temperature to obtain Mg-Al LDH; thiourea is subjected to a heating reaction, and g-C3N4 is obtained; the preparation method comprises the following steps: carrying out microwave treatment on g-C3N4 and Mg-Al LDH to obtain a composite intermediate; and drying a reaction product of 2-MIM, the composite intermediate and zinc nitrate hexahydrate, grinding into powder, and sieving. The invention further provides a preparation method and application. The anti-seepage performance of the vertical barrier material meets the anti-seepage requirement that the permeability coefficient of organic matter is lower than 10 <-9 > m / s under the stress of antibiotic polluted underground water, antibiotics can be effectively adsorbed, the leaching toxicity is low, and the vertical barrier material is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical fields of environmental engineering and geotechnical engineering, in particular to the technical field of groundwater vertical barrier materials, specifically to a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, as well as a preparation method and application thereof. Background Art

[0002] As core chemicals in modern medicine and agriculture, antibiotics inevitably enter the soil and groundwater systems through leakage, discharge, and other pathways during their production, use, and disposal, posing a high-risk pollution hazard. my country's annual antibiotic usage exceeds 160,000 tons, of which more than 50% enter the environment in the form of prototypes or metabolites, resulting in widespread detection of antibiotic residues in surface water, groundwater, and even drinking water. The pollution concentration is much higher than that in developed countries in Europe and the United States. Typical antibiotics such as tetracyclines and quinolones have highly polar functional groups (such as phenolic hydroxyl groups and amino groups) and aromatic structures. They are easily bioaccumulated and difficult to degrade naturally. They not only induce drug resistance in microorganisms, but also threaten human health through the food chain. They have been included in my country's first list of key controlled new pollutants ("List of Key Controlled New Pollutants (2023 Edition)").

[0003] The highly polar functional groups (such as phenolic hydroxyl groups and amino groups) and aromatic structures of antibiotics make them not only easily bioaccumulated, but also extremely difficult to degrade naturally. More seriously, long-term exposure to antibiotics can easily lead to the development of drug resistance in microorganisms. This phenomenon is transmitted through the food chain, posing a direct and far-reaching threat to human health. For example, the resistance rate of some common pathogens to antibiotics has been rising year by year, making some previously effective treatment options gradually ineffective, increasing the difficulty and cost of treating infectious diseases.

[0004] From the perspective of traditional vertical barrier technology, the current prevention and control of antibiotic contaminated groundwater mainly relies on vertical barrier materials. However, traditional vertical barrier materials have exposed many shortcomings when dealing with such pollution. Traditional bentonite-based vertical barrier materials should rely on the hydration and expansion of bentonite to form a low permeability barrier to resist the spread of pollutants. However, the unique low dielectric constant of antibiotic solution will seriously damage the double layer structure on the surface of bentonite particles, causing its expansion performance to decline sharply, and the permeability coefficient can drop from less than 10 under ideal conditions. -9 m / s, and climbed sharply to over 10 -9m / s, significantly reducing its anti-seepage effectiveness. Furthermore, traditional bentonite barrier materials primarily physically retain charged antibiotics due to a lack of specific binding sites, resulting in a generally low adsorption capacity, typically less than 20 mg / kg. This is insufficient for actual contaminated sites, where antibiotic concentrations can reach hundreds of mg / L (e.g., pharmaceutical wastewater leaks). Furthermore, there is currently no research and development of vertical barrier materials specifically for antibiotic-contaminated groundwater, necessitating an urgent need for this research.

[0005] Therefore, it is hoped to provide a vertical barrier material for antibiotic-contaminated groundwater, which has an anti-seepage performance that satisfies the organic matter permeability coefficient of less than 10 under the stress of antibiotic-contaminated groundwater. -9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, and is environmentally friendly. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, one object of the present invention is to provide a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, which has an anti-seepage performance under the stress of antibiotic-contaminated groundwater and meets the requirement of organic matter permeability coefficient less than 10 -9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, is environmentally friendly, and is suitable for large-scale promotion and application.

[0007] Another object of the present invention is to provide a method for preparing a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater. The anti-seepage performance of the ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater prepared by this method meets the requirement that the organic matter permeability coefficient is less than 10 -9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, is environmentally friendly, and is suitable for large-scale promotion and application.

[0008] Another object of the present invention is to provide an application of a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater is used to vertically block antibiotic-contaminated groundwater, and its anti-seepage performance satisfies the requirement that the organic matter permeability coefficient is less than 10 - 9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, is environmentally friendly, and is suitable for large-scale promotion and application.

[0009] To achieve the above objectives, in a first aspect of the present invention, a ternary nanocomposite-modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater is provided, comprising sodium-modified calcium-based bentonite and sand. The ternary nanocomposite-modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater further comprises a ternary nanocomposite of Mg-Al layered double hydroxide / graphitic carbon nitride / zeolite imidazolate framework-8, wherein:

[0010] The Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite is prepared by the following method:

[0011] (1) Preparation of Mg-Al layered double hydroxide: magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and urea are added to methanol and stirred uniformly, and then reacted in an autoclave at a first high temperature, cooled, washed with water and ethanol, and dried to obtain a white powdery Mg-Al layered double hydroxide;

[0012] (2) Preparing graphite-phase carbon nitride: heating thiourea to a second high temperature and maintaining the temperature to react, thereby obtaining yellow solid graphite-phase carbon nitride;

[0013] (3) Preparing a Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate: dispersing graphite phase carbon nitride in deionized water and ultrasonically treating the mixture; adding Mg-Al layered double hydroxide, stirring the mixture, and then subjecting the mixture to microwave treatment; washing the product with water and drying the resultant to obtain a Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate;

[0014] (4) Preparation of Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite: Disperse the Mg-Al layered double hydroxide / graphite carbon nitride composite intermediate in methanol, ultrasonically treat, add zinc nitrate hexahydrate, and stir to obtain solution A; dissolve 2-methylimidazole in additional methanol and stir to obtain solution B; add solution B dropwise to solution A for mixing reaction; wash the product with ethanol and dry it, then grind it into powder and sieve it to obtain Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite.

[0015] Preferably, the mass ratio of the sodium modified calcium-based bentonite, the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and the sand is 10:1 to 3:100.

[0016] Preferably, the particle size of the sodium modified calcium-based bentonite is less than 0.075 mm, the free expansion capacity of the sodium modified calcium-based bentonite is not less than 15 ml / 2 g, and the liquid limit of the sodium modified calcium-based bentonite is not less than 200%.

[0017] Preferably, in step (1), the amount of magnesium nitrate hexahydrate added is 1 g, the amount of aluminum nitrate nonahydrate added is 1.085 g, and the amount of urea added is 1.58 g; the amount of methanol used is 40 mL, the stirring time is 30 minutes, the first high temperature is 150° C., the reaction time is 6 hours, the drying temperature is 80° C., and the drying time is 6 hours.

[0018] Preferably, in the step (2), the amount of thiourea is 10 g, the second high temperature is 550° C., and the holding time is 3 hours.

[0019] Preferably, in the step (3), the graphite phase carbon nitride is 0.025 g; the deionized water is 50 ml, the ultrasonic treatment time is 1 hour, the amount of the Mg-Al layered double hydroxide added is 4 times the mass of the graphite phase carbon nitride, the stirring time is 1 hour, the microwave treatment power is 540 W, the microwave treatment time is 10 minutes, the drying temperature is 80°C, and the drying time is 6 hours.

[0020] Preferably, in the step (4), the Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate is 0.12 g, the amount of methanol added is 25 mL, the ultrasonic treatment time is 30 minutes, the amount of zinc nitrate hexahydrate added is 0.446 g, the 2-methylimidazole is 0.492 g, the additional amount of methanol added is 25 mL, the stirring time for each of the two times is 1 hour, the mixing reaction time is 24 hours, the drying temperature is 80°C, the drying time is 6 hours, and the sieving is through a 200 mesh sieve.

[0021] In a second aspect of the present invention, a method for preparing the above-mentioned ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater is provided, which is characterized by comprising the following steps:

[0022] The sodium modified calcium-based bentonite, the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and the sand are mixed evenly.

[0023] In the third aspect of the present invention, a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater is provided, which is characterized in that it is prepared using the above-mentioned preparation method of the ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater.

[0024] In a fourth aspect of the present invention, there is provided a use of the above-mentioned ternary nanocomposite modified bentonite-based vertical barrier material for vertically blocking antibiotic-contaminated groundwater.

[0025] The beneficial effects of the present invention are mainly:

[0026] 1. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater of the present invention comprises sodium-modified calcium-based bentonite, Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and sand, wherein the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite is prepared by the following method: (1) adding magnesium nitrate hexahydrate, aluminum nitrate nonahydrate and urea to methanol and stirring evenly, and then reacting them in an autoclave at a first high temperature, washing with water and ethanol after cooling, and drying to obtain white powdery Mg-Al layered double hydroxide; (2) heating thiourea to a second high temperature and maintaining the reaction to obtain yellow solid graphite phase carbon nitride; (3) dispersing the graphite phase carbon nitride in In deionized water, ultrasonic treatment; adding Mg-Al layered double hydroxide, stirring and then microwave treatment; the product is washed with water and dried to obtain Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate; (4) dispersing the Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate in methanol, ultrasonic treatment, adding zinc nitrate hexahydrate, stirring to obtain solution A; dissolving 2-methylimidazole in another methanol, stirring to obtain solution B; adding solution B dropwise to solution A for mixed reaction; washing the product with ethanol and drying, then grinding into powder and sieving to obtain Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazole ester framework-8 ternary nanocomposite, the vertical barrier material has anti-seepage performance under the stress of antibiotic contaminated groundwater that meets the organic permeability coefficient of less than 10 -9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, is environmentally friendly, and is suitable for large-scale promotion and application.

[0027] 2. The preparation method of the above-mentioned ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic contaminated groundwater of the present invention comprises the following steps: uniformly mixing sodium-modified calcium-based bentonite, Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and sand, and the anti-seepage performance of the ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic contaminated groundwater prepared by this method meets the organic matter permeability coefficient of less than 10 -9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, is environmentally friendly, and is suitable for large-scale promotion and application.

[0028] 3. The application of the above-mentioned ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic contaminated groundwater in the present invention in vertically blocking antibiotic contaminated groundwater, the anti-seepage performance of the ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic contaminated groundwater meets the requirement that the organic matter permeability coefficient is less than 10 -9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, is environmentally friendly, and is suitable for large-scale promotion and application.

[0029] These and other objects, features and advantages of the present invention are fully reflected in the following detailed description and drawings, and can be achieved by the means, devices and their combinations particularly pointed out in the summary of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 3 and Comparative Example 1 are graphs showing changes in permeability coefficients of the vertical barrier materials of Examples 1 to 3 and Comparative Example 1.

[0031] Figure 2 It is a curve chart showing the antibiotic adsorption capacity and 28-day antibiotic leaching rate change of the barrier materials of Examples 1 to 3 and Comparative Example 1. DETAILED DESCRIPTION

[0032] In order to solve the problems of anti-seepage failure and insufficient adsorption of traditional vertical barrier materials in antibiotic contaminated scenes and provide a new solution for emergency control and long-term treatment of high-risk antibiotic-contaminated groundwater, the inventors conducted in-depth and extensive research on traditional sodium-modified calcium-based bentonite, and thus proposed a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater. Its anti-seepage performance under the stress of antibiotic-contaminated groundwater meets the requirement of organic matter permeability coefficient less than 10 -9 m / s anti-seepage requirements (Technical Specifications for Vertical Barriers in Industrial Polluted Sites (HG / T 20715-2020)), can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, and is environmentally friendly.

[0033] The present invention first provides a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, comprising sodium-modified calcium-based bentonite, a ternary nanocomposite of Mg-Al layered double hydroxide / graphitic carbon nitride / zeolite imidazolate framework-8 (Mg-Al LDH / g-C3N4 / ZIF-8), and sand, wherein:

[0034] The raw materials required for the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazole framework-8 ternary nanocomposite include: magnesium nitrate hexahydrate (Mg(NO3)2·6H2O), aluminum nitrate nonahydrate (Al(NO3)3·9H2O), urea ((NH2)2CO), thiourea (CH4N2S), zinc nitrate hexahydrate (Zn(NO3)2·6H2O), 2-methylimidazole (2-MIM, C4H6N2), methanol (CH3OH), and ethanol (C2H5OH); the purity of the above raw materials is not less than 95% (analytical grade).

[0035] The Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite is prepared by the following method:

[0036] (1) Preparation of Mg-Al layered double hydroxide (Mg-Al LDH): Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O), aluminum nitrate nonahydrate (Al(NO3)3·9H2O) and urea ((NH2)2CO) were added to methanol (CH3OH) and stirred uniformly, and then reacted in an autoclave at a first high temperature. After cooling, the mixture was washed with water and ethanol (C2H5OH) and dried to obtain a white powdery Mg-Al layered double hydroxide.

[0037] (2) Preparation of graphite carbon nitride (g-C3N4): heating thiourea (CH4N2S) to a second high temperature and maintaining the reaction to obtain yellow solid graphite carbon nitride;

[0038] (3) Preparation of Mg-Al layered double hydroxide / graphite phase carbon nitride (Mg-AlLDH / g-C3N4) composite intermediate: dispersing graphite phase carbon nitride in deionized water and ultrasonically treating; adding Mg-Al layered double hydroxide, stirring and then microwave treating; washing the product with water and drying to obtain Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate;

[0039] (4) Preparation of Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite: The Mg-Al layered double hydroxide / graphite carbon nitride composite intermediate was dispersed in methanol, ultrasonically treated, and zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was added and stirred to obtain solution A; 2-methylimidazole (2-MIM, C4H6N2) was dissolved in another methanol and stirred to obtain solution B; solution B was added dropwise to solution A for mixing reaction; the product was washed with ethanol and dried, then ground into powder and sieved to obtain a Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite.

[0040] The mass ratio of the sodium-modified calcium-based bentonite, the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and the sand can be determined as needed. Preferably, the mass ratio of the sodium-modified calcium-based bentonite, the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and the sand is 10:1 to 3:100.

[0041] The particle size, free expansion volume and liquid limit of the sodium-modified calcium-based bentonite can be determined as needed. Preferably, the particle size of the sodium-modified calcium-based bentonite is less than 0.075 mm, the free expansion volume of the sodium-modified calcium-based bentonite is not less than 15 ml / 2 g, and the liquid limit of the sodium-modified calcium-based bentonite is not less than 200%.

[0042] In the step (1), the amount of magnesium nitrate hexahydrate added, the amount of aluminum nitrate nonahydrate added, the amount of urea added and the amount of methanol used, the stirring time, the first high temperature, the reaction time, the drying temperature and time can be determined as needed. Preferably, in the step (1), the amount of magnesium nitrate hexahydrate added is 1 g, the amount of aluminum nitrate nonahydrate added is 1.085 g, and the amount of urea added is 1.58 g; the amount of methanol used is 40 mL, the stirring time is 30 minutes, the first high temperature is 150° C., the reaction time is 6 hours, the drying temperature is 80° C., and the drying time is 6 hours.

[0043] In the step (2), the amount of thiourea used, the second high temperature and the holding time can be determined as needed. Preferably, in the step (2), the thiourea is 10 g, the second high temperature is 550° C., and the holding time is 3 hours.

[0044] In the step (3), the amount of the graphite phase carbon nitride used, the amount of the deionized water used, the time of the ultrasonic treatment, the amount of the Mg-Al layered double hydroxide added, the stirring time, the power and time of the microwave treatment, and the temperature and time of the drying can be determined as needed. Preferably, in the step (3), the graphite phase carbon nitride is 0.025 g; the deionized water is 50 ml, the ultrasonic treatment time is 1 hour, the amount of the Mg-Al layered double hydroxide added is 4 times the mass of the graphite phase carbon nitride (i.e., 0.1 g), the stirring time is 1 hour, the microwave treatment power is 540 W, the microwave treatment time is 10 minutes, the drying temperature is 80° C., and the drying time is 6 hours.

[0045] In the step (4), the amount of the Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate used, the amount of methanol added, the time of the ultrasonic treatment, the amount of zinc nitrate hexahydrate added, the amount of 2-methylimidazole used, the amount of additional methanol added, the stirring time, the time of the mixing reaction, the temperature and time of the drying, and the mesh number of the sieving can be determined as needed. Preferably, in the step (4), the Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate is 0.12g, the amount of methanol added is 25mL, the time of the ultrasonic treatment is 30 minutes, the amount of zinc nitrate hexahydrate added is 0.446g, the 2-methylimidazole (2-MIM) is 0.492g, the amount of additional methanol added is 25mL, the stirring time for both times is 1 hour, the time of the mixing reaction is 24 hours, the drying temperature is 80°C, the drying time is 6 hours, and the sieving is through a 200 mesh sieve.

[0046] The present invention also provides a method for preparing the above-mentioned ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, comprising the following steps:

[0047] The sodium modified calcium-based bentonite, the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and the sand are mixed evenly.

[0048] The present invention also provides a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, which is prepared using the above-mentioned method for preparing the ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater.

[0049] The present invention also provides an application of the above-mentioned ternary nanocomposite modified bentonite-based vertical barrier material for vertically blocking antibiotic-contaminated groundwater.

[0050] The antibiotic can be any suitable antibiotic, preferably, the antibiotic is tetracycline.

[0051] In order to more clearly understand the technical content of the present invention, the following examples are specifically described in detail. It should be understood that the specific examples described herein are merely illustrative of the present invention and are not intended to limit the present invention. Unless otherwise stated, the instruments, drugs, reagents, etc. used in the following examples can be obtained by conventional commercial means.

[0052] In the Examples and Comparative Examples:

[0053] The sandy soil was selected from the Yangtze River floodplain area, washed with tap water, dried at 105°C for 24 hours, and then sieved through a 2mm diameter mesh.

[0054] Among the raw materials required for the ternary nanocomposite, except for Mg(NO3)2·6H2O, urea and 2-MIM whose purities are not less than 98%, the purities of other raw materials are not less than 99%.

[0055] Example 1

[0056] The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater is prepared by the following method:

[0057] Step 1) Preparation of Mg-Al LDH: Weigh 1 g of Mg(NO3)2·6H2O, 1.085 g of Al(NO3)3·9H2O, and 1.58 g of urea, respectively, mix in a beaker, add 40 mL of methanol, and stir for 30 minutes; transfer to a polytetrafluoroethylene-lined stainless steel autoclave, react at 150°C for 6 hours; after cooling, wash with deionized water and ethanol several times, and dry at 80°C for 6 hours to obtain white powdered Mg-Al LDH;

[0058] Step 2) Preparation of g-C3N4: Weigh 10 g of thiourea, place in a ceramic crucible, cover with aluminum foil, and slowly heat to 550°C in an electric furnace for 3 hours; collect a yellow solid to obtain g-C3N4;

[0059] Step 3) preparing a Mg-AlLDH / g-C3N4 composite intermediate: dispersing 0.025 g of g-C3N4 in 50 mL of deionized water and ultrasonically treating for 1 hour; adding Mg-Al LDH (i.e., 0.1 g) with a mass four times the mass of graphite carbon nitride, stirring for 1 hour, transferring to a microwave oven, and irradiating at 540 W for 10 minutes; washing the product with deionized water and drying at 80°C for 6 hours to obtain a Mg-Al LDH / g-C3N4 composite intermediate;

[0060] Step 4) Preparation of Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite: 0.12 g of Mg-Al LDH / g-C3N4 composite intermediate was dispersed in 25 mL of methanol, ultrasonically treated for 30 minutes, 0.446 g of zinc nitrate hexahydrate was added, and stirred for 1 hour to obtain solution A; 0.492 g of 2-MIM was dispersed in 25 mL of methanol, stirred for 1 hour to obtain solution B; solution B was added dropwise to solution A, and the mixture was mixed and reacted for 24 hours; the product was washed with ethanol, dried at 80°C for 6 hours, ground into powder and passed through a 200-mesh sieve to obtain a Mg-AlLDH / g-C3N4 / ZIF-8 ternary nanocomposite.

[0061] Step 5) Prepare a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater: Sodium-modified calcium-based bentonite (Jurong Mufeng Bentonite Processing Plant, ordinary commercial sodium-modified calcium-based bentonite), Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite and sand are evenly mixed to obtain a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, wherein the particle size of the sodium-modified calcium-based bentonite is less than 0.075 mm, the free expansion volume is 16 ml / 2 g, and the liquid limit is 223%; the mass ratio of the sodium-modified calcium-based bentonite, Mg-Al layered double hydroxide / graphitic carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and sand is 10:1:100.

[0062] Example 2

[0063] The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater is prepared by the following method:

[0064] Step 1) Preparation of Mg-Al LDH: Weigh 1 g of Mg(NO3)2·6H2O, 1.085 g of Al(NO3)3·9H2O, and 1.58 g of urea, respectively, mix in a beaker, add 40 mL of methanol, and stir for 30 minutes; transfer to a polytetrafluoroethylene-lined stainless steel autoclave, react at 150°C for 6 hours; after cooling, wash with deionized water and ethanol several times, and dry at 80°C for 6 hours to obtain white powdered Mg-Al LDH;

[0065] Step 2) Preparation of g-C3N4: Weigh 10 g of thiourea, place in a ceramic crucible, cover with aluminum foil, and slowly heat to 550°C in an electric furnace for 3 hours; collect a yellow solid to obtain g-C3N4;

[0066] Step 3) preparing a Mg-AlLDH / g-C3N4 composite intermediate: dispersing 0.025 g of g-C3N4 in 50 mL of deionized water and ultrasonically treating for 1 hour; adding Mg-Al LDH (i.e., 0.1 g) with a mass four times the mass of graphite carbon nitride, stirring for 1 hour, transferring to a microwave oven, and irradiating at 540 W for 10 minutes; washing the product with deionized water and drying at 80° C. for 6 hours to obtain a Mg-Al LDH / g-C3N4 composite intermediate;

[0067] Step 4) Preparation of Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite: 0.12 g of Mg-Al LDH / g-C3N4 composite intermediate was dispersed in 25 mL of methanol, ultrasonically treated for 30 minutes, 0.446 g of zinc nitrate hexahydrate was added, and stirred for 1 hour to obtain solution A; 0.492 g of 2-MIM was dispersed in 25 mL of methanol, stirred for 1 hour to obtain solution B; solution B was added dropwise to solution A, and the mixture was mixed and reacted for 24 hours; the product was washed with ethanol, dried at 80°C for 6 hours, ground into powder and passed through a 200-mesh sieve to obtain a Mg-AlLDH / g-C3N4 / ZIF-8 ternary nanocomposite.

[0068] Step 5) Prepare a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater: Sodium-modified calcium-based bentonite (Jurong Mufeng Bentonite Processing Plant, ordinary commercial sodium-modified calcium-based bentonite), Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite and sand are evenly mixed to obtain a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, wherein the particle size of the sodium-modified calcium-based bentonite is less than 0.075 mm, the free expansion volume is 16 ml / 2 g, and the liquid limit is 223%; the mass ratio of the sodium-modified calcium-based bentonite, Mg-Al layered double hydroxide / graphitic carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and sand is 10:2:100.

[0069] Example 3

[0070] The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater is prepared by the following method:

[0071] Step 1) Preparation of Mg-Al LDH: Weigh 1 g of Mg(NO3)2·6H2O, 1.085 g of Al(NO3)3·9H2O, and 1.58 g of urea, respectively, mix in a beaker, add 40 mL of methanol, and stir for 30 minutes; transfer to a polytetrafluoroethylene-lined stainless steel autoclave, react at 150°C for 6 hours; after cooling, wash with deionized water and ethanol several times, and dry at 80°C for 6 hours to obtain white powdered Mg-Al LDH;

[0072] Step 2) Preparation of g-C3N4: Weigh 10 g of thiourea, place in a ceramic crucible, cover with aluminum foil, and slowly heat to 550°C in an electric furnace for 3 hours; collect a yellow solid to obtain g-C3N4;

[0073] Step 3) preparing a Mg-AlLDH / g-C3N4 composite intermediate: dispersing 0.025 g of g-C3N4 in 50 mL of deionized water and ultrasonically treating for 1 hour; adding Mg-Al LDH (i.e., 0.1 g) with a mass four times the mass of graphite carbon nitride, stirring for 1 hour, transferring to a microwave oven, and irradiating at 540 W for 10 minutes; washing the product with deionized water and drying at 80° C. for 6 hours to obtain a Mg-Al LDH / g-C3N4 composite intermediate;

[0074] Step 4) Preparation of Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite: 0.12 g of Mg-Al LDH / g-C3N4 composite intermediate was dispersed in 25 mL of methanol, ultrasonically treated for 30 minutes, 0.446 g of zinc nitrate hexahydrate was added, and stirred for 1 hour to obtain solution A; 0.492 g of 2-MIM was dispersed in 25 mL of methanol, stirred for 1 hour to obtain solution B; solution B was added dropwise to solution A, and the mixture was mixed and reacted for 24 hours; the product was washed with ethanol, dried at 80°C for 6 hours, ground into powder and passed through a 200-mesh sieve to obtain a Mg-AlLDH / g-C3N4 / ZIF-8 ternary nanocomposite.

[0075] Step 5) Prepare a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater: Sodium-modified calcium-based bentonite (Jurong Mufeng Bentonite Processing Plant, ordinary commercial sodium-modified calcium-based bentonite), Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite and sand are evenly mixed to obtain a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, wherein the particle size of the sodium-modified calcium-based bentonite is less than 0.075 mm, the free expansion volume is 16 ml / 2 g, and the liquid limit is 223%; the mass ratio of the sodium-modified calcium-based bentonite, Mg-Al layered double hydroxide / graphitic carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and sand is 10:3:100.

[0076] Comparative Example 1

[0077] Without adding the Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite, the sodium-modified calcium-based bentonite (same as in Example 1) and the sand (same as in Example 1) were evenly mixed to obtain a bentonite-based vertical barrier material that was not modified by the ternary nanocomposite, wherein the mass ratio of the sodium-modified calcium-based bentonite to the sand was 10:100.

[0078] Example 4

[0079] To investigate the anti-seepage, adsorption, and leaching properties of vertical barrier materials under the stress of antibiotic-contaminated groundwater, flexible wall permeation tests, batch adsorption tests, and toxicity leaching tests were conducted. Groundwater was simulated using a calcium chloride solution at a designed concentration of 20 mmol / L. Antibiotic-contaminated groundwater was simulated using a solution containing tetracycline, a typical antibiotic contaminant, calcium chloride, and deionized water at a designed concentration of 50 mg / L tetracycline and 20 mmol / L calcium chloride.

[0080] (1) In order to explore the anti-seepage performance of vertical barrier materials under the stress of antibiotic contaminated groundwater, a flexible wall penetration test was carried out. The test method of the flexible wall penetration test referred to ASTM specification D7100, which was a constant head penetration method. The penetration solutions were simulated groundwater and simulated antibiotic contaminated groundwater, respectively. The hydraulic gradient of the penetration was controlled to be 10, the effective stress was 15 kPa, and finally the chemical solution penetration termination conditions proposed by ASTM D7100 were achieved.

[0081] The vertical barrier materials of Examples 1 to 3 and Comparative Example 1 were mixed with water. They were then placed in the sample chamber of the flexible wall permeameter and tested according to the hydraulic gradient, effective stress, and permeation solution as described above. The permeability coefficient results of each vertical barrier material are shown in Figure 1 The results show that the comparative example 1 and examples 1 to 3 are all lower than 10 -9 m / s; However, under the stress of simulated antibiotic contaminated groundwater, the pressure of Examples 1 to 3 was still lower than 10 -9 m / s, while Comparative Example 1 exceeds the limit value requirement.

[0082] (2) In order to explore the adsorption performance of vertical barrier materials under the stress of antibiotic contaminated groundwater, a batch adsorption test was carried out. The batch adsorption test referred to the ASTM D4646 specification. The solution was simulated antibiotic contaminated groundwater, and the solid-liquid ratio was controlled at 1:20.

[0083] The vertical barrier materials of Examples 1 to 3 and Comparative Example 1 were mixed with water and then weighed and poured into a 250 mL plastic bottle. Then, antibiotic-contaminated groundwater with a corresponding solid-liquid ratio was added and shaken for 24 hours. The supernatant was then taken to test the antibiotic concentration. The antibiotic adsorption capacity results of each vertical barrier material are shown in Table 1. Figure 2 The results showed that the maximum adsorption capacity of the antibiotic in Comparative Example 1 was 15.5 mg / g, while the maximum adsorption capacity of the antibiotic in Examples 1 to 3 was 24.9 mg / g to 51.4 mg / g. The maximum adsorption capacity of the antibiotic in Examples 1 to 3 increased by 60% to 232%.

[0084] (3) In addition, in order to evaluate the antibiotic toxicity leaching behavior of the vertical barrier material, the vertical barrier material after the flexible wall penetration test of antibiotic-contaminated groundwater in (1) was subjected to toxicity leaching. The toxicity leaching test was based on HJ 557-2010 and was appropriately adjusted to simulate extreme leaching conditions. The leaching solution was deionized water, and the solid-liquid ratio was set to 1:10.

[0085] After the permeation test, the vertical barrier material was placed in a plastic bottle and deionized water was poured into it according to the water content of the material. The solid-liquid ratio of the mixture of the material and deionized water was controlled to be 1:10. After continuous shaking for 8 hours, it was left to stand for 28 days. After 28 days, the antibiotic concentration in the deionized water was tested. The 28-day antibiotic leaching rate of each vertical barrier material is shown in Figure 2. Figure 2 The results showed that the 28-day antibiotic leaching rate of Comparative Example 1 was 26.7%, while the 28-day antibiotic leaching rates of Examples 1 to 3 were 0.6% to 1.9%. The 28-day antibiotic leaching rates of Examples 1 to 3 were reduced by 92.9% to 97.8%.

[0086] The reasons for the insufficient barrier performance of the pseudo-antibiotic-contaminated groundwater in Example 1 are as follows: the traditional sodium-modified calcium-based bentonite vertical barrier material destroys the double-layer structure due to the electrostatic repulsion between tetracycline anions and the negative charges on the bentonite surface, resulting in the loss of cations between the bentonite layers, the decline of expansion performance, the increase of porosity, and the increase of permeability coefficient; it only adsorbs tetracycline through physical retention and weak van der Waals forces, lacks specific binding sites, and has a low adsorption capacity; and the pollutants are mainly physically adsorbed, the binding is not strong, and the toxic leaching rate is high.

[0087] The reason why the barrier performance of the bentonite-based vertical barrier material modified by the Mg-AlLDH / g-C3N4 / ZIF-8 ternary nanocomposite is high: The Mg-AlLDH / g-C3N4 / ZIF-8 ternary nanocomposite systematically improves the barrier performance of the material through multi-scale structural regulation and chemical mechanism coordination. (1) Construction of nanoscale physical barrier: The layered structure of Mg-Al LDH is embedded in the gaps between bentonite particles, reducing the average pore size from 50nm to below 5nm, forming a "size exclusion" effect, directly blocking the passage of tetracycline molecules (kinetic diameter ≈ 0.8nm); the microporous structure of ZIF-8 (pore size 1.1nm) fills the bentonite mesopores, allowing only water molecules to pass through, achieving "molecular sieve" type interception, and the permeability coefficient can be further reduced. (2) Multi-mechanism chemical adsorption enhancement: ion exchange and coordination: NO3- between the Mg-Al LDH layers specifically exchanges with tetracycline anions, Al 3+ Forming a coordination bond with the phenolic hydroxyl group of tetracycline; Zn 2+Coordinate with tetracycline amino groups; π-π stacking and hydrogen bonding: The triazine ring of g-C3N4 binds to the tetracycline aromatic ring through π-π interaction, and the surface amino group forms hydrogen bonds with the tetracycline hydroxyl group, further improving the adsorption stability. (3) Pollutant fixation and anti-leaching mechanism: Tetracycline forms an irreversible chemical bond with the complex through ionic bonds, coordination bonds, and hydrogen bonds, far exceeding the groundwater dynamic desorption energy; ZIF-8 micropores encapsulate tetracycline in the nanospace, forming a "molecular cage" effect, with a low toxicity leaching rate, ensuring environmental safety.

[0088] Therefore, the present invention adopts Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite to modify sodium-modified calcium-based bentonite, thereby preparing a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater. The Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite is composed of Mg-Al layered double hydroxide (Mg-Al LDH), graphite phase carbon nitride (g-C3N4) and zeolite imidazolate framework-8 (ZIF-8). Among them, the interlayer anions (such as NO3-) of Mg-Al LDH and antibiotic ions (such as tetracycline anions) exchange and adsorb, and the layered structure provides a physical barrier; the aromatic ring structure of g-C3N4 forms a π-π stacking effect with antibiotic molecules to enhance specific adsorption; the ZIF-8 microporous structure (pore size 1.1nm) captures small molecule antibiotics (such as sulfonamides), and its Zn 2+ The sites form coordination bonds with antibiotic functional groups (such as hydroxyl groups and amino groups); the above multiple adsorption mechanisms form a multi-level adsorption synergistic effect for antibiotics, targeting the removal of antibiotic pollutants.

[0089] Compared with the existing technology, the present invention realizes the "anti-seepage-adsorption" synergistic control of antibiotic-contaminated groundwater through the innovative design of Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite modified bentonite-based vertical barrier material. The specific advantages are as follows:

[0090] (1) The Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite fills the pores of bentonite and interacts with the interface chemistry to construct a nanoscale anti-seepage network. Under the stress of antibiotic-contaminated groundwater, the permeability coefficient of the ternary nanocomposite modified bentonite-based vertical barrier material is reduced by more than one order of magnitude compared with the traditional bentonite barrier material, achieving the anti-seepage performance under the stress of antibiotic-contaminated groundwater with a permeability coefficient of less than 10 -9 The anti-seepage requirement of m / s can effectively block the migration path of antibiotics through pore water.

[0091] (2) The Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite modified bentonite-based vertical barrier material has extremely high adsorption and fixation capacity for antibiotics in contaminated groundwater. The Mg-Al LDH / g-C3N4 / ZIF-8 ternary nanocomposite modified bentonite-based vertical barrier material improves the material's adsorption capacity for antibiotics by 60% to 232% compared to traditional soil-bentonite barrier materials, and reduces the 28-day antibiotic leaching rate by 92.9% to 97.8%.

[0092] In summary, the ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater of the present invention has an anti-seepage performance under the stress of antibiotic-contaminated groundwater that satisfies the requirement that the organic matter permeability coefficient is less than 10 -9 m / s anti-seepage requirements, can effectively adsorb antibiotics in antibiotic-contaminated groundwater, has low leaching toxicity, is environmentally friendly, and is suitable for large-scale promotion and application.

[0093] It can be seen that the objectives of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and illustrated in the embodiments. The embodiments may be modified as desired without departing from the principles described. Therefore, the present invention includes all variations within the spirit and scope of the claims.

Claims

1. A ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, comprising sodium-modified calcium-based bentonite and sand, characterized in that: The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater further comprises a ternary nanocomposite of Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8, wherein: The Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite is prepared by the following method: (1) Preparation of Mg-Al layered double hydroxide: magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and urea are added to methanol and stirred uniformly, and then reacted in an autoclave at a first high temperature, cooled, washed with water and ethanol, and dried to obtain a white powdery Mg-Al layered double hydroxide; (2) Preparing graphite-phase carbon nitride: heating thiourea to a second high temperature and maintaining the temperature to react, thereby obtaining yellow solid graphite-phase carbon nitride; (3) Preparing a Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate: dispersing graphite phase carbon nitride in deionized water and ultrasonically treating the mixture; adding Mg-Al layered double hydroxide, stirring the mixture, and then subjecting the mixture to microwave treatment; washing the product with water and drying the resultant to obtain a Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate; (4) Preparation of Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite: Disperse the Mg-Al layered double hydroxide / graphite carbon nitride composite intermediate in methanol, ultrasonically treat, add zinc nitrate hexahydrate, and stir to obtain solution A; dissolve 2-methylimidazole in additional methanol and stir to obtain solution B; add solution B dropwise to solution A for mixing reaction; wash the product with ethanol and dry it, then grind it into powder and sieve it to obtain Mg-Al layered double hydroxide / graphite carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite.

2. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater according to claim 1, characterized in that: The mass ratio of the sodium modified calcium-based bentonite, the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and the sand is 10:1 to 3:

100.

3. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater according to claim 1, characterized in that: The particle size of the sodium modified calcium-based bentonite is less than 0.075 mm, the free expansion volume of the sodium modified calcium-based bentonite is not less than 15 ml / 2 g, and the liquid limit of the sodium modified calcium-based bentonite is not less than 200%.

4. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater according to claim 1, characterized in that: In the step (1), the amount of magnesium nitrate hexahydrate added is 1 g, the amount of aluminum nitrate nonahydrate added is 1.085 g, the amount of urea added is 1.58 g, the amount of methanol used is 40 mL, the stirring time is 30 minutes, the first high temperature is 150° C., the reaction time is 6 hours, the drying temperature is 80° C., and the drying time is 6 hours.

5. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater according to claim 1, characterized in that: In the step (2), the amount of thiourea is 10 g, the second high temperature is 550° C., and the holding time is 3 hours.

6. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater according to claim 1, characterized in that: In the step (3), the graphite phase carbon nitride is 0.025 g; the deionized water is 50 ml, the ultrasonic treatment time is 1 hour, the amount of the Mg-Al layered double hydroxide added is 4 times the mass of the graphite phase carbon nitride, the stirring time is 1 hour, the microwave treatment power is 540 W, the microwave treatment time is 10 minutes, the drying temperature is 80°C, and the drying time is 6 hours.

7. The ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater according to claim 1, characterized in that: In the step (4), the Mg-Al layered double hydroxide / graphite phase carbon nitride composite intermediate is 0.12 g, the amount of methanol added is 25 mL, the ultrasonic treatment time is 30 minutes, the amount of zinc nitrate hexahydrate added is 0.446 g, the 2-methylimidazole is 0.492 g, the additional amount of methanol added is 25 mL, the stirring time for each of the two times is 1 hour, the mixing reaction time is 24 hours, the drying temperature is 80°C, the drying time is 6 hours, and the sieving is through a 200 mesh sieve.

8. A method for preparing a ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater according to any one of claims 1 to 7, characterized in that: The following steps are involved: The sodium modified calcium-based bentonite, the Mg-Al layered double hydroxide / graphite phase carbon nitride / zeolite imidazolate framework-8 ternary nanocomposite and the sand are mixed evenly.

9. A ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater, characterized in that: The vertical barrier material is prepared by the method for preparing the ternary nanocomposite modified bentonite-based vertical barrier material for antibiotic-contaminated groundwater as claimed in claim 8.

10. Use of the ternary nanocomposite modified bentonite-based vertical barrier material for vertically blocking antibiotic-contaminated groundwater according to any one of claims 1 to 7 and 9.

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