A method for testing the physicochemical properties of a seepage barrier material

Abstract

This application relates to the field of barrier materials, and provides a method for testing the physicochemical properties of a seepage-proof barrier material. The material comprises the following raw materials in parts by weight: calcium-based bentonite: 5g; Mg(OH)2: 0.25g-1.25g; Al2O3: 0.01g-0.5g; SDBS: 0.05g-0.35g. The calcium-based bentonite comprises the following raw materials in weight percentages: SiO2: 58.9%-60.9%, Al2O3: 16%-18%, Fe2O3: 4.4%-6.4%, CaO: 4.2%-6.2%, Na2O: 1.3%-3.3%, MgO: 0.3%-2.3%, K2O: 1.8%-3.8%, TiO2: 0.9%-2.9%, and other materials: 0.3%-2.3%. By synthesizing a modified bentonite seepage barrier material—Mg-Al LHCB (Mg-Al layered hydroxide gelled bentonite)—Mg(OH)2 and nano-Al2O3, under the action of surfactant SDBS, with bentonite as a carrier, can be loaded onto the bentonite surface or pillared between bentonite layers through their gelling properties, increasing the ion exchange capacity and spatial holding capacity of bentonite, thereby improving the seepage barrier performance of modified bentonite materials against metal ions.

Description

Technical Field

[0001] This invention relates to the field of barrier materials technology, specifically to a method for testing the physicochemical properties of a seepage-proof barrier material. Background Technology

[0002] In recent years, due to the increasing demand for metallic minerals, mines have been mined and developed, generating large amounts of tailings, most of which are stored in tailings ponds near mining areas. Through rainwater erosion and weathering, the pH value of the soil decreases, leading to highly acidic soil pollution, which further affects the surrounding air, groundwater, soil, and human health. Therefore, preventing the migration of heavy metals from tailings ponds is an urgent matter.

[0003] Lead-zinc ore is an important mineral resource in my country. After mining, tailings dam pollution is inevitable. Like zinc, lead (Pb) is amphoteric, dissolving under strong acid and alkali conditions, and has a narrow pH range for precipitation. Lead is much more harmful to the human body than zinc. It can enter the body not only through food and respiration but also through skin contact, accumulating in the body at a rate of 30%-50%. In severe cases, it can cause cancer, birth defects, and mutations, earning it the reputation of a silent killer. Given the significant environmental hazards of lead and zinc, and the potential for tailings dam leaks, multi-layered seepage prevention systems at the bottom of tailings dams are essential. my country is a major producer of bentonite resources. Due to its good adsorption and expansion properties, bentonite is commonly used as a seepage prevention material. However, the performance of natural bentonite can be greatly improved through modification. Therefore, based on previous research, further development and improvement of bentonite's superior performance in specific applications is urgent and meaningful. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for testing the physicochemical properties of seepage-proof barrier materials, which solves the problem of heavy metal solutions from tailings leaching polluting the surrounding soil and water resources.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a seepage-proof barrier material comprising the following raw materials in parts by weight:

[0006] Calcium-based bentonite: 5g;

[0007] Mg(OH)₂: 0.25g-1.25g;

[0008] Al2O3: 0.01g-0.5g;

[0009] SDBS: 0.05g-0.35g.

[0010] Preferably, the calcium-based bentonite comprises the following raw materials in the indicated mass percentages: SiO2: 58.9%-60.9%, Al2O3: 16%-18%, Fe2O3: 4.4%-6.4%, CaO: 4.2%-6.2%, Na2O: 1.3%-3.3%, MgO: 0.3%-2.3%, K2O: 1.8%-3.8%, TiO2: 0.9%-2.9%, and other materials: 0.3%-2.3%. The other materials include one or more of the following: sodium hydroxide, sodium chloride, magnesium oxide, nitric acid, hydrofluoric acid, zinc nitrate, lead nitrate, potassium bromide, strontium chloride, ammonium acetate, hydroxylamine hydrochloride, acetic acid, perchloric acid, silver nitrate, and potassium chromate.

[0011] Preferably, the optimal mass ratio of the raw materials in the calcium-based bentonite is: SiO2: 60.9%, Al2O3: 18%, Fe2O3: 6.4%, CaO: 6.2%, Na2O: 3.3%, MgO: 2.3%, K2O: 1.8%, TiO2: 0.9%, and other materials: 0.3%.

[0012] A method for testing the physicochemical properties of a seepage-proof barrier material includes the following steps:

[0013] Step 1: Weigh a certain amount of Mg(OH)2 and nano-Al2O3 and place them in 90mL of aqueous solution. Stir for 5 minutes until homogeneous, then sonicate for 10 minutes to fully disperse them into a suspension. Add the surfactant SDBS and sonicate for 15 minutes to reduce the tension between Mg(OH)2 and nano-Al2O3 and the water interface, allowing Mg(OH)2 and nano-Al2O3 to fully emulsify. Add 5g of bentonite and stir for 24 hours to ensure full contact with Mg(OH)2 and nano-Al2O3, activating the properties between the minerals. Allow to stand for hydration for 24 hours, then dry at 80℃, and finally pulverize and grind for later use. Step 2: Prepare single heavy metal contamination solutions and a 1:1 composite metal contamination solution using Pb(NO3)2 and Zn(NO3)2·6H2O, respectively, as stock solutions. Step 3: Dilute the stock solutions by different factors to obtain the corresponding initial metal ions Pb. 2+ and Zn 2+Step 4: Weigh 0.1g of Mg-Al LHCB into a 100mL centrifuge tube, add 50mL of metal ion contamination solutions of various concentrations, and adjust the pH of the solution to the corresponding value using NaOH and HNO3 if necessary; Step 5: Place the centrifuge tube containing the soil sample and metal ion contamination solution horizontally in a shaker to ensure sufficient contact between the material and the metal ion solution during shaking; Step 6: After shaking the sample, remove the centrifuge tube and centrifuge it. Use a disposable syringe to draw the supernatant and filter it through a 45µm filter. Dilute the filtered liquid by a certain factor according to the accuracy requirements of the testing instrument; Step 7: Use an inductively coupled plasma atomic emission spectrometer to test the concentration of the remaining metal ions in the diluted supernatant.

[0014] Preferably, in step one, the amount of Mg(OH)2 and nano Al2O3 is based on the amount of bentonite, and the experiment is designed according to the corresponding percentages.

[0015] Preferably, in step two, the concentration of the single heavy metal polluted solution is 400 mg / L, and the concentration of the compound metal polluted solution is 400 mg / L, wherein Pb 2+ and Zn 2+ The concentrations were 200 mg / L.

[0016] Preferably, in step three, the concentration of the diluted single heavy metal pollutant solution is 200 mg / L-1000 mg / L, and the concentration of the 1:1 composite metal pollutant solution is 50+50 mg / L-350+350 mg / L.

[0017] Preferably, in step four, the pH of the metal ion solution is calculated by the water environment software (Visual MINTEQ) under the corresponding concentration conditions, and the simulated ambient temperature is 25°C.

[0018] Preferably, in step five, the oscillation time is 0-6 hours and the rotation speed is 200 r / min.

[0019] Preferably, in step six, the centrifuge speed is 4000 r / s and the centrifugation time is 5 min.

[0020] This invention provides a method for testing the physicochemical properties of seepage-proof barrier materials. It has the following beneficial effects:

[0021] 1. This invention synthesizes a modified bentonite seepage barrier material—Mg-Al LHCB (Mg-Al layered hydroxide gelled bentonite). Utilizing Mg(OH)₂ and nano-Al₂O₃ under the action of the surfactant SDBS, with bentonite as a carrier, the gelling properties of Mg(OH)₂ can be loaded onto the bentonite surface or pillared between bentonite layers, increasing the ion exchange capacity and spatial holding capacity of the bentonite, thereby improving the seepage barrier performance of the modified bentonite material against metal ions. Furthermore, nano-Al₂O₃ is porous with a large surface area, can activate mineral surface groups, and possesses excellent adsorption and water purification properties, good stability, and strong corrosion resistance. This results in a final modified bentonite with high adsorption capacity, low permeability, and excellent stability.

[0022] 2. In this invention, the heavy metal ion solutions seeping from tailings ponds are mostly acidic. Modifying bentonite with Mg(OH)₂ can improve the pH environment of the soil and adjust the pH of the aquatic environment, providing a suitable pH range for the formation of Pb and Zn ions and complexes, causing them to precipitate and preventing re-dissolution. This increases the adsorption capacity of bentonite for Pb and Zn. Simultaneously, other metal ions tend to precipitate under alkaline conditions, thus also acting as a barrier against other heavy metals. Furthermore, Mg(OH)₂-modified bentonite creates an alkaline environment to precipitate metal ions for barrier purposes. Compared to strong alkali NaOH, Mg(OH)₂ has a slow-release OH⁻ effect. - The ability to prevent the immediate release of large amounts of OH groups into the environment. - This has an impact on the environment.

[0023] 3. This invention uses Mg-Al LHCB as the seepage barrier material, and the amphoteric metal Pb 2+ and Zn 2+ Using the polluted solution as the research object, the adsorption effect of Mg-Al LHCB on heavy metal ions was studied through a static adsorption experimental system. The optimal adsorption conditions were determined, and the adsorption model and corresponding adsorption isotherm curves under the experimental conditions were established to explore the adsorption mechanism. Dynamic experiments were used to study the migration ability, permeation law, and breakdown age prediction of Pb2+ and Zn2+ in the Mg-Al LHCB geomembrane. These studies have certain academic and practical application reference value. Attached Figure Description

[0024] Figure 1 A diagram showing the chemical composition of the calcium-based bentonite of this invention;

[0025] Figure 2 This is a graph showing the pH changes of the metal ion-contaminated liquid at different concentrations according to the present invention.

[0026] Figure 3This is a distribution diagram of metal ion speciation under different pH conditions according to the present invention;

[0027] Figure 4 This is a diagram of the metal ion isothermal adsorption model of the present invention. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] This invention provides a seepage-proof barrier material, comprising the following raw materials in parts by weight:

[0031] Calcium-based bentonite: 5g;

[0032] Mg(OH)2: 1g;

[0033] Al2O3: 0.25g;

[0034] SDBS: 0.15g.

[0035] Calcium-based bentonite comprises the following raw materials in weight percentages: SiO2: 58.9%-60.9%, Al2O3: 16%-18%, Fe2O3: 4.4%-6.4%, CaO: 4.2%-6.2%, Na2O: 1.3%-3.3%, MgO: 0.3%-2.3%, K2O: 1.8%-3.8%, TiO2: 0.9%-2.9%, and other materials: 0.3%-2.3%. Other materials include one or more of the following: sodium hydroxide, sodium chloride, magnesium oxide, nitric acid, hydrofluoric acid, zinc nitrate, lead nitrate, potassium bromide, strontium chloride, ammonium acetate, hydroxylamine hydrochloride, acetic acid, perchloric acid, silver nitrate, and potassium chromate.

[0036] The optimal mass ratio of raw materials for calcium-based bentonite is: SiO2: 60.9%, Al2O3: 18%, Fe2O3: 6.4%, CaO: 6.2%, Na2O: 3.3%, MgO: 2.3%, K2O: 1.8%, TiO2: 0.9%, and other materials: 0.3%.

[0037] A method for testing the physicochemical properties of a seepage-proof barrier material includes the following steps:

[0038] Step 1: Weigh a certain amount of Mg(OH)2 and nano-Al2O3 and place them in 90mL of aqueous solution. Stir for 5 minutes until homogeneous, then sonicate for 10 minutes to fully disperse them into a suspension. Add the surfactant SDBS and sonicate for 15 minutes to reduce the interfacial tension between Mg(OH)2 and nano-Al2O3 and water, ensuring complete emulsification of Mg(OH)2 and nano-Al2O3. Add 5g of bentonite and stir for 24 hours to ensure sufficient contact between the bentonite and Mg(OH)2 and nano-Al2O3, thereby activating the inter-mineral properties. After static hydration for 24 hours, the mixture was dried at 80℃, then pulverized and ground for later use. The amounts of Mg(OH)2 and nano-Al2O3 were based on the amount of bentonite, and the experiment was designed according to the corresponding percentages. Step 2: Pb(NO3)2 and Zn(NO3)2·6H2O were used to prepare single heavy metal contamination solution and composite metal contamination solution with a concentration of 1:1, respectively, as stock solutions. The concentration of single heavy metal contamination solution was 400 mg / L, and the concentration of composite metal contamination solution was 400 mg / L, of which Pb 2+ and Zn 2+ The concentrations were 200 mg / L; Step 3: Dilute the stock solution by different factors to obtain the corresponding initial metal ions Pb. 2+ and Zn 2+ The concentration of the diluted single heavy metal contaminant solution is 200 mg / L-1000 mg / L, and the concentration of the 1:1 composite metal contaminant solution is 50+50 mg / L-350+350 mg / L. Step four: Weigh 0.1 g of Mg-Al LHCB into a 100 mL centrifuge tube, add 50 mL of each metal ion contaminant solution, and adjust the pH of the solution to the appropriate value using NaOH and HNO3 if necessary. The pH of the metal ion solution is determined by the water environment software (Visual MI). The NTEQ (Non-Total Energy Emission Spectrometry) was calculated under the corresponding concentration conditions, with a simulated ambient temperature of 25℃. Step 5: Place the centrifuge tube containing the soil sample and the metal ion contamination solution horizontally in a shaker to ensure sufficient contact between the material and the metal ion solution during shaking. The shaking time is 0-6 hours, and the rotation speed is 200 r / min. Step 6: After the sample has shaken, remove the centrifuge tube and centrifuge it. Use a disposable syringe to draw the supernatant and filter it through a filter with a pore size of 45 μm. Dilute the filtered liquid by a certain factor according to the accuracy requirements of the testing instrument. The centrifuge speed is 4000 r / s, and the centrifugation time is 5 min. Step 7: The concentration of the remaining metal ions in the diluted supernatant is tested using an inductively coupled plasma atomic emission spectrometer.

[0039] Example 2:

[0040] The features that are the same as those in Embodiment 1 will not be repeated here. The difference is that in this embodiment, the following raw materials are included in parts by weight:

[0041] Calcium-based bentonite: 5g;

[0042] Mg(OH)₂: 0.25g;

[0043] Al2O3: 0.1g;

[0044] SDBS: 0.05g.

[0045] Example 3:

[0046] The features that are the same as those in Embodiment 1 will not be repeated here. The difference is that in this embodiment, the following raw materials are included in parts by weight:

[0047] Calcium-based bentonite: 5g;

[0048] Mg(OH)2: 0.75g;

[0049] Al2O3: 0.25g;

[0050] SDBS: 0.15g.

[0051] Example 4:

[0052] The features that are the same as those in Embodiment 1 will not be repeated here. The difference is that in this embodiment, the following raw materials are included in parts by weight:

[0053] Calcium-based bentonite: 5g;

[0054] Mg(OH)2: 1g;

[0055] Al2O3: 0.4g;

[0056] SDBS: 0.25g

[0057] Example 5:

[0058] The features that are the same as those in Example 1 will not be repeated here. The difference is that in step four of this example, 0.1g of Mg-Al LHCB is weighed into a 100mL centrifuge tube, and the concentrations of metal ion contaminants in the solution are as follows:

[0059]

[0060] Example 6:

[0061] The features that are the same as those in Example 1 will not be repeated here. The difference is that in step four of this example, 0.1g of Mg-Al LHCB is weighed into a 100mL centrifuge tube, the simulated ambient temperature is 25±3℃, and the shaking times are 0min, 5min, 10min, 30min, 60min, 90min, 120min, 180min, 240min, 300min, and 360min respectively.

[0062] Example 7:

[0063] The features that are the same as those in Example 1 will not be repeated here. The difference is that in step four of this example, 0.1g of Mg-Al LHCB is weighed into a 100mL centrifuge tube, the simulated ambient temperature is 25±3℃, and the pH values ​​of the solution are adjusted to 3, 4, 5, 6, 7, 8, 9, and 10 using NaOH and HNO3, respectively.

[0064] Comparative example:

[0065] This invention provides a comparative example of a method for testing the physicochemical properties of a seepage-proof barrier material, comprising the following steps:

[0066] Step 1: Pour 80 mL of metal ion contamination solution into a 100 mL graduated cylinder. Gradually and slowly sprinkle the air-dried bentonite into the solution in small amounts several times. After the previous sample has completely sunk to the bottom, slowly add more. After all the sample has been added, slowly add the solution along the wall of the graduated cylinder to the 100 mL mark. Each time, take 2 g of calcium-based bentonite and Mg-Al LHCB.

[0067] Step 2: After standing for 24 hours, read the expansion volume of the bentonite.

[0068] The concentrations of metal ion contamination in the solution for each instance were as follows:

[0069]

[0070] Physicochemical properties of seepage-proof barrier materials:

[0071] The reaction phenomena, water absorption and swelling properties, and Pb adsorption were observed during the preparation of modified bentonite according to Examples 1 to 7 and the comparative examples described above. 2+ Zn 2+ The ability of the modified bentonite to expand was tested and evaluated to determine the optimal synthesis conditions of Mg(OH)2 and nano-Al2O3 modified bentonite under the action of SDBS. Secondly, in the single-factor influence experiment, two parameters were used as evaluation indicators: the expansion volume of the modified bentonite and the total adsorption capacity for metal ions. The observed phenomena are shown in the table below.

[0072] Table 1:

[0073]

[0074]

[0075] In summary, the synthesis of Mg-Al LHCB mainly employs an emulsification / dispersion-supported synthesis method. Under the action of SDBS, Mg(OH)₂ is fully dispersed, emulsified, and suspended, forming a magnesium-aluminum layered hydroxide gel. The main conclusions are as follows: (See attached table) Figure 2-4 In Example 1, the optimal synthesis conditions for Mg-Al LHCB were as follows: the addition amount of Mg(OH)2 was 20% of the bentonite, and the addition amounts of γ-Al2O3 and SDBS were 5% and 3% of the Mg(OH)2 addition amount, respectively. Its adsorption capacity was 3-4 times that before modification. Throughout the adsorption process, whether it was single-metal adsorption or composite metal adsorption, Mg-Al LHCB showed good adsorption capacity for Pb. 2+ Its adsorption capacity is consistently stronger than that of Zn. 2+ In single-metal ion solutions, the adsorption of Pb ions is less active than that of Zn ions, which are 3.5 times heavier. Therefore, Pb ions have weaker migration ability, are less prone to desorption after adsorption, and are relatively stable. In mixed solutions, the two metal ions compete for adsorption sites, exhibiting antagonistic effects. This results in Mg-Al LHCB having a stronger adsorption capacity for single metals than for mixed metals in adsorption experiments at the same concentration. During the process of reaching equilibrium, the pH value of the leachate from different concentration samples is consistently lower than that of the samples with higher concentrations. This is mainly due to the different adsorption sites of Pb(NO3)2 and Zn(NO3)2. 3) Both heavy metal solutions are acidic, and the higher the concentration, the lower the pH value. Therefore, more hydroxide ions are consumed during the reaction. When the amount is insufficient, the pH value is higher, which is consistent with the theoretical results. As shown in the figure, after different concentrations of metal ion solutions pass through the packed column, the leachate concentration stabilizes and the pH value approaches neutral. At this point, the impact on environmental pollution is minimal. In practical applications, calcium-based bentonite accounts for more than 70%, which solves the problem of underground environment erosion by acidic mine wastewater, prevents further dissolution of heavy metals in the soil under the action of acidic mine wastewater, and effectively inhibits the harm of acidic mine wastewater to the environment.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A seepage-proof barrier material, characterized in that, The raw materials include the following parts by weight: Calcium-based bentonite: 5g; Mg(OH)₂: 0.25g-1.25g; Al2O3: 0.01g-0.5g; SDBS: 0.05g-0.35g; The raw material mass ratio of the calcium-based bentonite is as follows: SiO2: 60.9%, Al2O3: 18%, Fe2O3: 6.4%, CaO: 6.2%, Na2O: 3.3%, MgO: 2.3%, K2O: 1.8%, TiO2: 0.9%, and other materials: 0.3%.

2. The seepage-proof barrier material according to claim 1, characterized in that, The other materials include one or more of the following: sodium hydroxide, sodium chloride, magnesium oxide, nitric acid, hydrofluoric acid, zinc nitrate, lead nitrate, potassium bromide, strontium chloride, ammonium acetate, hydroxylamine hydrochloride, acetic acid, perchloric acid, silver nitrate, and potassium chromate.

3. A method for testing the physicochemical properties of a seepage-proof barrier material, characterized in that, The application of a seepage-proof barrier material according to any one of claims 1-2 includes the following steps: Step 1: Weigh a certain amount of Mg(OH)2 and nano Al2O3 and place them in 90mL of aqueous solution. Stir for 5 minutes until uniform, then sonicate for 10 minutes to fully disperse them into a suspension. Add the surfactant SDBS and sonicate for 15 minutes to reduce the tension between Mg(OH)2 and nano Al2O3 and the water interface, so that Mg(OH)2 and nano Al2O3 are fully emulsified. Add 5g of bentonite and stir for 24 hours to ensure full contact with Mg(OH)2 and nano Al2O3, thereby activating the properties between the minerals. Allow to stand for hydration for 24 hours, then dry at 80℃, and finally crush and grind for later use. Step 2: Prepare single heavy metal contaminated solution and composite metal contaminated solution with a concentration of 1:1 using Pb(NO3)2 and Zn(NO3)2·6H2O respectively, as stock solutions; Step 3: Dilute the stock solution by different factors to obtain the corresponding initial metal ions Pb. 2+ and Zn 2+ Contaminated solution; Step 4: Weigh 0.1g of Mg-AlLHCB into a 100mL centrifuge tube, add 50mL of metal ion contamination solution of various concentrations, and adjust the pH of the solution to the corresponding value using NaOH and HNO3. Step 5: Place the centrifuge tube containing the soil sample and the metal ion contamination solution horizontally in the shaker to ensure that the material and the metal ion solution can fully contact and vibrate during the shaking process. Step 6: After the sample has been shaken, remove the centrifuge tube and centrifuge it in the centrifuge. Use a disposable syringe to draw the supernatant and filter it through a filter with a pore size of 45um. Dilute the filtered liquid by a certain factor according to the accuracy requirements of the testing instrument. Step 7: The concentration of remaining metal ions in the diluted supernatant was measured using an inductively coupled plasma atomic emission spectrometer.

4. The method for testing the physicochemical properties of a seepage-proof barrier material according to claim 3, characterized in that, In step one, the amounts of Mg(OH)2 and nano Al2O3 are based on the amount of bentonite used, and the experiment is designed according to the corresponding percentages.

5. The method for testing the physicochemical properties of a seepage-proof barrier material according to claim 3, characterized in that, In step two, the concentration of the single heavy metal polluted solution is 400 mg / L, and the concentration of the compound metal polluted solution is 400 mg / L, of which Pb 2+ and Zn 2 + The concentrations were 200 mg / L.

6. The method for testing the physicochemical properties of a seepage-proof barrier material according to claim 3, characterized in that, In step three, the concentration of the diluted single heavy metal pollutant solution is 200 mg / L-1000 mg / L, and the concentration of the 1:1 composite metal pollutant solution is 50+50 mg / L-350+350 mg / L.

7. The method for testing the physicochemical properties of a seepage-proof barrier material according to claim 3, characterized in that, In step four, the pH of the metal ion solution is calculated by water environment software under the corresponding concentration conditions, and the simulated ambient temperature is 25℃.

8. The method for testing the physicochemical properties of a seepage-proof barrier material according to claim 3, characterized in that, In step five, the oscillation time is 0-6 hours and the rotation speed is 200 r / min.

9. The method for testing the physicochemical properties of a seepage-proof barrier material according to claim 3, characterized in that, In step six, the centrifuge speed is 4000 r / s and the centrifugation time is 5 min.

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