Magnesium-aluminum hydrotalcite / carbon nanotube composite material as well as preparation method and application thereof

Abstract

The invention discloses a magnesium-aluminum hydrotalcite / carbon nanotube composite material and a preparation method and application thereof, and the preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material comprises the following steps: S1, carrying out acid pretreatment on a carbon nanotube; and S2, preparing the magnesium-aluminum hydrotalcite / carbon nanotube composite material. Compared with the prior art, the preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material has the advantages that Mg (NO3) 2.6 H2O, Al (NO3) 3.9 H2O, CO (NH2) 2 and pretreated carbon nanotubes are adopted, and magnesium-aluminum hydrotalcite grows on the carbon nanotubes through a hydrothermal homogeneous precipitation method; through the synergistic effect of the carbon nanotubes and the magnesium-aluminum hydrotalcite, aggregation among nanoparticles is effectively prevented, the growth size of the particles is limited, and the magnesium-aluminum hydrotalcite / carbon nanotube composite material is good in crystallinity, small in particle size, high in specific surface area and high in adsorption performance. In a radioactive uranium element adsorption experiment, the adsorption efficiency is as high as 95.6%, and the adsorption capacity is as high as 17.32 mg / g.

Description

Technical Field

[0001] This invention belongs to the field of magnesium aluminum hydrotalcite preparation, and more specifically, this invention relates to a magnesium aluminum hydrotalcite / carbon nanotube composite material, its preparation method and application. Background Technology

[0002] Magnesium aluminum layered double hydroxides (Mg-Al-LDHs) are layered bimetallic hydroxide materials widely used as adsorbents, ion exchangers, alkaline catalysts, and catalyst supports. Due to their superior adsorption properties, Mg-Al-LDHs have broad research value and application prospects in dyeing, papermaking, electroplating, and nuclear wastewater treatment. In recent years, with the increasing demands in the field of environmental pollution control, Mg-Al-LDHs have become of great practical significance for removing pollutants from water bodies.

[0003] Traditionally synthesized Mg-Al-LDHs are characterized by high surface charge, strong hydrogen bonding, and hydrophilicity. They often aggregate in large quantities between particles, forming large crystal sizes. The adsorption efficiency is largely limited by the structure, morphology, crystallinity, and particle size of the hydrotalcite material. In practical applications, they suffer from poor selectivity and slow adsorption rate, resulting in low purification efficiency for complex wastewater.

[0004] In view of this, it is indeed necessary to provide a novel magnesium-aluminum hydrotalcite / carbon nanotube composite material, its preparation method, and its application. Summary of the Invention

[0005] The purpose of this invention is to overcome at least one defect of the prior art and provide a novel magnesium-aluminum hydrotalcite / carbon nanotube composite material, its preparation method, and its application.

[0006] To achieve the above-mentioned objective, this invention provides a method for preparing a magnesium-aluminum hydrotalcite / carbon nanotube composite material, comprising:

[0007] S1. Acid pretreatment of carbon nanotubes, including:

[0008] S11. Prepare a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid;

[0009] S12. Add carbon nanotube powder to the mixed acid solution prepared in S11, stir at room temperature, and then transfer it to an ultrasonic cleaner for ultrasonic dispersion to obtain a mixed solution.

[0010] S13. Pour the mixture containing carbon nanotubes in S12 into deionized water to dilute and stir to dissipate heat; filter the diluted mixture and discard the filtrate; wash the obtained product with deionized water and filter repeatedly to separate and collect the carbon nanotube precipitate; dry the collected carbon nanotubes to obtain the carbon nanotube pretreated product.

[0011] The preparation of S2, magnesium aluminum hydrotalcite / carbon nanotube composite materials includes:

[0012] S21. Pour CO(NH2)2, Mg(NO3)2·6H2O and Al(NO3)3·9H2O into a beaker in proportion, add deionized water, and stir to dissolve to obtain a mixed solution;

[0013] S22. Add the carbon nanotube pretreated product obtained in step S13 to the mixed solution in step S21, stir and apply ultrasound to completely disperse the carbon nanotubes to obtain a dispersion.

[0014] S23. Transfer the dispersion obtained in step S22 into a hydrothermal reactor, place it in a constant temperature drying oven, and carry out a hydrothermal reaction at a constant temperature to obtain a precipitate.

[0015] S24. After the hydrothermal reaction is complete, the hydrothermal reactor is removed and cooled to room temperature. The generated precipitate is centrifuged and filtered, and repeatedly washed with deionized water. Finally, ethanol is used instead of deionized water for centrifugation and filtration. After drying, magnesium-aluminum hydrotalcite / carbon nanotube composite material is obtained.

[0016] In one embodiment of the preparation method of magnesium-aluminum hydrotalcite / carbon nanotube composite material according to the present invention, in step S11, the product ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1.

[0017] In one embodiment of the preparation method of magnesium-aluminum hydrotalcite / carbon nanotube composite material according to the present invention, in step S12, the mixture is stirred at room temperature using a magnetic stirrer for 1-10 hours.

[0018] According to an embodiment of the preparation method of magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention, in step S12, the water temperature in the ultrasonic cleaner is 50℃-80℃, and the ultrasonic dispersion time is 1-5h.

[0019] According to an embodiment of the preparation method of magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention, in step S13, the drying temperature of carbon nanotubes is 60℃-100℃ and the drying time is 6-24h.

[0020] In one embodiment of the preparation method of magnesium aluminum hydrotalcite / carbon nanotube composite material according to the present invention, in step S13, during filtration, pH test paper is used to detect the pH value of the filtrate until pH = 7.

[0021] In one embodiment of the preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to the present invention, in step S21, the molar ratio of CO(NH2)2, Mg(NO3)2·6H2O, and Al(NO3)3·9H2O is n[CO(NH2)2]:n(Mg 2+ +Al3+ )]=10:1,n(Mg 2+ ): n(Al 3+ The ratio of 2.5:1 was used for mixing.

[0022] According to an embodiment of the preparation method of magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention, in step S23, the hydrothermal constant temperature of the hydrothermal reactor is 80℃-140℃, and the hydrothermal constant temperature time of the hydrothermal reactor is 10h-24h.

[0023] In one embodiment of the preparation method of magnesium aluminum hydrotalcite / carbon nanotube composite material according to the present invention, in step S24, the purity of the deionized water is EC < 1 μS / cm.

[0024] In one embodiment of the preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to the present invention, the mass ratio of carbon nanotubes to magnesium-aluminum hydrotalcite is 1:1 to 1:100.

[0025] To achieve the above-mentioned objectives, the present invention also provides a magnesium-aluminum hydrotalcite / carbon nanotube composite material, which is prepared by the method for preparing magnesium-aluminum hydrotalcite / carbon nanotube composite materials according to the present invention.

[0026] To achieve the above-mentioned objectives, the present invention also provides the application of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention as an adsorbent, ion exchanger, catalyst or flame retardant material.

[0027] Compared with existing technologies, the magnesium-aluminum hydrotalcite / carbon nanotube composite material and its preparation method of the present invention have at least the following advantages:

[0028] The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of this invention uses magnesium nitrate hexahydrate Mg(NO3)2·6H2O, aluminum nitrate nonahydrate Al(NO3)3·9H2O, urea CO(NH2)2, and pretreated carbon nanotubes. The method employs a hydrothermal homogeneous precipitation process, utilizing the spatial confinement effect of carbon nanotubes to allow magnesium-aluminum hydrotalcite to grow on the carbon nanotubes. The synergistic effect of carbon nanotubes and magnesium-aluminum hydrotalcite effectively prevents the aggregation of nanoparticles and limits their growth size, resulting in a magnesium-aluminum hydrotalcite / carbon nanotube composite material with good crystallinity, small particle size, high specific surface area, and high adsorption performance. This material effectively improves adsorption capacity, adsorption rate, and anti-interference ability; it is beneficial to environmental protection, improves pollution treatment efficiency, and performs excellently in the adsorption experiment of radioactive uranium, with an adsorption efficiency as high as 95.6% and an adsorption capacity as high as 17.32 mg / g.

[0029] The magnesium-aluminum hydrotalcite / carbon nanotube composite material prepared by the present invention is a novel functional modified material, comprising magnesium-aluminum hydrotalcite and carbon nanotubes distributed on the surface and with surface modification and functionalization in the interlayer. It combines the excellent properties of magnesium-aluminum hydrotalcite and carbon nanotubes. By optimizing and adjusting the composite carbon nanotubes, the shortcomings of magnesium-aluminum hydrotalcite and carbon nanotubes can be compensated, resulting in many advantages such as good catalytic performance, strong adsorption performance, and high mechanical strength.

[0030] The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention can be continuously operated in an industrial reactor under normal pressure, which can reduce equipment investment, reduce production costs and energy consumption, and significantly improve the utilization rate and recovery rate of raw materials. Attached Figure Description

[0031] The magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention, its preparation method, and its application are described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

[0032] Figure 1 This is a schematic flowchart of the preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention.

[0033] Figure 2A and Figure 2B These are two surface morphology images of the magnesium-aluminum hydrotalcite / carbon nanotube composite material prepared in Example 1 of this invention, taken from different shooting positions. Figure 2A The magnification is 1500 (scale bar: 10μm). Figure 2B The magnification is 1600 (scale bar: 10μm).

[0034] Figure 3 This experiment illustrates the selective adsorption of radioactive uranium onto the magnesium-aluminum hydrotalcite / carbon nanotube composite material prepared in Example 1 of this invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described in this specification are merely for explaining the invention and are not intended to limit the invention.

[0036] Example 1: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0037] Please refer to Figure 1 As shown, the preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention includes the following steps:

[0038] S1. Pretreatment of carbon nanotubes, including:

[0039] S11. Prepare a mixed acid solution with a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1: This is done in a fume hood. Take 30 ml of concentrated sulfuric acid and 10 ml of concentrated nitric acid in two 50 ml beakers respectively. Then slowly pour the concentrated sulfuric acid into the concentrated nitric acid along the beaker wall and stir continuously with a glass rod to dissipate heat.

[0040] S12. Ultrasonic dispersion and heat treatment of carbon nanotubes: Take 1.5g of carbon nanotube powder and put it into a 100ml beaker, then add the prepared mixed acid solution and stir evenly with a glass rod; seal the mouth of the beaker with plastic wrap and stir with a magnetic stirrer for 1 hour at room temperature. After stirring, transfer it to an ultrasonic cleaner, adjust the water temperature in the ultrasonic cleaner to 50℃, and ultrasonically disperse for 5 hours.

[0041] S13. Separation of carbon nanotubes: After dispersion, remove the small beaker; slowly pour the mixed solution containing carbon nanotubes into water along a glass rod to dilute it, while continuously stirring with the glass rod to dissipate heat; filter the diluted solution, discard the filtrate, add deionized water to the obtained product, and repeat the filtration process several times, using a pH meter to check the pH value of the filtrate until pH = 7. Finally, use ethanol instead of deionized water for filtration to separate the carbon nanotubes and collect the carbon nanotube precipitate.

[0042] S14. Drying carbon nanotubes: Place the collected carbon nanotubes in a drying oven and dry them at 80°C for 12 hours to obtain pretreated carbon nanotubes.

[0043] Preparation of S2, magnesium aluminum hydrotalcite and carbon nanotube composite materials

[0044] S21. Weigh out 42g CO(NH2)2, 12.8g Mg(NO3)2·6H2O and 7.5g Al(NO3)3·9H2O respectively, and dissolve them in 200mL of deionized water. Stir with a magnetic stirrer until dissolved.

[0045] S22. Add 0.6g of pretreated carbon nanotubes to the S21 solution, stir, and then sonicate for 30min to disperse them completely.

[0046] S23. Transfer the solution obtained in S22 to a 300ml hydrothermal reactor lined with polytetrafluoroethylene, place it in an oven, and crystallize at 120℃ for 12 hours.

[0047] S24. After the hydrothermal process is complete, remove the hydrothermal reactor and cool it to room temperature. Centrifuge and filter the generated precipitate, then wash it repeatedly with deionized water. Finally, centrifuge it with ethanol instead of deionized water and dry it at 60°C for 10 hours to obtain magnesium aluminum hydrotalcite / carbon nanotube composite material 1.

[0048] Figure 2A and2B Two surface morphology images of the magnesium-aluminum hydrotalcite / carbon nanotube composite material prepared by the preparation method of the present invention, taken at different locations, were obtained using a scanning electron microscope (JSM-IT500LV) manufactured by JEOL Ltd., Japan. Figure 2A and 2B As can be seen, the layered structure formed by the stacking of thin sheets is clearly visible, indicating that hydrotalcite was successfully synthesized during the composite process. In addition, a large number of rod-shaped carbon nanotubes can be seen attached to the surface and interior of the hydrotalcite, indicating that MWCNTs were successfully loaded onto the surface and interior of Mg-Al-LDHs.

[0049] Example 2: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0050] Except for stirring time of 4, 8, and 10 hours with a magnetic stirrer, the other steps were the same as in Example 1, and were referred to as magnesium-aluminum hydrotalcite / carbon nanotube composite materials 2, 3, and 4.

[0051] Example 3: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0052] Except for the ultrasonic water temperature being 60℃, 65℃, and 70℃, everything else is the same as in Example 1, and they are referred to as magnesium-aluminum hydrotalcite / carbon nanotube composite materials 5, 6, and 7.

[0053] Example 4: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0054] Except for the ultrasonic dispersion time being 1h, 2h, and 4h, everything else is the same as in Example 1, and they are referred to as magnesium-aluminum hydrotalcite / carbon nanotube composite materials 8, 9, and 10.

[0055] Example 5: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0056] Except for the drying temperatures of 70°C, 80°C, and 100°C, the other conditions are the same as in Example 1, and are referred to as magnesium-aluminum hydrotalcite / carbon nanotube composite materials 11, 12, and 13.

[0057] Example 6: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0058] Except for the drying time being 10h, 18h, and 24h, the other conditions were the same as in Example 1, and were referred to as magnesium-aluminum hydrotalcite / carbon nanotube composite materials 14, 15, and 16.

[0059] Example 7: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0060] Except for replacing the amount of multi-walled carbon nanotubes with 0.3g, 0.2g, and 0.1g, the rest is the same as in Example 1, and are referred to as magnesium aluminum hydrotalcite / carbon nanotube composite materials 17, 18, and 19.

[0061] Example 8: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0062] Except for changing the hydrothermal temperature to 80℃, 100℃, and 140℃, the other conditions are the same as in Example 1, and are referred to as magnesium-aluminum hydrotalcite / carbon nanotube composite materials 20, 21, and 22.

[0063] Example 9: Preparation of magnesium aluminum hydrotalcite / carbon nanotube composite material

[0064] Except for changing the hydrothermal time to 12h, 20h, and 24h, the other methods are the same as in Example 1, and are referred to as magnesium-aluminum hydrotalcite / carbon nanotube composite materials 23, 24, and 25.

[0065] In the above embodiments, all pharmaceutical products were purchased from Aladdin. The multi-walled carbon nanotubes had an outer diameter of 8-50 nm, a length of <50 μm, and a specific surface area >140 m². 2 / g, and all percentages in the examples are mass percentages.

[0066] Specific steps for conducting the uranium adsorption selectivity experiment:

[0067] Experimental instrument: ICP-AES (Inductively Coupled Plasma Optical Emission Spectrometer, HORIBA Corporation, Japan, model Ultima Expert).

[0068] Experimental steps:

[0069] S1. Weigh 16 mg UO2(NO3)2·6H2O, 16 mg potassium chloride (KCl), 16 mg sodium chloride (NaCl), 16 mg calcium chloride (CaCl2), and 16 mg magnesium chloride (MgCl2), dissolve them in 1 L of deionized water, and prepare U... 4+ :K + Na + Ca 2+ Mg 2+ A mixed ionic solution with a mass concentration ratio of 1:1:1:1:1 (1 ppm = 1 mg / L) was prepared. The above mixed solution was divided into three equal portions, and a small amount of dilute hydrochloric acid was added to adjust the pH value of the solution to obtain solutions with pH=4, pH=5, and pH=6, respectively.

[0070] S2. Take a small amount of the initial mixed solution with different pH values ​​and use an ICP-AES instrument to determine the initial concentration of U(IV) in the stock solution. Since adjusting the pH of the solution may cause changes in concentration, the actual initial concentration of U(IV) should be based on the result measured by the ICP-AES instrument.

[0071] S3. Take 5 mL of mixed ionic solutions under different pH conditions and place them in sealable transparent glass bottles. Then add 0.02 g of the magnesium-aluminum hydrotalcite / carbon nanotube composite material prepared in Example 1 to each bottle. Place the bottles in a 25°C constant temperature water bath shaker and shake at 160 rpm for 10 minutes to allow the material to react with various coexisting ions (K+, K+, K+, K+). + Na + Ca 2+ Mg 2+ Under the interference of ), it selectively adsorbs U(IV).

[0072] S4. After shaking, the remaining concentration of U(IV) in the supernatant was determined using an ICP-AES instrument, and the uranium adsorption rate was calculated using the formula: U adsorption rate = (initial U concentration - remaining U concentration) / initial U concentration. The experimental results are as follows: Figure 3 As shown, the adsorption efficiency is as high as 95.6%, and the adsorption capacity is as high as 17.32 mg / g.

[0073] The high-quality magnesium-aluminum hydrotalcite / carbon nanotube composite material prepared by the method of the present invention can be applied to various fields such as adsorbents in the water pollution control industry, catalysts and ion exchangers in the petrochemical industry, and flame retardant materials in the construction industry.

[0074] As can be seen from the above embodiments, compared with the prior art, the preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention has at least the following advantages:

[0075] The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of this invention uses magnesium nitrate hexahydrate Mg(NO3)2·6H2O, aluminum nitrate nonahydrate Al(NO3)3·9H2O, urea CO(NH2)2, and pretreated carbon nanotubes. The method employs a hydrothermal homogeneous precipitation process, utilizing the spatial confinement effect of carbon nanotubes to allow magnesium-aluminum hydrotalcite to grow on the carbon nanotubes. The synergistic effect of carbon nanotubes and magnesium-aluminum hydrotalcite effectively prevents the aggregation of nanoparticles and limits their growth size, resulting in a magnesium-aluminum hydrotalcite / carbon nanotube composite material with good crystallinity, small particle size, high specific surface area, and high adsorption performance. This material effectively improves adsorption capacity, adsorption rate, and anti-interference ability; it is beneficial to environmental protection, improves pollution treatment efficiency, and performs excellently in the adsorption experiment of radioactive uranium, with an adsorption efficiency as high as 95.6% and an adsorption capacity as high as 17.32 mg / g.

[0076] The magnesium-aluminum hydrotalcite / carbon nanotube composite material prepared by the present invention is a novel functional modified material, comprising magnesium-aluminum hydrotalcite and carbon nanotubes distributed on the surface and with surface modification and functionalization in the interlayer. It combines the excellent properties of magnesium-aluminum hydrotalcite and carbon nanotubes. By optimizing and adjusting the composite carbon nanotubes, the shortcomings of magnesium-aluminum hydrotalcite and carbon nanotubes can be compensated, resulting in many advantages such as good catalytic performance, strong adsorption performance, and high mechanical strength.

[0077] The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material of the present invention can be continuously operated in an industrial reactor under normal pressure, which can reduce equipment investment, reduce production costs and energy consumption, and significantly improve the utilization rate and recovery rate of raw materials.

[0078] Based on the above principles, the present invention can also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for preparing a magnesium-aluminum hydrotalcite / carbon nanotube composite material, characterized in that, The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material includes: S1. Acid pretreatment of carbon nanotubes, including: S11. Prepare a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid; S12. Add carbon nanotube powder to the mixed acid solution prepared in S11, stir at room temperature, and then transfer it to an ultrasonic cleaner for ultrasonic dispersion to obtain a mixed solution. S13. Pour the mixture containing carbon nanotubes in S12 into deionized water to dilute and stir to dissipate heat; filter the diluted mixture and discard the filtrate; wash the obtained product with deionized water and filter repeatedly to separate and collect the carbon nanotube precipitate; dry the collected carbon nanotubes to obtain the carbon nanotube pretreated product. The preparation of S2, magnesium aluminum hydrotalcite / carbon nanotube composite materials includes: S21. Pour CO(NH2)2, Mg(NO3)2·6H2O and Al(NO3)3·9H2O into a beaker in proportion, add deionized water, and stir to dissolve to obtain a mixed solution; S22. Add the carbon nanotube pretreated product obtained in step S13 to the mixed solution in step S21, stir and apply ultrasound to completely disperse the carbon nanotubes to obtain a dispersion. S23. Transfer the dispersion obtained in step S22 into a hydrothermal reactor, place it in a constant temperature drying oven, and carry out a hydrothermal reaction at a constant temperature to obtain a precipitate. S24. After the hydrothermal reaction is complete, the hydrothermal reactor is removed and cooled to room temperature. The generated precipitate is centrifuged and filtered, and repeatedly washed with deionized water. Finally, ethanol is used instead of deionized water for centrifugation and filtration. After drying, magnesium-aluminum hydrotalcite / carbon nanotube composite material is obtained.

2. The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S11, the product ratio of concentrated sulfuric acid to concentrated nitric acid is 3:

1.

3. The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S12, a magnetic stirrer is used to stir the mixture at room temperature for 1-10 hours.

4. The preparation method of the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S12, the water temperature in the ultrasonic cleaner is 50℃-80℃, and the ultrasonic dispersion time is 1-5h.

5. The method for preparing the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S13, the drying temperature of the carbon nanotubes is 60℃-100℃, and the drying time is 6-24h.

6. The method for preparing the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S13, during filtration, pH test paper is used to detect the pH value of the filtrate until pH = 7.

7. The method for preparing the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S21, the molar ratio of CO(NH2)2, Mg(NO3)2·6H2O, and Al(NO3)3·9H2O is n[CO(NH2)2]:n(Mg)2·6H2O. 2+ +Al 3+ )]=10:1,n(Mg 2+ ): n(Al 3+ The ratio of 2.5:1 was used for mixing.

8. The method for preparing the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S23, the hydrothermal constant temperature of the hydrothermal reactor is 80℃-140℃, and the hydrothermal constant temperature time of the hydrothermal reactor is 10h-24h.

9. The method for preparing the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 1, characterized in that, In step S24, the purity of the deionized water is EC < 1 μS / cm.

10. The method for preparing the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to any one of claims 1 to 9, characterized in that, The mass ratio of carbon nanotubes to magnesium aluminum hydrotalcite is 1:1 to 1:

100.

11. A magnesium-aluminum hydrotalcite / carbon nanotube composite material, characterized in that, The magnesium-aluminum hydrotalcite / carbon nanotube composite material is prepared by the method of any one of claims 1 to 10.

12. The application of the magnesium-aluminum hydrotalcite / carbon nanotube composite material according to claim 11 in adsorbents, ion exchangers, catalysts, and flame retardant materials.

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