Bimetal hydroxide material and preparation method thereof

Abstract

The invention belongs to the technical field of preparation of layered double hydroxides, and particularly relates to a double-metal hydroxide material and a preparation method thereof. In order to solve the key technical problem that large-size organic anions are difficult to insert between LDHs (Layered Double Hydroxides), the invention provides a step-by-step intercalation reconstruction method based on an electrostatic assembly mechanism, and finally, a double-metal hydroxide material with high-layer spacing can be obtained. The preparation method comprises the following steps: performing ultrasonic stripping to obtain LDHs nanosheets with high dispersity, introducing macromolecular organic anions subjected to deprotonation treatment, realizing organic molecule intercalation under the driving of electrostatic interaction, and meanwhile, assisting with a mild structure reconstruction process, so as to construct the LDHs material with obviously increased interlayer spacing. Compared with a traditional coprecipitation method or a calcination reconstruction method, the method has the advantages that the interlayer size of LDHs is remarkably increased, the interlayer spacing is larger than 12 angstroms and even 17.4 angstroms, and the bottleneck of regulation and control of the interlayer structure by organic molecule size limitation is broken through.

Description

Technical Field

[0001] This invention belongs to the field of layered bimetallic hydroxide preparation technology, specifically relating to a bimetallic hydroxide material and its preparation method. Background Technology

[0002] For concrete infrastructure operating in the harsh marine environment for extended periods, effectively improving its durability and delaying or even inhibiting steel corrosion has become a critical issue urgently needing to be addressed by the engineering community. Especially as infrastructure size increases and operational lifespan extends, early corrosion problems not only affect structural safety but can also lead to enormous maintenance costs and incalculable economic losses. Therefore, enhancing the erosion resistance and service life of concrete structures in marine environments is a key guarantee for achieving long-term, safe operation of infrastructure and is also one of the core tasks of sustainable development in modern civil engineering.

[0003] To address this practical need, researchers and engineers both domestically and internationally have proposed various anti-corrosion technologies for reinforced concrete, such as adding steel corrosion inhibitors to concrete, applying protective coatings to the surface, implementing cathodic protection measures, using rust-resistant coated steel bars, and developing new cement-based materials. Among these, layered double hydroxides (LDHs) corrosion inhibitors, a new type of functional material that has attracted much attention in recent years, have become an important research direction for next-generation concrete corrosion inhibitors due to their excellent ion exchange performance and tunable layered structure. LDHs not only have the ability to exchange with corrosive ions, but also release pre-embedded corrosion inhibitor molecules when stimulated by corrosion, thus achieving "responsive" protection and showing promising application prospects. Currently, researchers have successfully synthesized LDHs materials intercalated with various inorganic anions such as nitrite, vanadate, and chromate, and have achieved certain corrosion inhibition effects when applied to concrete. However, due to the small molecular size of traditional inorganic anions, the resulting interlayer spacing expansion is limited, leading to bottlenecks in the ion exchange rate and capacity of LDHs, especially when facing the attack of high concentrations of chloride ions, where their adsorption capacity and slow-release performance remain insufficient. Therefore, developing novel LDH structures with larger interlayer spacing and stronger exchange capacity has become an important research direction.

[0004] Studies have shown that the interlayer spacing in LDHs materials is one of the key structural parameters determining their ion exchange performance and corrosion inhibition effect. LDHs consist of positively charged metal hydroxide layers, which maintain charge balance and form a stable structure through intercalated anions and water molecules. The size of the interlayer spacing not only affects the type and stability of intercalated ions, but also directly determines the material's ability to adsorb, migrate, and release corrosive ions in actual engineering environments. When the interlayer spacing increases, the interlayer channels become wider, providing greater diffusion space and lower migration resistance, thus facilitating the efficient diffusion, penetration, and exchange of anions between layers. This structural advantage is particularly evident when dealing with small-sized, highly diffusive chloride ions, sulfate ions, and other typical marine corrosive ions, significantly improving the ion exchange rate, ion adsorption capacity, and corrosion inhibition efficiency of LDHs.

[0005] However, LDHs synthesized using traditional methods typically use inorganic anions (such as carbonate, nitrite, nitrate, and vanadate) as intercalators. These anions are small in size, resulting in low interlayer spacing (usually in the range of 7 to 9 angstroms), making it difficult to significantly improve the utilization of interlayer space. Limited by their compact structure, these LDHs have limited ability to capture and release corrosive ions, failing to meet the demands for high-efficiency corrosion inhibition under complex service environments. Especially under high-salt, high-humidity marine exposure conditions, traditional LDHs have significant shortcomings in preventing chloride ion penetration and releasing corrosion inhibitors. Therefore, increasing the interlayer spacing of LDHs and enhancing the openness and reactivity of their interlayer environment has become one of the core pathways to optimize their corrosion inhibition performance.

[0006] Studies have shown that rationally controlling the interlayer spacing of LDHs, especially by introducing structurally complex and functionally rich organic corrosion inhibitors to form large-interlayer intercalation structures, is a key technical approach to improve their ion exchange efficiency and corrosion ion capture ability. However, existing LDH synthesis methods (such as coprecipitation, ion exchange, and calcination-reduction methods) suffer from various problems during the intercalation process, including structural obstacles, kinetic limitations, and thermodynamic barriers, making it difficult for macromolecules to effectively enter the interlayer and form a stable structure. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a bimetallic hydroxide material and its preparation method. Based on the electrostatic assembly of LDHs, combined with a suitable macromolecular intercalation environment, the reaction conditions are controlled and the intercalation path is optimized to develop a method for preparing large-size organic anion-intercalated bimetallic hydroxide materials. The interlayer spacing of the prepared LDH materials is significantly increased. This method is simple to operate, highly adaptable, and can be widely used in the development of high-performance LDH materials.

[0008] The technical solution adopted is as follows: A bimetallic hydroxide material and its preparation method, comprising the following steps: (1) Preparation of inorganic LDHs raw materials: Take divalent metal nitrate ANO3 and trivalent metal nitrate BNO3 that are soluble in water, dissolve the two metal salts in equal amounts of water, and then mix them to obtain a mixed metal salt solution; Prepare an inorganic salt solution, titrate the inorganic salt solution into the mixed metal salt solution, and simultaneously titrate sodium hydroxide; after titration, heat the mixed solution in a water bath, wash with water, and dry to obtain inorganic LDHs raw materials; Where A is Mg 2+ Zn 2+ Ca 2+ Cu 2+ Ni 2+ Fe 2+ Any one of them; B is Al 3+ Ni 3+ Fe 3+ Mn 3+ Cr 3+ Any one of them; Inorganic salts are generally soluble nitrate solutions, such as NaNO3, KNO3, NH4NO3, etc.

[0009] (2) Preparation of LDHs nanosheets by ultrasonic exfoliation: The prepared inorganic LDHs raw material was placed in the exfoliation solvent and ultrasonically dispersed for 30 min to obtain a solvent containing LDHs nanosheets. (3) Titration of deprotonated organic molecule solution: Prepare organic molecule solution by adding sodium hydroxide to the solution and adjusting the pH to 10-12 to fully deprotonate the organic molecules and obtain deprotonated organic molecule solution; In an inert atmosphere, a deprotonated organic molecule solution is titrated into the solvent of the LDH nanosheets in step (2). During the titration, the solution is stirred using a cantilever stirrer to obtain an LDH precursor with a high-level spacing for organic molecule intercalation. (4) Post-processing: The prepared organic molecular intercalation high-level spacing LDH precursor was placed in a mixed solution water bath and heated for hours; then it was washed and dried to obtain high-level spacing bimetallic hydroxide material.

[0010] In the preferred step (1), the concentrations of the divalent and trivalent metal nitrates dissolved in water are 0.1–1.0 M; the molar ratio of A to B is 1:0.5–2.

[0011] Preferably, in step (1), the concentration of the inorganic salt is twice the sum of the concentrations of ANO3 and BNO3.

[0012] Preferably, in step (1), the titration flow rate of the inorganic salt solution and sodium hydroxide is 30 drops / min, and the pH is controlled at 10-12 (pH fluctuation is less than ±0.5 during the entire reaction process); during the titration process, a cantilever stirrer is used to stir the solution at a speed of 200-400 rpm.

[0013] Preferably, in step (2), the stripping solvent is acetone or formamide.

[0014] Preferably, the ultrasonic dispersion time is 20-30 minutes and the power is 120W.

[0015] Preferably, in step (3), the organic molecule is any one of phenol, eugenol, guaiacol, 2,3-dihydroxynaphthalene-6-sulfonic acid, 5-methyl-1,3,4-thiadiazole-2-mercapto, benzoic acid, lactic acid, or carboxylic acid, and the organic molecule has a molecular number greater than 20 and is capable of ionization. The concentration prepared is twice the sum of the concentrations of ANO3 and BNO3.

[0016] Preferably, the inert gas is nitrogen or argon, the titration flow rate is 30 drops / min, and a cantilever stirrer is used to stir the solution during the titration process at a speed of 200-400 rpm.

[0017] Preferably, in step (4), the water bath heating time is 36 to 48 hours; during cleaning, the water bath is used and anhydrous ethanol is used to clean the product 1 to 3 times in sequence.

[0018] A method for preparing a bimetallic hydroxide material yields a bimetallic hydroxide material with a high interlayer spacing, greater than 12 angstroms and reaching a maximum of 17.4 angstroms, which is at least 25% higher than the interlayer spacing of magnesium aluminum nitrate type bimetallic hydroxides in their natural state (interlayer spacing is around 8.8 angstroms).

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention addresses the key technical challenge of inserting large-sized organic anions into the interlayer space of LDHs by proposing a stepwise intercalation and reconstruction method based on electrostatic assembly, ultimately yielding high-interlayer-spaced bimetallic hydroxides. Highly dispersed LDH nanosheets are obtained through ultrasonic exfoliation, and deprotonated large-molecule organic anions are introduced. Organic molecule intercalation is achieved under electrostatic driving, supplemented by a mild structural reconstruction process, resulting in high-interlayer-spaced LDH materials with significantly increased interlayer spacing. Compared to traditional co-precipitation or calcination reconstruction methods, this method significantly improves the interlayer size of LDHs, overcoming the bottleneck of interlayer structure control limited by the size of organic molecules.

[0020] This invention achieves stable intercalation of large-sized organic anions between LDH layers by constructing a suitable macromolecular intercalation environment and a stable pH environment (pH fluctuation less than ±0.5 during titration). This successfully solves the problem in traditional methods where large organic molecules are difficult to intercalate due to large steric hindrance and poor charge compatibility. This method not only maintains the integrity of the LDH host structure but also significantly expands the interlayer spacing, endowing the material with greater functionalization potential. It has significant advantages such as large interlayer spacing in LDH preparation, wide applicability, and good structural innovation. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method for preparing high-layer spacing bimetallic hydroxides according to the present invention.

[0022] Figure 2 The electron microscope image shows the morphology of the LDH nanosheets prepared in this invention.

[0023] Figure 3 Electron microscopy morphology (a) and XRD pattern (b) of the high-level spacing bimetallic hydroxide (organic molecule is guaiacol) prepared in Example 1 of the present invention.

[0024] Figure 4 Electron microscopy morphology (a) and XRD pattern (b) of conventional magnesium aluminum nitrate type bimetallic hydroxides prepared as comparative examples of the present invention.

[0025] Figure 5 The images show the morphology of magnesium aluminum nitrate type LDH prepared in Comparative Example 1, where (a) is an electron microscope image and (b) is an XRD pattern.

[0026] Figure 6 The images show the morphology of calcium aluminum nitrate type LDH prepared in Comparative Example 2, where (a) is an electron microscope image and (b) is an XRD pattern. Detailed Implementation

[0027] The accompanying drawings are for illustrative purposes only; to enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples, but should not be construed as limiting the present patent.

[0028] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0029] Example 1 like Figure 1 As shown, a method for preparing a guaiacol-intercalated bimetallic hydroxide material includes the following steps: First, magnesium-aluminum nitrate-type LDH with a magnesium-to-aluminum ratio of 2:1 was prepared. Equal volumes of 100 ml of 0.5 M magnesium nitrate solution and 100 ml of 0.25 M aluminum nitrate solution were prepared and mixed to prepare 200 ml of a mixed salt solution. Then, 200 ml of 1.5 M sodium nitrate solution (i.e., an inorganic salt solution) was prepared. The mixed salt solution was then titrated into the inorganic salt solution, adjusting the pH to 12 during the titration process. After titration, the solution was centrifuged, dried, and the magnesium-aluminum nitrate-type LDH powder was obtained.

[0030] Next, take all the magnesium aluminum nitrate type LDH powder and place it in 100 ml of acetone. Shake the solvent container for 2 minutes to disperse the LDH powder in the acetone solvent. Obtain the acetone solvent in which the LDH powder is dispersed.

[0031] The LDH powder was dispersed in acetone solvent, and nitrogen gas was introduced into the container, which was then sealed to prevent carbonization of the LDH powder. It was then placed in an ultrasonic disperser and ultrasonically dispersed for 30 minutes at a power of 120W or higher. After this operation, the LDH bulk layer and the interlayer anions will be dispersed and exfoliated. The LDH bulk layer will be dispersed in the acetone solvent, such as... Figure 3 The electron microscope image shows the acetone solvent containing LDH nanosheets.

[0032] Prepare 100 ml of a 1.5 M guaiacol aqueous solution, adjust the pH to 12, and stir magnetically for 24 hours to obtain a deprotonated guaiacol anionic aqueous solution.

[0033] 100 ml of deprotonated guaiacol anionic aqueous solution was titrated into 100 ml of acetone containing LDH nanosheets at a flow rate of 30 drops / min, with the pH maintained at 12, under nitrogen protection. The solution was stirred using a cantilever stirrer at 200 rpm during titration to obtain a guaiacol-intercalated magnesium aluminum LDH precursor.

[0034] The guaiacol-intercalated magnesium-aluminum LDH precursor was heated in a water bath at 50°C for 48 hours. Then, it was centrifuged at 2000 rpm for 2 minutes. Finally, it was washed twice with water and twice with alcohol, and then naturally dried to obtain a high-layer-spacing bimetallic hydroxide.

[0035] like Figure 1 (a) is a schematic diagram of the synthesized inorganic bimetallic hydroxide raw material, (b) is a bimetallic hydroxide nanosheet exfoliated by ultrasonication, (c) is a mixed solution of bimetallic hydroxide nanosheets with added organic molecules, and (d) is a bimetallic hydroxide with high layer spacing.

[0036] Wherein, d1 is the interlayer spacing of the unmodified bimetallic hydroxide, and d2 is the interlayer spacing of the bimetallic hydroxide obtained using the preparation method of this invention. d2 is significantly larger than d1. Figure 2 The electron microscope image shows the morphology of the LDH nanosheets prepared in this invention.

[0037] The high-layer spacing bimetallic hydroxide prepared through the above steps has the following morphology: Figure 3 As shown in electron microscopy image (a), this high-level spacing bimetallic hydroxide exhibits a nanoflower-like structure, consistent with the common morphology of LDHs. Its XRD pattern is as follows: Figure 3 As shown in (b), two typical LDHs diffraction peaks (003) and (006) appeared in the XRD, and the interlayer spacing was about 17.4 Å, indicating a high layer spacing.

[0038] Example 2 A method for preparing a high-spacing bimetallic hydroxide material with eugenol intercalation includes the following steps: First, a nitrate-type LDH with a calcium-to-aluminum ratio of 2:1 was prepared. 200 ml of a 0.5 M calcium nitrate solution and 200 ml of a 0.25 M aluminum nitrate solution were mixed to obtain a 400 ml mixed salt solution. Separately, a 400 ml 1.5 M potassium nitrate solution was prepared as the inorganic salt solution. Under continuous stirring, the mixed salt solution was slowly titrated into the potassium nitrate solution, maintaining the pH at 12 throughout the process. After titration, the mixture was centrifuged, and the resulting precipitate was dried to obtain calcium-aluminum nitrate-type LDH powder.

[0039] Next, the LDH was exfoliated to obtain nanosheets. All of the calcium aluminum nitrate type LDH powder prepared above was added to 100 ml of formamide solvent, and the container was shaken for 2 minutes to initially disperse it. Nitrogen gas was then introduced into the container and sealed to isolate it from oxygen and prevent oxidation. The sealed container was placed in an ultrasonic disperser and ultrasonically treated at a power of at least 120 W for 30 minutes to fully exfoliate the LDH layers, ultimately obtaining a formamide solution containing LDH nanosheets.

[0040] Finally, the intercalation and post-treatment of eugenol anions were performed. A 100 ml solution of 1.5 M eugenol was prepared, and its pH was adjusted to 12 with alkali. The solution was then magnetically stirred for 24 hours to ensure complete deprotonation of the eugenol, yielding a deprotonated eugenol anion solution. Under nitrogen protection, 100 ml of this eugenol anion solution was titrated at a flow rate of 30 drops / min into 100 ml of a formamide dispersion containing LDH nanosheets, maintaining the pH at 12 while stirring the solution at 200 rpm to obtain an eugenol-intercalated calcium-aluminum LDH precursor. This precursor was heated in a water bath at 50°C for 48 hours for ion exchange and structural recombination. The precipitate was then collected by centrifugation at 2000 rpm for 2 minutes, washed twice each with water and ethanol, and finally air-dried to obtain a layered eugenol-intercalated calcium-aluminum layered bimetallic hydroxide with a high interlayer spacing.

[0041] The high-layer spacing bimetallic hydroxide prepared through the above steps has the following morphology: Figure 4 As shown in electron microscopy image (a), this high-layer-spaced bimetallic hydroxide exhibits a hexagonal plate-like structure, consistent with the common morphology of LDHs. Its XRD pattern is as follows: Figure 4 As shown in (b), two typical LDHs diffraction peaks (002) and (004) appeared in the XRD, and the interlayer spacing was about 15.6 Å.

[0042] Example 3 A method for preparing a high-layer-spacing bimetallic hydroxide material intercalated with 5-methyl-1,3,4-thiadiazole-2-mercapto (MTT) comprises the following steps: A mixed salt solution was prepared by thoroughly mixing 200 mL of 0.5 M zinc nitrate solution with 200 mL of 0.25 M aluminum nitrate solution. Separately, 400 mL of 1.5 M potassium nitrate solution was used as the inorganic salt solution. Under continuous stirring, the mixed salt solution was slowly added dropwise to the potassium nitrate solution, maintaining the pH of the system at 10. After titration, the resulting suspension was centrifuged, and the precipitate was collected and dried to obtain zinc-aluminum nitrate type LDH powder.

[0043] The LDH powder was then subjected to a peeling process. It was added entirely to 100 mL of formamide solvent and gently shaken for 2 minutes to achieve initial dispersion. Nitrogen gas was then introduced and the container sealed to prevent oxidation. The mixture was then ultrasonically treated at a power of at least 120 W for 30 minutes in an ultrasonic disperser to fully peel off its layered structure, ultimately obtaining a formamide dispersion containing LDH nanosheets.

[0044] Next, 100 mL of a 1.5 M aqueous solution of 5-methyl-1,3,4-thiadiazole-2-mercapto(MTT) was prepared and mixed with 100 mL of a 1.5 M NaOH solution. The mixture was reacted under magnetic stirring for 24 hours to ensure complete deprotonation of MTT and the formation of a stable MTT anionic solution. Under nitrogen protection, 100 mL of the MTT anionic solution was added dropwise at a rate of 30 drops / min to 100 mL of a formamide dispersion containing LDH nanosheets, maintaining the pH at 10 while stirring at 200 rpm to obtain an MTT-intercalated zinc-aluminum LDH precursor. This precursor was heated in a 50 °C water bath for 48 hours to promote ion exchange and structural recombination. The precipitate was then collected by centrifugation at 2000 rpm for 2 minutes, washed twice each with water and ethanol, and finally dried naturally to obtain a layered MTT-intercalated zinc-aluminum layered bimetallic hydroxide with a high interlayer spacing.

[0045] The product prepared by the above process can be clearly observed in the XRD pattern with two typical LDHs diffraction peaks (003) and (006), with an interlayer spacing of about 13.7 Å.

[0046] Example 4 A method for preparing a high-spacing bimetallic hydroxide material intercalated with 2,3-dihydroxynaphthalene-6-sulfonic acid includes the following steps: First, magnesium-aluminum nitrate-type LDH with a magnesium-to-aluminum ratio of 2:1 was prepared. Equal volumes of 100 ml of 1M magnesium nitrate solution and 100 ml of 0.5M aluminum nitrate solution were prepared and mixed to prepare a 200 ml mixed salt solution. Separately, 200 ml of 1.5M potassium nitrate solution was prepared as the inorganic salt solution. Other steps were the same as in Example 1. After titration, the solution was centrifuged, dried, and magnesium-aluminum nitrate-type LDH powder was obtained.

[0047] Then, following the steps in Example 1, magnesium aluminum nitrate type LDH powder was mixed with LDH nanosheets to obtain an acetone solvent containing LDH nanosheets.

[0048] Prepare 100 ml of 1.5 M 2,3-dihydroxynaphthalene-6-sulfonic acid aqueous solution and, following the method in Example 1, prepare a high-spacing magnesium-aluminum bimetallic hydroxide with 2,3-dihydroxynaphthalene-6-sulfonic acid intercalation.

[0049] The prepared 2,3-dihydroxynaphthalene-6-sulfonic acid intercalated high-layer-spaced magnesium-aluminum bimetallic hydroxide has an interlayer spacing of approximately 15.9 Å.

[0050] Example 5 A method for preparing a high-layer-spacing bimetallic hydroxide material intercalated with 2-mercaptoethanesulfonic acid includes the following steps: First, a nitrate-type LDH with a calcium-to-aluminum ratio of 2:1 was prepared. 100 ml of a 0.5 M calcium nitrate solution and 100 ml of a 0.25 M aluminum nitrate solution were mixed to obtain 200 ml of a mixed salt solution. Separately, 200 ml of a 1.5 M potassium nitrate solution was prepared as the inorganic salt solution. The remaining steps were the same as in Example 2, yielding calcium-aluminum nitrate-type LDH powder.

[0051] Then, following the steps in Example 2, LDHs nanosheets were processed to obtain a formamide solution containing LDHs nanosheets.

[0052] Prepare 100 ml of 1.5 M 2-mercaptoethanesulfonic acid aqueous solution and, following the method in Example 2, prepare a high-layer-spacing magnesium-aluminum bimetallic hydroxide with 2-mercaptoethanesulfonic acid intercalation.

[0053] The prepared 2-mercaptoethanesulfonic acid intercalated high-layer-spaced calcium-aluminum bimetallic hydroxide has an interlayer spacing of approximately 13.5 Å.

[0054] Compare with Example 1 Prepare 100 mL of 1 M magnesium nitrate aqueous solution and 100 mL of 0.5 M aluminum nitrate aqueous solution. Mix them thoroughly to prepare a mixed metal salt solution.

[0055] 100 mL of 3M sodium nitrate solution was titrated into a mixed metal salt solution at a flow rate of 30 drops / min, with the pH maintained at 12. During titration, the solution was stirred using a cantilever stirrer at 200 rpm, with nitrogen protection applied throughout the process. This yielded a magnesium aluminum nitrate-type LDH precursor. After titration, the magnesium aluminum nitrate-type LDH precursor was heated in a water bath for 48 hours, washed with water, and dried to obtain magnesium aluminum nitrate-type LDH.

[0056] This is a traditional co-precipitation method for preparing common small-interlayer-spacing magnesium aluminum nitrate-type LDH. The morphology of the prepared LDH is as follows. Figure 5 As shown in electron microscopy image (a), its morphology is hexagonal plate-like, consistent with the common microstructure of LDHs. Its XRD pattern is as follows: Figure 5 As shown in (b), the XRD pattern shows two typical LDH diffraction peaks, (003) and (006), with an interlayer spacing of approximately 8.8 Å. This interlayer spacing is much smaller than that of the high-interlayer-spacing bimetallic hydroxides obtained by this invention.

[0057] Compare with Example 2 Prepare 100 mL of 1 M calcium nitrate aqueous solution and 100 mL of 0.5 M aluminum nitrate aqueous solution. Mix them thoroughly to prepare a mixed metal salt solution.

[0058] 100 mL of 3M sodium nitrate solution was titrated into a mixed metal salt solution at a flow rate of 30 drops / min, with the pH maintained at 12. During titration, the solution was stirred using a cantilever stirrer at 200 rpm, with nitrogen protection applied throughout the process. A calcium-aluminum nitrate-type LDH precursor was obtained. After titration, the calcium-aluminum nitrate-type LDH precursor was heated in a water bath for 48 hours, washed with water, and dried to obtain calcium-aluminum nitrate-type LDH.

[0059] This is a traditional co-precipitation method for preparing common small-interlayer-spacing calcium-aluminum nitrate-type LDH. The morphology of the prepared LDH is as follows. Figure 6 As shown in electron microscopy image (a), its morphology is hexagonal plate-like, consistent with the common microstructure of LDHs. Its XRD pattern is as follows: Figure 6 As shown in (b), its interlayer spacing is approximately 8.6 angstroms. This interlayer spacing is much smaller than that of the high-spacing bimetallic hydroxides obtained by this invention.

[0060] The preparation conditions and interlayer spacing of the bimetallic hydroxides prepared in Examples 1-5 of the present invention were compared with those of the bimetallic hydroxides in Comparative Examples 1 and 2. The results are shown in Table 1.

[0061] Table 1. Comparison of interlayer spacing between the bimetallic hydroxides prepared in Examples 1-5 and the bimetallic hydroxides in Comparative Examples 1 and 2. The bimetallic hydroxide material prepared in Example 1 showed an increase in interlayer spacing of approximately 97% compared to Comparative Example 1, and approximately 99% compared to Comparative Example 2. The bimetallic hydroxide material prepared in Example 2 showed an increase in interlayer spacing of approximately 76% compared to Comparative Example 1, and approximately 77% compared to Comparative Example 2. The bimetallic hydroxide material prepared in Example 3 showed an increase in interlayer spacing of approximately 56% compared to Comparative Example 1, and approximately 57% compared to Comparative Example 2. The bimetallic hydroxide material prepared in Example 4 showed an increase in interlayer spacing of approximately 81% compared to Comparative Example 1, and approximately 82% compared to Comparative Example 2. The bimetallic hydroxide material prepared in Example 5 showed an increase in interlayer spacing of approximately 53% compared to Comparative Example 1, and approximately 54% compared to Comparative Example 2.

[0062] In summary, the bimetallic hydroxide material prepared by this invention has a high interlayer spacing and introduces large-sized organic anions, resulting in a significant increase in the interlayer spacing of the LDHs material and a significant improvement in the ion exchange capacity of the material.

[0063] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a bimetallic hydroxide material, characterized in that, Includes the following steps: (1) Preparation of inorganic LDHs raw materials: Take divalent metal nitrate ANO3 and trivalent metal nitrate BNO3, which are soluble in water, dissolve the two metal salts in equal amounts of water, and then mix them to obtain a mixed metal salt solution; Prepare an inorganic salt solution, titrate the inorganic salt solution into the mixed metal salt solution, and simultaneously titrate sodium hydroxide; after titration, heat the mixed solution in a water bath, wash with water, and dry to obtain inorganic LDHs raw materials; Where A is Mg 2+ Zn 2+ Ca 2+ Cu 2+ Ni 2+ Fe 2+ Any one of them; B is Al 3+ Ni 3+ Fe 3+ Mn 3+ Cr 3+ Any one of them; Inorganic salts are generally NaNO3, KNO3, and NH4NO3, and soluble nitrate solutions. (2) Preparation of LDHs nanosheets by ultrasonic exfoliation: The prepared inorganic LDHs raw material was placed in the exfoliation solvent and ultrasonically dispersed for 30 min to obtain a solvent containing LDHs nanosheets. (3) Titration of deprotonated organic molecule solution: Prepare organic molecule solution by adding sodium hydroxide to the solution and adjusting the pH to 10-12 to fully deprotonate the organic molecules and obtain a deprotonated organic molecule solution; In an inert atmosphere, a deprotonated organic molecule solution is titrated into the solvent of the LDH nanosheets in step (2). The solution is stirred using a cantilever stirrer during the titration process to obtain an organic molecule intercalated LDH precursor. (4) Post-processing: The prepared organic molecular intercalation high-level spacing LDH precursor was placed in a mixed solution water bath and heated for hours; then it was washed and dried to obtain the bimetallic hydroxide material.

2. The method for preparing a bimetallic hydroxide material according to claim 1, characterized in that, In step (1), the concentrations of the divalent and trivalent metal nitrates dissolved in water are 0.1–1.0 M; the molar ratio of A to B is 1:0.5–2.

3. The method for preparing a bimetallic hydroxide material according to claim 2, characterized in that, In step (1), the concentration of the inorganic salt is twice the sum of the concentrations of ANO3 and BNO3.

4. The method for preparing a bimetallic hydroxide material according to claim 1, characterized in that, In step (1), the titration flow rate of inorganic salt solution and sodium hydroxide is 30 drops / min, the pH is controlled at 10-12, and the pH fluctuation is less than ±0.5 throughout the reaction process; during the titration process, a cantilever stirrer is used to stir the solution at a speed of 200-400 rpm.

5. The method for preparing a bimetallic hydroxide material according to claim 1, characterized in that, In step (2), the stripping solvent is acetone or formamide.

6. The method for preparing a bimetallic hydroxide material according to claim 5, characterized in that, The ultrasonic dispersion time is 20-30 minutes, and the power is 120W.

7. The method for preparing a bimetallic hydroxide material according to claim 1, characterized in that, In step (3), the organic molecule is any one of phenol, eugenol, guaiacol, 2,3-dihydroxynaphthalene-6-sulfonic acid, 5-methyl-1,3,4-thiadiazole-2-mercapto, benzoic acid, lactic acid, or carboxylic acid, and the concentration of the prepared organic molecule is twice the sum of the concentrations of ANO3 and BNO3.

8. The method for preparing a bimetallic hydroxide material according to claim 7, characterized in that, The inert gas is nitrogen or argon, the titration flow rate is 30 drops / min, and the solution is stirred using a cantilever stirrer at a speed of 200-400 rpm during the titration.

9. The method for preparing a bimetallic hydroxide material according to claim 1, characterized in that, In step (4), the water bath heating time is 36-48 hours; during cleaning, the water bath is used and then anhydrous ethanol is used to clean the water 1-3 times in sequence.

10. The bimetallic hydroxide material prepared by the method for preparing a bimetallic hydroxide material according to any one of claims 1-9, characterized in that, The interlayer spacing of the bimetallic hydroxide is greater than 12 angstroms.

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