Synthetic method of hydrotalcite-like compound and hydrotalcite-like compound

Abstract

The invention provides a synthetic method of a hydrotalcite-like compound and the hydrotalcite-like compound, and relates to the technical field of layered mineral materials, and the synthetic method comprises the following steps: dropwise adding a metal salt solution into a mixed solution of an ammonia water-ammonium chloride buffer pair and a target anion salt to obtain a reaction mixed solution, and heating the reaction mixed solution to 100-180 DEG C, and aging for 8-48 hours to obtain the hydrotalcite-like compound. Metal ions in the metal salt solution comprise divalent metal ions and trivalent metal ions, and in the reaction mixed solution, the concentration of the divalent metal ions is 0.01-0.12 mol / L, and the concentration of the trivalent metal ions is 0.001-0.05 mol / L; in the mixed solution, the concentration of the target anions is 0.012 to 10 mol / L. The method comprises the following steps: directly dropwise adding a metal salt solution into a mixed solution of an ammonia water-ammonium chloride buffer pair and a target anion salt to obtain a reaction mixed solution, aging the reaction mixed solution at 100-180 DEG C for 8-48 hours, and controlling the concentration of target anions, the concentration of metal ions and aging conditions to obtain LDHs crystal grains with uniform particle size and larger size.

Description

Technical Field

[0001] This invention relates to the field of layered mineral materials technology, specifically to a method for synthesizing hydrotalcite-like materials and hydrotalcite-like materials. Background Technology

[0002] Layered double hydroxides (LDHs), also known as hydrotalcites, are a class of synthetic anionic clay materials with a layered structure. Their structure consists of positively charged metal hydroxide layers interlayered with exchangeable anions and water molecules, exhibiting excellent anion exchange capacity and a weakly alkaline surface. They are widely used in catalysis, adsorption, drug delivery, flame retardants, and environmental remediation. The general formula for LDHs is usually represented as [M...]. 2+ 1-x M 3+ x (OH)2] n+ ·A n- m ·yH2O, where M 2+ Represents divalent metal cations, such as Mg 2+ Zn 2+ Ni 2+ Cu 2+ or Fe 2+ M 3+ Representing trivalent metal cations, the most common being Al. 3+ Fe 3+ Cr 3+ or Ga 3+ Metal cations are uniformly distributed on layers composed of octahedral coordination polyhedra with shared edges. The layers carry a permanent positive charge, while the interlayer spaces are filled with freely moving anions A. n- And water of crystallization molecules. The crystal structure of hydrotalcite is similar to that of brucite, that is, a two-dimensional layered network formed by octahedrons connected by shared edges. When some divalent metals are isomorphously replaced by trivalent metals, the layers become positively charged due to charge imbalance, thereby attracting interlayer anions to maintain overall electroneutrality. This unique structure endows hydrotalcite with a series of excellent physicochemical properties. For example, its interlayer anions have high exchangeability, making hydrotalcite a highly efficient anion adsorbent or carrier, widely used in water treatment to remove harmful anions or to achieve the controlled release of functional molecules such as drugs, preservatives, and flame retardants.

[0003] Existing techniques typically involve controlling the pH value by adding alkaline solutions such as NaOH, followed by co-precipitation of selected divalent and trivalent metal ions under constant pH conditions to prepare hydrotalcite-like materials. However, direct addition of NaOH results in significant pH fluctuations, easily leading to localized over-alkalinity, heterogeneous precipitation, impurity phase formation, and potential residues of unreacted metal hydroxides or salt impurities. Furthermore, dynamic pH changes can cause uneven crystal growth rates, resulting in a wide particle size distribution and even agglomeration. To address the technical drawbacks of directly adding strong alkali, existing techniques use ammonia and ammonium chloride as buffer solutions to synthesize magnesium-aluminum LDHs with chloride ions as interlayer anions via co-precipitation. These are then aged at 55°C for 18 hours for treating Cr(VI) in wastewater. However, the resulting hydrotalcite crystals are relatively small, only about 36 nm in size. Summary of the Invention

[0004] To address the deficiencies in existing technologies, the present invention solves the technical problem of providing a method for synthesizing hydrotalcite-like materials and a hydrotalcite-like material that can yield hydrotalcite-like materials with larger grain sizes.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for synthesizing a hydrotalcite-like substance, comprising: The metal salt solution is added dropwise to a mixed solution of ammonia-ammonium chloride buffer and the target anionic salt to obtain a reaction mixture. The reaction mixture is heated to 100-180℃ and aged for 8-48 hours to obtain the hydrotalcite-like substance. The metal ions in the metal salt solution include divalent metal ions and trivalent metal ions. In the reaction mixture, the concentration of the divalent metal ions is 0.01-0.12 mol / L, and the concentration of the trivalent metal ions is 0.001-0.05 mol / L. The concentration of the target anion in the mixed solution is 0.012-10 mol / L.

[0006] Preferably, the molar ratio of the divalent metal ion to the trivalent metal ion is (2-4):1.

[0007] Preferably, the divalent metal ion is selected from Mg. 2+ Cu 2+ Zn 2+ Fe 2+ Co 2+ Ni 2+ and Ca 2+ One or more of them.

[0008] Preferably, the trivalent metal ion is selected from Al. 3+ Fe 3+ Cr 3+ and Ga 3+One or more of them.

[0009] Preferably, the target anion includes carbonate-type target anions and non-carbonate-type target anions.

[0010] Preferably, the non-carbonate target anion is selected from nitrate, sulfate, and acetate.

[0011] Preferably, when the target anion is a non-carbonate type target anion, both the metal salt solution and the mixed solution are prepared using deionized water that has been boiled and cooled to room temperature as the solvent.

[0012] Preferably, when the target anion is a non-carbonate type target anion, the step of adding the metal salt solution dropwise to a mixed solution of ammonia-ammonium chloride buffer and the target anion salt to obtain a reaction mixture is carried out under a nitrogen atmosphere.

[0013] Preferably, the pH value of the ammonia-ammonium chloride buffer solution is 9-10.

[0014] Secondly, the present invention also provides a hydrotalcite-like material, which is prepared by the hydrotalcite-like material synthesis method described in the first aspect.

[0015] Compared with the prior art, the advantages of the present invention are as follows: The present invention obtains a reaction mixture by directly adding a metal salt solution to a mixed solution of ammonia-ammonium chloride buffer and target anion salt, and aging the reaction mixture at 100-180℃ for 8-48 hours. By controlling the target anion concentration, metal ion concentration and aging conditions, LDHs crystals with uniform particle size and large size can be obtained. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The X-ray diffraction patterns of the hydrotalcite-like materials prepared in Examples 1-4 of this invention are shown below. Figure 2 Here is a SEM image of the hydrotalcite-like material prepared according to an embodiment of the present invention; Figure 3 The X-ray diffraction patterns of the hydrotalcite-like materials prepared in Examples 5-6 of this invention are shown below. Figure 4 The X-ray diffraction pattern of the hydrotalcite-like material prepared in Example 7 of this invention is shown. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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, not all, of the embodiments of the present invention. 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.

[0019] This invention provides a method for synthesizing hydrotalcite-like substances and the hydrotalcite-like substances themselves. The invention obtains a reaction mixture by directly adding a metal salt solution of a specific concentration dropwise to a mixed solution of an ammonia-ammonium chloride buffer and a target anionic salt. The reaction mixture is then aged at 100-180°C for 8-48 hours to obtain LDHs crystals with uniform particle size and large dimensions. This solves the technical problem of small crystal size in hydrotalcite prepared using the buffer solution method in the prior art, and also newly prepares LDHs with interlayer anions of carbonate, sulfate, nitrate, and acetate.

[0020] To achieve the above-mentioned technical effects, the overall concept of this invention is as follows: On one hand, the present invention provides a method for synthesizing a hydrotalcite-like substance, the method comprising: adding a metal salt solution dropwise to a mixed solution of an ammonia-ammonium chloride buffer and a target anionic salt to obtain a reaction mixture, and aging the reaction mixture at 100-180°C for 8-48 hours to obtain the hydrotalcite-like substance; The metal ions in the metal salt solution include divalent metal ions and trivalent metal ions. In the reaction mixture, the concentration of the divalent metal ions is 0.01-0.12 mol / L, and the concentration of the trivalent metal ions is 0.001-0.05 mol / L. The concentration of the target anion in the mixed solution is 0.012-10 mol / L.

[0021] The magnesium aluminum hydrotalcite synthesized by the buffer solution method in the prior art is small in size and cannot synthesize other anionic LDHs, which cannot meet the application requirements. To this end, the applicant has conducted a lot of experimental research and found that by directly adding a metal salt solution of a specific concentration to a mixed solution of buffer solution and target anionic salt solution to obtain a reaction mixture, and aging the reaction mixture at 100~180℃, different anionic hydrotalcites with uniform particle size and average particle size of 125-1000nm were successfully synthesized. The applicant analyzed that the reasons may be: (1) Using ammonia-ammonium chloride as a buffer solution can suppress local supersaturation of metal ions and promote uniform nucleation; (2) Controlling the appropriate aging temperature and aging time is conducive to further growth and maturation of crystals, thereby obtaining larger LDHs particles; Through a large number of experiments, the present invention found that when the aging temperature is too high, impurities are easily generated, reducing the purity of the crystals and hindering the growth and maturation of the crystal size. When the aging temperature is too low, it is not conducive to crystal growth, resulting in smaller crystal size; (3) In the nucleation stage, the concentration of metal ions has a greater impact on the particle size of the product. Reducing the concentration of metal ions results in fewer crystal nuclei, which allows each crystal nucleus to obtain more raw material supply in the subsequent aging and growth stage, thus making it easier to grow into larger particles; (4) The target anion concentration also has a greater impact on the size of hydrotalcite particles. When the target anion concentration is high, multiple anionic hydrotalcites without impurities can be synthesized, which is conducive to increasing the size of hydrotalcite particles.

[0022] Therefore, by controlling the concentration of metal ions, aging conditions, and the concentration of target anions in the mixed solution, the present invention obtains LDHs crystals with uniform particle size and large size through the combined effect of the above conditions, thus solving the technical problem of small LDHs crystals in the prior art.

[0023] Furthermore, this invention synthesizes various anionic hydrotalcites by directly adding the metal salt solution dropwise into a mixed solution of buffer solution and target anionic salt solution, followed by high-temperature aging of the reaction mixture. These hydrotalcites include, but are not limited to, carbonate, nitrate, sulfate, and acetic acid types. Compared with existing synthesis methods that employ two or more steps, the synthesis method of this application is simple and universal, making it suitable for industrial-scale production.

[0024] Preferably, the divalent metal ion is selected from Mg. 2+ Cu 2+ Zn 2+ Fe 2+ Co 2+ Ni 2+ and Ca 2+ One or more of the following; the trivalent metal ions are selected from Al 3+ Fe 3+ Cr 3+ and Ga3+ One or more of them.

[0025] Preferably, the molar ratio of the divalent metal ion to the trivalent metal ion is (2-4):1. This invention has found that the purity of LDHs can be adjusted by controlling the molar ratio of divalent and trivalent metal ions. More preferably, the purity of carbonate-type LDHs is highest when the molar ratio of divalent to trivalent metal ions is 3:1, and the purity of nitrate, acetate, and sulfate-type LDHs is highest when the molar ratio is 2:1. Higher purity results in larger crystallite sizes of the synthesized LDHs.

[0026] Preferably, the target anion includes carbonate-type target anions and non-carbonate-type target anions, wherein the carbonate-type target anion is a carbonate ion; and the non-carbonate-type target anion is selected from any one of nitrate ions, acetate ions, and sulfate ions. In this embodiment, the target anion salt of the present invention can be selected from any one of sodium carbonate, sodium nitrate, sodium acetate, and sodium sulfate. By controlling the concentration of the target anion salt and the type of target anion, the types of interlayer anions can be controlled, thereby obtaining various anionic hydrotalcite-like materials.

[0027] Preferably, when the target anion is a non-carbonate anion, the metal salt solution and the mixed solution are prepared using deionized water that has been boiled and cooled to room temperature as the solvent. The step of adding the metal salt solution dropwise to the mixed solution of the ammonia-ammonium chloride buffer pair and the target anion salt to obtain the reaction mixture is carried out in a nitrogen atmosphere. In the synthesis of non-carbonate LDHs, this invention uses deionized water that has been boiled and cooled to room temperature as the solvent to prepare the solution and introduces nitrogen to create an inert environment, which can eliminate the influence of carbonate ions in the water and carbonate ions generated by CO2 dissolved in the water on the interlayer anions, thereby improving the purity of LDHs. Carbonate LDHs can be synthesized using ordinary deionized water as the solvent (i.e., without boiling and cooling the deionized water to room temperature before use) and in an air atmosphere.

[0028] Preferably, the dropping time for adding the metal salt solution to the mixed solution of ammonia-ammonium chloride buffer and the target anionic salt is 8-12 minutes. In this invention, the metal salt solution is added dropwise to the mixed solution of ammonia-ammonium chloride buffer and the target anionic salt under stirring conditions, and the dropping time is controlled within 8-12 minutes.

[0029] Preferably, the pH value of the mixed solution of the ammonia-ammonium chloride buffer pair and the target anionic salt is 9-10. The mixed solution of this application contains the ammonia-ammonium chloride buffer pair; therefore, the mixed solution with a pH value of 9-10 can provide a stable aging reaction environment of pH 9-10 for the mixed reaction solution, which is an ideal pH environment for the synthesis of LDHs.

[0030] Preferably, the aging process further includes a post-processing step, which includes: washing the aged solid with deionized water and drying. After aging, the solid obtained after aging is washed with deionized water, and after cleaning, it is placed in an oven at 60-80℃ for 12-24 hours to obtain LDHs with high crystallinity, uniform particle size, and large size.

[0031] In this embodiment of the invention, a method for synthesizing a hydrotalcite-like substance specifically includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: The metal salt solution A includes a divalent metal salt solution and a trivalent metal salt solution, with a molar ratio of divalent metal ions to trivalent metal ions of (2~4):1; the pH value of the mixed solution B is 9~10; the target anionic salt is selected from any one of sodium carbonate, sodium nitrate, sodium acetate, and sodium sulfate; all the above solutions are prepared using cooled boiled deionized water (this step can be omitted when the target anion is carbonate ion). S2: Under nitrogen atmosphere (nitrogen can be omitted when the target anion is carbonate ion) and room temperature stirring conditions, metal salt solution A is added dropwise to mixed solution B to obtain a reaction mixture. In mixed solution B, the concentration of the target anion is 0.012-10 mol / L, and in the reaction mixture, the concentration of the divalent metal ion is 0.01-0.12 mol / L, and the concentration of the trivalent metal ion is 0.001-0.05 mol / L. The dropwise addition time is 10-12 minutes. S3: Place the reaction mixture into a reaction vessel and age it at 100-180℃ for 8-48 hours; S4: After aging, the solid material is washed with deionized water and then dried in an oven at 60-80℃ for 12-24 hours to obtain LDHs. The average particle size of the LDHs is 200m-1000nm.

[0032] Secondly, the present invention also provides a hydrotalcite-like material, which is prepared by the above-mentioned synthesis method of hydrotalcite-like material.

[0033] The hydrotalcite-like material prepared by the above synthesis method has good crystallization, uniform particles, and an average particle size of 200-1000 nm. Compared with the prior art, the particle size is significantly improved, which can meet the needs of different applications.

[0034] The following specific embodiments illustrate a method for synthesizing a hydrotalcite-like substance and the hydrotalcite-like substance of the present invention.

[0035] Example 1 The synthesis method of carbonate-type magnesium aluminum hydrotalcite includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: Metal salt solution A: Weigh 4.6154g magnesium nitrate hexahydrate and 2.2508g aluminum nitrate nonahydrate, and use deionized water to prepare 50mL of metal salt solution A. Mixed solution B: Weigh 0.7440g sodium carbonate and 1.1679g ammonium chloride, measure 8.4mL ammonia water, and prepare 100mL of mixed solution B using deionized water. The pH of mixed solution B is 10 (the carbonate ion concentration in mixed solution B is 0.07mol / L). S2: Under stirring conditions at room temperature, 50 mL of metal salt solution A is added dropwise to 100 mL of mixed solution B to obtain a reaction mixture (in the reaction mixture, Mg... 2+ The concentration is 0.12 mol / L, Al 3+ The concentration was 0.04 mol / L, and the dropping time was approximately ten minutes. S3: Place the reaction mixture into the reaction vessel and age it at 165℃ for 12 hours; S4: After aging, the solid was washed with deionized water and then dried in an oven at 70°C for 24 hours to obtain carbonate-type magnesium aluminum hydrotalcite.

[0036] Example 2 The synthesis method of nitrate-type magnesium aluminum hydrotalcite includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: Metal salt solution A: Weigh 0.513g magnesium nitrate hexahydrate and 0.375g aluminum nitrate nonahydrate, and use deionized water that has been boiled and cooled to room temperature to prepare 100mL of metal salt solution A. Mixed solution B: Weigh 0.7440g sodium carbonate and 0.3769g ammonium chloride, measure 4.5mL ammonia water, and prepare 100mL of mixed solution B using deionized water that has been boiled and cooled to room temperature. The pH of mixed solution B is 10 (the concentration of nitrate ions in mixed solution B is 0.375mol / L). S2: Under nitrogen atmosphere and stirring at room temperature, 100 mL of metal salt solution A is added dropwise to 100 mL of mixed solution B to obtain a reaction mixture (in the reaction mixture, Mg...). 2+ The concentration is 0.01 mol / L, Al 3+ The concentration was 0.005 mol / L, and the dropping time was approximately ten minutes. S3: Place the reaction mixture into a reaction vessel and age it at 120°C for 24 hours; S4: After aging, the solid was washed with deionized water and then dried in an oven at 70°C for 24 hours to obtain nitrate-type magnesium aluminum hydrotalcite.

[0037] Example 3 The synthesis method of acetate-type magnesium aluminum hydrotalcite includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: Metal salt solution A: Weigh 0.513g magnesium nitrate hexahydrate and 0.375g aluminum nitrate nonahydrate, and use deionized water that has been boiled and cooled to room temperature to prepare 100mL of metal salt solution A. Mixed solution B: Weigh 3.0758g of anhydrous sodium acetate and 0.3769g of ammonium chloride, measure 4.5mL of ammonia water, and prepare 100mL of mixed solution B using deionized water that has been boiled and cooled to room temperature. The pH of mixed solution B is 10 (the concentration of acetate ions in mixed solution B is 0.375mol / L). S2: Under nitrogen atmosphere and stirring at room temperature, 100 mL of metal salt solution A is added dropwise to 100 mL of mixed solution B to obtain a reaction mixture (in the reaction mixture, Mg...). 2+ The concentration is 0.01 mol / L, Al 3+ The concentration was 0.005 mol / L, and the dropping time was approximately ten minutes. S3: Place the reaction mixture into a reaction vessel and age it at 120°C for 24 hours; S4: After aging, the solid was washed with deionized water and dried in an oven at 70°C for 24 hours to obtain acetate-type magnesium aluminum hydrotalcite.

[0038] Example 4 The synthesis method of sulfate-type magnesium aluminum hydrotalcite includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: Metal salt solution A: Weigh 0.513g magnesium nitrate hexahydrate and 0.375g aluminum nitrate nonahydrate, and use deionized water that has been boiled and cooled to room temperature to prepare 100mL of metal salt solution A. Ammonia-Ammonium Chloride Buffer Solution B: Weigh 3.0758g of anhydrous sodium sulfate and 0.3769g of ammonium chloride, measure 4.5mL of ammonia water, and prepare 100mL of mixed solution B using deionized water that has been boiled and cooled to room temperature. The pH of mixed solution B is 10 (the sulfate ion concentration in mixed solution B is 0.1mol / L). S2: Under nitrogen atmosphere and stirring at room temperature, 100 mL of metal salt solution A is added dropwise to 100 mL of mixed solution B to obtain a reaction mixture (in the reaction mixture, Mg...). 2+ The concentration is 0.01 mol / L, Al 3+ The concentration was 0.005 mol / L, and the dropping time was approximately ten minutes. S3: Place the reaction mixture into a reaction vessel and age it at 120°C for 24 hours; S4: After aging, the solid was washed with deionized water and then dried in an oven at 70°C for 24 hours to obtain sulfate-type magnesium aluminum hydrotalcite.

[0039] Example 5 The synthesis method of nitrate-type magnesium aluminum hydrotalcite includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: Metal salt solution A: Weigh 1.28g magnesium nitrate hexahydrate and 0.94g aluminum nitrate nonahydrate, and use deionized water that has been boiled and cooled to room temperature to prepare 25mL of metal salt solution A. Mixed solution B: Weigh 21.25g sodium nitrate and 0.94g ammonium chloride, measure 11.25mL ammonia water, and prepare 25mL of mixed solution B using deionized water that has been boiled and cooled to room temperature. The pH of mixed solution B is 10 (the concentration of nitrate ions in mixed solution B is 10mol / L). S2: Under nitrogen atmosphere and stirring at room temperature, 25 mL of metal salt solution A is added dropwise to 25 mL of mixed solution B to obtain a reaction mixture (in the reaction mixture, Mg...). 2+ The concentration is 0.1 mol / L, Al 3+ The concentration was 0.05 mol / L, and the dropping time was approximately ten minutes. S3: Place the reaction mixture into a reaction vessel and age it at 120°C for 12 hours; S4: After aging, the solid was washed with deionized water and then dried in an oven at 70°C for 24 hours to obtain nitrate-type magnesium aluminum hydrotalcite.

[0040] Example 6 The synthesis method of nitrate-type magnesium aluminum hydrotalcite includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: Metal salt solution A: Weigh 1.28g magnesium nitrate hexahydrate and 0.94g aluminum nitrate nonahydrate, and use deionized water that has been boiled and cooled to room temperature to prepare 25mL of metal salt solution A. Mixed solution B: Weigh 21.25g sodium nitrate and 0.94g ammonium chloride, measure 11.25mL ammonia water, and prepare 25mL of mixed solution B using deionized water that has been boiled and cooled to room temperature. The pH of mixed solution B is 10 (the concentration of nitrate ions in mixed solution B is 10mol / L). S2: Under nitrogen atmosphere and stirring at room temperature, 25 mL of metal salt solution A is added dropwise to 25 mL of mixed solution B to obtain a reaction mixture (in the reaction mixture, Mg...). 2+ The concentration is 0.1 mol / L, Al 3+ The concentration was 0.05 mol / L, and the dropping time was approximately ten minutes. S3: Place the reaction mixture into the reaction vessel and age it at 165℃ for 12 hours; S4: After aging, the solid was washed with deionized water and then dried in an oven at 70°C for 24 hours to obtain nitrate-type magnesium aluminum hydrotalcite.

[0041] Example 7 The synthesis method of carbonate-type magnesium aluminum hydrotalcite includes the following steps: S1: Prepare a mixed solution of metal salt A, ammonia-ammonium chloride buffer pair, and target anionic salt B: Metal salt solution A: Weigh 0.7695g magnesium nitrate hexahydrate and 0.375g aluminum nitrate nonahydrate, and use deionized water to prepare 100mL of metal salt solution A. Mixed solution B: Weigh 0.1272g sodium carbonate and 0.3769g ammonium chloride, measure 4.5mL ammonia water, and prepare 100mL of mixed solution using deionized water. The pH of mixed solution B is 10 (the carbonate ion concentration in mixed solution B is 0.012mol / L). S2: Under stirring conditions at room temperature, 100 mL of metal salt solution A is added dropwise to 100 mL of mixed solution to obtain a reaction mixture (in the reaction mixture, Mg...).2+ The concentration is 0.015 mol / L, Al 3+ The concentration was 0.005 mol / L, and the dropping time was approximately ten minutes. S3: Place the reaction mixture into a 300mL reactor and age it at 165℃ for 24 hours; S4: After aging, the solid was washed with deionized water and then dried in an oven at 70°C for 24 hours to obtain carbonate-type magnesium aluminum hydrotalcite.

[0042] The various magnesium-aluminum hydrotalcites obtained in the above embodiments were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), yielding the following results: Figure 1 The XRD pattern shown Figure 2 The SEM image shown and as follows Figure 3 The XRD pattern shown.

[0043] Figure 1 From top to bottom, the XRD patterns of sulfate-type magnesium-aluminum hydrotalcite (LDHs) from Example 4, carbonate-type LDHs from Example 1, nitrate-type LDHs from Example 2, and acetate-type LDHs from Example 3 are shown. The 003 peak is a typical first-joint peak for LDHs, representing the interlayer spacing of the sulfate-type, carbonate-type, nitrate-type, and acetate-type LDHs. The absence of other impurity peaks in the XRD patterns indicates that the LDHs obtained using the synthesis method of this invention have high purity and uniform particle size.

[0044] Figure 2 (a) is a SEM image of the carbonate-type magnesium aluminum hydrotalcite from Example 1. Figure 2 (b) SEM image of the nitrate-type magnesium aluminum hydrotalcite from Example 2. Figure 2 (c) is a SEM image of the acetate-type magnesium aluminum hydrotalcite from Example 3. Figure 2 (d) is a SEM image of the carbonate-type magnesium aluminum hydrotalcite from Example 7. Figure 2 (e) is a SEM image of the sulfate-type magnesium aluminum hydrotalcite of Example 4. Figure 2 The results showed that the average particle size of the carbonate-type magnesium-aluminum hydrotalcite synthesized with high concentration metal ions in Example 1 was approximately 400 nm; the average particle size of the carbonate-type magnesium-aluminum hydrotalcite synthesized with low concentration metal ions in Example 7 was approximately 800 nm; the average particle size of the nitrate-type magnesium-aluminum hydrotalcite in Example 2 was 350 nm; the average particle size of the acetate-type magnesium-aluminum hydrotalcite in Example 3 was 550 nm; and the average particle size of the sulfate-type magnesium-aluminum hydrotalcite in Example 4 was 220 nm. Furthermore, from... Figure 2 As can be seen from the results, the LDHs prepared by this invention have good crystallization and uniform particle size.

[0045] Figure 3 From bottom to top, the images show the nitrate-type LDHs synthesized in Examples 5 and 6, respectively. The XRD patterns show the typical first multiple peak (003) of LDHs, along with other impurity peaks, confirming that Examples 5 and 6 synthesized impurity-free nitrate-type magnesium-aluminum hydrotalcite. Testing revealed that the average particle size of the nitrate-type LDHs synthesized in Example 5 was approximately 200 nm, and the average particle size of the nitrate-type LDHs synthesized in Example 6 was approximately 210 nm.

[0046] Figure 4 The image shows the XRD pattern of the carbonate-type LDHs obtained in Example 7. From... Figure 4 It can be seen that the typical first peak 003 of carbonate-type LDHs appeared, and other impurity peaks also appeared, proving that Example 7 synthesized impurity-free carbonate-type magnesium aluminum hydrotalcite.

[0047] Based on the above analysis, it can be seen that by controlling the concentration of metal ions, aging conditions and the concentration of target anions, this invention has successfully synthesized hydrotalcite-like materials with an average particle size of 200-1000 nm, which meets the current demand for large-sized hydrotalcite-like materials. Moreover, the synthesis method is simple, universal, and suitable for industrial scale-up production.

[0048] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0049] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and refinements without departing from the principles of this invention, and these improvements and refinements are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for synthesizing a hydrotalcite-like substance, characterized in that, include: The metal salt solution is added dropwise to a mixed solution of ammonia-ammonium chloride buffer and the target anionic salt to obtain a reaction mixture. The reaction mixture is heated to 100-180℃ and aged for 8-48 hours to obtain the hydrotalcite-like substance. The metal ions in the metal salt solution include divalent metal ions and trivalent metal ions. In the reaction mixture, the concentration of the divalent metal ions is 0.01-0.12 mol / L, and the concentration of the trivalent metal ions is 0.001-0.05 mol / L. The concentration of the target anion in the mixed solution is 0.012-10 mol / L.

2. The method for synthesizing hydrotalcite-like materials as described in claim 1, characterized in that, The molar ratio of the divalent metal ions to the trivalent metal ions is (2-4):

1.

3. The method for synthesizing hydrotalcite-like materials as described in claim 1, characterized in that, The divalent metal ions are selected from Mg 2+ Cu 2+ Zn 2+ Fe 2+ Co 2+ Ni 2+ and Ca 2+ One or more of them.

4. The method for synthesizing hydrotalcite-like materials as described in claim 1, characterized in that, The trivalent metal ions are selected from Al. 3+ Fe 3+ Cr 3+ and Ga 3+ One or more of them.

5. The method for synthesizing hydrotalcite-like materials as described in claim 1, characterized in that, The target anions include carbonate-type target anions and non-carbonate-type target anions.

6. The method for synthesizing hydrotalcite-like materials as described in claim 5, characterized in that, The non-carbonate target anion is selected from one of nitrate, sulfate, and acetate.

7. The method for synthesizing hydrotalcite-like minerals as described in claim 5, characterized in that, When the target anion is a non-carbonate type target anion, both the metal salt solution and the mixed solution are prepared using deionized water that has been boiled and cooled to room temperature as the solvent.

8. The method for synthesizing hydrotalcite-like materials as described in claim 5, characterized in that, When the target anion is a non-carbonate type target anion, the step of adding the metal salt solution dropwise to the mixed solution of ammonia-ammonium chloride buffer and the target anion salt to obtain the reaction mixture is carried out in a nitrogen atmosphere.

9. The method for synthesizing hydrotalcite-like materials as described in claim 1, characterized in that, The pH value of the mixed solution is 9-10.

10. A type of hydrotalcite, characterized in that, It is prepared by the synthetic method of hydrotalcite as described in any one of claims 1 to 9.

Images