Preparation method of diatomite-based LDHs composite structure material
By using metal salt solution dispersion and alkaline solution regulation at room temperature, the synchronous opening of diatomite pores and in-situ growth of LDHs were achieved, solving the problems of complex processes, high energy consumption and low carrier utilization in existing technologies. A composite material with high stability and high carrier utilization was obtained, which is suitable for environmental protection and chemical fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING INST OF NEW ENE STOR MATER & EQUIP
- Filing Date
- 2026-03-13
- Publication Date
- 2026-06-02
AI Technical Summary
Existing diatomaceous earth-based LDHs material preparation technologies suffer from problems such as complex processes, high energy consumption, low carrier utilization, and poor product consistency. In particular, traditional acid activation and high-temperature calcination lead to environmental pollution and structural damage, and LDHs are prone to agglomeration, making it impossible for them to effectively nucleate and grow inside the pores.
A room-temperature process using metal salt solution dispersion and alkali solution control is adopted. By stirring and adding alkali solution at room temperature, the pore size of diatomite is opened simultaneously and LDHs are grown in situ. This avoids the acid activation and high-temperature pore expansion steps. Metal ions form coordination adsorption on the surface of diatomite, and with the help of alkali solution etching, LDHs are nucleated in situ in the pores and on the surface.
The process was simplified, energy consumption was reduced, carrier utilization was improved, and LDHs were uniformly distributed on the surface and in the pores of diatomaceous earth, which improved the stability and consistency of the material and made it suitable for functional applications in the fields of environmental protection and chemical industry.
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Figure CN122124747A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of composite structural material preparation technology, specifically relating to a method for preparing a diatomaceous earth-based LDHs composite structural material. Background Technology
[0002] Diatomaceous earth, as a natural siliceous mineral, is often used as a carrier for composite adsorbents and catalytic materials due to its porous structure, high specific surface area, and low cost. Layered bimetallic hydroxides (LDHs) possess a unique layered structure and tunable metal ion composition, exhibiting excellent performance in adsorption and catalysis. LDHs The defects of nanosheets, such as easy aggregation and poor mechanical stability, limit their practical application. Combining LDHs with diatomaceous earth is an effective way to solve this problem.
[0003] Existing technologies for preparing diatomaceous earth-based LDHs materials have significant drawbacks: On the one hand, to address the issues of blocked pores and low carrier utilization in diatomaceous earth, traditional processes require separate pore-expansion steps such as acid activation and high-temperature calcination. This not only increases process complexity and production costs but may also lead to structural damage and environmental pollution of the diatomaceous earth. On the other hand, if the pore-expansion step is omitted, LDHs can only adhere simply to the surface of the diatomaceous earth, failing to penetrate the pores and easily agglomerating, making it difficult to achieve structural synergy and ultimately affecting material performance. Furthermore, some room-temperature preparation methods lack effective synergistic control mechanisms, failing to simultaneously achieve pore expansion and in-situ growth of LDHs, resulting in poor product consistency and significant challenges in large-scale production.
[0004] Therefore, developing a room-temperature preparation method that can simultaneously achieve diatomite pore opening and in-situ growth of LDHs without additional pore-expanding steps is of great significance for simplifying the process, reducing energy consumption, improving carrier utilization and material stability, and is also a key breakthrough for promoting the industrial application of diatomite-based composite functional materials.
[0005] This application is submitted in order to address the above issues. Summary of the Invention
[0006] This application discloses a method for preparing an acid-free, simultaneously activated, pore-expanding, and in-situ grown diatomaceous earth-based LDHs composite material. This method abandons traditional acid activation or high-temperature pore-expanding steps, using natural disc-shaped diatomaceous earth as a carrier. Through a room-temperature process of "metal salt solution dispersion - alkali solution control," it simultaneously opens the original blocked pores of the diatomaceous earth and allows LDHs to grow in situ on its surface and within the pores. This method is particularly suitable for the industrial production of functional composite materials requiring high carrier utilization and low preparation costs.
[0007] The first aspect of this application provides a method for preparing a diatomaceous earth-based LDHs composite structural material, the method comprising the following steps:
[0008] A. Preparation of mixed metal salt solution: Dissolve divalent and trivalent metal salts in water, stirring until completely dissolved, to obtain a total concentration of 0.5~1.0. A mol / L mixed solution of metal salts;
[0009] B. Synchronous pore-expanding-in-situ composite preparation: Diatomaceous earth is added to the metal salt mixed solution from step A, controlling the diatomaceous earth feeding ratio to be 33.3~66.6. g / L, at room temperature 300~500 Stirring speed 20~60 r / min min, allowing metal ions to be fully adsorbed onto the hydroxyl sites on the diatomaceous earth surface; then 2~5 min. Add NaOH aqueous solution dropwise at a rate of mL / min to adjust the pH of the system to 9-10;
[0010] The concentration of the NaOH aqueous solution is 0.5~1.0%. mol / L;
[0011] C. Post-processing: After adjusting the pH of the system to 9-10 in step B, filter the product, wash with water until the pH of the filtrate is 7-8, and dry at 60-80℃ for 24-48 days. h, diatomaceous earth-based LDHs composite structural material was obtained.
[0012] The LDHs loading of the material is calculated by the weight difference method. The calculation formula is: Loading (%) = (m2-m1) / m2×100%, where m1 is the mass of diatomaceous earth fed in step B and m2 is the dry mass of the composite structure material in step C.
[0013] Preferably, the metal salt is one of a nitrate, a chloride, or a sulfate.
[0014] Preferably, the divalent metal salt comprises one or two divalent metal ions, and the trivalent metal salt comprises one or two trivalent metal ions;
[0015] In the metal salt mixed solution, the ratio of the total moles of divalent metal ions to the total moles of trivalent metal ions is 2~4:1.
[0016] Preferably, the divalent metal ion is selected from one or more of magnesium ions, zinc ions, divalent nickel ions, and divalent iron ions;
[0017] The trivalent metal ion is an aluminum ion.
[0018] Preferably, the room temperature is 20-25 degrees Celsius.
[0019] Preferably, the diatomite is disc-shaped diatomite with a particle size of 25-50 micrometers.
[0020] In step B, the mechanism for simultaneous pore expansion and in-situ growth of LDHs is as follows: by controlling the stirring time after adding the metal salt mixed solution to the diatomaceous earth, metal ions form coordination adsorption with the hydroxyl groups on the surface of the diatomaceous earth, reducing the surface energy of the diatomaceous earth and rapidly enriching active sites. This, combined with the alkaline solution, promotes the absorption of Ca2+ ions adhering to the surface of the diatomaceous earth. 2+ Fe 3+ The slight etching of impurities simultaneously opens the pore size and enhances the interaction between metal ions and OH groups at room temperature through the "site enrichment effect". - The reaction rate ensures rapid nucleation and growth of LDHs (kinetics meet requirements). Simultaneously, metal ions react with OH- in the alkaline solution. - The reaction occurs, and LDHs form a layered structure through in-situ nucleation and growth within open pores and on the surface of diatomaceous earth.
[0021] In step C, the drying method is either forced air drying or vacuum drying, and the vacuum degree during vacuum drying is ≥0.08MPa.
[0022] The second aspect of this application provides a diatomaceous earth-based LDHs composite structural material obtained by the preparation method described in any one of the first aspects.
[0023] Preferably, the diatomaceous earth-based LDHs composite structural material contains diatomaceous earth and LDHs, with the LDHs loaded on the surface and inside the pores of the diatomaceous earth.
[0024] Preferably, the loading of LDHs in the diatomaceous earth-based LDHs composite structure is 55%~75% (mass fraction, calculated by weight difference method), based on the total mass of the diatomaceous earth-based LDHs composite structure material.
[0025] The material exhibits both the characteristic diffraction peaks of diatomaceous earth and the characteristic diffraction peaks of LDHs layered structure, with no extraneous peaks appearing. LDHs are distributed in thin sheets on the surface of diatomaceous earth and within open pores (SEM verification).
[0026] Compared with the prior art, this application has the following advantages:
[0027] (1) Significant process innovation: This application eliminates the traditional acid activation and high-temperature pore expansion steps, and achieves "pore expansion-in-situ growth" in one step through "metal ion adsorption + alkaline control". The traditional process requires additional energy for acid activation heating (50~80℃) and high-temperature calcination pore expansion (300~500℃). This application eliminates the need for this high-energy-consuming step, and only involves room temperature stirring and low-temperature drying (60~80℃). The process steps are simplified by more than 50%, and no acid reagents, high-temperature equipment and additional pore expansion agents are required. Compared with the traditional process, energy consumption is reduced by more than 40%. It is simple to operate, environmentally friendly, and meets the needs of low-cost industrial production.
[0028] (2) Outstanding structural synergistic advantages: After synchronous pore expansion, the original pore size of the diatomaceous earth is in an open state (SEM verification). LDHs grow in situ at two sites in the pores and on the surface (SEM verification). This not only effectively inhibits the aggregation of LDH nanosheets, but also expands the carrier utilization rate from the single site utilization on the surface in the traditional process to the dual site utilization on the surface and pores. Compared with traditional surface-attached materials, the carrier utilization rate of the composite material in this application is increased by 30%~50%, forming a synergistic structure of "open pores-layered LDHs".
[0029] (3) Wide range of applications: This material retains the porous properties of diatomite and the layered structure of LDHs, providing a good structural basis for functional applications such as adsorption of heavy metal ions and catalytic degradation of pollutants. It can be widely used in environmental protection, chemical industry and other fields, and has a broad market prospect.
[0030] (4) The existing technology generally involves adding diatomaceous earth to a mixed solution of metal salts, then directly adding NaOH aqueous solution and allowing it to stand for aging to improve the crystallinity of the material.
[0031] During the preparation process, this application unexpectedly discovered that stirring the diatomaceous earth after adding it to a metal salt mixture solution and before adding the NaOH aqueous solution resulted in an unexpected technical effect of "simultaneous pore expansion-in-situ growth of LDHs". The stirring time is particularly important. Insufficient stirring time (e.g., 2 minutes) prevents the metal ions from fully adsorbing onto the hydroxyl sites on the diatomaceous earth surface, leading to uneven reaction, the formation of non-target impurity phases, severe LDH aggregation, and insufficient pore opening, thus failing to achieve the synergistic effect of "simultaneous pore expansion-in-situ growth".
[0032] Furthermore, after the NaOH aqueous solution is added, the target material can be obtained directly by filtering, washing, and drying the product without aging.
[0033] (5) Another innovation of this application lies in room temperature pore expansion. The pore expansion process of this application at room temperature breaks through the bottleneck of traditional technology—traditional pore expansion processes require high-temperature calcination (300~500℃) or acid activation to open the pores of diatomaceous earth and promote the growth of LDHs. However, this application achieves simultaneous "pore expansion-in-situ growth" at room temperature through the synergistic design of "metal ion coordination adsorption + slight etching with single NaOH alkaline solution": by controlling the stirring time, metal ions are first adsorbed on the hydroxyl groups on the surface of diatomaceous earth, reducing the surface energy and providing sites for the nucleation of LDHs; when the alkaline solution is slowly added, it not only etches impurities to open the pores, but also reacts rapidly with the adsorbed metal ions to generate LDHs, avoiding the problem of slow reaction rate at room temperature. This is something that the prior art has not realized. Attached Figure Description
[0034] Figure 1 The images show the XRD patterns of the pretreated diatomaceous earth (DE) in Example 1, the composite structural material DE@MgAl-LDHs in Example 1, and the composite structural material DE@ZnNiAl-LDHs in Example 2.
[0035] Figure 2 The material used in Example 1 (stirred for 20 minutes) min DE@MgAl-LDHs, labeled DE@MgAl-LDHs-20), and the material of Comparative Example 1 (stirred for 2 hours). min DE@MgAl-LDHs, labeled DE@MgAl-LDHs-2), materials from Example 3 (stirred for 60 minutes) min XRD patterns of DE@MgAl-LDHs (labeled as DE@MgAl-LDHs-60).
[0036] Figure 3 This is a SEM image of the pretreated diatomaceous earth (DE) from Example 1.
[0037] Figure 4 This is a SEM image of DE@MgAl-LDHs-20 in Example 1.
[0038] Figure 5 This is a magnified SEM image of DE@MgAl-LDHs-20 in Example 1.
[0039] Figure 6 This is a SEM image of DE@ZnNiAl-LDHs in Example 2.
[0040] Figure 7 The image shows the SEM image of DE@MgAl-LDHs-2 in Comparative Example 1.
[0041] Figure 8 This is a SEM image of DE@MgAl-LDHs-60 in Example 3. Detailed Implementation
[0042] The present application will be described below with reference to specific embodiments, but the implementation of the present application is not limited thereto. Experimental methods not specifically described in the embodiments generally use conventional conditions, conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified. The raw materials required in the following embodiments and comparative examples are all commercially available.
[0043] Addressing the core pain points of existing diatomaceous earth-based LDHs preparation processes—namely, the need for separate pore expansion, cumbersome steps, high energy consumption, uneven LDHs dispersion, and low carrier utilization—this application aims to provide a method for preparing acid-free, simultaneous pore expansion and in-situ growth diatomaceous earth-based LDHs composite materials. Through process innovation, this method achieves a one-step "pore expansion-composite" process, simplifying operations, reducing energy consumption, and obtaining structurally stable LDHs. Composite structural materials with uniform dispersion and high carrier utilization.
[0044] The specific preparation method of this application is as follows:
[0045] Select disc-shaped diatomaceous earth and sieve it to remove large particles of impurities. No acid activation treatment is required, thus preserving the original structural integrity of the diatomaceous earth.
[0046] Based on the target composite structure requirements, select a binary or ternary metal salt (nitrate, chloride, or sulfate), dissolve it in deionized water, and stir until completely dissolved to prepare a concentration of 0.5~1.0 mol / L. A mixed solution of metal salts. In the binary metal salt system, the molar ratio of divalent metal ions to trivalent metal ions is controlled at 2~4:1; in the ternary metal salt system, the ratio of the total molar number of divalent metal ions to the total molar number of trivalent metal ions is controlled at 2~4:1. This ratio range can ensure the stable crystallization of the layered structure of LDHs.
[0047] Pretreated diatomaceous earth was added to a mixed solution of metal salts, with the diatomaceous earth feed ratio controlled at 33.3~66.6. g / L, at room temperature 300~500 Magnetic stirring speed 20~60 r / min The stirring process serves the following purposes: it allows metal ions to be fully adsorbed onto the hydroxyl sites on the diatomaceous earth surface through coordination, forming high-density active centers, thus enabling LDHs to function at room temperature. The kinetic rate of nucleation growth is significantly improved, and efficient composite can be completed without high temperature; at the same time, the surface energy of diatomaceous earth is reduced, and pore expansion is achieved simultaneously with the subsequent alkaline solution action.
[0048] Then 2~5 Slowly add NaOH alkaline solution (NaOH alkaline solution concentration 0.5~1.0 mL / min) dropwise. The system pH was adjusted to 9-10 by adjusting the alkali solution (mol / L). The hydroxide ions in the alkali solution slightly etched the impurities such as CaCO3 and Fe2O3 attached to the surface of diatomaceous earth, realizing the simultaneous opening of the original blocked pores of diatomaceous earth (SEM verification). On the other hand, it reacted with the adsorbed metal ions to promote the in-situ nucleation and growth of LDHs in the open pores and on the surface of diatomaceous earth.
[0049] After the reaction is complete, the product is centrifuged and filtered, and repeatedly washed with deionized water until the pH of the filtrate reaches 7-8 to remove unreacted metal ions and alkaline residue; the filter cake is then dried at 60-80℃ for 24-48 days. h (drying by forced air or vacuum, with a vacuum degree ≥0.08 during vacuum drying) The acid-free activated synchronous pore-expanding-in-situ growth type diatomite-based LDHs composite structural material was obtained by (MPa). The LDHs loading was calculated by the weight difference method, with the formula: Loading (%) = (m2-m1) / m2×100%, where m1 is the mass of dried diatomite fed in and m2 is the mass of the dried composite structural material.
[0050] The following provides further details about this application. The disc-shaped diatomaceous earth used herein was purchased from Shanghai McLean Biochemical Technology Co., Ltd.
[0051] Example 1: Binary Mg 2+ / Al 3+ System of diatomaceous earth-based LDHs composite structural materials
[0052] (1) Diatomite pretreatment: The purchased disc-shaped diatomite is passed through a 300-mesh sieve to remove large particle impurities, resulting in disc-shaped diatomite particles with a particle size of 25-50 micrometers.
[0053] (2) Preparation of mixed metal salt solution: Weigh 4.6154 g Mg(NO3)2 . 6H2O (0.018) mol) and 2.2508 g Al(NO3)3 . 9H2O (0.006) mol), dissolved in 30 In mL of deionized water, stir until completely dissolved to obtain Mg. 2+ / Al 3+ Molar ratio 3:1, total concentration 0.8 A mol / L mixed solution of metal salts;
[0054] (3) Synchronous pore enlargement-in-situ composite preparation: Weigh 1 g sieved diatomaceous earth (m1=1) g) Add to the above metal salt mixed solution, i.e., the diatomaceous earth feed ratio is 33.3 g / L, and at room temperature (approximately 25°C) at a rate of 300... Magnetic stirring at a speed of 20 r / min min; then 5 Add 0.5 mL / min dropwise. Add a mol / L NaOH aqueous solution, adjust the pH of the system to 9.5, and the reaction is complete;
[0055] (4) Post-treatment: After the reaction is complete, the solid product is filtered, washed with deionized water until the pH of the filtrate is 7.5, and dried in a 60℃ forced-air drying oven for 48 hours. h, a diatomaceous earth-based magnesium-aluminum layered bimetallic hydroxide composite material (DE@MgAl-LDHs, or denoted as DE@MgAl-LDHs-20) was obtained, with a mass of m2 = 2.41 after drying. g.
[0056] (5) Performance characterization and results
[0057] LDHs load calculation: According to the weight difference method, load = (2.41-1) / 2.41×100%≈59%.
[0058] XRD patterns: Figure 1 The pretreated raw diatomaceous earth (DE) and composite structural material in Example 1 XRD patterns of DE@MgAl-LDHs. (From...) Figure 1 As can be seen, DE@MgAl-LDHs exhibits the characteristic diffraction peak of diatomite at 2θ=21.9°, and also displays typical characteristic peaks of MgAl-LDHs at 2θ=11.4° and 61.0°. All characteristic peaks are sharp and free of obvious impurities, indicating good crystallinity and phase purity, fully demonstrating the successful composite of diatomite and MgAl-LDHs, and the successful synthesis of the target material.
[0059] SEM characterization: Figure 3 This is a SEM image of the original diatomaceous earth (DE) in Example 1. Figure 4 This is a SEM image of DE@MgAl-LDHs-20 in Example 1. Figure 5 This is a magnified SEM image of DE@MgAl-LDHs-20 in Example 1. Figure 5 It can be seen that, compared to Figure 3 Diatomite has a high degree of pore openness, and obvious LDH growth traces can be seen in the pores. The LDHs have a nanosheet structure.
[0060] Example 2: Ternary Zn 2+ / Ni 2+ / Al 3+ System of diatomaceous earth-based LDHs composite structural materials
[0061] (1) Diatomite pretreatment: The purchased disc-shaped diatomite is passed through a 300-mesh sieve to remove large particle impurities, resulting in disc-shaped diatomite particles with a particle size of 25-50 micrometers.
[0062] (2) Preparation of mixed metal salt solution: Weigh 2.6168 g Ni(NO3)2 . 6H2O (0.009) mol), 2.6774 g Zn(NO3)2 . 6H2O (0.009) mol) and 2.2508 g Al(NO3)3 . 9H2O (0.006) mol), dissolved in 30 Dissolved in mL of deionized water by stirring until completely dissolved, yielding (Zn) 2+ +Ni 2+ ) / Al 3+ Molar ratio 3:1, total concentration 0.8 A mol / L mixed solution of metal salts.
[0063] (3) Synchronous pore enlargement-in-situ composite preparation: Weigh 1 g sieved diatomaceous earth (m1=1) g) Add to the above metal salt mixed solution, i.e., the diatomaceous earth feed ratio is 33.3 g / L, and at room temperature (approximately 25°C) at a concentration of 500... r / min Magnetic Stirring 60 min; then 2 Drop 1 mL / min mol / L Use NaOH alkaline solution to adjust the pH of the system to 9.3, and the reaction will end.
[0064] (4) Post-processing: After the reaction was completed, the product was filtered, washed with deionized water until the pH of the filtrate was 7.5, and dried in an 80℃ forced-air drying oven for 24 h to obtain diatomaceous earth-based zinc-nickel-aluminum layered bimetallic hydroxide composite material (DE@ZnNiAl-LDHs). The mass after drying was m2 = 3.72. g.
[0065] (5) Performance characterization and results
[0066] LDHs load calculation: According to the weight difference method, load = (3.72-1) / 3.72×100%≈73%.
[0067] XRD patterns: The XRD pattern of the composite material DE@ZnNiAl-LDHs in Example 2 is shown below. Figure 1 .Depend on Figure 1 It can be seen that in the XRD pattern of the DE@ZnNiAl-LDHs composite material, a distinct diatomite characteristic diffraction peak appears at 2θ=21.9°, while typical ZnNiAl-LDHs layered bimetallic hydroxide characteristic diffraction peaks appear at 2θ=11.4° and 61.0°. All diffraction peaks are sharp and without obvious impurity peaks, indicating that the product has high crystallinity and phase purity, and that diatomite and LDHs were successfully composited without the formation of obvious impurity phases.
[0068] SEM characterization: Figure 6 This is a SEM image of DE@ZnNiAl-LDHs in Example 2. Figure 6 It is evident that diatomaceous earth has a high degree of pore openness, and obvious LDH growth traces can be seen in the pores, with LDHs appearing as nanosheets.
[0069] Comparative Example 1: DE@MgAl-LDHs (DE@MgAl-LDHs-2) were prepared by stirring for 2 minutes.
[0070] (1) Diatomite pretreatment: Same as in Example 1.
[0071] (2) Preparation of mixed metal salt solution: Same as in Example 1 (Mg 2+ / Al 3+ Molar ratio 3:1, concentration 0.8 mol / L).
[0072] (3) Synchronous pore enlargement-in-situ composite preparation: Weigh 1 g sieved diatomaceous earth (m1=1) g) Add to the above metal salt mixed solution, and at 25°C, use 300... magnetic stirring at a speed of r / min 2 min; then 5 Add 0.5 mL / min dropwise. mol / L Use NaOH alkaline solution to adjust the pH of the system to 9.5, and the reaction will end.
[0073] (4) Post-treatment: Same as in Example 1 (wash until the filtrate pH=7.5, dry at 60℃ for 48 hours). h), a diatomaceous earth-based magnesium-aluminum layered bimetallic hydroxide composite material (DE@MgAl-LDHs-2) was obtained, and its mass after drying was measured to be m2=2.79. g.
[0074] (5) Performance characterization and results:
[0075] LDHs Load calculation: According to the weight difference method, load = (2.79-1) / 2.79×100%≈64%.
[0076] XRD patterns: Comparative Example 1 material (stirred for 2 minutes) min The XRD pattern of DE@MgAl-LDHs (labeled as DE@MgAl-LDHs-2) is shown below. Figure 2 . Figure 2 As can be seen, the DE@MgAl-LDHs-2 spectrum shows characteristic peaks of diatomite and LDHs. The intensity of the LDHs peak is weaker than that in Example 1, and non-target impurity peaks (attributed to amorphous metal hydroxides) appear near 28.5°.
[0077] SEM characterization: Figure 7 The image shows the SEM image of DE@MgAl-LDHs-2 in Comparative Example 1. Figure 7 It is evident that LDHs are predominantly characterized by large aggregates, compared to... Figure 4 Diatomite has a low degree of pore opening.
[0078] Example 3: Preparation of DE@MgAl-LDHs (DE@MgAl-LDHs-60) by stirring for 60 minutes
[0079] (1) Diatomaceous earth pretreatment: Same as in Example 1, weigh 1 g sieved diatomaceous earth (m1=1) g).
[0080] (2) Preparation of mixed metal salt solution: Same as in Example 1 (Mg 2+ / Al 3+ Molar ratio 3:1, concentration 0.8 mol / L);
[0081] (3) Synchronous pore enlargement-in-situ composite preparation: Weigh 1 1 g of sieved diatomaceous earth (m1=1 g) was added to the above metal salt mixed solution, and the solution was heated at 300 °C at room temperature (25 °C). Magnetic stirring speed 60 r / min min; then 5 Add 0.5 mL / min dropwise. mol / L Use NaOH alkaline solution to adjust the pH of the system to 9.5, and the reaction will end.
[0082] (4) Post-treatment: Same as in Example 1 (wash until the filtrate pH=7.5, dry at 60℃ for 48 hours). h), a diatomaceous earth-based magnesium-aluminum layered bimetallic hydroxide composite material (DE@MgAl-LDHs-60) was obtained, and its mass after drying was measured to be m2=3.20. g.
[0083] (5) Performance characterization and results
[0084] LDHs Load calculation: According to the weight difference method, load = (3.20-1) / 3.20×100%≈69%.
[0085] XRD pattern: Example 3 (stirring for 60 minutes) min The XRD pattern of DE@MgAl-LDHs (labeled DE@MgAl-LDHs-60) is shown below. Figure 2 . Figure 2 It can be seen that characteristic peaks of diatomaceous earth and LDHs are present, with the LDHs peak intensity being stronger than that of Example 1 and Comparative Example 1.
[0086] SEM characterization: Figure 8 This is a SEM image of DE@MgAl-LDHs-60 from Example 3. The diatomaceous earth has a high degree of pore openness, and obvious LDHs growth traces are visible within the pores. The LDHs are in the form of nanosheets.
[0087] By comparing Example 1 with Comparative Examples 1 and 3, the following conclusions can be drawn:
[0088] The stirring time before adding NaOH aqueous solution after adding diatomaceous earth to the metal salt mixture in step A is particularly important.
[0089] 1. When the stirring time is insufficient (e.g., 2 min), metal ions cannot be fully adsorbed onto the hydroxyl sites on the diatomaceous earth surface, resulting in uneven reaction, generation of non-target impurity phases, severe LDH aggregation, and insufficient pore opening. Although the material loading is 64% (within the range of 55%~75%), significant structural and crystallization defects prevent the achievement of the synergistic effect of "synchronous pore expansion-in-situ growth".
[0090] 2. When the stirring time is 20~60min, metal ions form stable coordination adsorption, avoiding the formation of impurity phases. The LDHs loading is stable at 59%~69%, and the crystallinity is high and the pore size is fully open, proving that this range is the optimal range that balances process effect and energy consumption.
[0091] 3. When the stirring time was extended to 60 min, the crystallinity and pore opening rate of LDHs were slightly better than those of the 20 min group, but the loading increased by only 17%. This indicates that 20 min is sufficient to meet the requirement of "sufficient adsorption", and there is no significant gain from stirring for too long, which further verifies the scientific validity and rationality of the "20~60 min" limit in this application.
Claims
1. A method for preparing a diatomaceous earth-based LDHs composite structural material, characterized in that, The preparation method includes the following steps: A. Preparation of mixed metal salt solution: Dissolve divalent and trivalent metal salts in water and stir until completely dissolved to obtain a mixed metal salt solution with a total concentration of 0.5~1.0 mol / L; B. Synchronous pore expansion-in-situ composite preparation: Diatomaceous earth is added to the metal salt mixed solution in step A, and the diatomaceous earth feeding ratio is controlled at 33.3~66.6 g / L. The mixture is stirred at 300~500 r / min for 20~60 min at room temperature. Then, NaOH aqueous solution is added dropwise at a rate of 2~5 mL / min to adjust the pH of the system to 9~10. The concentration of the NaOH aqueous solution is 0.5~1.0 mol / L; C. Post-processing: After adjusting the pH of the system to 9-10 in step B, filter the product, wash it with water until the pH of the filtrate is 7-8, and dry it at 60-80℃ for 24-48 hours to obtain diatomaceous earth-based LDHs composite structural material.
2. The method for preparing the diatomaceous earth-based LDHs composite structural material according to claim 1, characterized in that, The metal salt is one of nitrate, chloride, or sulfate.
3. The method for preparing the diatomaceous earth-based LDHs composite structural material according to claim 1, characterized in that, The divalent metal salt comprises one or two divalent metal ions, and the trivalent metal salt comprises one or two trivalent metal ions; In the metal salt mixed solution, the ratio of the total moles of divalent metal ions to the total moles of trivalent metal ions is 2~4:
1.
4. The method for preparing the diatomaceous earth-based LDHs composite structural material according to claim 3, characterized in that, The divalent metal ions are selected from one or more of magnesium ions, zinc ions, divalent nickel ions, and divalent iron ions; The trivalent metal ion is an aluminum ion.
5. The method for preparing the diatomaceous earth-based LDHs composite structural material according to claim 3, characterized in that, The room temperature is 20-25 degrees Celsius.
6. The method for preparing the diatomaceous earth-based LDHs composite structural material according to claim 3, characterized in that, The diatomite is disc-shaped diatomite with a particle size of 25-50 micrometers.
7. The diatomaceous earth-based LDHs composite structural material obtained by the preparation method according to any one of claims 1-6.
8. The diatomaceous earth-based LDHs composite structural material according to claim 7, characterized in that, The diatomite-based LDHs composite structural material contains diatomite and LDHs, with the LDHs loaded on the surface and inside the pores of the diatomite.
9. The diatomaceous earth-based LDHs composite structural material according to claim 7, characterized in that, The loading of LDHs in the diatomaceous earth-based LDHs composite structural material is 55% to 75%, based on the total mass of the diatomaceous earth-based LDHs composite structural material.