Preparation method and application of polydisperse flower-ball-shaped magnesium silicate

Abstract

The invention provides a preparation method of polydisperse ball-flower-shaped magnesium silicate. The preparation method comprises the following steps: preparing silicon dioxide precursor particles; treating the silicon dioxide precursor particles with a hydrofluoric acid solution, and then washing and drying to obtain treated precursor particles; putting the treated precursor particles into a buffer solution, ultrasonically dispersing uniformly, adding magnesium salt and glutamic acid, and stirring uniformly to enable Mg < 2 + > and glutamic acid to form a chelate, so as to obtain mixed slurry; and carrying out a hydrothermal reaction on the mixed slurry, and drying and calcining a hydrothermal reaction product to obtain the polydisperse ball-flower-shaped magnesium silicate. The prepared polydisperse ball-flower-shaped magnesium silicate can be used for preparing an adsorbent. Magnesium silicate particles prepared by the method are not easy to agglomerate, have polydispersity and stability and are larger in specific surface area, so that more active sites are exposed out of magnesium silicate, the adsorption performance and catalytic activity of magnesium silicate are improved, and functional modification is easier to carry out.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic chemical materials, and particularly relates to a preparation method and application of polydisperse flower-like magnesium silicate. Background Art

[0002] The layered structure of magnesium silicate endows it with a high specific surface area, which provides abundant active sites for substance adsorption and chemical reactions. The magnesium ions between the layers of magnesium silicate have strong ion exchange ability and can undergo exchange reactions with other cations. This property enables magnesium silicate to exhibit excellent metal ion fixation ability in the field of wastewater treatment, especially for harmful heavy metal ions such as lead (Pb 2+ ), cadmium (Cd 2+ ), copper (Cu 2+ ) etc., showing significant adsorption and removal effects. In addition, the surface of magnesium silicate is rich in active silanol groups (Si-OH). Under acidic conditions, the silanol groups tend to be protonated, making the material surface positively charged; while under alkaline conditions, the silanol groups are deprotonated to form Si-O - , making the surface negatively charged. This controllability of surface charge enables magnesium silicate to exhibit excellent selective adsorption ability for polar substances in water (such as organic dyes, anionic pollutants, etc.), thus having broad application potential in the fields of environmental governance and water treatment.

[0003] There are various synthesis methods for magnesium silicate, mainly including solid-phase method, sol-gel method, hydrothermal method and microwave-assisted method, etc. The solid-phase method directly reacts silicon-containing and magnesium-containing solid raw materials under high-temperature conditions to generate magnesium silicate. However, due to insufficient contact between solid raw materials, the product has a large particle size and uneven distribution, and the morphology and structure are difficult to precisely control. The sol-gel method dissolves silicon source and magnesium source, and then forms a sol through hydrolysis and polycondensation reactions, and then prepares magnesium silicate through steps such as aging, drying and calcination. Although this method can achieve molecular-level mixing, it is prone to particle aggregation, resulting in a wider particle size distribution and a reduced specific surface area of the product. The hydrothermal method reacts under high-temperature and high-pressure conditions to generate magnesium silicate, but due to the complex reaction kinetics, the morphology of the product is difficult to regulate, and the dispersibility is poor, with uneven particle size distribution. The microwave-assisted method uses microwave heating to accelerate the reaction rate. However, the local overheating effect may lead to irregular product morphology, and it is difficult to obtain magnesium silicate materials with specific morphology.

[0004] As an efficient and controllable synthesis strategy, the template method has been widely used in the preparation of magnesium silicate. This method can precisely regulate the morphology, size, and pore structure of magnesium silicate through the guiding effect of the template agent, thereby preparing materials with specific properties, such as mesoporous magnesium silicate, layered magnesium silicate, or porous magnesium silicate. The template method shows significant advantages in morphology and structure regulation, but the magnesium silicate particles prepared by it often have agglomeration phenomena, which seriously affect the actual application performance of the materials. There are multiple factors for the occurrence of agglomeration phenomena: for example, during the removal process of the template agent (such as calcination or washing), if the template agent cannot be completely removed, the residual template agent may cause adhesion between particles; if the reaction conditions are not properly controlled, it may cause particles to aggregate due to excessive surface energy during the growth process. These factors work together to result in uneven particle size distribution and reduced specific surface area of magnesium silicate particles, thereby weakening their performance in actual application scenarios such as adsorption and catalysis. Therefore, the present invention proposes a preparation method of polydisperse flower-like magnesium silicate to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies existing in the prior art and provide a preparation method and application of polydisperse flower-like magnesium silicate. The prepared polydisperse flower-like magnesium silicate has the characteristics of uniform particle size, regular morphology, and good dispersibility.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] (1) The present invention provides a preparation method of polydisperse flower-like magnesium silicate, including:

[0008] S1. Prepare silicon dioxide precursor particles;

[0009] S2. Treat the silicon dioxide precursor particles with an HF solution (slightly etch the surface of the silicon dioxide precursor particles to increase Si-OH sites and open more reaction sites for the reaction between the magnesium source and silicon in the subsequent reaction), then wash and dry to obtain the treated precursor particles;

[0010] S3. Place the treated precursor particles in a buffer solution, ultrasonically disperse them evenly, add a magnesium salt and glutamic acid, and stir evenly to form a chelate of Mg 2+ and glutamic acid to obtain a mixed slurry;

[0011] S4. Perform a hydrothermal reaction on the mixed slurry, dry and calcine the hydrothermal reaction product to obtain polydisperse flower-like magnesium silicate.

[0012] Further, in step S1, the method for preparing the silica precursor particles specifically includes: mixing 1,2-butanediol and triethylene glycol uniformly to obtain a mixed solvent, adding aminopropyltriethoxysilane and a small amount of deionized water for pre-hydrolysis; then, adding choline hydroxide (hydroxyethyltrimethylammonium hydroxide) to adjust the pH of the system to alkaline to promote the polycondensation reaction, and adding sodium citrate, stirring evenly to dynamically control the particle growth and prevent agglomeration; heating the mixed solution for reaction, washing and drying after the reaction is completed to obtain the silica precursor particles.

[0013] Further, the addition ratio of the mixed solvent, aminopropyltriethoxysilane, and sodium citrate is 50-100 ml: 2-10 ml: 0.1-0.3 g; in the mixed solvent, the volume ratio of 1,2-butanediol to triethylene glycol is 2:1.

[0014] Further, the addition ratio of the mixed solvent, aminopropyltriethoxysilane, and sodium citrate is 50-90 ml: 4-8 ml: 0.1-0.3 g.

[0015] Further, the addition ratio of the mixed solvent, aminopropyltriethoxysilane, and sodium citrate is 60 ml: 4.82 ml: 0.147 g.

[0016] Further, after adding choline hydroxide, the pH of the system is adjusted to 9.5; the heating process of the mixed solution is to raise the temperature to 75 °C at a rate of 1 °C / min, and the reaction time is 15 h.

[0017] Further, the process of washing and drying is as follows: diluting the reaction solution obtained after the reaction with acetone to reduce the viscosity, then centrifuging at 8000 rpm for 10 min, washing the separated solid with acetone and ethanol three times each to remove the residual solvent and unreacted substances, and finally drying in vacuo at 60 °C to obtain the silica precursor particles.

[0018] Further, in step S3, the buffer solution is a carbonate buffer solution with pH = 10.5; the magnesium salt is magnesium chloride hexahydrate.

[0019] Further, in step S3, the molar ratio of the treated precursor particles to the magnesium salt is (1-2):(1-3); the molar ratio of the magnesium salt to glutamic acid is (0.5-2):1.

[0020] Further, in step S3, the molar ratio of the treated precursor particles to the magnesium salt is 1.67:1; the molar ratio of the magnesium salt to glutamic acid is 2:1.

[0021] Further, in step S4, the hydrothermal reaction temperature is 70 °C, and the reaction time is 24 h.

[0022] Further, in step S4, the drying process is as follows: putting the hydrothermal reaction product into a vacuum drying oven and drying for 24 hours; the calcination process is as follows: calcining the solid after vacuum drying in an N2 atmosphere at 200 °C for 1 h.

[0023] (II) The present invention also provides an application of the polydisperse flower-like magnesium silicate prepared by the above method in the preparation of an adsorbent.

[0024] Beneficial effects

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] The magnesium silicate particles prepared by the method of the present invention are not easily agglomerated, have polydispersity and stability. Therefore, there is less agglomeration between the particles, and the specific surface area is larger. As a result, more active sites of magnesium silicate are exposed, which is beneficial to improving the adsorption performance and catalytic activity of the material, and it is easier to carry out functional modification, such as grafting organic molecules, loading metal nanoparticles, etc., thereby endowing the material with new functions and characteristics. Description of the drawings

[0027] Figure 1 It is the X-ray powder diffraction pattern of the precursor prepared in step 3 of Example 1;

[0028] Figure 2 It is the scanning electron microscope image of the precursor prepared in step 3 of Example 1. Among them, (a) is the scanning electron microscope image at 2.00K, and (b) is the scanning electron microscope image at 1.00K;

[0029] Figure 3 It is the X-ray powder diffraction pattern of the magnesium silicate product prepared in Example 1;

[0030] Figure 4 It is the scanning electron microscope image of the magnesium silicate product prepared in Example 1. Among them, (a) is the scanning electron microscope image at 2.00K, and (b) is the scanning electron microscope image at 50.0K;

[0031] Figure 5 It is the nitrogen adsorption-desorption curve and BJH pore size analysis diagram of the magnesium silicate product prepared in Example 1;

[0032] Figure 6 It is the scanning electron microscope image of the magnesium silicate product prepared in the comparative example. Among them, (a) is the scanning electron microscope image at 30.0K, and (b) is the scanning electron microscope image at 5.00K. Specific embodiments

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0034] Example 1

[0035] The embodiment of the present invention provides a method for preparing polydisperse flower-like magnesium silicate, which includes the following steps:

[0036] Step 1: Mix 40.0 mL of 1,2-butanediol and 20.0 mL of triethylene glycol. Transfer the solvent to a 250 mL beaker and place it in a constant-temperature oil bath. Stir magnetically at 500 rpm for 30 min at 45 °C to obtain a mixed solvent.

[0037] Step 2: Add 4.82 mL of aminopropyltriethoxysilane to the mixed solvent, and slowly add 5.40 mL of deionized water. Control the feeding rate at 0.5 mL / min. Continuously stir at 45 °C and 500 rpm for 30 minutes to partially hydrolyze the silicon source.

[0038] Then, add 2.18 mL of 45 wt% choline hydroxide aqueous solution, dropwise add it to the reaction system at a rate of 1 mL / min, adjust to pH = 9.50 to promote the polycondensation reaction. Subsequently, add 0.147 g of sodium citrate (to dynamically control particle growth and prevent agglomeration), and continue stirring for 10 min.

[0039] Step 3: Transfer the mixed solution in Step 2 to a 100 mL reaction kettle lined with polytetrafluoroethylene, seal it, and place it in a programmable temperature drying oven to set the heating program: raise the temperature from room temperature to 75 °C at a rate of 1 °C / min, and keep it at the target temperature for 15 hours.

[0040] After the reaction is completed, naturally cool it to room temperature. Pour the reaction solution into a 200 mL beaker, add an equal volume of acetone for dilution to reduce the viscosity, and then centrifuge at 8000 rpm for 10 min to separate the solid product. Wash the separated solid with acetone and ethanol three times each to remove the residual solvent and unreacted substances. Finally, place the product in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain silica precursor particles with good dispersibility.

[0041] Step 4: Mix 2 g of silica precursor particles with 100 mL of a hydrofluoric acid solution with a concentration of 0.2%. After ultrasonic treatment for 90 s, immediately add 100 mL of precooled absolute ethanol to terminate the reaction. Subsequently, centrifuge at a speed of 5000 rpm for 10 min, wash three times with a mixed solution of ethanol and deionized water (1:1, v / v), and finally obtain the modified precursor through drying treatment.

[0042] Step 5: Weigh 2.12 g of anhydrous sodium carbonate (Na2CO3) and 1.680 g of sodium bicarbonate (NaHCO3), dissolve them in 400 mL of deionized water, stir magnetically for 20 min, and then adjust the pH to 10.5 to obtain a carbonate buffer solution.

[0043] Step 6: Take 1.00 g (0.0167 mol) of the modified silica precursor particles and place them in 160 mL of the carbonate buffer solution. After ultrasonic treatment for 10 min to make them evenly dispersed to obtain a suspension, add 2.032 g (0.01 mol) of magnesium chloride hexahydrate (MgCl2·6H2O) and 0.736 g (0.005 mol) of glutamic acid (Glu). Stir and react at a constant temperature of 35°C and 500 rpm for 30 min to form a chelate (which can slowly release magnesium ions) of Mg 2+ with glutamic acid to obtain a mixed slurry.

[0044] Step 7: Transfer the mixed slurry to a reaction kettle lined with polytetrafluoroethylene (PTFE), seal it, and place it in an oven. Heat it to 70°C at a heating rate of 2°C / min and react at a constant temperature for 24 h. After the reaction is completed, naturally cool it to room temperature. Subsequently, place the sample in a vacuum drying oven and dry it for 24 h to obtain the precursor powder. Calcinate the dried sample in a tubular furnace at 200°C under an inert N2 atmosphere for 1 h to remove the residual glutamic acid, and finally obtain a polydisperse flower-like magnesium silicate product.

[0045] Example 2

[0046] Example 2 provides a method for preparing polydisperse flower-like magnesium silicate, which is different from Example 1 in that:

[0047] In Step 2, the addition amounts of the mixed solvent, aminopropyltriethoxysilane, and sodium citrate are 90 ml, 6.57 ml, and 0.214 g, respectively. In the mixed solvent of Step 1, the volumes of 1,2-butanediol and triethylene glycol are 60 ml and 30 ml, respectively.

[0048] In Step 6, the addition amount of the silica precursor particles is 0.6 g (0.01 mol), the addition amount of magnesium chloride hexahydrate is 2.032 g (0.01 mol), and the addition amount of glutamic acid is 1.472 g (0.01 mol).

[0049] Example 3

[0050] Example 3 provides a method for preparing polydisperse flower-like magnesium silicate, which is different from Example 1 in that:

[0051] In step 2, the addition amounts of the mixed solvent, aminopropyltriethoxysilane, and sodium citrate are 80 ml, 7.64 ml, and 0.187 g, respectively. In the mixed solvent of step 1, the volumes of 1,2-butanediol and triethylene glycol are 54 ml and 27 ml, respectively.

[0052] In step 6, the addition amount of the silica precursor particles is 0.6 g (0.01 mol), the addition amount of magnesium chloride hexahydrate is 4.06 g (0.02 mol), and the addition amount of glutamic acid is 1.96 g (0.013 mol).

[0053] Example 4

[0054] Example 4 provides a method for preparing polydisperse flower-like magnesium silicate, which is different from Example 1 in that:

[0055] In step 2, the addition amounts of the mixed solvent, aminopropyltriethoxysilane, and sodium citrate are 70 ml, 5.48 ml, and 0.243 g, respectively. In the mixed solvent of step 1, the volumes of 1,2-butanediol and triethylene glycol are 46 ml and 24 ml, respectively.

[0056] In step 6, the addition amount of the silica precursor particles is 1.2 g (0.02 mol), the addition amount of magnesium chloride hexahydrate is 2.032 g (0.01 mol), and the addition amount of glutamic acid is 2.94 g (0.02 mol).

[0057] Example 5

[0058] Example 5 provides a method for preparing polydisperse flower-like magnesium silicate, which is different from Example 1 in that:

[0059] In step 2, the addition amounts of the mixed solvent, aminopropyltriethoxysilane, and sodium citrate are 50 ml, 4.47 ml, and 0.125 g, respectively. In the mixed solvent of step 1, the volumes of 1,2-butanediol and triethylene glycol are 34 ml and 17 ml, respectively.

[0060] In step 6, the addition amount of the silica precursor particles is 0.6 g (0.01 mol), the addition amount of magnesium chloride hexahydrate is 6.09 g (0.03 mol), and the addition amount of glutamic acid is 2.205 g (0.015 mol).

[0061] Comparative Example

[0062] The comparative example provides a method for preparing magnesium silicate, which is different from Example 1 in that:

[0063] In step 2, sodium citrate is not added, and in step 6, glutamic acid is not added.

[0064] Effect test:

[0065] 1. Morphology characterization:

[0066] The morphology and structure of the silica precursor particles prepared in step 3 of Example 1 were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to analyze their crystal structure and morphological characteristics. The results are as Figure 1 and Figure 2 shown. Figure 1 is the X-ray diffraction pattern, Figure 2 and Figure 1 is the scanning electron microscopy image. From Figure 2 it can be seen that the silica precursor prepared in Example 1 has good dispersibility.

[0067] The morphology and structure of the magnesium silicate product prepared in Example 1 were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results are as Figure 3 and Figure 4 shown. In addition, the specific surface area and pore structure of the material were characterized by nitrogen adsorption-desorption curves and BJH pore size distribution analysis, as Figure 5 shown.

[0068] The morphology of the magnesium silicate product prepared in the comparative example was characterized by scanning electron microscopy (SEM). The results are as Figure 6 shown.

[0069] From Figures 3 - 6 it can be seen that compared with the comparative example, the magnesium silicate prepared in Example 1 of the present invention is in the shape of a flower ball, has good dispersibility, and has a larger specific surface area.

[0070] 2. Adsorption test:

[0071] Test method: Add 20 mg of magnesium silicate sample to 50 mL of methylene blue solution with a concentration of 200 mg / L, and conduct an adsorption experiment at an oscillation rate of 150 rpm for 12 h. After adsorption, take 1 mL of the liquid sample and centrifuge to remove solid particles. After diluting the supernatant to an appropriate multiple, measure its absorbance using a UV-visible spectrophotometer at the maximum absorption wavelength of methylene blue (usually 664 nm). Calculate the remaining concentration of methylene blue in the solution according to the standard curve, and calculate the adsorption amount of magnesium silicate to methylene blue in combination with the initial concentration.

[0072] The adsorption performance of the magnesium silicate samples prepared in Examples 1 to 5 and the comparative example was tested according to the above method to obtain the adsorption amount of each sample. The specific data are shown in Table 1. It can be seen from Table 1 that compared with the comparative example, the magnesium silicate prepared in the present invention has a higher adsorption capacity and stronger adsorption performance.

[0073] Table 1: Adsorption capacity of magnesium silicate prepared in Examples 1-5 and Comparative Examples

[0074] Adsorption capacity (mg / g) Example 1 183.0673 Example 2 164.0673 Example 3 166.6434 Example 4 178.3447 Example 5 158.6767 Comparative example 99.5678

[0075] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any variations or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of polydisperse flower-like magnesium silicate, characterized in that, Comprising: S1. Prepare silica precursor particles; S2. Treat the silica precursor particles with a hydrofluoric acid solution, wash and dry them to obtain the treated precursor particles; S3. Place the treated precursor particles into a buffer solution, ultrasonically disperse them evenly, add a magnesium salt and glutamic acid, and stir evenly to obtain a mixed slurry; S4. Perform a hydrothermal reaction on the mixed slurry, dry and calcine the hydrothermal reaction product to obtain polydisperse flower-like magnesium silicate.

2. The method for preparing polydisperse flower-like magnesium silicate according to claim 1, wherein in step S1, the method for preparing the silica precursor particles specifically includes: Mix 1,2-butanediol and triethylene glycol evenly to obtain a mixed solvent, add 3-aminopropyltriethoxysilane and deionized water for pre-hydrolysis; then, add choline hydroxide to adjust the pH of the system, and add sodium citrate, and stir evenly; Heat the mixed solution for reaction, wash and dry after the reaction is completed to obtain silica precursor particles.

3. The method for preparing polydisperse flower-like magnesium silicate according to claim 2, wherein the addition ratio of the mixed solvent, 3-aminopropyltriethoxysilane, and sodium citrate is 50-100 ml: 2-10 ml: 0.1-0.3 g; in the mixed solvent, the volume ratio of 1,2-butanediol to triethylene glycol is 2:

1.

4. The method for preparing polydisperse flower-like magnesium silicate according to claim 2, wherein the pH of the system is adjusted to 9.5 after adding choline hydroxide; the heating process of the mixed solution is to raise the temperature to 75 °C at a rate of 1 °C / min, and the reaction time is 15 h.

5. The method for preparing polydisperse flower-like magnesium silicate according to claim 2, wherein the process of washing and drying is as follows: Dilute the reaction solution obtained after the reaction is completed with acetone, then centrifuge and separate, wash the separated solid with acetone and ethanol three times in sequence, and finally dry it in vacuum at 60 °C to obtain silica precursor particles.

6. The method for preparing polydisperse flower-like magnesium silicate according to claim 1, wherein in step S3, the buffer solution is a carbonate buffer solution with pH = 10.5; the magnesium salt is magnesium chloride hexahydrate.

7. The method for preparing polydisperse flower-like magnesium silicate according to claim 1, wherein in step S3, the molar ratio of the treated precursor particles to the magnesium salt is (1-2):(1-3); the molar ratio of the magnesium salt to glutamic acid is (0.5-2):

1.

8. The method for preparing polydisperse flower-like magnesium silicate according to claim 1, wherein in step S4, the hydrothermal reaction temperature is 70 °C, and the reaction time is 24 h.

9. The method for preparing polydisperse flower-like magnesium silicate according to claim 1, wherein in step S4, the drying process is: place the hydrothermal reaction product in a vacuum drying oven and dry for 24 hours; the calcination process is: calcine the solid after vacuum drying in an N2 atmosphere at 200 °C for 1 h.

10. Use of the polydisperse flower-like magnesium silicate prepared by the method according to any one of claims 1-9 in the preparation of an adsorbent.

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