Hydrophobic zeolite / cement / silica sol composite microspheres and a method for preparing the same

Abstract

The application discloses a hydrophobic zeolite / cement / silica sol composite microsphere and a preparation method thereof. The method comprises the following steps: step 1, mixing natural zeolite and an acid solution with a concentration of 3-8 mol / L according to a proportion of (80-160 g):1L, reacting at 70-90 DEG C for 12-48 hours, then washing, suction filtering, drying and grinding in sequence to obtain high-silicon zeolite; step 2, mixing and uniformly stirring high-silicon zeolite, cement and silica sol cementing material according to a proportion of (600-1000 g):(80-160 g):1L, then loading into a mold, demolding and drying in sequence after solidification to obtain the zeolite / cement / silica sol composite microsphere; and step 3, dissolving a coupling agent in alcohol to prepare a coupling agent / alcohol solution with a concentration of 0.05%-10%, then immersing the zeolite / cement / silica sol composite microsphere in the coupling agent / alcohol solution, and soaking for 24-48 hours at normal temperature to obtain the hydrophobic zeolite / cement / silica sol composite microsphere, which has good mechanical strength, high hydrophobicity and excellent VOCs adsorption performance.

Description

TECHNICAL FIELD

[0001] The present application relates to natural zeolite modification, in particular to a hydrophobic zeolite / cement / silica sol composite microsphere and a preparation method thereof. BACKGROUND

[0002] With the rapid development of social economy, a large amount of pollutants are continuously discharged, which causes the earth's ecological environment to be increasingly threatened, especially fuel combustion, chemical production, waste incineration and decoration material volatilization, which produces a large amount of VOCs and other pollutant gases, causing air pollution problems to be particularly prominent. Therefore, how to develop a material that can effectively adsorb these harmful gases has become a hot topic.

[0003] At present, researchers are constantly seeking and developing new air purification technologies and materials in order to solve the problem of air pollution. Among many air purification materials, gas adsorption materials are particularly valued due to their simple preparation process, convenience and efficiency. Some new gas adsorption materials, such as activated carbon and zeolite molecular sieves, have been widely used. However, there are still two key problems in the practical application of most gas adsorption materials: first, the adsorption materials used at present often preferentially adsorb water, resulting in a decrease in active adsorption sites and a decrease in the treatment performance of pollutants in the air; second, adsorption materials generally need to be formed and granulated before use, but most granular adsorbents need to be calcined after granulation to increase their strength, resulting in increased cost and energy consumption, which is not conducive to large-scale popularization and application.

[0004] Therefore, how to develop a gas adsorption material with low water vapor adsorption capacity, high VOCs and other pollutant gas adsorption capacity, low cost, simple process and low energy consumption is still an important topic that needs to be further researched and solved. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a hydrophobic zeolite / cement / silica sol composite microsphere and a preparation method thereof, which not only has a simple process, low energy consumption and high forming rate, but also has good mechanical strength, high hydrophobicity and excellent volatile organic gas adsorption performance.

[0006] In order to achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0007] A preparation method of a hydrophobic zeolite / cement / silica sol composite microsphere, comprising the following steps:

[0008] Step 1, according to the proportion (80-160g) : 1L, natural zeolite and acid solution with a concentration of 3-8mol / L are mixed, and the reaction is carried out at 70-90℃ for 12-48h, then washed, suction filtered, dried and ground in sequence to obtain high-silicon zeolite;

[0009] Step 2, mixing and stirring the high-silica zeolite, cement and silica sol cementing material in the proportion (600-1000g):(80-160g):1L, and then loading into a mold, waiting for solidification, and then demolding and air-drying in sequence to obtain zeolite / cement / silica sol composite microspheres;

[0010] Step 3, dissolving the coupling agent in alcohol to prepare a coupling agent / alcohol solution with a concentration of 0.05%-10%, and then immersing the zeolite / cement / silica sol composite microspheres in the coupling agent / alcohol solution, and then soaking at room temperature for 24-48h to obtain hydrophobic zeolite / cement / silica sol composite microspheres.

[0011] Further, the natural zeolite in step 1 is natural clinoptilolite or natural mordenite.

[0012] Further, the acid solution in step 1 is a nitric acid solution or a hydrochloric acid solution.

[0013] Further, the molar ratio of silicon to aluminum of the high-silica zeolite in step 1 is 16.6-21.8.

[0014] Further, the coupling agent in step 3 is dodecyltrimethylsilane, dodecyl(methyl)dimethoxysilane, dodecyltrichlorosilane or dodecyldimethylchlorosilane.

[0015] Further, the alcohol in step 3 is methanol, ethanol or propanol.

[0016] A hydrophobic zeolite / cement / silica sol composite microsphere, with a water contact angle of 105.2°-120°.

[0017] Further, the water vapor hygroscopicity is 3.85-5.21mg / g, and the acetic acid adsorption capacity is 37.86-40.25mg / g.

[0018] Compared with the prior art, the present application has the following technical effects:

[0019] Firstly, the high-silicon zeolite with high specific surface area and porosity is obtained by modifying the cheap and easily available natural zeolite with an acid solution, and the gas adsorption performance of the zeolite is effectively improved; secondly, the high-silicon zeolite is mixed with cement and silica sol cementitious material, the cement and silica sol can effectively bond the zeolite particles, realize the uniform mixing between the particles, and the obtained zeolite / cement / silica sol composite microspheres have rich pore channels and are rich in hydroxyl active groups; thirdly, the zeolite / cement / silica sol composite microspheres are completely immersed in an alcohol solution of an organic coupling agent for modification, the bonding between the hydroxyl groups on the surface of the composite microspheres and the coupling agent occurs, and thus the high-hydrophobic zeolite / cement / silica sol composite microspheres are obtained; in summary, the high-hydrophobic zeolite / cement / silica sol composite microspheres have the advantages of low water vapor adsorption capacity and high VOCs and other gas pollutant adsorption capacity, can be repeatedly used for adsorbing indoor VOCs pollutants, and are very suitable for use in the field of cultural relic protection. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 : XRD patterns of natural clinoptilolite, zeolite / cement / silica sol composite microspheres prepared in Example 1 and hydrophobic zeolite / cement / silica sol composite microspheres;

[0021] Figure 2(a) is an SEM diagram of natural clinoptilolite;

[0022] Figure 2(b) is an EDX energy spectrum of natural clinoptilolite;

[0023] Figure 2(c) is an SEM diagram of high-silicon zeolite prepared in Example 1;

[0024] Figure 2(d) is an EDX energy spectrum of high-silicon zeolite prepared in Example 1;

[0025] Figure 3(a) is a hygroscopicity and dehumidification capacity line graph of the zeolite / cement / silica sol composite microspheres and the hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0026] Figure 3(b) is a VOCs adsorption capacity line graph of the zeolite / cement / silica sol composite microspheres and the hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0027] Figure 4(a) is a compressive strength curve of a zeolite / cement / silica sol sample block prepared according to the process parameters of Example 1 and cured for 3 days;

[0028] Figure 4(b) is a compressive strength curve of a zeolite / cement / silica sol sample block prepared according to the process parameters of Example 1 and cured for 7 days;

[0029] Figure 5(a): water contact angle of hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0030] Figure 5(b): water contact angle of zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0031] Figure 6 SEM images of zeolite / cement / silica sol composite microspheres prepared in Example 1 at different magnifications;

[0032] Figure 7(a): EDX spectrum of zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0033] Figure 7(b): element distribution map of zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0034] Figure 8 SEM images of hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1 at different magnifications;

[0035] Figure 9(a): EDX spectrum of hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0036] Figure 9(b): element distribution map of hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1;

[0037] Figure 10 Actual image of hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1. DETAILED DESCRIPTION

[0038] The specific content of the present application is further explained in detail in the following combined with examples.

[0039] The preparation method of the silica sol cementitious material involved in Examples 1-37 of the present application is disclosed in the Chinese invention patent with the application number CN2024101515494 (publication number CN117797768A).

[0040] The cement involved in Examples 1-37 of the present application is commercially available white cement, ordinary Portland cement or composite cement.

[0041] Example 1

[0042] Step 1, preparation of high-silicon zeolite

[0043] Take 10g of natural zeolite and add it to 100mL of nitric acid solution with a concentration of 6mol / L, stir at 80℃ for 48h, then wash, suction filter, dry and grind in sequence to obtain high-silicon zeolite;

[0044] Step 2, preparation of zeolite / cement / silica sol composite microspheres

[0045] High silica zeolite, white cement and silica sol cementitious material were mixed and stirred evenly according to the ratio of 800g:100g:1L, and then poured into a mold. After solidification, demolding and air drying, zeolite / cement / silica sol composite microspheres were obtained.

[0046] Step 3: Preparation of hydrophobic zeolite / cement / silica sol composite microspheres

[0047] First, dodecyltrimethylsilane was dissolved in methanol to prepare a 0.5% dodecyltrimethylsilane / methanol solution. Then, zeolite / cement / silica sol composite microspheres were impregnated in the dodecyltrimethylsilane / methanol solution at room temperature and allowed to stand for 24 hours to obtain the desired product. Figure 10 The hydrophobic zeolite / cement / silica sol composite microspheres shown.

[0048] Depend on Figure 1 The XRD patterns of the samples show that natural zeolite mainly contains minerals such as clinoptilolite and quartz. The intensity of the characteristic peak of clinoptilolite in the XRD pattern of high-silica zeolite is significantly reduced, indicating that its crystallinity is reduced. This is mainly due to the removal of some aluminum from clinoptilolite by acid treatment. In addition to the characteristic peaks of clinoptilolite and quartz, the XRD pattern of zeolite / cement / silica sol composite microspheres also shows characteristic peaks of tricalcium silicate and calcium hydroxide, which mainly comes from the cement component in the composite microspheres. The intensity of the characteristic peaks of each phase in the XRD pattern of hydrophobic zeolite / cement / silica sol composite microspheres is weakened, which is due to the surface modification with silane coupling agents.

[0049] Figure 2(a) shows a SEM image of natural zeolite, which shows that the natural zeolite particles are irregular in shape and the particle size ranges from a few micrometers to several hundred nanometers. Figure 2(b) shows the EDX energy dispersive spectroscopy results of natural zeolite, which shows that the Si / Al ratio of the sample surface is about 5.4. Figure 2(c) shows a SEM image of high-silica zeolite, which shows that the morphology of high-silica zeolite particles has not changed significantly compared with natural zeolite. Figure 2(d) shows the EDX energy dispersive spectroscopy results of high-silica zeolite, which shows that the Si / Al ratio of the sample surface is 20.5, which is much higher than that of the natural zeolite sample.

[0050] 10g of the zeolite / cement / silica sol composite microsphere sample and the hydrophobic zeolite / cement / silica sol composite microsphere sample prepared in Example 1 were placed in a petri dish, and then the petri dish was placed in a desiccator containing a saturated potassium chloride salt solution. A moisture absorption experiment was conducted at 28°C. The samples were taken out and weighed at intervals. After the moisture absorption reached equilibrium, the moisture absorption was calculated. As shown in Figure 3(a), the moisture absorption of the zeolite / cement / silica sol composite microsphere and the hydrophobic zeolite / cement / silica sol composite microsphere were 23.79mg / g and 4.67mg / g, respectively, indicating that the zeolite / cement / silica sol composite microsphere modified with a 0.5% dodecyltrimethylsilane / methanol solution has good hydrophobicity.

[0051] 10g of the zeolite / cement / silica sol composite microsphere sample and the hydrophobic zeolite / cement / silica sol composite microsphere sample prepared in Example 1 were placed in a petri dish, and then the petri dish was placed in a desiccator containing saturated glacial acetic acid. Adsorption experiments were carried out at 28℃. The samples were taken out and weighed at regular intervals. After the moisture absorption equilibrium was reached, the adsorption capacity of acetic acid was calculated. The results are shown in Figure 3(b). The moisture absorption capacity of zeolite / cement / silica sol composite microspheres and hydrophobic zeolite / cement / silica sol composite microspheres for acetic acid were 37.96mg / g and 38.68mg / g, respectively, indicating that they have good adsorption performance for volatile gases.

[0052] The high-silica zeolite, cement, and silica sol cementitious material were mixed and stirred evenly according to the ratio of 800g:100g:1L. The mixture was then poured into a cylindrical mold with a diameter of 50cm and a height of 25cm. The mixture was shaken thoroughly to ensure uniform mixing. The mold containing the sample was sealed with plastic wrap and cured at room temperature for 3 and 7 days. The compressive strength of the sample blocks was then tested, as shown in Figures 4(a) and 4(b). The strengths of the sample blocks after 3 and 7 days of curing were 1.18MPa and 3.68MPa, respectively, indicating that they have good compressive strength and are not easily broken during use.

[0053] As shown in Figures 5(a) and 5(b), the water contact angle of the hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1 is 110.2°, and the water contact angle of the zeolite / cement / silica sol composite microspheres is 18.4°. This demonstrates that modification with a 0.5% dodecyltrimethylsilane / methanol solution gives the zeolite / cement / silica sol composite microspheres good hydrophobicity.

[0054] from Figure 6 It can be seen that the zeolite / cement / silica sol composite microspheres prepared in Example 1 have many pores on their surface, which is conducive to the adsorption of water vapor. As can be seen from Figure 7(a), its Si / Al ratio is 48.3. As can be seen from Figure 7(b), the sample surface contains elements such as Si, Al, Ca, Na, C and O.

[0055] From Figure 8 It can be seen that the hydrophobic zeolite / cement / silica sol composite microspheres prepared in Example 1 have many needles on the surface, which are coupling agents distributed on the surface of the zeolite / cement / silica sol composite microspheres, and can endow the zeolite / cement / silica sol composite microspheres with good hydrophobicity, so as to preferentially adsorb VOCs harmful gas; it can be seen from Fig. 9(a) that the Si / Al ratio thereof is 58.2, and it can be seen from Fig. 9(b) that the sample surface contains elements such as Si, Al, Ca, Na, C and O.

[0056] Examples 2-37

[0057] Examples 2-37 differ from the examples in the types, proportions and reaction conditions of raw materials, and specific reference can be made to Table 1.

[0058] The molar ratio of silicon to aluminum of the high-silicon zeolite prepared in Examples 2-37 is 16.6-21.8, and details are shown in Table 2.

[0059] The contact angle of the hydrophobic zeolite / cement / silica sol composite microspheres prepared in Examples 2-37 is 105.2°-120°, and details are shown in Table 3.

[0060] 5g of the zeolite / cement / silica sol composite microspheres sample and the hydrophobic zeolite / cement / silica sol composite microspheres sample prepared in Examples 2-37 were respectively taken into a culture dish, and then the culture dish was placed in a dry dish containing saturated potassium chloride solution, and the hygroscopic experiment was carried out at 28°C. The sample was taken out and weighed every certain period of time, and after the hygroscopic equilibrium was reached, the hygroscopic amount was calculated. The results are shown in Table 4-1 and Table 4-2. The hygroscopic amount of the zeolite / cement / silica sol composite microspheres is 22.15-24.25mg / g, and the hygroscopic amount of the hydrophobic zeolite / cement / silica sol composite microspheres is only 3.85-5.21mg / g.

[0061] 5g of the zeolite / cement / silica sol composite microspheres sample and the hydrophobic zeolite / cement / silica sol composite microspheres sample prepared in Examples 2-37 were respectively taken into a culture dish, and then the culture dish was placed in a dry dish containing saturated glacial acetic acid, and the adsorption experiment was carried out at 28°C. The sample was taken out and weighed every certain period of time, and after the hygroscopic equilibrium was reached, the adsorption amount of acetic acid was calculated. The results are shown in Table 4-1 and Table 4-2.

[0062] It can be seen from Table 4-1 and Table 4-2 that the acetic acid adsorption amount of the zeolite / cement / silica sol composite microspheres prepared in Examples 2-37 is 37.65-40.25mg / g; and the acetic acid adsorption amount of the hydrophobic zeolite / cement / silica sol composite microspheres is 37.86-40.25mg / g.

[0063] According to the proportions and parameters of examples 2-37 in table 1, high-silica zeolite, cement and silica sol cementing material were taken and loaded into a cylindrical mold with a diameter of 50 cm and a height of 25 cm to make 36 sample blocks of the same size. The sample blocks were cured for 3 days and 7 days at room temperature, and the compressive strength was tested, respectively. The results are shown in table 5 and table 6.

[0064] As can be seen from table 5 and table 6, the compressive strength of the sample blocks cured for 3 days is 1.05-1.57 MPa; the compressive strength of the sample blocks cured for 7 days is 3.24-4.58 MPa, indicating that the zeolite / cement / silica sol composite microspheres prepared in examples 2-37 have good compressive strength.

[0065] Table 1: raw materials and their proportions and reaction conditions of examples 2-37

[0066]

[0067]

[0068]

[0069] Table 2: silica-alumina ratio of high-silica zeolite prepared in examples 2-37

[0070] Example Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Silica to alumina ratio 20.5 16.6 18.4 25.4 20.5 20.4 20.8 20.4 21.1 Example Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Silica to alumina ratio 20.1 20.5 20.6 20.5 20.7 20.4 20.1 20.6 20.4 Example Example 20 Example 21 Example 22 Example 23 Example 24 Example 25 Example 26 Example 27 Example 28 Silica to alumina ratio 20.4 20.3 20.1 20.6 20.4 20.1 20.5 20.9 20.7 Example Example 29 Example 30 Example 31 Example 32 Example 33 Example 34 Example 35 Example 36 Example 37 Silica to alumina ratio 20.6 20.5 20.4 20.6 20.7 20.5 21.8 21.5 21.1

[0071] Table 3: surface water droplet contact angle of hydrophobic zeolite / cement / silica sol composite microspheres prepared in examples 2-37

[0072] Example Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Contact angle 105.2 108.5 110.2 110.8 115.2 115.6 118.5 119.2 120 Example Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Contact angle 108.2 110.3 110.6 110.8 110.5 110.9 115.8 116.3 116.9 Example Example 20 Example 21 Example 22 Example 23 Example 24 Example 25 Example 26 Example 27 Example 28 Contact angle 110.9 116.2 105.9 118.5 119.6 116.3 115.2 115.2 112.2 Example Example 29 Example 30 Example 31 Example 32 Example 33 Example 34 Example 35 Example 36 Example 37 Contact angle 110.5 111.2 116.2 113.2 111.2 111.5 115.2 118.2 114.1

[0073] Table 4-1: moisture absorption and acetic acid adsorption of zeolite / cement / silica sol composite microspheres prepared in examples 2-37

[0074]

[0075]

[0076] Table 4-2: moisture absorption and acetic acid adsorption of hydrophobic zeolite / cement / silica sol composite microspheres prepared in examples 2-37

[0077]

[0078] Table 5: compressive strength of sample blocks prepared according to the process parameters of examples 2-19

[0079]

[0080] Table 6: Compressive strengths of sample blocks prepared according to the process parameters of Examples 20-37

[0081]

Claims

1. A method for preparing hydrophobic zeolite / cement / silica sol composite microspheres, characterized by, The method comprises the following steps: Step 1, according to the proportion (80-160 g):1 L, taking natural zeolite and acid solution with a concentration of 3-8 mol / L, mixing, reacting at 70-90 ℃ for 12-48 h, then washing, suction filtering, drying and grinding in sequence to obtain high-silicon zeolite; Step 2, according to the proportion (600-1000 g):(80-160 g):1 L, mixing and uniformly stirring the high-silicon zeolite, cement and silica sol cementitious material, then loading into a mold, waiting for solidification, demolding and shade drying in sequence to obtain zeolite / cement / silica sol composite microspheres; Step 3, dissolving the coupling agent in alcohol to prepare a coupling agent / alcohol solution with a concentration of 0.05%-10%, then immersing the zeolite / cement / silica sol composite microspheres in the coupling agent / alcohol solution, and soaking at room temperature for 24-48 h to obtain hydrophobic zeolite / cement / silica sol composite microspheres. The coupling agent is dodecyltrimethylsilane, dodecyl(methyl)dimethoxysilane, dodecyltrichlorosilane or dodecyldimethylchlorosilane.

2. The method for preparing hydrophobic zeolite / cement / silica sol composite microspheres according to claim 1, characterized by, The natural zeolite in step 1 is natural clinoptilolite or natural mordenite.

3. The method for preparing hydrophobic zeolite / cement / silica sol composite microspheres according to claim 1, characterized in that, The acid solution in step 1 is nitric acid solution or hydrochloric acid solution.

4. The method for preparing hydrophobic zeolite / cement / silica sol composite microspheres according to claim 1, characterized in that, The high-silicon zeolite in step 1 has a silicon / aluminum molar ratio of 16.6-21.

8.

5. The method for preparing hydrophobic zeolite / cement / silica sol composite microspheres according to claim 1, characterized in that, The alcohol in step 3 is methanol, ethanol or propanol.

6. Hydrophobic zeolite / cement / silica sol composite microspheres prepared by the method of any one of claims 1 to 5, characterized in that, The water contact angle is 105.2°-120°.

7. The hydrophobic zeolite / cement / silica sol composite microspheres of claim 6, wherein, The water vapor absorption capacity is 3.85-5.21 mg / g, and the acetic acid adsorption capacity is 37.86-40.25 mg / g.

Images