A zeolite / silica sol-based psychrometer and a method for preparing the same

Abstract

The application discloses a kind of zeolite / silica sol-based humidity regulating balls and preparation method thereof, and the preparation method comprises the following steps: 1, according to the proportion (80-120g) :(2.5-12g) :1L take natural zeolite, sodium persulfate and alkali solution with concentration of 2-6mol / L are mixed, at 70-90 DEG C, reaction 12-48h, then sequentially wash, suction filtration, drying and grinding, obtain hydrophilic low-silicon zeolite;2, first use acid liquid to adjust the pH value of the mass fraction 30-50% of silica sol to weak acid, then according to the volume ratio (6-10) :1 silica sol and mass fraction 5-10% chlorinated salt solution are mixed, obtain silica sol gel material;3, according to the proportion (500-2000g) :1L hydrophilic low-silicon zeolite and silica sol gel material are mixed and stirred uniformly, then loaded into mould, sequentially through solidification, demoulding and drying, obtain zeolite / silica sol-based humidity regulating ball.The preparation process of the application does not need high-temperature calcination, not only simple process, low energy consumption, but also the prepared zeolite / silica sol-based humidity regulating ball has excellent humidity regulating performance.

Description

Technical Field

[0001] This invention relates to the modification of natural zeolite and silica sol, specifically a zeolite / silica sol-based wet bulb and its preparation method. Background Technology

[0002] Air humidity is an important parameter for measuring indoor environment, significantly impacting human health, indoor air quality, and the storage of items. Existing humidity control methods are mainly divided into passive and active types. Active humidity control uses humidity control equipment, such as humidifiers / dehumidifiers and central air conditioning, to set humidity conditions. This method consumes a large amount of energy, and the purchase and maintenance costs are relatively high. Passive humidity control uses humidity-regulating materials such as silica gel, inorganic salts, inorganic minerals, and organic polymers, which regulate the relative humidity of the environment through their moisture absorption and release properties. This method has advantages such as low energy consumption, ease of use, and low price. Among the aforementioned humidity-regulating materials, inorganic salts are unstable at room temperature and prone to salting out; silica gel and organic polymers have poor moisture release performance and are expensive; natural inorganic minerals have a lower moisture capacity than inorganic silica gel, but they have the advantages of fast moisture absorption and release speed and short moisture release lag time. Moreover, they are derived from the natural environment, are harmless to humans and the environment, and have low manufacturing and usage costs, making them a popular humidity-regulating material.

[0003] Natural zeolites are a class of porous hydrous aluminosilicate minerals with abundant pore structures and excellent adsorption, ion exchange, and catalytic properties. In recent years, they have received considerable attention in the field of humidity control. For example, Di Yonghao et al. from China University of Mining and Technology (Beijing) discovered that natural clinoptilolite and zeolite both possess good humidity-regulating properties, and that these properties are further enhanced after acid and alkali treatment. However, there are still some key issues to be resolved before natural zeolites can be used as humidity-regulating materials, limiting their large-scale application. Specifically: Firstly, the silica-to-alumina ratio of natural zeolites is generally low. In the range of 4 to 6, it is a medium-silica zeolite, which has lower hydrophilicity than zeolites with a low silica-to-alumina ratio. Therefore, its moisture absorption and conditioning performance is not good. Although the silica-to-alumina ratio of natural zeolite can be effectively reduced and its moisture absorption performance improved by alkali treatment, under the current alkali treatment conditions, it is still difficult to reduce the silica-to-alumina ratio of natural zeolite to the low silica-to-alumina ratio range of Si / Al = 1 to 2. Secondly, when natural zeolite is used as a moisture conditioning material, it needs to be granulated. During the granulation process, a binder needs to be added and high-temperature calcination is required. This results in high energy consumption and the heat treatment will damage the structure of the zeolite, leading to a decrease in the moisture conditioning performance of the zeolite balls.

[0004] Therefore, how to prepare a high-hydrophilic zeolite with a low silica-alumina ratio using natural zeolite, and obtain a humidity-regulating material with excellent humidity-regulating properties without high-temperature calcination, is a problem that needs to be studied and solved in depth. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a zeolite / silica sol-based humidity control ball and its preparation method, which can obtain a zeolite / silica sol-based humidity control ball with excellent humidity control properties without high-temperature calcination.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing zeolite / silica sol-based wet beads includes the following steps:

[0008] Step 1: Mix natural zeolite, sodium persulfate, and an alkaline solution with a concentration of 2-6 mol / L according to the ratio (80-120g): (2.5-12g): 1L. React at 70-90℃ for 12-48 hours. Then wash, filter, dry, and grind in sequence to obtain hydrophilic low-silica zeolite.

[0009] Step 2: First, adjust the pH of the silica sol (30-50% by mass) to weakly acidic using acid solution. Then, mix the silica sol with a chloride salt solution (5-10% by mass) at a volume ratio of (6-10):1 to obtain the silica sol gelling material.

[0010] Step 3: Mix the hydrophilic low-silica zeolite and silica sol gelling material according to the ratio (500~2000g): 1L and stir evenly. Then, pour the mixture into a mold and proceed with solidification, demolding and drying to obtain zeolite / silica sol-based wet bulbs.

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

[0012] Furthermore, the alkaline solution in step 1 is a sodium hydroxide solution or a potassium hydroxide solution.

[0013] Furthermore, the silicon / aluminum molar ratio of the hydrophilic low-silica zeolite in step 1 is less than 2.

[0014] Furthermore, the acid solution in step 2 is acetic acid, phosphoric acid, or hydrochloric acid.

[0015] Furthermore, the pH value in step 2 is 5 to 7.

[0016] Furthermore, the chloride salt in step 2 is calcium chloride, magnesium chloride, potassium chloride, or sodium chloride.

[0017] Furthermore, the drying in step 3 is carried out at 70–105°C for 1–4 hours.

[0018] A zeolite / silica sol-based moisture-absorbing bulb has a moisture absorption capacity of 30–40 mg / g and a moisture release capacity of 28–38 mg / g.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] This invention first involves alkali treatment of natural zeolite using an alkali and sodium persulfate solution. Under alkaline conditions, the highly reactive hydroxyl radicals (·OH) generated by sodium persulfate can react with OH-. - This invention synergistically promotes the removal of silicon and structural transformation in the natural zeolite structure, effectively reducing the silicon-to-aluminum ratio of zeolite and increasing the number of polar groups such as Si-O-Al and -OH, thereby obtaining a highly hydrophilic low-silica zeolite. Then, a weakly acidic silica sol and salt solution are mixed to obtain a silica sol gelling material with good gelling properties. The surface is rich in -OH polar groups, exhibiting good hydrophilicity. This material is mixed with highly hydrophilic low-silica zeolite, then injected into a mold, and after solidification, demolding, and low-temperature drying, zeolite / silica sol is obtained. No high-temperature calcination is required during this process. This method is not only simple, energy-efficient, and easy to control in terms of reaction conditions, but also environmentally friendly. Furthermore, it does not damage the zeolite structure. The low-silica zeolite and silica sol components are rich in polar groups such as Si-O-Al and -OH, giving the zeolite / silica sol-based moisture-regulating bulbs excellent humidity-regulating properties. Therefore, the preparation method of this invention has broad application prospects. Attached Figure Description

[0021] Figure 1 XRD patterns of natural clinoptilolite, hydrophilic low-silica zeolite prepared in Example 1, and zeolite / silica sol-based humidity control beads;

[0022] Figure 2 SEM images and corresponding EDX spectra of natural clinoptilolite and the hydrophilic low-silica zeolite prepared in Example 1;

[0023] Figure 3 Line graph showing the moisture absorption and release of the zeolite / silica sol-based moisture-regulating balls prepared in Example 1;

[0024] Figure 4 Photograph of the zeolite / silica sol-based moisture-regulating bulbs prepared in Example 1. Detailed Implementation

[0025] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0026] Example 1

[0027] Step 1: Preparation of hydrophilic low-silica zeolite

[0028] 10g of natural clinoptilolite and 0.357g of sodium persulfate were added to 100mL of sodium hydroxide solution with a concentration of 3mol / L. The mixture was stirred at 80℃ for 48h. Then, the mixture was washed, filtered, dried and ground in sequence to obtain hydrophilic low-silica zeolite with a Si / Al ratio of 1.78.

[0029] Step 2: Preparation of silica sol gelling materials

[0030] First, the pH value of 40% silica sol was adjusted to 7 with acetic acid. Then, the silica sol and 5% calcium chloride solution were mixed at a volume ratio of 7:1 to obtain silica sol gelling material.

[0031] Step 3: Preparation of zeolite / silica sol-based wet bulbs

[0032] Hydrophilic low-silica zeolite and silica sol gelling material were mixed and stirred evenly at a ratio of 1000g:1L. The mixture was then poured into a spherical mold with a diameter of 5mm. After solidification, the mixture was removed and dried at 105℃ for 1h to obtain zeolite / silica sol-based wet balls.

[0033] Depend on Figure 1 It can be seen that natural clinoptilolite mainly contains clinoptilolite minerals, while the hydrophilic low-silica zeolite prepared in Example 1 mainly contains Na-P zeolite. Furthermore, the zeolite / silica sol-based wet bulb prepared in Example 1 also showed obvious Na-P zeolite characteristic peaks. The bun peak in the figure corresponds to the characteristic peak of amorphous silica.

[0034] Depend on Figure 2 (a) and Figure 2 (b) It can be seen that the Si / Al ratio of natural clinoptilolite is 5.2; from Figure 2 (c) and Figure 2 (d) It can be seen that the Si / Al ratio of the hydrophilic low-silica zeolite prepared in Example 1 is 1.78, which is much lower than that of natural clinoptilolite.

[0035] Take 10g of the moisture-absorbing bulbs prepared in Example 1 and place them in a petri dish, then place the petri dish in a desiccator containing a saturated potassium chloride solution. Perform a moisture absorption experiment at 28°C. Remove and weigh the moisture-absorbing bulbs periodically. After the moisture-absorbing bulbs reach equilibrium, calculate the moisture absorption as 36.7mg / g. Place the moisture-absorbing bulbs, after they have reached saturation, in a petri dish, then place the desiccator in a desiccator containing a saturated magnesium chloride solution. Perform a moisture release experiment at 28°C. Remove and weigh the moisture-absorbing bulbs periodically. After the moisture-release bulbs reach equilibrium, calculate the moisture release as 35.5mg / g. Specifically, the moisture absorption and release of the moisture-absorbing bulbs at each time point are as follows: Figure 3 As shown.

[0036] The hydrophilic low-silica zeolite and silica sol gelling material prepared in Example 1 were taken at a ratio of 1000g:1L. First, the hydrophilic low-silica zeolite powder was added into a 5cm×5cm×5cm cube mold, and then the silica sol gelling material was poured into the mold. 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 days, 7 days, and 28 days. The compressive strength of the sample block was then tested, and the results were 0.71MPa, 1.3MPa, and 4.56MPa, respectively, indicating that it has good compressive strength and is not easily broken during use.

[0037] Figure 4 A photograph of the humidity-regulating ball prepared in Example 1.

[0038] Examples 2 to 31

[0039] The differences between Examples 2 to 31 and Example 1 lie in the types of raw materials, proportions, and reaction conditions, as shown in Table 1.

[0040] The silicon-to-aluminum ratios of the hydrophilic low-silica zeolites prepared in Examples 2 to 31 are detailed in Table 2, with Si / Al ratios all below 2.

[0041] Take 10g of each of the moisture-absorbing beads prepared in Examples 2 to 31 and place them in a petri dish, then place them in a desiccator containing a saturated potassium chloride solution. Conduct a moisture absorption experiment at 28°C. Remove and weigh the moisture-absorbing beads at regular intervals. Calculate the moisture absorption amount after the moisture-absorbing beads reach equilibrium. Place the moisture-absorbing beads, saturated with moisture, in a petri dish, then place them in a desiccator containing a saturated magnesium chloride solution. Conduct a moisture release experiment at 28°C. Remove and weigh the moisture-absorbing beads at regular intervals. Calculate the moisture release amount after the moisture release amount reaches equilibrium. The moisture absorption and release amounts of the moisture-absorbing beads prepared in Examples 2 to 31 are shown in Table 3. The moisture absorption amount is 30.4–39.7 mg / g, and the moisture release amount is 29.5–37.6 mg / g.

[0042] According to the addition ratio of hydrophilic low-silica zeolite and silica sol cementing material in Table 1, sample blocks were prepared from the hydrophilic low-silica zeolite and silica sol cementing materials prepared in Examples 2 to 31, respectively, ensuring that the sample blocks were exactly the same in size as those in Example 1. The samples were cured at room temperature for 3 days, 7 days, and 28 days, and the compressive strength was tested. The results are shown in Tables 4 and 5. The compressive strength after 3 days of curing was 0.71–0.73 MPa; the compressive strength after 7 days of curing was 1.28–1.3 MPa; and the compressive strength after 28 days of curing was 3.68–4.52 MPa, all showing good compressive strength.

[0043] Table 1: Raw material ratios and reaction conditions for Examples 2 to 31

[0044]

[0045]

[0046]

[0047]

[0048] Table 2: Si / Aluminum ratio of the hydrophilic low-silica zeolites prepared in Examples 2 to 31

[0049]

[0050] Table 3: Moisture absorption and release of humidity-regulating balls prepared in Examples 2 to 31

[0051]

[0052] Table 4: Compressive strength of zeolite / silica sol-based sample blocks prepared in Examples 2 to 16

[0053]

[0054] Table 5: Compressive strength of zeolite / silica sol-based sample blocks prepared in Examples 17 to 31

[0055]

Claims

1. A method for preparing zeolite / silica sol-based moisture-regulating beads, characterized in that, Includes the following steps: Step 1: Mix natural zeolite, sodium persulfate, and an alkaline solution with a concentration of 2-6 mol / L according to the ratio (80-120g): (2.5-12g): 1L. React at 70-90℃ for 12-48 hours. Then wash, filter, dry, and grind in sequence to obtain hydrophilic low-silica zeolite. Step 2: First, adjust the pH of the silica sol (30-50% by mass) to weakly acidic using acid solution. Then, mix the silica sol with a chloride salt solution (5-10% by mass) at a volume ratio of (6-10):1 to obtain the silica sol gelling material. Step 3: Mix the hydrophilic low-silica zeolite and silica sol gelling material according to the ratio (500~2000g): 1L and stir evenly. Then, pour the mixture into a mold and proceed with solidification, demolding and drying to obtain zeolite / silica sol-based wet bulbs.

2. The method for preparing zeolite / silica sol-based moisture-regulating beads according to claim 1, characterized in that, The natural zeolite used in step 1 is natural clinoptilolite or natural mordenite.

3. The method for preparing zeolite / silica sol-based moisture-regulating beads according to claim 1, characterized in that, The alkaline solution in step 1 is a sodium hydroxide solution or a potassium hydroxide solution.

4. The method for preparing zeolite / silica sol-based moisture-regulating bulbs according to claim 1, characterized in that, The silicon / aluminum molar ratio of the hydrophilic low-silica zeolite in step 1 is less than 2.

5. The method for preparing zeolite / silica sol-based moisture-regulating beads according to claim 1, characterized in that, The acid solution in step 2 is acetic acid, phosphoric acid, or hydrochloric acid.

6. The method for preparing zeolite / silica sol-based moisture-regulating bulbs according to claim 1, characterized in that, The pH value in step 2 is 5 to 7.

7. The method for preparing zeolite / silica sol-based moisture-regulating bulbs according to claim 1, characterized in that, The chloride salt in step 2 is calcium chloride, magnesium chloride, potassium chloride, or sodium chloride.

8. The method for preparing zeolite / silica sol-based moisture-regulating bulbs according to claim 1, characterized in that, The drying in step 3 is carried out at 70–105°C for 1–4 hours.

9. A zeolite / silica sol-based moisture-regulating bead prepared by the method according to any one of claims 1 to 7, characterized in that, The moisture absorption capacity is 30-40 mg / g, and the moisture release capacity is 28-38 mg / g.

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