Super-hydrophobic activated carbon adsorption material, and preparation method and application thereof

Abstract

The application belongs to the field of functional activated carbon materials, and relates to super-hydrophobic activated carbon adsorption material and a preparation method and application thereof. The preparation method comprises the following steps: in an alkaline aqueous solvent, hydroxyl nanoparticles and organosilane are subjected to hydrolysis polymerization to obtain super-hydrophobic nanoparticles; the super-hydrophobic nanoparticles are coated on the surface of activated carbon, and the super-hydrophobic activated carbon adsorption material is obtained; wherein, the chemical structural formula of the organosilane is: R1 is a linear alkyl group with 10-20 carbon atoms, R2, R3 and R4 are alkoxy groups with 1-5 carbon atoms or halogens. The super-hydrophobic activated carbon adsorption material provided by the application not only has excellent super-hydrophobic performance, but also can avoid the blockage of activated carbon pores, has excellent adsorption performance, and can be widely applied to the field of adsorption treatment of volatile organic compounds.

Description

Technical Field

[0001] This invention belongs to the field of functional activated carbon materials, and relates to a superhydrophobic activated carbon adsorption material, its preparation method and application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With the continuous development of the chemical industry, the emission of volatile organic compounds (VOCs) has increasingly attracted widespread attention from all sectors of society. VOCs, characterized by low boiling points, high vapor pressures, and high volatility, pose a significant threat to the ecological environment and human health, a fact widely confirmed by the scientific community. Adsorption methods are widely used due to their significant advantages such as high treatment efficiency and low operating costs. Among these, activated carbon, as the most traditional adsorption material, has become the most common VOCs adsorption material due to its high specific surface area, well-developed pore structure, low cost, and easy recovery. However, due to differences in process types and climatic conditions, the emitted VOCs waste gas contains varying amounts of water vapor. During the VOCs adsorption treatment process, because the surface of activated carbon is rich in oxygen-containing functional groups, water vapor preferentially occupies the adsorption sites of activated carbon, thus severely reducing the adsorption capacity of activated carbon for VOCs. Therefore, it is necessary to treat activated carbon to a certain extent to overcome the limitation of its poor adsorption performance for humid VOCs waste gas.

[0004] In recent years, researchers have modified activated carbon materials to be hydrophobic using various methods and applied them to the adsorption treatment of VOCs, thereby reducing the competitive adsorption of water molecules and VOC molecules on activated carbon. However, the inventors have found that in existing technologies, most hydrophobic activated carbon materials are modified by directly grafting modifiers (such as silane coupling agents, long-chain organic acids, etc.) onto the activated carbon surface. This method usually uses a large amount of modifiers and solvents, and also causes blockage of the pore structure of activated carbon, reducing the adsorption capacity of activated carbon. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a superhydrophobic activated carbon adsorbent material, its preparation method, and its application. The superhydrophobic activated carbon adsorbent material provided by the present invention not only possesses excellent superhydrophobic properties but also avoids clogging of activated carbon pores, exhibiting excellent adsorption performance. It can be widely applied in the adsorption and treatment of volatile organic compounds (VOCs).

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, a method for preparing a superhydrophobic activated carbon adsorbent material includes the following steps:

[0008] In an alkaline aqueous solvent, hydroxyl-containing nanoparticles undergo a hydrolysis-polymerization reaction with organosilanes to obtain superhydrophobic nanoparticles.

[0009] The superhydrophobic nanoparticles are coated onto the surface of activated carbon to obtain the product.

[0010] The chemical structural formula of the organosilane is as follows: R1 is a C10-C20 straight-chain alkyl group, and R2, R3, and R4 are C1-C5 alkoxy groups or halogens.

[0011] Currently, the main methods for modifying activated carbon into hydrophobic activated carbon are to load hydrophobic groups or remove hydrophilic groups on the surface of activated carbon. However, the hydrophobic activated carbon prepared by these methods is mainly chemically modified by directly using modifiers in solvents. This usually involves the use of large amounts of solvents and modifiers, which also causes blockage of the pore structure of activated carbon and reduces its adsorption capacity.

[0012] In this invention, during the hydrolysis-polymerization reaction, organosilanes are first hydrolyzed to form silanols. The hydroxyl groups of the hydroxyl-containing nanoparticles act as active sites, chemically grafting and bonding with the formed silanols. Simultaneously, under alkaline conditions, the organosilanes with hydrophobic long carbon chains polymerize, thereby firmly fixing the hydrophobic long carbon chains onto the surface of the hydroxyl-containing nanoparticles to form superhydrophobic nanoparticles. These superhydrophobic nanoparticles are then coated onto the surface of activated carbon. Due to van der Waals forces, electrostatic attraction, and the hydrophobic interaction between the hydrophobic long carbon chains and the hydrophobic carbon structure on the activated carbon surface, the superhydrophobic nanoparticles can adhere tightly to the activated carbon surface, reducing the difficulty of superhydrophobic material adhesion to the activated carbon surface. This ensures the superhydrophobic performance of the prepared superhydrophobic activated carbon adsorbent material and enhances the activated carbon's ability to repel water vapor. Furthermore, this method does not clog the internal pore structure of the activated carbon. The nanoparticle coating adhering to the activated carbon surface re-aggregates to form a new pore structure, increasing the specific surface area of ​​the activated carbon, preserving its adsorption performance, and enhancing the selective adsorption of humid VOCs waste gas.

[0013] Secondly, a superhydrophobic activated carbon adsorbent material is obtained by the above preparation method.

[0014] Thirdly, the application of the aforementioned superhydrophobic activated carbon adsorbent material in the adsorption of VOCs in humid environments.

[0015] The beneficial effects of this invention are as follows:

[0016] The superhydrophobic activated carbon adsorbent material prepared by this invention is obtained by first hydrolyzing and polymerizing organosilanes on the surface of hydroxyl-containing nanoparticles to obtain superhydrophobic nanoparticles, which are then coated onto the surface of activated carbon. Hexadecyltrimethoxysilane, after hydrolysis, polymerizes on the surface of hydroxyl-containing nanoparticles under alkaline conditions, thereby grafting a large number of hydrophobic long carbon chains onto the hydroxyl-containing nanoparticles. Superhydrophobic modification of activated carbon is achieved through a simple coating process. This method is simple to operate, inexpensive, and produces modified activated carbon with excellent hydrophobic properties, making it widely applicable in the adsorption of volatile organic compounds (VOCs) in humid environments. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a scanning electron microscope image of the superhydrophobic activated carbon obtained in Example 1 of the present invention;

[0019] Figure 2 This is a scanning electron microscope image of the activated carbon of Comparative Example 1 of the present invention;

[0020] Figure 3 This is a diagram showing the water contact angle of the superhydrophobic activated carbon obtained in Example 1 of the present invention.

[0021] Figure 4 This is a diagram showing the water contact angle of the activated carbon in Comparative Example 1 of the present invention;

[0022] Figure 5 These are diagrams showing the wetting state of the superhydrophobic activated carbon obtained in Example 1 of the present invention and that of Comparative Example 1 after being immersed in water;

[0023] Figure 6 This is a nitrogen adsorption-desorption curve of the superhydrophobic activated carbon obtained in Example 1 of the present invention and Comparative Example 1;

[0024] Figure 7 This is a breakthrough curve of the superhydrophobic activated carbon obtained in Example 1 of the present invention and Comparative Example 1 in an environment with a relative humidity of 0% toluene adsorption.

[0025] Figure 8 This is a breakthrough curve of the superhydrophobic activated carbon obtained in Example 1 of the present invention and Comparative Example 1 adsorbing toluene in an environment with a relative humidity of 80%. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] Existing methods for hydrophobic modification of activated carbon typically use large amounts of modifiers and solvents, which can clog the pore structure of the activated carbon and reduce its adsorption capacity. This invention, however, discovers that by using a simple spraying method to modify activated carbon with superhydrophobic hydroxyl-containing nanoparticles, not only is the cost of hydrophobic modification of activated carbon reduced, but the hydrophobic properties of the activated carbon are effectively improved, and the specific surface area of ​​the activated carbon is also increased. Therefore, this invention proposes a superhydrophobic activated carbon adsorbent material, its preparation method, and its applications.

[0029] A typical embodiment of the present invention provides a method for preparing a superhydrophobic activated carbon adsorbent material, comprising the following steps:

[0030] In an alkaline aqueous solvent, hydroxyl-containing nanoparticles undergo a hydrolysis-polymerization reaction with organosilanes to obtain superhydrophobic nanoparticles.

[0031] The superhydrophobic nanoparticles are coated onto the surface of activated carbon to obtain the product.

[0032] The chemical structural formula of the organosilane is as follows: R1 is a C10-C20 straight-chain alkyl group, and R2, R3, and R4 are C1-C5 alkoxy groups or halogens.

[0033] In the organosilanes described in this invention, R2, R3, and R4 may be the same or different. In some embodiments, R2, R3, and R4 are methoxy, ethoxy, or chlorine.

[0034] In some embodiments, the organosilane is one or a combination of dodecyltrichlorosilane, tetradecyltrichlorosilane, hexadecyltrichlorosilane, octadecyltrichlorosilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, dodecyltriethoxysilane, dodecyltriethoxysilane, tetradecyltriethoxysilane, and octadecyltriethoxysilane.

[0035] In some embodiments, the hydroxyl-containing nanoparticles may contain one or a combination of nano-silica, nano-titanium dioxide, nano-zirconium dioxide, and nano-hydroxyapatite. The size of the hydroxyl-containing nanoparticles is 5-100 nm.

[0036] In some embodiments, hydroxyl-containing nanoparticles are added to an alcohol solvent and dispersed evenly, then water is added, and the pH of the solvent system is adjusted to alkaline, followed by the addition of an organosilane to initiate the reaction. Specifically, ultrasonic dispersion is used to ensure uniform dispersion of the hydroxyl-containing nanoparticles in the alcohol solvent. The alcohol solvent used in this invention is a liquid alcoholic organic compound, such as methanol, ethanol, propanol, ethylene glycol, etc., which is miscible with water, thus facilitating the reaction.

[0037] In some embodiments, the mass ratio of organosilane to hydroxyl-containing nanoparticles is (0.7–1.0):1.

[0038] In some embodiments, the pH of the alkaline aqueous solvent is 9 to 11. The pH of the alkaline aqueous solvent is adjusted using ammonia.

[0039] In some embodiments, the mass ratio of water added to hydroxyl-containing nanoparticles is (1-2):1.

[0040] In some embodiments, the reaction time is 1 to 6 hours.

[0041] The activated carbon described in this invention is a non-powdered activated carbon, which facilitates the coating of superhydrophobic nanoparticles onto the surface of the activated carbon. In some embodiments, the activated carbon is one or more of cylindrical activated carbon, granular activated carbon, or clover-shaped activated carbon.

[0042] In some embodiments, the superhydrophobic nanoparticles are coated onto the surface of activated carbon by spraying. Spraying superhydrophobic nanoparticles directly onto the surface of activated carbon allows for superhydrophobic modification of activated carbon with minimal raw materials, reducing the amount of superhydrophobic nanoparticles used and further increasing the porosity of the prepared superhydrophobic activated carbon adsorbent material.

[0043] In one or more embodiments, during the spraying process, the distance between the spray gun nozzle and the activated carbon is 10-20cm, the spraying pressure is 0.3-1MPa, and the moving speed is 2-5cm / s.

[0044] Another embodiment of the present invention provides a superhydrophobic activated carbon adsorbent material, which is obtained by the above preparation method.

[0045] A third embodiment of the present invention provides an application of the above-mentioned superhydrophobic activated carbon adsorbent material in the field of VOCs adsorption.

[0046] In some embodiments, the relative humidity of the environment in which VOCs are adsorbed is above 60%.

[0047] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0048] Example 1

[0049] 1 g of 30 nm silica was added to 80 g of anhydrous ethanol and ultrasonically dispersed for 10 min. The mixture was then magnetically stirred for 10 min. 1 g of water was added, and ammonia was added to adjust the pH to 10. 1 g of hexadecyltrimethoxysilane was added, and the mixture was magnetically stirred for 2 h to obtain a superhydrophobic nano silica suspension.

[0050] A superhydrophobic nano-silica suspension was added to a spray gun and sprayed onto the surface of cylindrical wood-based activated carbon. The distance between the spray gun and the activated carbon was 15 cm, the spraying pressure was 0.5 MPa, the moving speed was 3 cm / s, and the carbon was air-dried at room temperature for 6 hours to obtain superhydrophobic activated carbon.

[0051] Scanning electron microscope (SEM) images of the superhydrophobic activated carbon obtained in Example 1 of this invention and Comparative Example 1 are shown below. Figure 1-2 As shown, the original activated carbon in Comparative Example 1 has a relatively smooth surface and uniform shape. After uniform spraying, superhydrophobic nano-silica deposits aggregated on the surface of the activated carbon, forming a rich pore structure and nanoscale roughness. Figure 3-4 The diagrams show the water contact angles of the superhydrophobic activated carbon obtained in Example 1 of this invention and Comparative Example 1. The water contact angles are 162.4° and 0°, respectively. After simple superhydrophobic modification by spraying, the activated carbon achieved a transformation from superhydrophilic to superhydrophobic. The diagrams also show the wetting state of the superhydrophobic activated carbon obtained in Example 1 and Comparative Example 1 after being immersed in water. Figure 5 As shown, due to the superhydrophilicity of the original activated carbon, water quickly occupies its pores, causing it to be completely wetted and then settle to the bottom of the container. However, due to the superhydrophobic multi-cavity nanostructure on the surface of the superhydrophobic activated carbon, it traps a layer of air as a protective layer and floats on the water surface after contact with water. Figure 6 The nitrogen adsorption-desorption curves of the superhydrophobic activated carbon obtained in Example 1 and Comparative Example 1 are shown. The superhydrophobic modification by spraying did not block the pores of the activated carbon and did not change the pore structure. The BET specific surface areas before and after modification are 895 m². 2 / g and 949m 2 / g, the BET specific surface area increased instead of decreased, which is because the nano-silica particles aggregated on the surface of activated carbon to form a new pore structure.

[0052] Example 2

[0053] The difference between this embodiment and Embodiment 1 is that, except for changing the 30nm silicon dioxide to 50nm silicon dioxide, everything else is the same as in Embodiment 1.

[0054] Example 3

[0055] The difference between this embodiment and Embodiment 1 is that, except for replacing the 30nm silicon dioxide with 20nm titanium dioxide, everything else is the same as in Embodiment 1.

[0056] Example 4

[0057] The difference between this embodiment and Embodiment 1 is that, except for replacing the 30nm silicon dioxide with 50nm zirconium dioxide, everything else is the same as in Embodiment 1.

[0058] Example 5

[0059] The difference between this embodiment and Embodiment 1 is that, except for replacing the 30nm silicon dioxide with 20nm hydroxyapatite, everything else is the same as in Embodiment 1.

[0060] Example 6

[0061] The difference between this embodiment and Embodiment 1 is that, except for changing the cylindrical wood-based activated carbon to clover-shaped coconut shell activated carbon, everything else is the same as in Embodiment 1.

[0062] Example 7

[0063] The difference between this embodiment and Embodiment 1 is that, except for adjusting the mass ratio of hexadecyltrimethoxysilane to 30nm silicon dioxide to 0.8:1, everything else is the same as in Embodiment 1.

[0064] Comparative Example 1

[0065] This comparative example provides a cylindrical wood-based activated carbon, which is not subjected to any modification treatment.

[0066] Performance testing

[0067] Table 1 shows the adsorption performance data of the activated carbon described in Comparative Example 1 on toluene before and after modification, under environments with relative humidity of 0% and 80%, respectively.

[0068] Table 1

[0069]

[0070] Figure 7 and Figure 8 The graphs show the breakthrough curves of the superhydrophobic activated carbon obtained in Example 1 of the present invention and Comparative Example 1, respectively, in the presence of 0% and 80% relative humidity.

[0071] Combination Figure 7 , Figure 8As shown in Table 1, at 0% RH, the adsorption capacity of Comparative Example 1 and Example 1 for toluene is basically the same. This is because the pores of the activated carbon obtained by the superhydrophobic modification by spraying method are not blocked. When the relative humidity increases to 80%, the adsorption capacity of Comparative Example 1 decreases by 47%. This is because the surface of the activated carbon is rich in oxygen-containing functional groups, and water molecules occupy a large number of adsorption sites on the activated carbon, competing with toluene for adsorption. However, at 80% RH, the adsorption capacity of the superhydrophobic activated carbon obtained in Example 1 for toluene only decreases by 16%. This is because the superhydrophobic nano-silica barrier on the surface of the superhydrophobic activated carbon resists most of the water vapor, preventing it from occupying the adsorption sites inside the activated carbon. The superhydrophobic modification enhances the selective adsorption of VOCs by the activated carbon. The above results show that the superhydrophobic activated carbon obtained by this invention not only has low modification cost but also exhibits excellent adsorption performance for VOCs in humid environments, showing broad prospects for industrial applications.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a superhydrophobic activated carbon adsorbent material, characterized by comprising: The process is as follows: In an alkaline aqueous solvent, hydroxyl-containing nanoparticles undergo a hydrolysis-polymerization reaction with organosilanes to obtain superhydrophobic nanoparticles. The superhydrophobic nanoparticles are coated onto the surface of activated carbon to obtain the product. The chemical structural formula of the organosilane is as follows: R1 is a C10-C20 straight-chain alkyl group, and R2, R3, and R4 are C1-C5 alkoxy groups or halogens; The hydroxyl-containing nanoparticles are one or a combination of nano-silica, nano-titanium dioxide, nano-zirconium dioxide, and nano-hydroxyapatite; the size of the hydroxyl-containing nanoparticles is 5-100 nm. The mass ratio of organosilane to hydroxyl-containing nanoparticles is (0.7 ~ 1.0):

1.

2. The preparation method of the superhydrophobic activated carbon adsorbent material as described in claim 1, characterized in that, R2, R3, and R4 are methoxy, ethoxy, or chlorine; Alternatively, the organosilane may be one or a combination of dodecyltrichlorosilane, tetradecyltrichlorosilane, hexadecyltrichlorosilane, octadecyltrichlorosilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, dodecyltriethoxysilane, tetradecyltriethoxysilane, and octadecyltriethoxysilane.

3. The preparation method of the superhydrophobic activated carbon adsorbent material as described in claim 1, characterized in that, Hydroxyl-containing nanoparticles were added to an alcohol solvent and dispersed evenly. Water was then added, and the pH of the solvent system was adjusted to alkaline. Organosilane was then added to carry out the reaction.

4. The method for preparing the superhydrophobic activated carbon adsorbent material as described in claim 1, characterized in that, The pH value of alkaline aqueous solvents is 9-11; Alternatively, the mass ratio of water added to hydroxyl-containing nanoparticles is (1~2):1; Alternatively, the reaction time is 1 to 6 hours.

5. The method for preparing the superhydrophobic activated carbon adsorbent material as described in claim 1, characterized in that, The activated carbon is one or more of cylindrical activated carbon, granular activated carbon, or clover-shaped activated carbon.

6. The method for preparing the superhydrophobic activated carbon adsorbent material as described in claim 1, characterized in that, The method of coating superhydrophobic nanoparticles onto the surface of activated carbon is spraying.

7. The method for preparing the superhydrophobic activated carbon adsorbent material as described in claim 6, characterized in that, During the spraying process, the distance between the spray gun nozzle and the activated carbon is 10-20 cm, the spraying pressure is 0.3-1 MPa, and the moving speed is 2-5 cm / s.

8. A superhydrophobic activated carbon adsorbent material, characterized in that, Obtained by the preparation method according to any one of claims 1 to 7.

9. The application of the superhydrophobic activated carbon adsorbent material according to claim 8 in the field of VOCs adsorption.

10. The application as described in claim 9, characterized in that, The relative humidity of the environment where VOCs are adsorbed is above 60%.

Images