A carbon-containing cloth for efficiently absorbing VOCs in the air and a preparation method thereof

Abstract

The present invention relates to a carbon-coated cloth for efficiently absorbing VOCs in the air and a preparation method thereof, comprising: ball-milling a mixture of first activated carbon and water until the activated carbon particles are evenly distributed, adding a modifier, and dispersing the mixture through ultrasonic impregnation to obtain a spray liquid; spraying the spray liquid onto a receiving substrate and drying it to obtain a highly absorbent skeleton layer; uniformly mixing a second activated carbon and activated alumina impregnated with an active component to obtain an adsorbent material; laying a first hot-melt adhesive web on the unsprayed surface of the highly absorbent skeleton layer, hot-pressing the surface, and then flattening the adsorbent material, followed by laying a second hot-melt adhesive web and hot-pressing and fixing it, and finally laying a melt-blown cloth to obtain the carbon-coated cloth. The present invention achieves high performance in high-humidity environments by disposing coconut shell activated carbon having a pore structure dominated by mesopores and carrying highly absorbent groups upstream of the receiving substrate. Furthermore, the moisture content of the VOCs in the mixed gas decreases after passing through the receiving substrate, and the active component also facilitates their adsorption on the microporous activated carbon.

Description

Technical Field

[0001] The present invention relates to the technical field of air purification, and in particular to a carbon-containing cloth capable of efficiently absorbing VOCs in the air and a preparation method thereof. Background Art

[0002] Activated carbon is currently the most commonly used adsorbent for air purification, widely used in air purifiers, due to its high adsorption capacity for various gases, mild operating conditions, low cost, strong regeneration, and suitability for operation in various environments. However, the hydrophobic nature of traditional activated carbon limits its ability to adsorb and purify volatile organic compounds (VOCs) in high-humidity, multi-component gas environments.

[0003] Due to water's conductivity and chemical reactivity, humidity control is essential in many fields, including chemicals and batteries, to extend the lifespan of materials and devices. Activated carbon, with its well-developed pore structure, large surface area, and low material cost, is an ideal base material for composite desiccants. Therefore, improving the hydrophilicity of activated carbon and increasing its gas adsorption efficiency and capacity at specific humidity levels is crucial. Summary of the Invention

[0004] In view of the problem that traditional activated carbon-coated carbon cloth in the prior art has weak adsorption and purification ability for volatile organic compounds (VOCs) in a high-humidity multi-component gas environment, the present invention proposes a carbon-coated carbon cloth that can efficiently absorb VOCs in the air and a preparation method thereof.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] One of the purposes of the present invention is to provide a method for preparing a carbon-containing cloth that efficiently absorbs VOCs in the air, comprising:

[0007] S1. Ball-milling a mixture of the first activated carbon and water until the activated carbon particles are evenly distributed, then adding a modifier and a dispersant, and dispersing the mixture by ultrasonic impregnation to obtain a spray liquid; spraying the spray liquid on a receiving substrate and drying the mixture, repeating the process multiple times to obtain a highly absorbent skeleton layer;

[0008] S2, mixing the second activated carbon and the activated alumina impregnated with the active component to obtain an adsorption material;

[0009] S3. Lay the first hot melt adhesive mesh on the unsprayed surface of the highly absorbent skeleton layer, continue to lay the adsorption material flat after hot pressing, then lay the second hot melt adhesive mesh and fix it with hot pressing, and finally lay the meltblown cloth to obtain a carbon-containing cloth that efficiently absorbs VOCs in the air.

[0010] Furthermore, in S1, the first activated carbon is dominated by mesopores and micropores, and the total specific surface area of ​​mesopores and micropores accounts for 75%-85% of the total specific surface area of ​​the activated carbon. The specific surface area of ​​the first activated carbon is 600-800m2 / g of coconut shell activated carbon based carbon.

[0011] Furthermore, in S1, the modifier is a solution composed of one or more solutes selected from CaCl2, MgCl2, and LiCl, preferably CaCl2, and the amount of the solute added is 15 to 30 wt%.

[0012] Furthermore, in S1, the spraying step is specifically as follows: spraying the spraying liquid on the receiving substrate and drying it at 90-100°C for 0.5-1.0h, repeating 2-3 times, so that the loading amount on the receiving substrate is 40-80g / m 2 .

[0013] Furthermore, in S1, the receiving substrate has a gram weight of 60-70 g / m 2 Polyethylene terephthalate (PET) non-woven fabric.

[0014] Furthermore, in S2,

[0015] The mass of the activated alumina is 10%-20% of the mass of the second activated carbon;

[0016] The particle size of the activated alumina is 0.30-0.40 mm;

[0017] The activated alumina is loaded with active components by ultrasonic impregnation of equal volume. During the impregnation process, the activated alumina is placed in a 40kHz ultrasonic water bath for 80 minutes, then allowed to stand for 12 hours, heated at 60°C, and continuously stirred until the liquid is completely eliminated. The active component is one of KMnO4, Mn(NO3)2, and K2FeO4 solutions, with a concentration of 0.8-2.0 mol / L, preferably 1.0-1.5 mol / L.

[0018] Furthermore, in S2, the second activated carbon has a specific surface area of ​​1300m 2 / g, microporous coconut shell activated carbon with a particle size of 0.18-0.25mm and an iodine value of 1200mg / g.

[0019] Furthermore, in S3,

[0020] The first hot melt adhesive web is a hot melt adhesive web composed of one or more of polyolefin (PO), polyethersulfone resin (PES) or polyamide (PA), with a gram weight of 10-15 g / m 2 , melting range is 80-120℃;

[0021] The second hot melt adhesive web is a polyethersulfone resin (PES) hot melt adhesive web with a gram weight of 18-25g / m 2 , melting range is 80-120℃;

[0022] The meltblown cloth is 25g / m 2 Polypropylene meltblown nonwoven fabric.

[0023] Among them, the second hot melt adhesive mesh has a heavier gram weight than the first hot melt adhesive mesh. This is because the hot melt adhesive mesh with a larger gram weight can maintain stable mechanical properties after hot pressing and has excellent strength and stiffness. While ensuring the fixation of the activated carbon layer, a certain gap can be generated between the carbon layers. The gas will be diverted when passing through the interface layer, reducing the resistance of the airflow through the carbon cloth.

[0024] Furthermore, in S3, the amount of the second activated carbon laid is 180-200 g / m 2 .

[0025] Furthermore, a desktop conveyor is provided below the highly absorbent skeleton layer and a high-voltage electrostatic powder sprinkler is provided above the layer to ensure that the adsorption material can be evenly distributed in the skeleton layer; the powder amount adjustment range of the high-voltage electrostatic powder sprinkler is 25%-35%, and the transmission frequency of the desktop conveyor is set to 15-20Hz, so as to achieve a uniform distribution effect of the adsorption material particles while avoiding the particles falling off the cloth surface due to excessive amplitude, high frequency, and long time.

[0026] Furthermore, in S3, the hot pressing temperature is 90-110°C.

[0027] The second object of the present invention is to provide a carbon cloth that can efficiently absorb VOCs in the air, which is prepared by the preparation method described above.

[0028] Mechanism of action: Water vapor is adsorbed by activated carbon through different adsorption mechanisms under different conditions. In a high humidity environment, water vapor mainly exists in the form of capillary condensation in the pore structure, while in a low humidity environment, water vapor is mainly chemically adsorbed in the microporous structure. The oxygen-containing functional groups on the surface of activated carbon tend to form hydrogen bonds with water molecules, causing water molecules to easily occupy the adsorption sites of VOCs, thereby reducing the amount of VOCs adsorbed by carbon-based materials. Alumina is added to microporous activated carbon as an active component. Since alumina is a polar adsorbent, it can preferentially react with polar gas molecules such as water vapor and SO2 in the mixed gas during gas treatment, reducing the competitive adsorption of these polar molecules with VOCs on the microporous material, thereby achieving the effect of effectively removing VOCs. Impregnation of active components can remove VOCs by chemical adsorption.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The carbon cloth material of the present invention provides a coconut shell activated carbon with a pore structure dominated by mesopores and loaded with strong water-absorbing groups upstream of the receiving substrate, so that the material still has high performance in a high-humidity environment; on the other hand, the moisture content of VOCs in the mixed gas is reduced after passing through the receiving substrate, and under the action of the active components, it also helps its adsorption on the microporous activated carbon.

[0031] (2) The middle layer of the carbon cloth material of the present invention is made of a PES hot melt adhesive mesh with high rigidity and high toughness. The PES hot melt adhesive mesh can maintain stable mechanical properties while being hot-pressed and flow-formed, and has excellent strength and rigidity. It enhances the stiffness of the carbon cloth material while also allowing certain gaps to exist in the activated carbon layer, thereby increasing the effective contact area between the gas and the activated carbon layer and reducing the filtration resistance of the carbon cloth material to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a comparison chart of toluene removal efficiency changes over time in Example 1;

[0033] Figure 2 1 is a comparison chart of toluene removal efficiency changes over time in Example 1, Comparative Example 1 and Comparative Example 4 under the conditions of 25° C. and 50% RH. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] To overcome the problem in the prior art that conventional activated carbon-coated carbon cloth has a weak ability to adsorb and purify volatile organic compounds (VOCs) in a high-humidity, multi-component gas environment, this embodiment provides a method for preparing a carbon-coated carbon cloth that efficiently absorbs VOCs in the air, comprising the following steps:

[0037] Step 1: Preparation of the drying layer

[0038] (1) The first activated carbon selected has a pore structure dominated by mesopores and a specific surface area of ​​650m 2 / g, the total specific surface area of ​​mesopores and micropores is about 500m 2 / g, coconut shell activated carbon-based carbon with a particle size of 0.25-0.60mm; preparing a 17wt% CaCl2 aqueous solution as an impregnation solution, immersing the first activated carbon in the CaCl2 impregnation solution, and ultrasonically impregnating for 120 minutes at a temperature of 45°C and a power of 30kHz; then drying at 120°C for 2 hours to obtain an impregnated activated carbon; by weight, 10 parts of the impregnated activated carbon, 1 part of polyvinyl alcohol, and 20 parts of deionized water were ball-milled to form a spray liquid, and the spray liquid was measured by a particle size distribution instrument to have a D90 of 102nm, which was then transferred to a sprayer for use;

[0039] (2) The receiving substrate has a gram weight of 60-70g / m 2 Polyethylene terephthalate non-woven fabric, fix the receiving substrate on the table with the sprayed surface facing up, laminate the protective film on the unsprayed surface, use a spray pump to spray the receiving substrate, and after spraying, transfer the receiving substrate to an oven at 85°C and dry for 1 hour. Repeat the above spraying and drying operations 3 times, and weigh and calculate the coating loading to be 40g / m 2 , a highly water-absorbent skeleton layer can be obtained.

[0040] Step 2: Preparation of adsorption materials

[0041] The second activated carbon is selected with a specific surface area of ​​1300m 2 / g, with a particle size of 0.18-0.25mm and an iodine value of 1200mg / g of microporous coconut shell activated carbon. The active component is a 1.0mol / L KMnO4 solution, and the activated alumina has a particle size of 0.30-0.40mm. 20g of activated alumina is immersed in 100mL of the active component solution, and ultrasonic dispersion is controlled at 40°C. During the impregnation process, the activated carbon is subjected to a 40kHz ultrasonic water bath for 80 minutes, then allowed to stand for 12 hours and heated at 60°C with constant stirring until the liquid is completely eliminated, resulting in the impregnated alumina. A second activated carbon is mixed with the impregnated alumina at a mass ratio of 9:1 to obtain the adsorption material.

[0042] Step 3: Preparation of carbon cloth

[0043] (1) After the first hot melt adhesive mesh is laid flat on the receiving substrate spray layer and fixed by hot pressing, the adsorption material is evenly laid on the surface, the second hot melt adhesive mesh is laid on the adsorption material layer and fixed by hot pressing, and then the melt-blown cloth is superimposed on the second hot melt adhesive mesh, wherein the melt-blown cloth has a gram weight of 25g / m 2 Polypropylene (PP) meltblown nonwoven fabric, the first hot melt adhesive mesh has a gram weight of 15g / m 2 Polyolefin hot melt adhesive mesh film, the second hot melt adhesive mesh film has a gram weight of 20g / m 2 The laying amount of polyethersulfone resin (PES) adsorption material is 200g / m 2 .

[0044] (2) A desktop conveyor is provided below the receiving substrate and a high-voltage electrostatic powder sprinkler is provided above the receiving substrate to ensure that the adsorption material can be evenly distributed on the receiving substrate, wherein the speed frequency of the desktop conveyor is 15 Hz and the powder amount adjustment range of the high-voltage electrostatic powder sprinkler is 25%-35%;

[0045] (3) The above-mentioned sequentially stacked materials are pressed and formed by hot pressing, and the hot pressing temperature is controlled at 100° C. to obtain a carbon-containing cloth.

[0046] The carbon cloth material prepared above was cut into disc-shaped filter materials with a diameter of 112.9 mm and applied to the toluene gas filtration treatment test. The toluene concentration was 80 ppm (air as the base gas), the surface wind speed was 0.1 m / s (the aggregate surface was facing the wind), and the experimental environment was: temperature 25 ° C, relative humidity 10%, 30%, 50%, 70% environment. The toluene removal efficiency change curve over time is shown in Figure 1 middle.

[0047] like Figure 1 As shown in Table 1, the carbon cloth can completely remove toluene within 10 minutes, and then the removal efficiency slowly decreases until it is completely deactivated after 90 minutes. The adsorption capacity can reach 41g / m 2 ;pass Figure 1 It can be seen that under a certain humidity environment, the impregnation-modified carbon cloth has a certain improvement in the removal efficiency and adsorption capacity of toluene. This is because water vapor condenses through capillaries and gathers in the microporous adsorption center of the upper activated carbon, reducing the competitive adsorption of water vapor and toluene on the activated carbon for the adsorption sites, thereby extending the toluene adsorption time and obtaining a higher adsorption capacity.

[0048] Comparative Example 1

[0049] Compared with Example 1, the difference is that in step 1, "the modifier is directly mixed with the first activated carbon and then ball milled", and the rest remains unchanged. The test results are shown in Table 1. Figure 2 It can be seen that in the adsorption environment of 25°C and 50% RH, without impregnation, the modifier failed to effectively combine with the activated carbon, resulting in a reduction in the water absorption sites in the drying layer. Under the same humidity conditions, the toluene adsorption efficiency and adsorption capacity both decreased. This is because the water vapor in the gas condensed and gathered in the microporous adsorption center of the activated carbon by capillary condensation, causing the toluene adsorption sites to be partially occupied, thereby reducing the adsorption efficiency and adsorption capacity.

[0050] Comparative Example 2

[0051] Compared with Example 1, the difference is that in step 1, "the first activated carbon is directly dried after being impregnated with the modifier" and then directly mixed evenly with the "modified adsorption material" in step 2, and the rest remains unchanged. The test results are shown in Table 1.

[0052] Compared with Example 1, the gas removal efficiency and adsorption capacity of Comparative Example 2 are slightly reduced. This is because the diversion effect of the airflow is weakened, the effective contact area between water vapor and the first activated carbon layer is reduced, and the water vapor in the gas exists in the form of capillary condensation in the pore structure of the activated carbon, which will block part of the adsorption channels and reduce the removal efficiency. Due to the presence of water vapor, the toluene adsorption sites are occupied, and the toluene adsorption capacity is greatly reduced.

[0053] Comparative Example 3

[0054] Compared with Example 1, the difference is that in step 2, "the second activated carbon does not load the active component", and the rest remains unchanged. The test results are shown in Table 1.

[0055] Compared with Example 1, the adsorption capacity of the material in Comparative Example 3 has decreased significantly. This is because the active components of the second activated carbon layer can effectively adsorb toluene molecules through chemical reactions. Therefore, the presence of the active components can increase the adsorption capacity of the material for toluene. Due to the presence of the hygroscopic skeleton layer, there are no water molecules in the gas entering the adsorption layer to compete with toluene for adsorption sites. Therefore, the initial adsorption efficiency of the material is similar to that of Example 1.

[0056] Comparative Example 4

[0057] Compared with Example 1, the difference is that in step 1, "the receiving substrate does not load the component", and the rest remains unchanged. The test results are shown in Table 1.

[0058] Compared with Example 1, the adsorption capacity of the material prepared in Comparative Example 4 decreases. The removal of the first activated carbon layer reduces the water absorption sites in the drying layer. Under the same humidity conditions, the toluene adsorption capacity decreases. This is because the water vapor in the gas condenses and gathers in the microporous adsorption center of the activated carbon by capillary condensation, so that the toluene adsorption sites are partially occupied, thereby reducing both the adsorption efficiency and the adsorption capacity.

[0059] Comparative Example 5

[0060] Compared with Example 1, the difference is that: in step (2) of step 3, the speed frequency of the desktop conveyor is 15 Hz; in step (3) of step 3, the hot pressing temperature is controlled at 100°C. The test results are shown in Table 1.

[0061] Table 1 Toluene removal efficiency at 50% RH

[0062]

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon cloth that efficiently absorbs VOCs in the air, characterized in that: include: S1. ball-milling a mixture of the first activated carbon and water until the activated carbon particles are evenly distributed, adding a modifier, and dispersing the mixture by ultrasonic impregnation to obtain a spraying liquid; Spraying the spraying liquid on the receiving substrate and drying it, repeating multiple times to obtain a highly water-absorbent skeleton layer; S2, mixing the second activated carbon and the activated alumina impregnated with the active component to obtain an adsorption material; S3. Lay the first hot melt adhesive mesh on the unsprayed surface of the highly absorbent skeleton layer, continue to lay the adsorption material flat after hot pressing, then lay the second hot melt adhesive mesh and hot press to fix it, and finally lay the meltblown cloth to obtain a carbon-containing cloth that efficiently absorbs VOCs in the air; In S1, the first activated carbon has a specific surface area of ​​600-800m 2 / g coconut shell activated carbon-based carbon, the first activated carbon is dominated by mesopores and micropores, and the total specific surface area of ​​mesopores and micropores accounts for 75%-85% of the total specific surface area of ​​the activated carbon; In S1, the modifier is a solution composed of one or more solutes selected from CaCl2, MgCl2, and LiCl, and the amount of the solute added is 15-30 wt%.

2. The method for preparing a carbon cloth for efficiently absorbing VOCs in the air according to claim 1, characterized in that: In S1, the spraying step is specifically as follows: spraying the spraying liquid on the receiving substrate and drying it at 90-100 ° C for 0.5-1.0h, repeating 2-3 times, so that the loading amount on the receiving substrate is 40-80g / m 2 .

3. The method for preparing a carbon cloth for efficiently absorbing VOCs in the air according to claim 1, characterized in that: In S1, the receiving substrate has a gram weight of 60-70 g / m 2 Polyethylene terephthalate non-woven fabric.

4. The method for preparing a carbon cloth for efficiently absorbing VOCs in the air according to claim 1, characterized in that: In S2, The mass of the activated alumina is 10%-20% of the mass of the second activated carbon; The particle size of the activated alumina is 0.30-0.40 mm; The activated alumina is loaded with active components by ultrasonic impregnation of equal volumes. During the impregnation process, the activated alumina is placed in a 40kHz ultrasonic water bath for 80 minutes, then allowed to stand for 12 hours, heated at 60°C, and continuously stirred until the liquid is completely eliminated. The active component is one of KMnO4, Mn(NO3)2, and K2FeO4 solutions with a concentration of 0.8-2.0 mol / L.

5. The method for preparing a carbon cloth for efficiently absorbing VOCs in the air according to claim 1, characterized in that: In S2, the second activated carbon has a specific surface area of ​​1300m 2 / g, microporous coconut shell activated carbon with a particle size of 0.18-0.25mm and an iodine value of 1200mg / g.

6. The method for preparing a carbon cloth for efficiently absorbing VOCs in the air according to claim 1, characterized in that: In S3, The first hot melt adhesive web is a hot melt adhesive web composed of one or more of polyolefin, polyethersulfone resin or polyamide, with a gram weight of 10-15g / m 2 , melting range is 80-120℃; The second hot melt adhesive mesh is a polyethersulfone resin hot melt adhesive mesh with a gram weight of 18-25g / m 2 , melting range is 80-120℃; The meltblown cloth is 25g / m 2 Polypropylene meltblown nonwoven fabric.

7. The method for preparing a carbon cloth for efficiently absorbing VOCs in the air according to claim 1, characterized in that: In S3, the amount of the second activated carbon laid is 180-200 g / m 2 .

8. A carbon cloth for efficiently absorbing VOCs in the air, characterized in that: The invention discloses a novel cellulose acetate resin composition comprising the steps of claim 1 , wherein the cellulose acetate resin composition comprises the steps of:

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