An activated carbon paper for formaldehyde removal and its preparation method

Abstract

The present invention discloses an activated carbon paper for removing formaldehyde and a preparation method thereof. First, the activated carbon is subjected to amination modification. Secondly, plant fibers and aminated activated carbon are mixed and then prepared into activated carbon paper through wire forming, pressing and dewatering, and drying and rewinding. Then, polyamide-amine, nano-zinc oxide, and nano-titanium dioxide are loaded on cellulose nanofibers through hydrogen bonding to prepare a composite finishing agent. Finally, the composite finishing agent is treated on the activated carbon paper to obtain the activated carbon paper for removing formaldehyde. On the one hand, the aminated activated carbon is used to remove a large amount of formaldehyde through physical adsorption and chemical neutralization. On the other hand, cellulose nanofibers with high reaction activity and large specific surface area are used to load polyamide-amine, zinc oxide, and titanium dioxide for chemical neutralization and photocatalytic decomposition of formaldehyde. The activated carbon paper prepared by the present invention has good formaldehyde removal effect and long persistence, and can be directly applied to the removal of formaldehyde in the air, and can also be used for air filtration components.

Description

Technical Field

[0001] The present invention belongs to the technical field of papermaking, and particularly relates to an activated carbon paper for removing formaldehyde and a preparation method thereof. Background Art

[0002] Formaldehyde, a colorless aqueous solution or gas with a pungent odor, has been recognized by the World Health Organization as a Class I carcinogen. It mainly shows a stimulating effect on the skin and mucous membranes. Long-term exposure has carcinogenic effects. Even low-concentration formaldehyde can cause various diseases such as chronic respiratory diseases, nasopharyngeal carcinoma, colon cancer, brain tumors, and menstrual disorders after long-term exposure. Especially for teenagers, it is extremely easy to cause chromosomal abnormalities and leukemia. Formaldehyde is the main pollutant released from decorated rooms and building materials into the air. Due to its potential sensitization, carcinogenesis, and teratogenesis, it has become a hot topic in indoor environment research in recent years.

[0003] At present, there are many formaldehyde removal products on the market. For example, activated carbon or diatom mud mainly based on physical adsorption can play a good adsorption role for indoor formaldehyde, but the adsorption capacity is limited, and it only targets free harmful gases in the air. And after the adsorption reaches saturation, if not processed in time, when the temperature rises, it will be desorbed from the material surface again, causing the formaldehyde concentration in the space environment to rise again; the method of adsorbing formaldehyde based on various plants can only absorb a small part of formaldehyde, only playing an auxiliary role, and is also very sensitive to a certain concentration of formaldehyde. In an environment with high-concentration formaldehyde, plants themselves are also difficult to bear; the amino acid spray made of penetrants, surfactants, etc. can be sprayed on the surface of wooden furniture and can also penetrate into the wood interior, decomposing formaldehyde into non-toxic and harmless hydroxymethyl derivatives and water, but it will cause the problem of discoloration of furniture and walls, and will bring secondary pollution to the environment. Summary of the Invention

[0004] The present invention aims to overcome the deficiencies existing in the above technical problems and provides an activated carbon paper with good formaldehyde removal effect and long persistence.

[0005] The specific steps for preparing the activated carbon paper for removing formaldehyde in the present invention are as follows:

[0006] A preparation method of activated carbon paper for formaldehyde removal, characterized by comprising the following steps: (1) Take a certain amount of activated carbon and place it in a beaker, add an amino-silane coupling agent, and oscillate it in a water bath constant temperature oscillator at 30-60°C for 1-3 hours, then filter and dry to obtain amino-modified activated carbon; (2) Mix plant fiber and amino-modified activated carbon evenly according to a mass ratio of 3:1-1:1, and then prepare activated carbon paper through web forming, pressing dehydration, drying and rewinding; (3) Disperse cellulose nanofibers in deionized water, then take a certain amount of polyamide-amine and add it to the cellulose nanofiber dispersion, stir at room temperature for 10-30 minutes, then add a certain amount of zinc oxide and titanium dioxide, and emulsify at 1000 rpm - 1500 rpm for 10-15 minutes to obtain a composite finishing agent; finally, post-treat the composite finishing agent on the activated carbon paper to prepare activated carbon paper for formaldehyde removal.

[0007] In the described preparation method, the activated carbon is coconut shell activated carbon powder with a particle size of 100-600 mesh.

[0008] In the described preparation method, the amino-silane coupling agent is any one of γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and 3-aminopropyl(diethoxy)methylsilane, and the addition amount is 30wt% - 50wt% of the activated carbon.

[0009] In the described preparation method, the plant fiber is one or more of cotton fiber, hemp fiber, bamboo fiber, softwood fiber, and hardwood fiber.

[0010] In the described preparation method, the polyamide-amine in the composite finishing agent is a 3.0-generation polyamide-amine type dendrimer with ethylenediamine as the core, and the mass ratio of polyamide-amine to cellulose nanofibers is 2:1-5:1.

[0011] In the described preparation method, the diameter of the cellulose nanofibers in the composite finishing agent is 5-30 nm, the length is 500-1000 nm, and the dosage of the cellulose nanofibers is 0.2-1.0 g.

[0012] In the described preparation method, the particle size of the zinc oxide in the composite finishing agent is 50-200 nm, preferably 100 nm, and the mass ratio of zinc oxide to nanofibrillated cellulose is 1:1-1:3.

[0013] In the described preparation method, the particle size of the titanium dioxide in the composite finishing agent is 5-20 nm, preferably 5 nm, and the mass ratio of titanium dioxide to nanofibrillated cellulose is 1:1-1:2.

[0014] In the described preparation method, the activated carbon paper for formaldehyde removal is prepared by post-treating the activated carbon paper by spraying, roll coating or dipping with a composite finishing agent, and the wet loading amount of the composite finishing agent is 30-60 g / m 2 .

[0015] The beneficial effects of the present invention include:

[0016] (1) By introducing aminated modified activated carbon, the present invention endows the paper with a certain formaldehyde removal ability. The coconut shell activated carbon powder used in the present invention has the advantages of developed pores, good adsorption performance, high strength, easy regeneration, economy and durability, etc., and can effectively adsorb formaldehyde. However, the adsorption capacity of activated carbon is limited, and if it is not treated in time after adsorption saturation, it will desorb from the material surface again when the temperature rises, resulting in a re-increase in the formaldehyde concentration in the space. The present invention further increases the specific surface area of the activated carbon by amination modification, further improving the formaldehyde adsorption ability. At the same time, the amino groups on the activated carbon can undergo a condensation reaction with formaldehyde to avoid formaldehyde desorption.

[0017] (2) By introducing cellulose nanofibers, a large number of binding points are provided for polyamide-amine, zinc oxide, and titanium dioxide, enabling each component to be firmly loaded on the activated carbon paper, avoiding the detachment of polyamide-amine, zinc oxide, and titanium dioxide materials from the activated carbon paper, and also avoiding the adsorption of polyamide-amine, zinc oxide, and titanium dioxide by the activated carbon, which affects the formaldehyde removal ability of each component. It also further avoids the problem that polyamide-amine forms a film on the surface of the activated carbon paper, and zinc oxide and titanium dioxide block the pores of the paper, affecting the air permeability of the paper. The cellulose nanofibers are prepared by mechanically grinding plant cellulose fibers. The diameter of the cellulose nanofibers is 5-30 nm, and the length is 500-1000 nm. They have the characteristics of a large aspect ratio, high strength, large specific surface area, and high reaction activity. The present invention uses the abundant hydroxyl and carboxyl groups on the surface of cellulose nanofibers to load polyamide-amine, zinc oxide, and titanium dioxide, and then through the super strong binding ability of cellulose nanofibers to the paper, polyamide-amine, zinc oxide, and titanium dioxide are firmly combined with the activated carbon paper, so that each component can synergistically play the maximum role in removing formaldehyde.

[0018] (3) The present invention gives the paper the ability to continuously remove formaldehyde through chemical neutralization and photocatalytic decomposition by introducing polyamidoamine, zinc oxide, and titanium dioxide to work synergistically. The polyamidoamine used in the present invention is a 3.0-generation polyamidoamine dendrimer with ethylenediamine as the core, and there are 16 primary amine groups in the molecule, which can adsorb a large amount of formaldehyde gas; under the light condition with a wavelength of about 387.5 nm, the hydroxyl radicals and superoxide ion radicals generated on the surface of TiO2 in titanium dioxide have strong oxidation ability. The reaction energy of the hydroxyl radicals is sufficient to break the C-C, C-H, C-N, C-O, N-H, etc. bonds in organic substances, so that organic pollutants are completely oxidized to CO2 and H2O under the action of hydroxyl radicals and superoxide ion radicals, but a large amount of formaldehyde will only be decomposed under the condition of ultraviolet light; zinc oxide has the electronic structure of a semiconductor catalyst, and under light irradiation, it decomposes toxic and harmful substances such as formaldehyde as a strong oxidant. The present invention screens materials, adjusts the formula, optimizes the dosage, and adjusts the combination between components, and uses the characteristics of polyamidoamine, zinc oxide, and titanium dioxide to load them on cellulose nanofibrils, giving the paper the ability to continuously and effectively remove formaldehyde.

[0019] (4) The activated carbon paper prepared by the present invention, on the one hand, uses the physical adsorption and chemical neutralization of aminated activated carbon to remove a large amount of formaldehyde, and on the other hand, uses cellulose nanofibers with high reaction activity and large specific surface area to load polyamidoamine, zinc oxide, and titanium dioxide to chemically neutralize and photocatalytically decompose formaldehyde. The activated carbon paper prepared by the present invention has good formaldehyde removal effect and long persistence, and can be directly applied to the removal of formaldehyde in the air, and can also be used in air filtration components. Specific embodiments

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other arbitrarily.

[0021] Example 1

[0022] (1) Take a certain amount of coconut shell activated carbon powder and place it in a beaker. Add 40 wt% N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane and oscillate it in a constant temperature water bath oscillator at 40 °C for 1 h. Then filter and dry to obtain amino-functionalized activated carbon. (2) Mix softwood fibers and amino-functionalized activated carbon evenly at a mass ratio of 3:1, then form it on a wire mesh, press and dehydrate, dry and rewind to prepare activated carbon paper. (3) Disperse 0.2 g of cellulose nanofibers in deionized water, then add 0.4 g of polyamidoamine to the cellulose nanofiber dispersion, stir at room temperature for 20 min, then add 0.05 g of zinc oxide with a particle size of 100 nm and 0.05 g of titanium dioxide with a particle size of 5 nm, and emulsify at 1000 rpm for 15 min to obtain a composite finishing agent. Finally, post-treat the activated carbon paper by spraying with the composite finishing agent to obtain activated carbon paper for removing formaldehyde, and the wet pick-up amount of the composite finishing agent is 30 g / m 2 。

[0023] Example 2

[0024] (1) Take a certain amount of coconut shell activated carbon powder and place it in a beaker. Add 40 wt% N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane and oscillate it in a constant temperature water bath oscillator at 40 °C for 1 h. Then filter and dry to obtain amino-functionalized activated carbon;

[0025] (2) Mix softwood fibers and amino-functionalized activated carbon evenly at a mass ratio of 1:1, then form it on a wire mesh, press and dehydrate, dry and rewind to prepare activated carbon paper. (3) Disperse 0.2 g of cellulose nanofibers in deionized water, then add 0.4 g of polyamidoamine to the cellulose nanofiber dispersion, stir at room temperature for 20 min, then add 0.05 g of zinc oxide with a particle size of 100 nm and 0.05 g of titanium dioxide with a particle size of 5 nm, and emulsify at 1000 rpm for 15 min to obtain a composite finishing agent. Finally, post-treat the activated carbon paper by dipping with the composite finishing agent to obtain activated carbon paper for removing formaldehyde, and the wet pick-up amount of the composite finishing agent is 30 g / m 2 。

[0026] Example 3

[0027] (1) Take a certain amount of coconut shell activated carbon powder and place it in a beaker. Add 40 wt% N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane and oscillate it in a constant temperature water bath shaker at 40 °C for 1 h. Then filter and dry to obtain amino-functionalized activated carbon. (2) Mix softwood fibers and amino-functionalized activated carbon evenly according to a mass ratio of 1:1, then form it on the net, press and dehydrate, dry and rewind to prepare activated carbon paper. (3) Disperse 0.2 g of cellulose nanofibers in deionized water, then add 1.0 g of polyamide-amine to the cellulose nanofiber dispersion, stir at room temperature for 20 min, then add 0.1 g of zinc oxide with a particle size of 100 nm and 0.1 g of titanium dioxide with a particle size of 5 nm, and emulsify at 1000 rpm for 15 min to obtain a composite finishing agent. Finally, post-treat the activated carbon paper with the composite finishing agent by roll coating to obtain activated carbon paper for removing formaldehyde, and the wet pick-up amount of the composite finishing agent is 30 g / m 2 。

[0028] Example 4

[0029] (1) Take a certain amount of coconut shell activated carbon powder and place it in a beaker. Add 40 wt% N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane and oscillate it in a constant temperature water bath shaker at 40 °C for 1 h. Then filter and dry to obtain amino-functionalized activated carbon. (2) Mix softwood fibers and amino-functionalized activated carbon evenly according to a mass ratio of 1:1, then form it on the net, press and dehydrate, dry and rewind to prepare activated carbon paper. (3) Disperse 0.4 g of cellulose nanofibers in deionized water, then add 1.2 g of polyamide-amine to the cellulose nanofiber dispersion, stir at room temperature for 20 min, then add 0.2 g of zinc oxide with a particle size of 100 nm and 0.2 g of titanium dioxide with a particle size of 5 nm, and emulsify at 1000 rpm for 15 min to obtain a composite finishing agent. Finally, post-treat the activated carbon paper with the composite finishing agent by roll coating to obtain activated carbon paper for removing formaldehyde, and the wet pick-up amount of the composite finishing agent is 60 g / m 2 。

[0030] Comparative Example 1

[0031] Mix softwood fibers and coconut shell activated carbon powder evenly according to a mass ratio of 3:1, then form it on the net, press and dehydrate, dry and rewind to prepare the obtained activated carbon paper as Comparative Example 1.

[0032] Comparative Example 2

[0033] (1) Take a certain amount of coconut shell activated carbon powder and place it in a beaker. Add 40wt% N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane and oscillate it in a constant temperature water bath shaker at 40 °C for 1 h. Then filter and dry to obtain amino-functionalized modified activated carbon. (2) Mix softwood fibers and amino-functionalized activated carbon evenly at a mass ratio of 1:1, then form it on a net, press and dehydrate, dry and rewind to prepare activated carbon paper. (3) Disperse 1.0 g of polyamide-amine in deionized water, add 0.1 g of zinc oxide with a particle size of 100 nm and 0.1 g of titanium dioxide with a particle size of 5 nm, and emulsify at 1000 rpm for 15 min to obtain a finishing agent. Finally, post-treat the activated carbon paper by roll coating, and the wet pick-up of the composite finishing agent is 60 g / m 2 , and the prepared activated carbon paper is used as Comparative Example 2.

[0034] Test the formaldehyde removal performance of the papers prepared in Examples 1, 2, 3, 4 and Comparative Examples 1 and 2. Formaldehyde removal performance test method: Take 500 g of paper and place it in a room with a formaldehyde concentration of 1 ppm and a volume of 10 m 3 . After 1 h, 2 h, 3 h, 5 h, 12 h, and 24 h respectively, use a detection instrument to test the formaldehyde concentration C1. The formaldehyde removal rate = (1 - C1) / C1 * 100%; after the 24-hour test is completed, continue to introduce 1 ppm of formaldehyde into the room, and use a detection instrument to test the formaldehyde concentration C2 after 5 h and 24 h respectively. The formaldehyde removal rate = (1 - C2) / C2 * 100%.

[0035] The following are the test results of the formaldehyde removal performance of the activated carbon papers for removing formaldehyde prepared in Examples 1, 2, 3, 4 and Comparative Examples 1 and 2, and the further formaldehyde removal performance test results after the 24-hour test, as shown in Table 1.

[0036] Table 1 Test results of the formaldehyde removal performance of the papers

[0037]

[0038] It can be seen from Example 1 and Comparative Example 1 that the addition of amino-functionalized modified activated carbon greatly improves the formaldehyde removal amount of the paper;

[0039] It can be seen from Example 4 and Comparative Example 2 that the addition of cellulose nanofibers greatly improves both the formaldehyde removal amount and the duration of the paper;

[0040] It can be seen from the examples and comparative examples in Table 1 that the papers prepared in Comparative Example 1 and Comparative Example 2 will reach the maximum saturated absorption amount within a certain period of time. After continuing to introduce formaldehyde, they almost no longer have adsorption ability; the

[0041] The papers in Examples 1, 2, 3, and 4 can achieve a formaldehyde removal rate of over 90% in a very short time and can continuously remove formaldehyde.

[0042] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of activated carbon paper for formaldehyde removal, characterized in that, It includes the following steps: (1) Take a certain amount of activated carbon and place it in a beaker. Add an amino-silane coupling agent and oscillate it in a water bath constant temperature oscillator at 30 - 60 °C for 1 - 3 h. Then filter and dry to obtain amino-functionalized activated carbon. The activated carbon is coconut shell activated carbon powder with a particle size of 100 - 600 mesh. The amino-silane coupling agent is any one of γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and 3-aminopropyl(diethoxy)methylsilane, and the addition amount is 30wt% - 50wt% of the activated carbon; (2) Mix plant fiber and amino-functionalized activated carbon evenly according to a mass ratio of 3∶1 - 1∶1, and then prepare activated carbon paper through forming on a net, pressing and dewatering, drying and rewinding. The plant fiber is one or more of cotton fiber, hemp fiber, bamboo fiber, softwood fiber, and hardwood fiber; (3) Disperse cellulose nanofibers in deionized water. Then take a certain amount of polyamide-amine and add it to the cellulose nanofiber dispersion. Stir at room temperature for 10 - 30 min, and then add a certain amount of zinc oxide and titanium dioxide. Emulsify at 1000 rpm - 1500 rpm for 10 - 15 min to obtain a composite finishing agent. Finally, post-treat the activated carbon paper with the composite finishing agent to obtain activated carbon paper for formaldehyde removal.

2. The preparation method according to claim 1, characterized in that, In the composite finishing agent in step (3), the diameter of the cellulose nanofibers is 5 - 30 nm, the length is 500 - 1000 nm, the dosage of the cellulose nanofibers is 0.2 - 1.0 g, the polyamide-amine is a 3.0-generation polyamide-amine type dendrimer with ethylenediamine as the core, and the mass ratio of polyamide-amine to cellulose nanofibers is 2∶1 - 5∶1. The particle size of the zinc oxide is 50 - 200 nm, and the mass ratio of zinc oxide to nanofibrillated cellulose is 1∶1 - 1∶3. The particle size of the titanium dioxide is 5 - 20 nm, and the mass ratio of titanium dioxide to nanofibrillated cellulose is 1∶1 - 1∶2.

3. The preparation method according to claim 1, characterized in that, The activated carbon paper for formaldehyde removal described in step (3) is prepared by post-treating the activated carbon paper by spraying, roll coating or dipping with a composite finishing agent, and the wet loading of the composite finishing agent is 30-60 g / m 2 .

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