Modified activated carbon, filter element and preparation method of modified activated carbon

Abstract

The invention discloses modified activated carbon, a filter element and a preparation method of the modified activated carbon. The preparation method comprises the following steps: S1, performing oxidation reaction on activated carbon and an oxidizing agent to obtain oxidized activated carbon; s2, reacting the oxidized activated carbon with a chitosan solution to obtain activated carbon with a chitosan layer on the surface; s3, enabling the activated carbon with the chitosan layer on the surface to react with a carboxymethyl cellulose solution, and enabling an obtained reaction product to react with a chitosan solution. The modified activated carbon provided by the invention has an excellent antibacterial effect, and can effectively prevent bacterial breeding and bacterial metabolite generation on the surface of the activated carbon, and the antibacterial rate of the filter element prepared from the modified activated carbon can reach 99.5% or above; an antibacterial material is introduced through chemical modification of activated carbon, and stable chemical bonds are formed through self-assembly of surface static layers, so that an antibacterial agent is not easy to lose; the modified formula improves the hydrophilicity of the activated carbon, so that the prepared filter element has smaller water resistance and larger system flux.

Description

Technical Field

[0001] The present invention specifically relates to a modified activated carbon, a modified activated carbon filter element and a preparation method thereof. Background Art

[0002] Due to its large specific surface area, activated carbon can adsorb organic substances and improve the taste of the water output of water purifiers, and is widely used in the field of water treatment. However, when organic substances accumulate on the surface of activated carbon, it provides nutrients for microorganisms, and the huge surface area provides a breeding ground for bacteria, resulting in the total number of colonies in the water produced by the activated carbon filter element exceeding the standard, and even the metabolites of bacteria such as nitrite exceeding the standard, affecting water quality.

[0003] At present, household water purifiers are developing in the direction of small volume and large flow rate. However, ordinary activated carbon itself has insufficient hydrophilicity, resulting in a large water resistance during use and affecting the flow rate of the whole machine system. In addition, most of the activated carbon with antibacterial functions on the market is a simple physical mixture of activated carbon and antibacterial agents, which has the problems of fast release of antibacterial components and short-lasting effects, and cannot improve the problem of large water resistance of the activated carbon filter element. Summary of the Invention

[0004] In order to overcome the defects of insufficient hydrophilicity of activated carbon and short-lasting antibacterial effect in the prior art, the present invention provides a preparation method of modified activated carbon. In the antibacterial activated carbon provided by the present invention, the activated carbon and the antibacterial agent are combined by electrostatic interaction, with excellent antibacterial effect and not easy to lose, and at the same time having the characteristics of good hydrophilicity and large system throughput.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The present invention provides a preparation method of modified activated carbon, which includes the following steps:

[0007] S1. Oxidize the activated carbon with an oxidant to obtain oxidized activated carbon;

[0008] S2. React the oxidized activated carbon with a chitosan solution to obtain activated carbon with a chitosan layer on the surface;

[0009] S3. React the activated carbon with a chitosan layer on the surface with a carboxymethyl cellulose solution, and react the reaction product with a chitosan solution.

[0010] In the present invention, the activated carbon is preferably coconut shell activated carbon.

[0011] In the present invention, the iodine value of the activated carbon is preferably 1050 - 1500 mg / g, such as 1200 mg / g.

[0012] In the present invention, the ash content of the activated carbon is preferably 8 - 15%, such as 10%.

[0013] In the present invention, the strength of the activated carbon is preferably 90-98%, for example, 98%;

[0014] Among them, the unit of the strength of the activated carbon is a percentage, which is the mass ratio of the activated carbon passing through the sieve before and after oscillation. Specifically, reference can be made to the national standard GBT 7702.3-2008 "Test Methods for Coal-based Granular Activated Carbon - Determination of Strength".

[0015] Specifically, the strength of the activated carbon refers to the anti-breakage property of the activated carbon, also known as the wear resistance of the activated carbon, generally expressed as a percentage. The larger the percentage, the higher the strength, the stronger the stability, and the higher the use efficiency.

[0016] In the present invention, the moisture content of the activated carbon is preferably 3-8%, for example, 5%;

[0017] Among them, the moisture content of the activated carbon is the weight lost when the activated carbon is dried to a constant weight divided by the weight before drying.

[0018] In the present invention, the particle size of the activated carbon is preferably 20-200 mesh, for example, 80 mesh.

[0019] In the present invention, before the oxidation reaction, the activated carbon preferably further includes a pretreatment, which is obtained by successively washing, filtering by suction, and drying the activated carbon; the detergent used for washing is preferably distilled water; the drying time is preferably 12-24 h, and the drying temperature is preferably 120-140 °C;

[0020] Preferably, the pretreatment step includes: washing the activated carbon with distilled water, filtering by suction, and drying at 120 °C for 24 h;

[0021] The purpose of the washing is to remove the scum and impurities on the surface of the activated carbon particles.

[0022] In the present invention, in steps S2 and S3, preferably, after the reaction with the chitosan solution and the carboxymethyl cellulose solution, a post-treatment is included, and the post-treatment is to immerse the reaction product in pure water and separate the solid phase; more preferably, after the reaction with the chitosan solution in step S3 and after the post-treatment, it further includes washing the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filtering by suction, and drying at 100 °C for 12 h.

[0023] In the present invention, the purpose of the oxidation reaction is to oxidize the oxygen-containing functional groups such as hydroxyl groups and carbon-oxygen double bonds on the surface of the activated carbon into carboxyl groups.

[0024] In step S1, the oxidant can be a hydrogen peroxide solution and / or ozone.

[0025] In the step S1, the concentration of the oxidant is preferably 2-8 wt%, such as 2 wt%, 5 wt%, 6 wt%, 7 wt% or 8 wt%, and more preferably 3-5 wt%.

[0026] In the step S1, the time of the oxidation reaction is preferably 30-120 min, such as 30 min, 40 min, 45 min or 120 min, and more preferably 40-50 min.

[0027] In the steps S2 and S3, the concentration of the chitosan solution is independently 0.5-2 mg / mL, such as 0.5 mg / mL, 1.5 mg / mL, 1.8 mg / mL or 2 mg / mL; more preferably 1-1.8 mg / mL.

[0028] In the steps S2 and S3, the reaction time with the chitosan solution is independently 30-120 min, such as 30 min, 40 min, 50 min or 120 min, and more preferably 40-50 min.

[0029] In the step S3, the concentration of the carboxymethyl cellulose solution is preferably 0.8-2.5 mg / mL, such as 0.8 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2.5 mg / mL, and more preferably 1-1.8 mg / mL.

[0030] In the step S3, the reaction time with the carboxymethyl cellulose solution is preferably 30-120 min, such as 30 min, 40 min, 50 min or 120 min, and more preferably 50-60 min.

[0031] The present invention also provides a modified activated carbon prepared by the preparation method as described above.

[0032] The present invention provides a modified activated carbon, which includes oxidized activated carbon and at least two layers of chitosan layers coated on the surface of the oxidized activated carbon. The oxidized activated carbon and the innermost chitosan layer are combined by electrostatic force. Carboxymethyl cellulose layers are distributed between the chitosan layers and are combined by the electrostatic force formed by chitosan and carboxymethyl cellulose; wherein, the surface of the oxidized activated carbon is carboxyl. In addition, there are also chemical bonds, namely amide bonds, between the oxidized activated carbon and the innermost chitosan layer and between chitosan and carboxymethyl cellulose. However, the improvement of the effect of the present invention mainly depends on the electrostatic force formed by the positive and negative charges between the raw materials, that is, the van der Waals force.

[0033] In the present invention, the carboxyl functional groups on the surface of oxidized activated carbon are negatively charged in water, carboxymethyl cellulose is negatively charged in water, and nitrogen-containing functional groups such as amino groups on the surface of chitosan are positively charged in water. Therefore, in water, oxidized activated carbon and chitosan are combined by electrostatic force to obtain activated carbon with a chitosan layer on its surface. The activated carbon with chitosan on its surface is combined with carboxymethyl cellulose by electrostatic force. Chitosan solution and carboxymethyl cellulose solution are alternately adsorbed on the surface of oxidized activated carbon by the method of layer-by-layer self-assembly to prepare the modified activated carbon.

[0034] The present invention provides a modified activated carbon, whose antibacterial property mainly comes from positively charged chitosan molecules and highly hydrophilic surface. Among them, the positive charges within the chitosan chain interact with the anionic components on the surface of microorganisms, destroying the cell wall of the bacteria. Chitosan penetrates into the bacterial nucleus to inhibit the synthesis of messenger ribonucleic acid and proteins, and chelates with metal ions in the bacteria to hinder the external nutrient supply, thereby inhibiting the adhesion, growth and reproduction of bacteria. The highly hydrophilic property of the hydrophilic and antibacterial activated carbon inhibits the bacteria from approaching the surface of the activated carbon, thus resisting their adhesion.

[0035] The present invention also provides a filter element made of the modified activated carbon prepared by the preparation method as described above. Preferably, the filter element is an activated carbon rod.

[0036] On the basis of conforming to common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0037] The reagents and raw materials used in the present invention are all commercially available.

[0038] The positive and progressive effects of the present invention are as follows:

[0039] (1) The modified activated carbon provided by the present invention has excellent antibacterial effect, can effectively prevent the growth of bacteria on the surface of activated carbon and the generation of bacterial metabolites. The antibacterial rate of the filter element made of the modified activated carbon can reach more than 99.5%, and in some preferred embodiments, the antibacterial rate can be 99.9%.

[0040] (2) By chemically modifying the activated carbon to introduce antibacterial materials and forming stable chemical bonds through surface electrostatic layer-by-layer self-assembly, the antibacterial agent is not easily lost.

[0041] (3) The modified formula improves the hydrophilicity of the activated carbon, so that the prepared filter element has a smaller water resistance and a larger system flux. The contact angle of the surface of the modified activated carbon can reach below 37°. Correspondingly, the flow rate of the activated carbon rod tested under the condition of 0.1 bar is more than 4.4 L / min. In some preferred embodiments, the contact angle can be reduced to 28°, and the corresponding flow rate of the activated carbon rod tested under the condition of 0.1 bar is 4.6 L / min.

[0042] (4) The modified formula endows activated carbon with both antibacterial and hydrophilic properties. The antibacterial property effectively inhibits the growth of microorganisms and bacteria, improving the hygienic performance of the filter element; the enhancement of hydrophilicity not only enables a larger flux in the water purification system, but also allows activated carbon to better adsorb impurities and pollutants in water; the combination of these two properties provides a more efficient water purification effect, thus broadening the scope of use of activated carbon. Detailed implementation manners

[0043] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions indicated in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0044] Unless otherwise specified, the raw material reagents used in the examples and comparative examples of the present invention are all commercially available.

[0045] Among them, the activated carbon particles used in the following examples are all coconut shell activated carbon with an iodine value of 1200 mg / g, an ash content of 10%, a strength of 98%, a moisture content of 5% and a particle size of 80 mesh, which are obtained after washing, suction filtration and drying at 120 °C for 24 h.

[0046] Example 1

[0047] (1) S1: Immerse 10 g of activated carbon particles in 2% hydrogen peroxide for 120 min to oxidize the surface of the activated carbon, hydrolyze in water to generate a large number of carboxyl groups with negative charges;

[0048] (2) S2: Immerse the oxidized and modified activated carbon in a 0.5 mg / mL chitosan (CHI) solution for 40 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body;

[0049] (3) S3: Then immerse the activated carbon in a 2.5 mg / mL carboxymethyl cellulose (CMC) solution for 50 min to introduce negative charge groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body;

[0050] Then immerse the activated carbon in a 0.5 mg / mL chitosan (CHI) solution for 40 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, obtaining modified activated carbon;

[0051] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, perform suction filtration, and dry at 100 °C for 12 h.

[0052] Example 2

[0053] (1) S1: Immerse 10 g of activated carbon particles in 8% hydrogen peroxide solution for 30 min to oxidize the surface of the activated carbon. After hydrolysis in water, it becomes negatively charged and a large number of carboxyl groups are generated.

[0054] (2) S2: Immerse the oxidized and modified activated carbon in 2 mg / mL chitosan (CHI) solution for 50 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body.

[0055] (3) S3: Then immerse the activated carbon in 0.8 mg / mL carboxymethyl cellulose (CMC) solution for 40 min to introduce negatively charged groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body.

[0056] Next, immerse the activated carbon in 2 mg / mL chitosan (CHI) solution for 50 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, and obtain the modified activated carbon.

[0057] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filter by suction, and dry at 100 °C for 12 h.

[0058] Example 3

[0059] (1) S1: Immerse 10 g of activated carbon particles in 5% hydrogen peroxide solution for 30 min to oxidize the surface of the activated carbon. After hydrolysis in water, it becomes negatively charged and a large number of carboxyl groups are generated.

[0060] (2) S2: Immerse the oxidized and modified activated carbon in 2 mg / mL chitosan (CHI) solution for 30 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body.

[0061] (3) S3: Then immerse the activated carbon in 1.5 mg / mL carboxymethyl cellulose (CMC) solution for 120 min to introduce negatively charged groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body.

[0062] Next, immerse the activated carbon in 2 mg / mL chitosan (CHI) solution for 30 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, and obtain the modified activated carbon.

[0063] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filter by suction, and dry at 100 °C for 12 h.

[0064] Example 4

[0065] (1) S1: Immerse 10 g of activated carbon particles in 6% hydrogen peroxide solution for 40 min to oxidize the surface of the activated carbon, which will hydrolyze in water to generate a large number of carboxyl groups with negative charges after hydrolysis;

[0066] (2) S2: Immerse the oxidized and modified activated carbon in 1.5 mg / mL chitosan (CHI) solution for 120 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body;

[0067] (3) S3: Then immerse the activated carbon in 1.5 mg / mL carboxymethyl cellulose (CMC) solution for 30 min to introduce negative charge groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body;

[0068] Then immerse the activated carbon in 1.5 mg / mL chitosan (CHI) solution for 120 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, and obtain the modified activated carbon;

[0069] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filter by suction, and dry at 100 °C for 12 h.

[0070] Example 5

[0071] (1) S1: Immerse 10 g of activated carbon particles in 7% hydrogen peroxide solution for 45 min to oxidize the surface of the activated carbon, which will hydrolyze in water to generate a large number of carboxyl groups with negative charges after hydrolysis;

[0072] (2) S2: Immerse the oxidized and modified activated carbon in 1.8 mg / mL chitosan (CHI) solution for 50 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body;

[0073] (3) S3: Then immerse the activated carbon in 1.8 mg / mL carboxymethyl cellulose (CMC) solution for 50 min to introduce negative charge groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body;

[0074] Then immerse the activated carbon in 1.8 mg / mL chitosan (CHI) solution for 50 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, and obtain the modified activated carbon;

[0075] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filter by suction, and dry at 100 °C for 12 h.

[0076] Comparative Example 1

[0077] In Example 5, activated carbon was directly reacted with a chitosan solution without oxidation treatment.

[0078] Comparative Example 2

[0079] In Example 1, oxidized activated carbon was directly reacted with a carboxymethyl cellulose (CMC) solution without prior immersion treatment with a chitosan (CHI) solution.

[0080] Comparative Example 3

[0081] In Example 1, only the activated carbon was oxidized without performing Steps S2 and S3.

[0082] Comparative Example 4

[0083] (1) S1: 10 g of activated carbon particles were immersed in 10% hydrogen peroxide for 20 min to oxidize the surface of the activated carbon, which became negatively charged and generated a large number of carboxyl groups after hydrolysis in water;

[0084] (2) S2: The oxidized and modified activated carbon was immersed in a 1.5 mg / mL chitosan (CHI) solution for 120 min. Then the activated carbon was immersed in pure water to remove the chitosan that was not electrostatically bound to the activated carbon body;

[0085] (3) S3: Then the activated carbon was immersed in a 1.5 mg / mL carboxymethyl cellulose (CMC) solution for 30 min to introduce negatively charged groups by electrostatic force. Then the activated carbon was immersed in pure water to remove the CMC that was not electrostatically bound to the activated carbon body;

[0086] Next, the activated carbon was immersed in a 1.5 mg / mL chitosan (CHI) solution for 120 min. Then the activated carbon was immersed in pure water to remove the chitosan that was not electrostatically bound to the activated carbon body, obtaining modified activated carbon;

[0087] (4) Finally, the reacted activated carbon was rinsed with distilled water until the surface scum and impurities were washed away, filtered by suction, and dried at 100 °C for 12 h.

[0088] Comparative Example 5

[0089] In Example 1, Steps S2 and S3 were carried out first, and then S1 was carried out.

[0090] Comparative Example 6

[0091] (1) S1: 10 g of activated carbon particles were immersed in 2% hydrogen peroxide for 120 min to oxidize the surface of the activated carbon, which became negatively charged and generated a large number of carboxyl groups after hydrolysis in water;

[0092] (2) S2: Immerse the oxidized activated carbon in a 0.3 mg / mL chitosan (CHI) solution for 40 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body;

[0093] (3) S3: Then immerse the activated carbon in a 3 mg / mL carboxymethyl cellulose (CMC) solution for 50 min to introduce negatively charged groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body;

[0094] Next, immerse the activated carbon in a 0.3 mg / mL chitosan (CHI) solution for 40 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, obtaining modified activated carbon;

[0095] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filter by suction, and dry at 100 °C for 12 h.

[0096] Comparative Example 7

[0097] (1) S1: Immerse 10 g of activated carbon particles in 8% hydrogen peroxide solution for 30 min to oxidize the surface of the activated carbon, and a large number of carboxyl groups are generated with negative charges after hydrolysis in water;

[0098] (2) S2: Immerse the oxidized activated carbon in a 0.6 mg / mL chitosan (CHI) solution for 50 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body;

[0099] (3) S3: Then immerse the activated carbon in a 3.5 mg / mL carboxymethyl cellulose (CMC) solution for 40 min to introduce negatively charged groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body;

[0100] Next, immerse the activated carbon in a 0.6 mg / mL chitosan (CHI) solution for 50 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, obtaining modified activated carbon;

[0101] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filter by suction, and dry at 100 °C for 12 h.

[0102] Comparative Example 8

[0103] (1) S1: Immerse 10 g of activated carbon particles in 2% hydrogen peroxide solution for 120 min to oxidize the surface of the activated carbon, and a large number of carboxyl groups are generated with negative charges after hydrolysis in water;

[0104] (2) S2: Immerse the oxidized activated carbon in a 0.5 mg / mL chitosan (CHI) solution for 40 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body;

[0105] (3) S3: Then immerse the activated carbon in a 2.5 mg / mL carboxymethyl cellulose (CMC) solution for 50 min to introduce negative charge groups by electrostatic force. Then immerse the activated carbon in pure water to remove the CMC that is not electrostatically bound to the activated carbon body;

[0106] Repeat the above S3 operation once;

[0107] Then immerse the activated carbon in a 0.5 mg / mL chitosan (CHI) solution for 40 min. Then immerse the activated carbon in pure water to remove the chitosan that is not electrostatically bound to the activated carbon body, obtaining the modified activated carbon;

[0108] (4) Finally, rinse the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filter by suction, and dry at 100 °C for 12 h.

[0109] The filter element that can be tested in the present invention is an activated carbon rod. Table 1 shows the process conditions of Examples 1-5 and Comparative Examples 1-8, as well as the corresponding surface contact angles of the products, the flow rates of the corresponding activated carbon rods, the iodine values of the modified activated carbon, and the antibacterial rates.

[0110] Table 1

[0111]

[0112]

[0113] It can be seen from Table 1 that the hydrophilic and antibacterial activated carbon prepared by the present invention has an antibacterial rate of more than 99.5%, and can reach 99.9% in some preferred schemes; the flow rate of the activated carbon rod tested under the condition of 0.1 bar is more than 4.4 L / min, and can reach 4.6 L / min in some preferred schemes; it greatly improves the defects of poor hydrophilicity, small system flow rate, and poor antibacterial performance of ordinary activated carbon.

[0114] Specifically, compared with Example 5 and Example 1, Comparative Example 1 and Comparative Example 5 did not oxidize the activated carbon and adjusted the oxidation sequence of the activated carbon respectively, resulting in weak negative charge on its surface, poor binding with chitosan, poor binding effect, and the chitosan that plays an antibacterial role is easily washed away by water, showing poor antibacterial effect and low flow rate of the corresponding activated carbon rod.

[0115] Compared with Example 1, Comparative Example 2 and Comparative Example 3 showed lower corresponding activated carbon rod flow rates and poor antibacterial effects due to the lack of chitosan (CHI) solution immersion and / or carboxymethyl cellulose reaction.

[0116] Compared with Example 4, in Comparative Example 4, neither the oxidant concentration nor the reaction time fell within the protection scope of this application, resulting in a low corresponding activated carbon rod flow rate and / or poor antibacterial rate performance of the modified activated carbon; compared with Example 1, in Comparative Example 6, neither the chitosan concentration nor the reaction time fell within the protection scope of this application, resulting in a low corresponding activated carbon rod flow rate and / or poor antibacterial rate performance of the modified activated carbon; compared with Example 2, in Comparative Example 7, neither the carboxymethyl cellulose concentration nor the reaction time fell within the protection scope of this application, resulting in a low corresponding activated carbon rod flow rate and / or poor antibacterial rate performance of the modified activated carbon. The above analysis shows that the oxidation reaction of activated carbon and the layer-by-layer self-assembly with chitosan and carboxymethyl cellulose solution cooperate synergistically, having a great impact on the activated carbon rod flow rate and antibacterial effect.

[0117] In addition, compared with Example 1, Comparative Example 8 shows that the more layers of chitosan are not necessarily better, and too many layers of chitosan will affect the adsorption performance of activated carbon.

[0118] The preparation process of the filter element in the present invention is conventional in the art, including sintering, cutting, and bonding end caps to the activated carbon rod. The sintering temperature is 200 °C. The filter element processed by sintering is cut into an appropriate length and the outer surface of the filter element is wrapped with non-woven fabric, and then end caps are bonded to both ends of the filter element to obtain a finished filter element.

[0119] The above specific embodiments have further detailed the purpose, technical solution, 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 principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of modified activated carbon, characterized in that, It includes the following steps: S1. Oxidize activated carbon with an oxidant to obtain oxidized activated carbon; S2. React the oxidized activated carbon with a chitosan solution to obtain activated carbon with a chitosan layer on the surface; S3. React the activated carbon with a carboxymethyl cellulose solution, and react the reaction product with a chitosan solution, and that's it.

2. The preparation method of the modified activated carbon according to claim 1, characterized in that, It meets one or more of the following conditions: (1) The activated carbon is coconut shell activated carbon; (2) The iodine value of the activated carbon is 1050 - 1500 mg / g, such as 1200 mg / g; (3) The ash content of the activated carbon is 8 - 15%, such as 10%; (4) The strength of the activated carbon is 90 - 98%, such as 98%; (5) The moisture content of the activated carbon is 3 - 8%, such as 5%; and (6) The particle size of the activated carbon is 20 - 200 mesh, such as 80 mesh.

3. The preparation method of the modified activated carbon according to claim 1, wherein, It meets one or more of the following conditions: (1) Before the oxidation reaction, the activated carbon further includes pretreatment, which is obtained by sequentially washing, filtering by suction and drying the activated carbon; the detergent used for washing is preferably distilled water; the drying time is preferably 12 - 24 h; The drying temperature is preferably 120 - 140 °C; further more preferably, the pretreatment step includes: washing the activated carbon with distilled water, filtering by suction, and drying at 120 °C for 24 h; and (2) In steps S2 and S3, after the reaction with the chitosan solution and the carboxymethyl cellulose solution, a post-treatment is included, which is to immerse the reaction product in pure water and separate the solid phase; in step S3, after the reaction with the chitosan solution and the post-treatment, preferably, it further includes rinsing the reacted activated carbon with distilled water until the surface scum and impurities are washed away, filtering by suction, and drying at 100 °C for 12 h, and that's it.

4. The preparation method of the modified activated carbon according to claim 1, characterized in that, It meets one or more of the following conditions: (1) The oxidant is hydrogen peroxide solution and / or ozone; (2) The concentration of the oxidant is 2 - 8 wt%, preferably 3 - 5 wt%; (3) The oxidation reaction time is 30 - 120 min, such as 30 min, 40 min, 45 min or 120 min, preferably 40 - 50 min.

5. The preparation method of the modified activated carbon according to claim 1, characterized in that, It meets one or more of the following conditions: (1) In steps S2 and S3, the concentration of the chitosan solution is independently 0.5 - 2.0 mg / mL, preferably 1 - 1.8 mg / mL; and (2) In steps S2 and S3, the reaction time with the chitosan solution is 30 - 120 min, preferably 40 - 50 min.

6. The preparation method of the modified activated carbon according to claim 1, characterized in that, It meets one or more of the following conditions: (1) In step S3, the concentration of the carboxymethyl cellulose solution is 0.8 - 2.5 mg / mL, preferably 1 - 1.8 mg / mL; and (2) In step S3, the reaction time with the carboxymethyl cellulose solution is 30 - 120 min, preferably 50 - 60 min.

7. A modified activated carbon, characterized in that, It is prepared by the preparation method described in any one of claims 1 - 6.

8. A modified activated carbon, characterized in that, It includes oxidized activated carbon and at least two layers of chitosan layers coated on the surface of the oxidized activated carbon. The oxidized activated carbon and the innermost chitosan layer are combined by electrostatic force. Carboxymethyl cellulose layers are distributed between the chitosan layers and are combined by the electrostatic force formed by chitosan and carboxymethyl cellulose. Among them, the surface of the oxidized activated carbon is a carboxyl group.

9. A filter element, which includes the modified activated carbon according to claim 7 or 8, or is made of the modified activated carbon according to claim 7 or 8.

10. The filter element according to claim 9, characterized in that, The filter element is an activated carbon rod.

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