Modified activated carbon with high specific surface area and preparation method thereof

Abstract

The application aims to provide a modified activated carbon with high specific surface area and a preparation method thereof, and belongs to the technical field of activated carbon preparation.The sawdust, crushed coconut shell and crushed wheat straw are mixed, then subjected to enzymatic pore-forming, washed and dried after being taken out, subjected to carbonization by programmed temperature, and then subjected to immersion treatment in a cationic surfactant and silica sol respectively, dried and activated after being washed, so as to obtain the modified activated carbon with high specific surface area.The application adopts composite enzyme for enzymatic pore-forming, so as to increase the specific surface area of the activated carbon, the programmed temperature carbonization process promotes the complete carbonization of the activated carbon, so as to further increase the specific surface area thereof, after the cationic surfactant is immersed, the combination and dispersion performance of the activated carbon and the silica sol are increased, so as to promote the dispersion and combination of the silica sol in the activated carbon, the nano silicon dioxide can play a role in enhancing the mechanical strength of the activated carbon, and meanwhile, the nano silicon dioxide adsorbed to the surface of the activated carbon can further increase the specific surface area of the activated carbon.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of activated carbon preparation, and relates to modified activated carbon with high specific surface area and a preparation method thereof. BACKGROUND

[0002] Activated carbon is a carbonaceous adsorbent material with rich pore structure and large specific surface area, and has the characteristics of strong adsorption capacity, good chemical stability, high mechanical strength, and convenient regeneration, and is widely used in industry, agriculture, national defense, transportation, medicine and health, environmental protection and other fields. With the development of society and the improvement of people's living standards, the demand for activated carbon is increasing year by year. Especially with the increasing demand for environmental protection, the demand for activated carbon at home and abroad is growing, and is increasing year by year. There are many types of activated carbon products, which can be divided into coal-based activated carbon, wood-based activated carbon, fruit shell activated carbon and synthetic activated carbon according to different raw materials.

[0003] Activated carbon is a very fine carbon particle with a large surface area and small pores - capillaries inside, so activated carbon has strong adsorption capacity and can purify air or water. The principle of activated carbon purifying water is to use its porosity to adsorb one or more substances in water in its surface pores, and the objects to be removed include organic matter, synthetic detergents, microorganisms, viruses or heavy metals, so as to produce decolorization and deodorization effect. In addition, there are many oxides on the surface of activated carbon, most of which exist in the form of -COOH, -OH, =C=O, etc. Among these surface oxides, -COOH and -OH exist in the form of acid in electrolyte solution, and -C=O exists in the form of base. If microorganisms are loaded on activated carbon, the surface proteins of the microorganisms are amphoteric compounds that can form salts with acids and bases, so they can be combined through chemical bond attraction to further purify water or air.

[0004] At present, the raw materials in the preparation process of activated carbon are generally single, and the specific surface area of the prepared activated carbon needs to be improved. At the same time, high specific surface area often leads to the decrease of mechanical strength of activated carbon, so the preparation of activated carbon with high specific surface area and high mechanical strength at the same time is a technology that needs to be broken through. SUMMARY

[0005] The application aims to provide a modified activated carbon with high specific surface area and a preparation method thereof, and belongs to the technical field of activated carbon preparation. The wood chips, the crushed coconut shells and the crushed wheat straws are mixed, then are subjected to enzymatic pore-forming, are taken out, washed and dried, are subjected to programmed temperature carbonization, are immersed in a cationic surfactant and a silica sol in sequence, are washed, dried and activated after washing, and the modified activated carbon with high specific surface area is obtained.

[0006] The application can be achieved by the following technical scheme.

[0007] A preparation method of a modified activated carbon with high specific surface area, the preparation method comprising the following steps:

[0008] (1) mixing wood chips, crushed coconut shells and crushed wheat straws to obtain mixed raw materials;

[0009] (2) adding the mixed raw materials into a buffer solution, heating in a water bath, then adding glucose enzyme, amylase and cellulase, and subjecting to constant temperature standing for enzymatic reaction, and then filtering and washing to neutral;

[0010] (3) drying and subjecting to programmed temperature carbonization to obtain carbonized materials;

[0011] (4) immersing the carbonized materials in a cationic surfactant solution and a silica sol in sequence, taking out, washing, drying and activating to obtain the modified activated carbon with high specific surface area.

[0012] As a preferred technical scheme of the application, the weight ratio of the wood chips, the crushed coconut shells and the crushed wheat straws in step (1) is 1:0.3-0.5:0.6-0.9.

[0013] As a preferred technical scheme of the application, the particle size of the mixed raw materials in step (1) is 60-80 mu m.

[0014] As a preferred technical scheme of the present application, the buffer solution in step (2) is an acetic acid-sodium acetate aqueous solution with a pH value of 4-5, the solid-liquid ratio of the mixed raw material to the buffer solution is 1g:10-25mL, and the weight ratio of the mixed raw material, the glucose enzyme, the amylase and the cellulase is 10:0.1-0.3:0.1-0.2:0.2-0.5.

[0015] As a preferred technical scheme of the present application, the heating and constant temperature in step (2) are both at a temperature of 40-45℃, and the enzymatic hydrolysis reaction time is 3-5h.

[0016] As a preferred technical scheme of the present application, the programmed temperature rising in step (3) refers to first rising the temperature to 300-350℃ at a speed of 2-5℃ / min for 10-15min, then rising the temperature to 450-480℃ at a speed of 1-2℃ / min for 20-30min, and finally rising the temperature to 600-650℃ at a speed of 2-3℃ / min for 20-25min.

[0017] As a preferred technical scheme of the present application, the cationic surfactant in step (4) is hexadecyl trimethyl ammonium bromide, and the cationic surfactant solution is a cationic surfactant solution at a critical micelle concentration.

[0018] As a preferred technical scheme of the present application, the cationic surfactant solution in step (4) is soaked for 1-3h, and the silica sol is soaked for 2-4h.

[0019] As a preferred technical scheme of the present application, the activation temperature in step (4) is 700-800℃, the activation time is 3-4h, and the activation agent is water vapor.

[0020] The high specific surface area modified activated carbon prepared by the preparation method.

[0021] The present application has the following advantages:

[0022] (1) The present application selects three different raw materials to be mixed as the activated carbon raw material according to a suitable ratio, sets a suitable programmed temperature rising speed and temperature and holding time according to the mixed raw materials, and uses a segmented carbonization process to promote the complete carbonization of the activated carbon and further improve the specific surface area thereof.

[0023] (2) The present application uses a composite enzyme to perform the pore forming, and the glucose enzyme, the amylase and the cellulase are reasonably matched and combined with specific reaction conditions to improve the enzyme hydrolysis pore forming efficiency of the mixed raw material, thereby effectively improving the specific surface area of the activated carbon.

[0024] (3) After soaking with the cationic surfactant, the activated carbon adsorbed with the cationic surfactant increases the binding force and dispersion performance with the silica sol, promotes the dispersion and binding of the silica sol in the activated carbon, and the nanometer-sized silicon dioxide can enhance the mechanical strength of the activated carbon, and the nanometer-sized silicon dioxide adsorbed on the surface of the activated carbon further increases the specific surface area of the activated carbon. DETAILED DESCRIPTION

[0025] In order to further clarify the technical means and effects adopted by the present application to achieve the predetermined object of the present application, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with the embodiments.

[0026] Embodiment 1

[0027] A preparation method of the modified activated carbon with high specific surface area, the preparation method comprising the following steps:

[0028] (1) Wood chips, crushed coconut shells and crushed wheat straw are mixed according to a weight ratio of 1:0.4:0.7 to obtain mixed raw materials with a particle size of 60-70 μm;

[0029] (2) The mixed raw materials are added to an acetic acid-sodium acetate buffer solution with a pH value of 4.5 according to a solid-liquid ratio of 1 g:15 mL, heated to 42℃ in a water bath, and then glucose enzyme, amylase and cellulase are added, and the enzyme hydrolysis reaction is carried out at a constant temperature of 42℃ for 4 h, and the weight ratio of the mixed raw materials, glucose enzyme, amylase and cellulase is controlled to be 10:0.2:0.1:0.4, and after the reaction, the mixture is filtered and washed to neutral;

[0030] (3) After drying, the carbonized material is obtained by programmed temperature carbonization, and the programmed temperature program is set as follows: first, the temperature is raised to 320℃ at a speed of 3℃ / min and kept for 12 min; then the temperature is raised to 450℃ at a speed of 1℃ / min and kept for 25 min, and finally the temperature is raised to 620℃ at a speed of 2℃ / min and kept for 22 min;

[0031] (4) The carbonized material is first soaked in a cetyltrimethylammonium bromide solution with a critical micelle concentration for 2 h, and then soaked in a silica sol for 3 h, and after taking out, it is washed and dried, and then water vapor is used as an activating agent to activate the carbonized material at a temperature of 750℃ for 3.5 h to obtain the modified activated carbon with high specific surface area.

[0032] The modified activated carbon with high specific surface area prepared by the above method.

[0033] Embodiment 2

[0034] A preparation method of the modified activated carbon with high specific surface area, the preparation method comprising the following steps:

[0035] (1) wood chips, crushed coconut shells, and crushed wheat straw are mixed according to a weight ratio of 1:0.5:0.6 to obtain mixed raw materials with a particle size of 70-80 μm;

[0036] (2) the mixed raw materials are added to an acetic acid-sodium acetate buffer solution with a pH value of 4.3 according to a solid-liquid ratio of 1 g:20 mL, heated to 40°C in a water bath, and then glucose enzyme, amylase, and cellulase are added, and the enzyme hydrolysis reaction is carried out at a constant temperature of 40°C for 5 h, with the weight ratio of the mixed raw materials, glucose enzyme, amylase, and cellulase being controlled to be 10:0.3:0.1:0.2, and after the reaction, the mixture is filtered and washed to neutral;

[0037] (3) the carbonized material is obtained by drying and programmed temperature carbonization, and the programmed temperature program is set as follows: first, the temperature is raised to 300°C at a rate of 2°C / min and maintained for 15 min; then, the temperature is raised to 480°C at a rate of 2°C / min and maintained for 20 min, and finally, the temperature is raised to 650°C at a rate of 2°C / min and maintained for 20 min;

[0038] (4) the carbonized material is first soaked in a cetyltrimethylammonium bromide solution with a critical micelle concentration for 1.8 h, and then soaked in a silica sol for 3.5 h, and after being taken out, it is washed and dried, and then activated at a temperature of 700°C for 4 h using water vapor as the activating agent, to obtain a modified activated carbon with a high specific surface area.

[0039] The modified activated carbon with a high specific surface area is prepared by the above method.

[0040] Example 3

[0041] A method for preparing a modified activated carbon with a high specific surface area, the method comprising the following steps:

[0042] (1) wood chips, crushed coconut shells, and crushed wheat straw are mixed according to a weight ratio of 1:0.3:0.9 to obtain mixed raw materials with a particle size of 65-75 μm;

[0043] (2) the mixed raw materials are added to an acetic acid-sodium acetate buffer solution with a pH value of 5 according to a solid-liquid ratio of 1 g:10 mL, heated to 45°C in a water bath, and then glucose enzyme, amylase, and cellulase are added, and the enzyme hydrolysis reaction is carried out at a constant temperature of 45°C for 3 h, with the weight ratio of the mixed raw materials, glucose enzyme, amylase, and cellulase being controlled to be 10:0.1:0.2:0.5, and after the reaction, the mixture is filtered and washed to neutral;

[0044] (3) the carbonized material is obtained by drying and programmed temperature carbonization, and the programmed temperature program is set as follows: first, the temperature is raised to 350°C at a rate of 5°C / min and maintained for 10 min; then, the temperature is raised to 480°C at a rate of 2°C / min and maintained for 20 min, and finally, the temperature is raised to 650°C at a rate of 3°C / min and maintained for 20 min;

[0045] (4) the carbonized material is first soaked in a cetyltrimethylammonium bromide solution at a critical micelle concentration for 3h, then soaked in a silica sol for 2h, washed and dried after being taken out, and then activated at 800℃ for 3h with water vapor as the activating agent to obtain the modified activated carbon with a high specific surface area.

[0046] The modified activated carbon with a high specific surface area prepared by the method.

[0047] Comparative Example 1

[0048] A preparation method of a modified activated carbon with a high specific surface area, comprising the following steps:

[0049] (1) wood chips, crushed coconut shells and crushed wheat straw are mixed according to a weight ratio of 1:0.3:0.9 to obtain mixed raw materials with a particle size of 65-75μm;

[0050] (2) the mixed raw materials are added to an acetic acid-sodium acetate buffer solution with a pH value of 5 according to a solid-liquid ratio of 1g:10mL, heated to 45℃ in a water bath, and then glucose enzyme and amylase are added, and the enzyme hydrolysis reaction is carried out at a constant temperature of 45℃ for 3h, the weight ratio of the mixed raw materials, glucose enzyme and amylase is controlled to be 10:0.6:0.2, and after the reaction, the mixture is filtered and washed to neutral;

[0051] (3) the carbonized material is obtained after drying and programmed temperature carbonization, and the programmed temperature program is set as follows: first, the temperature is raised to 350℃ at a speed of 5℃ / min and kept for 10min; then the temperature is raised to 480℃ at a speed of 2℃ / min and kept for 20min, and finally the temperature is raised to 650℃ at a speed of 3℃ / min and kept for 20min;

[0052] (4) the carbonized material is first soaked in a cetyltrimethylammonium bromide solution at a critical micelle concentration for 3h, then soaked in a silica sol for 2h, washed and dried after being taken out, and then activated at 800℃ for 3h with water vapor as the activating agent to obtain the modified activated carbon with a high specific surface area.

[0053] The modified activated carbon with a high specific surface area prepared by the method.

[0054] Comparative Example 2

[0055] A preparation method of a modified activated carbon with a high specific surface area, comprising the following steps:

[0056] (1) wood chips, crushed coconut shells and crushed wheat straw are mixed according to a weight ratio of 1:0.3:0.9 to obtain mixed raw materials with a particle size of 65-75μm;

[0057] (2) The mixed raw materials are added to an acetic acid-sodium acetate buffer solution with a pH value of 5 according to a solid-liquid ratio of 1 g:10 mL, heated to 45 DEG C in a water bath, and then glucose enzyme and cellulase are added, and the enzyme hydrolysis reaction is carried out at a constant temperature of 45 DEG C for 3 h, with the weight ratio of the mixed raw materials, glucose enzyme and cellulase being controlled to be 10:0.3:0.5, and after the reaction, the mixture is filtered and washed to neutral;

[0058] (3) After drying, the carbonized material is obtained by programmed temperature carbonization, and the programmed temperature program is set as follows: first, the temperature is raised to 350 DEG C at a speed of 5 DEG C / min, and then the temperature is raised to 480 DEG C at a speed of 2 DEG C / min, and finally the temperature is raised to 650 DEG C at a speed of 3 DEG C / min, and the temperature is kept for 20 min;

[0059] (4) The carbonized material is first soaked in a cetyltrimethylammonium bromide solution with a critical micelle concentration for 3 h, and then soaked in a silica sol for 2 h, and after being taken out, it is washed and dried, and then activated at a temperature of 800 DEG C for 3 h with water vapor as the activating agent, to obtain a modified activated carbon with a high specific surface area.

[0060] The modified activated carbon with a high specific surface area is prepared by the above method.

[0061] Comparative Example 3

[0062] A preparation method of a modified activated carbon with a high specific surface area, the preparation method comprising the following steps:

[0063] (1) Wood chips, crushed coconut shells and crushed wheat straw are mixed according to a weight ratio of 1:0.3:0.9 to obtain mixed raw materials with a particle size of 65-75 μm;

[0064] (2) The mixed raw materials are added to an acetic acid-sodium acetate buffer solution with a pH value of 5 according to a solid-liquid ratio of 1 g:10 mL, heated to 45 DEG C in a water bath, and then glucose enzyme, amylase and cellulase are added, and the enzyme hydrolysis reaction is carried out at a constant temperature of 45 DEG C for 3 h, with the weight ratio of the mixed raw materials, amylase and cellulase being controlled to be 10:0.3:0.5, and after the reaction, the mixture is filtered and washed to neutral;

[0065] (3) After drying, the carbonized material is obtained by programmed temperature carbonization, and the programmed temperature program is set as follows: first, the temperature is raised to 350 DEG C at a speed of 5 DEG C / min, and then the temperature is raised to 480 DEG C at a speed of 2 DEG C / min, and finally the temperature is raised to 650 DEG C at a speed of 3 DEG C / min, and the temperature is kept for 20 min;

[0066] (4) The carbonized material is first soaked in a cetyltrimethylammonium bromide solution with a critical micelle concentration for 3 h, and then soaked in a silica sol for 2 h, and after being taken out, it is washed and dried, and then activated at a temperature of 800 DEG C for 3 h with water vapor as the activating agent, to obtain a modified activated carbon with a high specific surface area.

[0067] The modified activated carbon with high specific surface area prepared by the method.

[0068] Comparative Example 4

[0069] A method for preparing a modified activated carbon with high specific surface area, the method comprising the following steps:

[0070] (1) mixing sawdust, crushed coconut shell and crushed wheat straw according to a weight ratio of 1:0.3:0.9 to obtain mixed raw materials with a particle size of 65-75 μm;

[0071] (2) adding the mixed raw materials into an acetic acid-sodium acetate buffer solution with a pH value of 5 according to a solid-liquid ratio of 1 g:10 mL, then adding glucose enzyme, amylase and cellulase after water bath heating to 45°C, and standing for enzymatic hydrolysis reaction at 45°C for 3 h, with the weight ratio of the mixed raw materials, glucose enzyme, amylase and cellulase being controlled at 10:0.1:0.2:0.5, and then performing suction filtration and washing until neutral;

[0072] (3) performing oven drying and programmed temperature carbonization to obtain carbonized materials, with the programmed temperature program being set as: first, increasing the temperature to 350°C at a speed of 5°C / min and maintaining for 10 min; then, increasing the temperature to 480°C at a speed of 2°C / min and maintaining for 20 min; finally, increasing the temperature to 650°C at a speed of 3°C / min and maintaining for 20 min;

[0073] (4) soaking the carbonized materials in silica sol for 2 h, then taking out and cleaning and drying, and then using water vapor as an activating agent to activate at a temperature of 800°C for 3 h to obtain the modified activated carbon with high specific surface area.

[0074] The modified activated carbon with high specific surface area prepared by the method.

[0075] Comparative Example 5

[0076] A method for preparing a modified activated carbon with high specific surface area, the method comprising the following steps:

[0077] (1) mixing sawdust, crushed coconut shell and crushed wheat straw according to a weight ratio of 1:0.3:0.9 to obtain mixed raw materials with a particle size of 65-75 μm;

[0078] (2) adding the mixed raw materials into an acetic acid-sodium acetate buffer solution with a pH value of 5 according to a solid-liquid ratio of 1 g:10 mL, then adding glucose enzyme, amylase and cellulase after water bath heating to 45°C, and standing for enzymatic hydrolysis reaction at 45°C for 3 h, with the weight ratio of the mixed raw materials, glucose enzyme, amylase and cellulase being controlled at 10:0.1:0.2:0.5, and then performing suction filtration and washing until neutral;

[0079] (3) after drying, the carbonized material is obtained by programmed temperature carbonization, and the programmed temperature program is set as follows: first, the temperature is raised to 350℃ at a speed of 5℃ / min and kept for 10min; then, the temperature is raised to 480℃ at a speed of 2℃ / min and kept for 20min, and finally, the temperature is raised to 650℃ at a speed of 3℃ / min and kept for 20min;

[0080] (4) the carbonized material is soaked in a cetyltrimethylammonium bromide solution at a critical micelle concentration for 3h, and after being taken out, it is cleaned, dried, and then activated at a temperature of 800℃ for 3h with water vapor as the activating agent to obtain the modified activated carbon with high specific surface area.

[0081] The modified activated carbon with high specific surface area prepared by the above method.

[0082] Performance test

[0083] The modified activated carbon with high specific surface area prepared from Examples 1-3 and Comparative Examples 1-5 is tested for specific surface area according to GB / T7702.21-1997 and for strength according to GB / T14296.6-1999, and the test results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] It can be seen from the above test data that in Comparative Example 1, only glucose enzyme and amylase are used for enzymatic pore-forming on the basis of Example 3, and the specific surface area of the activated carbon is significantly reduced; in Comparative Example 2, only glucose enzyme and cellulase are used for enzymatic pore-forming on the basis of Example 3, and the specific surface area of the activated carbon is significantly reduced; in Comparative Example 3, only amylase and cellulase are used for enzymatic pore-forming on the basis of Example 3, and the specific surface area of the activated carbon is significantly reduced; in Comparative Example 4, only silica sol soaking is used on the basis of Example 3, and the strength of the activated carbon is significantly reduced; and in Comparative Example 5, only cationic surfactant soaking is used on the basis of Example 3, and the strength of the activated carbon is significantly reduced.

[0088] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed with the preferred embodiment as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any modification, change, and modification of the above embodiments, which does not depart from the technical solution of the present application, are still within the scope of the present application.

Claims

1. A method for preparing modified activated carbon with high specific surface area, characterized in that, The preparation method includes the following steps: (1) Mix sawdust, crushed coconut shells and crushed wheat straw to obtain mixed raw materials; (2) Add the mixed raw materials to the buffer solution, heat in a water bath, then add glucase, amylase and cellulase, keep at constant temperature and let stand for enzymatic hydrolysis, filter and wash until neutral after reaction; (3) After drying, the carbonized material is obtained by programmed heating and carbonization. (4) The carbonized material was soaked in cationic surfactant solution and silica sol in turn, then taken out, cleaned, dried and activated to obtain modified activated carbon with high specific surface area. The buffer solution in step (2) is an aqueous solution of acetate-sodium acetate with a pH of 4-5. The solid-liquid ratio of the mixed raw material to the buffer solution is 1g:10-25mL. The weight ratio of the mixed raw material, glucase, amylase and cellulase is 10:0.1-0.3:0.1-0.2:0.2-0.

5. The heating and constant temperature in step (2) are both 40-45℃, and the enzymatic hydrolysis reaction time is 3-5h.

2. The method for preparing modified activated carbon with high specific surface area according to claim 1, characterized in that, The weight ratio of the sawdust, crushed coconut shell and crushed wheat straw in step (1) is 1:0.3-0.5:0.6-0.

9.

3. The method for preparing modified activated carbon with high specific surface area according to claim 1, characterized in that, The particle size of the mixed raw materials in step (1) is 60-80 μm.

4. The method for preparing modified activated carbon with high specific surface area according to claim 1, characterized in that, The programmed temperature rise in step (3) refers to first raising the temperature to 300-350℃ at a rate of 2-5℃ / min and holding it for 10-15min; then raising the temperature to 450-480℃ at a rate of 1-2℃ / min and holding it for 20-30min; and finally raising the temperature to 600-650℃ at a rate of 2-3℃ / min and holding it for 20-25min.

5. The method for preparing modified activated carbon with high specific surface area according to claim 1, characterized in that, The cationic surfactant in step (4) is hexadecyltrimethylammonium bromide, and the cationic surfactant solution is a cationic surfactant solution with critical micelle concentration.

6. The method for preparing modified activated carbon with high specific surface area according to claim 1, characterized in that, The immersion time of the cationic surfactant solution in step (4) is 1-3 hours, and the immersion time of the silica sol is 2-4 hours.

7. The method for preparing modified activated carbon with high specific surface area according to claim 1, characterized in that, The activation temperature in step (4) is 700-800℃, the activation time is 3-4h, and the activator is water vapor.

8. A modified activated carbon with high specific surface area prepared by the preparation method according to any one of claims 1-7.

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