A gradient pore structure honeycomb activated carbon and a preparation process thereof

Abstract

The present application relates to a kind of gradient pore structure honeycomb activated carbon and its preparation process, belong to activated carbon technical field.The present application provides a kind of preparation process, by mixing coconut shell powder, microencapsulated ammonium bicarbonate, diatomite, deionized water, honeycomb mould compaction, drying, obtain honeycomb body;Coconut shell powder, calcium hydroxide, sodium hydroxymethylcellulose solution are mixed, to obtain slurry;Again, honeycomb body is immersed in slurry, solidification, to obtain the honeycomb body after processing is carried out three-stage gradient temperature treatment, obtains gradient pore structure honeycomb activated carbon.The present application introduces microencapsulated ammonium bicarbonate and containing calcium hydroxide surface layer slurry in the process of preparing honeycomb activated carbon, and gradient pore is gradually formed by three-stage gradient temperature, so as to improve the adsorption performance of activated carbon.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon technology, and relates to a gradient pore structure honeycomb activated carbon and its preparation process. Background Technology

[0002] Honeycomb activated carbon is a porous honeycomb structure material made primarily from activated carbon through a special process. Its core lies in reconstructing traditional powdered or granular activated carbon into a regular honeycomb structure. Its applications cover industrial waste gas treatment, vehicle exhaust purification, indoor air purification equipment, and gas separation and purification in chemical production, playing a vital role in environmental engineering. Although honeycomb activated carbon is widely used in air adsorption, its performance still has significant limitations. For example, there is the issue of homogenization of the pore structure; existing products mostly employ a single pore size distribution (concentrated in the 2-4 nm mesoporous range), making it difficult to achieve simultaneous and efficient adsorption of mixed pollutants with significantly different molecular diameters. This severely restricts its reliability in complex operating conditions. Summary of the Invention

[0003] The purpose of this invention is to provide a gradient pore structure honeycomb activated carbon and its preparation process. In the process of preparing honeycomb activated carbon, this invention introduces microencapsulated ammonium bicarbonate and a surface slurry containing calcium hydroxide. Gradient pores are gradually formed through three-stage gradient heating, thereby improving the adsorption performance of activated carbon.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A process for preparing gradient pore structure honeycomb activated carbon, the process comprising the following steps:

[0006] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0007] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0008] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0009] Step A4: Perform a three-stage gradient heating process on the processed honeycomb to obtain the final product.

[0010] Further, in step A1, the mass ratio of coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water is 6.4-6.8:1.3-1.7:1.4-1.6:0.5-0.6; the coconut shell powder is obtained by crushing coconut shells and passing them through an 80-120 mesh sieve; the diatomaceous earth needs to be crushed and passed through a 150-250 mesh sieve.

[0011] Furthermore, the preparation method of microencapsulated ammonium bicarbonate in step A1 includes the following steps:

[0012] Step B1: Heat the paraffin wax to 75-77℃ to obtain pre-melted paraffin wax;

[0013] Step B2: Mix and stir the ethyl cellulose and ethanol solution to obtain an ethyl cellulose solution;

[0014] Step B3: Mix the pre-melted paraffin wax and ethyl cellulose solution evenly to obtain the wall material solution;

[0015] Step B4: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate.

[0016] Further, in step B2, the mass ratio of ethyl cellulose to ethanol solution is 1:8.1-8.3; the mass concentration of ethanol solution is 83-87 wt%; in step B3, the mass ratio of pre-melted paraffin to ethyl cellulose solution is 1:2.8-3.2; in step B4, the mass ratio of ammonium bicarbonate to wall material solution is 1:1.8-2.2; and the high-speed shearing refers to shearing at a speed of 16000-20000 rpm for 6-8 minutes.

[0017] Further, the mixing in step A1 refers to first stirring coconut shell powder and diatomaceous earth at 15-25 rpm for 20-30 minutes, then adding microencapsulated ammonium bicarbonate and stirring at 8-12 rpm for 10-12 minutes, and finally spraying in deionized water; drying refers to drying at 80℃ for 3.5-4.5 hours.

[0018] Further, in step A2, the mass ratio of coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution is 6.6-7:1.2-1.4:0.3-0.5; the coconut shell powder is obtained by crushing coconut shells and passing them through a 180-220 mesh sieve; the diatomaceous earth needs to be crushed and passed through a 250-350 mesh sieve; the sodium carboxymethyl cellulose solution contains 5-6 wt% sodium carboxymethyl cellulose.

[0019] Further, the mixing mentioned in step A2 refers to stirring at a speed of 30-40 rpm for 12-18 minutes.

[0020] Further, in step A3, the mass ratio of the honeycomb structure to the slurry is 1:1.1-1.3; the impregnation refers to setting the ultrasonic frequency to 30-50kHz, the ultrasonic power to 100-200W, and ultrasonic impregnation for 18-22s; the curing refers to pre-curing at 50-60℃ for 1.5-2.5h, and then curing at 100-120℃ for 3.5-4.5h.

[0021] Furthermore, the three-stage gradient heating process described in step A4 refers to first heating to 160-280℃ at a heating rate of 1-3℃ / min and holding for 1.2-1.8h, then heating to 580-660℃ at a heating rate of 2-4℃ / min and holding for 1.4-1.6h, and finally heating to 700-800℃ at a heating rate of 8-12℃ and holding for 1.8-2.2h.

[0022] The beneficial effects of this invention are:

[0023] (1) In the process of preparing honeycomb activated carbon, the present invention introduces microencapsulated ammonium bicarbonate and surface slurry containing calcium hydroxide. Gradient pores are gradually formed through three-stage gradient heating, thereby improving the adsorption performance of activated carbon. In addition, the present invention uses coconut shell powder with larger particle size to participate in the construction of honeycomb skeleton and coconut shell powder with smaller particle size to participate in the preparation of surface slurry, which is used to fill the gaps between large particles, increase the specific surface area, thereby optimizing the activation efficiency and improving the adsorption performance.

[0024] (2) The microencapsulated sodium bicarbonate in this invention uses a composite of paraffin and ethyl cellulose as the wall material and sodium bicarbonate as the core material. When the temperature does not reach 100°C, the paraffin in the capsule shell melts, causing the capsule shell structure to be destroyed. The core material of the microcapsule, sodium bicarbonate, decomposes first. The volatile gas after decomposition escapes along the porous structure of coconut shell powder and diatomaceous earth, forming small pores inside the activated carbon, i.e., the initial channel. When the temperature reaches the first heating range, the capsule shell of the microencapsulated sodium bicarbonate gradually decomposes. The volatile gas after decomposition will preferentially escape along the initial channel, further expanding the channel pore size. When the temperature reaches the second heating range, the calcium hydroxide in the surface slurry gradually decomposes, and the resulting water vapor forms pores on the surface. Calcium oxide particles act as hard templates to participate in the construction of the activated carbon skeleton, enhancing mechanical strength and preventing structural collapse. At this time, volatiles that have not completely escaped from the interior will preferentially escape through these pores, thus connecting with existing pores and forming a gradient pore channel from the activated carbon core to the surface. Finally, when the temperature reaches the third heating range, activation is mainly carried out by water vapor, further connecting and expanding the pores. The resulting honeycomb activated carbon with a gradient pore structure has good adsorption performance. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0026] The ammonium bicarbonate used in this invention was purchased from Shandong Jinghao Chemical Co., Ltd., the calcium hydroxide was purchased from Xing'an Nanguo Jinlei Powder Factory, the paraffin was purchased from Zhongrun (Shandong) New Materials Co., Ltd., and the ethyl cellulose was purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd.

[0027] Example 1

[0028] A process for preparing gradient pore structure honeycomb activated carbon, the process comprising the following steps:

[0029] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0030] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0031] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0032] Step A4: Perform a three-stage gradient heating process on the processed honeycomb to obtain the final product.

[0033] The mass ratio of coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water in step A1 is 6.4:1.3:1.4:0.5; the coconut shell powder is obtained by crushing coconut shells and passing them through an 80-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 150-mesh sieve.

[0034] The preparation method of microencapsulated ammonium bicarbonate in step A1 includes the following steps:

[0035] Step B1: Heat the paraffin wax to 75°C to obtain pre-melted paraffin wax;

[0036] Step B2: Mix and stir the ethyl cellulose and ethanol solution to obtain an ethyl cellulose solution;

[0037] Step B3: Mix the pre-melted paraffin wax and ethyl cellulose solution evenly to obtain the wall material solution;

[0038] Step B4: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate.

[0039] The mass ratio of ethyl cellulose to ethanol solution in step B2 is 1:8.1; the mass concentration of ethanol solution is 83 wt%; the mass ratio of pre-melted paraffin to ethyl cellulose solution in step B3 is 1:2.8; the mass ratio of ammonium bicarbonate to wall material solution in step B4 is 1:1.8; the high-speed shearing refers to shearing at 16000 rpm for 6 minutes.

[0040] The mixing in step A1 refers to first stirring coconut shell powder and diatomaceous earth at 15 rpm for 20 minutes, then adding microencapsulated ammonium bicarbonate and stirring at 8 rpm for 10 minutes, and finally spraying in deionized water; drying refers to drying at 80°C for 3.5 hours.

[0041] The mass ratio of coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution in step A2 is 6.6:1.2:0.3; the coconut shell powder is obtained by crushing coconut shells and passing them through an 180-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 250-mesh sieve; the sodium carboxymethyl cellulose solution contains 5 wt% sodium carboxymethyl cellulose.

[0042] The mixing mentioned in step A2 refers to stirring at 30 rpm for 12 minutes.

[0043] In step A3, the mass ratio of the honeycomb structure to the slurry is 1:1.1; the impregnation refers to setting the ultrasonic frequency to 30kHz, the ultrasonic power to 100W, and ultrasonic impregnation for 18s; the curing refers to pre-curing at 50℃ for 1.5h and then curing at 100℃ for 3.5h.

[0044] The three-stage gradient heating process described in step A4 refers to first heating to 160℃ at a heating rate of 1℃ / min and holding for 1.2h, then heating to 580℃ at a heating rate of 2℃ / min and holding for 1.4-1.6h, and finally heating to 700℃ at a heating rate of 8℃ and holding for 1.8h.

[0045] Example 2

[0046] A process for preparing gradient pore structure honeycomb activated carbon, the process comprising the following steps:

[0047] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0048] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0049] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0050] Step A4: Perform a three-stage gradient heating process on the processed honeycomb to obtain the final product.

[0051] The mass ratio of coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water in step A1 is 6.5:1.4:1.48:0.53; the coconut shell powder is obtained by crushing coconut shells and passing them through an 80-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 180-mesh sieve.

[0052] The preparation method of microencapsulated ammonium bicarbonate in step A1 includes the following steps:

[0053] Step B1: Heat the paraffin wax to 75°C to obtain pre-melted paraffin wax;

[0054] Step B2: Mix and stir the ethyl cellulose and ethanol solution to obtain an ethyl cellulose solution;

[0055] Step B3: Mix the pre-melted paraffin wax and ethyl cellulose solution evenly to obtain the wall material solution;

[0056] Step B4: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate.

[0057] The mass ratio of ethyl cellulose to ethanol solution in step B2 is 1:8.15; the mass concentration of ethanol solution is 84 wt%; the mass ratio of pre-melted paraffin to ethyl cellulose solution in step B3 is 1:2.9; the mass ratio of ammonium bicarbonate to wall material solution in step B4 is 1:1.9; the high-speed shearing refers to shearing at 17000 rpm for 6.5 min.

[0058] The mixing in step A1 refers to first stirring coconut shell powder and diatomaceous earth at 18 rpm for 22 minutes, then adding microencapsulated ammonium bicarbonate and stirring at 9 rpm for 10 minutes, and finally spraying in deionized water; drying refers to drying at 80°C for 3.7 hours.

[0059] The mass ratio of coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution in step A2 is 6.7:1.25:0.35; the coconut shell powder is obtained by crushing coconut shells and passing them through an 180-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 280-mesh sieve; the sodium carboxymethyl cellulose solution contains 5.2 wt% sodium carboxymethyl cellulose.

[0060] The mixing mentioned in step A2 refers to stirring at 32 rpm for 14 minutes.

[0061] The mass ratio of the honeycomb structure to the slurry in step A3 is 1:1.15; the impregnation refers to setting the ultrasonic frequency to 35kHz, the ultrasonic power to 100-200W, and ultrasonic impregnation for 19s; the curing refers to pre-curing at 53℃ for 1.8h and then curing at 105℃ for 3.8h.

[0062] The three-stage gradient heating process described in step A4 refers to first heating to 180℃ at a heating rate of 1.5℃ / min and holding for 1.4h, then heating to 600℃ at a heating rate of 2.5℃ / min and holding for 1.4h, and finally heating to 730℃ at a heating rate of 9℃ and holding for 1.9h.

[0063] Example 3

[0064] A process for preparing gradient pore structure honeycomb activated carbon, the process comprising the following steps:

[0065] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0066] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0067] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0068] Step A4: Perform a three-stage gradient heating process on the processed honeycomb to obtain the final product.

[0069] The mass ratio of coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water in step A1 is 6.6:1.5:1.5:0.55; the coconut shell powder is obtained by crushing coconut shells and passing them through a 100-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 200-mesh sieve.

[0070] The preparation method of microencapsulated ammonium bicarbonate in step A1 includes the following steps:

[0071] Step B1: Heat the paraffin wax to 76°C to obtain pre-melted paraffin wax;

[0072] Step B2: Mix and stir the ethyl cellulose and ethanol solution to obtain an ethyl cellulose solution;

[0073] Step B3: Mix the pre-melted paraffin wax and ethyl cellulose solution evenly to obtain the wall material solution;

[0074] Step B4: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate.

[0075] The mass ratio of ethyl cellulose to ethanol solution in step B2 is 1:8.2; the mass concentration of ethanol solution is 85 wt%; the mass ratio of pre-melted paraffin to ethyl cellulose solution in step B3 is 1:3; the mass ratio of ammonium bicarbonate to wall material solution in step B4 is 1:2; the high-speed shearing refers to shearing at 18000 rpm for 7 minutes.

[0076] The mixing in step A1 refers to first stirring coconut shell powder and diatomaceous earth at 20 rpm for 25 minutes, then adding microencapsulated ammonium bicarbonate and stirring at 10 rpm for 11 minutes, and finally spraying in deionized water; drying refers to drying at 80°C for 4 hours.

[0077] The mass ratio of coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution in step A2 is 6.8:1.3:0.4; the coconut shell powder is obtained by crushing coconut shells and passing them through a 200-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 300-mesh sieve; the sodium carboxymethyl cellulose content in the sodium carboxymethyl cellulose solution is 5.5 wt%.

[0078] The mixing mentioned in step A2 refers to stirring at 35 rpm for 15 minutes.

[0079] The mass ratio of the honeycomb structure to the slurry in step A3 is 1:1.2; the impregnation refers to setting the ultrasonic frequency to 40kHz, the ultrasonic power to 150W, and ultrasonic impregnation for 20s; the curing refers to pre-curing at 55℃ for 2h and then curing at 110℃ for 4h.

[0080] The three-stage gradient heating process described in step A4 refers to first heating to 220℃ at a heating rate of 2℃ / min and holding for 1.5h, then heating to 620℃ at a heating rate of 3℃ / min and holding for 1.5h, and finally heating to 750℃ at a heating rate of 10℃ and holding for 2h.

[0081] Example 4

[0082] A process for preparing gradient pore structure honeycomb activated carbon, the process comprising the following steps:

[0083] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0084] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0085] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0086] Step A4: Perform a three-stage gradient heating process on the processed honeycomb to obtain the final product.

[0087] The mass ratio of coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water in step A1 is 6.7:1.6:1.54:0.57; the coconut shell powder is obtained by crushing coconut shells and passing them through a 120-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 220-mesh sieve.

[0088] The preparation method of microencapsulated ammonium bicarbonate in step A1 includes the following steps:

[0089] Step B1: Heat the paraffin wax to 77°C to obtain pre-melted paraffin wax;

[0090] Step B2: Mix and stir the ethyl cellulose and ethanol solution to obtain an ethyl cellulose solution;

[0091] Step B3: Mix the pre-melted paraffin wax and ethyl cellulose solution evenly to obtain the wall material solution;

[0092] Step B4: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate.

[0093] The mass ratio of ethyl cellulose to ethanol solution in step B2 is 1:8.25; the mass concentration of ethanol solution is 86 wt%; the mass ratio of pre-melted paraffin to ethyl cellulose solution in step B3 is 1:3.1; the mass ratio of ammonium bicarbonate to wall material solution in step B4 is 1:2.1; the high-speed shearing refers to shearing at 19000 rpm for 7.5 min.

[0094] The mixing in step A1 refers to first stirring coconut shell powder and diatomaceous earth at 22 rpm for 28 minutes, then adding microencapsulated ammonium bicarbonate and stirring at 11 rpm for 12 minutes, and finally spraying in deionized water; drying refers to drying at 80°C for 4.2 hours.

[0095] The mass ratio of coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution in step A2 is 6.9:1.35:0.45; the coconut shell powder is obtained by crushing coconut shells and passing them through a 220-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 320-mesh sieve; the sodium carboxymethyl cellulose content in the sodium carboxymethyl cellulose solution is 5.7 wt%.

[0096] The mixing mentioned in step A2 refers to stirring at 36 rpm for 17 minutes.

[0097] The mass ratio of the honeycomb structure to the slurry in step A3 is 1:1.25; the impregnation refers to setting the ultrasonic frequency to 45kHz, the ultrasonic power to 180W, and ultrasonic impregnation for 21s; the curing refers to pre-curing at 58℃ for 2.2h and then curing at 115℃ for 4.2h.

[0098] The three-stage gradient heating process described in step A4 refers to first heating to 250℃ at a heating rate of 2.5℃ / min and holding for 1.6h, then heating to 640℃ at a heating rate of 3.5℃ / min and holding for 1.6h, and finally heating to 780℃ at a heating rate of 11℃ and holding for 2.1h.

[0099] Example 5

[0100] A process for preparing gradient pore structure honeycomb activated carbon, the process comprising the following steps:

[0101] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0102] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0103] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0104] Step A4: Perform a three-stage gradient heating process on the processed honeycomb to obtain the final product.

[0105] The mass ratio of coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water in step A1 is 6.8:1.7:1.6:0.6; the coconut shell powder is obtained by crushing coconut shells and passing them through a 120-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 250-mesh sieve.

[0106] The preparation method of microencapsulated ammonium bicarbonate in step A1 includes the following steps:

[0107] Step B1: Heat the paraffin wax to 77°C to obtain pre-melted paraffin wax;

[0108] Step B2: Mix and stir the ethyl cellulose and ethanol solution to obtain an ethyl cellulose solution;

[0109] Step B3: Mix the pre-melted paraffin wax and ethyl cellulose solution evenly to obtain the wall material solution;

[0110] Step B4: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate.

[0111] The mass ratio of ethyl cellulose to ethanol solution in step B2 is 1:8.3; the mass concentration of ethanol solution is 87 wt%; the mass ratio of pre-melted paraffin to ethyl cellulose solution in step B3 is 1:3.2; the mass ratio of ammonium bicarbonate to wall material solution in step B4 is 1:2.2; the high-speed shearing refers to shearing at 20,000 rpm for 8 minutes.

[0112] The mixing in step A1 refers to first stirring coconut shell powder and diatomaceous earth at 25 rpm for 30 minutes, then adding microencapsulated ammonium bicarbonate and stirring at 12 rpm for 12 minutes, and finally spraying in deionized water; drying refers to drying at 80°C for 4.5 hours.

[0113] The mass ratio of coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution in step A2 is 7:1.4:0.5; the coconut shell powder is obtained by crushing coconut shells and passing them through a 220-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 350-mesh sieve; the sodium carboxymethyl cellulose solution contains 6 wt% sodium carboxymethyl cellulose.

[0114] The mixing mentioned in step A2 refers to stirring at 40 rpm for 18 minutes.

[0115] The mass ratio of the honeycomb structure to the slurry in step A3 is 1:1.3; the impregnation refers to setting the ultrasonic frequency to 50kHz, the ultrasonic power to 200W, and ultrasonic impregnation for 22s; the curing refers to pre-curing at 60℃ for 2.5h and then curing at 120℃ for 4.5h.

[0116] The three-stage gradient heating process described in step A4 refers to first heating to 280℃ at a heating rate of 3℃ / min and holding for 1.8h, then heating to 660℃ at a heating rate of 4℃ / min and holding for 1.6h, and finally heating to 800℃ at a heating rate of 12℃ and holding for 2.2h.

[0117] Comparative Example 1

[0118] Based on Example 3, keeping other conditions unchanged, the preparation process of gradient pore structure honeycomb activated carbon was changed to include the following steps:

[0119] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, calcium hydroxide, diatomaceous earth, and deionized water, press the mixture using a honeycomb mold, and dry it to obtain a honeycomb structure; the mass ratio of the coconut shell powder, microencapsulated ammonium bicarbonate, calcium hydroxide, diatomaceous earth, and deionized water is 6.6:1.5:1.3:1.5:0.55.

[0120] Step A2: Perform a three-stage gradient heating process on the honeycomb structure to obtain the final product.

[0121] Comparative Example 2

[0122] Based on Example 3, keeping other conditions unchanged, the preparation process of gradient pore structure honeycomb activated carbon was changed to include the following steps:

[0123] Step A1: Mix coconut shell powder, ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure; the mass ratio of coconut shell powder, ammonium bicarbonate, calcium hydroxide, diatomaceous earth, and deionized water is 6.6:1.5:1.5:0.55.

[0124] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0125] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0126] Step A4: Perform a three-stage gradient heating process on the processed honeycomb to obtain the final product.

[0127] Comparative Example 3

[0128] Based on Example 3, keeping other conditions unchanged, the preparation process of gradient pore structure honeycomb activated carbon was changed to include the following steps:

[0129] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0130] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0131] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0132] Step A4: First, heat the processed honeycomb to 220℃ at a heating rate of 2℃ / min and hold for 1.5h. Then, heat it to 750℃ at a heating rate of 10℃ and hold for 3.5h to obtain the final product.

[0133] Comparative Example 4

[0134] Based on Example 3, keeping other conditions unchanged, the preparation process of gradient pore structure honeycomb activated carbon was changed to include the following steps:

[0135] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0136] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0137] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0138] Step A4: First, heat the processed honeycomb to 620℃ at a heating rate of 3℃ / min and hold for 3 hours. Then, heat it to 750℃ at a heating rate of 10℃ and hold for 2 hours to obtain the final product.

[0139] Comparative Example 5

[0140] Based on Example 3, keeping other conditions unchanged, the preparation process of gradient pore structure honeycomb activated carbon was changed to include the following steps:

[0141] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure;

[0142] Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry;

[0143] Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure;

[0144] Step A4: First, heat the treated honeycomb to 220℃ at a heating rate of 2℃ / min and hold for 1.5h. Then, heat it to 620℃ at a heating rate of 3℃ / min and hold for 3.5h to obtain the final product.

[0145] Comparative Example 6

[0146] Based on Example 3, the preparation method of microencapsulated ammonium bicarbonate was modified to include the following steps:

[0147] Step B1: Mix and stir the ethyl cellulose and ethanol solution to obtain the wall material solution;

[0148] Step B2: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate.

[0149] Using the honeycomb activated carbon prepared in Examples 1-5 and Comparative Examples 1-6 as samples, wastewater sampled on the same day was treated with a standard of 2g of sample per liter of wastewater. Following the test methods specified in "Methods for Detection and Analysis of Water and Wastewater" (Fourth Edition), a UV-Vis spectrophotometer (model Q-6, Shanghai Yuanxi Instrument Co., Ltd.) was used to detect COD in the wastewater, and the corresponding removal rates are recorded in Table 1 below. The adsorption value of the sample for methylene blue was tested according to GB / T 12496.10-1999 "Test Methods for Wood-based Activated Carbon - Determination of Methylene Blue Adsorption Value", and the results are recorded in Table 1 below.

[0150] Table 1

[0151] Example 1 83.39 16.8 Example 2 83.65 17.1 Example 3 83.91 17.5 Example 4 83.78 17.3 Example 5 83.53 16.9 Comparative Example 1 68.23 12.1 Comparative Example 2 62.47 9.8 Comparative Example 3 75.34 14.6 Comparative Example 4 71.85 13.2 Comparative Example 5 63.72 11.4 Comparative Example 6 59.16 8.3

[0152] As shown in Table 1, the gradient pore structure honeycomb activated carbon prepared by this invention has good adsorption performance.

[0153] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for preparing honeycomb activated carbon with a gradient pore structure, characterized in that: The preparation process of the gradient pore structure honeycomb activated carbon includes the following steps: Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb structure; Step A2: Mix coconut shell powder, calcium hydroxide, and sodium hydroxymethyl cellulose solution to obtain a slurry; Step A3: Immerse the honeycomb structure in the slurry and allow it to solidify to obtain the treated honeycomb structure; Step A4: Perform a three-stage gradient heating process on the processed honeycomb structure to obtain the final product. The preparation method of microencapsulated ammonium bicarbonate in step A1 includes the following steps: Step B1: Heat the paraffin wax to 75-77℃ to obtain pre-melted paraffin wax; Step B2: Mix and stir the ethyl cellulose and ethanol solution to obtain an ethyl cellulose solution; Step B3: Mix the pre-melted paraffin wax and ethyl cellulose solution evenly to obtain the wall material solution; Step B4: Add ammonium bicarbonate to the wall material solution, shear at high speed to obtain a suspension, freeze dry to obtain microencapsulated ammonium bicarbonate; The three-stage gradient heating process described in step A4 refers to first heating to 160-280℃ at a heating rate of 1-3℃ / min and holding for 1.2-1.8h, then heating to 580-660℃ at a heating rate of 2-4℃ / min and holding for 1.4-1.6h, and finally heating to 700-800℃ at a heating rate of 8-12℃ and holding for 1.8-2.2h.

2. The preparation process of a gradient pore structure honeycomb activated carbon according to claim 1, characterized in that: The mass ratio of coconut shell powder, microencapsulated ammonium bicarbonate, diatomaceous earth, and deionized water in step A1 is 6.4-6.8:1.3-1.7:1.4-1.6:0.5-0.6; the coconut shell powder is obtained by crushing coconut shells and passing them through an 80-120 mesh sieve; the diatomaceous earth needs to be crushed and passed through a 150-250 mesh sieve.

3. The preparation process of a gradient pore structure honeycomb activated carbon according to claim 1, characterized in that: The mass ratio of ethyl cellulose to ethanol solution in step B2 is 1:8.1-8.3; the mass concentration of ethanol solution is 83-87 wt%; the mass ratio of pre-melted paraffin wax to ethyl cellulose solution in step B3 is 1:2.8-3.2; the mass ratio of ammonium bicarbonate to wall material solution in step B4 is 1:1.8-2.2; the high-speed shearing refers to shearing at a speed of 16000-20000 rpm for 6-8 minutes.

4. The preparation process of a gradient pore structure honeycomb activated carbon according to claim 1, characterized in that: The mixing in step A1 refers to first stirring coconut shell powder and diatomaceous earth at 15-25 rpm for 20-30 minutes, then adding microencapsulated ammonium bicarbonate and stirring at 8-12 rpm for 10-12 minutes, and finally spraying in deionized water; drying refers to drying at 80℃ for 3.5-4.5 hours.

5. The preparation process of a gradient pore structure honeycomb activated carbon according to claim 1, characterized in that: The mass ratio of coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution in step A2 is 6.6-7:1.2-1.4:0.3-0.5; the coconut shell powder is obtained by crushing coconut shells and passing them through a 180-220 mesh sieve; the diatomaceous earth needs to be crushed and passed through a 250-350 mesh sieve; the sodium carboxymethyl cellulose content in the sodium carboxymethyl cellulose solution is 5-6 wt%.

6. The preparation process of a gradient pore structure honeycomb activated carbon according to claim 1, characterized in that: The mixing mentioned in step A2 refers to stirring at a speed of 30-40 rpm for 12-18 minutes.

7. The preparation process of a gradient pore structure honeycomb activated carbon according to claim 1, characterized in that: In step A3, the mass ratio of the honeycomb structure to the slurry is 1:1.1-1.3; the impregnation refers to setting the ultrasonic frequency to 30-50kHz, the ultrasonic power to 100-200W, and the ultrasonic impregnation time to 18-22s; the curing refers to pre-curing at 50-60℃ for 1.5-2.5h, and then curing at 100-120℃ for 3.5-4.5h.