Honeycomb activated carbon with gradient pore structure and preparation process of honeycomb activated carbon

Abstract

The invention relates to gradient pore structure honeycomb activated carbon and a preparation process thereof, and belongs to the technical field of activated carbon. The invention provides a preparation process which comprises the following steps: mixing coconut shell powder, microencapsulated ammonium bicarbonate, diatomite and deionized water, pressing with a honeycomb mold, and drying to obtain a honeycomb body; mixing coconut shell powder, calcium hydroxide and a carboxymethyl cellulose sodium solution to obtain slurry; dipping a honeycomb body in the slurry, curing to obtain the treated honeycomb body, and then carrying out three-section gradient heating treatment to obtain the honeycomb activated carbon with the gradient pore structure. The microencapsulated ammonium bicarbonate and the surface slurry containing calcium hydroxide are introduced in the process of preparing the honeycomb activated carbon, and gradient pores are gradually formed through three-section gradient heating, so that the adsorption performance of the activated carbon is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of activated carbon, and relates to a honeycomb activated carbon with a gradient pore structure and a preparation process thereof. Background Art

[0002] Honeycomb activated carbon is a porous honeycomb-structured material mainly made of activated carbon and processed by a special process. Its core lies in reconstructing traditional powdered or granular activated carbon into a regular honeycomb body. Its application fields cover industrial waste gas treatment, motor vehicle exhaust purification, indoor air purification equipment, gas separation and purification in chemical production, etc., and it plays an important role in the field of environmental engineering. Although honeycomb activated carbon is widely used in the field of air adsorption, its performance still has significant limitations. For example, the problem of pore structure homogenization. Existing products mostly adopt a single pore size distribution (concentrated in the mesopore range of 2 - 4 nm), and it is difficult to achieve synchronous and efficient adsorption of mixed pollutants with significantly different molecular diameters, which seriously restricts its application reliability under complex working conditions. Summary of the Invention

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

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A preparation process of a honeycomb activated carbon with a gradient pore structure, the preparation process of the honeycomb activated carbon with a gradient pore structure comprises the following steps:

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

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

[0008] Step A3: Immerse the honeycomb body in the slurry, cure to obtain a treated honeycomb body;

[0009] Step A4: Perform three-stage gradient heating treatment on the treated honeycomb body to obtain the product.

[0010] Furthermore, in step A1, the mass ratio of the coconut shell powder, microencapsulated ammonium bicarbonate, diatomite, 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 through a sieve with 80 - 120 meshes; the diatomite needs to be crushed and passed through a sieve with 150 - 250 meshes.

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

[0012] Step B1: Heat paraffin to 75 - 77 °C to obtain pre-melted paraffin.

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

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

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

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

[0017] Further, the mixing described in step A1 refers to first stirring coconut shell powder and diatomaceous earth at a rotation speed of 15 - 25 rpm for 20 - 30 min, then adding microencapsulated ammonium bicarbonate, stirring at a rotation speed of 8 - 12 rpm for 10 - 12 min, and finally spray-adding deionized water; drying refers to drying at 80 °C for 3.5 - 4.5 h.

[0018] Further, the mass ratio of the coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution described 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 through a 180 - 220 mesh sieve; the diatomaceous earth needs to be crushed and passed through a 250 - 350 mesh sieve; the content of sodium carboxymethyl cellulose in the sodium carboxymethyl cellulose solution is 5 - 6 wt%.

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

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

[0021] Further, the three-stage gradient temperature rise treatment described in step A4 means that the temperature is first raised to 160-280°C at a heating rate of 1-3°C / min and held for 1.2-1.8 h, then the temperature is raised to 580-660°C at a heating rate of 2-4°C / min and held for 1.4-1.6 h, and finally the temperature is raised to 700-800°C at a heating rate of 8-12°C and held for 1.8-2.2 h.

[0022] Beneficial effects of the present invention:

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

[0024] (2) In the present invention, the microencapsulated sodium bicarbonate 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, resulting in the destruction of the capsule shell structure. The core material sodium bicarbonate of the microcapsule decomposes first, and the decomposed gas volatiles escape along the porous structures of coconut shell powder and diatomaceous earth, forming fine pores inside the activated carbon, namely the initial channels; when the temperature reaches the first heating interval, the capsule shell of the microencapsulated sodium bicarbonate gradually decomposes, and the decomposed volatiles will preferentially escape along the initial channels, further expanding the channel pore diameter; when the temperature reaches the second heating interval, the calcium hydroxide in the surface layer slurry gradually decomposes, and the obtained water vapor forms pores on the surface layer. The calcium oxide particles participate in the construction of the activated carbon skeleton as a hard template to enhance the mechanical strength and prevent the structure from collapsing. At this time, the volatiles that have not completely escaped inside will preferentially escape from these pores, thereby communicating with the existing pores to form a gradient pore channel from the core of the activated carbon to the surface layer; finally, when the temperature reaches the third heating interval, mainly water vapor participates in the activation to further connect and expand the pores. The honeycomb activated carbon with the obtained gradient pore structure has good adsorption performance. Specific embodiments

[0025] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines examples to detail the specific embodiments, structures, features and their effects of the present invention as follows.

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

[0027] Example 1

[0028] A preparation process of honeycomb activated carbon with a gradient pore structure, the preparation process of the honeycomb activated carbon with a gradient pore structure comprises the following steps:

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

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

[0031] Step A3: Immerse the honeycomb body in the slurry, cure to obtain a treated honeycomb body;

[0032] Step A4: Perform a three-stage gradient temperature rise treatment on the treated honeycomb body to obtain it.

[0033] The mass ratio of the coconut shell powder, microencapsulated ammonium bicarbonate, diatomite, 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 through an 80-mesh sieve; the diatomite needs to be crushed and passed through a 150-mesh sieve.

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

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

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

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

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

[0039] The mass ratio of the ethyl cellulose and the ethanol solution in Step B2 is 1:8.1; the mass concentration of the ethanol solution is 83 wt%; the mass ratio of the pre-melted paraffin wax and the ethyl cellulose solution in Step B3 is 1:2.8; the mass ratio of the ammonium bicarbonate and the wall material solution in Step B4 is 1:1.8; the high-speed shearing refers to shearing at a speed of 16,000 rpm for 6 min.

[0040] The mixing in Step A1 refers to first stirring the coconut shell powder and diatomite at a speed of 15 rpm for 20 min, then adding microencapsulated ammonium bicarbonate, stirring at a speed of 8 rpm for 10 min, and finally spray-adding deionized water; drying refers to drying at 80 °C for 3.5 h.

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

[0042] The mixing described in step A2 means stirring at a speed of 30 rpm for 12 min.

[0043] The mass ratio of the honeycomb body and the slurry described in step A3 is 1:1.1; the impregnation means setting the ultrasonic frequency to 30 kHz, the ultrasonic power to 100 W, and ultrasonic impregnation for 18 s. The curing means pre-curing at 50 °C for 1.5 h and then curing at 100 °C for 3.5 h.

[0044] The three-stage gradient temperature rise treatment described in step A4 means first raising the temperature to 160 °C at a heating rate of 1 °C / min, holding for 1.2 h, then raising the temperature to 580 °C at a heating rate of 2 °C / min, holding for 1.4 - 1.6 h, and finally raising the temperature to 700 °C at a heating rate of 8 °C and holding for 1.8 h.

[0045] Example 2

[0046] A preparation process of a honeycomb activated carbon with a gradient pore structure, the preparation process of the honeycomb activated carbon with a gradient pore structure includes 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 body;

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

[0049] Step A3: Immerse the honeycomb body in the slurry and cure to obtain a treated honeycomb body;

[0050] Step A4: Perform a three-stage gradient temperature rise treatment on the treated honeycomb body to obtain it.

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

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

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

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

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

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

[0057] The mass ratio of the ethyl cellulose to the ethanol solution in Step B2 is 1:8.15; the mass concentration of the ethanol solution is 84 wt%; the mass ratio of the pre-melted paraffin to the ethyl cellulose solution in Step B3 is 1:2.9; the mass ratio of the ammonium bicarbonate to the wall material solution in Step B4 is 1:1.9; the high-speed shearing refers to shearing at a rotation speed of 17,000 rpm for 6.5 min.

[0058] The mixing in Step A1 refers to first stirring coconut shell powder and diatomite at a rotation speed of 18 rpm for 22 min, then adding microencapsulated ammonium bicarbonate, stirring at a rotation speed of 9 rpm for 10 min, and finally spray-adding deionized water; the drying refers to drying at 80 °C for 3.7 h.

[0059] The mass ratio of the coconut shell powder, calcium hydroxide, and sodium carboxymethylcellulose solution in Step A2 is 6.7:1.25:0.35; the coconut shell powder is obtained by crushing coconut shells and passing through a 180-mesh sieve; the diatomite needs to be crushed and passed through a 280-mesh sieve; the content of sodium carboxymethylcellulose in the sodium carboxymethylcellulose solution is 5.2 wt%.

[0060] The mixing in Step A2 refers to stirring at a rotation speed of 32 rpm for 14 min.

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

[0062] The three-stage gradient temperature rise treatment in Step A4 refers to first rising the temperature at a rate of 1.5 °C / min to 180 °C, holding for 1.4 h, then rising the temperature at a rate of 2.5 °C / min to 600 °C, holding for 1.4 h, and finally rising the temperature at a rate of 9 °C / min to 730 °C and holding for 1.9 h.

[0063] Example 3

[0064] A preparation process of a honeycomb activated carbon with a gradient pore structure, the preparation process of the honeycomb activated carbon with a gradient pore structure comprises the following steps:

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

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

[0067] Step A3: Immerse the honeycomb body in the slurry and cure it to obtain a treated honeycomb body;

[0068] Step A4: Perform a three-stage gradient temperature increase treatment on the treated honeycomb body to obtain the product.

[0069] The mass ratio of the 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 through a 100-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 200-mesh sieve.

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

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

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

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

[0074] Step B4: Add ammonium bicarbonate to the wall material solution, perform high-speed shearing to obtain a suspension, and freeze-dry it to obtain microencapsulated ammonium bicarbonate.

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

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

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

[0078] The mixing described in step A2 means stirring at a speed of 35 rpm for 15 min.

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

[0080] The three-stage gradient temperature rise treatment described in step A4 means first raising the temperature to 220 °C at a heating rate of 2 °C / min, holding for 1.5 h, then raising the temperature to 620 °C at a heating rate of 3 °C / min, holding for 1.5 h, and finally raising the temperature to 750 °C at a heating rate of 10 °C and holding for 2 h.

[0081] Example 4

[0082] A preparation process of a honeycomb activated carbon with a gradient pore structure, the preparation process of the honeycomb activated carbon with a gradient pore structure includes 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 body;

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

[0085] Step A3: Immerse the honeycomb body in the slurry and cure to obtain a treated honeycomb body;

[0086] Step A4: Perform a three-stage gradient temperature rise treatment on the treated honeycomb body to obtain it.

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

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

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

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

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

[0092] Step B4: Add ammonium bicarbonate to the wall material solution, perform high-speed shearing to obtain a suspension, and conduct freeze-drying to obtain microencapsulated ammonium bicarbonate.

[0093] In Step B2, the mass ratio of the ethyl cellulose to the ethanol solution is 1:8.25; the mass concentration of the ethanol solution is 86 wt%; in Step B3, the mass ratio of the pre-melted paraffin to the ethyl cellulose solution is 1:3.1; in Step B4, the mass ratio of the ammonium bicarbonate to the wall material solution is 1:2.1; the high-speed shearing refers to shearing at a rotation speed of 19,000 rpm for 7.5 min.

[0094] The mixing in Step A1 refers to first stirring coconut shell powder and diatomite at a rotation speed of 22 rpm for 28 min, then adding microencapsulated ammonium bicarbonate, stirring at a rotation speed of 11 rpm for 12 min, and finally spray-adding deionized water; the drying refers to drying at 80°C for 4.2 h.

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

[0096] The mixing in Step A2 refers to stirring at a rotation speed of 36 rpm for 17 min.

[0097] In Step A3, the mass ratio of the honeycomb body to the slurry is 1:1.25; the impregnation refers to setting the ultrasonic frequency at 45 kHz, the ultrasonic power at 180 W, and performing ultrasonic impregnation for 21 s; the curing refers to pre-curing at 58°C for 2.2 h first and then curing at 115°C for 4.2 h.

[0098] The three-stage gradient temperature rise treatment in Step A4 refers to first rising the temperature at a rate of 2.5°C / min to 250°C, holding for 1.6 h, then rising the temperature at a rate of 3.5°C / min to 640°C, holding for 1.6 h, and finally rising the temperature at a rate of 11°C / min to 780°C and holding for 2.1 h.

[0099] Example 5

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

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

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

[0103] Step A3: Immerse the honeycomb body in the slurry and cure it to obtain a treated honeycomb body;

[0104] Step A4: Perform a three-stage gradient temperature increase treatment on the treated honeycomb body to obtain the product.

[0105] The mass ratio of the 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 through a 120-mesh sieve; the diatomaceous earth needs to be crushed and passed through a 250-mesh sieve.

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

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

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

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

[0110] Step B4: Add ammonium bicarbonate to the wall material solution, perform high-speed shearing to obtain a suspension, and freeze-dry it to obtain microencapsulated ammonium bicarbonate.

[0111] The mass ratio of the ethyl cellulose and ethanol solution in Step B2 is 1:8.3; the mass concentration of the ethanol solution is 87 wt%; the mass ratio of the pre-melted paraffin and the ethyl cellulose solution in Step B3 is 1:3.2; the mass ratio of the ammonium bicarbonate and the wall material solution in Step B4 is 1:2.2; the high-speed shearing refers to shearing at a speed of 20000 rpm for 8 min.

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

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

[0114] The mixing described in step A2 means stirring at a speed of 40 rpm for 18 min.

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

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

[0117] Comparative Example 1

[0118] On the basis of Example 3, with other conditions remaining unchanged, the preparation process of the gradient pore structure honeycomb activated carbon is changed to include the following steps:

[0119] Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, calcium hydroxide, diatomite, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb body; the mass ratio of the coconut shell powder, encapsulated ammonium bicarbonate, calcium hydroxide, diatomite, and deionized water is 6.6:1.5:1.3:1.5:0.55;

[0120] Step A2: Perform three-stage gradient heating treatment on the honeycomb body to obtain the product.

[0121] Comparative Example 2

[0122] On the basis of Example 3, with other conditions remaining unchanged, the preparation process of the gradient pore structure honeycomb activated carbon is changed to include the following steps:

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

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

[0125] Step A3: Immerse the honeycomb body in the slurry, and cure it to obtain the treated honeycomb body;

[0126] Step A4: Perform a three-stage gradient temperature increase treatment on the treated honeycomb body to obtain the product.

[0127] Comparative Example 3

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

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

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

[0131] Step A3: Immerse the honeycomb body in the slurry, and cure it to obtain the treated honeycomb body;

[0132] Step A4: First, heat the treated honeycomb body at a heating rate of 2 °C / min to 220 °C, hold for 1.5 h, then heat it at a heating rate of 10 °C to 750 °C, and hold for 3.5 h to obtain the product.

[0133] Comparative Example 4

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

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

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

[0137] Step A3: Immerse the honeycomb body in the slurry, and cure it to obtain the treated honeycomb body;

[0138] Step A4: First, heat the treated honeycomb body at a heating rate of 3 °C / min to 620 °C, hold for 3 h, and finally heat it at a heating rate of 10 °C to 750 °C, and hold for 2 h to obtain the product.

[0139] Comparative Example 5

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

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

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

[0143] Step A3: Immerse the honeycomb body in the slurry and cure it to obtain a treated honeycomb body;

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

[0145] Comparative Example 6

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

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

[0148] Step B2: Add ammonium bicarbonate to the wall material solution, perform high-speed shearing to obtain a suspension, and freeze-dry it to obtain microencapsulated ammonium bicarbonate.

[0149] Using the honeycomb activated carbon prepared in Examples 1-5 and Comparative Examples 1-6 as samples, treating the sewage sampled on the same day according to the standard of putting 2 g of samples per liter of sewage, and adopting the test method specified in "Water and Wastewater Inspection and Analysis Methods" (Fourth Edition), using the ultraviolet-visible spectrophotometer model Q-6 of Shanghai Yuanxi Instruments Co., Ltd., detecting the COD of the sewage with the samples, and the corresponding removal rates are recorded as shown in Table 1 below; testing the methylene blue adsorption value of the samples according to GB / T 12496.10-1999 "Test Methods for Wood Activated Carbon - Determination of Methylene Blue Adsorption Value", and the records are shown in Table 1 below.

[0150] Table 1

[0151] COD removal rate (%) Methylene blue adsorption value (ml / 0.1 g) 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 can be seen from Table 1, the gradient pore structure honeycomb activated carbon prepared by the present invention has good adsorption performance.

[0153] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. Although the present invention has been disclosed above in its preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any indirect modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation process of honeycomb activated carbon with a gradient pore structure, characterized in that: The preparation process of the gradient pore structure honeycomb activated carbon comprises the following steps: Step A1: Mix coconut shell powder, microencapsulated ammonium bicarbonate, diatomite, and deionized water, press with a honeycomb mold, and dry to obtain a honeycomb body; Step A2: Mix coconut shell powder, calcium hydroxide, and sodium carboxymethyl cellulose solution to obtain a slurry; Step A3: Immerse the honeycomb body in the slurry and cure to obtain a treated honeycomb body; Step A4: Perform three-stage gradient temperature rise treatment on the treated honeycomb body to obtain the product.

2. The preparation process of a gradient pore structure honeycomb activated carbon according to claim 1, characterized in that: In Step A1, the mass ratio of the coconut shell powder, microencapsulated ammonium bicarbonate, diatomite, 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 through a sieve with 80 - 120 meshes; the diatomite needs to be crushed and passed through a sieve with 150 - 250 meshes.

3. The preparation process of a honeycomb activated carbon with a gradient pore structure according to claim 1, characterized in that: The preparation method of the microencapsulated ammonium bicarbonate in Step A1 comprises the following steps: Step B1: Heat paraffin wax to 75 - 77 °C to obtain pre-melted paraffin wax; Step B2: Mix ethyl cellulose and ethanol solution and stir to obtain an ethyl cellulose solution; Step B3: Mix the pre-melted paraffin wax and the ethyl cellulose solution evenly to obtain a wall material solution; Step B4: Add ammonium bicarbonate to the wall material solution, perform high-speed shearing to obtain a suspension, and freeze-dry to obtain microencapsulated ammonium bicarbonate.

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

5. The preparation process of a honeycomb activated carbon with a gradient pore structure according to claim 1, characterized in that: The mixing in Step A1 refers to first stirring the coconut shell powder and diatomite at a rotation speed of 15 - 25 rpm for 20 - 30 min, then adding the microencapsulated ammonium bicarbonate, stirring at a rotation speed of 8 - 12 rpm for 10 - 12 min, and finally spray-adding deionized water; drying refers to drying at 80 °C for 3.5 - 4.5 h.

6. The preparation process of a honeycomb activated carbon with a gradient pore structure according to claim 1, characterized in that: In Step A2, the mass ratio of the 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 through a sieve with 180 - 220 meshes; the diatomite needs to be crushed and passed through a sieve with 250 - 350 meshes; the content of sodium carboxymethyl cellulose in the sodium carboxymethyl cellulose solution is 5 - 6 wt%.

7. The preparation process of a honeycomb activated carbon with a gradient pore structure according to claim 1, characterized in that: The mixing in Step A2 refers to stirring at a rotation speed of 30 - 40 rpm for 12 - 18 min.

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

9. The preparation process of a honeycomb activated carbon with a gradient pore structure according to claim 1, characterized in that: The three-stage gradient temperature increase treatment described in step A4 means that the temperature is first increased at a rate of 1-3 °C / min to 160-280 °C and held for 1.2-1.8 h, then the temperature is increased at a rate of 2-4 °C / min to 580-660 °C and held for 1.4-1.6 h, and finally the temperature is increased at a rate of 8-12 °C to 700-800 °C and held for 1.8-2.2 h.