A phosphoric acid-activated activated carbon and its preparation process

Abstract

This invention relates to phosphoric acid-activated carbon and its preparation process, belonging to the field of activated carbon technology. The invention provides a preparation process for phosphoric acid-activated carbon, specifically involving sieving fir sawdust and mixing it with a penetrating agent. The resulting mixture is placed in an impregnation tank, and a low-concentration phosphoric acid solution is injected under vacuum. After returning to normal pressure, the carbon is impregnated. Then, half a volume of the low-concentration phosphoric acid solution is discharged, and an equal volume of a lower-concentration phosphoric acid solution is added to obtain a mixed solution. The mixture is heated and stirred, and then half a volume of the mixed solution is discharged again, and an equal volume of a phosphoric acid-oxalic acid mixed solution is added. The temperature is maintained constant, and the mixture is ultrasonically impregnated to obtain an impregnated material. This material undergoes variable-temperature treatment, three-stage washing, and microwave-vacuum drying to obtain the final product. This invention utilizes a penetrating agent for pretreatment of the raw material, followed by a three-stage gradient phosphoric acid impregnation. During impregnation, the solid-liquid ratio is kept constant while ultrasonic treatment is employed to achieve gradual phosphoric acid penetration and uniform pore formation, thereby improving the specific surface area and adsorption performance of the activated carbon.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon technology, and relates to a phosphoric acid activated carbon and its preparation process. Background Technology

[0002] Activated carbon activation refers to the process of processing carbon-containing materials through physical or chemical methods to form a well-developed pore structure, thereby increasing the specific surface area and adsorption performance of activated carbon to meet the adsorption capacity requirements of different application scenarios. Currently, activated carbon activation processes are divided into physical activation and chemical activation. Chemical activation is increasingly widely used due to its advantages such as low energy consumption and short process cycle. Phosphoric acid activation, as a representative chemical activation process, is widely used in water treatment. However, in practical applications, due to the inhomogeneity and lack of controllability of activation conditions, problems such as discrete pore distribution easily arise. For example, when the phosphoric acid concentration is too low, insufficient activation leads to the formation of non-uniform pores in the carbon skeleton, directly affecting the specific surface area and adsorption performance of the material. Furthermore, the penetration behavior of phosphoric acid in wood raw materials exhibits significant anisotropy, which also leads to a gradient distribution of the pore structure, affecting the non-uniform distribution of the medium during actual adsorption and increasing the risk of structural collapse under mechanical or thermal stress. These problems urgently need to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide a phosphoric acid-activated carbon and its preparation process. This invention pre-treats the raw materials with a permeation aid, followed by a three-stage gradient phosphoric acid impregnation. During the impregnation process, the solid-liquid ratio is kept constant while ultrasonic treatment is applied to achieve gradual phosphoric acid permeation and uniform pore formation, thereby improving the specific surface area and adsorption performance of the activated carbon.

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

[0005] A process for preparing phosphoric acid-activated activated carbon, the process comprising the following steps:

[0006] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0007] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0008] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0009] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0010] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0011] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0012] Further, in step X1, the mass ratio of cedar wood chips to penetrating agent is 10:0.14-0.18; the penetrating agent is obtained by compounding PEG-400 and sodium dodecyl sulfonate in a mass ratio of 1:1; sieving refers to passing through a 20-60 mesh sieve; mixing refers to stirring at a speed of 100-200 rpm for 8-14 minutes.

[0013] Further, in step X2, the ratio of the mixed raw material to the low-concentration phosphoric acid solution is 1:3-3.2 g / mL; the vacuuming refers to evacuating to -0.08 MPa and maintaining it for 15 min; the mass of phosphoric acid in the low-concentration phosphoric acid solution is 8-12 wt%; and the impregnation time is 30-40 min.

[0014] Further, the mass of phosphoric acid in the lower concentration phosphoric acid solution in step X3 is 18-22 wt%; the stirring after heating refers to stirring at a speed of 60-80 rpm for 30-40 minutes after heating to 48-52℃.

[0015] Further, in step X4, the mass of phosphoric acid in the phosphoric acid-oxalic acid mixture is 28-32 wt%, and the mass of oxalic acid is 4.5-5.5 wt%. The ultrasonic impregnation refers to setting the ultrasonic frequency to 40-50 kHz, the ultrasonic power to 100-200 W, and ultrasonicating for 20-30 min followed by impregnation for 1-1.6 h.

[0016] Furthermore, the variable temperature treatment mentioned in step X5 refers to, under a nitrogen atmosphere, first raising the temperature to 145-155℃ at 2.5-3.5℃ and holding it at that temperature for 1-1.4h, then raising the temperature to 450-460℃ at 4.5-5.5℃ and holding it at that temperature for 2-2.6h.

[0017] Further, the three-stage washing in step X6 refers to mixing the activated product and deionized water at a material-to-liquid ratio of 1:4.5-5.5 g / mL, stirring at 80°C for 20-30 min, washing with an equal volume of dilute hydrochloric acid with a concentration of 1-1.2 wt% for 20-30 min, and finally rinsing with deionized water until neutral.

[0018] Further, the microwave-vacuum drying in step X6 refers to setting the microwave drying power to 780-820W, using a pulse mode of 3s on / 2s off, and drying to a moisture content of less than 3wt% under a vacuum of -0.095MPa.

[0019] The beneficial effects of this invention are:

[0020] This invention uses a penetration aid before phosphoric acid treatment. PEG-400 reduces polarity differences, while sodium dodecyl sulfonate disrupts the hydrophobic barrier of lignin, allowing subsequent phosphoric acid to penetrate along the fiber axis and warp, reducing anisotropy. Based on this, a three-stage gradient impregnation process is employed: first, a low-concentration phosphoric acid is used to wet the micropores; then, an even lower concentration of phosphoric acid is used to expand the pore size; finally, a phosphoric acid-oxalic acid mixture is used at high temperature to generate uniform micropores. Oxalic acid synergistic activation replaces the use of high-concentration phosphoric acid, promoting the gradual penetration of phosphoric acid into the wood fibers. Furthermore, when changing the phosphoric acid concentration, this process maintains a constant solid-liquid ratio to avoid sudden changes in osmotic pressure caused by liquid level fluctuations, ensuring a smooth concentration gradient. During the phosphoric acid-oxalic acid mixture treatment, ultrasonic assistance is used to prevent high-concentration phosphoric acid from directly clogging surface pores, forming uniform penetration channels and achieving uniform pore formation, thereby effectively improving the specific surface area and adsorption capacity of activated carbon. Detailed Implementation

[0021] 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.

[0022] All the fir wood chips used in the embodiments and comparative examples of this invention were purchased directly from the market from Hebei Nordic New Material Technology Co., Ltd.; PEG-400 was purchased directly from the market from Shandong Chuangyi Chemical Co., Ltd.; sodium dodecyl sulfonate was purchased directly from the market from Shandong Haochen New Material Technology Co., Ltd.; phosphoric acid and dilute hydrochloric acid were purchased directly from the market from Sigma-Aldrich (Shanghai) Trading Co., Ltd.; and oxalic acid was purchased directly from the market from Jinan Jinyu Chemical Co., Ltd.

[0023] Example 1

[0024] A process for preparing phosphoric acid-activated activated carbon, the process comprising the following steps:

[0025] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0026] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0027] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0028] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0029] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0030] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0031] The mass ratio of cedar wood chips to penetrating agent in step X1 is 10:0.14; the penetrating agent is obtained by compounding PEG-400 and sodium dodecyl sulfonate in a mass ratio of 1:1; sieving refers to passing through a 20-mesh sieve; mixing refers to stirring at 100 rpm for 8 minutes.

[0032] In step X2, the ratio of the mixed raw material to the low-concentration phosphoric acid solution is 1:3 g / mL; the vacuuming refers to evacuating to -0.08 MPa and maintaining it for 15 min; the mass of phosphoric acid in the low-concentration phosphoric acid solution is 8 wt%; and the impregnation time is 30 min.

[0033] The phosphoric acid in the lower concentration phosphoric acid solution in step X3 is 18 wt%; the stirring after heating refers to stirring at 60 rpm for 30 minutes after heating to 48°C.

[0034] In step X4, the mass of phosphoric acid in the phosphoric acid-oxalic acid mixture is 28 wt%, and the mass of oxalic acid is 4.5 wt%. The ultrasonic impregnation refers to setting the ultrasonic frequency to 40 kHz, the ultrasonic power to 100 W, and ultrasonication for 20 min followed by impregnation for 1 h.

[0035] The variable temperature treatment mentioned in step X5 refers to first raising the temperature to 145°C at 2.5°C and holding it at that temperature for 1 hour under a nitrogen atmosphere, and then raising the temperature to 450°C at 4.5°C and holding it at that temperature for 2 hours.

[0036] The three-stage washing described in step X6 refers to mixing the activated product and deionized water at a material-to-liquid ratio of 1:4.5 g / mL, stirring at 80°C for 20 min, washing with an equal volume of 1 wt% dilute hydrochloric acid for 20 min, and finally rinsing with deionized water until neutral.

[0037] The microwave-vacuum drying described in step X6 refers to setting the microwave drying power to 780W, using a pulse mode of 3s on / 2s off, and drying under a vacuum of -0.095MPa until the moisture content is below 3wt%.

[0038] Example 2

[0039] A process for preparing phosphoric acid-activated activated carbon, the process comprising the following steps:

[0040] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0041] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0042] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0043] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0044] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0045] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0046] The mass ratio of cedar wood chips to penetrating agent in step X1 is 10:0.15; the penetrating agent is obtained by compounding PEG-400 and sodium dodecyl sulfonate in a mass ratio of 1:1; sieving refers to passing through a 30-mesh sieve; mixing refers to stirring at 120 rpm for 10 minutes.

[0047] In step X2, the ratio of the mixed raw material to the low-concentration phosphoric acid solution is 1:3.08 g / mL; the vacuuming refers to evacuating to -0.08 MPa and maintaining it for 15 min; the mass of phosphoric acid in the low-concentration phosphoric acid solution is 9 wt%; and the impregnation time is 32 min.

[0048] The phosphoric acid in the lower concentration phosphoric acid solution in step X3 is 19 wt%; the stirring after heating refers to stirring at 65 rpm for 32 minutes after heating to 49°C.

[0049] In step X4, the mass of phosphoric acid in the phosphoric acid-oxalic acid mixture is 29 wt%, and the mass of oxalic acid is 4.8 wt%. The ultrasonic impregnation refers to setting the ultrasonic frequency to 42 kHz, the ultrasonic power to 120 W, and ultrasonication for 23 min followed by impregnation for 1.2 h.

[0050] The variable temperature treatment mentioned in step X5 refers to first raising the temperature to 148°C at 2.8°C and holding it at that temperature for 1.1 hours under a nitrogen atmosphere, and then raising the temperature to 452°C at 4.6°C and holding it at that temperature for 2.1 hours.

[0051] The three-stage washing described in step X6 refers to mixing the activated product and deionized water at a material-to-liquid ratio of 1:4.8 g / mL, stirring at 80°C for 22 min, washing with an equal volume of 1.07 wt% dilute hydrochloric acid for 22 min, and finally rinsing with deionized water until neutral.

[0052] The microwave-vacuum drying described in step X6 refers to setting the microwave drying power to 790W, using a pulse mode of 3s on / 2s off, and drying under a vacuum of -0.095MPa until the moisture content is below 3wt%.

[0053] Example 3

[0054] A process for preparing phosphoric acid-activated activated carbon, the process comprising the following steps:

[0055] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0056] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0057] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0058] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0059] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0060] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0061] The mass ratio of cedar wood chips to penetrating agent in step X1 is 10:0.16; the penetrating agent is obtained by compounding PEG-400 and sodium dodecyl sulfonate in a mass ratio of 1:1; sieving refers to passing through a 40-mesh sieve; mixing refers to stirring at 150 rpm for 11 minutes.

[0062] In step X2, the ratio of the mixed raw material to the low-concentration phosphoric acid solution is 1:3.1 g / mL; the vacuuming refers to evacuating to -0.08 MPa and maintaining it for 15 min; the mass of phosphoric acid in the low-concentration phosphoric acid solution is 10 wt%; and the impregnation time is 35 min.

[0063] The phosphoric acid in the lower concentration phosphoric acid solution in step X3 is 20 wt%; the stirring after heating refers to stirring at 70 rpm for 35 minutes after heating to 50°C.

[0064] In step X4, the phosphoric acid-oxalic acid mixture contains 30 wt% phosphoric acid and 5 wt% oxalic acid. The ultrasonic impregnation refers to setting the ultrasonic frequency to 45 kHz, the ultrasonic power to 150 W, and ultrasonication for 25 min followed by impregnation for 1.3 h.

[0065] The variable temperature treatment mentioned in step X5 refers to first raising the temperature to 150°C at 3°C ​​under a nitrogen atmosphere and holding it at that temperature for 1.2 hours, and then raising the temperature to 455°C at 5°C and holding it at that temperature for 2.3 hours.

[0066] The three-stage washing described in step X6 refers to mixing the activated product and deionized water at a material-to-liquid ratio of 1:5 g / mL, stirring at 80°C for 25 min, washing with an equal volume of 1.1 wt% dilute hydrochloric acid for 25 min, and finally rinsing with deionized water until neutral.

[0067] The microwave-vacuum drying described in step X6 refers to setting the microwave drying power to 800W, using a pulse mode of 3s on / 2s off, and drying under a vacuum of -0.095MPa until the moisture content is below 3wt%.

[0068] Example 4

[0069] A process for preparing phosphoric acid-activated activated carbon, the process comprising the following steps:

[0070] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0071] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0072] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0073] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0074] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0075] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0076] The mass ratio of cedar wood chips to penetrating agent in step X1 is 10:0.17; the penetrating agent is obtained by compounding PEG-400 and sodium dodecyl sulfonate in a mass ratio of 1:1; sieving refers to passing through a 50-mesh sieve; mixing refers to stirring at 170 rpm for 12 minutes.

[0077] In step X2, the ratio of the mixed raw material to the low-concentration phosphoric acid solution is 1:3.16 g / mL; the vacuuming refers to evacuating to -0.08 MPa and maintaining it for 15 min; the mass of phosphoric acid in the low-concentration phosphoric acid solution is 11 wt%; and the impregnation time is 36 min.

[0078] The phosphoric acid in the lower concentration phosphoric acid solution in step X3 is 21 wt%; the stirring after heating refers to stirring at 75 rpm for 38 minutes after heating to 51°C.

[0079] In step X4, the mass of phosphoric acid in the phosphoric acid-oxalic acid mixture is 31 wt%, and the mass of oxalic acid is 5.2 wt%. The ultrasonic impregnation refers to setting the ultrasonic frequency to 46 kHz, the ultrasonic power to 180 W, and ultrasonication for 27 min followed by impregnation for 1.5 h.

[0080] The variable temperature treatment mentioned in step X5 refers to first raising the temperature to 152°C at 3.2°C under a nitrogen atmosphere, holding it at that temperature for 1.3 hours, and then raising the temperature to 458°C at 5.2°C and holding it at that temperature for 2.5 hours.

[0081] The three-stage washing described in step X6 refers to mixing the activated product and deionized water at a material-to-liquid ratio of 1:5.1 g / mL, stirring at 80°C for 26 min, washing with an equal volume of 1.13 wt% dilute hydrochloric acid for 26 min, and finally rinsing with deionized water until neutral.

[0082] The microwave-vacuum drying described in step X6 refers to setting the microwave drying power to 810W, using a pulse mode of 3s on / 2s off, and drying to a moisture content of less than 3wt% under a vacuum of -0.095MPa.

[0083] Example 5

[0084] A process for preparing phosphoric acid-activated activated carbon, the process comprising the following steps:

[0085] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0086] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0087] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0088] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0089] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0090] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0091] The mass ratio of cedar wood chips to penetrating agent in step X1 is 10:0.18; the penetrating agent is obtained by compounding PEG-400 and sodium dodecyl sulfonate in a mass ratio of 1:1; sieving refers to passing through a 60-mesh sieve; mixing refers to stirring at 200 rpm for 14 minutes.

[0092] In step X2, the ratio of the mixed raw material to the low-concentration phosphoric acid solution is 1:3.2 g / mL; the vacuuming refers to evacuating to -0.08 MPa and maintaining it for 15 min; the mass of phosphoric acid in the low-concentration phosphoric acid solution is 12 wt%; and the impregnation time is 40 min.

[0093] The phosphoric acid in the lower concentration phosphoric acid solution in step X3 is 22 wt%; the stirring after heating refers to stirring at 60-80 rpm for 40 minutes after heating to 52°C.

[0094] In step X4, the mass of phosphoric acid in the phosphoric acid-oxalic acid mixture is 32 wt%, and the mass of oxalic acid is 5.5 wt%. The ultrasonic impregnation refers to setting the ultrasonic frequency to 50 kHz, the ultrasonic power to 200 W, and ultrasonication for 30 min followed by impregnation for 1.6 h.

[0095] The variable temperature treatment mentioned in step X5 refers to first raising the temperature to 155°C at 3.5°C and holding it at that temperature for 1.4 hours under a nitrogen atmosphere, and then raising the temperature to 460°C at 5.5°C and holding it at that temperature for 2.6 hours.

[0096] The three-stage washing described in step X6 refers to mixing the activated product and deionized water at a material-to-liquid ratio of 1:5.5 g / mL, stirring at 80°C for 30 min, washing with an equal volume of 1.2 wt% dilute hydrochloric acid for 30 min, and finally rinsing with deionized water until neutral.

[0097] The microwave-vacuum drying described in step X6 refers to setting the microwave drying power to 820W, using a pulse mode of 3s on / 2s off, and drying at a vacuum of -0.095MPa until the moisture content is below 3wt%.

[0098] Example 6

[0099] Based on Example 3, PEG-400 in the penetration aid was removed and replaced with an equal weight of sodium dodecyl sulfonate, while other conditions remained the same as in Example 3.

[0100] Example 7

[0101] Based on Example 3, sodium dodecyl sulfonate was removed from the penetration aid and replaced with an equal weight of PEG-400, while other conditions remained the same as in Example 3.

[0102] Example 8

[0103] Based on Example 3, the low-concentration phosphoric acid solution was removed and replaced with an equal weight of phosphoric acid solution with a mass of 6 wt%, while other conditions remained the same as in Example 3.

[0104] Example 9

[0105] Based on Example 3, the phosphoric acid-oxalic acid mixed solution was removed and replaced with an equal weight of phosphoric acid solution with a mass of 35 wt%, while other conditions remained the same as in Example 3.

[0106] Example 10

[0107] Based on Example 3, the mass of phosphoric acid in the phosphoric acid-oxalic acid solution was changed to 33 wt%, and the mass of oxalic acid was changed to 2 wt%.

[0108] Comparative Example 1

[0109] Based on Example 3, while keeping other conditions the same, the preparation process was changed to the following steps:

[0110] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0111] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0112] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0113] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0114] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0115] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0116] Comparative Example 2

[0117] Based on Example 3, while keeping other conditions the same, the preparation process was changed to the following steps:

[0118] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0119] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0120] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0121] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0122] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0123] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0124] Comparative Example 3

[0125] Based on Example 3, while keeping other conditions the same, the preparation process was changed to the following steps:

[0126] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0127] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0128] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0129] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0130] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0131] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0132] Comparative Example 4

[0133] Based on Example 3, while keeping other conditions the same, the preparation process was changed to the following steps:

[0134] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0135] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0136] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0137] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0138] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0139] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0140] Comparative Example 5

[0141] Based on Example 3, while keeping other conditions the same, the preparation process was changed to the following steps:

[0142] Step X1: Crush and sieve the cedar wood chips, and mix them with the penetrating agent to obtain a mixed raw material;

[0143] Step X2: Place the mixed raw materials into the impregnation tank, evacuate, inject a low-concentration phosphoric acid solution, and impregnate after restoring normal pressure;

[0144] Step X3: After step X2, drain half the volume of the low-concentration phosphoric acid solution, add an equal volume of low-concentration phosphoric acid solution to obtain a mixture, heat and stir.

[0145] Step X4: After step X3, drain half the volume of the mixture, add an equal volume of phosphoric acid-oxalic acid mixture, keep the temperature constant, and impregnate after ultrasonication to obtain the impregnated material;

[0146] Step X5: Temperature-treat the impregnating material to obtain the activated product;

[0147] Step X6: Perform three-stage washing on the activated product and microwave-vacuum drying to obtain the final product.

[0148] Comparative Example 6

[0149] Based on Example 3, while keeping other conditions the same, the temperature change treatment in step X5 is changed to: under a nitrogen atmosphere, first raise the temperature by 5°C to 455°C and hold for 3.5 hours.

[0150] Comparative Example 7

[0151] Based on Example 3, while keeping other conditions the same, the temperature change treatment in step X5 is changed to: under a nitrogen atmosphere, first raise the temperature by 3°C to 455°C and hold for 3.5 hours.

[0152] Comparative Example 8

[0153] Based on Example 3, while keeping other conditions the same, the temperature change treatment in step X5 is changed to: under a nitrogen atmosphere, first raise the temperature to 200°C at 3°C ​​and hold for 1.2 hours, then raise the temperature to 500°C at 5°C and hold for 2.3 hours.

[0154] Comparative Example 9

[0155] Based on Example 3, keeping other conditions the same, the microwave-vacuum drying in step X6 was changed to drying at 80°C until the moisture content was less than 3 wt%.

[0156] The activated carbon prepared in Examples 1-10 and Comparative Examples 1-9 were used as samples. The BET test was performed on the samples using a fully automatic specific surface area analyzer (American Micron Instruments, ASAP2420-4MP). The test results are recorded in Table 1 below. The adsorption value of the samples 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". The results are recorded in Table 1 below.

[0157] Table 1

[0158]

[0159]

[0160] As shown in Table 1, the activated carbon obtained by phosphoric acid activation in this invention has good specific surface area and adsorption capacity.

[0161] 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 the preparation of phosphoric acid-activated activated carbon, characterized in that: The preparation process comprises the following steps: Step X1, crushing and sieving the fir sawdust, and mixing with penetration aids to obtain mixed raw materials; Step X2, placing the mixed raw materials into an impregnation tank, vacuumizing, injecting a low-concentration phosphoric acid solution, and impregnating after restoring normal pressure; Step X3, after Step X2, discharging half of the volume of the low-concentration phosphoric acid solution, supplementing with an equal volume of a lower-concentration phosphoric acid solution to obtain a mixed solution, and stirring after heating; Step X4, after Step X3, discharging half of the volume of the mixed solution, supplementing with an equal volume of a phosphoric acid-oxalic acid mixed solution, maintaining the temperature, and impregnating after ultrasonic treatment to obtain impregnated materials; Step X5, temperature treatment of the impregnated materials to obtain activated products; Step X6, three-stage washing of the activated products, and microwave-vacuum drying to obtain the product. In Step X1, the mass ratio of the fir sawdust to the penetration aids is 10:0.14-0.18; the penetration aids are obtained by compounding PEG-400 and sodium dodecyl sulfonate according to a mass ratio of 1:1; In Step X2, the solid-liquid ratio of the mixed raw materials to the low-concentration phosphoric acid solution is 1:3-3.2 g / mL; the mass fraction of phosphoric acid in the low-concentration phosphoric acid solution is 8-12 wt%; In Step X3, the mass fraction of phosphoric acid in the lower-concentration phosphoric acid solution is 18-22 wt%; In Step X4, the mass fraction of phosphoric acid in the phosphoric acid-oxalic acid mixed solution is 28-32 wt%, and the mass fraction of oxalic acid is 4.5-5.5 wt%; In Step X5, the temperature treatment refers to first increasing the temperature to 145-155℃ at a rate of 2.5-3.5℃ under a nitrogen atmosphere, maintaining the temperature for 1-1.4 h, and then increasing the temperature to 450-460℃ at a rate of 4.5-5.5℃, maintaining the temperature for 2-2.6 h.

2. The process for preparing phosphoric acid-activated activated carbon according to claim 1, characterized by: In Step X1, the sieving refers to passing through a 20-60 mesh sieve; the mixing refers to stirring at a speed of 100-200 rpm for 8-14 min.

3. The process for preparing phosphoric acid-activated activated carbon according to claim 1, characterized by: In Step X2, the vacuumizing refers to vacuumizing to -0.08 MPa and maintaining for 15 min; the impregnation time is 30-40 min.

4. The process for preparing phosphoric acid-activated activated carbon according to claim 1, characterized by: In Step X3, the stirring after heating refers to stirring at a speed of 60-80 rpm for 30-40 min after heating to 48-52℃.

5. The process for preparing phosphoric acid-activated activated carbon according to claim 1, characterized by: In Step X4, the impregnation after ultrasonic treatment refers to setting the ultrasonic frequency to 40-50 kHz and the ultrasonic power to 100-200 W, impregnating for 1-1.6 h after ultrasonic treatment for 20-30 min.

6. The process for preparing phosphoric acid-activated activated carbon according to claim 1, characterized by: In Step X6, the three-stage washing refers to mixing the activated products with deionized water according to a solid-liquid ratio of 1:4.5-5.5 g / mL, stirring at 80℃ for 20-30 min, then washing with an equal volume of dilute hydrochloric acid with a concentration of 1-1.2 wt% for 20-30 min, and finally washing with deionized water until neutral.

7. The process for preparing phosphoric acid-activated activated carbon according to claim 1, characterized by: In Step X6, the microwave-vacuum drying refers to setting the microwave drying power to 780-820 W, drying under a vacuum degree of -0.095 MPa in a pulse mode of 3 s on / 2 s off until the water content is less than 3 wt%.

Images