A method for preparing activated carbon

Abstract

A method for preparing activated carbon, relating to the field of activated carbon preparation, includes the following steps: S1, preparing a carbonaceous raw material into a powder; S2, mixing the powdered carbonaceous raw material and organophosphonic acid powder at a mass ratio of 1:0.2-1 to obtain a uniform mixture; S3, subjecting the mixture to carbonization activation treatment to obtain activated carbon. This method uses organophosphonic acid to activate the activated carbon, and can prepare activated carbon with high specific surface area and high porosity and strong adsorption performance without prior impregnation. This method has the advantages of simple operation, low cost, high efficiency, and environmental friendliness.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of activated carbon preparation, in particular to a method for preparing activated carbon. BACKGROUND

[0002] Activated carbon is a kind of porous carbon material widely used in various fields, which has strong adsorption capacity and catalytic performance. There are mainly two kinds of preparation methods for activated carbon: chemical activation method and physical activation method. The chemical activation method refers to using certain chemical substances as activators to react with carbonaceous raw materials at a certain temperature to generate a large number of micropores and form activated carbon; the physical activation method refers to using certain gases as activators to react with carbonaceous raw materials at a high temperature to generate a large number of micropores and form activated carbon. At present, the commonly used activators are as follows:

[0003] Alkali metal salts such as KOH, NaOH, K2CO3, Na2CO3, etc. can react with carbonaceous raw materials at high temperature to generate carbonates and hydrogen. This reaction can increase the porosity and specific surface area of activated carbon and improve its adsorption capacity;

[0004] Acidic substances such as H3PO4, H2SO4, HNO3, etc. can react with carbonaceous raw materials at low temperature to generate water and carbon dioxide. This reaction can increase the oxygen-containing functional groups of activated carbon and improve its hydrophilicity and catalytic performance;

[0005] Gaseous substances such as CO2, H2O, O2, etc. can react with carbonaceous raw materials at a high temperature to generate carbon monoxide, water and carbon dioxide. This reaction can increase the proportion of micropores of activated carbon and improve its adsorption selectivity for small molecules.

[0006] However, the above activators also have some disadvantages: the alkali metal salt activators and the acidic substance activators have strong corrosiveness and toxicity, among which the alkali metal salt activators have certain harm to equipment and environment and need to be cleaned and recycled in a complex manner, and the acidic substance activators are easy to cause excessive oxidation and loss of carbonaceous raw materials and need to be cleaned and recycled in a complex manner, in addition, both the alkali metal salt activators and the acidic substance activators need to be impregnated in advance before activating the activated carbon, thereby prolonging the activation time. The gaseous substance activators need high temperature and pressure, and also cause excessive oxidation and loss of carbonaceous raw materials and complex separation and recovery treatment.

[0007] Therefore, it is an urgent problem to be solved in the technical field to develop a new type of, environmentally friendly, high-efficiency and strong-adsorption activator preparation method. SUMMARY

[0008] The present application aims to provide a method for preparing activated carbon, which adopts organic phosphonic acid to activate activated carbon, and can prepare activated carbon with high specific surface area, high porosity and strong adsorption performance without pre-impregnation of activated carbon, and has the advantages of simple operation, low cost, high efficiency and environmental friendliness.

[0009] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0010] A method for preparing activated carbon, comprising the following steps:

[0011] S1, preparing carbonaceous raw materials into powder;

[0012] S2, uniformly mixing the powder-shaped carbonaceous raw materials and organic phosphonic acid powder in a mass ratio of 1:0.2-1 to obtain a mixture;

[0013] S3, performing carbonization activation treatment on the mixture to obtain activated carbon;

[0014] Further, in step S1, the carbonaceous raw materials include plants, and the plants include wood, bamboo, straw and fruit shells;

[0015] Further, in step S1, the carbonaceous raw materials are dried and crushed to obtain powder-shaped carbonaceous raw materials;

[0016] Further, in step S2, the molecular structure of the organic phosphonic acid powder is: wherein the value of n is 2, 3, 4 or 5;

[0017] Further, in step S2, an additive is added to the mixture, and the additive includes persulfate;

[0018] Further, in step S2, the addition amount of persulfate is 2-10% w / w of the addition amount of organic phosphonic acid powder;

[0019] Further, in step S3, one carbonization activation treatment is performed: under the protection of inert gas, the mixture is heated to 210-250℃, and kept at this temperature for 0.5-2h;

[0020] Further, on the basis of the one carbonization activation treatment, secondary carbonization activation is performed: under the protection of inert gas, the mixture is heated to 500-650℃, and kept at this temperature for 0.5-2h;

[0021] Further, after step S3, the obtained activated carbon is subjected to cleaning, filtration and drying treatment.

[0022] The present application has the following beneficial effects:

[0023] 1) The organic phosphonic acid has low corrosion and toxicity, less harm to equipment and environment, and can be recycled by simple water washing and filtration treatment;

[0024] 2) The organic phosphonic acid is used as an activator for carbonization activation treatment. In the activation process, the molten organic phosphonic acid penetrates into the interior of the carbonaceous raw material, promotes the degradation and dehydration of biomass, and prepares activated carbon with high specific surface area and high porosity. This method has the advantages of simple operation, low cost, high efficiency and environmental friendliness. By controlling the addition amount and molecular structure of the organic phosphonic acid, the pore structure and surface properties of the activated carbon can be adjusted, and the adsorption capacity of the activated carbon for different substances can be improved;

[0025] 3) The organic phosphonic acid activates the carbonaceous raw material without causing excessive oxidation and loss of the carbonaceous raw material. The small molecular compounds generated by the high-temperature decomposition of the organic phosphonic acid are used to carry away the ash in the pore channel when they are discharged, thereby improving the pore structure, specific surface area and pore volume of the activated carbon;

[0026] 4) By adding a persulfate additive, the activation effect of the organic phosphonic acid can be further improved to increase the porosity and specific surface area of the activated carbon. At the same time, the active oxygen generated by the thermal decomposition of the persulfate oxidizes the surface structure of the activated carbon, promotes the generation of oxygen-containing adsorption groups on the surface of the activated carbon, and improves its adsorption performance. DETAILED DESCRIPTION

[0027] In the description of the present application, it should be understood that the terms are used only for descriptive purposes and cannot be understood as indicating or implying the relative importance of the technical features indicated or implicitly indicating the number of technical features. The "includes" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0028] The examples are only used to explain the present application and not to limit the scope of the present application.

[0029] In one embodiment of the present application, the method for preparing activated carbon comprises the following steps:

[0030] 1) Carbonaceous raw material pretreatment. Selecting plant carbonaceous raw materials such as wood, bamboo, straw and fruit shells, in this embodiment, in order to simplify the description, straw is used as the carbonaceous raw material, the straw is dried and crushed to obtain a powdered carbonaceous raw material, and the powdered carbonaceous raw material is sealed and dried for storage;

[0031] 2) Mixing. The powdered carbonaceous raw material, organophosphonic acid powder, and additives are mixed evenly to obtain a mixture. The mass ratio of the powdered carbonaceous raw material to the organophosphonic acid powder is 1:0.2-1. In this embodiment, the molecular structure of the organophosphoric acid is... The additive is set as persulfate, and the amount of persulfate added is 2-10% w / w of the amount of organophosphonic acid powder added. Persulfates include perdisulfate and permonosulfate. Common perdisulfates include sodium perdisulfate (Na2S2O8) (hereinafter referred to as sodium persulfate), potassium perdisulfate (K2S2O8) (hereinafter referred to as potassium persulfate), and ammonium perdisulfate ((NH4)2S2O8) (hereinafter referred to as ammonium persulfate), etc. Common permonosulfates include sodium permonosulfate (Na2SO5) and potassium permonosulfate (K2SO5), etc.

[0032] 3) Primary carbonization activation. Under inert gas protection, the mixture is heated to 210-250℃ and held at this temperature for 0.5-2 hours. In this embodiment, the inert gas is nitrogen, and the same applies below.

[0033] 4) Secondary carbonization activation. Under nitrogen protection, the mixture is heated to 500-650℃ and held at this temperature for 0.5-2 hours;

[0034] 5) Clean, filter, and dry the activated carbon. Wash the obtained activated carbon until the pH of the supernatant is 6.5-7.0. Filter the cleaned activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours.

[0035] Based on the method for preparing activated carbon described herein, the following specific embodiments can be obtained:

[0036] Example 1

[0037] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0038] ② Mix 1000g of straw powder, 800g of organophosphonic acid powder, and 80g of ammonium persulfate evenly to obtain a mixture, wherein the molecular structure of the organophosphonic acid is:

[0039] ③ Under nitrogen protection, the above mixture was heated to 250°C at a heating rate of 10°C / min and held at this temperature for 2 hours;

[0040] ④ Under nitrogen protection, the temperature is further increased to 650℃ at a heating rate of 10℃ / min, and held at this temperature for 2 hours;

[0041] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0042] The prepared activated carbon had a specific surface area of ​​1356 m² after testing. 2 / g, pore volume 0.83cm³ 3 / g, with a methylene blue adsorption value of 301mg / g.

[0043] Example 2

[0044] This embodiment serves as a comparative embodiment to Example 1. This embodiment uses conventional acidic substances for activating activated carbon, such as phosphoric acid (which is considered to have a better activation effect on activated carbon among acidic substances, so it is used as an example for comparison, the same below). The method of activating activated carbon with phosphoric acid is used for comparison to clarify the effect of activation with ammonium persulfate in Example 1 on the specific surface area, pore volume and methylene blue adsorption value of activated carbon.

[0045] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0046] ② Add 1000g of straw powder and 80g of ammonium persulfate to 1000g of phosphoric acid solution with a mass percentage concentration of 80%, and stir for 2 hours to obtain a mixture;

[0047] ③ Under nitrogen protection, the above mixture was heated to 250°C at a heating rate of 10°C / min and held at this temperature for 2 hours;

[0048] ④ Under nitrogen protection, the temperature is further increased to 650℃ at a heating rate of 10℃ / min, and held at this temperature for 2 hours;

[0049] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0050] The prepared activated carbon was tested and found to have a specific surface area of ​​1026 m². 2 / g, pore volume 0.67cm³ 3 / g, with a methylene blue adsorption value of 186mg / g.

[0051] Example 3

[0052] This embodiment further removes the additives based on Example 1 to clarify the activation effect of activated carbon in the case of only organic phosphoric acid.

[0053] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0054] ② Mix 1000g of straw powder and 800g of organophosphonic acid powder evenly to obtain a mixture, wherein the molecular structure of the organophosphonic acid is:

[0055] ③ Under nitrogen protection, the above mixture was heated to 250°C at a heating rate of 10°C / min and held at this temperature for 2 hours;

[0056] ④ Under nitrogen protection, the temperature is further increased to 650℃ at a heating rate of 10℃ / min, and held at this temperature for 2 hours;

[0057] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0058] The specific surface area of ​​the prepared activated carbon was tested to be 1134 m². 2 / g, pore volume 0.72cm³ 3 / g, with a methylene blue adsorption value of 246mg / g.

[0059] Example 4

[0060] This embodiment serves as a comparative embodiment to Example 3. This embodiment uses phosphoric acid, a conventional acidic substance used to activate activated carbon, for comparison, to clarify the effect of organophosphonic acid on the specific surface area, pore volume, and methylene blue adsorption value of activated carbon in Example 3.

[0061] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0062] ② Add 1000g of the obtained straw powder to 1000g of a phosphoric acid solution with a mass percentage concentration of 80%, and stir for 2 hours to obtain a mixture;

[0063] ③ Under nitrogen protection, the above mixture was heated to 250°C at a heating rate of 10°C / min and held at this temperature for 2 hours;

[0064] ④ Under nitrogen protection, the temperature is further increased to 650℃ at a heating rate of 10℃ / min, and held at this temperature for 2 hours;

[0065] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0066] The prepared activated carbon had a specific surface area of ​​986 m² after testing. 2 / g, pore volume 0.62cm³ 3 / g, with a methylene blue adsorption value of 168mg / g.

[0067] Example 5

[0068] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0069] ② Mix 1000g of straw powder, 200g of organophosphonic acid powder, and 4g of sodium persulfate evenly to obtain a mixture. The molecular structure of the organophosphonic acid is as follows:

[0070] ③ Under nitrogen protection, the mixture was heated to 210°C at a heating rate of 10°C / min and held at this temperature for 1 hour;

[0071] ④ Under nitrogen protection, the temperature is further increased to 500℃ at a heating rate of 10℃ / min, and held at this temperature for 0.5h;

[0072] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0073] The specific surface area of ​​the prepared activated carbon was tested to be 1148 m². 2 / g, pore volume 0.72cm³ 3 / g, with a methylene blue adsorption value of 248mg / g.

[0074] Example 6

[0075] This embodiment serves as a comparative embodiment to Example 5. This embodiment uses phosphoric acid, a conventional acidic substance used to activate activated carbon, for comparison. The purpose is to clarify the effect of sodium persulfate, an activating agent, on the specific surface area, pore volume, and methylene blue adsorption value of activated carbon in Example 5.

[0076] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0077] ② Add 1000g of straw powder and 4g of sodium persulfate to 250g of phosphoric acid solution with a mass percentage concentration of 80%, and stir for 2 hours to obtain a mixture;

[0078] ③ Under nitrogen protection, the mixture was heated to 210°C at a heating rate of 10°C / min and held at this temperature for 1 hour;

[0079] ④ Under nitrogen protection, the temperature is further increased to 500℃ at a heating rate of 10℃ / min, and held at this temperature for 0.5h;

[0080] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0081] The prepared activated carbon had a specific surface area of ​​968 m² after testing. 2 / g, pore volume 0.59cm³ 3 / g, with a methylene blue adsorption value of 178mg / g.

[0082] Example 7

[0083] This embodiment further removes the additives based on Example 5 to clarify the activation effect of activated carbon in the case of only organic phosphoric acid.

[0084] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0085] ② Mix 1000g of straw powder and 200g of organophosphonic acid powder evenly to obtain a mixture, wherein the molecular structure of the organophosphonic acid is:

[0086] ③ Under nitrogen protection, the mixture was heated to 210°C at a heating rate of 10°C / min and held at this temperature for 1 hour;

[0087] ④ Under nitrogen protection, the temperature is further increased to 500℃ at a heating rate of 10℃ / min, and held at this temperature for 0.5h;

[0088] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0089] The prepared activated carbon was tested and found to have a specific surface area of ​​1028 m². 2 / g, pore volume 0.68cm³ 3 / g, with a methylene blue adsorption value of 218mg / g.

[0090] Example 8

[0091] This embodiment serves as a comparative embodiment to Example 7. This embodiment uses phosphoric acid, a conventional acidic substance used to activate activated carbon, for comparison, to clarify the effect of organophosphonic acid on the specific surface area, pore volume, and methylene blue adsorption value of activated carbon in Example 7.

[0092] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0093] ② Add 1000g of straw powder to 250g of 80% phosphoric acid solution and stir for 2 hours to obtain a mixture;

[0094] ③ Under nitrogen protection, the mixture was heated to 210°C at a heating rate of 10°C / min and held at this temperature for 1 hour;

[0095] ④ Under nitrogen protection, the temperature is further increased to 500℃ at a heating rate of 10℃ / min, and held at this temperature for 0.5h;

[0096] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0097] The prepared activated carbon was tested and found to have a specific surface area of ​​846 m². 2 / g, pore volume 0.56cm³ 3 / g, with a methylene blue adsorption value of 154mg / g.

[0098] Example 9

[0099] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0100] ② Mix 1000g of straw powder, 900g of the two organophosphonic acid powders, and 45g of potassium persulfate evenly to obtain a mixture. The molecular structures of the two organophosphonic acids are as follows: Furthermore, the mass ratio of the two organophosphonic acids is 1:2;

[0101] ③ Under nitrogen protection, the above mixture was heated to 220°C at a heating rate of 10°C / min and held at this temperature for 1 hour;

[0102] ④ Under nitrogen protection, the temperature is further increased to 600℃ at a heating rate of 10℃ / min, and held at this temperature for 1.5h;

[0103] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0104] The prepared activated carbon was tested and found to have a specific surface area of ​​1288 m². 2 / g, pore volume 0.77cm³ 3 / g, with a methylene blue adsorption value of 288mg / g.

[0105] Example 10

[0106] ①Dry and pulverize 1000g of rice straw to obtain straw powder;

[0107] ② Mix 1000g of straw powder, 600g of the two organophosphonic acid powders, and 42g of ammonium persulfate evenly to obtain a mixture. The molecular structures of the two organophosphonic acids are as follows:

[0108] The mass ratio of the two organophosphonic acids is 2:1;

[0109] ③ Under nitrogen protection, the above mixture was heated to 240°C at a heating rate of 10°C / min and held at this temperature for 1.5 hours;

[0110] ④ Under nitrogen protection, the temperature is further increased to 650℃ at a heating rate of 10℃ / min, and held at this temperature for 1 hour;

[0111] ⑤ Wash the activated carbon obtained in step ④ until the pH of the supernatant is 6.5-7.0. Filter the washed activated carbon and discard the filtrate. Place the sample in a vacuum drying oven at 100-110℃ and dry for 4-6 hours to obtain the activated carbon product.

[0112] The specific surface area of ​​the prepared activated carbon was tested to be 1122 m². 2 / g, pore volume 0.74cm³ 3 / g, with a methylene blue adsorption value of 254mg / g.

[0113] Through testing in the aforementioned specific embodiments, under the same conditions, carbonization activation treatment using organophosphonic acid as an activator can effectively open and expand pores, forming a more developed microporous structure and increasing the specific surface area. This results in the preparation of activated carbon with high specific surface area and high porosity. It has the advantages of simple operation, low cost, high efficiency, and fewer processes. Furthermore, by controlling the amount and molecular structure of organophosphonic acid, the pore structure and surface properties of activated carbon can be adjusted, thereby improving its adsorption capacity and catalytic performance for different substances.

[0114] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method of producing activated carbon, characterized by, The method comprises the following steps: S1, preparing a carbonaceous raw material into a powder; S2, mixing the powder of the carbonaceous raw material and an organic phosphonic acid powder in a mass ratio of 1:0.2-1 to obtain a mixture, and adding an additive to the mixture, wherein the additive comprises a persulfate, and the additive amount of the persulfate is 2-10% w / w of the additive amount of the organic phosphonic acid powder; S3, performing carbonization activation treatment on the mixture to obtain activated carbon; The molecular structure of the organic phosphonic acid powder is: wherein n has a value of 2, 3, 4, or 5.

2. The method of claim 1, wherein, In step S1, the carbonaceous raw material comprises plants, and the plants comprise wood, bamboo, straw, and fruit shells.

3. The method of claim 1, wherein the activated carbon is prepared by the process of: In step S1, the carbonaceous raw material is dried and crushed to obtain the powder of the carbonaceous raw material.

4. The method of claim 1, wherein the activated carbon is prepared by the process of: In step S3, one carbonization activation treatment is performed: under the protection of an inert gas, the mixture is heated to 210-250°C, and maintained at this temperature for 0.5-2h.

5. The method of claim 4, wherein the activated carbon is prepared by On the basis of the one carbonization activation treatment, secondary carbonization activation is performed: under the protection of an inert gas, the mixture is heated to 500-650°C, and maintained at this temperature for 0.5-2h.

6. The method of claim 1, wherein the activated carbon is prepared by the steps of: After step S3, the obtained activated carbon is subjected to cleaning, filtration, and drying treatment.

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