Method for preparing low-ash-content activated carbon from coconut shells

Abstract

The invention discloses a method for preparing low-ash-content activated carbon from coconut shells, and belongs to the technical field of activated carbon. Comprising the following steps: crushing, ball-milling and sieving coconut shells to obtain a material A; soaking the material A in a hydrochloric acid solution, heating, stirring, washing and drying in vacuum to obtain a material B; mixing the material B with deionized water, and adding sodium hydroxide, ammonium carbonate and diammonium hydrogen phosphate to obtain a material C; performing oxidation treatment on the material C to obtain a material D; the material D is taken for carbonization treatment and activation treatment, coconut shell activated carbon with low ash content is obtained, the ash content is reduced, and high-quality activated carbon is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of activated carbon, and particularly relates to a method for preparing low-ash activated carbon by utilizing coconut shells. Background Art

[0002] As a material with extremely developed pore structure, huge specific surface area and excellent adsorption capacity, activated carbon has a wide range of applications that are remarkable. In the food industry, activated carbon is used as a decolorant, deodorant and an important tool for removing impurities. In the field of environmental protection, it is widely used in water treatment, air purification and waste gas treatment to achieve effective protection and improvement of the environment. In the chemical industry, activated carbon plays a vital role as a catalyst or catalyst carrier, as well as in the production of synthetic materials and the refining of fine chemical products. In the pharmaceutical industry, activated carbon is used to make medicinal activated carbon, which plays an indispensable role in drug detoxification, adsorption of toxins and pigments. In addition, in the metallurgical industry, activated carbon also plays an important role in gold extraction, metal recovery and other processes. However, despite the many advantages and wide application of activated carbon, in some application fields, an important pretreatment step before the use of activated carbon is required-ash removal. In these specific application fields, such as the manufacture of catalysts, the preparation of electrode materials, the production of medicinal activated carbon and the purification of human blood, the ash content in activated carbon may have an adverse effect on the quality and performance of the final product. Therefore, in order to ensure the performance and use effect of activated carbon in these fields, it must be strictly deashed to remove ash and other impurities in the activated carbon and ensure the purity and quality of the product. This treatment process is of great significance for the efficient and safe application of activated carbon in these fields. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing low-ash activated carbon by using coconut shells, so as to reduce the ash content of the activated carbon.

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

[0005] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0006] S1, crush coconut shells, ball mill, and sieve to obtain material A;

[0007] S2, immersing the material A in a hydrochloric acid solution, stirring at 60-70°C for 1-2h, filtering, washing the solid phase, and vacuum drying at 80°C for 6-8h to obtain material B;

[0008] S3, taking the material B and deionized water, mixing, stirring at 100°C for 20-30min, cooling to room temperature, adding sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, ultrasonically dispersing for 20-30min, and vacuum drying at 80°C for 10-12h to obtain material C;

[0009] S4, taking the material C and placing it in a tube furnace, introducing an oxygen-nitrogen mixed gas, oxidizing it, and cooling it to obtain a material D;

[0010] S5, taking the material D and placing it in a tube furnace, and carbonizing it in a nitrogen atmosphere to obtain material E;

[0011] S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon.

[0012] As a preferred technical solution of the present invention, in step S1, the screening refers to screening through a 80-100 mesh sieve.

[0013] As a preferred technical solution of the present invention, in step S2, the dosage ratio of the material A and the hydrochloric acid solution is 18-22g:200mL.

[0014] As a preferred technical solution of the present invention, in step S2, the concentration of the hydrochloric acid solution is 3-5 mol / L.

[0015] As a preferred technical solution of the present invention, in step S3, the mass ratio of material B, deionized water, sodium hydroxide, ammonium carbonate and diammonium hydrogen phosphate is 1-2:20-30:0.6-0.8:0.07-0.09:0.04-0.05.

[0016] As a preferred technical solution of the present invention, in step S4, the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10-12g: 16-20m 3 .

[0017] As a preferred technical solution of the present invention, in step S4, the volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20.

[0018] As a preferred technical solution of the present invention, in step S4, the oxidation treatment refers to heating the temperature to 300-330°C at a heating rate of 2°C / min and keeping the temperature for 40-50 minutes.

[0019] As a preferred technical solution of the present invention, in step S5, the carbonization treatment refers to first heating the temperature to 250-280°C at a heating rate of 3°C / min and keeping it warm for 20-30 minutes; then heating the temperature to 600-700°C at a heating rate of 2°C / min and keeping it warm for 1-1.5 hours.

[0020] As a preferred technical solution of the present invention, in step S6, the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 800-850°C at a heating rate of 100°C / h, and keeping the temperature for 2-3h.

[0021] Beneficial effects of the present invention:

[0022] The method disclosed in the present invention uses coconut shells to prepare low-ash activated carbon. The preparation process is optimized. Alkaline reagents such as sodium hydroxide, ammonium carbonate and diammonium phosphate are doped into coconut shell powder before carbonization, so that the formation path of ash is changed during the carbonization process to form substances that are not easy to carbonize, thereby reducing the ash generated during the carbonization process; in addition, by oxidizing the coconut shell powder, organic matter in the coconut shell is partially oxidized and decomposed, thereby reducing non-carbonizable substances in the coconut shell; further, by setting a carbonization and activation temperature gradient, the generation of ash is further reduced. DETAILED DESCRIPTION

[0023] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0024] Example 1

[0025] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0026] S1, crush coconut shell, ball mill, and pass through 80 mesh sieve to obtain material A;

[0027] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 60°C for 1h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 6h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 18g:200mL; the concentration of the hydrochloric acid solution is 3mol / L;

[0028] S3, taking the material B and deionized water, mixing, stirring at 100 ° C for 20 minutes, cooling to room temperature, adding sodium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, ultrasonic dispersion for 20 minutes, vacuum drying at 80 ° C for 10 hours, and obtaining material C; the mass ratio of the material B, deionized water, sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate is 1:20:0.6:0.07:0.04;

[0029] S4, take the material C and place it in a tube furnace, introduce oxygen-nitrogen mixed gas, oxidize it, cool it, and obtain material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10g:16m 3; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating to 300°C at a heating rate of 2°C / min and keeping the temperature for 40 minutes;

[0030] S5. Place the material D in a tubular furnace and perform carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment refers to first heating the temperature to 250° C. at a heating rate of 3° C. / min and keeping the temperature for 20 min; then heating the temperature to 600° C. at a heating rate of 2° C. / min and keeping the temperature for 1 h;

[0031] S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 800°C at a heating rate of 100°C / h, and keeping the temperature for 2h.

[0032] Example 2

[0033] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0034] S1, crush coconut shell, ball mill, and pass through a 90-mesh sieve to obtain material A;

[0035] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 65°C for 1.5h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 7h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 20g:200mL; the concentration of the hydrochloric acid solution is 4mol / L;

[0036] S3, take the material B and deionized water, mix them, stir at 100°C for 25 minutes, cool to room temperature, add sodium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, ultrasonically disperse for 25 minutes, and vacuum dry at 80°C for 11 hours to obtain material C; the mass ratio of the material B, deionized water, sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate is 1.5:25:0.7:0.08:0.045;

[0037] S4, take the material C and place it in a tube furnace, introduce oxygen-nitrogen mixed gas, oxidize it, cool it, and obtain material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 11g:18m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating to 315°C at a heating rate of 2°C / min and keeping the temperature for 45 minutes;

[0038] S5, taking the material D and placing it in a tubular furnace, and carbonizing it in a nitrogen atmosphere to obtain material E; the carbonizing treatment refers to first heating the temperature to 265°C at a heating rate of 3°C / min, and keeping it warm for 25min; then heating the temperature to 650°C at a heating rate of 2°C / min, and keeping it warm for 1.2h;

[0039] S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 825°C at a heating rate of 100°C / h, and keeping the temperature for 2.5h.

[0040] Example 3

[0041] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0042] S1, crush coconut shell, ball mill, and pass through a 100-mesh sieve to obtain material A;

[0043] S2. The material A is immersed in a hydrochloric acid solution, stirred at 70°C for 2h, filtered, the solid phase is washed, and vacuum dried at 80°C for 8h to obtain material B; the dosage ratio of the material A to the hydrochloric acid solution is 22g:200mL; the concentration of the hydrochloric acid solution is 5mol / L;

[0044] S3, take the material B and deionized water, mix them, stir at 100°C for 30 minutes, cool to room temperature, add sodium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, ultrasonically disperse for 30 minutes, and vacuum dry at 80°C for 12 hours to obtain material C; the mass ratio of material B, deionized water, sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate is 2:30:0.8:0.09:0.05;

[0045] S4, take the material C and place it in a tube furnace, introduce oxygen-nitrogen mixed gas, oxidize it, cool it, and obtain material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 12g:20m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating to 330°C at a heating rate of 2°C / min and keeping the temperature for 50 minutes;

[0046] S5. Place the material D in a tubular furnace and perform carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment refers to first heating the temperature to 280° C. at a heating rate of 3° C. / min and keeping the temperature for 30 min; then heating the temperature to 700° C. at a heating rate of 2° C. / min and keeping the temperature for 1.5 h;

[0047] S6. Place the material E in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the material to 400°C at a heating rate of 200°C / h, then heating the material to 850°C at a heating rate of 100°C / h, and keeping the temperature for 3h.

[0048] Comparative Example 1

[0049] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0050] S1, crush coconut shell, ball mill, and pass through 80 mesh sieve to obtain material A;

[0051] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 60°C for 1h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 6h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 18g:200mL; the concentration of the hydrochloric acid solution is 3mol / L;

[0052] S3, taking the material B and deionized water, mixing, stirring at 100°C for 20 minutes, cooling to room temperature, adding ammonium carbonate and diammonium hydrogen phosphate, ultrasonically dispersing for 20 minutes, and vacuum drying at 80°C for 10 hours to obtain material C; the mass ratio of the material B, deionized water, ammonium carbonate, and diammonium hydrogen phosphate is 1:20:0.37:0.34;

[0053] S4, take the material C and place it in a tube furnace, introduce oxygen-nitrogen mixed gas, oxidize it, cool it, and obtain material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10g:16m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating to 300°C at a heating rate of 2°C / min and keeping the temperature for 40 minutes;

[0054] S5. Place the material D in a tubular furnace and perform carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment refers to first heating the temperature to 250° C. at a heating rate of 3° C. / min and keeping the temperature for 20 min; then heating the temperature to 600° C. at a heating rate of 2° C. / min and keeping the temperature for 1 h;

[0055] S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 800°C at a heating rate of 100°C / h, and keeping the temperature for 2h.

[0056] Comparative Example 2

[0057] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0058] S1, crush coconut shell, ball mill, and pass through 80 mesh sieve to obtain material A;

[0059] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 60°C for 1h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 6h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 18g:200mL; the concentration of the hydrochloric acid solution is 3mol / L;

[0060] S3, taking the material B and deionized water, mixing, stirring at 100°C for 20 minutes, cooling to room temperature, adding sodium hydroxide and diammonium hydrogen phosphate, ultrasonically dispersing for 20 minutes, and vacuum drying at 80°C for 10 hours to obtain material C; the mass ratio of the material B, deionized water, sodium hydroxide, and diammonium hydrogen phosphate is 1:20:0.6:0.11;

[0061] S4, take the material C and place it in a tube furnace, introduce oxygen-nitrogen mixed gas, oxidize it, cool it, and obtain material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10g:16m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating to 300°C at a heating rate of 2°C / min and keeping the temperature for 40 minutes;

[0062] S5. Place the material D in a tubular furnace and perform carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment refers to first heating the temperature to 250° C. at a heating rate of 3° C. / min and keeping the temperature for 20 min; then heating the temperature to 600° C. at a heating rate of 2° C. / min and keeping the temperature for 1 h;

[0063] S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 800°C at a heating rate of 100°C / h, and keeping the temperature for 2h.

[0064] Comparative Example 3

[0065] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0066] S1, crush coconut shell, ball mill, and pass through 80 mesh sieve to obtain material A;

[0067] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 60°C for 1h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 6h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 18g:200mL; the concentration of the hydrochloric acid solution is 3mol / L;

[0068] S3, taking the material B and deionized water, mixing, stirring at 100°C for 20 minutes, cooling to room temperature, adding sodium hydroxide and ammonium carbonate, ultrasonically dispersing for 20 minutes, and vacuum drying at 80°C for 10 hours to obtain material C; the mass ratio of the material B, deionized water, sodium hydroxide, and ammonium carbonate is 1:20:0.6:0.11;

[0069] S4, taking the material C and placing it in a tube furnace, introducing an oxygen-nitrogen mixed gas, oxidizing it, cooling it, and obtaining a material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10g:16m3; the volume ratio of oxygen and nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating the temperature to 300°C at a heating rate of 2°C / min and keeping the temperature for 40min;

[0070] S5. Place the material D in a tubular furnace and perform carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment refers to first heating the temperature to 250° C. at a heating rate of 3° C. / min and keeping the temperature for 20 min; then heating the temperature to 600° C. at a heating rate of 2° C. / min and keeping the temperature for 1 h;

[0071] S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 800°C at a heating rate of 100°C / h, and keeping the temperature for 2h.

[0072] Comparative Example 4

[0073] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0074] S1, crush coconut shell, ball mill, and pass through 80 mesh sieve to obtain material A;

[0075] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 60°C for 1h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 6h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 18g:200mL; the concentration of the hydrochloric acid solution is 3mol / L;

[0076] S3, taking the material B and deionized water, mixing, stirring at 100 ° C for 20 minutes, cooling to room temperature, adding sodium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, ultrasonic dispersion for 20 minutes, vacuum drying at 80 ° C for 10 hours, and obtaining material C; the mass ratio of the material B, deionized water, sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate is 1:20:0.6:0.07:0.04;

[0077] S4, taking the material C and placing it in a tubular furnace, and carbonizing it in a nitrogen atmosphere to obtain material e; the carbonizing treatment refers to first heating the temperature to 250°C at a heating rate of 3°C / min, and keeping it warm for 20min; then heating the temperature to 600°C at a heating rate of 2°C / min, and keeping it warm for 1h;

[0078] S5. Take the material e and place it in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 800°C at a heating rate of 100°C / h, and keeping the temperature for 2h.

[0079] Comparative Example 5

[0080] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0081] S1, crush coconut shell, ball mill, and pass through 80 mesh sieve to obtain material A;

[0082] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 60°C for 1h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 6h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 18g:200mL; the concentration of the hydrochloric acid solution is 3mol / L;

[0083] S3, taking the material B and deionized water, mixing, stirring at 100 ° C for 20 minutes, cooling to room temperature, adding sodium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, ultrasonic dispersion for 20 minutes, vacuum drying at 80 ° C for 10 hours, and obtaining material C; the mass ratio of the material B, deionized water, sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate is 1:20:0.6:0.07:0.04;

[0084] S4, taking the material C and placing it in a tube furnace, introducing an oxygen-nitrogen mixed gas, oxidizing it, cooling it, and obtaining a material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10g:16m3; the volume ratio of oxygen and nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating the temperature to 300°C at a heating rate of 2°C / min and keeping the temperature for 40min;

[0085] S5, taking the material D and placing it in a tube furnace, and carbonizing it in a nitrogen atmosphere to obtain material E; the carbonizing treatment refers to heating the temperature to 600° C. at a heating rate of 2° C. / min and keeping the temperature for 80 min;

[0086] S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, then heating the temperature to 800°C at a heating rate of 100°C / h, and keeping the temperature for 2h.

[0087] Comparative Example 6

[0088] A method for preparing low-ash activated carbon using coconut shells comprises the following steps:

[0089] S1, crush coconut shell, ball mill, and pass through 80 mesh sieve to obtain material A;

[0090] S2. Take the material A and immerse it in a hydrochloric acid solution, stir it at 60°C for 1h, filter it with suction, wash the solid phase, and vacuum dry it at 80°C for 6h to obtain material B; the dosage ratio of the material A and the hydrochloric acid solution is 18g:200mL; the concentration of the hydrochloric acid solution is 3mol / L;

[0091] S3, taking the material B and deionized water, mixing, stirring at 100 ° C for 20 minutes, cooling to room temperature, adding sodium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, ultrasonic dispersion for 20 minutes, vacuum drying at 80 ° C for 10 hours, and obtaining material C; the mass ratio of the material B, deionized water, sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate is 1:20:0.6:0.07:0.04;

[0092] S4, take the material C and place it in a tube furnace, introduce oxygen-nitrogen mixed gas, oxidize it, cool it, and obtain material D; the dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10g:16m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment refers to heating to 300°C at a heating rate of 2°C / min and keeping the temperature for 40 minutes;

[0093] S5. Place the material D in a tubular furnace and perform carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment refers to first heating the temperature to 250° C. at a heating rate of 3° C. / min and keeping the temperature for 20 min; then heating the temperature to 600° C. at a heating rate of 2° C. / min and keeping the temperature for 1 h;

[0094] S6. Place the material E in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment refers to heating the material to 800° C. at a heating rate of 100° C. / h and keeping the temperature for 2 h.

[0095] Performance Testing

[0096] The activated carbons prepared in Examples 1-3 and Comparative Examples 1-6 were tested for ash content according to the standard GB / T 36057-2018 "Analysis Methods for Forestry Biomass Raw Materials—Determination of Ash Content". The test results are shown in Table 1 below.

[0097] Table 1

[0098] Ash content / % Example 1 0.58 Example 2 0.54 Example 3 0.55 Comparative Example 1 2.72 Comparative Example 2 2.45 Comparative Example 3 2.51 Comparative Example 4 2.67 Comparative Example 5 1.35 Comparative Example 6 0.74

[0099] As can be seen from Table 1, the coconut shell activated carbons prepared in Examples 1-3 of the present application have a lower ash content; this is because the present application optimizes the preparation process, and alkaline reagents sodium hydroxide, ammonium carbonate and diammonium phosphate are doped into the coconut shell powder before carbonization, so as to change the ash formation pathway during the carbonization process, and form substances that are not easy to carbonize, thereby reducing the ash generated during the carbonization process; in addition, by oxidizing the coconut shell powder, the organic matter in the coconut shell is partially oxidized and decomposed, reducing the non-carbonizable substances in the coconut shell; further, by setting the carbonization and activation temperature gradients, the generation of ash is further reduced.

[0100] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing low-ash activated carbon using coconut shells, characterized in that: The following steps are involved: S1, crush coconut shells, ball mill, and sieve to obtain material A; S2, taking the material A and immersing it in a hydrochloric acid solution, stirring at 60-70°C for 1-2h, filtering, washing the solid phase, and vacuum drying at 80°C for 6-8h to obtain material B; S3, taking the material B and deionized water, mixing, stirring at 100°C for 20-30min, cooling to room temperature, adding sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, ultrasonically dispersing for 20-30min, and vacuum drying at 80°C for 10-12h to obtain material C; S4, taking the material C and placing it in a tube furnace, introducing an oxygen-nitrogen mixed gas, oxidizing it, and cooling it to obtain a material D; S5, taking the material D and placing it in a tube furnace, and carbonizing it in a nitrogen atmosphere to obtain material E; S6. Take the material E and place it in a tubular furnace for activation treatment to obtain the activated carbon.

2. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S1, the sieving refers to sieving through a 80-100 mesh sieve.

3. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S2, the dosage ratio of material A to hydrochloric acid solution is 18-22 g: 200 mL.

4. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S2, the concentration of the hydrochloric acid solution is 3-5 mol / L.

5. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S3, the mass ratio of material B, deionized water, sodium hydroxide, ammonium carbonate and diammonium hydrogen phosphate is 1-2:20-30:0.6-0.8:0.07-0.09:0.04-0.

05.

6. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S4, the ratio of material C to oxygen-nitrogen mixed gas is 10-12g:16-20m 3 .

7. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S4, the volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:

20.

8. The method for preparing low-ash activated carbon using coconut shells according to claim 1, characterized in that: In step S4, the oxidation treatment refers to heating the temperature to 300-330°C at a heating rate of 2°C / min and keeping the temperature for 40-50 minutes.

9. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S5, the carbonization treatment refers to first heating the temperature to 250-280°C at a heating rate of 3°C / min and keeping the temperature for 20-30min; then heating the temperature to 600-700°C at a heating rate of 2°C / min and keeping the temperature for 1-1.5h.

10. The method for preparing low-ash activated carbon using coconut shell according to claim 1, characterized in that: In step S6, the activation treatment refers to heating the temperature to 400°C at a heating rate of 200°C / h, and then heating the temperature to 800-850°C at a heating rate of 100°C / h, and keeping the temperature for 2-3h.