A method for preparing low-ash activated carbon using coconut shells

Abstract

The present invention discloses a method for preparing low-ash activated carbon from coconut shells, belonging to the technical field of activated carbon. The method comprises the following steps: crushing coconut shells, ball milling, and sieving to obtain material A; immersing material A in a hydrochloric acid solution, heating and stirring, washing, and vacuum drying to obtain material B; mixing material B and deionized water, and adding sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate to obtain material C; subjecting material C to oxidation treatment to obtain material D; subjecting material D to carbonization treatment and activation treatment, thereby obtaining coconut shell activated carbon with a low ash content, reducing the ash content, and obtaining high-quality activated carbon.

Description

Technical Field

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

[0002] As a material with an extremely developed pore structure, a huge specific surface area, and excellent adsorption capacity, activated carbon has a remarkable range of applications. In the food industry, activated carbon is used as an important tool for decolorization, deodorization, and impurity removal. In the field of environmental protection, it is widely used in water treatment, air purification, and waste gas treatment to effectively protect and improve the environment. In the chemical industry, activated carbon serves as a catalyst or catalyst carrier and plays a crucial role in the production of synthetic materials and the refining process of fine chemical products. In the pharmaceutical industry, activated carbon is used to manufacture medicinal activated carbon, which is indispensable for drug detoxification, adsorption of toxins and pigments, etc. In addition, in the metallurgical industry, activated carbon also plays an important role in gold extraction, metal recovery, etc. However, despite the many advantages and wide applications of activated carbon, in some application fields, an important pretreatment step - ash removal - is required before the use of activated carbon. 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 impact 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 is necessary to carry out strict ash removal treatment to remove the ash and other impurities in 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 from coconut shells to reduce the ash content of activated carbon.

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

[0005] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

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

[0007] S2. Immerse the material A in a hydrochloric acid solution, stir at 60 - 70 °C for 1 - 2 h, perform suction filtration, take the solid phase for washing, and vacuum-dry at 80 °C for 6 - 8 h to obtain material B;

[0008] S3. Mix the material B and deionized water, stir at 100 °C for 20 - 30 min, cool to room temperature, add sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, disperse ultrasonically for 20 - 30 min, and dry in vacuum at 80 °C for 10 - 12 h to obtain material C;

[0009] S4. Place the material C in a tubular furnace, introduce an oxygen-nitrogen mixed gas, perform oxidation treatment, and cool to obtain material D;

[0010] S5. Place the material D in a tubular furnace and perform carbonization treatment in a nitrogen atmosphere to obtain material E;

[0011] S6. Place the material E 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 sieving refers to sieving 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 to the hydrochloric acid solution is 18 - 22 g: 200 mL.

[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 the 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 to the oxygen-nitrogen mixed gas is 10 - 12 g: 16 - 20 m 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 at a heating rate of 2 °C / min to 300 - 330 °C and holding for 40 - 50 min.

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

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

[0021] Advantages of the present invention:

[0022] The method for preparing low - ash activated carbon using coconut shell disclosed by the present invention optimizes the preparation process. Before carbonization, alkaline reagents sodium hydroxide, ammonium carbonate, and ammonium dihydrogen phosphate are doped into coconut shell powder, and during carbonization, the formation path of ash is changed to form substances that are not easily carbonized, thereby reducing the ash generated during carbonization. In addition, by oxidizing the coconut shell powder, the organic substances in the coconut shell are 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. Specific embodiments

[0023] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines examples to detail the specific embodiments, structures, features, and their effects according to the present invention as follows.

[0024] Example 1

[0025] A method for preparing low - ash activated carbon using coconut shell, comprising the following steps:

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

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

[0028] S3. Mix the material B and deionized water, stir at 100 °C for 20 min, cool to room temperature, add sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, ultrasonically disperse for 20 min, and vacuum - dry at 80 °C for 10 h to obtain 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. Place the material C in a tube furnace, introduce an oxygen - nitrogen mixed gas for oxidation treatment, and cool to obtain material D; the dosage ratio of the material C to the oxygen - nitrogen mixed gas is 10 g:16 m 3; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment means heating to 300 °C at a heating rate of 2 °C / min and holding for 40 min;

[0030] S5. Place the material D in a tube furnace and carry out carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment means first heating to 250 °C at a heating rate of 3 °C / min and holding for 20 min; then heating to 600 °C at a heating rate of 2 °C / min and holding for 1 h;

[0031] S6. Place the material E in a tube furnace for activation treatment to obtain the activated carbon; the activation treatment means heating to 400 °C at a heating rate of 200 °C / h, and then heating to 800 °C at a heating rate of 100 °C / h and holding for 2 h.

[0032] Example 2

[0033] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

[0034] S1. Crush coconut shells, ball mill them, and pass through a 90-mesh sieve to obtain material A;

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

[0036] S3. Mix the material B with deionized water, stir at 100 °C for 25 min, cool to room temperature, add sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, ultrasonically disperse for 25 min, and vacuum dry at 80 °C for 11 h 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. Place the material C in a tube furnace, introduce an oxygen-nitrogen mixed gas, carry out oxidation treatment, and cool to obtain material D; the dosage ratio of the material C to the oxygen-nitrogen mixed gas is 11 g:18 m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment means heating to 315 °C at a heating rate of 2 °C / min and holding for 45 min;

[0038] S5. Place the material D in a tubular furnace and carry out carbonization treatment in a nitrogen atmosphere to obtain material E. The carbonization treatment means first heating up to 265°C at a heating rate of 3°C / min and holding for 25 min, then heating up to 650°C at a heating rate of 2°C / min and holding for 1.2 h.

[0039] S6. Place the material E in a tubular furnace for activation treatment to obtain the activated carbon. The activation treatment means heating up to 400°C at a heating rate of 200°C / h, then heating up to 825°C at a heating rate of 100°C / h and holding for 2.5 h.

[0040] Example 3

[0041] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

[0042] S1. Crush the coconut shells, ball-mill them, and pass through a 100-mesh sieve to obtain material A.

[0043] S2. Immerse the material A in a hydrochloric acid solution, stir at 70°C for 2 h, carry out suction filtration, take the solid phase for washing, and vacuum-dry at 80°C for 8 h to obtain material B. The dosage ratio of the material A to the hydrochloric acid solution is 22 g:200 mL. The concentration of the hydrochloric acid solution is 5 mol / L.

[0044] S3. Mix the material B and deionized water, stir at 100°C for 30 min, cool to room temperature, add sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, ultrasonically disperse for 30 min, and vacuum-dry at 80°C for 12 h to obtain material C. The mass ratio of the material B, deionized water, sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate is 2:30:0.8:0.09:0.05.

[0045] S4. Place the material C in a tubular furnace, introduce an oxygen-nitrogen mixed gas for oxidation treatment, and cool to obtain material D. The dosage ratio of the material C to the oxygen-nitrogen mixed gas is 12 g:20 m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20. The oxidation treatment means heating up to 330°C at a heating rate of 2°C / min and holding for 50 min.

[0046] S5. Place the material D in a tubular furnace and carry out carbonization treatment in a nitrogen atmosphere to obtain material E. The carbonization treatment means first heating up to 280°C at a heating rate of 3°C / min and holding for 30 min, then heating up to 700°C at a heating rate of 2°C / min and holding 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 means heating to 400°C at a heating rate of 200°C / h, then heating to 850°C at a heating rate of 100°C / h, and holding for 3 h.

[0048] Comparative Example 1

[0049] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

[0050] S1. Crush the coconut shells, ball-mill them, and pass through an 80-mesh sieve to obtain material A;

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

[0052] S3. Mix the material B with deionized water, stir at 100°C for 20 min, cool to room temperature, add ammonium carbonate and diammonium hydrogen phosphate, ultrasonically disperse for 20 min, and vacuum-dry at 80°C for 10 h 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. Place the material C in a tubular furnace, introduce an oxygen-nitrogen mixed gas for oxidation treatment, and cool to obtain material D. The dosage ratio of the material C to the oxygen-nitrogen mixed gas is 10 g:16 m 3 ; The volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20. The oxidation treatment means heating to 300°C at a heating rate of 2°C / min and holding for 40 min;

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

[0055] S6. Place the material E in a tubular furnace for activation treatment to obtain the activated carbon. The activation treatment means heating to 400°C at a heating rate of 200°C / h, then heating to 800°C at a heating rate of 100°C / h, and holding for 2 h.

[0056] Comparative Example 2

[0057] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

[0058] S1. Crush the coconut shell, ball-mill it, and pass through an 80-mesh sieve to obtain material A;

[0059] S2. Immerse the said material A in a hydrochloric acid solution, stir at 60 °C for 1 h, perform suction filtration, take the solid phase for washing, and vacuum-dry at 80 °C for 6 h to obtain material B; the dosage ratio of the said material A to the hydrochloric acid solution is 18 g: 200 mL; the concentration of the hydrochloric acid solution is 3 mol / L;

[0060] S3. Mix the said material B with deionized water, stir at 100 °C for 20 min, cool to room temperature, add sodium hydroxide and diammonium hydrogen phosphate, perform ultrasonic dispersion for 20 min, and vacuum-dry at 80 °C for 10 h to obtain material C; the mass ratio of the said material B, deionized water, sodium hydroxide, and diammonium hydrogen phosphate is 1: 20: 0.6: 0.11;

[0061] S4. Place the said material C in a tubular furnace, introduce an oxygen-nitrogen mixed gas for oxidation treatment, and cool to obtain material D; the dosage ratio of the said material C to the oxygen-nitrogen mixed gas is 10 g: 16 m 3 ; the volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1: 20; the oxidation treatment means heating to 300 °C at a heating rate of 2 °C / min and holding for 40 min;

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

[0063] S6. Place the said material E in a tubular furnace for activation treatment to obtain the said activated carbon; the activation treatment means heating to 400 °C at a heating rate of 200 °C / h, and then heating to 800 °C at a heating rate of 100 °C / h and holding for 2 h.

[0064] Comparative Example 3

[0065] A method for preparing low-ash activated carbon from coconut shell, comprising the following steps:

[0066] S1. Crush the coconut shell, ball-mill it, and pass through an 80-mesh sieve to obtain material A;

[0067] S2. Immerse the said material A in a hydrochloric acid solution, stir at 60 °C for 1 h, perform suction filtration, take the solid phase for washing, and vacuum-dry at 80 °C for 6 h to obtain material B; the dosage ratio of the said material A to the hydrochloric acid solution is 18 g: 200 mL; the concentration of the hydrochloric acid solution is 3 mol / L;

[0068] S3. Mix the material B and deionized water, stir at 100 °C for 20 min, cool to room temperature, add sodium hydroxide and ammonium carbonate, disperse ultrasonically for 20 min, and dry in vacuum at 80 °C for 10 h 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. Place the material C in a tubular furnace, introduce an oxygen-nitrogen mixed gas, carry out oxidation treatment, and cool to obtain material D; the dosage ratio of the material C to the oxygen-nitrogen mixed gas is 10 g:16 m³; the volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment means heating to 300 °C at a heating rate of 2 °C / min and holding for 40 min;

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

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

[0072] Comparative Example 4

[0073] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

[0074] S1. Crush coconut shells, ball-mill them, and pass through an 80-mesh sieve to obtain material A;

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

[0076] S3. Mix the material B and deionized water, stir at 100 °C for 20 min, cool to room temperature, add sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, disperse ultrasonically for 20 min, and dry in vacuum at 80 °C for 10 h to obtain 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. Place the material C in a tubular furnace and carry out carbonization treatment in a nitrogen atmosphere to obtain material e; the carbonization treatment means first heating up to 250 °C at a heating rate of 3 °C / min and holding for 20 min; then heating up to 600 °C at a heating rate of 2 °C / min and holding for 1 h.

[0078] S5. Place the material e in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment means heating up to 400 °C at a heating rate of 200 °C / h, and then heating up to 800 °C at a heating rate of 100 °C / h and holding for 2 h.

[0079] Comparative Example 5

[0080] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

[0081] S1. Crush the coconut shells, ball mill them, and pass through an 80-mesh sieve to obtain material A;

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

[0083] S3. Mix the material B with deionized water, stir at 100 °C for 20 min, cool to room temperature, add sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, ultrasonically disperse for 20 min, and vacuum dry at 80 °C for 10 h to obtain 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. Place the material C in a tubular furnace, introduce an oxygen-nitrogen mixed gas for oxidation treatment, and cool to obtain material D; the dosage ratio of the material C to the oxygen-nitrogen mixed gas is 10 g:16 m3; the volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment means heating up to 300 °C at a heating rate of 2 °C / min and holding for 40 min;

[0085] S5. Place the material D in a tubular furnace and carry out carbonization treatment in a nitrogen atmosphere to obtain material E; the carbonization treatment means heating up to 600 °C at a heating rate of 2 °C / min and holding for 80 min;

[0086] S6. Place the material E in a tubular furnace for activation treatment to obtain the activated carbon; the activation treatment means heating up to 400 °C at a heating rate of 200 °C / h, and then heating up to 800 °C at a heating rate of 100 °C / h and holding for 2 h.

[0087] Comparative Example 6

[0088] A method for preparing low-ash activated carbon from coconut shells, comprising the following steps:

[0089] S1. Take coconut shells, crush them, ball-mill them, and pass through an 80-mesh sieve to obtain material A;

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

[0091] S3. Mix the material B and deionized water, stir at 100°C for 20 min, cool to room temperature, add sodium hydroxide, ammonium carbonate, and diammonium hydrogen phosphate, ultrasonically disperse for 20 min, and vacuum-dry at 80°C for 10 h to obtain 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. Place the material C in a tube furnace, introduce an oxygen-nitrogen mixed gas, perform oxidation treatment, and cool to obtain material D; the dosage ratio of the material C to the oxygen-nitrogen mixed gas is 10 g:16 m 3 ; the volume ratio of oxygen to nitrogen in the oxygen-nitrogen mixed gas is 1:20; the oxidation treatment means heating to 300°C at a heating rate of 2°C / min and holding for 40 min;

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

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

[0095] Performance test

[0096] Take the activated carbon prepared in Examples 1-3 and Comparative Examples 1-6, and conduct ash content detection in accordance with the standard GB / T 36057-2018 "Analysis Methods for Forestry Biomass Raw Materials - Determination of Ash Content". The detection 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 carbon prepared in Examples 1-3 of the present application has a low ash content; this is because the present application optimizes the preparation process, dopes alkaline reagents sodium hydroxide, ammonium carbonate and ammonium dihydrogen phosphate in coconut shell powder before carbonization, changes the formation path of ash during carbonization, forms substances that are not easily carbonized, thereby reducing the ash generated during carbonization; in addition, by oxidizing the coconut shell powder, the organic substances in the coconut shell are 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 are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A 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, cooling it, and obtaining a material D; the oxidizing 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 min; 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 250-280° C. at a heating rate of 3° C. / min and keeping the temperature for 20-30 min; then heating the temperature to 600-700° C. at a heating rate of 2° C. / min and keeping the temperature for 1-1.5 h; 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 800-850°C at a heating rate of 100°C / h, and keeping the temperature for 2-3h.

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 dosage ratio of the material C and the oxygen-nitrogen mixed gas is 10-12g:16-20m3.

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.