Method for producing activated carbon by gradient impregnation of lignite composite acid

Abstract

The invention provides a method for producing activated carbon through lignite composite acid gradient impregnation, and relates to the technical field of activated carbon preparation. The method for producing the activated carbon by gradient impregnation of the lignite composite acid comprises the following steps: S1, pretreatment of raw materials; S2, gradient impregnation of the composite acid; S3, carbonization treatment; S4, activation treatment; the specific surface area of the prepared finished product activated carbon is greater than or equal to 1000m < 2 > / g through composite acid gradient impregnation and reasonable carbonization and activation processes, and the finished product activated carbon has a developed pore structure and can meet high requirements of different fields on the adsorption performance of the activated carbon. The lignite is used as the raw material, the source is wide, the cost is low, the production cost of the activated carbon is effectively reduced, the additional value of the lignite is improved, efficient utilization of resources is achieved, the whole preparation process is clear in step and relatively simple and convenient to operate, large-scale industrial production is easy to achieve, and good market application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of activated carbon preparation, and specifically to a method for producing activated carbon by gradient impregnation of lignite with composite acid. Background Art

[0002] As a porous carbon material with a high specific surface area and a developed pore structure, activated carbon has been widely used in many fields such as water treatment, air purification, food decolorization, and pharmaceutical purification. Traditional production of activated carbon mostly relies on high-grade raw materials such as wood, fruit shells, and coal. However, with the increasing resource tension and the continuous improvement of environmental protection requirements, the supply of these high-grade raw materials is gradually limited, and it is urgent to develop new raw material sources and preparation methods.

[0003] Lignite, as a resource with rich reserves and low price, has gradually become an important research direction for activated carbon production. Taking lignite as an example, it has characteristics such as high volatile matter, high ash content, and low calorific value. Direct combustion not only has low utilization efficiency but also causes serious environmental pollution. If lignite can be converted into activated carbon, it can not only increase the added value of lignite but also achieve clean and efficient utilization of resources, with significant economic and environmental benefits. However, the current methods for preparing activated carbon from lignite still have many deficiencies, such as unstable performance of the prepared activated carbon, complex processes, and high costs, which limit the large-scale application of lignite in the field of activated carbon production. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for producing activated carbon by gradient impregnation of lignite with composite acid, which solves the problems of unstable performance of the prepared activated carbon, complex processes, and high costs.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for producing activated carbon by gradient impregnation of lignite with composite acid, comprising the following steps:

[0006] S1. Raw material pretreatment: Crush lignite into particles with a particle size of 1 - 5 mm. This particle size range can not only ensure sufficient contact between lignite and acid solution, activator, etc. during subsequent processing but also facilitate operation and control. Subsequently, perform a drying treatment, and strictly control the moisture content below 5% to avoid the adverse impact of moisture on the subsequent reaction process and ensure the stability of reaction conditions;

[0007] S2. Composite acid gradient impregnation: Immerse the pretreated lignite particles successively in acid solutions of different concentrations. Specifically, first immerse them in a low-concentration acid for 1 hour. Hydrochloric acid can initially remove some mineral impurities in the lignite, creating better conditions for subsequent reactions. Then immerse them in a medium-concentration acid for 1 hour. Sulfuric acid further chemically treats the lignite and changes its internal structure. Finally, immerse them in a high-concentration acid for 1 hour. Phosphoric acid can form more pores inside the lignite, laying a foundation for the construction of the pore structure of activated carbon. Among them, the low-concentration acid is 5% hydrochloric acid, the medium-concentration acid is 10% sulfuric acid, and the high-concentration acid is 15% phosphoric acid. The successive impregnation of acids with different concentrations uses the concentration gradient of the acid to gradually treat the lignite, which can more effectively regulate the pore structure and surface properties of activated carbon;

[0008] S3. Carbonization treatment: Carbonize the impregnated lignite particles under an inert atmosphere, where the inert atmosphere is a nitrogen atmosphere. The carbonization temperature is controlled at 500 - 700 °C, and the carbonization time is 1 - 3 hours. During this process, the organic matter in the lignite undergoes pyrolysis reactions and gradually forms a carbonaceous skeleton. At the same time, the heating rate is controlled at 5 - 10 °C / min, which can ensure the uniform progress of the carbonization process, avoid local overheating or uneven reactions caused by too fast heating rate, and thus ensure the stability of the quality of the carbonized material;

[0009] S4. Activation treatment: Mix the carbonized material with the activator in a mass ratio of 1:1 - 1:3. The activator is selected from potassium hydroxide or phosphoric acid, and potassium hydroxide is preferably used because of its better activation effect on lignite. Carry out the activation treatment at 600 - 900 °C, and the activation time is 1 - 2 hours. During the activation process, the activator reacts chemically with the carbonized material, further expanding and enriching the pore structure of the carbonized material, and significantly improving the specific surface area and adsorption performance of the activated carbon;

[0010] S5. Washing and drying: First, neutralize with dilute hydrochloric acid to remove the residual activator, and then repeatedly wash the activated material with deionized water to remove the residual acid, activator, and soluble impurities generated by the reaction. Then dry at 100 - 120 °C to obtain granular activated carbon. This drying temperature can not only ensure the full removal of moisture but also will not damage the structure and performance of the activated carbon;

[0011] S6. Post-treatment: Screen the dried granular activated carbon to obtain the finished activated carbon with the required particle size according to different application requirements.

[0012] The present invention provides a method for producing activated carbon by using composite acid gradient impregnation of lignite. It has the following beneficial effects:

[0013] 1. Through composite acid gradient impregnation and reasonable carbonization and activation processes, the specific surface area of the finished activated carbon prepared by the present invention is ≥1000 m2 / g, has a developed pore structure and can meet the high requirements for the adsorption performance of activated carbon in different fields.

[0014] 2. The present invention uses lignite as the raw material, which has a wide source and low cost, effectively reduces the production cost of activated carbon, increases the added value of lignite, and realizes the efficient utilization of resources.

[0015] 3. The entire preparation process of the present invention is clear in steps and relatively simple to operate, is easy to realize large-scale industrial production, and has good market application prospects. Specific Embodiments

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0017] Example 1:

[0018] The embodiment of the present invention provides a method for producing activated carbon by gradient impregnation of lignite composite acid, including the following steps:

[0019] Raw material pretreatment: Select lignite, crush it into particles with a particle size of 2 mm, and then put it into a drying device for drying until the moisture content reaches 4%.

[0020] Composite acid gradient impregnation: Put the pretreated lignite particles into 5% hydrochloric acid solution, 10% sulfuric acid solution, and 15% phosphoric acid solution in sequence, and impregnate for 1 hour in each acid solution. During the impregnation process, stir regularly to ensure that the lignite particles are in full contact with the acid solution and make the reaction more uniform. Specifically, during the composite acid gradient impregnation, the concentration and impregnation time of the acid solution can be adjusted according to the properties of lignite and the performance requirements of activated carbon.

[0021] Carbonization treatment: Place the impregnated lignite particles in a carbonization furnace under a nitrogen atmosphere, heat them to 600 °C at a heating rate of 8 °C / min, and keep them for 2 hours to obtain carbonized material. During the carbonization process, monitor the temperature and atmosphere in the furnace in real time to ensure stable carbonization conditions.

[0022] Activation treatment: Mix the carbonized material and potassium hydroxide evenly according to a mass ratio of 1:2, put them into an activation furnace, and activate at 800 °C for 1.5 hours to obtain activated material. During the activation process, strictly control the temperature and activation time in the furnace to ensure that the activation reaction proceeds fully.

[0023] Washing and drying: First, neutralize with dilute hydrochloric acid to remove the residual activator, and then repeatedly wash the activated material with deionized water until the washing liquid is neutral. Then, place the washed material in a drying oven and dry it at 110 °C to obtain granular activated carbon.

[0024] Post-treatment: Screen the dried granular activated carbon to obtain finished activated carbon with a particle size of 1 - 3 mm. After testing, the specific surface area of this finished activated carbon is 1200 m 2 / g, with a well-developed pore structure and good adsorption performance.

[0025] In this example, through the composite acid gradient impregnation and reasonable carbonization and activation processes, activated carbon with a high specific surface area (≥1000 m 2 / g) and a well-developed pore structure was prepared using lignite. This method has a wide range of raw material sources, low cost, and simple process, and is suitable for large-scale industrial production.

[0026] Example Two:

[0027] This example of the present invention provides a method for producing activated carbon by composite acid gradient impregnation of lignite, including the following steps:

[0028] Raw material pretreatment: Take another batch of lignite, crush it into particles with a particle size of 3 mm, and dry it to a moisture content of 3%.

[0029] Composite acid gradient impregnation: Immerse the lignite particles in 5% hydrochloric acid, 10% sulfuric acid, and 15% phosphoric acid for 1 hour each in sequence. Specifically, during the composite acid gradient impregnation, the concentration of the acid solution and the impregnation time can be adjusted according to the properties of the lignite and the performance requirements of the activated carbon.

[0030] Carbonization treatment: Under a nitrogen atmosphere, heat the impregnated lignite particles to 700 °C at a heating rate of 10 °C / min and carbonize for 1 hour to obtain carbonized material.

[0031] Activation treatment: Mix the carbonized material with phosphoric acid in a mass ratio of 1:1.5 and activate it at 900 °C for 1 hour to obtain activated material.

[0032] Washing and drying: First, neutralize with dilute hydrochloric acid to remove the residual activator, and then wash the activated material with deionized water until neutral, and dry it at 105 °C to obtain granular activated carbon.

[0033] Post-treatment: Screen the granular activated carbon to obtain finished activated carbon with the required particle size. After testing, the specific surface area of this finished activated carbon reaches 1100 m 2 / g, meeting the performance requirements of high specific surface area activated carbon.

[0034] In this embodiment, through the composite acid gradient impregnation and reasonable carbonization and activation processes, activated carbon with a high specific surface area (≥1000 m 2 / g) and a well-developed pore structure is prepared using lignite. The method has a wide range of raw material sources, low costs, and a simple process, and is suitable for large-scale industrial production.

[0035] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing activated carbon by gradient impregnation with lignite composite acid, characterized in that: It includes the following steps: S1. Raw material pretreatment: Crush lignite into particles with a particle size of 1 - 5 mm, and conduct drying treatment to control the moisture content below 5%; S2. Composite acid gradient impregnation: Immerse the pretreated lignite particles successively in acid solutions with different concentrations. First, immerse them in a low - concentration acid for 1 hour, then in a medium - concentration acid for 1 hour, and finally in a high - concentration acid for 1 hour; S3. Carbonization treatment: Conduct carbonization treatment on the impregnated lignite particles under an inert atmosphere. The carbonization temperature is 500 - 700 °C, and the carbonization time is 1 - 3 hours to obtain carbonized material; S4. Activation treatment: Mix the carbonized material with an activator at a mass ratio of 1:1 - 1:3, and conduct activation treatment at 600 - 900 °C for 1 - 2 hours to obtain activated material; The activator is potassium hydroxide or phosphoric acid; S5. Washing and drying: Wash the activated material repeatedly with deionized water until it is neutral, and then dry it at 100 - 120 °C to obtain granular activated carbon; S6. Post - treatment: Screen the dried granular activated carbon to obtain the finished activated carbon with the required particle size.

2. The method for producing activated carbon by gradient impregnation with lignite composite acid according to claim 1, characterized in that: In the composite acid gradient impregnation step, the low - concentration acid is 5% hydrochloric acid, the medium - concentration acid is 10% sulfuric acid, and the high - concentration acid is 15% phosphoric acid.

3. A method for producing activated carbon by gradient impregnation of lignite composite acid according to claim 1, characterized in that: During the carbonization treatment, the heating rate is controlled at 5 - 10 °C / min.

4. A method for producing activated carbon by gradient impregnation of lignite composite acid according to claim 1, characterized in that: During the activation treatment, potassium hydroxide is preferably used as the activator.

5. A method for producing activated carbon by gradient impregnation of lignite composite acid according to claim 1, characterized in that: During the washing process, first use dilute hydrochloric acid for neutralization to remove the residual activator, and then wash with deionized water.

6. The method for producing activated carbon by gradient impregnation of lignite composite acid according to claim 1, wherein: The inert atmosphere is a nitrogen atmosphere.

7. A method for producing activated carbon by gradient impregnation of lignite composite acid according to claim 1, characterized in that: The specific surface area of the finished activated carbon ≥ 1000m 2 / g.