A high-performance activated carbon and its preparation method

Abstract

The present invention relates to a high-performance activated carbon and a preparation method thereof, belonging to the technical field of activated carbon preparation. The high-performance activated carbon is obtained by first pretreating the raw materials for preparing activated carbon with an activator, and then subjecting the pretreated raw materials to a synergistic activation treatment by microwave heating, electric heating and ultrasonic heating; wherein, the activator can be selected from potassium hydroxide, sodium hydroxide, potassium oxalate, zinc chloride, water vapor, polycarboxylic acid activators, etc., and the polycarboxylic acid activators include polycarboxylates or polycarboxylic acid-based acrylic polymers, etc. The activated carbon prepared by the present invention has a higher specific surface area and better pore structure characteristics, which promotes the improvement of the adsorption performance of the activated carbon. In addition, in the preparation method, the present invention adopts the synergistic cooperation of microwave heating, ultrasonic heating, electric heating and activator, which can ensure the quality and yield of the prepared activated carbon, improve the production efficiency, and has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of activated carbon preparation, and specifically relates to a high-performance activated carbon and a preparation method thereof. Background Technique

[0002] Activated carbon is a kind of carbon treated specially, and its shape is usually powdery or granular porous amorphous carbon. Because of its large specific surface area, developed pore structure and rich surface chemical groups on the surface, it is widely used in the fields of sewage treatment, air purification, electrode manufacturing, flue gas treatment, etc. The adsorption performance of activated carbon is based on its huge specific surface area, and is also affected by the pore structure and surface functional groups.

[0003] The preparation process of activated carbon is divided into two steps: carbonization and activation. Specifically, organic raw materials (such as raw materials like fruit shells, coal, wood, etc.) are heated at high temperature under the condition of isolating air to reduce non-carbon components, leaving carbonaceous materials mainly composed of carbon (this process is called carbonization), and then reacting with gases to erode its surface to produce a structure with developed micropores (this process is called activation). The activated activated carbon is washed with clean water or acid and alkali solutions to remove residual activators and impurities, and finally different particle sizes of activated carbon products can be obtained through drying and screening.

[0004] For the activation process during the preparation of activated carbon, according to specific production processes and product quality requirements, physical activation method, chemical activation method or physical-chemical activation method and other methods can also be adopted to prepare activated carbon. Among them, the physical activation method mainly uses gases such as water vapor and carbon dioxide for activation; the chemical activation method uses chemical drugs such as zinc chloride and phosphoric acid for activation; while the physical-chemical activation method combines the advantages of physical activation and chemical activation for preparation. At present, there are relatively few reports on using polycarboxylic acid activators as activators in the activation process of activated carbon preparation. The preparation process of activated carbon is a complex and delicate process. How to improve production efficiency while ensuring the acquisition of products with excellent properties has positive significance for promoting the development of the activated carbon industry.

[0005] Therefore, the present invention proposes a high-performance activated carbon and a preparation method thereof. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-performance activated carbon and a preparation method thereof in order to solve the above problems.

[0007] The present invention realizes the above purpose through the following technical solutions:

[0008] In the first aspect of the present invention, a high-performance activated carbon is provided. The high-performance activated carbon is obtained by first pretreating the raw materials for preparing the activated carbon with an activator, and then subjecting the pretreated raw materials to a synergistic activation treatment by microwave heating, electric heating, and ultrasonic heating; wherein, the activator is a polycarboxylic acid activator, and the polycarboxylic acid activator is one of polycarboxylate or polycarboxylic acid acrylic polymer.

[0009] As a further optimized scheme of the present invention, the raw materials for preparing the activated carbon are any one of biomass, biochar, or coke.

[0010] As a further optimized scheme of the present invention, the polycarboxylic acid acrylic polymer is polymethyl methacrylate or polymethyl ethyl acrylate.

[0011] As a further optimized scheme of the present invention, the polycarboxylate is sodium polyacrylate or calcium polyacrylate.

[0012] In the second aspect of the present invention, a method for preparing a high-performance activated carbon is further provided, including the following steps:

[0013] (1) Immerse the raw materials for preparing the activated carbon in a saturated solution of the activator and stir evenly to obtain the pretreated raw materials;

[0014] (2) Under an inert gas atmosphere, subject the pretreated raw materials obtained in step (1) to a synergistic activation treatment by microwave heating, electric heating, and ultrasonic heating to obtain an activation product;

[0015] (3) Cool, wash, filter, and dry the activation product obtained in step (2) to obtain the activated carbon.

[0016] As a further optimized scheme of the present invention, the mass ratio of the activator to the raw materials for preparing the activated carbon is (1-6):(5-10).

[0017] As a further optimized scheme of the present invention, the activation temperature is 400°C - 800°C, and the activation time is 5 min - 200 min.

[0018] As a further optimized scheme of the present invention, the inert gas atmosphere includes any one of nitrogen atmosphere, helium atmosphere, neon atmosphere, or argon atmosphere.

[0019] As a further optimized scheme of the present invention, the microwave power is 500 W - 100 KW, the ultrasonic power is 500 W - 20 KW, and the electric heating power is 1 KW - 100 KW.

[0020] Therefore, the beneficial effects of the present invention are as follows:

[0021] (1) The present invention uses a method of synergistic activation treatment with microwave heating, ultrasonic heating, electric heating and an activator to produce activated carbon. Microwave energy can penetrate deep into the raw materials, directly causing polar molecules to move and generate heat, with a fast heating speed and high thermal energy utilization rate. Ultrasonic waves promote molecular vibration, with strong intermolecular collision forces and high frequencies, accelerating the activation reaction. Supplementary electric heating can make the temperature field in the activation furnace uniform and have a high volumetric heat load, compensating for the defect of insufficient high-temperature energy in microwave heating. The synergistic cooperation of microwave, ultrasonic, auxiliary electric heating and activator can ensure the quality and yield of the prepared activated carbon and improve production efficiency.

[0022] (2) The method of synergistic activation treatment with microwave, ultrasonic, electric heating and activator adopted by the present invention can make the activated carbon production process more efficient, controllable and widely applicable. In addition, compared with harmful by-products such as dioxins that may be generated in the traditional pyrolysis process, the method of the present invention is more environmentally friendly and safe.

[0023] (3) The present invention uses polycarboxylic acid activators as activators in the preparation of activated carbon. Different from common activators such as potassium hydroxide, sodium hydroxide, potassium oxalate, phosphoric acid, zinc chloride and water vapor, the prepared activated carbon can obtain a higher specific surface area and better pore structure characteristics, promoting the improvement of the adsorption performance of activated carbon and having good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figures 1 to 8 Respectively are the nitrogen adsorption and desorption curves of the samples of treatment groups A-1 to A-8 provided by the present invention;

[0025] Figure 9 Is the nitrogen adsorption and desorption curve of the sample of blank control group a provided by the present invention;

[0026] Figures 10 to 19 Respectively are the nitrogen adsorption and desorption curves of the samples of treatment groups B-1 to B-10 provided by the present invention;

[0027] Figure 20 Is the nitrogen adsorption and desorption curve of the sample of blank control group b provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following further describes the present application in detail with reference to the drawings. It is necessary to point out here that the following specific embodiments are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0029] A preparation method of a high-performance activated carbon proposed by the present invention includes the following steps:

[0030] (1) Immerse the raw materials for preparing activated carbon in a saturated solution of an activating agent and stir evenly to obtain pretreated raw materials. Specifically, first dissolve 10 kg - 60 kg of the activating agent into a saturated solution. The solvent for dissolving the activating agent is selected according to the solubility of the selected activating agent. Take 50 kg - 100 kg of raw materials and immerse them in the above-mentioned saturated solution of the activating agent, and fully stir and mix them in a blender to obtain pretreated raw materials.

[0031] Further, the raw materials can be selected from biomass or biochar. More specifically, the biomass can be selected from agricultural wastes such as fruit shells, cereal husks, wood / wood chips or straw, and the biochar is a carbonized product obtained by high-temperature carbonization of the above-mentioned biomass raw materials. In addition to biomass and biochar, other carbon-containing raw materials such as peat and coke can also be selected.

[0032] Further, the activating agent can be selected from potassium hydroxide, sodium hydroxide, potassium oxalate, polycarboxylic acid-based activating agents, zinc chloride, water vapor, etc. The polycarboxylic acid-based activating agent is further preferably any one of polycarboxylate (K, Na salts), sodium polyacrylate, polymethyl methacrylate, polyethyl methacrylate, calcium polyacrylate.

[0033] (2) Under an inert gas atmosphere, perform a synergistic activation treatment of microwave heating, electric heating and ultrasonic heating on the pretreated raw materials obtained in step (1) to obtain an activated product.

[0034] The specific process is as follows. First, purge the activation furnace with nitrogen. The purging time can be 5 min, 10 min, etc. to fully discharge the oxygen inside the activation furnace. Other inert gases such as helium, neon or argon can also be selected as the gas. Subsequently, place the raw materials pretreated with the activating agent in the activation furnace. The activation furnace is equipped with microwave heating, ultrasonic heating and electric auxiliary heating. It can be heated individually, heated in pairs, or heated simultaneously by all three. During the activation process, nitrogen is stopped from being introduced into the activation furnace, or a small amount of nitrogen can be introduced to prevent air from entering the furnace and bringing in oxygen. After reaching the set activation temperature, stop heating and introduce nitrogen. The purpose is to prevent the high-temperature activated carbon from burning and to cool the high-temperature activated carbon. Further, the activation temperature is set to 400°C - 800°C, and the entire activation treatment time is 5 min - 200 min. The microwave power is 500 W - 100 KW, the ultrasonic power is 500 W - 20 KW, and the electric heating power is 1 KW - 100 KW. The microwave power, ultrasonic power and electric heating power are flexibly adjusted according to the activation temperature required and the length of the activation treatment.

[0035] During the activation process, the synergistic activation treatment by microwave heating, electric heating and ultrasonic heating can help improve the activation efficiency and product quality. Microwaves penetrate deep into the raw materials, directly causing the polar molecules inside the raw materials to move and generate heat. The heating rate is fast and the thermal energy utilization rate is high. By adjusting the microwave power, the heating condition of the raw materials can be adjusted accordingly. Ultrasonic and electric auxiliary heating are also introduced during the activation process. The ultrasonic wave can promote molecular vibration with its cavitation effect and vibration action. The intermolecular collision force is strong and the frequency is high, which promotes the acceleration of the activation reaction. Electric auxiliary heating can make the temperature field in the activation furnace uniform and the volumetric heat load high, making up for the defect of insufficient high-temperature energy in microwave heating.

[0036] (3) The activated product obtained through the treatment in step (2) can be cooled, washed, filtered and dried to obtain high-performance activated carbon. Specifically, after the activation is completed, the activated product can be placed in warm water at 50°C and stirred and washed, filtered and dried to obtain activated carbon. In addition, after the collected water-washing filtrate is allowed to stand, it is filtered and recycled, evaporated and concentrated, and can be used to prepare the saturated solution of the activator in step (1).

[0037] The beneficial effects of the present invention are illustrated below through specific examples.

[0038] Example 1: Influence of different activation treatment methods on the performance of the prepared activated carbon

[0039] This example discloses a specific preparation method of high-performance activated carbon, including the following steps:

[0040] (1) Prepare a saturated solution of the activator, impregnate the bamboo charcoal powder in the saturated solution of the activator and stir evenly to obtain the pretreated bamboo charcoal powder. The activator is specifically selected as sodium polyacrylate, and the dosage ratio of sodium polyacrylate to bamboo charcoal starch is 1 kg:5 kg;

[0041] The bamboo charcoal powder is obtained according to the following preparation method: Crush the collected flaky moso bamboo, pass it through a 200-mesh sieve to obtain bamboo powder, dry the bamboo powder, transfer the dried bamboo powder to a corundum crucible, and carbonize it at a temperature of 300°C for 2 h under the action of a catalyst and in a nitrogen atmosphere, controlling the heating rate at 2°C / min to obtain the carbonized product, which is the bamboo charcoal powder.

[0042] (2) Transfer the pretreated bamboo charcoal powder obtained in step (1) into the activation furnace. The activation furnace is equipped with microwave heating, ultrasonic heating and electric auxiliary heating. After purging with nitrogen in the activation furnace for 5 min, turn on the microwave heating, electric heating and ultrasonic heating. The microwave power raises the temperature inside the activation furnace to the activation required temperature, and stop heating after reaching the activation required temperature. In this example, the activation temperature is 800°C and the activation treatment time is 100 min.

[0043] (3) Place the activated product obtained through the treatment in step (2) into warm water at 50 °C, stir and wash it, then filter and dry to obtain high-performance activated carbon.

[0044] Table 1. Influence of Different Heating Activation Treatment Methods on the Performance of the Prepared Activated Carbon

[0045] ;

[0046] Note: "+" indicates that this treatment was carried out; "-" indicates that this treatment was not carried out.

[0047] Based on the activated carbon preparation method disclosed in Example 1, adjust different heating activation treatment methods according to Table 1 to prepare activated carbon. And use BET to conduct BET tests on the prepared activated carbon samples. In addition, use untreated bamboo charcoal powder as the blank control group a, and the results are shown in Table 2.

[0048] Table 2. Result Statistical Table

[0049] ;

[0050] From Table 2 combined with Figures 1 - 9 it can be seen that the blank control group is untreated bamboo charcoal powder, which has poor pore structure characteristics and a low specific surface area. By comparing the A-8 treatment group with the blank control group, it can be seen that the heating treatment of bamboo charcoal powder by microwave, ultrasonic, and electric heating has a certain positive effect on the improvement of its specific surface area, but it is much lower than that of the A-1 group. The activation method of combining microwave, ultrasonic, and electric heating with the activator (A-1 treatment group) has the best effect on improving the specific surface area of activated carbon. The activation methods of combining microwave, ultrasonic, and electric heating pairwise with the activator (A-2 to A-4 treatment groups) have a better effect on improving the specific surface area of the prepared activated carbon than the activation methods of combining microwave, ultrasonic, and electric heating alone with the activator (A-5 to A-7 treatment groups).

[0051] In addition, the present invention further statistically analyzed the activated carbon yields of the A-1 to A-8 treatment groups. The activated carbon yield is calculated by dividing the difference between the mass of the raw material (in this example, the mass of bamboo charcoal powder) and the mass of the finally prepared activated carbon by the mass of the raw material, and the results are shown in Table 3.

[0052] Table 3. Activated Carbon Yields of the A-1 to A-8 Treatment Groups

[0053] ;

[0054] From Table 3, it can be seen that the A-1 treatment group, which obtained activated carbon through the synergistic activation treatment of microwave heating, electric heating, and ultrasonic heating, has the best activated carbon yield.

[0055] Example 2. Influence of Adjusting Different Activators on the Performance of Prepared Activated Carbon

[0056] This example provides a specific method for preparing high-performance activated carbon, which includes the following steps:

[0057] (1) Prepare corn straw carbide powder according to the same method as in Example 1, and immerse it in a saturated activator solution and stir evenly to obtain pretreated corn straw carbide powder. The dosage ratio of the activator to the corn straw carbide powder is 6 kg:10 kg.

[0058] (2) First, introduce nitrogen into the activation furnace and purge for 10 min to evacuate the air in the furnace. Then, transfer the pretreated corn straw carbide powder obtained in step (1) into the activation furnace. The activation furnace is equipped with microwave heating, ultrasonic heating, and electric auxiliary heating. Turn on the microwave heating, ultrasonic heating, and electric auxiliary heating simultaneously to raise the temperature inside the activation furnace to the required activation temperature. After reaching the required activation temperature, stop heating. The activation temperature is set at 400 °C, and the total activation time is 200 min.

[0059] (3) Place the activated product obtained in step (2) in warm water at 50 °C, stir and wash, filter and dry to obtain activated carbon.

[0060] Table 4. Influence of Adjusting Different Activators on the Performance of Prepared Activated Carbon

[0061] ;

[0062] Based on the activated carbon preparation method disclosed in Example 2, adjust different activators for treatment to prepare activated carbon. Use BET of Beishide to conduct BET tests on the prepared activated carbon samples. In addition, use the untreated corn straw carbide powder as the blank control group b. The results are shown in Table 5.

[0063] It should be noted that for the B-10 treatment group, that is, using water vapor as the activator to prepare activated carbon, its preparation steps are different from those of other treatment groups. The specific difference is as follows: Transfer the prepared corn straw carbide powder into the activation furnace, prepare a water vapor emitter to ensure that stable and appropriate water vapor can be provided, turn on the microwave heating, ultrasonic heating, and electric auxiliary heating, and at the same time control the water vapor to enter the activation furnace and react fully with the carbonized material. Control the activation furnace to heat up from room temperature to 400 °C, and the total activation time is 200 min.

[0064] Table 5. Statistical Table of Results

[0065] ;

[0066] As can be seen from Table 5, under the same preparation method, different activators have varying degrees of influence on the specific surface area and pore structure distribution of the prepared activated carbon. Compared with commonly used activators such as phosphoric acid, zinc chloride, potassium hydroxide, sodium hydroxide, potassium oxalate, and water vapor, the polycarboxylic acid activator used in the present invention can enable the prepared activated carbon to obtain a better specific surface area and pore structure distribution. Moreover, by comparing different polycarboxylic acid activators, it can be seen that the effect of using ethyl polymethacrylate as the activator is the best.

[0067] Example 3. Adsorption performance test

[0068] Prepare methylene blue solutions with concentrations of 1, 2, 3, 4, 5, and 6 mg / L, measure their absorbance at the maximum absorption wavelength of 664 nm, and plot the standard curve of the concentration-absorbance of methylene blue.

[0069] The relationship curve between the absorbance and concentration of methylene blue is: ;

[0070] where x is the concentration of the methylene blue solution (mg / L) and y is the absorbance.

[0071] Weigh 10 mg of the samples in treatment groups B-1 to B-10 and 10 mg of the sample in the blank control group b respectively, place them in 50 mL conical flasks, then add 20 mL of methylene blue solution with a concentration of 50 mg / L, shake at room temperature. When the adsorption equilibrium time is reached, take out the samples, centrifuge them, take the supernatant, measure its absorbance, calculate the concentration of the solution after adsorption according to the standard curve of methylene blue, and calculate the adsorption rate through the formula.

[0072] The calculation formula for the adsorption rate of the material is:

[0073] ;

[0074] In the formula, C0 is the initial concentration of methylene blue before adsorption (mg / L); C1 is the concentration of the methylene blue solution at adsorption equilibrium (mg / L).

[0075] The adsorption rates of the samples in treatment groups B-1 to B-10 and the blank control group b are shown in Table 6.

[0076] Table 6. Adsorption rates of the samples in treatment groups B-1 to B-10 and the blank control group b

[0077] ;

[0078] As can be seen from Table 3, compared with the blank control group b, the adsorption rates of the activated carbon prepared with different activators for methylene blue are all above 85%. The adsorption rate of the activated carbon prepared with polyethyl methacrylate as the activator can reach more than 99%, obtaining better adsorption performance.

[0079] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A high performance activated carbon, characterized in that: The high-performance activated carbon is obtained by first pretreating the raw materials for preparing the activated carbon with an activator, and then subjecting the pretreated raw materials to a synergistic activation treatment using microwave heating, electric heating and ultrasonic heating; wherein the raw material for preparing the activated carbon is biochar, and the activator is polyethyl methacrylate.

2. A method for preparing high-performance activated carbon as claimed in claim 1, characterized in that: The preparation method comprises the following steps: (1) Immersing the raw materials for preparing activated carbon in a saturated solution of an activator and stirring the mixture evenly to obtain pretreated raw materials; (2) Under an inert gas atmosphere, the pretreated raw material obtained in step (1) is subjected to a coordinated activation treatment using microwave heating, electric heating and ultrasonic heating to obtain an activated product; (3) The activated product obtained in step (2) is cooled, washed, filtered and dried to obtain activated carbon.

3. The method for preparing high-performance activated carbon according to claim 2, characterized in that: In step (1), the mass ratio of the activating agent to the raw material for preparing activated carbon is (1-6): (5-10).

4. The method for preparing high-performance activated carbon according to claim 2, characterized in that: In step (2), the activation temperature is 400°C-800°C, and the activation time is 5 min-200 min.

5. The method for preparing high-performance activated carbon according to claim 2, characterized in that: In step (2), the inert gas atmosphere is any one of a nitrogen atmosphere, a helium atmosphere, a neon atmosphere or an argon atmosphere.

6. The method for preparing high-performance activated carbon according to claim 2, characterized in that: In step (2), the microwave power is 500W-100KW, the ultrasonic power is 500W-20KW, and the electric heating power is 1KW-100KW.

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