High-performance activated carbon and preparation method thereof

Abstract

The invention relates to high-performance activated carbon and a preparation method thereof, and relates to the technical field of activated carbon preparation, and the high-performance activated carbon is obtained by pretreating raw materials for preparing the activated carbon by using an activating agent and then performing microwave heating, electric heating and ultrasonic heating synergistic activating treatment on the pretreated raw materials; wherein the activating agent can be selected from potassium hydroxide, sodium hydroxide, potassium oxalate, zinc chloride, water vapor, a polycarboxylic acid activating agent and the like, and the polycarboxylic acid activating agent comprises polycarboxylate or a polycarboxylic acid acrylic acid polymer and the like. The activated carbon prepared by the method has higher specific surface area and better pore structure characteristics, and the adsorption performance of the activated carbon is promoted to be improved. Besides, in the preparation method, microwave heating, ultrasonic heating, electric heating and an activating agent are cooperated, so that the quality and the yield of the prepared activated carbon can be ensured, the production efficiency is improved, and the preparation method has a relatively good application prospect.

Description

Technical Field

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

[0002] Activated carbon is a specially treated carbon, usually in the form of powdered or granular porous amorphous carbon. It is widely used in sewage treatment, air purification, electrode manufacturing, flue gas treatment and other fields due to its large specific surface area, developed pore structure and rich surface chemical groups. 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, the organic raw materials (such as fruit shells, coal, wood and other raw materials) are heated at high temperature under air-tight conditions to reduce non-carbon components, leaving carbonaceous materials mainly composed of carbon (this process is called carbonization), and then react with gas to erode its surface to produce a microporous structure (this process is called activation). The activated activated carbon is washed with clean water or acid or alkali solution to remove residual activators and impurities, and finally dried and sieved to obtain activated carbon products of different particle sizes.

[0004] Regarding the activation process in the preparation of activated carbon, according to the specific production process and product quality requirements, physical activation, chemical activation or physical-chemical activation methods can also be used 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 chemicals such as zinc chloride and phosphoric acid for activation; and the physical-chemical activation method combines the advantages of physical activation and chemical activation for preparation. At present, there are relatively few reports on the use of polycarboxylic acid activators as activators in the activation process during the preparation of activated carbon. 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] To this end, the present invention provides 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 achieves the above-mentioned purpose through the following technical solutions: The first aspect of the present invention provides a high-performance activated carbon, which 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 a polycarboxylate or a polycarboxylic acid acrylic polymer.

[0008] As a further optimization scheme of the present invention, the raw material for preparing the activated carbon is any one of biomass, biochar or coke.

[0009] As a further optimization scheme of the present invention, the polycarboxylic acid acrylic polymer is polymethyl methacrylate or polyethyl methacrylate.

[0010] As a further optimization scheme of the present invention, the polycarboxylate is sodium polyacrylate or calcium polyacrylate.

[0011] The second aspect of the present invention also provides a method for preparing high-performance activated carbon, comprising 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.

[0012] As a further optimization scheme of the present invention, the mass ratio of the activating agent to the raw material for preparing activated carbon is (1-6): (5-10).

[0013] As a further optimization scheme of the present invention, the temperature required for the activation is 400° C.-800° C., and the time required for the activation is 5 min-200 min.

[0014] As a further optimization solution of the present invention, the inert gas atmosphere includes any one of a nitrogen atmosphere, a helium atmosphere, a neon atmosphere or an argon atmosphere.

[0015] As a further optimization scheme of the present invention, the microwave power is 500W-100KW, the ultrasonic power is 500W-20KW, and the electric heating power is 1KW-100KW.

[0016] Therefore, the beneficial effects of the present invention are: (1) The present invention adopts the method of microwave heating, ultrasonic heating, electric heating and activator coordinated activation treatment to produce activated carbon. Microwave energy penetrates deep into the raw materials, directly causing polar molecules to move and generate heat, resulting in fast heating speed and high thermal energy utilization rate. Ultrasonic waves promote molecular vibration, and the mutual collision force between molecules is strong and high in frequency, which promotes the acceleration of activation reaction. Assisted by electric heating, the temperature field in the activation furnace is uniform and the volume heat load is high, which makes up for the defect of insufficient high-temperature energy of microwave heating. The coordinated cooperation of microwaves, ultrasonic waves, auxiliary electric heating and activators can ensure the quality and yield of the prepared activated carbon and improve production efficiency.

[0017] (2) The present invention adopts a method of coordinated activation treatment using microwaves, ultrasound, electric heating, and an activator, which can make the activated carbon production process more efficient and controllable, and has a wide range of applicability. In addition, compared with the harmful byproducts such as dioxins that may be produced during the traditional pyrolysis process, the method of the present invention is more environmentally friendly and safe.

[0018] (3) The present invention adopts a polycarboxylic acid activator as an activator for the preparation of activated carbon, which is different from commonly used activators, such as potassium hydroxide, sodium hydroxide, potassium oxalate, phosphoric acid, zinc chloride and water vapor. The activated carbon prepared by the present invention can obtain a higher specific surface area and better pore structure characteristics, thereby improving the adsorption performance of the activated carbon and having a good application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figures 1 to 8 They are respectively the nitrogen adsorption-desorption curves of the samples in the treatment groups A-1 to A-8 provided by the present invention; Fig. 9 is the nitrogen adsorption-desorption curve of the blank control group a sample provided by the present invention; Figures 10 to 19 They are respectively the nitrogen adsorption-desorption curves of the samples in the treatment groups B-1 to B-10 provided by the present invention; Fig. 20 It is the nitrogen adsorption-desorption curve of the blank control group b sample provided by the present invention. DETAILED DESCRIPTION

[0020] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0021] The present invention provides a method for preparing high-performance activated carbon, comprising the following steps: (1) The raw materials for preparing activated carbon are immersed in a saturated solution of an activator and stirred evenly to obtain pretreated raw materials; specifically, 10kg-60kg of the activator is first dissolved into a saturated solution, and the solvent for dissolving the activator is selected according to the solubility of the selected activator. 50kg-100kg of the raw materials are immersed in the above saturated solution of the activator, and are fully stirred and mixed in a mixer to obtain pretreated raw materials.

[0022] Furthermore, the raw materials can be selected from biomass or biochar. Furthermore, biomass can be selected from agricultural waste such as fruit shells, grain shells, wood / wood chips or straw, and biochar is a carbonized product obtained by carbonizing the above biomass raw materials at high temperature. In addition to biomass and biochar, other carbon-containing raw materials can also be selected, such as peat, coke, etc.

[0023] Furthermore, the activator can be selected from potassium hydroxide, sodium hydroxide, potassium oxalate, polycarboxylic acid activators, zinc chloride, water vapor, etc., and the polycarboxylic acid activator is further preferably any one of polycarboxylates (K, Na salts), sodium polyacrylate, polymethyl methacrylate, polyethyl methacrylate, and calcium polyacrylate.

[0024] (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; The specific process is as follows: first, use nitrogen to purge the activation furnace. The purge time can be 5 minutes, 10 minutes, etc., to fully exhaust the oxygen inside the activation furnace. The gas can also be other inert gases, such as helium, neon or argon. Subsequently, the raw materials pretreated with the activator are placed in the activation furnace. The activation furnace is equipped with microwave heating, ultrasonic heating and electric auxiliary heating. The heating can be turned on individually, in pairs, or all three at the same time. During the activation process, nitrogen stops entering the activation furnace, and 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, heating is stopped and nitrogen is introduced. The purpose is to prevent the high-temperature activated carbon from burning and to cool the high-temperature activated carbon. Furthermore, the temperature required for activation is set to 400°C-800°C, and the entire activation treatment time is 5min-200min. The microwave power is 500W-100KW, the ultrasonic power is 500W-20KW, and the electric heating power is 1KW-100KW. The microwave power, ultrasonic power and electric heating power can be flexibly adjusted according to the activation temperature and the length of the activation treatment.

[0025] During the activation process, the coordinated activation treatment of 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 in the raw materials to move and generate heat, with a fast heating rate and high thermal energy utilization rate. By adjusting the microwave power, the heating of the raw materials can be adjusted accordingly. Ultrasonic waves and electric auxiliary heating are also introduced during the activation process. Ultrasonic waves can promote molecular vibrations with their cavitation effect and vibration, and the mutual collision force between molecules 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 volume heat load high, making up for the lack of high-temperature energy of microwave heating.

[0026] (3) The activated product obtained in step (2) is 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., stirred and washed, filtered and dried to obtain activated carbon. In addition, the collected water washing filtrate is allowed to stand, filtered, recovered, evaporated and concentrated, and can be used to prepare the saturated solution of the activator in step (1).

[0027] The beneficial effects of the present invention are described below through specific embodiments.

[0028] Example 1: Effects of different activation treatment methods on the properties of prepared activated carbon This embodiment discloses a specific method for preparing high-performance activated carbon, comprising the following steps: (1) preparing a saturated solution of an activator, immersing bamboo charcoal powder in the saturated solution of the activator and stirring the mixture to obtain pretreated bamboo charcoal powder, wherein the activator is specifically selected from sodium polyacrylate, and the ratio of sodium polyacrylate to bamboo charcoal starch is 1kg:5kg; The bamboo charcoal powder is obtained according to the following preparation method: the collected flaky bamboo is crushed, and bamboo powder is obtained by passing through a 200-mesh sieve, the bamboo powder is dried, and the dried bamboo powder is transferred to a corundum crucible, and carbonized at 300°C for 2h under the action of a catalyst and a nitrogen atmosphere, and the heating rate is controlled to be 2°C / min to obtain a carbonized product, namely the bamboo charcoal powder.

[0029] (2) The pretreated bamboo charcoal powder obtained in step (1) is moved into an activation furnace, wherein the activation furnace is equipped with microwave heating, ultrasonic heating and electric auxiliary heating. After nitrogen is introduced into the activation furnace for 5 minutes, microwave heating, electric heating and ultrasonic heating are turned on. The microwave power is used to heat the inside of the activation furnace to the temperature required for activation. After reaching the required activation temperature, heating is stopped. In this embodiment, the activation temperature is 800° C. and the activation treatment time is 100 minutes.

[0030] (3) The activated product obtained by the treatment in step (2) is placed in warm water at 50° C., stirred and washed, filtered and dried, to obtain high-performance activated carbon.

[0031] Table 1. Effects of different heating activation treatments on the properties of prepared activated carbon ; Note: “+” indicates that the treatment was performed; “-” indicates that the treatment was not performed.

[0032] Based on the activated carbon preparation method disclosed in Example 1, different heating activation treatment methods were adjusted according to Table 1 to prepare activated carbon. The prepared activated carbon samples were subjected to BET test. In addition, bamboo charcoal powder without any treatment was used as a blank control group a. The results are shown in Table 2.

[0033] Table 2. Results statistics ; Combining from Table 2 Figure 1-Figure 9 It can be seen that the blank control group is bamboo charcoal powder without any treatment, which has poor pore structure characteristics and low specific surface area. 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, ultrasound 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 microwave, ultrasound and electric heating combined with activator (A-1 treatment group) has the best effect on improving the specific surface area of ​​activated carbon. The activation method of microwave, ultrasound and electric heating combined with activator (A-2 to A-4 treatment groups) has a better effect on improving the specific surface area of ​​the prepared activated carbon than the activation method of microwave, ultrasound and electric heating combined with activator alone (A-5 to A-7 treatment groups).

[0034] In addition, the present invention further counted the activated carbon yields of the treatment groups A-1 to A-8, and the activated carbon yields were calculated based on the difference between the mass of the raw material (in this embodiment, the mass of the bamboo charcoal powder) and the mass of the finally prepared activated carbon divided by the mass of the raw material. The results are shown in Table 3.

[0035] Table 3. Activated carbon yields of treatment groups A-1 to A-8 ; As can be seen from Table 3, the activated carbon yield obtained by the A-1 treatment group using microwave heating, electric heating and ultrasonic heating synergistic activation treatment is the best.

[0036] Example 2: Effect of adjustment of different activators on the properties of prepared activated carbon This embodiment provides a specific method for preparing high-performance activated carbon, comprising the following steps: (1) Corn straw carbonized powder was prepared by the same method as in Example 1, and was immersed in a saturated solution of an activator and stirred evenly to obtain pretreated corn straw carbonized powder. The ratio of the activator to the corn straw carbonized powder was 6 kg:10 kg.

[0037] (2) First, nitrogen is introduced into the activation furnace for 10 minutes to exhaust the air in the furnace, and then the pretreated corn straw carbonized powder obtained in step (1) is moved into the activation furnace. The activation furnace is equipped with microwave heating, ultrasonic heating and electric auxiliary heating. The microwave heating, ultrasonic heating and electric auxiliary heating are turned on at the same time to heat the inside of the activation furnace to the required activation temperature. After reaching the required activation temperature, the heating is stopped. The activation temperature is set to 400°C, and the entire activation treatment time is 200 minutes.

[0038] (3) The activated product obtained by the treatment in step (2) is placed in warm water at 50°C, stirred and washed, filtered and dried to obtain activated carbon.

[0039] Table 4. Effect of adjustment of different activators on the properties of prepared activated carbon ; Based on the activated carbon preparation method disclosed in Example 2, different activating agents were adjusted according to Table 4 to prepare activated carbon. The prepared activated carbon samples were subjected to BET test. In addition, the corn straw carbonized powder without any treatment was used as blank control group b. The results are shown in Table 5.

[0040] It should be noted that the preparation steps of the B-10 treatment group, that is, the activated carbon was prepared using water vapor as the activating agent, were different from those of the other treatment groups. The specific differences were: the prepared corn straw carbonized powder was moved into the activation furnace, a water vapor emitter was prepared to ensure that a stable and appropriate amount of water vapor could be provided, microwave heating, ultrasonic heating and electric assisted heating were turned on, and at the same time, the water vapor was controlled to enter the activation furnace to fully contact and react with the carbonized material, and the activation furnace was controlled to heat up from room temperature to 400°C. The entire activation treatment time was 200 minutes.

[0041] Table 5. Result statistics ; It can be seen from Table 5 that under the same preparation method, different activators have different 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. By comparing different polycarboxylic acid activators, it can be seen that the use of polyethyl methacrylate as an activator has the best effect.

[0042] Example 3: Adsorption performance test Methylene blue solutions with concentrations of 1, 2, 3, 4, 5, and 6 mg / L were prepared, and their absorbance was tested at the maximum absorption wavelength of 664 nm, and a standard curve of methylene blue concentration-absorbance was drawn.

[0043] The relationship curve between the absorbance and concentration of methylene blue is: ; Where x is the concentration of methylene blue solution (mg / L) and y is the absorbance.

[0044] Weigh 10 mg of samples from the treatment groups B-1 to B-10 and 10 mg of sample b in the blank control group, respectively, and place them in 50 mL conical flasks, then add 20 mL of 50 mg / L methylene blue solution, shake at room temperature, and when the adsorption equilibrium time is reached, take out and centrifuge, 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 by the formula.

[0045] The adsorption rate of the material is calculated as follows: ; Where C0 is the initial concentration of methylene blue before adsorption (mg / L); C1 is the concentration of methylene blue solution at adsorption equilibrium (mg / L).

[0046] The adsorption rates of samples in treatment groups B-1 to B-10 and the blank control group b are shown in Table 6.

[0047] Table 6. Adsorption rate of samples in treatment groups B-1 to B-10 and blank control group b ; It can be seen from Table 3 that compared with the blank control group b, the adsorption rates of methylene blue by activated carbon prepared using different activators are all above 85%, and the adsorption rate of methylene blue by activated carbon prepared using polyethyl methacrylate as an activating agent can reach more than 99%, achieving better adsorption performance.

[0048] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which 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 by microwave heating, electric heating and ultrasonic heating; wherein the activator is a polycarboxylic acid activator, and the polycarboxylic acid activator is one of polycarboxylates or polycarboxylic acid acrylic polymers.

2. A high performance activated carbon according to claim 1, characterized in that: The raw material for preparing the activated carbon is any one of biomass, biochar or coke.

3. A high performance activated carbon according to claim 1, characterized in that: The polycarboxylic acid acrylic polymer is polymethyl methacrylate or polyethyl methacrylate.

4. A high performance activated carbon according to claim 1, characterized in that: The polycarboxylate is sodium polyacrylate or calcium polyacrylate.

5. A method for preparing high-performance activated carbon according to any one of claims 1 to 4, 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.

6. The method for preparing high-performance activated carbon according to claim 5, 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).

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

8. The method for preparing high-performance activated carbon according to claim 5, 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.

9. The method for preparing high-performance activated carbon according to claim 5, 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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