A method for preparing renewable magnetic porous carbon adsorbent materials

Abstract

This invention discloses a method for preparing renewable magnetic porous carbon adsorbent materials. Biomass carbon source is crushed and dried to obtain biomass carbon powder. FeCl3·6H2O is dissolved in ethylene glycol, NaAc is added, and then the mixture is transferred to a polytetrafluoroethylene (PTFE) reactor where the biomass carbon powder is added for high-temperature reaction. After separation, cleaning, and drying, the mixture is heat-treated under a protective atmosphere to form a biomass carbonized material. This biomass carbonized material is then ball-milled and activated to obtain a magnetic porous carbon adsorbent material, which can effectively remove pollutants. This method is not only low-cost and environmentally friendly, but the prepared magnetic porous carbon material also possesses a reasonable pore size structure, high specific surface area, and excellent magnetic properties, making it suitable for the adsorption and treatment of various pollutants. This invention uses biomass carbon source as raw material, which is low-cost and renewable. The entire preparation process does not require the use of large amounts of chemicals, reducing wastewater discharge and conforming to the concept of green chemistry.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of porous carbon adsorbent materials for environmental protection, and specifically relates to a method for preparing magnetic porous carbon adsorbent materials. Background Technology

[0002] With rapid industrialization and urbanization, pollutants such as heavy metals have posed a serious threat to the environment and human health. Heavy metal pollutants are not only difficult to degrade but can also accumulate in organisms, leading to various health problems. Traditional adsorption materials, such as activated carbon and resins, can remove these pollutants to some extent, but they suffer from limited adsorption capacity, regeneration difficulties, and high costs. Therefore, developing a highly efficient, renewable, and low-cost adsorption material is of great significance for environmental protection and human health.

[0003] Porous carbon materials have attracted widespread attention due to their high specific surface area, excellent adsorption performance, and good chemical stability. However, traditional porous carbon material preparation processes often require the use of large amounts of chemicals, which are not only costly but may also cause secondary pollution to the environment. In addition, ordinary porous carbon materials are difficult to effectively separate and recover after adsorption, limiting their widespread application in practice.

[0004] To overcome these challenges, researchers have begun exploring the use of biomass carbon sources as raw materials to prepare porous carbon materials. Biomass carbon sources are not only inexpensive and renewable, but their preparation processes are also generally more environmentally friendly. However, most porous carbon materials prepared using biomass carbon sources currently lack magnetism, which limits their application in adsorption treatment to some extent. Therefore, endowing porous carbon materials with magnetism and achieving rapid recovery and regeneration of adsorbent materials through magnetic separation technology is of great significance for significantly reducing usage costs and improving treatment efficiency.

[0005] Chinese patent application 201410128911.2 discloses a method for preparing agricultural biomass carbon-based magnetic adsorbent materials. This method uses agricultural biomass derived from plant organisms as raw material, employing a loading process involving ultrasonic blending of ferric ions and biomass, alkaline precipitation, and a low-temperature hydrothermal carbonization and magnetization process to obtain magnetic bio-carbon adsorbent materials. This method not only simultaneously achieves the preparation and magnetization of carbon adsorbent materials, but also utilizes widely available and inexpensive raw materials. However, the method requires ultrasonic treatment for 0.5-2 hours, resulting in prolonged exposure to a high-noise environment, which may be detrimental to the health of laboratory personnel.

[0006] Therefore, this invention aims to provide a method for synthesizing magnetic porous carbon materials using biomass carbon sources as raw materials through specific heat treatment and loading processes. This method is not only low-cost and environmentally friendly, but also produces magnetic porous carbon materials with excellent performance, suitable for the adsorption and treatment of various pollutants. Summary of the Invention

[0007] The purpose of this invention is to address the problem that most porous carbon materials prepared from biomass carbon sources lack magnetic properties. Existing methods for preparing porous carbon adsorbent materials suffer from technical difficulties such as the use of large amounts of chemicals, which increases production costs, leads to environmental pollution, and makes it difficult to effectively separate and recycle the adsorbed pollutants. Furthermore, the preparation of agricultural biomass carbon-based magnetic adsorbent materials is subject to high ultrasonic noise hazards. This invention provides a green and environmentally friendly method for preparing renewable magnetic porous carbon adsorbent materials with excellent magnetic properties, pore structure, and high specific surface area.

[0008] To address the above problems, this invention provides a method for preparing a renewable magnetic porous carbon adsorbent material, which is implemented using the following process:

[0009] (1) Preparation of biochar: Biomass carbon source is selected as raw material and obtained by crushing and drying to obtain biomass carbon powder. The particle size of biomass carbon powder is controlled in the range of 2-20μm.

[0010] (2) Loading of magnetic materials: Take an appropriate amount of FeCl3·6H2O and completely dissolve it in ethylene glycol. Then add an appropriate amount of NaAc and stir to obtain a uniform yellow solution. Then transfer the yellow solution to a polytetrafluoroethylene reactor. Add the biomass carbon powder from step (1) to the reactor, stir evenly, and heat to 180-280℃ for high-temperature reaction. After the reaction is completed, cool to room temperature, separate by centrifugation and wash three times with ethanol and deionized water, and then place in a vacuum drying oven for drying. Then heat the dried product in a protective atmosphere to 600℃-800℃ for heat treatment to carbonize the biomass and form a biomass carbonized material with a preliminary porous structure.

[0011] (3) Activation of porous carbon: The biomass carbonization material obtained in step (2) is ball-milled, and the particle size of the ball-milled product is controlled within the range of 1-15 micrometers; the ball-milled product is activated in a carbon dioxide atmosphere at a temperature of 800℃-1000℃ to obtain a magnetic porous carbon adsorption material product.

[0012] Preferably, the preparation method of the renewable magnetic porous carbon adsorbent material of the present invention further includes the following steps:

[0013] S1 parameter test: The pore structure of the prepared magnetic porous carbon adsorbent material was tested, including specific surface area, total pore volume, and average pore diameter.

[0014] S2 Application Effect Test: The adsorption performance of the prepared magnetic porous carbon material was tested, including adsorption capacity, adsorption rate, selectivity, recovery rate and cycle performance.

[0015] S3 Optimization Control: Based on the test results of S1 and S2, the relevant technical parameters of the control steps (1), (2), and (3) are further optimized to finally produce a product with a specific surface area >1250m². 2 / g, total pore volume >0.52cm³ 3 / g of magnetic porous carbon adsorption material products.

[0016] Preferably, in step (1), the drying process is drying at 60-100℃ for 18-24 hours; the biomass carbon source includes, but is not limited to, coconut shell, straw, rice husk, wood, bamboo, sugarcane bagasse, nut shell, wheat starch, and corn starch; in step (2), the protective atmosphere is nitrogen or argon.

[0017] Preferably, in step (2), the mass ratio of FeCl3·6H2O to NaAc is 1:

[0018] (1.5-4.5), the mass ratio of FeCl3·6H2O to ethylene glycol is 1:(30-40), the mass ratio of FeCl3·6H2O to biomass carbon source is 1:(1-5); the high-temperature reaction time is 8-15h; the vacuum drying conditions are drying at 60-100℃ for 6-10h; the dried product is heat-treated in a nitrogen protective atmosphere by gradually raising the temperature to 600℃-800℃ for 1.5-2.5h.

[0019] Preferably, in step (3), the ball milling conditions are 200-400 rpm for 1-5 min; the activation temperature is 850℃-950℃ and the activation time is 8-15 h.

[0020] Preferably, in step (2), the mass ratio of FeCl3·6H2O to NaAc is 1:

[0021] (2.5-3.5), the mass ratio of FeCl3·6H2O to ethylene glycol is 1:(33-39), the mass ratio of FeCl3·6H2O to biomass carbon source is 1:(1-2), the high-temperature reaction time is 8-15h, the vacuum drying conditions are drying at 60-100℃ for 6-10h, and the dried product is heat-treated at 650℃-750℃ in a nitrogen protective atmosphere for 1.5-2.5h by gradually raising the temperature to 650℃-750℃; in step (3), the ball milling conditions are treatment at 200-400rpm for 1-5min, the activation temperature is 850℃-950℃, and the activation time is 8-15h.

[0022] Further, in step (2), the high-temperature reaction temperature is 180-230℃, the high-temperature reaction time is 9-12h, the vacuum drying conditions are drying at 60-100℃ for 6-10h, and the heat treatment time is 1.8-2.5h; in step (3), the activation temperature is 890℃-900℃, and the activation time is 11-13h.

[0023] Further, in step (2), the dried product is heated to 150°C at 5°C / min in a nitrogen atmosphere and held for 30 min, then heated to 450°C at 1°C / min and held for 2 h, and then heated to 700°C at 5°C / min and held for 2 h.

[0024] Compared with the prior art, the preparation method of the renewable magnetic porous carbon adsorbent material of the present invention has the following beneficial effects:

[0025] (1) Low cost: Biomass carbon source is used as raw material, which is low cost and renewable.

[0026] (2) Environmentally friendly: The entire preparation process does not require the use of a large number of chemical reagents, reducing wastewater discharge and conforming to the concept of green chemistry.

[0027] (3) Excellent performance: The prepared renewable magnetic porous carbon material has a reasonable pore size structure, high specific surface area and excellent magnetic properties, with a specific surface area generally ranging from 1250 to 2000 m². 2 The total pore volume is generally in the range of 0.51-0.83 cm³ / g. 3 The average pore size is between 1.60 and 1.82 nm; the prepared renewable magnetic porous carbon material is suitable for the adsorption and treatment of various heavy metal ion pollutants, and is effective for Cr in wastewater. 6+ Cd 2+ Pb 2+ Cu 2+ It has a good adsorption effect on heavy metal ions, especially Cr 6+ The removal rate is as high as 75% or more, and it is effective against Cd. 2+ The removal rate is as high as 80% or more, for Pb 2+ The removal rate is as high as 85% or more, for Cu 2+ The removal rate is as high as 91% or more.

[0028] (4) Easy to recycle and regenerate: After loading magnetic materials onto porous carbon materials, the adsorption materials can be quickly recycled and reused through magnetic separation technology, reducing the cost of use. Detailed Implementation

[0029] To describe the present invention, the preparation method of a renewable magnetic porous carbon adsorbent material according to the present invention will be further described in detail below with reference to embodiments. However, the present invention is not limited to the embodiments.

[0030] Example 1

[0031] A suitable amount of soybean straw was crushed using a crusher and screened through a 5000-mesh sieve. The straw that passed through the sieve was dried at 100℃ for 18 hours. 2.6g of FeCl3·6H2O was completely dissolved in 80mL of ethylene glycol, and then 7.2g of NaAc was added. After stirring, a uniform yellow solution was obtained. The solution was then transferred to a 100mL polytetrafluoroethylene reactor. 4g of dried straw powder was added to the reactor, and the mixture was stirred until homogeneous. The mixture was then reacted at 200℃ for 10 hours. After cooling to room temperature, the mixture was centrifuged and washed three times with ethanol and deionized water. It was then dried in a 60℃ vacuum drying oven for 6 hours. The product was then heated in a nitrogen atmosphere to 150℃ at 5℃ / min and held for 30 minutes. Then, the temperature was increased to 450℃ at 1℃ / min and held for 2 hours. Finally, the temperature was increased to 700℃ at 5℃ / min and held for 2 hours. The mixture was then allowed to cool naturally to room temperature. At this point, the Fe3O4-loaded biochar had initially formed a porous structure. 1 g of the carbonized product was ball-milled at 300 rpm for 2 min, and then activated under a carbon dioxide atmosphere. The activation program was as follows: temperature increased to 850℃ at a rate of 5℃ / min, held for 12 h, and gas flow rate was 100 mL / min. The specific surface area of ​​the activated sample was measured to be 1257 m² / g. 2 / g, total pore volume 0.525cm³ 3 / g, average pore size 1.67nm. Take 1.0g of the activated product and add it to 50mL of Cr containing 10mg / L. 6+ In a solution, Cr was adsorbed by shaking at 150 rpm for 30 min at room temperature. 6+ The removal rate was 75%. After separating the adsorbent from the solution using a magnet, the adsorbent was desorbed in pure water. The adsorbent was recovered, and the adsorption-desorption process was repeated 5 times. Cr 6+ The removal rate was 67%.

[0032] Example 2

[0033] A suitable amount of bamboo stalks was crushed using a shredder and screened through a 2000-mesh sieve. The straw that passed through the sieve was dried at 100℃ for 18 hours. 3.0g of FeCl3·6H2O was completely dissolved in 100mL of ethylene glycol, and then 8.0g of NaAc was added. After stirring, a uniform yellow solution was obtained. The solution was then transferred to a 150mL polytetrafluoroethylene reactor. 3.0g of dried wood powder was added to the reactor, and the mixture was stirred until homogeneous. The mixture was then reacted at 200℃ for 10 hours. After cooling to room temperature, the mixture was centrifuged and washed three times with ethanol and deionized water. It was then dried in a 60℃ vacuum drying oven for 6 hours. The product was then heated in a nitrogen atmosphere to 150℃ at a rate of 5℃ / min and held for 30 minutes. Then, the temperature was increased to 450℃ at a rate of 1℃ / min and held for 2 hours. Finally, the temperature was increased to 700℃ at a rate of 5℃ / min and held for 2 hours. The mixture was then allowed to cool naturally to room temperature. At this point, the Fe3O4-loaded biochar had initially formed a porous structure. One g of the carbonized product was ball-milled at 300 rpm for 3 min, and then activated under a carbon dioxide atmosphere. The activation program was as follows: temperature increased to 870℃ at a rate of 5℃ / min, held for 12 h, and gas flow rate was 100 mL / min. The activated sample had a specific surface area of ​​1374 m². 2 / g, total pore volume 0.553cm³ 3 / g, average pore size 1.61nm. Take 1.0g of the activated product and add it to 50mL of a solution containing 10mg / L Cd. 2+ In the solution, adsorption was carried out by shaking at 150 rpm for 30 min at room temperature. 2+ The removal rate was 81%. After separating the adsorbent from the solution using a magnet, the adsorbent was desorbed in pure water. The adsorption-desorption process was repeated 5 times after recovering the adsorbent. 2+ The removal rate was 73%.

[0034] Example 3

[0035] Take an appropriate amount of nut shells and crush them using a crusher. Screen the shells through a 1000-mesh sieve and dry the sieved straw at 100℃ for 10 hours. Dissolve 4.2g of FeCl3·6H2O completely in 130mL of ethylene glycol, then add an appropriate amount of 11.1g of NaAc. Stir to obtain a uniform yellow solution. Transfer the solution to a 200mL polytetrafluoroethylene reactor. Add 4.5g of dried straw powder to the reactor, stir evenly, and react at 200℃ for 10 hours. After cooling to room temperature, centrifuge and wash three times with ethanol and deionized water. Dry in a 60℃ vacuum drying oven for 6 hours. Then, in a nitrogen atmosphere, heat the product to 150℃ at 5℃ / min and hold for 30 minutes, then heat to 450℃ at 1℃ / min and hold for 2 hours, then heat to 700℃ at 5℃ / min and hold for 2 hours. Finally, allow it to cool naturally to room temperature. At this point, the Fe3O4-loaded biochar has initially formed a porous structure. One g of the carbonized product was ball-milled at 300 rpm for 1 min, followed by activation under a carbon dioxide atmosphere. The activation program involved increasing the temperature to 890℃ at a rate of 5℃ / min and holding for 12 h, with a gas flow rate of 100 mL / min. The activated sample had a specific surface area of ​​1699 m². 2 / g, total pore volume 0.72cm³ 3 / g, average pore size 1.69nm. Take 1.0g of the activated product and add it to 50mL of a solution containing 10mg / L Pb. 2+ In a solution, Pb was adsorbed by shaking at 150 rpm for 30 min at room temperature. 2+ The removal rate was 86%. After separating the adsorbent from the solution using a magnet, the adsorbent was desorbed in pure water. The adsorption-desorption process was repeated 5 times after recovering the adsorbent. 2+ The removal rate was 78%.

[0036] Example 4

[0037] An appropriate amount of corn starch was crushed using a crusher and sieved through a 1000-mesh screen. The starch passing through the sieve was dried at 100℃ for 8 hours. 3.5g of FeCl3·6H2O was completely dissolved in 110mL of ethylene glycol, and then 11.3g of NaAc was added. After stirring, a uniform yellow solution was obtained. The solution was then transferred to a 150mL polytetrafluoroethylene reactor. 5.0g of dried straw powder was added to the reactor, and the mixture was stirred until homogeneous. The mixture was then reacted at 200℃ for 10 hours. After cooling to room temperature, the mixture was centrifuged and washed three times with ethanol and deionized water. It was then dried in a 60℃ vacuum drying oven for 6 hours. The product was then heated in a nitrogen atmosphere to 150℃ at 5℃ / min and held for 30 minutes. Then, the temperature was increased to 450℃ at 1℃ / min and held for 2 hours. Finally, the temperature was increased to 700℃ at 5℃ / min and held for 2 hours. The mixture was then allowed to cool naturally to room temperature. At this point, the Fe3O4-loaded biochar had initially formed a porous structure. 2.0 g of the carbonized product was ball-milled at 200 rpm for 1 min, and then activated under a carbon dioxide atmosphere. The activation program was as follows: heating to 900℃ at a rate of 5℃ / min and holding for 12 h, with a gas flow rate of 100 mL / min. The specific surface area of ​​the activated sample was measured to be 1932 m². 2 / g, total pore volume 0.818cm³ 3 / g, average pore size 1.81nm. Take 1.0g of the activated product and add it to 50mL of Cu containing 10mg / L. 2+ In the solution, Cu was adsorbed by shaking at 150 rpm for 30 min at room temperature. 2+ The removal rate was 92%. After separating the adsorbent from the solution using a magnet, the adsorbent was desorbed in pure water. The adsorbent was recovered, and the adsorption-desorption process was repeated 5 times. Cu 2+ The removal rate was 86%.

[0038] The pore structure of the porous carbon materials (Table 1) prepared by bio-carbon as carbon source in the above embodiments was detected, and the adsorption performance was verified. The results are shown in Tables 2 and 3.

[0039] Table 1. Distribution ratios of each group in Examples 1-4

[0040]

[0041]

[0042] Table 2 Pore structure parameters of porous carbon materials in Examples 1-4 of the present invention

[0043]

[0044] Table 3 Adsorption performance of porous carbon materials in Examples 1-4 of the present invention

[0045] project pollutants Initial concentration / mg / L Removal rate / % Removal rate after 5 cycles / % Example 1 <![CDATA[Cr 6+ ]]> 10 75 67 Example 2 <![CDATA[Cd 2+ ]]> 10 81 73 Example 3 <![CDATA[Pb 2+ ]]> 10 86 78 Example 4 <![CDATA[Cu 2+ ]]> 10 92 86

Claims

1. A method for preparing a renewable magnetic porous carbon adsorbent material, characterized in that... The following process is adopted: (1) Preparation of biochar: Biomass carbon source is selected as raw material and obtained by crushing and drying to obtain biomass carbon powder. The particle size of biomass carbon powder is controlled in the range of 2-20μm. (2) Loading of magnetic materials: Take an appropriate amount of FeCl3·6H2O and completely dissolve it in ethylene glycol. Then add an appropriate amount of NaAc and stir to obtain a uniform yellow solution. Then transfer the yellow solution to a polytetrafluoroethylene reactor. Add the biomass carbon powder from step (1) to the reactor, stir evenly, and heat to 180-280℃ for high-temperature reaction. After the reaction is completed, cool to room temperature, separate by centrifugation and wash three times with ethanol and deionized water, and then place in a vacuum drying oven for drying. Then heat the dried product in a protective atmosphere to 600℃-800℃ for heat treatment to carbonize the biomass and form a biomass carbonized material with a preliminary porous structure. (3) Activation of porous carbon: The biomass carbonization material obtained in step (2) is ball-milled, and the particle size of the ball-milled product is controlled within the range of 1-15 micrometers; the ball-milled product is activated in a carbon dioxide atmosphere at a temperature of 800℃-1000℃ to obtain a magnetic porous carbon adsorption material product.

2. The method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 1, characterized in that... It also includes the following steps: S1 parameter test: The pore structure of the prepared magnetic porous carbon adsorbent material was tested, including specific surface area, total pore volume, and average pore diameter. S2 Application Effect Test: The adsorption performance of the prepared magnetic porous carbon material was tested, including adsorption capacity, adsorption rate, selectivity, recovery rate and cycle performance. S3 Optimization Control: Based on the test results of S1 and S2, the relevant technical parameters of the control steps (1), (2), and (3) are further optimized to finally produce a product with a specific surface area >1250m². 2 / g, total pore volume >0.52cm³ 3 / g of magnetic porous carbon adsorption material products.

3. The method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 1 or 2, characterized in that: In step (1), the drying process is to dry at 60-100℃ for 18-24 hours.

4. The method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 1 or 2, characterized in that: In step (1), the biomass carbon source includes, but is not limited to, coconut shell, straw, rice husk, wood, bamboo, sugarcane bagasse, nut shell, wheat starch, and corn starch; in step (2), the protective atmosphere is nitrogen or argon.

5. A method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 1 or 2, characterized in that: In step (2), the mass ratio of FeCl3·6H2O to NaAc is 1:(1.5-4.5), the mass ratio of FeCl3·6H2O to ethylene glycol is 1:(30-40), and the mass ratio of FeCl3·6H2O to biomass carbon source is 1:(1-5).

6. A method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 1 or 2, characterized in that: In step (2), the high-temperature reaction time is 8-15h; the vacuum drying conditions are drying at 60-100℃ for 6-10h; the dried product is heat-treated in a nitrogen protective atmosphere by gradually raising the temperature to 600℃-800℃ for 1.5-2.5h; in step (3), the ball milling conditions are processing at 200-400rpm for 1-5min; the activation temperature is 850℃-950℃, and the activation time is 8-15h.

7. The method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 3, characterized in that: In step (1), the biomass carbon source includes, but is not limited to, coconut shell, straw, rice husk, wood, bamboo, sugarcane bagasse, nut shell, wheat starch, and corn starch; in step (2), the mass ratio of FeCl3·6H2O to NaAc is 1:(1.5-4.5), the mass ratio of FeCl3·6H2O to ethylene glycol is 1:(30-40), and the mass ratio of FeCl3·6H2O to biomass carbon source is 1:(1-5); in step (2), the high-temperature reaction time is 8-15h, the vacuum drying conditions are drying at 60-100℃ for 6-10h, and the dried product is heat-treated in a nitrogen protective atmosphere by gradually raising the temperature to 600℃-800℃ for 1.5-2.5h; in step (3), the ball milling conditions are treatment at 200-400rpm for 1-5min; the activation temperature is 850℃-950℃, and the activation time is 8-15h.

8. The method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 7, characterized in that: In step (2), the mass ratio of FeCl3·6H2O to NaAc is 1:(2.5-3.5), the mass ratio of FeCl3·6H2O to ethylene glycol is 1:(33-39), the mass ratio of FeCl3·6H2O to biomass carbon source is 1:(1-2), the high-temperature reaction time is 8-15h, the vacuum drying conditions are drying at 60-100℃ for 6-10h, and the dried product is heat-treated at 650℃-750℃ in a nitrogen protective atmosphere for 1.5-2.5h by gradually raising the temperature; in step (3), the ball milling conditions are processing at 200-400rpm for 1-5min, the activation temperature is 850℃-950℃, and the activation time is 8-15h.

9. The method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 8, characterized in that: In step (2), the high-temperature reaction temperature is 180-230℃ and the high-temperature reaction time is 9-12h, the vacuum drying conditions are drying at 60-100℃ for 6-10h, and the heat treatment time is 1.8-2.5h; in step (3), the activation temperature is 890℃-900℃ and the activation time is 11-13h.

10. The method for preparing a renewable magnetic porous carbon adsorbent material as described in claim 9, characterized in that: In step (2), the dried product is heated to 150°C at 5°C / min in a nitrogen atmosphere and held for 30 min, then heated to 450°C at 1°C / min and held for 2 h, and then heated to 700°C at 5°C / min and held for 2 h.

Images