Amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds, method of preparation and use thereof

Abstract

This invention provides an amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds, its preparation method, and its application, belonging to the field of water treatment technology. The preparation method includes: ultrasonically dispersing and reacting hydrophilic activated carbon and an amino modifier in a solvent, followed by washing and drying to obtain amino-functionalized activated carbon; wherein the amino modifier is selected from 3-aminopropyltrimethoxysilane.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and particularly relates to an amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds, its preparation method, and its application. Background Technology

[0002] Perfluorinated and polyfluoroalkyl substances (PFAS) are a class of synthetic persistent organic pollutants. Their molecular structure consists of stable hydrophobic fluorinated alkyl chains and hydrophilic end groups, leading to their widespread distribution in the environment and difficulty in degradation, posing a serious threat to ecosystems and human health. Among existing water treatment technologies, activated carbon adsorption is considered an effective means of deep removal of PFAS due to its advantages such as high specific surface area, abundant pore structure, and simple operation. However, the adsorption of PFAS by ordinary activated carbon mainly relies on hydrophobic interactions, but it has poor selectivity and low adsorption capacity for short-chain PFAS, which are more hydrophilic and have higher mobility, making it difficult to achieve synergistic and efficient removal of multiple types of long-chain and short-chain PFAS in complex water bodies.

[0003] To improve the adsorption performance of activated carbon for PFAS, surface functionalization modification, such as amino modification, has become a research focus. Although amino modification has improved the adsorption capacity for long-chain PFAS to some extent, it still has certain limitations, such as: the modification process is relatively complex and difficult to control, with poor reproducibility, which is not conducive to large-scale applications; after modification, it is easy to block the original pores of activated carbon, reducing the specific surface area and pore volume of activated carbon, which has an adverse effect on adsorption; the modified activated carbon is still hydrophobic, with insufficient affinity for short-chain PFAS, and cannot competitively adsorb PFAS of different chain lengths.

[0004] Therefore, developing a modified activated carbon that can simultaneously retain the specific surface area and pore volume of activated carbon, achieve uniform modification of surface functional groups, and possess both hydrophilic properties and high-efficiency adsorption capacity is of great significance for achieving efficient and stable removal of PFAS with different chain lengths from water. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds, its preparation method, and its applications, aiming to at least partially solve the above-mentioned technical problems. The technical solution provided by this invention is as follows.

[0006] As a first aspect of the present invention, a method for preparing amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds is provided, comprising: ultrasonically dispersing and reacting hydrophilic activated carbon and an amino modifier in a solvent, and then washing and drying to obtain amino-functionalized activated carbon; wherein the amino modifier is selected from 3-aminopropyltrimethoxysilane.

[0007] As a second aspect of the present invention, an amino-functionalized activated carbon prepared by the above-described preparation method is provided.

[0008] As a third aspect of the present invention, an application of the above-described amino-functionalized activated carbon in the adsorption of perfluorinated compounds is provided.

[0009] Based on the above technical solution, the amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds, its preparation method, and its application provided by the present invention have at least one of the following beneficial effects:

[0010] (1) In the technical solution of this invention, the surface of the hydrophilic activated carbon is rich in hydroxyl groups, which can provide sufficient adsorption sites for the loading of siloxanes in the subsequent amino modifier. Further aided by ultrasonic hydrolysis, grafting, and dispersion processes, the amino modifier is fully hydrolyzed and grafted and condensed with the hydrophilic activated carbon uniformly dispersed in the solvent. This process maximizes the preservation of the high specific surface area and pore structure advantages of the activated carbon while successfully grafting a high density of amino functional groups onto the activated carbon surface, forming a uniform and dense amino functionalized layer. Furthermore, it significantly shortens the grafting reaction time. The method for preparing amino-functionalized activated carbon in this invention is relatively simple, highly reproducible, can be mass-produced, and is inexpensive.

[0011] (2) In the technical solution of this invention, an amino-modifying agent is used for modification, followed by ultrasonic-assisted hydrolysis and dispersion. This results in amino-functionalized activated carbon with a rich pore structure and uniformly distributed amino groups grafted onto its surface. When applied to water treatment containing perfluorinated compounds, the synergistic mechanism of electrostatic and hydrophobic interactions enables the synergistic removal of PFAS of different chain lengths. This effectively solves the technical problem of low adsorption efficiency and easy desorption of short-chain perfluorinated compounds during the competitive adsorption process between long-chain and short-chain perfluorinated compounds. In addition, due to the unique amino surface and pore size distribution of amino-functionalized activated carbon, it has a strong ability to resist interference from environmental background matrix. At the same time, it has excellent adsorption capacity and separation efficiency for PFAS of different chain lengths, providing an economical and reliable solution for the removal of PFAS in actual water bodies. Attached Figure Description

[0012] Figure 1 This is a zeta potential diagram of amino-functionalized activated carbon NH2-AC-120 in Example 1 of the present invention;

[0013] Figure 2 The dispersion comparison diagram shows the unmodified activated carbon (AC) and the amino-functionalized activated carbon NH2-AC-120 in Example 1.

[0014] Figure 3The graph shows the removal effect of unmodified activated carbon (AC) and amino-functionalized activated carbon NH2-AC-120 in Example 1 on perfluorohexanoic acid (PFHxA).

[0015] Figure 4 The graph shows the adsorption effect of different amino modifiers on perfluorooctanoic acid (PFOA) in this invention.

[0016] Figure 5 This is an adsorption kinetic curve of perfluorooctanoic acid (PFOA) on amino-functionalized activated carbon NH2-AC-120 in Example 1 of the present invention.

[0017] Figure 6 This is the adsorption isotherm diagram of perfluorooctanoic acid by amino-functionalized activated carbon NH2-AC-120 in Example 1 of the present invention;

[0018] Figure 7 This is a diagram showing the competitive effect of dissolved organic matter (DOM) on the adsorption of PFOA by amino-functionalized activated carbon NH2-AC-120 in Example 1.

[0019] Figure 8 This is a diagram showing the competitive adsorption effect of amino-functionalized activated carbon NH2-AC-120 on perfluorinated compounds of different chain lengths in Example 1 of the present invention. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0021] In implementing this invention, it was discovered that while ordinary activated carbon can effectively remove long-chain PFAS through hydrophobic interactions, it is almost ineffective against short-chain PFAS, which are more hydrophilic and have higher mobility. Currently, to improve the adsorption performance of activated carbon for PFAS, amino-based surface modification is often employed to enhance the positive charge on the activated carbon surface, thereby strengthening the electrostatic interaction with the hydrophilic ends of PFAS and thus improving the adsorption performance of activated carbon for PFAS. Common amino-based surface functionalization modification methods include: in-situ synthesis of adsorbent materials containing quaternary ammonium groups or amino groups using polymer monomers, or modification of the activated carbon surface using aminosilane modifiers. Although the above methods have improved the adsorption capacity of long-chain PFAS to some extent, they still have significant limitations. For example, polymer modification usually requires complex synthesis steps and takes a long time; the degree of polymerization and grafting is difficult to control precisely, resulting in low reproducibility and hindering large-scale application; secondly, polymer reactions can easily clog the original pores of activated carbon, causing a reduction in specific surface area and pore volume, which adversely affects the adsorption performance of PFAS; finally, most modified activated carbon surfaces are still hydrophobic, lacking sufficient affinity for highly water-soluble short-chain PFAS, and cannot effectively cope with the challenges posed by the competitive adsorption of PFAS of different chain lengths in actual water bodies.

[0022] To address this issue, the present invention provides an amino-functionalized activated carbon with high mesoporousness and high hydrophilicity, along with its preparation method and applications. This invention aims to solve the problems caused by traditional amino-functionalization modification processes, such as reduced specific surface area of ​​activated carbon, uneven amino distribution, insufficient affinity for highly water-soluble short-chain PFAS, and low removal rate.

[0023] Specifically, the method for preparing amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds provided by the present invention includes: ultrasonically dispersing and reacting hydrophilic activated carbon and an amino modifier in a solvent, followed by washing and drying to obtain amino-functionalized activated carbon; wherein the amino modifier is selected from 3-aminopropyltrimethoxysilane (APTMS).

[0024] In the embodiments of this invention, the surface of the hydrophilic activated carbon is rich in hydroxyl groups, which can provide sufficient adsorption sites for the loading of siloxanes in the amino modifier. Room temperature ultrasonication achieves uniform dispersion of the activated carbon in the solvent, while simultaneously promoting the orderly hydrolysis of 3-aminopropyltrimethoxysilane (APTMS) as the amino functional modifier in the solvent. This hydrolysis leads to uniform and dense condensation on the hydroxyl-rich activated carbon surface, successfully grafting a high density of amino functional groups onto the activated carbon surface, forming a uniform and dense amino functionalized layer. This significantly shortens the grafting reaction time and maximizes the preservation of the activated carbon's high specific surface area and mesoporous structure advantages. The method for preparing amino-functionalized activated carbon according to this invention is simple and efficient, with mild reaction conditions and controllable grafting, high reproducibility, and can be mass-produced at a low cost.

[0025] According to embodiments of the present invention, hydrophilic activated carbon and an amino modifier are ultrasonically dispersed and reacted in a solvent, comprising: dispersing the hydrophilic activated carbon carrier and surface functionalizing the amino modifier. Specifically, the hydrophilic activated carbon is first dispersed in a solvent and ultrasonically treated to form a uniform dispersion; then the amino modifier is added to the dispersion and the ultrasonic reaction continues. The hydrophilic activated carbon can be sourced from at least one of wood, coconut shell, and coal-based activated carbon, and other sources are also acceptable, not limited to the foregoing limitations; the hydrophilic activated carbon can be in powder form. The solvent includes n-hexane; the volume ratio of the amino modifier (e.g., APTMS) to the dispersion is 1-3:2500, preferably 2:2500; the ultrasonic time is 10-60 min, preferably 10-30 min, more preferably 30 min; the temperature is 25-30°C, or room temperature is also acceptable.

[0026] In the embodiments of the present invention, under the aforementioned ultrasonic conditions, the hydrophilic activated carbon can be uniformly dispersed in the solvent, while simultaneously promoting the orderly hydrolysis of the amino modifier in the solvent. Furthermore, the silane in the amino modifier undergoes uniform and dense condensation and stable grafting onto the surface of the hydrophilic activated carbon. This helps the amino modifier regulate the pore structure of the activated carbon during the grafting condensation process, maximizing the retention of the activated carbon's own pore structure and high specific surface area, thus laying the foundation for PFAS adsorption. If the ultrasonic time is too long (e.g., greater than 2 hours), the amino modifier will agglomerate during the grafting process, affecting the pore size distribution and specific surface area of ​​the amino-functionalized activated carbon. If the ultrasonic time is too short, it will affect the grafting amount of the amino modifier and the degree of condensation on the surface of the hydrophilic activated carbon.

[0027] According to an embodiment of the present invention, the washing process includes: cleaning with a mixed solution of ethanol and water, wherein the volume ratio of ethanol to water is 1:1, and the washing can be performed multiple times, with no limitation on the number of washings, in order to remove ungrafted amino modifiers, solvents, etc. from the surface of the amino-functionalized activated carbon.

[0028] According to an embodiment of the present invention, the drying temperature is 80-160°C and the drying time is 12-24 hours. If the drying temperature is too high or the drying time is too long, the amino functionalized layer on the surface of the activated carbon will be damaged.

[0029] As a second aspect of the present invention, an amino-functionalized activated carbon prepared by the above preparation method is provided.

[0030] According to embodiments of the present invention, the water contact angle of the amino-functionalized activated carbon is 10-15°, and the specific surface area of ​​the amino-functionalized activated carbon is 500-750 m². 2 / g, the mesopore volume of amino-functionalized activated carbon accounts for 70%-80% of the total pore volume.

[0031] In the embodiments of the present invention, the amino-functionalized activated carbon material obtained by the above preparation method has a high specific surface area and a highly mesoporous structure. It also has the advantages of strong hydrophilicity and positive surface charge (provided by uniform amino distribution), which is conducive to the adsorption of PFAS on the activated carbon surface and diffusion within the pores. At the same time, based on the size exclusion effect of the activated carbon mesopores, it effectively prevents the entry of larger dissolved organic matter (DOM), thereby avoiding its competition for PFAS adsorption sites.

[0032] As a third aspect of the present invention, the application of the above-mentioned amino-functionalized activated carbon in the adsorption of perfluorinated compounds is provided.

[0033] In the embodiments of the present invention, the amino-functionalized activated carbon material of the present invention achieves efficient removal of PFAS of different chain lengths based on the synergistic mechanism of electrostatic interaction (provided by amino groups) and hydrophobic interaction. Furthermore, due to its unique pore size distribution and high specific surface area, it significantly inhibits the competitive adsorption of dissolved organic matter (DOM) in water, thereby maintaining high selectivity and high removal efficiency for PFAS even in complex water bodies with high background matrix.

[0034] According to embodiments of the present invention, amino-functionalized activated carbon of the present invention is used as the adsorbent material to achieve the adsorption and removal of PFAS under shaking conditions. Specifically, the pH of the adsorption reaction is 6.5±0.5, the adsorption reaction temperature is 25-28℃, preferably 26.5℃; the shaking speed is 120-160 rpm, preferably 140 rpm; and the shaking adsorption reaction time is 4-6 h. The concentration of perfluorinated compounds in the present invention is 1-200 μg / L, the dosage of amino-functionalized activated carbon is 10-30 mg / L, and the removal rate of perfluorinated compounds (PFAS) can reach 99%.

[0035] According to embodiments of the present invention, the perfluorinated compounds include short-chain perfluorinated compounds of C4-C7 and / or long-chain perfluorinated compounds of C7 or above; wherein the perfluorinated compounds are single or mixed perfluorinated carboxylic acid compounds or perfluorinated sulfonic acid compounds.

[0036] In embodiments of the present invention, the amino-functionalized activated carbon material of the present invention can remove long-chain PFAS based on electrostatic and hydrophobic interactions. Furthermore, in mixed perfluorinated compound systems, the amino-functionalized activated carbon material of the present invention can remove short-chain PFAS based on electrostatic adsorption and its unique pore structure, and exhibits excellent selective adsorption performance for short-chain perfluorinated compounds, with a desorption rate of less than 1%.

[0037] To make the objectives, technical solutions, and beneficial effects of this invention more apparent, the technical solutions of this invention are now fully described below. It should be noted that the embodiments described below are exemplary and are only used to explain this invention, but should not be construed as limiting the scope of implementation of this invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods; reagents and materials, unless otherwise specified, are commercially available.

[0038] Example 1

[0039] The preparation method of amino-functionalized activated carbon powder includes the following steps (1) to (3).

[0040] Step (1) Dispersing activated carbon carrier: Add 0.5g of coconut shell powder activated carbon to 249.8mL of n-hexane and sonicate for 30min to make the coconut shell powder activated carbon uniformly dispersed in the n-hexane solvent to form a dispersion.

[0041] Step (2) Amin surface functionalization modification: 0.2 mL of 3-aminopropyltrimethoxysilane (amino modifier) ​​was added to the dispersion in step (1) above and ultrasonically treated for 1 h.

[0042] Step (3) Post-processing steps: After the reaction in step (2) is completed, the solid product is collected by filtration and washed three times with a mixed solution of ethanol and deionized water (volume ratio of 1:1). Then, it is dried in ovens at 80℃, 120℃ and 160℃ for 12h respectively to finally obtain amino-functionalized activated carbon, which is labeled as NH2-AC-80 (80℃), NH2-AC-120 (120℃) and NH2-AC-160 (160℃), respectively. The corresponding water contact angles are 11.5°, 10.4° and 14.2°, respectively; the corresponding specific surface areas are 602 m² and 602 m², respectively. 2 / g、619m 2 / g、585m 2 / g.

[0043] The zeta potential of the obtained amino-functionalized activated carbon NH2-AC-120 was tested to determine its surface electronegativity. The specific test results are as follows: Figure 1 As shown.

[0044] Figure 1 This is a zeta potential diagram of amino-functionalized activated carbon NH2-AC-120 in Example 1 of the present invention.

[0045] like Figure 1As shown, unmodified activated carbon (AC) carries a negative charge in the pH range of 2-10. After amino-functionalization modification, the zeta potential of the obtained amino-functionalized activated carbon material changes from positive to negative with increasing pH, and its isoelectric point appears at pH=4.01. This significant change in charge characteristics confirms the successful grafting of 3-aminopropyltrimethoxysilane, which fundamentally alters the surface charge properties of activated carbon.

[0046] Furthermore, both unmodified activated carbon (AC) and amino-functionalized activated carbon NH2-AC-120 were sonicated for 3 minutes to test their dispersion properties. Specific test results are as follows: Figure 2 As shown.

[0047] Figure 2 This is a comparison diagram of the dispersion of unmodified activated carbon (AC) and amino-functionalized activated carbon NH2-AC-120 from Example 1.

[0048] like Figure 2 As shown, after ultrasonic dispersion for 3 minutes, the suspensions of unmodified activated carbon (AC) and amino-functionalized activated carbon in water exhibited significantly different stability. Unmodified activated carbon (AC) showed significant sedimentation after standing for 24 hours, while amino-functionalized activated carbon NH2-AC-120 (i.e., NH2-AC) maintained a highly dispersed state even after 24 hours of standing. This superior dispersibility is attributed to the enhanced hydrophilicity and steric stabilization effect of the amino groups grafted onto its surface.

[0049] Example 2

[0050] Amino-functionalized coal-based activated carbon powder was prepared using the same method as in Example 1, except that coal-based activated carbon was used and the drying temperature was 80°C. The resulting amino-functionalized coal-based activated carbon was labeled NH2-CAC-80, with a corresponding water contact angle of 10.9° and a specific surface area of ​​593 m². 2 / g.

[0051] To evaluate the removal efficiency of amino-functionalized activated carbon powder for perfluorooctanoic acid (PFOA) compounds, the following test examples were conducted.

[0052] Test Example 1

[0053] Step (1) Preparation of activated carbon stock solution: Weigh 45 mg of unmodified activated carbon (AC) and NH2-AC-80, NH2-AC-120 and NH2-AC-160 from Example 1 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an activated carbon stock solution with a concentration of 4.5 g / L. This stock solution should be prepared fresh for use.

[0054] Step (2) Preparation of activated carbon dispersion: Take 0.2 mL of the stock solution obtained in step (1) above and add it to 44.7 mL of ultrapure water. Sonicate for 3 min to obtain activated carbon dispersion (final concentration: 20 mg / L).

[0055] Step (3) Adsorption experiment: Prepare a PFOA stock solution with a concentration of 90 mg / L. Add 0.1 mL of the PFOA stock solution (final target pollutant concentration: 200 μg / L, pH=6.5) to the dispersion from step (2). Tighten the polypropylene bottle and place it in a constant temperature shaker. Shake the bottle at 26.4℃ and 140 rpm for 2 hours. After the reaction is complete, take a water sample, filter it through a 0.22 μm glass fiber membrane, and then detect the concentration of PFOA using liquid chromatography-mass spectrometry (LC-MS). The specific test results are shown in Table 1.

[0056] Table 1. Removal rate of long-chain PFOA by amino-functionalized activated carbon powder

[0057]

[0058] As shown in Table 1, the activated carbon modified with amino modifier has a higher PFOA removal rate than the unmodified activated carbon, and the highest PFOA removal rate is achieved at a drying temperature of 120℃, indicating that the drying temperature affects the adsorption performance of the obtained amino-functionalized coal-based activated carbon.

[0059] Furthermore, the effect of amino-functionalized activated carbon powder on the removal of short-chain perfluorinated compounds was investigated.

[0060] Test Example 2

[0061] Step (1) Preparation of adsorbent stock solution: Weigh 45 mg of AC and NH2-AC-120 from Example 1 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an adsorbent stock solution with a concentration of 4.5 g / L. The stock solution should be prepared fresh for use.

[0062] Step (2) Preparation of adsorbent dispersion: Take 0.2 mL of the stock solution obtained in step (1) above and add it to 44.7 mL of ultrapure water. Sonicate for 3 min to obtain the adsorbent dispersion (final concentration: 20 mg / L).

[0063] Step (3) Adsorption experiment: Prepare a PFHxA stock solution with a concentration of 22.5 mg / L. Add 0.1 mL of the PFHxA stock solution (final target pollutant concentration: 50 μg / L) to the dispersion from step (2). Tighten the polypropylene bottle and place it in a constant temperature shaker. Shake the bottle at pH=6.5, 26.4℃, and 140 rpm for 6 h. After the reaction is complete, take a water sample, filter it through a 0.22 μm glass fiber membrane, and then detect the concentration of PFOA using liquid chromatography-mass spectrometry (LC-MS). The specific test results are as follows: Figure 3 As shown.

[0064] Figure 3 The graph shows the removal effect of unmodified activated carbon (AC) and amino-functionalized activated carbon NH2-AC-120 in Example 1 on perfluorohexanoic acid (PFHxA).

[0065] like Figure 3 As shown, NH2-AC-120 exhibits superior adsorption capacity and rate for PFHxA compared to AC, indicating that aminosilane modification is an effective strategy for improving the adsorption performance of activated carbon for short-chain perfluorocarboxylic acid pollutants.

[0066] The effects of other amino modifiers on PFOA removal efficiency were further investigated, as detailed in Test Example 3.

[0067] Test Example 3

[0068] The effects of diethylenetriamine (DETA)-aminated graphene oxide powder (DETA-GO), 3-aminopropyltrimethoxysilane-aminated graphene powder (APTMS-rGO), aminated multi-walled carbon nanotubes (NH2-MWCNTs), AC, and NH2-AC-120 from Example 1 on PFOA removal efficiency were investigated. NH2-MWCNTs were prepared by vapor deposition of carboxylated multi-walled carbon nanotubes, which were first modified by amidation and then decarbonized at high temperature.

[0069] Step (1) Preparation of adsorbent stock solution: Weigh 45 mg of AC, NH2-AC-120, DETA-GO, APTMS-rGO and NH2-MWCNTs from Example 1 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an adsorbent stock solution with a concentration of 4.5 g / L. This stock solution should be prepared fresh for each use.

[0070] Step (2) Preparation of adsorbent dispersion: Take 0.2 mL of the stock solution obtained in step (1) above and add it to 44.7 mL of ultrapure water. Sonicate for 3 min to obtain the adsorbent dispersion (final concentration: 20 mg / L).

[0071] Step (3) Adsorption experiment: Prepare a PFOA stock solution with a concentration of 90 mg / L. Add 0.1 mL of the PFOA stock solution (final target pollutant concentration: 200 μg / L, pH=6.5) to the dispersion from step (2). Tighten the polypropylene bottle and place it in a constant temperature shaker. Shake the bottle at 26.4℃ and 140 rpm for 4 hours. After the reaction is complete, take a water sample, filter it through a 0.22 μm glass fiber membrane, and then detect the concentration of PFOA using liquid chromatography-mass spectrometry (LC-MS). The specific test results are as follows: Figure 4 As shown.

[0072] Figure 4 This is a graph showing the effect of different amino modifiers on the adsorption capacity of PFOA in this invention.

[0073] like Figure 4 As shown, under the conditions of an initial PFOA concentration of 200 µg / L, an adsorbent dosage of 20 mg / L, and an adsorption time of 4 h, the adsorption capacities of NH2-MWCNTs, DETA-GO, and APTMS-rGO were 6.6 mg / g, 5.1 mg / g, and 4.3 mg / g, respectively, all significantly lower than the 9.1 mg / g of NH2-AC-120 in Example 1 of this invention. This may be due to their superior pore size distribution and surface chemical properties.

[0074] Furthermore, the effect of the amount of amino-functionalized activated carbon powder on PFOA removal was explored, as detailed in Test Example 4.

[0075] Test Example 4

[0076] Step (1) Preparation of activated carbon stock solution: Weigh 45 mg of NH2-CAC-80 from Example 2 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an activated carbon stock solution with a concentration of 0.45 g / L. The stock solution should be prepared fresh for use.

[0077] Step (2) Prepare activated carbon dispersions of different concentrations:

[0078] Group 1: Take 0.1 mL of the stock solution obtained in step (1) and add it to 44.7 mL of ultrapure water (final concentration: 10 mg / L).

[0079] Group 2: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.6 mL of ultrapure water (final concentration: 20 mg / L).

[0080] Group 3: Take 0.3 mL of the stock solution obtained in step (1) and add it to 44.5 mL of ultrapure water (final concentration: 30 mg / L).

[0081] The amino-functionalized activated carbon was ultrasonically treated for 3 minutes to obtain a dispersion.

[0082] Step (3) Adsorption experiment: Prepare a PFOA stock solution with a concentration of 90 mg / L. Add 0.1 mL of the PFOA stock solution (final target pollutant concentration: 200 μg / L) to each of the different dispersions from step (2). Tighten the polypropylene bottle and place it in a constant temperature shaker. Shake the bottle at 26.4℃ and 140 rpm for 2 hours. After the reaction, take a water sample, filter it through a 0.22 μm glass fiber membrane, and then detect the concentration of PFOA using LC-MS. The specific test results are shown in Table 2.

[0083] Table 2. Removal rate of PFOA by amino-functionalized activated carbon powder at different concentrations

[0084]

[0085] As shown in Table 2, the removal rate of PFOA showed a significant upward trend with the increase of the initial concentration of the adsorbent NH2-CAC-80. When the initial concentration of NH2-CAC-80 was 30 mg / L, the removal rate of PFOA reached 92% after 2 hours of reaction.

[0086] Furthermore, the NH2-AC-120 obtained in Example 1 was subjected to adsorption kinetic experiments to investigate the time required for adsorption equilibrium and the removal rate of PFOA, as detailed in Test Example 5.

[0087] Test Example 5

[0088] Step (1) Preparation of activated carbon stock solution: Weigh 45 mg of NH2-AC-120 from Example 1 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an activated carbon stock solution with a concentration of 4.5 g / L. The stock solution should be prepared fresh for use.

[0089] Step (2) Preparation of activated carbon dispersion: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.7 mL of ultrapure water. Sonicate for 3 min to obtain the activated carbon dispersion (final concentration: 20 mg / L).

[0090] Step (3) Adsorption experiment: Prepare a PFOA stock solution with a concentration of 90 mg / L. Add 0.1 mL of the PFOA stock solution (final target pollutant concentration: 200 μg / L) to the dispersion from step (2). Tighten the polypropylene bottle and place it in a constant temperature shaker. Shake the bottle at 26.4℃ and 140 rpm for 12 h. Take water samples at preset time intervals, filter them through a 0.22 μm glass fiber membrane, and then detect the concentration of perfluorinated compounds using LC-MS. The specific test results are as follows: Figure 5 As shown.

[0091] Figure 5This is an adsorption kinetic curve of perfluorooctanoic acid (PFOA) on amino-functionalized activated carbon NH2-AC-120 in Example 1 of the present invention.

[0092] like Figure 5 As shown, when the initial concentration of PFOA was 200 μg / L and the initial dosage of adsorbent NH2-AC-120 was 20 mg / L, the time required for the reaction to reach adsorption equilibrium was only 4 h. This result indicates that amino-functionalized activated carbon exhibits rapid adsorption kinetics for PFOA.

[0093] Furthermore, the NH2-AC-120 obtained in Example 1 was subjected to an adsorption isotherm experiment to explore the type of interaction force between amino-modified activated carbon powder and PFOA, as specifically in Test Example 6.

[0094] Test Example 6

[0095] Step (1) Preparation of activated carbon stock solution: Weigh 45 mg of NH2-AC-120 from Example 1 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an activated carbon stock solution with a concentration of 4.5 g / L. The stock solution should be prepared fresh for use.

[0096] Step (2) Prepare activated carbon dispersions of different concentrations:

[0097] Group 1: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.75 mL of ultrapure water (final concentration: 20 mg / L).

[0098] Group 2: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.7 mL of ultrapure water (final concentration: 20 mg / L).

[0099] Group 3: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.6 mL of ultrapure water (final concentration: 20 mg / L).

[0100] Group 4: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.5 mL of ultrapure water (final concentration: 20 mg / L).

[0101] Group 5: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.2 mL of ultrapure water (final concentration: 20 mg / L).

[0102] Group 6: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44 mL of ultrapure water (final concentration: 20 mg / L).

[0103] The above six groups were subjected to ultrasonic treatment for 3 minutes to obtain a dispersion of amino-functionalized activated carbon.

[0104] Step (3) Adsorption experiment:

[0105] Prepare a stock solution of PFOA with a concentration of 22.5 mg / L.

[0106] Group 1: Take 0.05 mL of the PFOA mother liquor obtained in step (3) and add it to the first group solution in step (2) (final concentration: 25 μg / L).

[0107] Group 2: Take 0.1 mL of the PFOA mother liquor obtained in step (3) and add it to the Group 2 solution in step (2) (final concentration: 50 μg / L).

[0108] Group 3: Take 0.2 mL of the PFOA mother liquor obtained in step (3) and add it to the Group 3 solution in step (2) (final concentration: 100 μg / L).

[0109] Group 4: Take 0.3 mL of the PFOA mother liquor obtained in step (3) and add it to the Group 4 solution in step (2) (final concentration: 200 μg / L).

[0110] Group 5: Take 0.6 mL of the PFOA mother liquor obtained in step (3) and add it to the Group 5 solution in step (2) (final concentration: 300 μg / L).

[0111] Group 6: Take 0.8 mL of the PFOA mother liquor obtained in step (3) and add it to the Group 6 solution in step (2) (final concentration: 400 μg / L).

[0112] Tighten the polypropylene bottle and place it in a constant-temperature shaker at 26.4℃ and 140 rpm for 4 hours. After the reaction, take a water sample, filter it through a 0.22 μm glass fiber membrane, and then determine the concentration of perfluorinated compounds using LC-MS. The specific test results are as follows: Figure 6 As shown.

[0113] Figure 6 This is the adsorption isotherm diagram of perfluorooctanoic acid by amino-functionalized activated carbon NH2-AC-120 in Example 1 of the present invention.

[0114] like Figure 6 As shown, when the initial dosage of the adsorbent material NH2-AC-120 is 20 mg / L, its equilibrium adsorption capacity for PFOA reaches 17.49 mg / g, and its adsorption isotherm conforms to the linear adsorption isotherm, indicating that PFOA is uniformly adsorbed on the surface of amino-functionalized activated carbon. This result further confirms the high efficiency and selectivity of the adsorption process.

[0115] The competitive effect of dissolved organic matter (DOM) on the adsorption of PFOA by NH2-AC-120 in Example 1 was explored, as detailed in Test Example 7.

[0116] Test Example 7

[0117] Step (1) Preparation of activated carbon stock solution: Weigh 45 mg of NH2-AC-120 from Example 1 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an activated carbon stock solution with a concentration of 0.45 g / L. The stock solution should be prepared fresh for use.

[0118] Step (2) Preparation of activated carbon dispersion: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.35 mL of ultrapure water. Sonicate for 3 min to obtain the activated carbon dispersion (final concentration: 20 mg / L).

[0119] Step (3) Adsorption experiment: Prepare a DOM stock solution with a concentration of 300 mg / L (calculated as C), and a PFOA stock solution with a concentration of 90 mg / L. Add 0.45 mL of DOM stock solution and 0.1 mL of PFOA stock solution to the dispersion in step (2) (final target pollutant concentration: DOM = 3 mg / L (calculated as C), PFOA = 200 μg / L). Tighten the polypropylene bottle and place it in a constant temperature shaker. Shake the bottle at 26.4℃ and 140 rpm for 4 hours. After the reaction, take a water sample, filter it through a 0.22 μm glass fiber membrane, and then use LC-MS to detect the concentration of perfluorinated compounds. The specific test results are as follows. Figure 7 As shown.

[0120] Figure 7 This is a diagram showing the competitive effect of dissolved organic matter (DOM) on the adsorption of PFOA by amino-functionalized activated carbon NH2-AC-120 in Example 1.

[0121] like Figure 7 As shown, when the dissolved organic matter (DOM) concentration was 3 mg / L and the PFOA concentration was 200 μg / L, the removal rate of PFOA by the amino-functionalized activated carbon adsorbent NH2-AC-120 significantly increased with increasing concentration. When the initial concentration of the amino-functionalized activated carbon adsorbent NH2-AC-120 was 40 mg / L, its PFOA removal rate reached 72%. This result indicates that the amino-functionalized activated carbon of this invention can maintain good adsorption performance and exhibit excellent anti-interference ability even under complex environmental conditions.

[0122] The adsorption rate of amino-functionalized activated carbon NH2-AC-120 in Example 1 on a mixed solution of long-chain perfluorinated compounds, such as perfluorodecanoic acid (PFDA) and perfluorooctanoic acid (PFOA), and short-chain perfluorinated compounds, such as perfluorobutyric acid (PFBA) and perfluorohexanoic acid (PFHxA), was investigated, as specifically in Test Example 8.

[0123] Test Example 8

[0124] Step (1) Preparation of activated carbon stock solution: Weigh 45 mg of NH2-AC-120 from Example 1 into a 15 mL polypropylene bottle, add 10 mL of ultrapure water, sonicate for 3 min, and prepare an activated carbon stock solution with a concentration of 0.45 g / L. The stock solution should be prepared fresh for use.

[0125] Step (2) Preparation of activated carbon dispersion: Take 0.2 mL of the stock solution obtained in step (1) and add it to 44.4 mL of ultrapure water. Sonicate for 3 min to obtain the activated carbon dispersion (final concentration: 20 mg / L).

[0126] Step (3) Adsorption experiment: Prepare a mixed mother liquor containing PFBA, PFHxA, PFOA and PFDA, with each component having a concentration of 22.5 mg / L. Add 0.1 mL of the mixed mother liquor (final concentration of target pollutant: 50 μg / L, pH=6.5) to the dispersion from step (2). Tighten the polypropylene bottle and place it in a constant temperature shaker. Shake the bottle at 26.4℃ and 140 rpm for 4 h. After the reaction, take a water sample, filter it through a 0.22 μm glass fiber membrane, and then use LC-MS to detect the concentration of different perfluorinated compounds. The specific test results are as follows: Figure 8 As shown.

[0127] Figure 8 This is a diagram showing the competitive adsorption effect of amino-functionalized activated carbon NH2-AC-120 on perfluorinated compounds of different chain lengths in Example 1 of the present invention.

[0128] like Figure 8 As shown, when PFBA, PFHxA, PFOA, and PFDA are present in the solution simultaneously, the removal rate of perfluorinated compounds by the adsorbent material NH2-AC-120 shows a decreasing trend with decreasing chain length, specifically in the order of PFDA > PFOA > PFHxA > PFBA. It is generally believed that short-chain perfluorinated compounds, due to their strong hydrophilicity, are more easily migrated and diffused in the environment; while long-chain perfluorinated compounds, due to their stronger hydrophobicity, are more easily adsorbed by activated carbon and may desorb the adsorbed short-chain perfluorinated compounds into the aqueous phase through competitive adsorption. However, the amino-functionalized activated carbon of this invention utilizes its electrostatic and hydrophobic effects to achieve not only efficient removal of long-chain perfluorinated compounds but also efficient removal of short-chain perfluorinated compounds based on its electrostatic adsorption and mesoporous structure, effectively solving the desorption problem of short-chain perfluorinated compounds.

[0129] In summary, this invention utilizes short-duration ultrasonic treatment to uniformly and densely graft amino groups onto the surface of activated carbon, while preserving the high surface area and mesoporous structure of the activated carbon. This facilitates the adsorption of PFAS on the activated carbon surface and its diffusion through its pores, thereby improving PFAS removal efficiency. Simultaneously, it avoids competition for PFAS adsorption sites by large DOM molecules. Furthermore, the preparation method of the amino-functionalized activated carbon of this invention is simple, efficient, and highly reproducible.

[0130] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing amino-functionalized activated carbon for enhanced adsorption of perfluorinated compounds, comprising: Hydrophilic activated carbon and amino modifier are ultrasonically dispersed and reacted in a solvent. After washing and drying, amino-functionalized activated carbon is obtained. The amino modifier is selected from 3-aminopropyltrimethoxysilane.

2. The preparation method according to claim 1, wherein, The ultrasound duration is 10-60 minutes, and the temperature is 25-30℃.

3. The preparation method according to claim 1, wherein, The hydrophilic activated carbon includes at least one of wood, coconut shell, and coal-based activated carbon.

4. The preparation method according to claim 1, wherein, The solvent includes n-hexane.

5. The preparation method according to claim 1, wherein, The washing process includes: cleaning with a mixture of ethanol and water; The drying temperature is 80-160℃, and the drying time is 12-24 hours.

6. An amino-functionalized activated carbon prepared by any one of claims 1-5.

7. The amino-functionalized activated carbon according to claim 6, wherein: The water contact angle of the amino-functionalized activated carbon is 10-15°. The specific surface area of ​​the amino-functionalized activated carbon is 500-750 m². 2 / g; The mesopore volume of the amino-functionalized activated carbon accounts for 70%-80% of the total pore volume.

8. The application of amino-functionalized activated carbon as described in any one of claims 6-7 in the adsorption of perfluorinated compounds.

9. The application according to claim 8, wherein, The perfluorinated compounds include short-chain perfluorinated compounds of C4-C7 and / or long-chain perfluorinated compounds of C7 or above; The perfluorinated compound is a single or mixed perfluorinated carboxylic acid compound or a perfluorinated sulfonic acid compound.

10. The application according to claim 9, wherein, The pH at which the adsorption occurred was 6.5 ± 0.5; The concentration of the perfluorinated compound is 1-200 μg / L, and the dosage of the amino-functionalized activated carbon is 10-30 mg / L.

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