Synthesis method and application of colloidal activated carbon
By synthesizing colloidal activated carbon with wettability and rich pore structure, the problems of large particle size and poor stability of traditional activated carbon have been solved, achieving efficient and selective adsorption and long-term stability of perfluoroalkyl compounds, which is suitable for in-situ remediation of groundwater.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JILIN UNIVERSITY
- Filing Date
- 2026-02-06
- Publication Date
- 2026-04-21
AI Technical Summary
Existing granular activated carbon has a large particle size, resulting in high construction costs. It is difficult to inject it into groundwater layers through low-pressure methods, and its dispersion stability is poor in complex environments, making it difficult to achieve efficient, selective, and long-term stable adsorption of perfluoroalkyl compounds.
By designing colloidal activated carbon with wettability, rich pore structure and dense adsorption sites, and by using molten alkali and ball milling processes to adjust particle size and pore structure, quaternary ammonium salt groups are introduced to improve hydrophilicity and electrostatic sites, thus achieving rapid and selective adsorption of PFOA.
The prepared colloidal activated carbon has small particle size, large specific surface area, suitable pore structure, high adsorption performance, good stability, and is not easily desorbed in complex environments, making it suitable for in-situ groundwater remediation.
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Figure CN121894656A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of groundwater pollution remediation technology, and to a method for synthesizing colloidal activated carbon that can be directly injected into underground aquifers for in-situ construction of reaction zones, and the application of the colloidal activated carbon in removing perfluoroalkyl compounds from groundwater. Background Technology
[0002] Perfluorooctanoic acid (PFOA), a typical perfluoroalkyl compound, exhibits significant environmental persistence, bioaccumulation, and potential toxicity in groundwater environments due to its high carbon-fluorine bond energy and extremely stable chemical properties. This has raised widespread environmental concerns and health risks globally. Limited by its molecular structure, PFOA is difficult to effectively break down or degrade through in-situ chemical or biological processes under typical groundwater conditions. Currently, constructing in-situ reaction zones based on activated carbon to achieve in-situ fixation of PFOA is one of the main technical routes. However, traditional granular activated carbon has a large particle size, typically requiring excavation or the construction of filled reaction walls, resulting in high construction costs and limited applicability.
[0003] Colloidal activated carbon, as a micron or nano-sized carbon material, possesses excellent specific surface area and adsorption capacity, enabling it to enter aquifers via low-pressure injection. It shows promising application potential in the removal of persistent organic pollutants (PFOA) from groundwater. However, the pore structure and surface functional group composition of colloidal activated carbon are not functionally regulated to target the molecular characteristics of PFOA. It typically relies on polymeric stabilizers to maintain dispersibility. In complex groundwater environments, it is susceptible to changes in ionic strength, natural organic matter, and coexisting pollutants, leading to decreased dispersion stability and the risk of re-desorption of adsorbed pollutants. This makes it difficult to meet the long-term effectiveness requirements of in-situ remediation. Therefore, developing a novel colloidal activated carbon material that possesses both good injection performance and the ability to achieve efficient, selective, and long-term stable adsorption of PFOA in complex groundwater environments remains a pressing technical challenge in the field of in-situ groundwater remediation. Summary of the Invention
[0004] The purpose of this invention is to provide a method for synthesizing colloidal activated carbon, and the application of the synthesized colloidal activated carbon in the removal of perfluorinated compounds from groundwater.
[0005] Design ideas for the synthesis method of colloidal activated carbon: Based on the unique properties of PFOA, namely its amphiphilic structure, anionic chains, hydrophobic fluorinated chains, and Lewis basic sites, this study designed a novel colloidal activated carbon with the following characteristics: (i) wettability, which accelerates the mass transfer of PFOA to the colloidal activated carbon and improves the adsorption rate; (ii) abundant pore structure and suitable pore size, which can accommodate a large amount of PFOA while avoiding the co-adsorption of large molecular natural organic matter; (iii) dense adsorption active sites, which enable the adsorption of large amounts of PFOA; and (iv) good stability and mobility. To achieve this goal, the number of oxygen-containing functional groups was increased by using molten alkali and ball milling processes, the particle size range of the colloidal activated carbon was adjusted, and its pore structure was reconstructed to the range of micropores and narrow mesopores. The steric hindrance effect was used to achieve the rapid adsorption of low concentrations of PFOA in the actual groundwater environment, while improving the stability of the colloidal activated carbon suspension and its fluidity in the aquifer medium. Secondly, the introduction of quaternary ammonium salt groups improves hydrophilicity and achieves nitrogen doping. At the same time, it increases electrostatic and hydrophobic sites. This colloidal activated carbon with multifunctional binding sites can synergistically and effectively adsorb PFOA molecules with negative charge and hydrophobic chain characteristics, thereby improving the selective adsorption performance of PFOA.
[0006] A method for synthesizing colloidal activated carbon includes the following steps: 1. Pickling: Add 5g of activated carbon to a conical flask containing a mixture of water and 0.1mol / L dilute hydrochloric acid in a volume ratio of 7:3. Soak at room temperature for 24 hours, then place in a 50℃ water bath and heat for 2 hours, stirring constantly. Wash with deionized water several times until neutral, and dry at 80℃ for later use. 2. Calcination: The acid-washed activated carbon and the ground potassium hydroxide are mixed evenly at a mass ratio of 1:2 and placed in a tube furnace. Calcination is carried out at 700℃ under a nitrogen atmosphere for 2 hours with a heating rate of 10℃ / min. The calcined activated carbon is washed with deionized water several times until the pH is 9.5 and then dried at 80℃ for later use. III. Ball milling: The calcined activated carbon and the grinding agent ZrO2 were ball milled in air at a mass ratio of 1:100 for 1 hour at a speed of 300 r / min. IV. Modification: Take 1g of ball-milled activated carbon and add it to a high borosilicate glass bottle containing 20mL of quaternary ammonium salt solution. Stir on a magnetic stirrer at room temperature for 24h. Heat the solution to 50℃, adjust the pH to 12.5 with 5mol / L sodium hydroxide solution, and react for 48h. Cool to room temperature, add hydrochloric acid to stop the reaction when the pH is 6.5-7.0. Wash with ethanol and deionized water until the pH is neutral, and dry at 80℃ to obtain colloidal activated carbon.
[0007] The colloidal activated carbon synthesized in this invention is used to remove perfluorinated compounds from groundwater.
[0008] The method of this invention has a simple synthesis process and high yield. The resulting colloidal activated carbon has a high specific surface area, rich pore structure features and a large number of synergistic adsorption sites, exhibiting high efficiency in adsorption of perfluorooctanoic acid (PFOA). Moreover, it is not prone to desorption under different water chemistry conditions and can be used as an adsorbent material for in-situ fixation of PFOA in groundwater.
[0009] The colloidal activated carbon prepared by the method of this invention has the following advantages: 1) Small particle size, large specific surface area, such as Figure 1 As shown.
[0010] 2) It has a rich pore structure with micropores as the main component and mesopores as a secondary component, as shown in Table 1.
[0011] 3) Dense synergistic adsorption active sites enable efficient adsorption of PFOA, as shown in Tables 2 and 3. Figure 2 , Figure 3 and Figure 4 As shown.
[0012] 4) When groundwater environmental conditions change, the risk of desorption and re-release of adsorbed PFOA is significantly reduced, such as... Figure 5 As shown.
[0013] 5) Maintains good stability in aquifer media without relying on polymeric stabilizers. Figure 6 The stability shown and as Figure 7 and Figure 8 The mobility shown. Attached Figure Description
[0014] Figure 1 The nitrogen adsorption-desorption curve and pore size distribution diagram of the colloidal activated carbon prepared by the method of this invention are shown. Figure 2 This is a diagram showing the adsorption effect of colloidal activated carbon prepared by the method of this invention on PFOA in artificial groundwater. Figure 3 This is a graph showing the effect of different inorganic ions on the adsorption of PFOA by colloidal activated carbon prepared by the method of this invention. Figure 4 This is a graph showing the effect of different concentrations of natural organic matter on the adsorption of PFOA by colloidal activated carbon prepared by the method of this invention. Figure 5 This is a graph showing the desorption of activated carbon after adsorbing PFOA in different types of water. Figure 6 These are actual images showing the stability effects of powdered activated carbon and colloidal activated carbon suspensions prepared by the method of this invention. Figure 7 These are physical images showing the migration effects of powdered activated carbon and colloidal activated carbon prepared by the method of this invention in a one-dimensional simulated column. Figure 8 This is a graph showing the changes in concentration of powdered activated carbon and colloidal activated carbon prepared by the method of this invention at the four sampling ports of a one-dimensional simulated column.
[0015] Figure 2 Reaction conditions: In the adsorption experiment, the adsorption performance of the colloidal activated carbon prepared by the method of this invention on PFOA in artificial groundwater (3.33mM NaHCO3, 3.33mM CaCl, 3.33mM MgCO3 and 1mg / L humic acid) was determined by the following scheme: 100mL of artificial groundwater containing 5mg / L PFOA was prepared in a polypropylene bottle, 20mg of colloidal activated carbon was added, the polypropylene bottle was placed in a 298 K constant temperature shaker, and after sampling, it was filtered through a 0.22μm filter membrane. The concentration of the remaining PFOA in the solution was analyzed by liquid chromatography-mass spectrometry (U3000 / TSQquantum). The operation procedure was in accordance with the national standard "Determination of perfluorooctyl sulfonic acid and perfluorooctanoic acid and their salts in water - Isotope dilution / liquid chromatography-triple quadrupole mass spectrometry" (HJ 1333—2023). The adsorption removal rate of colloidal activated carbon on PFOA was calculated.
[0016] Figure 3 and 4 Reaction conditions: The effects of common cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) on adsorption were analyzed using inorganic salts NaCl, KCl, CaCl₂, and MgCl₂. The effects of common anions (SO₄²⁻, KHCO₃, KNO₃, and K₂CO₃) on adsorption were analyzed using K₂SO₄, KHCO₃, KNO₃, and K₂CO₃. 2- HCO3 - NO3 - With CO32 - The effect of different inorganic salts on adsorption was investigated. Each inorganic salt had a concentration of 10 mmol / L. PFOA solutions with a pH of 7 and a concentration of 5 mg / L, totaling 50 mL, were prepared. The control group contained no inorganic salts. 10 mg of colloidal activated carbon was accurately weighed into a 50 mL polypropylene bottle. The bottle was placed in a 298 K constant-temperature shaker for 24 h. Samples were then filtered through a 0.22 μm filter and the PFOA concentration was analyzed using liquid chromatography-mass spectrometry (LC-MS). The adsorption capacity q of colloidal activated carbon for PFOA under different coexisting ion conditions was calculated. t (mg / g); A series of 50 mL solutions of PFOA (pH=7) containing different concentrations (5, 10, 20 mg / L) of humic acid and fulvic acid (5 mg / L) were prepared. The control group contained no added organic matter. 10 mg of colloidal activated carbon was accurately weighed and added to each solution. After shaking at 298 K for 24 h, samples were filtered through a 0.22 μm filter and the PFOA concentration was analyzed using liquid chromatography-mass spectrometry (LC-MS). The adsorption capacity q of colloidal activated carbon for PFOA in solutions containing different concentrations of natural organic matter was calculated. t (mg / g).
[0017] Figure 5 Reaction conditions: 10 mg of colloidal activated carbon was accurately weighed and added to artificial groundwater containing 5 mg / L PFOA. The mixture was shaken at 298 K for 24 h. The novel colloidal activated carbon was then separated by a filtration device and placed in four different water types, including ultrapure water, high saline water (containing 200 mM NaCl), tap water, and high humic acid water (containing 20 mg / L humic acid), to investigate the desorption behavior of PFOA.
[0018] Figure 6 Reaction conditions: Add 100 mg of colloidal activated carbon to a colorimetric tube containing 10 mL of 1 mmol / L NaHCO3 solution. Sonicate for 15 min to ensure uniform dispersion of the colloidal activated carbon. Allow the colorimetric tube to stand and evaluate the stability of the activated carbon using the sedimentation observation method.
[0019] Figure 7 and 8 Reaction conditions: A water inlet was installed on the left side and an outlet on the right side of a one-dimensional simulation column with an inner diameter of 2.5 cm and a length of 50 cm. Two-cm lengths of quartz sand (average particle size 2-4 mm) were filled at both ends of the simulation column to prevent clogging during rinsing. Then, coarse sand (20-40 mesh fused silica sand) was uniformly filled in, and compacted with a small hammer after each 1 cm of sand was added. Quartz sand was then added again 2 cm from the outlet. Once the simulation column was filled, tap water was pumped into the column at a flow rate of 5 mL / min to fill five pore volumes (1 PV = 78 mL). 200 mg of colloidal activated carbon was weighed and dissolved in 1 L of water, then magnetically stirred and ultrasonically dispersed to form a colloidal activated carbon suspension. This suspension was injected into the simulation column using a peristaltic pump. After each PV of suspension was injected, samples were taken from four sampling ports, and the absorbance was immediately measured at a wavelength of 400 nm using a UV spectrophotometer. Detailed Implementation
[0020] A method for synthesizing colloidal activated carbon includes the following steps: 1. Pickling: Add 5g of activated carbon to a conical flask containing a mixture of water and 0.1mol / L dilute hydrochloric acid in a volume ratio of 7:3. Soak at room temperature for 24 hours, then place in a 50℃ water bath and heat for 2 hours, stirring constantly. Wash with deionized water several times until neutral, and dry at 80℃ for later use. 2. Calcination: The acid-washed activated carbon and the ground potassium hydroxide are mixed evenly at a mass ratio of 1:2 and placed in a tube furnace. Calcination is carried out at 700℃ under a nitrogen atmosphere for 2 hours with a heating rate of 10℃ / min. The calcined activated carbon is washed with deionized water several times until the pH is 9.5 and then dried at 80℃ for later use. III. Ball milling: The calcined activated carbon and the grinding agent ZrO2 were ball milled in air at a mass ratio of 1:100 for 1 hour at a speed of 300 r / min. IV. Modification: Take 1g of ball-milled activated carbon and add it to a high borosilicate glass bottle containing 20mL of quaternary ammonium salt solution. Stir on a magnetic stirrer at room temperature for 24h. Heat the solution to 50℃, adjust the pH to 12.5 with 5mol / L sodium hydroxide solution, and react for 48h. Cool to room temperature, add hydrochloric acid to stop the reaction when the pH is 6.5-7.0. Wash with ethanol and deionized water until the pH is neutral, and dry at 80℃ to obtain colloidal activated carbon.
[0021] The colloidal activated carbon prepared by the method of this invention has the following advantages: 1) Small particle size, large specific surface area, such as Figure 1 As shown; 2) It has a rich pore structure with micropores as the main component and mesopores as a secondary component, as shown in Table 1.
[0022] 3) Dense synergistic adsorption active sites enable efficient adsorption of PFOA, as shown in Tables 2 and 3. Figure 2 , Figure 3 and Figure 4 As shown.
[0023] 4) When groundwater environmental conditions change, the risk of desorption and re-release of adsorbed PFOA is significantly reduced, such as... Figure 5 As shown.
[0024] 5) Maintains good stability in aquifer media without relying on polymeric stabilizers. Figure 6 The stability shown and as Figure 7 and Figure 8 The mobility shown.
[0025] Table 1. Specific surface area and pore structure parameters of colloidal activated carbon prepared by the method of the present invention. Table 2. Pseudo-first-order and pseudo-second-order kinetic parameters of PFOA adsorption by colloidal activated carbon prepared by the method of the present invention. Table 3. Isotherm fitting parameters for PFOA adsorption by colloidal activated carbon prepared by the method of the present invention. The colloidal activated carbon prepared by this invention can be directly injected into underground aquifers to construct reaction zones in situ and remove perfluorinated compounds from groundwater.
Claims
1. A method for synthesizing colloidal activated carbon, characterized in that: Includes the following steps:
1. Pickling: Add 5g of activated carbon to a conical flask containing a mixture of water and 0.1mol / L dilute hydrochloric acid in a volume ratio of 7:
3. Soak at room temperature for 24 hours, then place in a 50℃ water bath and heat for 2 hours with constant stirring. Wash with deionized water several times until neutral, and dry at 80℃ for later use.
2. Calcination: The acid-washed activated carbon and the ground potassium hydroxide are mixed evenly at a mass ratio of 1:2 and placed in a tube furnace. Calcination is carried out at 700℃ under a nitrogen atmosphere for 2 hours with a heating rate of 10℃ / min. The calcined activated carbon is washed with deionized water several times until the pH is 9.5 and then dried at 80℃ for later use. III. Ball milling: The calcined activated carbon and the grinding agent ZrO2 were ball milled in air at a mass ratio of 1:100 for 1 hour at a speed of 300 r / min. IV. Modification: Take 1g of ball-milled activated carbon and add it to a high borosilicate glass bottle containing 20mL of quaternary ammonium salt solution. Stir on a magnetic stirrer at room temperature for 24h. Heat the solution to 50℃, adjust the pH to 12.5 with 5mol / L sodium hydroxide solution, and react for 48h. Cool to room temperature, add hydrochloric acid to the pH to 6.5-7.0 to terminate the reaction, wash with ethanol and deionized water until the pH is neutral, and dry at 80℃ to obtain colloidal activated carbon.
2. The application of the colloidal activated carbon according to claim 1 in the removal of perfluoroalkyl compounds from groundwater.