A hydrophobically modified quaternary ammonium cellulose adsorbent material, and a method of making and using the same
By constructing a dual adsorption mechanism through quaternization and hydrophobic modification of cellulose materials, the problem of low removal efficiency of short-chain PFAS by cellulose-based materials was solved, and efficient and stable PFAS adsorption and regeneration performance was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGXI UNIV
- Filing Date
- 2026-04-22
- Publication Date
- 2026-08-04
AI Technical Summary
Existing cellulose-based adsorbent materials have low removal efficiency for short-chain PFAS and insufficient repeated adsorption-desorption performance.
By employing a method of first quaternization followed by hydrophobic modification, a dual adsorption mechanism of electrostatic adsorption and fluorine-fluorine interaction was constructed. Quaternization introduced positively charged groups and loaded fluorine-containing compounds to enhance the specific recognition and adsorption of short-chain PFAS.
It achieves a high removal rate (over 83%) for short-chain PFAS and excellent recycling performance (the removal rate remains above 76% after 5 adsorption-desorption cycles), with good material stability and economy.
Smart Images
Figure CN122057487B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a hydrophobically modified quaternized cellulose adsorbent material, its preparation method, and its application, belonging to the field of new material preparation technology. Background Technology
[0002] Per- and polyfluoroalkyl substances (PFAS), as a typical class of emerging persistent organic pollutants, are widely distributed in aquatic environments, posing a potential threat to ecosystems and human health. Due to their extremely high environmental persistence, PFAS can accumulate in organisms through polluted water bodies and the food chain. Studies have shown that PFAS have a half-life of 2.3 to 5.4 years in the human body, and long-term exposure can induce hepatotoxicity, immunotoxicity, and genotoxicity, thereby interfering with the normal function of the endocrine system. Therefore, developing efficient remediation technologies to achieve precise removal of traditional and novel PFAS from the aquatic environment has become one of the key research directions in the field of future water environment management.
[0003] Adsorption technology, due to its simplicity, cost-effectiveness, and excellent removal performance for PFAS, has become a research hotspot in the field of PFAS pollution control. Cellulose and its derivatives, as widely available, low-cost, environmentally friendly, and highly malleable biomass-based materials, exhibit good potential for chemical modification thanks to their unique natural macromolecular structure and abundant hydroxyl functional groups. However, the removal efficiency of existing cellulose-based adsorbents for short-chain PFAS remains limited, and their repeated adsorption-desorption performance needs further improvement. Summary of the Invention
[0004] To address the problems of low removal efficiency and unfavorable repeated adsorption and desorption of short-chain PFAS by existing cellulose-based adsorbent materials, this invention provides a hydrophobically modified quaternized cellulose adsorbent material, its preparation method, and its application.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] One objective of this invention is to provide a method for preparing a hydrophobically modified quaternized cellulose adsorbent material, specifically comprising the following steps:
[0007] (1) Dissolve cellulose in an aqueous sodium hydroxide solution for alkalization reaction, then add glycidyltrimethylammonium chloride for quaternization reaction. After the reaction is completed, cool, filter, wash until no chloride ions remain, and dry to obtain quaternized cellulose.
[0008] (2) Disperse the quaternized cellulose obtained in step (1) in deionized water, and form a uniform cellulose suspension by ultrasonic treatment. Add fluorinated silane and ethyl silicate dropwise under heating and stirring conditions to carry out hydrophobic modification reaction. Adjust the pH to acidic. After the reaction is completed, vacuum filter, wash and dry to obtain hydrophobic modified quaternized cellulose adsorbent material.
[0009] Further, in step (1), the mass fraction of the sodium hydroxide aqueous solution is 5 wt%, and the solid-liquid ratio of the cellulose to the sodium hydroxide aqueous solution is 1:20 g / mL.
[0010] Further, in step (1), the temperature of the quaternization reaction is 40℃~80℃, the reaction time is 4 h~8 h, and the mass ratio of glycidyltrimethylammonium chloride to cellulose is (1:1)~(1:1.5).
[0011] Further, in step (2), the temperature is raised to 60 °C, the molar ratio of the fluorinated silane and ethyl silicate is 1:1, the pH is adjusted to 4, and the reaction time is 6 h.
[0012] Furthermore, the drying temperature described in steps (1) and (2) is 60 °C.
[0013] A second objective of this invention is to provide a hydrophobically modified quaternized cellulose adsorbent prepared by the above method. The surface of the adsorbent simultaneously possesses quaternary ammonium groups and perfluorinated hydrophobic groups, with a static contact angle of 128.5°±0.5°. The adsorbent achieves a PFBA removal rate of over 83%, and after five adsorption-desorption cycles, the PFBA removal rate remains above 76%.
[0014] A third objective of this invention is to provide an application of the aforementioned hydrophobically modified quaternized cellulose adsorbent material, specifically for adsorbing and removing perfluorinated and polyfluoroalkyl substances (PFAS) from water, particularly short-chain PFAS. The water can be tap water, lake water, artificial seawater, or electroplating wastewater.
[0015] Compared with the prior art, the present invention has the following beneficial effects:
[0016] (1) Dual mechanisms work together to achieve efficient removal of short-chain PFAS
[0017] This invention employs a specific time sequence of quaternization followed by hydrophobic modification to construct a dual adsorption mechanism of electrostatic adsorption and fluorine-fluorine interaction. The positively charged groups introduced by quaternization capture PFAS anions through electrostatic interactions, while the subsequently loaded fluorinated compounds enhance the specific recognition of short-chain PFAS (such as PFBA) through fluorine-fluorine affinity. The synergistic effect of these two mechanisms enables the material to achieve a PFBA removal rate of over 83%, significantly superior to single-modification materials (quaternization-only modification achieves a removal rate of 57%, and hydrophobic modification-only achieves a removal rate of 15%), breaking through the technical bottleneck of low removal efficiency of short-chain PFAS by existing cellulose-based materials.
[0018] (2) Excellent recyclability and service life
[0019] The material exhibits both chemical and structural stability. After five adsorption-desorption cycles, the removal rate of PFBA remains above 76%, with a decay rate of less than 8%. The quaternary ammonium groups are stably linked to the cellulose backbone via ether bonds, and the perfluorinated hydrophobic layer is firmly anchored by a siloxane crosslinking network. This overcomes the defect of conventional quaternized materials that easily lose active groups during ion exchange, significantly reducing long-term operating costs.
[0020] (3) The raw materials are cheap and readily available, and the process is green and environmentally friendly.
[0021] Using natural cellulose as the base material, which is widely available, biocompatible, and biodegradable, the reagents used for modification are all commercially available conventional chemical products (such as fluorosilanes and ethyl silicate). The preparation process is mild (reaction temperature 60℃, normal pressure operation), requiring no high temperature, high pressure, or toxic organic solvents, which conforms to the principles of green chemistry and provides a sustainable material solution for PFAS pollution control. Attached Figure Description
[0022] Figure 1 The images are scanning electron microscope (SEM) images, where (a) is an SEM image of unmodified cellulose in Example 1, (b) is an SEM image of quaternized cellulose prepared in Example 1, and (c) is an SEM image of hydrophobically modified quaternized cellulose adsorbent material prepared in Example 1.
[0023] Figure 2 The infrared spectra of the quaternized cellulose and hydrophobically modified quaternized cellulose adsorbent materials prepared in Example 1 are shown below.
[0024] Figure 3 The figures are contact angle diagrams, where (a) is the contact angle diagram of the quaternized cellulose prepared in Example 1, and (b) is the contact angle diagram of the hydrophobically modified quaternized cellulose adsorbent material prepared in Example 1.
[0025] Figure 4 The effect of the adsorbent materials prepared in Example 1 and Comparative Examples 5-7 on the removal of short-chain PFAS is shown in the figure.
[0026] Figure 5 The attached diagram shows the cyclic adsorption-desorption of the hydrophobically modified quaternized cellulose adsorbent material prepared in Example 1. Detailed Implementation
[0027] The present invention will be further described below with reference to specific embodiments.
[0028] Example 1
[0029] (1) Dissolve 1 g of cellulose powder in a 5 wt% sodium hydroxide aqueous solution at a solid-liquid ratio of 1:20 g / mL, and stir thoroughly to fully alkalize the cellulose and activate its surface hydroxyl sites. Add 1.5 g of glycidyltrimethylammonium chloride and react at 60 °C for 6 h. After the reaction is complete, cool to room temperature, separate the product by vacuum filtration, wash repeatedly with deionized water until no chloride ions remain in the filtrate, and dry at 60 °C to constant weight to obtain powdered quaternized cellulose.
[0030] (2) 0.3 g of quaternized cellulose powder was dispersed in 15 mL of deionized water and ultrasonically treated to prepare a uniform cellulose suspension. The suspension was heated to 60 °C under stirring. 0.2 mmol of fluorosilane and ethyl silicate were added dropwise to 30 mL of the cellulose suspension. Then, glacial acetic acid was added dropwise to the reaction system to adjust the pH to 4. The reaction was carried out for 6 h. The suspension was vacuum filtered to obtain a wet modified cellulose membrane. The membrane was repeatedly washed with deionized water to remove unreacted reagents and byproducts. The membrane was dried at 60 °C to constant weight to obtain a thin film of hydrophobic modified quaternized cellulose adsorbent.
[0031] Figure 1 The images show scanning electron microscope (SEM) images of the quaternized cellulose and hydrophobically modified quaternized cellulose adsorbents prepared in Example 1. According to... Figure 1 As can be seen, compared with the dense fiber morphology of unmodified cellulose (a), quaternized cellulose (b) exhibits a more porous morphology, and the fiber surface roughness is also significantly improved. This phenomenon is attributed to the chemical reaction between glycidyltrimethylammonium chloride and the hydroxyl sites on cellulose, a process that induces a swelling effect in the cellulose skeleton, leading to the loosening of the fiber bundles. The morphology of the hydrophobically modified quaternized cellulose adsorbent material (c) changed significantly, forming a more pronounced porous structure with densely distributed and interconnected pores, forming a three-dimensional interpenetrating network. The formation mechanism of this unique structure originates from the silicon-oxygen network structure formed by fluorinated silanes and ethyl silicate, which cross-links with the cellulose collective, driving the material's transformation from a discrete powder state to a continuous film state. The construction of this porous configuration has a dual advantage: on the one hand, it effectively expands the specific surface area of the material; on the other hand, it creates rich mass transfer pathways for PFAS pollutant molecules, ultimately synergistically enhancing the adsorption efficiency.
[0032] Figure 2 The images show the infrared spectra of the quaternized cellulose and hydrophobically modified quaternized cellulose adsorbents prepared in Example 1. Figure 2 It can be seen that the spectrum of quaternized cellulose is at 1106 cm⁻¹. -1 The addition of this information provides evidence of etherification, indicating that quaternary ammonium groups have been successfully incorporated into the cellulose backbone.
[0033] Figure 3 The figures show contact angle diagrams, where (a) is the contact angle diagram of the quaternized cellulose prepared in Example 1, and (b) is the contact angle diagram of the hydrophobically modified quaternized cellulose adsorbent prepared in Example 1. According to... Figure 3 (a) It can be seen that the static contact angle of the quaternized cellulose surface is 101.2°, indicating that the material surface exhibits hydrophobic properties. However, continuous monitoring of its dynamic wetting behavior (time span 0–30 s) shows that the test droplets spread significantly within 30 s and eventually disappear completely. This phenomenon confirms that some hydrophilic active sites are still retained on the material surface, possibly due to the quaternary ammonium groups, giving the material certain surface wetting properties. After hydrophobic modification, the static contact angle of the obtained hydrophobically modified quaternized cellulose adsorbent surface is as follows: Figure 3 (b) shows an increase to 128.5 ± 0.5°, a significant increase compared to the contact angle of quaternized cellulose. Simultaneously, the droplet geometry remained stable within 5 minutes, with no obvious spreading or substrate penetration observed. This result demonstrates that hydrophobic modification successfully introduced low surface energy functional groups (perfluorinated hydrophobic groups) into the material surface, thereby achieving a substantial enhancement of the material's surface hydrophobic properties.
[0034] Example 2
[0035] The preparation method of Example 2 is the same as that of Example 1. The only difference is that the reaction temperature in step (1) is 40°C and the amount of glycidyltrimethylammonium chloride added is 1 g.
[0036] Example 3
[0037] The preparation method of Example 3 is the same as that of Example 1, except that the reaction temperature in step (1) is 40°C and the reaction time is 8 h.
[0038] Example 4
[0039] The preparation method of Example 4 is the same as that of Example 1. The only difference is that the reaction time in step (1) is 4 h and the amount of glycidyltrimethylammonium chloride added is 1 g.
[0040] Example 5
[0041] The preparation method of Example 3 is the same as that of Example 1, except that the reaction temperature in step (1) is 80°C and the reaction time is 4 h.
[0042] Comparative Example 1
[0043] The preparation method of Comparative Example 1 is the same as that of Example 1. The only difference is that the reaction temperature in step (1) is 40°C, the reaction time is 4 h, and the amount of glycidyltrimethylammonium chloride added is 0.5 g.
[0044] Comparative Example 2
[0045] The preparation method of Comparative Example 2 is the same as that of Example 1, except that the reaction time in step (1) is 8 h and the amount of glycidyltrimethylammonium chloride added is 0.5 g.
[0046] Comparative Example 3
[0047] The preparation method of Comparative Example 3 is the same as that of Example 1, except that the reaction temperature in step (1) is 80°C and the amount of glycidyltrimethylammonium chloride added is 0.5 g.
[0048] Comparative Example 4
[0049] The preparation method of Comparative Example 4 is the same as that of Example 1. The only difference is that the reaction temperature in step (1) is 80°C, the reaction time is 8h, and the amount of glycidyltrimethylammonium chloride added is 1 g.
[0050] Comparative Example 5
[0051] 1 g of cellulose powder was dissolved in 15 mL of deionized water and sonicated to prepare a homogeneous cellulose suspension. The suspension was then heated to 60 °C with stirring. 0.2 mmol of fluorosilane and ethyl silicate were added dropwise to 30 mL of this cellulose suspension. Glacial acetic acid was then added dropwise to adjust the pH to 4, and the reaction was allowed to proceed for 6 h. The suspension was then vacuum filtered, repeatedly washed with deionized water to remove unreacted reagents and byproducts, and dried at 60 °C to constant weight to obtain hydrophobically modified cellulose powder.
[0052] Comparative Example 6
[0053] The preparation method of this comparative example is the same as that of Example 1, except that only step (1) is performed.
[0054] Comparative Example 7
[0055] (1) Dissolve 1 g of cellulose powder in 15 mL of deionized water and prepare a uniform cellulose suspension by ultrasonic treatment. Heat the suspension to 60 °C under stirring. Take 30 mL of the cellulose suspension and add 0.2 mmol of fluorosilane and ethyl silicate dropwise. Then, add glacial acetic acid dropwise to the reaction system to adjust the pH value to about 4. React for 6 h. Filter the suspension under vacuum, wash repeatedly with deionized water to remove unreacted reagents and byproducts, and dry at 60 °C to constant weight to obtain hydrophobic modified cellulose powder.
[0056] (2) Dissolve 0.5 g of hydrophobically modified cellulose powder in a 5 wt% sodium hydroxide aqueous solution at a solid-liquid ratio of 1:20 g / mL, and stir thoroughly to fully alkalize the cellulose and activate its surface hydroxyl sites. Add 1.5 g of glycidyltrimethylammonium chloride and react at 60 °C for 6 h. After the reaction is complete, separate the product by vacuum filtration, wash repeatedly with deionized water until no chloride ions remain in the filtrate, and dry at 60 °C to constant weight to obtain hydrophobically modified and then quaternized cellulose powder.
[0057] Adsorption performance test 1
[0058] The equilibrium adsorption capacity of the quaternized cellulose powders prepared in Examples 1-5 and Comparative Examples 1-4 was tested. The temperature was set at 25 °C, and a PFAS solution with an initial concentration of 1 mg / L was added during the equilibrium adsorption capacity test. The test results are shown in Table 1.
[0059] Table 1. Equilibrium adsorption capacity of quaternized cellulose powder on PFAS solution
[0060] As shown in Table 1, the amount of glycidyltrimethylammonium chloride modifier added is the main influencing factor, and the removal rate increases significantly with the increase of level, with the best result at 1.5 g.
[0061] Adsorption performance test 2
[0062] The equilibrium adsorption capacities of the hydrophobically modified quaternized cellulose adsorbent prepared in Example 1, the hydrophobically modified cellulose adsorbent prepared in Comparative Example 5, the quaternized cellulose adsorbent prepared in Comparative Example 6, and the pre-hydrophobicated-then-quaternized cellulose adsorbent prepared in Comparative Example 7 were tested. The temperature was set at 25 °C when testing the equilibrium adsorption capacity, and a PFAS solution with an initial concentration of 1 mg / L was added (common short-chain PFAS include perfluorobutyric acid (PFBA), perfluorovalerate (PFPeA), perfluorohexanoic acid (PFHxA), and perfluoroheptanoic acid (PFHpA). These short-chain substances often have weak hydrophobicity and are more difficult to be effectively retained by traditional treatment processes. Therefore, this invention uses these four short-chain PFAS as representatives to test the adsorption performance of the materials). The test results are as follows: Figure 4As shown, the removal rate of PFBA, a representative of short-chain PFAS, is a key indicator. The hydrophobically modified quaternized cellulose adsorbent prepared in Example 1 achieved a PFBA removal rate as high as 83%, far exceeding the PFBA removal rates of the hydrophobically modified cellulose adsorbent prepared in Comparative Example 5, the quaternized ammonium cellulose adsorbent prepared in Comparative Example 6, and the pre-hydrophobic-pre-quaternized cellulose adsorbent prepared in Comparative Example 7, which were 15%, 57%, and 18%, respectively. This indicates that the cellulose-based hydrogel is first modified with quaternary ammonium to acquire positive charge properties, enabling efficient adsorption of PFAS based on electrostatic adsorption. Further optimization by loading fluorine-containing compounds for cross-linking utilizes the fluorine-fluorine interactions between fluorides to further improve the selectivity and stability of adsorption. Figure 5 The attached figure shows the cyclic adsorption-desorption process of the hydrophobically modified quaternized cellulose adsorbent material prepared in Example 1. The removal rate of PFBA, a representative of short-chain PFAS, is the key indicator. As can be seen from the figure, after five adsorption-desorption cycles, the removal rate of PFBA is still 76.67%, demonstrating its ability to be recycled.
Claims
1. Use of a hydrophobically modified quaternary ammonium cellulose adsorbent material for adsorptive removal of short chain perfluoro- and polyfluoroalkyl substances PFAS in water bodies, characterized in that, The short-chain perfluoro and polyfluoroalkyl substances PFAS include perfluorobutyric acid PFBA, perfluorovalerate PFPeA, perfluorohexanoate PFHxA or perfluoroheptanoate PFHpA. The preparation method of the hydrophobically modified quaternized cellulose adsorbent material includes the following steps: (1) Dissolve cellulose in an aqueous sodium hydroxide solution for alkalization reaction, then add glycidyltrimethylammonium chloride for quaternization reaction. After the reaction is completed, cool, filter, wash until no chloride ions remain, and dry to obtain powdered quaternized cellulose. (2) Disperse the quaternized cellulose obtained in step (1) in deionized water, and form a uniform cellulose suspension by ultrasonic treatment. Add fluorinated silane and ethyl silicate dropwise under heating and stirring conditions to carry out hydrophobic modification reaction. Adjust the pH to acidic. After the reaction is completed, vacuum filter, wash and dry to obtain a thin film-like hydrophobic modified quaternized cellulose adsorbent material. The surface of the adsorbent material has both quaternary ammonium groups and perfluorinated hydrophobic groups, and the static contact angle is 128.5°±0.5°. In step (1), the mass fraction of the sodium hydroxide aqueous solution is 5 wt%, and the solid-liquid ratio of the cellulose to the sodium hydroxide aqueous solution is 1:20 g / mL; In step (1), the temperature of the quaternization reaction is 40℃~80℃, the reaction time is 4 h~8 h, and the mass ratio of glycidyltrimethylammonium chloride to cellulose is 1.5:
1. In step (2), the temperature is heated to 60 °C, the molar ratio of the fluorinated silane and ethyl silicate is 1:1, the pH is adjusted to 4, and the hydrophobic modification reaction time is 6 h. The drying temperature described in steps (1) and (2) is 60 °C.
2. Use according to claim 1, characterized in that, The hydrophobically modified quaternized cellulose adsorbent material achieves a removal rate of over 83% for perfluorobutyric acid (PFBA), and maintains a removal rate of over 76% after 5 adsorption-desorption cycles.
3. Use according to claim 1, characterized in that, The water bodies include tap water, lake water, artificial seawater, or electroplating wastewater.