Thermo-sensitive fluorinated material for efficiently adsorbing and desorbing PFAS in water and preparation method of thermo-sensitive fluorinated material

Abstract

The invention relates to the technical field of perfluorinated and polyfluoroalkyl substance treatment, in particular to a temperature-sensitive fluorinated material for efficiently adsorbing and desorbing PFAS in water and a preparation method of the temperature-sensitive fluorinated material. The invention provides a preparation method of a temperature-sensitive fluorinated material, which comprises the following steps: mixing a fluorine-containing alkene monomer, a nitrogen-containing temperature-sensitive monomer and a traditional Chinese medicine residue cellulose dispersion liquid, and carrying out ultraviolet-induced polymerization under the action of a photoinitiator and a cross-linking agent to obtain the temperature-sensitive fluorinated material. The prepared temperature-sensitive fluorinated material combines the F-F interaction provided by the fluorine-containing alkene monomer and the phase transition characteristic of the nitrogen-containing temperature-sensitive monomer, so that the temperature-sensitive fluorinated material has the temperature response characteristic, reversible switching of hydrophilicity and hydrophobicity under temperature change can be realized, and selective adsorption and controllable desorption of PFAS are remarkably enhanced.

Description

Technical Field

[0001] This invention relates to the field of perfluorinated and polyfluoroalkyl substances treatment technology, specifically to a temperature-sensitive fluorinated material for efficient adsorption and desorption of PFAS in water and its preparation method. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic organofluorine compounds that have been widely used in industries such as coatings, textiles, flame retardants, and surface treatment for decades due to their excellent chemical stability and surface activity. Among them, typical compounds such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) exhibit extremely strong environmental persistence and bioaccumulation, posing a serious threat to ecosystems and human health. Due to the high stability of the carbon-fluorine bond, PFAS are difficult to remove through microbial degradation or conventional advanced oxidation processes, becoming a challenge in the treatment of drinking water and environmental media.

[0003] To address the pollution problem of PFAS, adsorption methods, which are simple to operate, highly efficient, and environmentally friendly, are commonly used. Commonly used adsorbents include activated carbon and ion exchange resins, but these materials have significant limitations. For example, activated carbon has a low removal rate for short-chain PFAS, and the regeneration process is difficult, usually requiring high-temperature treatment, which not only increases energy consumption and operating costs but also causes performance degradation and waste disposal pressure. While ion exchange resins have a certain adsorption capacity, their selectivity is insufficient, and they require high-concentration organic solvents for regeneration during recycling, resulting in significant secondary pollution problems.

[0004] To address the poor treatment efficiency of traditional adsorbents, functional hydrogels based on natural or synthetic polymers have been used to replace traditional adsorbents such as activated carbon and ion exchange resins. This reduces the risk of secondary pollution and offers a degree of reusability. This is primarily due to the rich and highly tunable pore structure of functional hydrogels based on natural or synthetic polymers. However, existing functional hydrogel materials still generally rely on high concentrations of organic solvents during the desorption stage, making it difficult to balance efficient regeneration with environmental friendliness, and the risk of secondary pollution from organic solvents remains.

[0005] Therefore, there is an urgent need to develop a new type of green adsorbent material to reduce dependence on high-concentration organic solvents and thus reduce the risk of secondary pollution from organic solvents. Summary of the Invention

[0006] This invention aims to overcome the secondary pollution risks posed by organic solvents in existing technologies by providing a temperature-sensitive fluorinated material for the efficient adsorption and desorption of PFAS from water, and its preparation method. To achieve the above objective, this invention provides the following technical solution: This invention provides a method for preparing a thermosensitive fluorinated material, comprising: mixing a fluorinated olefin monomer, a nitrogen-containing thermosensitive monomer, and a cellulose dispersion of traditional Chinese medicine residue, and then performing ultraviolet light-initiated polymerization under the action of a photoinitiator and a crosslinking agent to obtain the thermosensitive fluorinated material.

[0007] This thermosensitive fluorinated material combines the F–F interaction provided by the fluorinated monomer with the phase transition characteristics of the thermosensitive monomer, giving it temperature-responsive properties and enabling reversible switching between hydrophilic and hydrophobic properties under temperature changes. At the same time, the thermosensitive monomer and the fluorinated monomer have a good synergistic effect, enabling the thermosensitive fluorinated material to not only achieve efficient adsorption and desorption of trace PFAS, but also maintain strong selectivity in complex aquatic matrices.

[0008] Specifically, the adsorption stage achieves efficient and selective capture of PFAS, while the desorption stage enables efficient release of PFAS through physical fields (such as temperature control). Furthermore, the amount of organic solvent required during desorption can be reduced by 4 to 5 times, thus controlling the risk of secondary pollution from organic solvents at the source.

[0009] Preferably, the fluorinated olefin monomer is hexafluorobutyl methacrylate, 1H,1H,5H-octafluoropentyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, or 2,2,3,3,4,4,5,5,6,6,7,7-dodecylfluoroheptyl methacrylate.

[0010] Preferably, the nitrogen-containing thermosensitive monomer is isopropylacrylamide; And / or, the photoinitiator is at least one of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, or 1-hydroxycyclohexylphenyl ketone; And / or, the crosslinking agent is at least one of N,N'-methylenebisacrylamide, N,N'-vinylbisacrylamide, or N,N'-diacrylamide.

[0011] Preferably, the molar ratio of fluorine in the fluorinated olefin monomer, nitrogen in the nitrogen-containing thermosensitive monomer, photoinitiator and crosslinking agent is (4~15):(9~20):(0.1~0.2):(0.1~0.15).

[0012] Temperature-sensitive fluorinated materials cannot be successfully synthesized in all proportions, so controlling the appropriate proportions is the key to obtaining temperature-sensitive fluorinated materials.

[0013] Preferably, the wavelength of the ultraviolet light is 320~410 nm, and the irradiation time of the ultraviolet light is 1~5 h.

[0014] Preferably, the preparation method of the Chinese herbal medicine residue cellulose dispersion includes: heating Chinese herbal medicine residue waste, potassium persulfate and water to undergo an oxidation reaction, then stopping the heating and diluting and washing with water to obtain Chinese herbal medicine residue cellulose, and dispersing it in dimethylformamide to obtain Chinese herbal medicine residue cellulose dispersion.

[0015] Preferably, the medicinal herb residue is at least one of the following: scutellaria baicalensis residue, astragalus membranaceus residue, peony root residue, or acorus tatarinowii residue. The mass ratio of the dry weight of the medicinal herb residue to the potassium persulfate is 1:5 to 20:100. The heating temperature is 20 to 100°C, and the heating time is 2 to 48 hours.

[0016] Preferably, it is diluted 10 times with water.

[0017] Preferably, the dispersion method is ultrasonic dispersion.

[0018] This invention provides a temperature-sensitive fluorinated material.

[0019] Preferably, the temperature-sensitive fluorinated material becomes opaque and hydrophobic as the temperature increases; and becomes transparent and hydrophilic as the temperature decreases.

[0020] This invention provides the application of temperature-sensitive fluorinated materials in PFAS in water adsorption / desorption.

[0021] Preferably, the water is at least one of tap water, lake water, river water, and purified water.

[0022] Thermosensitive monomers and fluorinated monomers have a good synergistic effect, which enables thermosensitive fluorinated materials to not only achieve efficient adsorption and desorption of trace PFAS, but also maintain strong selectivity in complex aquatic matrices.

[0023] Therefore, the present invention has the following beneficial effects: (1) The temperature-sensitive fluorinated material prepared by the present invention can save 4 to 5 times the amount of organic solvent used for desorption during the desorption process, thereby controlling the risk of secondary pollution caused by organic solvents from the source.

[0024] (2) The thermosensitive fluorinated material prepared by the present invention combines the F–F interaction provided by the fluorinated olefin monomer and the phase transition characteristics of the nitrogen-containing thermosensitive monomer, so that the thermosensitive fluorinated material has temperature response characteristics and can realize the reversible switching of hydrophilicity and hydrophobicity under temperature change, thereby significantly enhancing the selective adsorption and controllable desorption of PFAS.

[0025] (3) In this invention, the thermosensitive monomer and the fluorinated monomer have a good synergistic effect, which enables the thermosensitive fluorinated material to not only achieve efficient adsorption and desorption of trace PFAS, but also maintain strong selectivity in complex water matrix. Attached Figure Description

[0026] Figure 1 The images show the removal effects of the temperature-sensitive fluorinated material obtained in Example 1 on PFOA and PFOS at low temperature (25°C) and high temperature (50°C).

[0027] Figure 2 The image shows the removal effects of the temperature-sensitive fluorinated material obtained in Example 2 on PFOA and PFOS at low temperature (25°C) and high temperature (50°C).

[0028] Figure 3 The image shows the removal effect of the temperature-sensitive fluorinated material obtained in Example 3 on PFOA and PFOS at low temperature (25°C) and high temperature (50°C).

[0029] Figure 4 The infrared spectra of the thermosensitive fluorinated material obtained in Example 1 at different temperatures are shown.

[0030] Figure 5 The images show the changes in hydrophilicity / hydrophobicity and morphology of the thermosensitive fluorinated material obtained in Example 1 at different temperatures.

[0031] Figure 6 The graph shows the adsorption effect of the temperature-sensitive fluorinated material obtained in Example 1 on trace amounts of PFAS in different water bodies.

[0032] Figure 7 The graph shows the desorption effect of the temperature-sensitive fluorinated material obtained in Example 1 on PFOS under different elution conditions.

[0033] Figure 8 This is a comparison chart showing the adsorption effects of fluorinated materials and temperature-sensitive fluorinated materials on PFOA. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0035] The raw materials used in this section include: 2-(Perfluorobutyl)ethyl methacrylate (F9): CAS NO1799-84-4, molecular formula C 10 H9F9O2; Isopropylacrylamide (NIPAM): CAS NO2210-25-5, molecular formula C6H 11 NO; 2-Hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone (I2959): CAS 106797-53-9, molecular formula C 11 H 15 O3; N,N′-Methylenebisacrylamide (MBA): CAS NO110-26-9, molecular formula C7H 10 N2O2; N,N-Dimethylformamide (DMF): CAS NO68-12-2, molecular formula C3H7NO; Potassium persulfate (PMS): CAS NO70693-62-8, molecular formula HKO6S; Potassium perfluorooctyl sulfonate (PFOS): CAS NO2795-39-3, molecular formula C8F 17 KO3S; Perfluorooctanoic acid (PFOA): CAS NO335-67-1, molecular formula C8HF 15 O2; Perfluorohexyl sulfonic acid (PFHxS): CAS NO355-46-4, molecular formula C6HF 13 SO3; Perfluorononanoic acid (PFNA): CAS NO375-95-1, molecular formula C9HF 17 O2.

[0036] Example 1 1. Preparation of Cellulose Dispersion from Chinese Herbal Residue (1) Add 1 g of dried peony residue to a beaker containing 100 mL of distilled water, stir for 10 min, add PMS to the distilled water until the concentration of PMS is 0.3 mol / L, stir at 800 rpm for 10 h at 80℃, stop heating, and add distilled water to dilute and terminate the reaction. The volume ratio of dilution is 1:10.

[0037] (2) After the diluted reaction solution is allowed to stand, the supernatant is removed. The above operation is repeated 5 times until the supernatant is neutral. The supernatant is removed and the precipitate is separated by centrifugation at 10,000 rpm to obtain the cellulose solution of Chinese herbal medicine residue.

[0038] (3) The obtained high-purity Chinese herbal medicine residue cellulose solution was dispersed in DMF solution, and the above Chinese herbal medicine residue cellulose solution was ultrasonically treated for 15 min using a cell disruptor (1800W, 90%) to obtain a highly dispersed Chinese herbal medicine residue cellulose dispersion.

[0039] 2. Preparation of thermosensitive fluorinated materials Four mL of cellulose dispersion extracted from Paeonia lactiflora residue was used as the matrix. F9 (the amount of which corresponds to 15 mmol of theoretical fluorine monomer content) and NIPAM (9 mmol) were added, along with 42 mg of photoinitiator I2959 and 20 mg of crosslinking agent MBA. After vortex mixing for 5 min, the mixture was irradiated under a 365 nm ultraviolet light source for 4 h to obtain a thermosensitive fluorinated material.

[0040] Example 2 This embodiment is basically the same as Embodiment 1, except that in "2. Preparation of temperature-sensitive fluorinated materials", the amount of F9 fed corresponds to 9 mmol of theoretical fluorine monomer content, and the amount of NIPAM is 15 mmol.

[0041] Example 3 This embodiment is basically the same as Embodiment 1, except that in "2. Preparation of temperature-sensitive fluorinated materials", the amount of F9 fed corresponds to 4 mmol of theoretical fluorine monomer content, and the amount of NIPAM used is 20 mmol.

[0042] Comparative Example 1 This comparative example is basically the same as Example 1, except that NIPAM is not added in "2. Preparation of temperature-sensitive fluorinated material"; thus, the fluorinated material is obtained.

[0043] Comparative Example 2 This comparative example is basically the same as Example 1, except that in "2. Preparation of temperature-sensitive fluorinated materials", the amount of F9 fed corresponds to 20 mmol of theoretical fluorine monomer content, and the amount of NIPAM used is 4 mmol.

[0044] [Performance Testing] 1. Adsorption / Desorption Performance The thermosensitive fluorinated materials obtained in Examples 1-5 and Comparative Examples 1-2 were subjected to low-temperature (25°C) and high-temperature (50°C) conditions to remove PFOA and PFOS, respectively. Experimental conditions: PFOA / PFOS = 1 ppb, thermosensitive fluorinated material = 1 g / L.

[0045] Figures 1-3 The graphs show the removal effects of the temperature-sensitive fluorinated materials obtained in Examples 1, 2, and 3 on PFOA and PFOS at low temperature (25°C) and high temperature (50°C), respectively. Analysis and comparison are provided. Figures 1-3 It can be seen that in Example 1, the temperature-sensitive fluorinated material with F:N=5:3 showed an adsorption efficiency of over 40% for PFOA at low temperatures and approximately 15% for PFOS at high temperatures; in Example 2, the temperature-sensitive fluorinated material with F:N=3:5 showed an adsorption efficiency of over 70% for PFOA at low temperatures and approximately 20% for PFOS; and in Example 3, the temperature-sensitive fluorinated material with F:N=1:5 showed an adsorption efficiency of over 40% for PFOA at low temperatures and nearly 60% for PFOS. These results indicate that the introduction of temperature-sensitive monomers endows the temperature-sensitive fluorinated material with significant temperature response characteristics: it can efficiently remove PFAS at low temperatures, while the adsorption efficiency decreases significantly at high temperatures, thus providing a basis for its controllable desorption. Figure 8 The PFOA adsorption results of Comparative Example 1 and Examples 1-3 at 25°C show that the adsorption effect of Comparative Example 1 is significantly worse than that of the Examples. This demonstrates that there is a synergistic effect between the fluorinated monomer and the temperature-sensitive monomer, which can help to significantly improve the adsorption capacity of the temperature-sensitive fluorinated material.

[0046] 2. Microstructure To further determine the temperature regulation characteristics of the thermosensitive fluorinated material, infrared spectroscopy was performed on the thermosensitive fluorinated material obtained in Example 1 at different temperatures, and the results are as follows: Figure 4 As shown in the diagram, observations reveal that at low temperatures (25℃, 35℃), NIPAM forms hydrogen bonds with water molecules or hydrophilic groups, resulting in a strong infrared absorption peak. However, at high temperatures (40℃, 50℃), the NIPAM chains collapse and repel water molecules, leading to a more compact structure, increased hydrophobicity, a decrease in the number of hydrogen bonds, and a corresponding weakening of the absorption peak. This phenomenon perfectly illustrates the thermosensitive response mechanism of thermosensitive fluorinated materials.

[0047] To further clarify the mechanism of action of the thermosensitive fluorinated material obtained in Example 1 during temperature changes, contact angle tests and surface morphology observations were performed on the thermosensitive fluorinated material obtained in Example 1. The results are as follows: Figure 5 As shown, observations reveal a significant change in the morphology of the thermosensitive fluorinated material as temperature increases: the material gradually changes from transparent to opaque, while its volume continuously shrinks. This phenomenon is primarily due to the effect of the thermosensitive monomer: at low temperatures, the thermosensitive fluorinated material is hydrophilic and can maintain an expanded state; however, at high temperatures, the NIPAM chains collapse, the structure becomes more compact and exhibits stronger hydrophobicity, and the moisture within the pores is expelled, resulting in a significant reduction in the volume of the thermosensitive fluorinated material.

[0048] 3. Adsorption capacity The adsorption performance of trace PFAS by the thermosensitive fluorinated material obtained in Example 1 was studied in different water bodies. Experimental conditions: PFOA / PFOS / PFHxS / PFNA = 250 ppt, thermosensitive fluorinated material = 1 g / L.

[0049] The results are as follows Figure 6 As shown, the thermosensitive monomer and the fluorinated olefin monomer have a good synergistic effect, enabling the thermosensitive fluorinated material to not only achieve efficient adsorption of trace PFAS at room temperature, but also maintain strong selectivity in complex aquatic matrices. The removal efficiency can be maintained at 80-100% in pure water (DW), tap water (TW), and lake water (LW).

[0050] 4. Desorption capacity The desorption performance of PFOS on the thermosensitive fluorinated material obtained in Example 1 was studied under different elution conditions. Experimental conditions: PFOS = 1 ppb, thermosensitive fluorinated material = 1 g / L.

[0051] Traditional PFAS elution methods typically rely on large amounts of organic solvents to achieve near 100% desorption by disrupting weak interactions. For example... Figure 7 As shown, the thermosensitive fluorinated material constructed in this study can achieve enhanced elution through temperature response. At 50℃, only 20% MeOH is required to achieve a near-complete desorption efficiency comparable to 100% MeOH. Further addition of a small amount of salt solution can effectively reduce the amount of MeOH needed; for example, with the synergistic effect of 0.1% NaOH and 10% MeOH, a desorption rate of approximately 90% can be achieved, while with 0.1% NaOH and 20% MeOH, 100% can be reached. This highly efficient desorption performance is mainly attributed to the fact that NaOH enhances the surface charge repulsion of the thermosensitive fluorinated material, the alcohol solvent disrupts the weak interaction between the thermosensitive fluorinated material and PFAS, and the temperature-induced changes in the hydrophobicity of the thermosensitive fluorinated material structure also contribute to the synergistic effect.

Claims

1. A method for producing a temperature-sensitive fluorinated material, characterized by, The application relates to a preparation method of a temperature-sensitive fluorinated material. The fluorine-containing olefin monomer is hexafluorobutyl methacrylate, 1H, 1H, 5H-octafluoropentyl methacrylate, 2-(perfluorobutyl) ethyl methacrylate or 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl methacrylate.

2. The production method according to claim 1, wherein The nitrogen-containing temperature-sensitive monomer is isopropyl acrylamide.

3. The production method according to claim 1, wherein The photoinitiator is at least one of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone or 1-hydroxycyclohexyl phenyl ketone. The crosslinking agent is at least one of N,N'-methylene bisacrylamide, N,N'-vinyl bisacrylamide or N,N'-dipropyl acrylamide. The molar ratio of fluorine in the fluorine-containing olefin monomer, nitrogen in the nitrogen-containing temperature-sensitive monomer, the photoinitiator and the crosslinking agent is (4-15):(9-20):(0.1-0.2):(0.1-0.15).

4. The production method according to any one of claims 1 to 3, characterized by, The wavelength of the ultraviolet light is 320-410 nm, and the irradiation time of the ultraviolet light is 1-5 h.

5. The production method according to claim 4, wherein The preparation method of the traditional Chinese medicine residue cellulose dispersion liquid comprises the following steps: traditional Chinese medicine residue waste, potassium hydrogen persulfate and water are heated to generate an oxidation reaction, then heating is stopped, water is diluted and washed to obtain traditional Chinese medicine residue cellulose, and the traditional Chinese medicine residue cellulose is dispersed in dimethylformamide to obtain the traditional Chinese medicine residue cellulose dispersion liquid.

6. The production method according to any one of claims 1 to 3, wherein 7. The temperature-sensitive fluorinated material prepared by the preparation method in any one of claims 1-6. The temperature-sensitive fluorinated material turns to be opaque and shows hydrophobicity with the temperature rising, and turns to be transparent and shows hydrophilicity with the temperature falling.

8. The temperature-sensitive fluorinated material of claim 7, wherein, 9. Application of the temperature-sensitive fluorinated material prepared by the preparation method in any one of claims 1-6 or the temperature-sensitive fluorinated material in claim 7 or 8 in adsorption / desorption of PFAS in water. The water is at least one of tap water, lake water, river water and pure water.

10. Use according to claim 9, wherein ​

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