Biomass xerogel as well as preparation method and application thereof

Abstract

The invention relates to the field of environmental functional materials, in particular to biomass xerogel as well as a preparation method and application thereof. The invention provides biomass xerogel. The biomass xerogel comprises a framework and a fluoride siloxy group connected to the framework, the framework is formed by cross-linking quaternized cellulose, chitosan and a cross-linking agent. Cellulose is used as a main component of agricultural and forestry byproducts, has a stable hierarchical structure frame and rich hydroxyl groups, and is easy to carry out functional modification; chitosan is used as a natural polymer rich in amino groups, has complementarity with the structure of cellulose, and can realize crosslinking and generate electrostatic interaction; meanwhile, quaternary ammonium groups and fluoridized siloxy groups are introduced into a cellulose / chitosan skeleton, so that optimal balance and synergistic effects among hydrophilicity, surface positive charge density and fluorine affinity are realized, and excellent removal performance on various short-chain / ultra-short-chain PFAS is shown; and the composite material has excellent anti-interference capability, structural stability, good reproducibility and excellent recoverability after being discarded.

Description

Technical Field

[0001] This invention relates to the field of environmental functional materials, specifically to a biomass dry gel, its preparation method, and its applications. Background Technology

[0002] Perfluorinated and polyfluoroalkyl substances (PFAS) are known for their excellent thermal stability, chemical inertness, and surface activity in industrial production and consumer products. However, they have attracted significant global attention due to their widespread detection in aquatic environments, their bioaccumulation potential, and the associated health hazards. With increasing regulatory scrutiny and phasing out of long-chain PFAS (C≥6), the application of short-chain (C4-C6) and ultra-short-chain (C1-C3) PFAS alternatives is rapidly increasing. These substances are more water-soluble, have higher environmental mobility, and can form as degradation byproducts of long-chain PFAS in environmental matrices or during wastewater treatment, thus persisting in surface water and groundwater systems.

[0003] Granular activated carbon (GAC) is currently the most widely used commercial adsorbent, exhibiting excellent adsorption performance for long-chain PFAS. However, due to the reduced hydrophobicity and smaller molecular size of short-chain and ultrashort-chain PFAS, the microporous structure of GAC has limited affinity and adsorption capacity for these substances. Although ion exchange resins and metal-organic frameworks (MOFs) outperform GAC in some applications, each material has significant limitations: ion exchange resins have poor resistance to interference in complex aqueous matrices due to competition from coexisting ions; while MOFs face challenges such as high synthesis costs, poor stability in water, reliance on non-renewable precursors, and difficulty in scaling up production. Therefore, designing novel adsorbent materials that combine tunable functionality, environmental sustainability, and cost-effectiveness to achieve efficient capture of persistent short-chain and ultrashort-chain PFAS has become an urgent priority. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that the adsorbent materials in the prior art have poor adsorption performance for short-chain and ultra-short-chain PFAS, thereby providing a biomass dry gel, its preparation method and application.

[0005] In a first aspect, the present invention provides a biomass dry gel comprising a backbone and fluorinated siloxy groups attached to the backbone; the backbone is cross-linked from quaternized cellulose, chitosan, and a cross-linking agent; the fluorinated siloxy groups are formed by hydrolysis and condensation of a silane precursor; the silane precursor comprises at least one of 3,3,3-trifluoropropyltrimethoxysilane, 1H,1H,2H,2H-nonafluorohexyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane; the cross-linking agent comprises at least one of glutaraldehyde, epichlorohydrin, and 1,4-butanediol diglycidyl ether.

[0006] In some alternative embodiments, the porosity of the biomass dry gel is 87%-91%.

[0007] In some alternative embodiments, the biomass dry gel contains 14.30%-14.75% fluorine by mass.

[0008] In some alternative embodiments, the mass fraction of nitrogen in the biomass dry gel is 1.50%-1.85%.

[0009] In a second aspect, the present invention provides a method for preparing the biomass dry gel described in the first aspect, comprising the following steps: S1, mixing purified cellulose with an alkali and a quaternizing agent, and obtaining quaternized cellulose after reaction, filtration, and washing; S2, mixing quaternized cellulose with chitosan and fluorinated silane, adding a crosslinking agent after hydrolysis, and obtaining the biomass dry gel after crosslinking reaction, freezing, thawing, washing, and drying.

[0010] In some optional embodiments, in S1, the quaternizing agent includes at least one of glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and trimethyl[3-(triethoxysilyl)propyl]ammonium chloride.

[0011] In some alternative embodiments, the chitosan has a molecular weight of 9000-12000.

[0012] In some optional embodiments, in S1, the mass ratio of the purified cellulose to the alkali and the quaternizing agent is 1:(2-3):(1-4).

[0013] In some optional embodiments, in S1, the alkaline agent is at least one of NaOH aqueous solution, KOH aqueous solution, and ammonia solution.

[0014] In some optional embodiments, in S1, the concentration of the alkali is 4wt%-6wt%.

[0015] In some optional embodiments, in S1, the reaction temperature is 70°C-90°C; the reaction time is 5h-7h.

[0016] In some optional embodiments, in S1, the washing reagent is water; the pH after washing is 6-8.

[0017] In some optional embodiments, the method for preparing the purified cellulose includes the following steps: pulverizing the cellulose-containing raw material and mixing it with an oxidant, subjecting it to an oxidation reaction and filtration, mixing and stirring the solid with an alkali agent, filtering it, and washing the solid to obtain cellulose.

[0018] In some alternative embodiments, the cellulose-containing raw material includes at least one of office waste paper, pine wood, eucalyptus wood, fir wood, and corn stalks.

[0019] In some alternative embodiments, the mass ratio of the cellulose-containing raw material to the oxidant is 1:(1-1.5).

[0020] In some optional embodiments, the oxidant is at least one selected from NaClO2 aqueous solution, H2O2 aqueous solution, NaClO aqueous solution, and CH3COOOH aqueous solution; the concentration of the oxidant is 5wt%-7wt%; and the pH of the oxidant is 3-4.

[0021] In some optional embodiments, the oxidation reaction is carried out at a temperature of 70°C-90°C and for a duration of 0.5h-2h.

[0022] In some optional embodiments, the alkaline agent is at least one of NaOH solution, KOH aqueous solution, and ammonia solution.

[0023] In some optional embodiments, the concentration of the alkali is 4wt%-6wt%.

[0024] In some optional embodiments, the mixing temperature is 70℃-90℃; the mixing time is 0.5-2h.

[0025] In some alternative embodiments, the washing agent is water; the pH after washing is 6-8.

[0026] In some optional embodiments, in S2, the mass ratio of the quaternized cellulose, chitosan, fluorinated silane, and crosslinking agent is (0.3-0.5):(0.1-0.2):(0.8-1.2):(0.3-0.5).

[0027] In some alternative embodiments, in S2, the solvent for the hydrolysis reaction is deionized water.

[0028] In some optional embodiments, in S2, the concentration of the quaternized cellulose in the solvent is 0.02wt%-0.03wt%.

[0029] In some alternative embodiments, the fluorinated silane includes at least one of 3,3,3-trifluoropropyltrimethoxysilane, 1H,1H,2H,2H-nonafluorohexyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane.

[0030] In some alternative embodiments, the crosslinking agent includes at least one of glutaraldehyde, epichlorohydrin, and 1,4-butanediol diglycidyl ether.

[0031] In some optional embodiments, in S2, the temperature of the hydrolysis reaction is 25°C-30°C; and the time of the hydrolysis reaction is 0.5h-2h.

[0032] In some optional embodiments, in S2, the temperature of the crosslinking reaction is 25°C-30°C; the time of the crosslinking reaction is 1 min-5 min.

[0033] In some optional embodiments, in S2, the washing reagent is water; the pH after washing is 6-8.

[0034] Thirdly, the present invention provides the application of biomass dry gel as described in the first aspect or prepared by the preparation method described in the second aspect in the adsorption treatment of wastewater containing perfluorinated and / or polyfluoroalkyl substances.

[0035] The technical solution of this invention has the following advantages: 1. This invention provides a biomass degel, comprising a backbone and fluorinated silicate groups attached to the backbone; the backbone is cross-linked from quaternized cellulose, chitosan, and a cross-linking agent. In the biomass degel provided by this invention, cellulose, as a major component of agricultural and forestry byproducts, possesses a stable hierarchical structural framework and abundant hydroxyl groups, making it highly susceptible to functionalization. Chitosan, as a natural polymer rich in amino groups, is structurally complementary to cellulose, enabling efficient cross-linking and electrostatic interactions. Simultaneously, the introduction of quaternary ammonium groups and non-PFAS fluorinated silicate groups into the cellulose / chitosan backbone achieves an optimized balance and synergistic effect between hydrophilicity, surface positive charge density, and fluorinophilicity, exhibiting excellent removal performance for various short-chain / ultra-short-chain PFAS, and possessing excellent anti-interference ability, robust structural stability, good regenerability after multiple cycles, and excellent recyclability after disposal.

[0036] 2. The biomass degel provided by this invention is modified with fluorinated silanes of different chain lengths to optimize steric hindrance and adsorption selectivity. Using abundant renewable resources such as waste paper, forestry residues, and agricultural waste as the main sources, it not only significantly reduces raw material costs but also improves the sustainability and resource utilization level of the material, achieving high-value transformation of waste. This material exhibits excellent performance in adsorption, mechanical stability, and regeneration recycling, further highlighting the potential for large-scale application of the biomass degel provided by this invention in practical water treatment. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart illustrating the preparation and application of the biomass dry gel of this invention; Figure 2 These are examples of purified cellulose slurry and biomass dry gel from Example 1 of the present invention; wherein, (a) is the purified cellulose slurry; (b), (c), and (d) are the morphological structures of the prepared dry gel; Figure 3 This is a diagram showing the pore parameters of the biomass dry gels prepared in Examples 1-4 and Comparative Example 1 of this invention; Figure 4 This is a graph showing the mass fractions of F and N in the biomass dry gels prepared in Examples 1-3 of this invention; Figure 5 This is a graph showing the removal rate of perfluorobutyric acid by the biomass dry gels prepared in Examples 1 and 5-7 of this invention; Figure 6 This is a graph showing the effect of the biomass dry gel prepared in Example 1 of the present invention on the removal efficiency of perfluorobutyric acid under different pH conditions; Figure 7 This is a graph showing the removal efficiency of biomass dry gel and granular activated carbon prepared in Example 1 of this invention for different PFAS. Figure 8 The graph shows the effect of ions and natural organic matter on the removal of perfluorobutyric acid by the biomass dry gels prepared in Example 1 and Comparative Example 1 of this invention. Figure 9 This is a graph showing the cyclic adsorption-desorption performance of the biomass dry gel prepared in Example 1 for the removal of perfluorobutyric acid, perfluoropropionic acid, and trifluoroacetic acid. Figure 10These are verification diagrams of the recyclability of the biomass dry gel prepared in Example 1 of the present invention; (a) schematic diagram of the recycling process; (b) diagram of the removal efficiency of the initial dry gel and the secondary dry gel for different PFAS. Figure 11 This is a breakthrough curve of a fixed bed column of biomass dry gel prepared in Example 1 of the present invention against different PFAS. Detailed Implementation

[0039] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0040] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0041] Example 1 This embodiment provides a method for preparing biomass dry gel, including... Figure 1 The steps shown are as follows: (1) Disperse 10 g of pulverized office waste paper in 200 mL of 6.25 wt% NaClO2 solution (pH=3.5) and stir at 80 ℃ for 1 hour. After filtration and washing, transfer the solid to 200 mL of 5 wt% NaOH solution and continue stirring at 80 ℃ for 1 hour. Finally, wash until neutral to obtain purified cellulose. The slurry of purified cellulose is as follows: Figure 2 As shown in 'a'.

[0042] (2) Take 1 g of the above cellulose, add 50 mL of 5 wt% NaOH solution and 2 g of glycidyltrimethylammonium chloride, react at 80 °C for 6 hours, filter after the reaction is complete, wash the filter cake until neutral to obtain quaternized cellulose.

[0043] (3) Dissolve 0.16 g of chitosan with a molecular weight of 10000 in 7.84 g of deionized water to prepare a homogeneous solution; disperse 0.4 g of quaternized cellulose in 7.6 g of deionized water to form a suspension. Mix the two solutions and stir evenly. Add 0.82 g of trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane and continue stirring for 1 hour to allow for complete hydrolysis. Add 0.4 g of glutaraldehyde (Glu) and stir rapidly for 2 minutes to initiate cross-linking and form a hydrogel. Freeze the hydrogel immediately and then thaw it at room temperature to obtain a dry gel precursor. Wash with deionized water until neutral and dry at room temperature to obtain the final product N. + -NFC / CS / 9F dry gel, the pore parameters of the prepared dry gel are as follows Figure 3 As shown, the mass fractions of F and N are as follows: Figure 4 As shown.

[0044] The prepared dry gel morphology and structure are as follows Figure 2 As shown in b, c, and d, this material possesses excellent overall molding properties. Furthermore, it can be prepared into xerogel products of different sizes and shapes as needed, demonstrating high process adaptability and plasticity. The preparation process is simple to operate, has good repeatability, and high raw material utilization, possessing the potential for large-scale production and suitable for industrial-grade applications.

[0045] Example 2 This embodiment provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that 0.82g of trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane in step (3) is replaced with 0.93g of 3,3,3-trifluoropropyltrimethoxysilane, to obtain N + -NFC / CS / 3F dry gel, the pore parameters of the prepared dry gel are as follows Figure 3 As shown, the mass fractions of F and N are as follows: Figure 4 As shown.

[0046] Example 3 This embodiment provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that 0.82g of trimethoxy(3,3,3-trifluoropropyl)silane in step (3) is replaced with 0.98g of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, to obtain N + -NFC / CS / 13F dry gel, the pore parameters of the prepared dry gel are as follows Figure 3 As shown, the mass fractions of F and N are as follows: Figure 4 As shown.

[0047] Example 4 This embodiment provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that 0.82g of trimethoxy(3,3,3-trifluoropropyl)silane in step (3) is replaced with 1.10g of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, to obtain N + -NFC / CS / 17F dry gel, the pore parameters of the prepared dry gel are as follows Figure 3 As shown, the mass fractions of F and N are as follows: Figure 4 As shown.

[0048] Example 5 This embodiment provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that the office waste paper in step (1) is replaced with corn stalks to obtain N. + -NFC / CS / 9F-2 dry gel.

[0049] Example 6 This embodiment provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that the office waste paper in step (1) is replaced with pine wood to obtain N. + -NFC / CS / 9F-3 dry gel.

[0050] Example 7 This embodiment provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that the office waste paper in step (1) is replaced with cedar wood, resulting in N + -NFC / CS / 9F-4 dry gel.

[0051] Example 8 This embodiment provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that the office waste paper in step (1) is replaced with eucalyptus wood to obtain N. + -NFC / CS / 9F-5 dry gel.

[0052] Comparative Example 1 This comparative example provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that trimethoxy(3,3,3-trifluoropropyl)silane is not added in step (3), resulting in N + -NFC / CS, the pore parameters of the prepared dry gel are as follows Figure 3 As shown.

[0053] Comparative Example 2 This comparative example provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that the trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane in step (3) is replaced with 2,2,3,3,4,4,5,5,5-nonafluoropentyl ethylene oxide, to obtain N + -NFC / CS / 9F-C.

[0054] Comparative Example 3 This comparative example provides a method for preparing biomass dry gel, which is the same as the preparation method in Example 1, except that chitosan is not added in step (3) to obtain N. + -NFC / 9F.

[0055] Test case Test Example 1 Solutions of PFBA (perfluorobutyric acid), PFPrA (perfluoropropionic acid), and TFA (trifluoroacetic acid) with an initial concentration of 100 μg / L and an initial pH of 6 were added to 50 mL sample vials, respectively. Then, 100 mg of the N2O2 solution prepared in Example 1 was added to each vial. + -NFC / CS / 9F dry gel was shaken at 25 ℃ and 180 rpm for 2 h. After adsorption was completed, 1 mL of supernatant was taken for testing by HPLC-MS / MS. The test results are shown in Table 1.

[0056] Test Example 2-13 The method for test case 2-13 is the same as that for test case 1, except that N in test case 1 is changed. + - NFC / CS / 9F dry gels were replaced sequentially with the N gels prepared in Examples 2-8. + -NFC / CS / 3F dry gel, N + -NFC / CS / 13F dry gel, N + -NFC / CS / 17F dry gel, N + -NFC / CS / 9F dry gel-2,N + -NFC / CS / 9F dry gel-3, N + -NFC / CS / 9F dry gel-4, N + -NFC / CS / 9F dry gel-5, N prepared in Comparative Example 1 + -NFC / CS, N prepared in Comparative Example 2 + -NFC / CS / 9F-C, N prepared in Comparative Example 3 + -NFC / 9F, ion exchange resin, and granular activated carbon (GAC) were tested, and the results are shown in Table 1. + -NFC / CS / 9F-2 dry gel, N + -NFC / CS / 9F-3 dry gel, N+ -NFC / CS / 9F-4 dry gel, N + -The removal rate of PFBA by NFC / CS / 9F-5 dry gel is as follows: Figure 5 As shown.

[0057] Table 1 Removal rates of PFBA, PFPrA and TFA

[0058] From Table 1 and Figure 5 It can be seen that, in the adsorption equilibrium experiment, the dry gel prepared by this method showed better removal rates of PFBA, PFPrA, and TFA than the comparative example. Meanwhile, the N2O2 prepared from office waste paper... + -NFC / CS / 9F achieved removal rates of 97.1%, 96.2%, and 84.7% for PFBA, PFPrA, and TFA, respectively, significantly higher than GAC (33%-60%) and other fluorocarbon chain lengths in dry gels. The results indicate that the 9F chain length achieves an optimal balance between electrostatic attraction, FF interaction, and steric hindrance.

[0059] Test Example 14 (1) Prepare a 100 μg / L PFBA solution and adjust the initial pH to 3 with 1 M H2SO4 / 1 M NaOH to obtain solution a; (2) Take 100mg N + -NFC / CS / 9F was added to 50 mL of solution a, and the mixture was shaken at 25 ℃ and 180 rpm for 2 h. After adsorption was complete, 1 mL of the supernatant was taken for testing using LC-MS / MS. The test results are as follows. Figure 6 As shown.

[0060] Test Example 15-21 The method for Test Examples 15-21 is the same as that for Test Example 14, the difference being that the initial pH values ​​are 4, 5, 6, 7, 8, 9, and 10 respectively. The test results are as follows: Figure 6 As shown.

[0061] Depend on Figure 6 It can be seen that, at different pH levels, the N prepared in Example 1... + -NFC / CS / 9F all achieved a PFBA removal rate of over 95%, demonstrating excellent adsorption performance for PFBA.

[0062] Test Example 22 (1) Prepare a 100 μg / L solution of PFBA, PFOA (perfluorooctanoic acid), PFPrS (perfluoropropane sulfonic acid), PFPrA, PFEtS (perfluoroethane sulfonic acid), TFMS (trifluoromethane sulfonic acid), and TFA, and adjust the initial pH to 6 with 1 M H2SO4 / 1 M NaOH; (2) Take 100mg N + -NFC / CS / 9F were added to 50 mL of the above solution respectively, and the mixture was shaken at 25 °C and 180 rpm for 2 h. After adsorption was complete, 1 mL of the supernatant was taken for LC-MS / MS analysis. The test results are as follows. Figure 7 As shown.

[0063] Test Example 23 The method for test case 23 is the same as that for test case 22, the difference being that N in test case 22 is changed. + Replace NFC / CS / 9F with GAC, and the test results are as follows: Figure 7 As shown.

[0064] Depend on Figure 7 It can be seen that, under the same experimental conditions, the N prepared in Example 1... + -NFC / CS / 9F exhibits significantly higher removal efficiencies than traditional granular activated carbon (GAC) and N2O prepared in Comparative Example 1 for various perfluorinated and polyfluoroalkyl substances, including PFBA, PFOA, PFPrS, PFPrA, PFEtS, TFMS, and TFA. + -NFC / CS shows great potential in high-efficiency water treatment technology and pollution control applications.

[0065] Test Example 24 In 11 solutions (50 mL each) containing 100 μg / L PFBA, 1 mM F was added to each solution. - Cl - CO3 2- SO4 2- PO4 3- K + Na + Mg 2+ Ca 2+ PAEs (phthalates) or humic acids (HA) are used as interfering agents. Then N is added. + Adsorption experiments were conducted using NFC / CS / 9F dry gel (dosage 2 g / L). After adsorption, 1 mL of the supernatant was taken and analyzed by LC-MS / MS. The test results are as follows: Figure 8 As shown.

[0066] Test Case 25 The method for Test Example 25 is the same as that for Test Example 24, except that the N prepared in Example 1 is used instead of the N. + - Replace the NFC / CS / 9F dry gel with the N prepared in Comparative Example 1. + -NFC / CS dry gel, test results are as follows Figure 8 As shown.

[0067] Depend on Figure 8 It can be seen that, in the presence of multiple interfering factors, N + -NFC / CS / 9F reduced the PFBA removal rate by less than 3%, demonstrating excellent anti-interference ability, and was superior to the N prepared in Comparative Example 1. + -NFC / CS. This indicates that N + -NFC / CS / 9F dry gel exhibits excellent anti-interference ability and stability, indicating that the material can still maintain high removal performance under complex environmental conditions.

[0068] Test Case 26 (1) Adsorb saturated N + -NFC / CS / 9F dry gel was desorbed with a mixture of methanol and 100 mM ammonium hydroxide (5:95, v / v), then washed with deionized water for the next adsorption cycle.

[0069] (2) Prepare 100 μg / L solutions of PFBA, PFPrS and TFA respectively, and adjust the initial pH to 6 with 1 M H2SO4 / 1 M NaOH; (2) Take 250mg N + -NFC / CS / 9F were added to 50 mL of the above solution, and the mixture was shaken at 25 °C and 180 rpm for 2 h. After adsorption was complete, 1 mL of the supernatant was taken for LC-MS / MS analysis. The analysis was repeated 5 times. The test results are as follows. Figure 9 As shown.

[0070] Depend on Figure 9 It can be seen that after 5 adsorption-desorption cycles, its removal rate of PFBA, PFPrA and TFA still remains above 96%, proving that it has good regeneration performance and structural stability.

[0071] Test Example 27 (1) After one use, N + -NFC / CS / 9F dry gel was mechanically pulverized and dispersed in 10 mL of water.

[0072] (2) Add fresh chitosan solution (2 wt%) equivalent to 50% of the original formula and 0.4 g glutaraldehyde as a crosslinking agent to the above dispersion. After freeze-thaw cycles and drying at room temperature, regenerated N is obtained. + -NFC / CS / 9F dry gel.

[0073] (3) Prepare 100 μg / L solutions of PFBA, PFOA, PFPrS, PFPrA, PFEtS, TFMS, and TFA respectively, and adjust the initial pH to 6 with 1 M H2SO4 / 1 M NaOH; (4) Regenerate 100mg of N+ - NFC / CS / 9F dry gels were added to 50 mL of the above solution, and the mixture was shaken at 25 °C and 180 rpm for 2 h. After adsorption was complete, 1 mL of the supernatant was taken for LC-MS / MS analysis. The test results are as follows. Figure 10 As shown.

[0074] Depend on Figure 10 From b, we can know that, after Figure 10 N prepared by process a in + -NFC / CS / 9F regenerated dry gel maintains a stable removal rate of 83%-97% for seven perfluorinated and polyfluoroalkyl substances, including PFBA, PFOA, and TFA, comparable to the performance of the original dry gel, thus enabling the recycling of the material.

[0075] Test Example 28 (1) 3 gN + -NFC / CS / 9F dry gel is packed into a fixed-bed adsorption column.

[0076] (2) PFOA, PFBA, PFPrA, PFPrS, PFEtS, TFMS, TFA and interfering substance F were added at a concentration of 100 μg / L. - Cl - CO3 2- SO4 2- PO4 3- K + Na + Mg 2+ Ca 2+ A mixed solution of PAEs and HA was used as influent for a dynamic breakthrough experiment, and the results are as follows: Figure 11 As shown. The concentrations of PFOA, PFBA, PFPrA, PFPrS, PFEtS, TFMS, and TFA were 100 μg / L; F - Cl - CO3 2- SO4 2- PO4 3- K + Na + Mg 2+ Ca 2+ The concentrations of PAEs and HA were 1 mM.

[0077] Depend on Figure 11It can be seen that, taking the Chinese "Standards for Drinking Water Quality" (GB 5749-2022) as the breakthrough point, the dry gel column can handle 97 and 105 bed volumes (BV) of ultra-short chain TFA and TFMS, respectively, and 125 and 108 BV of short chain PFBA and PFPrA, respectively, indicating that it has excellent dynamic adsorption capacity and operational stability under simulated real water treatment conditions.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A biomass dry gel, characterized in that, Includes the framework and the fluorinated silicon oxides attached to the framework; The backbone is cross-linked from quaternized cellulose, chitosan and a cross-linking agent; The fluorinated siloxy group is formed by hydrolysis and condensation of a silane precursor; the silane precursor includes at least one of 3,3,3-trifluoropropyltrimethoxysilane, 1H,1H,2H,2H-nonafluorohexyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane. The crosslinking agent includes at least one of glutaraldehyde, epichlorohydrin, and 1,4-butanediol diglycyl ether.

2. The biomass dry gel according to claim 1, characterized in that, The porosity of the biomass dry gel is 87%-91%; And / or, the mass fraction of fluorine in the biomass dry gel is 14.30%-14.75%; And / or, the mass fraction of nitrogen in the biomass dry gel is 1.50%-1.85%.

3. The method for preparing biomass dry gel according to claim 1 or 2, characterized in that, Includes the following steps: S1. The purified cellulose is mixed with an alkali and a quaternizing agent, and after reaction, filtration and washing, quaternized cellulose is obtained. S2. Quaternized cellulose is mixed with chitosan and fluorinated silane. After hydrolysis, a crosslinking agent is added. The mixture undergoes crosslinking reaction, freezing, thawing, washing, and drying to obtain the biomass dry gel.

4. The preparation method according to claim 3, characterized in that, In S1, the quaternizing agent includes at least one of glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and trimethyl[3-(triethoxysilyl)propyl]ammonium chloride; And / or, the molecular weight of the chitosan is 9000-12000; And / or, in S1, the mass ratio of the purified cellulose to the alkali agent and the quaternizing agent is 1:(2-3):(1-4); And / or, in S1, the alkaline agent is at least one of NaOH aqueous solution, KOH aqueous solution, and ammonia solution; And / or, in S1, the concentration of the alkali is 4wt%-6wt%.

5. The preparation method according to claim 3 or 4, characterized in that, In S1, the reaction temperature is 70℃-90℃; the reaction time is 5h-7h. And / or, in S1, the washing reagent is water; the pH after washing is 6-8.

6. The preparation method according to claim 3 or 4, characterized in that, The method for preparing the purified cellulose includes the following steps: pulverizing the cellulose-containing raw material and mixing it with an oxidant, undergoing an oxidation reaction and filtration, mixing and stirring the solid with an alkali agent, filtering, and washing the solid to obtain cellulose.

7. The preparation method according to claim 6, characterized in that, The cellulose-containing raw materials include at least one of the following: office waste paper, pine wood, eucalyptus wood, fir wood, and corn stalks; And / or, the mass ratio of the cellulose-containing raw material to the oxidant is 1:(1-1.5); And / or, the oxidant is at least one selected from NaClO2 aqueous solution, H2O2 aqueous solution, NaClO aqueous solution, and CH3COOOH aqueous solution; the concentration of the oxidant is 5wt%-7wt%; and the pH of the oxidant is 3-4. And / or, the oxidation reaction temperature is 70℃-90℃; the oxidation reaction time is 0.5h-2h; And / or, the alkaline agent is at least one of NaOH solution, KOH aqueous solution, and ammonia solution; And / or, the concentration of the alkali is 4wt%-6wt%; And / or, the mixing temperature is 70℃-90℃; the mixing time is 0.5h-2h; And / or, the washing reagent is water; the pH after washing is 6-8.

8. The preparation method according to claim 3, characterized in that, In S2, the mass ratio of quaternized cellulose, chitosan, fluorinated silane, and crosslinking agent is (0.3-0.5):(0.1-0.2):(0.8-1.2):(0.3-0.5). And / or, in S2, the solvent for the hydrolysis reaction is deionized water; And / or, in S2, the concentration of the quaternized cellulose in the solvent is 0.02wt%-0.03wt%.

9. The preparation method according to claim 3, characterized in that, In S2, the fluorinated silane includes at least one of 3,3,3-trifluoropropyltrimethoxysilane, 1H,1H,2H,2H-nonafluorohexyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane. And / or, in S2, the crosslinking agent includes at least one of glutaraldehyde, epichlorohydrin, and 1,4-butanediol diglycidyl ether; And / or, in S2, the temperature of the hydrolysis reaction is 25℃-30℃; the time of the hydrolysis reaction is 0.5h-2h; And / or, in S2, the temperature of the crosslinking reaction is 25℃-30℃; the time of the crosslinking reaction is 1min-5min; And / or, in S2, the washing reagent is water; the pH after washing is 6-8.

10. The application of the biomass dry gel prepared by the preparation method according to any one of claims 3-9 or the biomass dry gel according to claim 1 or 2 in the adsorption treatment of wastewater containing perfluorinated and / or polyfluoroalkyl substances.

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