Organic amine cation cage or adsorbent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of new pollutant removal, and discloses an organic amine cation cage or adsorbent, a preparation method thereof and application of the organic amine cation cage or adsorbent to adsorption of PFASs wastewater. The preparation method comprises the following steps: firstly, synthesizing an organic amine molecular cage, and changing the organic amine molecular cage into a flexible organic amine cation cage with a strong adsorption effect on anions PFASs through a series of structural modifications; the organic amine cation cage has good water solubility, so that the PFASs in the concentration wastewater are difficult to precipitate and reduce, and the adsorption of the PFASs is realized by fully utilizing the organic amine cation cage. An organic amine cation cage is combined with an inorganic porous material, and the filler has the characteristics of high adsorption rate, high removal rate, good reusability and the like when being used for removing PFASs in wastewater, and is suitable for purification treatment of fluorinated wastewater in a sewage treatment plant.

Description

Technical Field

[0001] The present invention relates to the technical field of PFASs wastewater treatment, and particularly relates to an organic amine cationic cage or adsorbent, a preparation method thereof, and an application thereof. Background Art

[0002] Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of highly persistent compounds, and their inertness enables them to spread widely in water and soil. The pollution of surface water and groundwater has become an urgent environmental problem. Among them, the most common and toxic ones are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). PFASs have the ability to bind to proteins and accumulate in the body, and are associated with a series of harmful effects, such as kidney and liver damage, immunotoxicity, reproductive toxicity, and cancer. Therefore, developing technologies capable of removing PFASs from contaminated water is motivating.

[0003] Adsorption remains an attractive method for PFASs remediation because of its low operating cost, simple design, and mild nature. Adsorbents that have been studied for removing PFASs include activated carbon, ion exchange resins, minerals, metal-organic frameworks, and covalent organic frameworks. However, these adsorbents have some limitations to varying degrees, such as the need for long equilibrium times, low binding affinity, and poor stability. Ideally, an improved adsorbent for PFASs will exhibit the following characteristics: (i) a high density of binding sites, (ii) strong interaction with PFASs, (iii) a fast adsorption rate; (iv) water and chemical stability, and (v) good reusability, etc.

[0004] CN117920217A discloses an α-Fe 2 O 3 material and a preparation method and application thereof. The preparation method includes: a precursor preparation step: dissolving a trivalent iron source to obtain an iron salt solution, adding a dispersant under stirring conditions to coat and separate the iron ions, generating a flocculent brown precipitate to obtain a precursor suspension, separating the precipitate therefrom and successively performing washing and purification, drying, and pulverizing and sieving treatments on the precipitate to obtain a precursor; a calcination step: heat-treating the precursor in an inert atmosphere, and then pulverizing and sieving to obtain an α-Fe 2 O 3 material. The Fe 2 O 3 particles in this material have a hydrophobic surface, and there is a confined space between adjacent two Fe 2 O 3 particles, which can limit the movement of reactant molecules, broaden the degradation pathway, so that under ultraviolet light excitation, PFASs quickly aggregate on the hydrophobic Fe 2 O 3on the particle surface and degrade better in the confined space.

[0005] CN114752002A uses chitosan as the original modification matrix, and modifies chitosan through 3-aminopropyltriethoxysilane and 3-chloro-2-hydroxypropylammonium chloride to obtain an organically modified chitosan adsorbent. The maximum adsorption capacity for PFOA can reach 3730.2 mg / g, and it also has good removal efficiency for other common PFASs. The adsorbent for removing PFASs has stable physical and chemical properties and has great potential in the treatment of fluorine-containing industrial wastewater, especially suitable for the purification of medium and low-concentration PFASs.

[0006] As a kind of organic molecular cage, organic amine molecular cage not only has the common properties of organic molecular cages such as strong structural designability, open cavities, good solubility, uniformly adjustable cavities, and high internal surface area, but also has rich N sites on its structural skeleton, with high positive charge, and has good adsorption for PFASs with negative charges. However, organic amine molecular cages have high hydrophobicity, which is not conducive to the removal of PFASs in water, and organic amine molecular cages are independent molecular structures, which are not conducive to recycling when dispersed in water and are difficult to reuse. How to efficiently use organic amine molecular cages to remove PFASs in water is worthy of further exploration. Summary of the Invention

[0007] Aiming at the problem that the concentration of PFASs in wastewater is relatively low and the removal effect is difficult to meet the safety standards of domestic drinking water, the present invention provides a method for removing PFASs in wastewater by using organic amine molecular cages in combination with inorganic porous materials, which can achieve high-efficiency adsorption of PFASs at low concentrations.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A preparation method of an organic amine cation cage, comprising the steps of:

[0010] Step 1: Disperse phloroglucinol in a solvent, add a solution of diamine ligand and let it stand for crystallization, and obtain crystals, which are recrystallized, washed, and dried to obtain an organic imine cage;

[0011] Step 2: Dissolve the organic imine cage in a solvent, add sodium borohydride for reduction reaction to obtain a flexible organic amine molecular cage;

[0012] Step 3: Add inorganic acid to the flexible organic amine molecular cage until it is dissolved, and freeze-dry to obtain an organic amine cation cage.

[0013] Due to the relatively low concentrations of PFASs in domestic and industrial wastewater, there are great difficulties in the actual removal process. Although existing porous materials have a certain removal effect on PFASs, it is still difficult to meet the safety standards for domestic drinking water. The organic imine cage prepared in the present invention is structurally modified to prepare an organic amine molecular cage with a high positive charge density. The abundant cationic sites on the periphery of the organic amine cation cage can be used to achieve efficient adsorption of PFASs. Since the organic amine cation cage has good water solubility and is difficult to precipitate PFASs in low-concentration wastewater, in order to make full use of the organic amine cation cage to achieve the adsorption of PFASs.

[0014] In step 1, the solvent includes one or more of methanol, acetonitrile, dichloromethane, and ethyl acetate;

[0015] In step 1, the standing time is 5 min - 360 h, and the standing temperature is 15 - 180 °C; the longer the reaction time of the two raw materials, the better the crystallinity. However, the higher the probability of amine oxidation. Within this range, the crystallization effect is good and the yield is high. The method of synthesizing the organic imine cage by static crystallization in the present invention has the advantages of simple synthesis method and relatively high synthesis yield. The organic amine cation cage prepared by structural modification not only has abundant cationic sites but also has good water solubility, which can greatly improve the adsorption efficiency of PFASs and is expected to achieve efficient removal of PFASs at low concentrations.

[0016] The solvent used for recrystallization includes one or more of methanol, acetonitrile, dichloromethane, and ethyl acetate.

[0017] The diamine ligand includes any one or more of ethylenediamine, propylenediamine, (1R,2R)-cyclopentanediamine, (1S,2S)-cyclopentanediamine, (1R,2R)-cyclohexanediamine, and (1S,2S)-cyclohexanediamine;

[0018] Preferably, the diamine ligand is any one or more of (1R,2R)-cyclopentanediamine, (1S,2S)-cyclopentanediamine, (1R,2R)-cyclohexanediamine, and (1S,2S)-cyclohexanediamine; the amino group on this ligand has a more suitable condensation angle with the aldehyde group on mellitene trialdehyde, making it easier to synthesize the imine cage.

[0019] The molar ratio of the mellitene trialdehyde to the diamine ligand is 1:1 - 3;

[0020] In step 2, the solvent includes a mixed solvent of one or more of deionized water, methanol, ethanol, and dichloromethane;

[0021] The molar ratio of the organic imine cage to sodium borohydride is 1:12 - 60;

[0022] In Step 2, the reduction reaction temperature is 0 - 50 °C and the reaction time is 9 - 48 h.

[0023] In Step 3, the inorganic acid includes any one or more of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrobromic acid, and hydroiodic acid.

[0024] The present invention also provides a preparation method of an adsorbent of an organic amine molecular cage synergistic inorganic porous material. The organic amine cation cage prepared by the preparation method and the inorganic porous material are mixed or filled into a packing column in an interlayer manner to obtain the adsorbent.

[0025] In order to enhance the water permeability of the material and reduce the application cost, the present invention combines the organic amine cation cage with the inorganic porous material to make a filler capable of efficiently removing PFASs. The inorganic porous material can adsorb the organic amine cation cage so that it is neither washed away by the water flow nor sacrifices the cation adsorption sites on its surface, realizing efficient adsorption of low-concentration PFASs. Using this filler to remove PFASs from wastewater has the characteristics of fast adsorption rate, high removal rate, and good reusability, and is suitable for the purification treatment of fluorinated wastewater in sewage treatment plants.

[0026] The inorganic porous material includes one or more of silica gel, alumina, alum, and activated carbon; preferably, silica gel is selected as the inorganic porous material in the filler. The use cost of silica gel is low, and the organic amine molecular cage can be recovered by dissolving silica gel in an alkaline solution, enhancing the recycling rate of the molecular cage.

[0027] The mass ratio of the organic amine cation cage to the inorganic porous material is 1:5 - 100. The preparation cost of the organic amine cation cage is relatively high compared to the inorganic porous material. The filler mixed in this ratio can control the cost without affecting the removal effect. Further preferably, the mass ratio of the organic amine cation cage to the inorganic porous material is 1:2 - 10. Preparing the filler in an interlayer mode is mainly to more efficiently utilize the cation sites of the organic amine molecular cage, maintaining a high local concentration of the adsorbent when PFASs wastewater passes through the packing column and enhancing the adsorption efficiency of PFASs.

[0028] The present invention also provides the organic amine cation cage or adsorbent prepared by the above preparation method.

[0029] The present invention also provides the application of the organic amine cation cage or adsorbent in removing PFASs. This application specifically includes the steps of: putting the organic amine cation cage or adsorbent into the wastewater containing PFASs, and making the organic amine cation cage or adsorbent adsorb PFASs by the flow, stirring, or oscillation of the wastewater. The adsorption experiment of PFASs wastewater is simulated through a micro syringe device, controlling the flow rate of PFASs wastewater, and the concentration of the treated wastewater can reach the sanitary standard of domestic drinking water specified in GB 5749 - 2022 within a certain time.

[0030] The time for adsorbing PFASs in the application is 1 - 2000 h;

[0031] Preferably, during the adsorption process in the application, the flow rate of the wastewater is 10 - 1000 mL / h -1 .

[0032] After the organic amine cation cage or adsorbent adsorbing PFASs in the application is collected by filtration, it is treated with an inorganic base and then recycled to obtain a flexible organic amine molecular cage, which is reused after acidification in Step 3. This greatly reduces the cost and is expected to achieve industrial application.

[0033] The pH of the inorganic base treatment solution is > 10, and it is treated for 5 - 60 min, and the flexible organic amine molecular cage is obtained by filtration and recycling.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention prepares an organic amine cation cage as a material for removing PFASs-containing wastewater, which has a high positive charge density, high hydrophilicity, strong interaction with PFASs, and an extremely high adsorption rate. It is an ideal PFAS removal material. The filler for removing PFASs prepared from an organic molecular cage and an inorganic porous material not only solves the problem of difficult removal of PFASs at low concentrations, but also improves the reuse rate of the organic amine molecular cage, controls the economic cost, and is expected to further achieve industrial application. Description of the Drawings

[0036] Figure 1 It is the X-ray powder diffraction (XRD) pattern of the organic imine cage CC3-R obtained in Example 1.

[0037] Figure 2 It is the nuclear magnetic resonance hydrogen spectrum ( 1 1H NMR) pattern of the flexible organic amine molecular cage RCC3-R obtained in Example 2.

[0038] Figure 3 It is the Fourier transform infrared spectroscopy (FTIR) spectrum of the organic amine cation cage obtained in Example 3.

[0039] Figure 4 It is the adsorption effect diagram of CC3-R on PFASs in Application Example 1.

[0040] Figure 5 It is the adsorption effect diagram of RCC3-R on PFASs in Application Example 2.

[0041] Figure 6 It is the adsorption effect diagram of ICC3-R on PFASs in Application Example 3.

[0042] Figure 7It is a device diagram for treating PFASs wastewater by the cooperation of organic amine molecular cages and inorganic porous materials in Application Example 4. Detailed implementation manners

[0043] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Those skilled in the art make modifications or equivalent replacements on the basis of understanding the technical solutions of the present invention, and without departing from the spirit and scope of the technical solutions of the present invention, they should all be covered within the protection scope of the present invention.

[0044] The raw materials used in the following detailed implementation manners are all purchased from the market.

[0045] Example 1

[0046] Weigh equal masses (1 g) of benzene-1,3,5-tricarbaldehyde and (1R,2R)-cyclohexane-1,2-diamine (the molar ratio of the two is 1:1.4), and disperse and dissolve them in 50 mL of dichloromethane respectively. Mix the two solutions evenly in a 100 mL glass bottle. The mixed solution is a clear and transparent solution at the beginning. Let it stand for 5 min, and the solution gradually becomes turbid. Continue to stand and crystallize at room temperature for 168 h until a relatively thick crystal layer appears on the inner wall of the glass bottle. Pour out the mother liquor, add dichloromethane again to dissolve, and continue to stand and recrystallize for 168 h. The recrystallized crystals are centrifugally washed with methanol solution and dried in an oven at 60 °C to obtain the organic imine cage CC3-R. The yield of the organic imine cage synthesized by this method can reach 80%, and the structure of its X-ray powder diffraction (XRD) pattern is consistent with the fitting structure of single crystal diffraction, as Figure 1 .

[0047] Example 2

[0048] Weigh 0.5 g of the organic imine cage sample prepared in Example 1 and add it to 30 mL of a solution of methanol:dichloromethane = 1:1. Then add 0.5 g of sodium borohydride for reduction (the molar ratio of the organic imine cage to sodium borohydride is 1:30). Stir and reduce at room temperature. After the reaction lasts for 24 h, the obtained organic amine molecular cage removes the reaction solvent by vacuum distillation, and then adds deionized water for centrifugal washing to remove borides. The yield of the obtained flexible organic amine molecular cage RCC3-R can be as high as 90%. The nuclear magnetic resonance spectrum of the synthesized material is as Figure 2 shown, proving that the flexible organic amine molecular cage is successfully synthesized.

[0049] Example 3

[0050] Weigh 0.25 g of the flexible organic amine molecular cage sample of Example 2, add it to 10 mL of 0.5 M hydrochloric acid solution until the sample is completely dissolved. The obtained clear solution is subjected to freeze-drying treatment. Finally, the yield of the organic amine cation cage ICC3-R is 100%. The infrared spectrum of the synthesized material is as shown in Figure 3 shown, which proves the successful synthesis of the organic amine cation cage.

[0051] Example 4

[0052] Weigh 1 g of benzene-1,3,5-tricarbaldehyde and dissolve it in 700 mL of ethyl acetate, and weigh 0.56 g of ethylenediamine and dissolve it in 100 mL of ethyl acetate (the molar ratio of the two is 1:1.5). Mix the two solutions evenly in a 1000 mL beaker. The mixed solution is a clear and transparent solution at the beginning. Let it stand for 5 min, and the solution gradually becomes turbid. Continue to stand and crystallize at room temperature for 60 h until relatively thick white needle-like crystals appear on the inner wall of the beaker. Pour out the mother liquor, add 400 mL of ethyl acetate again for recrystallization for 60 h. After the recrystallized crystals are poured into the washed crystals and air-dried, the organic imine cage CC1 is obtained, and the yield is 0.23 g. The yield of CC1 synthesized by this method is relatively low, only 29%.

[0053] Application Example 1

[0054] Weigh 5 mg of the organic imine cage CC3-R of Example 1 and add it to 40 mL of 1 g L -1 solutions of PFOA and PFOS respectively. Stir continuously at a speed of 400 rpm for 12 h, then centrifuge the adsorbent, and use a triple quadrupole liquid chromatography-mass spectrometry (LC-MS / MS) to test the adsorption efficiency of CC3-R for PFOA and PFOS. Its adsorption effect is as shown in Figure 4 shown. It can be seen that the organic imine cage has a good adsorption effect on PFOS, indicating that the N site has a positive effect on the adsorption of PFASs.

[0055] Application Example 2

[0056] Weigh 5 mg of the flexible organic amine molecular cage RCC3-R of Example 2 and add it to 40 mL of 1 g L -1 solutions of PFOA and PFOS respectively. Stir continuously at a speed of 400 rpm for 12 h, then centrifuge the adsorbent, and use LC-MS / MS to test the adsorption efficiency of CC3-R for PFOA and PFOS. Its adsorption effect is as shown in Figure 5 shown.

[0057] It can be seen that the flexible organic amine molecular cage has good adsorption effects on both PFOA and PFOS, indicating that the modified N sites improve the adsorption ability of the molecular cage for PFASs. It can be seen that the reduction process can enhance the positively charged property of the N sites and improve the adsorption effect on negatively charged PFASs.

[0058] Application Example 3

[0059] Weigh 5 mg of the organic amine cationic cage ICC3-R of Example 3 and add it to 40 mL of 1 g L -1 PFOA and PFOS solutions respectively, continuously stir at a speed of 400 rpm for 12 h, then centrifuge the adsorbent, and use LC-MS / MS to test the adsorption efficiency of CC3-R for PFOA and PFOS. The adsorption effect is as Figure 6 shown.

[0060] It can be seen that further modifying the N sites to improve the positive charge property of the molecular cage can greatly improve the adsorption efficiency of the molecular cage for PFASs, indicating that the charged adsorption organic amine cationic cage has great application prospects in the field of PFASs adsorption.

[0061] Application Example 4

[0062] Weigh 10 mg of the organic amine cationic cage ICC3-R sample of Example 3 and uniformly mix it with 990 mg of silica gel, and fill it into the device as Figure 7 shown, and then configure a 1500 ng L -1 PFOA solution for a simulated PFASs wastewater adsorption experiment. Add 40 mL of 1500 ng L -1 PFOA solution to the syringe, control the flow rate of the micro syringe to be 40 mL h -1 , after 1 h of simulated wastewater treatment, the concentration of the treated simulated PFOA solution is detected by LC-MS / MS to be 62.5 ng L -1 , and its removal rate is as high as 95.8%, which is lower than the hygienic standard for domestic drinking water specified in GB 5749-2022.

[0063] And the used packing is added to 20 mL of sodium hydroxide solution with pH = 14 and treated for 10 min, centrifuged, dried and re-acidified for use, and the recovery rate of the organic amine molecular cage is as high as 92.1%.

Claims

1. A method for preparing an organic amine cationic cage, characterized in that: Includes steps: Step 1, dispersing trimesaldehyde in a solvent, adding a solution of a diamine ligand and standing for crystallization, and obtaining crystals through recrystallization, washing, and drying to obtain an organic imine cage; Step 2, dissolving the organic imine cage in a solvent, adding sodium borohydride for reduction reaction to obtain a flexible organic amine molecular cage; Step 3, adding inorganic acid to the flexible organic amine molecular cage until it is dissolved, and freeze-drying to obtain the organic amine cationic cage.

2. The method for preparing an organic amine cationic cage according to claim 1, characterized in that: In step 1, the solvent includes one or more of methanol, acetonitrile, dichloromethane and ethyl acetate; And / or, in step 1, the standing time is 5 min-360 h, and the standing temperature is 15-180° C.; And / or, the recrystallization uses a solvent including one or more of methanol, acetonitrile, dichloromethane, and ethyl acetate.

3. The method for preparing an organic amine cationic cage according to claim 1, characterized in that: The diamine ligand includes any one or more of ethylenediamine, propylenediamine, (1R, 2R)-cyclopentanediamine, (1S, 2S)-cyclopentanediamine, (1R, 2R)-cyclohexanediamine, and (1S, 2S)-cyclohexanediamine; And / or, the molar ratio of trimesaldehyde to the diamine ligand is 1:1-3.

4. The method for preparing an organic amine cationic cage according to claim 1, characterized in that: In step 2, the solvent includes one or two of deionized water, methanol, ethanol, and dichloromethane; and / or, the molar ratio of the organic imine cage to sodium borohydride is 1:12-60; And / or, in step 2, the reduction reaction temperature is 0-50°C and the reaction time is 9-48h; And / or, the inorganic acid in step 3 includes any one or more of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrobromic acid, and hydroiodic acid.

5. A method for preparing an adsorbent of an organic amine cationic cage in cooperation with an inorganic porous material, characterized in that: The organic amine cationic cage obtained by the preparation method according to any one of claims 1 to 4 is mixed with an inorganic porous material or filled into a packing column in an interlayer manner to obtain the adsorbent.

6. The method for preparing an adsorbent of organic amine cationic cages in cooperation with inorganic porous materials according to claim 5, characterized in that: The inorganic porous material includes one or more of silica gel, alumina, alum and activated carbon; And / or, the mass ratio of the organic amine cationic cage to the inorganic porous material is 1:5-100.

7. An organic amine cationic cage prepared by the preparation method according to any one of claims 1 to 4 or an adsorbent prepared by the preparation method according to claim 5 or 6.

8. Use of the organic amine cationic cage or adsorbent according to claim 7 in removing PFASs.

9. The use according to claim 8, characterized in that: The method comprises the following steps: putting the organic amine cationic cage or adsorbent into wastewater containing PFASs, and allowing the organic amine cationic cage or adsorbent to adsorb PFASs by flowing, stirring or oscillating the wastewater.

10. The use according to claim 1, characterized in that: The time for adsorption of PFASs in the application is 1-2000h; And / or, in the application, the organic amine cationic cage or adsorbent after adsorbing PFASs is collected by filtration, treated with an inorganic base, and then recovered to obtain a flexible organic amine molecular cage, which is then reused after acidification in step 3 of claim 1.

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