Preparation method and application of aminated MIL-101 (Cr) material for enhancing adsorption of perfluorinated compound

Abstract

The invention discloses a preparation method and application of an aminated MIL-101 (Cr) material for enhancing adsorption of perfluorinated compounds, relates to the technical field of metal organic framework materials, and aims to enhance the adsorption effect of the aminated MIL-101 (Cr) material on the perfluorinated compounds. The preparation method comprises the following steps: taking MIL-101 (Cr) as a skeleton raw material and tris (2-aminoethyl) amine as an amination raw material, and then synthesizing and modifying to prepare the MIL-101 (Cr)-TAEA, the average pore size of which can be more than 7 times of that of the MIL-101 (Cr); the MIL-101 (Cr)-TAEA can be applied to removal of perfluorinated compounds in water, and after four times of cyclic regeneration, the total removal rate of PFASs is reduced by less than 5% compared with that of first adsorption; the preparation steps are simple and easy to operate, the raw materials are easy to obtain, the preparation cost is low, the average pore size of the prepared aminated MIL-101 (Cr) material is greatly increased, the flexibility of the material is enhanced, the adsorption performance on perfluorinated compounds is good, the saturation adsorption capacity is high, and the cyclic regeneration performance of the material is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework materials, in particular to a preparation method of an aminated MIL-101 (Cr) material for enhanced adsorption of perfluorinated compounds and an application thereof. Background Art

[0002] Perfluorinated organic compounds (PFASs) are a class of synthetic chemicals widely used in numerous industrial and consumer products, including fluoroplastics, fire extinguishing foams, metal plating, textile processing, and semiconductors, due to their excellent chemical stability, heat resistance, hydrophobicity, oleophobicity, and surface activity. However, recent studies have revealed that PFASs possess significant environmental hazards, including persistence, bioaccumulation, and long-range transport, and can cause health risks such as reproductive toxicity, hepatotoxicity, developmental toxicity, and even cancer (Caron-Beaudoin et al., 2019; Chang et al., 2022). Given their significant hazards, PFASs have become a new class of persistent organic pollutants (POPs) of concern worldwide and have been included in the Ministry of Ecology and Environment's "List of New Pollutants Under Key Control (2023 Edition)." Therefore, the development of efficient PFASs removal materials is urgently needed to safeguard human health and ecological safety. Given the recalcitrant nature of PFASs, adsorption has become an effective method for removing this emerging class of pollutants. Metal-organic frameworks (MOFs) are a new class of crystalline porous hybrid materials. Their unsaturated metal sites, high specific surface area (SSA), and large porosity make them ideal for the adsorption of PFASs (Pauletto et al., 2022). Furthermore, MOFs possess tunable structures and properties, enabling specific functionalization. Improving the adsorption performance of functionalized MOF materials for PFASs is currently a key research direction for the efficient remediation of emerging pollutants.

[0003] At present, MOFs materials have also been used in the study of adsorption and removal of PFASs. The invention patent application with publication number CN113713773A, entitled Application of MOF-808 as an adsorbent in the adsorption of perfluorooctane sulfonic acid (PFOS) pollutants in water, discloses a method for preparing MOF-808 material with simple synthesis and high adsorption efficiency, and the maximum adsorption capacity of PFOS is 1.74 mmol / g. The invention patent application with publication number CN113385144A, entitled A porous material adsorbent and its preparation method and application, discloses a method for preparing a MOF-808 porous adsorbent material modified with disodium ethylenediaminetetraacetic acid (EDTA) with simple process and significant adsorption effect. The method improves the adsorption capacity of MOF-808 for PFASs in water by loading the functional functional group carboxyl on MOF-808. However, from its Figure 5It can be seen that the improvement of MOF-808-EDTA on the adsorption performance of PFOS is limited.

[0004] In summary, research on the adsorption of PFASs by functionalized MOFs materials still needs to be further developed in order to seek breakthroughs from different aspects, coordinate multiple mechanisms of action, and further enhance their adsorption effects. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing an aminated MIL-101(Cr) material with enhanced adsorption of perfluorinated compounds and its application, so as to enhance its adsorption and removal effect on perfluorinated compounds.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solution: a method for preparing an aminated MIL-101(Cr) material with enhanced adsorption of perfluorinated compounds, comprising using MIL-101(Cr) as a skeleton raw material, using tris(2-aminoethyl)amine as an aminated raw material, and then synthesizing and modifying to obtain MIL-101(Cr)-TAEA; the preparation process comprises adding the skeleton raw material and a reaction solvent into a reaction vessel, adding the aminated raw material under a nitrogen atmosphere and heating to reflux, centrifuging to obtain a crude product after the reaction is completed, washing and drying to obtain the aminated MIL-101(Cr) material, and the average pore size of the obtained MIL-101(Cr)-TAEA can reach more than 7 times that of the MIL-101(Cr) skeleton raw material.

[0007] Preferably, the above-mentioned preparation method includes the following specific steps: placing the MIL-101 (Cr) skeleton raw material into a reaction vessel filled with sufficient anhydrous toluene, connecting a condensation reflux device, connecting a balloon filled with nitrogen at the upper end, adding a certain amount of amination raw material after magnetic stirring to mix, maintaining magnetic stirring, slowly heating to a slight boiling point, condensing and refluxing until the reaction is complete, cooling and transferring to a centrifuge tube for centrifugation to obtain a crude product, washing it several times with hot ethanol, and then heating it in an oven and transferring it to a vacuum drying oven for drying to obtain the amination MIL-101 (Cr) material.

[0008] Preferably, the molar ratio of the skeleton raw material to the amination raw material is 1:(3-5); the ratio of the skeleton raw material to the reaction solvent is 1 g:(35-45) mL; the heating temperature is 110-120°C, the reflux time is 12 hours, the centrifugation parameter is 4000 r / min, and the centrifugation is performed for 5 minutes; the washing is performed three times with 60°C ethanol, each time for 3 hours; the drying comprises first heating in an oven at 70°C for 30 minutes, and then transferring to a vacuum drying oven and drying at 70°C for 12 hours;

[0009] The skeleton raw material is prepared by a hydrothermal synthesis method using terephthalic acid and chromium nitrate nonahydrate. The hydrothermal synthesis preparation process includes adding terephthalic acid and chromium nitrate nonahydrate to ultrapure water and stirring to mix them. The resulting suspension is ultrasonically dispersed at room temperature, and then heated to 220°C in a Teflon-lined autoclave and maintained at this temperature until the reaction is complete. After cooling to room temperature, the crude product is obtained by centrifugation. The centrifugal precipitate is washed several times with N,N-dimethylformamide in a 100°C autoclave and then washed several times with ethanol in a 100°C autoclave to remove excess unreacted terephthalic acid. The product is dried to obtain MIL-101(Cr).

[0010] Another technical solution provided by the present invention is an aminated MIL-101(Cr) material for enhanced adsorption of perfluorinated compounds, wherein the aminated MIL-101(Cr) material is MIL-101(Cr)-TAEA prepared by the above-mentioned preparation method.

[0011] Preferably, the average pore diameter of the MIL-101(Cr)-TAEA is greater than 11 nm, and the average pore diameter can exceed 19 nm.

[0012] The present invention also provides a technical solution: an application of MIL-101(Cr)-TAEA prepared by the above preparation method in adsorbing PFASs.

[0013] Preferably, the saturated adsorption capacities of MIL-101(Cr)-TAEA for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and 6:2 fluoro-tonic acid (6:2 FTS) are greater than 2.9 mmol / g, 4.1 mmol / g, and 2.5 mmol / g, respectively.

[0014] The present invention also provides a technical solution: an application of MIL-101(Cr)-TAEA prepared by the above-mentioned preparation method in removing PFASs pollutants in water. Specifically, the simulated contaminated water is treated with MIL-101(Cr)-TAEA at a concentration of 0.1 mg / ml, and the total removal rate of PFASs pollutants therein can reach 98.6%; the PFASs pollutants in the simulated contaminated water are composed of PFOA, PFOS, perfluorobutyric acid (PFBA), perfluorohexanoic acid (PFHxA) and 6:2 FTS, each with a concentration of 100 μg / L, representing a severe pollution level.

[0015] Another technical solution provided by the present invention is the use of MIL-101(Cr)-TAEA prepared by the above-mentioned preparation method in a regeneration cycle for repeatedly removing PFASs pollutants in water.

[0016] Preferably, after the PFASs in the contaminated water sample are first adsorbed to reach adsorption equilibrium using MIL-101(Cr)-TAEA with a concentration of 0.1 mg / ml, the MIL-101(Cr)-TAEA adsorbed with PFASs is eluted and recycled. After regeneration, the PFASs in the contaminated water sample are adsorbed again until adsorption equilibrium is reached. After four cycles of regeneration, the PFASs in the contaminated water sample are adsorbed for the fifth time until adsorption equilibrium is reached, and the total removal rate of PFASs in the contaminated water sample is reduced by less than 5% compared with the first adsorption.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The preparation method of the aminated MIL-101(Cr) material for enhanced adsorption of perfluorinated compounds adopts a post-synthesis method to aminate the MIL-101(Cr) skeleton material. The steps are simple and easy to operate, the raw materials are readily available, and the preparation cost is low. The average pore size of the prepared MIL-101(Cr)-TAEA material is greatly increased, and the flexibility of the material is enhanced. Through the raw material selection and amination method of the present invention, the saturated adsorption capacity of the functionalized metal organic framework material for PFASs is more efficiently increased, the adsorption performance is good, and the promotion and application prospects are good.

[0019] 2. The material prepared by the preparation method of the aminated MIL-101(Cr) material for enhanced adsorption of perfluorinated compounds can efficiently and simultaneously remove different types of PFASs pollutants in water, and has high application potential in PFASs pollution treatment.

[0020] 3. The MIL-101(Cr)-TAEA material prepared by the preparation method of the aminated MIL-101(Cr) material for enhanced adsorption of perfluorinated compounds not only has a greatly improved saturated adsorption capacity for PFASs compared to the MIL-101(Cr) skeleton material, but also has extremely excellent recycling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD patterns of MIL-101(Cr), MIL-101(Cr)-ED and MIL-101(Cr)-TAEA prepared in Example 1 of the present invention;

[0022] Figure 2 FTIR spectra of MIL-101(Cr), MIL-101(Cr)-ED and MIL-101(Cr)-TAEA prepared in Example 1 of the present invention;

[0023] Figure 3 SEM images of MIL-101(Cr), MIL-101(Cr)-ED and MIL-101(Cr)-TAEA prepared in Example 1 of the present invention;

[0024] Figure 4 N2 adsorption-desorption curves (a) and pore size distributions (b, c, d) of MIL-101(Cr), MIL-101(Cr)-ED, and MIL-101(Cr)-TAEA prepared in Example 1 of the present invention;

[0025] Figure 5 The adsorption kinetic curves of three PFASs on MIL-101(Cr), MIL-101(Cr)-ED and MIL-101(Cr)-TAEA prepared in Example 1 of the present invention are shown;

[0026] Figure 6 The adsorption isotherms of three PFASs on MIL-101(Cr), MIL-101(Cr)-ED and MIL-101(Cr)-TAEA prepared in Example 1 of the present invention are shown;

[0027] Figure 7 The pore size distribution of MIL-101(Cr) (a), MIL-101(Cr)-ED (b), and MIL-101(Cr)-TAEA (c) prepared in Example 1 of the present invention before and after adsorption of PFOA;

[0028] Figure 8 The figure is a histogram of the removal rates of each PFASs and ∑PFASs in simulated wastewater by MIL-101(Cr), MIL-101(Cr)-ED, and MIL-101(Cr)-TAEA prepared in Example 1 of the present invention in four cycle regeneration experiments;

[0029] Figure 9 This is a histogram of the removal rates of ∑PFASs in two actual contaminated groundwater samples (GW1 and GW2) by MIL-101(Cr), MIL-101(Cr)-ED, MIL-101(Cr)-TAEA and commercial activated carbon prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The perfluorinated compounds mentioned in the present invention are abbreviated as PFASs.

[0031] As mentioned in the above background technology, for the purpose of improving the comprehensive performance of modified MOFs materials in adsorbing perfluorinated compounds, the inventors consulted a large number of cutting-edge technologies in this field but did not find any usable materials. The inventors formulated a large number of schemes through principle hypothesis and analysis, but did not make any progress in early experiments. The ethylenediaminetetraacetic acid (EDTA) disodium modified MOF-808 provided in the patent CN113385144A that was consulted did not have any advantages in adsorption capacity. However, in the final accidental raw material adjustment and method improvement attempt, a new breakthrough was achieved, and a new amino modified material with high adsorption capacity for PFASs and good recycling performance was prepared. Based on this, the inventors reversely studied the key points of the preparation of the present invention and tested and analyzed the principle of good adsorption performance. The summary scheme is as follows:

[0032] The preparation method of the present invention comprises the following steps: using MIL-101(Cr) as a skeleton raw material, using tris(2-aminoethyl)amine as an amination raw material, and then synthesizing and modifying the MIL-101(Cr)-TAEA; the preparation process comprises adding the skeleton raw material and a reaction solvent into a reaction container, adding the amination raw material under a nitrogen atmosphere, heating the reaction to reflux, centrifuging the crude product after the reaction is complete, washing the crude product, and drying the crude product to obtain the amination MIL-101(Cr) material; and the average pore diameter of the prepared MIL-101(Cr)-TAEA can reach more than 7 times that of the MIL-101(Cr) skeleton raw material.

[0033] More specifically, the preparation process includes: placing the MIL-101 (Cr) skeleton raw material into a reaction vessel filled with sufficient anhydrous toluene, connecting a condensation reflux device, connecting a balloon filled with nitrogen to the upper end, adding a certain amount of amination raw material after magnetic stirring to mix, maintaining magnetic stirring, slowly heating to a slight boiling point, condensing and refluxing until the reaction is complete, cooling and transferring to a centrifuge tube for centrifugation to obtain a crude product, washing it several times with hot ethanol, and then heating it in an oven and transferring it to a vacuum drying oven for drying to obtain the amination MIL-101 (Cr) material.

[0034] The molar ratio of the skeleton raw material to the amination raw material is preferably 1:(3-5).

[0035] For reference, the ratio of the skeleton raw material to the reaction solvent can be 1 g: (35-45) mL, for example, 5 g of the skeleton raw material can be added to 200 ml of anhydrous toluene.

[0036] In a preferred embodiment, the temperature raised to a slight boiling point is 110-120°C, and the condensation reflux time is preferably 12 hours;

[0037] For reference: The centrifugation parameters are preferably 4000 r / min for 5 min; the crude product can be washed with 60°C ethanol three times, each time for 3 hours; the drying step can be first heated in an oven at 70°C for 30 minutes, then transferred to a vacuum drying oven and dried at 70°C for 12 hours.

[0038] In addition, the above-mentioned skeleton raw materials can be prepared by a hydrothermal method using terephthalic acid and chromium nitrate nonahydrate (Férey et al 2005, Liu et al 2015). For reference, the skeleton raw material preparation process includes adding terephthalic acid and chromium nitrate nonahydrate to ultrapure water and stirring to mix, ultrasonically dispersing the resulting suspension at room temperature, then heating to 220°C in a Teflon-lined autoclave and maintaining the temperature until the reaction is complete; after cooling to room temperature, centrifuging to obtain a crude product; the centrifugal precipitate is washed several times with N,N-dimethylformamide in a 100°C autoclave, and then washed several times with ethanol in a 100°C autoclave to remove excess unreacted terephthalic acid, and then dried to obtain MIL-101(Cr).

[0039] The MIL-101(Cr)-TAEA prepared by the above preparation method has an average pore diameter greater than 11 nm, specifically, an average pore diameter exceeding 19 nm; its saturated adsorption capacity for PFOA, PFOS, and 6:2 FTS is greater than 2.9 mmol / g, 4.1 mmol / g, and 2.5 mmol / g, respectively;

[0040] Using MIL-101(Cr)-TAEA at a concentration of 0.1 mg / ml to treat simulated contaminated water, the total removal rate of PFASs reached 98.6%. The PFASs in the simulated contaminated water consisted of PFOA, PFOS, PFBA, PFHxA, and 6:2 FTS, each at a concentration of 100 μg / L, representing a severe contamination level.

[0041] After the PFASs in the contaminated water sample were adsorbed for the first time using MIL-101(Cr)-TAEA with a concentration of 0.1 mg / ml to reach adsorption equilibrium, the MIL-101(Cr)-TAEA adsorbed with PFASs was eluted and recycled. After regeneration, the PFASs in the contaminated water sample were adsorbed again until adsorption equilibrium was reached. After four cycles of regeneration, the PFASs in the contaminated water sample were adsorbed for the fifth time until adsorption equilibrium was reached. The total removal rate of PFASs in the contaminated water sample was less than 5% compared with the reduction in the first adsorption.

[0042] The present invention is further described below through several embodiments and comparisons with other MOFs materials. The following are only some embodiments of the present invention and are not the optimal embodiments.

[0043] Example 1:

[0044] Step 1: 20 mmol of terephthalic acid (H2BDC, > 98%) and 20 mmol of chromium nitrate nonahydrate (Cr(NO3)3·9H2O, > 98%) were added to 100 mL of ultrapure water and stirred for 60 min. The resulting suspension was sonicated at room temperature for 30 min, then transferred to a 200 mL Teflon-lined autoclave and heated to 220°C at a ramp rate of 5°C / min and maintained at that temperature for 20 h. After cooling to room temperature, the crude product was collected by centrifugation at 4000 rpm for 15 min. The centrifugal precipitate was washed in an autoclave at 100°C with N,N-dimethylformamide (DMF) three times for 12 h each, and then washed in an autoclave at 100°C with ethanol three times for 12 h each to remove excess unreacted H2BDC. The resulting material was dried in a vacuum oven at 70°C for 12 h to obtain the MIL-101(Cr) sample.

[0045] Step 2: 5.034 g of the prepared dried MIL-101(Cr) sample was placed in a 500 mL three-necked flask containing 200 mL of anhydrous toluene, connected to a condensation reflux device, and a balloon filled with nitrogen was connected to the upper end. After mixing in a magnetic stirring pot, 3.15 mL of tris(2-aminoethyl)amine was added. Maintaining magnetic stirring, the temperature was slowly raised to a slight boiling point (110~120 °C), and condensed and refluxed for 12 hours. After cooling, it was transferred to a 50 mL glass centrifuge tube and centrifuged at 4000 r / min for 5 minutes to obtain a crude product. The crude product was washed with 60 °C ethanol three times for 3 hours each time, then heated in a 70 °C oven for 30 minutes and transferred to a vacuum drying oven. After drying at 70 °C for 12 hours, MIL-101(Cr)-TAEA was obtained.

[0046] In order to better explore the characterization and performance of the prepared MIL-101(Cr)-TAEA from more aspects, this example also adds another existing material MIL-101(Cr)-ED for comparison. However, in order to control variables, the same MIL-101(Cr) and preparation method as in step 2 are used:

[0047] Step 3: Same as step 2, except that the tris(2-aminoethyl)amine ligand was replaced with ethylenediamine and the added amount was changed to 1.28 mL. Other parameters remained the same to obtain MIL-101(Cr)-ED prepared by the same method.

[0048] Figures 1 to 4The X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) images, Fourier transform infrared (FTIR) spectra, and N2 adsorption-desorption curves ( Figure 4 a) and pore size distribution ( Figure 4 b. Figure 4 c. Figure 4 d);

[0049] from Figure 1 The XRD patterns show that the products prepared by the present invention have high crystallinity and purity. The peak positions and relative intensities of MIL-101(Cr)-ED and MIL-101(Cr)-TAEA are basically the same as those of the unmodified original MIL-101(Cr), indicating that the amino grafting has no significant effect on the crystal structure of MIL-101(Cr), and the original topological structure is well maintained. Figure 2 From the FTIR spectrum, it can be seen that after the material is aminated, the peak position and intensity of the characteristic peaks of the original MIL-101(Cr) have basically not changed, indicating the stable existence of the MIL-101(Cr) framework after amination. Figure 2 It can also be clearly seen that the amino ligand functional group was successfully grafted onto MIL-101(Cr). Figure 3 The SEM images show that the crystallinity of the aminated MIL-101(Cr) prepared in steps 2 and 3 above is reduced, and the crystal surface becomes rougher, which can provide more PFASs action sites.

[0050] Figure 4 It can be clearly seen from the nitrogen adsorption in a that the specific surface area of ​​the material is greatly reduced after the amino group is grafted, from 2078 m 2 / g decreased to 256 m / g for MIL-101(Cr)-ED 2 / g and 97 m of MIL-101(Cr)-TAEA 2 / g, the reduction of specific surface area is not conducive to adsorption performance; but surprisingly, the material after amination prepared by the method of the above embodiment has undergone a great change in the pore structure. The pore structure of MIL-101(Cr) is mostly microporous structure with a diameter of less than 2nm, and Figure 4 b It is obvious that almost no pores have a diameter greater than 3 nm. The average pore diameter is 2.47 nm. In the pore structures of MIL-101(Cr)-ED and MIL-101(Cr)-TAEA prepared in steps 2 and 3, most of them are mesoporous structures with a diameter greater than 2 nm ( Figure 4 c, Figure 4 d). It has been calculated that the average pore diameter of MIL-101(Cr)-ED is 11.6 nm, and the average pore diameter of MIL-101(Cr)-TAEA is 19.3 nm, which is more than 7 times the average pore diameter of the MIL-101(Cr) skeleton material. Obviously, the materials prepared by the method of the present invention have more mesopores rather than micropores, especially the MIL-101(Cr)-TAEA prepared by post-synthesis modification using MIL-101(Cr) as the skeleton raw material and tris(2-aminoethyl)amine as the amination raw material. The average pore diameter is significantly improved. It is precisely because of these mesopores that its adsorption performance for PFASs is greatly improved.

[0051] In addition to the specific examples in Example 1 above, the present invention also adjusted different parameter combinations within the parameter range of the above specific implementation methods to conduct a large number of preparation experiments in steps one and two. Consistent results show that the average pore diameter of MIL-101(Cr)-TAEA prepared by the method of the present invention is above 11 nm, and the average pore diameter can be reproduced in large quantities to exceed 19 nm, which is more than 7 times the average pore diameter of MIL-101(Cr).

[0052] In order to study the adsorption rate of MIL-101(Cr)-TAEA prepared by the method of the present invention on different types of PFASs, the pseudo-first-order kinetic model and the pseudo-second-order kinetic model were selected to evaluate the three MOFs materials prepared in Example 1;

[0053] like Figure 5 As shown in Table 1 below, the adsorption kinetics results of the three PFASs all showed that the adsorption rate of MIL-101(Cr)-TAEA was higher than that of MIL-101(Cr) and MIL-101(Cr)-ED.

[0054] Table 1 Adsorption kinetics simulation of different types of PFASs on three MOFs materials

[0055]

[0056] like Figure 6 As shown in Table 2 below, the adsorption isotherms of the three PFASs show that the saturated adsorption capacity of the material MIL-101(Cr)-TAEA prepared by the method of the present invention for the three PFASs is greatly improved. For example, the saturated adsorption capacity q of PFOA, PFOS, and 6:2 FTS prepared by the step 1 of Example 1 is 1. m The saturated adsorption capacities of MIL-101(Cr)-ED for PFOA, PFOS, and 6:2 FTS were only 1.5 mmol / g, 2.49 mmol / g, and 1.11 mmol / g, respectively.m The saturated adsorption capacity of MIL-101(Cr)-TAEA for PFOA, PFOS and 6:2 FTS increased to 2.35mmol / g, 3.09mmol / g and 2.05mmol / g respectively. m The adsorption capacities of MIL-101(Cr)-TAEA for the three PFASs were 1.76 to 2.40 times higher than those of the original MIL-101(Cr). The adsorption isotherm model parameters of the three MOFs prepared in Example 1 for different types of PFASs are shown in Table 2 below:

[0057] Table 2 Adsorption isotherm simulations of different types of PFASs on three MOFs materials

[0058]

[0059] In the parameter range of the above specific embodiment, in a large number of preparation experiments with different parameter combinations, the saturated adsorption capacity q of MIL-101(Cr)-TAEA for PFOA, PFOS, and 6:2 FTS prepared with different parameters was m They are all greater than 2.9 mmol / g, 4.1 mmol / g, and 2.5 mmol / g, respectively. Compared with existing functionalized MOFs materials, the present invention has great advantages in the adsorption performance of PFASs.

[0060] In addition, if Figure 7 As shown, the MIL-101(Cr) skeleton material, MIL-101(Cr)-ED and MIL-101(Cr)-TAEA prepared in the above Example 1 showed different material properties before and after adsorbing a near-saturated amount of PFOA. The pore volume of MIL-101(Cr)-TAEA with a pore diameter greater than 7 nm after adsorbing PFOA was significantly increased compared with the original MIL-101(Cr)-TAEA, which indicates that the flexibility of the originally rigid MIL-101(Cr) crystal structure increased, and after combining with PFOA, the pore volume of the mesopores was expanded, showing a more favorable adsorption ability; in comparison, after adsorbing PFOA, the pore diameter and pore volume of MIL-101(Cr) and MIL-101(Cr)-ED both decreased, and they failed to obtain properties similar to those of MIL-101(Cr)-TAEA.

[0061] In summary, the reason why the MIL-101(Cr)-TAEA material prepared by the present invention can achieve such excellent adsorption performance for PFASs is due to the change in the pore structure of the material, which increases the proportion of mesopore structure and greatly increases the average pore diameter. At the same time, it brings flexibility to the material that was originally rigid, enhances the pore filling effect of PFASs from many aspects, and cooperates with the polar adsorption effects such as electrostatics, hydrogen bonds, and coordination enhanced by amino grafting, thereby greatly improving the adsorption performance of PFASs. On the other hand, the related patent CN113385144A mentioned in the background technology also modified the MOF material with amino groups, but the average pore diameter did not increase significantly after modification, and even decreased, resulting in limited improvement in the adsorption performance of the modified MOFs material for PFOS. The present invention has also conducted more in-depth research on this, and the results show that the increase in the proportion of mesoporous structure is obviously beneficial to the adsorption process of PFASs. Therefore, the material prepared by the method of the present invention greatly improves the adsorption capacity of PFASs. The proportion of mesoporous structure can be intuitively seen from the average pore size. Fundamentally speaking, the skeleton raw materials and aminated raw materials used in the present invention, as well as the preparation method are the decisive factors for obtaining more larger pore size mesoporous structures and flexibility.

[0062] Example 2:

[0063] Simulated contaminated water was prepared, which contained four traditional PFASs (PFOA, PFOS, PFBA, PFHxA) and a new PFASs (6:2 FTS). The concentration of each PFASs was set to 100 μg / L (representing a heavy pollution level). This simulated contaminated water was used to test the PFASs adsorption, removal and recycling regeneration performance of the three MOFs powder materials, MIL-101(Cr), MIL-101(Cr)-ED and MIL-101(Cr)-TAEA, prepared in steps 1 to 3 in Example 1. The process was as follows: 2 mg of each of the three MOFs powders was accurately weighed using an electronic balance and added to 40 mL brown glass centrifuge tubes respectively. 20 mL of simulated contaminated water was then added to each tube. Each centrifuge tube was placed in a rotary shaking constant temperature incubator at 200 r / min and equilibrated at room temperature of 25.0 ± 1.0 °C for 12 h, which was sufficient to reach adsorption equilibrium. The suspension was then centrifuged at high speed to obtain a supernatant. 5 ng of PFASs isotope internal standard was added to the PFASs solution before and after adsorption, and after mixing, the PFASs in the solution were enriched and concentrated using a solid phase extraction (SPE) device. The specific process is as follows:

[0064] The Oasis WAX extraction column was pretreated with 4 mL of ammonia methanol (0.1% NH4OH), 4 mL of methanol, and 4 mL of deionized water, respectively. A PFASs solution containing an isotopic internal standard was then added and enriched at a rate of 1 drop / second. After air-drying overnight, the column was eluted successively with 4 mL of methanol and 4 mL of ammonia methanol (0.1% NH4OH). The column was concentrated to 1 mL under the gentle action of a high-purity nitrogen flow and transferred to a 1.5 mL brown injection bottle. PFASs were then quantitatively analyzed by liquid chromatography-tandem mass spectrometry (LC-MS / MS) based on the highly accurate internal standard method, thereby calculating the adsorption capacity and removal rate of the three MOFs materials for different PFASs.

[0065] After the initial adsorption of PFASs, the MOFs were placed in 40 mL of a methanol solution (2.5% NaCl, 2.5% Na₂SO₄) and shaken at room temperature for 3 hours. The precipitated MOFs were then centrifuged at 4500 rpm for 10 minutes to separate the three MOFs. The precipitated MOFs were then washed twice with methanol and once with ultrapure water according to the aforementioned procedure. The washed MOFs were then freeze-dried at -50°C for 8 hours to regenerate the MOFs. The adsorption (reaching adsorption equilibrium)-regeneration cycle was repeated using the same simulated contaminated water. After four cycles, PFASs were again adsorbed until equilibrium was reached. The adsorption capacity and removal efficiency of each PFAS were calculated to evaluate the performance of MIL-101(Cr), MIL-101(Cr)-ED, and MIL-101(Cr)-TAEA.

[0066] like Figure 9 As shown in the data, the initial total removal rates of MIL-101(Cr), MIL-101(Cr)-ED and MIL-101(Cr)-TAEA for different PFASs were 92.0%, 97.7% and 98.6%, respectively. Compared with the original MIL-101(Cr), the total removal capabilities of the two aminated materials were increased by 5.7% and 6.6%, respectively. After 4 cycles, the total removal rate of MIL-101(Cr)-TAEA was still 95.5%, while the total removal rates of the other two materials were both below 80%, indicating that MIL-101(Cr)-TAEA has superior cyclic performance, and the degree of decrease in the removal rate of MIL-101(Cr)-ED during the cycle is higher than that of MIL-101(Cr), indicating that amino functionalization does not necessarily improve the recycling performance of the material. Therefore, it can be further proved that the performance of the MIL-101(Cr)-TAEA material prepared by the present invention is particularly outstanding, and the discovery of this material with "double excellent" adsorption and recycling performance is somewhat accidental.

[0067] Based on this, the present invention continues to conduct more experiments on the MIL-101(Cr)-TAEA obtained in step 3 of Example 1. Within the condition range of the molar amount of MIL-101(Cr) to tris(2-aminoethyl)amine being 1:(3-5), and the amount ratio of MIL-101(Cr) to anhydrous toluene being 1g:(35-40) mL, the preparation conditions of the above-mentioned advantageous product are adopted, including heating to a slightly boiling temperature of 110-120°C, and condensing and refluxing for 12 h; the centrifugation parameter is 4000 r / min for 5 min; the crude product is washed with 60°C ethanol 3 times, each time for 3 h; drying is first heated in an oven at 70°C for 30 min, then transferred to a vacuum drying oven, and dried at 70°C for 12 h. The initial total removal rate of PFASs by MIL-101(Cr)-TAEA prepared under the above various conditions exceeded 98%, and after 4 cycles, the total removal rate of the 5th adsorption could still be maintained above 95%.

[0068] Example 3:

[0069] Water samples were collected from two underground contaminated water bodies, GW1 and GW2, next to a fluorine chemical plant in Hubei Province. A total of 10 PFASs were detected through analysis and testing. The pH value of GW1 was 8.03, and the conductivity was 6.59 mS / cm. The total concentration of various pollutants reached 142 μg / L, and the main pollutants were PFOA (101 μg / L), PFBA (27.2 μg / L), and PFBS (5.66 μg / L). The pH value of GW2 was 8.05, and the conductivity was 4.98 mS / cm. The total concentration of various pollutants reached 265 μg / L, and the main pollutants were PFBS (215.0 μg / L), PFOA (24.0 μg / L), and PFBA (17.1 μg / L).

[0070] The three MOFs materials prepared in the three steps of Example 1 and commercial activated carbon (wood activated carbon powder purchased from China Zhanyun Chemical Co., Ltd.) were used to test the purification performance of PFASs in the two actual contaminated water bodies mentioned above. The test process is as follows:

[0071] Using an electronic balance, 2 mg of each of the three MOFs powders and activated carbon powder (corresponding to the actual contaminated water bodies GW1 and GW2, respectively) were accurately weighed and added to 40 mL brown glass centrifuge tubes. 20 mL of the actual contaminated water body GW1 or GW2 was added to each centrifuge tube. Each centrifuge tube was placed in a rotary shaking constant temperature incubator at 200 rpm and equilibrated at room temperature of 25.0 ± 1.0°C for 12 hours to achieve adsorption equilibrium. The suspension was then centrifuged at high speed to obtain the supernatant. 5 ng of PFASs isotope internal standard was added to each PFASs solution before and after adsorption. After mixing, the PFASs in the solution were enriched and concentrated using a solid phase extraction (SPE) device. The specific process is as follows:

[0072] The Oasis WAX extraction column was pretreated with 4 mL of ammonia methanol (0.1% NH4OH), 4 mL of methanol, and 4 mL of deionized water, respectively. Then, a PFASs solution containing an isotopic internal standard was added and enriched at a rate of 1 drop / second. After air-drying overnight, the column was eluted successively with 4 mL of methanol and 4 mL of ammonia methanol (0.1% NH4OH). The column was concentrated to 1 mL under the gentle action of a high-purity nitrogen flow and transferred to a 1.5 mL brown injection bottle. PFASs were then quantitatively analyzed by liquid chromatography-tandem mass spectrometry (LC-MS / MS) based on the highly accurate internal standard method to analyze and calculate the adsorption capacity and removal rate of each PFASs.

[0073] The results are as follows Figure 9 As shown in the data, in these two contaminated groundwaters, the total removal rates of PFASs in GW1 and GW2 by MIL-101(Cr)-TAEA were 76.2% and 77.7%, respectively. The removal rates were much higher than those of MIL-101(Cr) and MIL-101(Cr)-ED, and 5 to 7 times the removal rates of commercial activated carbon (GW1: 10.5%, GW2: 15.1%). The results of PFASs removal rates in actual contaminated water bodies showed that MIL-101(Cr)-TAEA prepared by amination of the MIL-101(Cr) skeleton raw material using tris(2-aminoethyl)amine has higher practical application value.

[0074] According to the method in Example 2, the above-mentioned MIL-101(Cr)-TAEA was subjected to four cyclic regeneration tests. The results showed that after the fifth adsorption, the total removal rate of the MIL-101(Cr)-TAEA material for the actual contaminated water samples GW1 and GW2 could still reach about 72.5% and 74.1%, respectively;

[0075] For further verification, the present invention conducted more different homemade sample tests. The test samples included 11 perfluorocarboxylic acids (PFCAs) and 4 perfluorosulfonic acids (PFSAs) that are currently detected more frequently, as well as 2 new PFASs, specifically perfluorobutyric acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), perfluorotetradecanoic acid (PFTeDA), perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), perfluorooctanesulfonic acid (PFOS), perfluorodecanesulfonic acid (PFDS), hexafluoropropylene oxide dimer carboxylic acid (GenX), and 6:2 fluorotweensulfonic acid (6:2FTS). The concentration of each PFAS in each test sample ranged from 0.01 to 200 The concentrations of PFASs in the samples varied from 1 to 17 μg / L, and the number of PFASs species in each test sample ranged from 1 to 17. At the same time, we selected different test samples and conducted recycling tests according to the method in Example 2. The results showed that after 4 cycles, the total removal rate of PFASs adsorbed in the fifth adsorption was less than 5% compared with the reduction in the initial adsorption, proving that the material has excellent recycling performance in actual use.

[0076] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims.

[0077] Any matters not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. A method for preparing an aminated MIL-101(Cr) material for enhanced adsorption of perfluorinated compounds, characterized by: The method comprises using MIL-101(Cr) as a skeleton raw material, using tris(2-aminoethyl)amine as an amination raw material, and then synthesizing and modifying to obtain MIL-101(Cr)-TAEA. The preparation process comprises adding the skeleton raw material and a reaction solvent into a reaction container, adding the amination raw material under a nitrogen atmosphere and heating to reflux, centrifuging to obtain a crude product after the reaction is completed, washing and drying to obtain an amination MIL-101(Cr) material, and the average pore diameter of the obtained MIL-101(Cr)-TAEA can reach more than 7 times that of the MIL-101(Cr) skeleton raw material.

2. The preparation method according to claim 1, characterized in that The method comprises the following specific steps: placing a MIL-101(Cr) skeleton raw material into a reaction vessel filled with sufficient anhydrous toluene, connecting a condensation reflux device, connecting a balloon filled with nitrogen to the upper end of the condensation reflux device, adding a certain amount of amination raw material after magnetic stirring and mixing, maintaining magnetic stirring, slowly heating to a slight boiling point, condensing and refluxing until the reaction is complete, cooling, transferring the product to a centrifuge tube, and centrifuging to obtain a crude product, washing the product with hot ethanol several times, heating the product in an oven, and then transferring the product to a vacuum drying oven for drying to obtain the amination MIL-101(Cr) material.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the skeleton raw material to the amination raw material is 1:(3-5); the ratio of the skeleton raw material to the reaction solvent is 1 g:(35-45) mL; the heating temperature is 110-120°C, the reflux time is 12 hours, the centrifugation parameter is 4000 r / min, and the centrifugation is performed for 5 minutes; the washing is performed three times with 60°C ethanol, each time for 3 hours; the drying comprises first heating in an oven at 70°C for 30 minutes, and then transferring to a vacuum drying oven and drying at 70°C for 12 hours; The skeleton raw material is prepared by a hydrothermal synthesis method using terephthalic acid and chromium nitrate nonahydrate. The hydrothermal synthesis preparation process comprises the following steps: adding terephthalic acid and chromium nitrate nonahydrate into ultrapure water and stirring and mixing them uniformly; ultrasonically dispersing the obtained suspension at room temperature; then heating the suspension to 220°C in a Teflon-lined autoclave and maintaining the temperature until the reaction is complete; cooling the suspension to room temperature and centrifuging the resulting suspension to obtain a crude product; washing the resulting crude product several times with N,N-dimethylformamide in a 100°C autoclave and then washing the resulting crude product several times with ethanol in a 100°C autoclave to remove excess unreacted terephthalic acid; and drying the resulting crude product to obtain MIL-101(Cr).

4. An aminated MIL-101(Cr) material with enhanced adsorption of perfluorinated compounds, characterized by: The aminated MIL-101(Cr) material is MIL-101(Cr)-TAEA prepared by the preparation method according to any one of claims 1 to 3.

5. The aminated MIL-101(Cr) material for enhanced adsorption of perfluorinated compounds according to claim 4, characterized in that: The average pore size of the MIL-101(Cr)-TAEA is greater than 11 nm, and the average pore size can exceed 19 nm.

6. MIL-101(Cr)-TAEA prepared by the preparation method according to any one of claims 1 to 3, or use of MIL-101(Cr)-TAEA according to claim 4 or 5 in the adsorption of PFASs.

7. The use according to claim 6, characterized in that: The saturated adsorption capacity of the MIL-101(Cr)-TAEA for PFOA, PFOS, and 6:2FTS is greater than 2.9 mmol / g, 4.1 mmol / g, and 2.5 mmol / g, respectively.

8. Use of MIL-101(Cr)-TAEA prepared by the preparation method according to any one of claims 1 to 3, or MIL-101(Cr)-TAEA according to claim 4 or 5, in removing PFASs pollutants from water, characterized in that: The simulated contaminated water was treated with MIL-101(Cr)-TAEA at a concentration of 0.1 mg / ml, and the total removal rate of PFASs pollutants in it reached 98.6%; the PFASs pollutants in the simulated contaminated water were composed of PFOA, PFOS, PFBA, PFHxA and 6:2 FTS, each with a concentration of 100 μg / L, representing a severe pollution level.

9. The MIL-101(Cr)-TAEA prepared by the preparation method according to any one of claims 1 to 3, or the use of the MIL-101(Cr)-TAEA according to claim 4 or 5 for repeated regeneration and recycling to remove PFASs pollutants in water.

10. The use according to claim 9, characterized in that: After the PFASs in the contaminated water sample were adsorbed for the first time using MIL-101(Cr)-TAEA with a concentration of 0.1 mg / ml to reach adsorption equilibrium, the MIL-101(Cr)-TAEA adsorbed with PFASs was eluted and recycled. After regeneration, the PFASs in the contaminated water sample were adsorbed again until adsorption equilibrium was reached. After four cycles of regeneration, the PFASs in the contaminated water sample were adsorbed for the fifth time until adsorption equilibrium was reached. The total removal rate of PFASs in the contaminated water sample was less than 5% compared with the reduction in the first adsorption.

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