Multi-characteristic iron-carbon derivative material for adsorbing and repairing PFAS pollution of water body as well as preparation method and application of multi-characteristic iron-carbon derivative material

Abstract

The invention provides a multi-characteristic iron-carbon derivative material for adsorbing and repairing PFAS pollution of a water body as well as a preparation method and application of the multi-characteristic iron-carbon derivative material. The preparation method comprises the following steps: 1, dissolving a ferric salt in N, N-dimethylformamide, adding a ligand terephthalic acid under a stirring condition, and synthesizing a precursor through a solvothermal method; and 2, carrying out heat treatment on the precursor in an inert atmosphere to obtain the multi-characteristic iron-carbon derivative material. The application of the multi-characteristic iron-carbon derivative material in the aspect of environmental restoration comprises the following steps: by taking the multi-characteristic iron-carbon derivative material as an adsorbent, carrying out adsorption purification treatment on a PFAS polluted water body under the assistance of a cationic complexing agent. The multi-characteristic iron-carbon derivative material is synthesized through a solvothermal-thermal treatment two-step method, so that the multi-characteristic iron-carbon derivative material has high hydrophobicity, a two-dimensional-three-dimensional tight interface and magnetism, can quickly remove PFAS with various different structures and carbon chain lengths, can realize material separation within 30 seconds after the PFAS is removed through adsorption, and does not generate secondary pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of water environmental pollution control, and relates to a multi-property iron-carbon derivative material for adsorbing and repairing PFAS pollution in water, a preparation method thereof, and an application thereof. Background Art

[0002] Per- and polyfluoroalkyl substances (PFAS) have been proven to cause serious harm to the ecosystem and human health due to their stable chemical properties and long-term presence in the environment. Advanced oxidation technologies widely used for the control of organic pollutants have limited degradation of PFAS, and even advanced reduction technologies based on hydrated electrons are difficult to completely mineralize PFAS. A large number of short-chain intermediate products with strong water solubility, high toxicity, and difficult to remove will enter the environment, causing unpredictable harm, because many countries lack control and emission standards for PFAS degradation products. Some PFAS substitutes that are theoretically easier to harmlessly treat are designed for production and daily life, such as GenX, a substitute for perfluorooctanoic acid (PFOA) containing an ether bond. However, this strategy is obviously unsuccessful, because many toxicity studies have shown that GenX has similar toxicity to PFOA. The removal efficiency of GenX in wastewater treatment plants through precipitation, ozonation, biological filtration, and disinfection processes can be ignored, and the adsorption capacity of GenX on activated carbon and other adsorbents is also lower than that of PFOA. Therefore, many countries have strengthened the control of PFAS. Recently, the US Environmental Protection Agency (EPA) revised its lifetime health advisories for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in drinking water, setting more stringent limits of 0.004 and 0.02 ng L -1 respectively, while the previous combined concentration limit was 70 ng L -1 . The recommended standard for GenX in drinking water has also been reduced to 10 ng L -1 or less, which poses a more severe challenge to the rapid and safe removal of PFAS in contaminated water. In contrast, from the perspective of health and policy guidance, faster and safer adsorption methods all show unique advantages.

[0003] However, common activated carbon and resin adsorbents still have certain disadvantages, such as low adsorption capacity, low removal rate, difficult recovery and separation, especially the effective co-adsorption of long-chain and short-chain PFAS occurring simultaneously in water is difficult.

[0004] Therefore, the inventors of this application constructed an environmentally friendly iron-based MOF (Metal Organic Framework) derivative, H:MIL-101(Fe), which has a 3D / 2D structure of metal oxides fixed on a carbon substrate. It can not only completely remove PFOA in pure water within 5 minutes, but also achieve separation within 30 seconds. H:MIL-101(Fe) still maintains the initial adsorption percentage after four cycles of PFAS adsorption, and its structural properties are stable. In addition, CTAB and PFAS were mixed to synthesize a more hydrophobic long-chain complex. At pH 7.0, six PFASs with 4-8 carbon atoms in surface water can be completely co-adsorbed within ten minutes. This study developed a new type of adsorption material that can match the PFAS type and achieve effective co-adsorption of PFAS in water, promising to ensure water safety under the increasingly strict background of PFAS control. Summary of the Invention

[0005] The purpose of this application is to provide a multi-characteristic iron-carbon derivative material H:MIL-101(Fe) for adsorbing and repairing PFAS pollution in water bodies, its preparation method and application. This material is a multi-characteristic iron-carbon derivative material with high hydrophobicity, two-dimensional-three-dimensional tight interface and magnetism. It can completely remove PFASs with different carbon chain lengths and structures in natural water bodies within minutes, and overcome the interference of natural dissolved organic matter and anions, and can be used for actual water body repair.

[0006] To achieve the above purpose, this application adopts the following technical solutions:

[0007] In the first aspect, this application provides a preparation method of a multi-characteristic iron-carbon derivative material for adsorbing and repairing PFASs pollution in water bodies, including:

[0008] Step 1: Dissolve ferric salt in DMF (N,N-dimethylformamide), and add ligand terephthalic acid (H2BDC) under stirring conditions. The precursor, namely MIL-101(Fe), is synthesized by solvothermal method.

[0009] Step 2: Heat-treat the precursor in an inert atmosphere to obtain the multi-characteristic iron-carbon derivative material, namely H:MIL-101(Fe). This iron-carbon derivative material is black and has multiple characteristics, such as high hydrophobicity, rich in oxygen vacancies, two-dimensional-three-dimensional tight interface and magnetism.

[0010] In the above preparation method, as a preferred implementation method, it also includes:

[0011] In Step 2, the inert atmosphere refers to a nitrogen atmosphere or an inert gas atmosphere. This heat treatment is an incomplete carbonization heat treatment. Through heat treatment, part of the organic ligand terephthalic acid can be carbonized to form a hydrophobic surface, while a cubic Fe3O4 magnetic framework, oxygen vacancies, and π-π bonds are generated. The hydrophobic tail of long-chain PFAS is bound through hydrophobic interaction, and at the same time, the positively charged oxygen vacancies electrostatically attract the head carboxylic acid / sulfonic acid groups of the target pollutant PFAS, jointly achieving the rapid co-adsorption and removal of PFAS with different structures and different chain lengths.

[0012] In the above preparation method, as a preferred embodiment, it further includes:

[0013] Before the heat treatment, the precursor precipitate is washed twice with DMF and absolute ethanol alternately, and then transferred to methanol for purification treatment; preferably, the washing includes: centrifuging the precursor suspension generated by the solvothermal method in Step 1 to discard the supernatant, adding an appropriate amount of DMF or absolute ethanol washing solution, and shaking and washing at 2500 r / min on a shaker for 30 min; preferably, the purification treatment includes: soaking the precursor precipitate in methanol for 12 hours; preferably, after the purification treatment, it is separated, dried, and ground to obtain the precursor; more preferably, the separation treatment is centrifugation, and the drying treatment is vacuum drying.

[0014] In the above preparation method, as a preferred embodiment, in Step 1, the ferric salt can be selected from at least one of ferric chloride, ferric nitrate, ferric sulfate, etc.

[0015] In the above preparation method, as a preferred embodiment, in Step 1, the molar ratio of ferric salt to terephthalic acid is 1:1; as long as N,N-dimethylformamide as the solvent is sufficient to ensure the dissolution of the solid, more preferably, in Step 1, the molar ratio of N,N-dimethylformamide:ferric salt:terephthalic acid is 50 - 300:1:1.

[0016] In the above preparation method, as a preferred embodiment, in Step 1, after the ferric salt and H2BDC are added to DMF, they are stirred at a constant speed of 500 - 1000 r / min (such as 600 r / min, 700 r / min, 800 r / min, 900 r / min, etc.) for 10 - 60 min (such as 15 min, 20 min, 30 min, 40 min, 50 min, 55 min, etc.) to completely dissolve and mix the ferric salt and the organic ligand evenly, and then the precursor is synthesized by the solvothermal method. More preferably, the stirring speed is 800 r / min and the stirring time is 60 min.

[0017] In the above preparation method, as a preferred embodiment, in step one, in the solvothermal method, the reaction temperature is 140 - 160 °C (such as 142 °C, 145 °C, 150 °C, 155 °C, etc.), and the reaction time is 10 - 14 h (such as 10.5 h, 11 h, 12 h, 13 h, 13.5 h, etc.); more preferably, the reaction temperature is 150 °C and the reaction time is 12 h.

[0018] In the above preparation method, as a preferred embodiment, in step two, the heat treatment includes first heating to 280 - 320 °C (such as 290 °C, 300 °C, 310 °C, etc.) and then maintaining anaerobic calcination for 2 - 4 h (such as 2.5 h, 3 h, 3.5 h, etc.); subsequently, continue to heat to 400 - 1000 °C (such as 500 °C, 600 °C, 700 °C, 800 °C, 9000 °C, etc.) and then maintain anaerobic calcination for 4 - 12 h (such as 4.5 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, etc.). Preferably, the heating rate is 4 - 10 °C / min (such as 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, etc.).

[0019] In the above preparation method, as a preferred embodiment, in step two, the heat treatment includes: grinding the precursor into powder and placing it in a corundum boat, then introducing nitrogen or inert gas into a tube furnace, heating to the calcination temperature of 300 °C at a heating rate of 5 ± 1 °C / min and maintaining anaerobic calcination for 3 h; subsequently, continue to heat to 500 °C and hold for 5 h, and collect the product after natural cooling.

[0020] In the second aspect, the present application also provides a multi - characteristic iron - carbon derivative material for adsorbing and repairing PFAS - polluted water bodies, which is prepared by the above method.

[0021] In the third aspect, the present application also provides an application of the above multi - characteristic iron - carbon derivative material in environmental remediation, including: using the above multi - characteristic iron - carbon derivative material as an adsorbent, supplemented with a cationic complexing agent, to adsorb and purify PFAS - polluted water bodies.

[0022] Optionally, in the above application, the PFAS is selected from at least one of PFOA, PFHpA, PFHxA, GenX, PFPeA, and PFBA. Preferably, in the PFAS - polluted water body, the concentration of PFAS is 0.1 - 6 mg / L (such as 0.6 mg / L, 1 mg / L, 2 mg / L, 3 mg / L, 4 mg / L, 5 mg / L, etc.).

[0023] Optionally, in the above application, the cationic complexing agent is selected from at least one of cationic surfactants such as CTAB, dodecyldimethylamine oxide, cationic panthenol, and octadecyltrimethylammonium chloride.

[0024] Preferably, in the above application, CTAB is used as a complexing agent, and the dosage of CTAB is 10 - 25 mg / L (such as 12 mg / L, 15 mg / L, 18 mg / L, 20 mg / L, 22 mg / L, 24 mg / L, etc.), the dosage of the adsorbent is 0.1 - 0.5 g / L (such as 0.2 g / L, 0.3 g / L, 0.4 g / L, etc.), and the treatment time is within 8 h (such as 0.1 h, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, etc.); more preferably, the treatment time is within 30 min; further, the treatment time is within 10 min.

[0025] Compared with the prior art, the beneficial effects of the present application include but are not limited to:

[0026] 1) The preparation method provided by this application is a simple two-step solvothermal-thermal treatment method for synthesizing the multi-functional iron-carbon derivative material H:MIL-101(Fe), which endows the H:MIL-101(Fe) material with high hydrophobicity, two-dimensional to three-dimensional tight interface and magnetism, shortens the preparation time, and has simpler steps. The prepared H:MIL-101(Fe) material can rapidly remove various PFASs with different structures and carbon chain lengths, and the material can be separated within 30 s after adsorbing and removing per- and polyfluoroalkyl substances without generating secondary pollution.

[0027] 2) The water body remediation method provided by this application uses CTAB to enhance the adsorption and removal of PFASs by the H:MIL-101(Fe) material, establishing an efficient water body pollution remediation system; through the analysis of the adsorption performance of PFASs-contaminated water samples in simulated surface water, it is found that this system can achieve the purpose of efficiently remediating PFAS water body pollution.

[0028] 3) This application first develops a new type of magnetic iron-carbon derivative material with high hydrophobicity and two-dimensional to three-dimensional tight interface - the H:MIL-101(Fe) material, and verifies that this material can efficiently remove various PFASs in water. In practical applications, the dosage of the added material and complexing agent needs to be adjusted according to the different PFAS contents in the polluted water body. The H:MIL-101(Fe) material provided by this application can efficiently remove PFASs and achieve rapid material recovery, and can completely remove PFASs with different structures and carbon chain lengths, having high value for water body pollution treatment.

[0029] 4) In this application, the magnetic iron-carbon derivative H:MIL-101(Fe) material with high hydrophobicity and two-dimensional to three-dimensional tight interfaces was finally used to repair six PFASs (PFOA, PFHpA, PFHxA, GenX, PFPeA, and PFBA) with concentrations of 0.1 - 1 mg / L in surface water, and the effects of water source, adsorbent, complexing agent content, and pH on the adsorption and removal of PFAS were investigated.

[0030] H:MIL-101(Fe) achieved stable removal and rapid material recovery of 1 mg / L -1 of PFOA within 30 minutes. After further adding the complexing agent CTAB, the adsorption performance for six PFASs with different carbon chains and structures in surface water was significantly improved. When the dosage of H:MIL-101(Fe) was increased from 0.3 g / L -1 to 0.5 g / L -1 , it was found that at the natural pH value of surface water, six PFASs were completely removed within 10 minutes. Therefore, the novel magnetic iron-carbon derivative material with high hydrophobicity and two-dimensional to three-dimensional tight interfaces - H:MIL-101(Fe) material provides the possibility for the effective remediation of PFASs pollution in actual water bodies, and has important scientific research value and application significance. Description of the Drawings

[0031] Figure 1 and Figure 2 show the microstructures of the Fe-MOF material MIL-101(Fe) and its heat-treated derivative H:MIL-101(Fe) prepared in Example 1; among them, (a) is the SEM image of MIL-101(Fe) magnified 50,000 times; (b)-(g) are the SEM images of H:MIL-101(Fe) magnified 20,000 times, where (b) is the SEM image; (c) and (d) are TEM images; (e) and (f) are HRTEM images; and (g) is the SEM / EDS image, where (g1), (g2), and (g3) are the C element image, O element image, and Fe element image, respectively.

[0032] Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 are the structure determination diagrams of the Fe-MOF and its heat-treated derivative materials prepared in Example 1 and the comparative example; among them, (a) is the XRD pattern; (b) is the TFIR spectrum; Figure 4 is the Zeta potential diagram; Figure 5 , Figure 6 , Figure 7Nitrogen adsorption-desorption isotherms and pore size distribution diagrams of MIL-101(Fe), H:MIL-101(Fe), and H:NH2-MIL-101(Fe), respectively.

[0033] Figure 8 The curve of cyclic adsorption of 1 mg L -1 PFOA by H:MIL-101(Fe) prepared in Example 1 is shown; Figure 9 The schematic diagram of rapid separation and recovery of H:MIL-101(Fe) material is shown; Figures 10 - 13 Structure characterization diagrams of H:MIL-101(Fe) material after adsorption and desorption of PFOA, respectively; among them, Figure 10 is the XDR spectrum; Figure 11 is the XPS full-scan spectrum; Figure 12 is the Fourier transform infrared spectrum; Figure 13 is the SEM / EDS spectrum of H:MIL-101(Fe) material after desorption of PFOA.

[0034] Figure 14 The surface hydrophobicity of Fe-MOF and its derivative materials prepared in Example 1 and the comparative example is shown, where (a) shows the contact angle of MIL-101(Fe); (b) shows the contact angle of H:NH2-MIL-101(Fe); (c) shows the contact angle of H:MIL-101(Fe); Figure 15 In (d) and (e) shows the oxygen vacancy signal diagram measured by EPR (electron paramagnetic resonance), Figure 16 The surface potential distribution of undeprotonated PFOA at pH = 3 measured using the Fukui function is shown; Figure 17 is the XPS C 1s spectrum of MIL-101(Fe), H:MIL-101(Fe), and H:NH2-MIL-101(Fe).

[0035] Figure 18 The test results of the mixed adsorption performance of H:MIL-101(Fe) for six PFASs with a concentration of 1 mg / L each in surface water at pH = 3 and 0.3 g L -1 are shown.

[0036] Figure 19 The test results of the adsorption performance of H:MIL-101(Fe) for six PFASs with a concentration of 1 mg / L each in ultrapure water at pH = 3 and 0.3 g L -1 are shown respectively.

[0037] Figure 20 The comparison of the test results of the adsorption and removal of 1 mg / L PFBA in surface water with and without the addition of CTAB is shown.

[0038] Figure 21 shows the test results of the mixed adsorption removal performance at pH = 3.0, with an initial concentration of 1 mg / L for each of the six PFASs in surface water and a dosage of 0.3 g / L of H:MIL-101(Fe). -1 , the initial CTAB concentration C 0(CTAB) = 10 mg / L -1 .

[0039] Figure 22 shows the test results of the mixed adsorption removal performance at pH = 7.0, with an initial concentration of 1 mg / L for each of the six PFASs in surface water and a dosage of 0.5 g / L of H:MIL-101(Fe). -1 , C 0(CTAB) = 25 mg / L -1 .

[0040] Figure 23 shows the test results of the mixed adsorption removal performance at pH = 7.0, with an initial concentration (C 0(PFAS) ) of 0.1 mg / L for each of the six PFASs in surface water and a dosage of 0.3 g / L of H:MIL-101(Fe). -1 , C 0(CTAB) = 10 mg / L -1 .

[0041] Figure 24 shows the change in surface hydrophobicity after the combined adsorption of CTAB and H:MIL-101(Fe).

[0042] Figure 25 shows the change in surface hydrophobicity after the desorption of the combined use of CTAB and H:MIL-101(Fe).

[0043] Figure 26 shows a schematic diagram of the mechanism of CTAB-enhanced PFAS co-adsorption.

[0044] Figure 27 shows the comparison of the adsorption performance of 1 mg / L PFOA in ultrapure water at pH values of 3, 5, and 7 with a dosage of 0.3 g / L of the adsorbent H:MIL-101(Fe). Detailed implementation manners

[0045] The following examples facilitate a better understanding of the present application, but do not limit the present application.

[0046] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0047] Other test materials used in the following examples are all obtained from regular biochemical reagent stores unless otherwise specified.

[0048] Example 1

[0049] (I) Preparation of precursor MIL-101(Fe):

[0050] Add 2 mmol of FeCl3·6H2O to 43 mL of DMF (N,N-dimethylformamide). After complete dissolution, add 2 mmol of ligand H2BDC (terephthalic acid) to the above solution at a stirring rate of 800 r / min. The molar ratio of DMF:FeCl3·6H2O:H2BDC is approximately 279:1:1. Stir for 1 h to ensure complete dissolution. After complete dissolution, transfer it to a reaction kettle lined with polytetrafluoroethylene and react at 150 °C for 12 h to generate the precursor MIL-101(Fe). Centrifuge the precursor suspension, discard the supernatant, and obtain the precursor precipitate. Wash the precursor precipitate twice with DMF and absolute ethanol alternately (each washing is carried out on a shaker at 2500 r / min for 30 min) to remove unreacted iron salt impurities. Then transfer it to methanol and soak for 12 h to remove DMF in the material pores, complete the purification process, and then centrifuge for solid-liquid separation and freeze-dry to obtain the precursor MIL-101(Fe), which is ground into powder for standby.

[0051] (II) Synthesis of iron-carbon derivative material - H:MIL-101(Fe) material:

[0052] Weigh 1 g of the precursor MIL-101(Fe) and place it in a corundum boat. Transfer it to a tube furnace. After purging with nitrogen for 30 min, heat it to 300 °C at a heating rate of 5 ± 1 °C / min and keep it at a constant temperature for anaerobic calcination for 3 h. Subsequently, continue to heat it to 500 °C at a heating rate of 5 ± 1 °C / min and hold for 5 h. After natural cooling, collect the iron-carbon derivative H:MIL-101(Fe) material.

[0053] Comparative Example 1

[0054] (I) Preparation of precursor NH2-MIL-101(Fe):

[0055] This step is exactly the same as that in Example 1, except that the ligand is replaced with H2BDC-NH2 (2-aminoterephthalic acid) to obtain the precursor NH2-MIL-101(Fe).

[0056] (II) Synthesis of iron-carbon derivative material - H:NH2-MIL-101(Fe) material:

[0057] This step is exactly the same as that in Example 1, except that the precursor NH2-MIL-101(Fe) is used to obtain the iron-carbon derivative H:NH2-MIL-101(Fe) material.

[0058] Test Example

[0059] (III) Characterization of materials such as H:MIL-101(Fe):

[0060] The surface morphology of the samples was analyzed using a scanning electron microscope (SEM) (model: SU3500, Japan). The surface morphology of the samples was further analyzed using a transmission electron microscope (TEM) (model: TF20 Jeol 2100F). Before detection, the samples were dispersed in absolute ethanol, and the suspension was dropped onto a copper mesh and air-dried naturally. The surface structure of H:MIL-101(Fe) was analyzed using an X-ray powder diffractometer (XRD) (model: Rigaku Smartlab SE) and X-ray photoelectron spectroscopy (XPS) (model: Thermo Fisher Scientific K-Alpha spectrometer). The hydrophilicity and hydrophobicity of materials such as H:MIL-101(Fe) were analyzed using a contact angle / surface tension meter (Chengde Dingsheng JY-82C video contact angle measuring instrument).

[0061] (IV) Test on the rapid adsorption and removal performance of materials such as H:MIL-101(Fe) for PFAS in water:

[0062] The adsorption experiment method is as follows: First, prepare a 50 mL reaction solution containing PFAS in a 100 polypropylene (PP) beaker with surface water (collected from the Dagu Sewage River in Jinnan District) or ultrapure water. Subsequently, use 1 mol / L HCl or NaOH solution to adjust the pH of the solution to the specified pH. After the pH stabilizes, weigh a certain amount of adsorbent and add it to the reaction solution (the added material will not affect the pH value of the system). At a temperature of 25 °C, stir the adsorbent immersed in the reaction solution at a magnetic stirring speed of approximately 800 r / min for a certain period of time. In the dynamic adsorption experiment, pipette 1 mL of the suspension at a set time interval, then filter the adsorbent through a polyethersulfone membrane with a pore size of 0.22 μm, and discard the first 0.3 mL of the filtrate to eliminate the influence of membrane retention of PFAS. Pipette an appropriate amount of the filtrate, dilute it with methanol, mix it thoroughly, transfer it to a plastic liquid-phase injection vial, and use HPLC-MS / MS to analyze the concentration of PFAS in the filtrate.

[0063] The desorption experiment method is as follows: After the adsorption experiment is completed, filter the reaction solution through a polyethersulfone membrane with a pore size of 0.22 μm, transfer the retained adsorbent to a 15 mL plastic centrifuge tube, add 10 mL of analytical pure absolute methanol, and ultrasonicate for 10 min to elute the adsorbed PFAS. After ultrasonication, perform solid-liquid separation using a nylon organic membrane with a pore size of 0.22 μm. When no PFAS was detected in the eluate after repeating the elution process three times, the elution process was repeated three times with 10 mL of methanol.

[0064] (1) Adsorption effects of different PFAS species on different pollutants in different water environments: In this experiment, surface water was used to prepare a mixed solution of six PFASs with different carbon chain lengths and structures - PFOA (perfluorooctanoic acid, C8), PFHpA (perfluoroheptanoic acid, C7), PFHxA (perfluorohexanoic acid, C6), GenX (hexafluoropropylene dimer acid, C6), PFPeA (perfluoropentanoic acid, C5), and PFBA (perfluorobutyric acid, C4). The initial concentration of each PFAS solution was 1 mg L -1 , and the total initial concentration of PFAS was 6 mg L -1 ; at the same time, ultrapure water was used to prepare single-component solutions of six PFASs with different carbon chain lengths and structures - PFOA (C8), PFHpA (C7), PFHxA (C6), GenX (C6), PFPeA (C5), and PFBA (C4), and the initial concentration of each PFAS solution was set to 1 mg L -1 . An adsorption experiment was carried out at pH = 3 and an adsorbent dosage of H:MIL-101(Fe) of 0.3 g L -1 . The results are shown in Figure 18 and Figure 19 . Figure 18 shows the test results of the mixed adsorption performance of six PFASs in surface water by 0.3 g L -1 H:MIL-101(Fe) at pH = 3; Figure 19 shows the test results of the adsorption performance of six PFASs in ultrapure water by 0.3 g L -1 H:MIL-101(Fe) at pH = 3.

[0065] (2) Influence of adding complexing agents on the adsorption performance of CTAB in surface water under different pH conditions: This experiment had four groups. The pollutant PFAS was selected as PFBA (C4) with an initial concentration of 1 mg / L, and the reaction time was 8 h. The other process conditions were controlled differently as follows: 1) pH = 3.0, CTAB dosage 10 mg / L, adsorbent dosage of H:MIL-101(Fe) 0.3 g / L; 2) pH = 9.0, CTAB dosage 10 mg / L, adsorbent dosage of H:MIL-101(Fe) 0.3 g / L; 3) pH = 3.0, CTAB dosage 10 mg / L, adsorbent dosage of H:MIL-101(Fe) 0 g / L; 4) pH = 3.0, CTAB dosage 0 mg / L, adsorbent dosage of H:MIL-101(Fe) 0.3 g / L. The results are shown in Figure 20 .

[0066] (3) Adsorption performance test under the mixed pollution of six PFASs with different carbon chain lengths and structures - PFOA (C8), PFHpA (C7), PFHxA (C6), GenX (C6), PFPeA (C5), and PFBA (C4): This experiment has three groups: 1) Prepare a mixed polluted water of six PFASs with surface water. The initial concentration of each PFAS is 1 mg / L, the total mass concentration of each PFAS in the mixed polluted water is 6 mg / L, pH = 3.0, the dosage of CTAB is 10 mg / L, the dosage of adsorbent H:MIL-101(Fe) is 0.3 g / L, and the reaction time is 8 h; 2) Prepare a mixed polluted water of six PFASs with surface water. The initial concentration of each PFAS is 1 mg / L, the total mass concentration of each PFAS in the mixed polluted water is 6 mg / L, pH = 7.0, the dosage of CTAB is 25 mg / L, the dosage of adsorbent H:MIL-101(Fe) is 0.5 g / L, and the reaction time is 60 min; 3) Prepare a mixed polluted water of six PFASs with surface water. The initial concentration of each PFAS is 0.1 mg / L, the total mass concentration of each PFAS in the mixed polluted water is 0.6 mg / L, pH = 7.0, the dosage of CTAB is 10 mg / L, the dosage of adsorbent H:MIL-101(Fe) is 0.3 g / L, and the reaction time is 60 min. The results are shown in Figure 21 , Figure 22 , Figure 23 .

[0067] (4) Test the influence of CTAB-enhanced adsorption of PFAS (select PFOA) on the hydrophobicity of H:MIL-101(Fe) material: For the H:MIL-101(Fe) material after adsorption with CTAB added in the experiment (3) part 3) of this test example ( Figure 23 the experiment shown), filter and separate it. After drying at 105 °C, use a contact angle meter to test the contact angle of the H:MIL-101(Fe) material. The results are as shown in Figure 24 . At the same time, after filtering and separating the H:MIL-101(Fe) material after adsorption with CTAB added, use methanol to elute the PFAS on the H:MIL-101(Fe) material. After the elution is completed, dry it at 105 °C, and then use a contact angle meter to perform a contact angle test. The results are as shown in Figure 25 .

[0068] (5) Influence of the pH of the reaction system on the adsorption performance of the H:MIL-101(Fe) material: To further verify the anti-interference ability of the H:MIL-101(Fe) material to the water body pH, different pH values were set, which were 3, 5, and 7 respectively. The dosage of the adsorbent H:MIL-101(Fe) material was 0.3 g / L. The pollutant PFAS was selected as PFOA, dissolved in ultrapure water, with an initial concentration of 1 mg / L, and the reaction time was 8 h. The results are shown in Figure 27 . From Figure 27 it can be seen that the adsorption capacity of H:MIL-101(Fe) for PFOA is the best when the solution pH = 3, and the removal ability of PFOA is proportional to the solution acidity. Because the dissociation constant pKa value of the PFOA molecule is about 3.5, deprotonation does not occur at pH = 3, retaining a longer molecular length, making the hydrophobic interaction between the material and the PFOA molecule stronger, further confirming that the hydrophobic interaction is the main mechanism for H:MIL-101(Fe) to adsorb PFAS.

[0069] (6) Cyclic adsorption experiment of the H:MIL-101(Fe) material: The pollutant PFAS was selected as PFOA, and ultrapure water was used to add PFOA to prepare a solution with an initial concentration of 1 mg L -1 . The pH = 3.0, CTAB was not added, and the dosage of the adsorbent H:MIL-101(Fe) material was 0.3 g / L; after the adsorption and desorption experiments were completed, the adsorbent filter cake was dried at 105 °C for 12 h and then ground and collected. The adsorption-desorption-regeneration experiment was repeated with the regenerated adsorbent. In this way, the cyclic adsorption experiment results in Figure 8 were obtained.

[0070] (7) Separation performance test of the H:MIL-101(Fe) material after adsorbing 1 mg / L PFOA: After 0.3 g / L H:MIL-101(Fe) material completed the adsorption of 1 mg / L PFOA at pH = 3.0 (i.e., completed the first adsorption in the experiment of part (6) of this test example), a magnet was used to magnetically separate the H:MIL-101(Fe) material in the suspension. The results showed that solid-liquid separation could be achieved within 30 s, as shown in Figure 9 .

[0071] (V) Exploration of the adsorption mechanism of iron-carbon derivative H:MIL-101(Fe) material for PFASs:

[0072] To explore the adsorption mechanism of H:MIL-101(Fe) for PFAS, a contact angle / surface tension meter, a specific surface area and pore size and pore volume analyzer, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy were used to analyze and compare the surface properties and pore structures of H:MIL-101(Fe) and its precursor MIL-101(Fe). The results showed that MIL-101(Fe) is a magnetic iron-carbon material with a highly hydrophobic surface, rich in oxygen vacancies, micro-nano pores, and two-dimensional-three-dimensional tight interfaces. The excellent adsorption performance for PFAS is a process of multi-mechanism synergy of electrostatic attraction and π-π interaction under the dominance of hydrophobic interaction. In summary, H:MIL-101(Fe) realizes the efficient co-removal of various PFAS in surface water and can achieve the rapid recovery of the material.

[0073] (VI) Experimental results

[0074] 1. Material characterization

[0075] Figure 1 and Figure 2 show the microstructures of the Fe-MOF material MIL-101(Fe) and the heat-treated derivative H:MIL-101(Fe); among them, (a) is a scanning electron microscope (SEM) image of MIL-101(Fe) magnified 50,000 times; (b)-(g) are SEM images of H:MIL-101(Fe) magnified 20,000 times, where (b) is an SEM image; (c) and (d) are TEM images; (e) and (f) are HRTEM images; (g) is an SEM / EDS image, (g1) is a C element image, (g2) is an O element image, and (g3) is an Fe element image. Scanning electron microscopy (SEM) detected that MIL-101(Fe) is octahedral, with a uniform morphology, a smooth surface, and a size between 500-1000 nm (see (a) in Figure 1 . The escape of carbon ligands during the heat treatment process led to the fracture of the MOF structure, forming a 2D / 3D composite structure, where three-dimensional iron oxide particles grew on the two-dimensional carbon substrate (see (b)-(d) in Figure 1 . HRTEM observed a uniform lattice spacing of 0.24 nm on the octahedral particles, corresponding to the {222} crystal plane of Fe3O4, which confirmed the formation of a three-dimensional metal oxide framework due to the escape of organic ligands (see (e), (f) in Figure 1 . The SEM / EDS results of randomly selected areas showed that the distributions of C and O elements were relatively uniform, while the distribution of Fe elements was more concentrated at the particle level (see (g), (g1), (g2), (g3) in Figure 2 , which was consistent with the HRTEM results.

[0076] Figure 3 、 Figure 4, Figure 5 , Figure 6 , Figure 7 are the structure determination diagrams of Fe-MOF and its heat-treated derivatives; among them, (a) is the XRD pattern; (b) is the TFIR spectrum. Figure 4 is the Zeta potential diagram; Figure 5 , Figure 6 , Figure 7 are the nitrogen adsorption-desorption curves and pore size distribution diagrams of MIL-101(Fe), H:MIL-101(Fe), and H:NH2-MIL-101(Fe), respectively. Phase identification of the synthesized materials was carried out by XRD (see (a) in Figure 3 ), indicating that the diffraction peaks of Fe-MOF disappeared after heat treatment, and the emerging metal diffraction peaks corresponded to Fe3O4 (PDF (i.e., Powder Diffraction File) card number #99-0074), Fe 2.94 O4 (PDF card number #86-1361), and Fe (PDF card number #87-0721). According to the XRD diffraction peak signals and the use of different ligands H2BDC (terephthalic acid) and H2BDC-NH2 (2-aminoterephthalic acid), two Fe-MOF materials, namely MIL-101(Fe) and NH2-MIL-101(Fe), were synthesized. Fourier transform infrared (FT-IR) spectroscopic analysis was carried out on three materials, MIL-101(Fe), H:MIL-101(Fe), and H:NH2-MIL-101(Fe) (see (b) in Figure 3 ). The broad absorption band functional group near 3430 cm -1 was attributed to the O-H vibration of surface adsorbed water, and the vibration of the materials H:MIL-101(Fe) and H:NH2-MIL-101(Fe) obtained after heat treatment decreased significantly. The peaks at 1389 and 1600 cm -1 corresponded to the symmetric and asymmetric vibrations of the carboxylate linker, indicating that the organic linker had been successfully coordinated to the MOF structure and still showed weak vibrations after being converted into derivatives (see (b) in Figure 3 ). The peak at 745 cm -1 was the C-H stretching vibration of the aromatic ring (see (b) in Figure 3 ), and the intensity of the derivative H:MIL-101(Fe) was significantly higher than that of H:NH2-MIL-101(Fe).

[0077] The Zeta potential (ζ potential) of the three measured materials showed a similar pattern, with ζ potential greater than 0 in the range of pH ≤ 3.0 (see Figure 4) This is beneficial for electrostatic adsorption because the dissociation constant of PFAS is low, acidifying the solution. The nitrogen adsorption-desorption isotherm indicates that MIL-101(Fe) is a type I microporous Langmuir monolayer with reversible adsorption, consistent with the pore size distribution (see Figure 5 ). H:MIL-101(Fe) and H:NH2-MIL-101(Fe) both exhibit type IV desorption hysteresis with multilayer adsorption (see Figure 6 , Figure 7 ), but the pore size of H:MIL-101(Fe) is mainly concentrated in mesopores around 4 nm, with a specific surface area of 273.6 m 2 g -1 . H:NH2-MIL-101(Fe) is mainly microporous, with a specific surface area of 124.0 m 2 g -1 . Overall, the above characterizations jointly demonstrate the successful preparation of the highly hydrophobic, two-dimensional to three-dimensional tightly interfaced magnetic iron-carbon derivative H:MIL-101(Fe). And the single or multiple differences in the structure, surface properties, and morphology of the constructed Fe-MOFs and their derived materials determine their different adsorption performances for PFAS.

[0078] 2. Rapid adsorption and reuse of H:MIL-101(Fe) material for PFASs

[0079] Figure 8 shows the curve of H:MIL-101(Fe) for cyclic adsorption of 1 mg L -1 PFOA; Figure 9 shows the schematic diagram of rapid separation and recovery of H:MIL-101(Fe) material. Figures 10 - 13 are the structural characterization diagrams of H:MIL-101(Fe) after adsorption and desorption of PFOA, respectively; among them, Figure 10 is the XDR spectrum; Figure 11 is the XPS full-scan spectrum; Figure 12 is the Fourier transform infrared spectrum; Figure 13 is the SEM / EDS spectrum of H:MIL-101(Fe) material after completing adsorption and desorption of PFOA, where (f1), (f2), and (f3) are the element distributions and contents of C, O, and Fe, respectively.

[0080] The fourth-cycle adsorption of H:MIL-101(Fe) for 1 mg L -1 PFOA still maintains a removal rate of over 90% within 30 minutes, and the removal can be completed in almost 4 hours (see Figure 8 ). The H:MIL-101(Fe) material can also be completely separated by magnetic separation within 30 seconds (see Figure 9)。Characterizations by XRD, XPS and FTIR demonstrated the structural stability and elution regeneration performance of H:MIL-101(Fe) during the recycling process (see Figures 10 - 12 )。The XRD results showed that the number and intensity of the diffraction peaks of the material did not change after adsorbing and desorbing PFOA (see Figure 10 ), indicating that the structural properties of H:MIL-101(Fe) remained stable during the recycling process. Compared with the initial structure of H:MIL-101(Fe), some elemental Fe was converted into FeO during the adsorption process due to being in an open aerobic system (see Figure 3 (a) in Figure 10 , which are the figures before and after adsorption respectively). The FTIR spectra also showed that the structures of C-O, C-H and Fe-OH were stable during the adsorption and regeneration of H:MIL-101(Fe) (see Figure 12 ). During the dry cycle regeneration process, only the adsorbed water represented by O-H with a wave number of 3430 gradually decreased. Figure 13 It was shown that no F element was detected after H:MIL-101(Fe) completed PFOA adsorption and elution, indicating that the material is easy to recycle. In summary, H:MIL-101(Fe) exhibited excellent properties, including cyclic adsorption of PFOA, structural stability and convenient recycling. Therefore, a highly hydrophobic 3D / 2D interfacial magnetic material was prepared in this disclosure, which can be used to rapidly purify water contaminated by PFAS and further ensure the safety of drinking water.

[0081] 3. Mechanism of efficient adsorption of PFASs by H:MIL-101(Fe) material

[0082] Figure 14 shows the surface hydrophobicity of Fe-MOF and its derivative materials, where (a) shows the contact angle of MIL-101(Fe); (b) shows the contact angle of H:NH2-MIL-101(Fe); (c) shows the contact angle of H:MIL-101(Fe). Figure 15 (d) and (e) in Figure 16 show the oxygen vacancy signals measured by EPR (electron paramagnetic resonance). Figure 17 is the XPS C 1s spectrum of MIL-101(Fe), H:MIL-101(Fe) and H:NH2-MIL-101(Fe).

[0083] H:MIL-101(Fe) showed excellent adsorption performance for PFAS, mainly due to the contact angle of its hydrophobic surface being 144.0° (see Figure 14(c) in it is significantly higher than the contact angles of MIL-101 and H:NH2-MIL-101(Fe), which are approximately 48.0° and 64.0° respectively (see Figure 14 (a), (b) in it). The adsorption of PFOA by the three materials is proportional to their hydrophobicity, that is, H:MIL-101(Fe) = 99.9% > H:NH2-MIL-101(Fe) = 89.1% > MIL-101(Fe) = 22.5%. The fundamental reason for the highly hydrophobic surface of the H:MIL-101(Fe) material is not only attributed to the carbonization of some MOF structures during the heat treatment process, but also to the formation of a large number of unsaturated C-H bonds on the benzene ring at 3060 cm -1 .

[0084] In addition, MIL-101(Fe) and H:NH2-MIL-101(Fe) with hydrophilic surfaces also show adsorption capacity for PFOA. The contact angle of H:NH2-MIL-101(Fe) increased by 16.0° compared to MIL-101(Fe), but the adsorption percentage of PFOA increased by 26.6%, indicating the existence of other adsorption mechanisms. Heat treatment of the materials in an inert atmosphere usually generates positively charged oxygen vacancies. The EPR characterization results show that H:NH2-MIL-101(Fe) contains obvious oxygen vacancy signals and is stronger than H:MIL-101(Fe). The surface potential of the PFOA molecule was calculated using the Fukui function, and significant negative charge accumulation occurred at the head O atom far from the H atom end (see Figure 16 ), resulting in the anchoring of PFOA molecules on the oxygen vacancies through electrostatic interactions. This indicates that electrostatic attraction contributes to the adsorption of PFOA by H:NH2-MIL-101(Fe) and H:MIL-101(Fe) (see Figure 15 (d) and (e) in it). The XPS C 1s spectrum shows that both MIL-101(Fe) and H:MIL-101(Fe) enhance the adsorption of PFOA through π-π interactions (see Figure 17 ).

[0085] Therefore, H:MIL-101(Fe) can rapidly remove PFAS, which benefits from a synergistic adsorption mechanism dominated by hydrophobic interactions, including oxygen vacancies, π-π bonds, and micropores.

[0086] 4. Co-removal of PFASs in surface water by CTAB-enhanced H:MIL-101(Fe) material

[0087] When the mixed adsorption of 6 PFASs with a content of 1 mg / L in actual surface water was carried out, significant competitive adsorption was found (see Figure 18 ). That is, the removal effect of PFOA with the longest carbon chain is the best, and the adsorption of short-chain PFBA and PFPeA is limited. Figure 19It shows that when six PFASs are separately adsorbed in ultrapure water, their individual adsorption removal rates are significantly improved, and it also shows better adsorption of PFASs with longer carbon chains.

[0088] When CTAB is used in combination with PFBA, the removal rate of PFBA by H:MIL-101(Fe) increases from 21.2% to 82.4%. CTAB enhances the co-adsorption of long-chain and short-chain PFASs on H:MIL-101(Fe) in surface water, and the strong hydrophobic effect overcomes the electrostatic repulsion caused by the increase in pH (see Figure 20 ). Correspondingly, after adding CTAB to H:MIL-101(Fe), the adsorption of six mixed PFASs is significantly enhanced (see Figure 21 ), and PFOA (C8), PFHpA (C7), and GenX (C6) at 1 mg L -1 are almost completely removed within 30 minutes, and the removal rate of PFPeA (C5) exceeds 90%. After increasing the addition amount of CTAB to enhance the complexation with PFASs, it is found that the adsorption performance of six PFASs is significantly improved. However, due to the limitation of adsorption sites, PFPeA (C5) and PFBA (C4) cannot be completely removed (see Figure 22 ). It should be noted that excessive CTAB will occupy some adsorption sites and cannot achieve the optimal adsorption and removal of PFASs. Therefore, the loading amount of H:MIL-101(Fe) is increased from 0.3 g L -1 to 0.5 g L -1 , and at the same time, the initial concentration of PFASs is reduced to ensure sufficient adsorption sites. It is found that at the natural pH value of surface water, six PFASs are completely removed within 10 minutes (see Figure 23 ).

[0089] The effect of CTAB on the hydrophobic properties of H:MIL-101(Fe) was further investigated. It was found that after adsorbing and desorbing PFASs, the surface contact angle of H:MIL-101(Fe) did not change significantly (see Figure 24 , Figure 25 ), indicating that CTAB enhances the adsorption of PFASs by H:MIL-101(Fe) without affecting its recycling performance. This shows that using the cationic chelating agent CTAB to form head electrostatic interactions and hydrophobic tail binding with PFASs is a successful strategy to improve the surface hydrophobicity of the material to enhance its adsorption of PFASs in natural water (see Figure 26 ).

[0090] Finally, it should also be noted that in this application, the terms "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0091] Although the present application has been disclosed above through the description of specific embodiments of the present application, it should be understood that those skilled in the art can design various modifications, improvements or equivalents to the present application within the spirit and scope of the appended solutions. These modifications, improvements or equivalents should also be considered to be included within the scope claimed by the present application.

Claims

1. A method for preparing a multi-characteristic iron-carbon derivative material for adsorption and remediation of PFASs pollution in water, characterized in that: include: Step 1, dissolving trivalent iron salt in N,N-dimethylformamide, adding ligand terephthalic acid under stirring conditions, and synthesizing a precursor by a solvothermal method; Step 2: heat-treating the precursor in an inert atmosphere to obtain the multi-property iron-carbon derivative material.

2. The preparation method according to claim 1, characterized in that: Also includes: Before the heat treatment, the precursor precipitate is washed alternately with N,N-dimethylformamide and anhydrous ethanol twice each, and then transferred to methanol for purification; Preferably, the washing comprises: centrifuging the precursor suspension generated by the solvothermal method in step 1, discarding the supernatant, adding an appropriate amount of N,N-dimethylformamide or anhydrous ethanol washing solution, and washing on an oscillator at 2500 r / min for 30 minutes; Preferably, the purification treatment comprises: soaking the precursor precipitate in methanol for 12 hours; Preferably, after the purification treatment, the precursor is obtained by separation, drying and grinding. More preferably, the separation treatment is a centrifugal treatment, and the drying treatment is a vacuum drying treatment.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1, the trivalent iron salt can be selected from at least one of ferric chloride, ferric nitrate and ferric sulfate.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step 1, the molar ratio of ferric iron salt to terephthalic acid is 1:1; Preferably, in step 1, the molar ratio of N,N-dimethylformamide: ferric iron salt: terephthalic acid is 50-300:1:

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step 1, after the trivalent iron salt and terephthalic acid are added to N,N-dimethylformamide, they are stirred at a constant speed of 500-1000 r / min for 10-60 min to completely dissolve and mix evenly, and then the precursor is synthesized by a solvothermal method; preferably, the stirring speed is 800 r / min and the stirring time is 60 min.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step 1, in the solvothermal method, the reaction temperature is 140-160° C., and the reaction time is 10-14 h; more preferably, the reaction temperature is 150° C., and the reaction time is 12 h.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In step 2, the heat treatment includes first heating to 280-320°C and then anaerobic burning at a constant temperature for 2-4 hours; then continuing to heat to 400-1000°C and then anaerobic burning at a constant temperature for 4-12 hours; preferably, the heating rate is 4-10°C / min; preferably, the inert atmosphere refers to a nitrogen atmosphere or an inert gas atmosphere.

8. The preparation method according to any one of claims 1 to 6, characterized in that: In step 2, the heat treatment includes: grinding the precursor into powder and placing it in a corundum ark, then introducing nitrogen or inert gas into a tubular furnace, heating the temperature to 300°C at a heating rate of 5±1°C / min, and then anaerobic calcining at a constant temperature for 3 hours; then continue heating to 500°C and maintain for 5 hours, and collect the product after natural cooling.

9. A multi-characteristic iron-carbon derivative material for adsorption and remediation of PFAS pollution in water, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. Application of a multi-property iron-carbon derivative material in environmental remediation, characterized in that: include: Using the multi-characteristic iron-carbon derivative material as claimed in claim 9 as an adsorbent, supplemented by a cationic complexing agent, to perform adsorption purification treatment on PFAS-contaminated water bodies; Optionally, the PFAS is selected from at least one of PFOA, PFHpA, PFHxA, GenX, PFPeA and PFBA; preferably, in the PFAS-contaminated water body, the concentration of the PFAS is 0.1-6 mg / L; Optionally, the cationic complexing agent is selected from at least one of CTAB, dodecyldimethylamine oxide, cationic panthenol and octadecyltrimethylammonium chloride; Preferably, CTAB is used as the complexing agent, the dosage of CTAB is 10-25 mg / L, the dosage of the adsorbent is 0.1-0.5 g / L, and the treatment time is within 8 hours; more preferably, the treatment time is within 30 minutes; further, the treatment time is within 10 minutes.

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