Modified magnetite nanoparticles, method for preparing the same and use thereof

Abstract

The application discloses a modified magnetite nanoparticle, characterized in that the modified magnetite nanoparticle is a silane-modified magnetite nanoparticle.The modified magnetite nanoparticle material provided by the application has a high adsorption removal rate for PFOS in water, and the removal effect is much higher than that of conventional iron-containing mineral adsorption materials and reported activated carbon.The synthesized magnetite nanoparticle material can quickly and effectively remove PFOS in water under conditions of a wide pH range (4.0-9.0) and different ion strengths (0-0.5 mol / L). In addition, the modified material has a high removal rate for high and low concentrations of PFOS in actual wastewater. In addition, compared with traditional adsorption materials, the modified magnetite nanoparticle material has a stable structure and high magnetism, can be recycled, and will not cause secondary pollution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water pollution control, and particularly relates to modified magnetite nanoparticles as well as a preparation method and application thereof. BACKGROUND

[0002] The pollution problem of perfluorooctane sulfonate (PFOS) in water is increasingly serious worldwide, posing a great threat to the ecosystem and human health. As a typical persistent organic pollutant (POPs), PFOS is extremely difficult to be degraded in the environment due to the high stability of its carbon-fluorine bond, and is known as the forever chemical. PFOS is widely used in industrial products (such as fire extinguishing foam, waterproof coating, semiconductor manufacturing and electroplating industry, etc.), leading to its continuous accumulation in water, soil and organisms. PFOS can be transmitted through the food chain, and then cause serious threats to human health, including endocrine disruption, immune system disorder, developmental toxicity and carcinogenesis, etc. Therefore, there is an urgent need to develop efficient materials to remove PFOS in water to ensure the safety of drinking water and block further pollution of the ecological chain.

[0003] The existing PFOS treatment technologies mainly include adsorption, photocatalytic oxidation, membrane separation and combined process. The photocatalytic method can achieve complete decomposition of PFOS under mild conditions, but the application is limited by light dependence and catalyst stability. Patent No. CN 202411080852 uses Fe3O4 / ZnO / Ag3PO4 composite nanomaterials to realize the degradation of PFOS under visible light in cooperation with persulfate. The advantage of this method is that the double-effect catalyst can enhance the electron-hole separation efficiency and improve the oxidation capacity, and the material has magnetism and is easy to recover. However, the material has the problem of photo-corrosion, and the dosage of persulfate needs to be controlled, which is high in cost. Patent No. CN 39188250 enhances the surface functional groups of activated carbon through acid-alkali pretreatment, and combines with persulfate oxidation to degrade PFOS. This method is simple in process and low in cost, but it needs high-temperature incineration treatment after adsorption, which is high in energy consumption and has the risk of secondary pollution. The adsorption method is low in cost, easy to scale up, and practical in economy. Due to its high efficiency and selectivity, the adsorption method has attracted much attention in the field of PFOS removal. Patent CN 14209351 proposes a preparation method of a bifunctional monomer adsorbent based on molecular imprinting technology. This technology uses 2-(trifluoromethyl) acrylic acid (TFMAA) and 4-vinylpyridine as monomers, and perfluorooctanoic acid as template molecule to synthesize molecularly imprinted polymer, which can efficiently adsorb PFOS with an adsorption rate of 76.7%. In addition, the combination of adsorption with photocatalysis, membrane separation and other technologies can realize the integrated treatment of adsorption enrichment and in-situ degradation. For example, patent CN 119176607 combines adsorption with photocatalysis, and the PFOS removal rate is increased to 85%. Therefore, the adsorption method has both environmental safety and engineering applicability in dealing with PFOS pollution, and is an important direction for current technology research and industrial application. However, traditional adsorbents such as granular activated carbon and powdered activated carbon adsorption can effectively remove PFOS in wastewater, but the removal efficiency is low, and there are problems such as high cost and difficulty in recycling for high-concentration PFOS treatment. In addition, these adsorbents are not magnetic and cannot be recycled, which may cause secondary pollution. In the future, low-cost, environmentally friendly and recyclable functional nanomaterials need to be further developed for rapid and efficient adsorption removal of PFOS in wastewater. In summary, how to use synthetic nanomaterials with stable properties and no harm to the environment, and the synthesized nanomaterials have high adsorption capacity for PFOS, which is a problem that needs to be solved by technical personnel in this field. SUMMARY

[0004] In order to overcome the problems existing in the prior art, one of the purposes of the present application is to provide a modified magnetite nanoparticle. The second purpose of the present application is to provide a preparation method of the modified magnetite nanoparticle. The third purpose of the present application is to provide an application of the modified magnetite nanoparticle. The fourth purpose of the present application is to provide a method for removing perfluorooctane sulfonic acid in water.

[0005] To achieve the above object, the technical scheme adopted by the present application is:

[0006] The first aspect of the present application provides a modified magnetite nanoparticle, characterized in that the modified magnetite nanoparticle is a silane-modified magnetite nanoparticle.

[0007] Preferably, the particle size of the modified magnetite nanoparticle is 10-100 nm.

[0008] The second aspect of the present application provides a preparation method of the modified magnetite nanoparticle of the first aspect, comprising the following steps:

[0009] The magnetite nanoparticle is added to a silane coupling agent solution to perform a coupling reaction, thereby preparing the modified magnetite nanoparticle.

[0010] Preferably, the preparation method of the magnetite nanoparticle comprises the following steps: adding dissimilatory iron-reducing bacteria to a mixed solution containing amorphous and weakly crystalline iron minerals to perform a reduction reaction, thereby preparing the magnetite nanoparticle.

[0011] More preferably, the content ratio of the dissimilatory iron-reducing bacteria to the amorphous and weakly crystalline iron minerals in the mixed solution is (10 9 ~ 10 7 ) cells:(0.01~0.5) mmol.

[0012] More preferably, the reduction reaction is performed at 20~40℃.

[0013] More preferably, the time of the reduction reaction is 4~6 days.

[0014] More preferably, the reduction reaction is performed under oscillation conditions.

[0015] More preferably, the dissimilatory iron-reducing bacteria comprise at least one of Shewanella, Geobacter, Sulfococcus, and Desulfovibrio.

[0016] More preferably, the preparation method of the mixed solution containing amorphous and weakly crystalline iron minerals comprises the following steps: slowly adding sodium hydroxide to an aqueous ferric chloride solution, adjusting the pH of the above solution to 7.5-8.0, separating the solid product, re-adding the solid product to an anaerobic sterile culture medium to obtain the mixed solution containing amorphous and weakly crystalline iron minerals.

[0017] Further preferably, the concentration of ferric chloride in the aqueous ferric chloride solution is 0.01~0.1 g / mL.

[0018] Further preferably, the dropping speed of the sodium hydroxide is 1~3 mL min -1 .

[0019] Preferably, the silane coupling agent comprises at least one of hexadecyltrimethoxysilane, fluorosilane, octadecyltrimethoxysilane, dodecyltriethoxysilane, octyltriethoxysilane, gamma-aminopropyltriethoxysilane and gamma-methacryloyloxypropyltrimethoxysilane.

[0020] Preferably, the ratio of the magnetite nanoparticles to the silane coupling agent is 1g:(1-10)mL.

[0021] Preferably, the reaction time of the coupling reaction is 20-60 minutes.

[0022] The preparation method of the modified magnetite nanoparticles of the present application is to use ferric ions as raw materials, to synthesize amorphous weakly crystalline iron minerals (weakly crystalline ferrihydrite, chemical formula approximately Fe5HO8·4H2O) by regulating the hydrolysis rate of ferric ions, to use microorganisms with iron reduction function to catalyze the weakly crystalline ferrihydrite to transform into iron-containing minerals with magnetism (nano-magnetic iron oxide), to further use long-chain alkyl silanes such as hexadecyltrimethoxysilane to modify the iron-containing minerals with magnetism, and to obtain the modified magnetite nanoparticles by hydrophobic modification (exposure of alkyl chains).

[0023] The third aspect of the present application provides any one of the following applications of the modified magnetite nanoparticles of the first aspect:

[0024] a) application in treating perfluoro and polyfluoro alkyl substances;

[0025] b) application in preparing products for treating perfluoro and polyfluoro alkyl substances.

[0026] Preferably, the perfluoro and polyfluoro alkyl substances comprise perfluorooctane sulfonic acid, perfluorohexane sulfonic acid, perfluoroheptane sulfonic acid, perfluorononane sulfonic acid, perfluorooctane sulfonate and chlorinated perfluoropolyether sulfonic acid.

[0027] Specifically, the unmodified magnetic iron oxide has limited adsorption capacity for perfluoro and polyfluoro alkyl substances due to the hydrophilic surface, the modified magnetite nanoparticles in the present application are hydrophobically modified, the silane modification exposes alkyl chains on the surface of nano-magnetic iron oxide, can target the perfluoro chains of perfluoro and polyfluoro alkyl substances (such as PFOS), thereby achieving the capture of perfluoro and polyfluoro alkyl substances and greatly improving the adsorption capacity; in addition, the existing silane (such as 3-aminopropyltriethoxysilane) modified Fe3O4 is used for adsorption or catalytic materials, which is mainly used for enhancing dispersibility or fixing enzymes, and has obvious difference from the modified magnetite nanoparticles of the present application for perfluoro and polyfluoro alkyl substance adsorption.

[0028] The fourth aspect of the present application provides a method for removing PFOS in water, comprising the following steps: adding the modified magnetite nanoparticles of the first aspect to the water containing PFOS, and removing the PFOS by adsorption.

[0029] The present application has the following advantages:

[0030] The modified magnetite nanoparticles provided by the present application have a high adsorption removal rate for PFOS in water, and the removal effect is much higher than that of conventional iron-containing mineral adsorption materials and reported activated carbon. The synthesized magnetite nanoparticles can quickly and effectively remove PFOS in water under a wide pH range (4.0-9.0) and different ionic strength (0-0.5 mol / L) conditions. In addition, the modified material has a high removal rate for high and low concentrations of PFOS in actual wastewater. In addition, compared with traditional adsorption materials, the modified magnetite nanoparticles of the present application have a stable structure and high magnetism, can be recycled, and will not cause secondary pollution.

[0031] The synthesis process of the present application is simple, green, pollution-free, raw materials are easy to obtain, the synthesis cost is low, and it has good application prospect and can produce certain economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The transmission electron micrographs of the unmodified and modified magnetite nanoparticles synthesized in Example 1, wherein (a) is the unmodified magnetite nanoparticles; (b) is the modified magnetite nanoparticles;

[0033] Figure 2 The X-ray diffraction patterns of the unmodified and modified magnetite nanoparticles synthesized in Example 1;

[0034] Figure 3 The adsorption capacity comparison graphs of PFOS in water of the unmodified, modified magnetite nanoparticles synthesized in Example 1 and other iron minerals;

[0035] Figure 4 The adsorption capacity comparison graphs of PFOS in water of the unmodified and modified magnetite nanoparticles synthesized in Example 1 under different pH (a) and salinity (b) conditions;

[0036] Figure 5 The performance graphs of the modified magnetite nanoparticles synthesized in Example 1 adsorbing PFOS in wastewater 1 and 2. DETAILED DESCRIPTION

[0037] The present application will be further described in detail by specific examples. The raw materials used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels or prepared by simple synthesis and separation; the processes used, unless otherwise specified, are conventional processes in the art.

[0038] The solutions used in the following examples are prepared with deionized water. The reagents used, such as ferric chloride, PFOS, hexadecyltrimethoxysilane, sodium chloride, tryptone, yeast extract and sodium hydroxide, are purchased from National Pharmaceutical Reagent and are all of analytical purity;

[0039] The components of the anaerobic sterile culture medium used in the examples are: 10 mmol / L boric acid buffer, 5 mmol / L sodium chloride, 0.5 mmol / L magnesium chloride and 0.5 mmol / L calcium chloride.

[0040] Example 1

[0041] This example provides a modified magnetite nanoparticle, and the preparation method is as follows:

[0042] Step 1: Bacterial activation and enrichment. The Shewanella putrefaciens CN-32 in the preservation solution was inoculated into a conical flask containing 250 mL of lysing broth (containing 10 g L -1 tryptone, 10 g L -1 sodium chloride and 5 g L -1 yeast extract), and it was placed in a constant temperature shaking incubator for 16 hours of activation culture. During the culture process, the shaking speed of the shaking incubator was set to 180 rpm and the temperature was set to 30°C. After shaking, the bacterial solution was sequentially dispensed into 50 mL sterile centrifuge tubes, and centrifuged in a centrifuge at a speed of 8000 g and 4°C for 12 minutes. The supernatant was discarded, and anaerobic sterile culture medium was added to the centrifuge tube. The above operation was repeated 5 times, and the cleaned bacteria were resuspended in sterile culture medium. The bacterial suspension was purged with nitrogen for 30 minutes, and then sealed and stored in a sterile serum bottle. The absorbance of the bacterial suspension at 600 nm was measured using a UV-visible spectrophotometer. After conversion, the bacterial concentration was about 5×10 9 cells·mL -1 .

[0043] In addition to the above-mentioned Shewanella putrefaciens CN-32, other strains with dissimilatory iron reduction, such as Geobacter sulfurreducens and Geobacter metallireducens, Shewanella sp. C31 and Desulfuromonas acetoxidans, can be used alone or in combination to synthesize magnetite nanoparticles. For the sake of convenience and understanding, this patent only takes Shewanella putrefaciens CN-32 as an example for description.

[0044] Step 2: Microbial-mediated formation of magnetite nanoparticles. Weigh 4.04 g of ferric chloride solid into a 250 mL beaker, add 200 mL of deionized water to fully dissolve the solid. Then, at a rate of 2 mL / min... -1 The pH of the above solution was adjusted to 7.5-8.0 by adding 2.5 mol / L sodium hydroxide solution dropwise, forming a reddish-brown suspension. Stirring was performed at 220 rpm during this process. After the addition was complete, stirring was continued for 48 hours. The suspension was then transferred to a 50 mL centrifuge tube and centrifuged at 8000 rpm to remove the supernatant. The wet solid was washed three times with deionized water. The synthesized solid was then resuspended in a serum bottle containing anaerobic sterile culture medium to obtain 200 mL of a 50 mmol / L amorphous weakly crystalline iron mineral stock solution.

[0045] Step 3: Add 20 mL of a 10% concentration... 9 cells·mL -1 Shewanella putrefactive bacteria MR-1 was added dropwise to a serum bottle containing 50 mmol / L amorphous weakly crystalline iron minerals, bringing the bacterial concentration in the system to 10. 8 cells·mL -1 After thorough mixing, the serum bottles were placed in a 30°C constant temperature shaking incubator. Each treatment group was divided into three parallel groups. After 5 days of reaction, all suspensions were transferred to 50mL centrifuge tubes and centrifuged at 8000rpm for 12 minutes, discarding the supernatant. Deionized water was then added. The above steps were repeated 5 times to wash away impurities from the solid surface. The wet solid was collected and freeze-dried for 48 hours to obtain the dried solid powder, which was the synthesized magnetite nanoparticles (defined as unmodified magnetite nanoparticles). The collected solid powder samples were used for further synthesis of modified magnetite nanoparticles.

[0046] Step 4: Modification of magnetite nanoparticles. Weigh 1.0 g of the synthesized unmodified magnetite nanoparticles into a 1.0 L glass beaker, add 500 mL of methanol, and then add 5.0 mL of hexadecyltrimethoxysilane solution to the beaker using a pipette. Stir the resulting mixture on a magnetic stirrer at 220 rpm for 24 minutes. During stirring, the hydroxyl groups in the magnetite nanoparticles react with the methoxysilyl groups in the hexadecyltrimethoxysilane to form siloxane bonds, exposing the alkyl chains of the hexadecyltrimethoxysilane on the surface of the magnetite nanoparticles, thus making the magnetite nanoparticles hydrophobic. Use a magnet to hold the modified magnetite nanoparticles in the container, pour out the solution, and allow the wet solid in the beaker to air dry naturally at room temperature to obtain the modified magnetite nanoparticles.

[0047] Material characterization

[0048] A small amount of modified magnetite nanoparticles were dispersed in ethanol solution and ultrasonicated for 15 minutes to make them uniformly dispersed. The obtained suspension was used for transmission electron microscopy analysis. To prevent the change of iron mineral components during the ultrasonication process, the whole ultrasonication process was carried out in water at room temperature of 25 °C. The obtained suspension after ultrasonication was dropped onto a copper grid supported by 200 mesh copper grid and then placed under an infrared lamp for drying. The morphology of the modified magnetite nanoparticles was analyzed by transmission electron microscopy. To obtain reliable results, multiple areas of the sample were selected for characterization. In addition, the solid powder after natural air drying was ground in an agate mortar and the powder sample was collected in a 1.5 mL centrifuge tube. The sample was analyzed by X-ray diffractometer equipped with Cu Ka with a diffraction wavelength of 0.15418 nm. During the testing of all samples, the tube voltage was set to 40 kV and the tube current was set to 40 mA, and the step size and step rate were set to 0.02° and 2° min -1 respectively. The diffraction spectrum of all samples was collected in the range of 10°-70°. The sample components were analyzed by Jade software to test the purity of the synthesized unmodified and modified magnetite nanoparticles.

[0049] Figure 1 (a) and (b) are transmission electron microscopy images of the synthesized unmodified and modified magnetite nanoparticles, respectively, and the results show that the modification process does not change the morphology and size of the synthesized iron-containing minerals. The synthesized modified magnetite nanoparticles are ellipsoidal, have good dispersibility, and the particle size is less than 100 nm, indicating that they are nanoparticles. Figure 2 X-ray diffraction patterns of the synthesized unmodified and modified magnetite nanoparticles, based on comparison with the standard card of magnetite (JCPDS: 19-0629), it is found that the main component of the synthesized unmodified and modified iron-containing mineral nanoparticles is magnetite, and has certain magnetism, which is convenient for recovery; and the synthesized mineral has high crystallinity, and no other impurity minerals are found, indicating that the material has high purity.

[0050] Characterization of PFOS removal experiment

[0051] 1. Performance of modified magnetite nanoparticles and other iron minerals in removing PFOS

[0052] In order to compare the performance of modified magnetite nanoparticles and other iron minerals in removing PFOS in water, in addition to the synthesized modified magnetite nanoparticles, goethite, goethite and unmodified magnetite nanoparticles were also selected. In a 50 mL centrifuge tube, 40 mL of deionized water and 5 mL of adsorbent (suspension of different types of minerals) with a concentration of 10 g L -1 were added, shaken uniformly and then placed in a rotary shaker with a rotation speed of 120 rpm for 30 minutes. Then, 5 mL of 500 mg L -1PFOS solution, resulting in a total volume of 50 mL of reaction system, the final system PFOS concentration of 50 mg L -1 , adsorbent concentration of 1 g L -1 . All centrifuge tubes were placed in a constant temperature shaker at a temperature of 25 °C and continuously shaken, and samples were taken at 0, 0.5,

[0053] 1, 2, 4, 6 and 8 hours. All centrifuge tubes were centrifuged at a speed of 8000 rpm for 10 minutes, and the supernatant was filtered using a 0.22 μm polypropylene filter membrane. The filtrate was collected for determination of the PFOS concentration in the solution.

[0054] Determination of PFOS concentration: In order to determine the concentration of PFOS in the filtrate, all supernatant samples were measured using an Agilent Ultivo triple quadrupole liquid chromatograph mass spectrometer. The instrument is equipped with a Jet Stream electrospray, which has a detection limit of 10 μg L -1 -1for PFOS. The PFOS / PFOA extraction standard mixture was used to establish an internal standard calibration curve for quantification of the PFOS concentration. During the entire test process, mobile phase B was 50% methanol and mobile phase A was 0.02 mol / L ammonium acetate, and the flow rate was set to 0.5 mL min -1 -1. In order to ensure that reliable test results are obtained, all samples to be tested were diluted with deionized water and a certain amount of PFOS / PFOA extraction standard mixture was added. 13 C8) was added. The sample was equilibrated on the column with the initial mobile phase for 30 minutes before testing, until the baseline was stable. The PFOS concentration in the actual sample was calculated according to the peak area ratio of PFOS to 13 C8-PFOS.

[0055] Figure 3 A comparison of the adsorption performance of synthetic modified magnetite nanoparticles and other iron minerals for PFOS in water is shown in the figure. The results show that different minerals have a certain removal performance for PFOS in water, and PFOS can be quickly adsorbed by different minerals at the initial stage, and then tends to be stable with the increase of reaction time. After 8 hours of adsorption, the PFOS concentrations in the goethite, lepidocrocite, unmodified and modified magnetite nanoparticle treatment groups were reduced from 50 mg L -1 to 41.32, 38.89, 30.86 and 7.74 mg L -1 , respectively, indicating that the modified magnetite nanoparticles have the best removal effect on PFOS in water, can quickly and efficiently remove PFOS in water, and the effect is significantly better than that of nanometer ferroferric oxide (unmodified magnetite nanoparticles) and crystalline iron hydroxide (goethite and lepidocrocite).

[0056] 2. Removal performance of modified iron-containing mineral nanoparticles for PFOS under different environments

[0057] To determine the performance of modified magnetite nanoparticles in removing PFOS from water under different pH and salinity conditions, batch kinetic experiments were conducted. For the batch kinetic experiment on the effect of pH, 40 mL of deionized water with pH values ​​of 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0 but a salinity of 0.01 mol / L and 5 mL of 10 g L⁻¹ deionized water were added to 50 mL centrifuge tubes, respectively. -1 Modified magnetite nanoparticles. For batch kinetic experiments investigating the effect of salinity, 40 mL of deionized water with pH 7.0 but salinities of 0, 0.01, 0.1, and 0.5 mol / L, and 5 mL of 10 g L⁻¹ salinity solution were added to 50 mL centrifuge tubes. -1 Modified magnetite nanoparticles were used. The above mixture was placed in a rotary shaker at 120 rpm and shaken for 30 minutes. Then, 5 mL of 500 mg L was added to each centrifuge tube. -1 The PFOS solution was used to obtain a reaction system with a total volume of 50 mL, and the final concentration of PFOS in the system was 50 mg / L. -1 The adsorbent concentration is 1 g / L. -1 All centrifuge tubes were placed in a constant-temperature shaker at 25°C and shaken continuously for 4 hours. After shaking, all centrifuge tubes were centrifuged at 8000 rpm for 10 minutes, and the supernatant was filtered through a 0.22 μm polypropylene filter membrane. The filtrate was collected for analysis of the remaining PFOS concentration in the solution.

[0058] Figure 4 The graph shows the adsorption and removal effect of modified magnetite nanoparticles on PFOS in water under different pH and salinity conditions. The results show that as the pH increases from 4.0 to 9.0, the adsorption capacity of unmodified and modified magnetite nanoparticles for PFOS increases from 45.86 mg / L. -1 and 22.65mg L -1 The levels decreased to 37.31 mg / L. -1 and 16.93 mg L -1 This indicates that increased pH is detrimental to the adsorption and removal of PFOS from water by the material. Furthermore, under pH conditions of 4.0-9.0, the removal of PFOS from water by modified magnetic iron-bearing minerals was higher than that by unmodified magnetic iron-bearing minerals. As salinity increased from 0 to 0.5 mol / L, the removal rates of PFOS by unmodified and modified magnetite nanoparticles increased from 80.68% and 35.31% to 89.67% and 42.69%, respectively, indicating that increased salinity is beneficial for the adsorption and removal of PFOS from water by the material. Under salinity conditions of 0-0.5 mol / L, the removal rate of PFOS from water by modified magnetic iron-bearing minerals was higher than that by unmodified magnetic iron-bearing minerals. In summary, modified magnetite nanoparticles can rapidly and effectively remove PFOS from water over a wide range of pH and salinity.

[0059] 3. Performance of modified iron-bearing mineral nanoparticles in removing PFOS from real wastewater

[0060] Two kinds of wastewater with different pH and PFOS concentrations were selected, which were wastewater from semiconductor manufacturing and electroplating industry, and the pH of the two kinds of wastewater were 6.7 and 7.1, and the PFOS concentrations were 60.34 mg / L and 25.68 mg / L, respectively, which were marked as wastewater 1 and wastewater 2. The performance evaluation experiment of modified magnetite nanoparticles in removing PFOS from real wastewater was carried out by using the two kinds of wastewater. In a 50 mL centrifuge tube, 20 / 43 mL of deionized water and 5 mL of modified magnetite nanoparticles with a concentration of 10 g / L were added, and then shaken uniformly and placed in a rotary shaker with a rotation speed of 120 rpm for 30 minutes. Then 25 mL of wastewater 1 or 2 mL of wastewater 2 solution was added to the centrifuge tube to obtain a reaction system with a total volume of 50 mL, and the initial PFOS concentration in the final system was 30.17 / 1.03 mg / L, and the adsorbent concentration was 1 g / L. All the centrifuge tubes were placed in a constant temperature shaker at a temperature of 25°C and continuously shaken, and samples were taken at 0, 0.5, 1, 2, 4, 6 and 8 hours, respectively, and the PFOS concentration in the filtrate was determined, and the removal efficiency of PFOS by the adsorption material was calculated based on the initial PFOS concentration in the wastewater. -1 -1 -1 -1 -1

[0061] Figure 5 The performance of modified magnetite nanoparticles in adsorbing PFOS in wastewater 1 and 2 is shown in the figure. The results show that the synthesized modified magnetite nanoparticles can effectively remove PFOS in the two kinds of wastewater. In the initial adsorption stage, PFOS can be quickly adsorbed by the modified magnetite nanoparticles, and then tends to be stable. For wastewater containing high concentration of PFOS (wastewater 1), after 1 hour of adsorption, only 2.37% of PFOS remained in the wastewater; for wastewater containing low concentration of PFOS (wastewater 2), after 0.5 hours of adsorption, only 0.45% of PFOS remained in the wastewater. After 8 hours of continuous adsorption, the removal rates of PFOS in the two kinds of wastewater were as high as 99.57% and 99.78%, respectively, which indicated that the modified magnetite nanoparticles had high removal rate for PFOS in wastewater, and could quickly and effectively remove high and low concentrations of PFOS in wastewater.

[0062] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, which are all included in the protection scope of the present application.​​​​​

Claims

1. Use of modified magnetite nanoparticles, characterized in that, Any of the following applications: a) application in treating perfluoro and polyfluoroalkyl substances; b) application in preparing products for treating perfluoro and polyfluoroalkyl substances; The modified magnetite nanoparticles are silane-modified magnetite nanoparticles; The preparation method of the modified magnetite nanoparticles comprises the following steps: The magnetite nanoparticles are added into a silane coupling agent solution to perform a coupling reaction, so as to obtain the modified magnetite nanoparticles; the silane coupling agent is at least one selected from hexadecyltrimethoxysilane and octadecyltrimethoxysilane; The dosage ratio of the magnetite nanoparticles to the silane coupling agent is 1 g:(1-10) mL.

2. Use according to claim 1, characterized in that, The particle size of the modified magnetite nanoparticles is 10-100 nm.

3. Use according to claim 1, characterized in that, The preparation method of the magnetite nanoparticles comprises the following steps: a dissimilatory iron-reducing bacterium is added into a mixed solution containing amorphous and weakly crystalline iron minerals to perform a reduction reaction, so as to obtain the magnetite nanoparticles.

4. Use according to claim 3, characterized in that, The preparation method of the mixed solution containing amorphous and weakly crystalline iron minerals comprises the following steps: sodium hydroxide is slowly added into an aqueous solution of ferric chloride, the pH of the solution is adjusted to 7.5-8.0, a solid product is separated, and the solid product is re-added into an anaerobic sterile culture medium to obtain the mixed solution containing amorphous and weakly crystalline iron minerals.

5. Use according to claim 3, characterized in that, The dissimilatory iron-reducing bacterium comprises at least one selected from Shewanella, Geobacter, Sulfococcus and Desulfovibrio.

6. Use according to claim 1, characterized in that, The perfluoro and polyfluoroalkyl substances include perfluorooctane sulfonic acid, perfluorohexane sulfonic acid, perfluoroheptane sulfonic acid, perfluorononane sulfonic acid, perfluorooctane sulfonate and chlorinated perfluoropolyether sulfonic acid.

7. A method for removing perfluorooctanesulfonic acid from a body of water, characterized in that, The method comprises the following steps: the modified magnetite nanoparticles in any of the applications of claims 1-6 are added into a water body containing perfluorooctane sulfonic acid, so as to adsorb and remove the perfluorooctane sulfonic acid.

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