Functionalized magnetic nanoparticles, associated method for extracting a pfas pollutant

Abstract

The present invention relates to a nanoparticle that can be used to capture a pollutant, of the type comprising a core made of ferrimagnetic material, the core being covered with a layer of ethyl orthosilicate to which at least one cyclodextrin molecule is covalently attached by a linker comprising a main chain and side chains. Characteristically, the cyclodextrin molecule is linked to a triazole ring attached to the end of the chain of the linker and / or to the end of at least one side chain of the linker.

Description

[0001] Functionalized magnetic nanoparticles, method for extracting an associated PFAS-type pollutant

[0002] technical field

[0003] The present invention relates to nanoparticles and nanoparticle aggregates usable in a process for extracting a pollutant, in particular at least one PFAS, from a liquid medium, particularly water. The present invention also relates to this process and an installation for carrying out the process of the invention.

[0004] Previous art

[0005] Per- and polyfluoroalkyl substances (hereinafter referred to as PFAS) are synthetic organofluorine compounds containing one or more per- or polyfluoroalkyl functional groups. They contain at least one perfluoroalkyl group, -CnF2n-. There are probably between six and seven million PFAS.

[0006] Certain PFAS (PFOS, PFOA, and PFNA in particular) have attracted the attention of authorities due to their toxicity and ecotoxicity, their highly persistent nature, and their already widespread presence in the environment. They are found in living organisms across the globe. PFAS are known to increase cholesterol levels, induce cancers, affect fertility, and interfere with the endocrine system (particularly the thyroid system) and the immune system.

[0007] Furthermore, since PFAS are present in low concentrations, they are also difficult to measure.

[0008] Document CN110646526 A1 focuses on the detection of PFAS in food, particularly milk. The PFAS(s) are extracted from milk using FesCU (magnetite) magnetic nanoparticles. These nanoparticles have controlled porosity and are capable of adsorbing PFAS. The PFAS adsorbed into the nanoparticles is desorbed by contacting the nanoparticles with an aqueous solution of acetonitrile.

[0009] Document CN 107837792 A1 describes hollow microcapsules formed by evaporation of the oil phase of a Pickering emulsion containing FesO4@SiO2-NH2 nanoparticles that interact electrostatically with cyclodextrin molecules at the amine groups. These hollow capsules are used to capture the following metals: Mg, Cu, Ca, Na, Cd, and Pb. Since cyclodextrin is not covalently bonded, recycling the microcapsules by releasing the captured pollutant from the cyclodextrin molecule is impossible. Furthermore, the formation of a Pickering emulsion is costly and difficult to scale up industrially.

[0010] The publication by Usmann et al., entitled "Installation of synergetic binding sites in beta cyclodextrin-bipyridine ionic liquid based magnetic sorbent for simultaneous removal of anionic PFAS and Cr(VI) in water matrix," published in 2024 in the journal "Separation and Purification Technology," describes FesO4 nanoparticles covalently bonded to cyclodextrin molecules. The chain linking the nanoparticle to the cyclodextrin contains nitrogen and oxygen atoms. These nanoparticles have a diameter of 54 nm and are therefore difficult to separate from a liquid on an industrial scale. Furthermore, due to their size, they are hazardous to health and the environment. These nanoparticles exhibit a weak saturation magnetization (on the order of 24 EMU inductance, or 24 Am). 2 / kg) which does not allow for their rapid separation with a magnetic field. These nanoparticles capture PFAS with 4 or 5 carbon atoms due to electrostatic interactions, particularly at the two positively charged nitrogen rings linked to the cyclodextrin. These nanoparticles are capable of capturing a maximum of 4.16 mg / g of PFOA and 7.38 mg / g of PFOS. The adsorption capacity is highly pH-dependent, meaning that the majority of PFAS is captured via electrostatic interactions at the amine groups or the aforementioned rings. Thus, at pH 10, PFOA adsorption drops from 97% to 67%. All results were obtained after 40 hours of contact. This duration is not compatible with an industrial process.

[0011] Technical problem to solve

[0012] One goal is to propose magnetic nanoparticles that can be reused more than 5 times for the extraction of a pollutant present in a liquid medium.

[0013] Another goal is to offer magnetic nanoparticles that have improved capture capacity compared to the prior art, particularly with regard to PFOA.

[0014] Another goal is to develop magnetic nanoparticles that can be easily and quickly extracted from the environment after the pollutant has been captured, particularly by magnetization. Another goal is to develop magnetic nanoparticles that enable pollutant extraction and are derived from the recycling of existing materials.

[0015] Another aim of the invention is to provide nanoparticles that minimize risks to health and the environment.

[0016] Another objective of the present invention is to offer an alternative to the prior art process for capturing PFAS and magnetic nanoparticles.

[0017] Another goal is to propose a process for extracting a pollutant, in particular a PFAS, which can be implemented for other pollutants possibly in mixtures.

[0018] Another objective of the present invention is to provide nanoparticles capable of agglomerating and forming clusters large enough that they are stable and do not release nanoparticles and / or are easy to extract from the liquid to be treated.

[0019] Another objective of the present invention is to provide nanoparticles capable of adsorbing at least one PFAS in less than 4 hours or less than 40 hours.

[0020] Another goal is to propose a process for extracting a pollutant, in particular a PFAS, which allows for the analysis and quantification of the pollutant(s) thus concentrated.

[0021] Another goal is to propose an extraction process that allows the recovery of the extracted pollutant in solution.

[0022] Another goal is to propose a pollutant extraction process that is energy-efficient and therefore does not require the use of pumps, heating equipment and / or toxic solvents.

[0023] Brief description of the invention

[0024] The present invention relates to a nanoparticle usable for capturing a pollutant, of the type comprising a core made of a ferrimagnetic material, said core being coated with a layer of ethyl orthosilicate to which at least one cyclodextrin molecule is covalently attached by means of a linker comprising a main chain and side chains. Characteristically, according to the invention, said cyclodextrin molecule is linked to a triazole ring attached to the end of the main chain of said linker and / or to the end of at least one side chain of said linker.

[0025] Preferably, all side chains have at their free end a triazole ring linked to a cyclodextrin molecule.

[0026] The presence of the triazole ring at the end of the linker appears to allow for faster and more efficient adsorption of PFAS, particularly PFOA, likely because a nitrogen atom in this group can be positively charged. Adjacent triazole groups therefore tend to repel each other, leading to the spreading of the linker chains around the core of the nanoparticle. The grafted chains occupy more space, and the cyclodextrin is more likely to come into contact with a PFAS and form an inclusion complex with it. A given quantity of PFAS can be adsorbed in less time, and / or a greater quantity will be adsorbed within a given timeframe. Equilibrium is reached within 15 minutes or more and 30 minutes or less.Furthermore, triazole rings also allow the capture by electrostatic interactions of negatively charged pollutants, such as PFAS (especially those containing 4 or 5 carbon atoms) or other pollutants such as aromatic compounds, for example, in particular phenolates.

[0027] Preferably, the cyclodextrin is free, meaning it is not bound to any molecule other than the triazole ring. When the cyclodextrin is at the end of the main chain or side chains of the linker without being bound to another group, the side chain is more flexible and mobile and can even rotate. The cyclodextrin is thus more accessible and is not hindered by the presence of another group, such as the two charged rings described in the prior art.

[0028] Such a nanoparticle allows for faster capture of a PFAS; equilibrium is reached in 15 minutes or 30 minutes maximum.

[0029] Moreover, such nanoparticles make it possible to decontaminate an effluent even when the quantity of pollutant is very low (on the order of 0.1 pg / L), as can be the case with per and poly fluoroalkyl compounds in the environment.

[0030] These nanoparticles are simple to manufacture and can be recovered without the use of filters that could become clogged.

[0031] Preferably, said main chain and / or at least one of said side chains of said linker comprise at least one secondary amine function.

[0032] Preferably, all side chains of said linker contain at least one secondary amine function. These secondary amine functions allow for the capture of PFAS, particularly PFAS containing 4 or 5 carbon atoms, and also other charged pollutants.

[0033] Detailed description Preferably, cyclodextrin is linked without a spacer arm to the triazole ring, that is to say, an atom of the cyclodextrin molecule is directly linked to an atom of the triazole ring.

[0034] The triazole ring can be linked to the linker at a carbon atom of the triazole ring or at a nitrogen atom of the triazole. When the triazole ring is linked to said end (lateral or otherwise) of the linker by a nitrogen atom, the cyclodextrin is preferentially linked to the carbon atom furthest from the nitrogen atom linked to the linker.

[0035] When the triazole ring is linked to the end of the linker at a carbon atom, cyclodextrin is preferentially linked to the nitrogen atom furthest from the carbon atom linked to the linker.

[0036] According to a first embodiment of the nanoparticle of the invention, said tetraethyl orthosilicate-coated core is linked to at least one silane molecule of the following formula (1): in which x1 and x2 are distinct integers or equal to and greater than or equal to 1 and less than or equal to 10, preferably x1=3 and x2=2, y is an integer such that 0 <y<6, de préférence y=5 et z est un entier tel que 1 <z<4, de préférence z=1 la molécule de cyclodextrine CD étant de préférence liée à l’atome de carbone le plus éloigné de l’atome d’azote lié au groupement (CH2) y .

[0037] According to a second particular embodiment of the invention, said tetraethyl orthosilicate-coated core is linked to at least one silane molecule of the following formula (2): in which x1 and x2 are distinct integers or equal to and greater than or equal to 1 and less than or equal to 10, preferably x1 = 3 and x2 = 2, y is an integer such that 1 <y<10, de préférence y=6 et z est un entier tel que 1 <z<4, de préférence z=1 la molécule de cyclodextrine CD étant de préférence liée à l’atome de carbone le plus éloigné de l’atome d’azote lié au groupement (CH2) y .

[0038] According to a third particular embodiment of the invention, said core coated with tetraethyl orthosilicate is linked to a molecule of the following formula (3): in which x1 and x2 are distinct integers or equal to and greater than or equal to 1 and less than or equal to 10, preferably x1 = 3 and x2 = 2, y1 is an integer such that 1 <y1 <10, de préférence yi=1 , y2 est un entier tel que 1<y2^10, de préférence y2=1 et z est un entier tel que 1 <z<4, de préférence z=1 la molécule de cyclodextrine

[0039] CD being preferably bonded to the nitrogen atom furthest from the carbon atom bonded to the (CH2) group y 2.

[0040] This third embodiment proves particularly advantageous. While the inventors are not directly involved in this explanation, it appears that there is a synergy between the secondary amine groups and the triazole rings. This synergy increases the pollutant capture capacity. Indeed, due to physicochemical interactions, the cyclodextrin molecules are optimally distributed in space, increasing the nanoparticle's capture capacity and kinetics, particularly when the pollutant is a PFAS.

[0041] It turned out that each of the three aforementioned embodiments presents 300 to 500 pmol of accessible cyclodextrins per gram of nanoparticles (in the form of clusters). Since the nanoparticles form easily recoverable clusters, it was not obvious that all the bound cyclodextrin molecules would be accessible.

[0042] Regardless of the embodiment, the nature of the cyclodextrin is not limited according to the invention (a, P and y). Advantageously, the cyclodextrin is beta-cyclodextrin, which allows for easy capture of PFAS.

[0043] Preferably, the nanoparticle has a size greater than or equal to 130 nm and less than or equal to 570 nm. Such nanoparticles do not pose any problems for the environment or health. Furthermore, these nanoparticles form aggregates that are easily and rapidly extracted from the medium by the action of an electromagnetic field, without the formation of fine particles that could disperse into the natural environment.

[0044] The core of the nanoparticle is not limited according to the invention. It can be a synthetic and spherical core, possibly with an irregular surface, obtained from iron chloride.

[0045] Preferably, said heart is not spherical and has an irregular shape.

[0046] It preferably has a size greater than or equal to 100nm or 200nm and less than or equal to 300nm or 500nm.

[0047] The irregular shape of the core allows for a thicker orthosilicate layer (greater than 20 nm). This thicker layer further increases the core's size, thus enabling the grafting of a greater number of linker molecules. Consequently, it is capable of capturing a greater quantity of pollutants. The irregular shape also allows for the formation of clusters or aggregates larger than those formed by spherical cores. These clusters therefore exhibit a higher saturation magnetization than those obtained from spherical cores and are thus more easily and quickly separated from the liquid medium by the action of a magnetic field. Furthermore, cores of irregular shapes and sizes such as those described above are inexpensive and can be produced in large quantities from recycled industrial materials.

[0048] Advantageously, said core has an isoelectric point PIE greater than or equal to 6 and less than or equal to 7 and in particular equal to 6.6. Such a core can easily be used to be coated with a layer of tetraethyl orthosilicate; it does not cause any electrostatic interaction repelling silane.

[0049] The thickness of the tetraethyl orthosilicate layer is not limited according to the invention. In addition to serving as a grafting surface for the pollutant-capturing molecules, the silicate layer also protects the core from environmental and solvent damage. It also protects the core from attrition due to friction, particularly with other nanoparticles.

[0050] Thus, said ethyl orthosilicate layer may have a thickness greater than or equal to 25 nm, 30 nm, 100 nm or 120 nm and less than or equal to 200 nm, preferably greater than or equal to 100 nm and less than or equal to 150 nm.

[0051] Advantageously, the core contains magnetite, iron(II) oxide (FeO), and iron hydroxide. It is advantageously composed of magnetite, iron(II) oxide (FeO), and iron hydroxide.

[0052] Advantageously, the functionalized nanoparticle exhibits a saturation magnetization greater than or equal to 17 Am 2 / kg, particularly above 37 17 Am 2 / kg and in particular equal to 44.9 Am 2 / kg. These nanoparticles are easily separated from a liquid effluent using a magnetic field.

[0053] The core preferably exhibits a saturation magnetization greater than or equal to 40 Am 2 / kg at and less than or equal to 99 A. m 2 / kg and in particular equal to 94 A. m 2 / kg. Irregularly shaped cores such as those mentioned above exhibit such saturation magnetization.

[0054] The present invention also relates to a nanoparticle aggregate comprising or consisting of nanoparticles according to the invention and having a maximum size greater than or equal to 1000 nm and less than or equal to 3000 nm. These aggregate sizes are obtained, in particular, with nanoparticles having an irregularly shaped (non-spherical) core and containing magnetite, iron(II) oxide (FeO), or iron hydroxide. The aggregates form due to electrostatic interactions between the nanoparticles, even when they are functionalized and notably contain cyclodextrins. They can be reduced by agitation but tend to reform when agitation ceases. They allow for faster separation of the nanoparticles from the medium using a magnetic field. They also prevent the formation of small clusters of nanoparticles or even of single nanoparticles that could disperse in the medium.

[0055] The present invention also relates to a method for producing nanoparticles according to the invention. According to this method, a) a core of magnetic material is coated with a layer of ethyl orthosilicate; b) the coated core is reacted with a silane having a linear chain that has a primary amine function at its end and optionally one or more secondary amine functions on said chain; c) optionally the nanoparticle obtained in step b) is reacted with a chain having an azide function to obtain a nanoparticle that has azide functions, and then said nanoparticle obtained is reacted with a modified cyclodextrin bearing an alkyne group to obtain a nanoparticle that has at least one cyclodextrin molecule;d) optionally the nanoparticle obtained in step b) is reacted with a halogenated compound bearing an alkyne function to obtain a nanoparticle which has alkyne functions then the said nanoparticle obtained is reacted with a modified cyclodextrin bearing an azide group to obtain a nanoparticle which has at least one cyclodextrin molecule.;

[0056] The azide in question can correspond to the following formula: XR 5 -Ns in which R 5 is an alkyl group containing from 1 to 10 carbon atoms, preferably 6 carbon atoms, X being a halogen, preferably a bromine atom, or with the following formula: Ns-R 6 -COOH in which R 6 - is an alkyl chain consisting of 1 to 8 carbon atoms.

[0057] The said halogenated compound containing an alkyne function can correspond to the following formula: X-(CH2) y i-CO-NH-(CH2) y2-CCH with yi being an integer such that 1 <y 1 < 10, de préférence y1 =1 , y2 étant un entier tel que 1 <y2^10, de préférence y2=1 . La présente invention concerne également une installation permettant la mise en œuvre du procédé de l’invention et qui comporte une première cuve contenant le milieu à traiter et éventuellement munie d’une agitation, ladite première cuve étant connectée à un séparateur magnétique, la sortie des solides dudit séparateur magnétique étant reliée à une deuxième cuve contenant un solvant de relargage. Ledit séparateur magnétique n’est pas limité selon l’invention. Il peut être du type vis sans fin ou une tige aimantée ce qui permet de facilement récupérer les nanoparticules pour les introduire dans le solvant de relargage. Le procédé peut ainsi être mis en oeuvre de façon continue.

[0058] The present invention also relates to a method for extracting at least one pollutant present in a liquid medium, said pollutant being chosen from perfluoroalkyl compounds, polyfluoroalkyl compounds, metals in the form of ions, in particular cobalt, according to which the nanoparticles of the invention are brought into contact with said medium for a given time, optionally under agitation and then optionally separated said nanoparticles from said medium by application of a magnetic field.

[0059] According to a particular method of implementation, after extraction of said pollutant, i.e. after the given duration of contact, said nanoparticles are placed in a release solvent chosen from aqueous solutions of nitric acid for the capture of metals and aqueous solutions containing at least one alcohol such as ethanol or methanol and ammonia.

[0060] A mixture of ethanol and an aqueous ammonia solution may preferably be used.

[0061] The medium to be treated is not limited according to the invention. It can be any liquid effluent or any effluent containing a liquid, such as contaminated wet soil. In particular, the medium can be an aqueous medium, and especially water containing at least one pollutant as mentioned above. It can also be a contaminated solid (soil, earth, sand, for example) that is suspended in water.

[0062] The per or polyfluoroalkylated compound(s) to be extracted are not limited according to the invention. The perfluoroalkylated compound may be selected from perfluorooctanoic acid (PFOA), heptafluorobutyric acid (PFBA), undecafluorohexanoic acid (PFHxA), perfluoroactanesulfonic acid (PFOS), 6:2 fluorotelomersulfonic acid, perfluorodecanoic acid and perfluorononanoic acid (PFNA) and mixtures thereof.

[0063] The present invention also relates to nanoparticles consisting of an irregularly shaped core made of magnetite, iron(II) oxide (FeO) and iron(II) hydroxide (FeOH) and covered with a layer of tetraethyl orthosilicate.

[0064] Preferably, the core contains at least 80% magnetite. Preferably, the tetraethyl orthosilicate layer has a thickness as indicated above. Preferably, the nanoparticle has a size as indicated above (functionalization not significantly changing the size). Preferably, the nanoparticle has a magnetic saturation as described above.

[0065] For the purposes of this invention, the term "size" refers to the largest dimension of an irregularly shaped nanoparticle (core or functionalized nanoparticle); a nanoparticle may be spherical and have an irregular surface. A nanoparticle may be irregularly shaped and have either a regular or irregular surface.

[0066] For the purposes of the invention, the terms "irregular shape" refer to a shape having at least one concave or convex angle and / or a change in curvature, for example due to an outgrowth or a hollow.

[0067] The present invention, its features and the various advantages it provides will become clearer upon reading the following description, presented by way of non-limiting example and which refers to the accompanying drawings in which:

[0068] Figures

[0069] - Fig. 1 represents the infrared absorption spectrum of cores made of a magnetic material comprising magnetite and iron (II) oxide (FeO);

[0070] - Fig. 2 represents the infrared absorption spectrum of the synthetic cores referenced synth FesO4;

[0071] - Fig. 3 is a photograph of a transmission electron microscope view of FesO4 nanoparticles containing ferrite, iron oxide and iron hydroxide, either alone (A) or aggregated with different sizes and irregular geometries (B and C) and of these nanoparticles coated with a layer of ethyl orthosilicate FesO4@SiO2 (D).

[0072] - Fig. 4 represents the infrared absorption spectrum of the nanoparticles referenced FesO4@SiO2@NH2 (top) and FesO4@SiO2@N3 (bottom);

[0073] - Fig. 5 is a photograph of a transmission electron microscope (TEM) view of nanoparticles functionalized with amines FesO4@SiO2@NH2; on the right, the irregular shape of the core can be clearly seen;

[0074] - Fig. 6 represents the masses of PFOA captured with the MNPs obtained FesO4, FesO4@SiO2, FesO4@SiO2@NH2, FesO4@SiO2@p-CD. After contact of the PFOA solution with the MNPs, the MNPs are removed by magnetism and the supernatant is analyzed. Then the MNPs are washed with a mixture of ethanol and aqueous ammonia solution;

[0075] - Fig. 7 represents the amount of PFOA in pg adsorbed per g of MNPs (FesO4@SiO2@P-CD) as a function of the number of washes with the extraction solvent; the lower part of the bars represents the amount of PFOA adsorbed after the number of washes with the solvent and the upper part of the bars represents the PFOA not adsorbed by the nanoparticles;

[0076] - Fig. 8 represents the Langmuir isotherms during the competitive adsorption of 6 PFAS; and

[0077] - Fig. 9 represents an SEM image of an aggregate of the nanoparticles used in example 14, the aggregate has a maximum dimension of 12 pm, the nanoparticles have a size greater than or equal to 100nm and less than or equal to 300nm, the ethyl orthosilicate layer + the functionalization (including cyclodextrin) represent a layer with a thickness greater than or equal to 70nm and less than or equal to 120nm.

[0078] Examples

[0079] The following techniques are used throughout the description that follows for the measurement of certain parameters.

[0080] Nanoparticle Size Measurement. The diameter of the nanoparticle cores or the diameter of the cores coated with ethyl orthosilicate were measured using a transmission electron microscope (TEM / TEM JEOL, JEM 2100 HR). TEM is an analytical technique based on the transmission of an electron beam through a sufficiently thin sample, allowing the electrons to pass through and be resolved by a lens system. After sonicating 10 mg of solid in 10 mL of ethanol, a drop was deposited onto a commercial copper TEM grid and dried for 10 min before analysis. ImageJ software was used to analyze the TEM images and measure the nanoparticle sizes.

[0081] SEM-EDS (scanning electron microscopy coupled with energy-dispersive spectroscopy) images were obtained using a Gemini 3 SEM 600 device (same sample preparation as above)

[0082] Isoelectric Point (IEP) Measurement. The Isoelectric Point (IEP) is determined from the measurement of the zeta potential at different pH values ​​using the ZetaSizer Nano ZS (Malvern). The Smoluchowski equation was used to convert the electrophoretic mobility measurements into zeta potential. MNPs are dispersed in a 1 mM NaCl solution, the pH is then adjusted using a 0.1 M NaOH or HCl solution to between 2 and 11, and the potential is measured in Malvern® DTS1070 cells. After an equilibration time of 30 seconds, three measurements are taken, each with a number of passes between 10 and 50. The reported potential corresponds to the average of these three measurements. The potential zeta=f(pH) curve is then plotted using the Origine® software, thus allowing the determination of the PIE, i.e. the pH for which the potential is zero and which is characteristic of a nanoparticle.

[0083] Infrared spectrometry. The infrared spectra of the compounds were recorded using a PerkinElmer Spectrum 100 FTIR spectrophotometer, 16 scans, in a 4000–450 cm⁻¹ window. -1 with a resolution of 1 cm -1 The compounds to be analyzed were mixed with dry KBr to form pellets for analysis.

[0084] UV-Visible Spectrometry. UV-vis absorbance spectra were measured using an Agilent Cary 60 spectrophotometer and a 10 mm quartz cuvette at different wavelengths between 200-800 nm.

[0085] HPLC-MS analyses were performed using a ThermoScientific UHPLC Vanquish Horizon / Flex liquid chromatograph coupled to a ThermoScientific ISQ EC mass spectrometer. For mass spectrometry, heated electrospray ionization (HESI) in negative mode was used. Optimized ionization source parameters included a capillary voltage set at -2000 V, a collision-induced dissociation (CID) of 5 V, a vaporization temperature of 320°C, and a transfer tube temperature of 300°C, with a spray gas pressure of 60 psi. Analyses were performed in single-ion monitoring (SIM) mode throughout the analysis on the m / z 413 and m / z 299 ions, which are PFOA and PFBS, respectively. For calibration, an internal PFBS standard was used at a concentration of 20 pg / L and the calibration curve was established over a range of concentrations from 1 pg / L to 25 pg / L in PFOA.

[0086] Example 1: Characterization of nanoparticle cores

[0087] The cores used are nanoparticles (MNPr) with a size between 200 and 300 nm (TEM measurement). Isolated particles of 250 nm are observed. They are composed of a material containing magnetite (Fe2Os) and iron(II) oxide (FeO). In this specific example, this material contains at least 80% magnetite by mass, iron(II) oxide (FeO), and iron(II) hydroxide (FeOH). They do not have a smooth surface. The MNPr form clusters due to their electrostatic interactions and because they originate from industrial recycling.

[0088] The MNPr particles are washed with dichloromethane, ethanol, and water. They are then dried under vacuum and ground in a mortar for analysis. In the IR analysis, the band corresponding to the Fe-O stretching vibration is visible at 580 cm⁻¹ -1(Fig. 1). These bare MNPr nanoparticles have an isoelectric point (PIE) of 5.7. The PIE is the pH at which the positive charges are equal to the negative charges, so the surface of the MNPs is globally neutral.

[0089] Magnetite FesC nanoparticles were also synthesized from the following reference: J. Magn. Magn. Mat. 2007, 310, 2408-2410. NaNOs were added to a 21 mM NaOH solution, followed by a degassed FeCl2·4H2O solution. The mixture was stirred at 4°C for 24 h, and the magnetites were then washed with water. These nanoparticles, designated synthFesC, are spherical with a diameter of 100 nm. Fig. 2 shows the infrared spectrum of these synthetic nanoparticles. Fig. 2 shows that the spectrum has a broad band around 630 cm⁻¹. 1 which corresponds to the Fe-O vibration characteristic of iron oxides. The bands at 3422 cm -1 and 1640 cm -1These correspond to the vibration of OH groups present in FesO4 and in water (adsorbed onto magnetite and present in KBr). Therefore, the synthetic synthFesCu nanoparticles contain more physisorbed water and Fe-OH. Nevertheless, both cores are composed of magnetite, iron oxide, and iron hydroxide.

[0090] Example 2: Formation of the ethyl orthosilicate layer: synthesis of nanoparticles referenced FesO4@SiO2

[0091] The clusters formed by the aforementioned nanoparticles (MNPs) are optionally ground before being coated with a layer of ethyl orthosilicate (inspired by J. Phys. Chem. Lett. 2010, 1, 1, 379-382). The method for coating a nanoparticle with an ethyl orthosilicate layer is well-established. Here, we use the Stober method described in RSC Adv. 2014, 4, 22606-22612. The MNPs are optionally sonicated in 1 M HCl for 5 min, then washed with MilliQ water until they reach a neutral pH. Because the MNPs form clusters, it is necessary to dilute them significantly. It turns out that without acid treatment, the ethyl orthosilicate layer is thicker. After adding the ethyl orthosilicate layer, the PIE decreases sharply due to the Si-OH present on the surface of FesO4@SiO2 and goes from 5.7 to 4.5. The PIE of the silicate layer is about 2. MNP cores coated with an ethyl orthosilicate layer are obtained.Clusters or aggregates of nanoparticles are obtained as shown in Fig. 3.

[0092] Example 3: Functionalization of the ethyl orthosilicate layer by amines: formation of FesO4@SiO2@NH2 nanoparticles

[0093] The silane TMSPDTA (N1-(3-trimethoxysilylpropyl)diethylenetriamine) was used to functionalize the nanoparticles formed from the core coated with the ethyl orthosilicate layer. The silane grafting conditions were optimized to maximize the number of amine groups available for reaction.

[0094] Two g of MNPr are dispersed in 160 mL of anhydrous toluene, and the mixture is stirred ultrasonically for 15 min. A mechanical stirrer is then used, and the mixture is heated to 50°C. Next, 2.6 mL of N1-(3-trimethoxysilylpropyl)diethylenetriamine diluted in 40 mL of toluene is added dropwise over 6 h. At the end of the addition, the temperature is increased to 70°C, and the reaction is continued for 16 h. The MNPr are then separated using a magnet and washed three times with toluene, then five times with ethanol, and finally dried under vacuum. A method for quantifying amine functions present on MNPr was developed by back titration with a UV-Vis aldehyde, 4-nitrobenzaldehyde (NBA), via the formation of an imine function (Langmuir, 2005, 21, 7029-35; Nanoscale Adv. 2019, 1, 1598-1607). PIE=10.3±0.5.

[0095] Assay of MNPs functionalized with an amine group

[0096] Ten mg of MNPr from Example 3 are introduced into an Eppendorf tube, and 1 mL of a 0.8% (v / v) glacial acetic acid in anhydrous methanol solution containing 7.5 mg of NBA (N-bromoacetamide) is added. The mixture is stirred at 70 rpm for 16 h at room temperature. The supernatant is removed, and the MNPr are washed 6 times with anhydrous methanol. Then, 1 mL of a hydrolysis solution containing 50:50 H₂O / MeOH and 1.4% glacial acetic acid is added, and the solution is stirred for 1 h at 70 rpm. The supernatants are retained, and the MNPs are washed 5 times with the hydrolysis solution. The supernatants are combined and diluted, if necessary, before the absorbance measurement at 267.5 nm. The amount of NBA in the supernatant was determined using a calibration curve. All measurements were acquired on an Agilent Technologies Cary 60 scanning spectrometer using a quartz cell.The UV adsorption curves of NBA were recorded on several standard solutions prepared in the washing solution described above. It was confirmed that NBA adsorption follows Beer-Lambert's law at Å = 267.5 nm.

[0097] Heating the reaction mixture to 70°C results in more grafted amine groups than when the reaction is carried out at room temperature or 110°C. A concentration of 50 mM yields more grafted amines than higher or lower concentrations (25 mM, 75 mM, and 100 mM). The reaction time also impacts the amine content. 16 hours of reaction time appears to be necessary to achieve a maximum amine content. Beyond 16 hours, no further increase in the number of grafted amine molecules is observed.

[0098] Under optimized conditions, amine concentrations ranging from 200 to 600 pmol of amine per gram are obtained. A assay was performed on magnetites coated with a layer of ethyl orthosilicate; the detection limit appears to be around 2 pmol / g.

[0099] By repeating the amine grafting reaction, the grafted amine concentration is increased to 400 pmol / g of nanoparticles. Fig. 4 shows the infrared spectrum of these FesO4@SiO2@NH2 nanoparticles. The spectrum exhibits a broad band around 630 cm⁻¹. -1 which corresponds to the Fe-O vibration characteristic of iron oxides. The bands at 3422 cm -1 and 1640 cm -1 correspond to the vibration of OH present in FesO4 and in water (adsorbed on magnetite and present in KBr).

[0100] After the addition of silane, the PIE increases sharply due to the amine functions on the surface of FesO4@SiO2@NH2 and rises to 10.3.

[0101] Fig. 5 is a photograph of the amine-functionalized nanoparticles. The core is dark in color; it is irregularly shaped and surrounded by a layer of ethyl orthosilicate; the lighter outer layer represents the layer formed by the amine groups.

[0102] Example 4: Adding azide functions to FesO4@SiO2@NH2 to obtain FesO4@SiO2@N3 referenced nanoparticles

[0103] Two reactions were tested.

[0104] Azide is added via a coupling reaction between amines and a carboxylic acid to obtain nanoparticles containing azide groups according to the reaction scheme below:

[0105] 6-Azidohexanoic acid was obtained according to the synthesis described in Macromol. Rapid Comm. 2020, 41, 1900476-1900482.

[0106] We obtain nanoparticles referenced FesO4@SiO2@N3.

[0107] The acid is then activated either by the coupling agents NHS / DCC (N-Hydroxysuccinimide / Dicyclohexylcarbodiimide) in DMF at room temperature for 24 hours, or with the coupling agents HOBT / EDC (1-Hydroxybenzotriazole / 1-Ethyl-3-(3-Dimethylaminopropyl)carbodiimide) and N-methylmorpholine in DMF at room temperature overnight. Both conditions give approximately 70% of the desired product. The reaction can be repeated to achieve a yield of 85% after a second cycle and over 95% after a third cycle (percentage calculated relative to residual primary amines). Secondary and primary amines can react, with a maximum of four azides per silane. The C / N ratio is 1.67 after the addition of the azide. This ratio decreases compared to the FesO4@SiO2@NH2 ratio which was between 2.28 and 2.65. PIE=7.3±0.5.

[0108] Fig. 4 clearly shows the appearance of the band corresponding to azide at 2095 cm -1A shoulder around 1767 cm -1 is visible corresponding to the C=O band, however, it may be hidden by the wide band around 1630 cm -1 .

[0109] Example 5: Adding azide functions to FesO4@SiO2@NH2 to obtain FesO @SiO2@alkN3 referenced nanoparticles

[0110] In order to increase the number of azide groups grafted onto the FesO4@SiO2@NH2 nanoparticles (4), a second precursor was used. This is the compound with the formula Br(CH2)eN3, the synthesis of which is reported in the article Tetrahedron 2018, 74, 5102-5112. It is obtained by reacting 1,6-dibromohexane with sodium azide in an 80 / 20 DMF / H2O mixture for 28 h at 60°C, as shown below.

[0111] The reaction scheme is as follows:

[0112] (7)

[0113] FesO4@SiO2@NH2 nanoparticles were dispersed in DMF in the presence of 3 equivalents of triethylamine and 2 equivalents of 1-azido-6-bromohexane for 24 hours at 70°C, then for 3 days at room temperature. The grafting rate was monitored by back titration of primary amines with para-nitrobenzaldehyde (until the primary amine groups disappeared).

[0114] Example 6: Addition of acidic functional groups to Fe3O4@SiO2@NH2 nanoparticles to obtain FesO4@SiO2@ / nCOOH nanoparticles

[0115] The following reaction is implemented:

[0116] To determine if the acid addition was successful, we rely on the PIE (Peak Inertial Efficiency) and the measurement of residual primary amines. The reaction takes place in DMF (Dry Metal Fiber) at 70°C for 24 or 48 hours with 10 anhydride equivalents relative to the number of amines. By repeating the aforementioned reaction three times, the primary amine measurement indicates that no primary amine groups remain on the nanoparticle.

[0117] The PIE goes from 10.3 to 2.6, which indicates the presence of carboxylic acid functions.

[0118] Example 7: Addition of alkyne groups to FesO @SiO2@NH2 obtained in Example 3 to produce nanoparticles referenced FesO4@SiO2@alkyne. Synthesis of 2-bromo-N-(prop-2-yn-1-yl)acetamide

[0119] The synthesis of this compound was carried out according to the protocol described in the journal Org. Biomol. Chem. 2015, 13, 8912-8918.

[0120] Synthesis of FesO4@SiO2@alkyne from FesO4@SiO2@NH2 (Example 3)

[0121] (9) Fe3O4@SiO2@NH2 (0.98 g, 200 pmol NH2 / g MNP) synthesized in Example 3 were dispersed in dry dimethylformamide (10 mL) and triethylamine (0.13 mL, 0.9 mmol, 5 eq.) and stirred under ultrasound for 5 min. Then, 2-bromo- / V-(prop-2-yn-1-yl) acetamide (0.95 g, 5.4 mmol, 30 eq.) was added to the reaction mixture and activated under ultrasound for 5 min. The reaction mixture was stirred for 48 h at 70 °C under argon. After washing with water and ethanol, the resulting Fe3O4@SiO2@alkyne was dried (0.92 g).

[0122] After titration, 12 pmol of residual NFh / g MNPr were present out of the initial 200 pmol NFh / g, representing a maximum of 600 pmol of alkyne groups / g MNP for two secondary amines per chain. The PIE of 10.5 remained stable in the presence of alkyne groups on the surface of FesO4@SiO2@alkyne. PIE = 10.5 ± 0.5.

[0123] Example 8: Grafting of cyclodextrin-Ns using the "click chemistry" method onto FesO4@SiO2@alkyne referenced nanoparticles to obtain FesO4@SiO2@P-CD referenced nanoparticles

[0124] Mono-6-azido-6-deoxy-P-cyclodextrin p-CD-Ns is marketed by CycloLab and its synthesis is described in Molecules 2019, 24 (21), 3849-3860. Synthesis of FesO4@SiO2@ -CD from -CD-Ns and FesO4@SiO2@alkyne

[0125] Fe3O4@SiO2@alkyne (Example 7) (0.650 g, 390 pmol alkyne / g MNPr) were dispersed in dimethyl sulfoxide (10 mL) and distilled water (5 mL) and stirred under ultrasound for 5 minutes. During this time, a solution of N,N,N,N,N-pentamethyldiethylamine (0.135 g, 0.780 mmol, 2 eq.), CuSO4·5H2O (0.146 g, 0.585 mmol, 1.5 eq.) and sodium ascorbate (0.154 g, 0.780 mmol, 2 eq.) was prepared in water (5 mL) and added to the reaction mixture. Finally, mono-6-azido-6-deoxy-P-cyclodextrin p-CD-Ns (0.680 g, 0.585 mmol, 1.5 eq.) was added to the reaction mixture and stirred under ultrasonication for 2 h. The reaction was stirred for 24 h at room temperature. After washing with water and ethanol, the resulting FesO4@SiO2@p-CD was dried (0.630 g). The PIE decreases in the presence of surface cyclodextrins, dropping from 10.5 to 8.0. PIE = 8.0 ± 0.5.

[0126] Example 9: Grafting of cyclodextrin by the so-called "click chemistry" method onto FesO4@SiO2@N3 referenced nanoparticles to obtain FesO4@SiO2@NP-CD referenced nanoparticles

[0127] Synthesis of FesO4@SiO2@NP-CD from FesO @SiO2@N3 and p-CD-alkyne

[0128] The reaction scheme is as follows with the aforementioned beta-cyclodextrin having at position 6 an alkyne function of the following formula, the synthesis of which is described in Macromol. Rapid Commun. 2021, 42, 2100083-2100091.

[0129] FesO4@SiO2@Ns nanoparticles (0.030 g, 390 pmol Ns / g MNP, i.e., 12 pmol) were dispersed in dimethyl sulfoxide (1 mL) and distilled water (0.5 mL) and stirred under ultrasound for 5 minutes. Meanwhile, a solution of N,N,N,N,N-pentamethyldiethylamine (10 pL, 4 eq. / Ns), CuSO4·5H2O (6 mg, 2 eq. / Ns), and sodium ascorbate (9.5 mg, 4 eq. / Ns) was prepared in water (0.5 mL) and added to the reaction mixture. Finally, mono-6-alkyne-6-deoxy-P-cyclodextrin p-CD-alkyne (56 mg, 4 eq / Ns) was added to the reaction mixture and stirred under ultrasonication for 2 h. The reaction was stirred for 24 h at room temperature. After washing with water and ethanol, the resulting FesO4@SiO2@Np-CD was dried (0.025 g). PIE = 7.5 ± 0.5.

[0130] Example 10. Synthesis of FesO4@SiO2@alk-P-CD from FesO4@SiO2@alkN3 and p-CD-alkyne

[0131] The reaction scheme is as follows with beta-cyclodextrin having an alkyne function at position 6, formula (11), the synthesis of which is described in Macromol. Rapid Commun. 2021, 42, 2100083-2100091.

[0132] FesO4@SiO2@alkN3 (0.100 g, 100 pmol azide / g MNP) were dispersed in dimethyl sulfoxide (10 mL) and distilled water (5 mL) and stirred under ultrasound for 5 minutes. During this time, a solution of N,N,N,N,N-pentamethyldiethylamine (0.035 g, 0.200 mmol, 2 eq.), CuSO4.5H2O (0.037 g, 0.150 mmol, 1.5 eq.) and sodium ascorbate (0.040 g, 0.200 mmol, 2 eq.) was prepared in water (5 mL) and added to the reaction mixture. Finally, mono-6-deoxy-6-propargylamine-P-cyclodextrin P-CD-alkyne (0.352 g, 0.300 mmol, 3 eq.) was added to the reaction mixture and stirred under ultrasonication for 2 h. The reaction was stirred for 24 h at room temperature. After washing with water and ethanol, the resulting FesO4@SiO2@alkyne P-CD was dried (0.630 g). The PIE decreases in the presence of cyclodextrins on the surface, from 10.5 to 6.2. PIE = 6.2 ± 0.5.

[0133] Example 11. Synthesis of a probe for titrating the number of accessible cyclodextrin cavities

[0134] To quantify the number of accessible P-cyclodextrin cavities on FesO4@SiO2@P-CD magnetites (Example 8, Formula 10), a UV-Vis back titration method was developed. Initially, an adamantane-coumarin UV-Vis probe capable of incorporating into the cavity of a P-cyclodextrin was developed. The adamantane group is known to incorporate into the cavity of P-cyclodextrins with a very good association constant (4.2 x 10⁻¹²). 4 M' 1 for adamantane derivatives) (J. Incl. Phenom. Macrocycl. Chem. 2015, 83 (1-2), 159-166. Analytical Biochem. 1986, 154 (2), 400-408). A coumarin group confers UV-visible properties to the entire molecule through its chromophore function.

[0135] The synthesis of this probe is carried out in two steps (Formula 14). First, an SN2 reaction between coumarin and 1,2-dibromoethane adds an aliphatic chain while introducing a new end-chain group. The next step is a second SN2 reaction to introduce adamantane with an overall yield of 23%.

[0136] An optimization of the inclusion of the probe in the CD cavities of the MNP@SiO2@p- CD was carried out by UV-Visible analysis and decomplexation with ethanol revealed grafting rates of the order of 450 pmol of CD cavity / gram of magnetite.

[0137] UV titration method for the number of cavities of cyclodextrins grafted onto accessible FesO4@SiO2@ -CD nanoparticles

[0138] 7-Hydroxy-4-methyl-2H-chromen-2-one (1.00 g, 5.68 mmol, 1 eq.) and K₂CO₃ (4.71 g, 34.06 mmol, 6 eq.) are dissolved in anhydrous aceto-nitrile (75.0 mL), then 1,2-dibromoethane (1.47 mL, 17.03 mmol, 3 eq.) is added and stirred at 70 °C overnight. Excess K₂CO₃ is filtered and washed with acetonitrile. The crude mixture is concentrated under reduced pressure. The residue is absorbed into 100 mL of water, and the aqueous phase is extracted three times with ethyl acetate (100 mL). The organic phase was washed with water and brine, dried over anhydrous magnesium sulfate (MgSO4), and evaporated under reduced pressure. The crude product was purified on a 40 g Puriflash silica column with a dry sample using an AcOELPE gradient (20:80 to 100:0) as the eluent to give the desired compound as an off-white solid (0.69 g, 2.44 mmol, 43% yield). 1H NMR (400 MHz, Chloroform-d) 5 7.52 (d, J = 8.8 Hz, 1 H), 6.89 (dd, J = 8.8, 2.5 Hz, 1 H), 6.82 (d, J = 2.5 Hz, 1 H), 6.16 (d, J = 1 .3 Hz, 1 H), 4.36 (t, J = 6.1 Hz, 2H), 3.68 (t, J = 6.1 Hz, 2H), 2.41 (d, J = 1 .2 Hz, 3H).

[0139] 7-(2-bromoethoxy)-4-methyl-2H-chromen-2-one (0.83 g, 2.92 mmol, 1 eq.), adamantan-1-ylmethanamine (0.52 mL, 2.92 mmol, 1 eq.), and K₂CO₃ (0.81 g, 5.85 mmol, 2 eq.) were dissolved in anhydrous DMF (20 mL). The mixture was then stirred at 40 °C for 48 h under an inert atmosphere. The mixture was concentrated, absorbed with water (100 mL), and extracted with EtOAc (3 x 100 mL). The organic phase was washed with water (100 mL) and brine (100 mL). The organic phase was dried over anhydrous magnesium sulfate (MgSO₄) and evaporated under reduced pressure. The crude product was purified on a 24 g puriflash silica column with a dry sample using an EtOAc:PE gradient (25:75 to 100:0) as eluent to provide the desired compound as an off-white solid (0.57 g, 1.55 mmol, 53% yield).

[0140] 1H NMR (400 MHz, Chloroform-d) 5 7.49 (d, J = 8.8 Hz, 1 H), 6.91 - 6.81 (m, 2H), 6.14 (d, J = 1.4 Hz, 1 H), 4.13 (t, J = 5.3 Hz, 2H), 3.02 (t, J = 5.2 Hz, 2H), 2.40 (d, J = 1.3 Hz, 3H), 2.32 (s, 2H), 1.97 (d, J = 4.3 Hz, 3H), 1.72 (d, J = 12.5 Hz, 7H), 1.53 (s, 6H).

[0141] Operating procedure for the capture of adamantane-coumarin

[0142] In an Eppendorf tube, approximately 2 mg of adamantane-coumarin are brought into contact with 10 mg of FesO4@SiO2@P-CD. 1 mL of water is added, and the Eppendorf tube is ultrasonically cleaned for 5 minutes and then placed on a wheel at 40 rpm overnight at room temperature.

[0143] Procedure for releasing adamantane-coumarin

[0144] The supernatant is collected by gathering the magnetite FesO4@SiO2@P-CD with a magnet and placed in a pillbox. Washes are performed using 1 mL of solution, and the Eppendorf tube is shaken vigorously for 5 to 10 seconds. The magnetite is first rinsed three times with water, then twice with ethanol.

[0145] The ethanol solutions are placed in a sand bath at 35°C until total evaporation, then 1 mL of EtOH is poured and vortexed, then the solution is placed in a UV cuvette for analysis.

[0146] An adamantane-coumarin uptake rate of approximately 300–500 pmol / g is obtained for the three magnetites FesO4@SiO2@P-CD, FesO4@SiO2@NP-CD, and FesO4@SiO2@alk-P-CD, corresponding to the number of available cavities. Example 12: Characterization of ethyl orthosilicate-coated nanoparticle aggregates

[0147] In the aforementioned examples, it appears that the nanoparticles always form aggregates, as shown in Fig. 5. Fig. 5 represents an aggregate of nanoparticles designated MNP@SiO2. Aggregates of varying sizes are obtained depending on the size of the nanoparticles and the thickness of the ethyl orthosilicate layer. The diameter is the diameter measured using a transmission electron microscope (TEM). ImageJ software was used to analyze the TEM images. Furthermore, the size difference of the aggregates obtained for MNP nanoparticles derived from recycled steel waste and coated with a tetraethyl orthosilicate layer (FesO4@SiO2) was compared with those of the aggregates obtained with nanoparticles containing a synthetic core made from soluble iron (FeCl2), designated synf / 7FesO4@SiO2. The results are grouped in Table 1 below.

[0148] Table 1

[0149] It has been observed that recycled material MNP nanoparticles (FesO4@SiO2) form larger aggregates than those formed by synthetic particles; these particles also have a thicker layer of ethyl orthosilicate. Consequently, they have more grafted molecules on their surface than the synthetic synf / 7FesO4@SiO2 particles due to their larger diameter. They therefore form larger clusters than those formed by synthetic nanoparticles, due to their greater size and surprisingly greater aggregation. While the inventors are not involved in this explanation, the greater aggregation could stem from the larger size of the nanoparticles and their irregular shape (non-spherical, visible in Fig. 5). These particles are of interest because they prevent the release of excessively fine nanoparticles into the environment.Indeed, nanoparticles smaller than 10 µm can cause respiratory complications ranging from inflammation to reversible obstruction of the pulmonary alveoli, or cardiovascular complications (ischemic myocardial disease). The MNPs synf / 7FesO4@SiO2 nanoparticles themselves have a size of approximately 100 nm.

[0150] Example 13: Capture of PFOA using FesO4, FesO4@SiO2, FesO4@SiO2@NH2 and FesO4@SiO2@P-CD nanoparticles

[0151] The operating procedure for the capture

[0152] This protocol is identical regardless of the nanoparticle's functionalization. The PFAS used is PFOA (perfluorooctanoic acid) solubilized in water.

[0153] In an Eppendorf tube, 1 mL of a 6 mg / L PFOA solution is mixed with 50 mg of magnetite. The Eppendorf tube is then spun on a wheel at 40 rpm at room temperature for 15 min (pH 6-7).

[0154] Release procedure

[0155] The supernatant is collected with a polypropylene pipette, gathering the magnetite with the magnet, and placed in a polypropylene vial. The PFOA is then released with 2 x 1 mL of a 25% EtOH / NF OH mixture (4.5 / 0.5; v:v) and vigorous shaking for 5 to 10 seconds.

[0156] PFOA analysis is performed by LC-MS with a detection limit of 2 pg / L.

[0157] The PFOA uptake for magnetites is respectively around 238 pmol / g for FesO4 (27%), 142 pmol / g for FesO4@SiO2 (16%), 290 pmol / g for FesO4@SiO2@NH2 (33%) and 856 pmol / g for FesO4@SiO2@P-CD (98%) (Fig. 6, Table 2).

[0158] Table 2 Recycling procedure

[0159] The same steps as the protocol described above are repeated, rinsing the magnetite twice (1 mL) with water for 10 seconds beforehand to remove residual ethanol. It was observed that FesO4@SiO2@NH2 captures 33% of PFOA, which is released mainly via simple water washing due to the weak ionic bonds present between the amine groups and the triazole and acidic groups of PFOA (see Fig. 6).

[0160] 98% of PFOA is captured by FesO4@SiO2@P-CD nanoparticles. Washing with water does not release the PFOA. Washing the PFOA-loaded nanoparticles with an EtOH / NFUOH mixture (ammonia solution) releases the host-guest complex formed between the perfluorinated chain and the cyclodextrin cavity. The FesO4@SiO2@P-CD nanoparticles were thus recycled 15 times (see Fig. 7) without any change in their capture capacity. This means that all of the captured PFAS is subsequently released during washing.

[0161] It is observed that nanoparticles coated only with ethyl orthosilicate capture very little PFOA.

[0162] Example 14: Establishing Langmuir isotherms for various PFAS

[0163] An aqueous solution of PFBS (nonafluorobutanesulfonic acid) (100pg / l) was used as an internal standard.

[0164] The experiments were repeated three times. The contact time between the PFAS and the nanoparticles was 30 minutes. For the release of the PFAS, an aqueous solution of ethanol and ammonia (EtOH / NF OH 4.5 / 0.5 v / v) was used. 50 mL of aqueous solutions, each containing a concentration of a given PFAS chosen from the following 6 PFAS: TFA, PFBA, PFHxA, PFOA, PFDA and FTS 6:2 (see Fig. 8 for their formula), were used.

[0165] The nanoparticles used are the following: (obtained from reaction scheme 10)

[0166] Each solution is poured into a polypropylene tube containing 50 mg of the aforementioned nanoparticles. The mixture is shaken on a rotary wheel for 30 minutes. After 30 minutes, the nanoparticles are removed by magnetization (it takes 30 seconds to remove all the nanoparticles) and the supernatant is collected.

[0167] The adsorption capacity was determined by measuring the amount of each PFAS remaining in the supernatant after 30 minutes of contact by liquid chromatography coupled with mass spectrometry.

[0168] The nanoparticles were rinsed three times with 1 mL of the EtOH / NH4OH 4, 5 / 0, 5 v / v solution, then reused.

[0169] The experiments were repeated three times, allowing the plotting of isotherms. The error is the standard deviation between the three experiments. A standard curve for each PFAS was previously generated using the same liquid chromatography-mass spectrometry setup. The concentrations of the standard solutions for each PFAS ranged from 50 to 1250 pg / L for TFA (due to detection issues at low concentrations) and from 20 to 500 pg / L for the other PFAS. The results for maximum adsorption capacities per gram are shown in Table 3 below.

[0170] Table 3

[0171] With a PFOA concentration of 18,000 pg / L, it is possible to capture 19 mg / g of PFOA with the aforementioned nanoparticles in a maximum of 30 minutes.

[0172] It is observed that the nanoparticles preferentially adsorb PFOA and PFDA in only 30 minutes, the maximum time to obtain equilibrium, whereas in the prior art (publication by Usman et al), equilibrium is obtained after 4 to 5 hours and the experiments are always continued for 40 hours.

[0173] Example 15: Competitive adsorption in a solution containing 6 PFAS

[0174] The same experiments as described above were performed with solutions as indicated in Example 14, but containing the same concentration of each PFAS (i.e., 6 PFAS of the same concentration in each solution), as shown in Table 4 below. The nanoparticles used are the same as those used in Example 14.

[0175] Table 4

[0176] The results are shown in Fig. 8. This figure shows that PFOA (7 fluorinated carbons) is preferentially adsorbed, followed by FTS 6:2 (6 fluorinated carbons) and then PFDA (9 fluorinated carbons). It is likely that these negatively charged PFAS are captured by the amine groups due to electrostatic interactions, or by a nitrogen atom of the triazole ring to which the cyclodextrin is attached (one of the three nitrogen atoms can become positively charged), and / or by the cyclodextrin itself, with which they form a hydrophobic complex.

[0177] Example 16: Measurement of the saturation magnetization of the nanoparticles used in Example 14 and comparison with commercial and synthetic nanoparticles

[0178] The magnetism of the samples was measured as a function of the applied magnetic field (poH) at room temperature using an MPMS-XL (magnetic properties measurement system) Quantum Design SQUID (superconducting quantum interference device), with an applied magnetic field of 5 T.

[0179] The cores of Example 1, containing magnetite and iron oxide and obtained from recycled materials (referred to here as MNPr), commercially available spherical ferrimagnetic cores (referred to here as MNPco, marketed by Sigma Aldrich under reference 637106-25G and composed of Fe II, Fe III (97% iron by mass) with a diameter greater than or equal to 50 nm and less than or equal to 100 nm), and the synthetic cores of Example 1 (referred to here as MNPs) were used as samples. These cores were functionalized identically to the nanoparticles of Example 14; only the core itself differs. The functionalized nanoparticles are referenced by adding "@PCD" next to the reference of the core in question. The core, when functionalized, is obviously surrounded by a layer of ethyl orthosilicate.

[0180] The results of the saturation magnetization measurements are summarized in Table 5 below. In Table 5, the measurements were obtained in emu / g and converted to SI units based on 1 emu / g = 1 Am 2 / kg

[0181] Table 5

[0182] As shown in Table 5, after functionalization, the nanoparticles used in Example 14 exhibit a saturation magnetization of approximately 45 emu / g, or 45 Am 2 / Kg. These nanoparticles are therefore sufficiently magnetic to be quickly and easily attracted by a magnetic field. Surprisingly, the saturation magnetization of the functionalized nanoparticles in Example 14 is also higher than that of nanoparticles with a commercial core, and especially higher than that of nanoparticles with a synthetic magnetite core, even though the core of both types of nanoparticles is surrounded by a thinner layer of ethyl orthosilicate. This effect is likely due to the greater aggregation of nanoparticles with irregularly shaped cores. Since the clusters are larger, the saturation magnetization is higher.

Claims

DEMANDS 1. Nanoparticle usable for the capture of a pollutant, of the type comprising a core of ferromagnetic or ferrimagnetic material, said core being covered with a layer of ethyl orthosilicate on which is fixed by covalent bond at least one cyclodextrin molecule by means of a linker comprising a main chain and side chains, characterized in that said cyclodextrin molecule is linked to a triazole ring fixed to the end of the chain of said linker and / or to the end of at least one side chain of said linker.

2. Nanoparticle according to claim 1, characterized in that said main chain and / or at least one of said side chains of said linker comprise at least one secondary amine function.

3. Nanoparticle according to claim 1 or 2, characterized in that an atom of said cyclodextrin molecule is directly linked to an atom of said triazole ring.

4. Nanoparticle according to any one of claims 1 or 3, characterized in that said ethyl orthosilicate-coated core is bonded to at least one silane molecule of the following formula (1): in which x1 and x2 are distinct integers or equal to and greater than or equal to 1 and less than or equal to 10, preferably x1 = 3 and x2 = 2, y is an integer such that 0 <y<6, de préférence y=5 et z est un entier tel que 1 <z<4, de préférence z=1 , la molécule de cyclodextrine CD étant de préférence liée à l’atome de carbone le plus éloigné de l’atome d’azote lié au groupement (CH2) y .

5. Nanoparticle according to any one of claims 1 or 3, characterized in that said ethyl orthosilicate-coated core is bonded to at least one silane molecule of the following formula (2): in which x1 and x2 are distinct integers or equal to and greater than or equal to 1 and less than or equal to 10, preferably x1 = 3 and x2 = 2, y is an integer such that 0 <y<6, de préférence y=5 et z est un entier tel que 1 <z<4, de préférence z=1 , la molécule de cyclodextrine CD étant de préférence liée à l’atome de carbone le plus éloigné de l’atome d’azote lié au groupement (CH2) y .

6. Nanoparticle according to any one of claims 1 to 3, characterized in that said ethyl orthosilicate-coated core is linked to a molecule of the following formula (3): in which x1 and x2 are distinct integers or equal to and greater than or equal to 1 and less than or equal to 10, preferably x1 = 3 and x2 = 2, y is an integer such that 0 <y<6, de préférence y=5 et z est un entier tel que 1 <z<4, de préférence z=1, la molécule de cyclodextrine CD étant de préférence liée à l’atome de carbone le plus éloigné de l’atome d’azote lié au groupement (CH2) y .

7. Nanoparticle according to any one of claims 1 to 6, characterized in that the cyclodextrin is beta-cyclodextrin.

8. Nanoparticle according to any one of claims 1 to 7, characterized in that it has a diameter greater than or equal to 130 nm and less than or equal to 570 nm.

9. Nanoparticle according to any one of claims 1 to 8, characterized in that said core has an irregular shape.

10. Nanoparticle according to any one of claims 1 to 9, characterized in that said core has a size greater than or equal to 100 nm or 200 nm and less than or equal to 300 nm or 500 nm.

11. Nanoparticle according to any one of claims 1 to 10, characterized in that said core is coated with a layer of tetraethyl orthosilicate having a thickness greater than or equal to 25 nm, 30 nm, 100 nm or 120 nm and less than or equal to 200 nm.

12. Nanoparticle according to any one of claims 1 to 11, characterized in that said core contains magnetite, iron (II) oxide FeO and iron hydroxide.

13. Nanoparticle according to any one of claims 1 to 12, characterized in that it has a saturation magnetization greater than or equal to 17 Am 2 / kg, particularly above 37 Am 2 / kg and in particular equal to 44.9 Am 2 / kg.

14. Nanoparticle aggregate comprising or consisting of nanoparticles according to any one of claims 1 to 13, characterized in that it has a maximum dimension greater than or equal to 1000 nm and less than or equal to 3000 nm.

15. A method for extracting at least one pollutant present in a liquid medium, said pollutant being chosen from perfluoroalkyl compounds, polyfluoroalkyl compounds, metals in the form of ions, in particular cobalt, according to which nanoparticles are brought into contact with said medium for a given time, optionally under agitation, and then said nanoparticles are optionally separated from said medium by application of a magnetic field, characterized in that said nanoparticles are according to any one of claims 1 to 12.

16. A process according to claim 15, characterized in that after extraction of said pollutant, said nanoparticles are placed in a release solvent selected from aqueous acid solutions and aqueous solutions containing at least one alcohol, in particular ethanol and ammonia.

17. A process according to any one of claims 15 and 16, characterized in that the perfluoroalkyl compound is selected from perfluorooctanoic acid (PFOA), heptafluorobutyric acid (PFBA), undecafluorohexanoic acid (PFHxA), perfluoroactanesulfonic acid (PFOS), 6:2 fluorotelomersulfonic acid, perfluorodecanoic acid and perfluorononanoic acid (PFNA) and mixtures thereof.

18. A process for synthesizing a nanoparticle according to any one of claims 1 to 13, characterized in that: a) a core of magnetic material is coated with a layer of ethyl orthosilicate; b) the coated core is reacted with a silane having a linear chain which has a primary amine function at its end and optionally one or more secondary amine functions on said chain; c) optionally the nanoparticle obtained in step b) is reacted with a chain having an azide function to obtain a nanoparticle which has azide functions and then said nanoparticle obtained is reacted with a modified cyclodextrin bearing an alkyne group to obtain a nanoparticle which has at least one cyclodextrin molecule;d) optionally the nanoparticle obtained in step b) is reacted with a halogenated compound bearing an alkyne function to obtain a nanoparticle which includes alkyne functions then the said nanoparticle obtained is reacted with a modified cyclodextrin bearing an azide group to obtain a nanoparticle which includes at least one cyclodextrin molecule.; 19. A process according to claim 18, characterized in that said azide corresponds to the following formula: XR 5 -Ns in which R 5 is an alkyl group containing from 1 to 10 carbon atoms, preferably 6 carbon atoms, X being a halogen, preferably a bromine atom, or with the following formula: Ns-R 6 -COOH in which R 6 - is an alkyl chain consisting of 1 to 8 carbon atoms.

20. A process according to claim 18, characterized in that said halogenated compound comprising an alkyne function corresponds to the following formula: X (CH2)y1CO-NH-(CH2)y2-CCH with yi being an integer such that 1 <yi<10, de préférence yi="1" , y2="1" étant un entier tel que 1 <y2^10, .

21. Installation enabling the implementation of the process according to any one of claims 15 to 17, characterized in that it comprises a first tank containing the medium to be treated and optionally equipped with an agitator, said first tank being connected to a magnetic separator, the outlet of the solids from said magnetic separator being connected to a second tank containing a salting-out solvent.< / yi<10,>

Images