DE102021200731A1 - core-shell particles - Google Patents

Abstract

A core-shell particle (2) is specified that is particularly suitable for the selective removal of micro- and nanoplastic particles (32) from water (34). The core-shell particle (2) comprises a core (4) containing at least one magnetic nanoparticle and a shell (6) which encloses the core (4) and is formed from a monolayer of molecules (8). Each molecule (8) of the shell (6) has an anchor group (12), a molecular backbone (14) and a head group (16, 16a, 16b). The molecule (8) is connected to a surface (10) of the core (4) via the anchor group (12). The molecular backbone (14) connects the anchor group (12) to the head group (16, 16a, 16b), which in turn faces away from the surface (10) of the core (4). A first group (20) of molecules (8) of the shell (6) has non-polar head groups (16, 16a) which form a lipophilic surface (18) of the shell (6). A second group (22) of molecules (8) of the shell (6) carries positive electrical charges (24), so that the core-shell particle (6) has an overall positive electrical surface charge. As a result, the core-shell particle (6) can be dispersed in an aqueous environment despite the lipophilic surface (18) of the shell (6).

Description

The invention relates to a core-shell particle according to the preamble of claim 1. Such a core-shell particle is made of WO 2018/006959 A1 as well as off DE 20 2018 005 341 U1 known.

One of the biggest environmental problems of today is the pollution of water and air with micro- and nanoplastics (i.e. plastic particles with typical sizes in the micrometer or nanometer range). Such plastic particles are deliberately produced and used as additives in the cosmetics industry, for example to to adjust the material properties of creams and gels such as shampoos or peelings. However, a significantly larger proportion of the existing micro- and nanoplastic particles are created unintentionally through abrasion during mechanical stress on plastic parts such as car tires, or through weathering and decomposition of plastic waste under the influence of environmental influences such as wind, sun and water.

The focus of attention is currently on microplastic particles in the size range from 1 to 5000 µm (microns), especially since research has recently increasingly observed the accumulation of such plastic particles in biological systems. Even more serious effects on biological systems can be expected from nanoplastic particles, i.e. plastic particles with sizes below 1 µm. The smaller the size, the more likely it is that such particles will penetrate human, animal or plant tissue and cause inflammation or poisoning.

Recently, the use of magnetic core-shell nanoparticles (or core-shell nanoparticles, English: Magnetic Core Shell Nano Particles, abbreviated: MCSNP) for cleaning liquids, in particular water or oils, from various contaminants has been proposed on various occasions.

Such MCSNPs usually consist of a core made of a magnetic (i.e. magnetized or magnetizable) material and a shell that encloses the core and is made up of a monolayer of chain-like organic molecules. Each molecule of the shell is connected to the surface of the core with an anchor group and protrudes from this surface. At their chain ends opposite to the anchor groups, the molecules of the shell carry a head group that is functionalized to bind the respective impurity to be removed.

In WO 2018/006958 A1 the use of MCSNP for the selective removal of heavy metal ions and cations of radioactive isotopes from water is recommended. The shell of this MCSNP comprises matrix molecules that form a hydrophilic matrix and a number of different functionalized molecules that are integrated into the matrix in such a way that the shell is designed with a three-dimensional cage structure for the selective binding of metallic cations.

In WO 2018/006959 A1 the use of MCSNP for the selective binding of hydrocarbons, in particular crude oil or other fossil fuels, is recommended. The shell of this MCSNP includes matrix molecules that form a hydrophobic matrix for binding the hydrocarbons. The shell of the in WO 2018/006959 A1 The described MCSNP also contains a number of different functionalized molecules.

In DE 20 2018 005 341 U1 the use of MCSNP, among other things, for the removal of micro- and nanoplastics is discussed. For this application, it is proposed to use molecules with CH ₃ head groups to form the shell, which form a hydrophobic surface of the shell and interact with the plastic particles to be bound via van der Waals forces. As an alternative to binding nanopolyester, it is proposed to use molecules with OH, NH ₂ , COOH or SH head groups to form the shell, which interact with the particles to be bound via van der Waals forces, hydrogen bridges or covalent linkages.

The invention is based on the object of specifying a core-shell particle that enables particularly effective binding of microplastic and nanoplastic particles in an aqueous environment and which can therefore be used particularly effectively for cleaning water contaminated with microplastic and nanoplastic.

According to the invention, this object is achieved by a core-shell particle having the features of claim 1. The core-shell particle then has—in principle analogously to FIG WO 2018/006959 A1 and DE 20 2018 005 341 U1 known MCSNP - a core which contains at least one magnetic, ie magnetized or magnetizable, nanoparticle. The core-shell particle also has a shell which encloses the core and which is formed from a monolayer of (especially chain-like, organic) molecules. Each molecule of the shell has an anchor group, a molecular backbone, and a head group. The molecules of the shell are each connected to a surface of the core via the anchor group (preferably via a covalent bond or a salt bridge), while the head group, which is connected to the anchor group via the molecular backbone, faces away from the surface of the core.

According to the invention, the shell comprises a first group of molecules, each of which has at least one non-polar head group. The head groups of this first group of molecules form a lipophilic surface of the shell. The shell also includes a second group of molecules that carry positive electrical charges. Each molecule of the second group carries at least one positive charge. An increased charging effect is optionally achieved in that some or even all of the molecules of the second group contain several identical and/or different positive charge groups. This second group of molecules is selected in such a way that the core-shell particle has an overall positive electrical surface charge. Overall, the two groups of molecules of the shell are selected in such a way that the core-shell particle is dispersible in an aqueous environment.

The assignment of the molecules of the shell to the first or second group is to be understood as purely functional and is defined exclusively by the molecular properties described above (non-polar head groups or positive charges). Within the scope of the invention, the two groups can be disjoint (ie have no intersection) and thus each be formed from completely different molecules. Alternatively, however, they can also overlap or even be completely identical and thus be formed entirely or partially from the same molecules. In other words, a specific molecule of the shell can belong both to the first group and to the second group, namely whenever this molecule has both a non-polar head group and at least one positive charge.

The invention is based on the knowledge that conventional MCSNP with a hydrophobic surface, as they are made of WO 2018/006959 A1 and DE 20 2018 005 341 U1 are known, although in principle they can also bind micro- and nanoplastic particles in addition to liquid hydrocarbons such as petroleum, the conventional MCSNP are comparatively ineffective for the latter purpose. This is primarily due to the fact that the micro- and nanoplastic particles to be bound are comparatively large (especially in comparison to individual hydrocarbon molecules in a liquid that are mixed with the WO 2018/006959 A1 known MCSNP should be bound). Due to their size, micro- and nanoplastic particles are exposed to comparatively large forces (gravity, inertia, flow pressure, etc.), so that the comparatively weak van der Wals forces through which the plastic particles interact with the hydrophobic surface of the MCSNP are not sufficient to effectively remove the MCSNP along with the attached plastic particles from the aqueous environment.

Another recognized problem is that micro- and nanoplastic particles are generally finely distributed in an aqueous environment and, in contrast to liquid hydrocarbons such as petroleum, do not form separate phases. In the WO 2018/006959 A1 and DE 20 2018 005 341 U1 However, due to its hydrophobic surface, the known MCSNP is difficult to mix with water without the addition of surfactants. Therefore, in an aqueous environment, they cannot be effectively brought into contact with the micro- and nanoplastic particles to be removed.

While are, for example, from WO 2018/006958 A1 , per se also known as MCSNP with a hydrophilic surface, which are readily miscible with water. However, the binding ability of these MCSNPs is not selective for micro- and nanoplastic particles. Such MCSNPs, if they can bind micro- and nanoplastic particles at all, would also bind other micro- and nanoparticles occurring in the aqueous environment, such as inorganic sediment particles or biological suspended matter. They could therefore also not be used effectively to remove micro- and nanoplastic particles.

However, in order to enable an effective removal of micro- and nanoplastic particles with MCSNP, in the case of the core-shell particle according to the invention, structures with opposite effects are purposefully built into the shell.

The non-polar head groups of the first group of shell molecules create a lipophilic (and per se hydrophobic) surface of the shell, which ensures sufficient selectivity for micro- and nanoplastic particles and prevents agglomeration of other micro- and nanoparticles occurring in the aqueous environment ( especially inorganic sediment particles).

The positive charges of the second group of shell molecules ensure on the one hand that the core-shell particle is dispersible in the aqueous environment and that a binder containing the core-shell particles is soluble in water. Because a positive surface potential of the core-shell particle is created by means of the positive charges, on the other hand, micro- and nanoplastic particles are additionally attracted by electrical forces of attraction (Coulomb interaction) bound. The binding ability of the core-shell particles achieved in this way has turned out to be sufficiently strong to bind the core-shell particles together with the adhering micro- and nanoplastic particles to form larger agglomerates under the effect of magnetic fields and to remove them from the aqueous phase.

In order to ensure the opposing properties of the core-shell particle, namely on the one hand the lipophilic property of the surface of the shell and on the other hand the positive surface charge and thus the dispersibility in water, in a particularly effective manner, without these opposing properties interfering with or compensating for each other, are the positive charge is preferably not located on the surface of the shell but within the shell.

In order to achieve this, in a first embodiment variant of the invention, the shell comprises (first) molecules which both have a non-polar head group and (below the head group) carry positive electrical charges. In this variant embodiment of the invention, the first group and the second group of shell molecules are therefore completely or partially identical.

In a second embodiment of the invention, the second group of shell molecules includes (second) molecules with a positively charged head group, these second molecules having a shorter chain length than molecules of the first group. The shorter chain length of the second molecules in turn ensures that the positive charges are located inside the shell (ie below the lipophilic surface of the shell).

Mixed forms of the two embodiment variants of the invention described above also lie within the scope of the invention. In such mixed forms, the shell thus includes both the (first) molecules with a non-polar head group and positive electrical charges below the head group and the comparatively short-chain (second) molecules with a positively charged head group.

To realize the positive charges, the molecules of the second group preferably contain ammonium groups, pyridinium groups and/or imidazolium groups. The non-polar head groups of the first group of shell molecules are preferably formed by alkyl chains and/or fluoroalkyl chains with chain lengths greater than or equal to 2 (i.e. with at least two carbon atoms in the chain).

In certain embodiments of the invention - particularly in preferred embodiments in which the core consists of iron oxide (FeO _x ), for example magnetite or maghemite - the core has a negative electrical surface charge. In this case, the shell molecules are always selected in such a way that the negative surface charge is overcompensated by the positive electrical charges of the second group of shell molecules. In other words, the polarity of the negative surface charge of the core is reversed by the positive charges of the shell, so that the core-shell particle has a positive electrical surface charge overall.

In an advantageous dimensioning, the core-shell particle has a zeta potential of more than 10 mV (millivolts), preferably more than 20 mV, in particular more than 35 mV, in an aqueous environment. Additionally or alternatively, the shell has a (total) surface energy of less than 45 mN/m (milli-Newtons per meter), preferably less than 30 mN/m, in particular less than 25 mN/m. The polar proportion of the surface energy of the shell is in particular less than 50%, preferably less than 40% and in particular less than 25% of the total surface energy.

The molecules of the shell preferably cover the surface of the core at a density of 0.5 to 7 molecules/nm ² (square nanometers)), preferably about 4 molecules/nm ² .

In particularly suitable embodiments of the invention, the core has a diameter of 10 to 70 nm (nanometers), in particular approximately 30 nm. The average diameter of the core-shell particle increases through the shell compared to the core diameter, preferably by 2 to 10 nm, in particular by about 4 nm.

Depending on the field of application of the core-shell particle, the core can have paramagnetic, diamagnetic, ferromagnetic or ferrimagnetic properties within the scope of the invention. It is preferably designed to be superparamagnetic.

The shell molecules are preferably formed by phosphonic acid derivatives. The anchor group of the shell molecules is therefore preferably formed by a phosphonic acid group. In this embodiment, the shell molecules have in particular the generalized chemical structure R—PO(OH) ₂ , where OH can also be substituted by OR′ with R′=Me, Et. The abbreviations “Me” and “Et” stand for a methyl group and an ethyl group, respectively. In the molecular formula mentioned above, "R" designates the molecular backbone and the head group, ie generally one molecular chain structure (particularly formed by alkyl chains), the chain length of this structure preferably being between 2 and 20. Within the scope of the invention, one or more carbon atoms in the molecular backbone of at least some of the shell molecules can be replaced by heteroatoms such as oxygen or sulfur or by phenyl groups. The molecular backbone and the head group can also be fully or partially fluorinated. In particular, the shell molecules are at an average angle of inclination of 90° to the surface of the core. Variations in the average molecular inclination are possible depending on the molecules used and are up to 45°.

Values whose values are given with suffixes such as “approximately”, “approximately”, etc. can deviate in particular by ±10%, preferably ±5%, from the value given in each case.

• 1 im Querschnitt ein grob schematisch dargestelltes Kern-Hülle-Partikel mit einem Kern aus einem superparamagnetischen Nanopartikel und einer Hülle aus kettenförmigen Hüllen-Molekülen,
• 2 in einem grob schematischen Querschnitt einen Ausschnitt einer ersten Ausführungsform des Kern-Hülle-Partikels gemäß 1, wobei eine erste Gruppe der Hüllen-Moleküle jeweils eine unpolare Kopfgruppe tragen und eine zweite Gruppe von Hüllen-Molekülen jeweils mindestens eine elektrisch positiv geladene Kopfgruppe tragen, und wobei die Moleküle der zweiten Gruppe eine geringere Kettenlänge aufweisen als die Moleküle der ersten Gruppe,
• 3 fünf Strukturformeln von Hüllen-Molekülen, die alternativ oder in Kombination zur Bildung der Hülle des Kern-Hülle-Partikels gemäß 2 einsetzbar sind, nämlich in 3(a) bis 3(d) vier Phosponsäurederivate mit jeweils eine positiv geladenen Kopfgruppe, die alternativ oder in Kombination als Moleküle der zweiten Gruppe einsetzbar sind sowie in 3(e) ein Phosphonsäurederivat mit einer unpolaren Kopfgruppe, das als Molekül der ersten Gruppe einsetzbar ist,
• 4 in Darstellung gemäß 2 einen Ausschnitt einer zweiten Ausführungsform des Kern-Hülle-Partikels gemäß 1, wobei hier alle Hüllen-Moleküle jeweils eine unpolare Kopfgruppe tragen, und wobei eine Untergruppe dieser Hüllen-Moleküle unterhalb der Kopfgruppe mindestens eine positive Ladung tragen,
• 5 drei Strukturformeln von Hüllen-Molekülen in Form von Phosponsäurederivaten mit einer unpolaren Kopfgruppe und mindestens einer positiven Ladung, die alternativ oder in Kombination zur Bildung der Hülle des Kern-Hülle-Partikels gemäß 4 einsetzbar sind, und
• 6 in schematischer Darstellung eine Reinigungsvorrichtung zur Entfernung von Mikro- und Nanoplastikpartikeln aus Wasser unter Verwendung der Kern-Hülle-Partikel, und
• 7 in schematischer Darstellung die Bindung von Mikro- und Nanoplastikpartikeln mittels der Kern-Hülle-Partikel.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. show:

• 1 in cross section, a roughly schematic core-shell particle with a core of a superparamagnetic nanoparticle and a shell of chain-like shell molecules,
• 2 in a roughly schematic cross section a section of a first embodiment of the core-shell particle according to FIG 1 , wherein a first group of shell molecules each carry a non-polar head group and a second group of shell molecules each carry at least one electrically positively charged head group, and the molecules of the second group have a shorter chain length than the molecules of the first group,
• 3 five structural formulas of shell molecules, alternatively or in combination to form the shell of the core-shell particle according to 2 can be used, namely in 3(a) until 3(d) four phosphonic acid derivatives, each with a positively charged head group, which can be used alternatively or in combination as molecules of the second group, and in 3(e) a phosphonic acid derivative with a non-polar head group, which can be used as a molecule of the first group,
• 4 in representation according to 2 according to a section of a second embodiment of the core-shell particle 1 , where all shell molecules each carry a non-polar head group, and where a subgroup of these shell molecules below the head group carry at least one positive charge,
• 5 three structural formulas of shell molecules in the form of phosphonic acid derivatives with a non-polar head group and at least one positive charge, which alternatively or in combination to form the shell of the core-shell particle according to 4 can be used, and
• 6 a schematic representation of a purification device for removing micro- and nanoplastic particles from water using the core-shell particles, and
• 7 a schematic representation of the binding of micro- and nanoplastic particles by means of the core-shell particles.

Corresponding parts, sizes and structures are given the same reference numerals throughout the figures.

1 shows a (core-shell) particle 2 (as previously also referred to as “MCSNP”) in a roughly schematic cross section. The core-shell particle 2 comprises a core 4 and a shell 6 enclosing the core 4. The core 4 is formed by a superparamagnetic nanoparticle of magnetite (Fe ₃ O ₄ ). Alternatively, the core 4 can also consist of another superparamagnetic material. Suitable magnetic nanoparticles are manufactured and marketed, for example, by GetNanoMaterials (St-Cannat, France; www.getnanomaterials.com) or Comar Chemicals (South Africa, www.comarchemicals.com). The core 4 has a diameter of 30 nm, for example.

The shell 6 is formed by a self-organizing monolayer (self-assembled monolayer, SAM for short) of chain-shaped organic (shell) molecules 8 which each protrude from a surface 10 of the core 4 . The average diameter of the core-shell particle 2 increases by approximately 4 nm compared to the core diameter, so that the core-shell particle 2 has a total diameter of approximately 34 nm.

How out 2 As can be seen, the shell molecules 8 generally each comprise an anchor group 12, a molecular backbone 14 and at least one head group 16. The anchor group 12 connects each of the shell molecules 8 to the surface 10 of the core 4. In contrast, the head group 16 faces away from the surface 10 of the core 4 . The head groups 16 of the shell molecules 8 or - if the shell 6 contains shell molecules 8 of different lengths - at least the head groups 16 of the longer shell molecules 8 form a surface 18 of the shell 6 (and thus of the entire core-shell particle 2). The molecular backbone 14 connects the anchor group 12 of each core Shell particle 2 with the associated head group 16.

The shell molecules 8 are formed by phosphonic acid derivatives. They therefore each comprise a phosphonic acid group with the general chemical molecular formula --PO(OH) ₂ as the anchor group 12, which is bonded to the surface 10 of the core 4 via a covalent bond. The molecular backbone 14 of each shell molecule 8 is essentially formed by an alkane chain.

In the example according to 2 the shell molecules 8 are divided into two groups 20 and 22 which are different in terms of their structure and effect. The shell molecules 8 of a first group 20 each contain at least one non-polar head group 16, which is also referred to below as the head group 16a and which is formed in particular by an ethyl group or by a longer alkane radical. In the example according to 2 the molecular backbone 14 and the head group 16a of the shell molecules 8 of the first group 20 are formed by a single alkane chain. In this case, the molecular backbone 14 and the head group 16a thus merge seamlessly into one another.

The shell molecules 8 of a second group 22 each contain at least one head group 16 which carries at least one positive electrical charge 24 . The positively charged head groups 16 (hereinafter also referred to as head groups 16b) are, for example, by ammonium groups, by pyridinium groups and / or - as in 2 shown - formed by imidazolium groups.

How out 2 As can be seen, the shell molecules 8 of the second group 22 have a smaller chain length and longitudinal extent than the shell molecules 8 of the first group 20. Thus, the surface 18 of the shell 6 is covered by the non-polar head groups 16a of the first group 20 of shell Molecules 8 formed, whereby the surface 18 has a low surface energy, and consequently a lipophilic effect. The positively charged head groups 16b of the second group 22 of shell molecules 8, on the other hand, are accommodated inside the shell 6 (below the surface 18). The positively charged head groups 16b overcompensate for a negative electrical surface charge of the core 4 and thus bring about an overall positive surface charge of the core-shell particle 2. This positive surface charge enables the core-shell particle 2 to be dispersible in an aqueous environment without the lipophilic property of the surface 18 to destroy.

By varying the respective density of the shell molecules 8 of the first group 20 and the shell molecules 8 of the second group 22 on the surface 10 of the core 4, by varying the chain lengths of the shell molecules 8 of the first group 20 and the shell molecules 8 of the second group 22 and by selecting the head groups 16a and 16b (and thus in particular by varying the positive charges per shell molecule 8 of the second group 22), the positive electrical surface charge and the surface energy of the surface 18 can be adjusted.

For example, the core-shell particle 2 in an aqueous environment has a zeta potential of 20 mV and a (total) surface energy of less than 30 mN/m with a polar fraction of 25%.

• - 3(a): 1-Methyl-3-(( )_n-Phosphonsäure)-Imidazoliumbromid, wobei ( )_n für verschiedene Alkan-Kettenlängen des molekularen Rückgrats steht, z.B. 1-Methyl-3-(Dodecylphosphonsäure)-Imidazoliumbromid (Cas N ° [2230266-36-9]; MW: 411,32), 1-Methyl-3-(Hexylphosphonsäure)-Imidazoliumbromid (Cas N ° [1852452-65-3]; MW: 327,16), 1-Methyl-3-(Propylphosphonsäure)-Imidazoliumbromid (Cas N ° [1373155-57-7]; MW: 285,08) oder 1-Methyl-3-(Butylphosphonsäure)-Imidazoliumbromid (MW: 299,1),
• - 3(b): (( )_n-Phosphonsäure)-Pyridinbromid, wobei ( )_n wiederum für verschiedene Alkan-Kettenlängen des molekularen Rückgrats steht, z.B. (12-Dodecylphosphonsäure)-Pyridinbromid (Ref: SIK7712-10; MW: 408,12),
• - 3(c): (1,3-Diaminopropan-N,N,N,N',N'-Pentamethyl-N'-( )_n-Phosphonsäure)-Dichlorid, wobei ( )_n wiederum für verschiedene Alkan-Kettenlängen des molekularen Rückgrats steht, z.B. (1,3-Diaminopropan-N,N,N,N',N'-Pentamethyl-N'-Dodecylphosphonsäure)-Dichlorid (Ref : SIK7728-10; MW: 465,48), und
• - 3(d): (1-Methyl-4,4'-Bipyridin-1,1'-Diium -1'-( )_n-Phosphonsäure)-Dichlorid, wobei ( )_n wiederum für verschiedene Alkan-Kettenlängen des molekularen Rückgrats steht, z.B. (1-Methyl-4,4'-Bipyridin-1,1'-Diium-1'-Dodecylphosphonsäure)-Dichlorid (Ref: SIK7733-10; MW: 491,43).

In the 3(a) until 3(d) four different molecules are shown as examples, which are used in various embodiments of the invention alternatively or in any combination as shell molecules 8 of the second group 22. Shown in detail are in

• - 3(a) : 1-methyl-3-(( ) _n -phosphonic acid)-imidazolium bromide, where ( ) _n stands for different alkane chain lengths of the molecular backbone, e.g. 1-methyl-3-(dodecylphosphonic acid)-imidazolium bromide (Cas N ° [2230266- 36-9]; MW: 411.32), 1-methyl-3-(hexylphosphonic acid)-imidazolium bromide (Cas N°[1852452-65-3]; MW: 327.16), 1-methyl-3-(propylphosphonic acid )-imidazolium bromide (Cas N ° [1373155-57-7]; MW: 285.08) or 1-methyl-3-(butylphosphonic acid)-imidazolium bromide (MW: 299.1),
• - 3(b) : (( ) _n -phosphonic acid) pyridine bromide, where ( ) _n in turn stands for different alkane chain lengths of the molecular backbone, e.g. (12-dodecylphosphonic acid) pyridine bromide (Ref: SIK7712-10; MW: 408.12),
• - 3(c) : (1,3-diaminopropane-N,N,N,N',N'-pentamethyl-N'-( ) _n -phosphonic acid) dichloride, where ( ) _n in turn stands for different alkane chain lengths of the molecular backbone, e.g (1,3-diaminopropane-N,N,N,N',N'-pentamethyl-N'-dodecylphosphonic acid) dichloride (Ref : SIK7728-10; MW: 465.48), and
• - 3(d) : (1-Methyl-4,4'-bipyridine-1,1'-diium -1'-( ) _n -phosphonic acid) dichloride, where ( ) _n in turn stands for different alkane chain lengths of the molecular backbone, e.g. (1 -Methyl 4,4'-bipyridine-1,1'-diium-1'-dodecylphosphonic acid) dichloride (Ref: SIK7733-10; MW: 491.43).

The shell molecule 8 out 3(a) carries a positively charged head group 16b in the form of an imidazolium group. At the shell molecule len 8 off 3(b) and 3(d) the positively charged head groups 16b are each formed by a pyridinium group or two pyridinium groups. The shell molecule 8 out 3(c) has a positively charged head group 16b in the form of an ammonium group (-NR ₃ ⁺ ). Another ammonium group (-NR ₂ ⁺ -) and thus another positive charge 24 are arranged in the molecular backbone 14 here.

In 3(e) a molecule is shown as an example, which in the example according to 2 is used for the shell molecules 8 of the first group 20, namely n-( ) _n -phosphonic acid, where ( ) _n in turn stands for different alkane chain lengths of the molecular backbone, e.g. n-octadecylphosphonic acid (Cas N ° [4724-47- 4]; MW: 334.48) or n-dodecylphosphonic acid (Cas N° [5137-70-2]; MW: 250.32).

• - 3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluoroktylphosphonsäure (Ref: SIK7112-10; Cas N ° [252237-40-4]; MW: 428,08),
• - 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluordecylphosphonsäure (Ref.: SIK7114-10; Cas N ° [80220-63-9]; MW: 528,1),
• - 12,12,13,13,14,14,15,15,15,15-Nonafluorpentadecylphosphonsäure (Ref : SIK7120-10; CAS Nr. [627909-21-1]; MW: 454,31),
• - 12,12,13,13,14,14,15,15,16,16,17,17-Tridecafluorseptadecylphosphonsäure (Ref : SIK7121-10; Cas N° [1980085-69-5]; MW: 554,33),
• - 2,12,13,13,14,14,15,15,16,16,17,17,18,18,19,19,19-Heptadecafluornonadecylphosphonsäure (Ref : SIK7122-10; Cas N ° [625095-76-3]; MW: 654,34),
• - 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-Henicosafluordodecylphosphonsäure (Ref: SIK7130-10; Cas N ° [252237-39-1]; MW: 628,12), und
• - 12,12,13,13,14,14,15,15,16,16,17,17,18,18,18-Pentadecafluoroctadecylphosphonsäure (Ref : SIK7134-10; Cas N ° [1258004-90-8]; MW: 604,34).

In further (not explicitly shown) exemplary embodiments, instead of the 3(e) Molecule shown fluorinated phosphonic acid derivatives used, eg

• - 3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctylphosphonic acid (Ref: SIK7112-10; Cas N ° [252237-40-4]; MW: 428, 08),
• - 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluorodecylphosphonic acid (Ref.: SIK7114-10; Cas N ° [80220- 63-9]; MV: 528.1),
• - 12,12,13,13,14,14,15,15,15,15-nonafluoropentadecylphosphonic acid (Ref : SIK7120-10; CAS No. [627909-21-1]; MW: 454.31),
• - 12,12,13,13,14,14,15,15,16,16,17,17-tridecafluoroseptadecylphosphonic acid (Ref : SIK7121-10; Cas N° [1980085-69-5]; MW: 554.33) ,
• - 2,12,13,13,14,14,15,15,16,16,17,17,18,18,19,19,19-heptadecafluorononadecylphosphonic acid (Ref : SIK7122-10; Cas N ° [625095-76 -3]; MV: 654.34),
• - 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-henicosafluorododecylphosphonic acid (Ref: SIK7130-10 ; Cas N° [252237-39-1]; MW: 628.12), and
• - 12,12,13,13,14,14,15,15,16,16,17,17,18,18,18-pentadecafluorooctadecylphosphonic acid (Ref : SIK7134-10; Cas N ° [1258004-90-8]; MV: 604.34).

the 4 shows an alternative embodiment of the core-shell particle 2, which corresponds to the above-described embodiment of the core-shell particle 2 in terms of its basic structure. Deviating from this, according to the example 4 but all shell molecules 8 have a non-polar head group 16a. Thus, all the shell molecules 8 belong to the first group 20 described above, which give the surface 18 of the shell 6 a lipophilic effect due to the non-polar head groups 16a.

In the example according to 4 contains a subgroup of the shell molecules 8 below the or each head group 16a and/or within the molecular backbone 14 at least one positive electrical charge 24. These shell molecules 8 thus also belong to the second group 22 described above, which due to the positive charges 22 bring about the overall positive surface charge of the core-shell particle 2 and thus the dispersibility of the core-shell particle 2 in an aqueous environment.

As in 4 is shown, the shell 6 optionally has further shell molecules 8 without positive charges 24 in addition to the shell molecules 8 of the second group 22 . These further shell molecules 8 preferably have a similar or greater chain length and longitudinal extent than the shell molecules 8 of the second group 22.

In a further exemplary embodiment (not shown explicitly), the shell 6 contains only shell molecules 8 with non-polar head groups 16a and at least one positive charge below the head group 16a. In this case, the first group 20 of shell molecules 8 is identical to the second group 22.

By varying the respective density of the shell molecules 8 of the second group 20 and optionally the shell molecules 8 without positive charges 24, by varying the chain lengths of the molecular backbone 14 and the head group 16a of the shell molecules 8 of the second group 22 and by variation of the positive charges per shell molecule 8 of the second group 22, the positive electrical surface charge and the surface energy of the surface 18 of the shell 6 can be adjusted.

For example, the core-shell particle 2 according to 4 in an aqueous environment, it has a zeta potential of 25 mV and a (total) surface energy of less than 23 mN/m with a polar fraction of 12%.

• - 5(a): (( )_n-Phosphonsäure)-N,N-Dimethyl-N-( )_m-Ammonium-Bromid, wobei ( )_n und ( )_m für verschiedene Alkan-Kettenlängen des molekularen Rückgrats bzw. der unpolaren Kopfgruppe stehen, z.B. (12-Dodecylphosphonsäure)-N,N-Dimethyl-N-Octadecylammonium-Bromid (Ref: SIK7716-10; MW: 626,79), (3-Propylphosphonsäure)-N,N-Dimethyl-N-Octadecylammonium-Bromid (Ref: SIK7716-11; MW: 500,54), (6-Hexylphosphonsäure)-N,N-Dimethyl-N-Tetradecylammonium-Bromid (Ref: SIK7716-12; MW: 486,52), (3-Propylphosphonsäure)-N,N-Dimethyl-N-Tetradecylammonium-Bromid (Ref: SIK7716-13; MW: 444,43) oder (12-Dodecylphosphonsäure)-N,N-Dimethyl-N-Dodecylammonium-Bromid (Ref: SIK7716-14; MW: 542,62),
• - 5(b): (12-Dodecylphosphonsäure)-Triethylammonium Bromid (Ref: SIK7709-10; MW: 430,41) und
• - 5(c): Mono(1-Decyl-1'-(12-Phosphonododecyl)-[4,4'-Bipyridin]-1,1'-Diium) Dichlorid.

In 5 (a) until 5(c) three different molecules are shown as an example, which according to different variants of the core-shell particle 2 4 alternatively or in any combination tion as shell molecules 8 of the second group 22 are used. Shown in detail are in

• - 5(a) : (( ) _n -phosphonic acid)-N,N-dimethyl-N-( ) _m -ammonium bromide, where ( ) _n and ( ) _m stand for different alkane chain lengths of the molecular backbone or the non-polar head group, e.g. ( 12-dodecylphosphonic acid)-N,N-dimethyl-N-octadecylammonium bromide (ref: SIK7716-10; MW: 626.79), (3-propylphosphonic acid)-N,N-dimethyl-N-octadecylammonium bromide (ref: SIK7716-11; MW: 500.54), (6-hexylphosphonic acid)-N,N-dimethyl-N-tetradecylammonium bromide (Ref: SIK7716-12; MW: 486.52), (3-propylphosphonic acid)-N, N-dimethyl-N-tetradecylammonium bromide (ref: SIK7716-13; MW: 444.43) or (12-dodecylphosphonic acid)-N,N-dimethyl-N-dodecylammonium bromide (ref: SIK7716-14; MW: 542 ,62),
• - 5(b) : (12-dodecylphosphonic acid)-triethylammonium bromide (Ref: SIK7709-10; MW: 430.41) and
• - 5(c) : Mono(1-decyl-1'-(12-phosphonododecyl)-[4,4'-bipyridine]-1,1'-diium) dichloride.

In addition or as an alternative to the in 5(b) The molecule shown can also be used with 12-dodecylphosphonic acid)-tripropylammonium iodide (Ref: SIK7724-10; MW: 519.24).

The in the 3 and 5 Molecules shown and described above are marketed, for example, by Sikemia (Montpellier, France; www.sikemia.com).

The shell molecule out 5(b) has three short-chain, non-polar head groups 16a in the form of ethyl groups, which are adjacent to a positively charged end of the molecular backbone 14. The positively charged end of the molecular backbone 14 is formed here by an ammonium group (-NR ₃ ⁺ ). With the shell molecules 8 out 5(a) and 5(c) the non-polar head group 16a, on the other hand, is in each case formed by a longer-chain alkane chain. The positive charges 24 are here in the case of the shell molecule 8 according to 5(a) again by an ammonium group (-NR ₃ ⁺ ) and in the case of the shell molecule 8 according to 5(c) formed by two pyridinium groups at the end of each molecular backbone 14.

The production of the core-shell particle 2 (functionalization), that is to say the application of the shell molecules 8 to the core 4, takes place, for example, by a wet-chemical process or by a gas-phase process.

In the wet-chemical production, the magnetic particles forming the core 4 and the shell molecules 8 are added to the solvent and mixed. The functionalization occurs spontaneously and self-terminated in the mixture. Optionally, the mixture is treated with ultrasound for better distribution and reinforcement of the functionalization. The particles are then separated from the solvent using magnetic fields and/or centrifugation and washed several times in solvents. Finally, the particles are either separated from the solvent again and stored as a powder or stored as a dispersion in solvent. The basic manufacturing principle is described in L. Portilla, M. Halik, "Smoothly Tunable Surface of Aluminum Oxide Core-Shell Nanoparticles By a Mixed-Ligand Approach", ACS Appl. mater Interfaces 2014, 6, 8, 5977-5982 (DOI: 10.1021/am501155e).

In the case of production in the gas phase process, the magnetic particles forming the core 4 and the shell molecules 8 are dispersed or dissolved in solvent. The particle dispersion and the molecular solution are injected separately but in parallel into a hot gas stream. This causes the solvents to evaporate; the substances are mixed in the gas phase and come into contact there. In the gas phase, the covalent surface deposition of the shell molecules 8 takes place spontaneously and in a self-terminated manner. The core-shell particles 2 functionalized in this way are transported with the gas flow into a separation device. In this, the core-shell particles 2 are separated from the gas flow by means of magnetic fields and/or by filtering.

In 6 a cleaning device 30 is shown roughly schematically, with which a method for the continuous removal of (micro- or nano-)plastic particles 32 from water 34 is carried out. The cleaning device 30 comprises a tubular cleaning unit 36. The water 34 contaminated with the microplastic or nanoplastic particles 32 is introduced at an inlet side 38 of this cleaning unit 36. The micro or nano plastic particles 32 are in the schematic 6 shown greatly enlarged in comparison to the dimensions of the cleaning unit 36. The contaminated water 34 is, for example, waste water from a sewage treatment plant. Alternatively, the contaminated water 34 can also be taken from the environment, in particular from the subsoil or from rivers, lakes or the sea, for example in order to reduce the environmental pollution with microplastics or nanoplastics or to prepare this water 34 for use.

Furthermore, the core-shell particles 2 described above (and also shown greatly enlarged) are also supplied to the cleaning unit 36 via an MCSNP inlet 40 . The core-shell particles 2 are, for example removed from a reservoir 41 and preferably fed to the cleaning unit 36 in an aqueous solution. Alternatively, the core-shell particles 2 can also be blown into the cleaning unit 36 by means of compressed air.

The core-shell particles 2 are adsorbed on the surface of the plastic particles 32 in the cleaning unit 36 . The lipophilic effect of the surface 18 of the shell 6 ensures that the core-shell particles 2 adhere selectively to the plastic particles 32, but not to biological suspended matter or inorganic sediment particles. However, the majority of the adhesive force that binds the core-shell particles 2 to the surface of the plastic particles 32 is achieved through the electrical interaction of the positive charges 24 concealed in the shell 6 with a negative surface charge of the plastic particles 32 . In practice, the core-shell particles 2 also bind to resins and paints with a high nitrogen content (e.g. melamine paints) and other plastic materials which, in their new state, would have a positive surface potential, since such plastic particles are also known to degrade when stored in water for a long time develop a negative surface potential through surface oxidation.

To remove the plastic particles 32 and the core-shell particles 2 adhering thereto, the cleaning device 30 comprises a removal unit 42 by means of which a magnetic field is generated in the cleaning unit 36 using at least one permanent magnet or electromagnet. The superparamagnetic cores 4 of the core-shell particles 2 are magnetized by this magnetic field and thus attract each other magnetically. The plastic particles 32 with the core-shell particles 2 adhering thereto are - as also in 7 is illustrated schematically - thus connected to larger agglomerates 44. These agglomerates 44 are removed from the cleaning unit 36 and thus from the water 34 by a filter and/or a conveying mechanism of the removal unit 42 . As a result of the electrical interaction of the positively charged core-shell particles 2 with the negatively charged plastic particles 32, a sufficiently strong bond of the agglomerates 44 is achieved, which allows the agglomerates 44 to be removed from the water 34 without destroying the agglomerates 44 .

The water 34 cleaned from the plastic particles 32 is discharged from the cleaning unit 36 on an outlet side 46 . Excess core-shell particles 2 remaining in the purified water 34 are harmless because the core-shell particles 2 are non-toxic to humans and the environment.

After removal from the water 34, the plastic particles 32 with the core-shell particles 2 adhering thereto are fed to a separating unit 48, which is formed, for example, by a centrifuge. The core-shell particles 2 are separated from the plastic particles 32 in the separating unit 48 . The plastic particles 32 are then disposed of. In contrast, the core-shell particles 2 separated from the plastic particles 32 are returned to the storage container 41 for reuse.

In an alternative embodiment, the cleaning process described above can also be operated discontinuously. In this case, the water 34 contaminated with the plastic particles 32 is mixed with the core-shell particles 2 in a container (not explicitly shown), the core-shell particles 2 in turn being adsorbed on the surface of the plastic particles 32 . The plastic particles 32 are then agglomerated with the core-shell particles 2 adhering thereto by applying a magnetic field. The water 34 is eventually emptied from the container. Before or during emptying, the agglomerates 44 are removed from the water 34, for example by filtering. The core-shell particles 2 are then in turn separated from the plastic particles 32, for example by centrifugation, and thus recovered for reuse.

The invention is particularly clear from the exemplary embodiments described above, but is in no way limited to these examples. Rather, further embodiments of the invention can be derived from the claims and the above description.

Reference List

2

(core-shell) particles

4

core

6

Covering

8th

(shell) molecules

10

surface (of the core)

12

anchor group

14

(molecular) backbone

16, 16a, 16b

head group

18

surface (of the shell)

20

(first) group

22

(second) group)

24

(positive) charge

30

cleaning device

32

(Micro or nano) plastic particles

34

water

36

cleaning unit

38

inlet side

40

MCSNP inlet

41

reservoir

42

extraction unit

44

agglomerate

46

outlet side

48

separation unit

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2018/006959 A1 [0001, 0007, 0010, 0013, 0014]
• DE 202018005341 U1 [0001, 0008, 0010, 0013, 0014]
• WO 2018/006958 A1 [0006, 0015]

Claims (12)

Core-shell particles (2) with a core (4) containing at least one magnetic nanoparticle and with a shell (6) which encloses the core (4) and is formed from a monolayer of molecules (8), - Wherein each molecule (8) of the shell (6) has an anchor group (12), a molecular backbone (14) and a head group (16, 16a, 16b), the molecule (8) having an anchor group (12) with a surface (10) of the core (4), wherein the molecular backbone (14) connects the anchor group (12) to the head group (16, 16a, 16b) and wherein the head group (16, 16a, 1b) is connected from the surface ( 10) facing away from the core (4), and - wherein a first group (20) of molecules (8) of the shell (6) has non-polar head groups (16, 16a), wherein the head groups (16, 16a) of the first group (20) of molecules (8) of the shell (6 ) form a lipophilic surface (18) of the shell (6), characterized in that - that a second group (22) of molecules (8) of the shell (6) carry positive electrical charges (24), so that the core-shell particle (6) has an overall positive electrical surface charge, and - That the core-shell particle (6) is dispersible in an aqueous environment. core-shell particles (2). claim 1 , wherein the first group (20) and the second group (22) are wholly or partially identical in that the shell (6) comprises first molecules (8) which have both a non-polar head group (16, 16a) and positive electrical charges (24) wear. core-shell particles (2). claim 1 or 2 , Wherein the second group (22) of molecules (8) of the envelope (6) comprises second molecules (8) with positively charged head groups (16, 16b) which, in comparison to the molecules (8) of the first group (20) have a have a shorter chain length. Core-shell particles (2) according to one of Claims 1 until 3 , wherein the core (4) has a negative electrical surface charge which is overcompensated by the positive electrical charges (24) of the second group (22) of molecules (8) of the shell (6). Core-shell particles (2) according to one of Claims 1 until 4 , which has a zeta potential of more than more than 10 mV, preferably more than 20 mV, in particular more than 35 mV in an aqueous environment. Core-shell particles (2) according to one of Claims 1 until 5 , wherein the shell has a surface energy of less than 45 mN/m, preferably less than 30 mN/m, in particular less than 25 mN/m. core-shell particles (2). claim 6 , wherein the polar portion of the surface energy of the shell (6) is less than 50%, preferably less than 40% and in particular less than 25%. Core-shell particles (2) according to one of Claims 1 until 7 , wherein the positive electric charges of the second group (22) of molecules (8) of the shell (6) are formed by ammonium groups, pyridinium groups and/or imidazolium groups. Core-shell particles (2) according to one of Claims 1 until 8th , wherein the non-polar head groups (16, 16a) of the first group (20) of molecules (8) of the shell (6) are formed by alkyl chains and/or fluoroalkyl chains with chain lengths greater than or equal to 2. Core-shell particles (2) according to one of Claims 1 until 9 , the molecules of the shell (6) covering the surface (10) of the core (4) with a density of 0.5 to 7 molecules/nm ² , preferably about 4 molecules/nm ² . Core-shell particles (2) according to one of Claims 1 until 10 , wherein the core (4) has a diameter of 10 to 70 nm, in particular approximately 30 nm. Core-shell particles (2) according to one of Claims 1 until 11 , wherein the core (4) consists of magnetite or maghemite.

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