Method of separation of a pollutant from a liquid

Abstract

The present invention relates to a method for the separation of at least one pollutant from a liquid by means of a membrane wherein a complexing compound is provided to complexing the at least one pollutant.

Description

[0001] METHOD OF SEPARATION OF A POLLUTANT FROM A LIQUID

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for the separation of at least one pollutant from a liquid by means of a membrane wherein a complexing compound is provided to complexing the at least one pollutant.

[0004] BACKGROUND TO THE INVENTION

[0005] The exponential growth of pollutant discharges into the environment due to increasing industrial and agricultural activities is a rising threat for human health and a biggest concern for environmental health globally. Several synthetic chemicals, categorized as potential environmental endocrine-disrupting chemicals (EDCs), are evident to affect the health of not only livestock and wildlife but also humankind. In recent years, human exposure to environmental EDCs has received increased awareness due to their association with altered human health as documented by several epidemiological and experimental studies. EDCs are associated with deleterious effects on male and female reproductive health; causes diabetes, obesity, metabolic disorders, thyroid homeostasis and increase the risk of hormone-sensitive cancers. Sewage effluents are a major source of several EDCs, which eventually reach large water bodies and potentially contaminate the drinking water supply. Similarly, water storage material such as different types of plastics also leaches out EDCs in drinking Water. Domestic wastewater containing pharmaceutical ingredients, metals, pesticides and personal care product additives also influences endocrine activity. These EDCs act via various receptors through a variety of known and unknown mechanisms including epigenetic modification. They differ from classic toxins in several ways such as low-dose effect, non-monotonic dose and trans- generational effects.

[0006] In particular, endocrine-disrupting chemicals (EDCs) or simply endocrine disruptors, are chemicals that mimic, block, or interfere with hormones in the body's endocrine system, thereby having endocrine disrupting (ED) properties. In other words, an endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub)populations. EDCs have been associated with a diverse array of health issues. Hormones act in very small amounts and at precise moments in time to regulate the body's development, growth, reproduction, metabolism, immunity and behavior. Endocrine disruptors interfere with natural hormone systems, and the health effects can be felt long after the exposure has stopped. Exposure to endocrine disruptors in the womb can have life-long effects and can even have consequences for the next generation.

[0007] KR201 10083275A discloses a method for separating one or more EDCs from a water stream, by means of a cyclodextrin-modified membrane. The cyclodextrin-modified membrane provides for the formation of an inclusion compound with an environmental hormone through a donorreceiving reaction. A disadvantage of the method described therein is that the method rely on cyclodextrin-modified membranes which require multiple production steps, and require chemical tolerance of the membrane to the reaction condition the modification takes place.

[0008] There is hence a need for a method which allows one or more pollutants, such as EDCs, to be separated efficiently in a less labor intensive way and by utilizing membranes readily available in the state of the art.

[0009] SUMMARY OF THE INVENTION

[0010] According to a first aspect, the present invention pertains to a method for the separation of a pollutant, in particular for the separation of one or more micropollutants, more in particular persistent micropollutants, from a liquid, such a liquid from a wastewater stream, in which it is dissolved and / or suspended, comprising the steps of: a) providing a membrane comprising a first side, and second side; b) providing a first liquid stream e.g. an aqueous stream, at said first side, wherein said first liquid stream comprises at least one pollutant to be separated and a liquid; c) providing a complexing compound for the at least one pollutant at either the first side or the second side of the membrane, thereby forming a molecular complex of said pollutant with said complexing compound, and preferably wherein the complexing compound is provided in a dissolved state and / or dissolved at either the first side or the second side of the membrane, preferably wherein the complexing compound is a cyclodextrin; d) permeating either the at least one pollutant or the liquid provided at step b) through the membrane provided at step a), thereby collecting at one side of the membrane, an amount of pollutant higher than the amount of pollutant at the other side of the membrane, thereby separating, at least partially, the at least one pollutant from the liquid as the molecular complex of said pollutant with said complexing compound.

[0011] An advantage of the present aspects described herein, is that the pollutants, which are particularly difficult to remove in liquid streams can be efficiently separated. The present invention is carried out in the presence of complexing compounds complexing said pollutants, either at a “feed” side of a membrane or an “extractant” side, with the membrane being permeable to ‘the liquid’ respectively ‘the at least one pollutant’ of the first liquid stream. The complexing compound is preferably provided in a dissolved state and / or dissolved. This is beneficial since the resulting driving forces are better in such a condition which allows for an improved complexion between the complexing compound and the pollutant, as a result the pollutant can be separated in an improved manner, such as in a more timely and more efficient manner.

[0012] Preferably, the membrane is configured to allow the liquid to pass through while retaining one or more pollutants that formed a complex with the complexing compound. This feature can be common to both having the complex provided at either side of the membrane. The benefit is that pollutants, such as organic compounds, can be separated. This way, the first liquid stream can be purified as desired.

[0013] The pollutant can have a molar mass below 500 g / mol, preferably below 400 g / mol, such as a molecular weight between 200 - 400 g / mol. Such pollutants can be separated by using the complexing compound, which is preferably cyclodextrin. Preferably, the pollutant has a molar mass between 50 g / mol to 500 g / mol

[0014] Preferably, the membrane has molecular weight cut off of lower than 1000 Da, preferably lower than 950 Da, more preferably lower than 750 Da, most preferably lower than 500 Da. By having a cutoff of lower than 1000 Da an improved separation and / or better use of the complexing compound can be achieved, in particular when using cyclodextrins as complexing compounds. Additionally, a more efficient use of the complexing compound can be achieved as it will be better retained at the respective side of the membrane. With other words, loss of complexing compound is avoided. Notably, a membrane having a cut off lower than 1000 Da is intended to “block” passage of components that are large in size and / or have high mass. Preferably, the cut off is lower than 950 Da, more preferably lower than 750 Da, most preferably lower than 500 Da. By designing the membrane with a lower cut off, the complexing compound can be better retained which results in a more efficient use thereof.

[0015] Preferably, the complexing compound has a molar mass of more than 900 g / mol, preferably more than 950 g / mol, even more preferably more than 1000 g / mol, most preferably more than 1100 g / mol. In this manner, the complexing compound can be better retained by the membrane.

[0016] In a preferred embodiment, the pollutants have a molar mass below 500 g / mol and the membrane has a cut off lower than 1000 Da, preferably lower than 950 Da, more preferably lower than 750 Da, most preferably lower than 500 Da. The complexing compound will form a complex with the pollutant thereby reducing the passage capability of the pollutant through the membrane. As a result, the pollutant stays at one side of the membrane and can be separated from the liquid stream. By setting the membrane cut off even lower, the complexing compound will be better retained which allows a more efficient use thereof.

[0017] Even more preferably, the membrane is impermeable to the complexing compound. This way, an efficient use of the complex compound is ensured. Namely, the compound will remain at the intended side of the membrane and perform its function to form complexes with the pollutants.

[0018] In an embodiment, the membrane is permeable to the at least one pollutant provided at the first side of the membrane, whereby the complexing compound is provided at the second side (e.g. extraction) or the membrane is permeable to the liquid of the first liquid stream, whereby the complexing compound is provided at the first side (e.g. filtration) of the membrane such that the complexing compound binds with the pollutant at the first side and wherein the membrane is impermeable to the pollutant bound to the complexing compound.

[0019] The complexing compound is preferably a cyclodextrin. Cyclodextrins are believed to have a structure that allows them to form complexes with several types of molecules or pollutants. The structure may catch and trap the pollutants in the cavity of the cyclodextrin. In this way, the pollutants can be separated as described herein, in particular by way of a membrane separation technique, more in particular membrane extraction and / or membrane filtration.

[0020] The present method has been found to be useful in separating several types of pollutants, including a pollutant chosen from an organic compound, hydrophobic compound, a hydrogen bonding compound, a drug, an agrochemical, an industrial chemical, a hormone, a steroid, a medication, an environmental contaminant, a persistent micropollutant, an endocrine disrupting compound (EDC) or combinations thereof, more in particular chosen from a hormone, including EE (Ethinyl Estradiol), T (Testosterone), BPA (Bisphenol A), tOP (tert-OctylPhenol), a pesticide (such as Diazinon), a medical drug (such as Citalopram), an EDC (endocrine disrupting compound) or combination thereof.

[0021] Generally desired herein, the pollutant to be separated is a persistent micropollutant, such as an endocrine disrupting compound (EDC), industrial organic waste chemicals, or combinations thereof. It is desired to separate these micropollutants as they can have adverse effects on human health and the environment. More in particular, it is desired to separate persistent micropollutants occurring in wastewater streams, even more in particular persistent organic micropollutants.

[0022] According to an embodiment, the pollutant to be separated is a persistent micropollutant organic compound. Namely, such pollutant can resist degradation and thereby remains in the environment for long periods. Examples include pesticides (like DDT), industrial chemicals (such as polychlorinated biphenyls or PCBs), and unintentional by-products of industrial processes (like dioxins and furans).

[0023] According to an embodiment of the present invention, step a) further comprises providing an hydrophobic membrane which is permeable to the at least one pollutant and impermeable to the complexing compound; and step b) further comprises providing a second liquid stream comprising the complexing compound at said second side; and step d) further comprises permeating the at least one pollutant from the first liquid stream to the second liquid stream, thereby separating the at least one pollutant from the liquid. An advantage of the present embodiment is that the separation of the pollutant is more efficient. The method according to the present invention provides separation of pollutants without recurring to sorbents such as a solid phase extraction (SPE) resin, activated carbon or p-cyclodextrin comprising sorbents. Polymeric membranes have several advantages, they can be easily modified and have a relatively low preparation cost. This makes the method according to the present invention advantageous in that the separation of pollutants can be more easily tuned according to the type of stream to separate pollutants from, while maintaining the costs for the separation low. According to the present embodiment, the pollutant is separated from the liquid by membrane extraction, which extraction is assisted by at least one complexing agent present at the extractant side. An advantage of the present embodiment is that the separation can be effected with relatively low or no over pressure at the feed side (based on the hydrophobic membranes utilized), due to the driving force provided by the presence of a complexing compounds for said pollutant at the extractant side. In addition, this embodiment only extracts the pollutants from the first liquid stream without having to pass the majority of the liquid through the membrane. A further advantage is lower fouling potential of the membranes compared to when a nanofiltration / reverse osmosis configuration is used in accordance with other embodiments of the present invention.

[0024] According to an embodiment of the present invention, step a) further comprises providing the membrane impermeable to the at least one pollutant and the complexing compound, and permeable to the liquid of the first liquid stream; and step b) comprises providing the liquid stream with a complexing compound adapted to complex the at least one pollutant; and step d) further comprises permeating the liquid from the first liquid stream, thereby separating the at least one pollutant from the liquid. According to the present embodiment the complexing agent and the pollutant will be concentrated at the feed side of the membrane. An advantage of the present embodiment is that it is fast, easy scalable and based on proven technology. In said embodiment wherein step d) of permeating the liquid from the first liquid stream is pressure driven, i.e. pressure difference generated over the membrane to pull the liquid from the first liquid stream across the membrane, the proven technology will be nanofiltration. In said embodiment wherein step d) of permeating the liquid from the first liquid stream is osmotic pressure driven, i.e. osmotic pressure difference generated over the membrane to pull the liquid from the first liquid stream across the membrane, the proven technology will be reverse osmosis.

[0025] Aspects of the invention can be explained by the following numbered embodiments as set out in the clauses below.

[0026] 1 . A method for the separation of a pollutant from a liquid, comprising the steps of: a) providing a membrane comprising: a first side, and a second side; b) providing a first liquid stream at said first side, comprising: at least one pollutant to be separated and, a liquid; c) providing a complexing compound for the at least one pollutant at either the first side or the second side of the membrane; and preferably such that the complexing compound, preferably cyclodextrin, such as p-cyclodextrin is present in a solution at either the first side or the second side of the membrane; d) permeating either the at least one pollutant or the liquid provided at step b) through the membrane provided at step a), thereby collecting at one side of the membrane, an amount of pollutant higher than the amount of pollutant at the other side of the membrane, thereby separating the at least one pollutant from the liquid.

[0027] 2. The method according to clause 1 , wherein step a) further comprises providing the membrane being hydrophobic and permeable to the at least one pollutant and impermeable to the complexing compound, and step b) further comprises providing a second liquid stream comprising the complexing compound at said second side, wherein the membrane separates the first liquid stream from the second liquid stream; and step d) further comprises permeating the at least one pollutant from the first liquid stream to the second liquid stream, thereby separating the at least one pollutant from the liquid.

[0028] 3. The method according to clause 2, wherein step d) is performed with an overpressure at the feed side of from 50 mbar to 200 mbar. The term overpressure, as used herein, refers to the feed phase pressure being above extractant phase pressure, preferably the feed phase pressure around 100 mbar more than the extractant phase pressure. In this manner, the extractant phase is better kept at the desired side of the membrane. 4. The method according any one of clauses 2 to 3, wherein at step a) the hydrophobic membrane has a contact angle of at least 90° for the liquid of the first liquid stream, preferably at least 100°.

[0029] The contact angle of a liquid on a surface theoretically ranges from 0 for highly hydrophilic surfaces to 180° for highly hydrophobic surfaces: < 30° are highly hydrophilic ; 30 and 60° are hydrophilic ; 60 and 90° are semi-hydrophilic / semi-hydrophobic or amphiphilic ; 90 and 120° are hydrophobic ; >120° are highly hydrophobic. It was found that a desired rate of separation is achieved for membranes that are characterized by having a contact angle of at least 90° for the liquid of the first liquid stream, preferably at least 100°. More in particular, the contact angle is measured using a Kruss DSA10 goniometer, Kruss GmbH, Germany, equipped with commercial contact angle calculation software (Drop Shape Analysis, Kruss GmbH). The standard procedure of this analysis is to put a drop of water on the top layer of the membrane and to determine the contact angle using a special camera. When the surface is non-porous the camera captures an image of the drop in equilibrium on the surface. However, when the surface is porous, the contact angle is measured by capturing a short video during the falling of the drop on the surface of the membrane piece. The first image capturing the first contact of the drop to the surface is considered for calculation of the contact angle.

[0030] 5. The method according to clause 1 , wherein step a) further comprises providing the membrane impermeable to the at least one pollutant and the complexing compound, and permeable to the liquid of the first liquid stream; and step b) comprises providing the first liquid stream with a complexing compound adapted to complex the at least one pollutant; and step d) further comprises permeating the liquid from the first liquid stream, thereby separating the at least one pollutant from the liquid.

[0031] 6. The method according to the previous clause, wherein step a) comprises providing the membrane having a molecular weight cut off from 0.1 Da to 500 Da, preferably between 50 and 500 Da, more preferably between 100 and 500 Da.

[0032] 7. The method according to the previous clause, wherein the membrane has a molecular weight cut off from 0.1 Da to 300 Da, preferably between 50 and 300 Da, more preferably between 100 and 300 Da.

[0033] 8. The method according to clauses 5 to 7, wherein the membrane is a ceramic membrane functionalized with alkyl groups, preferably methyl groups.

[0034] 9. The method according to any one of clauses 5 to 8, wherein step d) is performed with a transmembrane pressure from 5 to 60 bar.

[0035] 10. The method according to the previous clause, wherein step d) is performed with a transmembrane pressure from 10 to 30 bar.

[0036] 11. The method according to any one of clauses 5 to 10, wherein step d) is performed with a cross-flow velocity from 0.1 m / s to 4 m / s, preferably 0.3 m / s to 2 m / s.

[0037] 12. The method according to the previous clauses, wherein the pollutant is an endocrine disrupting compound (EDC).

[0038] 13. The method according to any one of the previous clauses, wherein the pollutant is an EDC and the complexing compound is p-cyclodextrin.

[0039] 14. The method according to any one of the previous clauses, wherein the complexing compound provided at step c) is p-cyclodextrin.

[0040] 15. The method according clause 14, wherein the p-cyclodextrin is provided at a concentration lower than the solubility of p-cyclodextrin in water, preferably 75% of the solubility of p- cyclodextrin or lower, more preferably 60% of the solubility of p-cyclodextrin or lower.

[0041] 16. A method for the separation of a pollutant from a liquid, comprising the steps of:

[0042] 1 ) providing a membrane comprising: a first side, and a second side; ii) providing a first liquid stream at said first side, comprising: at least one pollutant to be separated, such as an organic pollutant, and, a liquid; ill) providing a complexing compound, preferably cyclodextrin, for the at least one pollutant at either the first side or the second side of the membrane iv) permeating either the at least one pollutant or the liquid provided at step ii) through the membrane provided at step i), thereby collecting at one side of the membrane, an amount of pollutant higher than the amount of pollutant at the other side of the membrane, thereby separating the at least one pollutant from the liquid; whereby the membrane has a molecular weight cut off below 1000 Da, preferably below 750 Da, more preferably from 0.1 Da to 500 Da, even more preferably 0.1 Da to 300 Da.

[0043] 17. The method of clause 16 having any of the features presented in clause 1 - 15.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] With specific reference now to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the different embodiments of the present invention only. They are presented in the cause of providing what is believed to be the most useful and readily description of the principles and conceptual aspects of the invention. In this regard no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

[0046] Fig. 1 illustrates a schematic representation of an embodiment of the method according to the present invention, wherein one or more pollutants are separated from a water stream through a membrane by means of membrane extraction. The number references in the present figures show: [1] Wastewater containing pollutants (feed), [2] Purified water, [3] beta-cyclodextrin solution (extractant), [4] beta-cyclodextrin-pollutant complex solution, [5] membrane. As can be seen from fig. 1 , the beta-cyclodextrin [3] is provided in a dissolved state.

[0047] Fig. 2 illustrates the results of the extraction of EDCs from a complex mixture of EDCs using membrane extraction in accordance with an embodiment of the present invention. Feed: mixture of EDCs (4.3 ppm 17-alpha-ethinylestradiol (EE2), 3 ppm 4-tert-octylphenol (4-tOP), 3.32 ppm bisphenol A (BPA), and 4.19 ppm testosterone, extractant: 1 g / L p-cyclodextrines. Borsig membrane impregnated in heptane, 20 l / h. Results shown for A (see Fig. 2A): EE2, B (see Fig. 2B): 4-tOP, C (see Fig. 2C): BPA and D (see Fig. 2D): testosterone.

[0048] Fig. 3 illustrates a schematic representation of an embodiment of the method according to the present invention, wherein one or more pollutants are separated by concentrating / filtrating them from a water stream. The number references in the present figures show: [1] Wastewater containing pollutants (feed), [2] Purified water, [3] beta-cyclodextrin solution, [4] beta- cyclodextrin-pollutant complex solution, [5] membrane. As can be seen from fig. 3, the beta- cyclodextrin [3] is provided in a dissolved state.

[0049] Fig. 4 illustrates the separation of an EDC (BPA) from a water stream using nanofiltration.

[0050] DETAILED DESCRIPTION OF THE INVENTION The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. When describing the compounds of the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0051] The term "about" or "approximately" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / - 10 % or less, preferably + / - 5 % or less, more preferably + / - 1 % or less, and still more preferably + / - 0.1 % or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" or "approximately" refers is itself also specifically, and preferably, disclosed.

[0052] As used in the specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. By way of example, “a polymer” means one polymer or more than one polymer.

[0053] The term “alkyl” by itself or as part of another substituent refers to a fully saturated hydrocarbon of formula CXH2X+I wherein x is a number greater than or equal to 1 . Generally, alkyl groups of this invention comprise from 1 to 20 carbon atoms. Alkyl groups may be linear or branched and may be substituted as indicated herein. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, for example, Ci-4alkyl means an alkyl of one to four carbon atoms. Examples of alkyl groups are methyl, ethyl, n-propyl, i-propyl, butyl, and its isomers (e.g. n-butyl, i-butyl and t- butyl); pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers; decyl and its isomers. Ci-Ce alkyl includes all linear, branched, or cyclic alkyl groups with between 1 and 6 carbon atoms, and thus includes methyl, ethyl, n-propyl, i- propyl, butyl and its isomers (e.g. n-butyl, i-butyl and t-butyl); pentyl and its isomers, hexyl and its isomers, cyclopentyl, 2-, 3-, or 4-methylcyclopentyl, cyclopentylmethylene, and cyclohexyl.

[0054] According to a first aspect, the present invention pertains to a method for the separation of a pollutant from a liquid in which said pollutant is dissolved, at least partially, and / or suspended, comprising step a) of providing a membrane, which can be porous or non-porous, the membrane comprising a first side, and a second side. According to the present invention the first side faces liquid provided to contain different concentration of said pollutants.

[0055] By means of the term “pollutant”, reference is made to a compound which presence is not desired i.e. an unwanted compound to be removed from a liquid, e.g. water. In other words reference is made to a contaminant.

[0056] The pollutant can be present in concentrations that may harm organisms (humans, plants and animals) or exceed an environmental quality standard. A large variety of pollutants can be beneficially separated from a liquid stream by means of the method of the present invention. The kind of pollutant separated would depend on the type of complexing compound used and its complexation constant. The pollutant to be separated is preferably a persistent micropollutant organic compound. Namely, such pollutant can resist degradation and thereby remains in the environment for long periods. Pollutants that can be efficiently separated include, and are not limited to: EDCs such as estradiol, testosterone, BPA, t-octyl- and n-nonylphenol; pro-EDCs such as triton-X and tergitol, and other pharmaceutically active compounds such as abiraterone acetate. Cyclodextrin, particularly p-cyclodextrin (also referred to as beta-cyclodextrin), was found particularly useful for the complexation of those pollutants.

[0057] Complexation constants can be easily measured according to methodologies in the state of the art. By knowing complexation constants it is possible to determine the removal rates and capacity for pollutants complexed by a specific complexing compound. At equilibrium, a complexation constant (Kc) of 1000 would reduce the concentration of a compound by > 99,95% at a CD concentration of 3 g / L..

[0058] Very fast kinetics of complexation and hence removal are of paramount importance for the separation of pollutants from liquid streams, especially for large volumes, as this allows high flow rates (hence small ecological footprint) for water treatment.

[0059] The majority of persistent micropollutants, by virtue of their physicochemical properties (size, low water solubility), form complexes with p-cyclodextrin. For complexation of pollutants, the logKc should be > 1 , preferentially >2. The logK is 2-3 for phenols, nitro-aromatics, chemicals of the AOX class; 2-4 for many antibiotics, barbiturates, hydrophobic APIs and 3-5 for azoles, steroids and prostaglandins.

[0060] It has been found that several pollutants can be separated from the liquid stream, e.g. a wastewater stream. By doing so, the wastewater stream can be purified. The foundation of such desired separation relies on the use of the complexing compound which can form a complex with the pollutant.

[0061] The pollutants are typically organic compounds having covalent bonds between carbon atoms. The pollutant that can be separated by aid of the complexing compound can be a pollutant chosen from the group comprising a drug, agrochemical, industrial chemical, hormones, steroid, a medication, endocrine disrupting compound (EDC) or combinations thereof.

[0062] Drugs may end up in wastewater. It is beneficial to separate these components. Drugs can be used for treating various medical conditions, such as pain relief, antibiotics, antivirals, antifungals, antipsychotics, and cardiovascular medications.

[0063] Other pollutants can be agrochemicals are used as pesticides and herbicides, for example carbamazepine, chloramphenicol, and chlorophenol.

[0064] Pollutants can also be hormones and steroids like estradiol, testosterone, and corticosteroids.

[0065] Pollutants can also be a medication that ended up in the liquid, e.g. certain medication components that ended up in wastewater. An example is cardiovascular medication, such as atenolol, atenolol acid, atorvastatin, and nitroglycerin. Another example is antidepressant and / or a psychotropic medication, such as sertraline, amisulpride, and bupropion. Another example is a anti pain and / or anti-inflammatory drugs, such as drugs like ibuprofen, diclofenac, and prednisolone. Examples of an antifungal medication are compounds like itraconazole and fluconazole. An example of an antiviral medications are acyclovir and abacavir.

[0066] Other pollutants can be as insecticides (e.g., diazinon), immunosuppressants (e.g., tacrolimus), and anticoagulants (e.g., warfarin).

[0067] Clearly, several types of pollutants can end up in the first liquid stream, for example a wastewater stream. It is desired to have these removed from the wastewater. It has been found that the use of the complexing compound as described herein provides the possibility to do so. Thereby, a beneficial technique to separate several types of pollutants is provided.

[0068] Remarkably is that several types of pollutants can be separated by aid of the complexing compound, a particular preferred complexing compound is cyclodextrin. Cyclodextrins can be a family of cyclic oligosaccharides composed of glucose units linked together in a ring-like structure. Preferred cyclodextrins are alpha-cyclodextrin, beta-cyclodextrin, and gammacyclodextrin, which consist of 6, 7, and 8 glucose units, respectively.

[0069] It was found that the cyclodextrins can interact with ample types of pollutants (including pollutants having different chemistries, among others pollutants chosen from the group of: hydrophobic molecules, aromatic compounds, steroids, molecules with hydrogen bonding capacity, molecules with a suitable size such as below 500 g / mol, preferably below 450 g / mol or combinations thereof.

[0070] Namely, cyclodextrins hydrophobic cavities are effective at encapsulating hydrophobic or nonpolar molecules. Also, aromatic molecules, such as aromatic hydrocarbons, can be accommodated within the cyclodextrin cavity due to their shape and hydrophobicity. Molecules with a suitable size, i.e. fitting in the cavity of the cyclodextrin may also be separated.

[0071] A non-limiting list of pollutants which can be separated according to the present invention comprises: abacavir, acebutolol, acyclovir, , albendazole, amcinonide, 2-aminobenzimidazole, amisulpride, androsterone, aripiprazole, artemisinin, atomoxetine, atenolol, atenolol acid, atorvastatin, atropine, azoxystrobin, benexate HCI, benzophenone, 6-benzylaminopurine, bisphenol A, bromophenol, bupropion, candesartan, carbamazepine, carbendazim, cephanosporin, cetirizine, chlarithromycin, chloramphenicol, chlordiazepoxide, chlorophenol, cinnarizine, cis-diltiazem, cisapride, climbazole, codeine, cyflufenamid, desvenlafaxine, dexamethasone, dextromethorphan, diazepam, diazinon, dioxin, dioxin-like (PBDE), diphenhydramine, dipyridamole, diuron, efavirenz, estradiol, estrone ethinylestradiol, ethofumesate, famciclovir, famotidine, flufenamic acid, flurbiprofen, glibenclamide, griseofulvin, hydrocodone, ibuprofen, indomethacin, irbesartan, itraconazole, ketamine, ketoprofen, lamotrigine, lidocaine, linuron, losartan, manuterol, maropitant, meloxicam, methadone, metopropol mitomycin, morphine, venlafaxine (nor), nadolol, naproxen, nicotine, nifedipine, nimesulide, nitroglycerin, nonylphenol, 4-tOctylphenol, ofloxacin, omeprazole, oxybenzone, PGE2, pirimicarb, pirimiphos-ethyl, piroxicam, prednisolone, propranolol, pyrazophos, ranitidine, rutin, sertraline, siduron, sitagliptin, spironolactone, tacrolimus, tefenadine, ter-octyphenol, testosterone, thiabendazole, tiaprofenic acid, tolbutamide, tramadol, tributylphosphate (TBP), triclosan, trimethoprim, venlafaxine, voriconazole, warfarin, zisprasidone.

[0072] By means of the term “endocrine disrupting compound (EDC)”, reference is made to a compound having ED (Endocrine Disrupting) properties. In accordance with the present invention, a compound is considered to have ED properties if it shows an adverse effect, which is a consequence of its endocrine mode of action, in an intact organism or its progeny, or a nontarget organism, which adverse effect is a change in the morphology, physiology, growth, development, reproduction or life span of an organism, system or (sub)population that results in an impairment of functional capacity, an Impairment of the capacity to compensate for additional stress or an increase in susceptibility to other influences. By means of the term “endocrine mode of action”, reference is made to the action of altering the function(s) of the endocrine system.

[0073] EDCs are a group of highly heterogeneous synthetic chemicals used in a variety of settings. Some of the common chemicals included in this group are chemicals used in industries and their by-products such as polychlorinated biphenyls [PCBs], polybrominated biphenyls [PBBs] and dioxins; plastics such as bisphenol A (BPA); plasticizers (phthalates) and pesticides such as methoxychlor (MXC); chlorpyrifos and dichlorodiphenyltrichloroethane (DDT). Some EDCs were designed to have long half-lives for industrial purposes and are known as “persistent organic pollutants” (POPs) exemplified by PCBs, dichlorodiphenyldichloroethylene (DDE), dioxin, organochlorine pesticides and hexachlorobenzene (HCB). Examples of EDC compounds are, and not limited to: 1 ,7,7-trimethyl-3-(phenylmethylene)bicyclo[2.2.1]heptan-2-one, 2,2-dibromo- 2-cyanoacetamide, 4,”-(1-methylpropylidene)bisphenol; bisphenol B, 4,”- isopropylidenediphenol, 4-heptylphenol, branched and linear, 4-heptylphenol, Phenol, heptyl derivs. , Phenol, 4-(1 , 1 -diethylpropyl)-, Phenol, 4-(1 ,1 -dimethylpentyl)-, Phenol, 4-(1 ,2,2- trimethylbutyl)-, Phenol, 4-(1 ,2-dimethylpentyl)-, Phenol, 4-(1 ,3,3-trimethylbutyl)-, Phenol, 4- (1 ,3-dimethylpentyl)-, Phenol, 4-(1 ,4-dimethylpentyl)-, Phenol, 4-(1-ethyl-2,2-dimethylpropyl)-, Phenol, 4-(1-ethyl-1 ,2-dimethylpropyl)-, Phenol, 4-(1 -ethylpentyl)-, Phenol, 4-(1 -methylhexyl)-, Phenol, 4-(1 -propylbutyl)-, Phenol, 4-(3-ethylpentyl)-, Phenol, 4-(3-methylhexyl)-, Phenol, 4-(4- methylhexyl)-, Phenol, 4-(5-methylhexyl)-, Phenol, 4-[2-methyl-1-(1-methylethyl)propyl]-, 4-(2,3- dimethylpentan-2-yl)phenol, 4-(3-methylhexan-3-yl)phenol, Phenol, 4-tert-heptyl-, Phenol, 4- (1 ,1 ,3-trimethylbutyl)-, Phenol, 4-(1 ,1 ,2,2-tetramethylpropyl)-, Phenol, 4-(1-ethyl-3-methylbutyl)- , 4-tert-butylphenol, Ammonium perchlorate, Cyanamide, p-(1 ,1-dimethylpropyl)phenol, Phenol, alkylation products (mainly in para position) with C12-rich branched alkyl chains from oligomerization, covering any individual isomers and / or combinations thereof (PDDP), Phenol, dodecyl-, branched, phenol, (tetrapropenyl) derivatives, phenol, 4-dodecyl-, branched, Phenol, 4-isododecyl-, Phenol, tetrapropylene-, Phenol, 4-isododecyl-, Phenol, dodecyl-, branched, Sodium perchlorate, 4,’'-isopropylidenediphenol, butyl 4-hydroxybenzoate, Dicyclohexyl phthalate. Examples of pro-EDCs are 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol (Triton- Xi 00®) and nonylphenol polyethoxylates (nPnEOs). Both compounds are easily converted into EDCs in aerobic circumstances, thereby causing major damages especially in aquatic environments.

[0074] The membrane provided at step a) of the present invention is particularly beneficial in allowing the separation of pollutants such as EDCs in their complexed form. By means of the term “membrane”, reference is made to a layer of semi-permeable material suitable for separating a compound from a liquid. Various membranes can be used in the context of the present invention, such as and not limited to: non-porous polymeric nanofiltration (NF) and reverse osmosis (RO) membranes, mixed-matrix membranes, ceramic supported membranes, open-porous hydrophobic contactor membranes, non-porous hydrophobic polymeric membranes.

[0075] Further, the present invention comprises step b) of providing a first liquid stream e.g. an aqueous stream, at said first side, wherein said first liquid stream comprises the least one pollutant to be separated and a liquid.

[0076] In accordance with the present invention, by means of the term “stream”, reference is made to a stream of a liquid, such as a water stream. Water streams that can be treated according to the present invention are water streams from various sources, such as sewage streams, wastewater streams and industry effluents.

[0077] In accordance with the present invention, by means of the term “liquid stream”, reference is made to a stream of a liquid, such as a water stream. Water streams that can be treated according to the present invention are water streams from various sources, such as sewage streams, wastewater streams and industry effluents.

[0078] The present invention further comprises step c) of providing a complexing compound provided to complexing the at least one pollutant at either the first side or the second side of the membrane, thereby forming a molecular complex of said pollutant with said complexing compound.

[0079] By means of the term “complexing compound”, reference is made to a compound which is capable of forming a molecular complex, such as an inclusion complex, wherein one chemical compound (the "host") has a cavity into which a "guest" compound can be accommodated, which interaction between the host and guest involves van der Waals bonding.

[0080] The present invention further comprises step d) of permeating either the at least one pollutant or the liquid provided at step b) thorough the membrane provided at step a), thereby collecting at one side of the membrane, an amount of pollutant higher than the amount of pollutant at the other side of the membrane, thereby separating, at least partially, the at least one pollutant from the liquid as the molecular complex of said pollutant with said complexing compound. An advantage of the present aspect is that the use of a membrane allows for a fast, easy scalable separation that is based on proven technology.

[0081] The method according to the present invention hence provides a method for the separation of pollutants, such as EDCs, by means of a membrane, wherein a complexing compound is provided to allow said separation to be effective. According to a preferred embodiment of the present invention, the pollutant is an endocrine disrupting compound (EDC). According to an embodiment of the present invention, the pollutant is the EDC and the complexing compound is cyclodextrin, preferably p-cyclodextrin. Notably, other embodiments are not limited to EDC as it was found that several types of pollutants can be separated as described herein.

[0082] According to yet an embodiment of the present invention, the p-cyclodextrin is provided at a concentration lower than the solubility of p-cyclodextrin in water, preferably 75% of the solubility of p-cyclodextrin or lower, more preferably 60% of the solubility of p-cyclodextrin or lower.

[0083] According to an embodiment of the present invention, step a) further comprises providing an hydrophobic membrane which is permeable to the at least one pollutant and impermeable to the complexing compound, and step b) further comprises providing a second liquid stream comprising the complexing compound to said second side, wherein the membrane separates the first liquid stream from the second liquid stream; and step d) further comprises permeating the at least one pollutant from the first liquid stream to the second liquid stream, thereby separating the at least one pollutant from the liquid. An advantage of the present embodiment is that it selectively pulls the pollutant across the membrane without the need of passing the majority of the liquid of the first liquid stream through the membrane.

[0084] The present embodiment is represented in Fig. 1. According to the present embodiment, a pollutant is extracted (membrane extraction) from a liquid through a membrane, from a first side of said membrane to a second side, where at said second side a complexing compound is present, which drives the extraction and hence separation of said pollutant from said liquid. The pollutant may also be separated by filtration (membrane filtration), as illustrated in Fig. 3, both techniques (membrane extraction and membrane filtration) rely on the having the complexing compound present which “captures” the pollutant by forming a complex therewith at a side of the membrane. Typically, the pollutant in a “captured condition” cannot go through the membrane anymore. In this manner, the pollutant can be separated from the liquid, via both membrane extraction and membrane filtration.

[0085] In particular, Fig. 1 illustrates an embodiment of the present invention wherein the first liquid stream, comprising the pollutant is represented at the left of the membrane, and the second liquid stream, comprising the complexing compound is represented at the right of the membrane. The membrane, which is semi-permeable to the pollutant is positioned vertically, at the center of the image. By means of the embodiment of the present invention the pollutant is carried over to the second liquid stream from the first liquid stream. After the pollutant found itself at the other side of the membrane, it is complexed by the complexing agent. In Fig. 1 , the complexing agent is p-cyclodextrin, nevertheless, other complexing agents could be used, which choice of complexing agent depends on the pollutant to be separated, which complexing agents are known in the state of the art. It was found that p-cyclodextrin is particularly effective at complexing pollutants, specifically EDCs and / or the other (micro)pollutants as described herein. Fig. 1 (showing a membrane extraction) illustrates that the complexing compound [3] is provided in a dissolved state and / or is dissolved at the second side (back side or downstream side, also called the permeate side) of the membrane. The complexing compound in dissolved condition has the benefit of moving more freely so as to improve the complexing with the pollutant. The pollutants [1] are provided at the first side (front side or upstream side, also called feed side), pass through the membrane [5] and complex with the complexing compound. It the complexed condition, they typically cannot go back through the membrane. In a likewise manner, Fig. 3 (showing a membrane filtration) illustrates that the pollutants [1] form a complex with the complexing compound [3] at the feed side. In complexed condition, they cannot go through the membrane and are thus kept at one side of the membrane. Fig. 3 further shows that the complexing compound is provided in a dissolved state and / or is dissolved at the first side (feed side) of the membrane [5].

[0086] The “dissolved state” refers to the condition where a substance, i.e. the complexing compound becomes uniformly distributed in a solvent (i.e. the liquid with the pollutant itself or another solvent), forming a solution. In this state, individual complexing compounds are evenly dispersed throughout.

[0087] Preferably, the complexing compound is provided at either the first side or the second side of the membrane in a concentration below 280 g / L within the liquid as measured at 25°C, 1 atm, preferably below 260 g / L.

[0088] Preferably, the complexing compound is Beta Cyclodextrin and is provided at either the first side or the second side of the membrane in a concentration below 100 g / L within the liquid as measured at 25°C, 1 atm, preferably below 50 g / L, more preferably below 20 g / L, most preferably below 19 g / L; and / or preferably, the complexing compound is Alfa Cyclodextrin and is provided at either the first side or the second side of the membrane in a concentration below 150 g / L within the liquid as measured at 25°C, 1 atm, preferably below 140 g / L, more preferably below 130 g / L, most preferably below 128 g / L.

[0089] Fig. 2A-2B illustrates the monitoring of the concentration of various EDCs separated according to the embodiment of the invention also described in accordance with Fig. 1 , wherein said the complex mixture comprises 17-alpha-ethinylestradiol (EE2) (Fig. 2A), 4-tert-octyl phenol (4tOP) (see Fig. 2B), BPA (see Fig. 2C) and testosterone (see Fig. 2D). Based on said figures, it appears clear that according to the present method EDCs can be separated in good amounts in a matter of 5 to 10 minutes, in particular, the concentration of these pollutants on the feed side decreases drastically after just 5 minutes of separation.

[0090] For the present embodiment of the invention, it was found particularly beneficial to provide membranes with a high hydrophobicity, i.e. membranes that have a contact angle of at least 90°, preferably at least 100° for the liquid of the first liquid stream. This allows avoiding wetting with the aqueous feed and extractant phases. Further beneficial membranes comprise open-porous hydrophobic contactor membranes like polytetrafluoroethylene (PTFE) based membranes with pore sizes below 0.2 pm and preferably below 0.1 pm. Other possible chemistries are polyvinylidene fluoride (PVDF), polypropylene (PP) and polyethylene (PE). In this case of open- porous ultrafiltration (UF) or microfiltration (MF) membranes, these membranes need to be impregnated with a suitable non-polar organic solvent. Examples of solvents utilized to impregnate such membranes are heptane and undecane. Due to the impregnation, there is a risk of leakage of the solvent to the feed or extractant phase, and typically a small overpressure at the feed side (typically 100 mbar) is maintained to avoid this. Further, to avoid any leakage of impregnated solvents, non-porous hydrophobic polymeric membranes, like polydimethyl siloxane (PDMS) based membranes can be used in the dry state. E.g. PDMS membrane of supplier Pervatech. The extraction rate of bisphenol A (BPA), an EDC, with this membrane was 30 mg / m2h. To increase the extraction rate organic solvent impregnation can be used (leakage risk much smaller due to the non-porosity of the membranes), as was seen for the same membrane impregnated with heptane, the extraction rate of BPA increased to 88 mg / m2h. Other beneficial membranes are open or fine-porous ceramic membranes, functionalized for high hydrophobicity as e.g. silanated 0.1 pm alumina membranes as mentioned in Schnittger et al., 2021 , (in case of open pores with impregnation, in case of fine pores with or without impregnation); or membranes with hydrophobic polymeric brushes grafted to their pore surface created through the SI-ATRP technique as disclosed in W02020016068A1 . Yet membranes beneficial to carry out the present embodiment are ceramic supported membranes with a dense hydrophobic polymeric.

[0091] According to an embodiment of the present invention, step a) further comprises providing the membrane impermeable to the at least one pollutant and the complexing compound, and permeable to the liquid of the first liquid stream; and step b) comprises providing the liquid stream with a complexing compound adapted to complex the at least one pollutant; and step d) further comprises permeating the liquid from the first liquid stream, thereby separating the at least one pollutant from the liquid. An advantage of the present embodiment is that is fast and easy scalable.

[0092] The present embodiment is represented in Fig. 3. According to the present embodiment, a pollutant is complexed by a complexing agent at one side of a membrane. In Fig. 3, the complexing agent is p-cyclodextrin, nevertheless, other complexing agents could be used, depending on the pollutant to be separated, which complexing agents are known in the state of the art. In Fig. 3, the first liquid stream is represented at the top of the figure. At the bottom of the Fig. 3, (and at the opposite side of the membrane the pollutant was provided) liquid non comprising the pollutant is collected, thereby allowing separation of said pollutant from said liquid. By means of the present embodiment liquid such as wastewater is concentrated in pollutant and complexing agent amount.

[0093] According to the present embodiment, various membranes can be provided, nevertheless, it was found advantageous to provide non-porous polymeric nanofiltration (NF) and reverse osmosis (RO) membranes, like polyamide-based membranes with molecular weight cut off below 500 Da and preferably below 300 Da. According to an embodiment of the present invention, the membrane has molecular weight cut off (MWCO) from 0.1 Da to 500 Da, preferably from 0.1 Da to 300 Da. The present MWCO is particularly beneficial at retaining complexed pollutants. Preferably, the membrane has a molecular weight cut off between 50 and 300 Da and / or an average pore size between 0.5 and 150 nm.

[0094] By means of the term “molecular weight cut off”, also abbreviated as MWCO, reference is made to a parameter used to describe pore size distribution and retention capabilities of membranes. It is defined as the lowest molecular weight (in Daltons) at which greater than 90% of a solute with a known molecular weight is retained by the membrane.

[0095] Other possible chemistries are cellulose acetate and polypiperazine amide. Eg. HRX high rejection reverse osmosis polyamide membrane from Koch Separation Solutions showed >99% retention of cyclodextrin. Fine-porous inorganic membranes functionalized with an organic functional group have also been found advantageous.

[0096] In particular, according to yet a further embodiment of the present invention, the membrane is a ceramic membrane functionalized with alkyl groups, preferably methyl groups. An advantage of the present embodiment is that such alkyl functionalized membranes show higher retentions but without affecting the fluxes across the membrane. For example tests with methyl grafted 0,9 nm TiO2 membranes have shown higher retentions and similar fluxes compared to native 0,9 nm TiO2 membranes. Without being bound by theory, this is probably due to the somewhat lower polarity of the membrane pore surface (due to the methyl grafting). It was even found that these alkyl functionalized inorganic membranes have slightly higher but definitely quite comparable fluxes with the hydrophobic polymeric membranes.

[0097] Preferred pore sizes range from about 0.5 or 1 nm. Good results were obtained with a 0.9 nm titania membrane of supplier Inopor, grafted with a methyl group using the Grignard grafting technology as disclosed in WG2010106167A1 . This membrane gave >97% retention of cyclodextrin. We remark that for the native 0.9 nm titania membrane without the functionalization, we obtained lower retentions for the cyclodextrin (60%). This lower retention is attributed to a higher membrane-solute interaction. Other membranes expected to be suitable: mixed-matrix membranes (polymeric membranes filled with inorganic particles), or ceramic supported membranes with a polymeric NF / RO top layer, all with a cut-off below 500 Da.

[0098] The present embodiment, which allows the separation of pollutants such as EDCs from a liquid, was found to be preferably carried out with a transmembrane pressure form 5 bar to 60 bar, preferably 10 to 30 bar. In particular, according to this embodiment of the invention step d) is performed with a transmembrane pressure from 5 to 60 bar, preferably 10 to 30 bar. An advantage of the present embodiment is that the separation is more efficient. According to yet a further embodiment of the present invention, step d) is performed with a crossflow velocity from 0.1 m / s to 4 m / s, preferably 0.3 m / s to 2 m / s.

[0099] By means of the term “cross-flow velocity”, also abbreviated as CFV, reference is made to the linear velocity of the flow tangential to the membrane surface.

[0100] EXPERIMENTAL PART

[0101] Materials and Methods

[0102] Materials

[0103] The experiments were executed using bisphenol A (BPA, >99%, Sigma-Aldrich), 4-tert- octylphenol (4-tOP, 97%, Sigma-Aldrich), 17-alpha-ethinylestradiol (EE2, >98%, Sigma-Aldrich) and testosterone (>99%) from Sigma-Aldrich. Beta-cyclodextrin was obtained from Merck. For the UPLC-MS measurements, all analytes were obtained in UPLC-MS grade from Sigma- Aldrich. UPLC-MS grade water and methanol were obtained from Biosolve and NFUOH (20% solution, UPLC-MS grade) was obtained from Sigma-Aldrich.

[0104] Test set up

[0105] Membrane extraction experiments were performed with the set-up presented in Fig. 1. The membrane module physically separates the feed solution (left side) and the extractant solution (right side) which are both kept in glass bottles with 0.4 L working volume. In order to avoid leakage of the extractant solution into the feed solution, the system was always started by first switching on the feed phase pump. Samples of feed and extractant solution were taken at the start and at regular intervals.

[0106] Methods

[0107] All samples resulting from the experiment depicted in Example 1 were analyzed using the LCK 345 test kits from Hach (phenols). For the other examples, the samples were analyzed by UPLC- MS (ACQUITY UPLC H-Class PLUS System). The analysis was performed using a ACQUITY UPLC® BEH C18 column (particle diameter: 1.7pm, 2.1 mm x 50mm). The mobile phase used was a mixture of 0.05% NFUOH in water (A) and methanol (B). Gradient elution was performed, starting at 65% A, to 5% A in 3 minutes. After that, 5% A was held for 1 .2 minutes, whereafter the column was preconditioned again with 65% A for 2.8 minutes. The flow was set at 0.6 mL / min, column temperature at 60°C and injection volume at 10 pL. Analytes were detected using a Acquity qDa Mass detector in negative mode, at a capillary voltage of 0.8 kV, cone voltage of 15 V, source temperature of 120 °C and probe temperature of 600°C. Bisphenol A was detected at m / z 227.11 , 17-alfa-ethinylestradiol at m / z 295.17, testosterone at m / z 287.2 and 4-tert-octyl phenol at m / z 205.16.

[0108] Results Example 1 -Separation of EDCs by Nanofiltration / Reverse Osmosis

[0109] Experimental details of our experiments:

[0110] Transmembrane pressure: 10-30 bar (broader useful range: 5-60 bar);

[0111] Cross-flow velocity: 0.3- 2 m / s (broader useful range: 0.1-4 m / s);

[0112] Temperature: 20 °C (many other temperatures possible, depending on T-stability of membranes and compounds, influence on economics).

[0113] Example 2 - Separation of mixture of EDCs by Membrane Extraction

[0114] According to an embodiment of the present invention, extraction experiments were conducted with the following parameters: at the extractant side a concentration of p-cyclodextrin of 10 g / L, a temperature of 20 °C, feed and extractant volumes of 400 mL.

[0115] The table here below illustrates the results of comparative Experiments conducted by variating the membrane type, flow, feed mixture, impregnation.

[0116] Table 1

[0117] Table 1 illustrates that the method according to an embodiment of the present invention can be applied to a variety of feed compositions in an effective way (high extraction efficiency). Further, The present method is compatible with different membranes and works well with or without membrane impregnation.

[0118] In table 1 , and the experiments, by “Complex mixture” reference is made to a mixture comprising 3.32 ppm of BPA, 3 ppm of 4-tert-octylphenol (4tOP), 4.3 ppm of 17-alpha-ethinylestradiol (EE2), 4.19 ppm testosterone (Test). For this complex mixture, the results of extraction of BPA, 4tOP, EE2, and Test, are illustrated in Fig. 2A-D. These figures show that several pollutants can be removed simultaneously by the claimed method.

[0119] Example 3A-3B

[0120] In the examples 3A and 3B below, it is shown that the separation of different types of pollutants has been researched. It was found that the complexing compound could be used on several types of pollutants. The pollutant can be EDC or can be another pollutant, such as ciprofloxacin, citalopram, diazinon, diclofenac, ibuprofen.

[0121] Example 3A - Separation of other pollutants by Membrane Extraction

[0122] Several pollutants (including pollutants other than EDC) can also be separated by the method as described herein. To review several types of pollutants, the complexing concept for separation was tested on several components having a wide range of biological and physicochemical properties.

[0123] Table 2

[0124] In this example 3A, the separation of several hormones (EE, T, BPA, tOP), as wel as pollutants with a non-charged or charged chemistries, i.e. see diazinon, citalopram, was tested. The separation was performed by using cyclodextrin.

[0125] Thus, according to embodiment and generally applicable herein, the pollutant to be separated is chosen from a hormone, including EE (Ethinyl Estradiol), T (Testosterone), BPA (Bisphenol A), tOP (Tri-ortho-cresyl phosphate), a pesticide (such as Diazinon), a medical drug (such as Citalopram), an EDC (endocrine disrupting compound) or combinations thereof. In particular, and generally applicable herein, the pollutant is chosen from a pesticide, a medical drug, an EDC or combinations thereof.

[0126] Example 3B - Separation of other pollutants by Membrane Filtration

[0127] It is believed that the same or similar benefits could be achieved irrespective of providing the complexing agent (or compound, both terms are used interchangeably herein) at the first side (filtration) or the second side (extraction) of the membrane.

[0128] The cyclodextrin thus provides for benefit acquiring and separating several types of pollutants.

[0129] Generally, the findings indicate that the cyclodextrin may accommodate several types of pollutants. It is believed that the ample types pollutants can be held by the cyclodextrin as a guest molecule in the central cavity of the cyclodextrin.

[0130] The pollutants that can be separated by aid of the cyclodextrin as a complexing compound can thus, in general, be chosen from: hydrophobic compounds, steroids, aromatic compounds, or compounds with hydrogen bonding capabilities of combinations thereof.

[0131] It is believed that cyclodextrins' hydroxyl groups on the exterior surface can form hydrogen bonds with guest molecules that have polar or hydrogen-bonding functional groups. For instance, drugs and organic molecules containing hydroxyl, carbonyl, or amino groups can interact with cyclodextrins through hydrogen bonding in addition to hydrophobic interactions.

[0132] Additionally, any pollutant that is a compound with a size fitting into the cavity of the cyclodextrin can be separated, such as pollutants having a molar mass below 500 g / mol, preferably below 400 g / mol, such as between 10 g / mol to 500 g / mol, in particular between 200 - 400 g / mol.

[0133] Example 4 - different types of cyclodextrin

[0134] Cyclodextrin can have several forms, examples are a-cyclodextrin, p-cyclodextrin, and y- cyclodextrin. Several forms of cyclodextrin have been considered and the following cyclodextrins are identified as useful.

[0135] Alpha-Cyclodextrin has six glucose units and has a molar mass of approximately 972.85 grams per mole (g / mol). Beta-Cyclodextrin has seven glucose units and has a m molar mass of approximately 1134.99 g / mol. Gamma-Cyclodextrin has eight glucose units and has a molar mass of approximately 1297.12 g / mol.

[0136] References

[0137] 1 . Schnittger, J., et al. "Hydrophobic ceramic membranes in MD processes-lmpact of material selection and layer characteristics." Journal of Membrane Science 618 (2021 ): 118678.

Claims

CLAIMS1 . A method for the separation of a pollutant from a liquid, comprising the steps of: a) providing a membrane comprising: a first side, and a second side; b) providing a first liquid stream at said first side, comprising: at least one pollutant to be separated and, a liquid; c) providing a complexing compound for the at least one pollutant at either the first side or the second side of the membrane, and wherein the complexing compound is provided in a dissolved state and / or is dissolved at either the first side or the second side of the membrane, preferably wherein the complexing compound is a cyclodextrin; d) permeating either the at least one pollutant or the liquid provided at step b) through the membrane provided at step a), thereby collecting at one side of the membrane, an amount of pollutant higher than the amount of pollutant at the other side of the membrane, thereby separating the at least one pollutant from the liquid.

2. The method according to claim 1 , wherein the membrane is configured to allow the liquid to pass through while retaining one or more pollutants that formed a complex with the complexing compound.

3. The method according to any of the previous claims, wherein the pollutant has a molar mass below 500 g / mol, preferably below 400 g / mol, such as a molecular weight between 200 - 400 g / mol.

4. The method according to any of the previous claims, wherein the membrane has molecular weight cut off of lower than 1000 Da, preferably lower than 950 Da, more preferably lower than 750 Da, even more preferably lower than 500 Da.

5. The method according to any of the previous claims, wherein the membrane is impermeable to the complexing compound.

6. The method according to the previous claim, wherein the membrane is permeable to the at least one pollutant provided at the first side of the membrane, whereby the complexingcompound is provided at the second side; or wherein the membrane is permeable to the liquid of the first liquid stream, whereby the complexing compound is provided at the first side of the membrane such that the complexing compound binds with the pollutant at the first side and wherein the membrane is impermeable to the pollutant bound to the complexing compound.

7. The method according to any of the previous claims, wherein step a) comprises providing the membrane being hydrophobic and permeable to the at least one pollutant and impermeable to the complexing compound, and step b) further comprises providing a second liquid stream comprising the complexing compound at said second side, wherein the membrane separates the first liquid stream from the second liquid stream; and step d) further comprises permeating the at least one pollutant from the first liquid stream to the second liquid stream, thereby separating the at least one pollutant from the liquid, wherein step d) is preferably performed with an overpressure at the feed side of from 50 mbar to 200 mbar and / or wherein at step a) the hydrophobic membrane preferably has a contact angle of at least 90° for the liquid of the first liquid stream, preferably at least 100.

8. The method according to claim 1 , wherein step a) comprises providing the membrane impermeable to the at least one pollutant and the complexing compound, and permeable to the liquid of the first liquid stream; and step b) comprises providing the first liquid stream with a complexing compound adapted to complex the at least one pollutant; and step d) further comprises permeating the liquid from the first liquid stream, thereby separating the at least one pollutant from the liquid, the membrane preferably having a molecular weight cut off from 0.1 Da to 500 Da, more preferably 0.1 Da to 300 Da.

9. The method according to the previous claim, wherein the membrane is a ceramic membrane functionalized with alkyl groups, preferably methyl groups.

10. The method according to any one of the previous two claims, wherein step d) is performed with a transmembrane pressure from 5 to 60 bar, preferably 10 to 30 bar.11 . The method according to any one of the previous three claims, wherein step d) is performed with a cross-flow velocity from 0.1 m / s to 4 m / s, preferably 0.3 m / s to 2 m / s.

12. The method according to any of the previous claims, wherein the pollutant is chosen from an organic compound, hydrophobic compound, a hydrogen bonding compound, a drug, an agrochemical, an industrial chemical, a hormone, a steroid, a medication, an environmental contaminant, a persistent micropollutant, an endocrine disrupting compound (EDC) or combinations thereof.

13. The method according to any one of the previous claims, wherein the pollutant is an endocrine disrupting compound (EDC) and the complexing compound is a cyclodextrin, preferably p-cyclodextrin.

14. The method according to any one of the previous claims, wherein the complexing compound provided at step c) is cyclodextrin, preferably p-cyclodextrin.

15. The method according claim 14, wherein the first liquid stream comprises water and wherein the p-cyclodextrin is provided at a concentration lower than the solubility of p-cyclodextrin in water, preferably 75% of the solubility of p-cyclodextrin or lower, more preferably 60% of the solubility of p-cyclodextrin or lower.

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