"APPARATUS AND METHOD FOR A SEPARATION THROUGH MAGNETIC

NANOPARTICLES"

[0001] This invention relates to an apparatus and a method for separating at least one target substance from a liquid ' phase .

[0002] A constant problem in production and industrial purification plants relates to the low cost separation of specific substances dissolved, suspended or dispersed in a solvent. These substances can be pollutants or have an economic value that is sufficiently high to justify their isolation from the related solution, suspension or dispersion, and subsequent recovery.

[0003] In the past, the use of magnetic particles was attempted for this purpose, as illustrated for example in the prior. art document US8158007B2. However, the difficulty of creating stable colloidal suspensions of nanoparticles in an aqueous phase drastically limits their exploitation on an industrial scale.

[0004] This invention relates to the preceding context, proposing to provide a method and an apparatus based on the use of stable colloidal suspensions of magnetic nanoparticles, able to overcome the aforesaid drawbacks, and in particular to provide a system capable of making possible the separation of a variety of target substances in a simple and repeatable way and at an extremely low cost.

[0005] This goal is achieved by means of an apparatus according to claim 1 and by means of a method according to claim 11. Advantageously, the method and apparatus, of this invention ensure maintenance of the colloidal stability in aqueous phase of the discussed stable colloidal suspension of nanoparticles , even when in complex form with the target substance. The claims dependent on these show preferred embodiments.

[0006] The purpose of this invention will now be described in detail, with the help of the accompanying drawings, provided by way of a non-limiting example, in which:

[0007] - Figures la, lb and lc respectively show a perspective view, a top view and a front view of an apparatus covered by this invention, according to a possible embodiment;

[0008] - Figures 2a, 2b and 2c respectively show a perspective view, a top view and a front view of a separation module according to a possible embodiment;

[0009] - Figure 3 is a diagram of the process according to a variant of this invention.

[0010] In reference to the above figures, reference number 1 identifies, in its entirety, an apparatus for separating at least one target substance from a liquid phase .

[0011] For example, the target substance may be solubilised, dispersed or suspended. in such phase.

[0012] According to different embodiments, the target substance could comprise or consist of one or more substances selected from curcumin, avidin, xanthine oxidase, rhodamine isothiocyanate, polyphenols, enzymes, peptides, proteins, DNA, RNA, oligonucleotides, phosphates, chromates, arsenites, arsenates, citrinin, oxytetracyline, tannic acid, pioverdine, chlorine, or mixtures thereof.

[0013] According to a particularly advantageous embodiment, the target substance could comprise or consist of lactoferrin, optionally in combination with one or more substances selected among those mentioned above.

[0014] Preferably, this apparatus is modular, which is to say, expandable at will, or as needed, by selecting a suitable number of the modules described below.

[0015] The apparatus 1 comprises at least a module 2 for mixing at least one target substance and a stable colloidal liquid suspension of magnetic nanoparticles to obtain substance-nanoparticle complexes.

[0016] In other words, in the mixing module 2 not only the target substance and the nanoparticles are mixed homogeneously with each other, but in such module 2 the necessary conditions (for example the temperature, pressure, composition and saline concentration and/or nature of the solvent) are also created for the formation of these complexes, which in turn remain in a stable colloidal liquid suspension.

[0017] According to a variant, the mixing module 2 could be temperature-controlled to promote formation of the substance-nanoparticle complexes.

[0018] According to a further variant, the mixing module 2 delimits an internal compartment for receiving the target substance and the colloidal suspension of magnetic nanoparticles , in which a mechanical mixing member could be inserted in a rotatable manner.

[0019] For example, the mixing module 2 could be fed through supply tanks 78, 80 respectively of the target substance and the liquid colloidal suspension of magnetic nanoparticles (for example in water) . For example, the target substance could be pre-mixed in a further liquid, so that liquid and substance can be supplied through a single tank.

[0020] According to a particularly advantageous embodiment, the magnetic _, nanoparticles comprise or consist of superparamagnetic nanoparticles of stoichiometrically pure maghemite.

[0021] Preferably, the magnetic nanoparticles usable in this invention could be manufactured according to the procedure discussed in document WO2012010200A1.

[0022] Still more preferably, the magnetic nanoparticles used should be able to create stable colloidal suspensions in aqueous phase for at least six months, without the need of a coating, by means of treatment in an ultrasonic bath.

[0023] According to these variants, the concentration of magnetic nanoparticles in colloidal suspension in the liquid phase is preferably about 100-1000 mg/l, optionally 200-800 mg/l, advantageously 400-600 mg/l, preferably about 500 mg/l.

[0024] According to a first embodiment, the magnetic nanoparticles are free of a superficial functionalisation .

[0025] According to a second embodiment, the magnetic nanoparticles are functionalised, directly or indirectly, in order to bind the target substance. According to an advantageous aspect, the possible functionalisation (or plurality of functionalisations ) may be carried out in aqueous phase and ensure the colloidal stability of the suspension of magnetic nanoparticles.

[0026] According to other embodiment variants, the size distribution of the magnetic nanoparticles could be in the range 5-50 nm (for example 10-12 nm) , and/or the polydispersity index of the magnetic nanoparticles could be in the range 1.02 to 1.05.

[0027] Apparatus 1 comprises at least a first magnetic separation module 4 comprising a separation chamber 6, in fluidic communication with the mixing module 2 to receive therefrom a stable colloidal liquid suspension of the substance-nanoparticle complexes, and at least a first magnetic element 8 functionally connected to the separation chamber 6 to magnetically attract said complexes .

[0028] In this way, the substance-nanoparticle complexes remain anchored to the element by virtue of the magnetic properties of the nanoparticles, separating from the colloidal suspension and concentrating the complexes in the region adjacent to said magnetic element, while the liquid surrounding the complexes will not undergo any magnetic influence of relevance.

[0029] In the embodiments shown, the first magnetic element 8 could comprise a magnetised plate 74, preferably arranged below the separation chamber 6.

[0030] For example, the plate 74 may be at least partially made of iron, advantageously steel, preferably FE360.

[0031] According to a variant, a plurality of permanent magnets (not shown) could be placed in correspondence of the magnetised plate 74 (for example, placed at least partly inside it) in order to generate a substantially homogeneous magnetic field in said chamber 6.

[0032] It should be clarified that, in this description, any feature referring to the first magnetic separation module 4 could be equally applied also to the second magnetic separation module 14, described below. In fact, in a preferred embodiment, these modules could function and be shaped in a substantially corresponding or identical way.

[0033] According to an embodiment, the first magnetic separation module 4 could also serve as a washing module of the substance-nanoparticle complexes. Specifically, once the liquid containing the aforesaid complexes has flowed out, and with the magnetic element still magnetised, a magnetically inert washing liquid could be introduced into the separation chamber 6 in order to remove any unwanted substances from, the complexes.

[0034] According to a further embodiment, fluidically downstream of the first magnetic separation module, there could be provided a separate washing module, for example having a magnetic functioning according to a mode constructively similar to the above-mentioned first module, or suitable to cause the separation of the complexes according to a different principle, for example, physical, chemical or chemical-physical. [0035] According to a still further embodiment, the washing in the first magnetic separation module 4, or in the separate washing module, could be pressurised, for example by spraying.

[0036] For example, the separation chamber 6 and the mixing module 2 communicate via a first conduit 36, along which at least a first pump 38 is optionally arranged.

[0037] Optionally, the apparatus 1 could comprise a plurality of first magnetic separation modules 4, for example arranged mutually in parallel, suppliable through the mixing module 2.

[0038] Merely by way of example, between the mixing module 2 and ^' the first magnetic separation modules 4, the apparatus 1 could comprise (not illustrated) deviating means in order to direct the liquid phase containing the substance-nanoparticle complexes - also defined stable colloidal suspension of the substance-nanoparticle complexes - towards the different modules, in a selective manner. According to a variant, the deviating means could comprise one or more solenoid valves.

[0039] According to an advantageous variant, the separation chamber 6 is supported in an oscillating way with respect to the first magnetic separation module 4, in order to distribute the contents of this chamber (preferably uniformly) . [0040] For example, the separation chamber 6 could be reciprocating in a plane, or it could be rotatable about at least a rotation axis.

[0041] Preferably, the apparatus 1 comprises at least a splitting module 10 of the substance-nanoparticle complexes which defines a mixing compartment 12 communicating with the separation chamber 6 and which contains one or more release reactants of the target substance from said complexes.

[0042] In other words, inside the splitting module 10, the aforesaid complexes in the stable colloidal suspension are again separated into their constituents (which is to say, target substance, magnetic nanopart icles and liquid) , in particular through the action of at least one release reactant. Advantageously, in the splitting module, the nanoparticles disconnected from the target substance remain in a colloidal solution of magnetic nanoparticles .

[0043] According to a possible variant, the transport of the substance-nanoparticle complexes from the separation chamber 6 to the splitting module 10 could occur by means of a further liquid (for example a washing liquid) supplied to the aforesaid chamber 6, in particular, after the first magnetic element 8 has been deactivated or moved sufficiently away from the chamber (in this regard, see below) .

[0044] Preferably, in -the inner compartment of the splitting module 10, a mechanical mixing member could be inserted.

[0045] In the embodiment shown in Figure lb, the apparatus 1 could comprise a splitting module 10 alongside the mixing module 2. According to this variant, each module 2, 10 could include its own mechanical mixing member 28, 28' wherein, preferably, these members may be moved by motor means 70 common to both.

[0046] In the diagram of Figure 3, the washing liquid tank is indicated by the number 40. The second conduit that leads from this tank 40 to the separation chamber 6 is instead indicated by the number 42. From the separation chamber 6 to the splitting module 10, the connection is instead made through a third conduit 46. Optionally, along one or both of such conduits 42, 46 at least one pump 44,48 could be arranged.

[0047] With regard to the liquid from which the substance- nanoparticle complexes were taken (which is to say, the aqueous phase that previously created the stable colloidal suspension) , it could be conveyed to a discard tank 58 via a fifth conduit 60.

[0048] For example, depending on the nature of the substance-nanoparticle bond operating in the complexes, the release reactant could be a saline solution at suitable pH, composition and concentration, or one or more organic solvents.

[0049] In the diagram of Figure 3, the release reactant is fed via a reactant tank 50 and a respective fourth conduit 52 terminating in the splitting module 10.

[0050] According to a preferred embodiment, the release reactant could comprise a buffer solution of suitable pH, composition and concentration, or one or more organic solvents. For example, the release reactant could comprise a concentration between 0.5 and 2.5 M of NaOH, NaCl, KC1, KOH, NH40H, NH4C1 or mixtures thereof, and ethanol between 10 and 100%wt.

[0051] The apparatus 1 also comprises at least a second magnetic separation module 14, placed fluidically downstream of the splitting module 10, to separate the. target substance from a stable colloidal liquid suspension of magnetic nanoparticles.

[0052] It follows that, since the target substance is by now disconnected from the magnetic nanoparticles and the latter are returned in stable colloidal suspension, in the second magnetic separation module 14 the mixture is again separated to isolate the target substance.

[0053] More precisely, the magnetic nanoparticles will be magnetically anchored in the module analogously to what was discussed with regard to the first magnetic separation module, while the target substance and the liquid of the said suspension will not undergo any magnetic influence and can be separated from the magnetic nanoparticles, for example by flowing out from the module, in particular for a possible subsequent purification .

[0054] For example, the splitting module 10 and the second separation module 14 could be connected by means of a sixth conduit 54, along which is optionally arranged a pump 56.

[0055] Advantageously, · the second magnetic separation module 14 comprises a recovery chamber 16, located downstream of the splitting module 10 to receive from the latter the target substance divided from the magnetic nanoparticles, and at least a second magnetic element 18 to attract the magnetic nanoparticles.

[0056] As discussed, with regard to advantageous or preferred variants of the second magnetic separation module 14, reference is made to the features of the first magnetic separation module 4.

[0057] According to a particularly advantageous embodiment, the second separation module 14 is . fluidically connected to the mixing module 2 so as to create a recirculation of at least part of the stable colloidal liquid suspension of magnetic nanoparticles .

[0058] According to a variant, the transport of the magnetic nanopartxcles in stable liquid suspension from the second separation module 14 to the mixing module 2 could be performed through a seventh conduit 62, effecting the related transport by means of a further liquid. For example, the further liquid could comprise the washing liquid coming from the tank 40, through an eighth conduit 64 terminating in the second separation module 14.

[0059] Optionally, downstream of the second separation module 14 there could be provided a collection tank 72 inside which can be made to flow the magnetic nanoparticles in stable liquid suspension, for example through the seventh conduit 62, optionally effecting the transport by means of. a further liquid (for example the washing liquid) .

[0060] It follows that, since the magnetic nanoparticles do not undergo a substantial physical or chemical deterioration, they may be reused for an indefinite number of cycles.

[0061] As regards the target substance, it may finally be conveyed to a product tank 64 through a ninth conduit 66 exiting from the recovery chamber 16. Optionally, along this conduit 66 a pump 68 could be arranged. [0062] According to the illustrated variants, the first magnetic element 8 (and optionally the second magnetic element 18) is functionally connected to a bottom wall 20 of the separation chamber 6 (and optionally to a bottom wall 22 of the recovery chamber 16) , where the first magnetic element (and optionally the second magnetic element) and the aforesaid wall could be moved together/apart to modulate the intensity of the magnetic field acting on the substance-nanoparticle complexes (and optionally on the magnetic nanoparticles ) .

[0063] According to an embodiment, the first magnetic element 8 (and optionally the second magnetic element 18) comprises the magnetised plate 74 placed below the separation chamber 6 (and optionally below the recovery chamber 16) , and where the bottom wall 20 of the separation chamber 6 (and optionally the bottom wall 22 of the recovery chamber 16) is movable in relation to the aforesaid plate 74 to modulate the magnetic field.

[0064] According to a further variant, apparatus 1 could comprise, as first magnetic element and/or as second magnetic element, one or ^' more electromagnets operatively connected to a bottom wall of the separation chamber and/or to a bottom wall of the recovery chamber, wherein the intensity of the magnetic field acting on the substance-nanoparticle complexes and/or on the magnetic nanoparticles is adjustable by modulating the current intensity fed to the electromagnet or to the plurality thereof .

[0065] In any case, whatever the magnetic field generation mode selected, the magnetic field in correspondence, of the bottom wall 20, 22 of at least one of the modules 4, 14 described above is preferably adjusted in intensity to a value equal to, or smaller than, about 150 millitesla (for example in a range between 20-80 millitesla), in order to promote a re-suspension of the substance- nanoparticle complexes and/or of magnetic nanoparticles in a stable colloidal suspension.

[0066] In fact, the authors of this invention have understood that the application of an excessively intense magnetic field to the nanoparticles, even when possibly bound in complexes, produces a magnetic alteration of the colloidal stability of these such as to prevent a subsequent stay in suspension, and thus, purely by way of example, affecting the subsequent phases of washing and/or release of the target substance, as well as possible re-use in the recirculation phase.

[0067] In other words, the application of a magnetic field of excessive intensity to the magnetic nanoparticles, optionally bound in the complexes, could destabilise the corresponding suspensions, thus making the nanoparticles unsuitable for separation of the target substance or the plurality of them.

[0068] With regard to the conformation of the bottom wall 20 of the separation chamber 6, and optionally of the bottom wall 22 of the recovery chamber 16, according to an exemplary embodiment, at least one of said walls could have a surface roughness equal to or less than 0.01 Ra mm (for example of approximately 0.001 to 0.005 Ra mm), in order to limit the surface adhesion of the substance- nanoparticle complexes and/or of the magnetic nanoparticles .

[0069] According to an advantageous embodiment, at least the bottom wall 20 of the separation chamber 6 and/or at least the bottom wall 22 of the recovery chamber 16 could comprise a glass surface, which interiorly delimits the separation chamber 6 and/or the recovery chamber 16.

[0070] According to a further embodiment, at least the bottom wall 20 of the separation chamber 6 and/or at least the bottom wall 22 of the recovery chamber 16 could comprise a non-stick surface, in .order to reduce the possible surface adhesion phenomena of the magnetic nanoparticles and/or of the substance-nanoparticle complexes.

[0071] Preferably, in the first 4 and/or second 14_ magnetic separation module, the liquid head is adjusted so as to reach a maximum level equal to, or smaller than, about 7 mm, for example 0.1 to 5 mm.

[0072] In fact, according to this variant, it has proved to be advantageous to work on reduced heads, and preferably on broad distribution surfaces of the liquid on the bottom wall 20, 22 since, as it has been discussed previously, too high intensities of the magnetic field lead to a risk of impossibility to re-suspend the magnetic nanoparticles .

[0073] For example, such level adjustment could be. effected through the first pump 38, optionally connected from the operational point of view to (not illustrated) management and control means of the apparatus 1.

[0074] According to a still further variant, the separation chamber 6 and/or the recovery chamber 16 could be inclinable (for example laterally), in order to make flow out, naturally or forcibly, a washing liquid, only the liquid of the aforesaid suspension, and/or the stable colloidal suspension containing the magnetic nanoparticles and/or the substance-nanoparticle complexes .

[0075] Preferably, such outflow of the washing liquid and/or of the liquid of the suspension could be effected when the first 8 and/or the second 18 magnetic element is activated and/or positioned to magnetically retain the substance-nanoparticle complexes and/or the magnetic nanoparticles .

[0076] According to an advantageous variant, the apparatus 1 comprises oscillation motor means 24, 76 of the separation chamber 6, and optionally oscillation motor means 24', 76' of the recovery chamber 16.

[0077] Preferably, the apparatus 1 comprises first oscillation motor means 24, 24' for moving the separation chamber 6 and/or the recovery chamber 16 in a plane substantially parallel to the bottom wall 20, 22 of this chamber.

[0078] According to a further advantageous variant, the apparatus 1 comprises second oscillation motor means 76, 76' for moving the separation chamber 6 and/or the recovery chamber 16 in a plane substantially orthogonal to the bottom wall 20, 22 of this chamber.

[0079] For reference, Figure 2a shows the Cartesian system with respect to which the first oscillation motor means 24, 24' are configured to move the chamber 6, 16 in the plane Y, Z, while the second oscillation motor means 76, 76' are delegated to perform movements of this chamber in the plane X, Y.

[0080] According to an embodiment, the apparatus could include approaching/distancing motor means 26 between the first magnetic element 8 and the bottom wall 20, and/or approaching/distancing motor means 26' between the second magnetic element 18 and the bottom wall 20.

[0081] Optionally, the apparatus 1 could comprise management and control means operatively connected to the oscillation motor means 24, 24', 76, 76' and/or the approaching/distancing motor means 26, 26' for controlling these means 24, 24', 76, 76', 26, 26' in a mutually independent way.

[0082] According to a further variant, the management and control means could be functionally connected to one or more pumps among those described above and/or the deviating means, when provided.

[0083] According to a possible variant, the oscillation motor means and/or the approaching/distancing motor means could comprise one or more linear actuators for moving the respective chamber 6, 16, the respective magnetic element 8, 18 and/or the respective bottom wall 20, 22. For example, one or more linear actuators may be of the pneumatic, hydraulic, mechanical and/or electromechanical type.

[0084] This invention also relates to a method for separating at least one target substance from a liquid phase.

[0085] Since this method is preferably implemented by means of the apparatus described above, even if not expressly indicated, preferred or advantageous variants of this method could comprise any step deducible, from a structural point of view, from the preceding context.

[0086] The method covered by this invention comprises ^' steps of :

[0087] i) mixing at least one target substance and at least one stable colloidal liquid suspension of magnetic nanoparticles to obtain substance-nanoparticle complexes;

[0088] ii) separating the substance-nanoparticle complexes from the stable colloidal liquid suspension of said substance-nanoparticle complexes, by magnetically attracting said complexes;

[0089] iii) splitting the substance-nanoparticle complexes by means of one or more release reactants of the target substance from said complexes, and re-suspending the nanoparticles released by said complexes in a stable colloidal liquid suspension;

[0090] iv) magnetically separating the magnetic nanoparticles from the target substance.

[0091] According to a preferred variant, the method comprises a step of re-introducing in step i) at least part of the magnetic nanoparticles of step iv) in a stable colloidal suspension in order to perform a recirculation thereof.

[0092] According to a further preferred variant, one or both steps ii) and iv) comprise a step of modulating the intensity of the magnetic field acting on the substance- nanoparticle complexes and/or on the magnetic nanoparticles , by moving a magnetic element (for example permanent) towards/away from said complexes and/or said nanoparticles , or by adjusting the current intensity fed to one or more electromagnets.

[0093] Preferably, step ii) and/or step iv) comprise a step of magnetically retaining the substance-nanoparticle complexes and/or magnetic nanoparticles, and a step of making flow out, naturally or forcibly, the liquid only of the aforesaid suspension.

[0094] Optionally, step i) comprises a sub-step of functionalising the magnetic nanoparticles, directly or indirectly.

[0095] According to a particularly advantageous embodiment of this method, the magnetic nanoparticles comprise or consist of superparamagnetic nanoparticles of stoichiometrically pure maghemite.

[0096] Preferably, such nanoparticles are capable of creating stable colloidal suspensions without any coating in the aqueous phase.

[0097] In other words, in an uncoated form, said nanoparticles are configured to give rise to stable colloidal suspensions in aqueous phase by treatment with ultrasonic bath.

[0098] Innovatively, . the apparatus and method of this invention are suitable to brilliantly overcome the drawbacks complained of previously.

[0099] More precisely, the apparatus and the above method allow separating a potentially infinite variety of target substances, in a simple and repeatable way and at an extremely low cost.

[00100] In fact, although the foregoing description■ has made reference to only one target substance with a single stage of separation from the liquid, this apparatus/method allows making the nanoparticles specific for a plurality of target substances, and of separating such substances in a controlled manner during several stages.

[00101] Advantageously, the stable colloidal suspensions of the nanoparticles of this invention allow their easy production on an industrial scale.

[00102] Advantageously, the nanoparticles used in this invention are suitable for forming stable colloidal suspensions in water, and have a surface reactivity suitable to reversibly bind organic or biological molecules of any kind.

[00103] Advantageously, the apparatus and method of this invention method could be used, without affecting the colloidal stability of the colloidal suspensions of nanoparticles in the process of separation of. the target substance, 'for the reclamation of civil or industrial water on a large scale.

[00104] Advantageously, the apparatus of this invention is designed to minimise the amount of residual substances in the treatment chambers.

[00105] Advantageously, the apparatus and the method of this invention allow attracting the nanoparticles and the complexes formed by them in an intelligent way, without damaging the stability of the re-suspensions of such particles.

[00106] Advantageously, the apparatus of this invention is designed to deploy the components in a homogeneous way inside the treatment tanks, to improve the yield and separation times of the various substances.

[00107] Advantageously, the apparatus and method of this invention method could be automated, so as to speed up and optimise the separation . times of the target substances.

[00108] To the embodiments of the aforesaid apparatus and method, one skilled in the art, in order to meet specific needs, may make variants or substitutions of elements with others functionally equivalent.

[00109] Even these variants are contained within the scope of protection, as defined by the following claims.

[00110] Moreover, each of the variants described as belonging to a possible embodiment can be realised independently of the other variants described.