WO2014095717A1

WO2014095717A1 - Mixed matrix membranes comprising vanadium pentoxide nanoparticles and methods for their preparation

Info

Publication number: WO2014095717A1
Application number: PCT/EP2013/076699
Authority: WO
Inventors: Michael BRÄU; Claudia Staudt; Dawid Marczewski
Original assignee: Basf Se
Priority date: 2012-12-17
Filing date: 2013-12-16
Publication date: 2014-06-26

Abstract

Membrane comprising vanadium pentoxide.

Description

MIXED MATRIX MEMBRANES COMPRISING VANADIUM PENTOXIDE NANOPARTICLES AND METHODS FOR THEIR PREPARATION

The present invention relates to membranes comprising vanadium pentoxide, methods for their preparation and their use for water treatment.

The invention further relates to a method of increasing the flux through a membrane by incorporating vanadium pentoxide into a membrane.

Different types of membranes play an increasingly important role in many fields of technology. In particular, methods for treating water rely more and more on membrane technology.

An important issue with the application of membranes is fouling. The problem of biofouling is pronounced in semipermeable membranes used for separation purposes like reverse osmosis, forward osmosis, nanofiltration, ultrafiltration and micro filtration. Membranes may be classified according to their separation mechanism and/or pore sizes. For example, in water filtration ap- plications ultrafiltration and microfiltration membranes (approximate pore diameter: 5 - 1000 nm) are used for wastewater treatment retaining organic and bioorganic material. In reverse osmosis and forward osmosis membranes, where monovalent ions and all components with larger diameter are rejected, the separation mechanism is based mainly on solution-diffusion mechanism.

In all applications where the ambient medium is an aqueous phase, potential blockage may occur by adhesion of microorganisms and biofilm formation. As a consequence, a membrane is desired, which reduces biofilm formation and thus requires fewer cleaning cycles. This can for example be achieved through membranes with anti-adhesive or antifouling properties.

Thus, fouling is currently one of the major remaining problems for filtration membranes. Fouling causes deterioration of the membrane performance and shortens membrane lifetime, limiting further application of membrane technology. It is thus desirable to improve antifouling and antibacterial properties to membranes without impairing their separation characteristics in order to enhance their resistance. Several approaches have been tried to solve the problem of fouling and biofouling and to prevent the formation and deposition of organic materials from organisms.

Recent research has focused on three strategies to prevent biofouling of membranes: 1 ) blending of hydrophilic or amphiphilic copolymers for the manufacture of membranes; 2) surface modification of membranes and 3) bulk modification of membrane materials.

The following documents describe approaches undertaken in recent years:

H. Yamamura, K. Kimmura, Y. Watanabe, Mechanism involved in the evolution of physically irreversible fouling in microfiltration and ultrafiltration membranes used for drinking water treatment, Environ. Sci. Technol. 41 (2007) 6789-6794. V. Kochkodan, S. Tsarenko, N. Potapchenko, V. Kosinova, V. Goncharuk, Adhesion of microorganisms to polymer membranes: a photobactericidal effect of surface treatment with ΤΊ02, Desalination 220 (2008) 380-385.

J. Mansouri, S. Harrisson, Vivki Chen, Strategies for controlling biofouling in membrane filtration systems: challenges and opportunities. J. Mater. Chem., 20 (2010)

US 4,277,344 discloses antifouling approaches on RO layers, formed by interfacial reaction.

Desalination 275 (201 1 ) 252-259, describes the grafting of PEG on a polyamide layer.

US 6,280,853 and US 2010/043,733 disclose coatings of composite membranes with various polymers including polyalkylene oxide compounds or polyacrylamide compounds.

A. V.R. Reddy, D. J. Mohan, A. Bhattacharya, V. J. Shah, P. K. Ghosh, Surface modification of ultrafiltration membranes by preadsorption of a negatively charged polymer: I. Permeation of water soluble polymers and inorganic salt solutions and fouling resistance properties, J. Membr. Sci. 214 (2003) 21 1-221 .

K. C. Khulbe, C. Feng, T. Matsuura, The art of surface modification of synthetic polymeric membranes, J. Appl. Polym. Sci. 1 15 (2010) 855-895.

B. Van der Bruggen, Chemical modification of polyethersulfone nanofiltration membranes: A review, J. Appl. Polym. Sci. 1 14 (2009) 630-642.

Tsai et al., Desalination, Elsevier, vol. 233, no. 1 - 3, pages 232 - 238 discloses characteristics and properties of polyimide/vanadium oxide hybrid membranes with respect to their thermal stability, morphology and mechanical properties.

Felipe Natalio et al. nature nanotechnology, vol. 7, no.8, 1 January 2012, pages 530-535 discloses Vanadium pentoxide nanoparticles for mimicing vanadium haloperoxidases and thwarting biofilm formation.

US 201 1/005997 discloses hybrid TFC RO membranes with nitrogen additives that can comprise various nanoparticles like metal oxides.

It was an object of the invention to provide membranes that are less prone to fouling.

This objective has been solved my membranes comprising vanadium pentoxide. The concept of a membrane is generally known in the art. In the context of this application a membrane shall be understood to be a thin, semipermeable structure capable of separating two fluids or separating molecular and/or ionic components or particles from a liquid. A membrane acts as a selective barrier, allowing some particles, substances or chemicals to pass through while retaining others. Membranes according to the invention can for example be microporous (average pore diameter smaller than 2 nm), mesoporous (average pore diameter from 2 nm to 50 nm) or macroporous (average pore diameter above 50 nm). Average pore diameters in this context are determined according to DIN 14652:2007-09 through correlation with the molecular weight cutoff of a mem- brane.

Suitable membranes or the separation layer of suitable membranes can be made of at least one inorganic material like a ceramic or at least one organic polymer.

Examples of inorganic materials are clays, silicates, silicon carbide, aluminium oxide, zirconium oxide or graphite. Such membranes made of inorganic materials are normally made by applying pressure or by sintering of finely ground powder. Membranes made of inorganic materials may be composite membranes comprising two, three or more layers.

In one embodiment, membranes made from inorganic materials comprise a macroporous support layer, optionally an intermediate layer and a separation layer.

In a preferred embodiment, suitable membranes and/or the separation layer of a membrane comprise organic polymers, hereinafter referred to as polymers as the main components. A polymer shall be considered the main component of a membrane if it is comprised in said membrane or in the separation layer of said membrane in an amount of at least 50 %by weight, preferably at least 60%, more preferably at least 70%, even more preferably at least 80% and particularly preferably at least 90% by weight.

Examples of suitable polymers are polyarylene ether, polysulfone, polyethersulfones (PES), polyphenylensulfone (PPSU), polyamides (PA), polyvinylalcohol (PVA), cellulose acetate (CA), cellulose diacetate, cellulose triacetate (CTA), CA-triacetate blend, cellulose ester, cellulose nitrate, regenerated cellulose, aromatic , aromatic/aliphatic or aliphatic polyamide, aromatic, aromatic/aliphatic or aliphatic polyimide, polybenzimidazole (PBI), polybenzimidazolone (PBIL), polyacrylonitrile (PAN), polyetheretherketone (PEEK), sulfonated polyetheretherketone

(SPEEK),PAN-poly(vinyl chloride) copolymer (PAN-PVC), PAN-methallyl sulfonate copolymer, poly(dimethylphenylene oxide) (PPO), polycarbonate, polyester, polytetrafluroethylene PTFE, poly(vinylidene fluoride) (PVDF), polypropylene (PP), polyelectrolyte complexes, poly(methyl methacrylate) PMMA, polydimethylsiloxane (PDMS), aromatic, aromatic/aliphatic or aliphatic polyimide urethanes, aromatic, aromatic/aliphatic or aliphatic polyamidimides, crosslinked poly- imides or mixtures thereof.

In one preferred embodiment, membranes according to the invention comprise less than 1 % by weight polyimide or do not comprise a polyimide. Preferably, membranes according to the invention comprise polysulfones, polyethersulfones (PES), polyphenylenesulfone (PPSU), polyamides (PA), polyvinylalcohols (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA) Poly(vinylidene fluoride) (PVDF) or mixtures thereof as main components.

Suitable polyethersulfones can for example be obtained from BASF SE under the brand name Ultrason<^R>.

Preferred polyarylene ether sulfones (A) are composed of units of the general formula I

where the definitions of the symbols t, q, Q, T, Y, Ar and Ar¹ are as follows: t, q: independently of one another 0, 1 , 2, or 3,

Q, T, Y: independently of one another in each case a chemical bond or group selected from

-0-, -S-, -SO2-, S=0, C=0, -N=N-, and -CR^aR^b-, where R^a and R^b independently of one another are in each case a hydrogen atom or a Ci-Ci2-alkyl, Ci-Ci2-alkoxy, or C6-Ci8-aryl group, and where at least one of Q, T, and Y is -SO2-, and

Ar and Ar¹: independently of one another an arylene group having from 6 to 18 carbon atoms.

If, within the abovementioned preconditions, Q, T or Y is a chemical bond, this then means that the adjacent group on the left-hand side and the adjacent group on the right-hand side are pre- sent with direct linkage to one another via a chemical bond.

However, it is preferable that Q, T, and Y in formula I are selected independently of one another from -O- and -SO2-, with the proviso that at least one of the group consisting of Q, T, and Y

If Q, T, or Y is -CR^aR^b-, R^a and R^b independently of one another are in each case a hydrogen atom or a Ci-Ci2-alkyl, Ci-Ci2-alkoxy, or C6-Ci8-aryl group.

Preferred Ci-Ci2-alkyl groups comprise linear and branched, saturated alkyl groups having from 1 to 12 carbon atoms. The following moieties may be mentioned in particular: Ci-C6-alkyl moiety, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, 2- or 3-methylpentyl, and longer chain moieties, e.g. unbranched heptyl, octyl, nonyl, decyl, undecyl, lauryl, and the singly branched or multibranched analogs thereof. Alkyl moieties that can be used in the abovementioned Ci-Ci2-alkoxy groups that can be used are the alkyl groups defined at an earlier stage above having from 1 to 12 carbon atoms. Cyclo- alkyl moieties that can be used with preference in particular comprise C3-Ci2-cycloalkyl moieties, e.g. cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cydoheptyl, cyclooctyl, cyclopropylme- thyl, cyclopropylethyl, cyclopropylpropyl, cyclobutylmethyl, cyclobutylethyl, cyclopen- tylethyl, -propyl, -butyl, -pentyl, -hexyl, cyclohexylmethyl, -dimethyl, and -trimethyl.

Ar and Ar¹ are independently of one another a C6-Ci8-arylene group. On the basis of the starting materials described at a later stage below, it is preferable that Ar derives from an electron-rich aromatic substance that is very susceptible to electrophilic attack, preferably selected from the group consisting of hydroquinone, resorcinol, dihydroxynaphthalene, in particular 2,7- dihydroxynaphthalene, and 4,4'-bisphenol. Ar¹ is preferably an unsubstituted C6- or Ci2-arylene group.

Particular C6-Ci8-arylene groups Ar and Ar¹ that can be used are phenylene groups, e.g. 1 ,2-, 1 ,3-, and 1 ,4-phenylene, naphthylene groups, e.g. 1 ,6-, 1 ,7-, 2,6-, and 2,7-naphthylene, and also the arylene groups that derive from anthracene, from phenanthrene, and from naph- thacene.

In the preferred embodiment according to formula I, it is preferable that Ar and Ar¹ are selected independently of one another from the group consisting of 1 ,4-phenylene, 1 ,3-phenylene, naphthylene, in particular 2, 7-dihydroxynaphthylene, and 4,4'-bisphenylene.

Preferred polyarylene ether sulfones (A) are those which comprise at least one of the following repeat units la to lo:

Other preferred units, in addition to the units la to lo that are preferably present, are those in which one or more 1 ,4-phenylene units deriving from hydroquinone have been replaced by 1 ,3-phenylene units deriving from resorcinol, or by naphthylene units deriving from dihy- droxynaphthalene.

Particularly preferred units of the general formula I are the units la, Ig, and Ik. It is also particularly preferable that the polyarylene ether sulfones of component (A) are in essence composed of one type of unit of the general formula I, in particular of one unit selected from la, Ig, and Ik.

In one particularly preferred embodiment, Ar = 1 ,4-phenylene, t = 1 , q = 0, T is a chemical bond, and Y = SO2. Particularly preferred polyarylene ether sulfones (A) composed of the abovemen- tioned repeat unit are termed polyphenylene sulfone (PPSU) (formula Ig).

In another particularly preferred embodiment, Ar = 1 ,4-phenylene, t = 1 , q = 0, T = C(CH3)2, and Y = SO2. Particularly preferred polyarylene ether sulfones (A) composed of the abovementioned repeat unit are termed polysulfone (PSU) (formula la). In another particularly preferred embodiment, Ar = 1 ,4-phenylene, t = 1 , q = 0, T = Y = SO2. Particularly preferred polyarylene ether sulfones (A) composed of the abovementioned repeat unit are termed polyether sulfone (PESU or PES) (formula Ik). This embodiment is very particularly preferred.

For the purposes of the present invention, abbreviations such as PPSU, PESU, and PSU are in accordance with DIN EN ISO 1043-1 :2001 . The weight-average molar masses M_w of the polyarylene ether sulfones (A) of the present invention are preferably from 10 000 to 150 000 g/mol, in particular from 15 000 to 120 000 g/mol, particularly preferably from 18 000 to 100 000 g/mol, determined by means of gel permeation chromatography in dimethylacetamide as solvent against narrowly-distributed polymethyl meth- acrylate as standard.

In one embodiment of the invention, suitable polyarylene ether sulfones , particularly polysul- fones or polyethersulfones comprise sulfonic acids, carboxylic acid, amino and/or hydroxy groups on some or all of the aromatic rings in the polymer.

Production processes that lead to the abovementioned polyarylene ethers are known to the person skilled in the art and are described by way of example in Herman F. Mark, "Encyclopedia of Polymer Science and Technology", third edition, volume 4, 2003, chapter "Polysulfones" pages 2 to 8, and also in Hans R. Kricheldorf, "Aromatic Polyethers " in: Handbook of Polymer Synthesis, second edition, 2005, pages 427 to 443.

Suitable membranes are for example membranes suitable as reverse osmosis (RO) mem- branes, forward osmosis (FO) membranes, nanofiltration (NF) membranes, ultrafiltration (UF) membranes or microfiltration (MF) membranes. These membrane types are generally known in the art.

Suitable membranes are for example those disclosed in US 201 1/0027599 in [0021 ] to [0169]; US 2008/0237126 in col 4, In 36 to col 6, In 3; US 2010/0224555 in [0147] to [0490]; US

2010/0062156 in [0058] to [0225]; US 201 1/0005997 in [0045] to [0390], US 2009/0272692 in [0019] to [0073], US 2012/0285890 in [0016] to [0043]; these documents are incorporated herein by reference. Further suitable membranes are for example those disclosed in US6787216,col. 2, In 54 to col 6, In 19; US 6,454,943, col. 3; In 25 to col. 6, In 12; and WO 2006/012920, p. 3, last paragraph to p. 10, first paragraph.

FO membranes are normally suitable for treatment of seawater, brackish water, sewage or sludge streams. Thereby pure water is removed from those streams through a FO membrane into a so called draw solution on the back side of the membrane having a high osmotic pressure. Typically, FO type membranes, similar as RO membranes are separating liquid mixtures via a solution diffusion mechanism, where only water can pass the membrane whereas monovalent ions and larger components are rejected.

In a preferred embodiment, suitable FO membranes are thin film composite (TFC) FO membranes. Preparation methods and use of thin film composite membranes are principally known and, for example described by R. J. Petersen in Journal of Membrane Science 83 (1993) 81 - 150.

In a further preferred embodiment, suitable FO membranes comprise a fabric layer, a support layer, a separation layer and optionally a protective layer. Said protective layer can be considered an additional coating to smoothen and/or hydrophilize the surface.

Said fabric layer can for example have a thickness of 10 to 500 μηη. Said fabric layer can for example be a woven or nonwoven, for example a polyester nonwoven.

Said support layer of a TFC FO membrane normally comprises pores with an average pore diameter of for example 0.5 to 100 nm, preferably 1 to 40 nm, more preferably 5 to 20 nm. Said support layer can for example have a thickness of 5 to 1000 μηη, preferably 10 to 200 μηη. Said support layer may for example comprise a main component a polysulfone, polyethersulfone, polyphenylensulfone (PPSU), PVDF, polyimide, polyimideurethane or cellulose acetate. Nano particles such as zeolites, particularly zeolite LTA, may be comprised in said support membrane. This can for example be achieved by including such nano particles in the dope solution for the preparation of said support layer.

Said separation layer can for example have a thickness of 0.05 to 1 μηη, preferably 0.1 to 0.5 μηη, more preferably 0. 15 to 0.3 μηη. Preferably, said separation layer can for example comprise polyamide or cellulose acetate as the main component.

Optionally, TFC FO membranes can comprise a protective layer with a thickness of 30-500 nm, preferably 100-300 nm. Said protective layer can for example comprise polyvinylalcohol (PVA) as the main component. In one embodiment, the protective layer comprises a halamine like chloramine.

In one preferred embodiment, suitable membranes are TFC FO membranes comprising a support layer comprising polyethersulfone as main component, a separation layer comprising poly- amide as main component and optionally a protective layer comprising polyvinylalcohol as the main component.

In a preferred embodiment suitable FO membranes comprise a separation layer obtained from the condensation of a polyamine and a polyfunctional acyl halide. Said separation layer can for example be obtained in an interfacial polymerization process. RO membranes are normally suitable for removing molecules and ions, in particular monovalent ions. Typically, RO membranes are separating mixtures based on a solution/diffusion mechanism.

In a preferred embodiment, suitable membranes are thin film composite (TFC) RO membranes. Preparation methods and use of thin film composite membranes are principally known and, for example described by R. J. Petersen in Journal of Membrane Science 83 (1993) 81 -150.

In a further preferred embodiment, suitable RO membranes comprise a fabric layer, a support layer, a separation layer and optionally a protective layer. Said protective layer can be considered an additional coating to smoothen and/or hydrophilize the surface Said fabric layer can for example have a thickness of 10 to 500 μηη. Said fabric layer can for example be a woven or nonwoven, for example a polyester nonwoven.

Said support layer of a TFC RO membrane normally comprises pores with an average pore diameter of for example 0.5 to 100 nm, preferably 1 to 40 nm, more preferably 5 to 20 nm. Said support layer can for example have a thickness of 5 to 1000 μηη, preferably 10 to 200 μηη. Said support layer may for example comprise a main component a polysulfone, polyethersulfone, PVDF, polyimide, polyimideurethane or cellulose acetate. Nano particles such as zeolites, particularly zeolite LTA, may be comprised in said support membrane. This can for example be achieved by including such nano particles in the dope solution for the preparation of said support layer.

Said separation layer can for example have a thickness of 0.02 to 1 μηη, preferably 0.03 to 0.5 μηη, more preferably 0.05 to 0.3 μηη. Preferably, said separation layer can for example comprise polyamide or cellulose acetate as the main component.

Optionally, TFC RO membranes can comprise a protective layer with a thickness of 5 to 500 preferable 10 to 300 nm. Said protective layer can for example comprise polyvinylalcohol (PVA) as the main component. In one embodiment, the protective layer comprises a halamine like chloramine.

In one preferred embodiment, suitable membranes are TFC RO membranes comprising a nonwoven polyester fabric, a support layer comprising polyethersulfone as main component, a separation layer comprising polyamide as main component and optionally a protective layer comprising polyvinylalcohol as the main component. In a preferred embodiment suitable RO membranes comprise a separation layer obtained from the condensation of a polyamine and a polyfunctional acyl halide. Said separation layer can for example be obtained in an interfacial polymerization process. Suitable polyamine monomers can have primary or secondary amino groups and can be aromatic (e. g. a diaminobenzene, a triaminobenzene, m-phenylenediamine, p-phenylenediamine, 1 ,3,5-triaminobenzene, 1 3,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2, 4-diaminoanisole, and xylylenediamine) or aliphatic (e. g. ethylenediamine, propylenediamine, piperazine, and tris(2-diaminoethyl)amine).

Suitable polyfunctional acyl halides include trimesoyl chloride (TMC), trimellitic acid chloride, isophthaloyl chloride, terephthaloyl chloride and similar compounds or blends of suitable acyl halides. As a further example, the second monomer can be a phthaloyl halide. In one embodiment of the invention, a separation layer of polyamide is made from the reaction of an aqueous solution of meta-phenylene diamine (MPD) with a solution of trimesoyl chloride (TMC) in an apolar solvent.

In another embodiment of the invention, the separation layer and optionally other layers of the membrane contain nanoparticles other than of vanadium pentoxide. Suitable nanoparticles normally have an average particle size of 1 to 1000 nm, preferably 2 to 100 nm, determined by dynamic light scattering. Suitable nanoparticles can for example be zeolites, silica, silicates or aluminium oxide. Examples of suitable nanoparticles include Aluminite, Alunite, Ammonia Alum, Altauxite, Apjohnite, Basaluminite, Batavite, Bauxite, Beideilite, Boehmite, Cadwaladerite, Cardenite, Chalcoalumite, Chiolite, Chloraluminite, Cryolite, Dawsonite, Diaspore, Dickite,

Gearksutite, Gibbsite, Hailoysite, Hydrobasaluminite, Hydrocalumite, Hydrotalcite, lllite, Kalinite, Kaolinite, Mellite, Montmoriilonite, Natroalunite, Nontronite, Pachnolite, Prehnite, Prosopite, Ralstonite, Ransomite, Saponite, Thomsenolite, Weberite, Woodhouseite, and Zincaluminit, kehoeite, pahasapaite and tiptopite; and the silicates: hsianghualite, lovdarite, viseite, partheite, prehnite, roggianite, apophyllite, gyrolite, maricopaite, okenite, tacharanite and tobermorite.

Nanoparticles may also include a metallic species such as gold, silver, copper, zinc, titanium, iron, aluminum, zirconium, indium, tin, magnesium, or calcium or an alloy thereof or an oxide thereof or a mixture thereof. They can also be a nonmetallic species such as Si3N4, SiC, BN, B4C, or TIC or an alloy thereof or a mixture thereof. They can be a carbon-based species such as graphite, carbon glass, a carbon cluster of at least C~, buckminsterfullerene, a higher fuller- ene, a carbon nanotube, a carbon nanoparticle, or a mixture thereof. In yet another embodiment the separation layer and optionally other layers of the membrane contain zeolites, zeolite precursors, amorphous aluminosilicates or metal organic frame works (MOFs) any preferred MOFs. Preferred zeolites include zeolite LTA, RHO, PAU, and KFI. LTA is especially preferred.

Preferably, the nanoparticles other than vanadium pentoxide comprised in the membrane have a polydispersity of less than 3.

In another embodiment of the invention the separation layer of the membrane contains a further additive increasing the permeability of the RO membrane. Said further additive can for example be a metal salt of a beta-diketonate compound, in particular an acetoacetonate and/or an at least partially fluorinated beta-diketonate compound.

NF membranes are normally especially suitable for removing separate multivalent ions and large monovalent ions. Typically, NF membranes function through a solution/diffusion or/and filtration-based mechanism.

NF membranes are normally used in cross filtration processes.

NF membranes can for example comprise as the main component polyarylene ether, polysul- fone, polyethersulfones (PES), polyphenylensulfone (PPSU), polyamides (PA), polyvinylalcohol (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA), CA-triacetate blend, Cellulose ester, Cellulose Nitrate, regenerated Cellulose, aromatic , aromatic/aliphatic or aliphatic Polyamide, aromatic, aromatic/aliphatic or aliphatic Polyimide, Polybenzimidazole (PBI), Polybenzimidazo- lone (PBIL), polyetheretherketone (PEEK), sulfonated polyetheretherketone (SPEEK), Polyacry- lonitrile (PAN), PAN-poly(vinyl chloride) copolymer (PAN-PVC), PAN-methallyl sulfonate copolymer, Polysulfone, Poly(dimethylphenylene oxide) (PPO), Polycarbonate, Polyester, Polytetra- fluroethylene PTFE, Poly(vinylidene fluoride) (PVDF), Polypropylene (PP), Polyelectrolyte complexes, Poly(methyl methacrylate) PMMA, Polydimethylsiloxane (PDMS), aromatic, aromatic/aliphatic or aliphatic polyimide urethanes, aromatic, aromatic/aliphatic or aliphatic polyam- idimides, crosslinked polyimides or mixtures thereof. In a preferred embodiment, said main components are positively or negatively charged.

Nanofiltration membranes often comprise charged polymers comprising sulfonic acid groups, carboxylic acid groups and/or ammonium groups.

Preferably, NF membranes comprise as the main component polyamides, polyimides or polyi- mide urethanes, Polyetheretherketone (PEEK) or sulfonated polyetheretherketone (SPEEK). UF membranes are normally suitable for removing suspended solid particles and solutes of high molecular weight, for example above 1000 Da. In particular, UF membranes are normally suitable for removing bacteria and viruses. UF membranes normally have an average pore diameter of 0.5 nm to 50 nm, preferably 1 to 40 nm, more preferably 5 to 20 nm.

UF membranes can for example comprise as main component a polyarylene ether, polysulfone, polyethersulfones (PES), polyphenylensulfone (PPSU), polyamides (PA), polyvinylalcohol (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA), CA-triacetate blend, Cellulose ester, Cellulose Nitrate, regenerated Cellulose, aromatic , aromatic/aliphatic or aliphatic Polyamide, aromatic, aromatic/aliphatic or aliphatic Polyimide, Polybenzimidazole (PBI), Polybenzimidazo- lone (PBIL), Polyacrylonitrile (PAN), PAN-poly(vinyl chloride) copolymer (PAN-PVC), PAN- methallyl sulfonate copolymer, Polysulfone, Poly(dimethylphenylene oxide) (PPO), Polycarbonate, Polyester, Polytetrafluroethylene PTFE, Poly(vinylidene fluoride) (PVDF), Polypropyl- ene (PP), Polyelectrolyte complexes, Poly(methyl methacrylate) PMMA, Polydimethylsiloxane (PDMS), aromatic, aromatic/aliphatic or aliphatic polyimide urethanes, aromatic, aromatic/aliphatic or aliphatic polyamidimides, crosslinked polyimides or mixtures thereof.

Preferably, UF membranes comprise as main component polysulfone, polyethersulfone, poly- phenylenesulfone, PVDF, polyimide, polyamidimide, crosslinked polyimides, polyimide urethanes or mixtures thereof.

In one embodiment, UF membranes comprise further additives like polyvinyl pyrrolidones.

In one embodiment, UF membranes comprise further additives like block copolymers of polyarylene sulfones and alkyleneoxides like polyethyleneoxide.

In a preferred embodiment, UF membranes comprise as major components polysulfones or polyethersulfone in combination with further additives like polyvinylpyrrolidone.

In one preferred embodiment, UF membranes comprise 80 to 50% by weight of polyethersulfone and 20 to 50 %by weight of polyvinylpyrrolidone.

In another embodiment UF membranes comprise 95 to 80% by weight of polyethersulfone and 5 to 15 %by weight of polyvinylpyrrolidone.

In another embodiment UF membranes comprise 99.9 to 80% by weight of polyethersulfone and 0.1 to 15 %by weight of polyvinylpyrrolidone.

In one embodiment of the invention, UF membranes are present as spiral wound membranes. In another embodiment of the invention, UF membranes are present as tubular membranes. In another embodiment of the invention, UF membranes are present as flat sheet membranes. In another embodiment of the invention, UF membranes are present as hollow fiber membranes.

In yet another embodiment of the invention, UF membranes are present as single bore hollow fiber membranes.

In yet another embodiment of the invention, UF membranes are present as multi bore hollow fiber membranes.

MF membranes are normally suitable for removing particles with a particle size of 0.1 μηη and above.

MF membranes normally have an average pore diameter of 0.1 μηη to 10 μηη, preferably 1.0 μηη to 5 μηη.

Microfiltration can use a pressurized system but it does not need to include pressure.

MF membranes can be hollow fibers, flat sheet, tubular, spiral wound, hollow fine fiber or track etched. They are porous and allow water, monovalent species (Na+, CI-), dissolved organic matter, small colloids and viruses through while retaining particles, sediment, algae or large bacteria through.

Microfiltration systems are designed to remove suspended solids down to 0.1 micrometres in size, in a feed solution with up to 2-3% in concentration. MF membranes can for example comprise as main component polyarylene ether, polysulfone, polyethersulfones (PES), polyphenylensulfone (PPSU), polyamides (PA), polyvinylalcohol (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA), CA-triacetate blend, Cellulose ester, Cellulose Nitrate, regenerated Cellulose, aromatic , aromatic/aliphatic or aliphatic Polyamide, aromatic, aromatic/aliphatic or aliphatic Polyimide, Polybenzimidazole (PBI), Polybenzimidazo- lone (PBIL), Polyacrylonitrile (PAN), PAN-poly(vinyl chloride) copolymer (PAN-PVC), PAN- methallyl sulfonate copolymer, Polysulfone, Poly(dimethylphenylene oxide) (PPO), Polycarbonate, Polyester, Polytetrafluroethylene PTFE, Poly(vinylidene fluoride) (PVDF), Polypropylene (PP), Polyelectrolyte complexes, Poly(methyl methacrylate) PMMA, Polydimethylsiloxane (PDMS), aromatic, aromatic/aliphatic or aliphatic polyimide urethanes, aromatic, aro- matic/aliphatic or aliphatic polyamidimides, crosslinked polyimides or mixtures thereof. Membranes according to the invention comprise vanadium pentoxide.

Vanadium pentoxide, is vanadium(V) oxide of the formula V2O5 and is also called divanadium pentoxide.

Preferably, at least 90 mol%, more preferably 95, 98, 99 or 99.9 mol % of the Vanadium com- prised in the vanadium pentoxide are in the oxidation state +V (determined by redox titration). Vanadium pentoxide may be present in crystalline form or in an amorphous form.

In a preferred embodiment, vanadium pentoxide is at least partly present in crystalline form. Vanadium pentoxide useful according to the invention may, in additions to impurities comprised in the vanadium pentoxide, comprise other components, like water, or other metal ions and/or anions in small amounts. Normally, vanadium pentoxide used for the manufacture of membranes according to the invention, does not comprise more than 5 % by weight of components different from V2O5.

For example, vanadium pentoxide may comprise water that may be part of the crystal lattice, as a ligand to a metal center, as a hydrate or as a physical mixture.

In one embodiment of the invention, V2O5 comprises at least one metal ion as a dopant. Suitable metal ion dopants can for example be selected from ions of Mo, W, Ta, Nb, Ru, Re, Ti, Fe, Sn, Cr, Ga, Zn, Al, Ge, Mn, Co, Ni, Cu, Ag, and Se.

In another embodiment of the invention, V2O5 comprises at least one anion as a dopant. Suitable anions as dopants can for example be selected from fluoride, nitride, chloride, bromide, and iodide. In a preferred embodiment of the invention, vanadium pentoxide is present in the form of particles with an average particle size of 5 nm to 1 mm, preferably 10 nm to 1 μηη, more preferably 10 nm to 500 nm and especially preferably 20 nm to 200 nm.

In another preferred embodiment of the invention, vanadium pentoxide is present in the form of nanoparticles or nanowires.

Nanoparticles are particles with one, two or three external dimensions between approximately 1 nm and 100 nm. "Nanowires" are to be understood as needle-like nanoparticles with an aver- age length of 100 to 500 nm, preferably ca. 300 nm, and an average width of 10 to 40 nm, preferably ca. 20 nm.

Preferably, suitable vanadium pentoxide particles have a polydispersity of less than 3.

Membranes according to the invention may also comprise Vanadium pentoxide particles that are not limited to nanoparticles or nanowires. It is possible to grind vanadium pentoxide (e.g. in aqueous suspension or in other organic liquids) to an average particle size of between 100 nm and 100 μηι. These larger particles, too, show a suitable catalytic (biocidal) effect when in contact with the oxidizing agent and the halide.

Normally, vanadium pentoxide is dispersed in the polymer matrix that forms the membrane, the separating layer and/or another part of the membrane.

In one embodiment, vanadium pentoxide is dispersed throughout the polymer matrix with a uniform concentration. In another embodiment, vanadium pentoxide is dispersed in the polymer matrix such that there is concentration gradient within the polymer matrix.

Membranes according to the invention normally comprise from 0.0001 % by weight to 10.0 % by weight of vanadium pentoxide, preferably 0.001 to 1 .0 % by weight, more preferably 0.01 % to 0.5 % by weight relative to the matrix material. Matrix material in this context is to be understood as the polymer layer, in which the vanadium pentoxide is distributed.

In another embodiment, vanadium pentoxide is present in a combination with at least one further compound of other metals selected from Mo, W, Ta, Nb, Ru, Re, Ti, Fe, Sn, Cr, Ga, Zn, Al, Ge, Mn, Co, Ni, Cu, Ag, Se ("other metals"). Said at least one further metal compound can for example be present in the form of particles with a particle size of 5 nm to 1 mm, preferably 10 nm to 1 μηη, more preferably 10 nm to 500 nm and especially preferably 20 nm to 200 nm.

In another preferred embodiment of the invention, said at least one further metal compound is present in the form of nanoparticles or nanowires.

Vanadium pentoxide and the at least one other further metal compound may be present as a mixed chemical compound, for example in the same crystal lattice or in the form of mixed metal compounds. Vanadium pentoxide and the at least one other metal compound may be present as physical mixtures. Vanadium pentoxide and the at least one other metal compound may be present in separate domains of the polymer matrix.

In one embodiment, vanadium pentoxide is present in combination with at least one copper compound. For example, vanadium pentoxide may present as a mixture with copper compounds like oxides, hydroxides, iodide, bromide, chloride of Cu(l) or Cu(ll), preferably as a io- dide, bromide, chloride of Cu(l).

Membranes according to the invention can comprise from 0.0001 % by weight to 10.0 % by weight of at least one compound of other metals, preferably 0.001 to 1 .0 % by weight, more preferably 0.01 % to 0.5 % by weight relative to the matrix material. In case a membrane comprises more than one layers, the vanadium pentoxide is normally at least comprised in the separation layer and/or in a protective layer on said separation layer facing the feed water side of the membrane. It is also possible that more layers or all layers of a membrane comprise vanadium pentoxide.

In one embodiment of the invention, vanadium pentoxide is comprised in a protective layer on said separation layer facing the feed water side of the membrane, wherein said protective layer has a thickness of 1 nm to 1 μηη, preferably 10 nm to 50 nm. Said protective layer can for example comprise polyvinylalcohol as the main component or can be a sol-gel layer comprising Si0₂ and/or Ti0₂.

Sol-Gel layers are known in the art and are normally obtained by decomposition of silicon- or titanium-organic compounds.

Sol-Gel layers can be made to certain template components that can be removed from said layer after its formation, thus creating a porosity of the layer. Templated sol-gel layer can be applied in higher thicknesses than untemplated sol-gel layers.

In one embodiment of the invention, the vanadium pentoxide is homogenously distributed in a layer. In another embodiment of the invention, the vanadium pentoxide is not homogenously distributed in a layer. For example, a concentration gradient may exist between one surface of a layer and the other surface of a layer.

In one embodiment of the invention, the membrane according to the invention is an RO membrane that comprises Vanadium pentoxide in the separation layer.

In one embodiment of the invention, the membrane according to the invention is an RO mem- brane that comprises Vanadium pentoxide in the separation layer, wherein said separation layer is a polyamide layer.

In one embodiment of the invention, the membrane according to the invention is an RO membrane that comprises Vanadium pentoxide in the protective layer.

In one embodiment of the invention, the membrane according to the invention is an RO membrane that comprises Vanadium pentoxide in the protective layer, wherein said protective layer is a polyvinyl alcohol.

In one embodiment of the invention, the membrane according to the invention is an RO membrane that comprises Vanadium pentoxide in the protective layer, wherein said protective layer is a sol-gel layer comprising S1O2 and/or ΤΊΟ2 as the main components with a thickness of 1 nm to 1 μηη, preferably 5 nm to 50 nm. Preferably, said protective layer is less thick than the separation layer.

In one embodiment of the invention, the membrane according to the invention is a UF mem- brane that comprises Vanadium pentoxide distributed in the membrane, wherein said UF membrane comprises at least one polyethersulfone as the main component. In one embodiment of the invention, the membrane according to the invention is a UF membrane that comprises Vanadium pentoxide in a protective layer on the feed water side of the membrane.

In one embodiment of the invention, said protective layer consists of a sol-gel layer comprising S1O2 and/or ΤΊΟ2 as the main components with a thickness of 1 nm to 1 μηη, preferably 5 nm to 50 nm.

In one embodiment of the invention, membranes, particularly NF, UF and MF membranes are prepared in a process comprising the following steps: a) providing a dope solution of at least one polymer

b) dispersing the vanadium pentoxide in said solution

c) precipitating or coagulating said at least one polymer.

A dope solution in the context of this application shall mean a solution of at least one polymer, from which a membrane or one layer of a membrane or a precursor thereof is prepared by pre- cipitation and/or coagulation

Examples of suitable polymers are polyarylene ether, polysulfone, polyethersulfones (PES), polyphenylensulfone, polyamides (PA), polyvinylalcohol (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA), CA-triacetate blend, Cellulose ester, Cellulose Nitrate, regenerated Cel- lulose, aromatic , aromatic/aliphatic or aliphatic Polyamide, aromatic, aromatic/aliphatic or aliphatic Polyimide, Polybenzimidazole (PBI), Polybenzimidazolone (PBIL), Polyacrylonitrile (PAN), PAN-poly(vinyl chloride) copolymer (PAN-PVC), PAN-methallyl sulfonate copolymer, Polysulfone, Poly(dimethylphenylene oxide) (PPO), Polycarbonate, Polyester, Polytetrafluroeth- ylene PTFE, Poly(vinylidene fluoride) (PVDF), Polypropylene (PP), Polyelectrolyte complexes, Poly(methyl methacrylate) PMMA, Polydimethylsiloxane (PDMS), aromatic, aromatic/aliphatic or aliphatic polyimide urethanes, aromatic, aromatic/aliphatic or aliphatic polyamidimides, cross- linked polyimides or mixtures thereof.

Preferably, said at least one polymer is a polysulfone, polyethersulfone (PES), polyamide (PA), polyvinylalcohol (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA) Poly(vinylidene fluoride) (PVDF) or a mixture thereof as the main component.

Said dope solution may further comprise nanoparticles other than vanadium pentoxide as described above or further flux enhancing additives as discussed above. According to another embodiment of the invention, membranes or layers of membranes, particularly separation layers of RO and FO membranes are prepared in a process comprising the following steps: f) dispersing of vanadium pentoxide in at least one monomer or a solution of at least one monomer

g) polymerizing said at least one monomer to form a membrane or a layer of a membrane. Depending on the nature of the monomers involved, the polymerization of said at least one monomer or a solution of at least one monomer can be carried out as a single phase polymerization or as an interfacial polymerization with at least one more monomer or crosslinker being present in a second phase. For example, the polymer which forms the separation layer or an RO or FO membrane can be prepared by reaction of two or more monomers. The first monomer can be a dinucleophilic or a polynucleophilic monomer and the second monomer can be a dielectrophilic or a polyelectro- philic monomer. That is, each monomer can have two or more reactive (e. g. , nucleophilic or electrophilic) groups. The first and second monomers can also be chosen so as to be capable of undergoing an interfacial polymerization reaction to form a polymer matrix (i.e. a three- dimensional polymer network) when brought into contact. The first and second monomers can also be chosen so as to be capable of undergoing a polymerization reaction when brought into contact to form a polymer product that is capable of subsequent crosslinking by, for example, exposure to heat, light radiation, or a chemical crosslinking agent.

The first monomer can be selected so as to be soluble in a polar liquid, preferably water, to form a polar mixture.

In one embodiment of the invention, the separation layer of an RO or FO membrane is produced in an interfacial polymerization process comprising:

Contacting on a porous support membrane

m) a first solution containing a difunctional or polyfunctional nucleophilic monomer like a polyamine monomer, and

n) a second solution containing a polyfunctional acyl halide monomer,

wherein at least one of solutions m) and n) contains dispersed vanadium pentoxide.

In one embodiment of the invention, only solution m) comprises dispersed vanadium pentoxide. In one embodiment of the invention, only solution n) comprises dispersed vanadium pentoxide. In one embodiment of the invention, solution m) and solution n) both comprise dispersed vanadium pentoxide.

The difunctional or polyfunctional nucleophilic monomer can have primary or secondary amino groups and can be aromatic or heteroaromatic (e. g. , a diaminobenzene, a triaminobenzene, diaminofurane, m-phenylenediamine, p-phenylenediamine, 1 , 3, 5-triaminobenzene, 1 , 3, 4- triaminobenzene, 3, 5-diaminobenzoic acid, 2, 4-diaminotoluene, 2, 4-diaminoanisole, and xy- lylenediamine) or aliphatic (e. g. , ethylenediamine, propylenediamine, piperazine, and tris(2- diaminoethyl)amine). In a yet further example, the polar liquid and the first monomer can be the same compound; that is, the first monomer can provided and not dissolved in a separate polar liquid.

Examples of suitable polyamine species include primary aromatic amines having two or three amino groups, for example m-phenylene diamine, and secondary aliphatic amines having two amino groups, for example piperazine. The polyamine can typically be applied to the support layer as a solution in a polar liquid, for example water. The resulting polar mixture typically includes from about 0. 1 to about 20 weight percent, preferably from about 0. 5 to about 6 weight percent, polyamine. Once coated on a porous support, excess polar mixture can be optionally removed. The polar mixture need not be aqueous, but the polar liquid should be immiscible with the apolar liquid. Although water is a preferred solvent, non-aqueous polar solvents can be uti- lized, such as acetonitrile and dimethylformamide (DMF).

The polar mixture can typically be applied to a porous support layer by dipping, immersing, coating or other well known techniques. Once coated on a porous support membrane, excess polar mixture can be optionally removed by evaporation, drainage, air knife, rubber wiper blade, nip roller, sponge, or other devices or processes.

The organic phase used during interfacial polymerization may also include one of the reactants, nanoparticles, or other relatively insoluble carriers, and processing aids such as catalysts, co- reactants, co-solvents, etc.

A second monomer can be selected so as to be miscible with the apolar (organic) liquid forming an apolar mixture, although for monomers having sufficient vapor pressure, the monomer can be optionally delivered from a vapor phase. The second monomer can optionally also be selected so as to be immiscible with a polar liquid. Typically, the second monomer can be a dielectro- philic or a polyelectrophilic monomer. The electrophilic monomer can be aromatic in nature and can contain two or more, for example three, electrophilic groups per molecule. The second monomer can for example be a trimesoyl halide. For the case of acyl halide electrophilic monomers, acyl chlorides are generally more suitable than the corresponding bromides or iodides because of the relatively lower cost and greater availability.

Suitable polyfunctional acyl halides include trimesoyl chloride (TMC), trimellitic acid chloride, isophthaloyl chloride, terephthaloyl chloride and similar compounds or blends of suitable acyl halides. As a further example, the second monomer can be a phthaloyl halide.

In another embodiment of the invention, at least one of solutions m) and n) contains nanoparticles other than of vanadium pentoxide with an average particle size of 1 to 1000 nm, preferably 2 to 100 nm when said solutions are first contacted. Suitable nanoparticles can for example be zeolites, silica, silicates or aluminium oxide. Examples of suitable nanoparticles include Alu- minite, Alunite, Ammonia Alum, Altauxite, Apjohnite, Basaluminite, Batavite, Bauxite, Beideilite, Boehmite, Cadwaladerite, Cardenite, Chalcoalumite, Chiolite, Chloraluminite, Cryolite, Daw- sonite, Diaspore, Dickite, Gearksutite, Gibbsite, Hailoysite, Hydrobasaluminite, Hydrocalumite, Hydrotalcite, lllite, Kalinite, Kaolinite, Mellite, Montmoriilonite, Natroalunite, Nontronite, Pachno- lite, Prehnite, Prosopite, Ralstonite, Ransomite, Saponite, Thomsenolite, Weberite, Wood- houseite, and Zincaluminit, kehoeite, pahasapaite and tiptopite; and the silicates: hsianghualite, lovdarite, viseite, partheite, prehnite, roggianite, apophyllite, gyrolite, maricopaite, okenite, tacharanite and tobermorite. Nanoparticles or other relatively insoluble carriers may also include a metallic species such as gold, silver, copper, zinc, titanium, iron, aluminum, zirconium, indium, tin, magnesium, or calcium or an alloy thereof or an oxide thereof or a mixture thereof. They can also be a nonmetallic species such as Si3N4, SiC, BN, B4C, or TIC or an alloy thereof or a mixture thereof. They can be a carbon-based species such as graphite, carbon glass, a carbon cluster of at least C~, buckminsterfullerene, a higher fullerene, a carbon nanotube, a carbon nanopartide, or a mixture thereof.

In yet another embodiment the separation layer and optionally other layers of the membrane contain zeolites, include zeolite precursors, amorphous aluminosilicates or metal organic frame works (MOFs) any preferred MOFs. Preferred zeolites include zeolite LTA, RHO, PAU, and KFI. LTA is especially preferred.

In one embodiment solution m) includes dispersed zeolite LTA nanoparticles in water and/or second solution n) includes dispersed zeolite LTA nanoparticles in an organic solvent that is immiscible with water.

In another embodiment of the invention at least one of solutions m) and n) contains a further additive increasing the permeability of the resultant RO membrane produced by interfacial polymerization, and recovering a highly permeable RO membrane. Preferably, said further additive is a metal salt of a beta-diketonate compound, in particular an acetoacetonate and/or an at least partially fluorinated beta-diketonate compound.

In one embodiment of the invention, the separation layer of an RO or FO membrane is prepared by dispersing vanadium pentoxide in an aqueous solution of m-phenylenediamine (MPD) and forming the separation layer of said membrane an interfacial polymerization with a solution of and trimesoyl chloride (TMC) in a C6-C18 alkane such as dodecane. In one embodiment of the invention, the separation layer of an RO or FO membrane is prepared by dispersing vanadium pentoxide in a solution of and trimesoyl chloride (TMC) in a C6-C18 al- kane such as dodecane and forming the separation layer of said membrane an interfacial polymerization with an aqueous solution of m-phenylenediamine (MPD).

In one embodiment of the invention, the separation layer of an RO or FO membrane is prepared by dispersing vanadium pentoxide in an aqueous solution of m-phenylenediamine (MPD) and in a solution of and trimesoyl chloride (TMC) in a C6-C18 alkane such as dodecane, followed by the formation of the separation layer of said membrane an interfacial polymerization of both solutions comprising dispersed vanadium pentoxide

In another embodiment of the invention at least one of solutions m) and n) contains a further additive increasing the permeability of the RO membrane. Said further additive can for example be a metal salt of a beta-diketonate compound, in particular an acetoacetonate and/or an at least partially fluorinated beta-diketonate compound.

Another aspect of the present invention is the use of vanadium pentoxide for enhancing the flux properties of membranes and imparting biocidal properties to a membrane.

In the context of this application, "improving the flux" or "enhancing the flux" shall also be understood to mean "reducing the decrease of flux through a membrane over time".

The term "flux" denotes the flux of the medium that is subjected to a separation operation. In many cases, "flux" means the flux of water through the membrane. For example in the case of water treatment applications, "flux" means the amount of water that permeates through the specified membrane area in a certain period of time.

Membranes according to invention show improved properties with respect to the decrease of flux over time and their fouling and particularly biofouling properties.

It is also possible the membranes according to the invention show improved properties with respect to their ability to restore the flux after cleaning. Also membranes according to the invention can be easier to clean. Furthermore less cleaning agents may be requires for cleaning membranes according to the invention.

Membranes according to the invention can be cleaned more easily and with lower amounts of cleaning agents.

Membranes according to the invention have longer cleaning cycles meaning that they need to be cleaned less often than membranes known from the art. Membranes according to the invention show very favorable properties with respect to leaching of vanadium. Leaching of vanadium from membranes according to the invention is negligible.

Membranes according to the invention have a long lifetime and allow for the treatment of water. Membranes according to the invention are easy and economical to make.

Membranes according to the invention turned out to be particularly efficient for the treatment of water that comprises sufficiently high amounts of bromide and traces of peroxides like hydrogen peroxide. In a preferred embodiment, Membranes according to the invention are used for the treatment, especially the filtration or desalination of water comprising at least 1 mg/l of bromide, preferably 10 mg/l, more preferably 20 mg/l, even more preferably 40 mg/l, end especially preferably at least 50 mg/l. Membranes according to the invention turned out to be particularly efficient for the treatment of seawater or brackish water. In a preferred embodiment, membranes according to the invention are therefore used for the treatment of sea water or brackish water.

In one preferred embodiment of the invention, membranes according to the invention, particular- ly RO, FO or NF membranes are used for the desalination of sea water or brackish water.

Membranes according to the invention, particularly RO, FO or NF membranes are used for the desalination of water with a particularly high salt content . For example membranes according to the invention are suitable for the desalination of water from mining and oil/gas production and fracking processes, to obtain a higher yield in these applications.

In another preferred embodiment, membranes according to the invention, particularly NF, UF or MF membranes are used in a water treatment step prior to the desalination of sea water or brackish water.

In a less preferred embodiment membranes according to the invention, particularly NF, UF or MF membranes are used for the treatment of industrial or municipal waste water.

Examples

Example 1 :

A Solution which comprises of 32 g of polyethersulfone, (Ultrason<^R> E6020P (BASF SE)), 12 g of Polyvinylpyrrolidone (PVP), (Luvitec^(R) K30 (BASF SE), and 0,32 g of vanadium pentoxide particles (170 nm in diameter), and 156 g of dimethylacetamide, 99% Sigma-Aldrich are heated at 60 °C. The degassed solution is cast by a casting machine at speed of 60 mm per second at room temperature and 50% of humidity. Film thickness is 200 μηη. Coagulation is done in the bath which is composed of a mixture of water and isopropanol (weight ratio 7:3). After coagulation membrane is immersed for two hours at 60°C into 0.2% (weight%) aqueous solution of NaOCI. After this treatment membranes are washed with ionized water and stored in deionized water.

The so prepared membranes show increased antimicrobial and antiadhesive activity. Determination of antiadhesive properties (proteins):

RO membranes were painted black at the macroporous backside. Pieces of 9 mm in diameter were punched out and put into a 48 well plate. Into each well, 500 μΙ_ of buffer solution (10 mmol/l HEPES, pH 7.4) was added and the samples equilibrated for 30 min. Then 100 μΙ_ of the buffer solution were replaced with 100 μΙ_ of a solution of 0.2 g/l fluorescently-labelled fibrinogen (from human plasma, AlexaFluor® 647 Conjugate, Molecular Probes®) in buffer (10 mmol/l HEPES, pH 7.4) and the samples equilibrated for 2 hours at 30°C. Subsequently, the samples were rinsed by 5 times replacing 400 μΙ_ of the 500 μΙ_ solution in each well with 400 μΙ_ pure buffer (10 mmol/l HEPES, pH 7.4). Samples were then transferred to a new 48 well plate and covered with 500 μΙ_ of buffer solution (10 mmol/l HEPES, pH 7.4). The well plates were ana- lysed in a microarray fluorescence scanner.

Determination of antiadhesive properties (bacteria):

Coated membranes were tested against bacterial adhesion (Styphylococcus aureus). The membrane was cut and sealed in a holder such that only the coated upper surface was acces- sible to liquids. The coated surface was then covered with approximately 1 ml of a bacterial suspension (Staphylococcus aureus, OD600 ~ 1 , in 0.5% TSBY/0.9% NaCI supplemented with Syto9® and propidium iodide fluorescent dyes as specified by the supplier (Film Tracer

Live/Dead® Biofilm Viability Kit, Invitrogen)). After incubation of the bacteria on the surface for one hour at 37°C, planktonic cells were rinsed off by repeated (10 times) exchange of 90% of the liquid supernatant with bacteria-free 0.9% NaCI solution. This way, the membrane surface was kept moist during all steps of the procedure. Bacteria attached to the membrane surface (sessile cells) were then detected and enumerated either by fluorescence microscopy or by punching out a small piece, followed by bacteria recovery by ultrasonication and serial dilution plating.

Determination of antimicrobial activity:

Antimicrobial activity of coated membranes was determined either by testing according to ISO 22196 (JIS Z2801 ) or by a fluorescence microscopy assay as detailed below:

1 . Bacterial culture: 50 ml of DSM 92 medium (= TSBY Medium, Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH) in an Erlenmeyer flask with chicane are inoculated with a single colony of Staphylococcus aureus ATCC 6538P and incubated at 190 rpm and 37°C for 16 hours. The resulting preliminary culture has a cell density of approximately 108 CFU/ml, corresponding to an optical density of OD = 7.0-8.0. Using this preliminary culture, 15 ml of main culture in 5% DSM 92 medium with an optical density of OD = 1 .0 are prepared.

2. Fluorescence staining:

500 μΙ of the main bacterial culture are stained in accordance with the manufacturer

recommendation using 1.5 μΙ of Syto 9 fluorescent dye and 1 .5 μΙ of propidium iodide fluorescent dye (Film Tracer™ LIVE/DEAD^® Biofilm Viability Kit, from Invitrogen). 10 μΙ of this bacterial suspension are applied to the surface under investigation, and covered with a cover slip. A homogeneous film of liquid is formed, with a thickness of about 30 μηη. The test substrates are incubated in the dark at 37°C for up to 2 hours. After this time, > 95% living bacterial cells are found on untreated reference substrates (including pure glass).

3. Microscopy:

The test substrates are examined under a Leica DMI6000 B microscope with the cover slip facing the lens. Each test substrate is advanced automatically to 15 pre-defined positions, and images are recorded in the red (R) and green (G) fluorescence channel. The absorbance and emission wavelengths in the fluorescence channels are adapted to the dyes used. Bacteria with an intact cell membrane (living) are detected in the green channel, bacteria with a defective cell membrane (dead) are detected in the red channel. For each of the 15 positions, the number of bacteria in both channels is counted. The percentage of dead bacteria is calculated from the numbers in R/(R + G). The percentage of dead bacteria is averaged over the 15 positions and reported as the result.

Claims

1 . Membrane comprising vanadium pentoxide, wherein vanadium pentoxide is dispersed in the polymer matrix that forms the membrane, the separating layer and/or another part of the membrane, wherein said membrane does not comprise polyimide.

2. Membrane according to claim 1 , wherein vanadium pentoxide is present in the form of particles with an average particle size of 5 nm to 1 mm.

3. Membrane according to at least one of the preceding claims, wherein vanadium pentoxide is present in the form of nanoparticles with an average particle size of 1 to 1000 nm or nanowires.

Membrane according to at least one of the preceding claims, wherein vanadium pentoxide is present in an amount of 0.0001 % by weight to 10.0 % by weight of vanadium pentoxide relative to the matrix material.

Membrane according to at least one of the preceding claims, wherein vanadium pentoxide is present in combination with at least one other compound of a metal selected from Mo, W, Ta, Nb, Ru, Re, Ti, Fe, Sn, Cr, Ga, Al, Ge, Mn, Co, Ni, Cu, Ag, Se.

Membrane according to at least one of the preceding claims, in which said membrane is suitable as a reverse osmosis membrane, forward osmosis membrane, nanofiltration membrane, ultrafiltration membranes and/or microfiltration membrane.

Membrane according to at least one of the preceding claims, in which said membrane or at least one layer of said membrane comprises as the main component at least poly- arylene ether, polysulfone, polyethersulfones (PES), polyphenylensulfone, polyamides (PA), polyvinylalcohol (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA), CA- triacetate blend, Cellulose ester, Cellulose Nitrate, regenerated Cellulose, aromatic , aromatic/aliphatic or aliphatic Polyamide, aromatic, aromatic/aliphatic or aliphatic Polyimide, Polybenzimidazole (PBI), Polybenzimidazolone (PBIL), Polyacrylonitrile (PAN), PAN-poly(vinyl chloride) copolymer (PAN-PVC), PAN-methallyl sulfonate copolymer, Polysulfone, Poly(dimethylphenylene oxide) (PPO), Polycarbonate, Polyester, Polytetra- fluroethylene PTFE, Poly(vinylidene fluoride) (PVDF), Polypropylene (PP), Polyelectro- lyte complexes, Poly(methyl methacrylate) PMMA, Polydimethylsiloxane (PDMS), aromatic, aromatic/aliphatic or aliphatic polyimide urethanes, , aromatic, aromatic/aliphatic or aliphatic polyamidimides or mixtures thereof.

8. Membrane according to at least one of the preceding claims, in which said membrane or the separation layer of said membrane comprises as the main component at least one polyamide.

9. Process for making membranes according to at least one of claims 1 to 8, comprising the following steps: a) providing a dope solution of at least one polymer,

b) dispersing the vanadium pentoxide in said dope solution,

c) precipitating or coagulating said at least one polymer to form a membrane.

10. Process according to Claim 9 wherein said dope solution comprises at least one polymer selected from polyarylene ether, polysulfone, polyethersulfones (PES), polyphenylensul- fone, polyamides (PA), polyvinylalcohol (PVA), Cellulose Acetate (CA), Cellulose Triacetate (CTA), CA-triacetate blend, Cellulose ester, Cellulose Nitrate, regenerated Cellulose, aromatic , aromatic/aliphatic or aliphatic Polyamide, aromatic, aromatic/aliphatic or aliphatic Polyimide, Polybenzimidazole (PBI), Polybenzimidazolone (PBIL), Polyacrylo- nitrile (PAN), PAN-poly(vinyl chloride) copolymer (PAN-PVC), PAN-methallyl sulfonate copolymer, Polysulfone, Poly(dimethylphenylene oxide) (PPO), Polycarbonate, Polyester, Polytetrafluroethylene PTFE, Poly(vinylidene fluoride) (PVDF), Polypropylene (PP), Polyelectrolyte complexes, Poly(methyl methacrylate) PMMA, Polydimethylsiloxane (PDMS), , aromatic, aromatic/aliphatic or aliphatic polyamidimides, or mixtures thereof.

1 1 . Process for making a membrane or the separation layer of a membrane according to at least one of claims 1 to 8, comprising the following steps: f) dispersing of vanadium pentoxide in a solution of at least one monomer g) polymerizing said solution comprising at least one monomer.

12. Process according to claim 1 1 , wherein said membrane is a reverse osmosis (RO) or forward osmosis (FO) membrane and is made in an interfacial polymerization process comprising:

Contacting on a porous support membrane

m) a first solution containing a polyamine monomer, and

n) a second solution containing a polyfunctional acyl halide monomer, wherein at least one of solutions m) and n) contains dispersed vanadium pentoxide.

13. Use of membranes according to any of claim 1 to 8 or of membranes made according to any of claims 9 to 12 for the treatment of water, particularly sea water or brackish water.

14. Use according to claim13, in which said membranes are used for the desalination of sea water or brackish water or in a water treatment step prior to the desalination of sea water or brackish water.

15. Use of vanadium pentoxide for enhancing the flux through membranes.

16. Use of vanadium pentoxide for imparting biocidal properties to a membrane.