Water purification membranes with improved fouling resistance

1. A method of decreasing membrane fouling comprising the steps of:

depositing dopamine on a membrane to form a polydopamine coated membrane, wherein the polydopamine coated membrane has a higher water flux and a higher fouling resistance and an increased membrane surface hydrophilicity than an unmodified membrane.

2. The method of claim 1 , wherein the pure water flux of the polydopamine coated membrane comprises between 50 and 150% of the flux of the unmodified membrane.

3. The method of claim 1 , wherein filtration results in the water flux of the polydopamine coated membrane comprises about between 75 and 200% of the flux of the unmodified membrane.

4. The method of claim 1 , wherein the dopamine comprises one or more substitutions selected from the addition of halogens, hydroxyl groups, lower alkyl groups, lower alkoxy groups, monocyclic aryl, lower acyl groups and combinations thereof.

5. The method of claim 1 , wherein the membrane comprises a RO membrane, a UF membrane, a NF membrane, an MF membrane or a combination thereof.

6. The method of claim 1 , wherein the polydopamine coated membrane comprises one or more of the following polymethylmethacrylates, polystyrenes, polycarbonates, polyimides, epoxy resins, cyclic olefin copolymers, cyclic olefin polymers, acrylate polymers, polyethylene teraphthalate, polyphenylene vinylene, polyether ether ketone, poly (N-vinylcarbazole), acrylonitrile-styrene copolymer, or polyetherimide poly(phenylenevinylene).

7. The method of claim 1 , wherein the dopamine comprises one or more functional groups chosen from ROOH, ROSH, RSSH, OH, SO3H, SO3R, SO4R, COOH, NH2, NHR, NR2, CONH2, and NH—NH2, wherein R denotes: linear or branched hydrocarbon-based chains, capable of forming at least one carbon-based ring, being saturated or unsaturated; alkylenes, siloxanes, silanes, ethers, polyethers, thioethers, silylenes, and silazanes.

8. The method of claim 1 , wherein the polydopamine coated membrane comprises one or more polysulfone, copolymer of styrene and acrylonitrile poly(arylene oxide), polycarbonate, cellulose acetate, polysulfones; poly(styrenes), styrene-containing copolymers, acrylonitrilestyrene copolymers, styrene-butadiene copolymers, styrene-vinylbenzylhalide copolymers; polycarbonates; cellulosic polymers, cellulose acetate-butyrate, cellulose propionate, ethyl cellulose, methyl cellulose, nitrocellulose, polyamides, polyimides, aryl polyamides, aryl polyimides, polyethers, poly(arylene oxides), poly(phenylene oxide), poly(xylene oxide); poly(esteramide-diisocyanate), polyurethanes, polyesters (including polyarylates), poly(ethylene terephthalate), poly(alkyl methacrylates), poly(acrylates), poly(phenylene terephthalate), polysulfides, poly (ethylene), poly(propylene), poly(butene-1), poly(4-methyl pentene-1), polyvinyls, poly(vinyl chloride), poly(vinyl fluoride), poly(vinylidene chloride), poly(vinylidene fluoride), poly(vinyl alcohol), poly(vinyl esters), poly(vinyl acetate), poly(vinyl propionate), poly(vinyl pyridines), poly(vinyl pyrrolidones), poly(vinyl ethers), poly(vinyl ketones), poly(vinyl aldehydes), poly(vinyl formal), poly(vinyl butyral), poly(vinyl amides), poly(vinyl amines), poly(vinyl urethanes), poly(vinyl ureas), poly(vinyl phosphates), poly(vinyl sulfates), polyallyls; poly(benzobenzimidazole), polyhydrazides, polyoxadiazoles, polytriazoles, poly (benzimidazole), polycarbodiimides, polyphosphazines and combinations thereof.

9. The method of claim 1 , further comprising the step of applying one or more second coatings to the polydopamine coated membrane.

10. The method of claim 9 , further comprising the step of applying one or more second coatings to the polydopamine coated membrane, wherein the one or more second coatings are polyethylene glycol (PEG) using polydopamine as an adhesion layer.

11. The method of claim 1 , further comprising the step of applying one or more hydrophilic coatings to the polydopamine coated membrane.

12. A liquid separation apparatus comprising:

a purification membrane;

a polydopamine layer deposited on the purification membrane to form a polydopamine coated membrane, wherein the polydopamine layer increases the hydrophilicity of the purification membrane and the polydopamine coated membrane has a high water flux; and

one or more containers positioned on different sides of the polydopamine coated membrane to contain the separated liquid.

13. A purification membrane comprising:

a hydrophobic purification membrane;

a polydopamine layer in contact with the hydrophobic purification membrane to form a polydopamine coated hydrophobic purification membrane with a high water flux and a high hydrophilicity than an unmodified hydrophobic membrane; and

a hydrophilic coating in contact with the polydopamine layer to form a multi layer hydrophobic-polydopamine-hydrophilic purification membrane.

14. A purification membrane comprising:

a polymer matrix purification membrane; and

one or more monomers comprising an aromatic dihydroxy and an amine deposited on the purification membrane to form an aromatic dihydroxy and amine-coated purification membrane; and

a polydopamine layer in contact with the dihydroxy and amine-coated purification membrane to form a polydopamine coated purification membrane with a higher water flux and a higher hydrophilicity than an unmodified dihydroxy and amine-coated purification membrane.

15. A purification membrane comprising:

a polymer matrix purification membrane; and

a polydopamine layer deposited on the purification membrane to form a polydopamine coated purification membrane with a high water flux and a high hydrophilicity than an unmodified membrane.

16. A polydopamine coated purification membrane system for modification of conventional purification membranes comprising:

a dopamine solution disposed in a feed tank;

a pump connected to the feed tank to move the dopamine solution;

a membrane inlet connection to connect the pump to a membrane to allow the polydopamine to be deposited on the membrane; and

a membrane outlet connection to connect the membrane to the feed tank to return the dopamine solution to the feed tank.