Hybrid TFC RO membranes with nitrogen additives
RO membranes using chlorinated water as a feed stream maybe protected from damage by the chlorine with a protective layer including reactive nitrogen which forms chloromines on the surface of the membrane that reduce chlorine penetration. This protective layer also provides substantial anti-fouling capabilities, whether used with a chlorinated or unchlorinated feed stream because the chloramines are anti-bacterial. Although chlorine is lost in use, the anti-fouling layer or coating can be recharged with additional chlorine without damaging the discrimination layer. The anti-fouling layer or coating may be advantageously used with Thin film composite, TFC, membranes for use in forward and reverse osmosis may include nanoparticles, monohydrolyzed and/or di-hydrolyzed TMC, and/or alkaline earth alkaline metal complexes or other additives.
1. A reverse osmosis membrane having a surface accessible to a feed stream, the reverse osmosis membrane comprising:
(a) a porous support membrane;
(b) a discrimination layer on the porous support membrane comprising the interfacially polymerized product of a polyamine and a polyfunctional acid halide;
(c) optionally an anti-fouling layer on the discrimination layer; and
(d) nitrogen-containing species that are included with the discrimination layer, the anti-fouling layer, or both, which, upon exposure to halogens, reversibly react to form halamines on the surface of the reverse osmosis membrane,
wherein the nitrogen-containing species are derived from a source other than the polyamine and are selected from the group consisting of imides, sulfonamides, hydantoins, imidazolidin-4-ones, and combinations thereof.
2. A reverse osmosis membrane according to claim 1 wherein the nitrogen-containing species are included within the discrimination layer.
3. A reverse osmosis membrane according to claim 1 wherein the nitrogen-containing species are grafted to the discrimination layer.
4. A reverse osmosis membrane according to claim 1 wherein the nitrogen-containing species are coated on the discrimination layer.
5. A reverse osmosis membrane according to claim 1 wherein the reverse osmosis membrane further comprises an anti-fouling layer on the discrimination layer, and the nitrogen-containing species are included in the anti-fouling layer.
6. A reverse osmosis membrane according to claim 1 wherein the discrimination layer further comprises nanoparticles.
7. A reverse osmosis membrane according to claim 1 wherein the discrimination layer comprises the interfacially polymerized product of a polyamine, a polyfunctional acid halide, and a flux increasing additive.
8. A method of making an anti-fouling, reverse osmosis membrane comprising:
(a) providing the reverse osmosis membrane of claim 1 ; and
(b) exposing the surface of the reverse osmosis membrane to an aqueous feed stream comprising halogens to form halamines on the surface of the reverse osmosis membrane.
9. A method according to claim 8 wherein the aqueous feed stream comprises chlorine and the halamines comprise chloramines.