Coated ion exchange membranes

1. An ion exchange membrane, comprising:

a polymeric microporous substrate;

a cross-linked ion transferring polymeric layer on the substrate; and

a hydrophobic coating on the cross-linked ion transferring polymer, the hydrophobic coating comprising at least one of a weak base copolymer and an organosilicate compound.

2. The ion exchange membrane of claim 1 , wherein the membrane comprises a total thickness of about 20 μm to about 255 μm.

3. The ion exchange membrane of claim 2 , wherein the cross-linked ion transferring polymer is a cross-linked cation transfer polymer.

4. The ion exchange membrane of claim 2 , wherein the microporous support comprises polypropylene, high molecular weight polyethylene, ultrahigh molecular weight polyethylene, or polyvinylidene fluoride.

5. The ion exchange membrane of claim 3 , wherein the cross-linked ion transferring polymer comprises the polymerization product of 2-sulfoethylmethacrylate and a cross-linking monomer.

6. The ion exchange membrane of claim 5 , wherein the cross-linking monomer comprises at least one of ethyleneglycol-dimethacrylate, m-divinylbenzene, and a mixture of m-divinylbenzene and p-divinylbenzene.

7. The ion exchange membrane of claim 3 , wherein the cross-linked ion transferring polymer comprises the polymerization product of 2-sulfoethylmethacrylate, a low value r 2 /r 8 monomer, and a cross-linking monomer.

8. The ion exchange membrane of claim 7 , wherein the cross-linking monomer comprises at least one of ethyleneglycol-dimethacrylate, m-divinylbenzene, and a mixture of m-divinylbenzene and p-divinylbenzene.

9. The ion exchange membrane of claim 7 , wherein the low value r 2 /r 8 monomer has an r 2 /r 8 value of less than about 1.3.

10. The ion exchange membrane of claim 7 , wherein the low value r 2 /r 8 monomer is acrylic acid or methacrylic acid, glycidyl methacrylate, methylmethacrylate, or styrene.

11. The ion exchange membrane of claim 1 , wherein the weak base copolymer comprises a thermoplastic copolymer.

12. The ion exchange membrane of claim 11 , wherein the thermoplastic copolymer comprises poly (2-vinylpyridine-co-styrene).

13. The ion exchange membrane of claim 1 , wherein the organosilicate compound comprises tetraethoxysilane.

14. The ion exchange membrane of claim 1 , wherein the membrane has an apparent permselectivity of greater than about 95%.

15. The ion exchange membrane of claim 1 , wherein the membrane has a resistivity of less than about 1.5 Ohm-cm 2 .

16. A method of reducing water loss in an electrochemical separation device comprising at least one ion exchange membrane, the method comprising:

coating the at least one ion exchange membrane with a hydrophobic weak base copolymer or a hydrophobic organosilicate compound; and

integrating the at least one coated ion exchange membrane into the electrochemical separation device.

17. The method of claim 16 , wherein the weak base copolymer comprises a thermoplastic copolymer.

18. A water treatment system, comprising:

an electrochemical separation device comprising at least one ion exchange membrane coated with a hydrophobic weak base copolymer or a hydrophobic organosilicate compound.

19. The water treatment system of claim 18 , wherein the weak base copolymer comprises poly (2-vinylpyridine-co-styrene).

20. The water treatment system of claim 18 , wherein the organosilicate compound comprises an acryl-silano-melamine compound.