Thin film composite membrane structures

1. A thin film composite membrane structure comprising: a selective membrane layer for ion rejection attached to a hydrophilic support layer, the hydrophilic support layer comprising a multi-zone microfiltration membrane that is asymmetric comprising:

a porous support material; and

at least two microfiltration zones, where a first zone comprises a first membrane and a second zone that is attached to the first zone and that coats at least a portion of the depth of the porous support material;

wherein the first zone comprises a pore size that is smaller than a pore size of the second zone; and the pore size of the second zone is greater than the pore size of the first zone by a factor in the range of 1.1 to 500.

2. The thin film composite membrane structure of claim 1 , wherein the selective membrane layer comprises a polyamide membrane formed by interfacial polymerization on the hydrophilic support layer.

3. The thin film composite membrane structure of claim 2 , wherein the polyamide comprises piperazine (PIP), m-phenylenediamine (MPD), or combinations thereof.

4. The thin film composite membrane structure of claim 1 , wherein the first zone comprises a pore size in the range of 0.02 microns to 0.45 microns.

5. The thin film composite membrane structure of claim 1 , wherein the first zone comprises a thickness of at least 2.0 microns.

6. The thin film composite membrane structure of claim 1 , wherein the second zone comprises a pore size in the range of 0.65 microns to 10.0 microns.

7. The thin film composite membrane structure of claim 1 , wherein the second zone is continuously joined to the first zone through molecular entanglement.

8. The thin film composite membrane structure of claim 1 , wherein the first zone of the multi-zone microfiltration support layer is attached to the selective membrane layer.

9. The thin film composite membrane structure of claim 1 , wherein the support layer comprises a polyamide.

10. The thin film composite membrane structure of claim 1 , wherein the support layer comprises a modified membrane formed from a polyethersulfone, a polysulfone, a polyvinylidene difluoride (PVDF), ethylene chlorotrifluoroethylene (ECTFE), and/or polypropylene.

11. A thin film composite membrane structure comprising:

a selective membrane layer for ion rejection, the selective membrane layer comprising a polyamide; and

a multi-zone microfiltration hydrophilic support layer attached to the selective membrane, the multi-zone microfiltration support layer being asymmetric and comprising:

a porous support material comprising a nonwoven, woven, or extruded material selected from the group consisting of polypropylene, polyester, polyethylene, and combinations thereof; and

two microfiltration zones only, each comprising a polyamide, where a first zone comprises a first membrane and a second zone that is attached to the first zone and that coats at least a portion of the depth of the porous support material;

wherein the first zone comprises a pore size in the range of 0.02 microns to 0.45 microns and a thickness in the range of 2.0 microns to 10 microns, and the second zone comprises a pore size in the range of 0.65 microns to 10.0 microns.

12. The thin film composite membrane structure of claim 11 , wherein the polyamide of the selective membrane layer comprises piperazine (PIP), m-phenylenediamine (MPD), or combinations thereof.

13. A method of making a thin film composite membrane structure, the method comprising:

forming a multi-zone microfiltration hydrophilic membrane that is asymmetric comprising a porous support material; and at least two microfiltration zones, where a first zone comprises a first membrane and a second zone that is attached to the first zone and that coats at least a portion of the depth of the porous support material; and

forming a selective membrane on the multi-zone microfiltration membrane to form the thin film composite membrane structure;

wherein the first zone comprises a pore size in the range of 0.02 microns to 0.45 microns and a thickness in the range of 2.0 microns to 10 microns, and the second zone comprises a pore size in the range of 0.65 microns to 10.0 microns.

14. The method of claim 13 , wherein the selective membrane is formed on the multi-zone microfiltration membrane by interfacial polymerization.

15. A method of treating a liquid stream containing ions, the method comprising:

providing a thin film composite membrane structure comprising a selective membrane layer for ion rejection attached to a hydrophilic support layer, the hydrophilic support layer comprising a multi-zone microfiltration membrane that is asymmetric comprising:

a porous support material; and

at least two microfiltration zones, where a first zone comprises a first membrane and a second zone that is attached to the first zone and that coats at least a portion of the depth of the porous support material;

wherein the first zone comprises a pore size that is smaller than a pore size of the second zone; and the pore size of the second zone is greater than the pore size of the first zone by a factor in the range of 1.1 to 500; and

contacting the liquid stream with the thin film composite membrane structure.

16. The method of claim 15 , wherein the thin film composite membrane structure is provided in a reverse osmosis system, a nanofiltration system, a direct osmotic concentration system, a forward osmosis system, or a pressure retarded osmosis system.

17. The thin film composite membrane structure of claim 1 , wherein the multi-zone microfiltration membrane that is asymmetric consists of two zones.

18. The method of claim 13 , wherein the multi-zone microfiltration membrane that is asymmetric consists of two zones.