Forward osmosis membranes
Forward osmosis membranes include an active layer and a thin support layer. A bilayer substrate including a removable backing layer may allow forward osmosis membranes with reduced supporting layer thickness to be processed on existing manufacturing lines.
1. A method of making a forward osmosis membrane, comprising:
providing a support structure comprising a bilayer substrate including first and second separable layers;
applying a material to the first layer of the bilayer substrate of the support structure to form a membrane support layer;
applying a barrier material to the membrane support layer to form the forward osmosis membrane; and
separating the second layer of the bilayer substrate from the first layer of the bilayer substrate to form the forward osmosis membrane.
2. The method of claim 1 , wherein the first layer of the bilayer substrate has a Frazier air permeability of greater than about 50 cfm/ft 2 min and a thickness of less than about 2 mils.
3. The method of claim 1 , wherein the material applied to the first layer of the bilayer substrate comprises a polymer loading of between about 5 and 20 g/m 2 .
4. The method of claim 1 , wherein the support layer has an overall thickness of less than about 50 microns.
5. The method of claim 1 , wherein the barrier material comprises a semipermeable material.
6. The method of claim 5 , wherein the barrier material comprises a polymer.
7. The method of claim 6 , wherein the barrier material comprises a polyamide urea, polypiperazine, or a block co-polymer.
8. The method of claim 1 , wherein the bilayer substrate comprises a polymeric paper.
9. The method of claim 8 , wherein the bilayer substrate comprises polyethylene terephthalate or polypropylene.
10. The method of claim 1 , further comprising rewetting the forward osmosis membrane.
11. The method of claim 1 , further comprising adding an additive to one or more layers of the membrane.
12. The method of claim 1 , wherein the step of separating the second layer of the bilayer substrate from the first layer of the bilayer substrate comprises modifying a pore structure in the support layer.
13. The method of claim 1 , further comprising reusing the second layer of the bilayer substrate.
14. A method of making a forward osmosis membrane, comprising:
providing a support structure comprising a bilayer substrate including first and second separable layers;
applying a material to the first layer of the bilayer substrate to form a membrane support layer, such that the material penetrates at least a portion of the first layer of the bilayer substrate and only partially penetrates the second layer of the bilayer substrate;
applying a barrier material to the membrane support layer to form the forward osmosis membrane;
separating the second layer of the bilayer substrate from the first layer of the bilayer substrate; and
modifying a pore structure of the support layer.
15. A method of making a forward osmosis membrane, comprising:
providing a support structure comprising a bilayer substrate including first and second separable layers, wherein the first layer has a Frazier air permeability of greater than 100 cfm/ft 2 -min;
applying a material to the first layer of the bilayer substrate to form a membrane support layer;
applying a barrier material to the membrane support layer to form the forward osmosis membrane; and
separating the second layer of the bilayer substrate from the first layer of the bilayer substrate to form the forward osmosis membrane.