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 including at least a first layer and a second layer;
applying a material to a first layer 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
releasing the forward osmosis membrane by separating the first layer of the support structure from the second layer of the support structure.
2 . The method of claim 1 , wherein the support structure comprises a bilayer structure.
3 . The method of claim 1 , wherein the first layer of the support structure has a Frazier air permeability of greater than about 50 cfm/ft 2 min.
4 . The method of claim 1 , wherein the material applied to the first layer of the support structure is applied in a coating of between about 5 and 20 g/m 2 .
5 . The method of claim 1 , wherein the forward osmosis membrane has an overall thickness of less than about 125 microns.
6 . The method of claim 1 , wherein the barrier material comprises a semipermeable material.
7 . The method of claim 6 , wherein the barrier material comprises a polymer.
8 . The method of claim 7 , wherein the barrier material comprises a polyamide urea, polypiperazine, or a block co-polymer.
9 . The method of claim 1 , wherein the support structure comprises a polymeric paper.
10 . The method of claim 9 , wherein the support structure comprises PET or polypropylene.
11 . The method of claim 1 , further comprising rewetting the forward osmosis membrane.
12 . The method of claim 1 , further comprising adding an additive to one or more layers of the membrane.
13 . The method of claim 1 , wherein the step of releasing the forward osmosis membrane by separating the first and second layers of the support structure comprises modifying a pore structure in at least a section of the forward osmosis membrane.
14 . The method of claim 1 , further comprising reusing the second layer of the support structure.
15 . A method of making a forward osmosis membrane, comprising:
casting a paperless support structure on a fabrication belt or drum;
depositing a barrier material on the paperless support structure; and
delaminating the paperless support structure from the fabrication belt to form the forward osmosis membrane.
16 . The method of claim 15 , wherein the belt or drum is constructed and arranged to provide a surface which retains a portion of the support structure.
17 . The method of claim 15 , wherein retained support structure is removed prior to full rotation of the belt or drum.
18 . A method of facilitating a forward osmosis separation operation, comprising:
providing a support structure;
applying a material to the support structure to form a membrane support layer;
applying a barrier layer to the membrane support layer to form a forward osmosis membrane; and
configuring the forward osmosis membrane in a forward osmosis membrane module such that the support structure may provide a spacer or a flow channel for a draw solution or a feed solution supplied to the module during the forward osmosis separation operation.
19 . The method of claim 18 , wherein providing the support structure comprises providing a bilayer structure.
20 . The method of claim 18 , further comprising providing a source of the draw solution.
21 - 23 . (canceled)