Asymmetric forward osmosis membranes
AssigneeHydration Technologies Inc.
InventorJack Herron
Life of this patent
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Abstract
There is disclosed a membrane formulation having high flux for forward osmosis applications. There is disclosed a forward osmosis filtration membrane having a salt rejection 99+% or greater, and comprising an asymmetric hydrophobic porous backing and cellulosic fibers. The membranes of the present invention find use in a variety of applications including osmotic-driven water purification and filtration, desalination of sea water, purification of contaminated aqueous waste streams, and the like. Specifically, there is disclosed a forward osmosis filtration membrane having a skin layer for salt rejection and a porous scaffold layer having a woven or non-woven mesh embedded within it.
Claims14
An asymmetric forward osmosis membrane having three layers comprising:
- (a) a skin layer made from polymeric material having a top surface as a rejection surface of the asymmetric forward osmosis membrane, and a bottom surface, wherein the density of the skin layer is greater than 50% polymer by volume, and wherein the skin layer has an average thickness of from about 8 to about 18 microns;
- (b) a porous scaffold layer having a first surface bonded to the bottom surface of the skin layer and a second surface, wherein the scaffold layer is made from the same polymeric material as the skin layer and wherein the density of the scaffold layer is from about 15% to about 30% by volume, and wherein the scaffold layer has an average thickness of from about 25 to about 75 microns;
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- (c) a hydrophilic support fabric.
An asymmetric forward osmosis membrane having three layers comprising:
- (a) a skin layer made from polymeric material having a top surface as a rejection surface of the asymmetric forward osmosis membrane, and a bottom surface, wherein the density of the skin layer is greater than 50% polymer by volume;
- (b) a microporous scaffold layer having a first surface bonded to the bottom surface of the skin layer and a second surface, wherein the scaffold layer is made from the same polymeric material as the skin layer and wherein the density of the scaffold layer is from about 15% to about 30% polymer by volume;
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- (c) a support fabric having greater than 50% open area embedded in the scaffold layer.
An immersion/precipitation process for making preparing a supported forward osmosis filtration membrane comprising:
- (a) providing a porous nonwoven or woven support material having greater than 50% open area;
- (b) applying a casting solution slurry onto a rotating drum to form a casting solution layer having a substantially uniform surface, wherein the casting solution comprises from about 70% to about 90% (by volume) of a solvent formulation and from about 10% to about 30% (by volume) of a polymeric solid material;
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- (c) embedding the support fabric into the layer of casting solution by pulling the support into the layer;
- (d) forming a skin layer with an air knife;
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- (e) immersing the casting solution into a water bath to coagulate the polymeric material into a FO membrane backed with the support material.
Dependencies are inferred from the claim text.