Membrane post treatment
View Patent ↗Hydrophilic porous polymeric membranes with high permeabilities, and processes for the preparation thereof are disclosed. Membranes may be prepared by including a preferably hydrophilic cross-linkable component such as PVP (either by inclusion into the polymer dope prior to casting, or coating or quenching cast membranes); and treating the polymeric microfiltration or ultrafiltration membrane with a crosslinking agent to cross-link said cross-linkable component. Preferred cross-linking agents include Fenton's reagent.
1. A method of forming a hydrophilic polymeric microfiltration or ultrafiltration membrane comprising the steps of:
preparing a dope comprising a polymeric material comprising polyvinylidene fluoride and a cross-linkable component;
preparing a polymeric microfiltration or ultrafiltration membrane from the dope; and
treating the polymeric microfiltration or ultrafiltration membrane at a pH in the range of 2.0-9.0 with a hydroxyl radical generated by an aqueous solution comprising a transition metal catalyst, hydrogen sulfate, and hydrogen peroxide to cross-link said cross-linkable component.
2. The method according to claim 1 , wherein the transition metal catalyst is selected from the group consisting of iron, molybdenum, chromium and cobalt.
3. The method according to claim 2 , wherein the transition metal catalyst is iron.
4. The method according to claim 3 , wherein the transition metal catalyst is a mixture of iron II and iron III.
5. The method according to claim 1 , wherein the cross-linkable component is a hydrophilic cross-linkable component.
6. The method according to claim 1 , wherein the cross-linkable component is selected from the group consisting of monomers, oligomers, polymers and copolymers of one or more of the following: vinyl pyrrolidone, vinyl acetate, vinyl alcohol, vinyl methyl ether, vinyl ethyl ether, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate propyl methacrylate, butyl methacrylate and maleic anhydride.
7. The method according to claim 1 , wherein the cross-linkable component is selected from poly(vinyl pyrrolidone), poly(vinyl acetate) or copolymers of vinyl pyrrolidone and vinyl acetate.
8. The method according to claim 1 , wherein the cross-linkable component is added in an amount which produces only a minimal attenuation of the hydrophilicity/hydrophobicity balance of the membrane.
9. The method according to claim 1 , wherein the polymeric microfiltration or ultrafiltration membrane comprises a non-cross-linkable component.
10. The method according to claim 9 , wherein the non-cross-linkable component is a polymer or a copolymer of oxidation resistant material.
11. The method according to claim 9 wherein the non-cross-linkable component is a polymer or a copolymer resistant to base attack.
12. The method according to claim 9 wherein the non-cross-linkable component comprises a monomer selected from the group consisting of chlorotrifluoroethylene, vinyl fluoride, vinyl chloride, vinylidene fluoride/vinylidene chloride/hexafluoropropylene, ethylene-chlorotrifluoroethlyene, and tetrafluoroethylene.
13. The method according to claim 1 , wherein the hydrogen sulfate comprises sodium hydrogen_sulfate (NaHSO 4 ).
14. The method according to claim 1 , wherein treating the polymeric microfiltration or ultrafiltration membrane with a hydroxyl radical generated by an aqueous solution comprising a transition metal catalyst and hydrogen peroxide comprises treating the membrane with a hydroxyl radical generated by an aqueous solution comprising ferric chloride, hydrogen peroxide and sodium hydrogensulfate.
15. The method according to claim 1 , wherein the aqueous solution further comprises sulphuric acid.
16. The method according to claim 1 , wherein further comprises citric acid.
17. The method according to claim 1 , further comprising applying ultraviolet radiation.
18. The method according to claim 1 , comprising at least one of soaking, filtering, or recirculating to cross-link the cross-linkable compound to the polymer matrix.
19. The method according to claim 1 , further comprising, after cross-linking, leaching an unbound amount of the cross-linkable component from the porous polymeric microfiltration or ultrafiltration membrane.
20. The method according to claim 19 , wherein leaching further comprises leaching with water.
21. The method according to claim 19 , wherein leaching further comprises leaching with a solvent compatible with the cross-linkable component.
22. The method according to claim 19 , wherein leaching further comprises leaching for a predetermined period of time.
23. The method according to claim 19 , wherein leaching further comprises leaching using a predetermined level of leachate.