Method of cleaning membranes
View Patent ↗The present invention relates a method for cleaning polymeric microfiltration membranes and membrane units, and to compositions useful in such methods. The compositions include at least one soluble sulfite reducing agent and a compatible solvent.
1. A method of cleaning a porous polymeric membrane contaminated with a contaminant comprising ferric floc, the method comprising the step of:
contacting the contaminant with a composition comprising a sulfite reducing agent, and a solvent, wherein the sulfite reducing agent is soluble in the solvent, and wherein the solvent is compatible with the porous polymeric membrane.
2. The method according to claim 1 , wherein the contaminant comprises an organic compound.
3. The method according to claim 1 , wherein the solvent comprises water.
4. The method according to claim 1 , wherein the sulfite reducing agent is selected from the group consisting of sodium metabisulfite, sodium hydrosulfite, sodium sulfite, potassium metabisulfite, potassium hydrosulfite, potassium sulfite, and mixtures thereof.
5. The method according to claim 1 , further comprising the step of:
reducing a valence state of an atom of the contaminant to a lower valence state, whereby the contaminant is solublized and removed from the membrane.
6. The method according to claim 1 , wherein the enhancing agent is selected from the group consisting of inorganic acids, organic acids, and mixtures thereof.
7. The method according to claim 1 , wherein the enhancing agent comprises citric acid.
8. A method of cleaning a porous polymeric membrane contaminated with a contaminant, the method comprising the step of:
contacting the contaminant with a composition comprising a sulfite reducing agent and a solvent, wherein the sulfite reducing agent is soluble in the solvent, and wherein the solvent is compatible with the porous polymeric membrane, wherein the solvent comprises water and the sulfite reducing agent comprises sodium metabisulfite and sodium hydrosulfite.
9. The method according to claim 8 , wherein the sulfite reducing agent comprises from about 0.1 wt. % to about 5 wt. % of a component selected from the group consisting of sodium metabisulfite, sodium hydrosulfite, and mixtures thereof.
10. The method according to claim 8 , wherein the sulfite reducing agent comprises from about 0.5 wt. % to about 2 wt. % of a component selected from the group consisting of sodium metabisulfite, sodium hydrosulfite, and mixtures thereof.
11. A method according to claim 8 , wherein the composition comprises from about 0.5 wt. % to about 1.5 wt. % sodium metabisulfite and from about 0.5 wt. % to about 1.5 wt. % sodium hydrosulfite.
12. The method according to claim 8 , wherein the membrane comprises a hollow fiber microfiltration membrane or a hollow fiber ultrafiltration membrane.
13. The method according to claim 8 , wherein the membrane comprises a flat microfiltration membrane or a flat ultrafiltration membrane.
14. The method according to claim 8 , wherein the membrane comprises a polyvinylidene fluoride polymer.
15. A composition for cleaning a porous polymeric membrane contaminated with a contaminant, the composition comprising a sulfite reducing agent, an enhancing agent, and a solvent, wherein the sulfite reducing agent is soluble in the solvent, wherein the sulfite reducing agent comprises sodium metabisulfite and sodium hydrosulfite, and wherein the solvent is compatible with the membrane.
16. The composition according to claim 15 , wherein the contaminant comprises a metal oxide or a metal hydroxide.
17. The composition according to claim 15 , wherein the contaminant is ferric floc.
18. The composition according to claim 15 , wherein the enhancing agent comprises an inorganic acid or an organic acid.
19. The composition according to claim 18 , wherein the organic acid comprises citric acid.
20. A composition for cleaning a porous polymeric membrane contaminated with a contaminant, the composition comprising a sulfite reducing agent, an enhancing agent, and a solvent, wherein the sulfite reducing agent is soluble in the solvent, wherein the sulfite reducing agent comprises sodium metabisulfite and sodium hydrosulfite, wherein the solvent is compatible with the membrane, wherein the composition comprises from about 20 wt. % to about 65 wt. % sodium metabisulfite and about 20 wt. % to about 65 wt. % sodium hydrosulfite.
21. The composition according to claim 20 , wherein the contaminant comprises a metal oxide or a metal hydroxide.
22. The composition according to claim 20 , wherein the contaminant is ferric floc.
23. The composition according to claim 20 , further comprising an enhancing agent.
24. The composition according to claim 23 , wherein the enhancing agent comprises an inorganic acid or an organic acid.
25. The composition according to claim 24 , wherein the organic acid comprises citric acid.
26. The composition according to claim 20 , wherein the sulfite reducing agent is capable of dilution to a working concentration of from about 0.5 wt. % to about 2 wt. % of sulfite reducing agent in a solubilized form.
27. The composition according to claim 26 , wherein the sulfite reducing agent comprises from about 0.5 wt. % to about 2 wt. % sodium metabisulfite.
28. The composition according to claim 20 , wherein the sulfite reducing agent is capable of dilution to a working concentration of from about 0.5 wt. % to about 2 wt. % soluble sulfite reducing agent present in solubilized form.
29. The composition according to claim 20 , wherein the sulfite reducing agent comprises from about 0.5 wt. % to about 2 wt. % sodium hydrosulfite.
30. The composition according to claim 20 , wherein the sodium metabisulfite and sodium hydrosulfite are capable of dilution to a working concentration of about 0.5 wt. % to about 2 wt. % sulfite reducing agent in solubilized form.
31. The composition according to claim 20 , comprising from about 0.5 wt. % to about 2 wt. % sodium metabisulfite and sodium hydrosulfite.