Process for opening reverse osmosis membranes

• US 5,262,054 A
• Filed: 12/30/1992
• Issued: 11/16/1993
• Est. Priority Date: 12/30/1992
• Status: Expired due to Fees

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Wheeler, James W.
• Primary Examiner(s): SPEAR JR, FRANK
• Application Number:
  US07/998,486
• Time in Patent Office: 321 Days
• Field of Search: 210/639, 210/654, 210/500.38
• US Class Current: 210/639
• CPC Class Codes: B01D 67/0093 Chemical modification

Abstract

The salt passage of a reverse osmosis membrane is increased by: (a) contacting the membrane with ions to form a membrane-ion complex; (b) treating the membrane-ion complex with an aqueous solution of an alkali metal permanganate to form manganese dioxide crystals in the membrane; and (c) dissolving the manganese dioxide crystals. The process can be repeated any number of times to further open the membrane.

Claims

1. A process for increasing the salt passage of a reverse osmosis membrane comprising:

(a) contacting the membrane with ions to form a membrane-ion complex;

(b) treating the membrane-ion complex with an aqueous solution of an alkali metal permanganate to form manganese dioxide crystals in the membrane; and

(c) dissolving the manganese dioxide crystals.

2. The process of claim 1, wherein the membrane is an asymmetric hollow fiber polyamide reverse osmosis membrane.

3. The process of claim 1, wherein the membrane is an asymmetric thin film polyamide reverse osmosis membrane.

4. The process of claim 1, wherein the membrane is a thin film composite hollow fiber polyamide reverse osmosis membrane.

5. The process of claim 1, wherein the membrane is a thin film composite polyamide reverse osmosis membrane.

6. The process of claim 1, wherein step (a) comprises contacting the membrane with an inorganic ion selected from the group of divalent manganese, divalent tin, divalent iron, divalent lead, monovalent gold, monovalent thallium and trivalent uranium.

7. The process of claim 1, wherein step (a) comprises contacting the membrane with an organic amine salt selected from the group of hydroxylamine hydrochloride and ethanolamine hydrochloride.

8. The process of claim 1, wherein step (b) comprises treating the membrane-ion complex with an aqueous solution of 0.02 to 0.5 wt. % of an alkali metal permanganate.

9. The process of claim 1, wherein step (b) comprises treating the membrane-ion complex with an aqueous solution of 0.2 to 1.0 wt. % of an alkali metal permanganate.

10. The process of claim 1, wherein step (b) comprises treating the membrane-ion complex for 30 seconds to 50 hours.

11. The process of claim 1, wherein step (c) comprises dissolving the manganese dioxide crystals with a reagent selected from the group of sodium nitrite, potassium iodide, sodium bisulfite and hydrogen peroxide.

12. The process of claim 1, wherein after step (c) the membranes are flushed with water.

13. The process of claim 1 or 12, wherein steps (a) through (c) are repeated.