Method of cleaning membranes

Abstract

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 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 membrane and wherein the contaminant comprises a metal oxide or a metal hydroxide.    
   
   
       2 . (canceled)  
   
   
       3 . The method according to  claim 1 , wherein the contaminant comprises ferric floc.  
   
   
       4 - 17 . (canceled)  
   
   
       18 . A composition for cleaning a membrane contaminated with a contaminant, the 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 membrane and 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.  
   
   
       19 - 21 . (canceled)  
   
   
       22 . The composition according to  claim 18 , wherein the sulfite reducing agent comprises sodium metabisulfite and sodium hydrosulfite.  
   
   
       23 . The composition according to  claim 18 , further comprising an enhancing agent.  
   
   
       24 - 26 . (canceled)  
   
   
       27 . The composition according to  claim 18 , wherein the sulfite reducing agent comprises from about 0.5 wt. % to about 2 wt. % sodium metabisulfite.  
   
   
       28 . The composition according to  claim 18 , wherein the sulfite reducing agent comprises from about 20 wt. % to about 65 wt. % sodium hydrosulfite, and wherein the sulfite reducing agent is capable of dilution to a working concentration of about 0.5. wt. % to about 2 wt. % soluble sulfite reducing agent present in solubilized form.  
   
   
       29 . The composition according to  claim 18 , wherein the sulfite reducing agent comprises from about 0.5 wt. % to about 2 wt. % sodium hydrosulfite.  
   
   
       30 . The composition according to  claim 18 , comprising from about 20 wt. % to about 65 wt. % sodium metabisulfite and from about 20 wt. % to about 65 wt. % sodium hydrosulfite, 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 18 , comprising from about 0.5 wt. % to about 2 wt. % sodium metabisulfite and sodium hydrosulfite.  
   
   
       32 . A method for cleaning a membrane, the method comprising the step of: 
 cleaning the membrane using 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 membrane.    
   
   
       33 . A membrane, wherein the membrane is capable of cleaning by 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 membrane.  
   
   
       34 . A membrane, wherein the membrane is contaminated with a contaminant comprising a metal oxide or a metal hydroxide, and wherein the membrane is capable of cleaning by 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 membrane.  
   
   
       35 . The membrane of  claim 32 , wherein the membrane comprises a hollow fiber or a flat sheet.  
   
   
       36 . The membrane according to  claim 35 , wherein the membrane comprises a polyvinylidene fluoride polymer.