Method for making high flux, high salt rejection cellulose desalting membranes
AssigneesThe United States of America as represented by the Secretary of the Interior, The Bereau of Reclamation, Separation Systems Technology Inc.
InventorsAndrew Patrick MURPHY, Saied DELAGAH, Robert Lee RILEY
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Abstract
A method is provided for producing a high flux, high salt rejection cellulose acetate desalination membrane. In this method, cellulose acetate polymer is dissolved in a first solvent such as methylene chloride or 2-methyltetrahydrofuran to produce a solution. Further steps involve stirring the solution, and thereafter permitting the solution to settle, for a time sufficient for a majority of the cellulose acetate to precipitate out of the solution to form a cellulose acetate precipitate. Next, the cellulose acetate precipitate is stirred into an excess methanol. Thereafter, the cellulose acetate is filtered out and used in making the desalination membrane.
Claims21
A method of producing high flux, high salt rejection cellulose acetate desalination membranes, said method comprising the steps of:
- (a) mixing cellulose acetate polymer in a first solvent to produce a slurry
- (b) stirring the slurry, and thereafter permitting the slurry to settle for a time sufficient for a majority of the cellulose acetate to precipitate out of solution to form a cellulose acetate precipitate
- (c) decanting off the solvent containing impure components so as to leave the cellulose acetate precipitate behind;
- (d) stirring the cellulose acetate precipitate into an excess of a further solvent;
- (e) repeating steps (c) and (d) two to four times;
- (f) adding the cellulose acetate slurry into a second solvent that results in solvent exchange of the first solvent for the second solvent;
- (g) evaporating the second solvent to leave cellulose acetate polymer;
- (h) using the cellulose acetate polymer of step (g) to make casting solutions.
- (i) filtering the casting solutions;
- and
- (j) using the filtered casting solutions to make a desalination membrane.
A method of producing high flux, high salt rejection cellulose acetate desalination membranes, said method comprising the steps of:
- (a) dissolving cellulose acetate polymer in a first solvent to produce a solution;
- (b) stirring the solution, and thereafter permitting the solution to settle for a settling time sufficient for a majority of the cellulose acetate to precipitate out of the solution to form a cellulose acetate precipitate;
- (c) stirring the cellulose acetate precipitate into an excess of methanol to effect a solvent exchange that results in solvent exchange of methanol for the first solution;
- (d) evaporating the methanol to leave cellulose acetate polymer
- (e) using the cellulose acetate polymer produced by step (d) in making a desalination membrane.
A method as claimed in claim 11 wherein the step (b) of stirring the solution takes place at a stir rate between 10 to 10,000 rpm and the settling time is between 1 minute to 15 days
A method of producing high flux, high salt rejection cellulose acetate desalination membranes, the method comprising the steps of:
- (a) mixing cellulose acetate polymer in a first solvent to produce a slurry;
- (b) stirring the slurry, and thereafter permitting the slurry to settle, for a time sufficient for a majority of the cellulose acetate to precipitate out of the solution to form a cellulose acetate precipitate;
- (c) decanting off the solvent containing impure components so as to leave the cellulose acetate precipitate behind;
- (d) stirring the cellulose acetate precipitate into an excess of a further solvent;
- (e) repeating steps (c) and (d) two to four times;
- (f) adding the cellulose acetate slurry into a second solvent that results in solvent exchange of the first solvent for the second solvent;
- (g) decanting off the second solvent containing impure components so as to leave the cellulose acetate polymer behind;
- (h) stirring the cellulose acetate precipitate into an excess of another solvent
- (i) repeating steps (g) and (h) two to four times;
- and
- (j) evaporating the solvent to leave cellulose acetate polymer;
- (k) using the cellulose acetate polymer of step (j) to make casting solutions.
- (l) filtering the casting solutions;
- and
- (m) using the filtered casting solutions to make a desalination membrane.
Dependencies are inferred from the claim text.