Claims
- 1. A method for recovering carboxylic acids from a dilute aqueous solution thereof, said dilute acid solution having an acid concentration below about ten percent (10%) by weight, said carboxylic acids being from the class consisting of acids having from one (1) to seven (7) carbon atoms and mixtures thereof, said method comprising the steps of:
- passing said dilute acid solution through a reverse osmosis membrane separator to thereby produce an aqueous permeate substantially free of acid and an aqueous retentate having an acid concentration more concentrated than the initial concentration of said dilute acid solution and above about ten percent (10%) by weight;
- treating said retentate in an acid separation step comprising the steps of contacting said retentate with a liquid extractant for acids to thereby produce an acid-rich extractate and a substantially acid-free raffinate; and
- recovering acid from said acid-rich extractate.
- 2. A method in accordance with claim 1 in which said acid separation step comprises extractive distillation.
- 3. A method in accordance with claim 1 in which said acid separation step comprises classical distillation.
- 4. A method in accordance with claim 1 in which said acids are from the class of acids consisting of acids having from two (2) to four (4) carbon atoms and mixtures thereof.
- 5. A method in accordance with claim 1 in which acid is recovered from said acid-rich extractate by distillation.
- 6. A method in accordance with claim 1 in which said reverse osmosis separator employs a semi-permeable membrane formed from a material selected from the class consisting of polysulfone, polyether sulfone, cellulose acetate, polyamide, cellulose esters, cellulose triacetate, polyether urea, polyvinyl alcohol, polypiperiazamide, polyfuren, cellulose acetate butyrate, aromatic polyamide, polyethyleneimine, and thin film composites of any of the above.
Parent Case Info
This application is a continuation of application Ser. No. 08/224,601 filed Apr. 7, 1994, now U.S. Pat. No. 5,492,625.
US Referenced Citations (10)
Foreign Referenced Citations (3)
Number |
Date |
Country |
0091799 |
Jun 1982 |
JPX |
118538 |
Jul 1983 |
JPX |
9323150 |
Nov 1993 |
WOX |
Continuations (1)
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Number |
Date |
Country |
Parent |
224601 |
Apr 1994 |
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