IL29555A - Process for the manufacture of reverse osmosis membranes and membranes produced thereby - Google Patents
Process for the manufacture of reverse osmosis membranes and membranes produced therebyInfo
- Publication number
- IL29555A IL29555A IL29555A IL2955568A IL29555A IL 29555 A IL29555 A IL 29555A IL 29555 A IL29555 A IL 29555A IL 2955568 A IL2955568 A IL 2955568A IL 29555 A IL29555 A IL 29555A
- Authority
- IL
- Israel
- Prior art keywords
- membrane
- solvent
- casting
- range
- zinc chloride
- Prior art date
Links
- 239000012528 membrane Substances 0.000 title claims description 45
- 238000000034 method Methods 0.000 title claims description 38
- 238000004519 manufacturing process Methods 0.000 title claims description 6
- 238000001223 reverse osmosis Methods 0.000 title description 5
- 238000005266 casting Methods 0.000 claims description 40
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims description 36
- 239000002904 solvent Substances 0.000 claims description 27
- 235000005074 zinc chloride Nutrition 0.000 claims description 18
- 239000011592 zinc chloride Substances 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 229920002678 cellulose Polymers 0.000 claims description 14
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 12
- 238000007654 immersion Methods 0.000 claims description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 10
- 239000003960 organic solvent Substances 0.000 claims description 8
- 229920002301 cellulose acetate Polymers 0.000 claims description 6
- 230000007062 hydrolysis Effects 0.000 claims description 5
- 238000006460 hydrolysis reaction Methods 0.000 claims description 5
- 150000002148 esters Chemical class 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 125000000218 acetic acid group Chemical group C(C)(=O)* 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- ZJZXSOKJEJFHCP-UHFFFAOYSA-M lithium;thiocyanate Chemical compound [Li+].[S-]C#N ZJZXSOKJEJFHCP-UHFFFAOYSA-M 0.000 claims description 3
- 238000012986 modification Methods 0.000 claims description 3
- 230000004048 modification Effects 0.000 claims description 3
- 238000007127 saponification reaction Methods 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims 1
- 239000000243 solution Substances 0.000 description 22
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 229920000742 Cotton Polymers 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- MPCRDALPQLDDFX-UHFFFAOYSA-L Magnesium perchlorate Chemical compound [Mg+2].[O-]Cl(=O)(=O)=O.[O-]Cl(=O)(=O)=O MPCRDALPQLDDFX-UHFFFAOYSA-L 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000011021 bench scale process Methods 0.000 description 1
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical class [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 1
- 235000011132 calcium sulphate Nutrition 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012527 feed solution Substances 0.000 description 1
- 239000005457 ice water Substances 0.000 description 1
- 239000003295 industrial effluent Substances 0.000 description 1
- TWNIBLMWSKIRAT-VFUOTHLCSA-N levoglucosan Chemical group O[C@@H]1[C@@H](O)[C@H](O)[C@H]2CO[C@@H]1O2 TWNIBLMWSKIRAT-VFUOTHLCSA-N 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 230000003204 osmotic effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/08—Polysaccharides
- B01D71/12—Cellulose derivatives
- B01D71/14—Esters of organic acids
- B01D71/16—Cellulose acetate
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0016—Coagulation
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Dispersion Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Description
l'DnitUI |Π3 ΤϊΙΠ1, ,Ί 'Π PATENT ATTORNEYS □ •BIOS 'Dim PATENTS AND DESIGNS ORDINANCE SPECIFICATION Process for the manufacture of reverse osmosis membranes and membranes produced thereby miysatn o'nxi'an can i BABCOCK & WILCOX LIMITED, a British company, of Babcock House, 209 Euston Road, London, N.W.i, Great Britain do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement :- The present invention relates to a process for the manufacture of reverse osmosis membranes, and to membranes produced thereby.
Reverse osmosis is a process in which pressure, in excess of the net osmotic pressure, is applied to a solution in contact with a membrane to force the solvent but not the solute through the membrane. Among the commercial applications of such a process may be mentioned desalinisation of salt water to render it potable, treatment of sewage and industrial effluents, and concentration of heat-sensitive and other solutions or suspensions (for example, sols and lattices).
It is known to produce cellulose acetate desalination membranes from a easting solution containing 22,2% by weight cellulose acetate, 1.1% by weight magnesium perchlorate, 0$ by weight water and 66.7% by weight acetone.
- It has been reported that improvements have been achieved by the addition of small quantities of a fifth componenty such as hydrochloric acid to the casting solution.
Casting was performed at a temperature in the range of -5° and -10°C, after an evaporation of three minutes the membrane was immersed in ice water for 1 hour, the membrane was then heated by immersion in water at a temperature of 65p to 85°C for 5 minutes.
It was found that it was desirable to cast with both the casting solution and the necessary equipment at a temperature in the range of -5° and -10°C as it was found that films cast at room temperature were not cons1s ant.
Another investigator fabricated membranes for bench-scale tests from solutions containing zinc chloride. However, no details or directions were given.
The present invention provides a process for the manufacture of a semi-permeable membrane, which includes (a) Casting a solution at ambient temperature comprising 18 to 25% by weight of a cellulose ester, 2 to 0% by weight of zinc chloride, an organic solvent for the cellulose ester and a solvent for zinc chloride miscible with the solvent for the cellulose ester, the solution having an acidity such that hydrolysis of the zinc chloride and saponification of the ester are substantially prevented, by evaporating at least a portion of the organic solvent to form a membrane, (b) immersing he membrane in a solvent for zinc chloride which is miscible with the solvent for the cellulose ester, and (c) heating the membrane in a liquid in which cellulose ester is not soluble.
While the invention is in no way to be regarded as being limited by any theoretical explanation, it is believed that satisfactory membrane performance depends upon removal of at least sufficient solvent to form a solidified surface layer.
Preferably, the immersion solvent and the liquid in which the membrane is heated are the same, such that the membrane heated while immersed in the immersion solvent.
The immersion solvent and the solvent for zinc chloride in the casting solution preferably include water or are water. For example the solvent may*, in either case, be an aqueous alcohol. Alternatively, the solvents used may be non-aqueous, for example an alcohol such as methyl alcohol.
Advantageously the cellulose ester is cellulose acetate. Preferably, the acetyl content of the ester is within the range of frim 38 to 4-2% (i.e. approximately 2.3 to 2.7 out of the 3 possible positions on tbe anhydroglucose unit are acetylated). One suitable form of cellulose acetate is that sold by Eastman Kodak under the designation Ε398-3» having an acetyl content of 39«8%. This cellulose acetate is believed to be derived from cotton linters.
The organic solvent in the casting solution may be, for example, acetone, and when water is used as the zinc chloride solvent in the casting solution, the ratio of acetone to water ie advantageously within the range of from 18:1 to 2.8:1 by weight.
Preferably, the acidity of the solution is maintained within the desired range by addition of hydrochloric acid, conveniently in a concentrated form, to the casting solution. The acidity is, however, not critical provided that, at one extreme, saponification of the cellulose ester is prevented or does not take place to any significant extent, and at the other, hydrolysis of zinc chloride is prevented or does not take place to any significant extent.
Hydrolysis may readily be detected by observation; if the solution becomes cloudy after standing, then precipitation of the hydrolysis product is taking place.
Casting is carried out at ambient temperature, preferably between 10°0 and 23°C.
The casting may be carried out for example on a flat horizontal place or on the inner or outer surface of a tube, The proportions by weight of the casting solution may be, for example, as follows: Preferred Range Cellulose ester (acetate) 18 to 25$ 18.? + 0.5$ Organic solvent (acetone) 55 to 70$ 56.2 + 1.0$ Zinc chloride 2 to 10$ 8.3 + 0.5$ Water 4 to 20$ 16,7 + 1.0$ Concentrated (10$ by weight) hydrochloric acid 0.1 to 0.5$ about 0.4$ If casting takes place on a plate, the casting time may be, for example, within the range of from 10 to 100, advantageously 30 to 75 seconds, preferably about 45 seconds. If casting takes place on a tube, for example on the inner surface of a vertical tube being lowered over a bob which retains the casting composition, allowing a thin film to be applied to the tube, a shorter interval may be employed between application and immersion.
The membrane may have a thickness within the range of from 0.15 to 0.75 mm, preferably about 0«30 mm.
The cast membrane may be immersed for example in water, after evaporation of organic solvent, at any temperature, advantageously a temperature within the range of from 0° to 30°C, preferably 5°C to 21°C, advantageously for 3 to 10 minutes.
The membrane may be heated, preferably in water, advantageously at a temperature within the range of from 50°C to 90°C, preferably from 60° to 80°C. The heating may he, for example, for a period within the range of from 5 minutes to 30 minutes.
Within the ranges given above, membranes having a high degree of efficiency in rejecting solutes whilst allowing a practical throughput of solvent may be obtained. For a given casting solution, the casting conditions and subsequent treatment steps may be varied to increase throughput at the expense of solute rejection.
In order to give a true comparison, the Examples which follow all refer to the use of the membranes with an aqueous solution of sodium chloride. The same membranes may, however, have a higher rejection of solutes other than sodium chloride at the same throughput, for example magnesium and calcium sulphates or organic compounds, for example, sugar. Thus, a range of useful products may be obtained from the same basic casting solution by variation in the preparation steps, and products which would not give an acceptable rejection of sodium chloride may have an acceptable rejection of another solute at a high throughput.
Simple experiment will show the effect of the various parameters; the direction of the effect can be ascertained from the Examples which follow. Certain precautions should be taken in casting to ensure a reproducibly consistent membrane from the given casting solution. For example, it is important that when casting is carried out on a plate the casting surface "be horizontal with the thickness of the cast film "being constant across the plate, furthermore by maintaining the "blade edge of the casting knife accurately straight and moving the knife in a smooth manner the quality of the cast film is increased.
In a modification of the process of the invention, the zinc chloride in the casting solution may "be replaced "by lithium thiocyanate.
The invention accordingly provides a modification of the process, wherein the zinc chloride is replaced "by lithium thiocyanate and the acid is, if desired, omitted.
The invention also includes semi-permeable membranes made by the process, . The invention further includes reverse osmosis apparatus containing at least one of the membranes and means for applying a solution or suspension under pressure to the membrane.
The following Examples illustrate the invention: on a of ¬ solution. The throughput was 2360 litres per square metre of membrane per day and the rejection was 89 . The rejection $ is fo decrease in salinity from feed solution obtained after passage through membrane.
Examples 2 to 7 Examples 2 to 7 illustrate the effect of variation of the constituents of the casting solution on the throughput and rejection. The casting time and other conditions of preparation were as in Example 1.
Examples 8 to 15 Examples 8 to 15 illustrate the effect on the throughput and rejection of variation of the immersion temperature. The other process steps were as described in Example 1· ng the ame etate c e 29555/2
Claims (28)
1. A process for the manufacture of a semi-permeable membrane, which includes (a) casting a solution at ambient temperature comprising 18 to 25% by weight of a cellulose ester, 2 to 10% by weight zinc chloride, an organic solvent for the cellulose ester and a solvent for zinc chloride miscible with the solvent for the cellulose ester, the solution having an acidity such that hydrolysis of the zinc chloride and saponification of the ester are substantially prevented, by evaporating at least a portion of the organic solvent to form a membrane, (b) immersing the membrane in a solvent for zinc chloride miscible with the solvent for the cellulose ester, (c) heating the membrane in a liquid in which cellulose ester is not soluble.
2. A process as claimed in claim 1, wherein the immersion solvent and the .liquid in which the membrane is heated are the same.
3. A process as claimed in claims 1 or 2 wherein the immersion solvent includes water.
4. . A process as claimed in Claims 1 or 2, wherein the immersion solvent is water.
5. A process as claimed in any one of Claims 1 to . wherein the solvent for zinc chloride in the casting solution includes water. 29555/2
6. A process as claimed in any one of Claims 1 to , wherein the solvent for sine chloride in the casting solution is water.
7. A process as claimed in ,any■ one-, of Claims 1 to 6, wherein the · cellulose ester is cellulose acetate.
8. A process as claimed in Claim'7» wherei -the acetyl content of the ester is within the range of from 38% to 2?έ. . :
9. A process as claimed in any one of claims 1 to 8, wherein the organic solvent in the casting solution is acetone.
10. A process as claimed in Claim 9, wherein the solvent for zinc chloride in the casting solution is water and the ratio of acetone to water in the casting solution is within the range of from 18:1 to 2.8:1 by weight.
11. 1 . A process as claimed in any one of claims 1 to 10, wherein the acidity of the casting solution is maintained within the desired range by addition of hydrochloric acid. 29555/2
12. A process as claimed in claim 11 , wherein the acidity of the casting solution is maintained by-addition of concentrated (10 by weight )' hydrochloric acid in the amount of 0.1 to 0.5'Jc by weight of the casting solution.
13. · A process as claimed in any one of claims 1 to 12, wherein the casting step is carried out between 10°G and 23°C
14. A process as claimed in any one of claims 1 to 13, wherein the membrane is cast on a flat horizontal plate.
15. - A process as claimed in any one of claims 1 to 13, wherei the membrane is- cast on a surface of a tube.
16. A process as claimed in any one of claims 1 to 15 , wherein the time of casting is within the range of from 10 to 100 seconds.
17. · A process as claimed in claim 16, wherein the time of casting is within the range of from 30 to 75 seconds.
18. A process as claimed in claim 17» wherein the time of casting, is about 5 - seconds.
19. 9· A process as claimed in any one of claims 1 · to 18, wherein the membrane has a thickness within the range of from 0.15 to 0.75 ram.
20. A process as claimed in claim 19> wherein 'the membrane has a thickness of about 0.30 mm.
21. A process as claimed in any one of claims 1 to 20, wherein the cast membrane is immersed in the immersion solvent at a temperature within the range of from 0°G to 30°0.
22. A process as claimed in claim 21, wherein the cast membrane is immersed in the immersion solvent at a temperature within the range of from 5°C to 21°G.
23. · process as claimed in any one of claims 1 to 22, wherein the membrane is heated while immersed in the immersion solvent at a temperature within the range of from 50°C to 90°G. .
24. -. A process as claimed in claim 23, wherein the membrane is heated at a temperature within the range of from 60°C to 30°C.
25. A process for the manufacture of a semipermeable membrane substantially as hereinbefore described with reference to any one of Examples 1 to 35·
26. A modification of the process as claimed in any one of claims 1 to 25, wherein the zinc chloride is replaced by lithium thiocyanate.
27. · ■ A process as claimed in Claim 26, wherein acid is not added to the casting solution.
28. A process as claimed in Claim 27, substantially as described in Example 36.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB11015/67A GB1158512A (en) | 1967-03-08 | 1967-03-08 | Process for the manufacture of Reverse Osmosis Membranes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| IL29555A true IL29555A (en) | 1972-04-27 |
Family
ID=9978486
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| IL29555A IL29555A (en) | 1967-03-08 | 1968-03-01 | Process for the manufacture of reverse osmosis membranes and membranes produced thereby |
Country Status (8)
| Country | Link |
|---|---|
| BE (1) | BE711950A (en) |
| CH (1) | CH516942A (en) |
| DE (1) | DE1642792B2 (en) |
| ES (1) | ES351354A1 (en) |
| FR (1) | FR1555331A (en) |
| GB (1) | GB1158512A (en) |
| IL (1) | IL29555A (en) |
| NL (1) | NL6803244A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4176668A (en) * | 1977-05-02 | 1979-12-04 | Amf Incorporated | Novel reconstituted tobacco sheets and process |
| EP0026399B1 (en) * | 1979-09-19 | 1984-03-14 | Aligena Ag | Porous semipermeable cellulose acetate membranes modified by ionic groups, process for their production and their use |
-
1967
- 1967-03-08 GB GB11015/67A patent/GB1158512A/en not_active Expired
-
1968
- 1968-03-01 IL IL29555A patent/IL29555A/en unknown
- 1968-03-05 FR FR1555331D patent/FR1555331A/fr not_active Expired
- 1968-03-07 NL NL6803244A patent/NL6803244A/xx unknown
- 1968-03-07 ES ES351354A patent/ES351354A1/en not_active Expired
- 1968-03-08 DE DE1642792A patent/DE1642792B2/en not_active Withdrawn
- 1968-03-08 BE BE711950D patent/BE711950A/xx unknown
- 1968-03-08 CH CH344268A patent/CH516942A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FR1555331A (en) | 1969-01-24 |
| DE1642792A1 (en) | 1971-02-25 |
| DE1642792B2 (en) | 1978-09-07 |
| CH516942A (en) | 1971-12-31 |
| GB1158512A (en) | 1969-07-16 |
| NL6803244A (en) | 1968-09-09 |
| BE711950A (en) | 1968-07-15 |
| ES351354A1 (en) | 1969-12-01 |
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