US4316772A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Composite membrane for a membrane distillation system
Assignee: Individual
•
Filing: 1980-02-04
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Granted: 1982-02-23
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Expires: 2000-02-04
Abstract
Abstract A composite membrane separates a distilland and a distillate, such as salt water and fresh water. The composite membrane comprises a thin lyophobic microporous layer or membrane and a thin lyophilic layer or membrane on both sides of the lyophobic membrane or on the distillate side. Evaporation and condensation takes place within the micropores of the lyophobic membrane. The lyophilic layer on the distilland side prevents intrusion of distilland into the pores of the lyophobic layer. The lyophilic layer on the distillate side changes the surface curvature of the liquid/vapor interface in a manner which enhances the distillation rate through the membrane.
Inventors
- 👤 Dah Y. Cheng
- 👤 Steve J. Wiersma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 00:59
CPC Classifications
B; B01; B01D; B01D69/00; B01D69/12; B01D69/1216; B01D61/00; B01D61/36; B01D61/364; B01D61/3641; B01D69/1218; B32; B32B; B32B27/00; B32B27/06; B32B27/08
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
87 words
Thermal membrane distillation apparatus for separating pure water from an aqueous solution comprising: a composite membrane separating an aqueous solution to be purified from purified water; said composite membrane comprising a thin porous hydrophobic layer sandwiched between two thin hydrophilic layers; and, means for providing a sufficient temperature differential across said composite membrane so that liquid water evaporates on the aqueous solution side of the pores of the hydrophobic layer and condenses as pure water on the pure water side of the pores of the hydrophobic layer.
Claim 2
Dependent Claim
87 words
Thermal membrane distillation apparatus for separating pure water from an aqueous solution comprising: a composite membrane separating an aqueous solution to be purified from purified water; said composite membrane comprising a thin porous hydrophobic layer sandwiched between two thin hydrophilic layers; and, means for providing a sufficient temperature differential across said composite membrane so that liquid water evaporates on the aqueous solution side of the pores of the hydrophobic layer and condenses as pure water on the pure water side of the pores of the hydrophobic layer.
Claim 3
Dependent Claim
15 words
Apparatus as in claim 1 wherein at least one of said hydrophilic layers is porous.
Claim 4
Dependent Claim
25 words
Apparatus as in claim 2 wherein the mean pore diameter of the hydrophilic layers is less than the mean pore diameter of the hydrophobic layer.
Claim 5
Dependent Claim
11 words
Apparatus as in claim 3 wherein the hydrophobic layer is polytetrafluoro-ethylene.
Claim 6
Dependent Claim
12 words
Apparatus as in claim 3 wherein the hydrophobic layer is polyvinylidene fluoride.
Claim 7
Dependent Claim
19 words
Apparatus as in claim 2 or 5 wherein at least one of the hydrophilic layers is cellulose acetate/cellulose nitrate.
Claim 8
Dependent Claim
18 words
Apparatus as in claim 2 or 5 wherein at least one of the hydrophilic layers is cellulose acetate.
Claim 9
Dependent Claim
17 words
Apparatus as in claim 2 or 5 wherein at least one of the hydrophilic layers is polysulfone.
Claim 10
Dependent Claim
17 words
Apparatus as in claim 2 or 5 wherein at least one of the hydrophilic layers is polyallylamine.
Claim 11
Dependent Claim
22 words
Apparatus as in claim 2 or 5 wherein the average pore size diameter of the hydrophilic layers is less than 0.5 μm.
Claim 12
Dependent Claim
20 words
Apparatus as in claim 1 wherein the average pore size diameter of the hydrophobic layer is less than 0.5 μm.
Claim 13
Dependent Claim
15 words
Apparatus as in claim 1 wherein at least one of said hydrophilic layers is non-porous.
Claim 14
Dependent Claim
74 words
In an improved thermal membrane distillation apparatus comprising a porous lyophobic membrane separating a distilland from a distillate, wherein evaporation and condensation occurs through the pores of the lyophobic membrane when the temperature of the distilland is elevated sufficiently above that of the distillate to create a vapor pressure gradient from the distilland to the distillate, and wherein the improvement comprises the addition of a lyophilic layer on each side of the lyophobic membrane.
Claim 15
Dependent Claim
74 words
In an improved thermal membrane distillation apparatus comprising a porous lyophobic membrane separating a distilland from a distillate, wherein evaporation and condensation occurs through the pores of the lyophobic membrane when the temperature of the distilland is elevated sufficiently above that of the distillate to create a vapor pressure gradient from the distilland to the distillate, and wherein the improvement comprises the addition of a lyophilic layer on each side of the lyophobic membrane.
Claim 16
Dependent Claim
15 words
The improved thermal membrane distillation apparatus of claim 13 wherein said lyophilic layers are porous.
Claim 17
Dependent Claim
15 words
The improved thermal membrane distillation apparatus of claim 13 wherein said lyophilic layers are non-porous.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-02-22 | 1985-08-24 | 1986-02-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-02-22 | 1989-08-24 | 1990-02-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-02-22 | 1993-08-24 | 1994-02-23 | $7700.00 | Window Closed / Lapsed |