Patent US4155820A successfully refreshed from Google Patents.
US4155820A
Expired / Lapsed
US
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Purification of aqueous sodium chloride solution
Assignee: Asahi Kasei Corp
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Filing: 1978-04-14
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Granted: 1979-05-22
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Expires: 1998-04-14
Abstract
Abstract An aqueous sodium chloride solution for use in production of caustic soda in an electrolytic cell having a cation exchange membrane is purified by adding to said solution a chemical reagent for precipitation separation of impurities remove silica through co-precipitation with a slurry of the precipitates of impurities which are circulated through said solution.
Inventors
- 👤 Shinsaku Ogawa
- 👤 Takashi Nishimori
- 👤 Tsutomu Kanke
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 21:45
CPC Classifications
C; C25; C25B; C25B15/00; C25B15/08; C25B15/085
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
68 words
A process for the purification of an aqueous sodium chloride solution containing dissolved silica which is fed to an electrolytic cell having a cation exchange membrane for use in the production of caustic soda, which comprises adding a chemical reagent to said aqueous solution for the precipitation-separation of impurities therefrom and also circulating a slurry of precipitates of impurities into the solution, thereby co-precipitating silica with the impurities.
Claim 2
Dependent Claim
68 words
A process for the purification of an aqueous sodium chloride solution containing dissolved silica which is fed to an electrolytic cell having a cation exchange membrane for use in the production of caustic soda, which comprises adding a chemical reagent to said aqueous solution for the precipitation-separation of impurities therefrom and also circulating a slurry of precipitates of impurities into the solution, thereby co-precipitating silica with the impurities.
Claim 3
Dependent Claim
21 words
A process as in claim 1, wherein a slurry comprising precipitates of impurities and a thickener are circulated into said solution.
Claim 4
Dependent Claim
16 words
A process as in claim 2, wherein said thickener is a high molecular weight agglomerating agent.
Claim 5
Dependent Claim
27 words
A process as in claim 3, wherein said high molecular weight agglomerating agent is an alkali starch, or a polysodium acrylate or acrylamide high molecular weight compound.
Claim 6
Dependent Claim
31 words
A process as in claim 1 or claim 2, wherein the precipitates of impurities are selected from the group consisting of magnesium hydroxide, calcium carbonate, iron hydroxide, barium sulfate and gypsum.
Claim 7
Dependent Claim
41 words
A process as in claim 1 or claim 2, wherein the chemical reagent employed for the precipitation-separation of impurities is selected from the group consisting of caustic soda, sodium carbonate, calcium hydroxide, calcium chloride, barium chloride, barium carbonate and ferric chloride.
Claim 8
Dependent Claim
26 words
A process as in claim 1 or claim 2, wherein the pH at the time of co-precipitation of the silica is maintained at 8 to 11.
Claim 9
Dependent Claim
44 words
A process as in claim 1 or claim 2, wherein the sodium chloride is dissolved in a dilute aqueous sodium chloride solution discharged from an anode chamber of an electrolytic cell and maintained at pH 4 to 9 with the addition of an alkali.
Claim 10
Dependent Claim
26 words
A process as in claim 1, wherein the slurry of precipitates of impurities being circulated is maintained at a concentration of at least 0.3 wt. %.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-05-21 | 1982-11-20 | 1983-05-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-05-21 | 1986-11-20 | 1987-05-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-05-21 | 1990-11-20 | 1991-05-22 | $7700.00 | Window Closed / Lapsed |