US4243501A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process and apparatus for the regeneration of chromic acid baths
Assignee: Individual
•
Filing: 1979-03-30
•
Granted: 1981-01-06
•
Expires: 1999-03-30
Abstract
Abstract A process and electrodialysis cell for regenerating used chromic acid baths for reuse. The process and apparatus have an anolyte chamber and a catholyte chamber separated by a cation permeable membrane and utilize as an improved catholyte solution an aqueous mixture of a water soluble salt such as sodium sulfate. A preferred anode which is not decomposed by the chromic acid bath comprises by weight about 1.5% of silver, about 5% of antimony, about 3% of tin and the balance lead.
Inventors
- 👤 Leslie S. Wright, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 10:41
CPC Classifications
C; C25; C25D; C25D21/00; C25D21/16; C25D21/18; Y; Y10; Y10S; Y10S204/00; Y10S204/13
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
131 words
In an electrochemical process of treating baths containing trivalent chromium, to convert such trivalent chromium to hexavalent chromium in which a bath containing trivalent chromium is circulated in the anode compartment of an electrodialysis cell, is in contact with an anode, and is separated from a cathode compartment having a cathode therein by a cation permeable membrane, the improvement comprising an aqueous catholyte mixture in contact with the cathode and consisting essentially of a mildly acidic and water soluble inorganic salt and electrically energizing the cell with a sufficient potential difference between the anode and the cathode such that any dissolved foreign metal ions in the used chromic bath will move through the membrane and into the catholyte mixture and trivalent chromium in the chromium bath is reoxidized into hexavalent chromium.
Claim 2
Dependent Claim
131 words
In an electrochemical process of treating baths containing trivalent chromium, to convert such trivalent chromium to hexavalent chromium in which a bath containing trivalent chromium is circulated in the anode compartment of an electrodialysis cell, is in contact with an anode, and is separated from a cathode compartment having a cathode therein by a cation permeable membrane, the improvement comprising an aqueous catholyte mixture in contact with the cathode and consisting essentially of a mildly acidic and water soluble inorganic salt and electrically energizing the cell with a sufficient potential difference between the anode and the cathode such that any dissolved foreign metal ions in the used chromic bath will move through the membrane and into the catholyte mixture and trivalent chromium in the chromium bath is reoxidized into hexavalent chromium.
Claim 3
Dependent Claim
36 words
The improvement as defined in claim 1 wherein the catholyte consists essentially of an aqueous mixture of inorganic sodium or calcium salts selected from the group of sodium sulfate, sodium bisulfate, sodium carbonate and calcium sulfate.
Claim 4
Dependent Claim
25 words
The improvement as defined in claim 1 wherein the anode and the cathode are subjected to a potential difference of at least about 14 volts.
Claim 5
Dependent Claim
24 words
The improvement as defined in claim 3 wherein the cathode is subjected to a current density of at least 100 amps per square foot.
Claim 6
Dependent Claim
30 words
The improvement as defined in claim 1 wherein the difference in the electric potential applied to the anode and the cathode is in the range of 14 to 20 volts.
Claim 7
Dependent Claim
42 words
The improvement as defined in claim 1 wherein the composition of the anode consists essentially of at least 1% by weight of silver, at least 3% by weight of antimony, at least 2% by weight of tin and the balance is lead.
Claim 8
Dependent Claim
45 words
The improvement as defined in claim 1 wherein the composition of the anode consists essentially of about 1 to 20% by weight of silver, about 3 to 8% by weight of antimony, about 2 to 6% by weight of tin and the balance is lead.
Claim 9
Dependent Claim
44 words
The improvement as defined in claim 1 wherein the rate of flow in gallons per minute of chromic acid solution through the anode compartment is at least about two fifths the quantity of the chromic acid solution in gallons contained in the anode compartment.
Claim 10
Dependent Claim
43 words
The improvement as defined in claim 8 wherein the rate in gallons per minute at which the catholyte mixture is circulated through the cathode compartment is at least about fifteen times the quantity in gallons of the catholyte mixture in the cathode compartment.
Claim 11
Dependent Claim
43 words
The improvement as defined in claim 1 wherein the rate in gallons per minute at which the catholyte mixture is circulated through the cathode compartment is at least about fifteen times the quantity in gallons of the catholyte mixture in the cathode compartment.
Claim 12
Dependent Claim
33 words
The improvement as defined in claim 1 wherein the composition of said anode consists essentially of about 1.5% of silver, about 5% of antimony, about 3% of tin, and the balance is lead.
Claim 13
Dependent Claim
22 words
The improvement as defined in claim 1 wherein the catholyte consists essentially of an aqueous mixture of inorganic sodium or calcium salts.
References Cited (Backward Citations)
US3481851A
Cited
US3761369A
Cited
US3764503A
Cited
US3948738A
Cited
US3909381A
Cited
US4118295A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-01-06 | 1984-07-07 | 1985-01-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-06 | 1988-07-07 | 1989-01-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-06 | 1992-07-07 | 1993-01-06 | $7700.00 | Window Closed / Lapsed |