US4445987A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrolytic purification and reconcentration of wash and rinse caustic solutions recovered from the regeneration of ion exchange resins
Assignee: Oronzio de Nora SA
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Filing: 1983-03-30
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Granted: 1984-05-01
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Expires: 2003-03-30
Abstract
Abstract Diluted and contaminated caustic solutions coming from the regeneration and washing of ion exchange resins may advantageously be purified and reconcentrated to be reused during the subsequent regeneration cycles, by subjecting the contaminated solution to electrolysis in the anodic compartment of an electrolytic cell provided with a cation-exchange membrane and recovering concentrated and purified caustic solution from the cathodic compartment of the cell, whereto demineralized water is fed. The process of the invention may advantageously be carried out in subsequent electrolytic stages in order to maintain optimum working conditions and a high overall efficiency of the process.
Inventors
- 👤 Enrico Benedetto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 21:46
CPC Classifications
C; C25; C25B; C25B1/00; C25B1/01; C25B1/14; C25B1/16
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
138 words
An electrolytic process for the purification of contaminated caustic solutions which comprises feeding the contaminated caustic solution to the anodic composition of an electrolysis cell separated from the cathodic compartment by a cation exchange membrane; feeding demineralized water to said cathodic compartment; recovering purified caustic solution from said cathodic compartment; conducting the electrolysis at a current density between 1500 and 3000 ampere per square meter until the caustic concentration in the anolyte is reduced to a value not lower than 10 grams per liter; and conducting the electrolysis at a current density between 1000 and 500 ampere per square meter to further reduce the caustic concentration in the anolyte to below 2 grams per liter while maintaining the caustic concentration constant in the catholyte by regulating the rate of feeding of the demineralized water to said cathode compartment.
Claim 2
Dependent Claim
138 words
An electrolytic process for the purification of contaminated caustic solutions which comprises feeding the contaminated caustic solution to the anodic composition of an electrolysis cell separated from the cathodic compartment by a cation exchange membrane; feeding demineralized water to said cathodic compartment; recovering purified caustic solution from said cathodic compartment; conducting the electrolysis at a current density between 1500 and 3000 ampere per square meter until the caustic concentration in the anolyte is reduced to a value not lower than 10 grams per liter; and conducting the electrolysis at a current density between 1000 and 500 ampere per square meter to further reduce the caustic concentration in the anolyte to below 2 grams per liter while maintaining the caustic concentration constant in the catholyte by regulating the rate of feeding of the demineralized water to said cathode compartment.
Claim 3
Dependent Claim
33 words
The process of claim 1 characterized in that the caustic concentration in the catholyte is kept constant and within the range between 100 and 200 gr/l by regulating the demineralized water feed rate.
Claim 4
Dependent Claim
79 words
The electrolytic process of claim 1 which further comprises conducting the electrolysis in at least two electrolysis cells, passing the contaminated caustic solution in cascade through the anode compartments of said cells starting from the cell operating at a higher current density through to the cell operating at the lowest current density, and discharging the contaminated caustic solution having a residual caustic concentration of less than 2 grams per liter from said cell operating at the lowest current density.
Claim 5
Dependent Claim
33 words
The process of claim 3 characterized in that the caustic concentration in the catholyte is kept constant and within the range between 100 and 200 gr/l by regulating the demineralized water feed rate.
Claim 6
Dependent Claim
14 words
The process of claim 3 wherein the cell voltage is below about 5 volts.
Claim 7
Dependent Claim
65 words
The process of claim 3 wherein the caustic concentration in the anolyte is reduced to a value of 15 to 10 grams per liter in the electrolysis conducted at a current density between 1500 and 3000 ampere per square meter; and to a value of 1 to below 2 grams per liter in the electrolysis conducted at a current density of between 1000 and 500.
Claim 8
Dependent Claim
53 words
The process of claim 6 wherein the contaminated caustic solution is from the regeneration of ion exchange resins, the cell voltage is below about 5 volts, and wherein the caustic concentration in the catholyte is kept constant and within the range between 100 and 200 gr/l by regulating the demineralized water feed rate.
Claim 9
Dependent Claim
18 words
The process of claim 1 wherein said contaminated caustic solution is from the regeneration of ion exchange resins.
Claim 10
Dependent Claim
14 words
The process of claim 1 wherein the cell voltage is below about 5 volts.
Claim 11
Dependent Claim
33 words
The process of claim 9 characterized in that the caustic concentration in the catholyte is kept constant and within the range between 100 and 2.0 gr/l by regulating the demineralized water feed rate.
Claim 12
Dependent Claim
65 words
The process of claim 1 wherein the caustic concentration in the anolyte is reduced to a value of 15 to 10 grams per liter in the electrolysis conducted at a current density between 1500 and 3000 ampere per square meter; and to a value of 1 to below 2 grams per liter in the electrolysis conducted at a current density of between 1000 and 500.
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) | 1987-05-01 | 1987-10-31 | 1988-05-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-01 | 1991-10-31 | 1992-05-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-01 | 1995-10-31 | 1996-05-01 | $7700.00 | Window Closed / Lapsed |