US3896209A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reduction of hexavalent chromium
Assignee: EIDP Inc
•
Filing: 1973-01-22
•
Granted: 1975-07-22
•
Expires: 1993-01-22
Abstract
Abstract Under acidic conditions the hexavalent chromium present in aqueous solutions is chemically reduced to trivalent chromium with hydrogen peroxide. This process is improved if the pH of the aqueous solution is maintained below 1.5 and the hydrogen peroxide is gradually added to the solution to keep the chromate in excess as long as possible.
Inventors
- 👤 Louis Byron Fournier
- 👤 Raymond Alan Meyer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:42
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/72; C02F1/722; C01; C01G; C01G37/00; C02F1/70; C02F2101/00; C02F2101/10; C02F2101/20; C02F2101/22
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
116 words
A METHOD FOR TREATING AN AQUEOUS INDUSTRIAL WASTE SOLUTION CONTAINING HEXAVALENT CHROMIUM IONS TO REDUCE THE HEXAVALENT CHROMIUM IONS TO TRIVELENT CHROMIUM IONS COMPRISING THE STEPS OF A. ADJUSTING AND MAINTAINING THE PH OF THE ION SOLUTION TO A LEVEL BELOW 1.5 BY THE ADDITION AS NECESSARY OF MINERAL ACID, AND B. SLOWLY ADDING HYDROGEN PEROXIDE TO THE THUSLY ACIDIFIED ION SOLUTION WITH CONTAINING AGITATION TO AVOID LOCAL EXCESSES OF THE PEROXIDE AND TO PROMOTE AN EXCESS OF CHROMATE UNTIL ADDITION OF THE PEROXIDE IS SUBSTANTIALLY COMPLETE, THE AMOUNT OF HYDROGEN PEROXIDE ADDED BEING AT LEAST EQUAL TO THE STOICHIOMETRIC AMOUNT NECESSARY TO REDUCE ALL OF THE HEXAVALENT CHROMIUM IN THE ION SOLUTION TO TRIVALENT CHROMIUM.
Claim 2
Independent Claim
116 words
A METHOD FOR TREATING AN AQUEOUS INDUSTRIAL WASTE SOLUTION CONTAINING HEXAVALENT CHROMIUM IONS TO REDUCE THE HEXAVALENT CHROMIUM IONS TO TRIVELENT CHROMIUM IONS COMPRISING THE STEPS OF A. ADJUSTING AND MAINTAINING THE PH OF THE ION SOLUTION TO A LEVEL BELOW 1.5 BY THE ADDITION AS NECESSARY OF MINERAL ACID, AND B. SLOWLY ADDING HYDROGEN PEROXIDE TO THE THUSLY ACIDIFIED ION SOLUTION WITH CONTAINING AGITATION TO AVOID LOCAL EXCESSES OF THE PEROXIDE AND TO PROMOTE AN EXCESS OF CHROMATE UNTIL ADDITION OF THE PEROXIDE IS SUBSTANTIALLY COMPLETE, THE AMOUNT OF HYDROGEN PEROXIDE ADDED BEING AT LEAST EQUAL TO THE STOICHIOMETRIC AMOUNT NECESSARY TO REDUCE ALL OF THE HEXAVALENT CHROMIUM IN THE ION SOLUTION TO TRIVALENT CHROMIUM.
Claim 3
Dependent Claim
12 words
The method of claim 1 wherein the pH is maintained below 1.
Claim 4
Dependent Claim
13 words
The method of claim 1 wherein the aqueous solution is an electroplating rinse.
Claim 5
Dependent Claim
13 words
The method of claim 1 wherein the aqueous solution is an electroplating bath.
Claim 6
Dependent Claim
27 words
The method of claim 1 wherein subsequently the solution is treated with alkali to precipitate chromium trihydroxide and the chromium trihydroxide is separate from the aqueous solution.
Claim 7
Dependent Claim
21 words
The method of claim 5 wherein a reducing agent is added to the solution prior to the addition of the alkali.
Claim 8
Dependent Claim
14 words
The method of claim 1 wherein the aqueous solution is a zinc dip bath.
Claim 9
Dependent Claim
23 words
The method of claim 1 in which the amount of hydrogen peroxide added is up to 27% in excess of the stoichiometric amount.
Claim 10
Dependent Claim
23 words
The method of claim 8 in which the amount of hydrogen peroxide added is up to 10% in excess of the stoichiometric amount.
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) | 1978-07-21 | 1979-01-20 | 1979-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-21 | 1983-01-20 | 1983-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-21 | 1987-01-20 | 1987-07-22 | $7700.00 | Window Closed / Lapsed |