US4560546A
Expired / Lapsed
US
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Chromium hydroxide precipitate obtained by a continuous process for the removal of chromium from waste waters
Assignee: Luigi Stoppani SpA
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Filing: 1983-04-13
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Granted: 1985-12-24
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Expires: 2003-04-13
Abstract
Abstract A chromium hydroxide precipitate obtained by a continuous process is described, wherein chromium containing waste waters are subjected to continuous hot treatment with acetic acid or with alkaline acetates and alkaline hydroxides at a temperature from 40° C. to boiling point and at atmospheric pressure, at a pH higher than 6.5, preferably between 7 and 10, particularly about 7.5. Thus, a "sandy" type of chromium hydroxide is obtained, having a titer in Cr 2 O 3 of 20 to 40% by weight, which quickly filters, is easily soluble in acids, and thereby affords an easy valorization both as a tanning agent and as a raw material for preparing other chromium compound.
Inventors
- 👤 Diego Perrone
- 👤 Alberto Patrone
- 👤 Elvio Caffarelli
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:57
CPC Classifications
C; C22; C22B; C22B34/00; C22B34/30; C22B34/32; C01; C01G; C01G37/00; C01G37/02; C01P; C01P2006/00; C01P2006/80; C01P2006/82; C02; C02F; C02F2103/00; C02F2103/22; C02F2103/24; Y; Y10; Y10S; Y10S210/00; Y10S210/902; Y10S210/911; Y10S210/912; Y10S210/913
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
128 words
Chromium hydroxide precipitate characterized by being perfectly filterable and at least 99% soluble in acids obtained by a process for removing Cr 2 O 3 from waste waters comprising the steps of: pretreating the waste water with at least 0.3% by weight acetic acid or acetate ion, and adding an alkaline material selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and magnesium oxide continuously to the pretreated waste waters at a temperature of between 40° C. and the boiling point, at atmospheric pressure, wherein the pH is maintained above 6.5, wherein a sandy precipitate of chromium hydroxide is obtained which is separated from the waste water by filtering, said sandy precipitate containing Cr 2 O 3 in an amount of about 20-40% by weight.
Claim 2
Dependent Claim
128 words
Chromium hydroxide precipitate characterized by being perfectly filterable and at least 99% soluble in acids obtained by a process for removing Cr 2 O 3 from waste waters comprising the steps of: pretreating the waste water with at least 0.3% by weight acetic acid or acetate ion, and adding an alkaline material selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and magnesium oxide continuously to the pretreated waste waters at a temperature of between 40° C. and the boiling point, at atmospheric pressure, wherein the pH is maintained above 6.5, wherein a sandy precipitate of chromium hydroxide is obtained which is separated from the waste water by filtering, said sandy precipitate containing Cr 2 O 3 in an amount of about 20-40% by weight.
Claim 3
Dependent Claim
22 words
The chromium hydroxide of claim 1, wherein the alkalis for the precipitation are selected among sodium hydroxide, potassium hydroxide and ammonium hydroxide.
Claim 4
Dependent Claim
18 words
The chromium hydroxide of claim 1, wherein the pH is set to a value between 7 and 10.
Claim 5
Dependent Claim
11 words
The chromium hydroxide of claim 3, wherein the pH is 7.5.
Claim 6
Dependent Claim
25 words
The chromium hydroxide of claim 4, wherein the CH 3 CO 2 - ion is introduced during the precipitation step of chromium hydroxide with alkali.
Claim 7
Dependent Claim
170 words
Chromium hydroxide precipitate characterized by being perfectly filterable and at least 99% soluble in acids obtained according to a process for the removal of chromium from waste waters wherein the chromium is present in the trivalent state, comprising the steps of: treating waste waters, containing from about 0.1% to about 10% Cr 2 O 3 , with at least 0.3% weight acetic acid or CH 3 CO 2 - ; adding an alkaline material, selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and magnesium oxide continuously at a temperature of from 40° C. to about 100° C., at atmospheric pressure, wherein the pH of the waste water is maintained above 6.5, wherein the pH of the medium of reaction is set by automatically setting a flow rate of the waste water, and wherein a sandy precipitate of chromium hydroxide is obtained which is separated from the waste water by filtering, said sandy precipitate containing Cr 2 O 3 in an amount of about 20-40% by weight.
Claim 8
Dependent Claim
170 words
Chromium hydroxide precipitate characterized by being perfectly filterable and at least 99% soluble in acids obtained according to a process for the removal of chromium from waste waters wherein the chromium is present in the trivalent state, comprising the steps of: treating waste waters, containing from about 0.1% to about 10% Cr 2 O 3 , with at least 0.3% weight acetic acid or CH 3 CO 2 - ; adding an alkaline material, selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide and magnesium oxide continuously at a temperature of from 40° C. to about 100° C., at atmospheric pressure, wherein the pH of the waste water is maintained above 6.5, wherein the pH of the medium of reaction is set by automatically setting a flow rate of the waste water, and wherein a sandy precipitate of chromium hydroxide is obtained which is separated from the waste water by filtering, said sandy precipitate containing Cr 2 O 3 in an amount of about 20-40% by weight.
Claim 9
Dependent Claim
21 words
The chromium hydroxide of claim 6, wherein the CH 3 CO 2 - ion is introduced together with the alkaline hydroxides.
Claim 10
Dependent Claim
23 words
The chromium hydroxide of claim 6, wherein the CH 3 CO 2 - is supplied by acetic acid, or acetates of alkaline metals.
Claim 11
Dependent Claim
14 words
The chromium hydroxide of claim 6, wherein the pH of the medium is 7.5.
Claim 12
Dependent Claim
55 words
The chromium hydroxide of claim 6, wherein waste water containing 5.27% by weight Cr 2 O 3 is treated by the steps of: adding 80% acetic acid to obtain a 3.3% by weight solution of acetic acid; stirring the waste water at 95° C. at pH 7.8; adding 25% sodium hydrate to precipitate chromium hydroxide.
Claim 13
Dependent Claim
55 words
The chromium hydroxide of claim 6, wherein waste water containing 1% by weight Cr 2 O 3 is treated by the steps of: adding 80% acetic acid to obtain a 0.6% by weight solution of acetic acid; stirring the waste water at 95° C. at pH 7.8; adding 25% sodium hydrate to precipitate chromium hydroxide.
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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) | 1988-12-23 | 1989-06-24 | 1989-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-23 | 1993-06-24 | 1993-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-23 | 1997-06-24 | 1997-12-24 | $7700.00 | Window Closed / Lapsed |