US3926754A
Expired / Lapsed
US
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Electrochemical contaminant removal from aqueous media
Assignee: ANDRO ENVIRONMENTAL PROCESSES Inc A COROP OF NY
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Filing: 1973-02-16
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Granted: 1975-12-16
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Expires: 1993-02-16
Abstract
Abstract Contaminating ions are removed from an aqueous medium, e.g., hexavalent chromium ions from cooling tower waters, by an electrochemical method which includes formation of an insoluble iron compound or complex of the contaminant ion, utilizing an anode of iron, iron alloy or insoluble iron compound. The hexavalent chromium contaminant, as chromate or dichromate, is changed to trivalent chromium, a less toxic form. The method is applicable to the removal of other contaminant ions, e.g., cyanide, which also converts to less toxic form. Also described are electrolytic cells and apparatuses useful in effecting the method.
Inventors
- 👤 Sung Ki Lee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:57
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/46; C02F1/461; C02F1/463; C02F1/467; C02F1/4676; C02F1/52; C02F1/5236; C02F2101/00; C02F2101/10; C02F2101/16; C02F2101/18; C02F2101/20; C02F2101/22; C02F2103/00; C02F2103/02; C02F2103/023
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
124 words
A METHOD FOR ELECTROCHEMICALLY REMOVING FROM AN IONIZING MEDIUM A CONTAMINANT ION WHICH IS CAPABLE OF FORMING AN INSOLUBLE IRON COMPOUND OR COMPLEX, WHICH COMPRISES PASSING ANELECTRIC CURRENT THROUGH THE IONIZING MEDIUM CONTAINING THE ION TO BE REMOVED BETWEEN AN ANODE WHICH HAS A SURFACE OR A PORTION OF A SURFACE THEREOF OF IRON, IRON ALLOY OR INSOLUBLE IRON COMPOUND, AND A CATHODE SO AS TO PRODUCE ANODICALLY AS INSOLUBLE IRON COMPOUND SPECIES OR COMPLEX IN SAID IONIZING MEDIUM WHILE CATHODICALLYY REACTING SAID CONTAMINANT ION WITH THE IONIZING MEDIUM TO GENERATE AN INSOLUBLE HYDROXIDE THEREOF AND WHEREBY AN INSOLUBLE IRON COMPOUND OR COMPLEX WITH THE CONTAMINANT ION IS PRODUCED, AND REMOVING SAID INSOLUBLE IRN COMPOUND COMPLEX WITH THE CONTAMINANT ION FROM THE IONIZING MEDIUM.
Claim 2
Independent Claim
124 words
A METHOD FOR ELECTROCHEMICALLY REMOVING FROM AN IONIZING MEDIUM A CONTAMINANT ION WHICH IS CAPABLE OF FORMING AN INSOLUBLE IRON COMPOUND OR COMPLEX, WHICH COMPRISES PASSING ANELECTRIC CURRENT THROUGH THE IONIZING MEDIUM CONTAINING THE ION TO BE REMOVED BETWEEN AN ANODE WHICH HAS A SURFACE OR A PORTION OF A SURFACE THEREOF OF IRON, IRON ALLOY OR INSOLUBLE IRON COMPOUND, AND A CATHODE SO AS TO PRODUCE ANODICALLY AS INSOLUBLE IRON COMPOUND SPECIES OR COMPLEX IN SAID IONIZING MEDIUM WHILE CATHODICALLYY REACTING SAID CONTAMINANT ION WITH THE IONIZING MEDIUM TO GENERATE AN INSOLUBLE HYDROXIDE THEREOF AND WHEREBY AN INSOLUBLE IRON COMPOUND OR COMPLEX WITH THE CONTAMINANT ION IS PRODUCED, AND REMOVING SAID INSOLUBLE IRN COMPOUND COMPLEX WITH THE CONTAMINANT ION FROM THE IONIZING MEDIUM.
Claim 3
Dependent Claim
120 words
A method according to claim 1 wherein the ion removed is a toxic ion, harmful to animal life, the ionizing medium is aqueous, the contaminant is at a concentration of 0.03 to 50,000 parts per million before production of insoluble iron compound or complex, the electric current is direct or essentially direct, the current density is from 0.05 to 500 ASF, the electrolyte communicates freely with the anode and cathode without the interposition of a diaphragm, the anode surface is of iron or iron alloy and the pH of the aqueous medium is in a range in which the solubility of the insoluble iron compound or complex with the contaminant ion is less than 5 p.p.m. in the aqueous medium.
Claim 4
Dependent Claim
33 words
A method according to claim 2 wherein the electric charge supplied is from about 100 to 500% of the theoretical charge to convert the contaminant present to insoluble iron compound or complex form.
Claim 5
Dependent Claim
67 words
A method according to claim 2 wherein the aqueous medium containing contaminant is continuously passed through an electrolytic cell, the electrodes of which are covered by the medium, the dwell time of the contaminated aqueous medium in the cell is from 0.001 minute to one hour, and the electrical energy input to the cell is from 2 to 5 Faradays per equivalent weight of contaminant ion reacted.
Claim 6
Dependent Claim
111 words
A method according to claim 2 wherein the aqueous medium containing contaminant ion to be removed is continuously passed through an electrolytic cell, the dwell time of the contaminated aqueous medium in the treating cell is from 0.1 min. to one hour, after completion of treatment the treated medium is continuously removed from the cell, together with insoluble metal salt or complex of the contaminant ion and the pH of the effluent from the cell is regulated to be in the range of 4 to 11, at which pH essentially no soluble contaminant compound or complex is present, and the insoluble contaminant compound or complex is removed from the aqueous medium.
Claim 7
Dependent Claim
64 words
A method according to claim 1 wherein the ionizing medium containing contaminant is water containing hexavalent Cr in chromate or dichromate ion to be removed therefrom, the concentration of such ion in the aqueous medium charged to the cell is from 0.03 to 5,000 p.p.m. and the pH of the aqueous medium in the cell is in the range of about 4 to 11.
Claim 8
Dependent Claim
17 words
A method according to claim 6 wherein the pH is in the range of 6 to 10.
Claim 9
Dependent Claim
66 words
A method according to claim 6 wherein the aqueous chromate solution being treated is selected from the group consisting of chromate-containing purge streams from cooling tower water in which hexavalent chromate ion is present as a corrosion inhibitor, microbicide and slimicide; chrome plating rinse solutions; chrome phosphatizing solutions; and aluminum anodizing solutions; anD the chromate is converted to and is removed as a trivalent chromium compound.
Claim 10
Dependent Claim
61 words
A method according to claim 4 wherein the ion to be removed is hexavalent chromate or dichromate, the ionizing medium is water, the concentration of said ion is from 1 to 5,000 p.p.m., as chromate ion, and the cathode has a surface or a portion of a surface thereof selected from the group consisting of metallic iron, steel and iron alloys.
Claim 11
Dependent Claim
110 words
A method according to claim 9 wherein the chromate or dichromate solution from which chromate contaminant is removed is continuously passed through an electrolytic cell, the dwell time of the chromate solution in the cell is from 0.1 minute to one hour and the pH of the solution is maintained in about the range of 6 to 10, at least in part by the electrochemical generation of hydroxyl ions in the electrolytic cell, and after completion of the electrolytic treatment and precipitation of insoluble iron compound or complexes of trivalent chromium therein, the treated medium is continuously removed from the cell, together with the insoluble trivalent chromium compound or complex.
Claim 12
Dependent Claim
24 words
A method according to claim 6 wherein the electric energy input is from 1 to 5 Faradays per equivalent weight of contaminant ion reacted.
Claim 13
Dependent Claim
28 words
A method according to claim 10 wherein the electric energy input is from 2 to 5 Faradays per equivalent weight of hexavalent chromium, as reduced to trivalent chromium.
Claim 14
Dependent Claim
29 words
A method according to claim 1 wherein the ionizing medium is aqueous and plural contaminant ions are present therein, including hexavalent chromium in chromate or dichromate ion, and cyanide.
Claim 15
Dependent Claim
104 words
A method according to claim 13 wherein the total contaminant concentration is from 0.03 to 50,000 p.p.m. before production of insoluble iron compounds or complexes, the electric current is direct or essentially direct, the current density is from 0.05 to 500 ASF, the electrolyte communicates freely with the anode and cathode without the interposition of a diaphragm, the anode surface is of iron or iron alloy and the pH of the aqueous medium is in the range in which the solubility of the insoluble iron compounds or complexes with the contaminant ions or products thereof is less than 5 p.p.m. in the aqueous medium.
Claim 16
Dependent Claim
116 words
A method according to claim 14 wherein the porportion of chromate or dichromate to cyanide is in the range of 1:50 to 50: 1, the aqueous medium is continuously passed through an electrolytic cell, the dwell time of the medium in the treating cell is from 0.1 minute to one hour, after completion of treatment to treated medium is continuously removed from the cell, together with insoluble metal salts or complexes of the contaminants, and the pH of the effluent from the cell is in the range of 4 to 8, at which pH essentially no soluble contaminant compounds or complexes are present, and the insoluble contaminant compounds or complexes are removed from the aqueous medium.
Claim 17
Dependent Claim
56 words
A method according to claim 15 wherein the aqueous medium containing chromate or dichromate contaminant is mixed with an aqueous medium containing cyanide contaminant to produce a medium having a pH in the 4 to 7 range, which is then treated according to the method of claim 15 for the removal of hexavalent chromium and cyanide.
Claim 18
Dependent Claim
24 words
A method according to claim 1, wherein said ionizing medium is water, the reaction products include an insoluble iron oxide, or hydroxide and hydrogen.
Claim 19
Dependent Claim
19 words
A method according to claim 17, wherein the contaminant ion is hexavalent chromium which is reduced to trivalent chromium.
Claim 20
Independent Claim
121 words
A method for electrochemically removing from an ionizing medium a contaminent ion which is capable of forming an insoluble iron compound or complex which comprises passing an electric current through an ionizing medium containing the ion to be removed between an anode which has a surface or a portion of a sUrface thereof of iron, iron alloy or insoluble iron compound and a cathode to form iron hydroxide in said ionizing medium, said iron hydroxide reducing the contaminant ion and forming an insoluble hydroxide of the reduced contaminant ion, said hydroxide of the reduced contaminant ion combining with said iron hydroxide to produce an insoluble iron compound or complex and removing said insoluble iron compound or complex from the ionizing medium.
Claim 21
Independent Claim
121 words
A method for electrochemically removing from an ionizing medium a contaminent ion which is capable of forming an insoluble iron compound or complex which comprises passing an electric current through an ionizing medium containing the ion to be removed between an anode which has a surface or a portion of a sUrface thereof of iron, iron alloy or insoluble iron compound and a cathode to form iron hydroxide in said ionizing medium, said iron hydroxide reducing the contaminant ion and forming an insoluble hydroxide of the reduced contaminant ion, said hydroxide of the reduced contaminant ion combining with said iron hydroxide to produce an insoluble iron compound or complex and removing said insoluble iron compound or complex from the ionizing medium.
Claim 22
Dependent Claim
19 words
A method according to claim 19, wherein the contaminant ion is hexavalent chromium which is reduced to trivalent chromium.
References Cited (Backward Citations)
US937210A
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US2600171A
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US2982608A
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US3347786A
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US3682796A
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US3719570A
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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) | 1978-12-15 | 1979-06-16 | 1979-12-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-15 | 1983-06-16 | 1983-12-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-15 | 1987-06-16 | 1987-12-16 | $7700.00 | Window Closed / Lapsed |