US3766037A
Expired / Lapsed
US
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Electrochemical processes for the removal of contaminants from aqueous media
Assignee: ANDRO ENVIRONMENTAL PROCESSES Inc A COROP OF NY
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Filing: 1972-02-11
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Granted: 1973-10-16
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Expires: 1992-02-11
Abstract
Abstract Contaminating anions are removed from aqueous media by reacting them indirectly with lead from an anode to produce an insoluble lead compound which is subsequently separated from the aqueous medium. The lead is obtained from an anode containing lead or an insoluble lead compound which reacts with an activating ion, such as acetate or chloride, to produce soluble lead ions, which subsequently react with the contaminant anion, e.g., chromate from a purge stream of cooling tower water or from rinses of chrome plated articles. Also described are electrolytic cells and apparatuses useful in the practice of the method.
Inventors
- 👤 Lee S Ki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:36
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: 16
Claim 1
Independent Claim
206 words
A method according to claim 1 wherein the lead-precipitatable anionic contaminant is selected from the group consisting of chromate, dichromate, cyanide, cyanate, ferrocyanide, borate, arsenate, pyroarsenate, antimonate, selenate, tungstate, phosphite, sulfate, sulfite, persulfate, carbonate, and silicate, the ionizing medium is an aqueous one, the anionic contaminant is at a concentration of 1 to 5,000 parts per million before production of insoluble lead salt, the electric current is direct or essentially direct, the current density is from 0.005 to 50 ASF, the electrolyte communicates freely with the anode and cathode, without interposition of a diaphragm, the anode surface is of lead or lead dioxide, the activating ion is selected from the group consisting of acetate, chloride, nitrate, chlorate and mixtures thereof and is present in the electrolyte at a concentration of 5 to 200 parts per million and the pH of the electrolyte is in a range in which the solubility of the lead salt of the anionic contaminant is less than 10 parts per million in the aqueous medium and is sufficiently low so that the anionic contaminant in the soluble portion of the lead contaminant salt produced is less than half the quantity thereof in the aqueous medium before production of said insoluble lead salt.
Claim 2
Dependent Claim
119 words
A method according to claim 2 wherein the aqueous medium containing anionic contaminant is continuously passed through an electrolytic cell, activating ion is continuously added to maintain the desired concentration thereof, the dwell time of the contaminated aqueous medium in the treating cell is from 0.1 minute to 1 hour, after completion of treatment the treated medium is continuously removed from the cell, together with insoluble lead salt of the anionic contaminant and any soluble lead salt of the activating ion produced and after removal the soluble lead salt of the activating ion is reacted with an anion capable of producing an insoluble lead salt, to produce such salt, and the insoluble salts are removed from the aqueous medium.
Claim 3
Dependent Claim
86 words
A method according to claim 3 wherein the aqueous medium containing anionic contaminant is continually pumped through an electrolytic cell, the electrodes of which are covered by the medium, after which the insoluble lead salt of the anionic contaminant is removed from the aqueous medium by filtration, with the rate of flow of the aqueous medium and the conditions in the electrolytic cell being controlled so as to remove at least 90 percent of the anionic contaminant from the aqueous medium charged to the electrolytic cell.
Claim 4
Dependent Claim
60 words
A method according to claim 4 wherein after removal of the aqueous medium from the electrolytic cell it is treated with a soluble phosphate at a pH of 6.5 to 7.5 to precipitate out any soluble lead ions present as an insoluble lead phosphate and the insoluble lead salt of the contaminant and insoluble lead phosphate are filtered out together.
Claim 5
Dependent Claim
72 words
A method according to claim 4 wherein the electrolytic treatment and filtering removal of anionic contaminant are repeated, with the aqueous medium being returned to a storage tank after filtration and recirculated from said tank through the electrolytic cell until the concentration of the anionic contaminant in the storage tank is sufficiently reduced to permit re-use or sewering and the aqueous medium is discharged from the tank for such re-use or sewering.
Claim 6
Dependent Claim
101 words
A method according to claim 4 wherein the aqueous medium containing anionic contaminant is water containing chromate or dichromate ion to be removed therefrom, the concentration of activating ion is 15 to 150 parts thereof per million, the concentration of chromate ion in the medium charged to the cell is from 10 to 500 parts per million, the pH of the aqueous medium in the cell is in the range of 2 to 9, preferably 3 to 4, and the medium is treated, after chromate precipitation, with a soluble phosphate at a pH of 3 to 11, pReferably 6.5 to 9.
Claim 7
Dependent Claim
58 words
A method according to claim 7 wherein the aqueous chromate solution being treated is selected from the group consisting of chromate-containing purge stream from cooling tower water in which chromate ion is present as a corrosion inhibitor, microbicide and slimicide, a chrome plating rinse solution and a chrome phosphatizing solution, and the chrome is recovered as lead chromate.
Claim 8
Dependent Claim
75 words
A method according to claim 1 wherein the anionic contaminant is chromate or dichromate and the ionizing medium is water, the low concentration of chromate is from 10 to 500 parts per million, as chromate ion, the anode has on the surface thereof lead, lead alloy or lead dioxide and the cathode has on the surface thereof a material selected from the group consisting of lead, lead dioxide, iron, steel, lead alloys and iron alloys.
Claim 9
Dependent Claim
88 words
A method according to claim 9 wherein the electric current is essentially direct and of a current density from 0.005 to 50 ASF, the electrolyte communicates freely with the anode and cathode, without interposition of a diaphragm, the activating ion is selected from the group consisting of acetate, chloride and nitrate and is present in the electrolyte at a concentration of 5 to 200 parts per million, and the pH of the aqueous medium containing chromate contaminant and activating ion is in the range of 2 to 9.
Claim 10
Dependent Claim
147 words
A method according to claim 10 wherein the chromate solution from which chromate contaminant is being removed is continuously passed through an electrolytic cell, the activating ion is continuously added to maintain it at a concentration of 15 to 150 parts per million, the dwell time of the chromate solution in the treating cell is from 1 minute to 1 hour and its pH is from 3 to 6.5, after completion of the electrolytic treatment and precipitation of insoluble lead chromate or lead dichromate therein the treated medium is continuously removed from the cell, together with insoluble lead chromate or lead dichromate and any soluble lead acetate, lead chloride or lead nitrate, and after removal the soluble lead salt is reacted with phosphate ion to produce insoluble lead phosphate, following which the insoluble lead chromate or lead dichromate and lead phosphate are separated from the aqueous medium.
Claim 11
Dependent Claim
22 words
A method according to claim 11 wherein the aqueous chromate solution being treated is a purge stream from chromate-containing cooling tower water.
Claim 12
Dependent Claim
25 words
A method according to claim 11 wherein the aqueous chromate solution being treated is rinse water from a chrome plating process or a phosphatizing process.
Claim 13
Dependent Claim
22 words
A method according to claim 4 wherein the pH control of the electrolyte is effected by means of a chemical buffering system.
Claim 14
Dependent Claim
39 words
A method according to claim 14 wherein the chemical buffering system is a sodium acetate-acetic acid buffer, the activator includes acetate and chloride ions and the anion reacted with the soluble lead salt is phosphate, charged as trisodium phosphate.
Claim 15
Dependent Claim
41 words
A method according to claim 11 wherein banks of cells are operated in cascade so that any chromate in the effluent from a treatment cell is further lowered in concentration by production of insoluble lead chromate in a subsequent treatment cell.
Claim 16
Dependent Claim
112 words
A method according to claim 2 wherein the aqueous medium containing anionic contaminant is continuously passed through an electrolytic cell, activating ion is continuously added to maintain the desired concentration thereof, the dwell time of the contaminated aqueous medium in the treating cell is from 0.1 to 1 hour, after completion of treatment the treated medium is continuously removed from the cell, together with insoluble lead salt of the anionic contaminant, and the pH of the effluent from the cell is regulated to be in the range of 6.5 to 7.5, at which pH essentially no soluble lead salt is present, and the insoluble contaminant salt is removed From the aqueous medium.
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) | 1976-10-15 | 1977-04-16 | 1977-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-15 | 1981-04-16 | 1981-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-15 | 1985-04-16 | 1985-10-16 | $7700.00 | Window Closed / Lapsed |