Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1975-12-30
1976-11-02
Mack, John H.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204130, 204152, 210 44, C25B 102, C25B 104
Patent
active
039896080
ABSTRACT:
This invention is an improved form of a conventional electrochemical process for removing hexavalent chromium or other metal-ion contaminants from cooling-tower blowdown water. In the conventional process, the contaminant is reduced and precipitated at an iron anode, thus forming a mixed precipitate of iron and chromium hydroxides, while hydrogen being evolved copiously at a cathode is vented from the electrochemical cell. In the conventional process, subsequent separation of the fine precipitate has proved to be difficult and inefficient.
In accordance with this invention, the electrochemical operation is conducted in a novel manner permitting a much more efficient and less expensive precipitate-recovery operation. That is, the electrochemical operation is conducted under an evolved-hydrogen partial pressure exceeding atmospheric pressure. As a result, most of the evolved hydrogen is entrained as bubbles in the blowdown in the cell. The resulting hydrogen-rich blowdown is introduced to a vented chamber, where the entrained hydrogen combines with the precipitate to form a froth which can be separated by conventional techniques. In addition to the hydrogen, two materials present in most blowdown act as flotation promoters for the precipitate. These are (1) air, with which the blowdown water becomes saturated in the course of normal cooling-tower operation, and (2) surfactants which commonly are added to cooling-tower recirculating-water systems to inhibit the growth of certain organisms or prevent the deposition of insoluble particulates.
REFERENCES:
patent: 478048 (1892-06-01), Collins
patent: 820482 (1906-05-01), Dion
patent: 2997430 (1961-08-01), Foyn
patent: 3222269 (1965-12-01), Stanton
patent: 3505188 (1970-04-01), Pan
patent: 3523891 (1970-08-01), Mehl
DeMonbrun James R.
Schmitt Charles R.
Williams Everett H.
Carlson Dean E.
Lewis Fred O.
Mack John H.
Prescott A. C.
The United States of America as represented by the United States
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