Electrochemical device for generating hydroxyl free radicals and oxidizing chemical substances dissolved in water

• US 5,439,577 A
• Filed: 11/10/1994
• Issued: 08/08/1995
• Est. Priority Date: 03/16/1994
• Status: Expired due to Fees

• Current Assignee: Nancy Weres
• Original Assignee: Michael R. Hoffman, Oleh Weres
• Inventors: Hoffman, Michael R., Weres, Oleh
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Phasge, Arun S.
• Application Number:
  US08/337,288
• Time in Patent Office: 271 Days
• Field of Search: 204/268, 204/270, 204/278, 204/284, 204/290 F
• US Class Current: 204/268
• CPC Class Codes: C02F 1/001 Processes for the treatment of water whereby the filtration technique is of importance C02F1/44 takes precedence; construction of filters in general B01D24/00 - B01D41/00
• CPC Class Codes: C02F 1/38 by centrifugal separation
• CPC Class Codes: C02F 1/46104 Devices therefor; Their operating or servicing
• CPC Class Codes: C02F 1/46109 Electrodes
• CPC Class Codes: C02F 1/4672 by electrooxydation
• CPC Class Codes: C02F 2001/46128 Bipolar electrodes
• CPC Class Codes: C02F 2001/46133 characterised by the material
• CPC Class Codes: C02F 2001/46138 Electrodes comprising a substrate and a coating
• CPC Class Codes: C02F 2001/46161 Porous electrodes
• CPC Class Codes: C02F 2101/30 Organic compounds
• CPC Class Codes: C02F 2101/301 Detergents, surfactants
• CPC Class Codes: C02F 2101/36 containing halogen
• CPC Class Codes: C02F 2201/4611 Fluid flow
• CPC Class Codes: C02F 2201/4612 Controlling or monitoring
• CPC Class Codes: C02F 2201/4613 Inversing polarity
• CPC Class Codes: C02F 2201/4615 Time
• CPC Class Codes: C02F 2201/46155 Heating or cooling
• CPC Class Codes: C02F 2201/4617 DC only
• CPC Class Codes: C02F 2201/4619 Supplying gas to the electrolyte gas diffusion electrodes C02F2001/46166
• CPC Class Codes: C02F 2209/003 Downstream control, i.e. outlet monitoring, e.g. to check the treating agents, such as halogens or ozone, leaving the process
• CPC Class Codes: C02F 2209/02 : Temperature
• CPC Class Codes: C02F 2209/06 : pH
• CPC Class Codes: C02F 2301/024 : Turbulent
• CPC Class Codes: C02F 2305/023 : Reactive oxygen species, singlet oxygen, OH radical
• CPC Class Codes: Y02W 10/37 : using solar energy

Abstract

This invention provides an electrochemical water treatment device for producing hydroxyl free radicals and decomposing by oxidation chemical substances dissolved in water. It utilizes a novel electrode which is capable of operation at sufficiently positive anodic potential to produce hydroxyl radicals.

Claims

1. A water treatment module for decomposing chemical substances dissolved or dispersed in an electrically conductive aqueous medium, including

a bipolar electrochemical cell, wherein said bipolar electrochemical cell includes an array of bipolar electrodes, wherein said bipolar electrodes include a surface part and an internal part, wherein

said surface part has a semiconducting metal oxide composition including an additive metal having valence states,

wherein at least part of said additive metal is in a valence state which n-dopes said semiconducting metal oxide composition, and

wherein concentration of platinum group metals in said semiconducting metal oxide composition is zero or too small to exert a significant electrocatalytic effect favoring the generation of oxygen, and

wherein said cell is provided with water circulation means, and consists of further providing

flow baffles defining a serpentine fluid flow path through said array of bipolar electrodes, and

insulating baffles substantially blocking electrical conduction paths through said electrically conductive aqueous medium between bipolar electrodes which are not immediately adjacent within said array.

2. The water treatment module of claim 1, wherein

said internal part of said bipolar electrodes comprises a metallic substrate having a composition selected from the group consisting of titanium and titanium alloys, and

said semiconducting metal oxide composition contains titanium dioxide, and

said additive metal is selected from the group consisting of Nb and Ta, and

mole fraction of said additive metal in the +4 valence state is at least 0.25 percent relative to total metal in said semiconducting metal oxide composition.

3. The water treatment module of claim 2, wherein

total mole fraction of said additive metal in said semiconducting metal oxide composition relative to total metal in said semiconducting metal oxide composition is between 1 and 50 percent, and

mole fraction of said additive metal in the +4 valence state relative to total metal in said semiconducting metal oxide composition is at least 1 percent.

4. The water treatment module of claim 3 further provided with gas separating means.

5. The water treatment module of claim 2 further provided with turbulence promoting means.

6. The water treatment module of claim 2 further provided with a power supply module, wherein said power supply module includes periodic polarity reversing means.

7. The water treatment module of claim 2, wherein said array of said bipolar electrodes includes

mounting gaskets having mounting windows containing said bipolar electrodes, and flow windows allowing flow of said electrically conductive aqueous medium through said array, and

spacer gaskets maintaining proper separation between adjacent bipolar electrodes and retaining said bipolar electrodes in said mounting windows.

8. A water treatment device for decomposing chemical substances dissolved or dispersed in an electrically conductive aqueous medium, including at least one electrochemical cell, wherein said electrochemical cell includes at least one anode having a surface and a surface part and an internal part, wherein

said surface part has a semiconducting metal oxide composition including an additive metal having valence states,

wherein at least part of said additive metal is in a valence state which n-dopes said semiconducting metal oxide composition, and wherein concentration of platinum group metals in said semiconducting metal oxide composition is zero or too small to exert a significant electrocatalytic effect favoring the generation of oxygen,

said semiconducting metal oxide composition contains titanium dioxide, and said additive metal is selected from the group consisting of Nb and Ta, and

mole fraction of said additive metal in the +4 valence state is at least 0.25 percent relative to total metal in said semiconducting metal oxide composition, and

wherein said water treatment device is further provided with a source of electric power, and

water propulsion means for moving said electrically conductive aqueous medium through said water treatment device.

9. The water treatment device of claim 8, wherein

said internal part of said anodes comprises a metallic substrate having a composition selected from the group consisting of titanium and titanium alloys, and

total mole fraction of said additive metal in said semiconducting metal oxide composition relative to total metal in said semiconducting metal oxide composition is between 1 and 50 percent, and

mole fraction of said additive metal in the +4 valence state relative to total metal in said semiconducting metal oxide composition is at least 1 percent.

10. The water treatment device of claim 8, further provided with water treatment means selected from the group consisting of water filtration means, oil-water separation means, heavy metal ion removal means, and chemical addition means.

11. The water treatment device of claim 8, wherein said electrochemical cell is a porous anode cell.

12. The water treatment device of claim 11, wherein said water treatment device is further provided with pressurization means allowing operation of said porous anode cell at pressure greater than atmospheric.

13. The water treatment device of claim 8, further provided with process control means, and effluent water quality monitoring means.

14. The water treatment device of claim 8, wherein said electrochemical cells are grouped into multiple treatment stages, whereby current density at said surfaces of said anodes within said cells within each of said treatment stages may be adjusted to optimize energy efficiency of said water treatment device.

15. The water treatment device of claim 14, further provided with chemical addition means and pH monitoring means, whereby pH of said electrically conductive aqueous medium can be maintained within a predetermined range beneficial to operation of said water treatment device.

16. The water treatment device of claim 15, wherein said electrochemical cells are selected from the class consisting of bipolar cells and porous anode cells.

17. The water treatment device of claim 16, wherein

said internal part of said anodes comprises a metallic substrate having a composition selected from the class consisting of titanium and titanium alloys, and

total mole fraction of said additive metal in said semiconducting metal oxide composition relative to total metal in said semiconducting metal oxide composition is between 1 and 50 percent, and

mole fraction of said additive metal in the +4 valence state relative to total metal in said semiconducting metal oxide composition is at least 1 percent.

18. The water treatment device of claim 17, additionally provided with temperature regulating means, whereby temperature of said aqueous electrically conductive medium can be maintained in a predetermined range beneficial to operation of said water treatment device, and whereby heat generated by operation of said water treatment device can be recovered from said electrically conductive aqueous medium exiting said water treatment device.

19. The water treatment device of claim 17, wherein mole fraction of said additive metal in the +4 valence state in said semiconducting metal oxide composition is between two to six percent relative to total metal in said semiconducting oxide composition.