HK1163364A - Electrodes for use in bacterial fuel cells and bacterial electrolysis cells and bacterial fuel cells and bacterial electrolysis cells employing such electrodes - Google Patents

Description

Electrode for use in bacterial fuel cells and bacterial electrolysis cells and bacterial fuel cells and bacterial electrolysis cells employing the same

Reference to related applications

Reference is made to the applicant's co-pending U.S. provisional patent application No.61/198,027 filed on 30.10.2008 and entitled "Electrodes For Microbial Fuel Cells and Microbial Electrolysis Cells", the disclosure of which is incorporated herein by reference and entitled to priority in accordance with 37 CFR 1.78(a) (4) and (5) (i).

Reference is made to co-pending U.S. provisional patent application No.61/182,727, entitled "Microbial Fuel Cell", filed on 31/5/2009, the disclosure of which is incorporated herein by reference and which claims priority in accordance with 37 CFR 1.78(a) (4) and (5) (i).

Technical Field

The present invention relates generally to bioelectrochemical devices and more particularly to bacterial fuel cells and bacterial electrolysis cells.

Background

The following publications are considered to represent the current state of the art:

Microbial Fuel Cells：Methodology and Technology，Bruce E.Logan et al，Environ.Sci.Technol.，40(17)，5181-5192，2006.

Microbial Fuel Cells-Challenges and Applications，Bruce E.Logan & John M.Regan，Environ Sci.Tech.，Vol.40，17

Stefano Freguia，Korneel Rabaey，Zhiguo Yuan，Jurg Keller，Non-catalyzed cathodic oxygen reduction at graphite granules in microbial fuel cells，Electrochimica Acta 53(2007)598-603

Hong Liu et al.，Quantification of the internal resistance distribution in microbial fuel cells，Environmental Science and Technology

U.S. published patent application 20070259217

Disclosure of Invention

The present invention seeks to provide improved bioelectrochemical devices, more particularly improved bacterial fuel cells and bacterial electrolysis cells.

There is thus provided in accordance with a preferred embodiment of the present invention a bacterial fuel cell including a plurality of anodes and a plurality of cathodes in liquid communication with a liquid to be purified, each of the plurality of anodes and the plurality of cathodes including: a metallic electrical conductor arranged to electrically couple across a load in an electrical circuit; and an electrically conductive coating at least between the metallic electrical conductor and the liquid to be purified, for sealing the liquid and the electrical conductor relative to each other.

There is thus provided in accordance with another preferred embodiment of the present invention a bacterial fuel cell including a plurality of anodes and a plurality of cathodes in liquid communication with a liquid to be purified, each of the plurality of anodes and the plurality of cathodes including: a metallic electrical conductor arranged to electrically couple across a load in an electrical circuit; and an electrically conductive coating at least between the metal electrical conductor and the liquid to be purified for sealing the liquid and the electrical conductor against each other, at least two of the cathodes being arranged adjacent to each other and separated from each other by a gap filled with an oxygen-containing gas.

According to a preferred embodiment of the invention, the bacterial fuel cell further comprises at least one surface adapted for biofilm growth on a surface thereof, said surface being in liquid communication with said liquid and in electrical communication with said metal electrical conductor through said electrically conductive coating. Preferably, said at least one surface suitable for biofilm growth is defined by a fabric (fabric) covering the surface of said conductive coating.

According to a preferred embodiment of the invention, the metal electrical conductor is a coated metal electrical conductor, the electrically conductive coating comprising an electrically conductive coating formed onto the metal electrical conductor. Additionally or alternatively, the conductive coating comprises a conductive sheet.

Preferably, the electrically conductive coating of at least one of the plurality of cathodes comprises a water-permeable, electrically conductive sheet.

Preferably, the coated metal electrical conductor of at least one of the plurality of cathodes is water permeable.

Preferably, at least one cathode of the plurality of cathodes comprises an adhesion layer. More preferably, the attachment layer is formed of a plastic fabric.

According to a preferred embodiment of the invention, holes are formed in said plurality of anodes and cathodes, and the bacterial fuel cell comprises a conduit bounded by adjacent cathodes and a volume bounded between adjacent said cathodes and said anodes, providing communication of said liquid to be purified with said plurality of anodes and said plurality of cathodes, said holes providing communication of said liquid to be purified between said conduit and said volume.

According to a preferred embodiment of the invention, the plurality of anodes and cathodes are formed as embossed (embossed) elements. Preferably, the plurality of anodes and cathodes are sealed together.

There is also provided in accordance with another preferred embodiment of the present invention a bacterial electrolysis cell including: a plurality of anodes and cathodes in liquid communication with a liquid to be purified located in a tank, the tank comprising: an inlet for receiving water to be purified; an outlet for outputting purified water; and an outlet for hydrogen, the plurality of anodes and cathodes being connected via an electrical circuit across a power supply, at least one of the anodes and cathodes comprising a metal electrical conductor arranged to be electrically coupled in the electrical circuit, and an electrically conductive coating at least between the metal electrical conductor and a liquid in the cell for sealing the liquid and the electrical conductor relative to each other.

According to a preferred embodiment of the invention, the bacterial electrolysis cell further comprises at least one surface adapted for biofilm growth on a surface thereof, said surface being in liquid communication with said liquid and in electrical communication with said metal electrical conductor through said electrically conductive coating.

According to a preferred embodiment of the invention, each of the plurality of cathodes further comprises an oxygen permeable, liquid impermeable layer adjacent to the electrically conductive coating, wherein the oxygen permeable, liquid impermeable layer is exposed to an oxygen containing gas. Preferably, the oxygen permeable, liquid impermeable layer comprises an electrically conductive sheet. Alternatively, the oxygen-permeable, liquid-impermeable layer is formed from silicone rubber.

Preferably, the metal electrical conductor of at least one of the plurality of anodes is in the form of a foil.

Preferably, the metallic electrical conductor is in the form of a wire grid. Alternatively, the metal electrical conductor is in the form of a perforated (perforated) planar element. Alternatively, the metallic electrical conductors are in the form of an array of substantially parallel wires.

There is also provided in accordance with another preferred embodiment of the present invention an electrode for use in at least one of a bacterial fuel cell and an electrolysis cell, the electrode including: a metallic electrical conductor arranged to be electrically coupled in an electrical circuit; and an electrically conductive coating at least between the metal electrical conductor and a liquid in the cell, the electrically conductive coating for sealing the liquid and the electrical conductor relative to each other.

According to a preferred embodiment of the invention, the electrode comprises at least one surface adapted for biofilm growth on a surface thereof, said surface being in liquid communication with said liquid and in electrical communication with said metal electrical conductor through said conductive coating.

Preferably, the conductive coating is adapted to grow a biofilm on its surface.

According to a preferred embodiment of the invention, said at least one surface adapted for biofilm growth is defined by a cylindrical surface of a plurality of elongated elements formed of an electrically conductive plastic and extending substantially radially outwardly from said coated metal electrical conductor. Preferably, the coated metallic electrical conductor is twisted to retain a plurality of the plurality of elongate elements in the bundle along its elongate dimension. Preferably, the elongate elements are non-metallic electrical conductors having a conductivity less than the coated metallic electrical conductors. Preferably, the elongate element is formed from an electrically conductive plastic. Alternatively, the elongate elements are formed from graphite fibres.

According to a preferred embodiment of the invention, said at least one surface adapted for biofilm growth is defined by a plurality of sparsely wound helical elements formed of an electrically conductive plastic and blade elements extending generally radially outwardly from said coated metal electrical conductor.

According to a preferred embodiment of the invention, said at least one surface suitable for biofilm growth is defined by a cylindrical element formed of conductive plastic around a coated metal electrical conductor.

Preferably, the coated metal electrical conductor is in the form of a wire. Alternatively, the coated metal electrical conductor is in the form of a cable. Alternatively, the coated metal electrical conductor is in the form of a rod.

According to a preferred embodiment of the invention, said at least one surface suitable for biofilm growth is defined by a fabric covering the surface of the conductive coating.

According to a preferred embodiment of the invention, the conductive coating comprises a conductive sheet.

Preferably, the metal electrical conductor is in the form of a foil. Alternatively, the metallic electrical conductor is in the form of a wire grid. Alternatively, the metal electrical conductor is in the form of a perforated planar element. Alternatively, the metallic electrical conductors are in the form of an array of substantially parallel wires.

Preferably, the metallic electrical conductor is formed of copper or aluminum. Preferably, the conductive coating is formed from a conductive plastic.

Drawings

The present invention will be more fully understood and appreciated from the detailed description given below in conjunction with the drawings, in which:

FIG. 1 is a simplified pictorial illustration of a bacterial fuel cell constructed and operative in accordance with a preferred embodiment of the present invention;

FIGS. 2A, 2B, 2C and 2D are simplified pictorial illustrations of four alternative embodiments of electrodes constructed and operative in accordance with a preferred embodiment of the present invention, and usable in bacterial fuel cells and bacterial electrolysis cells;

FIGS. 3A, 3B and 3C are simplified pictorial illustrations of three alternative embodiments of a cathode constructed and operative in accordance with a preferred embodiment of the present invention and usable in a bacterial fuel cell;

FIGS. 4A, 4B and 4C are simplified pictorial illustrations of three alternative embodiments of a cathode constructed and operative in accordance with another preferred embodiment of the present invention and usable in a bacterial fuel cell;

FIGS. 5A and 5B are simplified side and top views, respectively, of a bacterial fuel cell constructed and operative in accordance with a preferred embodiment of the present invention;

FIG. 6 is a simplified schematic illustration of an electrode constructed and operative in accordance with a preferred embodiment of the present invention, useful in bacterial fuel cells and bacterial electrolysis cells;

FIG. 7 is a simplified schematic illustration of an electrode constructed and operative in accordance with a preferred embodiment of the present invention, useful in a bacterial fuel cell;

FIG. 8 is a simplified schematic illustration of a cathode constructed and operative in accordance with a preferred embodiment of the present invention, useful in a bacterial fuel cell; and

fig. 9A and 9B are respective simplified side and top views of a bacterial electrolysis cell constructed and operative in accordance with a preferred embodiment of the present invention.

Detailed Description

Referring now to fig. 1, fig. 1 is a simplified pictorial illustration of a bacterial fuel cell, constructed and operative in accordance with a preferred embodiment of the present invention, and including a plurality of anodes 100 (each anode represented by character a) and a plurality of cathodes 102 (each cathode represented by character C) in fluid communication with a liquid 104 to be purified, such as industrial waste water. In the embodiment of fig. 1, the water to be purified is supplied at an inlet 105, the inlet 105 communicating with a series of volumes 107 defined between adjacent anodes 100 and cathodes 102 (which are sealed together, for example, by an elastomeric seal (not shown)) and with an outlet 108 through apertures formed in the anodes 100 and cathodes 102 and a conduit 106 defined between adjacent cathodes.

According to an embodiment of the present invention, the anode and the cathode may be formed into embossed elements having a shape similar to that used in a conventional flat plate heat exchanger. In us patent 4,014,385; 3,792,730, respectively; 3,731,737, respectively; 3,661,203, respectively; 2,787,446 and 2,550,339, the disclosures of which are incorporated herein by reference.

According to a preferred embodiment of the invention, each of the plurality of anodes 100 and the plurality of cathodes 102 comprises a metallic electrical conductor surrounded by an electrically conductive coating.

The construction of each anode 100 is shown in an enlarged view 109. It can be seen that the metal conductor, here designated by reference numeral 110, preferably copper or aluminum, is surrounded by a conductive coating.

In the illustrated embodiment, the conductive coating is provided by laminating a pair of liquid-impermeable, conductive plastic sheets 112 to encase the metal conductors 110. Preferably, sheet 112 is formed of a plastic, such as polyethylene, polypropylene, and PET, which is mixed with a conductive powder, such as carbon or graphite, to produce a conductive plastic sheet.

Biofilm growth is preferably supported on the outer surface of the sheet 12. Optionally, a biofilm growth support 116 is provided on at least one outer surface of the sheet 112. The biofilm growth support 116 can be a fabric preferably formed of polyester or other suitable material.

Typical thicknesses of the elements of anode 100 are as follows:

conductor 110-20-200 micron

Tablet 112-50-400 micron

Biofilm growth support 116-10-50 microns

Four alternative embodiments of the anode 100 are shown in fig. 2A-2D. In fig. 2A, conductor 110 is in the form of a foil, indicated by reference numeral 120. In fig. 2B, the conductor 110 is in the form of a wire grid, indicated by reference numeral 122. In fig. 2C, the conductor 110 is in the form of a perforated planar element, indicated by reference numeral 124. In fig. 2D, the conductors 110 are in the form of a generally parallel wire array, indicated by reference numeral 126.

One embodiment of the construction of each cathode 102 is shown in enlarged view 128. It can be seen that the perforated metal conductor 130 is preferably copper or aluminum, surrounded by a conductive coating.

In the illustrated embodiment, the conductive coating is preferably provided by: the metal conductor 130 is coated with a liquid-impermeable, electrically conductive plastic, and the coated metal conductor is encapsulated on its liquid-facing side by an apertured sheet 132 formed of an electrically conductive plastic. Preferably, the conductive plastic is formed by mixing plastic such as polyethylene, polypropylene, and PET with conductive powder such as carbon or graphite.

Biofilm growth is preferably supported on the outer surfaces of the coated conductor 130 and the sheet 132. Optionally, a biofilm growth support 136 is provided on at least one outer surface of the sheet 132. Biofilm growth support 136 may be a fabric preferably formed of polyester or other suitable material.

On the opposite, air-facing side of the perforated, conductively coated metal conductor 130, an optional adhesion layer 138 is preferably provided, which typically comprises a woven or non-woven fabric formed of a plastic such as polyester. The attachment layer 138 preferably provides a liquid-tight, oxygen-permeable layer 140, preferably formed of silicone rubber, in addition to the attachment layer. An adhesion layer 138 aids in the adhesion of the oxygen permeable layer 140 to the coated conductor 130. Optionally, a mechanical support layer 142, preferably a grid of harder plastic, is provided outside the oxygen permeable layer 140.

Typical thicknesses of the elements of the cathode 102 shown in the enlarged view 128 are as follows:

three alternative embodiments of the cathode embodiment shown in enlarged view 128 are shown in fig. 3A-3C. In FIG. 3A, the perforated conductor 130 is in the form of a wire grid including conductive wires 144, all of which are coated with a liquid-impermeable, electrically-conductive coating 146, as shown in enlarged view 148. In FIG. 3B, the perforated conductor 130 comprises a perforated planar metal member 150 having all surfaces coated with a liquid-impermeable, electrically-conductive coating 152, as shown in enlarged view 154. In FIG. 3C, the perforated conductor 130 is in the form of an array of generally parallel wires 156, all of which are coated with a liquid-impermeable conductive coating 158, as shown in enlarged view 160.

Another embodiment of the construction of each cathode 102 is shown in enlarged view 168. It can be seen that the perforated metal conductor 170 is preferably copper or aluminum, surrounded by a conductive coating.

In the illustrated embodiment, the conductive coating is preferably provided by: the metal conductor 170 is coated with a liquid-impermeable, electrically conductive plastic, and the coated metal conductor is encapsulated on its liquid-facing side with an oxygen-permeable, liquid-impermeable sheet 172 of electrically conductive plastic. Preferably, the conductive plastic is formed by mixing plastic such as polyethylene, polypropylene, and PET with conductive powder such as carbon or graphite.

Biofilm growth is preferably supported on the outer surface of the conductive sheet 172. Optionally, a biofilm growth support 176 is provided on at least one outer surface of the sheet 172. The biofilm growth support 176 can be a fabric preferably formed of polyester or other suitable material.

On the opposite, air-facing side of the perforated, conductively coated metal conductor 170, a mechanical support layer 178 is optionally provided, which is preferably a grid of relatively hard plastic.

Typical thicknesses of the elements of the cathode 102 shown in the enlarged view 168 are as follows:

porous coated conductor 170-

Oxygen permeable sheet 172-50-400 micron

Biofilm growth support 176-10-50 microns

Mechanical support layer 178-

Three alternative embodiments of the cathode embodiment shown in enlarged view 168 are shown in fig. 4A-4C. In FIG. 4A, the perforated conductor 170 is in the form of a wire grid including conductive wires 180, all of which are coated with a liquid-impermeable, electrically-conductive coating 182, as shown in enlarged view 184. In FIG. 4B, the perforated conductor 170 comprises a perforated planar metal member 186 having all surfaces coated with a liquid-impermeable conductive coating 188, as shown in enlarged view 190. In FIG. 4C, the perforated conductor 170 is in the form of an array 192 of generally parallel wires, all of which are coated with a liquid-impermeable, electrically-conductive coating 194, as shown in enlarged view 196.

As shown in fig. 1, all anodes 100 and all cathodes 102 are electrically coupled in a circuit across the load 197. In the bacterial fuel cell of fig. 1, organic matter in liquid 104, represented as COD, is oxidized by electricity-generating (electrogenic) bacteria, such as Geobacter and Shewanella, typically present in biofilm 198, which is preferably supported by biofilm growth support 116 (enlarged view 109) provided on anode 100.

This oxidation produces CO₂Protons and electrons. The protons diffuse through the liquid 104 toward the cathode 102, and the electrons are provided by the bacteria to the anode 100 and travel through the circuit to the cathode 102.

In the cathode 102, oxygen O in the atmosphere₂A layer of electrically conductive plastic such as layer 132 (enlarged view 128) or 172 (enlarged view 168) on the cathode is permeated by an oxygen permeable layer such as layer 140 (enlarged view 128) or 172 (enlarged view 168). On the water-facing side of the electrically conductive plastic layer, oxygen O₂Reacts with protons and electrons to produce water H₂And O. Such reactions typically require a catalyst, preferably provided by a biofilm 199, preferably supported by a biofilm growth support 136 (enlarged 128) or 176 (enlarged 168), preferably provided on the cathode 102.

It can then be considered that the operation of the bacterial fuel cell of figure 1 both provides power and effects the purification of the liquid having organic material therein.

Reference is now made to fig. 5A and 5B, which are simplified side and top views of a bacterial fuel cell, constructed and operative in accordance with another preferred embodiment of the invention, comprising a plurality of anodes 300 interspersed among a plurality of cathodes 302, the anodes and cathodes, and a liquid 304 to be purified, for exampleSuch as industrial wastewater. The anode 300 and cathode 302 are located in a tank 306, the tank 306 having an inlet 308 for receiving water to be purified and an outlet 309 for outputting purified water. Circulation of the water 304 in the tank 306 is preferably provided by a suitable agitator or pump (not shown). Preferably, low pressure atmospheric oxygen O is blown by a fan (not shown) through the interior of cathode 302₂。

Referring also to fig. 6, fig. 6 shows a preferred embodiment of an anode 300 that can be used in the bacterial fuel cell of fig. 5A and 5B. As shown in fig. 6, a central elongated metal conductor 310, preferably a wire, cable or rod formed of copper or aluminum, is molded into and extends outwardly from a radially extending multi-lobed element 312 such that the element 312 provides a liquid-tight, electrically-conductive coating to the conductor 310. Optionally, additional elongated conductors 314 may be molded into and extend outwardly from the radially outer ends of one or more blades 316 of element 312 such that element 312 provides a liquid-tight, electrically-conductive coating for conductors 314. The element 312 is preferably formed from a liquid-impermeable, electrically-conductive plastic, such as polyethylene, polypropylene, and PET, which is mixed with an electrically-conductive powder, such as carbon or graphite.

The peripheral electrode portion 318 is preferably located near the radially outer end of the vane 316, preferably formed as a sparsely wound spiral element of conductive plastic, which allows relatively free communication of liquid with the surface of the element 312. Preferably, the element 312 and the peripheral electrode portion 318 are formed as a single element by an extrusion process. Optionally, some or all of the surfaces of element 312 and electrode portion 318 are coated with conductive powder or conductive fibers (not shown) formed of carbon or graphite. The surfaces of the element 312 and the electrode portion 318 are preferably all used to support biofilm growth and to enable power generation and purification of the liquid 304.

Referring now to fig. 7, fig. 7 shows an electrode assembly that may be used as an anode 300 in the bacterial fuel cell of fig. 5A and 5B, and the like. As shown in fig. 7, the electrode assembly preferably comprises a brush-like structure in which a plurality of elongated conductive elements 350 are held by and extend substantially radially outwardly from a twisted metal electrical conductor 352, the electrical conductor 352 being coated with a liquid-impermeable conductive coating 354, preferably a conductive plastic. Preferably, the conductive plastic is formed by mixing plastic such as polyethylene, polypropylene, and PET with conductive powder such as carbon or graphite.

The element 350 is preferably formed of a conductive plastic, or may be graphite fiber. The twisted conductor 352 is preferably formed of a metal such as copper or aluminum. When the conductor 352 is connected to an electrical load as shown, the surfaces of the coated conductor 352 and the element 350 are preferably all used to support biofilm growth and to effect power generation and purification of the fluid 304.

Preferably, the radially outer tips of the elements 350 may be coated with an electrically insulating material (not shown), such as a silicone rubber material, to prevent inadvertent shorting between adjacent electrodes.

Referring now to fig. 8, fig. 8 illustrates a preferred cathode 302 that can be used in the bacterial fuel cell of fig. 5A and 5B. Cathode 302 preferably includes a cylinder 360 formed of a perforated or porous conductive plastic, such as polyethylene, polypropylene, and PET, mixed with a conductive powder, such as carbon or graphite. Optionally, some or all of the surface of cylinder 360 is coated with conductive powder or conductive fibers (not shown) formed of carbon or graphite. The surface of the cylinder 360 is preferably used to support biofilm growth and to enable power generation and purification of the liquid 304.

The outer surface of the cathode 302 is permeated by the liquid 304 and the inner surface of the cathode 302 is sealed from contact with the liquid 304 by a liquid-impermeable, oxygen-permeable coating 362 formed alongside the inner surface of the cylinder 360. The coating 362 is preferably formed of silicone rubber. One or more elongated metallic conductors 364, preferably wires, cables or rods formed of copper or aluminum, are preferably molded into the cylinder 360 and extend outwardly therefrom such that the cylinder 360 provides the conductors 364 with a liquid-tight, electrically-conductive coating.

As shown in fig. 5A and 5B, all anodes 300 and all cathodes 302 are electrically coupled in a circuit across a load 320. In the bacterial fuel cell of fig. 5A and 5B, organic matter in the liquid 304, represented as COD, is oxidized by electricity-producing bacteria, such as Geobacter and Shewanella, typically present in a biofilm 370 supported on the anode 300.

This oxidation produces CO₂Protons and electrons. The protons diffuse through the liquid 304 toward the cathode 302, and the electrons are provided by the bacteria to the anode 300 and travel through the circuit to the cathode 302.

In the cathode 302, oxygen O in the atmosphere₂Permeate through an oxygen permeable layer such as layer 362 (fig. 8) to a conductive plastic layer such as layer 360 on the cathode. On the water-facing side of the conductive plastic layer 360, oxygen O₂Reacts with protons and electrons to produce water H₂And O. Such reactions typically require a catalyst, preferably provided by a biofilm 372, preferably on cathode 302.

The bacterial fuel cell of fig. 5A and 5B can then be considered to operate both to provide power and to effect purification of the liquid having organic material therein.

It should be appreciated that a variety of bacterial fuel cells of the type shown and described above with reference to fig. 1-8 may be connected in series and/or in parallel both hydraulically and electrically. The parallel interconnection increases the volume of water purified and provides a greater current output, while the series interconnection increases the degree of purification and provides a greater voltage output. Various combinations of parallel and series connections may be advantageously utilized to provide optimal water treatment and electrical power generation.

Referring now to fig. 9A and 9B, fig. 9A and 9B are simplified side and top views, respectively, of a bacterial electrolysis cell constructed and operative in accordance with a preferred embodiment of the present invention.

The bacterial electrolytic cell of fig. 9A and 9B includes a plurality of anodes 400 interspersed between a plurality of cathodes 402, the cathodes and anodes being in liquid communication with a liquid 404 to be purified, such as industrial wastewater. The anode 400 and cathode 402 are located in a tank 406, the tank 406 having an inlet 408 for receiving water to be purified and an outlet 409 for outputting purified water. Circulation of the water 404 in the tank 406 is preferably provided by a suitable agitator or pump (not shown).

It should be appreciated that the anode 400 and cathode 402 may be identical in structure, as shown. In this case, the anode 400 and the cathode 402 are distinguished from each other only from their electrical connections. Thus, the anode 400 and cathode 402 may each be of the type shown in fig. 2A-2D or of the type shown in fig. 6 or of the type shown in fig. 7, or any other suitable configuration. Preferably, the anode 400 is of the type shown in fig. 6 and the cathode is of the type shown in fig. 7, or vice versa.

As shown in fig. 9A and 9B, all anodes 400 and all cathodes 402 are electrically coupled in a circuit across a power supply 420. In the bacterial electrolysis cell of fig. 9A and 9B, organic matter in the liquid 404, represented as COD, is oxidized by electricity-producing bacteria, such as Geobacter and Shewanella, which are typically present in a biofilm 430 supported on an anode 400.

This oxidation produces CO₂Protons and electrons. The protons diffuse through the liquid 404 toward the cathode 402, and the electrons are provided by the bacteria to the anode 400 and travel through the circuit to the cathode 402.

In the cathode 402, the protons are reduced to hydrogen H by electrons driven by the power supply 420 through the circuit₂. Hydrogen and CO₂Accumulates in the headspace defined by the cover 440 covering the trough 406 and is discharged and separated at the outlet 442 in a suitable manner.

The bacterial electrolysis cell of fig. 9A and 9B can then be considered to operate to achieve hydrogen generation and to purify liquids having organic materials therein at a lower level of power consumption than conventional processes.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as modifications and variations thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not in the prior art.

Claims (90)

1. A bacterial fuel cell comprising:

a plurality of anodes and a plurality of cathodes in liquid communication with a liquid to be purified, each of the plurality of anodes and the plurality of cathodes comprising:

a metallic electrical conductor arranged to be electrically coupled across a load in an electrical circuit; and

an electrically conductive coating at least between the metallic electrical conductor and the liquid to be purified, the electrically conductive coating for sealing the liquid and the electrical conductor relative to each other.

2. A bacterial fuel cell according to claim 1 and also comprising at least one surface adapted for biofilm growth on a surface thereof, said surface being in liquid communication with said liquid to be purified and in electrical communication with said metal electrical conductor via said electrically conductive coating.

3. A bacterial fuel cell according to claim 1 and wherein said electrically conductive coating is adapted to grow a biofilm on a surface thereof.

4. A bacterial fuel cell according to claim 2 and wherein said at least one surface adapted for biofilm growth is defined by a fabric overlying a surface of said electrically conductive coating.

5. A bacterial fuel cell according to any of the preceding claims and wherein said metal electrical conductor is a coated metal electrical conductor and said electrically conductive coating comprises an electrically conductive coating formed onto said metal electrical conductor.

6. A bacterial fuel cell according to any of the preceding claims and wherein said electrically conductive coating comprises an electrically conductive sheet.

7. A bacterial fuel cell according to any of claims 1-5 and wherein said electrically conductive coating of at least one of said plurality of cathodes comprises an electrically conductive sheet that is permeable to water.

8. A bacterial fuel cell according to any of the preceding claims and wherein said coated metal electrical conductor of at least one of said plurality of cathodes is water permeable.

9. A bacterial fuel cell according to any of the preceding claims and wherein said plurality of cathodes each further comprises an oxygen permeable, liquid impermeable layer adjacent said electrically conductive coating and wherein said oxygen permeable, liquid impermeable layer is exposed to an oxygen containing gas.

10. A bacterial fuel cell according to any of claims 1-6 and 8-9 and wherein said oxygen permeable, liquid impermeable layer comprises an electrically conductive sheet.

11. A bacterial fuel cell according to claim 9 and wherein said oxygen permeable, liquid impermeable layer is formed from silicone rubber.

12. A bacterial fuel cell according to any of the preceding claims and wherein said metal electrical conductor of at least one of said plurality of anodes is in the form of a foil.

13. A bacterial fuel cell according to any of claims 1-11 and wherein said metal electrical conductor is in the form of a wire grid.

14. A bacterial fuel cell according to any of claims 1-11 and wherein said metal electrical conductor is in the form of a perforated planar element.

15. A bacterial fuel cell according to any of claims 1-11 and wherein said metal electrical conductor is in the form of a generally parallel wire array.

16. A bacterial fuel cell according to any of the preceding claims and wherein at least one of said plurality of cathodes comprises an adhesion layer.

17. A bacterial fuel cell according to claim 16 and wherein said attachment layer is formed from a plastic fabric.

18. A bacterial fuel cell according to any of the preceding claims and wherein pores are formed in said plurality of anodes and cathodes and said bacterial fuel cell comprises:

a conduit defined between adjacent said cathodes; and

a volume defined between adjacent ones of the cathodes and the anodes that provides communication of the liquid to be purified with the plurality of anodes and the plurality of cathodes,

the aperture provides communication of the liquid to be purified between the conduit and the volume.

19. A bacterial fuel cell according to any of the preceding claims and wherein said plurality of anodes and cathodes are formed as embossed elements.

20. A bacterial fuel cell according to claim 19 and wherein said plurality of anodes and cathodes are sealed together.

21. A bacterial fuel cell according to claim 2 and wherein said at least one surface adapted for biofilm growth is defined by cylindrical surfaces of a plurality of elongate elements formed of an electrically conductive plastic and extending generally radially outwardly from said metal electrical conductor, wherein said metal electrical conductor is a coated metal electrical conductor and said electrically conductive coating comprises an electrically conductive coating formed onto said metal electrical conductor.

22. A bacterial fuel cell according to claim 21 and wherein said coated metallic electrical conductor is twisted to retain a plurality of said plurality of elongated elements in a bundle along an elongated dimension thereof.

23. A bacterial fuel cell according to claims 21-22 and wherein said elongated elements are non-metallic electrical conductors having a conductivity less than said coated metallic electrical conductors.

24. A bacterial fuel cell according to any of claims 21-23 and wherein said elongated elements are formed from an electrically conductive plastic.

25. A bacterial fuel cell according to any of claims 21-23 and wherein said elongated elements are formed from graphite fibers.

26. A bacterial fuel cell according to claim 2 and wherein said at least one surface adapted for biofilm growth is defined by a plurality of blade elements surrounded by a sparsely wound helical element formed of electrically conductive plastic and extending generally radially outwardly from said metal electrical conductor, wherein said metal electrical conductor is a coated metal electrical conductor and said electrically conductive coating comprises an electrically conductive coating formed onto said metal electrical conductor.

27. A bacterial fuel cell according to any of claims 2, 9 and 11 and wherein said at least one surface adapted for biofilm growth is defined by a cylindrical element formed of electrically conductive plastic surrounding said metal electrical conductor, wherein said metal electrical conductor is a coated metal electrical conductor and said electrically conductive coating comprises an electrically conductive coating formed onto said metal electrical conductor.

28. A bacterial fuel cell according to any of claims 21-27 and wherein said coated metal electrical conductor is in the form of a wire.

29. A bacterial fuel cell according to any of claims 21-27 and wherein said coated metal electrical conductor is in the form of a cable.

30. A bacterial fuel cell according to any of claims 21-27 and wherein said coated metal electrical conductor is in the form of a rod.

31. A bacterial fuel cell according to any of the preceding claims and wherein said metal electrical conductor is formed from copper or aluminium.

32. A bacterial fuel cell according to any of the preceding claims and wherein said electrically conductive coating is formed from an electrically conductive plastic.

33. A bacterial fuel cell comprising:

a plurality of anodes and a plurality of cathodes in liquid communication with a liquid to be purified, each of the plurality of anodes and the plurality of cathodes comprising:

a metallic electrical conductor arranged to be electrically coupled across a load in an electrical circuit; and

an electrically conductive coating at least between the metallic electrical conductor and the liquid to be purified, for sealing the liquid and the electrical conductor against each other,

at least two of the cathodes are arranged adjacent to each other and separated from each other by a gap filled with an oxygen-containing gas.

34. A bacterial fuel cell according to claim 33 and also comprising at least one surface adapted for biofilm growth on a surface thereof, said surface being in liquid communication with said liquid to be purified and in electrical communication with said metal electrical conductor via said electrically conductive coating.

35. A bacterial fuel cell according to claim 33 and wherein said electrically conductive coating is adapted to grow a biofilm on a surface thereof.

36. A bacterial fuel cell according to claim 34 and wherein said at least one surface adapted for biofilm growth is defined by a fabric overlying a surface of said electrically conductive coating.

37. A bacterial fuel cell according to any of claims 33-36 and wherein said metal electrical conductor is a coated metal electrical conductor and said electrically conductive coating comprises an electrically conductive coating formed onto said metal electrical conductor.

38. A bacterial fuel cell according to any of claims 33-37 and wherein said electrically conductive coating comprises an electrically conductive sheet.

39. A bacterial fuel cell according to any of claims 33-37 and wherein said electrically conductive coating of at least one of said plurality of cathodes is a water permeable electrically conductive sheet.

40. A bacterial fuel cell according to any of claims 33-39 and wherein said coated metal electrical conductor of at least one of said plurality of cathodes is water permeable.

41. A bacterial fuel cell according to any of claims 33-40 and wherein said plurality of cathodes each comprise an oxygen permeable, liquid impermeable layer adjacent said electrically conductive coating, and wherein said oxygen permeable, liquid impermeable layer is exposed to an oxygen containing gas.

42. A bacterial fuel cell according to any of claims 33-38 and 40-41 and wherein said oxygen permeable, liquid impermeable layer comprises an electrically conductive sheet.

43. A bacterial fuel cell according to claim 42 and wherein said oxygen permeable, liquid impermeable layer is formed from silicone rubber.

44. A bacterial fuel cell according to any of claims 33-43 and wherein said metal electrical conductor of at least one of said plurality of anodes is in the form of a foil.

45. A bacterial fuel cell according to any of claims 33-44 and wherein said metal electrical conductor is in the form of a wire grid.

46. A bacterial fuel cell according to any of claims 33-45 and wherein said metal electrical conductor is in the form of a perforated planar element.

47. A bacterial fuel cell according to any of claims 33-46 and wherein said metal electrical conductor is in the form of a generally parallel wire array.

48. A bacterial fuel cell according to any of claims 33-47 and wherein at least one of said plurality of cathodes comprises an adhesion layer.

49. A bacterial fuel cell according to claim 48 and wherein said attachment layer is formed from a plastic fabric.

50. A bacterial fuel cell according to any of claims 33-49 and wherein apertures are formed in said plurality of anodes and cathodes and said bacterial fuel cell comprises:

a conduit defined between adjacent said cathodes; and

a volume defined between adjacent ones of the cathodes and the anodes that provides communication of the liquid to be purified with the plurality of anodes and the plurality of cathodes,

the aperture provides communication of the liquid to be purified between the conduit and the volume.

51. A bacterial fuel cell according to any of claims 33-50 and wherein said plurality of anodes and cathodes are formed as embossed elements.

52. A bacterial fuel cell according to claim 51 and wherein said plurality of anodes and cathodes are sealed together.

53. A bacterial fuel cell according to any of claims 33-52 and wherein said metal electrical conductor is formed from copper or aluminum.

54. A bacterial fuel cell according to any of claims 33-53 and wherein said electrically conductive coating is formed from an electrically conductive plastic.

55. An electrode for use in at least one of a bacterial fuel cell and an electrolysis cell, the electrode comprising:

a metallic electrical conductor arranged to be electrically coupled in an electrical circuit;

an electrically conductive coating at least between the metal electrical conductor and a liquid in the cell, the electrically conductive coating for sealing the liquid and the electrical conductor relative to each other.

56. The electrode of claim 55 further comprising at least one surface adapted for biofilm growth on a surface thereof, said surface in liquid communication with said liquid to be purified and in electrical communication with said metal electrical conductor via said conductive coating.

57. The electrode of claim 55 wherein said conductive coating is adapted to grow a biofilm.

58. The electrode of any one of claims 55-57, wherein said metal electrical conductor is a coated metal electrical conductor, said conductive coating comprising a conductive coating formed onto said metal electrical conductor.

59. The electrode of any one of claims 56-58 wherein the at least one surface adapted for biofilm growth is defined by cylindrical surfaces of a plurality of elongate elements formed of an electrically conductive plastic and extending generally radially outwardly from the coated metal electrical conductor.

60. The electrode of claim 59 wherein said coated metallic electrical conductor is twisted to retain a plurality of said plurality of elongated elements in a bundle along an elongated dimension thereof.

61. The electrode of any one of claims 59-60, wherein said elongate element is a non-metallic electrical conductor having a conductivity less than said metallic electrical conductor.

62. The electrode of any one of claims 59-61, wherein said elongated element is formed of an electrically conductive plastic.

63. The electrode of any one of claims 59-61, wherein said elongated elements are formed from graphite fibers.

64. The electrode of any one of claims 56-58 wherein said at least one surface adapted for biofilm growth is defined by a plurality of blade elements surrounded by a sparsely wound helical element formed of conductive plastic and extending generally radially outwardly from said coated metal electrical conductor.

65. The electrode of any one of claims 55-64 wherein said metallic electrical conductor is in the form of a wire.

66. The electrode of any one of claims 55-64 wherein said metallic electrical conductor is in the form of a cable.

67. The electrode of any one of claims 55-64 wherein the metallic electrical conductor is in the form of a rod.

68. The electrode according to claim 56 wherein said at least one surface adapted for biofilm growth is defined by a fabric covering a surface of said conductive coating.

69. The electrode of any one of claims 57 and 68, wherein said conductive coating comprises a conductive sheet.

70. The electrode of claim 69 wherein said metal electrical conductor is in the form of a foil.

71. The electrode according to claim 69 wherein said metallic electrical conductor is in the form of a wire grid.

72. The electrode according to claim 69 wherein said metal electrical conductor is in the form of a perforated planar element.

73. The electrode of claim 69 wherein said metallic electrical conductor is in the form of an array of generally parallel wires.

74. The electrode of any one of claims 55-73, wherein said metallic electrical conductor is formed of copper or aluminum.

75. The electrode of any one of claims 55-74, wherein said conductive coating is formed from a conductive plastic.

76. A bacterial electrolysis cell comprising:

a plurality of anodes and cathodes in liquid communication with a liquid to be purified located in a tank, the tank comprising:

an inlet for receiving water to be purified;

an outlet for outputting purified water; and

an outlet for the hydrogen gas, and a hydrogen gas outlet,

the plurality of anodes and cathodes are connected via a circuit across a power supply,

at least one of the anode and cathode includes:

a metallic electrical conductor arranged to be electrically coupled in an electrical circuit;

an electrically conductive coating at least between the metal electrical conductor and a liquid in the cell, the electrically conductive coating for sealing the liquid and the electrical conductor relative to each other.

77. A bacterial electrolysis cell according to claim 76 and also comprising at least one surface adapted for biofilm growth on a surface thereof, said surface being in liquid communication with the liquid to be purified and in electrical communication with said metal electrical conductor via said electrically conductive coating.

78. A bacterial electrolysis cell according to claim 76 wherein the electrically conductive coating is adapted to grow a biofilm.

79. The bacterial electrolysis cell according to any one of claims 76-78 wherein said metal electrical conductor is a coated metal electrical conductor, said electrically conductive coating comprising an electrically conductive coating formed onto said metal electrical conductor.

80. A bacterial electrolysis cell according to any one of claims 77 to 79 wherein the at least one surface adapted for biofilm growth is defined by cylindrical surfaces of a plurality of elongate elements formed of an electrically conductive plastic and extending generally radially outwardly from the coated metal electrical conductor.

81. A bacterial electrolysis cell according to claim 80 wherein the coated metallic electrical conductor is twisted to retain a plurality of the plurality of elongate elements in a bundle along an elongate dimension thereof.

82. A bacterial electrolysis cell according to any of claims 80 to 81 and wherein said elongate element is a non-metallic electrical conductor having a conductivity less than the metallic electrical conductor.

83. A bacterial electrolysis cell according to any of claims 80 to 82 and wherein the elongate element is formed from an electrically conductive plastic.

84. A bacterial electrolysis cell according to any of claims 80 to 82 and wherein said elongate elements are formed from graphite fibres.

85. A bacterial electrolysis cell according to any one of claims 77 to 79 wherein the at least one surface adapted for biofilm growth is defined by a plurality of blade elements surrounded by a sparsely wound helical element formed of electrically conductive plastic and extending generally radially outwardly from the coated metal electrical conductor.

86. A bacterial electrolysis cell according to any of claims 76 to 85 and wherein said metal electrical conductor is in the form of a wire.

87. A bacterial electrolysis cell according to any of claims 76 to 85 and wherein said metal electrical conductor is in the form of an electrical cable.

88. A bacterial electrolysis cell according to any of claims 76 to 85 and wherein said metal electrical conductor is in the form of a rod.

89. A bacterial electrolysis cell according to any of claims 76 to 88 and wherein said metal electrical conductor is formed from copper or aluminium.

90. The bacterial electrolysis cell according to any one of claims 76-89 wherein said conductive coating is formed from a conductive plastic.