GB2557185A

GB2557185A - Electrochemical cell assembly and method for operation of the same

Info

Publication number: GB2557185A
Application number: GB1620195.6A
Authority: GB
Inventors: Simon Bray Patrick
Original assignee: Roseland Holdings Ltd
Current assignee: Roseland Holdings Ltd
Priority date: 2016-11-29
Filing date: 2016-11-29
Publication date: 2018-06-20
Also published as: WO2018100356A1; GB201620195D0

Abstract

A device for producing ozonated water from a reservoir of water provided, the apparatus comprising an electrochemical cell to electrolyse water to produce ozone and having a first and second electrode assembly; an electrical supply for providing an electrical energy source to the electrochemical cell; a conductivity sensor for determining the conductivity of fluid in the region of the electrode assemblies of the cell; a processor for receiving an indication of fluid conductivity from the conductivity sensor and determining if the conductivity of the fluid in the region of the electrode assemblies is above a threshold value and, if the conductivity is above the threshold value, activating the electrochemical cell. A method of use is also provided. The electrical supply may be a battery, cable, or solar panel or array. The electrodes can be formed of a diamond material with a conductive coating.

Description

(54) Title of the Invention: Electrochemical cell assembly and method for operation of the same Abstract Title: Water ozonising device (57) A device for producing ozonated water from a reservoir of water provided, the apparatus comprising an electrochemical cell to electrolyse water to produce ozone and having a first and second electrode assembly; an electrical supply for providing an electrical energy source to the electrochemical cell; a conductivity sensor for determining the conductivity of fluid in the region of the electrode assemblies of the cell; a processor for receiving an indication of fluid conductivity from the conductivity sensor and determining if the conductivity of the fluid in the region of the electrode assemblies is above a threshold value and, if the conductivity is above the threshold value, activating the electrochemical cell. A method of use is also provided. The electrical supply may be a battery, cable, or solar panel or array. The electrodes can be formed of a diamond material with a conductive coating.

Formulae in the printed specification were reproduced from drawings submitted after the date of filing, in accordance with Rule 20(13) of the Patents Rules 1995

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ELECTROCHEMICAL CELL ASSEMBLY AND METHOD FOR OPERATION OF THE SAME

The present invention relates to an electrochemical cell assembly and a method of operating the same. The present invention concerns in particular an electrochemical cell assembly for the production of ozone and to a method of operating the cell.

Electrochemical cells find use in a range of applications for conducting a variety of electrochemical processes. In general, the cells comprise an anode and a cathode, separated by a semi-permeable membrane, in particular a Cation Exchange Membrane that may also be described as a Proton Exchange Membrane. One particular application for electrochemical cells is the production of ozone by the electrolysis of water.

Ozone is one of the strongest and fastest acting oxidants and disinfectants available for water treatment. Although ozone is only partially soluble in water, it is sufficiently soluble and stable to disinfect water contaminated by pathogenic microorganisms and can be utilised for a wide range of disinfection applications. Microorganisms of all types are destroyed by ozone and ozonated water, including bacteria, viruses, fungi and fungal spores, oocysts, protozoa and algae.

Ozone decomposes rapidly in water into oxygen and has a relatively short half life. The half life of ozone in water is dependant upon temperature, pH and other factors. However, the short half-life of ozone is a further advantage, as once treatment has been applied, the ozone will rapidly disappear, rendering the treated water safe. Once treatment has been applied, ozone that remains in solution will rapidly decay to oxygen. Unlike chorine based disinfectants, ozone does not form toxic halogenated intermediates and undesirable end products such as trihalomethanes (THMs).

The concentration of ozone dissolved in water determines the rate of oxidation and the degree of disinfection in any given volume of water, with the higher the concentration ozone, the faster the rate of disinfection of micro-organisms.

Electrolysis of water at high electrode potential produces ozone at the anode in an electrochemical cell according to the following equations:

3H₂O Os + 3H⁺ + 6eand

2H₂O O₂ + 4H⁺ + 4e- (E_o = 1.23 V_SHe)

H₂O + O₂ Os + 2H⁺ + 2e- (E_o = 2.07 V_SHE)

Ozone may be produced in higher concentrations from low conductivity water, deionised water, demineralised water, and softened water. Ozone dissolved in water is described as ozonated water.

The production of ozone and ozonated water by electrolysis using an electrolytic cell is known in the art. DE 10025167 discloses an electrode assembly for use in a cell for the electrolytic production of ozone and/or oxygen. The cell comprises an anode and a cathode separated by a membrane in direct contact with each of the electrodes.

WO 2005/058761 discloses an electrolytic cell for the treatment of contaminated water. The cell comprises an anode and a cathode, with water being passed between the two electrodes. The cathode is preferably formed from nickel, titanium, graphite or a conductive metal oxide. The cathode is provided with a coating, preferably boron doped diamond (BDD), activated carbon or graphite. The anode is preferably formed from titanium, niobium, or a conductive non-metallic material, such as p-doped silicon. The anode is preferably provided with a coating, with preferred coatings being boron doped diamond (BDD), lead oxide (PbO₂), tin oxide (SnO₂), platinised titanium, platinum, activated carbon and graphite.

US 2007/0023273 concerns a method of sterilization and an electrolytic water ejecting apparatus. Raw water is sterilized by electrolysis in a unit comprising a cell having a cathode and an anode at least having a part containing a conductive diamond material.

US 2008/156642 concerns a system for the disinfection of low-conductivity liquids, in particular water, the system comprising an electrochemical cell in which electrodes are arranged to allow the liquid to flow therearound. Oxidizing agents, such as ozone, are produced from the liquid by the application of an electrical current.

US 2010/0006450 discloses a diamond electrode arrangement for use in an electrochemical cell for the treatment of water and/or the production of ozone. The cell comprises an anode and a cathode separated by a proton exchange membrane (PEM). The electrode is formed with a diamond plate and is configured to have one or more slots (described as elongated apertures) therein, to provide a minimum specified apertures length per unit of working area ofthe electrode.

An electrolytic apparatus and an electrolytic method are disclosed in JP 2011038145.

The electrolysis of water to produce ozone using a cell comprising a solid polymer electrolyte sandwiched between diamond electrodes is described by A. Kraft, et al. ‘Electrochemical Ozone Production using Diamond Anodes and a Solid Polymer Electrolyte’, Electrochemistry Communications 8 (2006), pages 883 to 886.

The production of high-concentration ozone-water by electrolysis is described by K. Arihara et al. ‘Electrochemical Production of High-Concentration Ozone-Water using Freestanding Perforated Diamond Electrodes’, Journal of the Electrochemical Society, 154 (4), E71 to E75 (2007).

EP 1 741676 describes and shows a apparatus for electrolyzing and dispensing water for sterilisation purposes. The apparatus comprises an electrolysis cell having a cathode and an anode having at least a part formed from conductive diamond. The apparatus comprises a manually operated spray assembly for distributing the electrolysed water.

There is a need for an apparatus for producing ozonated water for disinfection purposes. It would be most advantageous if the apparatus could be used for the disinfection of water, such as drinking water at the point of consumption, for example in a glass, bottle or other receptacle. In addition, it would be most advantageous if the apparatus could also be arranged for use in larger containers of water, such as domestic water tanks and the like.

In a first aspect, the present invention provides a device for producing ozonated water from a reservoir of water, the apparatus comprising:

an electrochemical cell operable to electrolyse water to produce ozone and having a first electrode assembly and a second electrode assembly;

an electrical supply for providing an electrical energy source to the electrochemical cell;

a conductivity sensor for determining the conductivity of fluid in the region of the electrode assemblies of the cell;

a processor for receiving an indication of fluid conductivity from the conductivity sensor and determining if the conductivity of the fluid in the region of the electrode assemblies is above a threshold value and, if the conductivity is above the threshold value, activating the electrochemical cell.

In a second aspect, the present invention provides a method for producing ozonated water from a reservoir of water, the method comprising:

providing an electrochemical cell operable to electrolyse water to produce ozone having a first electrode assembly and a second electrode assembly;

determining the conductivity of the fluid in the region of the electrode assemblies of the cell;

comparing the conductivity of the fluid in the region of the electrode assemblies with a threshold value; and if the conductivity of the fluid in the region of the electrodes is above the threshold value, activating the electrochemical cell.

The device of the present invention is for use in disinfecting a body of water by the electrochemical generation of ozone. The device has a range of applications and may be provided in a number of different embodiments, depending upon the circumstances of the intended use, in particular the nature, location and amount of water to be ozonated. The general principles of construction and operation of the device remain the same for all embodiments, with the differences being size or scale of the device and the volume of water that can be processed in a given time. The size or scale of the device may be varied by varying such features as the size and/or number of electrochemical cells. The size of the electrochemical cell may be varied, for example by varying the size and/or number of electrodes within the cell.

The various embodiments of the present invention have the general features recited above in common. These features arise from the intended use of the devices, in particular in the ozonation of a body of water at a point of consumption, such as, on a small scale, a glass or bottle and, on a larger scale, a tank or other reservoir from which water is dispensed directly to the user. These uses have in common that the amount of water present in the vessel or container may vary considerably, in particular from the vessel or container being empty to being completely full. In light of this, the device of the present invention has been arranged to operate only when the presence of water in the vessel or container is detected. In particular, the device determines whether sufficient water for safe and effective operation of the electrochemical cell is present and, only when sufficient water has been detected, allows the electrochemical cell to be activated. In this way, damage to the electrochemical cell by applying an electric potential across the electrodes without water being present is avoided.

In one embodiment, the device is particularly intended for use with small volumes of water, that is water volumes of less than 1 litre up to a few litres. The device may be adapted for use intermittently to disinfect different bodies of water, as required by the user. In one application, the device is intended for use with a body of water intended to be consumed and held in a suitable container, such as a glass, bottle or the like. In another application, the device is intended for the disinfection of water required for other purposes, in particular the disinfection of water in which flowers are standing.

In one particular embodiment, the device is a portable device, preferably hand held, and is arranged to have part or all of the device inserted into a container, such as a bottle, jug, vase or glass, containing water and immersed in the body of water to be treated sufficiently to allow the electrochemical cell to be operated to ozonate the water. The device may then be removed once treatment of the water has completed.

In another embodiment, the device is comprised in the container or vessel holding water, for example a bottle, flask, jug or the like. The device is operated as the container or vessel is charged with a fresh volume of raw water to be treated or when the required volume of water is present in the container or vessel and before water is dispensed from the container or vessel.

In a further embodiment, the device is arranged to be immersed in a body of water and to ozonate the water until deactivated by the user and removed therefrom. Such an embodiment is of use, for example, in the treatment of water in which flowers are standing.

In a further embodiment, the device of the present invention is of a larger scale and is for use in the ozonation of larger volumes of water in a container, such as a tank. In such cases, the device is of a size sufficient to ozonate a body of water of from a few litres to several tens or several hundreds of litres in volume. One example of such a use is in the treatment of water in a domestic water tank. The principles of the operation of the device are as described above. The device may be provided as a stand alone or separate device for insertion into the container so as to contact the water therein, when present. Alternatively, the device may be incorporated into and form part of the container, as with the smaller scale devices.

Uses for the devices of the present invention include the disinfection of volumes of water in glasses or other containers for drinking; as a portable device for the disinfection of water by travellers; the disinfection of water from a mains water supply in domestic water tanks; the disinfection of water from boreholes, wells, lakes, rivers and streams; the disinfection of water to be stored for extended periods of time, for example in marine vessels. The devices also find uses in the medical sector, for example in the disinfection of dentures and the treatment of dental conditions, such as oral infections, gum disease (periodontal disease) and procedures for root canals (endodontic disease), as well as the disinfection of medical and dental equipment. Still further applications include the disinfection of fruit and vegetables, the sanitising of refrigerators and stored food products. As also noted above, the devices are advantageously used to disinfect the water in vases and other vessels to prevent the proliferation of bacteria and extend the life of cut flowers.

The device of present invention may be arranged to be modular in form. In this respect, a single module having the general features recited above is of a small scale, suitable for treatment of the lower volumes of water mentioned hereinbefore. Embodiments of the device for treating larger volumes of water may be provided by combining two or more modules. The number of modules required in the device will be determined by the duty to be performed. The device of the present invention may comprise a single electrochemical cell or may comprise a plurality of electrochemical cells, for example 2, 3, 4 5 or 6 cells. The plurality of electrochemical cells are preferably connected to and controlled by a single processor. The device may comprise a single conductivity sensor, for the plurality of electrochemical cells. Alternatively, the device may comprise two or more conductivity sensors, for example with each of the plurality of electrochemical cells being provided with a respective conductivity sensor. In one preferred embodiment, the electrochemical cell is modular.

In this respect, the duty required of the device is determined by such factors as the volume of water to be ozonated, the concentration of ozone required to be provided and maintained, and the length of time required to reach the desired degree of ozonation.

The device of the present invention comprises means for providing electrical energy for powering the components of the device.

In one embodiment, the electrical supply for providing electrical energy comprises an electrical energy source, in particular one or more batteries. The use of batteries as the source of electrical energy is particularly preferred for the smaller sized and/or portable devices. Suitable batteries are known and are commercially available. A preferred battery is a rechargeable battery. The device may comprise means for recharging the battery, for example by inductive coupling. Such rechargeable batteries and the means for recharging the batteries are also known in the art and are commercially available. The capacity and number of batteries provided in the device will depend upon the duty rating of the electrochemical cell, which is in turn determined by the volume of water to be treated by the device, and can be readily determined by the person skilled in the art.

Alternatively, or in addition to the use of one or more batteries, the electrical supply for providing a source of electrical energy may comprise a cable or the like, for connecting to a source of electrical energy. For example, in a domestic location, the device may be connected to a domestic electrical supply by way of a cable. Embodiments in which the device is connectable to a remote source of electrical power, such as a domestic mains electricity supply, are preferred for the larger scale devices and/or those devices that are to be used in one location for an extended period of time, such as in the treatment of domestic water supply.

Alternatively or in addition, the electrical supply may comprise a solar panel or solar array, by which electricity may be generated and provided to the electrochemical cell.

The device further comprises an electrochemical cell. The cell is operable to electrolyse water to produce ozone. The cell comprises a first electrode assembly and a second electrode assembly, each having one or more electrodes. The electrode assemblies are separated by a membrane. In operation, one of the first and second electrode assemblies functions as the anode and the other of the first and second electrode assemblies functions as the cathode, depending upon the polarity of the supply of electrical energy. Ozone is produced at the anode.

The cell is most preferably a passive cell, that is water is not pumped or otherwise forced through the cell. Rather, the cell is immersed in the body of water to be ozonated and operates to electrolyse water in contact with the electrodes and the membrane. The products of the electrolysis, including ozone, diffuse away from the electrodes and the membrane. In this way, ozone is produced in high concentrations at the electrodes and is rapidly dispersed by diffusion into the bulk of the water. This is in contrast to known electrochemical cells, in which water to be electrolysed is pumped or otherwise forced through the cell into contact with the electrodes and the membrane.

As noted above, the cell comprises a first electrode assembly and a second electrode assembly. Each of the electrode assemblies comprises one or more electrodes. Each electrode comprises one or more diamond electrodes having an active edge or surface. In particular, it has been found that the electrolysis reactions forming ozone occur at edges of the diamond electrodes.

Suitable diamond materials for forming the active edge or surface of each electrode are known in the art. The electrically conductive diamond material may be a layer of single crystal synthetic diamond, natural diamond, or polycrystalline diamond. Polycrystalline diamond is particularly preferred. Synthetic diamond may be prepared using high pressure high temperature (HPHT) or chemical vapour deposition (CVD) processes. CVD diamond is especially preferred.

The diamond material may consist essentially of carbon, but is preferably doped with one or more elements that provide electrical conductivity. Suitable dopants to provide the diamond with electrical conductivity are known in the art. The diamond of the electrodes is preferably doped with boron to confer electrical conductivity and is described as boron doped diamond (BDD). A particularly suitable and preferred diamond material is polycrystalline boron doped diamond (BDD).

The electrodes of the cell may be of a solid diamond material or a substrate material coated with diamond, that is a substrate material having a layer of diamond formed on a surface thereof.

Most preferably, each electrode comprises a solid diamond material, that is a diamond material formed as a free-standing solid. The solid diamond material may be accompanied by a substrate in the electrode, for example to support the diamond material. The preferred electrode material is electrically conductive, solid, free standing polycrystalline Boron-doped diamond. This diamond material may be manufactured in the form of a wafer by way of a process of chemical vapour deposition (CVD) in a microwave plasma system. The electrode may then be formed by being cut from the wafer, for example by using a laser.

This diamond material of each electrode is preferably from 200 to 1000 microns in thickness, more preferably from 300 to 800 microns thick. It is particularly preferred that the solid diamond material has a thickness of from 350 to 700 microns, more particularly from 400 to 600 microns. A thickness of 500 microns for the solid diamond material is particular preferred.

Alternatively, the active electrode material may be a substrate material coated with conductive diamond. The substrate material may be any suitable material, examples of which include silicon (Si), tungsten (W), niobium (Nb), molybdenum (Mo) or tantalum (Ta). This diamond material is manufactured by known techniques, for example by way of a process of chemical vapour deposition in a hot filament system. The active diamond layer at the surface of the electrode material, in this case, is typically from 1 to 10 microns in thickness, more preferably from 3 to 5 microns thick.

Suitable techniques for manufacturing both solid free-standing electrically conductive boron-doped diamond material and diamond coated material are known in the art. It has been found that diamond material provided as a layer formed on the substrate material is prone to blistering and delaminating under the conditions prevailing in the electrochemical cell during operation. This in turn significantly reduces the longevity and operating life of the cell. Accordingly, it is preferred that the diamond material is provided as a layer of pre-formed solid diamond, preferably as a free-standing solid diamond material, such as the Boron-doped diamond material referred to hereinbefore.

In a particularly preferred embodiment, the electrodes of the cell comprise a free-standing, pre-formed solid diamond material, especially boron-doped diamond as described above. The solid diamond material is preferably in the form of a chip or wafer, that is a sheet of material having opposing major surfaces and a width and length that are at least an order of magnitude greater than the thickness of the chip or wafer.

As noted above, the dimensions of the electrode body are selected according to the duty to be performed when in use. In addition, the dimensions of the electrode body may be determined by the construction of the electrode body and its method of manufacture. For many applications, the electrode body is preferably at least 3 mm in length, more preferably 5 mm in length, more preferably at least 10 mm, still more preferably at least 20 mm, more preferably still at least 30 mm. The maximum electrode body length may be limited by the construction and method of manufacture. Lengths of up to 200 mm may be employed, for example up to 150 mm. In the case of one preferred embodiment, in which the electrode body is cut from a wafer of solid diamond material prepared by chemical vapour deposition (CVD), the maximum length of the electrode body is up to about 140 mm. For many embodiments, a length of from 30 to 50 mm, in particular from 35 to 45 mm, for example about 40 mm, is particularly suitable.

When forming the electrode body from a wafer formed by techniques, such as CVD, in which the wafer has a growth surface, the electrode body is preferably cut such that the growth surface forms one of the first or second major surfaces of the electrode body. In use, one major surface of the chip or wafer is in contact with the membrane, as discussed in detail below, and contacts the water being electrolysed to produce ozone. Preferably, the membrane is in contact with the growth surface of the wafer.

It is particularly preferred that the other major surface of the chip or wafer is coated with an electrically conductive material, such as a metal or a mixture of metals. The coating allows the chip or wafer to be connected to a conductor, through which an electrical current may be provided to the chip of wafer. In particular, the coating allows the chip or wafer to be connected to the conductor by convenient means, such as soldering. The coating of electrically conductive material is preferably applied to the nucleation surface of the electrode body, that is not the major surface corresponding to the growth side of the wafer.

The layer of electrically conductive material may be applied to the electrode body using any suitable technique. One particularly preferred technique is sputter deposition or sputter coating. Different sputter deposition techniques may be employed, with radio frequency (RF) sputter coating being preferred.

As noted above, the surface of the diamond chip or wafer is coated with an electrically conductive material, for example a metal or a mixture of metals. Metals or a mixture of metals applied to the surface of the diamond material form an electrically conductive bond with the diamond material. In particular, it is preferred that the coating applied to the surface of the diamond material includes one or more metals that form carbides with the diamond material. Suitable metals for use in coating the surface of the diamond material include metals in Groups IVB and VB of the Periodic Table of the Elements. Preferred metals for use in the coating are platinum, tungsten, niobium, gold, copper, titanium, tantalum and zirconium.

A particularly preferred metal to coat the surface of the diamond material is titanium, especially a titanium coating applied by sputter coating as mentioned above. Titanium may be used in combination with other metals to coat the surface of the diamond material. When the surface of the diamond material is coated with titanium, in particular by sputter coating, titanium carbide (TiC) forms at the interface between the metal coating and the diamond material, providing a strong covalent bond between the metal coating and the diamond material. The metal coating allows the diamond material to be connected to an electrical conductor, such as a metal bus or wire.

Alternatively, the layer of electrically conductive material comprises two or more metals. One preferred metal composition is a mixture of copper and silver or gold.

The electrode body may be provided with a single layer of conductive material or a plurality of layers of conductive material. In one preferred embodiment, the electrode body is provided with a first layer of a first conductive material adjacent the surface of the electrode body and a second layer of a second conductive material adjacent the surface of the first layer. In one preferred embodiment, the first layer consists essentially of a single metal. Titanium is a particularly preferred metal for forming the first layer. In one preferred embodiment, the second layer comprises a mixture of metals. An amalgam of copper and silver is one particularly preferred material for forming the second layer.

The layer of electrically conductive material is preferably at least 200 nm in thickness, more preferably at least 300 nm, still more preferably at least 400 nm, more preferably still at least 500 nm. A thickness of at least 600 nm is particularly preferred, especially at least 1000 nm. The layer may have a thickness of up to 10000 nm, more preferably up to 7500 nm. A thickness of 5000 nm is particularly suitable for many embodiments and provides for an improved current distribution and an even current density across the surface of the electrode body. In general, increasing the thickness of the layer of conductive material increases the electrical conductivity of the layer. Thicker layers may be employed. For example, copper may be applied to a thickness of 300 pm.

In embodiments comprising a plurality of layers of conductive material, the layer adjacent the surface of the electrode body is preferably relatively thin and the successive layer or layers relatively thick. In one preferred embodiment, the electrode body is provided with a first layer adjacent the surface of the electrode body and having a thickness of from 600 to 1000 nm, more preferably about 900 nm, and a second layer adjacent the surface of the first layer and having a thickness of from 2000 to 2500 nm, more preferably about 2400 nm.

The layer of electrically conductive material may extend across all or part of a major surface of the electrode body. Preferably, the layer of electrically conductive material extends over a major portion of a major surface of the electrode body. More preferably, the layer of electrically conductive material extends over a major portion of the major surface of the electrode body, with a portion at an edge of the major surface, preferably all edges of the major surface, not being covered by the conductive material. This edge portion may be at least 0.5 mm in width, that is the distance from the edge of the major surface of the electrode body to the edge of the layer of conductive material measured perpendicular to the edge, preferably at least 1.0 mm. An edge portion having a width of 1.5 mm or greater is particularly preferred for many embodiments. An edge portion having a width of 2.0 mm or greater is also suitable for many embodiments.

The electrical conductor may be connected to the conductive coating by any suitable technique, with soldering being one convenient and preferred way of forming the electrical connection. As noted above, the metal coating may comprise a mixture of metals. In this respect, it is preferred to include in the metal coating metals that allow a conductor to be connected to the coating, in particular by soldering. In one preferred embodiment, the diamond material is coated with a conductive material having at its outer surface a mixture comprising copper and silver, to facilitate the connection of a conductor to the coating by soldering.

The electrode body is preferably provided with a layer of electrically insulating material over its major surface. In one preferred arrangement, the electrode body is provided on a major surface with a first layer of an electrical conductive material, as discussed above, and a second layer of an electrically insulating material. The first layer of electrically conductive material may comprise separate layers of one or more electrically conductive materials, as discussed above. The second layer extends over the first layer. In one embodiment, the second layer comprises a material that is both electrically insulating and exhibits hydrophobic properties. Suitable materials for forming the second layer include nitrides, for example of silicon, titanium, zirconium or hafnium. Preferred compounds for inclusion in the second layer are silicon nitride (S13N4), titanium nitride (TiN), Zirconium nitride (ZrN) and hafnium nitride (HfN). Anodised aluminium oxide may also be used as an electrically insulating material.

The electrically insulating material may be applied using any suitable technique. A preferred embodiment employs a material for the second layer that can be applied by sputter coating, for example the silicon, titanium, zirconium and hafnium nitrides mentioned above.

The electrode assembly may comprise a single layer of an electrically insulating material. Alternatively, two or more different insulating materials may be employed in two or more layers.

Alternatively, or in addition to the second layer, the electrode body may be coated in a resin, preferably a hydrophobic resin, more preferably a thermosetting hydrophobic resin. Examples of suitable resins include polyester resins and epoxy resins. The resin acts to seal the layers of conductive material and insulating material. The resin may also be employed to seal the conductor connection, discussed in more detail below.

It has been found that the adhesion of the resin is improved if the aforementioned layer of insulating material is employed. Accordingly, it is particularly preferred to provide the electrode body with a layer of electrically conductive material as hereinbefore described, a layer of insulating material, as hereinbefore described extending over the conductive layer, and a layer of resin extending over the insulating layer.

As noted above, the electrode body is connected in use to a supply of electrical current by a suitable conductor. In embodiments in which the electrode body is provided with a layer of electrically conductive material, a conductor connector terminal is preferably connected to the said layer. The layer of electrically conductive material preferably has a composition that allows the terminal to be connected to the layer by soldering. Preferably, the terminal is coated in a resin, as described hereinbefore.

The electrical conductor, such as a cable, may be connected to the conductor connector terminal. Again, this connection is preferably formed by soldering.

The diamond material of the electrodes may have any suitable shape. As discussed below, the electrolysis reactions producing ozone are preferably allowed to occur at the edges of the diamond electrode and a polygonal shape for the diamond material is preferred. In a preferred embodiment, the diamond material is rectangular in shape, for example square. Other shapes may be employed.

The electrochemical cell comprises first and second electrode assemblies, as noted above. Each of the first and second electrode assemblies may comprise a single electrode or, a plurality of electrodes electrically connected to act together. The size and number of the electrodes will be determined by the intended use of the device, which in turn determines such factors as the current to be applied to the electrodes. For example, for an electrochemical cell drawing 100 mA, a diamond electrode having dimensions of 3 mm x 3 mm is suitable. For a larger current, for example 250 mA, an electrode of 5 mm x 5 mm is suitable, with a current 500 mA be appropriate for an electrode having a size of 5 mm x 10 mm.

The electrochemical cell may have two electrodes, an anode and a cathode, as indicated above.

The electrochemical cell comprises a cation exchange membrane disposed between the electrodes. The semi-permeable membrane functions as a cation exchange membrane and is also referred to as a proton exchange membrane (PEM) when the electrochemical cell is in use, selectively allowing the passage of certain cations and protons (hydrogen ions) from one of the first and second electrodes to the other of the first and second electrodes, depending upon the polarity of operation of the cell, that is from the anode to the cathode, while preventing the passage of anions. The membrane permits the movement of ions, including hydrogen ions (protons), in either direction, depending upon the polarity of the current applied to the cell at any given time.

The membrane is in contact with each electrode. Each electrode is preferably formed to have edges to the active surface of the diamond, with the semi-permeable membrane being in contact with the edges of the diamond material. In this way, at the interface between the edge of the anode electrode, the membrane and the water adjacent the anode, ozone is produced in the water (ozonated water). Hydrogen ions (protons) pass through the membrane to the cathode side of the cell where hydrogen gas is produced. Other positively charged metal cations, such as calcium, magnesium, iron and manganese also pass through the membrane and are deposited on the cathode.

Suitable materials for the membrane are known in the art and are commercially available. One particularly preferred class of materials for use in the membrane are sulfonated tetrafluoroethylene-based fluoropolymers. Such materials are known in the art and are commercially available, for example the Nafion® range of products.

The device of the present invention further comprises a conductivity sensor for determining the conductivity of fluid in which the electrochemical cell is immersed.

It has been found that operation of the electrochemical cell when the electrodes are not immersed in water damages the membrane (PEM) and may also damage the electrodes in some circumstances. If the electrochemical cell is switched on when not immersed in water, the voltage of the cell increases to the maximum value permitted and, at this point, the electrical current falls significantly. The increased voltage causes the cell to heat up and this may damage the membrane and, in some circumstances, the electrodes. Accordingly, to avoid the electrochemical cell from being damaged in this way, the conductivity sensor is used to determine whether the electrodes are immersed in water.

The conductivity of water may vary according to the composition of the water, in particular the concentration of conductive ions in solution in the water. For example, distilled water has a conductivity at 25°C of from about 0.5 to 3.0 pS/cm. Water from a domestic water supply has a conductivity at 25°C of from about 500 to

2000 pS/cm. By comparison, air typically has a conductivity at 25°C closely approaching zero pS/cm.

The conductivity sensor is located in the device at a location such that the conductivity of the fluid between the electrodes of the electrochemical cell is measured. As described in more detail below, the conductivity measurement is used to ensure that the electrodes of the cell are immersed in water, before the cell is activated. The location of the conductivity sensor should be such, therefore, that it can be ensured that the electrodes are fully immersed in water, thereby permitting the membrane (PEM) to become fully wetted. As the membrane becomes wetted, the conductivity of the membrane increases and the voltage required to drive the cell decreases. Preferably, the conductivity sensor is located in the region of the electrodes of the electrochemical cell. More preferably, the conductivity sensor is located at a position relative to the electrodes such that, in normal use of the device, the conductivity sensor is above the electrodes. In this way, it can be ensured that the electrodes and the membrane are fully immersed in water whenever the conductivity sensor provides an indication that water is present.

The conductivity sensor comprises a pair of spaced apart, electrically conducting electrodes. The conductivity sensor may be either an amperometric device or a potentiometric device, with the latter being more accurate. For simplicity the preferred conductivity sensor is amperometric. This sensor applies a known potential (Volts) to a pair of electrodes and measures the current (Amps) between the two electrodes, the higher the current obtained the greater the conductivity of the medium between the electrodes.

In operation, the sensor provides an indication of the conductivity of the medium between the electrodes. The conductivity sensor is comprised in the device, for example in or above the electrochemical cell.

The device of the present invention further comprises a processor. The processor controls the operation of the electrochemical cell, in particular switching the cell on and turning the cell off. Any suitable arrangement for the processor may be employed and suitable components and processors are known in the art and can be programmed for operation according to the methodology of the present invention using techniques known in the art.

The processor receives an input signal from the conductivity sensor indicating whether the electrochemical cell is immersed in water. If it is determined that the conductivity of the water is sufficiently high, indicating that the electrodes are immersed in water, the processor operates to switch on the electrochemical cell, in particular to allow an electrical current to be provided to the electrodes from the source of electrical energy. In this respect, the processor is provided with a threshold value of conductivity, against which the conductivity measured by the conductivity sensor is compared. In the event the conductivity measured by the sensor exceeds the threshold value, indicating that the electrodes are immersed in water, the processor operates to switch on the electrochemical cell. In the event the conductivity measured by the sensor does not exceed the threshold value, the cell is not switched on.

Preferably, the threshold conductivity value to turn the electrochemical cell on is 500 pS/cm. Below this value of conductivity, no electrical current is supplied by the processor to the electrochemical cell. During operation of the device, if the conductivity detected by the conductivity sensor falls below 500 pS/cm, the electrical current to the electrochemical cell is switched off by the processor.

Preferably, the processor is provided with a first threshold value of conductivity, as discussed above and below which the processor prevents electrical current being supplied to the electrochemical cell, and a second threshold value of conductivity, higher than the first threshold value. Preferably, the second threshold value is about 1,000 pS/cm. In operation, if the conductivity sensor indicates to the processor that the conductivity of the water exceeds the second threshold value, the processor shuts off the supply of electrical current to the electrochemical cell. If the conductivity of the water is determined to be below the second threshold value and above the first threshold value, the processor supplies electrical current to the cell. In this way, the electrochemical cell is only provided with electrical current and operated when the conductivity value measured by the conductivity sensor is between the first and second thresholds.

It is possible to arrange the processor to determine the presence of water at the electrodes of the electrochemical cell using the signal received from the conductivity sensor and, once water has been determined to be present, simply to activate the cell to commence the production of ozone. Preferably, however, the processor monitors the signal output by the conductivity sensor periodically to ensure that the electrodes are still in contact with sufficient water for safe operation of the cell. The processor may check the conductivity of the fluid to confirm the presence of water at the electrodes of the electrochemical cell at any time during the operating cycle of the device. Preferably, the processor checks the output signal of the conductivity sensor at least every 60 seconds to ensure that the electrodes are in sufficient water, more preferably at least every 50 seconds, still more preferably at least every 40 seconds, more preferably still at least every 30 seconds. The presence of water may be checked more frequently during operation, for example at least every 25 seconds, preferably at least every 20 seconds, more preferably at least every 15 seconds, still more preferably at least every 10 seconds. The presence of water may be determined more frequently still, if desired, for example every 5 seconds or less.

As discussed in more detail below, in a preferred operating regime, the polarity of the electrochemical cell is periodically reversed. It is preferred that the conductivity of the fluid is checked by the processor every time the polarity of the electrochemical cell is reversed.

If one of the aforementioned checks determines that the conductivity of the fluid between the electrodes is above the aforementioned threshold value, indicating that insufficient water is present in the region of the electrodes of the cell, the processor switches the cell off by cutting the electrical energy supply. The processor may be arranged to continue monitoring the conductivity of the fluid in the region of the electrodes, for example by checking periodically as discussed above, and when the presence of water is indicated by the signal received from the conductivity sensor, the processor may reactivate the cell to recommence production of ozone. Alternatively, for example, the processor may be configured to switch off the device after one or a preset number of failed conductivity tests, thereafter requiring the user to switch the device back on and restart the operating procedure.

As noted above, the electrochemical cell comprises a membrane, preferably a Nation membrane, between the electrodes. The cell can be operated as soon as the electrodes and the membrane are immersed in water, as determined by the conductivity sensor discussed above. However, it has been found that operation of the cell while the membrane is dry or substantially dry gives rise to the cell having a high resistance, in turn drawing a high voltage from the electrical energy source. This can lead to damage to the cell. In contrast, allowing the membrane to hydrate once immersed in water reduces the resistance of the cell, resulting in a lower voltage draw when the cell is activated. As a result, it is especially preferred that the membrane is allowed hydrate, once the electrodes have been immersed in water, before the cell is activated and electrical energy provided to the cell for electrolysis of the water to ozone commences.

Accordingly, it is especially preferred that the processor is arranged to delay activating the electrochemical cell once it has been determined that the electrodes of the cell are immersed in water for a period of time sufficient to allow the membrane to hydrate.

The time required for the membrane to hydrate will depend upon such factors as the material of the membrane. It is preferred to allow at least 5 seconds for the membrane to hydrate before commencing operation of the electrochemical cell, more preferably at least 10 seconds, still more preferably at least 20 seconds. In one embodiment, the processor delays activating the electrochemical cell for from 5 to 100 seconds after it has been determined that the electrodes of the cell are in contact with water, more preferably from 10 to 80 seconds, still more preferably from 20 to 75 seconds, more preferably still from 30 to 70 seconds. A delay of about 60 seconds is preferably for many embodiments.

During operation and the production of ozone at the anode in the electrochemical cell, the metal anions in solution, such as calcium and magnesium migrate to the cathode, causing a build up of these metals and their compounds on the active surface of the cathode. The deposition of these metals and their compounds individually and collectively causes passivation of the cathode and a consequential reduction in the flow of electrical current through the electrochemical cell. This process of electro-deposition of materials on the cathode passivates the electrodes in the electrochemical cell causing the current flowing through the cell to reduce over a period of time, thereby reducing the productivity of the cell over time, to the point when ozone may no longer be produced by the electrodes.

Compounds of calcium and magnesium are found in significant concentration in hard water and it is known that these compounds are the principal cause of electrode passivation within electrochemical cells used in the production of ozone or ozonated water. In particular, it is known that calcium cations readily pass through the cation exchange membrane present between the electrodes in the cell and that calcium is rapidly deposited on the cathode, in the form of insoluble calcium hydroxide within the electrochemical cell.

In the absence of a cathode cleaning system, the cathodes in an electrochemical cell become passivated by the metal cations in solution in the feed water. The build up of substances on the cathode will inevitably cause the cell to fail. Accordingly, to prevent the passivation of the electrochemical cell the polarity of the electric current flowing through the cell is periodically reversed. The processor is therefore arranged to reverse the polarity of the electrodes periodically. When the polarity is reversed in this manner, the deposits on the cathode that, if allowed to build up would passivate the cell, are reconverted into ions that pass back into solution, reversing the deposition process.

The time intervals between successive polarity reversals can be varied within wide limits, in particular to optimise cell performance and take account of such operating parameters as the concentration of metal cations, such as calcium and magnesium, and other cations present in the water.

The length of time that the cell is operated in one polarity, so as to produce ozone at one electrode acting as the anode, may be determined by monitoring the condition of the second electrode, that is acting as the cathode, and the amount of substances deposited thereon. This may be achieved, for example, by monitoring one or more operating parameters of the cell, such as the electrical current, measured in Amps, and the potential of the cell, measured in Volts. The processor may therefore be arranged to monitor one or more of the aforementioned parameters of the cell and adjust the period of time that is allowed to elapse between polarity reversals accordingly.

The polarity may be reversed after operation for a period of operation of several minutes, preferably no more than 2 minutes, more preferably less than 1 minute. It is preferred that the processor reverses the polarity of the electrodes after a period of operation at one polarity of no more than 50 seconds, more preferably no more than 40 seconds, still more preferably no more than 30 seconds, more preferably still no longer than 20 seconds, in particular for water with a hardness below 200 mg/L. Reversing the polarity every 15 seconds or less is preferred, more preferably about every 10 seconds, in particular for higher levels of water hardness, that is above 200 mg/L, for example about 300 mg/L.

In operation, the electrodes of the electrochemical cell have a capacitance and, therefore can hold an electrical charge. The procedure for reversing the polarity of the electrochemical cell preferably allows the charge arising due to the capacitance of the electrodes to discharge. More particularly, the polarity reversal procedure preferably comprises shutting off the supply of electrical current to the electrochemical cell, waiting for a discharge period and thereafter switching on the electrical supply in the reverse polarity. The discharge period will vary depending upon the design of the electrochemical cell and is preferably at least 10 ms, more preferably at least 20 ms, still more preferably at least 40 ms, more preferably still at least 50 ms. A discharge period of from 50 to 100 ms is particularly suitable for many embodiments, preferably from 60 to 90 ms, more preferably from 70 to 85 ms. A discharge period of about 80 ms is preferred for many embodiments.

It is particularly preferred that the period of time that the first and second electrodes each function as the anode and the cathode is substantially the same, in particular when averaged over an extended period of operation of the cell.

In operation, an electric current is provided to the electrodes of the electrochemical cell. The operating current density, measured in Amps/cm², at the electrodes is a function of the electrical current applied to the cell, measured in Amps, from the electrical power supply, divided by the active surface area of the diamond anodes. The current applied to the electrochemical cell, and therefore the current density at the anodes, may be selected to optimise the performance of the cell and to optimise the production of ozone and ozonated water. In practice, the maximum current density that can be applied to the electrodes in the electrochemical cell is limited by the semi permeable proton exchange membrane (PEM). In the case of the preferred Nafion® membrane, the maximum current density is about 1.0 Amps /cm² (10,000 Amps/cm²). The amount of ozone generated by the electrochemical cell is directly proportional to the current applied and is dependent upon the current efficiency of the particular cell.

The electrochemical cell may be operated at current densities up to 1.0 Amps/cm². Preferably, the current density is in the range of from 0.1 to 1.0 Amps/cm², more preferably from 0.5 to 1.0 Amps/cm², and still more preferably in the range 0.75 to 1.0 Amps/cm² for the production of ozonated water for most applications.

The maximum current that can be applied to the electrochemical cell is a function of the surface area of the electrodes of the cell and the maximum current density. For example, in the case of a cell having electrodes with a surface area of 2.4 cm² (4 cm x 0.6 cm), the maximum current to be applied is 2.4 Amps, giving the maximum current density of 1.0 Amps/cm².

The electrochemical cell may be operated at applied voltages up to 36 Volts, depending upon the conductivity of the water stream being treated. According to the operating conditions the voltage is preferably at least 10 Volts, more preferably at least 12 Volts, still more preferably at least 15 Volts, still more preferably at least 18 Volts. Voltages in excess of 24 Volts may also be applied, for example a voltage up to 30 Volts or up to 36 Volts, as required. A voltage of between 12 and 24 Volts is particularly preferred.

The processor is operable to deliver to the electrochemical cell a current appropriate for the desired operation of the cell. The voltage applied to the cell is allowed float (that is increase or decrease) in order to maintain the current at the required level. If the electrical resistance across the cell is high, for example due to reduced conductivity of the water being treated, the voltage is increased up to a preset maximum value. Once the voltage has reached the maximum permitted value, any further changes in the conductivity affect the current being applied, for example a reduction in the conductivity causing the current to fall.

In one embodiment of the device for the treatment of small volumes of water, such as in drinking vessels, the electrochemical cell comprises electrodes of the order of 3 mm x 3 mm (that is 0.09 cm²), permitting a maximum current of 90 milliamps to be applied at the maximum current density of 1.0 Amps/cm². The device of this embodiment is very electrically efficient and typically only requires 9 Volts to operate with a current of 90 milliamps. The device may be powered by a battery.

In an alternative embodiment, the device comprises four separate electrochemical cells, each having a pair of electrodes of the order of 5 mm x 5 mm (that is 0.25 cm²), permitting a maximum current of 250 milliamps to be applied to each cell at the maximum current density of 1.0 Amps/cm². The device of this embodiment is electrically efficient and typically requires from 12 to 24 Volts to operate with a current of 250 milliamps. The device may be powered by a battery, but is more preferably powered by connection to a mains supply.

Embodiments of the method and apparatus of the present invention will now be described, by way of example only, having reference to the accompanying figures, in which:

Figure 1 is a schematic representation of one embodiment of the device of the present invention;

Figure 2 is a diagrammatical representation of one embodiment of the method of operation of the present invention;

Figure 3a is a perspective side view of a device of one embodiment of the present invention;

Figure 3b is a side view of the device of Figure 3a in an operating position;

Figure 4a is a perspective side view of an electrochemical cell assembly for use in the device of Figures 3a and 3b;

Figure 4b is a cross-sectional view of the upper portion of the electrochemical cell of Figure 4a; and

Figure 5 is a perspective side view of a device of a further embodiment of the present invention.

Referring to Figure 1, there is shown a schematic representation of a device of one embodiment of the present invention. The device, generally indicated as 2, comprises an electrochemical cell, generally indicated as 4, having a pair of opposing electrodes 6, 8 separated by a Nafion membrane 10. The electrochemical cell 4 is connected to a source of electrical energy, in the form of a battery 12. An alternative electrical energy source may used, for example by connecting the cell 4 to a mains supply, such as a domestic mains electricity supply.

A conductivity sensor 20 is located in the region of the electrochemical cell 4 and positioned to measure the conductivity of fluid close to the electrodes 6, 8 of the cell 4.

A processor 22 is connected to receive signals from the conductivity sensor 20. The processor 22 is arranged to be switched on manually by a user and is operable to compare the signals from the conductivity sensor 20 indicating a sensed fluid conductivity and to compare these with a preset value corresponding to a threshold fluid conductivity. Depending upon the nature of the signal received from the conductivity sensor 20, the processor 22 operates a switch 24 to provide electrical power to the cell 4, as described in more detail below.

A further operation of the processor 22 is periodically to reverse the polarity of the electrical supply to the electrodes 6, 8 of the electrochemical cell 4, which it achieves by appropriate operation of the switch 24.

Referring to Figure 2, there is shown a diagrammatical representation of one embodiment of the method of the present invention in the form of a process scheme for the operation of a processor for controlling the functioning of the electrochemical cell of the device.

The process scheme, generally indicated as 102, is initiated by at 104 by starting the device. This may be by way of the user operating a switch to turn on the device. Alternatively, the process scheme may be started as a result of a reset function of the processor.

Once the device has been activated and the process scheme 102 begun, the next stage is to start the wetting timer function 106 within the processor. The membrane of the electrochemical cell requires a period of time to hydrate, once the cell has been immersed in water. Hydration of the membrane improves the performance of the cell and prolongs the working life of the membrane, whereas operation of the cell with the membrane incompletely hydrated with water reduces the working efficiency of the cell and can damage the membrane, in particular due to the elevated cell voltage. As indicated in Figure 2, the timer 106 is set to wait for a period of 30 seconds for the membrane to hydrate. During this period, the processor delays starting the operation of the other components of the device.

A further function 108 of the processor of the embodiment of Figure 2 is to set the polarity of the electrodes of the electrochemical cell. As discussed above, a preferred mode of operation is periodically to reverse the polarity of the electrodes of the cell, in order to reduce the build up of material deposited on the electrode surfaces, leading to passivation of the electrodes. Accordingly, as shown in Figure 2, once the wetting period has elapsed, the processor sets the polarity of the electrodes of the electrochemical cell.

Thereafter, the processor conducts a conductivity test 110. In this test, the signal received from the conductivity sensor is used by the processor to determine the conductivity of the fluid in the region of the electrodes, in particular by comparing the signal received from the conductivity sensor with a preset value representing a minimum required or threshold conductivity. In the event the fluid conductivity sensed by the conductivity sensor exceeds the minimum required or threshold value, indicating that the cell is in water, the processor passes to the next stage in the process scheme. Should the fluid conductivity sensed by the conductivity sensor be below the preset value set in the processor, that is below the minimum fluid conductivity, indicating the device is not properly immersed in water to provide water between the electrodes, the processor returns to an early stage in the process scheme. In the embodiment shown in Figure 2, the processor repeats the conductivity test 110 and repeats this test every 80 ms until the fluid conductivity is determined to be above the preset minimum threshold value.

It is to be understood that the processor may return to an earlier stage in the process scheme, for example to repeat the wetting timer function 106. As a further alternative, the processor may simply switch off the device, in the event that the measurement of conductivity determines that the conductivity of the fluid in the region of the electrodes of the electrochemical cell is below that of water and required to operate.

As noted, once the processor determines that the fluid in the region of the electrodes of the electrochemical cell is water, as indicated by the signal from the conductivity sensor, the processor switches the electrochemical cell on in stage 112. In the embodiment shown in Figure 2, the processor conducts a voltage check 114, in which the voltage applied to the electrodes of the electrochemical cell is measured. Should the voltage be below the required value for operation, the cell is switched off and the processor moves ahead in the process scheme, in particular to a conductivity test, described below. If at any time the processor determines that the voltage supplied to the electrodes is too low, the processor registers a fault in a fault counter 116. Provided the number of faults is below a set limit (a low fault count), the processor returns to the process scheme, as shown in Figure 2. In the event the fault count exceeds a threshold value, the device is switched off.

As indicated in Figure 2, the cell is operated for a period of 10 seconds, after which the cell is switched off by the processor in step 118, the polarity of the electrodes of the cell is reversed, and the cell is restarted and continues to run with the reverse polarity. The electrode polarity is reversed after every 10 seconds of cell operation.

In the embodiment indicated in Figure 2, at each polarity reversal, the processor switches the supply of electrical current to the cell off and conducts another conductivity test 120, in which the conductivity of the fluid in the region of the electrodes of the cell is checked by the processor using the signal received from the conductivity sensor. In this way, the processor monitors that the electrochemical cell is immersed in water. In the event that the processor receives a signal from the conductivity sensor indicating a fluid conductivity above the minimum threshold conductivity, the processor does not restart the electrochemical cell. In the embodiment shown in Figure 2, the processor repeats the conductivity test 120. Alternatively, the processor may be configured to switch off the device.

As indicated in Figure 2, after switching off the supply to the electrochemical cell, the processor waits 80 ms, during which time the aforementioned conductivity test 120 is conducted. This waiting time allows the electrical charge retained in the electrochemical cell due to the capacitance of the electrodes to dissipate.

When the conductivity test 120 is passed, the processor restarts the cell at 112. Thereafter, the processor follows a loop as indicated in Figure 2 of switching on the cell, operating for 10 seconds, switching the cell off, reversing the electrode polarity, conducting a conductivity test during the waiting period, and switching the cell on, until a fault occurs, such as a loss of electrical power, or the user switches off the device.

Turning to Figures 3a and 3b, there is shown a view of a device of one embodiment of the present invention. The device, generally indicated as 202, is a handheld device for use in treating small bodies of water, such as water in a glass, cup or jug or the like. The device is shown in Figure 3b in the orientation it would be used to treat water in such a vessel, that is with the lower end portion of the device, as viewed in Figure 3b, immersed in the water.

The device 202 comprises a generally rectangular body 204 having an upper portion 206 and a lower portion 208, having an arm 210 extending therefrom, as shown in Figure 3b. In use, at least the distal end portion of the arm 210 is immersed in water in the vessel. The arm 210 and the body 204 may be formed from plastic or stainless steel.

The device 202 comprises a switch 212 for activating the device mounted in the upper portion 206 of the body 204. The upper portion 206 provides a housing for components of the device 202, such as a battery for storing electrical energy, a processor and a switch, for example as indicated schematically in Figure 1 and described above. In the embodiment shown in Figures 3a and 3b, the arm 210 is pivotably mounted to the body 204 by means of a circular hinge 210a in the lower portion 208 of the body and may be moved from the extended position shown in Figure 3b to a stowed position, in which the arm 210 lies within the body 204.

A conductivity sensor 214 is mounted on the arm 210.

An electrochemical cell assembly 216 is mounted in the distal end of the arm 210, details of which are described below.

As noted above, the arm 210 may be moved to a stowed position by rotation about the hinge 210a. In this position, the electrochemical cell assembly 214 is held within the housing 204, where it is protected from damage. In use, the arm 210 is moved to the extended position shown in Figure 3b and at least the distal end portion containing the conductivity sensor 212 and the electrochemical cell assembly 214 is immersed in the water to be treated. The device is activated by the user pressing the switch 212 in the body 204.

The electrochemical cell assembly 216 is shown in more detail in Figures 4a and 4b. As shown in Figure 4a, the assembly 216 comprises an upper body portion

220 and a lower body portion 222, each provided with two integrally formed clips 224 to engage with the other body portion. Electrodes 226 and 228 are mounted to respective body portions 220 and 222. A membrane 230 is sandwiched between the electrodes 226, 228. The membrane is a Nafion® N117 membrane.

Each electrode 226, 228 is a square chip of solid boron-doped diamond. Current feeders 240, 242 extend through the respective body portions 220, 222 and are electrically connected to the respective electrodes 226, 228.

As can be seen in Figure 4a, the spaced apart clips 224 define passages therebetween, providing access for water to the electrodes 226, 228 and the membrane 230, once the electrochemical cell is immersed in water. During use, the products of electrolysis, in particular ozone, diffuse away from the electrodes through the passages and away from the cell into the bulk of the water.

The electrochemical cell assembly 216 shown in Figures 4a and 4b may be used in a modular manner. In particular, a plurality of the assemblies may be linked together, for example to a central processor and a central electrical power supply, and employed to treat a larger volume of water. The number of assemblies employed will be determined by such factors as the volume of water to be treated and the rate at which the desired ozone concentration is to be achieved. An example of such a device is shown in Figure 5.

The device, generally indicated as 252, is suitable for treating a tank of water, such as water in a domestic tank, and comprises a body 254 having a plurality of cavities 256 formed on its outer surface. Each cavity 256 contains an electrochemical cell assembly 216 as shown in Figures 4a and 4b and hereinbefore described. As can be seen, the electrochemical cell assemblies 216 are exposed to water in which the body 254 is immersed, with water entering the cell assemblies 216 and ozone diffusing out from the assemblies as described above, when the device is in use.

The body 254 is held within upper and lower shaped stainless steel wires

260, 262, which together form a frame 264. The frame 264 performs a number of functions. First, the frame 264 protects the body 254 and the electrochemical cells 216. Further, the frame 264 holds the body 254 and the electrochemical cells clear of the bottom of the tank or vessel in which the device is located. In this way, water is free to flow through the cavities 256 holding the electrochemical cells, allowing ozone to diffuse out of the cavities 256, away from the electrochemical cells 216 and into the bulk of the body of water.

Claims

1. A device for producing ozonated water from a reservoir of water, the apparatus comprising:

2. The device according to claim 1, wherein the device is portable.

3. The device according to claim 2, wherein the device is hand held.

4. The device according to claim 1, wherein the device is comprised in a vessel for holding water.

5. The device according to any preceding claim, comprising a plurality of electrochemical cells.

6. The device according to claim 5, wherein each of the plurality of electrochemical cells is operated by the processor.

7. The device according to any preceding claim, comprising a plurality of conductivity sensors.

8. The device according to any preceding claim, wherein the electrical supply comprises one or more batteries.

9. The device according to any preceding claim, wherein the electrical supply comprises a cable for connecting the device to a source of electrical energy.

10. The device according to any preceding claim, wherein the electrical supply comprises a solar panel or solar array.

11. The device according to any preceding claim, wherein the electrochemical cell is passive.

12. The device according to any preceding claim, wherein the first and the second electrode assemblies comprise a polycrystalline diamond.

13. The device according to claim 12, wherein the diamond is doped.

14. The device according to claim 13, wherein the dopant comprises boron.

15. The device according to any of claims 12 to 14, wherein the first and second electrode assemblies each comprise an electrode formed from a solid diamond material.

16. The device according to claim 15, wherein the diamond material has a thickness of from 300 to 800 microns.

17. The device according to any of claims 12 to 16, wherein the diamond material has a growth surface, the membrane being in contact with the growth surface of the diamond of each of the first and second electrode assemblies.

18. The device according to any of claims 12 to 17, wherein the first and second electrode assemblies each have an electrode body having a length of at least 3 mm.

19. The device according to claim 18, wherein the electrode body has a length of at least 5 mm.

20. The device according to either of claims 18 or 19, wherein the electrode body has a length of up to 140 mm.

21. The device according to any of claims 12 to 20, wherein the major surface of the electrode of each of the first and second electrode assemblies is coated in a layer of electrically conductive material.

22. The device according to claim 21, wherein the electrically conductive material is applied by sputter coating.

23. The device according to either of claims 21 or 22, wherein the electrically conductive material comprises a metal.

24. The device according to claim 23, wherein the metal is selected from platinum, tungsten, niobium, gold, copper, titanium, tantalum, zirconium and mixtures thereof.

25. The device according to claim 24, wherein the metal is titanium.

26. The device according to any of claims 21 to 25, wherein the layer of electrically conductive material comprises a first layer of a first electrically conductive material and a second layer of a second electrically conductive material, different to the first electrically conductive material.

27. The device according to claim 26, wherein the first electrically conductive material comprises titanium.

28. The device according to either of claims 26 or 27, wherein the second electrically conductive material comprises copper and silver.

29. The device according to any of claims 21 to 28, wherein the layer of conductive material has a thickness of at least 500 nm.

30. The device according to any of claims 21 to 29, wherein the layer of electrically conductive material extends over a major portion of the surface of the electrode body, with an edge portion not being covered by the said material.

31. The device according to claim 30, wherein the edge portion has a width of at least 0.5 mm.

32. The device according to any preceding claim, wherein the electrode body of each of the first and second electrode assemblies is provided with a layer of electrically insulating material.

33. The device according to claim 32, wherein the electrically insulating material comprises a nitride of silicon, titanium, zirconium or hafnium.

34. The device according to any preceding claim, wherein the electrode body of each of the first and second electrode assemblies is provided with a layer of resin over its major surface.

35. The device according to any preceding claim, wherein the membrane comprises a sulfonated tetrafluoroethylene-based fluoropolymer.

36. The device according to any preceding claim, wherein the conductivity sensor is located above the electrochemical cell, when the device is its normal orientation for use.

37. The device according to any preceding claim, wherein the threshold value of conductivity is at least 500 pS/cm.

38. The device according to any preceding claim, wherein the processor is provided with a first threshold value for conductivity and a second threshold value for conductivity, the second threshold value being greater than the first.

39. The device according to claim 38, wherein the first threshold value is 500 pS/cm.

40. The device according to either of claims 38 or 39, wherein the second threshold value is 1,000 pS/cm.

41. A vessel for holding a volume of water comprising a device according to any preceding claim.

42. A method for producing ozonated water from a reservoir of water, the method comprising:

43. The method according to claim 42, wherein the threshold value of conductivity is at least 500 pS/cm.

44. The method according to claim 42, wherein the electrochemical cell is activated if the conductivity is between a first threshold value for conductivity and a second threshold value for conductivity, the second threshold value being greater than the first.

45. The method according to claim 44, wherein the first threshold value is 500 pS/cm.

46. The method according to either of claims 44 or 45, wherein the second threshold value is 1,000 pS/cm.

47. The method according to any of claims 42 to 46, wherein the electrochemical cell is activated only after a delay, to allow the membrane to hydrate.

48. The method according to claim 47, wherein the delay is at least 5 seconds.

49. The method according to any of claims 42 to 46, wherein the polarity of the electrochemical cell is periodically reversed after the electrochemical cell has been activated.

50. The method according to claim 49, wherein the conductivity of the fluid in the region of the electrode assemblies is determined each time the polarity is reversed.

51. The method according to either of claims 49 or 50, wherein reversing the polarity comprises deactivating the electrochemical cell, allowing the electrical charge present in the electrodes to dissipate, and reactivating the electrochemical with the reverse polarity.

52. A device for producing ozonated water substantially as hereinbefore described having reference to any of Figure 1, Figure 2, Figures 3a and 3b, Figure 4a and 4b, and Figure 5.

53. A method for producing ozonated water substantially as hereinbefore described, having reference to any of the accompanying figures.

Intellectual

Property

Office

Application No: GB1620195.6 Examiner: Mr Will Jeffries