WO2018100352A1

WO2018100352A1 - Electrochemical cell and method for operation of the same

Info

Publication number: WO2018100352A1
Application number: PCT/GB2017/053574
Authority: WO
Inventors: Patrick Simon Bray
Original assignee: Roseland Holdings Limited
Priority date: 2016-11-29
Filing date: 2017-11-28
Publication date: 2018-06-07
Also published as: GB2556947B; GB2556947A; GB201620217D0

Abstract

A device for the ozonation of a body of water is provided, the device comprising a handle assembly for being held in the hand of a user, the handle assembly comprising a housing; and an electrical storage device disposed within the housing; an electrochemical cell, the electrochemical cell receiving electrical energy from the electrical storage device when in use; and a support assembly holding the electrochemical cell, the support assembly being moveably connected to the handle assembly and moveable between a retracted position and an extended position, wherein in the retracted position the electrochemical cell is at least partially disposed within the housing and in the extended position the electrochemical cell is disposed outside of and a distance from the housing.

Description

ELECTROCHEMICAL CELL AND METHOD FOR OPERATION OF THE SAME

The present invention relates to an electrochemical cell device and a method of operating the same. The present invention concerns in particular an electrochemical cell device 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 including sterilisation. 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: 3H₂0 ^ 0₃ + 3H⁺ + 6e- and

2H₂0 - 0₂ + 4H⁺ + 4e- (E₀ = 1 .23 V_SHE)

H₂0 + 0₂ ^ 0₃ + 2H⁺ + 2e- (Eo = 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 electrochemical 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 (Pb0₂), tin oxide (Sn0₂), 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 of the electrode.

An electrolytic apparatus and an electrolytic method are disclosed in

JP 201 1038145.

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 1741676 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.

US 2008/0181832 discloses an ozone generator for the in-situ sterilization of water. WO 2010/043898 discloses an apparatus for water purification.

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 treatment and disinfection of water, such as drinking water at the point of consumption, for example in a glass or bottle.

According to the present invention, there is provided a device for the ozonation of a body of water, the device comprising:

a handle assembly for being held in the hand of a user, the handle assembly comprising:

a housing; and

an electrical storage device disposed within the housing; an electrochemical cell, the electrochemical cell receiving electrical energy from the electrical storage device when in use; and

a support assembly holding the electrochemical cell, the support assembly being moveably connected to the handle assembly and moveable between a retracted position and an extended position, wherein in the retracted position the electrochemical cell is at least partially disposed within the housing and in the extended position the electrochemical cell is disposed outside of and a distance from the housing.

The device of the present invention is for use in treating and disinfecting a body of water by the electrolytic generation of ozone. 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 is adapted for use intermittently to disinfect different bodies of water, as required by the user. For example, the device may be employed to ozonate 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 treatment and disinfection of water required for other purposes, for example the disinfection of water in which cut flowers are to be stood.

The device is a portable device, in particular hand held. The device can be moved between the operating condition, in which the support assembly and the electrochemical cell is in the extended position, and a stowed condition, in which the support assembly is in the retracted position, with the electrochemical cell preferably wholly contained within the housing. In the operating condition, the electrochemical cell may be immersed in the body of water to be ozonated and the device operated for a time sufficient to provide the required concentration of ozone. In the stowed condition, the electrochemical cell is at least partially disposed within the housing, whereby the housing provides protection to the electrochemical cell.

The device comprises a handle assembly. The handle assembly allows the device to be held in the hand of a user and is sized accordingly. The handle assembly comprises a housing. The housing may be any suitable size and shape that allows it to be held in the hand of a user.

The device further comprises an electrical storage device disposed within the housing. Any suitable electrical storage device may be used, in particular a battery. The electrical storage device may be rechargeable. Suitable rechargeable storage devices are well known in the art. For example, the device may comprise means for recharging the battery by inductive coupling.

The device also comprises an electrochemical cell. When the device is in use, the electrochemical cell receives electrical energy from the electrical storage device and operates to generate ozone from water in contact with the electrochemical cell. In one preferred embodiment, the electrochemical cell is arranged to be contacted by water when immersed in a body of water. The electrochemical cell comprises an anode assembly and a cathode assembly separated by a membrane.

The electrochemical cell is preferably a passive cell, that is water is not pumped or otherwise forced through the cell and the cell 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 membrane. This is in contrast to known electrolytic cells, in which water to be electrolysed is pumped or otherwise forced through the cell into contact with the electrodes and the membrane. In this way, the electrochemical cell may simply be immersed in a body of water to be treated and the water ozonated with little or even no movement or agitation of the water required.

As noted above, the electrochemical cell comprises an anode assembly and a cathode assembly. Both the anode assembly and the cathode assembly comprise active surfaces formed from diamond.

Suitable diamond materials for forming the active surface of each electrode are known in the art and are commercially available. The electrically conductive diamond material may be a layer of single crystal synthetic diamond, or polycrystalline diamond. Polycrystalline diamond is particularly preferred. The diamond may be high pressure high temperature (HPHT) synthesised diamond or chemical vapour deposition (CVD) diamond, with CVD diamond again being preferred.

The diamond material may consist essentially of carbon, but is doped with one or more elements that provide electrical conductivity. Suitable dopants to provide the diamond with electrical conductivity are known in the art. Diamond 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). Again, BDD is a known and commercially available material. The active electrodes of the cell may be of a solid diamond material or a substrate material coated with diamond. Most preferably, the active electrodes of the cell comprise a solid diamond material. The preferred electrode material is electrically conductive, solid, free standing polycrystalline Boron-doped diamond. This solid diamond material may be manufactured by way of a process of chemical vapour deposition in a microwave plasma system.

The solid diamond material of the active electrodes 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 is a layer of thickness from 400 to 700 microns, more particularly from 500 to 600 microns.

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.

In the case of the active diamond surface of the electrode material being coated, the diamond coating is typically from 1 to 10 microns in thickness, more preferably from 3 to 5 microns thick.

Suitable techniques for manufacturing both solid diamond, such as freestanding electrically conductive Boron-doped diamond material, and diamond coated materials are known in the art. It has been found that diamond material provided as a layer or coating formed on the substrate material delaminates and blisters under the conditions prevailing in the electrochemical cell during operation. This in turn significantly reduces the longevity and operating life of the cell. Accordingly, in embodiments in which the active electrode comprises a substrate with a layer of diamond material thereon, it is preferred that the diamond material is provided as a layer of pre-formed solid diamond, such as the Boron-doped diamond material referred to hereinbefore, which is then attached to the surface of the substrate. The electrochemical cell comprises first and second electrodes, as noted above. Each of the first and second electrodes may comprise a single electrode or a plurality of electrodes electrically connected to act together as a bipolar cell where each pair of electrodes is separated by a membrane. In one preferred embodiment, the electrochemical cell comprises a single electrode for each of the anode and the cathode.

The electrochemical cell comprises a Proton Exchange Membrane (PEM) disposed between the electrodes. The membrane permits the movement of hydrogen ions (protons) and also positively charged metal cations, such as calcium and magnesium, present in the water to pass through the membrane to the cathode, in either direction, depending upon the polarity of the current applied to the cell at any given time. The Proton Exchange Membrane (PEM) is in contact with the surface of 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 anode, the membrane and the water in the region of the anode, ozone is produced in solution 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 that may be present in the water, such as calcium and magnesium, 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 Nation™ range of products available from Dow Chemical.

The device of the present invention preferably further comprises a conductivity sensor. In use, the conductivity sensor detects the conductivity of the fluid surrounding the electrochemical cell. In this way, the electrochemical cell is only activated when the cell is in contact with or immersed in sufficient volume of water. The conductivity sensor is preferably arranged to be activated to detect the conductivity of the fluid when the device is activated by the user with the intention of producing ozonated water. Suitable conductivity sensors, such as amperometric and potentiometric sensors, are known in the art and are commercially available. A preferred conductivity sensor is an amperometric sensor. The conductivity sensor measures the electrical conductivity of the fluid surrounding the electrochemical cell, in particular the fluid in contact with and between the electrodes of the electrochemical cell. In particular, in the case of an amperometric sensor, the sensor comprises a pair of electrodes and applies a known potential (voltage) across the electrodes. The sensor measures the current (Amps) flowing between the electrodes and determines the conductivity of the fluid between the electrodes. The conductivity sensor is arranged to generate a signal, in particular an electrical signal, corresponding to the measured fluid conductivity. This signal is used to operate a switch allowing the electrochemical cell to be activated. For example, the device may comprise a processor, with the signal generated by the conductivity sensor being processed by the processor.

As noted above, the conductivity sensor measures the electrical conductivity between its electrodes and, hence of the fluid therebetween. The flow of electricity in the fluid is by way of ions, with a higher concentration of ions giving rise to a higher conductivity. In the present case, the purpose of the conductivity sensor is to determine whether or not the electrochemical cell is in contact with a fluid with a sufficiently high conductivity, in particular water, as opposed to a low or non- conductive fluid, in particular air. Operation of the electrochemical cell, in particular attempting to pass a current through the electrodes, when the electrodes are in a non-conductive fluid, in particular air, damages the cell. Accordingly, the conductivity sensor advantageously ensures that the electrodes in the electrolytic cell are in contact with a conductive fluid, in particular water.

The conductivity sensor is provided to determine the conductivity of fluid in contact with the electrodes of the electrochemical cell. To this end, the conductivity sensor is preferably located adjacent or in close proximity to the electrochemical cell. In one preferred embodiment, the conductivity sensor is disposed on the support assembly in a position relative to the electrochemical cell, whereby in normal use of the device with the electrochemical cell immersed in the liquid to be treated, the conductivity sensor is above the electrochemical cell. In this way, the signal generated by the conductivity sensor will provide an indication of the conductivity of the fluid in which the electrochemical cell is immersed.

As noted above, the device of the present invention may further comprise a processor. In use, the processor receives a signal from the conductivity sensor corresponding to the conductivity of the fluid in and surrounding the electrolytic cell. Suitable processors for use in the device are known in the art and are commercially available. The electrochemical cell of the device and, if present, the conductivity sensor, is held in a support assembly. The support assembly is moveably connected to the handle assembly. In one preferred embodiment, the support assembly is pivotably connected to the handle assembly, in particular by a hinge assembly, more preferably by a ring hinge assembly. The support assembly is moveable between a retracted position and an extended position. In the retracted position the electrochemical cell is at least partially within the housing, more preferably wholly within the housing. In the extended position the electrochemical cell is disposed outside of and at a distance from the housing. In the extended position, the electrochemical cell may be contact the water to be treated, most preferably be immersed in the body of water, for example by inserting the electrochemical cell and the portion of the support assembly holding the electrochemical cell, and if present the conductivity sensor, into the water, for example within a vessel.

The support assembly may have any suitable form. In one preferred embodiment, the support assembly comprises a support member, more preferably an elongate support member or support arm. The support member preferably lies at least partly, more preferably wholly, within the housing when in the retracted position. As noted the support assembly holds the electrochemical cell. The support assembly preferably comprises a support housing, with the electrochemical cell being disposed within the support housing. The support housing is provided with at least one opening to allow for the movement of water and ozone into and out of the support housing. More preferably the support housing comprises a plurality of openings. In one preferred embodiment, the support housing is tubular with opposing open ends, for example cylindrical. The support housing preferably lies at least partly, more preferably wholly, within the housing when in the retracted position. In the present invention, the device is preferably arranged to be operated whereby the electrochemical cell is operated in a first mode, that is with a current density applied to the electrodes in a first polarity, whereby the first electrode acts as the anode and the second electrode acts as the cathode. When the electrochemical cell is in contact with water, ozone is produced at the anode, according to the electrochemical reactions described above. The operation of the electrochemical cell in the first mode is continued for a first period of time. During this mode of operation, material is deposited on the second electrode acting as the cathode, as described above. When it is required to remove material deposited on the second electrode, acting as the cathode in normal operation, the polarity of the current applied to the electrodes is reversed and the electrochemical cell operated in the second mode for a second period of time. This polarity reversal removes the materials deposited on the cathode during the first mode of operation of the cell. The device preferably comprises a processor to reverse the polarity of the electrochemical cell, according to the aforementioned regime.

The use of reverse polarity to clean the electrodes of electrochemical cells is known in the art. A system for applying a reverse polarity to an electrochemical cell is described in US 2009/0229992. However, in general, it is known that reversing the polarity of electrodes in an electrochemical cell may cause damage to the structure and fabric of the electrodes within the cell, particularly the active surfaces of the electrodes, typically causing erosion and attrition of the surface of the electrodes, thereby reducing the operating lifetime of the electrodes and also reducing the performance of the electrochemical cell. In particular, it is known that electrode materials, notably materials with metal oxide and mixed metal oxide coatings, are unsuitable for electrochemical processes where polarity reversal is required. For example, titanium electrodes that have a single or mixed metal oxide coating of ruthenium, iridium and tantalum, such as DSA™ electrodes, the active surface oxide layer breaks down as a result of frequent polarity reversals.

Lead dioxide (Pb0₂) has been used as an anode material in electrochemical cells for the production of ozone and ozonated water. However, this material is unstable and erodes rapidly over time under the application of high current densities. It is has also been found that polarity reversal increases the rate of erosion of the lead dioxide electrode. Further, it is accepted that lead, as an electrode material, is unsuitable for application in drinking water processes as a result of its known toxicity. However, surprisingly, it has been found that when employing electrodes having an active surface formed from diamond, in particular polycrystalline boron doped diamond (BDD) the aforementioned erosion of the electrodes is not observed.

As noted above, during the first mode of operation of the electrochemical cell, ozone is produced at the first electrode acting as the anode. When the polarity of the electrical current is reversed through the cell, the first electrode becomes the cathode, and the second electrode becomes the anode. The conditions prevailing in the vicinity of the anode in the electrochemical cell are acidic as a result of the generation of hydrogen ions on the surface of the anode. When the polarity of the applied current is reversed and the second electrode becomes the anode, acidic conditions are quickly established in the vicinity of the second electrode. Any substance that has been deposited on the electrode by the process of electro- deposition is dissolved and removed by the acidic conditions prevailing at the electrode. In particular, calcium and magnesium compounds formed on the surfaces of the electrodes are simply removed each time the polarity of the current applied to the electrochemical cell is reversed.

The process of polarity reversal is an effective means of cleaning the working electrodes in the electrochemical cell. The performance and current efficiency of the cell and, hence, the production of ozone is maintained in this way. One significant advantage of polarity reversal of the applied electrical current is that no chemical cleaning agents are required to maintain the performance of the electrochemical cell and the production of ozone at the electrodes.

In general, in accordance with the present invention, the electrochemical cell is operated for repeated periods of time in the first mode with a first operating current polarity, separated by operation for a second period of time in the second mode with the polarity of the current reversed. The length of operation of the cell in the first and second modes and the frequency at which the polarity of the applied current is reversed in the electrochemical cell can be varied to optimise the performance and efficiency of the cell, according to the prevailing operating conditions. In particular, the length of operation in each of the first and second modes may be increased or decreased to optimise performance and current efficiency.

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 substances present in the water being treated.

The length of time that the cell is operated in the first mode of operation, so as to produce ozone at the first electrode, may be determined by monitoring the condition of the second electrode 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 condition of the second electrode may be similarly monitored during the operation in the second mode of operation.

The length of time of the first period of operation in the first mode, that is the time between successive polarity reversals may be varied as required to maintain efficient operation of the cell. This time may be from several seconds to one or more hours, depending upon the operation conditions of the cell. The length of time between successive polarity reversals is preferably in the range of from 5 seconds to 60 minutes, depending upon the purity of the water and, in particular, the concentration of metal cations, such as calcium and magnesium, and other substances present in the water being fed to the cell, more preferably from 5 seconds to 30 minutes, still more preferably from 5 seconds to 10 minutes, still more preferably from 5 seconds to 5 minutes, still more preferably from 5 seconds to 60 seconds. In the case of 'soft' water, the length of time of the first period of operation in the first mode is preferably from 10 seconds to 60 seconds. In the case of 'hard' water, the length of time of operation in the first mode is more preferably from 5 seconds to 30 seconds. The polarity of the applied current is reversed and the electrochemical cell is operated in the second mode with the reversed polarity for a sufficient period of time to reduce or remove the material deposited on the second electrode. Again, this may be achieved, for example, by monitoring one or more operating parameters of the cell, such as the electrical current or the potential of the cell. Once the second electrode has been cleaned by operation in the second mode, operation of the electrochemical cell may be switched to the first mode, which in this case may be considered to be normal operation.

Typically, to remove deposits and clean the second electrode, the cell will require operation in the second mode with the reversed polarity of current for the same periods of time required for the periods of operation in the first mode. Preferably, to remove substances deposited on the second electrode, the cell is operated in the second mode with the polarity of the current reversed for a period of time in the range of from 5 seconds to 60 minutes, more preferably from 5 seconds to 30 minutes, still more preferably from 5 seconds to 10 minutes, still more preferably from 5 seconds to 5 minutes, still more preferably from 5 seconds to 60 seconds. In one preferred embodiment, the polarity is reversed so as to operate the electrochemical cell for about 10 seconds at each polarity. 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 supply, divided by the active surface area of the anode. The electrochemical cell may be operated at current densities up to 1 .0 Amps/cm², depending upon the size and duty of the cell. Preferably, the current density is in the range of from 0.1 to 1 .0 Amps/cm², more preferably from 0.4 to 1 .0 Amps/cm², and still more preferably in the range 0.5 to 1 .0 Amps/cm².

The electrochemical cell may be operated at an applied current depending upon the size of the electrodes. For example, applied currents of 90 mA, 150 mA and 250 mA may be applied. The maximum current that may be applied depends upon the size of the electrode and the maximum current density that may be tolerated by the cell, in particular the membrane. For example, a current of 90 mA may be applied to an electrochemical cell having electrodes with an area of 9 mm² at a current density of 1 Amp/cm², while an electrode area of 25 mm² may have a current of 250 mA applied, to give a current density of 1 Amp/cm².

The electrochemical cell may be operated at any suitable applied voltage, depending upon the conductivity of the water stream being treated. According to the operating conditions the voltage is preferably up to 12 Volts, more preferably up to 10 Volts, still more preferably up to 8 Volts A voltage of between 8 and 10 Volts is particularly preferred.

In use, the device is generally stored and carried in the stowed condition, that is with the support assembly and the electrochemical cell in the retracted position. When it is desired to ozonate a volume of water, the support assembly is moved to the extended position, thereby exposing the electrochemical cell. The electrochemical cell is contacted with the water to be treated, for example by being immersed in the water. The device is activated by the user. In this respect, the device preferably comprises a switch that is operated by the user. In one preferred embodiment, the device comprises a locking assembly that prevents the switch being operated when the support assembly is in a position other than an extended position. In this way, inadvertent operation of the electrochemical cell is prevented. The device is operated for a sufficient period of time to provide the desired concentration of ozone in the water being treated. Thereafter, the support assembly is moved to the retracted position. Embodiments 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 side view of one embodiment of the device of the present invention in the stowed condition;

Figure 2 is a view of the device of Figure 1 in the direction of the arrow II;

Figure 3 is a perspective view of the device of Figure 1 with the support assembly in a first extended position;

Figure 4 is a perspective view of the device of Figure 1 with the support assembly in a second, fully extended position; Figure 5 is a schematic diagram of the components of the device of Figure 1 ;

Figure 6 is a side view of an electrochemical cell assembly for use in the device of Figure 1 ; and Figure 7 is a cross-sectional view of one half of the cell assembly of Figure 6.

Turning to Figure 1 , there is a shown a device for ozonating water, generally indicated as 2. The device 2 comprises a handle assembly 4 having a generally rectangular housing 6. A generally cylindrical ring hinge assembly 8 is disposed at one end of the housing 6 and comprises an inner ring hinge member 10.

A support assembly, generally indicated as 20, comprises a generally cylindrical outer ring hinge member 22 extending around and moveable about the inner ring hinge member 10. A generally rectangular, elongate support member or arm 24 extends from the outer hinge member 22, as shown in Figures 2 to 4. The distal end 24a of the support member 24 is provided with a cylindrical support housing 26, in which is mounted an electrochemical cell 28. In the retracted position, the elongate member 24 and the support housing 26 lie within the housing, as can be seen in Figures 1 and 2. Rotation of the support assembly 20 about the inner ring hinge member 10 allows the support assembly to be extended into the positions shown in Figures 3 and 4, in which the support housing 26 and the electrochemical cell 28 are free to be contacted with water. In particular, in the extended position shown in Figure 4, the support housing 26 and the electrochemical cell 28 may be immersed in water. A switch 30 is mounted in one side of the housing 6, as shown in the figures.

Turning to Figure 5, there is shown a schematic representation of the device of Figure 1 . As shown in Figure 5, the device comprises a battery 40 disposed within the housing 6 of the handle assembly 4. A processor 42 is also disposed within the housing 6 and receives electrical power from the battery 40 by leads 44a, 44b. The processor 42 is further connected to the switch 30 by leads 46a, 46b. Leads 48a, 48b connect the processor 42 with the electrochemical cell 28.

Finally, the device comprises a conductivity sensor 50 connected to the processor 42 by leads 52a, 52b. The conductivity sensor 50 is located on the elongate member 24 between the cylindrical support housing 26 and the outer ring hinge member 22. In this way, with the elongate member 24 extended and the distal end 24a with the electrochemical cell 28 extending downwards and immersed in water, the conductivity sensor 50 is above the electrochemical cell. As a result, the conductivity sensor can only indicate that the conductivity is above the minimum threshold value for safe operation of the electrochemical cell when the cell is fully immersed in water. This provides a safeguard against the electrochemical cell being activated when not fully immersed in water. In operation, movement of the support assembly 20 into an extended position allows the processor 42 to be activated by the user using the switch 30. The processor 42 receives signals from the conductivity sensor 50 indicating the conductivity of the fluid in the region of the electrochemical cell 28. If the processor 42 determines the conductivity is above the minimum threshold for safe operation of the electrochemical cell, an electrical current is supplied to the electrochemical cell 28. The processor 42 monitors the condition of the electrochemical cell, for example by measuring the current draw for a given applied voltage. The processor 42 reverses the polarity of the electrochemical cell 28, as required to maintain efficient operation of the cell.

The electrochemical cell assembly 28 is shown in more detail in Figures 6 and 7. As shown in Figure 6, the assembly 28 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 Nation^® N1 17 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 7.

As can be seen in Figure 6, 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.

Claims

1 . A device for the ozonation of a body of water, the device comprising:

a housing; and

an electrical storage device disposed within the housing;

an electrochemical cell, the electrochemical cell receiving electrical energy from the electrical storage device when in use; and

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

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

4. The device according to any preceding claim, wherein in the retracted position the electrochemical cell is disposed wholly within the housing.

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

6. The device according to wherein the electrochemical cell comprises an anode assembly and a cathode assembly, each comprising an active surface formed from diamond.

7. The device according to claim 6, wherein the diamond is polycrystalline diamond.

8. The device according to claim 7, wherein the diamond is formed by chemical vapour deposition (CVD).

9. The device according to any of claims 6 to 8, wherein the diamond is doped.

10. The device according to claim 9, wherein the diamond is boron doped diamond (BDD).

1 1 . The device according to any of claims 6 to 10, wherein the anode and cathode assemblies each comprise an electrode, the electrode comprising a body of solid diamond material.

12. The device according to claim 1 1 , wherein the solid diamond material has a thickness of from 500 to 600 microns.

13. The device according to any preceding claim, wherein the electrochemical cell comprises a membrane, the membrane comprising a sulfonated

tetrafluoroethylene-based fluoropolymer.

14. The device according to any preceding claim, further comprising a conductivity sensor.

15. The device according to claim 14, wherein the conductivity sensor is disposed on the support assembly and is moveable with the electrochemical cell.

16. The device according to claim 15, wherein the conductivity sensor is disposed adjacent or in close proximity to the electrochemical cell.

17. The device according to claim 16, wherein the conductivity sensor is disposed on the support assembly in a position whereby, in normal use of the device with the electrochemical cell immersed in the liquid to be treated, the conductivity sensor is above the electrochemical cell.

18. The device according to any of claims 14 to 17, wherein the conductivity sensor is an amperometric sensor.

19. The device according to any preceding claim, wherein the support assembly is pivotably connected to the handle assembly.

20. The device according to claim 19, wherein the support assembly is connected to the handle assembly by a hinge assembly.

21 . The device according to any preceding claim, wherein the support assembly comprises a support member, the electrochemical cell being held in the support member.

22. The device according to claim 21 , wherein the support member is an arm.

23. The device according to any preceding claim, wherein the support assembly comprises a support housing, with the electrochemical cell being held in the support housing.

24. The device according to claim 23, wherein the support housing is tubular, with opposing open ends.

25. The device according to either of claims 23 or 24, wherein the support housing lies at least partially within the housing in the retracted position.