TECHNOLOGICAL FIELD

The present disclosure concerns systems for producing electrolyzed water. More specifically, the disclosure concerns systems for producing water enriched with hypochlorous acid (HOC1) by means of electrolysis.

BACKGROUND ART

References considered to be relevant as background to the presently disclosed subject matter are listed below:

- Patent application publication no. US20070280042

- Patent application publication no. US20080289976

- Patent publication no. US 3,696,919

- Patent publication no. US 3,443,726

- Patent application publication no. US20140331942 Patent publication no. WO2019/106387

- Patent application publication no. JP2017222535

- Patent application publication no. WO2019159181

Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

BACKGROUND

Surfaces have been shown to be a source of various contaminants, e.g. microbiological contaminants such as viruses, fungi, bacteria, etc. Sanitization of such contaminants has proven to be a challenge, and is often carried out by irradiation with disinfecting radiation in the UV wavelengths which hinder the capability of microorganisms to reproduce, or by applying various decontamination substances onto the surface which reduce or eliminate the microbial load on the surface. One of the decontamination substances that can be used is hypochlorous acid (HOC1) - a weak, unstable acid that, in low concentrations, is safe for use onto surfaces. Aqueous solutions of hypochlorous acid can be produced by electrolysis from solutions containing chloride ions, with the resulting product being referred to as electrolyzed water. Due to its instability, there is a need for processes and systems which can produce and dispense electrolyzed water, e.g. at the point of use, having relatively low content of destabilizing by-products.

GENERAL DESCRIPTION

The present disclosure provides processes and systems for producing electrolyzed water, typically albeit not exclusively, at the point of use. Processes and systems of this disclosure utilize an electrolysis process to obtain hypochlorous acid aqueous solutions having relatively low concentrations of destabilizing by-products, hence maintaining and prolonging the effectiveness of the hypochlorous acid. The systems utilize an electrolysis reactor comprising an electrolysis cell, or plurality of electrolysis cells/units, designed to obtain such electrolyzed water.

Thus, in one of its aspects, the present disclosure provides a process for producing electrolyzed water, the processes comprises causing an aqueous solution containing chloride ions to flow in one or more elongated conduits extending between an inlet end and an outlet end, each conduit being defined between two oppositely charged electrodes, to thereby electrolyze the aqueous solution to form electrolyzed water containing hypochlorous acid; wherein the flow of the aqueous solution is at a flow rate such as to carry gas bubbles formed during electrolyzation to the outlet.

By another aspect, the disclosure provides an electrolyzation reactor for producing electrolyzed water, that comprises a reactor inlet configured for liquid communication with a source of chlorine ions-comprising aqueous solution, for feeding the solution into the electrolyzation reactor, and a reactor outlet configured for draining electrolyzed water from the electrolyzation reactor; one or more elongated conduits, each extending between a conduit inlet and a conduit outlet at a higher elevation than the conduit inlet, the conduit inlet and conduit outlet being in respective liquid communication with the reactor inlet and the reactor outlet; and at least two electrodes, with each of the conduits being defined between two electrodes of said at least two electrodes that are configured to be oppositely charged; the length of each conduit being such to allow gas bubbles formed in the electrolyzation to flow with the electrolyzed water out of said conduit outlet.

The term electrolyzed water refers to an aqueous solution of hypochlorous acid (HOC1) obtained by electrolysis reaction, which in the context of the present disclosure, is utilized as a disinfectant material. The electrolysis reaction occurs by applying an electrical current through an aqueous solution containing chloride (CT) ions, the electrical current being applied between a positively-charged electrode and a negatively-charged electrode, such that transfer of electrons through the solution causes a cascade of chemical reactions, according to the following general schemes:

At the positive electrode (anode):

2NaCl(aq) Ch(g) + 2Na ⁺ ( _aq) + 2e

Ch(g) + H20(l) - HCl(aq) + HOCl(aq)

At the negative electrode (cathode):

2H20(i) + 2e Ά 20H ( _aq) + ¾¾)

While in the above schemes the source of chloride ions is sodium chloride (NaCl), it is to be understood that any water-soluble chloride salt can be used. Thus, in some embodiments, the chloride ions can be obtained by dissolving one or more chloride salts in water, such chloride salts can be selected from sodium chloride, aluminum chloride, ammonium chloride, potassium chloride, calcium chloride, magnesium chloride, phosphorus chloride, phosphoryl chloride, phosphorus trichloride, phosphorus pentachloride, zinc chloride, manganese chloride and others.

As can be seen, the electrolysis reaction forms gaseous species, i.e. hydrogen, chlorine and oxygen, that exude from the reaction solutions as gas bubbles. The gas bubbles tend to accumulate onto the surface of the electrodes, thereby reducing the effective surface area of the electrodes that is in contact with the solution, and reducing the efficiency of the electrolysis process.

As noted, in the process of the present disclosure, aqueous solution of chloride ions is caused (e.g. pumped) to flow through elongated conduits. Two opposite walls of each conduit are constituted by two oppositely charged electrodes - i.e. a positively- charged electrode and a negatively-charged electrode. During its flow through the conduit, the solution is exposed to electrical current ( e.g . direct current) applied between the two electrodes, thereby causing an electrochemical reaction that forms electrolyzed water. In order to obtain higher electrolysis efficiency, the electrodes in the presently disclosed processes and reactors are brought to proximity with one another, thereby reducing the electrical resistance through the solution. However, such proximity also increases the effect caused by accumulation of gas bubbles onto the surface of the electrodes, thus causing reduction of efficiency.

Thus, the presently disclosed process and reactor are designed to reduce the effect of bubbles by flowing the aqueous solution within the reactor in narrow conduits (or channels), formed between the electrodes, thereby carrying the gas bubbles away from the electrodes together with the flow of the solution. The flow of the solution in the conduit is such that the gas bubbles formed during the electrochemical reaction are carried along with the flow away from the electrodes' surfaces and towards the outlet of the conduit.

In order to assist in gas removal from the system, the reactor is vertically arranged, such that the conduits are arranged generally vertically, with the outlet end being above the inlet end, and the flow of the aqueous solution is essentially upwards (e.g. vertical). Namely, the aqueous solution is caused to flow against the gravitational direction, assisting the gas bubbles to float towards the outlet end of the conduits.

Thus, in some embodiments, the aqueous solution flows at a flow rate through a conduit ranges between about 0.02 L/hr/cm ² to about 0.25 L/hr/cm ² . The unit of L/hr/cm ² denotes liters of aqueous solution passing through the conduit over one hour per unit area of electrode. By other embodiments, the aqueous solution passes through the conduit at a volumetric flow rate of about 8 ml/min to about 100 ml/min.

As noted, increasing the efficiency of the electrochemical reaction can be obtained by bringing the oppositely charged electrodes into proximity with one another. Such proximity also assists in reducing the overall size of the reactor in which the process is carried out, as will be explained further below. In some embodiments, the distance between the two electrodes (i.e. the thickness dimension of the conduit) ranges between about 1 mm to about 5 mm.

The conduits are typically elongated, and can extend along a conduit axis defined between the inlet end and the outlet end. The length of the conduit, defined between the conduit inlet and the conduit outlet, can range between about 5 cm and about 25 cm, as to allow sufficient path length to cause removal of the bubbles from the conduit during solution flow therethrough.

According to some embodiments, the electrodes utilized in the process and reactor of this disclosure are planar electrodes. Thus, the reactor can comprise one or more electrolysis units, each having two planar, oppositely-charged electrodes, separated by a planar separator element made of a non-electrically conducting material. The separator element typically comprises parallelly arranged elongated ribs that extend between the surfaces of the electrodes that face one another, and is in tight contact with the surfaces of the electrodes, thereby defining the conduits between two neighboring ribs and the electrodes.

In other words, the separator element comprises elongated ribs and is sandwiched between two electrodes. As the ribs are in tight contact with the surface of the electrodes, elongated conduits are formed, with their walls constituted by the electrodes and two adjacent ribs.

For providing a compact arrangement of the reactor, a plurality of electrolysis units can be stacked one on top of the other, such that two neighboring units share a common electrode. In such a manner, a stacked arrangement of alternatingly arranged electrodes and separators are formed.

The flow of the aqueous solution is typically parallel in the plurality of conduits along the longitudinal axes of the conduits. By some embodiments, the reactor comprises an inlet manifold arrangement for feeding the aqueous solution from the reactor inlet to the conduit inlets and an outlet manifold arrangement for collecting electrolyzed water from the conduits outlets and draining it to the reactor outlet. The inlet manifold arrangement can comprise one or more inlet cavities that are in liquid communication with (i) each of the conduits’ inlets and (ii) a source of the aqueous solution, and the outlet manifold arrangement can comprise one or more outlet cavities that is in liquid communication with (i) each of the conduits’ outlets and (ii) a drain of the electrolyzed water. By utilizing such manifolds, even distribution of the aqueous solution between the conduits can be obtained, while collection of electrolyzed water from the conduits is facilitated.

During the electrolysis process various simultaneous chemical reactions can take place, including recombination of various ionic species that form byproducts. One desired byproduct that can be formed is hydrogen peroxide (H2O2), which also functions as a sanitizer. However, other, undesired byproducts can be, and typically are, formed - for example other forms of chlore ions, such as chlorates and chlorites, that are considered highly corrosive. Hence, it is desired to reduce the amount of such byproducts in the electrolyzed water.

In processes and reactors of this disclosure, high efficiency electrochemical reactions can be obtained, thus producing high yields of electrolyzed water production. The processes and reactions of this disclosure enable utilization or relatively low concentrations of chloride salts in order to obtain relatively high concentration of hypochlorous acid in the electrolyzed water.

Unlike other processes which require utilization of high concentration of salts (which is disadvantageous due to environmental impacts and often results in corrosion of electric components in the production systems), the process and reactor of the present disclosure, due to their high efficiency, enable utilization of aqueous solutions having relatively low chloride ions concentration. According to some embodiments, the concentration of the chloride ions in the aqueous solution can be up to the solubility upper threshold of the chloride ions in a given temperature at a specific pH (for example, up to about 250 g/L of sodium chloride at pH 0 at 25°C). In other embodiments, the concentration of the chloride ions in the aqueous solution is up to 9000 ppm. By other embodiments, the concentration of the chloride ions ranges between 50 ppm and about 9000 ppm. For example, in the process and reactor of this disclosure, about 1000 ppm of NaCl can be used to produce 500 ppm of hypochlorous acid, with low amounts of undesired byproducts, such as chlorates (CIO3 )·

It was found that utilizing the process and reactor of this disclosure, significant reduction in the concentration of byproducts in the electrolyzed water can be obtained by utilizing a set of defined process conditions. It was found that various process and reactor parameters can result in low concentrations of undesired byproducts while maintaining high process efficiency.

While the process can be carried out at room temperature, it was found that utilizing heated solutions can yield less undesired byproducts. Without wishing to be bound by theory, the higher the temperature of the solution, the lower the required electrical potential difference between the electrodes, thus reducing the resistivity of the solution and increasing the efficiency of hypochlorous acid production. It was found that the higher the temperature of the solution, the less formation of chlorate will be obtained (as the balance of the chemical equation will be shifted towards decomposition of chlorates). Thus, in some embodiments, the temperature of the aqueous solution at the inlet end ranges between about 30 °C to about 50 °C.

Another factor found to be of influence on the production of byproducts is the pH of the aqueous solution. Water, e.g. tap water, often includes various metal ions, which under the electrolysis reaction conditions can form metal salts and precipitate onto the electrodes. For example, calcium and magnesium ions that may be present in water can form, during electrolysis, carbonate salts with CO2 naturally dissolved in water. Reducing the pH of the aqueous solution can prevent such byproducts formation. Reducing the pH to below 7 was also found to prevent formation of undesired chlorate ions byproducts. Hence, by some embodiments, the pH value of the aqueous solutions is below about 7.

Alternatively, the process can be operated with aqueous solutions having neutral pH ( i.e . of about 7), and in such embodiments, the polarity of the electrodes is periodically reversed during the process, thus preventing accumulation of undesired precipitants thereon. For example, the polarity of the electrodes can be inversed every 2 hours of process, such that the positive electrodes become the negative electrodes and the negative electrodes become the positive electrodes in a defined periodicity.

In order to further prevent formation of undesired byproducts, the water utilized for preparation of the aqueous solution can undergo, prior to dissolving therein the chloride ions, one or more pre-treatments for removal of various contaminants (organic and/or inorganic) therefrom. Such pre-treatments can, by some embodiments, include one or more of filtration, ultrafiltration, absorption, ion exchanging, desalination, distillation, reverse osmosis, UV radiation, electrodialysis, solvent extraction, chemical reduction or oxidation treatments, etc.

According to some embodiments, the process comprises adjusting one or more parameters of the aqueous solution prior to carrying out the electrolysis. For example, the aqueous solution can undergo pH adjustment, temperature adjustment, composition adjustment, etc ., before carrying out the electrolysis. By other embodiments, the process can comprise adjusting one or more parameters of the formed electrolyzed water after electrolysis, e.g. adjusting pH, temperature, addition of buffers (such as phosphate- buffered saline (PBS)), adjusting concentration of the electrolyzed water (for example diluting by non-electrolyzed water), etc. As noted above, the electrolysis reactor comprises oppositely-charged electrodes. The electrodes can be identical one to another or different one from the other in terms of any one of composition, geometry, surface and/or surface area. In some embodiments, all of the electrodes are made of the same material. In other embodiments, all of the electrodes have the same geometry and/or the same area, and/or the same surface area. By other embodiments, all of the electrodes are identical (i.e. the electrochemical cell formed by the electrodes is a symmetrical cell).

By other embodiments, the positively-charged electrode is different from the negatively-charged electrode by at least one parameter selected from composition, geometry, size, area, and surface area. When the electrodes differ one from the other, an asymmetrical electrochemical cell is formed.

The electrodes can be made of, or coated by, a material functioning as catalytic surfaces for chloride oxidation. According to some embodiments, each of the electrodes can be made of, or coated by, a material independently selected from titanium and titanium alloys, ruthenium and ruthenium alloys, tantalum and tantalum alloys, iridium and iridium alloys, platinum and platinum alloys, carbonaceous materials (such as graphite, graphene, glassy carbon and carbon nanotubes), and others.

The electrolysis reactor described herein can be incorporated into a system for dispensing of electrolyzed water. The system can be for domestic use, semi-industrial, industrial, or for producing and dispensing electrolyzed water at a point of use. Thus, by another aspect, this disclosure provides a system for producing electrolyzed water, comprising one or more reactors as described herein, a chloride ions-comprising aqueous solution feeding sub-system in liquid communication with the reactor inlet; and an electrolyzed water dispensing sub-system in liquid communication with the reactor outlet for dispensing electrolyzed water.

The system can be configured for dispensing the electrolyzed water into reservoirs or containers, from which the electrolyzed water is to be used/dispensed. By other arrangements, the system can be configured for spraying, misting, or atomizing the electrolyzed water over various surfaces or into various spaces. Hence, the system can be utilized to sanitize various hard or soft surfaces by application of electrolyzed water in various environments and conditions. The system can be used, for example, to sanitize medical facilities and medical equipment, domestic surfaces, communal surfaces, office equipment and spaces, public transportation facilities, food production and packaging means, agricultural produce (before or after harvesting), etc.

In the system, water is fed in order to obtain the aqueous solution. In some embodiments, the chloride ions-comprising aqueous solution feeding sub-system, comprises one or more water feeding lines, at least one chlorine ions source, and a mixing arrangement for mixing the water and chloride ions source to obtain the aqueous solution to be fed to the reactor inlet.

The chloride ions source can be in the form of solid chloride salt, a brine, a super saturated solution or a concentrate.

The chloride ion source can be provided as a container, that, by some amendments, is configured for association with the aqueous solution feeding sub-system. The container can be a re-fillable container that is permanently associated, i.e. integral, with the system.

Alternatively, the container can be detachably associated with the system, as to permit its removal for replenishment or for replacement. Such a container can be configured with a removable or breakable seal, such that association of the container with the aqueous feeding sub-system will cause removal or break-up of the seal to permit the chloride ion source to be transferred from the container to the aqueous feeding sub system. The container can be hard or pliable. The container can be configured for single use, dispensable and/or recyclable.

The container can comprise the chloride ion source in an amount sufficient for production of several batches of electrolyzed water. Alternatively, the container can hold chloride ion source sufficient for production of a single batch of electrolyzed water.

By some embodiments, the container can be in the form of a pod or a capsule, containing chloride ion source for a single process cycle of electrolyzed water preparation, or containing chloride ion source in an amount sufficient for several such production cycles.

By some embodiments, when the container includes chloride ion source sufficient for several production cycles, the system can comprise dosing arrangements for dosing the required amount of chloride ion source to be fed into the water. The dosing and feeding means can also be integral with the container.

The container typically includes one or more identifying means, such as an RFID tag, a barcode, a QR code, a serial number, or any other type of label that provides information about the container. Such information may concern the content of the container, the production date, the expiration date, a producer identifier, authentication data, etc. Accordingly, the system can comprise one or more reading utilities, configured for reading such one or more identification elements associated with said container and processing the data carried thereby.

As noted above, pre-treating the water to remove various contaminates before electrolysis is often desired in order to improve the process yield and reduce production of undesired byproducts. Thus, in some embodiments, the aqueous solution feeding sub system comprises one or more water treatment modules for pre-treatment of the water. Such water treatment modules can be selected from one or more of filtration unit, ultrafiltration unit, absorption unit, ion exchanger, desalination unit, distillation unit, reverse osmosis unit, UV radiation unit, electrodialysis unit, solvent extraction unit, reduction or oxidation chemical cell, etc.

The aqueous solution feeding sub-system can further comprise one or more of (i) heating modules for heating the water or the aqueous solution, (ii) a pH adjusting module, (iii) salinity adjusting module and (iv) product control module.

Mixing of water and chloride ions source can be made in various arrangements. In some embodiments, the chloride ions source can be fed directly into a water feed line ( i.e . in-line feeding), utilizing the flow of water through the feed line in order to dissolve the chloride ions source and obtained the aqueous solution. In other embodiments, mixing can be carried out through a static mixer positioned in the water feed line, and the chloride ions source is added to the water upstream the static mixer. By some other embodiments, the system comprising a mixing tank, into which water and the chloride ions source are fed and mixed to obtain the aqueous solution.

Feeding of chloride ions source and water can be done batchwise or continuously, depending on the design of the system and the requirements for dispensing of electrolyzed water. Hence, the system can be configured for continuous or batchwise production or dispensing of electrolyzed water.

The system can comprise one or more sensors configured to measure or provide indication of one or more parameters of the process. Such sensors can be selected from pH sensors, oxidation-reduction potential (ORP) sensors, temperature sensors, conductivity sensors, turbidity sensors, liquid level sensors, flow sensors, multimeters (to measure the Ampere and Voltage), etc. The system can further comprise one or more electrolyzed water reservoirs for accumulating electrolyzed water produced by the reactor before dispensing out of the system. The reservoir is typically located in the system between the reactor and the dispensing sub-system. The reservoir can have any shape or size, and is preferably made on non-reactive materials, such as glass or polymeric material. The reservoir can be made of, or coated by, transparent, translucent or opaque materials as to control the exposure of the electrolyzed water to light.

The reservoir can also comprise one or more air removal units to remove air from the reservoir to prevent exposure to CO ₂ . The reservoir can be maintained under pressure in order to minimize evaporation of the electrolyzed water during their storage in the reservoir.

The dispensing sub-system can include any suitable dispensing means, depending on the form in which electrolyzed water is to be dispensed (i.e. liquid or aerosolized). Thus, the dispensing sub-system can comprise one or more of a tap, one or more pumping arrangements, a spraying unit, an aerosolization unit, an atomizer, a dripping unit, or any other suitable dispensing means.

According to some embodiments, the system comprises one or more control utilities, for controlling and operating the system and its various sub-systems. The control utility can communicate, either wirelessly or by wired-means with a central database or a central command, transmitting and receiving various data to and therefrom, respectively. For example, the control utility can transmit various parameters and data to permit monitoring the proper operation of the system by the central command, carrying out authentication of chloride ions source containers, identifying various malfunctions at real time, etc. By another example, the control utility can communicate with a database containing data specific for the system, e.g. how much chloride ions source (for example, containers) was provided for operation of the system. By correlating the amount of electrolyzed water produced and the amount of chloride ions source provided for use with a specific system operating in a point-of-use - one can monitor the efficiency of electrolyzed water production in the specific system, as well as whether use of unauthorized chloride ion sources was made.

By another aspect of this disclosure, there is provided a chloride ions source container configured for detachable coupling with and feeding said source to a system described herein. The container, by some embodiments, comprising one or more identifying elements, for example selected from an RFID tag, a barcode, a QR code, a serial number, or any other type of label that provides information about the container, the identifying means being configured to be read and processed by a reader of the system.

The container can be made of, or coated by, any material insensitive to chloride ions and/or non-corroding material, such as aluminum, stainless steel, polymers, carbonaceous material, etc.

The container can be configured for a single, non-refillable use. For example, the container can include a removable or non-rev ersible rupturable seal, that is respectively removed before or ruptured during coupling of the container to the system.

By another aspect, the present disclosure provides a device for spraying electrolyzed water over surface or into spaces comprising one or more systems described herein.

As used herein, the term about is meant to encompass deviation of ±10% from the specifically mentioned value of a parameter, such as temperature, pressure, concentration, etc.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases ranging/ranges between a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1A is an isometric view of a reactor according to an embodiment of this disclosure; Fig. IB shows the reactor of Fig. 1A, however with some elements made transparent in order to view internal structural details; Fig. 1C shows the direction of flow through the reactor; Fig. 2A shows a top view of the reactor of Fig. 1 A, with the top and bottom cover plates removed; Fig. 2B is a top perspective view of the reactor of Fig. 2A, with an electrode plate removed from the separator plate; Fig. 2C is a top perspective view of the reactor of Fig. 2B, with the electrode plate in place within the separator plate; Fig. 2D is a perspective cross-section along line II-II in Fig. 2C;

Fig. 3 is a top perspective view of an exemplary separator utilized in the reactor of Figs. 1A-2D;

Fig. 4 is a schematic representation of a system according to an embodiment of this disclosure;

Fig. 5 shows the amount of chlorate by-product as a function of the pH of the aqueous solution;

Fig, 6 shows the amount of chlorate by-product as a function of the temperature of the aqueous solution;

Fig. 7 shows the amount of chlorate by-product as a function of the temperature difference between the inlet and outlet of the reactor;

Fig. 8 shows the amount of chlorate by-product as a function of the concentration of NaCl salt in the aqueous solution.

DETAILED DESCRIPTION OF EMBODIMENTS

For the sake of simplicity, the following example will be made with reference to sodium chloride as the chloride-ion source, and the aqueous solution as a pure solution of NaCl in water. However, as will be apparent to the skilled person, that other chemical entities can be present in the solution ( e.g . other salt traces), and hence additional electrochemical reactions (not discussed herein) can occur.

In addition, the exemplified reactor is shown to have a certain number of electrodes, separator plates and conduits. It is understood that the reactor and system of this disclosure is not limited by the exemplified number of electrodes, separator plates and/or conduits.

Turning first to Figs. 1 A-1C, shown is a reactor 100 according to an embodiment of the present disclosure. Reactor 100 comprises a bottom plate 102 and a top plate 104, enclosing between them a stack of planar, alternatingly arranged separator elements and electrodes, the stack being generally designated 106. A reactor inlet 108 is defined at the bottom plate 102 to permit feeding of a chloride ions-comprising aqueous solution, and a reactor outlet 110 defined in top plate 104 out of which electrolyzed water is dispensed from the reactor.

The reactor inlet 108 is in liquid communication with inlet manifold arrangement 112, that receives the aqueous solution fed through the inlet, and channels it into inlet cavities 114 (in this example two cavities are shown, however it is to be understood that different number of cavities can be utilized), from which the aqueous solution is fed into a plurality of elongated conduits, generally designated 116, the structure of which will be described further below. Solution flows along the cavities, during which electrolysis of the chlorine ions occurs, until reaching outlet cavities 118, from which electrolyzed water is collected to outlet manifold arrangement 120 and dispensed out of the reactor through reactor outlet 110.

As can clearly be seen in Fig. 1C, the general direction of flow through the reactor is vertical, namely the reactor outlet is positioned at a higher elevation with respect to the reactor inlet, such that forced flow of the liquid is in a general upward direction from the inlet to the outlet. Such flow configuration enables clearing gas bubbles (e.g. oxygen and hydrogen) that form as reaction products during electrolysis by forced flow of the aqueous solution against gravitational direction, thereby carrying the gas bubbles away from the electrodes together with the flow of the liquid towards the reactor outlet.

Seen in Fig. 2A is a top view of the reactor with the top and bottom covers removed. Separator elements 122 (seen also in isolation in Fig. 3) are typically planar, and made of non-electrically conductive material, as to provide separation between two- oppositely charged electrodes (one of which, electrode 128 is seen in Fig. 2A below the separator element 122). The separator elements comprise a plurality of (n) elongated ribs 124, parallelly arranged and extending along a longitudinal direction from inlet cavities 114 towards outlet cavities 118. Together with the two electrodes sandwiching the separator element (better seen in Fig. 2D), the ribs form (n-1) elongated conduits 126, each extending between a conduit inlet 130 and a conduit outlet 132.

As seen in Figs. 2B-2C, the planar separator elements 122 define an electrode holding cavity 134, sized to accommodate an electrode in the form of plate 128. Cavity 134 can be formed only on one face of the separator element, or the separator element can comprise two such electrode-holding cavities, each on each of its opposing faces. Seen also are linking struts 125, extending between adjacent ribs 124 and perpendicular thereto. Linking struts 125 function to provide mechanical support to the ribs 124 and the electrode plate 128 positioned over the ribs in the electrode-holding cavity. However, it is to be understood that utilizing different construction materials, linking struts 125 can be removed, and hence these do not necessarily constitute a mandatory constructional element. Further, while the electrodes 128 are describes as being placed into the planar separator elements, it is to be understood that electrodes 128 can be integrated into the separator elements 122, e.g. by casting the separator element over edge segments of the electrodes, thereby integrating the electrodes with the separator elements.

As can be seen in Fig. 2D, when separator elements 122 are stacked one over the other, electrodes 128 are also stacked, such that a plurality of electrolysis units is formed, each including two electrodes separated by the separator element. Each of the electrodes 128 in a unit are oppositely-charged, for example electrodes 128A being positively charged, while electrodes 128B is negatively charged. As positive and negative electrodes 128A,128B are altematingly arranged in the stack, two neighboring electrolysis units share a common electrode. Thus, (m) electrodes 128 give rise to (m-l) electrolysis units. As can also be seen, two adjacent ribs 124, together with a pair of oppositely charged erodes 128A,128B form together the conduit 126.

In order to provide electrical current to the electrodes 128, each separator element includes an electrical -lead orifice 136 formed at a side wall of the separator element 122, through which a wire can be threaded in order to establish electrical connection with the electrodes, charge the electrodes and supply electrical current during the electrolysis process.

In a process utilizing the reactor 100, an aqueous solution of chloride ions is pumped through inlet 108 to manifold arrangement 112, and into inlet cavities 114. As each of the inlet cavities is in liquid communication with conduit inlet ends 130, the aqueous solution is evenly distributed between parallel conduits 126 under the pressurized flow. As the solution flows through conduits 126 towards the conduit outlet ends 132, electrical current is applied between the two oppositely charged electrodes 128A,128B, thus causing electrolysis of the chloride ions in the solution during its flow. Electrolyzed water is then collected into the outlet cavities 118, and from there are dispensed through outlet manifold arrangement 120 to reactor outlet 110. As noted, increasing the efficiency of the electrochemical reaction can be obtained by bringing the oppositely charged electrodes into proximity with one another; for example, the distance between two adjacent electrodes can be between about 1 and about 5 mm. Such proximity can reduce the electrical resistivity within the conduit during electrolysis, as well as assist in reducing the overall size of the reactor in which the process is carried out. However, such proximity also increases the effect caused by accumulation of gas bubbles onto the surface of the electrodes, thus causing reduction of efficiency. Thus, the forced flow of the solution through the narrow conduits in a flow rate sufficient to remove the bubbles from the surface of the electrode, together with the generally vertical flow direction through the reactor, permit effective removal of the bubbles and preventing their accumulation onto the electrodes. Such flow rate can be, for example, at least about 0.02 L/hr/cm ² .

An exemplary system utilizing the reactor is shown schematically in Fig. 4. Elements shown in consecutive lines are mandatory in the system, while elements in dashed lines are optional.

System 200 is fed water from a water source 210 ( i.e . tap water, bottled water, municipal or domestic water line, etc) into mixing tank 240, to which chloride ions source is added from container 230. As noted, the chloride ions source can be in the form of solid chloride salt, a brine, a super-saturated solution or a concentrate. Container 230 can contain chloride ions source in an amount sufficient for a single production cycle; alternatively, container 230 can contain chloride ions source in an amount sufficient to produce more than one batch of aqueous solution (in such a case the system includes also dosing arrangement, not shown, to ensure proper dosing of the chloride ions source into tank 240).

The container can be a container integral with the system, or a detachably attached container. The container can typically include one or more identifying means, such as an RFID tag, a barcode, a QR code, a serial number, or any other type of label that provides information about the container. Accordingly, the system can comprise one or more reading utilities (not shown), configured for reading such one or more identification elements associated with said container and processing the data carried thereby.

Water can optionally undergo one or more pre-treatments in one or more water treatment modules, generally designated 220. Such water treatment modules can be selected from one or more of filtration unit, ultrafiltration unit, absorption unit, ion exchanger, desalination unit, distillation unit, reverse osmosis unit, UV radiation unit, electrodialysis unit, solvent extraction unit, reduction or oxidation chemical cell, etc.

The chloride ions source and the water are mixed in tank 240 to form the chloride ion-containing aqueous solution, that is fed, under pressure, into reactor 100 (of the kind described above) for the electrolysis process. The resulting electrolyzed water can be directly dispensed for immediate use through dispensing outlet 260. Alternatively, the electrolyzed water can be accumulated in one or more reservoirs, generally designated 250, in which electrolyzed water is collected and maintained for later use. The reservoir can be maintained under partial pressure ( e.g . partial N2 pressure) in order to minimize penetration of air and/or evaporation of the electrolyzed water.

The system can be for domestic use, semi-industrial, industrial or for producing and dispensing electrolyzed water at a point of use. The system can be configured for dispensing the electrolyzed water into reservoirs or containers, from which the electrolyzed water is to be used/dispensed. Further, the system can be configured for spraying, misting, or atomizing the electrolyzed water over various surfaces or into various spaces.

Examples:

As noted, the process and reactor described herein are designed to obtain efficient and high yielding electrolysis of chloride ions into hypochlorous acid from relatively low concentrations of chloride ions in the aqueous solution, with relatively low content of undesired byproducts (such as chlorate ions).

All chlorate ions detections in the examples below were carried out using ion chromatography analysis using ion-chromatography system ICS-3000 which consisted of quaternary pump, KOH eluent generator, thermal compartment, autosampler and conductivity detector (Thermo Scientific). Chromatographic separation was achieved using hydroxide-selective anion-exchange analytical column (AS25, 250x4 mm, Thermo Scientific). For the sample preparation - the samples were diluted before the injection. Calibration was made externally, with freshly prepared perchlorate and chlorate solution.

1. Effect of chloride ions concentration in the aqueous solution

The test was conducted producing HOC1 concentration of 200 ppm, while using solution feed having pH of 2.3. As can be seen in Fig. 8, the higher the concentration of NaCl in the aqueous solution, the lower the amount of chlorate byproducts in the electrolyzed water. Without wishing to be bound by theory, the higher the salt concentration, the higher the electric conductivity of the solution; hence, in the faradaic reaction that take place at the positive electrodes, most of the charge will be utilized for the oxidation of the chloride ions to obtain chlorine molecules, instead of other side- reactions that could lead to the production of chlorate ions.

However, solutions having a high concentration of NaCl can be corrosive and are considered environmentally hazardous. Hence, the process and reactor of the present disclosure, due to their high efficiency, enable utilization of aqueous solutions having relatively low chloride ions concentration, e.g. up to 9000 ppm. For example, in the process and reactor of this disclosure, about 1000 ppm of NaCl can be used to produce 500 ppm of hypochlorous acid, with low amounts of chlorates (CIO3 )· The solution flow rate was about 8 L/hour, and the electrodes were polarized using constant current of 4 Amp at potential of about 13 Volt. The feed solution starting pH was acidic at pH of about 2. Purified water containing different concentrations of NaCl were used as the aqueous solution. The electrodes were made of titanium, coated by ruthenium oxide.

2. Effect of pH of the aqueous solution

21 g/L of NaCl saline water was prepared, electrolyzed in a reactor. The solution flow rate was about 8 L/hour and the electrodes were polarized using constant current of 4 Amp at potential of about 13 Volt. The feed solution starting pH was acidic at pH of about 2. Purified water containing different concentrations of NaCl was used. The electrodes were made of titanium coated by ruthenium oxide. Electrolyzed water having a concentration of that produced 500 ppm of HOC1 were produced. The electrolyzed water was diluted by 5 and 10 times to reach concentrations of 100 ppm and 50 ppm of HOC1, accordingly. The pH of the electrolyzed water and the chlorate ion concertation was measured.

As can be seen in Fig. 5, the pH of the aqueous solution has a significant effect on the formation of chlorate byproducts: the lower the pH of the solution, the less chlorates are formed. The positive electrodes produced chlorine gas that turned to HOC1 and HC1 inside the water. In acidic solutions, the HOC1 is stable, thus the reaction produced low amount of chlorite ions, which mitigate the production of chlorate ions at the surface of the positive electrodes according to the equation: 3C10 + 1.5H ₂ 0 - C10 ₃ +3H ⁺ +2C1- + 0.75O ₂ +3e

Controlling the pH of the aqueous solution can also assist in preventing precipitation of various metal carbonate salts, which can result in non-acidic pH values during electrolysis. Hence working at pH of below 7 can be beneficial in reducing formation of undesired byproducts.

3. Effect of aqueous solution temperature

To assess the effect of temperature of the aqueous solution on the formation of chlorates, 1000 ppm NaCl feed solution in about 2.3 pH was used, that produced 200 ppm ofHOCl.

As seen in Figs. 6 and 7, the solution temperature at the entry point of the reactor (or at the outlet of the mixing tank), as well as the temperature difference in the liquid between the reactor inlet and the reactor outlet have an effect on chlorate formation - the higher the temperature at the reactor inlet and the smaller the temperature difference between the reactor inlet and the reactor outlet, the less chlorate by products are formed.

Without wishing to be bound by theory, the higher the temperature of the solution, the lower is the required electrical potential difference between the electrode, thus reducing the resistivity of the solution, increasing the efficiency of hypochlorous acid production. As chlorate formation reaction is exothermal, it is assumed that the higher the temperature of the solution is, the less formation of chlorate will be obtained (as the balance of the chemical equation will be shifted towards decomposition of chlorates).