FIELD OF THE INVENTION

The present invention relates to a device and method for generating oxidized water, in particular, to generation of oxidized water using a photocatalyst.

BACKGROUND OF THE INVENTION

Oxidized water is widely used in people's daily life and work. For example, people need to prevent spread of infectious virus in family life, hence, oxidized water is usually required in hand hygiene, respiratory hygiene, food and water hygiene, general home hygiene, care of domestic animals, and home healthcare for sterilization, disinfection and cleaning.

The skilled person in the art ever assumes to immerse the photocatalyst Ti0 ₂ in water solution, the UV light passes through the solution to the photocatalyst surface, where the radicals are generated. These radicals diffuse in water solution for water disinfection or cleaning the object in the water solution. The radicals are major oxidant substance in photocatalysis process. The concentration and lifetime of the radicals characterize the sterilization, disinfection and cleaning effects of the oxidizing aqueous solution. However, these radicals generated in the prior art have low concentration and short lifetime. For example, in the water environment, the hydroxyl radical OH- has a very short in vivo half-life of approximately 10 ⁹ seconds. The short life time limits the application of photocatalysis, and also limits the sterilization, disinfection and cleaning effects of the oxidizing aqueous solution.

Therefore, there is an urgent need in the art to make improvement to the prior art.

OBJECT AND SUMMARY OF THE INVENTION

In view of this, the present invention provides a device for generating oxidative water vapour and a method thereof, which can solve or at least release at least part of the defects in the prior art. According to a first aspect of the present invention, it provides a device for generating oxidative water vapour, which may comprise: a generating unit for generating water vapour containing oxygen; and a photocatalytic unit comprising a light source and a photocatalyst, the light source irradiating the water vapour containing oxygen from the generating unit and the photocatalyst contacted with the water vapour containing oxygen, so as to generate water vapour with oxidative radicals. By means of the device for generating oxidative water vapour of the present invention, the lifetime of the oxidative radicals generated such as hydro xyl radical OH-, hydrogen peroxide radical Η02·, or superoxide radical 02· ^" in gas phase can reach 1-3 seconds. Thus, the existence time or lifetime of the oxidative radicals in the water vapour is prolonged, and the sterilization, disinfection and cleaning efficiency in subsequent use is improved.

In one embodiment of the present invention, the photocatalyst may comprise semiconductor photocatalyst and nonmetal doping photocatalyst.

In another embodiment of the present invention, the semiconductor photocatalyst may comprise Ti0 ₂ > ZnC" ₂ > SnC" ₂ and ZrC" ₂ etc., the nonmetal doping photocatalyst comprises N, S or C doped Ti0 ₂ etc.

In a further embodiment of the present invention, the generating unit may comprise an electrode pair, a membrane between the two electrodes of the electrode pair, the electrode pair heats and electrolyzes a liquid when being applied with a voltage, oxygen and water vapour generated on one of the electrodes are provided to the photocatalytic unit. The membrane is applied between two electrodes in order to prevent the hydrogen generated near another electrode, i.e. the cathode, from entering into the oxygen and the water vapour, thereby influencing the subsequent photocatalytic reaction.

In one embodiment of the present invention, the device for generating oxidative water vapour may further comprise a cooler for cooling the water vapour with oxidative radicals into water mist. The purpose of cooling the water vapour into water mist is for the convenience of subsequent use, for example, for use in sterilization, disinfection or cleaning processing etc.

In another embodiment of the present invention, the device for generating oxidative water vapour may further comprise a pump for pumping the water vapour with oxidative radicals to the cooler, and spraying the water mist to a target surface, so as to perform sterilization, disinfection or cleaning processing etc.

According to a second aspect of the present invention, it provides a method for generating oxidative water vapour, which may comprise the steps of: generating water vapour containing oxygen; and irradiating the water vapour containing oxygen and a photocatalyst contacted with the water vapour containing oxygen, so as to generate water vapour with oxidative radicals. By means of the method for generating oxidative water vapour of the present invention, the lifetime of the oxidative radicals generated such as hydroxyl radical OFF , hydrogen peroxide radical Η0 ₂ ·, or superoxide radical 0 ₂ * ^" in gas phase can reach 1-3 seconds. Thus, the existence time or lifetime of the oxidative radicals in the water vapour is prolonged, and the sterilization, disinfection and cleaning efficiency in subsequent use is improved.

In one embodiment of the present invention, the photocatalyst may comprise semiconductor photocatalyst and nonmetal doping photocatalyst.

In another embodiment of the present invention, the semiconductor photocatalyst may comprise Ti0 ₂ > Zn0 ₂ > Sn0 ₂ and Zr0 ₂ etc., the nonmetal doping photocatalyst comprises N, S or C doped Ti0 ₂ etc.

In a further embodiment of the present invention, the method for generating oxidative water vapour may further comprise: cooling the water vapour with oxidative radicals into water mist.

In yet another embodiment of the present invention, the method for generating oxidative water vapour may further comprise: spraying the water mist to a target surface. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows a schematic diagram of a device for generating oxidative water vapour according to one aspect of the present invention.

Fig. 2 schematically shows a flow chart of a method for generating oxidative water vapour according to another aspect of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Respective embodiments of the present invention will be described in detail with reference to the drawings of the present invention as below.

Fig. 1 schematically shows a schematic diagram of a device 10 for

generating oxidative water vapour according to one aspect of the present invention, which may comprise: a generating unit 12 for generating water vapour containing oxygen 14; and a photocatalytic unit 16, comprising: a light source 18 and a photocatalyst 22, the light source 18 irradiating the water vapour containing oxygen 14 from the generating unit 12 and the photocatalyst 22 contacted with the water vapour containing oxygen 14, so as to generate water vapour with oxidative radicals 23.

In one embodiment of the present invention, the generating unit 12 may comprise an electrode pair 24, 26, a membrane 28 between the two electrodes of the electrode pair 24, 26, the electrode pair 24, 26 heats and electrolyzes a liquid 32 when being applied with a voltage, oxygen and water vapour generated on one of the electrodes are provided to the photocatalytic unit 16. During the operation of the generating unit 12, a DC voltage is applied to the electrode pair 24, 26 via a power supply 34. The liquid 32 filled in the electrolyte tank constituted by the electrode pair 24, 26 and the membrane 28 can be for example tap water, deionized water, etc. The voltage applied on the electrode pair 24, 26 on the one hand can electrolyze the water, for example, the following reaction occurs near the first electrode 26 as the anode: 2H ₂ 0 - 4e = 0 ₂ +4 FT, i.e., oxygen is generated, the oxygen gets into the photocatalytic unit 16 via a channel connected with the anode chamber. The following reaction occurs near the second electrode 24 as the cathode: 4H ₂ 0 + 4e = 2H ₂ + 40H ^" , i.e., hydrogen is generated. In order to prevent the hydrogen from getting into the anode chamber so as to influence the subsequent phototalytic reaction, a membrane 28 is preferably arranged between the two electrodes of the electrode pair 24, 26. The membrane 28 can play function of prevent the hydrogen from getting into the anode chamber. The material, from which the membrane 28 is made, can be easily learnt by one skilled in the art based on the prior art, which will not be described in detail here.

Alternatively, a unidirectional pH adjustment electrode can also be used as a cathode to suppress generation of hydrogen. Or a hydrogen-absorbing alloy, metal hydride is used as a cathode to store the hydrogen. Alternatively, a one-way valve is used to connect the cathode chamber to release the hydrogen generated near the cathode from the generating unit 12, so as to avoid the hydrogen from getting into the anode chamber. On the other hand, applying a voltage on the electrode pair 24, 26 can heat the water so as to generate water vapour. In this way, water vapour is also generated in the anode chamber where the first electrode 26 is located. The water vapour also gets into the photocatalytic unit 16 via a channel connected with the anode chamber. The oxygen and the water vapour generated in the anode chamber are usually mixed together, hence, they are generally called water vapour containing oxygen 14. It is shown in Fig. 1 that the water vapour containing oxygen 14 is provided to the photocatalytic unit 16 via a channel connected with the anode chamber.

It should be further pointed out that the contents of the water vapour and the oxygen in the water vapour containing oxygen 14, or the contents of the water vapour and the oxygen filled in the photocatalytic unit 16 are in proportion to the voltage and/or current value applied on the electrode pair 24, 26. This is not difficult for the skilled person in the art to understand. For example, in the case of applying a larger voltage and/or current on the electrode pair 24, 26, there will be more and more water vapour and oxygen generated in the anode chamber, and vice versa. The skilled person in the art can control the amount or concentration of the water vapour containing oxygen 14 by controlling the voltage and/or current value applied on the electrode pair 24, 26 by the power supply 34.

In one embodiment of the present invention, the light source 18 in the photocatalytic unit 16 can be Vacuum ultraviolet VUV light source, Near ultraviolet UVA light source, Medium ultraviolet UVB light source, Extreme ultraviolet UVC light sourer or visible light. The selection of the light source depends on the photocatalyst used. That is, a corresponding light source 18 should be selected for a different photocatalyst used. The skilled person in the art can select a corresponding light source based on the teaching of the prior art if a corresponding photocatalyst is selected. A matching photocatalyst can also be selected in the case of the light source in existence. This is not difficult for the skilled person in the art to understand.

Alternatively, the photocatalyst 22 may comprise semiconductor photocatalyst and nonmetal doping photocatalyst. Wherein the semiconductor

photocatalyst comprises Ti0 ₂ > Zn0 ₂ > Sn0 ₂ and Zr0 ₂ etc., the nonmetal doping photocatalyst comprises N, S or C doped Ti0 ₂ etc. The skilled person in the art should understand that the photo catalysts listed above are only schematic, not indicating that the photocatalysts used in the present invention are limited to this. The photocatalyst 22 can be coated on the inner wall of the photocatalytic unit 16, for example, such a situation is just shown in Fig. 1. The photocatalyst 22 can also be placed at any position within the photocatalytic unit 16, as long as the light source can irradiate on the photocatalyst 22.

Since the water vapour containing oxygen 14 that gets into the photocatalytic unit 16 via the channel exists in gas form, the water vapour containing oxygen 14 within the photocatalytic unit 16 will fill the whole interior space of the photocatalytic unit 16. Thus the photocatalyst 22 arranged on the inner wall of the photocatalytic unit 16 or at any other position will be sufficiently contacted with the water vapour containing oxygen 14.

For example, in the case of using Ti0 ₂ as the photocatalyst and using Ultraviolet UV light to irradiate the water vapour containing oxygen 14, the following reaction will occur:

Ti(> , 4 hv ■ h~ 4· e~

k* 4 H,0→ 0Η·4-Η ⁺

0 ₂ -;- e ^' · -~» 0;;· ·

0 ₂ + H* + e~→ H0 ₂ - 20H-— H ₂ 0 ₂

Namely, in the reaction of the first step, Ti0 ₂ reacts with the photon to generate photo hole h ⁺ and photo electron e ^" . The photo hole h ⁺ has very strong oxidability so that the water is activated and oxidized. In the reaction of the second step, the photo hole h ⁺ oxidizes the water into hydroxyl radicals ΟΗ· and ions H ⁺ . The photo electron e ^" has strong reducibility, thereby reducing part of the oxygen 0 ₂ into superoxide radical 0 ₂ · ^" in the reaction of the third step. The other part of oxygen O ₂ reacts with ions H ⁺ and photo electron e ^" , thereby reducing the other part of oxygen O ₂ into hydrogen peroxide radicals ΗΟ ₂ · in the reaction of the fourth step. In the fifth step, part of the hydroxyl radicals ΟΗ· can combine to generate hydrogen peroxid H ₂ 0 ₂ . The substances obtained, e.g. hydroxyl radicals ΟΗ·, hydrogen peroxide radicals Η0 ₂ ·, hydrogen peroxid H ₂ 0 ₂ and superoxide radical 0 ₂ · ^~ all have strong oxidability. Just because of these radicals and hydrogen peroxid H ₂ 0 ₂ , the water vapour containing oxygen 14 becomes water vapour with strong oxidability. The above is described only taking Ti0 ₂ as the photocatalyst. The skilled person in the art should understand that the similar reaction will also occur if other photocatalysts are used, which will not be described in detail here.

The existence time or lifetime of the above radicals can reach 1-3 seconds through the experiment of the present invention. Therefore, compared with the in vivo half- life of approximately 10 ⁹ seconds in the prior art, the lifetime of the radicals is greatly prolonged, and the sterilization, disinfection and cleaning efficiency in subsequent use is improved.

The experimental effect of the present invention will be explained further through the following embodiment.

Embodiment 1

The inventor uses air containing oxygen of 21wt%, the absolute humidity of the air is 10g/M ³ , the air with such absolute humidity can be regarded as water vapour containing oxygen. Ti0 ₂ (AEROXIDE ^® Ti0 ₂ , P25) is used as the photocatalyst, the light source is a high pressure mercury lamp, the central wavelength of the light source is 365nm, the power of the light source is 600w, the high pressure mercury lamp is used to irradiate the photocatalyst and the air containing oxygen of 21wt% (with the absolute humidity of 10g/M ³ ), and to enable them to react for 10 minutes, then the inventor uses methylthionine chloride as the indicator to test the oxidability of the outputted water vapour. The skilled person in the art knows that the methylthionine chloride is a blue dye, which is generally used in photocatalysis field to perform test of oxidability. The peak value of the absorption wavelength of the methylthionine chloride is 664nm. When the methylthionine chloride is oxidized, it will absorb less UV light.

Table 1 shows the processing result of gas phase photocatalysis

air (with the absolute humidity of 0.295

1 Og/M ³ ) + Ti0 ₂ + UV light irradiation

From the first set of experimental data it can be seen that the UV light absorbed by the methylthionine chloride under the above experiment condition is 0.360. From the second set of experimental data it can be seen that in the case of using T1O ₂ and the air with the absolute humidity of 10g/M ³ (without UV light irradiation) for reaction, the outputted water vapour reacts with the methylthionine chloride indicator, the subsequently measured UV light absorbed by the methylthionine chloride indicator is 0.350. From the third set of experimental data it can be seen that in the case of using UV light and the air with the absolute humidity of 10g/M ³ (without T1O ₂ ) for reaction, the outputted water vapour reacts with the methylthionine chloride indicator, the subsequently measured UV light absorbed by the methylthionine chloride indicator is 0.330. From the fourth set of experimental data it can be seen that in the case of using T1O ₂ , UV light and the air with the absolute humidity of 10g/M ³ , the outputted water vapour reacts with the methylthionine chloride indicator, the subsequently measured UV light absorbed by the methylthionine chloride indicator is 0.300.

The above experimental result indicates that the air with the absolute humidity of 1 Og/M ³ does not influence the methylthionine chloride indicator greatly if the T1O ₂ (the second set) or UV light (the third set) is used only. This means that the oxidability of the water vapour obtained is relatively weak if the T1O ₂ (the second set) or UV light (the third set) is used only. In contrast, the UV light absorbed by the methylthionine chloride indicator is reduced distinctly in the case of using Ti0 ₂ , UV light and the air with the absolute humidity of 1 Og/M ³ for reaction (the fourth set), which is reduced approximately by 18%. This further proves that the technical solution of the embodiment of the present invention realizes the assumption of enhancing the oxidability of the water vapour by prolonging the life time of the radicals with oxidation in the water vapour, so as to increase the sterilization, disinfection and cleaning efficiency in subsequent use.

In one embodiment of the device for generating oxidative water vapour of the present invention, the device may further comprise a cooler 36 for cooling the water vapour with oxidative radicals 23 into water mist 38, thus it is benefit for the use of the water mist 38. For example, relative to the use of the water vapour, the water mist 38 in liquid phase can be directly sprayed to the target surface in a visible manner, which is convenient for user use.

Alternatively, the device for generating oxidative water vapour may further comprise a pump 42 for pumping the water vapour with oxidative radicals 23 to the cooler 36, and spraying the water mist 38 to a target surface.

According to the second aspect of the present invention, it may further provide a method 40 for generating oxidative water vapour, which may comprise the steps of: generating 46 water vapour containing oxygen 14; and irradiating 48 the water vapour containing oxygen 14 and a photocatalyst 22 contacted with the water vapour containing oxygen 14, so as to generate water vapour with oxidative radicals 23. Alternatively, the method 40 for generating oxidative water vapour according to one embodiment of the present invention may further comprise: cooling 52 the water vapour with oxidative radicals 23 into water mist 38. Alternatively, the method 40 for generating oxidative water vapour according to a modified embodiment of the present invention may further comprise: spraying 54 the water mist 38 to a target surface. Then the method for generating oxidative water vapour may end at step 56. The photocatalyst 22 used in respective embodiments of the method 40 for generating oxidative water vapour of the present invention may comprise semiconductor photocatalyst and nonmetal doping photocatalyst, wherein the semiconductor photocatalyst comprises Ti0 ₂ > Zn0 ₂ > Sn0 ₂ and Zr0 ₂ etc., the nonmetal doping photocatalyst comprises N, S or C doped Ti0 ₂ etc. The radicals generated in the method 40 for generating oxidative water vapour of the present invention may comprise hydroxyl radicals, superoxide radicals and hydrogen peroxide radicals etc.

By means of the method for generating oxidative water vapour in respective embodiments of the present invention, the lifetime of the oxidative radicals generated such as hydroxyl radical OH- , hydrogen peroxide radical Η0 ₂ ·, or superoxide radical 0 ₂ ^»" in gas phase can reach 1-3 seconds. Thus, the existence time or lifetime of the oxidative radicals in the water vapour is prolonged, the oxidability of the water vapour is enhanced, and the sterilization, disinfection and cleaning efficiency in subsequent use is improved.

Although the present invention has been described with reference to the currently considered embodiments, it should be understood that the present invention is not limited to the disclosed embodiments. On the contrary, the present invention aims to cover various modifications and equivalent arrangements comprised within the spirit and scope of the claims as attached. The scope of the following claims complies with the broadest explanation so as to comprise all such modifications and equivalent structures and functions.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.