Liquid treatment apparatus and liquid treatment method

Abstract

To provide an efficient means of accelerated oxidation treatment.SOLUTION: A liquid treatment apparatus by OH radicals according to the present invention includes an excimer lamp, an ozone gas generation tank in which a raw material gas containing oxygen is irradiated with an excimer lamp to generate ozone gas, and a liquid treatment tank in which the liquid containing the generated ozone gas is irradiated with ultraviolet rays from the excimer lamp.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] TECHNICAL FIELD The present invention relates to a liquid treatment device and a liquid treatment method. [Background technology]

[0002] Advanced oxidation process is known as a method for decomposing organic matter in liquids such as wastewater or sewage. Advanced oxidation process is a method to generate hydroxyl radicals (OH radicals) by reacting multiple oxidants such as ozone / UV, hydrogen peroxide / UV, or ozone / hydrogen peroxide with water. There have been reported advanced oxidation treatment devices using ozone / UV (Patent Document 1), advanced oxidation treatment devices using ozone / hydrogen peroxide (Patent Document 2), and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-262122 A [Patent Document 2] JP 2020-124655 A [Patent Document 3] Japanese Unexamined Patent Publication No. 52-11643 [Patent Document 4] Japanese Patent Application Publication No. 01-275404 [Patent Document 5] Patent No. 6423642 specification [Patent Document 6] Patent No. 6537418 Specification [Patent Document 7] Patent No. 6573513 specification [Patent Document 8] JP 2020-198146 A [Patent Document 9] JP 2021-103622 A [Patent Document 10] Patent Application No. 2022-133038 Summary of the Invention [Problem to be solved by the invention]

[0004] The present applicant has developed a technique for generating ozone gas by ultraviolet irradiation (Patent Documents 3 to 5), and in particular a technique for generating ozone and generating ozone water by using an excimer lamp (Patent Documents 6 to 9). Furthermore, the present inventors have developed an ozone water generating device that efficiently mixes ozone gas with water (Patent Document 10). The present inventors have investigated conventional accelerated oxidation treatments and found that there are various problems, such as decomposition of ozone by ultraviolet irradiation using a low-pressure mercury lamp, increased costs and adverse effects of wastewater containing hydrogen peroxide due to the addition of hydrogen peroxide, and generation of nitrogen oxides during ozone generation by electrical discharge. It is therefore an object of the present invention to provide a means for efficient advanced oxidation treatment. [Means for solving the problem]

[0005] The present inventors have intensively studied means for efficient accelerated oxidation treatment and, surprisingly, have found that an efficient accelerated oxidation treatment can be achieved by generating ozone using an excimer lamp and irradiating the resulting ozone water with vacuum ultraviolet light from the excimer lamp. They have also found that the generated hydroxyl radicals (OH radicals) can easily decompose difficult-to-decompose organic substances (e.g., surfactants, organic acids, endocrine disrupters, and pesticides). The present invention is based on these findings. Thus, the present invention provides [1] A liquid treatment device using OH radicals, comprising an excimer lamp, an ozone gas generation tank for irradiating a raw material gas containing oxygen with the excimer lamp to generate ozone gas, and a liquid treatment tank for irradiating a liquid containing the generated ozone gas with ultraviolet light from the excimer lamp; [2] The liquid treatment device according to [1], further comprising a gas-liquid mixing section for mixing ozone gas with the liquid. [3] A liquid treatment device according to [1] or [2], wherein the nitrogen oxide concentration in the liquid containing ozone gas is 3.0 vol% or less relative to the ozone gas concentration. [4] A liquid treatment device according to [1] or [2], wherein the efficiency of generating OH radicals by ozone gas and ultraviolet irradiation from the excimer lamp is 8 μM / hW or more, and the efficiency of generating OH radicals by ultraviolet irradiation from the excimer lamp is 5 μM / hW or more. [5] The liquid treatment device according to [1] or [2], wherein H radicals and OH radicals are generated from water molecules by the excimer lamp, and the concentration of hydrogen peroxide generated by self-decomposition of the generated OH radicals is less than 0.5 mg / L. [6] A liquid treatment method including the steps of: irradiating an oxygen-containing raw material gas with an excimer lamp to generate ozone gas; mixing the generated ozone gas with a liquid; and irradiating the liquid containing the ozone gas with ultraviolet light from the excimer lamp to generate OH radicals, thereby treating the liquid. [7] The liquid treatment method according to [6], wherein the liquid containing ozone gas has a nitrogen oxide concentration of 3.0 vol% or less relative to the ozone gas concentration. [8] The liquid treatment method according to [6] or [7], wherein the efficiency of generating OH radicals by ozone gas and ultraviolet irradiation from the excimer lamp is 8 μM / hW or more, and the efficiency of generating OH radicals by ultraviolet irradiation from the excimer lamp is 5 μM / hW or more; and [9] The liquid treatment method according to [6] or [7], wherein H radicals and OH radicals are generated from water molecules by the excimer lamp, and the concentration of hydrogen peroxide generated by self-decomposition of the generated OH radicals is less than 0.5 mg / L. Regarding. Effect of the Invention

[0006] According to the liquid treatment device and liquid treatment method of the present invention, ozone gas can be produced by one excimer lamp, and hydroxyl radicals can be generated from ozone water. In addition, persistent organic substances (e.g., surfactants, organic acids, endocrine disrupters, and pesticides) can be easily decomposed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing a first embodiment of a liquid treatment device. [Diagram 2] FIG. 2 is a cross-sectional view showing one embodiment of a gas-liquid mixing section. [Diagram 3] FIG. 2 is a cross-sectional view showing a second embodiment of a liquid treatment device. [Figure 4] FIG. 2 is a cross-sectional view showing one embodiment of a gas-liquid separation section. [Diagram 5] FIG. 2 is a block diagram (connection diagram) of a liquid treatment device. [Figure 6] FIG. 2 is a schematic diagram of the internal structure of the liquid treatment device. [Figure 7] This is a graph showing the efficiency of hydroxyl radical generation when a liquid containing ozone gas is irradiated with ultraviolet rays from an excimer lamp (VUV+O3), when a liquid not containing ozone gas is irradiated with ultraviolet rays from an excimer lamp (VUV), or when ozone gas is added to a liquid (O3). [Figure 8] 1 is a graph showing the amount of nitrogen oxide produced when ozone gas is generated by a discharge method or an excimer lamp. [Figure 9] 1 is a graph showing the dissolved ozone gas concentration and hydrogen peroxide concentration when a liquid containing ozone gas is irradiated with ultraviolet rays from an excimer lamp (wavelength 172 nm) or a low-pressure mercury lamp (wavelength 254 nm). [Figure 10] This is a graph showing the decomposition of persistent organic matter when a liquid containing ozone gas is irradiated with ultraviolet rays from an excimer lamp (VUV+O3), when a liquid not containing ozone gas is irradiated with ultraviolet rays from an excimer lamp (VUV), or when ozone gas is added to a liquid (O3). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [1] Liquid treatment equipment The liquid treatment device of the present invention is a liquid treatment device that uses OH radicals and includes an excimer lamp, an ozone gas generation tank in which the excimer lamp is irradiated to a raw material gas containing oxygen to generate ozone gas, and a liquid treatment tank in which ultraviolet light from the excimer lamp is irradiated to a liquid containing the generated ozone gas.

[0009] <<Accelerated oxidation treatment>> The accelerated oxidation treatment is a method of accelerating the decomposition of ozone by the reaction of water with multiple oxidizing agents such as ozone / UV, hydrogen peroxide / UV, or ozone / hydrogen peroxide, to generate hydroxyl radicals (OH radicals). Among these accelerated oxidation treatments, ozone / UV uses a low-pressure mercury lamp as ultraviolet light. The low-pressure mercury lamp generates ultraviolet light with wavelengths of 185 nm and 254 nm. The 185 nm ultraviolet light generates ozone from oxygen contained in air, and the 254 nm ultraviolet light decomposes the ozone. It is believed that the decomposition of dissolved ozone by the 254 nm wavelength generates hydroxyl radicals. However, the decomposition of ozone by the 254 nm wavelength also reduces the amount of ozone gas generated, so that a sufficient concentration of ozone gas cannot be supplied, and hydroxyl radicals cannot be generated efficiently.

[0010] According to the accelerated oxidation treatment using the excimer lamp of the present invention, sufficient ozone gas is generated by ultraviolet irradiation from the excimer lamp, and since decomposition of the ozone gas does not occur due to ultraviolet irradiation, hydroxyl radicals can be generated efficiently. It is believed that the generation of hydroxyl radicals by the excimer lamp of the present invention is achieved by irradiating an oxygen-containing raw material gas with an excimer lamp, mixing the ozone gas produced with a liquid, and then irradiating the liquid containing the ozone gas with vacuum ultraviolet light (VUV) from the excimer lamp. It is also possible to generate hydroxyl radicals by only irradiating a liquid that does not contain ozone with vacuum ultraviolet light. It is also possible to generate hydroxyl radicals by only mixing ozone gas with a liquid. However, it is believed that irradiation of a liquid containing ozone gas with vacuum ultraviolet light (VUV) causes efficient generation of hydroxyl radicals.

[0011] <Excimer Lamp> The excimer lamp used in the present invention is a lamp filled with rare gas or a mixture of rare gas and halogen gas. Xe gas emits ultraviolet rays with wavelengths of 172 nm, Ar gas with 126 nm, Kr gas with 146 nm, ArBr gas with 165 nm, ArF gas with 193 nm, KrCl gas with 222 nm, and KrBr gas with 207 nm. The excimer lamp used in the present invention is not particularly limited as long as the effects of the present invention can be obtained, but in order to generate ozone, it is preferable to use a lamp that radiates a wavelength (127 nm or more and 243 nm or less) at which oxygen molecules are decomposed but not nitrogen molecules are decomposed. Furthermore, it is preferable to use a lamp that does not emit a wavelength (240 nm or more and 340 nm or less) at which the generated ozone gas is decomposed. As mentioned above, ozone can be decomposed by absorbing photons with a wavelength of 254 nm that are generated by low-pressure mercury lamps. Excimer lamps do not generate ultraviolet light with a wavelength of 254 nm. In particular, xenon excimer lamps have a wavelength peak of 172 nm, and ozone is generated by this wavelength. Therefore, in order to obtain high-concentration ozone, excimer lamps are preferred, and xenon excimer lamps are particularly preferred.

[0012] Furthermore, in the generation of hydroxyl radicals by irradiating a liquid containing ozone gas with vacuum ultraviolet light, a xenon excimer lamp having a wavelength peak of 172 nm is preferred, although not limited thereto. It is believed that a wavelength of 127 nm or more and 243 nm or less makes it possible to produce a large amount of ozone gas and a large amount of hydroxyl radicals.

[0013] The structure of the excimer lamp is not particularly limited, but may have, for example, the structure shown in Fig. 1. The discharge vessel can be formed by welding together a bottomed cylindrical inner tube 3 and an outer tube 4, each made of a dielectric material such as quartz glass. The discharge vessel is provided with an inner electrode 5 disposed inside the inner tube 3, an outer electrode (not shown) disposed in a non-contact state with the outer tube 4, a lead wire (not shown) and a power supply wire (not shown) electrically connected to the inner electrode 5, and an outer power supply wire (not shown) electrically connected to the outer electrode (not shown), and is electrically connected to an AC high-voltage power supply to supply power to the excimer lamp.

[0014] 《Embodiments of the present invention》 The liquid treatment device of the present invention generates ozone gas and hydroxyl radicals by one excimer lamp. That is, in an ozone gas generation tank, an excimer lamp is irradiated to a raw material gas containing oxygen to generate ozone gas. Then, the generated ozone gas is mixed with a liquid, and in a liquid treatment tank, hydroxyl radicals are generated by irradiating the liquid containing ozone gas with ultraviolet light from the excimer lamp. That is, it is necessary to irradiate ultraviolet light to the ozone gas generation tank and the liquid treatment tank by one excimer lamp. Therefore, although not limited, it is preferable to arrange the ozone gas generation tank around the excimer lamp and arrange the liquid treatment tank around the ozone gas generation tank in order to efficiently irradiate ultraviolet light to the raw material gas containing oxygen and the liquid containing ozone gas. However, the effect of the present invention can also be obtained by, for example, arranging the ozone gas generation tank on one side of the excimer lamp and arranging the liquid treatment tank on the opposite side of the ozone gas generation tank with the excimer lamp as the center. Furthermore, the effect of the present invention can also be obtained by arranging the ozone gas generation tank at the upper part of the excimer lamp and the liquid treatment tank at the lower part.

[0015] A first embodiment of the liquid treatment device of the present invention includes, but is not limited to, a one-pass system (circulation system) shown in Fig. 1. Furthermore, a second embodiment includes, but is not limited to, a batch treatment system shown in Fig. 3.

[0016] <Ozone gas generator> In the ozone gas generation tank of the liquid treatment device 1 of the present invention, an excimer lamp is irradiated onto a raw material gas containing oxygen to generate ozone gas. In the first embodiment, as shown in Fig. 1, a raw material gas 12 containing oxygen is introduced into an ozone gas generation tank 6 from a gas inlet 8. The raw material gas 12 containing oxygen is irradiated with ultraviolet light by an excimer lamp 2, and ozone gas is produced from the oxygen. The gas containing ozone gas is discharged from a gas outlet 9. The discharged gas containing ozone gas is mixed with a liquid, for example, by a gas-liquid mixer described later, and the liquid containing ozone is introduced into a liquid treatment tank 7 from a liquid inlet 10. In the second embodiment, as shown in FIG. 3, a raw material gas 12 containing oxygen is introduced into an ozone gas generation tank 6 from a gas inlet 8. The raw material gas 12 containing oxygen is irradiated with ultraviolet light by an excimer lamp 2 in the same manner as in the first embodiment, and ozone gas is produced from oxygen. In the second embodiment, a gas containing ozone gas is directly supplied to a liquid treatment tank 7. Specifically, the gas containing ozone gas is mixed with the liquid in the liquid treatment tank 7 from a bubble supply unit 18 provided at the bottom of the ozone gas generation tank 6, and is contained in the liquid. The gas containing ozone gas is contained in the liquid by, for example, dissolving in the liquid while moving from the bottom to the top.

[0017] The oxygen-containing raw gas, for example, air, to be introduced into the ozone gas generation tank can be introduced into the ozone gas generation tank by a pump as shown in Fig. 3. In this case, it is preferable to remove moisture in a dehumidifying unit before the introduction. The pump and the dehumidifying unit can also be provided in the first embodiment.

[0018] (Oxygen-containing source gas) The oxygen-containing raw material gas is not particularly limited as long as it contains oxygen, and examples thereof include air, nitrogen, and raw material gas containing oxygen. The oxygen content is not particularly limited, but for example, the lower limit is 5 vol% or more, in one embodiment it is 10 vol% or more, and in one embodiment it is 15 vol% or more. The upper limit is also not particularly limited, but is 50 vol% or less, in one embodiment it is 40 vol% or less, in one embodiment it is 30 vol% or less, and in one embodiment it is 25 vol% or less. The lower limit and the upper limit can be appropriately combined.

[0019] The shape of the ozone gas generation tank is not particularly limited as long as ultraviolet light is irradiated from the excimer lamp and ozone is generated from a raw material gas containing oxygen, but as shown in Fig. 1 or 3, it is preferably provided in a cylindrical shape around the excimer lamp. Alternatively, the excimer lamp may be divided into an upper part and a lower part, and the tank may be provided in a cylindrical shape around the upper part, or around the lower part. (In this case, a liquid treatment tank may be provided around the lower part of the excimer lamp, or around the upper part.) Alternatively, the side of the excimer lamp may be divided into two, and a semi-cylindrical ozone gas generation tank may be provided on one side. (In this case, a liquid treatment tank may be provided on the other side.) The material of the ozone gas generating tank is not particularly limited, but examples thereof include quartz, PTFE, PFA, stainless steel, and aluminum.

[0020] (Gas-liquid mixing section) In the first embodiment, although not limited thereto, ozone gas generated in an ozone gas generating tank is mixed with liquid by a gas-liquid mixing section. The gas-liquid mixing section includes an intake pipe and a water supply pipe. The water supply pipe of the gas-liquid mixing section includes, but is not limited to, for example, a small diameter section, a large diameter section upstream of the small diameter section, and an expanded diameter section downstream of the small diameter section, and the opening of the air supply pipe is disposed in the small diameter section or the expanded diameter section, and ozone water is generated by mixing ozone gas with water flowing through the water supply pipe from the opening of the air supply pipe by utilizing the suction effect caused by the flow of water in the water supply pipe. The gas-liquid mixing section includes, but is not limited to, for example, an inlet section upstream of the large diameter section and an outlet section downstream of the expanded diameter section, the inner diameters of the inlet section and the outlet section are equal to or less than the inner diameter of the large diameter section, and the inner diameter of the inlet section and the inner diameter of the outlet section are equal to each other.

[0021] FIG. 2 shows a cross-sectional view of one embodiment of the gas-liquid mixing section, and the gas-liquid mixing section 21 will be described based on FIG. 2, but the gas-liquid mixing section is not limited to this embodiment. The gas-liquid mixing section 21 includes an intake pipe 22 and a water supply pipe 23. The intake pipe 22 of the gas-liquid mixing section 21 supplies the ozone gas generated in the ozone generating section to the gas-liquid mixing section. The water supply pipe 23 includes an inlet section 24 into which water flows in upstream, and an outlet section 25 from which ozone water flows out downstream. The water supply pipe 23 includes a large diameter section 26, a reduced diameter section 27, a small diameter section 28, and an expanded diameter section 29 from upstream. The intake pipe 23 is installed along the liquid flow 30 of the water supply pipe 23 and has an opening 31 at its end. Ozone gas flows through the intake pipe and is released from the opening 31 into the water in the water supply pipe. Thus, the liquid flow 30 and the ozone gas flow 32 are parallel at the opening 31 of the water supply pipe 23 where the ozone gas and the water are mixed. In the embodiment of FIG. 2, the intake pipe is inserted parallel (coaxially) into the water supply pipe from the top. However, the intake pipe may be inserted into the water supply pipe from any direction in the gas-liquid mixing section, for example, from the side, as long as the ozone gas flow 32 from the opening 31 of the intake pipe is parallel to the liquid flow 30 of the water supply pipe. For example, when the intake pipe is inserted into the water supply pipe from the side, the intake pipe can be bent downward in the water supply pipe to open the opening 31 of the intake pipe downward. This allows the ozone gas flow 32 and the liquid flow 30 to be parallel. That is, at the opening of the intake pipe, the water supply pipe and the air supply pipe are preferably coaxial with each other.

[0022] The inner diameter of the large diameter part of the water supply pipe is not particularly limited, but is 13 to 26 mm, preferably 13 to 15 mm, and more preferably 14 mm. The length of the large diameter part is also not particularly limited, but is, for example, 16 to 50 mm. The inner diameter of the small diameter part of the water supply pipe is not particularly limited, but is 3 to 6 mm, preferably 3 to 4 mm, and more preferably 3 mm. The length of the small diameter part is also not particularly limited as long as the effects of the present invention can be obtained, but is, for example, 1 to 15 mm, preferably 1 to 4 mm, and more preferably 1 mm.

[0023] (liquid) The liquid to be treated by the liquid treatment device of the present invention is not particularly limited as long as it contains a component that can be decomposed by hydroxyl radicals, and examples of the liquid include wastewater, wastewater (industrial wastewater, medical wastewater, agricultural wastewater, or domestic wastewater), and hydroponic cultivation solutions. When the liquid to be treated contains persistent organic matter, the persistent organic matter can be decomposed by the hydroxyl radicals. Examples of the persistent organic matter include surfactants, organic acids, endocrine disrupters, pharmaceuticals, and agricultural chemicals.

[0024] (Air bubble supply section) In the second embodiment, the gas containing ozone gas is mixed with the liquid in the liquid treatment tank 7 from the bubble supply unit 18 provided at the bottom of the ozone gas generation tank 6, and is contained (dissolved) in the liquid. The structure of the bubble supply unit is not particularly limited as long as it can supply the gas containing ozone gas to the liquid treatment tank.

[0025] Liquid treatment tank In the liquid treatment tank of the liquid treatment device of the present invention, a liquid containing ozone gas is irradiated with ultraviolet light from an excimer lamp to generate hydroxyl radicals, which can decompose persistent organic matter in the liquid. In the first embodiment, as shown in Fig. 1, an untreated liquid containing ozone is introduced into a liquid treatment tank 7 through a liquid inlet 10. The untreated liquid containing ozone is irradiated with ultraviolet light by an excimer lamp 2, and hydroxyl radicals are generated. The hydroxyl radicals can decompose difficult-to-decompose organic matter and the like, and turn the liquid into a harmless treated liquid. The treated liquid can be discharged, for example, through a liquid outlet 11. In the second embodiment, as shown in FIG. 3, an untreated liquid is introduced into a liquid treatment tank 7. An ozone-containing gas is supplied to the untreated liquid from an air bubble supply unit 18, and the ozone gas is mixed (dissolved) in the untreated liquid by aeration. The liquid mixed with the ozone gas is irradiated with ultraviolet light by an excimer lamp 2, and hydroxyl radicals are produced. The hydroxyl radicals can decompose difficult-to-decompose organic matter in the liquid, and turn it into a harmless treated liquid. In the second embodiment, as in the first embodiment, the liquid treatment tank is provided with a liquid inlet 10 and a liquid outlet 11, and the liquid treatment can be carried out as a one-pass method (circulation method).

[0026] (Gas-liquid separation section) In the first or second embodiment of the present invention, the treated liquid may be discharged as it is, but the treated liquid may be separated from the excess ozone gas that is not dissolved in water by a gas-liquid separation section. The gas-liquid separation section includes an inner pipe to which the treated liquid and excess ozone gas are supplied, and an outer pipe which separates the excess ozone gas from the treated liquid and discharges each of them. The gas-liquid separation section includes an inner pipe and an outer pipe arranged coaxially along the vertical direction, and the inner pipe is inserted into the outer pipe from the lower part of the outer pipe and has an upper opening inside the outer pipe. The liquid treated in the liquid treatment tank is made to flow in from the lower part of the inner pipe and discharged from the upper opening into the outer pipe, and the excess ozone gas that is not dissolved in water is separated. The excess ozone gas is discharged from the upper opening of the outer pipe, and the treated liquid from which the excess ozone gas has been separated is discharged from the lower opening of the outer pipe.

[0027] FIG. 4 shows a cross-sectional view of one embodiment of the gas-liquid separation section, and the gas-liquid separation section 41 will be described with reference to FIG. 4, however, the present invention is not limited to this embodiment. An inner pipe 43 is inserted from the lower part of the outer pipe 42, and has an opening 44 at the upper end of the inner pipe 43. The treated liquid flowing out from the outlet 25 of the gas-liquid mixing section contains excess ozone gas, and the ozone-containing liquid containing the excess ozone gas flows in from the lower part of the inner pipe, rises in the inner pipe along with the flow 45 of the ozone-containing liquid, and flows into the outer pipe 42 from the opening 44. The treated liquid that flows into the outer pipe flows downward in the outer pipe 42 and is discharged from the lower opening 46 of the outer pipe 42. On the other hand, the excess ozone gas moves upward in the outer pipe 42 and is discharged from the upper opening 47 along with the flow 48 of the ozone gas.

[0028] The flows of the oxygen-containing raw material gas, ozone gas, ozone-containing liquid, and treated liquid in the liquid treatment apparatus of the present invention will be described with reference to FIG. The raw gas containing oxygen is taken into the ozone gas generating tank (ultraviolet ray irradiation unit) from outside the apparatus through the dehumidification unit. The dehumidification unit is not particularly limited as long as it can dehumidify the raw gas, but it can dehumidify water by using silica gel, for example. The ozone gas generated in the ozone gas generation tank (ultraviolet ray irradiation section) is supplied to the gas-liquid mixing section. Meanwhile, the liquid is supplied to the gas-liquid mixing section from the flow rate adjustment section. In the gas-liquid mixing section, the liquid and the ozone gas are mixed, and an ozone-containing liquid is generated as described above. The generated ozone-containing liquid is transferred to the liquid treatment tank (ultraviolet ray irradiation section). The liquid treated in the liquid treatment tank is separated into the treated liquid and excess ozone gas as described above in the gas-liquid separation section, and the treated liquid is supplied to the outside of the device. Meanwhile, the excess ozone gas is discharged to the outside of the device through the ozone removal section. The ozone removal section is not particularly limited as long as it can remove ozone gas, but for example, ozone can be removed by activated carbon.

[0029] The piping, power supply unit, control unit, etc. in the liquid treatment device of the present invention will be described with reference to FIG. The liquid treatment device of the present invention can be divided into a front region, a central region, and a rear region, although it is not limited thereto. For example, the rear region can be provided with a lamp power supply unit that applies a high-frequency high voltage to the excimer lamp, a control unit that controls the lamp power supply unit and the flow rate adjustment unit, a low-voltage power supply unit that supplies power to the lamp power supply unit and the control unit, and an ultraviolet ray irradiation unit (ozone gas generation tank and liquid treatment tank). The central region can be provided with a flow rate adjustment unit that adjusts the flow rate of water supplied to the gas-liquid mixing unit, a gas-liquid mixing unit, and a gas-liquid separation unit. Furthermore, the front region can be provided with an ozone removal unit and a dehumidification unit. The liquid treatment device may have a partition that divides the internal space of the device, and piping through which a liquid flows, including the flow rate control unit, the gas-liquid mixing unit, and the gas-liquid separation unit, can be arranged in the spatial region on one side of the partition, and piping through which a gas flows, including the ultraviolet irradiation unit, the control unit, a low-voltage circuit operating at a low voltage including the low-voltage power supply unit, and a high-frequency high-voltage circuit generating a high-frequency high voltage including the lamp power supply can be arranged in the spatial region on the other side of the partition.

[0030] Furthermore, the liquid treatment device of the present invention can have an inlet for supplying liquid to the flow rate control section from the rear side of the device, an outlet for discharging treated liquid from the front side of the device from which excess ozone gas has been separated by the gas-liquid separator, a dehumidification section for dehumidifying the raw material gas flowing into the ultraviolet irradiation section, and an ozone removal section for removing the ozone gas separated in the gas-liquid separation section. Furthermore, the dehumidification section and the ozone removal section can be arranged in the spatial region on one side of the partition wall, on the front side of the device relative to piping through which liquid flows, including the flow rate control section, the gas-liquid mixing section, and the gas-liquid separation section.

[0031] When a discharge method is used to generate ozone gas, nitrogen oxides are generated. Therefore, when ozone gas generated by a discharge method is mixed with a liquid, nitrogen oxides are contained in the liquid. On the other hand, in the present invention, ozone gas is generated using an excimer lamp. That is, as shown in FIG. 8(A), nitrogen oxides are not generated when ozone gas is generated by an excimer lamp. Therefore, the liquid containing ozone gas in the liquid treatment device of the present invention has a nitrogen oxide concentration of 3.0 vol% or less, preferably 2.5 vol% or less, more preferably 2.0 vol% or less, more preferably 1.5 vol% or less, more preferably 1.0 vol% or less, more preferably 0.5 vol% or less, more preferably 0.3 vol% or less, and more preferably 0.1 vol% or less, relative to the ozone gas concentration. Nitrogen oxides exist as nitrate ions or nitrite ions in aqueous solutions, lowering the pH. It is presumed that a low nitrogen oxide concentration suppresses the decrease in pH of the liquid containing ozone gas, thereby suppressing the self-decomposition of ozone and not adversely affecting the self-decomposition of ozone.

[0032] Hydroxy radicals can be generated by irradiating a liquid with ultraviolet light alone or by supplying ozone gas alone to a liquid. However, as in the liquid treatment device of the present invention, irradiating a liquid containing ozone gas with ultraviolet light can efficiently generate hydroxyl radicals. FIG. 7 shows the efficiency of generating hydroxyl radicals by irradiating a liquid with ultraviolet light alone, by supplying ozone gas alone to a liquid, or by irradiating a liquid containing ozone gas with ultraviolet light, using sodium terephthalate. In the liquid treatment device of the present invention, although not limited thereto, the efficiency of generation of hydroxyl radicals by ozone gas and ultraviolet irradiation from an excimer lamp is 8 μM / hW or more, preferably 9 μM / hW or more, more preferably 10 μM / hW or more, even more preferably 11 μM / hW or more, and even more preferably 12 μM / hW or more. Furthermore, the efficiency of generating OH radicals by ultraviolet irradiation from an excimer lamp is not limited, but is 5 μM / hW or more, preferably 6 μM / hW or more, and more preferably 7 μM / hW or more.

[0033] The hydroxyl radicals generated in the liquid treatment device of the present invention undergo self-decomposition to produce hydrogen peroxide. In the liquid treatment device of the present invention, it is believed that the excimer lamp generates H radicals and OH radicals from water molecules, and hydrogen peroxide is decomposed by the H radicals, so that the hydrogen peroxide concentration can be maintained low. The hydrogen peroxide concentration generated by the liquid treatment device of the present invention is less than 0.5 mg / L, preferably less than 0.4 mg / L, more preferably less than 0.3 mg / L, even more preferably less than 0.2 mg / L, and even more preferably less than 0.1 mg / L.

[0034] [2] Liquid treatment method The liquid treatment method of the present invention includes a step of irradiating an oxygen-containing raw material gas with an excimer lamp to generate ozone gas, a step of mixing the generated ozone gas with a liquid, and a step of irradiating the liquid containing the ozone gas with ultraviolet light from the excimer lamp to generate OH radicals to treat the liquid. The liquid treatment method of the present invention can be carried out using the liquid treatment device, although it is not limited thereto.

[0035] <<Process for generating ozone gas (1)>> In the step (1) of generating ozone gas, an excimer lamp is irradiated to a raw material gas containing oxygen to generate ozone gas. The "raw material gas containing oxygen" and the "excimer lamp" can be any of those described in the above section "(1) Liquid treatment device" without being limited thereto.

[0036] <Step (2) of mixing ozone gas into liquid> In the step (2) of mixing the ozone gas with the liquid, the generated ozone gas is mixed with the liquid. Although there is no limitation on the mixing method of the ozone gas with the liquid, for example, the gas-liquid mixing unit or the bubble supply unit described in the above section "[1] Liquid treatment device" can be used.

[0037] <<Liquid Processing Step (3)>> In the step (3) of treating the liquid, the liquid containing ozone gas is irradiated with ultraviolet light from an excimer lamp to generate OH radicals, thereby treating the liquid. The treatment of the liquid with hydroxyl radicals can be carried out using the liquid treatment tank described in the above section "[1] Liquid Treatment Apparatus."

[0038] In the liquid treatment method of the present invention, the liquid containing ozone gas has a nitrogen oxide concentration of 3.0 vol% or less relative to the ozone gas concentration. The nitrogen oxide concentration is preferably 2.5 vol% or less, more preferably 2.0 vol% or less, more preferably 1.5 vol% or less, more preferably 1.0 vol% or less, more preferably 0.5 vol% or less, more preferably 0.3 vol% or less, and more preferably 0.1 vol% or less relative to the ozone gas concentration.

[0039] In the liquid treatment method of the present invention, the efficiency of generating OH radicals by ozone gas and ultraviolet irradiation from the excimer lamp is 8 μM / hW or more, preferably 9 μM / hW or more, more preferably 10 μM / hW or more, even more preferably 11 μM / hW or more, and even more preferably 12 μM / hW or more. In the liquid treatment method of the present invention, the efficiency of generating OH radicals by ultraviolet irradiation from the excimer lamp is not limited, but is 5 μM / hW or more, preferably 6 μM / hW or more, and more preferably 7 μM / hW or more.

[0040] In the liquid treatment method of the present invention, H radicals and OH radicals are generated from water molecules by the excimer lamp, and the concentration of hydrogen peroxide generated by self-decomposition of the generated OH radicals is less than 0.5 mg / L, preferably less than 0.4 mg / L, more preferably less than 0.3 mg / L, even more preferably less than 0.2 mg / L, and even more preferably less than 0.1 mg / L. EXAMPLES

[0041] The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited thereto.

[0042] Example 1 In this example, sodium terephthalate was used to examine the efficiency of generating hydroxyl radicals when a liquid containing ozone gas was irradiated with ultraviolet light from an excimer lamp, when a liquid not containing ozone gas was irradiated with ultraviolet light from an excimer lamp, or when ozone gas was added to a liquid. Using one excimer lamp, VUV irradiation and / or ozone gas supply were performed on 450 mL of 4 mM disodium terephthalate aqueous solution. The ozone gas flow rate was 0.2 L / min, and the treatment time was a maximum of 10 min. It is known that disodium terephthalate reacts with hydroxyl radicals to become 2-hydroxyterephthalic acid, which exhibits specific fluorescence. Therefore, to measure the concentration of 2-hydroxyterephthalic acid in the treated aqueous solution, a fluorescence spectrophotometer was used to measure the fluorescence intensity at an excitation wavelength of 310 nm and a measurement wavelength of 425 nm, and the concentration was calculated from a calibration curve prepared using a standard substance. The OH radical trapping rate of disodium terephthalate is said to be 35%, and the amount of OH radical generation was estimated from the 2-hydroxyterephthalic acid concentration and trapping rate. As shown in FIG. 7, when ultraviolet light was applied from an excimer lamp to a liquid containing ozone gas, the efficiency of generating hydroxyl radicals was high.

[0043] Example 2 In this example, the amounts of nitrogen oxides produced were compared when ozone gas was generated by a discharge method and when ozone gas was generated by an excimer lamp. The ozone bubbling treatment was carried out with 300 mL of pure water, with the gas flow rate adjusted to 3 L / min. A hollow-type smart excimer UV lamp (Oak Manufacturing) was used as the ozone generator for the excimer UV type, and an ozone unit (GLOGLOW) was used for the discharge type. The input voltage for the discharge type was adjusted so that the ozone concentration was equivalent to that of the excimer UV type. Figure 8(A) shows the ozone concentration measured from the absorbance at 254 nm using a UV-visible spectrophotometer (V-660, JASCO). The ozone generation rate for each was 29 mg / h for the excimer UV type and 30 mg / h for the discharge type. 1 mL of the treatment liquid was periodically sampled, and NO3 was detected using an ion chromatograph (Ion Chromatography System, JASCO). - The concentration was measured. The pH was measured using pH test paper (Isis). The discharge type was used to measure the NO3 - The concentration increased significantly, and the estimated NO3 -The production amount was 1.0mg / h (P<0.001, regression analysis). On the other hand, the production amount of the excimer UV type was estimated to be 0.012mg / h (P<0.001, regression analysis), which was lower than that of the discharge type. - No increase in concentration was observed. - The ratio of the amount generated was 3.3% for the discharge type and 0.042% for the excimer UV type, which is 79 times higher for the discharge type. Figure 8(B) shows the pH change due to ozone bubbling with different ozone generation methods. With the discharge type, a clear change was observed on the test paper after 24 hours of treatment, and the pH had dropped to 2 after 72 hours of treatment. On the other hand, there was almost no change with the excimer UV type, confirming that the difference in the amount of NOx generated affects the drop in pH. As shown in FIG. 8(A), when ozone gas was generated by the discharge method, nitrogen oxides were produced, but when ozone gas was generated by the excimer lamp, almost no nitrogen oxides were produced.

[0044] Example 3 In this example, we investigated the dissolved ozone gas concentration and hydrogen peroxide concentration when a liquid containing ozone gas was irradiated with ultraviolet light from an excimer lamp (172 nm) or a low-pressure mercury lamp (254 nm). Using the device shown in Figure 9(A), the ozone concentration and hydrogen peroxide concentration in water were measured for 100 minutes. As shown in Figure 9(B), the hydrogen peroxide concentration was high at 254 nm, which is believed to be due to the self-decomposition of hydroxyl radicals into hydrogen peroxide upon exposure to ultraviolet light.

[0045] Example 4 In this example, we investigated the decomposition of refractory organic matter when a liquid containing ozone gas was irradiated with ultraviolet light from an excimer lamp (VUV+O3), when a liquid not containing ozone gas was irradiated with ultraviolet light from an excimer lamp (VUV), or when ozone gas was added to a liquid (O3). As shown in Figure 10, the decomposition of refractory organic matter progressed in the order of O3, VUV, and VUV+O3. In particular, VUV+O3 showed a better decomposition rate than the combined decomposition rates of O3 alone and VUV alone. [Industrial Applicability]

[0046] The liquid treatment apparatus and liquid treatment method of the present invention are capable of efficiently decomposing difficult-to-decompose organic matter in waste liquid or drainage water. [Explanation of symbols]

[0047] 1. Liquid treatment equipment; 2. Excimer lamp; 3...inner tube; 4...outer tube; 5...inner electrode; 6. Ozone gas generator; 7···Liquid treatment tank; 8 Gas inlet; 9 Gas outlet; 10...Liquid inlet; 11...liquid outlet; 12... Oxygen-containing feed gas; 13...liquid; 14...· A stream of oxygen-containing feed gas; 15 · · · Ozone-containing gas stream; 16···Untreated liquid stream containing ozone; 17···Treatment liquid flow; 18... Air bubble supply section; 21... Gas-liquid mixing section; 22···Intake pipe; 23...liquid supply pipe; 24...Inflow part; 25···Outflow section; 26 ···Large diameter section; 27...Reduced diameter part; 28...small diameter section; 29... Expanded diameter part; 30... Liquid flow; 31....Feed pipe opening; 32···Ozone gas flow; 41... Gas-liquid separation section; 42...outer tube; 43...inner tube; 44...opening; 45···Stream of ozone-containing liquid; 46...downward opening; 47...Upper opening; 48···Ozone gas flow;

Claims

1. A liquid treatment device using OH radicals, Excimer lamps, An ozone gas generating tank for generating ozone gas by irradiating an oxygen-containing raw material gas with an excimer lamp; and A liquid treatment tank in which the liquid containing the generated ozone gas is irradiated with ultraviolet light from an excimer lamp; A liquid treatment device comprising:

2. The liquid treatment device according to claim 1 , further comprising a gas-liquid mixing section for mixing ozone gas with the liquid.

3. 3. The liquid treatment apparatus according to claim 1, wherein the concentration of nitrogen oxides in the liquid containing ozone gas is 3.0 vol % or less with respect to the concentration of ozone gas.

4. 3. The liquid treatment device according to claim 1, wherein the efficiency of generating OH radicals by ozone gas and ultraviolet irradiation from the excimer lamp is 8 μM / hW or more, and the efficiency of generating OH radicals by ultraviolet irradiation from the excimer lamp is 5 μM / hW or more.

5. 3. The liquid treatment device according to claim 1, wherein the excimer lamp generates H radicals and OH radicals from water molecules, and the concentration of hydrogen peroxide generated by self-decomposition of the generated OH radicals is less than 0.5 mg / L.

6. A step of irradiating an oxygen-containing raw material gas with an excimer lamp to generate ozone gas; Mixing the generated ozone gas with a liquid; and A step of treating the liquid by irradiating the liquid containing ozone gas with ultraviolet light from an excimer lamp to generate OH radicals; A method for treating a liquid comprising the steps of:

7. 7. The liquid treatment method according to claim 6, wherein the liquid containing ozone gas has a nitrogen oxide concentration of 3.0 vol.% or less with respect to the ozone gas concentration.

8. 8. The liquid treatment method according to claim 6, wherein the efficiency of generating OH radicals by ozone gas and ultraviolet irradiation from the excimer lamp is 8 μM / hW or more, and the efficiency of generating OH radicals by ultraviolet irradiation from the excimer lamp is 5 μM / hW or more.

9. 8. The liquid treatment method according to claim 6, wherein H radicals and OH radicals are generated from water molecules by the excimer lamp, and the concentration of hydrogen peroxide generated by self-decomposition of the generated OH radicals is less than 0.5 mg / L.

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