Processing method for organic fluorine compound

Abstract

Provided is a processing method with which it is possible to efficiently process an organic fluorine compound contained in a processing target liquid.　This processing method for processing an organic fluorine compound contained in a processing target liquid comprises: a step (a) for supplying electrons in and through the processing target liquid between a first electrode and a second electrode disposed apart from the first electrode; and a step (b) for, while said step (a) is being executed, irradiating the processing target liquid with ultraviolet rays exhibiting light emission intensity at least in a wavelength range of 200 nm or less.

Description

Method for treating organic fluorine compounds

[0001] The present invention relates to a method for treating an organic fluorine compound.

[0002] Because of their excellent chemical stability, organic fluorine compounds are used in a variety of industries, such as for water-repellent clothing, coatings for cookware, food packaging containers, cosmetics, fire extinguishing materials, etc. Representative examples of organic fluorine compounds include perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS).

[0003] Due to their stability, organic fluorine compounds are difficult to decompose even when released into the environment, and their accumulation in aquatic environments such as rivers and groundwater has been confirmed. Furthermore, it has been pointed out that organic fluorine compounds are toxic to the environment and have adverse effects on the human body, such as carcinogenicity. Therefore, various techniques for decomposing organic fluorine compounds have been proposed, as shown in Patent Documents 1 and 2 below, for example.

[0004] Incineration is one example of a method for decomposing organic fluorine compounds. For example, in Patent Document 1 listed below, organic fluorine compounds contained in a liquid to be treated are adsorbed by an adsorbent such as activated carbon, and the adsorbent is heated in a high-temperature environment of about 1000°C, thereby vaporizing the liquid to be treated and decomposing the organic fluorine compounds.

[0005] In addition, in Patent Document 2 listed below, an oxidizing agent such as hypochlorite is added to the liquid to be treated, and then ultraviolet light is irradiated to treat odorous substances such as organic fluorine compounds.

[0006] JP 2021-146326 A JP 2022-129495 A

[0007] The technology described in Patent Document 1 requires heating the liquid to be treated to a high temperature in order to treat the organic fluorine compounds, which requires a great deal of energy. Furthermore, the technology described in Patent Document 2 requires the use of an oxidizing agent such as hypochlorite in addition to irradiating the liquid to be treated with ultraviolet light. Therefore, even if the organic fluorine compounds in the liquid to be treated can be decomposed, it becomes necessary to remove components derived from the oxidizing agent remaining in the liquid to be treated. Thus, conventional technologies have not been able to efficiently treat organic fluorine compounds in the liquid to be treated.

[0008] Recently, in consideration of the toxicity of organic fluorine compounds to the environment, etc., expanded restrictions on the use of organic fluorine compounds are being considered. Because organic fluorine compounds are used in a wide variety of industries, realizing a method for efficiently treating organic fluorine compounds is an urgent issue for maintaining industrial activity while suppressing their impact on the environment.

[0009] In view of the above circumstances, an object of the present invention is to provide a treatment method capable of efficiently treating organic fluorine compounds contained in a liquid to be treated.

[0010] A method for treating an organic fluorine compound according to the present invention is a method for treating an organic fluorine compound contained in a liquid to be treated, and includes: a step (a) of supplying electrons into the liquid to be treated via the liquid to be treated between a first electrode and a second electrode disposed at a distance from the first electrode; and a step (b) of irradiating the liquid to be treated with ultraviolet light that exhibits an emission intensity in a wavelength range of at least 200 nm or less during the execution of the step (a).

[0011] In this specification, "exhibiting luminescence intensity" means that the luminescence intensity is 40% or more of the luminescence intensity at the peak wavelength on the luminescence spectrum. Typically, the luminescence intensity at the peak wavelength means the maximum luminescence intensity on the luminescence spectrum.

[0012] Although details will be described later in the section "Mode for Carrying Out the Invention," in the above method, the electrons supplied to the liquid to be treated and the ultraviolet light irradiated onto the liquid to be treated provide energy to the organic fluorine compounds in the liquid to be treated, thereby accelerating the reaction of decomposing the organic fluorine compounds. For example, the electrons may be electrons supplied by discharging the liquid to be treated. Furthermore, the irradiation of ultraviolet light can generate hydroxyl radicals in the liquid to be treated, thereby accelerating the decomposition reaction of the organic fluorine compounds.

[0013] In other words, the above method does not require a temperature high enough to vaporize the liquid to be treated. Furthermore, the above method can decompose and treat the organic fluorine compounds in the liquid to be treated without requiring an oxidizing agent such as hypochlorite. Thus, the above method makes it possible to efficiently treat the organic fluorine compounds in the liquid to be treated.

[0014] In the method for treating an organic fluorine compound, the step (a) may include a step of supplying electrons between the first electrode located in the liquid to be treated and the second electrode located outside the liquid to be treated.

[0015] Furthermore, in the above-mentioned method for treating an organic fluorine compound, the step (b) may include a step of irradiating the liquid to be treated with ultraviolet light from an arc tube located within the liquid to be treated and containing a light-emitting gas, and the step (a) may include a step of generating a discharge between the first electrode located inside the arc tube and the second electrode located at a distance from the arc tube.

[0016] In the above method, a voltage required to light the arc tube is applied to the first electrode and the second electrode, thereby generating a discharge in the liquid to be treated and irradiating the liquid with ultraviolet light. Therefore, according to the above method, a common power source can be used to generate a discharge in the liquid to be treated and to obtain the ultraviolet light to irradiate the liquid to be treated, thereby reducing the space required to install a system that performs the treatment method.

[0017] In the above-described method for treating an organic fluorine compound, the supply of electrons between the first electrode and the second electrode may be effected by interposing a dielectric between the first electrode and the liquid to be treated and / or between the second electrode and the liquid to be treated.

[0018] According to the above method, one or both of the first electrode and the second electrode can generate a discharge without contacting the liquid to be treated, which is preferable because deterioration of the electrodes due to contact with the liquid to be treated is suppressed.

[0019] Furthermore, deterioration of the first electrode or the second electrode is also expected due to the accumulated operating time of the system performing the treatment method. If the first electrode and the second electrode were in contact with the liquid to be treated, impurities from the electrodes would be expected to be mixed into the liquid to be treated. In contrast, according to the above method, at least one of the first electrode and the second electrode is kept out of contact with the liquid to be treated, thereby reducing the mixing of the impurities. In view of the above, it is more preferable that both the first electrode and the second electrode are kept out of contact with the liquid to be treated. In other words, it is a more preferable embodiment that a dielectric is interposed between both the first electrode and the liquid to be treated and between the second electrode and the liquid to be treated.

[0020] In the method for treating an organic fluorine compound, the liquid to be treated may be in a flowing state during the steps (a) and (b).

[0021] In the method for treating an organic fluorine compound, the step (b) may include a step (b1) of irradiating the liquid to be treated with ultraviolet light having an emission intensity in the wavelength range of more than 200 nm and less than 280 nm.

[0022] According to the above method, hydroxyl radicals that contribute to the decomposition reaction of organic fluorine compounds are more likely to be generated in the liquid to be treated, thereby enabling the treatment of organic fluorine compounds to proceed more efficiently.

[0023] The method for treating an organic fluorine compound may further include a step (c) of adding a calcium compound or a sodium compound to the liquid to be treated after the step (b).

[0024] According to the above method, it is possible to immobilize fluorine generated in the liquid to be treated after decomposition of the organic fluorine compounds. By immobilizing fluorine in the liquid to be treated, the environmental impact of fluorine derived from the organic fluorine compounds can be suppressed, which is preferable.

[0025] According to the present invention, there is provided a treatment method capable of efficiently treating organofluorine compounds contained in a liquid to be treated.

[0026] 1 is a diagram schematically showing an example of the configuration of a processing system for organic fluorine compounds. FIG. 2 is a flow diagram showing an example of a processing method according to the present invention. FIG. 3 is a diagram showing a state in which the liquid to be processed is stored in a chamber in FIG. 1. FIG. 4 is a diagram showing a decomposition flow of organic fluorine compounds. FIG. 5 is a diagram showing another example of the decomposition flow of organic fluorine compounds, similar to FIG. 4. FIG. 6 is a diagram showing yet another example of the decomposition flow of organic fluorine compounds. FIG. 7 is a diagram schematically showing an experimental system used for verification. FIG. 8 is a graph showing the results of the verification. FIG. 9 is a diagram schematically showing the configuration of a second embodiment of a processing system. FIG. 10 is a flow diagram showing another example of a processing method, similar to FIG. 2. FIG. 11 is a diagram schematically showing the configuration of a third embodiment of a processing system. FIG. 12 is a diagram schematically showing the configuration of a fourth embodiment of a processing system. FIG. 13 is a diagram schematically showing another example of the configuration of a processing system according to the fourth embodiment. FIG. 14 is a diagram schematically showing another embodiment of a processing system. FIG. 15 is a diagram schematically showing yet another example of the configuration of a processing system.

[0027] Hereinafter, embodiments of the method for treating an organic fluorine compound according to the present invention (sometimes simply referred to as a "treatment method") will be described with reference to the drawings as appropriate. Note that the drawings are all schematic illustrations, and the dimensional ratios and numbers in the drawings do not necessarily correspond to the actual dimensional ratios and numbers.

[0028] 1 is a diagram schematically illustrating an example of the configuration of a processing system 1 for organic fluorine compounds, which is capable of executing a processing method according to the present invention. The configuration of the processing system 1 will be described with reference to FIG. 1, and then the processing method executed by the processing system 1 will be described.

[0029] As shown in FIG. 1, the processing system 1 includes an arc tube 11, a chamber 12, a lighting power supply 20, and an electrode 13a.

[0030] The chamber 12 is a container capable of storing the treatment target liquid W1 (not shown in FIG. 1 , see FIG. 3 described later) therein. As an example, the chamber 12 has a pipe 14a and a pipe 14b, as shown in FIG. 1 . A valve 15a that switches the open / close state of the pipe 14a is installed in the pipe 14a. Furthermore, a valve 15b that switches the open / close state of the pipe 14b is installed in the pipe 14b. When the treatment target liquid W1 has flowed into the chamber 12, the valves (15a, 15b) are closed, thereby allowing the treatment target liquid W1 to be stored in the internal space of the chamber 12.

[0031] In this embodiment, the side wall 12a of the chamber 12 is made of a conductive metal material. In Fig. 1, the side wall 12a of the chamber 12 is hatched. As shown in Fig. 1, the side wall 12a is connected to the lighting power supply 20 and is electrically grounded. In other words, the chamber 12 in this embodiment functions as both a container for storing the treatment target liquid W1 and as the electrode 13b.

[0032] The electrode 13b comes into contact with the liquid W1 to be treated when the liquid W1 is fed into the chamber 12. In view of this, the metal material constituting the electrode 13b (side wall portion 12a) is preferably, for example, platinum, gold, silver, or stainless steel. The electrode 13b may be electrically conductive and may have a coating or plating made of the above-mentioned metal material at the portion that contacts the liquid W1 to be treated. This reduces the cost of the material constituting the electrode 13b. The electrode 13b may also be coated with glass or ceramics. This allows the electrode 13b to be kept out of contact with the liquid W1 to be treated. In other words, the above-mentioned metal materials are merely examples, and the metal material constituting the electrode 13b can be selected as appropriate.

[0033] The chamber 12 also has an insertion portion 16 at a portion of the outer wall surface for inserting the arc tube 11 therein.

[0034] The arc tube 11 is made of a dielectric material. For example, the arc tube 11 is a tube made of a glass material such as quartz glass. In this embodiment, the arc tube 11 is inserted through the insertion portion 16 and placed in the chamber 12. As a result, the arc tube 11 is positioned in the liquid W1 to be treated when the liquid W1 is fed into the chamber 12 (see FIG. 3 , described later). While FIG. 1 shows an example in which the arc tube 11 is supported at one end, the arc tube 11 may also be supported at both ends. In this case, it is preferable that the member supporting the arc tube 11 is electrically insulated from the electrode 13b and that creeping discharge on the surface of the member is suppressed. It is also preferable that the insertion portion 16 is sealed to prevent leakage of the liquid W1 to be treated therein.

[0035] Furthermore, xenon (Xe) gas, for example, is sealed as a light-emitting gas in the light-emitting space 11a of the light-emitting tube 11. As an example, the pressure of the sealed light-emitting gas is 0.1 MPa to 0.5 MPa.

[0036] As shown in FIG. 1 , the electrode 13a is disposed within the light-emitting space 11a of the arc tube 11. As a result, when the liquid W1 to be treated is introduced into the chamber 12, the electrode 13a is positioned within the liquid W1 together with the arc tube 11 (see FIG. 3 , described below). As an example, the electrode 13a is rod-shaped and made of a metal material such as tungsten, molybdenum, titanium, or aluminum. Selecting one of these metal materials is preferable because it suppresses evaporation of the electrode 13a during lighting. The electrode 13a may also be coated with glass or ceramics. In other words, the material of the electrode 13a is not limited to the above. The electrode 13a is connected to the lighting power supply 20 via a pinch seal 17 formed at one end of the arc tube 11. Multiple arc tubes 11 may be used.

[0037] In this embodiment, the electrode 13a corresponds to the "first electrode" and the electrode 13b corresponds to the "second electrode."

[0038] The lighting power supply 20 applies to the electrodes 13a and 13b a voltage required to light the arc tube 11. As an example, the lighting power supply 20 applies a high-frequency AC voltage of 10 kHz to 5 MHz between the electrodes 13a and 13b.

[0039] As an example, the diameter of the arc tube 11 is 10 mm to 30 mm, and the overall length of the arc tube 11 is 100 mm to 200 mm. The overall length of the electrode 13a is 80 mm to 180 mm. The internal volume of the chamber 12 is, for example, 200 mL to 700 mL. Note that these are merely examples, and the configuration of the processing system 1 can be designed appropriately depending on, for example, the total amount of the liquid to be processed W1.

[0040] (Method for Treating Organic Fluorine Compounds) Next, a method for treating organic fluorine compounds, which is executed by the treatment system 1, will be described.

[0041] 2 is a flow chart showing an example of a processing method according to the present invention. In the following description, reference will be made to the reference numerals assigned to the steps in FIG. 2 as appropriate.

[0042] (Preparation step S1) The liquid to be treated W1 is prepared in the chamber 12 via the pipe 14a. As an example, when the liquid to be treated W1 has flowed into the chamber 12, the valves (15a, 15b) are closed, thereby storing the liquid to be treated W1 in the chamber 12. Fig. 3 is a diagram showing the state in Fig. 1 where the liquid to be treated W1 is stored in the chamber 12.

[0043] 3, the light emitting tube 11 and the electrode 13a are located in the liquid W1 to be treated when the liquid W1 is stored in the chamber 12. Also, the electrode 13b is located outside the liquid W1 to be treated, as shown in FIG.

[0044] Examples of the liquid to be treated W1 include industrial wastewater from a chemical plant that uses or produces organic fluorine compounds, or groundwater on or around the premises of such a chemical plant. The liquid to be treated W1 may also be groundwater on or around the premises of a facility where a large amount of extinguishing material is installed, or may be, for example, wash water used to wash soil contaminated by the above-mentioned groundwater. Furthermore, the liquid to be treated W1 may also be wash water generated in a process for washing and regenerating activated carbon or ion exchange resin used for the purpose of reducing the concentration of organic fluorine compounds in the above-mentioned groundwater, etc. Similarly, the liquid to be treated W1 may also be a separated liquid containing organic fluorine compounds obtained when the above-mentioned groundwater, etc., is passed through a separation membrane such as a reverse osmosis membrane or a nanofiltration membrane.

[0045] (Discharge Step S2) Next, a voltage is applied to the electrodes (13a, 13b) by the lighting power supply 20. This generates a discharge E1 through the light-emitting space 11a of the arc tube 11, the tube wall of the arc tube 11, and the liquid to be treated W1. This is because the liquid to be treated W1 has an impedance, similar to the arc tube 11 made of a dielectric material. Specifically, when a voltage is applied to the electrodes (13a, 13b), an electric charge accumulates on the tube wall of the arc tube 11, and then the electric charge is discharged by periodic changes in the applied voltage. This process is repeated. FIG. 3 schematically shows the electric discharge E1 generated in the liquid to be treated W1, and electrons are supplied to the liquid to be treated W1 by the electric discharge E1. In other words, in this specification, the term "discharge" is used in a broad sense to encompass all manners in which an electric charge is released from a charged body.

[0046] From the viewpoint of generating the discharge E1 over as wide an area as possible in the liquid to be treated W1, it is preferable that the electrode 13b is configured to cover the periphery of the arc tube 11. In other words, it is preferable that the entire periphery of the side wall portion 12a of the chamber 12 is configured from a metallic material.

[0047] At least the tube wall of the arc tube 11 is interposed between the electrode 13a and the electrode 13b. As described above, the arc tube 11 is made of a dielectric. In other words, the discharge E1 is conducted via a "dielectric barrier discharge." The presence of the tube wall of the arc tube 11, which is a dielectric, between the electrode 13a and the liquid to be treated W1 keeps the electrode 13a out of contact with the liquid to be treated W1, thereby reducing deterioration of the electrode 13a due to contact with the liquid to be treated W1 and the incorporation of impurities from the electrode 13a into the liquid to be treated W1.

[0048] Thus, step S2 of generating discharge E1 between electrode 13a and electrode 13b corresponds to step (a).

[0049] (Ultraviolet Light Irradiation Step S3) Then, a discharge E1 is generated between the electrodes (13a, 13b), which generates ultraviolet light L1 within the light-emitting space 11a of the light-emitting tube 11, and the ultraviolet light L1 is irradiated onto the treatment target liquid W1 (see FIG. 3). That is, in this embodiment, the discharge step S2 and the ultraviolet light irradiation step S3 are started simultaneously.

[0050] In this embodiment, the power supply for generating the discharge E1 and the power supply for obtaining the ultraviolet light L1 are the same, which is preferable because the space required for installing the processing system 1 is reduced.

[0051] As mentioned above, xenon (Xe) gas is sealed in the light-emitting space 11a as the light-emitting gas, so the ultraviolet light L1 exhibits an emission intensity in the range of 200 nm or less. More specifically, the ultraviolet light L1 exhibits a peak wavelength near 172 nm. The wording "near" here is intended to allow for an error of about 1 nm to 5 nm that may occur due to the mixing ratio of the gas sealed in the light-emitting space 11a, individual differences in the materials that make up the light-emitting tube, lighting conditions, etc.

[0052] As will be described in detail below, irradiation of the liquid to be treated W1 with ultraviolet light L1 generates hydroxyl radicals from the water and dissolved oxygen in the liquid to be treated W1. From the viewpoint of efficiently imparting energy to the water and dissolved oxygen, it is preferable that the ultraviolet light L1 exhibits an emission intensity in the range of 200 nm or less. More preferably, the ultraviolet light L1 exhibits an emission intensity in the range of 160 nm to 200 nm, and particularly preferably, the ultraviolet light L1 exhibits an emission intensity in the range of 160 nm to 180 nm. It is preferable that the ultraviolet light L1 be in the short wavelength range, and ultraviolet light of 180 nm or less is particularly preferable because it is easily absorbed by relatively short-chain organic fluorine compounds in the liquid to be treated and more significantly promotes the decomposition reaction of the organic fluorine compounds.

[0053] Ultraviolet light with wavelengths of 200 nm or less is easily absorbed by oxygen in the air. Therefore, from the viewpoint of efficiently irradiating the liquid W1 with ultraviolet light L1, it is preferable that the light-emitting tube 11 be located within the liquid W1 to be treated, as shown in FIG. 3 . However, the light-emitting tube 11 may be located outside the liquid W1 to be treated. In this case, the light-emitting tube 11 may be disposed close to the liquid W1 to be treated, or the oxygen concentration between the light-emitting tube 11 and the liquid W1 to be treated may be reduced. In other words, the present invention is not limited to whether the light-emitting tube 11 is located within the liquid W1 to be treated.

[0054] Thus, the step S3 of irradiating the liquid to be treated W1 with ultraviolet light corresponds to the step (b).

[0055] 14, the step (a) is not limited to the discharge step S2. In the present invention, it is optional whether the discharge step S2 and the ultraviolet irradiation step S3 are started simultaneously.

[0056] (Post-Process) By performing the discharge step S2 and the ultraviolet light irradiation step S3, the organic fluorine compounds in the liquid to be treated W1 are decomposed, as described below. The decomposition of the organic fluorine compounds reduces the concentration of the organic fluorine compounds in the liquid to be treated W1, and increases the concentration of fluorine ions. For example, a portion of the liquid to be treated W1 may be extracted at a predetermined timing to measure the concentration of the organic fluorine compounds or the concentration of fluorine ions in the liquid to be treated W1. When the concentration of the organic fluorine compounds becomes equal to or less than a predetermined value, or when the concentration of fluorine ions becomes equal to or greater than a predetermined value, it may be determined that the decomposition of the organic fluorine compounds in the liquid to be treated W1 is complete.

[0057] Thereafter, the liquid to be treated W1 can be subjected to a predetermined process and discharged as industrial wastewater, etc. For example, in view of the fact that fluorine ions are generated in the liquid to be treated W1 as the decomposition of the organic fluorine compounds progresses, the liquid to be treated W1 may be passed through a predetermined adsorbent that adsorbs fluorine ions.

[0058] By decomposing the organic fluorine compounds in the liquid to be treated W1, the environmental impact of the organic fluorine compounds when the liquid to be treated W1 is discharged is suppressed.

[0059] Furthermore, as will be described later in the section "Second Embodiment," the fluorine concentration in the treatment target liquid W1 may be reduced by supplying a calcium compound to the treatment target liquid W1 after decomposition of the organic fluorine compound, thereby immobilizing the fluorine.

[0060] In the above description, the discharge step S2 and the ultraviolet irradiation step S3 are performed with the valves (15a, 15b) closed and the liquid to be treated W1 stored in the chamber 12. However, the discharge step S2 and the ultraviolet irradiation step S3 may be performed with the liquid to be treated W1 flowing through the chamber 12. This allows a quantity of the liquid to be treated W1 that cannot be contained in the chamber 12 to be treated all at once. The liquid to be treated W1 may be circulated through the treatment system 1.

[0061] Next, the mechanism by which the decomposition of organic fluorine compounds proceeds through the discharge step S2 and the ultraviolet irradiation step S3 will be described with reference to FIG. 4. FIG. 4 is a diagram showing the decomposition flow of organic fluorine compounds. In FIG. 4, the target substance P1 to be decomposed is PFOA (structural formula: CF 15 COOH) is shown as an example.

[0062] 4, in the solution to be treated W1, the target substance P1 is in an ionized state (state A1). The target substance P1 then transitions from state A1 to state A2 via paths X1 to X4 (described below) through a discharge step S2 and an ultraviolet irradiation step S3. State A2 is a state in which one carbon atom and two fluorine atoms have been removed from state A1.

[0063] The present inventors consider the transition of the target substance P1 from state A1 to state A2 as follows.

[0064] First, a discharge E1 is generated in the solution W1 to be treated by the discharge step S2 (see FIG. 3), and it is believed that electrons collide with the target substance P1. Furthermore, a photon collides with the target substance P1 by the ultraviolet irradiation step S3. That is, the collision of the electrons or photons cleaves the bond near the ketone group, which is relatively easy to cleave within the main chain, in state A1. It is believed that the tendency to act near the oxygen double bond is due to the lower electron density in the vicinity compared to a main chain having many fluoro groups. After the cleavage, the radicalized substance is unstable, and undergoes a decarboxylation reaction to become a fluorocarbon radical and a carbon dioxide anion (pathway X1).

[0065] Thus, the progress of path X1 is not only contributed by the energy of the electrons due to the discharge E1, but also by the energy hν imparted to the target substance P1 by the ultraviolet light L1 irradiated onto the target solution W1. However, it is considered that the effective irradiation distance of the ultraviolet light L1 is extremely short compared to the area in the target solution W1 where the discharge E1 acts. Therefore, it is considered that the contribution of photons to the above-mentioned cleavage reaction is limited compared to that of electrons, and that electrons primarily contribute to the progress of the above-mentioned cleavage reaction.

[0066] Furthermore, since the liquid W1 to be treated is an aqueous solution, hydroxyl radicals (.OH) are generated from the water content in the liquid W1 by irradiation with ultraviolet light L1. That is, as shown in the following formula (1), ultraviolet light L1 acts on the water content in the liquid W1 to generate hydroxyl radicals. Furthermore, as shown in the following formulas (2) to (3), ultraviolet light L1 acts on oxygen dissolved in the liquid W1 to generate O( 1 D). "hv" in the following formulas (1) to (3) represents the energy of ultraviolet light L1. The hydroxyl radical reacts with the part of the fluorocarbon radical where the carboxyl group has been removed, and the target substance P1 transitions to state A11 (path X2). hv + HO → OH + H ... (1) hv + O2 → O( 1 D) + O( 3 P) ...(2) O( 1 D) + H2O → 2(・OH) ...(3)

[0067] It is also believed that hydroxyl radicals are generated when electrons generated by the discharge E1 act on the water in the treatment target liquid W1.

[0068] In state A11, the carbon atom bonded to the fluoro group and the carbon atom bonded to the hydroxy group are the same, so the hydrogen atom in the hydroxy group and the fluorine atom constituting the fluoro group are close to each other. Because fluorine atoms have a large electron affinity and are more energetically stable when bonded to hydrogen atoms, it is believed that hydrogen fluoride (HF) is released from state A11. This causes the target substance P1 to transition from state A11 to state A12 (path X3).

[0069] Subsequently, State A12 transitions to State A2 by replacing the terminal fluoro group with a hydroxy group (path X4). This is thought to be due to the presence of hydroxy radicals and atomic hydrogen generated in the discharge step S2 and ultraviolet irradiation step S3 in the solution to be treated W1 (see formula (1) above). In other words, fluorine atoms have a large electron affinity and are easily bonded to hydrogen atoms, making State A2 more energetically stable than State A12, and therefore State A12 transitions to State A2.

[0070] Then, by continuing to execute the discharge step S2 and the ultraviolet light irradiation step S3, as shown in FIG. n F (2n+1) Using state A2 represented by COOH as a reference, the same reactions as those described in pathways X1 to X4 proceed. In other words, using state A2 as a reference, the molecular weight of target substance P1 decreases and decomposition proceeds as a result of the repeated reactions of reducing one carbon atom and two fluorine atoms (pathways X1 to X4).

[0071] In this way, the discharge step S2 and the ultraviolet light irradiation step S3 can decompose PFOA in the treatment target liquid W1. In particular, this decomposition reaction starts from the reaction of pathway X1, as described with reference to FIG. 4 . In treatment method 1a, electrons generated in the discharge step S2 and photons irradiated with ultraviolet light L1 act on the target substance P1, thereby promoting the reaction of pathway X1. As described above, electrons are considered to be the main contributor to pathway X1. In other words, treatment method 1a can significantly decompose PFOA compared to, for example, irradiating the treatment target liquid W1 with ultraviolet light without generating discharge E1 in the treatment target liquid W1.

[0072] Furthermore, from the viewpoint of generating sufficient hydroxyl radicals in the treatment target liquid W1 for the reaction of pathway X2 etc. to proceed, it is preferable to perform an ultraviolet irradiation step S3 in addition to the discharge step S2. That is, according to the treatment method 1a, for example, PFOA can be decomposed significantly more effectively than when, for example, the treatment target liquid W1 is not irradiated with ultraviolet light L1 but discharge is generated in the treatment target liquid W1.

[0073] 5 is a diagram showing another example of the decomposition flow of an organic fluorine compound, following the example of FIG. 4. In FIG. 5, the target substance P2 to be decomposed is PFOS (structural formula: CF 17 An example is shown where the cation is SO3H.

[0074] As shown in FIG. 5, the target substance P2 is in an ionized state (state B1) in the liquid to be treated W1, which is the same as state A1 in FIG.

[0075] 5 differs from FIG. 4 in that a sulfo group is eliminated from the target substance P2, but the mode of reaction progress of pathway Y1 is the same as pathway X1 in FIG. 4. That is, electrons and photons collide with the target substance P2 through the discharge step S2 and ultraviolet irradiation step S3, cleaving the SO group. Then, the target substance P2 undergoes a desulfurization reaction to become a fluorocarbon radical (pathway Y1).

[0076] Furthermore, the hydroxyl radicals in the treatment target solution W1 react with the part of the fluorocarbon radical from which the sulfo group has been eliminated, and the target substance P2 transitions to state B11 (path Y2).

[0077] 4, in state B11, the carbon atom to which the fluoro group is bonded and the carbon atom to which the hydroxy group is bonded are the same, so the hydrogen atom in the hydroxy group and the fluorine atom constituting the fluoro group are close to each other. Fluorine atoms have a large electron affinity and are energetically more stable when bonded to hydrogen atoms. Therefore, hydrogen fluoride (HF) is released from state B11, and the target substance P2 transitions from state B11 to state B12 (pathway Y3).

[0078] 4, the terminal fluoro group in state B12 is substituted with a hydroxy group (pathway Y4). n F (2n+1) It transitions to state A2, represented by COOH.

[0079] The target substance P2 that has transitioned to state A2 is decomposed by the reactions of pathways X1 to X4 described with reference to FIG. 4. In other words, by continuing to execute the discharge step S2 and the ultraviolet irradiation step S3, C n F(2n+1) PFOS in the solution to be treated W1 can be decomposed via state A2 represented by COOH. In Fig. 5, electrons generated in the discharge step S2 act on the target substance P2 to promote the reaction related to pathway Y1, as described with reference to pathway X1 in Fig. 4.

[0080] 6 is a diagram showing yet another example of the decomposition flow of an organic fluorine compound, in which the target substance P2 is PFOS, as in FIG.

[0081] 6 differs from FIG. 5 in that, in the pathway Y4 described in FIG. 5, sulfonic acid in the solution to be treated W1 contributes to the reaction, and sulfonic acid is desorbed from the target substance P2 together with hydrogen fluoride, resulting in a transition from state B12 to state B2 (path Z1). State B2 is a state in which one carbon atom and two fluorine atoms have been lost from state B1. Note that even when transitioning to state B2 occurs, as shown in FIG. 6, by continuing to execute the discharge step S2 and the ultraviolet irradiation step S3, C n F (2n+1) Using state B2 represented by SO3H as a reference, the same reactions as those described in pathways Y1 to Y3 and pathway Z1 proceed repeatedly, and the decomposition of target substance P2 proceeds.

[0082] As described with reference to FIGS. 5 and 6, there are several possible reaction pathways in the decomposition process of PFOS, but whichever reaction pathway is followed, the decomposition of PFOS will proceed.

[0083] [Verification] Next, the effect of actually decomposing organic fluorine compounds using the treatment system 1 was verified, which will be described below.

[0084] FIG. 7 is a diagram schematically illustrating the experimental system used in this verification. In this verification, the chamber 12 was constructed as a container made of quartz glass. Furthermore, the electrode 13b was arranged on the outer wall surface of the chamber 12, as shown in FIG. 7. The electrode 13b was made of aluminum. Furthermore, in this verification, an agitating member (not shown) for agitating the treatment target liquid W1 was arranged in the chamber 12.

[0085] 7, the arc tube 11 and the electrode 13a are placed in the liquid to be treated W1. The light emitting gas of the arc tube 11 is xenon gas, as in the first embodiment.

[0086] In this test, an aqueous solution containing PFOA and PFOS at concentrations of approximately 30 μg / L each was prepared using reagents manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. This aqueous solution was designated as the treatment target solution W1. In this test, the volume of the treatment target solution W1 was set to 200 mL.

[0087] An AC voltage was applied to the electrodes 13a and 13b to generate a discharge E1 between the electrodes 13a and 13b, and the arc tube 11 was made to emit light, irradiating the treatment target liquid W1 with ultraviolet light L1 (see FIG. 3). The AC voltage was set to approximately 3 kVp-p at a frequency of 200 kHz.

[0088] A portion of the solution W1 to be treated was extracted at predetermined times, and the changes in the concentrations of PFOA and PFOS over time were evaluated. The concentrations of PFOA and PFOS were measured by liquid chromatography-mass spectrometry (LC-MS / MS) using an apparatus manufactured by Agilent Technologies, Inc. In this verification, the concentrations of multiple samples were measured every predetermined treatment time.

[0089] Figure 8 is a graph showing the results of this verification. In Figure 8, the horizontal axis represents the treatment time, and the vertical axis represents the concentration of each organic fluorine compound. In Figure 8, the approximate curves obtained from the measurement results of each concentration are shown by dashed lines.

[0090] 8 shows that the concentrations of both PFOA and PFOS in the treatment target solution W1 decrease with the passage of treatment time. More specifically, the PFOA concentration decreased to about one-third of the initial concentration after two hours of treatment and approached 0 μg / L after six hours of treatment. Furthermore, the PFOS concentration decreased to about half of the initial concentration after five hours of treatment and continued to decrease thereafter. It can be seen that the PFOS concentration takes a longer time to decrease than the PFOA concentration, but it is estimated that the PFOS concentration will eventually approach 0 as the treatment time passes. This is clear in light of the PFOS decomposition mechanism described with reference to FIGS. 5 and 6.

[0091] This verification demonstrated that treatment method 1a can treat organic fluorine compounds such as PFOA and PFOS. As described above, treatment method 1a does not require a temperature high enough to vaporize the treatment target liquid W1, nor does it require the addition of hypochlorite or the like. Thus, treatment method 1a makes it possible to efficiently treat PFOA and PFOS in the treatment target liquid W1.

[0092] In this test, the initial concentration of the liquid W1 to be treated was approximately 30 μg / L, but the present invention is not limited to this concentration. This is clear from the fact that the decomposition of organofluorine compounds such as PFOA and PFOS proceeds continuously, as described with reference to Figures 4 to 6. In other words, the execution times of the discharge step S2 and the ultraviolet light irradiation step S3 can be adjusted appropriately in consideration of the concentration of the organofluorine compounds in the liquid W1 to be treated, the total amount of the liquid W1 to be treated, the number and power consumption of the arc tubes 11, the electrode area and current amount that generate the discharge E1, etc.

[0093] In the above, the decomposition of PFOA and PFOS has been described. These are classified as perfluoroalkyl compounds. Like PFOA and PFOS, organic fluorine compounds classified as perfluoroalkyl compounds include perfluorohexane sulfonic acid (PFHxS) and perfluorocarboxylic acids (PFCAs). As such, even among perfluoroalkyl compounds, there are many organic fluorine compounds with different structures. However, perfluoroalkyl compounds are similar to PFOA and PFOS in that they have a main chain composed of fluorocarbon and various functional groups bonded to the terminal carbon. As an example, the structures of PFHxS and PFCAs are shown below.

[0094] That is, it is presumed that even for perfluoroalkyl compounds other than PFOA and PFOS, the electrons obtained in the discharge step S2 act on portions of the compound that have a lower electron density than the main chain, causing compounds derived from functional groups to be eliminated and hydrogen fluoride to be eliminated, resulting in a stepwise decomposition reaction. In other words, it is believed that treatment method 1a can decompose not only PFOA and PFOS, but also organic fluorine compounds classified as perfluoroalkyl compounds.

[0095] The same applies to polyfluoroalkyl compounds such as 6:2 fluorotelomer alcohol (6:2FTOH) and 8:2 fluorotelomer alcohol (8:2FTOH) shown below, which have a main chain composed of fluorocarbon and functional groups such as hydroxyl groups with lower electron density than the main chain. In other words, it is believed that treatment method 1a can decompose not only perfluoroalkyl compounds but also organic fluorine compounds classified as polyfluoroalkyl compounds.

[0096] Perfluoroalkyl compounds and polyfluoroalkyl compounds are collectively referred to as PFAS. In other words, to summarize the above, according to the treatment method 1a, it is possible to decompose PFAS in addition to at least PFOA and PFOS among the organic fluorine compounds contained in the treatment target liquid W1.

[0097] Second Embodiment Next, a second embodiment of the processing method 1a will be described, focusing on the differences from the first embodiment.

[0098] 9A is a diagram schematically illustrating the configuration of a second embodiment of the processing system 1. FIG. 9B is a flow diagram illustrating another example of the processing method 1a, following FIG. 2. As shown in FIG. 9A, the processing system 1 may have a chamber 30 downstream of the chamber 12 for feeding the processing target liquid W1 in which the organic fluorine compounds have been decomposed. Hereinafter, the processing target liquid W1 in which the organic fluorine compounds have been decomposed may be referred to as the "processing target liquid W2" in order to distinguish it from the processing target liquid W1 before being subjected to processing.

[0099] 9A, the chamber 30 is connected to the chamber 12 via a pipe 14b. The solution to be treated W2 in the chamber 12 can be sent to the chamber 30 by a liquid-sending pump (not shown) or the like. The chamber 30 has a supply part 31 that supplies the calcium compound M1 to the solution to be treated W2.

[0100] 9B , the present embodiment differs from the first embodiment in that, after the discharge step S2 and the ultraviolet light irradiation step S3 are performed, a step S4 is performed in which the supply unit 31 supplies a calcium compound M1 to the treatment target solution W2. Examples of the calcium compound M1 include calcium hydroxide, calcium chloride, and calcium carbonate.

[0101] As described with reference to FIGS. 4 to 6 , treatment of the organic fluorine compound in the liquid to be treated W1 generates hydrogen fluoride (HF) in the liquid to be treated W1. The hydrogen fluoride is ionized into fluorine ions and hydrogen ions in the liquid to be treated W1. By supplying a calcium compound M1, such as calcium hydroxide, to the liquid to be treated W1, the fluorine can be immobilized as calcium fluoride (CaF2). In other words, by supplying the calcium compound M1 to the liquid to be treated W2, calcium fluoride can be generated in the liquid to be treated W2. In the present invention, the calcium compound M1 can be supplied by any method. For example, the calcium compound M1 may be supplied in a solid state or in an aqueous solution state.

[0102] In this way, by immobilizing fluorine in the liquid to be treated W2, it is possible to reduce the amount of fluorine derived from organic fluorine compounds in the liquid to be treated W2. From the viewpoint of suppressing the release of fluorine-derived compounds remaining in the liquid to be treated W2 into the environment, it is preferable to immobilize fluorine in the liquid to be treated W2.

[0103] The calcium fluoride obtained in the calcium compound supplying step S4 can be used, for example, as a concrete material or a roadbed material. Furthermore, the calcium fluoride can also be used as a raw material for optical lenses after undergoing a predetermined purification step. Furthermore, the calcium fluoride may be reused as a raw material for organic fluorine compounds.

[0104] Thus, the step S4 of supplying a calcium compound to the liquid to be treated W2 corresponds to the step (c).

[0105] In step S4, in order to immobilize fluorine in the treatment target liquid W2, a sodium compound such as sodium hydroxide, sodium chloride, or sodium bicarbonate may be supplied instead of the calcium compound M1. Similarly, a magnesium compound such as magnesium hydroxide may be supplied. This makes it possible to obtain, for example, sodium fluoride or magnesium fluoride.

[0106] 10 is a diagram schematically illustrating the configuration of a third embodiment of the processing system 1. As shown in Fig. 10, the discharge step S2 and the ultraviolet irradiation step S3 may be performed while the liquid to be processed W1 is flowing.

[0107] In this embodiment, the arc tube 11 is inserted into the chamber 12 and the electrode 13a is disposed in the arc tube 11's arc space 11a, as in the first embodiment.

[0108] 10, the electrode 13b may be disposed on the outer wall surface of the chamber 12. In this case, the chamber 12 is made of a dielectric material such as quartz glass. As a result, the tube wall of the arc tube 11 and the outer wall of the chamber 12 are interposed between the electrode 13a and the electrode 13b, and therefore the discharge E1 is conducted via a "dielectric barrier discharge."

[0109] Furthermore, the presence of a dielectric between the electrode 13a and the liquid W1 to be treated, and between the electrode 13b and the liquid W1 to be treated, keeps both the electrode 13a and the electrode 13b out of contact with the liquid W1 to be treated, which is advantageous in that it reduces deterioration of the electrodes (13a, 13b) and the inclusion of impurities from the electrodes (13a, 13b) into the liquid W1 to be treated.

[0110] The electrode 13b is made of a metal material such as platinum, gold, silver, tungsten, molybdenum, titanium, stainless steel, aluminum, copper, iron, etc. When the electrode 13b is not in contact with the liquid W1 to be treated, relatively inexpensive materials such as aluminum, copper, and iron may be used as the material for the electrode 13b.

[0111] The electrode 13b may have a mesh or line shape. Fig. 10 shows a schematic cross section of the mesh-shaped electrode 13b. The electrode 13b may have a film shape. As described with reference to Fig. 1, the outer wall surface of the chamber 12 may constitute the electrode 13b in Fig. 10.

[0112] 11 is a diagram schematically illustrating the configuration of a fourth embodiment of the processing system 1. As shown in Fig. 11, the processing system 1 may further include a light source unit 40 in addition to the configuration described with reference to the first embodiment.

[0113] 11 , the light source unit 40 irradiates the liquid to be treated W1 with ultraviolet light L2. In this case, at least a portion of the outer wall surface of the chamber 12 is transparent to the ultraviolet light L2. For example, the outer wall surface of the chamber 12 facing the light source unit 40 may be made of a glass material such as quartz glass. Alternatively, the chamber 12 may be made of a glass material, and an electrode 13b may be disposed on the outer wall surface of the chamber 12.

[0114] The ultraviolet light L2 has an emission intensity in the wavelength range of more than 200 nm and less than 280 nm, thereby facilitating the generation of hydroxyl radicals in the treatment target liquid W1.

[0115] More specifically, by the irradiation of ultraviolet light L1 in the ultraviolet irradiation step S3, the O( 3 P) causes the reaction of the following formula (4). In other words, just as ozone is generated by irradiating water with ultraviolet light (wavelength 411 nm or less), ozone is generated in the treatment target liquid W1 by irradiating it with ultraviolet light L1. Here, by irradiating the treatment target liquid W1 with ultraviolet light L2 in the above wavelength range, the ozone is converted into O( 1 D) can be generated. 1 As shown in the following formula (6), O( reacts with the water in the liquid W1 to generate hydroxyl radicals. Note that "M" in formula (4) represents a third body, and "hv" in formula (5) represents the energy of ultraviolet light L2. 3 P) + O2 + M → O3 + M (4) O3 + hν → O( 1 D) + O2 (5) O( 1 D) + H2O → 2(・OH) (6)

[0116] 4 to 6, hydroxyl radicals contribute to the decomposition of the organic fluorine compounds in the treatment target liquid W1. Therefore, by irradiating the treatment target liquid W1 with ultraviolet light L2 in addition to ultraviolet light L1 to generate hydroxyl radicals, it is possible to promote the decomposition of the organic fluorine compounds.

[0117] That is, the ultraviolet irradiation step S3 may include a step of irradiating the liquid to be treated W1 with ultraviolet light L2. In this way, the step of irradiating the liquid to be treated W1 with ultraviolet light L2 during the ultraviolet irradiation step S3 corresponds to the step (b1).

[0118] To efficiently generate hydroxyl radicals from ozone, and from the viewpoint of enhancing the absorption of ultraviolet light L2 by ozone, ultraviolet light L2 preferably exhibits emission intensity in the wavelength range of more than 200 nm and less than 280 nm, more preferably in the wavelength range of more than 240 nm and less than 270 nm, and particularly preferably in the wavelength range of more than 250 nm and less than 260 nm.

[0119] Preferably, the light source unit 40 is configured from a low-pressure mercury lamp, which produces ultraviolet light L2 with a peak wavelength around 254 nm. The light source unit 40 may be configured from a solid-state light source such as an LED, or may be configured from an excimer lamp containing krypton gas and chlorine gas as light-emitting gases.

[0120] 12 is a diagram schematically illustrating another configuration example of the processing system 1 according to the fourth embodiment. As shown in Fig. 12, a light source unit 40 may be incorporated into the example of Fig. 10. In this case, the electrode 13b preferably has a mesh or linear shape.

[0121] In Figures 11 and 12, the light source unit 40 is described as being positioned outside the chamber 12, but the light source unit 40 may also be housed in the chamber 12 and positioned within the liquid to be treated W1.

[0122] In addition, in the ultraviolet irradiation step S3, the step of irradiating ultraviolet light L1 and the step of irradiating ultraviolet light L2 may be carried out simultaneously by using a light source that emits ultraviolet light that exhibits emission intensity in both the wavelength range of 200 nm or less and the wavelength range of more than 200 nm but less than 280 nm.

[0123] Another embodiment of the processing system 1 will now be described.

[0124] <1> Figure 13 is a diagram schematically illustrating another embodiment of the processing system 1. As shown in Figure 13, the electrode 13b may be disposed on the outer wall surface of the chamber 12. It is also optional whether the electrode 13b covers the periphery of the arc tube 11. The arrangement of the electrode 13b can be changed as appropriate to suit the configuration of the chamber 12.

[0125] <2> Fig. 14 is a diagram schematically illustrating yet another configuration example of the processing system 1. As shown in Fig. 14, the processing system 1 may have a pair of electrodes (23a, 23b) in the liquid to be processed W1, separate from the arc tube 11.

[0126] The electrodes 23a and 23b supply electrons into the treatment-target liquid W1 when a DC or AC voltage is applied from the power source 21. As an example, the power source 21 applies a high-frequency AC voltage of 10 kHz to 5 MHz between the electrodes 23a and 23b. In this embodiment, the electrode 23a corresponds to the "first electrode" and the electrode 23b corresponds to the "second electrode."

[0127] As shown in FIG. 14 , the electrodes 23a and 23b are in contact with the target liquid W1. In view of this, the electrodes (23a, 23b) are preferably made of a metal material such as platinum, gold, silver, or stainless steel, or a carbon material such as diamond or graphite. The electrodes 23a and 23b may be coated with glass or ceramics to create a dielectric between the electrodes (23a, 23b) and the target liquid W1, thereby generating a discharge E1. In this case, the electrodes (23a, 23b) may be made of relatively inexpensive materials such as aluminum, copper, or iron. The coating may be applied to either or both of the electrodes 23a and 23b. Preferably, the coating is applied to both the electrodes 23a and 23b. FIG. 14 illustrates a case where the coating is applied and the current between the electrodes (23a, 23b) generates a discharge E1.

[0128] As shown in FIG. 14 , the arc tube 11 has an electrode 13b on its outer wall surface. The electrode 13b has, for example, a mesh or linear shape. When the arc tube 11 is turned on, ultraviolet light L1 is irradiated onto the treatment target liquid W1 (ultraviolet light irradiation step S3). The same discussion as in the third embodiment applies to the constituent material of the electrode 13b. Considering that the electrode 13b comes into contact with the treatment target liquid W1, the electrode 13b may be gold-plated, for example.

[0129] 14, a power supply 21 for generating the discharge E1 and a lighting power supply 20 for lighting the arc tube 11 may be configured separately. This is preferable because it makes it easier to adjust the conditions for generating the discharge E1 in the liquid to be treated W1 and the conditions for irradiating the liquid to be treated W1 with ultraviolet light L1.

[0130] In this embodiment, from the viewpoint of causing hydroxyl radicals to react with the target substances (P1, P2) on which the discharge E1 has acted (see FIG. 4, etc.), the arc tube 11 is lit while the electron supply by the discharge step S2 is being executed. That is, in the above embodiment, it has been described that the electron supply by the discharge step S2 and the ultraviolet light irradiation step S3 are started simultaneously by applying a voltage to the electrodes 13a and 13b, but the present invention is not limited to this.

[0131] Specifically, the arc tube 11 may be caused to emit light after generating the discharge E1 between the electrodes 23a and 23b. Alternatively, the arc tube 11 may be caused to emit light to increase the hydroxyl radicals in the treatment target solution W1, and then the discharge E1 may be generated between the electrodes 23a and 23b. In other words, the present invention is not limited to the order in which the electron supply by the discharge step S2 and the ultraviolet irradiation step S3 are started.

[0132] Although not shown, in this embodiment, the light source unit 40 may irradiate the treatment target liquid W1 with ultraviolet light L2 in the same manner as described with reference to FIG.

[0133] <3> For example, the processing system 1 may have an agitation unit that agitates the processing target liquid W1 in the chamber 12. A conventionally known technique can be used to agitate the processing target liquid W1.

[0134] <4> In the above description, the ultraviolet light L1 is irradiated by the light-emitting tube 11. However, as long as the ultraviolet light L1 has an emission intensity in the range of 200 nm or less, the method of irradiating the liquid to be treated W1 with the ultraviolet light L1 is arbitrary.

[0135] <5> In the present invention, the step (a) of supplying electrons to the liquid to be treated W1 is not limited to the above-described discharging step S2. For example, as described in the example of FIG. 14 , electrodes 13a and 13b may be directly immersed in the liquid to be treated W1 and current may be applied. Various other methods for supplying electrons to the liquid to be treated W1 may be employed. The method of applying a voltage to the pair of electrodes is not limited to the above, and a DC voltage may be applied, for example. Furthermore, there is no limitation as to whether the applied voltage is pulsed or not. The voltage application method may be appropriately selected depending on the embodiment. For example, when applying a voltage via a dielectric, it is preferable that the voltage be pulsed, considering that charge is accumulated by applying a voltage and then discharged. The electrons and the ultraviolet light irradiated onto the liquid to be treated W1 provide energy to the organic fluorine compounds in the liquid to be treated W1, thereby accelerating the decomposition reaction of the organic fluorine compounds.

[0136] <6> The configuration of the processing system 1 described above is merely an example, and the present invention is not limited to the illustrated configurations. Furthermore, the above configurations can be realized by combining them appropriately.

[0137] 1: Processing system 1a: Processing method 11: Arc tube 12: Chamber 13a, 13b: Electrodes 14a, 14b: Pipes 15a, 15b: Valves 16: Insertion section 17: Pinch seal section 20: Lighting power supply 21: Power supply 23a, 23b: Electrodes 30: Chamber 31: Supply section 40: Light source section

Claims

1. A method for treating an organic fluorine compound contained in a liquid to be treated, comprising: a step (a) of supplying electrons into the liquid to be treated via the liquid to be treated between a first electrode and a second electrode disposed at a distance from the first electrode; and a step (b) of irradiating the liquid to be treated with ultraviolet light that exhibits an emission intensity in a wavelength range of at least 200 nm or less while the step (a) is being performed.

2. The method for treating an organic fluorine compound according to claim 1, characterized in that step (a) includes a step of supplying electrons between the first electrode located within the liquid to be treated and the second electrode located outside the liquid to be treated.

3. The method for treating an organic fluorine compound according to claim 2, wherein step (b) includes a step of irradiating the liquid to be treated with ultraviolet light from an arc tube located within the liquid to be treated and containing a light-emitting gas, and step (a) includes a step of generating a discharge between the first electrode located inside the arc tube and the second electrode located at a distance from the arc tube.

4. A method for treating an organic fluorine compound according to claim 1 or 2, characterized in that electrons are supplied between the first electrode and the second electrode by the presence of a dielectric between the first electrode and the liquid to be treated and / or between the second electrode and the liquid to be treated.

5. A method for treating an organic fluorine compound according to any one of claims 1 to 3, characterized in that the liquid to be treated is in a flowing state during the execution of steps (a) and (b).

6. A method for treating an organic fluorine compound according to any one of claims 1 to 3, characterized in that step (b) includes step (b1) of irradiating the liquid to be treated with ultraviolet light that exhibits an emission intensity in the wavelength range of more than 200 nm and less than 280 nm.

7. The method for treating an organic fluorine compound according to any one of claims 1 to 3, further comprising a step (c) of adding a calcium compound or a sodium compound to the liquid to be treated after carrying out the step (b).

8. A treatment system for treating organic fluorine compounds contained in a liquid to be treated, comprising: a chamber for storing the liquid to be treated; a light-emitting tube disposed in the chamber and containing a light-emitting gas; a first electrode disposed inside the light-emitting tube; a second electrode disposed at a distance from the light-emitting tube; and a power source for applying a voltage to the first electrode and the second electrode to light the light-emitting tube and supply electrons to the liquid to be treated, wherein a dielectric is interposed between the liquid to be treated and the second electrode.

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