JP2014205103A - Method of treating to-be-treated water containing hydrogen peroxide and hydrogen peroxide removal apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of treating drainage which decomposes hydrogen peroxide present in drainage to reduce the concentration of hydrogen peroxide to such a level as to allow easy reuse in cleaning of electronic parts and a hydrogen peroxide removal apparatus for realization of the method.SOLUTION: A hydrogen peroxide removal apparatus is provided with a method of decomposing hydrogen peroxide by adjusting the amount of oxygen dissolved in to-be-treated water containing hydrogen peroxide to a level equal to or lower than a predetermined value and decomposing hydrogen peroxide by using UV rays and a photocatalyst, a dissolved oxygen reduction unit, and a hydrogen peroxide decomposition tank housing a photocatalyst and a UV light source capable of irradiating the photocatalyst with UV rays.

Description

  TECHNICAL FIELD The present invention relates to a method for treating water to be treated containing hydrogen peroxide and a hydrogen peroxide removal apparatus used therefor, and more particularly, waste water treatment suitable for collecting and reusing waste water containing hydrogen peroxide from an electronic component manufacturing process. The present invention relates to a method and a hydrogen peroxide removing apparatus used therefor.

  Ultrapure water production equipment used in factories that manufacture electronic components, such as semiconductors and liquid crystals, generally uses wastewater from the viewpoints of reducing raw water use costs and wastewater treatment costs, and complying with regulations on the total amount of discharged water. A recovery system is provided, and wastewater with a relatively low pollution level is recovered and reused as raw water for ultrapure water. However, since wastewater discharged from the cleaning process of semiconductors and liquid crystal panels and its treated water generally contain hydrogen peroxide in general, it is necessary to recycle such treated water. It is necessary to remove hydrogen oxide.

  As a hydrogen peroxide treatment method in the treatment of wastewater discharged from a semiconductor manufacturing process, for example, Patent Document 1 discloses a residual hydrogen peroxide added to promote the decomposition of COD components in COD (chemical oxygen demand) -containing wastewater. A method of decomposing components by activated carbon treatment is shown.

  Further, Patent Document 2 discloses a method of decomposing and removing hydrogen peroxide by bringing a photocatalyst irradiated with ultraviolet light into contact with hydrogen peroxide in a liquid. It is said that the amount of hydrogen peroxide in the hydrogen peroxide-containing waste liquid used for cleaning the parts can be reduced to 0 mg / L, so that it can be discharged into the river.

JP-A-10-000461 Japanese Patent Laid-Open No. 10-151451 International Publication No. 2009/63737

  However, in the treatment method described in Patent Document 1, that is, activated carbon treatment, in order to reduce the hydrogen peroxide concentration to a low level, it is necessary to enlarge the activated carbon packed tower or reduce the space velocity in the activated carbon packed tower. Therefore, there is a problem that the installation space is increased and the processing amount is reduced, which is not economical.

  In addition, the method described in Patent Document 2, that is, the method of using ultraviolet rays and a photocatalyst for the decomposition of hydrogen peroxide is an economically advantageous method because the processing apparatus can be made compact and the configuration thereof can be simplified. Since a small amount of hydrogen peroxide is generated simultaneously with the decomposition of hydrogen peroxide by the photochemical reaction of the photocatalyst, the concentration of hydrogen peroxide is low, for example, 5 ppb or less, so that the water to be treated can be reused for cleaning electronic components. There is a problem that it cannot be reduced by this.

  The present invention has been made in view of the above problems, and effectively reduces hydrogen peroxide having a ppb level concentration in wastewater by an economically advantageous method using a combination of ultraviolet rays and a photocatalyst. An object of the present invention is to provide a wastewater treatment method that can be decomposed and reduced to 5 ppb or less so that it can be easily reused for cleaning electronic components.

  In order to achieve the above object, as a result of intensive studies, the present inventors made dissolved oxygen in water to be treated containing hydrogen peroxide to be a predetermined value or less in the treatment of water to be treated containing hydrogen peroxide. In the above, it has been found that by decomposing hydrogen peroxide using ultraviolet rays and a photocatalyst, the concentration of hydrogen peroxide in the water to be treated can be reduced to a very low level, specifically to 5 ppb or less. .

  That is, the present invention is a method for treating water to be treated containing hydrogen peroxide, the first step of reducing the dissolved oxygen concentration in the water to be treated to 0.1 mg / L or less, and a peak of 190 nm or more in the photocatalyst. A second step of decomposing hydrogen peroxide in the water to be treated by bringing the water to be treated treated in the first step into contact with the photocatalyst while being irradiated with ultraviolet rays having a wavelength. The present invention relates to a method for treating water to be treated containing hydrogen peroxide.

  The present invention also relates to a method for treating water to be treated containing hydrogen peroxide, characterized in that the water to be treated is wastewater discharged from an electronic component manufacturing process.

  Furthermore, the present invention relates to a method for treating water to be treated containing hydrogen peroxide, wherein the photocatalyst is a non-woven fabric of photocatalytic fibers having titanium oxide on the surface.

  Still further, in the invention, the photocatalytic fiber is a fiber composed of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti, wherein the second phase is Water to be treated containing hydrogen peroxide, characterized in that it is a silica-based composite oxide fiber having a photocatalytic function, in which the Ti content of the constituent metal oxide increases in a gradient manner toward the surface layer of the fiber Relates to the processing method.

  The present invention also provides a dissolved oxygen reducing device for reducing the dissolved oxygen concentration in the water to be treated containing hydrogen peroxide to a predetermined value or less, and a peroxidation in which the dissolved oxygen concentration is reduced to a predetermined value or less by the dissolved oxygen reducing device. The present invention relates to a hydrogen peroxide removal apparatus comprising a photocatalyst for treating water to be treated containing hydrogen and a hydrogen peroxide decomposition tank containing an ultraviolet light source capable of irradiating the photocatalyst with ultraviolet light.

  Furthermore, the present invention relates to a hydrogen peroxide removing device, wherein the predetermined value is 0.1 mg / L.

  Furthermore, the present invention relates to a hydrogen peroxide removing device, wherein the water to be treated is waste water discharged from an electronic component manufacturing process.

  In the present invention, the photocatalyst fiber is a fiber composed of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti, and constitutes the second phase. The present invention relates to a hydrogen peroxide removing device characterized by being a silica-based composite oxide fiber having a photocatalytic function in which the proportion of Ti present in the metal oxide increases in a gradient manner toward the surface layer of the fiber.

  As described above, according to the present invention, the hydrogen peroxide concentration in the water to be treated is reduced to an extremely low level by an economically advantageous method using ultraviolet rays and a photocatalyst in combination, which does not require a large apparatus, specifically, It is possible to provide a method for treating water to be treated containing hydrogen peroxide and a hydrogen peroxide removing device that can be reduced to 5 ppb or less.

It is a figure which shows the structure of the hydrogen peroxide removal apparatus of this invention. It is a figure which shows an example of embodiment of the hydrogen peroxide decomposition tank of this invention.

  Next, referring to FIG. 1 which is a schematic view of the hydrogen peroxide removing apparatus of the present invention and FIG. 2 which is an example of a hydrogen peroxide decomposition tank used in the second step of the present invention, the peroxidation of the present invention is performed. A method for treating water to be treated containing hydrogen and a hydrogen peroxide removing apparatus will be specifically described.

  The treatment method of the water to be treated containing hydrogen peroxide according to the present invention includes a first step for reducing the dissolved oxygen concentration in the water to be treated, and an ultraviolet ray and a photocatalyst for the water to be treated whose dissolved oxygen concentration is reduced in the first step. And a second step in which the dissolved oxygen concentration is reduced to 0.1 mg / L or less in the first step.

  Moreover, as shown in FIG. 1, the hydrogen peroxide removal apparatus 1 of the present invention includes a dissolved oxygen removal apparatus 2 that reduces the dissolved oxygen concentration in the water to be treated containing hydrogen peroxide to a predetermined value or less, and a dissolved oxygen removal apparatus. A hydrogen peroxide decomposition tank 3 containing a photocatalyst and an ultraviolet light source capable of irradiating the photocatalyst with ultraviolet light, which decomposes hydrogen peroxide in the water to be treated whose dissolved oxygen concentration is reduced to a predetermined value or less in 2; I have. According to the hydrogen peroxide removing apparatus having this configuration, the method for treating water to be treated containing hydrogen peroxide according to the present invention can be realized.

  The treated water containing hydrogen peroxide to be treated by the treated water treatment method of the present invention is not particularly limited as long as the treated water has a dissolved oxygen concentration of more than 0.1 mg / L. For example, waste water for use Treatment water or wastewater that has been oxidized, reduced, sterilized, washed, etc. by adding hydrogen peroxide to the system, and washing wastewater and rinse washing wastewater discharged from the manufacturing process of electronic parts such as semiconductors and liquid crystals are recovered as ultrapure water. Processed water in which organic substances are oxidized and decomposed by irradiating ultraviolet rays in the presence of hydrogen peroxide for reuse, ultrapure water containing a small amount of hydrogen peroxide used in the manufacturing process of electronic components such as semiconductors and liquid crystals, etc. Can be mentioned. Among these, the treatment method of the water to be treated according to the present invention is used in the presence of hydrogen peroxide in order to collect and reuse cleaning wastewater discharged from the manufacturing process of electronic components such as semiconductors and liquid crystals as ultrapure water. The present invention can be particularly suitably applied to the removal of ppb level hydrogen peroxide in treated water that has been oxidatively decomposed by irradiating ultraviolet rays.

  In general, ultrapure water used in an electronic component manufacturing process has a dissolved oxygen content reduced to about 1 μg / L in order to prevent oxidation of the electronic component. However, when ultrapure water is used as cleaning water or rinsing water for electronic components, the ultrapure water is in contact with the atmosphere and absorbs oxygen in the atmosphere, and at least 0.5 mg / L is dissolved in the cleaning wastewater. It will contain oxygen. Ultra pure water may be added with hydrogen peroxide, ozone, etc. as a cleaning chemical, or hydrogen peroxide and ozone may be added in the same way to promote TOC decomposition during wastewater treatment. Dissolved oxygen increases due to decomposition of hydrogen peroxide and ozone. Therefore, by reducing hydrogen peroxide and dissolved oxygen according to the present invention, it is possible to minimize the deterioration of the apparatus accompanied by oxidation with hydrogen peroxide or oxygen in the subsequent steps, and further reuse as recovered water. In this case, the load on the ultrapure water production line can be reduced and the cost can be reduced as a whole.

  The hydrogen peroxide concentration in the water to be treated is preferably 500 ppb or less, and more preferably 50 ppb or less. The method for treating water to be treated and the hydrogen peroxide removing apparatus of the present invention have a relatively low hydrogen peroxide concentration, specifically 500 ppb or less, as compared with the prior art. This is because hydrogen peroxide in water is an advantageous method and apparatus for reducing its concentration to a very low level. When the concentration of hydrogen peroxide in the water to be treated is 500 ppb or more, a known hydrogen peroxide removing method, for example, a process such as activated carbon or ultraviolet irradiation may be provided before the first process.

  In the first step of the present invention, the dissolved oxygen concentration in the water to be treated is preferably reduced to 0.1 mg / L or less, and particularly preferably 0.07 mg / L or less.

  The photocatalyst is excited by ultraviolet light or visible light having energy higher than the band gap of the photocatalyst. Holes are generated in the valence band by photoexcitation, and these radicals generate strong radical species such as OH radicals, which oxidatively decompose organic matter and hydrogen peroxide. On the other hand, electrons excited in the conduction band are usually consumed by reducing oxygen and generating superoxide radicals. However, it is known that the generated superoxide radical generates hydrogen peroxide by reaction with water. Therefore, in the presence of dissolved oxygen, decomposition and generation of hydrogen peroxide occur simultaneously by the photocatalyst. Further, it is known that when hydrogen peroxide has a high concentration, the hydrogen peroxide is reduced by photoexcited electrons and decomposed into OH radicals and hydroxide ions. That is, even in the reduction by photoexcited electrons, the generation of hydrogen peroxide by oxygen reduction and the decomposition by reduction of hydrogen peroxide occur simultaneously. At this time, whether priority is given to the reduction of dissolved oxygen or hydrogen peroxide is based on the relative difference between the dissolved oxygen concentration and the hydrogen peroxide concentration in the water to be treated. Therefore, in order to further reduce the extremely low concentration of hydrogen peroxide, it is necessary to relatively reduce the amount of dissolved oxygen and suppress the production of hydrogen peroxide by oxygen reduction. As a result of the study in the present invention, if the dissolved oxygen concentration is 0.1 mg / L or less, the decomposition of hydrogen peroxide is prioritized, an extremely small amount of hydrogen peroxide is decomposed, and the hydrogen peroxide concentration in the water to be treated is 5 ppb. It turned out that it can reduce to the following.

  There is no restriction | limiting in particular in the dissolved oxygen removal apparatus 2, For example, a vacuum deaeration apparatus, a nitrogen deaeration apparatus, a membrane deaeration apparatus, a deoxygenation catalyst apparatus etc. can be mentioned. Among these, a membrane deaeration device and a deoxygenation catalyst device can be suitably used.

  A membrane degassing apparatus as an example of an embodiment of the dissolved oxygen removing apparatus 2 of the present invention will be described. As a membrane deaerator, a space (hereinafter referred to as “liquid chamber”) through which water to be treated is introduced through a deaeration membrane and a space (hereinafter referred to as “intake chamber”) in which gas in the water to be treated is transferred. ) And are formed. The suction chamber is depressurized by a vacuum pump or the like, and the gas contained in the water to be treated introduced into the liquid chamber is transferred to the suction chamber side through the deaeration film to remove the gas in the water to be treated.

  The deaeration membrane provided in the membrane deaeration device can be used without particular limitation as long as it is a membrane that allows gas such as oxygen, nitrogen, and carbon dioxide to pass therethrough but does not allow liquid to pass. Specific examples of the degassing membrane include hydrophobic polymer membranes such as silicon rubber, tetrafluoroethylene, polytetrafluoroethylene, polyolefin, and polyurethane. Examples of the shape of the deaeration membrane include a hollow fiber membrane shape and a flat membrane shape. Among these, a membrane deaerator equipped with a polyolefin-based hollow fiber membrane can be suitably used.

  The concentration of dissolved oxygen in the water to be treated is selected by selecting a membrane deaerator with appropriate specifications (degree of ultimate vacuum) according to the dissolved oxygen concentration in the water to be treated and the flow rate of the water to be treated. It can be reduced below a predetermined value. Alternatively, the dissolved oxygen concentration in the treated water can be controlled by adjusting the flow rate of the treated water in accordance with the dissolved oxygen concentration in the treated water introduced into the membrane deaerator. For example, even if the dissolved oxygen concentration in the water to be treated introduced into the membrane deaerator increases, the dissolved oxygen concentration in the treated water after treatment can be kept constant by reducing the flow rate of the water to be treated. it can.

  As shown in FIG. 1, the dissolved oxygen concentration in the water to be treated is installed in the flow path on the near side of the fluid inflow portion of the dissolved oxygen removing device 2 and on the near side of the fluid inflow portion of the hydrogen peroxide decomposition tank 3. The dissolved oxygen measuring device 4 is used. If the dissolved oxygen concentration measured by the dissolved oxygen measuring device 4 installed in the flow path on the near side of the fluid inflow portion of the hydrogen peroxide decomposition tank 3 cannot be reduced to a predetermined value, the flow rate of untreated water is reduced. The oxygen concentration can be reduced to a predetermined value.

  The dissolved oxygen measuring device is not particularly limited, and examples thereof include a fluorescent dissolved oxygen measuring device, a diaphragm galvanic electrode dissolved oxygen measuring device, a diaphragm polarographic dissolved oxygen measuring device, and a zirconia dissolved oxygen measuring device. it can. Among these, a diaphragm type galvanic electrode type dissolved oxygen measuring device can be suitably used.

  In the second step of the present invention, the water to be treated containing hydrogen peroxide whose dissolved oxygen concentration is reduced to a predetermined value or less in the first step is treated with ultraviolet rays and a photocatalyst. In the second step, in a state where the photocatalyst is irradiated with ultraviolet rays having a peak wavelength of 190 nm or more, the water to be treated treated in the first step is brought into contact with the photocatalyst to decompose hydrogen peroxide in the water to be treated. . Therefore, in the hydrogen peroxide decomposition tank 3, the ultraviolet light source is installed so as to irradiate the photocatalyst with ultraviolet rays, and the photocatalyst exists in the flow path of the water to be treated. Since the hydrogen peroxide decomposition tank 3 is configured in this manner, hydrogen peroxide in the water to be treated introduced into the hydrogen peroxide decomposition tank 3 is decomposed by ultraviolet rays and a photocatalyst. Here, the photocatalyst only needs to be present in the flow path of the water to be treated and come into contact with the water to be treated. Therefore, the photocatalyst may be fixed to the flow path of the water to be treated. The hydrogen peroxide decomposition tank 3 may be placed so as to float in the flow path.

  The photocatalyst according to the present invention may be a composition itself having a photocatalytic function or a structure on which a composition having a photocatalytic function is supported.

Constituting the photocatalyst according to the present invention, the composition having a photocatalytic function is not particularly limited, usually, titanium oxide _(TiO 2), strontium titanate (SrTiO _2), cadmium sulfide (CdS), molybdenum sulfide (MoS ₂ ), zinc oxide (ZnO), tungsten oxide (WO ₃ ), copper oxide (CuO ₂ ), iron oxide (Fe ₂ O ₃ ), silicon (Si), etc. are often used, and these compositions In addition, any material that can be excited by light irradiation to decompose and remove hydrogen peroxide may be used, and titanium oxide, particularly anatase-type titanium oxide is preferable. In addition, the photocatalyst according to the present invention may be in any shape such as a granular shape, a film shape, a net shape, a lashing shape, or a fibrous shape of the composition itself that exhibits the photocatalytic function, or the composition that exhibits the photocatalytic function may be a carrier. It may be in the form of particles, film, net, lashing, fiber, etc.

  The carrier carrying the composition exhibiting the photocatalytic function is made of particulate activated carbon, silica, alumina, glass, or the like, or is made of quartz, hard glass, or the like in the shape of a net, lascil, or fiber. A carrier or the like is used. Further, for the purpose of fixing the composition itself exhibiting the photocatalytic function or the carrier carrying the composition exhibiting the photocatalytic function to the hydrogen peroxide decomposition tank, only itself or a mold retaining member or the like is used. It can also be used after being molded into a specific shape.

  As the photocatalyst according to the present invention, a non-woven fabric of a photocatalyst fiber having a photocatalyst on its surface, particularly a non-woven fabric of a photocatalyst fiber having titanium oxide on its surface is preferable, and further, an oxide phase (first phase) mainly composed of a silica component; It consists of composite oxide fibers with a metal oxide phase (second phase) containing Ti, and the proportion of Ti in the metal oxide composing the second phase increases in a gradient toward the surface layer of the fibers. A non-woven fabric of photocatalyst fibers made of silica-based composite oxide fibers is preferred.

  The first phase of the silica-based composite oxide fiber is an oxide phase mainly composed of a silica component, which may be amorphous or crystalline, and forms a solid solution or a eutectic compound with silica. The obtained metal element or metal oxide may be contained. Examples of the metal element (A) that can form a solid solution with silica include titanium. Examples of the metal element (B) of the metal oxide that can form a solid solution with silica include aluminum, zirconium, yttrium, lithium, sodium, barium, calcium, boron, zinc, nickel, manganese, magnesium, and iron. It is done.

  The first phase forms the internal phase of the silica-based composite oxide fiber and plays an important role in bearing the mechanical properties. The proportion of the first phase with respect to the entire silica-based composite oxide fiber is preferably 40 to 98% by mass, and the desired function of the second phase is sufficiently exhibited, and also high mechanical properties are exhibited. For this purpose, it is more preferable to control the ratio of the first phase within the range of 50 to 95% by mass.

  On the other hand, the second phase is a metal oxide phase containing titanium and plays an important role in developing the photocatalytic function. An example of the metal constituting the metal oxide is titanium. The metal oxide may be a simple substance, or may be a co-melting compound or a substance in which a substitutional solid solution is formed by a specific element, but is preferably titania. The second phase forms the surface layer phase of the silica-based composite oxide fiber, and the proportion of the second phase of the silica-based composite oxide fiber varies depending on the type of metal oxide, but is 2 to 60% by mass. Preferably, it is more preferable to control within the range of 5 to 50% by mass in order to sufficiently develop the function and simultaneously develop high strength. The crystal grain size of the metal oxide containing Ti of the second phase is preferably 15 nm or less, particularly preferably 10 nm or less.

  The proportion of titanium in the metal oxide contained in the second phase increases in a gradient toward the surface of the silica-based composite oxide fiber, and the thickness of the region where the composition gradient is clearly recognized is the surface layer. From 5 to 500 nm, but may be about 1/3 of the fiber diameter. The “existence ratio” of the first phase and the second phase refers to the first phase with respect to the metal oxide constituting the first phase and the entire metal oxide constituting the second phase, that is, the entire silica-based composite oxide fiber. The mass% of the metal oxide and the second phase metal oxide are shown.

  The photocatalyst fiber having the inclined structure as described above can be manufactured by a known method, for example, based on the method described in Patent Document 3.

  The ultraviolet ray according to the present invention is not particularly limited as long as it is an ultraviolet ray having a peak wavelength of 190 nm or more and has an energy equal to or higher than the energy corresponding to the band gap of the photocatalyst, and an ultraviolet ray having a peak wavelength of 250 to 260 nm is preferable. . Ultraviolet light having a peak wavelength of less than 190 nm is not preferable because it directly decomposes water and generates hydrogen peroxide, but may be included as long as the irradiation amount is enough to generate hydrogen peroxide of 1 ppb or less. The type of light source for irradiating ultraviolet rays is not particularly limited as long as it is a light source that has a peak wavelength of 190 nm or more and irradiates a wavelength having energy equal to or higher than the band gap of the photocatalyst. A lamp, an amalgam lamp, a xenon lamp, a black light, and an ultraviolet LED can be used, and an amalgam lamp is particularly preferable.

  An example of the embodiment of the hydrogen peroxide decomposition tank 3 according to the present invention will be specifically described with reference to FIG. 2, but it is not intended to limit the scope of the present invention.

  A hydrogen peroxide decomposition tank 3 of FIG. 2 which is an example of an embodiment of the hydrogen peroxide decomposition tank according to the present invention has a fluid inflow portion 11 and a fluid discharge portion 12, and is to be treated which has flowed from the fluid inflow portion 11. It has a structure that allows water to flow to the fluid discharge unit 12, and is disposed between the ultraviolet light source 13 that can irradiate ultraviolet light toward the flowing water to be treated, and between the inner surface of the hydrogen peroxide decomposition tank and the ultraviolet light source. A photocatalyst filter 15 disposed opposite to the ultraviolet light source and through which the water to be treated can pass, and the water to be treated existing between the inner surface of the hydrogen peroxide decomposition tank and the photocatalyst are guided between the photocatalyst and the ultraviolet light source. A first guide plate 18 and a second guide plate 19 for guiding the water to be treated existing between the ultraviolet irradiation section and the photocatalyst filter between the inner surface of the hydrogen peroxide decomposition tank and the photocatalyst, The first guide plate 18 and the photocatalytic filter It arrange | positions so that the to-be-processed water induced | guided | derived between a linear light source and the to-be-processed water induced | guided | derived between the inner surface of a hydrogen peroxide decomposition tank and a photocatalyst by the 2nd guide plate 19 may be passed. . Here, the photocatalytic filter is a stainless steel holding material 16 in which a nonwoven fabric of silica-based composite oxide fibers is wound in a cylindrical shape, and the nonwoven fabric is held by a cylindrical stainless steel wire mesh 17 and covered. The treated water is configured to pass between them.

  Two or more photocatalyst filter cartridges 14 in which one photocatalyst filter, one first guide plate, and one second guide plate are integrated are arranged in the same direction with respect to the arrangement direction. Each photocatalyst filter cartridge 14 is fixed by the connecting member 20. A predetermined gap (W2) is provided between the first guide plate 18 of one photocatalyst filter cartridge 14 adjacent to the second guide plate 19 of the other photocatalyst filter cartridge 14, and the first guide plate The to-be-processed water distribute | circulates the space | interval W2 of 18 and the 2nd guide plate 19. FIG. The interval W2 is narrower than the interval (W1) between the first guide plate and the second guide plate disposed in the same photocatalytic filter cartridge 14.

  The distance W2 may be a distance that allows the water to be treated to flow. For example, the height of the photocatalyst cartridge 14 (that is, between the first guide plate 18 and the second guide plate 19 disposed in the same photocatalyst cartridge). Interval) The length can be appropriately set to 1/20 to 1/2 with respect to W1, but depending on the flow rate in the hydrogen peroxide decomposition tank 3 of the water to be treated and the decomposition efficiency due to the energy of ultraviolet rays It can be changed appropriately. That is, if the interval W2 is increased, the flow rate is improved, but the number of photocatalyst cartridges 14 in the limited space of the hydrogen peroxide decomposition tank 3 is reduced, and the repeated flow in the radial direction of the water to be treated is reduced. As a result, the decomposition efficiency decreases as will be described later. On the other hand, when the interval W2 is narrowed, the flow rate becomes slow, but the number of the photocatalyst cartridges 14 in the limited space of the hydrogen peroxide decomposition tank 3 can be increased, and the flow of water to be flowed in the radial direction can be repeated. As a result, the decomposition efficiency is improved. Note that the interval W2 between the first guide plate 18 of the one adjacent photocatalyst cartridge 14 and the second guide plate 19 of the other photocatalyst cartridge 14 can be appropriately adjusted by sliding the photocatalyst cartridge 14 in the axial direction. It is preferable that By making the interval W2 adjustable in this way, the flow resistance can be appropriately set by adjusting the flow resistance of the water to be treated in the hydrogen peroxide decomposition tank 3. Thereby, the processing efficiency by a photocatalyst can be improved.

  Therefore, in the hydrogen peroxide decomposition tank 3 which is an example of the embodiment of the present invention, the water to be treated which has flowed from the fluid inflow portion 11 is irradiated with ultraviolet rays from the ultraviolet light source 13 by the first guide plate 18. , Induced between the photocatalytic filter 15 and the ultraviolet light source 13. Thereafter, the second guide plate 19 is guided between the inner surface of the hydrogen peroxide decomposition tank 3 and the photocatalytic filter 15 through the first photocatalytic filter 15 at the lowest stage. Next, the light is guided between the photocatalytic filter 15 and the ultraviolet light source 13 through the space W2 between the first guide plate 18 and the second guide plate 19, and then is moved up by one step by the second guide plate 19. The second photocatalytic filter 15 is guided between the inner surface of the hydrogen peroxide decomposition tank 3 and the photocatalytic filter 15. By repeating this alternately, hydrogen peroxide in the water to be treated is decomposed.

  The method for treating water to be treated containing hydrogen peroxide and the apparatus for removing hydrogen peroxide according to the present invention are particularly effective for treating waste water discharged from an electronic component manufacturing process. That is, while performing the hydrogen peroxide decomposition by ultraviolet rays while the ultraviolet rays are sufficiently irradiated to the water to be treated, the contact efficiency between the photocatalyst and the water to be treated is excellent, and the irradiation efficiency of the ultraviolet rays to the photocatalyst is high. It can decompose hydrogen peroxide in the water to be treated to the maximum extent.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited at all by these Examples.

(Production Example 1)
In a 5-liter three-necked flask, 2.5 liters of anhydrous toluene and 400 g of metallic sodium were added and heated to the boiling point of toluene under a nitrogen gas stream, and 1 liter of dimethyldiethyl silane was added dropwise over 1 hour. After completion of the dropwise addition, the mixture was heated to reflux for 10 hours to form a precipitate. This precipitate was filtered, washed with methanol and then with water to obtain 420 g of white powder of polydimethylsilane. 250 g of polydimethylsilane was charged into a three-necked flask equipped with a water-cooled reflux condenser, and heated and reacted at 420 ° C. for 30 hours under a nitrogen stream to obtain polycarbosilane having a number average molecular weight of 1200.

  To 16 g of polycarbosilane synthesized by the above method, 100 g of toluene and 64 g of tetrabutoxytitanium are added, preheated at 100 ° C. for 1 hour, then slowly heated to 150 ° C. and reacted for 5 hours to give modified polycarbosilane. Synthesized. In order to intentionally allow the low molecular weight organometallic compound to coexist with the modified polycarbosilane, 5 g of tetrabutoxytitanium was added to obtain a mixture of the modified polycarbosilane and the low molecular weight organometallic compound. After the mixture of this modified polycarbosilane and low molecular weight organometallic compound was dissolved in toluene, it was charged into a melt-bore single spinning device, the interior was sufficiently purged with nitrogen, and the temperature was raised to distill off the toluene. Spinning was performed at 0 ° C. The spun nonwoven fabric is heated to 150 ° C stepwise in air and then infusible, followed by firing in air at 1200 ° C for 1 hour to obtain silica-based composite oxide fibers composed of titania and silica as photocatalyst fibers. It was.

  The silica-based composite oxide fiber obtained in Production Example 1 had a first phase content of 80% by weight and a second phase content of 20% by weight. The abundance ratio was determined by fluorescent X-ray analysis. The titania crystal particles contained in the second phase were 8 nm. The particle diameter was determined by TEM (transmission electron microscope observation). From the surface of the silica-based composite oxide fiber, the abundance of titanium metal oxide was inclined at a depth of 300 nm. The inclination depth was determined by Auger electron spectroscopy.

Example 1
For the dissolved oxygen removing device 2 in the first step, a polyolefin-based hollow fiber membrane degassing device (PolyPore's Lixel (registered trademark) separation membrane contactor X40) having an ultimate vacuum of 100 Pa was used.

  In the second step, the hydrogen peroxide decomposition tank 3 shown in FIG. 2 was used. The hydrogen peroxide decomposition tank 3 is made of stainless steel and has an inner diameter of 100 mm and a height of 400 mm. A photocatalytic filter 15 made of a flat nonwoven fabric of silica-based composite oxide fibers obtained in Production Example 1 is attached to a stainless steel cylindrical holding material 16 and held by a stainless steel wire mesh 17 to form a cylindrical molded product. The photocatalyst cartridge 14 was produced by installing the 1st guide plate 18 and the 2nd guide plate 19 in each edge part of this cylindrical molding. The non-woven fabric attachment portion of the holding material 16 had an outer diameter of 60 mm, a height W1 of 30 mm, and a diameter of the first guide plate 18 in contact with the inner surface of the hydrogen peroxide decomposition tank 3 was 100 mm. The second guide plate 19 in contact with the ultraviolet light source was a disk-shaped object having an outer diameter of 60 mm, which is the same as the holding material 16, and has a hole having a diameter of 25 mm inscribed in the quartz tube of the ultraviolet light source at the center. Similarly to the embodiment shown in FIG. 2, the photocatalyst cartridge 14 having the above-described configuration was connected by the connecting member 20 with the interval W2 being 6 mm, thereby producing a 10-step photocatalyst cartridge. This was installed in the hydrogen peroxide decomposition tank 3 as shown in FIG. A protective tube made of transparent quartz having a diameter of 25 mm is inserted into the internal ultraviolet light source 13 of the hydrogen peroxide decomposition tank 3, and an amalgam lamp (NNI 60 / 35XL manufactured by Heraeus Co., Ltd.) having a peak wavelength of 254 nm and an output of 65 W is inserted into the protective tube. ) Was placed.

  The membrane deaerator and the hydrogen peroxide decomposition tank 3 are connected by a flow path so that the water to be treated flows from the membrane deaerator used as the dissolved oxygen removal apparatus 2 to the hydrogen peroxide decomposition tank 3. A removal apparatus 1 was configured. Also, a dissolved oxygen concentration measuring device 4 is installed in the flow path on the front side of the fluid inflow portion of the membrane degassing apparatus and on the front side of the fluid inflow portion of the hydrogen peroxide decomposition tank 3, so that the dissolved oxygen in the water to be treated. Concentration was measured.

  The treatment water containing hydrogen peroxide in Example 1 was treated as follows. Water to be treated containing 14 ppb hydrogen peroxide prepared by adding hydrogen peroxide to ultrapure water is introduced into the membrane deaerator at a flow rate of 1 L / min to reduce dissolved oxygen, and then the membrane The water to be treated treated by the deaerator was introduced into the hydrogen peroxide decomposition tank 3 while maintaining a flow rate of 1 L / min, and the hydrogen peroxide was decomposed by ultraviolet rays and a photocatalyst. During the treatment of the water to be treated, the membrane deaerator was operated to keep the degree of vacuum of the membrane deaerator at 0.8 kPa.

  The dissolved oxygen concentration measuring device 4 installed on the front side of the fluid inflow part of the membrane deaerator confirms that the dissolved oxygen concentration of the ultrapure water treated in Example 1 is 5.8 mg / L. The dissolved oxygen concentration measuring device 4 installed on the front side of the fluid inflow portion of the hydrogen oxide decomposition tank 3 confirmed that the dissolved oxygen concentration of the water to be treated was reduced to 0.07 mg / L by the membrane deaerator. It was.

  The treated water discharged from the hydrogen peroxide decomposition tank 3 after the hydrogen peroxide decomposition treatment was recovered, and the concentration of the hydrogen peroxide was measured to be 2 ppb. The hydrogen peroxide removal rate in Example 1 was It was confirmed to be 86%.

(Comparative Example 1)
A hydrogen peroxide removing device similar to that of the example is provided except that a dissolved oxygen removing device is not provided and the dissolved oxygen concentration measuring device 4 is installed only on the front side of the fluid inflow portion of the hydrogen peroxide decomposition tank 3. The water to be treated containing 18 ppb of hydrogen peroxide was introduced into the hydrogen peroxide decomposition tank 3 at a flow rate of 1 L / min, and the hydrogen peroxide was decomposed by ultraviolet rays and a photocatalyst.

  It is confirmed by the dissolved oxygen concentration measuring device 4 installed in front of the fluid inflow part of the hydrogen peroxide decomposition tank 3 that the dissolved oxygen concentration of the water to be treated to be treated in Comparative Example 1 is 5.5 mg / L. It was.

  The treated water discharged from the hydrogen peroxide decomposition tank 3 after the hydrogen peroxide decomposition treatment was recovered, and the hydrogen peroxide concentration was measured. As a result, it was 22 ppb, and the hydrogen peroxide concentration increased. confirmed.

(Comparative Example 2)
The hydrogen peroxide in the water to be treated was decomposed by the same method as in Example 1 except that the degree of vacuum of the membrane deaerator was kept at 8 kPa. In the same manner as in Example 1, it was confirmed that the dissolved oxygen concentration of the water to be treated was reduced to 0.7 mg / L by the membrane deaerator.

  The treated water discharged from the hydrogen peroxide decomposition tank 3 after the hydrogen peroxide decomposition treatment was recovered and the hydrogen peroxide concentration was measured. As a result, it was 9 ppb and the hydrogen peroxide removal rate was 36%. Was confirmed.

(Comparative Example 3)
In the same manner as in Example 1 except that the vacuum degree of the membrane deaerator was kept at 28 kPa and the hydrogen peroxide concentration of the water to be treated introduced into the membrane deaerator was 17 ppb. Hydrogen peroxide was decomposed. In the same manner as in Example 1, it was confirmed that the dissolved oxygen concentration of the water to be treated was reduced to 2.4 mg / L in the membrane deaerator.

  The treated water discharged from the hydrogen peroxide decomposition tank 3 after the hydrogen peroxide decomposition treatment was recovered and the hydrogen peroxide concentration measured was 11 ppb, and the hydrogen peroxide removal rate was 35%. Was confirmed.

(Comparative Example 4)
The photocatalytic filter (photocatalyst) 15 was removed from the hydrogen peroxide decomposition tank 3 of Example 1, and the hydrogen peroxide decomposition tank used in Comparative Example 4 was configured. In the same manner as in Example 1 except that this hydrogen peroxide decomposition tank not equipped with a photocatalyst was used and the hydrogen peroxide concentration of the water to be treated introduced into the membrane deaerator was 13 ppb. The hydrogen peroxide was decomposed. In the same manner as in Example 1, it was confirmed that the dissolved oxygen concentration of the water to be treated was reduced to 0.07 mg / L in the membrane deaerator.

  The treated water discharged from the hydrogen peroxide decomposition tank was recovered and the concentration of hydrogen peroxide in the treated water was measured. As a result, it was 12 ppb, and the hydrogen peroxide removal rate was 7%. Met. Except for the photocatalyst, when the hydrogen peroxide decomposition treatment was performed only by ultraviolet irradiation, the decomposition efficiency of hydrogen peroxide was significantly reduced.

  According to the method for treating water to be treated containing hydrogen peroxide and the hydrogen peroxide removing apparatus of the present invention, the hydrogen peroxide concentration of water to be treated containing hydrogen peroxide is reduced to an extremely low level, specifically to 5 ppb or less. it can.

  According to the present invention, ultrapure water cleaning wastewater used in factories that manufacture electronic components such as semiconductors and liquid crystals, etc., can be put into wastewater by an economically advantageous method using a combination of ultraviolet rays and a photocatalyst. Since the existing hydrogen peroxide having a concentration of ppb level can be effectively decomposed, such cleaning waste water can be easily reused for cleaning electronic components and the like.

DESCRIPTION OF SYMBOLS 1 Hydrogen peroxide removal apparatus 2 Dissolved oxygen removal apparatus 3 Hydrogen peroxide decomposition tank 4 Dissolved oxygen concentration measuring apparatus 11 Fluid inflow part 12 Fluid discharge part 13 Ultraviolet light source 14 Photocatalyst filter cartridge 15 Photocatalyst filter (photocatalyst)
16 Holding Material 17 Wire Mesh 18 First Guide Plate 19 Second Guide Plate 20 Connecting Member

Claims (9)

A method for treating water to be treated containing hydrogen peroxide,
A first step of reducing the dissolved oxygen concentration in the water to be treated to 0.1 mg / L or less by a dissolved oxygen removing device;
A second process for decomposing hydrogen peroxide in the treated water by bringing the treated water treated in the first step into contact with the photocatalyst while irradiating the photocatalyst with ultraviolet light having a peak wavelength of 190 nm or more. Process,
A method for treating water to be treated containing hydrogen peroxide, comprising:   The method for treating water to be treated containing hydrogen peroxide according to claim 1, wherein the water to be treated is waste water discharged from an electronic component manufacturing process.   The method for treating water to be treated containing hydrogen peroxide according to claim 1 or 2, wherein the photocatalyst is a non-woven fabric of photocatalyst fibers having titanium oxide on the surface.   The photocatalyst fiber is a fiber composed of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti, and a metal oxide constituting the second phase. 4. The water to be treated containing hydrogen peroxide according to claim 3, which is a silica-based composite oxide fiber having a photocatalytic function, in which the proportion of Ti increases in a gradient manner toward the surface layer of the fiber. Processing method. A dissolved oxygen removing device that reduces the dissolved oxygen concentration in the water to be treated containing hydrogen peroxide to a predetermined value or less;
Hydrogen peroxide decomposition that treats water to be treated containing hydrogen peroxide whose dissolved oxygen concentration is reduced to a predetermined value or less by the dissolved oxygen removal apparatus, and that contains a photocatalyst and an ultraviolet light source capable of irradiating the photocatalyst with ultraviolet light A tank,
An apparatus for removing hydrogen peroxide, comprising:   6. The hydrogen peroxide removing apparatus according to claim 5, wherein the predetermined value is 0.1 mg / L.   The hydrogen peroxide removing apparatus according to claim 5 or 6, wherein the water to be treated is waste water discharged from an electronic component manufacturing process.   The hydrogen peroxide removing apparatus according to any one of claims 5 to 7, wherein the photocatalyst is a non-woven fabric of photocatalyst fibers having titanium oxide on a surface thereof.   The photocatalyst fiber is a fiber composed of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti, and a metal oxide constituting the second phase. 9. The hydrogen peroxide removing apparatus according to claim 8, wherein the presence ratio of Ti is a silica-based composite oxide fiber having a photocatalytic function, which gradually increases toward the surface layer of the fiber.

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