JP5512358B2 - Pure water production method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for producing pure water by ultraviolet oxidation treatment.

  Conventionally, pure water such as ultrapure water from which organic substances, ionic components, fine particles, bacteria, and the like have been highly removed has been used as an application for washing water and the like in the manufacturing process of a semiconductor device and the manufacturing process of a liquid crystal display device. . In particular, when manufacturing an electronic component including a semiconductor device, a large amount of pure water is used in the cleaning process, and the demand for the water quality is increasing year by year. Pure water used in the cleaning process of electronic component manufacturing is one of the water quality management items in order to prevent the organic matter contained in the pure water from carbonizing in the subsequent heat treatment process and causing poor insulation. There is a growing demand for extremely low levels of total organic carbon (TOC). In ITRS (International Technology Roadmap for Semiconductors), which indicates the direction of technological development in the field of semiconductor device manufacturing, the required water quality of TOC in ultrapure water is 1 μg / L, that is, 1 ppb or less. It is demanded.

  As such high demands for pure water quality become apparent, various methods for decomposing and removing trace amounts of organic substances contained in pure water have been studied in recent years. As a representative example of such a method, a process for decomposing and removing organic substances by ultraviolet oxidation treatment has been introduced.

  In general, when organic substances are decomposed and removed by ultraviolet oxidation treatment, for example, an ultraviolet oxidation apparatus including a stainless steel reaction tank and a tubular ultraviolet lamp installed in the reaction tank is used. The water to be treated is introduced into the water and irradiated with ultraviolet rays. As the ultraviolet lamp, for example, a low-pressure ultraviolet lamp that generates ultraviolet rays having wavelengths of 254 nm and 185 nm, or a low-pressure ultraviolet lamp that generates ultraviolet rays having wavelengths of 254 nm, 194 nm, and 185 nm is used. When the water to be treated is irradiated with ultraviolet rays having a wavelength of 185 nm, oxidizing species such as hydroxyl radicals (.OH) are generated in the water to be treated, and trace organic substances in the water to be treated are oxidized by the oxidizing power of the oxidizing species. Decomposes into carbon and organic acids. The treated water obtained by subjecting the water to be treated in this way to the ultraviolet oxidative decomposition treatment is then sent to an ion exchange device disposed in the subsequent stage to remove carbon dioxide and organic acid.

  However, in the method of oxidative decomposition of organic matter using a general ultraviolet oxidizer, an ultraviolet lamp is used. However, although the ultraviolet lamp is very expensive, the ultraviolet intensity decreases with the passage of time of use. It is necessary to exchange about once a year. In addition, since the decomposition efficiency of organic matter in the UV oxidation device decreases as the concentration of organic matter in the treated water decreases, the organic matter in the treated water is targeted for treated water with a low TOC concentration as in pure water production. Furthermore, in order to oxidatively decompose, the required power amount per TOC concentration in the water to be treated becomes very large. Therefore, the oxidative decomposition of organic substances using a general ultraviolet oxidation apparatus for producing pure water has a problem that the running cost of the apparatus becomes extremely high.

By the way, as a technology for treating TOC in water to be treated with a relatively high concentration of organic matter, for example, a technology for treating and further collecting wastewater containing TOC components after use at a use point (drainage treatment technology, As a wastewater recovery treatment technology, there is a technology in which an oxidant such as hydrogen peroxide (H ₂ O ₂ ) or ozone (O ₃ ) is added to the water to be treated, and the TOC component is oxidatively decomposed by ultraviolet irradiation. In this case, it is assumed that the TOC concentration in the water to be treated is on the order of ppm, and since the water to be treated originally contains a large amount of various impurities, it is generally an open reaction. The container is used for UV irradiation. As the ultraviolet light source, a high-pressure ultraviolet lamp that generates a wavelength of 254 nm is generally used, the irradiation amount is several kWh / m ³ , and the residence time of the water to be treated in the reaction vessel is, for example, several tens of minutes to one hour. Is a standard.

  Hereinafter, an example of a technique for decomposing and removing TOC in water to be treated having a relatively high organic matter concentration will be described.

In Patent Document 1, as a technique for treating acidic wastewater containing organic matter, H ₂ O ₂ is added to permeate obtained by passing raw water having a TOC concentration of 2 ppm through a reverse osmosis membrane separation device (RO). An example is described in which 30 ppm of addition is followed by ultraviolet irradiation with a high-pressure ultraviolet lamp (high-pressure mercury lamp) to decompose and remove the TOC component.

In Patent Document 2, 30 ppm of H ₂ O ₂ is added to raw water having a TOC concentration of 1 ppm as an organic substance in the treated water for the purpose of decomposing and removing wastewater in the recovery of wastewater and the like. An example is described in which ultraviolet irradiation treatment is performed under the conditions of m ³ and a residence time of 1 hour.

Patent Document 3 discloses that a TOC concentration is 6 ppm as a pretreatment step for reducing the amount of organic matter in advance when decomposing and removing organic matter in water to be treated using a sulfur compound containing a peroxide group (for example, sodium peroxydisulfate). An example is described in which 60 ppm of H ₂ O ₂ is added to a certain water to be treated and irradiated with ultraviolet rays. Although the irradiation amount of ultraviolet rays is not described, the volume of the reaction vessel is 50 liters (L), and the flow rate is 100 liters / hour.

Patent Document 4 describes that 71 ppm of H ₂ O ₂ is added to water to be treated having a TOC concentration of 20 ppm, and ultraviolet rays are irradiated in an open reaction tank with a residence time of 25 minutes.

In Patent Document 5, in order to produce pure water from tap water (city water), a biological reaction tank and an ultraviolet oxidation treatment tank are combined as a pretreatment device disposed in front of the pure water production device. While circulating the water to be treated, 5 ppm of H ₂ O ₂ was added to the water to be treated in the ultraviolet oxidation treatment tank, and ultraviolet rays were irradiated from a medium pressure ultraviolet lamp at an irradiation dose of 0.1 to 0.3 kWh / m ^3. Thus, it is described that treated water having a TOC concentration of about 55 to 60 ppb was obtained.

Patent Document 6 shows an example in which O ₃ is added to water to be treated having a TOC concentration of 18 ppb for the production of pure water, and an ultraviolet oxidation treatment is performed. In the device described in Patent Document 6, in order to remove excess O ₃ , O ₃ is reduced to water by adding hydrogen (H ₂ ) and irradiating ultraviolet rays after the ultraviolet oxidation treatment. Patent Document 6, H ₂ O ₂ instead of O ₃ has also been described as usable, but for specific conditions of the added embodiment and H ₂ O ₂ added H ₂ O ₂ have been described at all Absent.

Thus, the conventional technology using both the addition of H ₂ O ₂ and ultraviolet irradiation is intended for a case where the TOC concentration in the water to be treated is relatively high, and the TOC concentration is 10 ppb or less. It is not intended for water to be treated, nor does it provide a guideline for H ₂ O ₂ addition conditions or UV oxidation treatment conditions when the TOC concentration of the water to be treated is 10 ppb. In addition, the amount of UV irradiation is large, and the residence time of the water to be treated in the reaction tank is long. These conditions also reduce the equipment cost and running cost and enable high-speed treatment, while producing pure water. In addition, it cannot be said that it is appropriate for the purpose of reducing the TOC concentration to the limit. Since H ₂ O ₂ itself is an impurity for pure water, adding H ₂ O ₂ also means adding an impurity. For this reason, H ₂ O ₂ is used in pure water treatment. It has not been generally considered to add and perform an ultraviolet oxidation treatment.

  In general, the reaction mechanism of decomposition and removal of organic substances by UV oxidation using a low-pressure UV lamp is that the hydroxyl radicals (OH radicals) generated by the decomposition of water with light having a wavelength of 185 nm react with the TOC component in the water to be treated. It is considered that the TOC component is oxidatively decomposed. Light having a wavelength of 185 nm is very well absorbed by water and therefore hardly transmits. The low-pressure ultraviolet lamp emits light having a wavelength of 254 nm in addition to light having a wavelength of 185 nm. However, light having a wavelength of 254 nm can be transmitted without being absorbed by water.

This light with a wavelength of 254 nm reacts with H ₂ O ₂ to generate OH radicals. In addition, since light having a wavelength of 185 nm has higher energy than light having a wavelength of 254 nm, it can react with H ₂ O ₂ to generate OH radicals as shown in formula (1).

The generated OH radical can oxidatively decompose the TOC component, but has a short lifetime. The OH radical that cannot be encountered with the TOC component molecule, that is, the organic molecule, and could not react with the TOC component returns to H ₂ O ₂ by the reverse reaction as shown in the formula (2).

In order to improve the decomposition efficiency of organic matter, the amount of OH radicals generated should be increased. When used in combination with changes and UV irradiation of H ₂ O _2, to increase the production amount of OH radicals, it may be Susumere reaction of formula (1) in right side. For this purpose, H ₂ O ₂ concentration Must be increased, the amount of UV irradiation should be increased, or both. However, even if the amount of OH radicals generated is increased, the OH radicals that did not encounter the TOC component and could not react with them will only return to H ₂ O ₂ in the reaction shown in formula (2). May be wasted and costly. Further, in a pure water system having a low TOC concentration, even if the amount of OH radicals generated is increased based on the equation (1) by using both H ₂ O ₂ addition and ultraviolet irradiation, the formula ( There is a possibility that only the reaction of 2) occurs and the processing efficiency does not increase.

Furthermore, since H ₂ O ₂ also absorbs light with a wavelength of 185 nm, when there is a reaction mechanism in which the light with a wavelength of 185 nm directly contributes to the oxidation of the TOC component, H ₂ O ₂ is added, so the wavelength of 185 nm It is also conceivable that the efficiency of decomposition of the organic matter deteriorates conversely because the amount of photons decreases.

As described above, when pure water is produced, adding H ₂ O ₂ also means adding impurities. Therefore, when H ₂ O ₂ is added, it is required to exhibit the maximum effect with the addition of a small amount as much as possible.

In pure water production, downsizing of the apparatus and high-speed processing are required, so that the residence time in the reaction vessel at the time of ultraviolet irradiation is better. Since the residence time in a conventional general ultraviolet oxidation apparatus for producing pure water is within 1 minute, even when H ₂ O ₂ and ultraviolet irradiation are used in combination, a treatment within 1 minute is required. .

JP-A-5-305297 Japanese Patent Laid-Open No. 10-277572 JP-A-11-99394 Japanese Patent No. 2500968 JP 7-284799 A Japanese Examined Patent Publication No. 6-47105

In pure water production, in order to decompose and remove the TOC component in the water to be treated, an ultraviolet oxidation treatment is generally performed. However, when the TOC concentration in the water to be treated is low, the required power becomes large and the running cost of the apparatus is increased. Becomes larger. In order to improve the decomposition efficiency of organic matter, it is conceivable to use both H ₂ O ₂ addition and ultraviolet irradiation. However, in the prior art, when the TOC concentration in the water to be treated is low, addition of H ₂ O ₂ and ultraviolet irradiation It does not show the processing conditions and effects when combined with irradiation.

  The object of the present invention is to produce pure water that can reduce the size and speed of the apparatus even when the TOC concentration in the water to be treated is low, reduce the running cost, and improve the decomposition efficiency of organic matter. It is to provide a method and apparatus.

In the pure water production method of the present invention, hydrogen peroxide (H ₂ O ₂ ) is added so as to be 20 ppb or more and 400 ppb or less to water to be treated having a TOC (total organic carbon) of 10 ppb or less, and then irradiated with ultraviolet rays. Including at least the step of:

  The pure water production apparatus of the present invention includes an addition means for adding hydrogen peroxide to 20 ppb or more and 400 ppb or less to water to be treated having a TOC of 10 ppb or less, and a treatment target to which hydrogen peroxide has been added by the addition means. It comprises at least an ultraviolet oxidation device that performs ultraviolet oxidation treatment by irradiating the treated water with ultraviolet rays.

Even if H ₂ O ₂ is added in a large amount when the TOC concentration is low, OH radicals are generated wastefully and the reaction shown in Formula (2) occurs, and an efficient treatment cannot be performed. By adding H ₂ O _{2 so} that the TOC concentration is 10 ppb or less to 20 ppb or more and 400 ppb or less, the organic substance is efficiently decomposed without generating OH radicals wastefully. become able to.

  The water to be treated in the present invention is assumed to have a TOC concentration of, for example, 1 ppb or more.

According to the present invention, H ₂ O ₂ is added to water to be treated having a TOC of 10 ppb or less so as to be 20 ppb or more and 400 ppb or less, so that a small amount of H ₂ can be produced without generating OH radicals. With the addition amount of O ₂ , the TOC removal efficiency can be greatly improved. As a result, the scale of the ultraviolet oxidation apparatus can be reduced, and the number of necessary ultraviolet lamps and the power consumption cost can be greatly reduced.

It is a figure which shows an example of a structure of the pure water manufacturing system of one Embodiment of this invention. It is a figure which shows the structure of the pure water manufacturing system of other embodiment of this invention. It is a figure which shows the structure of the pure water manufacturing system of further another embodiment of this invention. It is a figure which shows the structure of the water treatment apparatus in an Example.

  Next, embodiments of the present invention will be described with reference to the drawings.

The pure water manufacturing method based on this invention aims at performing decomposition | disassembly removal of the TOC component in to-be-processed water, for example in the process of manufacture of pure water. As the water to be treated, at least demineralized water at a pure water level is assumed, and the TOC concentration is 10 ppb or less. The lower limit of the TOC concentration in the water to be treated is, for example, 1 ppb. Therefore, the pure water production method according to the present invention includes at least a step of adding H ₂ O ₂ so as to be 20 ppb or more and 400 ppb or less to water to be treated having a TOC of 10 ppb or less and irradiating with ultraviolet rays. And The pure water production apparatus used for executing such a pure water production method is an addition means for adding H ₂ O ₂ so as to be 20 ppb or more and 400 ppb or less to the water to be treated having a TOC concentration of 10 ppb or less. And an ultraviolet oxidation apparatus that performs ultraviolet oxidation treatment by irradiating ultraviolet rays to the water to be treated to which H ₂ O ₂ has been added by the adding means. The resistivity of the water to be treated is preferably 1 MΩcm or more.

  Such a pure water production apparatus can be applied not only to a pure water production system for producing primary pure water, but also to a system for producing secondary pure water, a so-called subsystem. Hereinafter, an embodiment of the present invention will be described by taking the case where the present invention is applied to a subsystem as an example.

Here, the amount of H ₂ O ₂ added to the water to be treated will be described. When the TOC concentration of the water to be treated is 10 ppb or less, H ₂ O ₂ is added so as to be 20 ppb or more and 400 ppb or less from the viewpoint of improving TOC removal efficiency without generating OH radicals unnecessarily. As will be apparent from the examples and comparative examples described later, when the TOC concentration of the water to be treated is 10 ppb or less, when a small amount of H ₂ O ₂ is added, that is, within a range of up to 400 ppb, The TOC removal efficiency is improved as compared with the case where H ₂ O ₂ is not added. However, when the H ₂ O ₂ concentration exceeds 400 ppb, the TOC removal efficiency is higher than the case where H ₂ O ₂ is not added. descend. Therefore, the present invention provides an effect by adding H ₂ O ₂ so as to be in the range of more than 20 ppb and not more than 400 ppb.

  FIG. 1 shows a pure water production system according to an embodiment of the present invention.

This system includes a tank 11 for storing pure water, and a pump (P) 12 for sending pure water from the tank 11. A heat exchanger 15, an ultraviolet oxidizer (UV) 16, and a non-regenerative type are connected to the pump 12. A mixed bed ion exchange device (CP) 17 and an ultrafiltration device (UF) 19 are connected in this order, and water from the ultrafiltration device 19 is returned to the tank 11. A membrane deaerator (MD) 18 may be inserted between the non-regenerative mixed bed ion exchange device 17 and the ultrafiltration device 19 as necessary. It is assumed that the TOC concentration of water supplied to the ultraviolet oxidizer 16 is 10 ppb or less. The system further includes a H ₂ O ₂ storage tank 13 to store the H ₂ O _2, connected to a pipe connecting the heat exchanger 15 and the ultraviolet oxidation device 16, with respect to the for-treatment water in the pipe, H ₂ the O ₂ from H ₂ O ₂ reservoir 13 to be added to be equal to or less than 400ppb a pump 14 for supplying H ₂ O _2, and a.

In such a system, pure water stored in the tank 11 is first sent to the heat exchanger 15 by the pump 12 as water to be treated, and the temperature is adjusted. Thereafter, H ₂ O ₂ is added, and ultraviolet rays are irradiated in the ultraviolet oxidizer 16. As a result, the TOC component in the for-treatment water is decomposed. Thereafter, the water to be treated is sent to the non-regenerative mixed bed ion exchange device 17, so that the organic acid and carbon dioxide (CO ₂ ) generated by the ultraviolet oxidation treatment are removed by the non-regenerative mixed bed ion exchange device 17. Is done. Furthermore, the water to be treated is sent to the ultrafiltration device 19 (in some cases, sent to the ultrafiltration device 19 via the membrane deaeration device 18), and becomes water from which impurities have been highly removed. Will be sent to the point. The unused water is circulated and returned to the tank 11.

  In this configuration, the ultraviolet oxidizer 16 includes, for example, a sealed flow type reaction vessel in which an interface between the water to be treated and the gas phase is not formed, and an ultraviolet lamp that irradiates the water to be treated in the reaction vessel with ultraviolet rays It is preferable to provide. As the ultraviolet lamp, for example, a low-pressure ultraviolet lamp that generates at least light having a wavelength of 185 nm can be used.

The light from the low-pressure ultraviolet lamp includes a component having a wavelength of 254 nm in addition to a component having a wavelength of 185 nm. In the prior art, light with a wavelength of 185 nm can efficiently contribute to the decomposition of the TOC component, while light with a wavelength of 254 nm has little contribution to the decomposition of the TOC component. However, in this embodiment, H ₂ O ₂ is added. As a result, light having a wavelength of 254 nm can also contribute to the decomposition of the TOC component.

Although it is possible to decompose the TOC component by using H ₂ O ₂ in combination with a high-pressure ultraviolet lamp that mainly emits light with a wavelength of 254 nm, the residence time of the water to be treated in the reactor is improved by improving the decomposition efficiency. In order to shorten the size and reduce the size of the apparatus, it is preferable to use a low-pressure ultraviolet lamp (radiating a component having a wavelength of 185 nm) for ultraviolet irradiation.

In this embodiment, it is preferable that the irradiation amount in ultraviolet irradiation is 0.3 kWh / m ³ or less. Since the TOC concentration in the water to be treated is low, even if a large amount of OH radicals are generated with a high irradiation dose, the OH radicals are consumed in the reaction shown in the formula (2), so that efficient treatment is performed. I can't. By setting the irradiation amount to 0.3 kWh / m ³ or less, efficient treatment can be performed without generating OH radicals in vain.

  By using a closed flow type reaction vessel in which the interface between the water to be treated and the gas phase is not formed as the reaction vessel of the ultraviolet oxidizer, light having a wavelength of 254 nm that has passed through the water does not escape to the gas phase, so The OH radical is effectively used for the reaction of generating OH radicals represented by the formula (1). From the viewpoint of effective use of light having a wavelength of 254 nm, the inner surface of the reaction vessel is preferably made of a metal such as stainless steel (SUS) and mirror-finished.

  FIG. 2 shows a pure water production system according to another embodiment.

The system shown in FIG. 2 is the same as the pure water production system shown in FIG. 1 in order to remove residual H ₂ O ₂ from the treated water flowing out from the ultraviolet oxidizer 16, and the ultraviolet oxidizer 16 and the non-regenerative mixed bed ion. A catalyst tower 20 is disposed between the exchange devices 17. A platinum group metal catalyst is provided in the catalyst tower 20, and when the treated water comes into contact with the platinum group metal catalyst, the residue of H ₂ O ₂ is removed by catalytic decomposition. Activated carbon is also known as a decomposition catalyst for H ₂ O ₂ , but it is preferable to use a platinum group metal catalyst with little eluate in view of application in a pure water system. The platinum group metal here is ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), and one of these is used alone. You may use, and may use it in combination of 2 or more types. Among these platinum group metals, Pt and Pd can be preferably used, and Pd is preferable from the viewpoint of cost and the like.

  Such a platinum group metal catalyst is supported on, for example, an anion exchanger in the catalyst tower 20. The anion exchanger may be a granular anion exchange resin, or may be a monolithic organic porous anion exchanger formed by integrating the anion exchange resin. Examples of the monolithic organic porous anion exchanger that can be used here are described in JP-A Nos. 2002-306976 and 2009-62512. Supporting a platinum group metal catalyst on the anion exchanger is effective in exhibiting high catalytic ability and reducing the amount of eluate from the catalyst.

The catalyst tower 20 having a platinum group metal catalyst is provided, by contacting the H ₂ O ₂ of a platinum group metal catalyst generated in H ₂ O ₂ and UV oxidation apparatus 16 is added to the water to be treated, the H ₂ O ₂ It can be removed to very low concentrations. As a result, it is possible to prevent adverse effects such as oxidative degradation of the ion exchange resin in the non-regenerative mixed bed ion exchange apparatus 17 in the subsequent stage due to the oxidizing substance H ₂ O ₂ .

  In the system shown in FIG. 2, a non-regenerative mixed bed ion exchanger (CP) 17, a membrane deaerator (MD) 18, and an ultrafiltration device (UF) 19 are provided at the rear stage of the catalyst tower 20. Although connected in order, the membrane deaerator (MD) 18, the non-regenerative mixed bed ion exchanger (CP) 17, and the ultrafilter (UF) 19 may be connected in this order.

  FIG. 3 shows a pure water production system in still another embodiment.

The system shown in FIG. 3 is obtained by adding hydrogen (H ₂ ) to remove dissolved oxygen (DO) in the system shown in FIG. In order to add H ₂ , a gas dissolution membrane device 22 is provided between the ultraviolet oxidation device 16 and the catalyst tower 20, and H ₂ is supplied from the H ₂ storage tank 21 to the gas dissolution membrane device 22.

In this configuration, the treated water from the ultraviolet oxidizer 16 is brought into contact with the platinum group metal catalyst after H ₂ is dissolved. A platinum group metal catalyst such as Pd or Pt can remove dissolved oxygen in the presence of dissolved hydrogen. By treating with a platinum group metal catalyst after dissolving H ₂ , removal of residual H ₂ O ₂ and removal of DO can be performed simultaneously.

  The present invention will be described in more detail based on examples performed by the present inventors.

[Example 1]
A water treatment apparatus having the configuration shown in FIG. 4 was assembled. This equipment generates water to be treated with controlled TOC concentration by adding methanol (CH ₃ OH) as an organic substance to ultrapure water, and further, H ₂ O ₂ is added to carry out ultraviolet oxidation treatment. Is to do.

To pipe ultrapure water is supplied, the methanol is supplied from the methanol reservoir 31 via a pump (P), H ₂ O ₂ from H ₂ O ₂ storage tank 32 through a pump (P) is supplied, methanol And H ₂ O ₂ added ultrapure water is sent to the line mixer 33 where they are mixed well. The ultrapure water used here has a resistivity of 18 MΩ · cm or more, TOC 0.5 ppb (μg / L) or less, H ₂ O _{2 of 12} to 15 ppb (μg / L), and dissolved oxygen (DO) of 5 ppb ( μg / L). The water flowing out from the line mixer 33 was treated water, and the TOC concentration in the treated water was measured online by a TOC meter 39 (SIEVERS900 TOC meter manufactured by Seaverse). The H ₂ O ₂ concentration of the water to be treated was measured with an absorptiometer using the phenol phthaline method after sampling as shown in the figure (S).

A part of the water to be treated flowing out from the line mixer 33 was branched and supplied to the ultraviolet oxidizer 35 via the flow meter 34. As the ultraviolet oxidation device 35, ADF-4 manufactured by Chiyoda Corporation was used. In the ultraviolet oxidizer 35, four low-pressure ultraviolet lamps (200 W ultraviolet lamp SV-1500 manufactured by Chiyoda Corporation) that emit both light having a wavelength of 254 nm and light having a wavelength of 185 nm were installed as ultraviolet lamps. A part of the treated water flowing out from the ultraviolet oxidizer 35 is branched (36 L / h) and passed through the flow meter 36 in the order of the catalyst tower 37 and the non-regenerative mixed bed ion exchanger (CP) 38. In addition, the TOC concentration of the treated water of the non-regenerative mixed bed ion exchanger 38 is measured by a TOC meter 40 (A-1000XP TOC meter manufactured by ANATEL), and the treated water is sampled and residual H ₂ O is sampled. _Two concentrations were measured with an absorptiometer using the phenolphthalin method.

  As the catalyst tower 37, a cylindrical container made of acrylic resin (inner diameter 25 mm, height 300 mm) was used, and the container filled with 100 ml of catalyst resin (layer height about 200 mm) was used. As the catalyst resin, an anion exchange resin carrying Pd and having a Pd loading of 100 mg-Pd / LR (gel form, OH form: 95% or more) was used. The non-regenerative mixed bed type ion exchange device 38 has a cylindrical container made of acrylic resin (inner diameter 25 mm, height 1000 mm), and this container is filled with 300 ml of mixed bed ion exchange resin (layer height of about 600 mm). What was done was used.

The TOC removal rate was determined by the following formula:
TOC removal rate (%) = ((TOC0−TOC1) / TOC0) × 100
Here, TOC0 is the TOC concentration of the water to be treated, that is, the TOC concentration measured by the TOC meter 39, and TOC1 is the TOC concentration of the treated water from the non-regenerative mixed bed ion exchanger 38, that is, the TOC meter 40. TOC concentration measured in

As water to be treated, methanol and H ₂ O ₂ are added to ultrapure water so that the TOC concentration is ³ ppb and the H ₂ O ₂ concentration is 100 ppb with respect to a water flow rate of 20 m ³ / h. What was mixed with the mixer 33 was used. Then, in the ultraviolet oxidizer 35, the ultraviolet oxidization treatment was performed so that the ultraviolet ray irradiation amount was 0.04 kWh / m ³ and the residence time in the ultraviolet oxidizer 35 was 1.3 seconds. The TOC concentration of the treated water from the non-regenerative mixed bed ion exchanger 38 was measured to calculate the TOC removal rate. The results are shown in Table 1.

As shown in Table 1, the TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 was 0.54 ppb, and the TOC removal rate was 82%. By comparing with Comparative Example 1 described later, by adding a small amount of H ₂ O ₂ , the TOC removal efficiency is improved even when pure water having a very low TOC concentration is treated water. And it turned out that the treated water in which the TOC density | concentration was further reduced is obtained. Further, the residual H ₂ O ₂ concentration in the treated water at the outlet of the non-regenerative type mixed bed ion exchanger 38 was less than 1 ppb.

[Examples 2 and 3]
The test was performed under the same conditions as in Example 1 except that the H ₂ O ₂ concentration of the water to be treated was 200 ppb and 400 ppb, respectively. The results are shown in Table 1.

The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 in Example 2 was 0.55 ppb, and the TOC removal rate was 82%. Further, the TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Example 3 was 0.73 ppb, and the TOC removal rate was 76%. Compared to Comparative Example 1 below, the addition in a range of up to 400ppb the H ₂ O ₂ water to be treated has been found to improve the TOC removal efficiency. In any case, the residual H ₂ O ₂ concentration in the treated water at the outlet of the non-regenerative mixed bed ion exchanger 38 was less than 1 ppb.

[Comparative Example 1]
The test was performed under the same conditions as in Example 1 except that H ₂ O ₂ was not added to the water to be treated. The results are shown in Table 1. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 0.78 ppb, and the TOC removal rate was 74%.

[Comparative Example 2]
The test was performed under the same conditions as in Example 1 except that the H ₂ O ₂ concentration of the water to be treated was 600 ppb. The results are shown in Table 1. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 1.16 ppb, and the TOC removal rate was 61%. When H ₂ O ₂ was added excessively, the TOC removal rate was decreased as compared with the case where H ₂ O ₂ was not added.

[Examples 4, 5, and 6]
The water flow rate is 16 m ³ / h, the TOC concentration of the water to be treated is 5 ppb, the H ₂ O ₂ concentrations are 100 ppb, 200 ppb and 400 ppb, respectively, and the UV irradiation amount is 0.05 kWh / The test was performed under the same conditions as in Example 1 except that m ³ and the residence time in the ultraviolet oxidizer 35 was 1.6 seconds. The results are shown in Table 2.

As shown in Table 2, the TOC concentrations at the outlet of the non-regenerative mixed bed ion exchanger 38 in Examples 4, 5, and 6 were 0.76 ppb, 0.65 ppb, and 0.79 ppb, respectively, and the TOC removal rate. Were 85%, 87% and 84%, respectively. Compared to Comparative Example 3, below, by adding in the range of up to 400ppb the H ₂ O ₂ water to be treated has been found to improve the TOC removal efficiency. In any case, the residual H ₂ O ₂ concentration in the treated water at the outlet of the non-regenerative mixed bed ion exchanger 38 was less than 1 ppb.

[Comparative Example 3]
The test was performed under the same conditions as in Example 4 except that H ₂ O ₂ was not added to the water to be treated. The results are shown in Table 2. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 1.36 ppb, and the TOC removal rate was 73%.

[Comparative Example 4]
The test was performed under the same conditions as in Example 4 except that the H ₂ O ₂ concentration of the water to be treated was 1000 ppb. The results are shown in Table 2. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 1.67 ppb, and the TOC removal rate was 67%. When H ₂ O ₂ was added excessively, the TOC removal rate was decreased as compared with the case where H ₂ O ₂ was not added.

[Examples 7 and 8]
The water flow rate is 10.6 m ³ / h, the TOC concentration of the water to be treated is 10 ppb, the H ₂ O ₂ concentrations are 200 ppb and 400 ppb, respectively, and the UV irradiation amount is 0.075 kWh / The test was performed under the same conditions as in Example 1 except that m ³ and the residence time in the ultraviolet oxidizer 35 was 2.4 seconds. The results are shown in Table 3.

As shown in Table 3, the TOC concentrations at the outlet of the non-regenerative mixed bed ion exchanger 38 in Examples 7 and 8 were 0.70 ppb and 0.91 ppb, respectively, and the TOC removal rates were 93% and 91, respectively. %Met. It was found that the TOC removal efficiency was improved by adding H ₂ O ₂ to the water to be treated in the range up to 400 ppb as compared with Comparative Example 5 described later. In any case, the residual H ₂ O ₂ concentration in the treated water at the outlet of the non-regenerative mixed bed ion exchanger 38 was less than 1 ppb.

[Comparative Example 5]
The test was performed under the same conditions as in Example 7 except that H ₂ O ₂ was not added to the water to be treated. The results are shown in Table 3. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 1.73 ppb, and the TOC removal rate was 83%.

[Comparative Example 6]
The test was performed under the same conditions as in Example 7 except that the H ₂ O ₂ concentration of the water to be treated was 1000 ppb. The results are shown in Table 3. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 2.10 ppb, and the TOC removal rate was 79%. When H ₂ O ₂ was added excessively, the TOC removal rate was decreased as compared with the case where H ₂ O ₂ was not added.

[Example 9]
An apparatus similar to that illustrated in FIG. 4 and described in Example 1 was assembled and tested. However, the apparatus used here uses TFL-1 manufactured by Chiyoda Kogyo Co., Ltd. as the ultraviolet oxidizer 35, and the ultraviolet oxidizer 35 emits both light with a wavelength of 254 nm and light with a wavelength of 185 nm as an ultraviolet lamp. The apparatus differs from the apparatus of Example 1 in that one ultraviolet lamp (200 W ultraviolet lamp SV-1500 manufactured by Chiyoda Corporation) is installed. Further, the TOC concentration of the water to be treated was 10 ppb, the H ₂ O ₂ concentration was 50 ppb, the water flow rate of the water to be treated was 1.1 m ³ / h, and the ultraviolet irradiation amount was 0.06 kWh / m ³ . The other experimental conditions were the same as in Example 1 except for the residence time. The results are shown in Table 4.

As shown in Table 4, the TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 was 2.40 ppb, and the TOC removal rate was 76%. By comparing with Comparative Example 7 described later, it was found that the TOC removal efficiency was improved by adding a small amount of H ₂ O ₂ . Further, the residual H ₂ O ₂ concentration in the treated water at the outlet of the non-regenerative type mixed bed ion exchanger 38 was less than 1 ppb.

[Examples 10, 11, 12, 13]
The test was performed under the same conditions as in Example 9 except that the H ₂ O ₂ concentrations were 100 ppb, 200 ppb, 300 ppb and 400 ppb, respectively. The results are shown in Table 4.

As shown in Table 4, the TOC concentrations at the outlet of the non-regenerative mixed bed ion exchanger 38 in Examples 10, 11, 12, and 13 were 2.08 ppb, 2.12 ppb, 2.35 ppb, and 2.53 ppb, respectively. TOC removal rates were 79%, 79%, 77% and 75%, respectively. It was found that the TOC removal efficiency was improved by adding H ₂ O ₂ to the water to be treated in the range up to 400 ppb as compared with Comparative Example 7 below. In any case, the residual H ₂ O ₂ concentration in the treated water at the outlet of the non-regenerative mixed bed ion exchanger 38 was less than 1 ppb.

[Comparative Example 7]
The test was performed under the same conditions as in Example 9 except that H ₂ O ₂ was not added to the water to be treated. The results are shown in Table 4. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 was 2.72 ppb, and the TOC removal rate was 73%.

[Comparative Examples 8 and 9]
The test was performed under the same conditions as in Example 9 except that the H ₂ O ₂ concentration of the water to be treated was 600 ppb and 1000 ppb, respectively. The results are shown in Table 4. The TOC concentrations at the outlet of the non-regenerative mixed bed ion exchanger 38 were 2.89 ppb and 3.72 ppb, respectively, and the TOC removal rates were 71% and 63%, respectively. When H ₂ O ₂ was added excessively, the TOC removal rate was decreased as compared with the case where H ₂ O ₂ was not added.

11 Tank 12, 13 Pump (P)
14, 32 H ₂ O ₂ storage tank 15 Heat exchanger 16, 35 Ultraviolet oxidizer (UV)
17,38 Non-regenerative mixed bed ion exchanger (CP)
18 Membrane deaerator (MD)
19 Ultrafiltration equipment (UF)
20, 37 Catalyst tower 21 H ₂ storage tank 22 Gas dissolution membrane device 31 Methanol storage tank 33 Line mixer 34, 36 Flow meter 39, 40 TOC meter

Claims (6)

To treated water TOC is less than 10 ppb, adding hydrogen peroxide so that less than 20 ppb 400 ppb, at least viewed including the step of irradiating ultraviolet rays,
The ultraviolet ray includes light having a wavelength of 185 nm and is generated by a low-pressure ultraviolet lamp,
The method for producing pure water, wherein an irradiation amount of the ultraviolet rays to the water to be treated is less than 0.3 kWh / m ³ .   The method for producing pure water according to claim 1, wherein the irradiation with ultraviolet rays is performed in a closed flow reaction vessel having no interface between the water to be treated and the gas phase.   The pure water manufacturing method of Claim 1 or 2 which further includes the process of performing an ion exchange process with respect to the said to-be-processed water after the process of irradiating the said ultraviolet-ray. The pure water manufacturing method of any one of Claims 1 thru | or 3 whose resistivity of the said to-be-treated water is 1 MΩcm or more. An addition means for adding hydrogen peroxide to 20 ppb or more and 400 ppb or less to water to be treated having a TOC of 10 ppb or less;
An ultraviolet oxidation apparatus that performs ultraviolet oxidation treatment by irradiating ultraviolet rays to the water to be treated to which the hydrogen peroxide has been added by the adding means;
With at least,
The ultraviolet oxidation apparatus includes a sealed flow type reaction vessel in which an interface between the water to be treated and a gas phase is not formed, and generates at least light having a wavelength of 185 nm to emit ultraviolet rays to the water to be treated in the reaction vessel. An ultraviolet lamp for irradiation,
An apparatus for producing pure water, wherein an irradiation amount of the ultraviolet light to the water to be treated is less than 0.3 kWh / m ³ . The pure water production apparatus according to claim 5 , further comprising an ion exchange device connected to an outlet of the ultraviolet oxidation device.

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