JP6125244B2 - Ultrapure water production method - Google Patents

Description

  The present invention relates to an ultrapure water production method for producing ultrapure water having a lower oxidizing substance concentration.

  Conventionally, ultrapure water with an extremely low content of ionic components, fine particles, organic matter, dissolved gas, viable bacteria, and the like has been used in semiconductor manufacturing processes. In particular, the presence of an oxidizing substance such as dissolved oxygen or hydrogen peroxide in ultrapure water causes various problems such as the promotion of the formation of a natural oxide film on the surface of the silicon wafer. Along with the increasing integration of semiconductor elements, the demand for the purity of ultrapure water is becoming more and more severe, and in particular, the reduction of oxidizing substances has become a bigger issue.

  In general, such ultrapure water is produced by an ultrapure water production apparatus that combines a pretreatment system, a primary pure water system, and a secondary pure water system. That is, the raw water is made pretreated water by removing suspended substances, colloidal substances, and the like in a pretreatment system configured by combining a coagulation treatment device, a filtration device, an adsorption device, and the like. Next, pretreatment water is removed from ionic components, organic substances, fine particles, dissolved gas, etc. in a primary pure water system that combines an ion exchange device, a reverse osmosis membrane device, a deaeration device, an ultraviolet irradiation device, etc. The primary pure water has an organic carbon (hereinafter also referred to as TOC) concentration of 5.0 μg C / L or less and a resistivity of 16.0 MΩ · cm or more. Then, the primary pure water is sequentially processed in the secondary pure water system by an ultraviolet oxidizer, a non-regenerative mixed bed ion exchanger (polisher), a membrane deaerator, etc., for example, a TOC concentration of 1.0 μgC. / L or less, and the resistivity is 17.0 MΩ · cm or more.

  Incidentally, it is known that a trace amount of hydrogen peroxide remains in the treated water of the ultraviolet oxidizer of the secondary pure water system. This is considered to be generated by the reaction between the hydroxyl radicals generated by ultraviolet irradiation that did not contribute to the decomposition of organic matter. In addition, hydrogen peroxide may remain in the primary pure water when the recovered water obtained by collecting and treating the used ultrapure water in the semiconductor cleaning process or the like is used as raw water. This hydrogen peroxide degrades the ion exchange resin of the subsequent ion exchange device and the deaeration membrane of the membrane deaeration device, and at the same time, it is decomposed and dissolved oxygen concentration in ultrapure water (hereinafter also referred to as DO). To raise. Therefore, it is necessary to remove hydrogen peroxide as much as possible.

  As such a method, for example, an ultrapure water production method (see Patent Document 1) in which primary pure water is brought into contact with a reducing resin to remove oxidizing substances in treated water, or ultraviolet light is applied to treated water. There has been proposed a deaeration device (see Patent Document 2) that reduces dissolved oxygen by contact with a palladium catalyst after irradiation.

Japanese Patent Application Laid-Open No. 07-16580 Japanese Patent Laid-Open No. 08-168756

  However, in the method of removing hydrogen peroxide using a reducing resin, there is a problem that if the water is continuously passed for a long time, the reducing resin loses the reducing ability and the hydrogen peroxide leaks into the treated water. . In the method using a palladium catalyst, the dissolved oxygen concentration of the treated water increases, and there is a problem that equipment such as a degassing membrane is necessary to remove the dissolved oxygen.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an ultrapure water production method capable of producing ultrapure water having a lower hydrogen peroxide concentration and a lower dissolved oxygen concentration. And

  When primary pure water is irradiated with ultraviolet rays, water molecules are decomposed to generate hydroxy radicals and hydrogen radicals as shown in the following formula (1). This hydroxyl radical decomposes a trace amount of dissolved organic matter in the water to be treated, but the hydroxyl radicals that have not contributed to the decomposition react as shown in the formula (2) to generate a trace amount of hydrogen peroxide. At the same time, as shown in Formula (3), hydrogen radicals react to generate hydrogen.

(1) H ₂ O → OH + 2H
(2) 2HO · → H ₂ O ₂
(3) 2H · → H ₂

  FIG. 4 shows the dissolved oxygen concentration, hydrogen peroxide concentration, and hydrogen concentration when water to be treated containing oxygen, hydrogen peroxide, and hydrogen is brought into contact with the reducing resin in a general secondary pure water system. The change with time of is schematically shown. Hydrogen peroxide is reduced and removed in the process of contact with the reducing resin. Oxygen and hydrogen pass through the reducing resin as they are. When the contact between the water to be treated and the reducing resin is continued, the reducing resin gradually loses its reducing ability, and eventually hydrogen peroxide begins to leak from the reducing resin.

  Further, in a general secondary pure water system, treated water when treated water containing hydrogen peroxide and hydrogen is brought into contact with a metal catalyst having hydrogen adsorption ability (hereinafter also simply referred to as a metal catalyst). FIG. 5 schematically shows changes with time in dissolved oxygen concentration, hydrogen peroxide concentration, and hydrogen concentration. Although the mechanism of mutual reaction of oxygen, hydrogen peroxide and hydrogen during treatment in the process of contacting with the metal catalyst is not necessarily clear, for example, when a palladium catalyst resin is used, the following formula (4) to It seems that (6) seems to be the case.

(4) (Resin-Pd) + H ₂ → (Resin-Pd) -H ₂
(5) 2H ₂ O ₂ → 2H ₂ O + O ₂
(6) O ₂ +2 (resin—Pd—H ₂ ) → 2H ₂ O + (resin—Pd)

  As shown in Formula (4), hydrogen in the water to be treated is activated by being weakened in the bond between hydrogen atoms due to the presence of the catalyst, and activated and adsorbed on the surface of the metal catalyst. Further, as in (5), hydrogen peroxide in the water to be treated is decomposed into oxygen. And it is estimated that activated hydrogen decomposes | disassembles this oxygen like (6). At this time, since hydrogen peroxide and hydrogen react in equimolar stoichiometric amounts, if hydrogen peroxide is present in a greater number of moles than hydrogen in the water to be treated, it is generated by decomposition of excess hydrogen peroxide. As a result, the dissolved oxygen concentration of the treated water increases.

  As described above, when water is irradiated with ultraviolet light, equimolar amounts of hydrogen peroxide and hydrogen are generated in terms of stoichiometry. However, the present inventors have considered that when primary pure water is treated water, It was found that the hydrogen peroxide in the treated water of the UV oxidizer of the next pure water system was slightly in excess of the number of moles compared to hydrogen. This is because, among hydrogen peroxide and hydrogen generated in an equimolar amount in the ultraviolet irradiation device of the primary pure water system, a part of the hydrogen is replaced with nitrogen when passing through the primary pure water tank, and is discharged from the water. It is considered that hydrogen peroxide dissolved in the ultrapure water used in the semiconductor manufacturing process remains without being removed by the treatment after recovery or the primary pure water system.

  Therefore, in the present invention, the primary pure water is irradiated with ultraviolet rays, the treated water is brought into contact with the reducing resin to remove hydrogen peroxide, and then the reducing resin-treated water is brought into contact with the metal catalyst. FIG. 6 schematically shows changes over time in the dissolved oxygen concentration, hydrogen peroxide concentration, and hydrogen concentration of treated water in the metal catalyst at this time.

  In the method of the present invention, hydrogen peroxide in the UV-oxidized water is almost removed by the reducing resin. Then, it is considered that hydrogen peroxide remaining in the reducing resin-treated water is reduced by hydrogen generated in the ultraviolet oxidation apparatus and passing through the reducing resin in the process of contact with the metal catalyst.

  That is, the ultrapure water production method of the present invention is an ultrapure water production method for producing ultrapure water using primary pure water as water to be treated, wherein the primary pure water is passed through an ultraviolet oxidizer, and the ultraviolet oxidizer is used. The outlet water is brought into contact with a reducing resin and a metal catalyst having hydrogen adsorption capability in this order.

  In the ultrapure water production method of the present invention, the metal catalyst having hydrogen adsorption ability is preferably palladium or a palladium compound.

  In the ultrapure water production method of the present invention, the reducing resin is preferably a strongly basic anion exchange resin having a sulfite group and / or a bisulfite group on the surface.

  The removal of hydrogen peroxide with the metal catalyst described above is continued until all of the hydrogen in the treated water of the reducing resin reacts with hydrogen peroxide. Therefore, when the hydrogen concentration of the treated water of the reducing resin becomes almost zero, oxygen begins to leak into the treated water (outlet water) that is in contact with the metal catalyst.

  Therefore, the ultrapure water production method of the present invention measures the hydrogen concentration of the treated water contacted with the metal catalyst, and when the hydrogen concentration exceeds a predetermined value, It is preferable to stop the contact with the reducing resin.

  In the ultrapure water production method of the present invention, the treated water contacted with the metal catalyst is passed through at least one selected from a cation exchange resin device, a mixed bed ion exchange resin device, and an ultrafiltration membrane device. It is preferable to water.

  In the ultrapure water production method of the present invention, it is preferable to produce ultrapure water having a dissolved oxygen concentration of 1.0 μg / L or less and a hydrogen peroxide concentration of 1.0 μg / L or less.

  Moreover, it is preferable that the ultrapure water manufacturing method of this invention is obtained from the collection | recovery water of a semiconductor manufacturing process, and uses the primary pure water containing hydrogen peroxide as to-be-processed water.

  ADVANTAGE OF THE INVENTION According to this invention, the oxidizing substance in to-be-processed water can be removed efficiently, and the high purity ultrapure water with lower dissolved oxygen concentration and hydrogen peroxide concentration can be obtained.

  Further, according to the present invention, it is possible to stably produce high quality ultrapure water stably for a long period of time.

It is a schematic block diagram which shows the ultrapure water manufacturing apparatus of embodiment. It is a schematic block diagram which shows the ultrapure water manufacturing apparatus used in the Example. It is a graph which shows DO of metal catalyst treated water in an Example, hydrogen peroxide concentration, and hydrogen concentration. It is a graph which shows typically the density | concentration of oxygen, hydrogen peroxide, and hydrogen of the treated water by the conventional method using only reducing resin. It is a graph which shows typically the concentration of oxygen, hydrogen peroxide, and hydrogen of treated water in the conventional method using only a metal catalyst. It is a graph which shows typically oxygen, hydrogen peroxide, and hydrogen concentration of treated water in a device of an embodiment using a reducing resin and a metal catalyst.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment.

  FIG. 1 is a schematic configuration diagram showing the ultrapure water production apparatus of the present embodiment. The ultrapure water production apparatus 10 is disposed on the downstream side of the primary pure water tank 1 along the treatment line L1 with an ultraviolet oxidation apparatus 2, a reducing resin apparatus 3, a metal catalyst apparatus 4, a non-regenerative mixed bed ion exchange apparatus ( Polisher) 5 and ultrafiltration membrane device 6 are provided in this order. The processing line L1 is connected to a use point (POU), and a hydrogen concentration meter 7 is provided on a sample line L2 that is branched near the end of the processing line L1.

  A pump P1 is provided in front of the ultraviolet oxidizer 2 to adjust the flow rate of the water to be treated. Further, the water supply pipe 8 for supplying the water to be treated to the reducing resin device 3 is provided with an opening / closing valve 9 so that the water supply to the reducing resin device 3 is started or stopped.

  Further, the ultrapure water production apparatus 10 includes a return circulation line L3 that returns excess ultrapure water that has not been used at the use point to the primary pure water tank.

  The production of ultrapure water is performed as follows.

  In the ultrapure water production apparatus 10, primary pure water treated by the primary pure water system is stored in the primary pure water tank 1, supplied to the ultraviolet oxidizer 2 through the pump P 1, and irradiated with ultraviolet rays.

  The ultraviolet oxidizer 2 is preferably one that generates ultraviolet rays having a wavelength of 180 to 190 nm, particularly one that generates ultraviolet rays having a wavelength of 184.9 nm. The ultraviolet oxidation apparatus is not particularly limited, but it is preferable to use a low-pressure ultraviolet lamp for ultraviolet oxidation.

Moreover, although the ultraviolet irradiation amount in an ultraviolet-ray oxidation apparatus changes also with the flow rates of to-be-processed water, it is preferable that it is a ratio of 1.0-5.0 kW with respect to the water flow rate of 10 m < ³ > / hr.

  Next, the ultraviolet oxidation treated water (outlet water) treated by the ultraviolet oxidation device 2 is supplied to the reducing resin device 3 and brought into contact with the reducing resin.

  In the present embodiment, the reducing resin device 3 is not particularly limited, and a device filled with the reducing resin can be used.

  The reducing resin is a resin having a reducing group, for example, a sulfite group, a hydrogen sulfite group, a nitrous acid group, etc. The resin which has can be used. As such a reducing resin, typically, a resin introduced by exchanging an ion exchange group of a strongly basic anion exchange resin with a reducing group can be used.

In the reducing resin apparatus 3, if the space velocity of the water to be treated is too slow, components eluted from the resin may increase the TOC concentration of the treated water, and if it is too fast, the oxidizing substance may not be sufficiently removed. Therefore, it is preferable that the space velocity SV is 20～60Hr ^-1, is preferably 25~60hr ^-1.

In particular, the lifetime of the pure water production apparatus can be greatly extended by setting the space velocity SV to preferably 20 to 40 hr ⁻¹ , more preferably 20 to 30 hr ⁻¹ . Moreover, since the metal catalyst is provided in the latter stage of the reducing resin, the space velocity can be preferably 30 to 60 hr ⁻¹ , more preferably 40 to 60 hr ⁻¹ . In this case, it is possible to reduce the amount of the reducing resin used, to further reduce the elution component from the resin, and to reduce the TOC concentration of the reducing resin treated water.

  In this embodiment, the metal catalyst device 4 is installed after the reducing resin device 3 to decompose and remove oxidizing substances in the reducing resin treated water. The metal catalyst device 4 is a device having a metal catalyst having hydrogen adsorption ability as an active component.

  As a metal catalyst having hydrogen adsorption ability, for example, a catalyst capable of reducing a substance to be reduced by adsorbing and holding hydrogen in an activated state can be used.

  As a metal catalyst having hydrogen adsorption ability, for example, a metal catalyst using a metal element such as palladium or platinum can be used. Specifically, a palladium compound such as metal palladium, palladium oxide or palladium hydroxide, and palladium. / Platinum alloy etc. can be used. Especially, it is preferable to use the palladium catalyst which consists of metal palladium or a palladium compound from a viewpoint of availability or economical efficiency. The shape of the metal catalyst used may be any shape such as powder or pellet, and the average primary particle size is not particularly limited, but is preferably about 2 to 4 nm.

  The carrier is not particularly limited as long as it can support a metal catalyst having hydrogen adsorption ability, and alumina, activated carbon, silica, zeolite, ion exchange resin, and the like can be used. In addition, the supported amount of the metal catalyst is usually about 0.01 to 10% by mass, and when using the anion exchange resin described later, it is preferably 0.01 to 5% by mass relative to the total mass of the anion exchange resin. %, More preferably 0.05 to 2% by mass.

  As described above, the metal catalyst having hydrogen adsorption ability can be applied to the metal catalyst device by supporting it on the carrier as described above.

  As the carrier, among the above, it is preferable to use an ion exchange resin because the elution of impurities is small. The shape of the ion exchange resin used is generally spherical or pellet-like, and may be a macropore structure having pores. In order to enhance the catalytic activity, it is preferable to support palladium on a resin having finer pores and a large surface area.

  When a palladium catalyst is used as a metal catalyst having hydrogen adsorption ability, it is particularly preferable to use an anion exchange resin because the bond between the resin and the palladium catalyst is strong and the palladium catalyst is less detached.

In the metal catalyst device 4, hydrogen peroxide may not be sufficiently removed when the space velocity of the water to be treated is too fast, and if it is too slow, components eluted from the resin may increase the TOC concentration of the treated water. . Therefore, when using a palladium catalyst resin mentioned above is preferably a space velocity SV is 50～1000Hr ^-1, and more preferably 90~800hr ^-1.

  Further, instead of using the reducing resin device 3 and the metal catalyst device 4, the reducing resin and the metal catalyst may be filled into a single device as a double bed.

  As described above, the ultraviolet oxidation apparatus 2 generates equimolar amounts of hydrogen peroxide and hydrogen. Although the molar ratio of the generated hydrogen peroxide and hydrogen depends on the quality of the water to be treated, the primary pure water having an extremely small impurity content is used as the water to be treated, and therefore, the molar ratio of the hydrogen peroxide and hydrogen is almost the same even in the outlet water of the ultraviolet oxidation apparatus 2. It is thought that it will be maintained.

  At this time, for example, when the recovered water from the semiconductor manufacturing process is used as the raw water, the primary pure water may already contain a trace amount of hydrogen peroxide.

  As shown by the above formulas (5) and (6), the amount of hydrogen peroxide that can be removed by the metal catalyst depends on the number of moles of hydrogen present. In the conventional method using only the metal catalyst, If hydrogen peroxide is high, oxygen may be generated and remain in the treated water. However, in the present embodiment, a reducing resin is provided in the preceding stage of the metal catalyst, and the generation of oxygen in the metal catalyst is prevented by bringing the reducing resin treated water from which hydrogen peroxide has been removed into contact with the metal catalyst. Thus, the dissolved oxygen concentration can be lowered. Therefore, in the conventional case using only a metal catalyst, it is possible to omit equipment such as a degassing membrane that was indispensable in the subsequent stage of the metal catalyst device.

  In addition, even if hydrogen peroxide leaks into the reducing resin treatment water due to a reduction in the reducing ability of the reducing resin by passing water for a long period of time, as long as hydrogen is dissolved in the reducing resin treatment water, It can be removed with a metal catalyst. Therefore, the ultrapure water production apparatus 10 can be operated continuously for a long time, and high quality ultrapure water with lower dissolved oxygen concentration and lower hydrogen peroxide concentration can be produced stably during that time.

  In order to continue removing hydrogen peroxide for a longer period of time, it is necessary to replace the reducing resin before losing the reducing ability. The hydrogen peroxide concentration of reducing resin-treated water varies greatly depending on the operating conditions of the ultrapure water production equipment, and it is difficult to accurately predict hydrogen peroxide leaks using conventional methods that use only reducing resins. there were.

  However, in the present embodiment, when the amount of hydrogen peroxide leaked to the reducing resin treatment water increases for a long period of time, the metal catalyst consumed to decompose and remove the leaked hydrogen peroxide. As the amount of hydrogen increases, the hydrogen concentration in the metal catalyst treated water eventually approaches zero.

  When the amount of hydrogen retained in the metal catalyst becomes almost zero, the reaction of the above formula (6) does not occur in the metal catalyst, and the dissolved oxygen concentration of the treated water increases. Therefore, it is preferable to replace or regenerate the reducing resin when the hydrogen concentration of the metal catalyst treated water becomes zero. Thereby, the dissolved oxygen concentration of reducing resin process water can be made lower, and it is possible to manufacture high quality ultrapure water stably.

  In the present embodiment, it is preferable to monitor the dissolved hydrogen concentration in the treated water in contact with the metal catalyst in the ultrapure water production apparatus 10. As a result, the degree of deactivation of the reducing resin can be predicted almost accurately, and the time when the hydrogen concentration becomes zero can be predicted from the rate of decrease in the hydrogen concentration, thereby making it easy to determine the replacement time. Can do.

  Specifically, the water concentration of the reducing resin treatment water in order to determine the time of replacement, etc., by measuring the quality of the water to be treated in the reducing resin device 3 in advance and taking into account the exchange capacity of the reducing resin. It is preferable to determine a predetermined value and actually replace the reducing resin when the hydrogen concentration of the reduction treated water reaches this predetermined value.

  The hydrogen concentration meter 7 for monitoring the hydrogen concentration is not particularly limited as long as it can measure the hydrogen concentration in ultrapure water. For example, a diaphragm type hydrogen concentration meter can be used.

  As described above, according to the present embodiment, it is possible to automatically monitor the deterioration of the reducing resin on-line, and to operate the ultrapure water production apparatus more safely.

Furthermore, it is preferable to install the reducing resin apparatus by connecting a plurality of towers in parallel. In this case, by passing water to at least one of these multiple towers and stopping water flow to the other towers, the exchange time of the reduced resin devices of the multiple towers is shifted, and the towers are exchanged one by one. Is possible.
Therefore, ultrapure water can be produced continuously for a longer period without stopping the ultrapure water production apparatus.

  In this embodiment, since a metal catalyst is used, the amount of metal components leaks into the ultrapure water as ions, oxides, and colloids while the production of ultrapure water continues for a long time. There is also a case. Therefore, it is preferable to install at least one selected from a cation exchange resin device, a mixed bed ion exchange device, or an ultrafiltration membrane device that can remove this metal component in the subsequent stage of the metal catalyst device 4. . Thereby, the raise of the resistivity by the leak of a metal component can be prevented, and ultrapure water quality can be kept stable with higher quality.

  Moreover, in this embodiment, the primary pure water which processed the raw water, such as city water, well water, and industrial water, in order by the pre-processing system and the primary pure water system can be used as treated water. In addition, ultrapure water used in the semiconductor manufacturing process is treated, and recovered water from which dissolved organic solvents, acids, alkalis and other chemicals are removed to some extent is passed through the primary pure water system to produce primary pure water. The primary pure water can be used as water to be treated. The recovered water usually contains hydrogen peroxide, but in this embodiment, when the primary pure water obtained from the recovered water is treated water, a more remarkable effect is obtained. The primary pure water preferably has a TOC concentration of 5.0 μg C / L or less, a resistivity of 16.0 MΩ · cm or more, and a dissolved oxygen concentration of 5.0 μg / L or less.

  As described above, according to the present embodiment, ultrapure water having a hydrogen peroxide concentration of 1.0 μg / L or less and a dissolved oxygen concentration of 1.0 μg / L or less can be stably produced.

  In addition, in the conventional method, the dissolved oxygen concentration and the hydrogen peroxide concentration are at the same level as before the shutdown when the operation is resumed after the operation of the apparatus is temporarily stopped for replacement of the reducing resin and the palladium catalyst carrier resin. However, according to the ultrapure water production apparatus of the present embodiment, it is possible to operate safely for a longer period of time. The frequency of raising can be reduced.

Next, examples of the present invention will be described.
Examples 1 to 10 and 13 are examples, and examples 11 and 12 are comparative examples.

(Example 1)
Ultrapure water was produced using the ultrapure water production apparatus 20 having the configuration shown in FIG.
The ultrapure water production apparatus 20 includes a pump P2, a membrane degassing device 22, an ultraviolet oxidation device 23, a polisher 24, and a secondary pure water tank 25 in this order along the processing line L1 at the subsequent stage of the primary pure water tank 21. The ultrapure water that is the treated water of the polisher 24 can be temporarily stored in the secondary pure water tank 25. Downstream of the secondary pure water tank 25, a heat exchanger 26, a polisher 27, an ultrafiltration membrane device 28, and an ultraviolet oxidation device 29 are sequentially provided via a pump P3. While being maintained at a substantially constant water temperature of 25 ° C. at 26, water is passed through each water treatment device in turn.

  Further, in order to keep the quality of the ultrapure water in the secondary pure water tank 25 stable, the circulation line L4 for circulating the treated water of the ultraviolet oxidizer 29 to the secondary pure water tank 25 and the ultrafiltration membrane device 28 A circulation line L5 for circulating the treated water to the secondary pure water tank 25 is provided.

In the pure water production apparatus 20, the processing line L 1 is connected to branch lines L 6 and L 7 downstream of the ultraviolet oxidation apparatus 29.
On the branch line L6, a reducing resin device 30, a metal catalyst device 31, and a non-regenerative mixed bed ion exchange resin device (polisher) 32 are installed in this order, and on the branch line L7, a metal catalyst is provided. A device 33 is installed. Further, a sample line is connected as necessary, and a hydrogen concentration meter 34 is provided.

  The quality of ultrapure water stored in the secondary pure water tank 25 is such that the TOC concentration is 0.5 μg C / L or less, the resistivity is 17.0 MΩ · cm or more, and the dissolved oxygen concentration is 5.0 μg / L or less.

Each water treatment device used in the examples is shown below.
Ultraviolet oxidation device (TOC-UV) 29: AUV (manufactured by Nippon Photo Science Co., Ltd.), irradiation amount 0.3 kWh / m ³ ,
Reducing resin device 30: a strongly basic anion exchange resin, Duolite A-113 plus (manufactured by Rohm and Haas) converted into SO ₃ type using sodium sulfite in a transparent polyvinyl chloride container, 2L filled (layer height about 1m),
Metal catalyst device 31: A container made of transparent polyvinyl chloride filled with 0.4 L of Lewatit (trade name (registered trademark), manufactured by LANXESS) K7333 as a palladium catalyst resin (layer height: about 0.2 m),
Metal catalyst device 33: In the metal catalyst device 31, a palladium catalyst resin (Lewatit) (trade name (registered trademark), manufactured by LANXESS) K7333 configured as 0.6 L (layer height of about 0.3 m),
Polisher 32: MBGP (trade name, manufactured by Rohm and Haas),
Hydrogen concentration meter 34: Orbisphere MOCA3600 (trade name, manufactured by HACH),
Hydrogen peroxide concentration meter: NOXIA-L II (trade name (registered trademark), manufactured by Nomura Micro Science Co., Ltd.),
TOC meter: Anatel A1000XP (trade name, manufactured by HACH),

  The water to be treated was introduced into the ultraviolet oxidizer 29 at a flow rate of 4.8 L / hr, and then passed through the branch line L6.

The space velocity SV of the water to be treated in the reducing resin device 30 at this time was 24 hr ⁻¹ , and the space velocity SV in the metal catalyst device 31 was 120 hr ⁻¹ .

(Example 2)
An accelerated test was conducted assuming long-term ultrapure water production operation. That is, the supply flow rate to the reducing resin device 30 was about three times that of Example 1 (13.8 L / hr) so as to forcibly leak hydrogen peroxide. Other than that, water was passed under the same conditions as in Example 1. In addition, Example 2 assumes the time of passing water for 12 months under the conditions of Example 1.

(Example 3)
The acceleration test was conducted in the same manner as in Example 2. That is, the supply flow rate to the reducing resin device 30 is about 3 times (13.8 L / hr) of Example 1, and the supply flow rate to the metal catalyst device 31 is about 3 times (13.8 L / hr) of Example 1. The water was passed under the same conditions as in Example 1. In addition, Example 3 assumes the time of passing water for 12 months under the conditions of Example 1.

In Examples 1 to 3, the water to be treated and treated water of the ultraviolet oxidation device 29, the treated water of the reducing resin device 30, the treated water of the metal catalyst device 31, the dissolved oxygen concentration (DO), hydrogen peroxide (H ₂ O ₂ ) Concentration, hydrogen (H ₂ ) concentration, and space velocity (SV) in each apparatus are shown in Table 1. Moreover, the palladium concentration of the treated water of the metal catalyst device 31 and the treated water of the polisher 32 when water is passed under the conditions of Example 1 is shown in the lower column of Table 1. Regarding the palladium concentration, Example 1 is a value when continuous water flow is performed and the palladium concentration becomes steady (after two weeks), and Example 4 is a value immediately after the start of water flow in Example 1. The palladium concentration was measured by ICP (inductively coupled plasma) mass spectrometry. In each table, an inequality sign indicates that it is below the measurement limit value.

(Examples 5 to 11)
Accelerated tests were conducted assuming long-term operation. That is, water was passed under the same conditions as in Example 1 except that the supply flow rate to the reducing resin device 30 was changed to leak hydrogen peroxide at a predetermined concentration.

Table 2 shows the space velocity (SV) in each apparatus in Examples 5 to 11 and the H ₂ O ₂ concentration and DO of treated water in the reducing resin apparatus 30. Table 2 shows the H ₂ O ₂ concentration, DO, and H ₂ concentration of the treated water of the metal catalyst device 31.

(Example 12)
In Example 1, the treated water of the ultraviolet oxidizer 29 was passed through the line L7.

Water was passed under the same conditions as in Example 1 except that the supply flow rate to the metal catalyst device 33 was 95 L / hr (space velocity SV = 158 hr ⁻¹ ).

The H ₂ O ₂ concentration, DO, and H ₂ concentration of the treated water in the metal catalyst device 33 in Example 12 are shown in Table 1 together with Examples 1 to 4.

(Example 13)
When the space velocity SV of the reducing resin device 30 is 30 hr ⁻¹ and the space velocity SV of the metal catalyst device 31 is 120 hr ⁻¹ , the water passage time and the metal catalyst device when the other conditions are the same as in Example 1 are used. The graph of the relationship between the dissolved oxygen concentration (DO) of 31 treated water and hydrogen concentration is shown in FIG.

As shown in Table 1, in Examples 1 to 3, hydrogen peroxide in the ultraviolet oxidation-treated water is removed by the reducing resin device. Then, since the treated water of the reductive resin system is brought into contact with the metal catalyst, H ₂ O ₂ concentration of the metal catalyst treated water 0.2 [mu] g / L or less, DO has been reduced to 0.2 [mu] g / L I understand that.

Among them, as an accelerated test, passed through the examples 2 and 3 even concentration of _H 2 _{O 2} as the concentration of _H 2 _{O 2} becomes 2 [mu] g / L of reducing resin treated water 0.2 [mu] g / L or less, DO is 0. Even when there is a leak of H ₂ O ₂ from the reducing resin, it can be seen that the DO and H ₂ O ₂ concentrations are greatly reduced by contacting with the metal catalyst. Regarding this, in Example 3, since the H ₂ O ₂ concentration was reduced in the reducing resin apparatus and H ₂ was dissolved in the reducing resin treated water at 0.62 μg / L, this H ₂ was a metal. It is considered that the catalyst device 31 contributed to the removal of H ₂ O ₂ .

On the other hand, in Example 12 using only the metal catalyst device, DO in the metal catalyst treated water has increased to 7.8 μg / L. This is because the H ₂ O ₂ in the treated water of the ultraviolet oxidation device 29 is present in excess over H ₂ in moles, presumably because of H ₂ O ₂ excess was decomposed in the metal catalyst device 33.

  Further, in Table 1, when the palladium concentration is seen, as shown in Examples 1 and 4, it is found that the leakage of palladium can be extremely suppressed by installing the mixed bed type ion exchange resin device in the subsequent stage of the metal catalyst device.

Further, from Table 2, when H ₂ O ₂ leaks from the reducing resin, H ₂ remains in the metal catalyst treated water at a predetermined amount or more with respect to the amount of H ₂ O _{2 in} the reducing resin treated water. In Examples 5 to 10, the H ₂ O ₂ concentration of the metal catalyst treated water is 0.2 μg / L or less, and the DO is 0.2 μg / L. On the other hand, in Example 11 where the H ₂ O ₂ concentration increased and the H ₂ concentration decreased, it can be seen that H ₂ O ₂ was not removed and, as a result, DO increased.

  FIG. 3 shows that the ultrapure water production apparatus 20 of the embodiment can obtain a water quality of 0.2 μg / L or less even after 19 months from the start of water flow.

  As described above, according to the present embodiment, ultrapure water having a hydrogen peroxide concentration of 1.0 μg / L or less and a dissolved oxygen concentration of 1.0 μg / L or less can be stably produced.

  Furthermore, it is possible to extend the life of the ultrapure water production apparatus and produce high quality ultrapure water stably for a long period of time. Moreover, the degree of deterioration of the reducing resin can be estimated by measuring the hydrogen concentration of the metal catalyst treated water.

  DESCRIPTION OF SYMBOLS 10,20 ... Ultrapure water production apparatus, 1 ... Primary pure water tank, 2 ... Ultraviolet oxidation apparatus, 3 ... Reducing resin apparatus, 4 ... Metal catalyst apparatus, 5 ... Non-regenerative mixed bed type ion exchange apparatus (polisher) , 6 ... Ultrafiltration membrane device, 7 ... Hydrogen concentration meter, 8 ... Water supply pipe, 9 ... Open / close valve, 21 ... Primary pure water tank, 22 ... Membrane degassing device, 23, 29 ... UV oxidation device, 24, 27, 32 ... Non-regenerative mixed bed ion exchanger (polisher), 25 ... Secondary pure water tank, 26 ... Heat exchanger, 28 ... Ultrafiltration membrane device, 30 ... Reducing resin device, 31, 33 ... Metal catalyst device, 34 ... hydrogen concentration meter, L1 ... treatment line, L2 ... sample line, L3, L4, L5 ... circulation line, L6, L7 ... branch line, P1, P2, P3 ... pump.

Claims (7)

An ultrapure water production method for producing ultrapure water using primary pure water as treated water,
Pass primary pure water through UV oxidizer,
A method for producing ultrapure water, comprising bringing the outlet water of an ultraviolet oxidizer into contact with a reducing resin and a metal catalyst having hydrogen adsorption capability in this order.   The ultrapure water production method according to claim 1, wherein the metal catalyst having hydrogen adsorption ability is palladium or a palladium compound.   The method for producing ultrapure water according to claim 1 or 2, wherein the reducing resin is a strongly basic anion exchange resin having a sulfite group and / or a bisulfite group on the surface. Measure the hydrogen concentration of the treated water contacted with the metal catalyst,
The method for producing ultrapure water according to any one of claims 1 to 3, wherein when the hydrogen concentration exceeds a predetermined value, contact between the outlet water of the ultraviolet oxidizer and the reducing resin is stopped.   The treated water brought into contact with the metal catalyst is passed through at least one selected from a cation exchange resin device, a mixed bed ion exchange resin device, and an ultrafiltration membrane device. The ultrapure water manufacturing method as described. The method for producing ultrapure water according to any one of claims 1 to 5, wherein ultrapure water having a dissolved oxygen concentration of 1.0 µg / L or less and a hydrogen peroxide concentration of 1.0 µg / L or less is produced.
Ultrapure water production method.   The method for producing ultrapure water according to any one of claims 1 to 6, wherein primary pure water obtained from recovered water of a semiconductor production process and containing hydrogen peroxide is treated water.

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