JPH11114584A - Treatment of water and water treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose the org. matter contained in such raw water as washing water, city water and industrial water with high efficiency to produce pure water by dissolving ozone in the water to a specified concn. to oxidize and decompose the org. matter in the water to be treated and applying ion exchange to the water. SOLUTION: The water to be treated contg. org. matter is supplied to a tank 1 and then introduced into a reaction tank 2, and ozone is added to the water to be 10-25 ppm. Subsequently, hydrogen peroxide and an aq. soln. of such a base as potassium hydroxide and sodium hydroxide is added to oxidize the org. matter. When the oxidation reaction is completed in the reaction tank 2, the oxidated water is supplied to a removal device 3, and such oxidizing agents as ozone and hydrogen peroxide remaining in the water are removed. The water is then introduced into an ion exchanger 4, and various org. acids and trace of carbon dioxide and ionic components are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment method used in the electronics industry and the pharmaceutical industry, and more particularly, to a water treatment method used in a semiconductor washing process, which is contained in raw water such as washing water, city water and industrial water. The present invention relates to a water treatment method for treating pure organic matter (TOC) to produce pure water from which the TOC has been substantially removed.

[0002]

2. Description of the Related Art In the manufacturing process of liquid crystals, semiconductor devices (LSI), or pharmaceuticals, ionic substances, fine particles,
Pure water with extremely low contents of organic matter, dissolved gas, viable bacteria and the like is used. Above all, in the electronics industry, a large amount of pure water is used, and with the increase in the degree of integration of ULSI (ultra-high-density large-scale integrated circuit), the demand for the purity of pure water is becoming increasingly severe.

In a semiconductor production process represented by ULSI or the like, an organic solvent is frequently used for stripping a photoresist or the like, and an organic substance such as an organic solvent is mixed in wastewater discharged in the semiconductor production process. Therefore, in order to regenerate the wastewater and reuse it in a semiconductor production process, it is necessary to remove organic substances contained in the wastewater.

Conventionally, as a method of removing organic substances contained in wastewater, a method of adding ozone to wastewater to decompose hardly decomposable organic substances, followed by treatment with activated carbon to remove organic substances from the wastewater. Alternatively, a method has been adopted in which ozone is dissolved in wastewater, and then ultraviolet irradiation is performed to decompose and remove organic substances.

However, these conventional methods have a problem that the decomposition efficiency of organic substances is low and it is difficult to remove organic substances from wastewater. In addition, the method using both the addition of ozone and the irradiation of ultraviolet rays has a problem that the power consumption associated with the irradiation of ultraviolet rays is large and the maintenance and management of the ultraviolet irradiation lamps and the like are required, so that the economic burden is large. Was.

Further, a method of adding ozone and hydrogen peroxide to wastewater has been studied, but even with this method, no significant improvement in removal efficiency has been found.

[0007] In the above method, a diffuser or an aeration method is used as a method for dissolving ozone in water, and this method can only dissolve ozone up to about 3 to 8 ppm.

Further, a method has been developed in which ozone is forcibly dissolved in water to be treated at a high concentration to decompose organic substances in the water to be treated. The removal rate does not improve so much, but rather is lower than that of hydrogen peroxide.

[0009]

Heretofore, as a method for removing organic substances contained in wastewater, a method in which ozone is added to wastewater to decompose hardly decomposable organic substances and then treated with activated carbon, A method of decomposing and removing organic substances by performing ultraviolet irradiation after dissolving, a method of adding ozone and hydrogen peroxide to wastewater, and a method of forcibly dissolving ozone at a high concentration in treated water to remove organic substances in the treated water. Decomposition methods are known, but none of these methods has provided a sufficient organic matter removal rate.

[0010] The present inventors have conducted intensive studies to solve the conventional disadvantages, and surprisingly found that ozone was dissolved at a high concentration in the water to be treated in which hydrogen peroxide was dissolved. In this case, the removal efficiency is dramatically improved, even when compared to the case where ozone is dissolved at a high concentration, as well as the case where each is used alone. It has been found that a high removal rate that could not be realized until now can be achieved.

The present invention has been made on the basis of such knowledge, and is intended to reduce the amount of organic substances (TOC: total organic carbon) contained in raw water such as cleaning water, city water and industrial water used in a semiconductor cleaning step. An object of the present invention is to provide a water treatment method and a water treatment apparatus that can decompose efficiently and produce pure water from which TOC is almost removed.

[0012]

According to the present invention, hydrogen peroxide is added to water to be treated and ozone is dissolved to a concentration of 10 ppm or more to oxidize organic substances dissolved in the water to be treated. A water treatment method comprising: a step of decomposing; and a step of performing ion exchange on the water to be treated after the step of oxidatively decomposing organic substances.

According to a second aspect of the present invention, there is provided a process for supplying hydrogen peroxide and a base to water to be treated, dissolving ozone to a concentration of 10 ppm or more, and oxidatively decomposing organic substances dissolved in the water to be treated. Performing ion exchange on the water to be treated that has undergone the oxidative decomposition step.

According to a third aspect of the present invention, in the first or the second aspect of the invention, before the step of performing ion exchange,
A water treatment method comprising a step of removing an unreacted residue in a step of oxidatively decomposing an organic substance.

A fourth aspect of the present invention is the water treatment method according to any one of the first to third aspects, wherein the pH of the water to be treated in the step of oxidatively decomposing an organic substance is 5 to 8.

According to a fifth aspect of the present invention, there is provided a water treatment method according to the first to fourth aspects, wherein the ozone concentration of the water to be treated in the step of oxidatively decomposing organic substances is 10 to 25 ppm. .

According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, the ozone concentration of the water to be treated and the concentration ratio of hydrogen peroxide (H ₂ O
₂ / O ₃ (weight ratio) is 1.0 to 5.0. According to a seventh aspect of the present invention, there is provided an ozone dissolving tank for dissolving ozone to a concentration of 10 ppm or more in the water to be treated, an oxidizing agent removing tank for removing unreacted oxidizing agent, and an ion exchange device. Water treatment provided along a path and provided with a hydrogen peroxide supply device for supplying hydrogen peroxide to an oxidizing agent dissolving tank or a flow path for supplying water to be treated to the oxidizing agent dissolving tank. Device.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, a base supply device for supplying a base to an ozone dissolving tank or a flow path for supplying water to be treated to the ozone dissolving tank is provided. It is a water treatment device.

According to a ninth aspect of the present invention, there is provided a water treatment apparatus characterized in that an oxidizing agent removing tank for removing unreacted oxidizing agent is provided in a stage preceding the ion exchanging device.

The invention according to claim 10 is the invention according to claims 7 to 9
A water treatment apparatus according to the invention described above, wherein a reverse osmosis membrane device is provided before the ozone dissolution tank and / or before the ion exchange device.

According to the eleventh aspect, the present invention provides the seventh aspect to the first aspect.
0. The water treatment apparatus according to claim 0, further comprising a tank for supplying water to be treated.

According to the first aspect, the oxidation reaction of the organic matter in the water to be treated is remarkably promoted, so that the organic matter in the water to be treated is decomposed efficiently and effectively, and the product generated by the decomposition is subjected to the treatment. It can be removed from water.

According to the water treatment method of the present invention, ozone is supplied to the water to be treated so that the concentration of ozone in the water to be treated becomes 10 ppm or more, preferably 13 ppm.
The supply state of the ozone, that is, the concentration of ozone in the water to be treated is 10 p
pm or more while supplying hydrogen peroxide and a base while maintaining the supply state of ozone continuously
Since the oxidation reaction of the organic matter in the water to be treated is remarkably promoted, it is possible to efficiently and effectively decompose the organic matter in the water to be treated, and remove the product generated by the decomposition from the water to be treated. In general, when decomposing organic substances in water to be treated by using the above-described addition of ozone and irradiation with ultraviolet rays, the organic substances are usually decomposed into water and carbon dioxide by excessively oxidizing the organic substances in the water to be treated. . However, in this case, it is necessary to input a large amount of energy to oxidize organic substances in the water to be treated into water and carbon dioxide gas. In the present invention, it is dissolved in the water to be treated in the presence of H ₂ O ₂ at 10 ppm or more, preferably up to supersaturation. Organic acids generated by the oxidation of organic substances are removed by ion exchange, and a high TOC removal rate is realized. According to experiments performed by the present inventors, it has been confirmed that acetic acid and a small amount of formic acid are generated by decomposition of IPA (isopropyl alcohol) in the same manner as in the case of using ultraviolet light even in a combination of hydrogen peroxide and ozone. .

According to a second aspect of the present invention, the pH of the water to be treated is inclined toward the alkali side by adding a base at this time. This allows
The inclination of the pH to the acidic side by the organic acid generated by the decomposition of the organic substance can be suppressed.

According to the third aspect, since the oxidizing agent which is an unreacted residue in the step of oxidatively decomposing the organic substance is removed, the ion exchange resin and the like are prevented from being decomposed by the oxidizing agent. Means for removing unreacted residues include:
For example, an adsorption process using activated carbon or the like can be used.

According to the fourth aspect of the present invention, the pH of the liquid to be treated generally decreases due to the decomposition of the organic substance by the oxidizing agent. And when an oxidizing agent removing means is provided, the load thereof is reduced.

The range of the ozone concentration according to the fifth aspect is an optimum range in consideration of the efficiency of dissolving ozone in the water to be treated and the efficiency of oxidative decomposition of organic substances. Ozone can be dissolved in the water to be treated up to supersaturation.

Claim 6 is a range where a synergistic effect due to the combined use of ozone and hydrogen peroxide is remarkably recognized.

[0029] Claim 7 is a basic configuration of the water treatment apparatus of the present invention. The ozone dissolution tank has an inlet pipe that simultaneously supplies the water to be treated and gaseous ozone, and a gas-liquid mixture of the water to be treated and ozone is guided into the vessel from a hollow rotating shaft, and the vessel is provided near a rotating blade provided at the tip. A stirrer for supplying ozone into the inside is provided, and this stirrer is rotated at a high speed to dissolve ozone at a high concentration in the water to be treated by a cavitation phenomenon at the time of high speed rotation. The hydrogen peroxide supply device is composed of an injection pipe that opens in the tank or the inlet pipe, an injection apparatus that injects hydrogen peroxide of a predetermined concentration into the injection pipe, a concentration adjusting device, and the like. An eighth aspect of the present invention is an apparatus for supplying a base that suppresses a decrease in pH of a liquid to be treated, and has a mechanism similar to that of a hydrogen peroxide supply apparatus.

A ninth aspect of the present invention is an oxidizing agent removing device such as an activated carbon tank, which is disposed before the ion exchanging device to suppress the ion exchange resin of the ion exchanging device from being decomposed by the oxidizing agent.

According to a tenth aspect of the present invention, a reverse osmosis membrane device is provided, whereby the removal rate of organic substances is further improved. The reverse osmosis membrane device may be installed either before the ozone dissolution tank or before the ion exchange device, or in some cases, both. Also, in this case, if each is installed in two stages,
More effective. When a reverse osmosis membrane device is provided before the ion exchange device, an oxidizing agent removing device is preferably provided before the ion exchange device in order to prevent the membrane from being oxidized and deteriorated.

In the eleventh aspect, a tank for supplying the water to be treated is disposed at the front stage of the water treatment apparatus, so that a water treatment operation can be performed according to the use condition of the treated water.

In the present invention, the oxidation reaction of the organic matter contained in the water to be treated is presumed to proceed by the following mechanism.

[0034] In other words, ozone and hydrogen _{peroxide, H 2 O 2 + O 3} → · OH + HO 2 - + O 2 ··· [1] HO 2 - + O 3 → · OH + O 2 - + O ₂ ... [2] As shown, they react with each other to form an OΗ radical (· O
H: hydroxyl radical).

On the other hand, on the alkaline side, ozone and hydrogen peroxide are H ₂ O ₂ + OH ⁻ → HO ₂ ⁻ + H ₂ O... [3] H ₂ O ₂ → HO ₂ ⁻ + H ⁺ . ^{_{] O 3 + OH - → ·}} HO 2 + O 2 - reacts with a base as shown in ··· [5], HO ₂ radical (
HO ₂ ) are produced. The HO generated here
₂ ^- is also involved in the generation of the OΗ radicals by reacting with the ozone. Therefore, it is understood that the higher the concentration of ozone in the water to be treated, the greater the generation of OΗ radicals and HO ₂ radicals.

Then, the OΗ radical and the HO ₂ radical generated by the above reaction cause RH + .OH → R + H ₂ O [6] R + O ₃ (O ₂ ) → oxidation product [7] RH + HO ₂ → oxidation product + H ₂ O The reaction shown in [8] proceeds and organic matter is oxidized and decomposed.

That is, in the present invention, ozone is supplied to the water to be treated so as to be supersaturated or the concentration of the water in the water to be treated becomes 10 ppm or more. And by inclining the pH of the water to be treated toward the alkali side,
By increasing the amount of OΗ radical and HO ₂ radical generated in the water to be treated, the decomposition of organic substances can be remarkably promoted. Here, the concentration of ozone that can increase the amount of OΗ radical and HO ₂ radical in the water to be treated and significantly promote the decomposition of organic substances will be examined. First, if there is sufficient hydrogen peroxide during the treatment and the oxidation reaction is performed on the alkali side, the greater the amount of ozone present in the treatment water, the more the decomposition of organic matter in the treatment water is promoted. You. That is, by adding ozone so that the ozone becomes supersaturated in the water to be treated, the decomposition of organic substances in the water to be treated is further promoted. Ozone solubility ( _CL )
, As shown in FIG. _{6, C L = 0.604 (1} + t / 273) 1 + 0.063t * C G ( however, t is temperature (° C.), C _G is aerial ozone concentration (mg
/ L), when ozone is dissolved in the water to be treated until supersaturation is reached, ozone is added to the water to be treated so as to exceed the solubility at each temperature. In this case, the amount of hydrogen peroxide added to the water to be treated is such that the amount of ozone added to the water to be treated is sufficiently high so that the above-mentioned reaction proceeds smoothly. Further, OH ^- in order to suppress a decrease in the reactions associated with the consumption of, addition of a base in an amount commensurate to neutralize the organic acids produced by the decomposition of organic matter in the water to be treated. However,
In consideration of economics and the like, for example, when decomposing and removing organic matter in wastewater discharged in the semiconductor production process, ozone should not be added to the water to be treated (effluent) until supersaturation is reached. In both cases, it is possible to efficiently decompose organic substances contained in the water to be treated (drainage). In this case, by adding ozone to the water to be treated so that the concentration of ozone in the water to be treated is 10 to 25 ppm, it is possible to promote the oxidation reaction of organic substances in the water to be treated. When the concentration of ozone in the water to be treated is lower than 10 ppm, it is difficult to sufficiently promote the oxidation reaction of organic substances in the water to be treated. In addition, the concentration of ozone in the water to be treated is 2
If it exceeds 5 ppm, the progress of the oxidation reaction of organic substances is promoted, but the economic efficiency is reduced. Therefore, the oxidation reaction of organic substances in the water to be treated sufficiently proceeds,
From the viewpoint of improving economic efficiency, the concentration of ozone in the water to be treated is preferably adjusted to 10 to 25 ppm. The oxidation reaction of organic substances in the water to be treated also changes depending on the temperature conditions of the reaction system. That is, when the temperature of the reaction system is increased, the solubility of ozone in the water to be treated is reduced, so that the progress of the oxidation reaction tends to be stagnant. on the other hand,
When the temperature of the reaction system decreases, the solubility of ozone in the water to be treated increases, but the progress of the oxidation reaction tends to be stagnant due to the low temperature of the reaction system. Therefore, in general, the oxidation reaction of organic substances in the water to be treated may be allowed to proceed in a temperature range of 10 to 40C, more preferably 20 to 30C.

Next, in the case where ozone is continuously supplied to the water to be treated so that the concentration in the water to be treated becomes 10 to 25 ppm, the excess of the ozone to the water to be treated which is continuously supplied. The form of addition of hydrogen oxide and a base (a substance for neutralizing the organic acid of the decomposition product) and the amounts of these additions are examined.

First, the mode of adding hydrogen peroxide and a base to the water to be treated to which ozone is continuously supplied will be examined.

In the present invention, the form of addition of hydrogen peroxide and a base to the water to be treated to which ozone is continuously supplied depends on the reaction conditions such as the type, amount and temperature of the organic substance to be oxidized. Any form can be used as long as it can be controlled so that the reaction represented by the formulas 1] to [8] proceeds smoothly. That is, as typical addition forms, 1) for the water to be treated to which ozone is continuously supplied,
A sufficient amount of hydrogen peroxide and a base are supplied only once to advance the reaction represented by the above formulas [1] to [8] (batch method). 2) A treatment to which ozone is continuously supplied Against water
Hydrogen peroxide and a base are supplied as needed so as not to hinder the progress of the reaction shown in the above equations [1] to [8] (intermittent supply method). 3) To the water to be treated to which ozone is continuously supplied On the other hand,
Hydrogen peroxide and a base are continuously supplied (continuous supply method) so that the progress of the reaction shown in the above formulas [1] to [8] is always optimized (the reaction rate is maximized). Can be mentioned.

In the case of the above 2) intermittent supply method,
Although hydrogen peroxide and a base can be added at predetermined intervals, it is possible to monitor elements such as the concentration of hydrogen peroxide in the water to be treated and the pH of the water to be treated, and to provide these elements. By adding hydrogen peroxide and a base so as to keep the range out of the specified range, the above reaction can proceed more smoothly. Also. 3) In the case of the continuous supply method, the concentration of hydrogen peroxide in the water to be treated, the pH of the water to be treated, etc. are monitored, and the peroxidation is optimized so that the above reaction is optimized (the reaction rate is maximized). By optimizing the amounts of hydrogen and base added, highly accurate control of the oxidation reaction can be performed.

Here, when ozone is continuously supplied to the water to be treated so that the concentration in the water to be treated becomes 10 to 25 ppm, the amount of hydrogen peroxide and base added to the water to be treated will be examined. .

FIGS. 7 to 10 show removal rates of organic substances contained in the water to be treated when IPA and DMSO (dimethyl sulfoxide) were used and oxidized by ozone oxidation in combination with hydrogen peroxide. FIG. Note that these removal rates were determined in Example 1 (FIGS. 7 to 9) described later.
And the value obtained when the water treatment apparatus used in Example 2 (case of FIG. 10) was used and the reaction time was 30 minutes. Where IPA and DMSO
Water to be treated (20 ppm)
° C). Also, the KOH shown in FIG.
Is expressed as the total amount of KOH when only KOH is evenly injected three times at 10-minute intervals. This is to prevent the pH of the water to be treated from dropping rapidly to about 4.0 to 4.2 due to sulfuric acid generated by the decomposition of DMSO, thereby preventing the oxidation reaction of DMSO from decreasing. Here, the amounts of hydrogen peroxide and base added were examined using two types of organic substances, IPA and DMSO.

As is clear from FIGS. 7 and 8, when the initial concentration of KOH in the water to be treated is 13 ppm and the initial concentration of ozone is 20 ppm, the initial concentration of hydrogen peroxide is about 20 ppm for IPA, and about 20 ppm for DMSO. When the initial concentration of hydrogen peroxide is about 60 ppm, the increase in the removal rate of organic substances becomes slow. On the other hand, as is clear from FIGS. 9 and 10, the initial concentration of hydrogen peroxide in the water to be treated (20 ° C.) was 20 ppm, and the initial concentration of ozone was 17 ppm.
In the case of IPA, the initial concentration of KOH is about 10 p
pm or more, and the KOH concentration is about 40p for DMSO.
Above pm, no increase in the removal rate of organic substances is observed.

Therefore, 1) In the case of the batch system,
Hydrogen peroxide and a base (KOH) are added to the water to be treated so that the concentration of hydrogen peroxide in the water to be treated becomes 20 to 60 ppm and the concentration of KOH becomes 10 to 40 ppm, and the organic matter in the water to be treated is added. It can be understood that can be reliably decomposed. As described above, sulfuric acid is generated when DMSO is oxidized and decomposed, and the oxidation reaction may be stopped by the sulfuric acid. Therefore, it is preferable to use an intermittent or continuous supply system when oxidizing and decomposing DMSO.
In addition, 2) the intermittent supply method was examined, and hydrogen peroxide and base (KOH) were maintained in a range where the concentration of hydrogen peroxide in the water to be treated was 20 to 60 ppm and the concentration of KOH was 5 to 20 ppm. It was confirmed that the organic matter in the water to be treated can be surely decomposed if supplied so as to be dripped.

3) In the case of a continuous supply method, hydrogen peroxide and a base (KOH) are used in a range of 5 to 20 ppm of hydrogen peroxide in the water to be treated and pH of 5 to 8 in the water to be treated. If it is supplied so as to be preferably maintained at approximately 7, organic substances in the water to be treated can be surely decomposed. In any of the batch method, intermittent supply method, and continuous supply method, when supplying hydrogen peroxide and a base to the water to be treated, optimal conditions are taken in consideration of the amount and type of organic substances contained in the water to be treated. Is set, and by performing the setting within the above range, organic substances in the water to be treated can be surely decomposed. In addition, when supplying ozone so that it may become 10 ppm or more with respect to the water to be treated, and supplying hydrogen peroxide and a base while maintaining the supply state, as described above, the hydrogen peroxide in the water to be treated is addition, with the addition of an amount of commensurate sufficient amount of ozone added to the treatment water so that the reaction proceeds smoothly, OH ^- in order to suppress the reduction of the reaction due to the consumption of the treated As for the base for controlling the water on the alkaline side, an amount sufficient for the amount of ozone added to the water to be treated is added to the water to be treated, so that the batch method, the intermittent supply method, and the continuous method are used. Regardless of the supply method, a larger amount can be supplied as needed.

In the present invention, the method of adding a base to the water to be treated is not particularly limited, and usually, since it is easy to carry out, the base or an aqueous solution of the base is directly added to the water to be treated as described above. It is preferred to add. As the base, for example, a strongly basic substance such as potassium hydroxide or sodium hydroxide can be used. In addition, the supply of hydrogen peroxide is usually easily performed by supplying an aqueous solution of hydrogen peroxide to the water to be treated. In addition,
The steps of adding ozone and hydrogen peroxide and controlling the pH of the water to be treated can be performed in any order, or may be performed almost simultaneously. Further, in the present invention, the method of adding ozone during the treatment is not particularly limited. For example, a photochemical reaction method, a chemical method, a plasma method, a radiation method, a silent discharge method, and an electrolysis method may be used from oxygen in the atmosphere. Ozone is generated by a method or the like, and the generated ozone is added to the water to be treated by high-speed stirring. When dissolving ozone in the water to be treated until it reaches supersaturation, for example, pressurizing ozone, or
The treatment can be carried out by placing the treatment water in which ozone is dissolved under reduced pressure and forcibly adding ozone to the treatment water.

Further, after oxidizing organic substances contained in the water to be treated, decomposition products typified by organic acids and various ions are generated and present in the treated water. Therefore, these products are removed from the treated water. There is a need. Here, as a method of removing the product generated along with the oxidation of the organic matter,
For example, there is a method of introducing treated water into an ion exchange means to remove products in the treated water. At this time,
As the ion exchange means, a regenerative or non-regenerating mixed-bed type packed with a strongly basic anion exchange resin and a cation exchange resin for removing organic acids, trace amounts of carbon dioxide or other ionic components in the water to be treated. An ion exchange apparatus can be preferably used, and as the ion exchange resin, a new resin or a resin having no similar crushing, high ion exchange performance, and no elution is desirable. Further, when a mixed-bed ion exchange device or the like is used as the ion exchange means, if ozone or hydrogen peroxide is dissolved in the water to be treated introduced into the mixed-bed ion exchange device, these oxidizing effects occur. The ion exchange resin charged in the mixed bed type ion exchange apparatus is deteriorated, and the ion exchange resin crushed by the deterioration and the substance captured by the ion exchange resin are dissolved in the water to be treated, thereby deteriorating the water quality. Therefore, it is desirable to previously remove ozone and hydrogen peroxide from the water to be treated introduced into the mixed bed type ion exchange apparatus. In addition, the present invention
Needless to say, the present invention can be applied not only to a pure water production process using city water, river water, industrial water, and industrial wastewater as raw water, but also to a sterilization process of water containing bacteria and viruses.

[0049]

Embodiments of the present invention will be described below in detail with reference to the drawings. In each of the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted. In addition, the present invention is not limited to the present embodiment unless departing from the gist thereof.

(Example 1 and Comparative Example 1) FIG. 1 is a diagram showing a configuration of a water treatment apparatus used in Examples 1 to 10 and Comparative Example.

In FIG. 1, reference numeral 1 denotes a tank for temporarily storing water to be treated, and reference numeral 2 denotes an aqueous solution of ozone, hydrogen peroxide, and a basic substance such as potassium hydroxide or sodium hydroxide generated by an ozone generator. Is supplied, and an oxidation reaction of organic substances in the water to be treated is performed. Reference numeral 3 denotes an oxidizing agent such as ozone and hydrogen peroxide remaining in the water to be treated supplied from the reaction tank 2 from the water to be treated. A removing device (activated carbon adsorption device) 4 for removing the organic acid, a small amount of carbon dioxide or other ionic components from the water to be treated supplied from the removing device 3 is an ion exchange device. The ion exchange capacity of the ion exchange device 4 is 4.0.
eq / l-Resin. According to the present water treatment device,
When water to be treated containing organic matter is supplied to the tank 1,
The water to be treated, which is to be treated, is introduced into the reaction tank 2 and supplied with ozone, and an aqueous solution of hydrogen peroxide and a base such as potassium hydroxide or sodium hydroxide is supplied while the supply state of the ozone is maintained. Is added, and the oxidation reaction of the organic matter proceeds in the reaction tank 2. At this time, the temperature of the water to be treated is controlled to be kept at 25 ° C. during the oxidation reaction in the reaction tank 2. When the oxidation reaction in the reaction tank 2 is completed, the water to be treated is supplied from the reaction tank 2 to the removing device 3, and the oxidizing agent such as ozone and hydrogen peroxide remaining in the water to be treated is removed from the water to be treated. Then, the water to be treated from which the oxidizing agent such as hydrogen peroxide has been removed is introduced into the ion exchange device 4 to remove various organic acids, trace amounts of carbon dioxide and ionic components from the water to be treated.

In Example 1 and Comparative Example 1, both of the water treatment apparatuses shown in FIG. 1 were used so that the ozone concentrations in the water to be treated were 15 ppm (Example 1) and 8 ppm (Comparative Example 1). Ozone was added to the water to be treated, and the water treatment was performed so as to maintain the supply state of the ozone during the reaction process. The other conditions in Example 1 and Comparative Example 1 were completely the same, and IPA was added to the water to be treated so that the TOC concentration became 10 ppm. Also,
For the water to be treated, hydrogen peroxide and KO
Hydrogen peroxide and KOH were added so that the initial concentrations of H were 20 ppm and 15 ppm, respectively. Also,
The reaction temperature in the reaction layer 2 was 25 ° C., and the reaction time was 30 minutes. Further, the TOC in the water to be sampled in the process of being supplied from the tank 1 to the reaction tank 2 and the TOC in the water that has passed through the ion exchange device 4 are analyzed by a combustion-non-dispersion type infrared gas analyzer (Shimadzu: TOC). −5000), and the TOC removal rate was calculated based on this detection result. Table 1 shows the results.

[0053]

[Table 1] As is clear from Table 1, it can be understood that in Example 1, the removal rate of TOC from the water to be treated was significantly improved as compared with Comparative Example 1.

Therefore, in Example 1 in which the concentration of ozone in the water to be treated was 15 ppm, it was confirmed that the oxidation reaction of IPA proceeded smoothly compared to Comparative Example 1 in which the concentration of ozone in the water to be treated was 8 ppm. Was done. In Example 1, the concentration of TOC in the treated water was 0.5 pp.
m, it was confirmed that, for example, it is sufficiently possible to regenerate wastewater discharged from the semiconductor production process and reuse it in the semiconductor production process.

(Example 2) Water treatment was carried out in exactly the same manner as in Example 1 except that the concentration of ozone in the water to be treated was changed, and the decomposition rate and the removal rate of TOC in the treated water were calculated. At this time, the decomposition rate of TOC in the treated water
It was calculated based on the results of measuring the TOC in the treated water sampled in the process of being supplied to the reaction tank 2 and the TOC in the treated water sampled at the outlet of the reaction tank 2. Further, the removal rate of TOC in the treated water was the same as in Example 1, except that the TOC in the treated water sampled in the process of being supplied from the tank 1 to the reaction tank 2 and the TOC in the treated water that passed through the ion exchange device 4 were used. It was calculated based on the result of measuring the TOC. In addition,
TOC in the treated water was detected by a combustion-non-dispersive infrared gas analyzer in the same manner as in Example 1. The result is shown in FIG. In FIG. 2, the decomposition rate of TOC in the treated water is indicated by a broken line, and the removal rate of TOC in the treated water is indicated by a solid line.

As is clear from FIG. 2, TO in the treated water
It can be understood that both the decomposition rate and the removal rate of C sharply increase when the concentration of ozone in the water to be treated exceeds 10 ppm.

Therefore, it was confirmed that the oxidation reaction of IPA proceeded smoothly by setting the concentration of ozone in the water to be treated to 10 ppm or more. If the concentration of ozone in the water to be treated is 10 ppm or more, the TOC
Since both the decomposition rate and the removal rate of water rapidly increase, the time required for decomposing and removing organic substances in the water to be treated is reduced, for example, by regenerating wastewater discharged from the semiconductor production process, It has been confirmed that efficient reuse in the semiconductor production process is sufficiently possible. (Examples 3 to 9) Water treatment was performed in the same manner as in Example 1 except that the concentration of ozone in the water to be treated was 20 ppm and the compounds shown in Table 2 were used as organic substances. The removal rate of TOC in water was calculated. Table 2 shows the results.

[0058]

[Table 2] As is clear from Table 2, it can be understood that in Examples 3 to 9, even when the organic substance was changed, the TOC removal rate was substantially equal to or higher than that in Example 1.

Therefore, when the concentration of ozone in the water to be treated was 20 ppm, it was confirmed that the oxidation reaction of the organic matter proceeded smoothly regardless of the kind of the organic matter. In Examples 3 to 9, the oxidation reaction of the organic matter proceeded smoothly irrespective of the kind of the organic matter. For example, not only the wastewater containing IPA but also various kinds of wastewater discharged from the semiconductor production process. It has been confirmed that it is sufficiently possible to regenerate the wastewater and reuse it in the semiconductor production process.

(Embodiments 10 and 11) FIG.
FIG. 14 is a diagram showing a configuration of a water treatment apparatus used in Examples 10 and 11. In the water treatment apparatus shown in FIG. 3, each component is the same as that of the water treatment apparatus shown in FIG. 1, but when water to be treated containing an organic substance is supplied to the tank 1, the water to be treated is 2 and ozone is supplied,
The difference is that hydrogen peroxide and an aqueous solution of a base such as potassium hydroxide or sodium hydroxide are intermittently supplied while the ozone supply state is maintained. In the present water treatment apparatus, the water to be treated is configured to be treated at a rate of 1 m ³ / h. In this example, ozone was added to the water to be treated so that the concentration of ozone in the water to be treated was 15 ppm, and water treatment was performed during the reaction step so as to maintain the supply state of the ozone. In Examples 10 and 11, IPA (Example 10) or DMSO (Example 11) was added so that the water to be treated became 10 ppm.
The other conditions were exactly the same, except that hydrogen peroxide and KOH were supplied, and the concentrations of hydrogen peroxide and KOH in the water to be treated at the time of the supply were 60 p, respectively.
pm and 7 ppm, hydrogen peroxide and KO
H was added. Further, hydrogen peroxide was supplied to the water to be treated every 30 minutes, and KOH was supplied to the water to be treated every 5 minutes, and the reaction temperature in the reaction layer 2 was 25 ° C.
Further, the TOC in the water to be sampled in the process of being supplied from the tank 1 to the reaction tank 2 and the TOC in the water that has passed through the ion exchange device 4 are analyzed by a combustion-non-dispersion type infrared gas analyzer (Shimadzu: TOC). −5000), and the removal rate of TOC from the treated water was calculated based on the detection result. As a result, the removal rate of TOC from the water to be treated was 98.2% in Example 10 and Example 1
In No. 1, it was 95.5%.

Therefore, it was confirmed that the oxidation reaction of DMSO as well as the oxidation reaction of IPA proceeded smoothly. Further, since the removal rate of TOC in the treated water was improved as compared with Example 1, it was confirmed that the oxidation reaction of organic substances could be more optimally controlled. Therefore, for example, it was confirmed that it is sufficiently possible to regenerate wastewater discharged from a semiconductor production process and reuse the wastewater in a semiconductor production process.

(Example 12) The concentration of ozone in the water to be treated was varied, and the concentration of
Water treatment was carried out in exactly the same manner as in Examples 10 and 11, except that the pm and DMSO were 7 ppm, and the TOC decomposition rate and the removal rate of the treated water were calculated. At this time, the decomposition rate of the TOC in the treated water depends on the TOC in the treated water sampled in the process of being supplied from the tank 1 to the reaction tank 2.
And it calculated based on the result of having measured TOC in the process water sampled at the outlet of the reaction tank 2. Further, the removal rate of TOC in the treated water was the same as in Example 1, and the TOC in the treated water sampled in the process of being supplied from the tank 1 to the reaction tank 2 was measured.
C and TOC in the treated water that has passed through the ion exchange device 4
Was calculated based on the measurement results. The TOC in the treated water was detected by a combustion-non-dispersion type infrared gas analyzer in the same manner as in Example 1. FIG. 4 shows the results. In FIG. 4, the decomposition rate of TOC in the treated water is represented by a broken line, and the removal rate of the TOC in the treated water is represented by a solid line. Also, by setting the concentration of ozone in the water to be treated to 25 ppm, almost all TOC
It is understood that decomposition and removal of In addition, it can be understood that both the decomposition rate and the removal rate of TOC in the treated water rapidly increase when the concentration of ozone in the treated water exceeds 10 ppm.

Therefore, it was confirmed that by setting the concentration of ozone in the water to be treated to 25 ppm, the oxidation reaction of the organic substance in which IPA and DMSO were mixed proceeded sufficiently. Also, for the treated water containing IPA and DMSO, if the concentration of ozone in the treated water is set to 10 ppm or more, both the decomposition rate and the removal rate of TOC in the treated water sharply increase. The time required for the decomposition and removal of organic matter in the water to be treated can be shortened, for example, it is possible to regenerate wastewater discharged from the semiconductor production process and efficiently reuse it in the semiconductor production process Was confirmed.

(Embodiments 13 and 14) FIG.
FIG. 14 is a diagram illustrating a configuration of a water treatment apparatus used in Examples 13 and 14. The water treatment apparatus shown in FIG. 5 has the same configuration as the water treatment apparatus shown in FIG. 1 except that the water to be treated is supplied with ozone during the process of supplying the water to the reaction tank 2 from the tank 1. Is supplied and an aqueous solution of hydrogen peroxide and a base such as potassium hydroxide or sodium hydroxide is continuously supplied while the supply state of the ozone is maintained. In the present water treatment apparatus, the water to be treated is configured to be treated at a rate of 1 m ³ / h. In this embodiment, the concentration of ozone in the water to be treated is 15
Ozone was added to the water to be treated so as to be ppm, and the water treatment was performed while maintaining the supply state of the ozone during the reaction process. In Examples 13 and 14, IPA (Example 1) was added so that the water to be treated was 10 ppm.
Other conditions were exactly the same except that 3) or DMSO (Example 14) was added.
When supplying H, the concentration of hydrogen peroxide in the water to be treated is 30
Hydrogen peroxide and KOH were added so that the pH of the water to be treated was 8 to 10 ppm, and the reaction temperature in the reaction layer 2 was 25 ° C. Further, TOC in the water to be treated which is sampled in the process of being supplied from the tank 1 to the reaction tank 2 and TOC in the water which has passed through the ion exchange device 4 are combusted.
Non-dispersive infrared gas analyzer (Shimadzu: TOC-5)
000), and the removal rate of TOC in the treated water was calculated based on the detection result. As a result, the removal rate of TOC from the water to be treated was 9 in Example 13.
9.8% and 99.5% in Example 14.

Therefore, it was confirmed that the oxidation reaction of IPA and DMSO proceeded more smoothly. In addition, the removal rate of TOC in the treated water was improved as compared with Examples 10 and 11, confirming that the oxidation reaction of organic substances could be controlled more optimally. Therefore, for example, it was confirmed that it is possible to regenerate the wastewater discharged from the semiconductor production process and reuse the wastewater in the semiconductor production process (Example 15). In order to confirm the effect of the base on the decomposition reaction, the ozone concentration was set to 11 pp.
m, the weight ratio of hydrogen peroxide to ozone is 3.0 (weight ratio),
Examples 13 and 14 except that the reaction time was 24 minutes.
Under the same conditions as in the above, the pH value was changed by measuring the amount of the base added to oxidize water containing 10 ppm of DMSO. In addition, NaOH was used as a base.

As a result, when the pH was set to 7, the TOC removal rate was 98%, and when the pH was set to 5, the TOC removal rate was 9%.
When the pH was 1% and the pH was 10, the TOC removal rate was 79%, and it was confirmed that the TOC removal rate was highest near pH7.

(Examples 16 and 17) Except that the reaction tank 1 in the apparatus used in Example 1 was divided into two tanks, an ozone dissolution tank and a reaction tank, the same method as in Example 1 was used. Oxidized [Tank-Ozone dissolution tank-Reaction tank-
Removal device-ion exchange device] (Example 15). In addition, the reaction tank 1 in the apparatus used in Example 1 was divided into two tanks, an ozone dissolution tank and a reaction tank, and the same as Example 1 except that a reverse osmosis membrane apparatus was arranged in front of the ion exchange apparatus. The oxidation treatment of the water to be treated was performed using the method [Tank-
Ozone dissolution tank-reaction tank-removal device-reverse osmosis membrane device (SU-710 manufactured by Toray Industries, Inc.)-Ion exchange device] (Example 1)
6).

The ozone dissolving tank in these examples is a tank only for adding ozone, hydrogen peroxide and a base to the water to be treated and mixing them uniformly, in which ozone, hydrogen peroxide and a base are dissolved. The liquid to be treated is sent from the ozone dissolving tank to another reaction tank where the oxidizing agent reacts. By dividing the ozone dissolution tank and the reaction tank in this way, the size of the ozone dissolution tank could be reduced.

The treatment conditions of the water to be treated in the reaction tank are as follows.

Ozone concentration 13 ppm, H ₂ O ₂ / O ₃ =
1.5, pH = 7 (controlled by NaOH) The inlet TOC concentration is 2 ppm.

The TOC concentration at the outlet pipe of each device in this example was as follows.
(Unit ppm)

[0072]

As described above in detail, according to the water treatment method of the present invention, ozone is supplied to the water to be treated so as to have a concentration of 10 ppm or more. Since the supply state of the ozone, that is, the oxidative decomposition of the organic matter is performed by using ozone and hydrogen peroxide at a concentration of 10 ppm or more in combination, the oxidation reaction of the organic matter in the water to be treated is remarkably promoted, and the ion exchange treatment is further performed. By using them together, it becomes possible to efficiently and effectively decompose and remove organic substances in the water to be treated.

Accordingly, in the ozone oxidation using hydrogen peroxide, the organic matter (TOC) contained in the raw water such as cleaning water, city water and industrial water used in the semiconductor cleaning step.
Can be provided with high efficiency, and a water treatment method for producing pure water from which the TOC has been substantially removed can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a water treatment apparatus used in Example 1-9 and a comparative example.

FIG. 2 is a view showing a result of calculating a decomposition rate and a removal rate of TOC in treated water in Example 2.

FIG. 3 is a diagram showing a configuration of a water treatment apparatus used in Examples 10-12.

FIG. 4 is a view showing a result of calculating a decomposition rate and a removal rate of TOC in treated water in Example 12.

FIG. 5 is a diagram showing a configuration of a water treatment apparatus used in Examples 13 and 14.

FIG. 6 is a graph showing ozone solubility (C _L ).

FIG. 7 is a diagram showing the results of performing ozone oxidation with hydrogen peroxide using IPA as the organic substance contained in the water to be treated and changing the concentration of hydrogen peroxide.

FIG. 8 is a diagram showing the results of performing ozone oxidation with hydrogen peroxide by using DMSO as the organic substance contained in the water to be treated and changing the concentration of hydrogen peroxide.

FIG. 9 is a view showing the results of ozone oxidation combined with hydrogen peroxide using IPA as the organic substance contained in the water to be treated and changing the concentration of the basic substance (KOH).

FIG. 10 shows DMSO as an organic substance contained in the water to be treated.
FIG. 5 is a diagram showing the results of ozone oxidation using hydrogen peroxide in combination with changing the concentration of a basic substance (KOH).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tank 2 ... Reaction tank 3 ... Removal device 4 ... Ion exchange device

Claims (11)

[Claims] 1. A process comprising adding hydrogen peroxide to water to be treated, dissolving ozone to a concentration of 10 ppm or more, and oxidatively decomposing organic substances to be dissolved in the water to be treated, and oxidizing and decomposing the organic substances. Performing a process of ion exchange on the treated water. 2. A process for supplying hydrogen peroxide and a base to the water to be treated, dissolving ozone to a concentration of 10 ppm or more to oxidatively decompose organic substances dissolved in the water to be treated, and oxidizing and decomposing the organic substances. Performing a ion exchange on the water to be treated that has passed through, a water treatment method comprising: 3. Prior to the step of performing said ion exchange,
The water treatment method according to claim 1, further comprising a step of removing an unreacted residue in the step of oxidatively decomposing the organic substance. 4. The pH of the water to be treated in the step of oxidatively decomposing organic matter is 5 to 8.
The water treatment method according to any one of claims 1 to 3. 5. The water treatment method according to claim 1, wherein the ozone concentration of the water to be treated in the step of oxidatively decomposing organic substances is 10 to 25 ppm. 6. A concentration ratio of ozone concentration and hydrogen peroxide of the water to be treated in the step of oxidative decomposition of the organic matter (H ₂ O ₂ /
The water treatment method according to any one of claims 1 to 5, wherein O ₃ (weight ratio) is 1.0 to 5.0. 7. An ozone dissolving tank for dissolving ozone in a water to be treated to a concentration of 10 ppm or more, an oxidizing agent removing tank for removing an unreacted oxidizing agent, and an ion exchange device along a flow path of the water to be treated. And a hydrogen peroxide supply device for supplying hydrogen peroxide to the oxidizing agent dissolving tank or a flow path for supplying water to be treated to the oxidizing agent dissolving tank. 8. The water treatment apparatus according to claim 7, further comprising a base supply device for supplying a base to the ozone dissolution tank or a flow path for supplying water to be treated to the ozone dissolution tank. 9. The water treatment apparatus according to claim 7, wherein an oxidizing agent removing tank for removing unreacted oxidizing agent is provided upstream of the ion exchange device. 10. The water treatment apparatus according to claim 7, wherein a reverse osmosis membrane device is provided upstream of the ozone dissolving tank and / or upstream of the ion exchange device. 11. The water treatment apparatus according to claim 7, further comprising a tank for supplying the water to be treated.