JP2001170663A - Decomposition method and decomposition device for organic matter in water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decomposition method and decomposition device for organic matter in water adequately usable for recovering and recycling of the water, such as waste rinsing water, containing the organic matter used in a semiconductor manufacturing stage and a liquid crystal manufacturing stage. SOLUTION: This decomposition method for the organic matter in the water has a stage for regulating the pH of the water to be treated to 7 to 10, a stage for regulating the cemp. of the water to be treated to >=35 deg.C, a stage for adding hydrogen peroxide and ozone to the heated water to be treated, a stage for oxidation decomposing the organic matter included in the water to be treated and a stage for decomposing and removing the hydrogen peroxide and ozone remaining in the water to be treated in which the organic matter is oxidation decomposed. The decomposition device for the organic matter in the water has a means for regulating the pH of the water to be treated to 7 to 10, a means for regulating the temperature of the water to be treated to >=35 deg.C, a means for adding the hydrogen peroxide and the ozone to the heated water to be treated, a means for oxidation decomposing the organic matter included in the water to be treated and a means for decomposing and removing the hydrogen peroxide and ozone remaining in the water to be treated in which the organic matter is oxidation decomposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for decomposing organic substances in water. More specifically, the present invention relates to a method and apparatus for decomposing organic substances in water, which can be suitably used for recovery and reuse of water containing organic substances such as rinsing wastewater used in a semiconductor manufacturing process or a liquid crystal manufacturing process. .

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a large amount of ultrapure water is used for cleaning a silicon substrate and the like. Widely used. However, since the rinse wastewater contains organic substances such as alcohol and surfactant, it is necessary to remove these substances in order to reuse the rinse wastewater. Conventionally, as a technique for removing organic substances in rinse wastewater, a technique for performing accelerated oxidation by combining ozone and hydrogen peroxide, ozone and ultraviolet light, ultraviolet light and hydrogen peroxide, ozone and alkali, and the like has been proposed. These techniques generate hydroxyl radicals having a very strong oxidizing power and decompose organic substances using the strong oxidizing power. In addition, ozone and hydrogen peroxide used in these methods have the advantage that they are only decomposed to oxygen or water after treatment and do not generate secondary waste. However, it is difficult to completely decompose organic substances using these technologies alone.
Since only intermediate products can be decomposed, a method has been adopted in which a deionization facility is provided at the subsequent stage of the decomposition process, or a two-stage decomposition process is performed in which another one-stage decomposition process is performed. For example, Japanese Patent Application Laid-Open No. 11-99394 discloses, as a method for removing organic substances in water, a first step in which hydrogen peroxide and / or ozone is added to water to be treated to decompose and remove organic substances, and a treated water in the first step. A method has been proposed in which a second step of decomposing and removing organic substances by adding a sulfur compound containing a peroxide group is performed. By performing the treatment in multiple stages in this manner, the removal rate of organic substances can be increased, but disadvantages arise such as an increase in initial cost and an increase in installation space. Further, even when the two-stage decomposition treatment is performed, since by-products are generated in the latter stage, it is necessary to provide a deionization treatment facility further in the subsequent stage, and there is a problem that the load applied to the facility is large. On the other hand, a method has been found in which hydrogen peroxide and ozone are added to the rinse wastewater, and a reaction tank is filled with a catalyst to accelerate the oxidation reaction and increase the decomposition rate of organic substances. The catalyst promotes the decomposition reaction, and the catalyst also promotes the decomposition of ozone. However, since a hydroxyl radical effective for decomposing organic substances is not generated, a remarkable catalyst filling effect cannot be obtained.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a method for decomposing organic substances in water which can be suitably used for recovery and reuse of water containing organic substances such as rinse wastewater used in a semiconductor manufacturing process or a liquid crystal manufacturing process. It is intended to provide a method and a disassembly apparatus.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor adjusted the pH of the water to be treated containing organic matter to 7 to 10 and then heated it. By adding hydrogen peroxide and ozone to oxidatively decompose organic substances, it was found that organic substances in water could be effectively decomposed and removed in a single step, and based on this finding, the present invention was completed. . That is, in the present invention, (1) the step of adjusting the pH of the water to be treated to 7 to 10,
° C or more, a step of adding hydrogen peroxide and ozone to heated water to be treated, a step of oxidatively decomposing organic substances contained in the water to be treated, and a step in which the organic substances remain in the water to be oxidized and decomposed. A method for decomposing organic substances in water, comprising a step of decomposing and removing hydrogen peroxide and ozone,
And (2) means for adjusting the pH of the water to be treated to 7 to 10,
Means for adjusting the temperature of the water to be treated to 35 ° C. or higher; means for adding hydrogen peroxide and ozone to the heated water to be treated; means for oxidatively decomposing organic substances contained in the water to be treated; A device for decomposing organic matter in water, comprising means for decomposing and removing hydrogen peroxide and ozone remaining in the water to be treated. further,
As a preferred embodiment of the present invention, (3) the method for decomposing organic substances in water according to item 1, wherein the concentration of organic carbon in the water to be treated is 1 to 100 mg / L; 2. The method for decomposing organic matter in water according to item 1, wherein the method is adjusted to 5.5.
2. The method for decomposing organic substances in water according to claim 1, further comprising a step of adding hydrogen peroxide and ozone after the step of adjusting the temperature of the water to be treated, (6) adding ozone after adding hydrogen peroxide. The method for decomposing organic matter in water according to claim 1,
(7) The method for decomposing organic matter in water according to (1), wherein the amount of hydrogen peroxide added is 2 to 20 times the weight of organic carbon in the water to be treated, and (8) the amount of ozone added is 2. The method for decomposing organic matter in water according to item 1, which is 2 to 20 times by weight of organic carbon in treated water.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for decomposing organic matter in water according to the present invention, the step of adjusting the pH of the water to be treated to 7 to 10, the step of adjusting the temperature of the water to be treated to 35 ° C. or more, and the steps of A step of adding hydrogen peroxide and ozone to the water to be treated, a step of oxidatively decomposing organic substances contained in the water to be treated, and a step of decomposing and removing hydrogen peroxide and ozone remaining in the water to be treated by oxidative decomposition of the organic substances. Have. The apparatus for decomposing organic matter in water according to the present invention includes means for adjusting the pH of the water to be treated to 7 to 10, means for adjusting the temperature of the water to be treated to 35 ° C. or more, and adding hydrogen peroxide to the heated water to be treated. And ozone, a means for oxidatively decomposing organic substances contained in the water to be treated, and a means for decomposing hydrogen peroxide and ozone remaining in the water to be treated in which the organic substances are oxidized and decomposed. There is no particular limitation on the water to be treated to which the method of the present invention and the apparatus of the present invention are applied.
It is particularly suitable for water at 100 mg / L.

[0006] In the present invention, the pH of the water to be treated is 7 to 1
Adjust to 0, preferably 8 to 9.5. If the pH is less than 7 or more than 10, the decomposition removal rate of organic substances may decrease. There is no particular limitation on the method of adjusting the pH of the water to be treated. For example, the pH can be adjusted by adding an alkali such as sodium hydroxide or potassium hydroxide. The pH of the water to be treated can be adjusted at any stage as long as it is a step before the addition of hydrogen peroxide and ozone to the water to be treated. In the present invention, the temperature of the water to be treated is adjusted to 35 ° C. or higher, and the subsequent treatment is performed in a heated state. If the temperature of the water to be treated is lower than 35 ° C., organic substances may not be sufficiently decomposed and removed. When the temperature of the water to be treated is increased, the decomposition removal rate of organic substances is improved, but the removal rate approaches equilibrium around 45 ° C. Therefore, the temperature of the water to be treated is preferably adjusted to 45 to 60 ° C.
Heating to 60 ° C. or higher may increase thermal energy costs. In the present invention, the method for adjusting the temperature of the water to be treated is not particularly limited. However, after heat exchange between the water to be treated and the water to be treated, the water to be treated is heated to a predetermined temperature, thereby saving heat energy. Is preferred from above. In the present invention, there is no limitation on the order of the adjustment of the pH of the water to be treated to 7 to 10 and the adjustment of the temperature of the water to be treated to 35 ° C. or more. PH can be adjusted after the temperature of the water to be treated is adjusted, or the pH can be adjusted while adjusting the temperature of the water to be treated.

In the present invention, the temperature of the water to be treated is adjusted,
There is no particular limitation on the order of addition of hydrogen peroxide and ozone.For example, after adjusting the temperature of the water to be treated, hydrogen peroxide and ozone can be added, and hydrogen peroxide and ozone are added to the water to be treated. After that, the temperature can be adjusted, and hydrogen peroxide and ozone can be added while adjusting the temperature of the water to be treated, or ozone can be added after adding hydrogen peroxide to the water to be treated and adjusting the temperature. It can also be added. Among them, the method of adding hydrogen peroxide and ozone after adjusting the temperature of the water to be treated can prevent the corrosion of the heat exchanger piping and prevent the loss due to the self-decomposition of ozone,
Since decomposition of organic substances starts immediately after the addition of hydrogen peroxide and ozone, it can be suitably used. In the present invention, the order of adding hydrogen peroxide and ozone to the water to be treated is not particularly limited, and ozone can be added after adding hydrogen peroxide, and hydrogen peroxide is added after adding ozone. Alternatively, hydrogen peroxide and ozone can be added simultaneously. However, ozone is a substance that is easily decomposed by itself, and it is preferable to add ozone last in order to efficiently use ozone for decomposing organic substances.

In the method of the present invention, the amount of hydrogen peroxide added to the water to be treated is not particularly limited, but is preferably 2 to 20 times the weight of the organic carbon in the water to be treated.
More preferably, it is 5 to 10 times by weight. If the amount of added hydrogen peroxide is less than 2 times the weight of organic carbon, organic substances may not be sufficiently decomposed and removed. The amount of hydrogen peroxide to be added is usually sufficient to be not more than 20 times by weight of the organic carbon, and the addition of hydrogen peroxide exceeding 20 times by weight of the organic carbon increases the load of the subsequent hydrogen peroxide removing step. At the same time, the corrosion of the equipment may be caused. In the method of the present invention, the amount of ozone added to the water to be treated is not particularly limited, but is preferably 2 to 20 times by weight, and preferably 5 to 10 times by weight, based on the amount of organic carbon in the water to be treated. Is more preferable. If the amount of ozone added is less than 2 times the weight of organic carbon, organic substances may not be sufficiently decomposed and removed. The addition amount of ozone is usually sufficient to be 20 times by weight or less of the organic carbon, and the addition of ozone exceeding 20 times by weight of the organic carbon increases the amount of ozone which is self-decomposing unnecessarily and increases the amount of ozone in the latter stage. The load of the removal step may increase. In the present invention, there is no particular limitation on the method of adding ozone to the water to be treated, for example, ozone can be added to the water supply pump suction port using a pump such as 15UPD02S manufactured by Fukukoku Kikai Kogyo Co., Ltd. Ozone can be added by installing an ejector, or ozone can be directly diffused into the lower part of the dissolution tank or the reaction tank. The ozone added to the water to be treated does not necessarily need to be in a physically completely dissolved state, but may be in a state of being dispersed in the water to be treated as fine bubbles.

In the present invention, there is no particular limitation on the method of decomposing organic substances contained in the water to be treated to which hydrogen peroxide and ozone have been added. For example, the decomposition can be carried out batchwise in a reactor, or It can also be processed continuously. The form of the reaction apparatus is not particularly limited. For example, the reaction apparatus may be a reaction tank in which the water to be treated is uniformly mixed, or may be a reaction tower through which the water to be treated is continuously passed. In the present invention, after oxidatively decomposing organic substances contained in the water to be treated, hydrogen peroxide and ozone remaining in the water to be treated are decomposed. By adding hydrogen peroxide and ozone to the temperature-controlled water to be treated and treating it, most of the organic matter in the water to be treated is oxidatively decomposed. Hydrogen peroxide and ozone remain. After oxidative decomposition of organic matter, by decomposing and removing remaining hydrogen peroxide and ozone,
The quality of the recovered water can be improved. The method for decomposing hydrogen peroxide and ozone is not particularly limited.For example, by passing water through a reaction tank or a packed tower filled with an oxidizing agent decomposition catalyst such as activated carbon or platinum or ruthenium, the remaining hydrogen peroxide and ozone are removed. Can be decomposed and removed.

FIG. 1 is a process flow diagram of one embodiment of the apparatus of the present invention. In the heat recovery heat exchanger 1, heat exchange is performed between the water to be treated and the treated water, heat energy is recovered from the treated water, and the water to be treated is preheated. Next, in the heating heat exchanger 2, the water to be treated is heated to a predetermined temperature.
The alkali is added to the heated water to be treated to adjust the pH to a predetermined value, then hydrogen peroxide is added, and further, ozone is added in the ozone dissolving tank 3. The surplus gas in the ozone dissolving tank is returned to the ejector 4 provided between the heating heat exchanger and the ozone dissolving tank, and is re-dissolved. By returning the surplus gas in the ozone dissolving tank to the water supply line, the burden of the exhaust ozone gas treatment can be reduced. The water to be treated to which hydrogen peroxide and ozone have been added is sent to the reaction tank 6 by the pump 5, and the organic substances contained in the water are oxidized and decomposed. The water in which the organic matter has been oxidatively decomposed is sent to the oxidizing agent decomposition tower 8 by the pump 7, and the hydrogen peroxide and ozone remaining in the water are decomposed into treated water. The treated water is
Releasing heat energy via the heat exchanger 1 for heat recovery,
It is reused after being cooled. The gas discharged from the reaction tank 6 is decomposed and removed by the ozone gas decomposing tower 9 and then released into the atmosphere. ADVANTAGE OF THE INVENTION According to the method and apparatus of this invention, organic substance in to-be-processed water can be decomposed | removed and removed efficiently by single-step processing with a single reaction tank, without performing multi-step processing. Further, high-quality treated water can be obtained by further passing the water that has passed through the reaction tank to the oxidizing agent decomposition tower to decompose the remaining hydrogen peroxide and ozone. further,
Ozone and hydrogen peroxide are efficiently used for the decomposition reaction of organic substances by the effects of pH adjustment and heating, so that the cost of the oxidizing agent and the cost of the decomposition treatment of the oxidizing agent can be reduced.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. FIG. 2 is an explanatory diagram of the devices used in the examples and comparative examples. The water to be treated is charged into the reaction tank 10, and the temperature is adjusted and the pH is adjusted by adding an alkali. Next, the organic matter is oxidatively decomposed while stirring the water to be treated for a predetermined time. The water to be treated, in which organic substances have been oxidatively decomposed, is sent to an oxidizing agent decomposition tower 12 by a pump 11 to decompose hydrogen peroxide and ozone remaining in the water to obtain treated water. In Examples and Comparative Examples, the organic carbon (TOC) concentration was measured according to JIS K0551. Also,
The hydrogen peroxide (H ₂ O ₂ ) concentration was measured by the DMP method (absorbance measurement by reduction of neocloproin) using ozone (O ₃ ).
The concentration was measured by absorbance (wavelength 254 nm). However, the liquid from which ozone was desorbed by aeration was measured as a control sample. Comparative Example 1 5.0 mg / L of isopropyl alcohol was added to ultrapure water to prepare water containing 3.0 mgC / L of organic carbon (TOC), which was used as test water to be treated. The pH of the water to be treated was 7.0, and the water temperature was 25 ° C. 2 L of the water to be treated is put into a reaction tank, and the hydrogen peroxide solution is supplied with a hydrogen peroxide concentration of 30 mg.
/ L, and then ozone generated by an electrolytic ozone generator [Sakura Co., Ltd., Ozone Master OM-2] was added to a concentration of 30 mg / L. While maintaining the temperature of the water to be treated at 25 ° C., the mixture was stirred in a reaction tank for 30 minutes to perform oxidative decomposition of isopropyl alcohol.
The TOC concentration of the water after the oxidative decomposition treatment was 2.4 mgC / L, and the TOC removal rate was 20.0%. The residual hydrogen peroxide concentration was 5.5 mg / L, and the residual ozone concentration was 2 mg / L. This water was plated with a platinum-plated wire with a diameter of 0.
Water was passed at a space velocity of 5 h ^-1 through a catalytic reactor packed with 0.4 L of a 4 mm stainless steel mesh. Neither hydrogen peroxide nor ozone was detected in the treated water flowing out of the catalytic reaction tower. Example 1 Isopropyl alcohol was decomposed by using the same water to be treated as in Comparative Example 1 and changing the treatment temperature. 2 L of the water to be treated is placed in a reaction vessel, heated to 35 ° C., an aqueous solution of hydrogen peroxide is added so that the concentration of hydrogen peroxide becomes 30 mg / L, and then an electrolytic ozone generator [Sakura Co., Ltd. Ozone Master OM-
2] was added so that the concentration became 30 mg / L. While maintaining the temperature of the water to be treated at 35 ° C., the mixture was stirred in a reaction tank for 30 minutes to perform oxidative decomposition treatment of isopropyl alcohol. The TOC concentration of the water after the oxidative decomposition treatment was 1.2 mgC / L, and the TOC removal rate was 60.0%. The residual hydrogen peroxide concentration was 3.1 mg / L, and the residual ozone concentration was 1.2 mg / L. This water is applied to a platinum-plated 0.4 mm stainless steel net 0.4.
Water was passed through the catalyst reaction tower filled with L at a space velocity of 5 h ^-1 while maintaining the temperature at 35 ° C. Neither hydrogen peroxide nor ozone was detected in the treated water flowing out of the catalytic reaction tower. The temperature of the water to be treated is 45 ° C, 55 ° C, 65 ° C and 90 ° C.
The same operation was repeated at a temperature of ° C. Temperature of treated water 45
At ℃, TOC concentration of water after oxidative decomposition treatment is 0.3mg
C / L, and the TOC removal rate was 90.0%. The residual hydrogen peroxide concentration was 1.2 mg / L, and the residual ozone concentration was 0.8 mg / L. Neither hydrogen peroxide nor ozone was detected in the treated water after passing through the catalyst reaction tower. When the temperature of the water to be treated was 55 ° C., the TOC concentration of the water after the oxidative decomposition treatment was 0.06 mgC / L, and the TOC removal rate was 98.0%. The residual hydrogen peroxide concentration was 0.4 mg / L, and the residual ozone concentration was 0.3 mg / L. In the treated water after passing through the catalyst reaction tower, hydrogen peroxide,
Ozone was not detected. Temperature of treated water 65 ° C
In this case, the TOC concentration of the water after the oxidative decomposition treatment is 0.006 m
gC / L, and the TOC removal rate was 99.8%. The residual hydrogen peroxide concentration was 0.2 mg / L, and the residual ozone concentration was 0.08 mg / L. Neither hydrogen peroxide nor ozone was detected in the treated water after passing through the catalyst reaction tower. When the temperature of the water to be treated is 90 ° C., TOC is not detected in the water after the oxidative decomposition treatment, and the TOC removal rate is 100%.
Met. The residual hydrogen peroxide concentration was 0.02 mg / L.
And the residual ozone concentration was 0.01 mg / L. Neither hydrogen peroxide nor ozone was detected in the treated water after passing through the catalyst reaction tower. Table 1 shows the results of Comparative Example 1 and Example 1.

[0012]

[Table 1]

As can be seen from Table 1, by adjusting the temperature of the water to be treated to 35 ° C. and adding hydrogen peroxide and ozone to oxidatively decompose, 60% of the organic matter in the water is removed. When the temperature of the treated water is adjusted to 55 ° C., the removal rate is 9
Reaches 8%. In addition, hydrogen peroxide and ozone remaining in water after oxidative decomposition of organic substances are completely decomposed and removed by passing water through a catalyst reaction tower filled with a platinum catalyst. In general, gas solubility decreases as Henry's law constant increases with increasing water temperature. In this case, too, the solubility of ozone decreases as the temperature of the reaction system increases, and there is a concern that the oxidation reaction may stagnate due to a shortage of dissolved ozone. However, as is evident from Table 1, the results show that the heating effect contributes to the improvement of the organic carbon removal rate. This is because, by heating, the decomposition of hydrogen peroxide and ozone is efficiently promoted, the generation of hydroxyl radicals required for organic matter decomposition is promoted, and the activation energy in the isopropyl alcohol decomposition process is reduced. Conceivable. In addition, the higher the temperature, the higher the organic carbon removal rate. However, since the removal rate approaches equilibrium at around 45 ° C., the temperature of the water to be treated is preferably 45 to 60 ° C. In order to heat the temperature to 60 ° C. or higher, the heating cost increases. Example 2 5.0 mg / L of isopropyl alcohol was added to ultrapure water to prepare water containing 3.0 mgC / L of organic carbon (TOC), which was used as test water to be treated. 2 L of the water to be treated is put into a reaction tank, the pH is adjusted to 7.3 and the temperature is adjusted to 60 ° C., and then hydrogen peroxide is added so that the concentration of hydrogen peroxide becomes 30 mg / L. Generator [Sakura
Ozone generated by Ozone Master OM-2] was added so as to have a concentration of 30 mg / L. While maintaining the temperature of the water to be treated at 60 ° C., the mixture was stirred in a reaction tank for 30 minutes to perform oxidative decomposition treatment of isopropyl alcohol. TOC was not detected in the water after the oxidative decomposition treatment, and the TOC removal rate was 100%. The residual hydrogen peroxide concentration is 0.2 m
g / L, and the residual ozone concentration was 0.08 mg / L. This water was placed in a catalytic reaction tower filled with 0.4 L of a platinum-plated stainless steel net having a wire diameter of 0.4 mm for a space velocity of 5 h.
^Water was passed at ^-1 . In the treated water flowing out of the catalytic reaction tower,
Neither hydrogen peroxide nor ozone was detected. further,
The same operation was repeated while adjusting the pH of the water to be treated to 9.0. TOC is not detected in the water after the oxidative decomposition treatment.
The C removal rate was 100%. The residual hydrogen peroxide concentration was 0.02 mg / L, and the residual ozone concentration was 0.03 mg / L.
/ L. This water is platinum-plated with a wire diameter of 0.4 mm.
Was passed at a space velocity of 5 h ^-1 through a catalytic reaction tower filled with 0.4 L of a stainless steel mesh. Neither hydrogen peroxide nor ozone was detected in the treated water flowing out of the catalytic reaction tower. Comparative Example 2 Using the same water to be treated as in Example 2, the pH was adjusted to 2.3, 3.2 and 11.8, the temperature was adjusted to 60 ° C., and isopropyl alcohol was decomposed in the same manner as in Example 2. The TOC concentration, the residual hydrogen peroxide concentration, and the residual ozone concentration of the water after the oxidative decomposition treatment, and the hydrogen peroxide concentration and the ozone concentration in the treated water flowing out of the catalytic reaction tower were measured. When the pH of the water to be treated was adjusted to 2.3, the TOC concentration of the water after the oxidative decomposition treatment was 0.3.
The content was 65 mgC / L, and the TOC removal rate was 78.3%. When the pH of the water to be treated was adjusted to 3.2, the TOC concentration of the water after the oxidative decomposition treatment was 0.18 mgC / L.
The C removal rate was 94.0%. PH of the water to be treated is 11.8
, The TOC concentration of the water after the oxidative decomposition treatment was 0.82 mgC / L, and the TOC removal rate was 72.7%. Comparative Example 3 Using the same water to be treated as in Example 2, the pH was 2.3, 3.2,
7.3, 9.0 and 11.8, adjusting the temperature to 25 ° C,
Isopropyl alcohol was decomposed in the same manner as in Example 2, and the TOC concentration, the residual hydrogen peroxide concentration, and the residual ozone concentration of the water after the oxidative decomposition treatment, the hydrogen peroxide concentration in the treated water flowing out of the catalytic reaction tower, and the ozone concentration were measured. The concentration was measured. When the pH of the water to be treated was adjusted to 2.3, the TOC concentration of the water after the oxidative decomposition treatment was 2.7 mgC / L, and the TOC removal rate was 10.0%. When the pH of the water to be treated was adjusted to 3.2, the TOC concentration of the water after the oxidative decomposition treatment was 2.53 mgC /
L, and the TOC removal rate was 15.7%. When the pH of the water to be treated was adjusted to 7.3, the TOC concentration of the water after the oxidative decomposition treatment was 2.33 mgC / L, and the TOC removal rate was 22.3%. When the pH of the water to be treated was adjusted to 9.0, the TOC concentration of the water after the oxidative decomposition treatment was 2.25 mgC /
L, and the TOC removal rate was 25.0%. When the pH of the water to be treated was adjusted to 11.8, the TOC concentration of the water after the oxidative decomposition treatment was 2.37 mgC / L, and the TOC removal rate was 21.0%. Table 2 shows the results of Example 2 and Comparative Examples 2 and 3.

[0014]

[Table 2]

As shown in Table 2, when the pH of the water to be treated is adjusted to 7.3 or 9.0 and the temperature is adjusted to 60 ° C., hydrogen peroxide and ozone are added to oxidize and decompose. Thereby, the isopropyl alcohol in the water is completely decomposed and removed. On the other hand, if the pH is too low or too high, the removal rate of organic carbon decreases. When the temperature of the water to be treated is 25 ° C., the removal rate of the organic carbon reaches only up to 25%. In addition, hydrogen peroxide and ozone remaining in water after oxidative decomposition of organic substances are completely decomposed and removed by passing water through a catalyst reaction tower filled with a platinum catalyst. From this result, it can be seen that in all pH ranges, removal of organic carbon is promoted by heating. This is because the decomposition reaction of ozone and hydrogen peroxide by heating is accelerated, the generation of hydroxyl radicals necessary for the decomposition of organic substances is promoted, and the activation energy in the decomposition process of isopropyl alcohol is reduced. Conceivable. In addition, although the removal rate of organic carbon is improved by inclining the pH of the water to be treated toward the alkali side,
In the region of 11 or more, the organic carbon removal rate decreases. This decrease in the removal rate is considered to be due to the strong effect of carbonate ions, which are strong scavengers of hydroxyl radicals, in a high pH range. From the above results, the pH range that promotes the decomposition reaction of organic substances and minimizes the scavenging effect on hydroxyl radicals is 7 to
10, and preferably 8 to 9.5.

[0016]

According to the method and apparatus of the present invention, the pH of the water to be treated containing an organic substance is adjusted to 7 to 10, the temperature is increased to 35 ° C. or more, and hydrogen peroxide and ozone are added. In addition, it is possible to recover and reuse rinse water and the like in the electronic material washing step without performing multi-stage treatment such as decomposing organic matter to remove organic carbon and installing an ion exchange tower at a later stage. In addition, since hydrogen peroxide and ozone are consumed for the decomposition of organic substances, the burden of the cost for decomposition treatment of hydrogen peroxide and ozone in the subsequent stage can be reduced, and the processing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of one embodiment of the apparatus of the present invention.

FIG. 2 is an explanatory diagram of an apparatus used in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat exchanger for heat recovery 2 Heat exchanger for heating 3 Ozone dissolution tank 4 Ejector 5 Pump 6 Reaction tank 7 Pump 8 Oxidizing agent decomposition tower 9 Exhaust ozone gas decomposition tower 10 Reaction tank 11 Pump 12 Oxidizing agent decomposition tower

Claims (2)

[Claims] A step of adjusting the pH of the water to be treated to 7 to 10,
A step of adjusting the temperature of the water to be treated to 35 ° C. or higher; a step of adding hydrogen peroxide and ozone to the heated water to be treated; a step of oxidatively decomposing organic substances contained in the water to be treated; A process for decomposing and removing hydrogen peroxide and ozone remaining in the water to be treated. 2. A means for adjusting the pH of the water to be treated to 7 to 10,
Means for adjusting the temperature of the water to be treated to 35 ° C. or higher; means for adding hydrogen peroxide and ozone to the heated water to be treated; means for oxidatively decomposing organic substances contained in the water to be treated; An apparatus for decomposing organic substances in water, comprising means for decomposing and removing hydrogen peroxide and ozone remaining in the water to be treated.