JP2000180430A - Measuring method of hydroxy radical in water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly sensitive, highly accurate and handy measuring method of hydroxy radical which can inhibit a self oxidizing reaction such as photochemical reaction while eliminating the need for sophisticated analysis technique. SOLUTION: A radical trapping method suggested as a method for measuring a radical in a living being is modified to obtain a hydroxide radical measuring method applicable for a water treatment technology. When an oxidizing treatment is conducted for a solution containing dimethyl sulfoxide, the hydroxy radical generated in water by the oxidizing treatment reacts with dimethylsulfoxide to form methansulfinic acid. The methansulfinic acid produced as a result of the oxidizing reaction is extracted and determined to estimate the quantity of the hydroxide radical generated. This enables sensitive and handy measurement of the hydroxy radical even when a spectrophotometer generally employed in the water treatment field is used by comparing and studying the quality of reagents used in the measurements, a solvent addition quantity ratio during the extraction of the solvent and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring the concentration of hydroxyl radicals in water. Oxidation technology such as ozone, ultraviolet light, hydrogen peroxide, photocatalyst, etc. is a new water treatment technology for the purpose of decomposing hardly decomposable substances and trace harmful substances and disinfecting pathogenic protozoa that cannot be handled by conventional water treatment technologies. AOP method (Advanced Oxidation Processes;
(Promoted oxidation method) is attracting attention.

[0002] The AOP method is said to be based on a mechanism by which a strong oxidizing hydroxyl radical generated in water by a chemical oxidizing agent or a photochemical reaction oxidizes and decomposes pollutants (for example, edited by Isao Soumiya). "Ozone Water Treatment Technology" Pollution Control Technology Doyukai). However, since there is no technique for accurately quantifying hydroxyl radicals, the action mechanism of the AOP method has not been clarified. If the amount of generated hydroxyl radicals can be quantified, not only scientific progress such as elucidation of the action mechanism of the AOP method but also an index necessary for designing a water treatment apparatus using the AOP method can be presented.

[0003]

2. Description of the Related Art As a purification technique based on the oxidizing action of a hydroxyl radical, there are a photocatalyst technique such as titanium dioxide and an ozone oxidation technique. As a method for quantifying the effects of these purification techniques, the potassium iodide method is used (for example,
R. Harvey and R. Rudham (1988) "Photocatalytic ox
idation of iodine ions by titanium dioxide ", J. Ch
em. Soc., Trans. 1., vol.84, no.11, p4181; Kobayakawa, Koichi (1988) "Photocatalytic activity of titanium (IV) oxide"
The Chemical Society of Japan, No. 8, p. 1175; Hidetoshi Sugimoto et al. (19
98) “Standardization of ozone generation measurement method”, 7th Annual Meeting of the Ozone Society of Japan Annual Meeting, p. 101). Har
Vey and Rudham (PR Harvey and R. Rudham (1
988) "Photocatalytic oxidation of iodine ions by t
itanium dioxide ", J. Chem. Soc., Trans. 1., vol.8
4, no.11, p4181), the potassium iodide method is based on the formula 1
The iodine ion [I
^- ] Is oxidized to produce an iodine molecule [I ₂ ]. The resulting iodine molecule further associate with iodine ions iodide Moto錯ion [I ₃ ^-]
(Formula 2).

[0004] _{^{2I - + · OH → I 2}} ( Formula ^{_{1) I 2 + I - →}} I 3 - ( Equation 2) iodine Moto錯ion has a characteristic of absorbing a concentration dependent manner the near-ultraviolet light of a wavelength near 350nm Therefore, by utilizing this characteristic, the amount of iodine complex ion produced can be quantified, and the amount of hydroxyl radical produced can be estimated from the amount of iodine complex ion produced. However, iodine ions in an aqueous solution have a property of undergoing a photochemical reaction by ultraviolet light having a wavelength of 253.7 nm and being oxidized to iodine molecules (for example, "Chemical Handbook (Application)", p. 417). For this reason, application to a chemical oxidizing agent such as ozone or hydrogen peroxide without ultraviolet irradiation, or application to a photocatalyst under irradiation conditions of near ultraviolet light not including ultraviolet light having a wavelength of around 254 nm is limited. It can be applied to the conditions, but cannot be applied to the test conditions involving irradiation of ultraviolet light having a wavelength of about 254 nm.

In the field of biochemistry such as medicine and pharmacy, a radical scavenging method has been proposed as a method for quantifying a radical molecule in a biological reaction (for example, S. Fukui).
etal. (1993) "High-performance Liquid chromatogra
phic determination of methansulphinic acid as a me
thod for the determination of hydroxyl radicals ",
J. Chromatogr., Vol.630, p.187). In this method, methanesulfinic acid [CH ₃ SO ₂ H] generated by a chemical reaction estimated as in Equation 3 is extracted with a solvent,
It is based on the principle of evaluating the amount of hydroxyl radical from the methanesulfinic acid concentration. That is, the hydroxyl radical [•
As a result of the reaction between OH] and dimethyl sulfoxide [(CH ₃ ) ₂ SO], methanesulfinic acid and a methane radical [CH ₃ ] are produced. The by-produced methane radical causes a radical chain reaction as shown in Formulas 4 to 6, but it is said that no hydroxyl radical is generated or consumed in the process. This means that the amount of methanesulfinic acid is It shows that it is reflected. (CH ₃ ) ₂ SO + · OH → CH ₃ SO ₂ H + · CH ₃ (Formula 3) · CH ₃ + O ₂ → CH ₃ OO · (Formula 4) 2CH ₃ OO · → HCHO + CH ₃ OH + O ₂ (Equation 5) CH ₃ + R → CH ₄ + R ′ (Equation 6) In this method, the amount of hydroxyl radical can be reduced without being affected by the photochemical reaction which was regarded as a problem in the potassium iodide method. Although detection can be performed with high sensitivity in the concentration range of 20 to 80 μM, an advanced analysis technique using a high-performance liquid chromatography device is required to quantify methanesulfinic acid. Furthermore, there is no precedent for studying its application to the water treatment field.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a wavelength of 254 is used because auto-oxidation such as photochemical reaction of iodine ion occurs.
Problems of the potassium iodide method, which cannot accurately determine hydroxyl radicals under ultraviolet light irradiation conditions in the vicinity of nm, and radical scavenging for biological analysis that requires advanced analytical techniques using high-performance liquid chromatography equipment It is an object of the present invention to provide a highly sensitive, accurate and simple method for measuring hydroxyl radicals in water, which overcomes the problems of the method.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for measuring hydroxyl radicals based on a radical scavenging method which has been proposed as a radical quantification method for examining biological reactions in the field of biochemistry (for example, S. Fukui et al. 1993) "High-performanc
e Liquid chromatographic determination ofmethansul
phinic acid as a method for the determination of h
ydroxyl radicals ", J. Chromatogr., vol.630, p.18
In order to improve the problem of 7) and provide a method for measuring hydroxyl radicals applicable to the field of water treatment, comparative examination of the quality of reagents used in the measurement, the ratio of the amount of solvent added during solvent extraction, etc. As a result, even when using a spectrophotometer that is widely used in the field of water treatment, a method for measuring hydroxyl hydroxide radicals with high sensitivity and simply as in the case of using a high-performance liquid chromatography apparatus was found. Was completed.

The present invention is as described below in 1) to 6). 1) A method for measuring hydroxyl radicals in water, comprising measuring methanesulfinic acid generated when a hydroxyl radical in water reacts with dimethyl sulfoxide. 2) For the aqueous solution to which dimethyl sulfoxide is added,
The first step of performing water treatment using a water treatment method selected from the group consisting of ultraviolet light, ozone, photocatalyst, and hydrogen peroxide alone or in combination of two or more to obtain treated water, and then mixing the dye liquid with the treated water The method for measuring hydroxyl radicals in water according to the above 1), comprising a second step of separating the solvent extract after the reaction, and a third step of spectrally analyzing a sample containing the solvent extract.

[0009] 3) As a second step, a dye solution is added to the treated water and then extracted with an organic solvent solution to collect a solvent layer sample. Measuring method. 4) The method for measuring hydroxyl radicals in water according to 2) or 3), wherein the absorbance is measured using a spectrophotometer as a third step.

5) As a post-processing step of the second step, a post-processing step of extracting a solvent layer sample to be subjected to spectroscopic analysis with an organic solvent saturated water to recover a solvent layer, and / or a solvent layer to be subjected to spectroscopic analysis The method for measuring hydroxyl radicals in water according to the above 2) to 4), further comprising a post-treatment step of adding pyridine to the sample. 6) As a pretreatment step of the second step, an acid solution is added to the treated water and then extracted with an acidic solvent solution to collect a solvent layer, and the collected solvent layer is extracted with an acidic buffer solution to collect an aqueous layer. The method for measuring hydroxyl radicals in water according to the above 2) to 5), which comprises a pretreatment step.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a flow chart for measuring hydroxyl radicals in the present invention, which will be described in detail below. Water treatment step: In a water treatment apparatus (for example, a water treatment apparatus in which a water treatment method selected from ultraviolet rays, ozone, a photocatalyst, and hydrogen peroxide is used alone or in combination of two or more kinds), the dimethyl sulfoxide is to be measured. Water treatment is performed by using the aqueous solution to which is added as the raw water for treatment to obtain treated water. If the concentration of dimethyl sulfoxide is too high, the viscosity increases and it is not suitable for accurate measurement of hydroxyl radicals.If the concentration is too low, the efficiency of capturing hydroxyl radicals is low, so that accurate measurement of hydroxyl radicals is difficult. And 1 mM to 10 M, preferably 50 mM to 1 M
It is prepared as an aqueous solution of The pH of the dimethyl sulfoxide solution may be adjusted by a pH buffer.

Pretreatment step: When a dimethylsulfoxide solution prepared by adding dimethylsulfoxide or a pH buffer to pure water such as deionized water or distilled water is used, the pretreatment step described below is not performed. Alternatively, it may be used in the coloring step described below, but if it is expected that impurities are contained in the treated water, the impurities in the treated water can be accurately removed by removing the impurities in the treated water by the pretreatment step described below. The concentration of the oxidized radical can be measured.

As a pretreatment step, first, an acid solution is added to treated water, then an acidic solvent solution is added and mixed, and the mixture is allowed to stand until an aqueous layer and a solvent layer are separated. Collect. The acid solution is not particularly limited as long as it does not cause an oxidation reaction, but a 1 to 10 M, preferably 1 to 4 M sulfuric acid aqueous solution is preferably used. The acid used in the acidic solvent liquid is not particularly limited as long as it does not cause an oxidation reaction. However, it is preferable to use a 1 to 10 M, preferably 1 to 4 M aqueous sulfuric acid solution. Is not particularly limited as long as it can extract methanesulfinic acid and can separate two layers when mixed with water. For example, n-butanol, n-hexane, and ethyl acetate can be used. Although it is possible, n-butanol is preferably used.

After the acidic buffer is added to the recovered solvent layer and mixed, the mixture is allowed to stand until the aqueous layer and the solvent layer are separated, and then the aqueous layer is recovered. The pH of the acidic buffer may be selected in a range that satisfies the pH conditions under which methanesulfinic acid can be extracted from the solvent layer. For example, when n-butanol sulfate is used as the acidic solvent, acetate buffer is used as the acidic buffer. Methanesulfinic acid can be extracted by using the liquid (pH 5.0).

When the present invention is applied to water treatment using an oxidizing agent such as ozone or hydrogen peroxide, a reducing agent such as sodium sulfite or sodium thiosulfate is treated before adding an acid solution to treated water. By adding to water, the effect of residual components of the oxidizing agent can also be eliminated. Coloring step: adding a dye solution to the treated water or to the aqueous layer recovered through the above step, mixing and reacting in a dark place, and further adding an organic solvent solution to the solution after the reaction. After mixing, the mixture is allowed to stand until the aqueous layer and the solvent layer separate, and then the solvent layer is recovered. A dye solution may be directly added to the above-mentioned treated water, but the pH may be adjusted in order to promote a color-forming reaction described later. The dye solution is not particularly limited as long as it is an azo dye capable of producing a diazosulfate compound by reacting with methanesulfinic acid. Fast Yellow GC salt, Fast Red
TR salt, Fast Blue BB salt, Fast Red AL salt, Fast
Black K salt, Fast Blue RR salt, Fast Red ITR sal
t, etc., but from the viewpoint of solvent extraction efficiency, spectral characteristics, and detection sensitivity of the diazosulfate compound as a reaction product, Fast Yellow GC salt, Fast Red TR s
alt, Fast Blue BB salt and Fast Red AL salt, more preferably Fast Yellow GC salt and Fast Blue BB salt. The organic solvent used for the organic solvent liquid is not particularly limited as long as it is an organic solvent having a property capable of efficiently extracting the diazosulfate compound from the aqueous layer.
Butanol, n-hexane, ethyl acetate, toluene, dichloromethane, dichloromethane, ethanol, and methanol can be used alone or as a mixture of two or more. However, when n-butanol is used as the acidic solvent solution, toluene and It is preferable to use a mixture of n-butanol at a ratio of 3: 1.

Post-treatment step: The solvent layer recovered above can be subjected to spectroscopic analysis as it is or after adding pyridine as described later, but it may be washed with water saturated with an organic solvent. That is, after adding an organic solvent saturated water to the solvent layer and mixing, the mixture is allowed to stand until the aqueous layer and the solvent layer are separated, and then the contaminant impurities can be removed by collecting the solvent layer. It can be expected to increase the sensitivity and accuracy of the analysis. The organic solvent used for the organic solvent saturated water is not particularly limited as long as it is an organic solvent having a property that only the impurities can be efficiently extracted without extracting the diazosulfate compound from the aqueous layer. For example, n-butanol, n -Hexane and ethyl acetate can be used, but it is preferable to use n-butanol when n-butanol is basically used as the acidic solvent liquid or the organic solvent mixed liquid.

Although the recovered solvent layer may be directly used for spectroscopic analysis, a stable absorbance can be obtained by adding pyridine before the spectroscopic analysis. Spectroscopic analysis step: The absorbance of the solvent layer sample obtained in the above-described solvent extraction step or the solvent layer sample subjected to the above-described pretreatment step is measured using a spectrophotometer. The wavelength at which the absorbance is measured may be selected according to the spectral characteristics of the diazo compound described above.
Yellow GC salt, Fast Red TR salt, Fast Blue BB sa
lt, Fast Red AL salt, each wavelength 28
Around 5 nm, around 310 nm, around 430 nm, 330
The absorbance around nm may be measured.

The solvent layer sample collected by the above-mentioned solvent extraction step for the dimethyl sulfoxide solution to which the methanesulfinic acid reagent is added at various concentrations, or the solvent layer prepared by the above-mentioned pretreatment step after the solvent extraction step Spectroscopic analysis of the sample provides a calibration curve for calculating methanesulfinic acid concentration. Based on the prepared calibration curve, the concentration of methanesulfinic acid in a desired water treatment sample can be calculated, and the amount of hydroxyl radical generated can be known from the concentration. (Example 1) 5 to 100 µm of dimethyl sulfoxide solution
A calibration curve was prepared using a standard sample in which the methanesulfinic acid reagent was dissolved in the concentration range of M, and the validity of the methanesulfinic acid determination was clarified.

An aqueous solution in which dimethyl sulfoxide (manufactured by Kanto Chemical Co., Ltd.) was dissolved to a concentration of 0.5 M was prepared, and this was used as a solvent to prepare methanesulfinic acid sodium salt (Aldr).
ich Chem Co. 5-100
A μM methanesulfinic acid standard solution was prepared. 10m
1 ml of methanesulfinic acid standard solution in 5 ml of 15 mM F
An aqueous solution of ast Blue BB salt (manufactured by Kanto Chemical Co., Ltd.) was added, mixed, and allowed to stand at room temperature in a dark place for 10 minutes. Subsequently, 2.5 ml of an organic solvent mixture obtained by mixing toluene and n-butanol at a ratio of 3: 1 was added, and after mixing, the mixture was allowed to stand at room temperature until the solvent layer was separated. 5 ml was collected. 1 ml of n-butanol saturated water was added to the collected solvent layer, mixed, and allowed to stand at room temperature until the solvent layer was separated, and 0.8 ml of the solvent layer was recovered. 0.4 ml of pyridine (manufactured by Kanto Chemical Co.) was added to the collected solvent layer, mixed, and the absorbance at a wavelength of 420 nm was measured with a spectrophotometer. 0.5M without methanesulfinic acid reagent
The same solvent extraction and subsequent spectroscopic analysis were performed on the aqueous dimethyl sulfoxide solution.

The results are shown in FIG. FIG. 2 plots the concentration of methanesulfinic acid as a standard substance on the horizontal axis, and the measured absorbance of each methanesulfinic acid standard solution on the vertical axis. As is clear from this figure, the methanesulfinic acid concentration and the absorbance are in a proportional relationship, and the methanesulfinic acid determination method of the present invention was able to quantitatively evaluate the methanesulfinic acid concentration up to 100 μM with high sensitivity. (Example 2) 62.5-1 dimethyl sulfoxide solution
A calibration curve was prepared using a standard sample in which the methanesulfinic acid reagent was dissolved in a concentration range of 000 μM, and the validity of the methanesulfinic acid determination was clarified.

An aqueous solution in which dimethyl sulfoxide (manufactured by Kanto Chemical Co., Ltd.) was dissolved to a concentration of 0.5 M was prepared, and this was used as a solvent to prepare sodium methanesulfinate (Aldr).
ich Chem Co. 62.5)
A 1000 μM methanesulfinic acid standard solution was prepared. 5m for 10ml of methanesulfinic acid standard solution
After adding 1 L of 2M sulfuric acid and 10 ml of 1M sulfuric acid saturated n-butanol and mixing, the mixture was allowed to stand at room temperature until the solvent layer was separated, and 8 ml of the solvent layer was recovered. 1 mM in the collected solvent layer
After adding 4 ml of an acetate buffer (pH 5.0) and mixing,
The mixture was allowed to stand at room temperature until the solvent layer was separated, and 3 ml of an aqueous layer was recovered. 15 mM FastBlue B is added to the collected aqueous layer.
1.5 ml of an aqueous solution of B salt (manufactured by Kanto Chemical Co.) was added, mixed, and allowed to stand at room temperature in a dark place for 10 minutes. continue,
1.5 ml of an organic solvent mixture in which toluene and n-butanol were mixed at a ratio of 3: 1 was added, and after mixing, the mixture was allowed to stand at room temperature until the solvent layer was separated, and 1.2 ml of the solvent layer was recovered. . N-Butanol saturated water was added to the recovered solvent layer in an amount of 1.2.
After adding and mixing, the mixture was allowed to stand at room temperature until the solvent layer was separated, and 0.8 ml of the solvent layer was recovered. 0.4 ml of pyridine (manufactured by Kanto Chemical Co.) was added to the collected solvent layer, mixed, and the absorbance at a wavelength of 420 nm was measured with a spectrophotometer. The same solvent extraction and subsequent spectroscopic analysis were performed on a 0.5 M dimethyl sulfoxide aqueous solution containing no methanesulfinic acid reagent.

The results are shown in FIG. In FIG. 3, the abscissa plots the concentration of methanesulfinic acid as a standard substance, and the ordinate plots measured values of absorbance for each methanesulfinic acid standard solution. As is clear from this figure, the absorbance tends to change according to the methanesulfinic acid concentration, and the methanesulfinic acid quantification method of the present invention was able to accurately and quantitatively evaluate the methanesulfinic acid concentration up to 1000 μM. (Example 3) 10 to 100 parts of dimethyl sulfoxide solution
A calibration curve was prepared using a sample in which the methanesulfinic acid reagent was dissolved in the concentration range of μM, and the detection sensitivity and accuracy of methanesulfinic acid determination were clarified.

An aqueous solution in which dimethyl sulfoxide (manufactured by Kanto Chemical Co., Ltd.) was dissolved to a concentration of 0.5 M was prepared, and this was used as a solvent to prepare sodium methanesulfinate (Aldr).
ich Chem Co. 10-10
A μM methanesulfinic acid standard solution was prepared. 5 ml of 2M sulfuric acid and 10 ml of 1M sulfuric acid-saturated n-butanol were added to 10 ml of the methanesulfinic acid standard solution, mixed, and allowed to stand at room temperature until the solvent layer was separated, thereby collecting 8 ml of the solvent layer. 4 ml of 1 mM acetate buffer (pH 5.0) was added to the collected solvent layer, mixed, and allowed to stand at room temperature until the solvent layer was separated. 15 mM Fast Blue BBs was added to the collected aqueous layer.
alt (manufactured by Kanto Chemical Co.) was added in an amount of 1.5 ml, mixed, and allowed to stand at room temperature in a dark place for 10 minutes. Subsequently, 1.5 ml of an organic solvent mixture obtained by mixing toluene and n-butanol at a ratio of 3: 1 was added, and after mixing, the mixture was allowed to stand at room temperature until the solvent layer was separated. 2 ml were collected.
1.2 ml of n-butanol-saturated water was added to the collected solvent layer, mixed, and allowed to stand at room temperature until the solvent layer was separated, to collect 0.8 ml of the solvent layer. 0.4 ml of pyridine was added to the collected solvent layer, mixed, and the absorbance at a wavelength of 420 nm was measured with a spectrophotometer. The same solvent extraction and subsequent spectroscopic analysis were performed on a 0.5 M dimethyl sulfoxide aqueous solution containing no methanesulfinic acid reagent.

FIG. 4 shows the results. In FIG. 4, the abscissa plots the concentration of methanesulfinic acid as a standard substance, and the ordinate plots the average value and the standard deviation of absorbances of four samples of each methanesulfinic acid standard solution. As is clear from this figure, the absorbance tended to change in proportion to the methanesulfinic acid concentration, and the standard deviation was extremely small. The method for determining methanesulfinic acid in the present invention is a conventional method (for example, S. Fukui et al. (1993) "High-perfor
mance Liquid chromatographic determination of meth
ansulphinic acid as a method for the determination
of hydroxyl radicals ", J. Chromatogr., vol.630,
p. 187), the methanesulfinic acid concentration in a concentration range of 10 to 100 μM, which could not be detected without using high performance liquid chromatography, could be quantitatively evaluated with high accuracy. (Example 4) There is an ultraviolet disinfection technique as a water treatment method for disinfecting microorganisms in water or wastewater, and a photocatalyst-ultraviolet disinfection technique is beginning to attract attention as a disinfection technique that further enhances the disinfection effect (for example, Kumiko Oguma et al.) (1998)
"Study on Light Recovery of Escherichia coli by UV Irradiation Photocatalyst Treatment," 53rd Annual Scientific Meeting of the Japan Society of Civil Engineers). Photocatalyst-
In UV disinfection, a wavelength of 254 n
In addition to direct sterilization of microorganisms by ultraviolet light of m, hydroxyl radicals generated when the photocatalyst is irradiated with ultraviolet rays are considered to enhance the sterilizing effect. Therefore, the correlation between the bactericidal effect in photocatalyst-ultraviolet disinfection and the amount of hydroxyl radical generated was examined. The measurement of the amount of hydroxyl radical generated based on the methanesulfinic acid concentration in the present invention was taken as an example, and the measurement of the amount of hydroxyl radical generated based on the iodine complex ion concentration in the conventional potassium iodide method was examined as a comparative example. In each of the sterilization test, the examples, and the comparative examples, a photocatalyst in which a sample is put in a glass container having a titanium dioxide photocatalyst coated on the inner wall and irradiated with ultraviolet light from above-
An ultraviolet irradiation device was used.

First, in a sterilization experiment, E. coli was
A sample of physiological saline containing N / ml was irradiated with ultraviolet rays, and samples were collected with time.
1984 edition "(Japan Sewer Association), the number of viable coliform bacteria was examined according to the most probable number method. Two types of mercury lamps having different emission characteristics, namely, a low-pressure mercury lamp that efficiently emits a germicidal line, and a high-pressure mercury lamp that emits near-ultraviolet light having a wavelength of 400 nm or less that can activate a photocatalyst besides the germicidal line are used as ultraviolet light sources. The case where it used was compared. The results are shown in FIG. FIG.
The ultraviolet irradiation intensity in nm is plotted on the abscissa, and the survival rate obtained by dividing the number of viable Escherichia coli after irradiation with the initial number of viable bacteria before irradiation is plotted on the ordinate. The survival rate when a high-pressure mercury lamp was used as an ultraviolet light source was indicated by a black circle, and the survival rate when a low-pressure mercury lamp was used as an ultraviolet light source was indicated by a circle. Wavelength 254nm
Comparing the germicidal effects of the two types of mercury lamps with the ultraviolet irradiation intensity of, the germicidal effect is clearly higher when the high-pressure mercury lamp is used as the ultraviolet light source. This is because the high-pressure mercury lamp that emits near-ultraviolet light, which is effective in activating the photocatalyst, has a germicidal effect due to the photocatalytic activity, compared to the low-pressure mercury lamp that uses only the germicidal line as the main luminescence. It is high.

Next, the amount of hydroxyl radical produced was evaluated by the amount of iodine produced by the potassium iodide method. A comparison was made between a high-pressure mercury lamp and a low-pressure mercury lamp as ultraviolet sources. That is, a 100 mM aqueous solution of potassium iodide was used as a sample, and the sample was irradiated with ultraviolet light, a sample was collected over time, and PR Harvey and R. Rudham (19).
88) "Photocatalytic oxidation of iodine ions by ti
tanium dioxide ", J. Chem. Soc., Trans. 1., vol.84,
According to the method described in no.
The absorbance at nm was measured. The amount of iodine produced in the sample irradiated with ultraviolet light was calculated from a calibration curve prepared by spectral analysis of a standard solution prepared by adding an iodine solution (manufactured by Wako Pure Chemical Industries, Ltd.) to a 100 mM potassium iodide solution in a concentration range of 10 to 100 μM. did. The results are shown in FIG. FIG.
The UV irradiation intensity in nm is plotted on the horizontal axis, and the iodine generation after UV irradiation is plotted on the vertical axis. The amount of iodine generated when a high-pressure mercury lamp was used as an ultraviolet light source was indicated by a black circle, and the amount of iodine generated when a low-pressure mercury lamp was used as an ultraviolet light source was indicated by a circle. With the UV irradiation intensity of 254 nm wavelength, 2
When comparing the amount of iodine produced by the two types of mercury lamps, it is clear that the amount of iodine produced is higher when the low-pressure mercury lamp is used as the ultraviolet light source, and this result is opposite to the bactericidal effect on Escherichia coli described above. This shows that the potassium halide method cannot accurately evaluate the hydroxyl radical generation activity in the photocatalyst-ultraviolet method.

Further, the production amount of hydroxyl radical was evaluated by the production amount of methanesulfinic acid according to the present invention. A comparison was made between a high-pressure mercury lamp and a low-pressure mercury lamp as ultraviolet sources. That is, a 0.5 M dimethyl sulfoxide aqueous solution was used as a sample, and the sample was irradiated with ultraviolet light, a sample was collected over time, and methanesulfinic acid was solvent-extracted according to the method described in Example 2, and the wavelength was 42
The absorbance at 0 nm was measured. The methanesulfinic acid concentration was calculated from the absorbance based on the calibration curve shown in Example 3. The results are shown in FIG. FIG. 7 plots the irradiation intensity of methanesulfinic acid after irradiation with ultraviolet light on the vertical axis, with the irradiation intensity of ultraviolet light with a wavelength of 254 nm on the horizontal axis. The amount of methanesulfinic acid generated when a high-pressure mercury lamp was used as the ultraviolet light source
The mark indicates the amount of methanesulfinic acid generated when the low-pressure mercury lamp was used as an ultraviolet light source, and the mark indicates the mark. Wavelength 254nm
Comparing the amount of methanesulfinic acid produced by the two types of mercury lamps with the ultraviolet irradiation intensity of, the amount of iodine produced is clearly higher when the high-pressure mercury lamp is used as the ultraviolet light source,
This result has the same tendency as the bactericidal effect on Escherichia coli described above, and the method for measuring the hydroxyl radical of the present invention evaluated by the amount of methanesulfinic acid produced accurately evaluates the hydroxyl radical generating activity in the photocatalyst-ultraviolet method. It indicates that (Example 5) Using the photocatalyst-ultraviolet irradiation apparatus used in Example 4, the amount of hydroxyl radical generated due to photocatalytic activity was evaluated. In this embodiment, a high-pressure mercury lamp was used as an ultraviolet light source.

A 0.5 M aqueous solution of dimethyl sulfoxide was used as a sample, and the sample was irradiated with ultraviolet light.
According to the method described in Example 3, methanesulfinic acid was subjected to solvent extraction, and the absorbance at a wavelength of 420 nm was measured. The test was performed using a glass container having a photocatalytic coating and a glass container having no photocatalytic coating. Based on the calibration curve shown in Example 3, the methanesulfinic acid concentration was calculated from the absorbance, and this was defined as the amount of hydroxyl radical generated. Fig. 8 shows the results.
It was shown to.

FIG. 8 plots the intensity of ultraviolet irradiation at a wavelength of 365 nm as the representative wavelength of near-ultraviolet light effective for photocatalytic activation on the horizontal axis, and plots the amount of hydroxyl radical generated after ultraviolet irradiation on the vertical axis. The case with the photocatalyst coating is shown by a black circle as an example, and the case without the photocatalyst coating is shown by a black square as a comparative example. As is clear from the figure, a slight amount of hydroxyl radical generation was also observed in the comparative example, but in the example, significant hydroxyl radical generation was observed as compared with the comparative example. The radical measurement method was able to evaluate the amount of hydroxyl radical generated in the photocatalyst-ultraviolet disinfection method. (Embodiment 6) Ozone treatment is one of the water treatment techniques for oxidatively decomposing hardly decomposable raw materials in water and wastewater. As described above, ozone treatment is a water treatment technique based on the oxidizing power of hydroxyl radicals, and the oxidizing power can be evaluated by the hydroxyl radical measuring method of the present invention.

7.5 mg / Nl of ozone gas was added to 0.5
M dimethylsulfoxide aqueous solution was aerated for 10 minutes, and methanesulfinic acid was solvent-extracted with the dimethylsulfoxide aqueous solution before and after ozone gas aeration according to the method described in Example 3, and the absorbance at a wavelength of 420 nm was measured. Based on the calibration curve shown in Example 2, the methanesulfinic acid concentration was calculated from the absorbance, and the calculated concentration was defined as the amount of hydroxyl radical generated. The results are shown in FIG.

As is clear from FIG. 9, the concentration of hydroxyl radicals detected by the method of the present invention is hardly detected before ozone gas aeration, but remarkable generation of hydroxyl radicals can be detected in the aqueous solution after ozone gas aeration. Was. This indicates that the method for measuring a hydroxyl radical of the present invention is applicable to ozone treatment.

[0032]

According to the present invention, the amount of hydroxyl radicals produced can be reduced even in a water treatment apparatus with ultraviolet irradiation, which is difficult to apply the potassium iodide method proposed as a method for measuring hydroxyl radicals in water in the field of water treatment. Can be quantified and evaluated. Further, according to the present invention, a method for oxidizing water or wastewater using a chemical oxidizing agent such as ozone or hydrogen peroxide, a photocatalyst, or a photochemical reaction such as ultraviolet light alone or in combination of two or more thereof, or a hydroxyl radical in a water treatment apparatus. The amount of generation can be measured with high sensitivity and accuracy.

Since the present invention can be applied to any of the above-mentioned oxidation treatment methods, it can be used not only for the purpose of examining the effect of water treatment in an existing water treatment apparatus, but also for
It can be used for the development of new technologies for water treatment or for the design of new equipment.The amount of hydroxyl radical generated measured according to the present invention is an index for understanding the operating conditions and design specifications of water treatment equipment. It is possible to use as.

The present invention greatly contributes not only to industrial applications such as water treatment technology development but also to scientific development for elucidating the action mechanism of oxidation treatment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a procedure for measuring a hydroxyl radical in the present application.

FIG. 2 is a diagram showing an example of a calibration curve when a pretreatment step is omitted for a methanesulfinic acid standard solution of 100 μM or less.

FIG. 3 is a diagram showing an example of a calibration curve for a methanesulfinic acid standard solution of 1000 μM or less.

FIG. 4 is a diagram showing an example of a calibration curve for a methanesulfinic acid standard solution of 100 μM or less.

FIG. 5 is a diagram showing an example of a sterilization effect when a photocatalyst-ultraviolet disinfection treatment is performed.

FIG. 6 is a view showing a comparative example in which hydroxyl radicals were measured using a potassium iodide method in a photocatalyst-ultraviolet disinfection treatment.

FIG. 7 is a diagram showing an example in which hydroxyl radicals were measured using the present invention in a photocatalyst-ultraviolet disinfection treatment.

FIG. 8 is a diagram showing an example in which hydroxyl radicals were measured using the present invention in a photocatalyst-ultraviolet disinfection treatment.

FIG. 9 is a diagram showing an example in which hydroxyl radicals were measured using the present invention in ozone treatment.

Continued on the front page F term (reference) 2G042 AA01 BA03 BA04 BA07 BA08 BD01 BD15 CA02 CB03 DA08 EA03 EA20 FA11 FB02 GA04 GA05 HA07 2G054 AA02 AB10 BA10 BB01 BB02 BB08 BB10 BB20 CA30 CB10 CD04 CE02 EA06 GA03 EB06 4D037 AA01 AA11 AB02 AB03 AB05 BA18 BB02 BB08 CA12 4D050 AA01 AA12 AB06 AB11 BB02 BB09 BC06 BC09 CA05 CA07 CA12 CA20

Claims (6)

[Claims] 1. A method for measuring hydroxyl radicals in water, comprising measuring methanesulfinic acid generated when hydroxyl radicals in water react with dimethyl sulfoxide. 2. An aqueous solution to which dimethyl sulfoxide has been added is subjected to water treatment using a water treatment method selected from the group consisting of ultraviolet light, ozone, a photocatalyst, and hydrogen peroxide, alone or in combination of two or more. A first step of obtaining, a second step of separating the solvent extract after mixing the dye solution with the treated water, and a third step of spectroscopically analyzing a sample containing the solvent extract. Item 4. The method for measuring hydroxyl radicals in water according to Item 1. 3. The method according to claim 2, wherein, as a second step, a dye solution is added to the treated water, and then extracted with an organic solvent solution to collect a solvent layer sample. Measuring method. 4. The method for measuring hydroxyl radicals in water according to claim 2, wherein in the third step, absorbance is measured using a spectrophotometer. 5. A post-processing step of extracting a solvent layer sample to be subjected to spectroscopic analysis with an organic solvent-saturated water to recover a solvent layer as a post-processing step of the second step, and / or a solvent layer to be subjected to spectroscopic analysis. 5. The method for measuring hydroxyl radicals in water according to claim 2, further comprising a post-treatment step of adding pyridine to the sample. 6. As a pretreatment step of the second step, an acid solution is added to the treated water, followed by extraction with an acidic solvent solution to collect a solvent layer. The collected solvent layer is extracted with an acidic buffer solution to form a water solution. The method for measuring hydroxyl radicals in water according to any one of claims 2 to 5, further comprising a pretreatment step of recovering the layer.