JP5740138B2 - Hydroxy radical measuring device and measuring method - Google Patents

Description

  The present invention relates to a measurement apparatus and measurement method for hydroxy radicals, and more particularly to a measurement apparatus and measurement method for hydroxy radicals generated in a liquid.

  Discharges in liquids and gas-liquid interfaces have many applications such as the creation of novel nanomaterials from water treatment, sterilization, and plasma medicine, and are attracting high attention (for example, see Non-Patent Document 1). ).

Hydroxy radicals (OH radicals) having high oxidizing power generated by discharge in contact with water (H ₂ O) are effective for sterilizing microorganisms contained in the liquid and treating dissolved hardly decomposable organic compounds. In particular, the discharge generated from the discharge electrode installed just above the water surface or the discharge electrode installed in water can efficiently generate hydroxy radicals. Therefore, monitoring of hydroxy radicals is important, but methods that can be used for detection of hydroxy radicals in liquid are limited, and so far emission spectroscopy (OES) has been frequently used.

  On the other hand, in the fields of ultrasonic chemistry and radiation science, the chemical probe method is used for measuring hydroxy radicals in liquid (see, for example, Non-Patent Document 2). Among these, the method using the hydroxylation reaction of terephthalic acid (TA) is simple and excellent in reproducibility and sensitivity.

B.R.Locke, M.Sato, P.Sunka, M.R.Hoffmann, J.-S.Chang: Ind.Eng.Chem.Res., 45 (2006) 882 X.Fang, G.Mark, C.Von Sonntag: Ultrason.Sonochem., 3 (1996) 57

However, in the conventional measurement of hydroxy radicals in the liquid, measurement was performed with a commercially available fluorescence spectrophotometer. In that case, it is necessary to measure a solution in which a hydroxyl radical is generated and trapped in a fluorescence spectrophotometer.
In that case, there is a possibility that the production apparatus may be temporarily stopped for collecting the solution or a chemical change may occur during the transportation of the solution. For this reason, there are problems that the situation in the liquid immediately after the generation of hydroxy radicals cannot be observed in real time.

  In order to solve the above problems, an object of the present invention is to provide a hydroxy radical measuring apparatus and measuring method capable of observing in real time a state in a liquid immediately after the generation of a hydroxy radical.

  In order to achieve the above object, a hydroxy radical measuring apparatus and measuring method according to the present invention are configured as follows.

The first hydroxy radical measuring device (corresponding to claim 1) is a liquid hydroxy radical generated in liquid by a hydroxy radical generating means for generating a hydroxy radical by intermittently repeating discharge between a pair of electrodes. Is a hydroxy radical measuring device for measuring terephthalic acid, a container containing therein a hydroxy radical generating means, a light source that emits light having a wavelength in the ultraviolet region, and an optical expansion that expands the width of the light. A light irradiating means for irradiating the liquid in the container with light, a light detecting means for detecting the intensity of the fluorescence emitted from the liquid in the container by the light irradiation, and when the discharge is repeated intermittently. in a period in which discharge is not performed, and a control means for detecting the intensity of fluorescence light detecting means, submerged hydroxylase from the intensity of the fluorescent And measuring the local.
In the second hydroxy radical measuring device (corresponding to claim 2), in the above configuration, preferably, the light expanding means is attached to an optical fiber for extending the width of light from the light source and to the tip of the optical fiber. It consists of a lens.
The first method for measuring hydroxy radicals (corresponding to claim 3) is a hydroxy radical measurement in which the hydroxy radicals generated in the liquid in the container are measured by intermittently repeating the discharge between the pair of electrodes. In the method, the liquid in the container is mixed with terephthalic acid, the liquid in the container is irradiated with ultraviolet light, and fluorescence is generated in the terephthalic acid in which the hydroxy radicals are trapped. In the period when the discharge is not performed when intermittently repeated, the fluorescence intensity is detected, and the hydroxy radicals in the liquid are measured from the fluorescence intensity .

  According to the present invention, the means characterized in that the formation of hydroxyterephthalic acid from the hydroxy radical generated by using the terephthalic acid solution is performed one or more times in a predetermined time, each time or continuously. In addition, it is possible to detect the fluorescence by irradiating hydroxyterephthalic acid with ultraviolet light, and to accurately measure the content of hydroxy radicals by its intensity. As a result, about the total amount of the hydroxy radical content can be measured quickly and accurately in real time in the place where the short-lived hydroxy radical is generated.

It is a whole lineblock diagram of the measuring device of hydroxy radical concerning this embodiment of the present invention. It is a figure explaining the principle of the measurement by the measuring device of hydroxy radical concerning this embodiment of the present invention. It is a flowchart of the control program in measurement using the measuring device of hydroxy radical concerning this embodiment of the present invention. It is the schematic of the apparatus for sampling the liquid processed with the pulse discharge generator on the water surface, and discharging, and measuring a hydroxyl radical. It is an observation image by ICCD when the terephthalic acid (TA) aqueous solution exposed to the pulse discharge on the water surface for 5 minutes is sampled, put into a cuvette, and irradiated with LED light. It is a graph which shows the change with respect to the discharge time of the fluorescence spectrum measured with the spectrometer for quantification. It is a graph which shows the relationship between the density | concentration of the hydroxyl radical calculated | required from FIG. 6, and discharge time. It is a figure which shows a mode that the mode of the fluorescence which generate | occur | produced the hydroxyl radical which generate | occur | produced by reaction with terephthalic acid was observed in real time. It is the graph which plotted the generation amount (fluorescence intensity) of the hydroxy radical with respect to discharge time progress based on the figure shown in FIG.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of a hydroxy radical measuring apparatus according to this embodiment of the present invention. In this embodiment, a description will be given using a discharge generator as a hydroxy radical generating means for generating a hydroxy radical. The hydroxy radical measuring device 10 includes, for example, a water tank 11, a discharge generator (discharge generator) 12, a light irradiation device (light irradiation device) 13, a light detection device (light detection device) 14, and a control device 15 as containers. The

The water tank 11 is formed of a transparent body (for example, a transparent resin such as quartz glass or plastic) that transmits light in a range from ultraviolet light to visible light, and generates hydroxy radicals by water surface discharge or underwater discharge. It is a water tank for containing a liquid 16 containing terephthalic acid that traps hydroxy radicals.
The water tank 11 is provided with a light irradiating means device 13 and a light detecting device (light detecting means) 14 above the liquid surface of the water tank 11 to directly irradiate the liquid 16 in the water tank and receive the fluorescence. There is no need to make it.

  The discharge generator 12 is a device for causing discharge on the water surface or discharge in water between the electrodes 12 a and 12 b provided in the water tank 11. The electrode 12a and the electrode 12b are movable up and down, and an underwater discharge is generated when the electrode 12a, which is a discharge electrode, is inserted into the water, and an over-surface discharge is generated when the electrode 12a and the electrode 12b are placed in contact with the water surface or lifted from the water surface.

  The light irradiation device 13 is a device that irradiates the liquid 16 in the water tank 11 with ultraviolet light, and includes a light source 13a that emits ultraviolet light having a wavelength of 310 nm and an optical fiber 13b that transmits light from the light source 13a. The light source 13a is, for example, a monochromatic light source such as a semiconductor laser or a light emitting diode, or a light source having an ultraviolet wavelength such as a mercury lamp or a xenon lamp. Further, light from a light source having a continuous spectrum may be irradiated through a plurality of filters such as an interference filter that transmits light of a single wavelength.

  The light irradiation device 13 includes a light source 13a that emits light having a wavelength in the ultraviolet region and a light expansion unit 13e that spreads light from the light source 13a. The light expanding means 13e includes an optical fiber 13b that extends the width of light from the light source 13a and a lens 13c attached to the tip of the optical fiber 13b.

  This ultraviolet light is irradiated with terephthalic acid that traps hydroxy radicals, that is, hydroxyterephthalic acid, thereby generating fluorescence in the visible light region. And the quantity of the hydroxy radical in a liquid can be measured by measuring this fluorescence intensity. Moreover, the spatial distribution of fluorescence can be observed by expanding the ultraviolet light by the optical fiber 13b and the lens 13c which are the light expansion means 13e.

  The light detection device 14 shown in FIG. 1 is a device that detects fluorescence emitted by hydroxyterephthalic acid formed by terephthalic acid trapped by hydroxyl radicals generated by surface discharge or underwater discharge by the discharge generator 12. As the photodetector 14, a spectrometer can be used to observe the fluorescence spectrum, and a digital camera or ICCD can be used to observe the fluorescence distribution. FIG. 1 shows an example in which an ICCD is used as the light detection device 14.

  The control device 15 is composed of a personal computer or the like, and controls the operation and timing of the discharge generator 12 and the light detection device 14, and causes the discharge generator 12 to discharge on the surface of the water or discharge in water at predetermined time intervals. Fluorescence is detected by the light detection device 14 during discharge. The control device 15 adjusts the discharge time interval, controls the measurement timing of the light detection device 14, and the like according to an operation instruction from an operation unit (not shown).

  FIG. 2 shows the principle of measurement by the hydroxy radical measuring apparatus 10. Terephthalic acid (TA) becomes a scavenger of hydroxy radicals, and hydroxyterephthalic acid (HTA) is generated by a hydroxylation reaction. When excitation light having a wavelength of 310 nm is incident on the HTA, fluorescence having a wavelength of 425 nm is emitted. Information on the amount of hydroxy radicals can be obtained by measuring the fluorescence.

  Next, the operation of the hydroxy radical measuring apparatus 10 will be described with reference to FIGS.

  The measurement using the hydroxy radical measurement device 10 according to the present embodiment is performed by the control device 15 formed using, for example, a personal computer equipped with an operation unit, a calculation unit, a storage unit, and a display unit. It is controlled and executed by a control program stored in the storage unit of the personal computer. FIG. 3 is a flowchart of the control program.

  First, the operator puts the liquid 16 into the water tank 11 and then starts the operation of the hydroxy radical measuring apparatus 10 of the present embodiment by inputting an execution command from a personal computer. The hydroxy radical measurement apparatus 10 executes a control program according to a flowchart described below when the operation starts. The light irradiation device 13 irradiates the liquid in the water tank 11 formed of a transparent body with ultraviolet light. First, a discharge generator 12 performs surface discharge or underwater discharge at a predetermined time interval on a liquid containing terephthalic acid in a water tank 11 formed of a transparent body by a control signal from the personal computer 15 (step S11: discharge process). ). The surface of the water generated by the discharge generator 12 by the light detector 14 during or immediately after the discharge process in a state where the liquid 16 in the water tank 11 formed of a transparent body is irradiated with ultraviolet light by the light irradiation device 13. Fluorescence emitted from hydroxyterephthalic acid formed by terephthalic acid trapped by hydroxy radicals generated by upper discharge or underwater discharge is detected (step S12: light detection step). The detected result is displayed as numerical data, a graph, or a distribution chart on the display unit of the personal computer 15 (step S13). The hydroxy radical measurement device 10 ends the measurement after obtaining an operator stop instruction or a predetermined amount of data.

  The amount of hydroxy radicals can be measured by the above measurement.

(Example 1)
First, in Example 1, the following example was shown using the measuring apparatus 19 shown in FIG. 4 as confirmation of the measuring method by this invention of the hydroxy radical in the liquid produced | generated by the surface discharge. In the first water tank 21 provided with the discharge generator 20, a discharge process in which a liquid 22 containing terephthalic acid is discharged on the surface of the water by the discharge generator 20, and in the second water tank 23 formed of a transparent body, The liquid moving step of putting the liquid 22 after discharging on the surface of the water from the water tank 21 and the light irradiating device 13 irradiates the liquid 22 in the second water tank 23 formed of a transparent body with light. An example of a measurement method including a light detection step of detecting fluorescence emitted from hydroxyterephthalic acid formed by terephthalic acid formed by terephthalic acid trapped by hydroxyl radicals generated by discharge on the water surface by the discharge generator 20 by the detection device 14 will be described.

  FIG. 4 shows a schematic view of a water surface pulse discharge generator (discharge generator) 20 and an apparatus for measuring hydroxy radicals by sampling a liquid 22 treated by discharge. The discharge unit is a rectangular reactor (first water tank) 21 (80 mm × 20 mm) filled with a nozzle electrode 20 a (outer diameter 0.57 mm, inner diameter 0.31 mm, length 15 mm) and a liquid 22 attached to a stainless steel pipe having a diameter of 6 mm. , Depth 20 mm). The tip of the nozzle electrode 20a is set to a position of about 1 mm on the water surface, and the bottom surface of the rectangular reactor 21 is a flat plate electrode (carbon plate) 20b that is grounded. The discharge on the surface of the water was generated by applying a pulse voltage generated by charging and discharging the capacitor with a spark gap switch to the nozzle electrode 20a.

  In this example, a measurement system including an LED light source (light irradiation device) 13 (Sandhouse Design, center wavelength 310 nm, FWHM 10 nm) and a simple spectroscope (light detection device) 14b (Ocean Optics, USB2000) was constructed. The fluorescence was measured by sampling the liquid at an arbitrary time from the start of discharge. Fluorescence was also observed with an ICCD camera (photodetector) 14a (Andor, i-Star). For quantification of OH radicals, a calibration curve was created using the standard substance HTA and converted. The sample used is a 0.2 mM TA aqueous solution. Since TA does not dissolve in acidic or neutral water, distilled water adjusted to a concentration of NaOH 1.4 mM was used as a solvent. The liquid has a conductivity of 105 μS / cm and a pH of 8. In addition, the code | symbol 30 in FIG. 4 shows a mirror, and the code | symbol 31 shows a dark box.

  FIG. 5 shows an observation image by the ICCD (light detection device) 14a when the TA aqueous solution 22 exposed to the pulse discharge on the water surface for 5 minutes is sampled and put in the cuvette (second water tank) 23 and irradiated with the LED light. . While the OH radicals generated by the discharge are diffused from the water surface to a very shallow portion of the water, it reacts with TA and becomes stable HTA. It can be seen from FIG. 5 that fluorescence is emitted from the portion through which the LED light is transmitted. As the discharge time increased, the fluorescence intensity also increased. When the room was darkened, fluorescence was observed visually.

The change with respect to the discharge time of the fluorescence spectrum measured with the spectrometer for quantification is shown in FIG. FIG. 7 shows the relationship between the OH radical concentration obtained from FIG. 6 and the discharge time. It is corrected in consideration of the OH supplement efficiency in water. In the case of this example, OH radicals generated by discharge react with TA and do not change when it becomes HTA, so the OH radicals observed here increase with time. When the OH radical production rate is estimated, it is on the order of 10 ⁻⁹ M / s.

(Example 2)
Next, examples of the hydroxy radical measuring apparatus and measuring method described in this embodiment of the present invention will be described.

  Using the hydroxy radical measuring apparatus 10 shown in FIG. 1, underwater discharge was generated by applying a pulse voltage generated by charging and discharging a capacitor by a spark gap switch to the nozzle electrode 12a. The positive pulse voltage is 24.5 kV.

  The liquid was observed in real time with an ICCD camera (photodetection device) 14 (Andor, i-Star) at an arbitrary time from the start of discharge. The sample used is a 0.2 mM TA aqueous solution. Since TA does not dissolve in acidic or neutral water, distilled water adjusted to a concentration of NaOH 1.4 mM was used as a solvent. The conductivity of the liquid is 127 μS / cm and the pH is 9.6.

  OH radicals are generated by direct discharge in a reactor containing terephthalic acid. The generated OH radical generates fluorescence by reaction with terephthalic acid. A photograph (Fig. 8) shows the situation observed in real time on the spot. The band-like portion in the figure is excited by LED light (width is about 3.8 mm). Fluorescence image is 20 shots of images taken with 1ms shutter. Since the timing of the discharge is shifted, there is no overlap. The left side and the tip of the electrode are scattered light.

FIG. 9 shows a graph in which the amount of OH radicals generated (fluorescence intensity) with respect to time is plotted based on the photograph shown in FIG. Radicals are generated with the start of discharge, and the first plot is immediately after discharge (taken between about 30 seconds from the start). Thereafter, radicals increase with time, but tend to be saturated after about 10 minutes. This seems to be because terephthalic acid in the solution used reaches the limit of the amount capable of trapping OH radicals. (In this case, the initial concentration is increased in advance).
Therefore, by storing a terephthalic acid solution having a concentration necessary and sufficient for the expected amount of generated OH radicals, the saturated state can be about the total amount of contained OH radicals.

  As shown in the above examples, according to the present invention, it is possible to provide a hydroxy radical measuring device and a measuring method capable of observing in real time the situation in the liquid immediately after the generation of the hydroxy radical.

  In the present embodiment, the discharge generator is used as the hydroxy radical generating means, but further, ultrasonic irradiation in water, photocatalytic reaction, hydrogen peroxide, ozone, and ultraviolet rays, which are known as hydroxy radical generating methods, are used. This technique can also be applied to in vivo reactions typified by accelerated oxidation reactions and Fenton reactions.

  The configurations, shapes, sizes, and arrangement relationships described in the above embodiments are merely schematically shown to the extent that the present invention can be understood and implemented, and the numerical values and the compositions (materials) of the respective components Is just an example. Therefore, the present invention is not limited to the described embodiments, and can be variously modified without departing from the scope of the technical idea shown in the claims.

The apparatus and method for measuring hydroxy radicals according to the present invention are used for measuring hydroxy radicals in liquid generated by discharge in contact with water (H ₂ O) typified by surface discharge or underwater discharge. Furthermore, it is also used for measurement of hydroxy radicals in liquids generated by in-vivo reaction represented by ultrasonic irradiation in water, photocatalytic reaction, accelerated oxidation reaction by hydrogen peroxide and ozone and ultraviolet rays, and Fenton reaction.

DESCRIPTION OF SYMBOLS 10 Hydroxyl radical measuring apparatus 11 Water tank 12 Discharge generator 13 Light irradiation apparatus 13a Light source 13b Optical fiber 13c Lens 14 Photodetection apparatus 15 Control apparatus 16 Liquid

Claims (3)

A hydroxy radical measuring device that measures hydroxy radicals in liquid generated by a hydroxy radical generating means that generates hydroxy radicals by intermittently repeating discharge between a pair of electrodes,
A container containing terephthalic acid-containing liquid and the hydroxy radical generating means;
A light source that emits light having a wavelength in the ultraviolet region; and a light expansion unit that expands a width of the light; and a light irradiation unit that irradiates the light in the liquid in the container;
Light detecting means for detecting the intensity of fluorescence emitted by the liquid in the container by the light irradiation;
Control means for causing the light detection means to detect the intensity of the fluorescence in a period in which the discharge is not performed when the discharge is intermittently repeated;
Equipped with a,
A hydroxy radical measuring apparatus for measuring hydroxy radicals in the liquid from the intensity of the fluorescence .   2. The hydroxy radical measuring apparatus according to claim 1, wherein the light expanding means includes an optical fiber that extends a width of light from the light source and a lens attached to a tip of the optical fiber. A hydroxy radical measuring method for measuring hydroxy radicals in a liquid generated in a liquid in a container by intermittently repeating discharge between a pair of electrodes,
Mixing terephthalic acid into the liquid in the container;
Irradiating the liquid in the container with ultraviolet light to generate fluorescence in the terephthalic acid trapped by the hydroxy radicals, in a period when the discharge is not performed when the discharge is repeated intermittently, A method for measuring hydroxy radicals, comprising detecting fluorescence intensity and measuring hydroxy radicals in the liquid from the fluorescence intensity .