JP3291879B2 - Photo-oxidative decomposition apparatus, method and apparatus for analyzing nitrogen compounds and phosphorus compounds in water using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing trace amounts of nitrogen compounds and phosphorus compounds contained in wastewater discharged from factories and offices and in environmental water such as rivers and lakes. The present invention also relates to an oxidative decomposition apparatus that oxidizes nitrogen compounds and phosphorus compounds in sample water to nitrate ions and phosphate ions, respectively, by such an analysis method.

[0002]

2. Description of the Related Art In Japan, methods for analyzing nitrogen compounds and phosphorus compounds in water are publicly standardized by JIS K0102 and Notification No. 140 of the Environment Agency. Nitrogen compounds in water are present as nitrate ions, nitrite ions, ammonium ions or organic nitrogen. In the TN (total nitrogen) analysis method for measuring all of the nitrogen in water, all the nitrogen compounds are changed to nitrate ions for measurement. However, ammonium ions and organic nitrogen are hardly oxidized to nitrate ions. Therefore, in the TN measurement, an alkaline potassium peroxodisulfate solution is added to the sample water and heated at 120 ° C. for 30 minutes to oxidize all nitrogen compounds to nitrate ions. After cooling, the pH was adjusted to 2-3 and the UV absorbance at a wavelength of 220 nm due to nitrate ions was measured.

On the other hand, phosphorus compounds in water are phosphate ions,
Present as hydrolysable phosphorus or organic phosphorus.
In the TP (total phosphorus) measurement, potassium peroxodisulfate is added as an oxidizing agent in a neutral state, and all phosphorus compounds are oxidized to phosphate ions by heating at 120 ° C. for 30 minutes. Since phosphate ions do not have a specific light absorption,
In order to measure phosphate ions, after cooling, an ammonium molybdate solution and an L-ascorbic acid solution are added as color formers to develop color, and the absorbance at a wavelength of 880 nm is measured.

In another TN measurement method, after oxidation to nitrate ions at a high temperature of 500 ° C. or more using an oxidation catalyst, measurement is made as nitrogen oxide by a chemiluminescence method, or nitrogen oxide is further added to a redox reaction tube ( (About 600 ° C.) to decompose into nitrogen gas and measure it as nitrogen by gas chromatography. As another method, ozone is supplied to a sample water to oxidize ozone. The ozone oxidation is performed under alkaline conditions in TN measurement and under acidic conditions in TP measurement.

[0005]

There is no apparatus for analyzing TN measurement and TP measurement in sample water with a common analyzer. This is because, in the oxidation by an oxidizing agent or ozone oxidation, the pH conditions at the time of oxidation are different, such that oxidation of a nitrogen compound is performed under alkaline conditions and oxidation of a phosphorus compound is performed under neutral or acidic conditions. . In addition, the oxidizing method using an oxidizing agent heats to a high temperature such as 120 ° C., which is higher than the boiling point of water. is there.
Since the oxidizing agent is consumed, it must be replenished frequently, and there is a problem that the running cost is increased.

The method of oxidizing a nitrogen compound using a catalyst requires a high temperature of 500 ° C. or more, and the catalyst is severely deteriorated. Not only is the device complicated in structure and difficult to maintain, but the analytical method using a catalyst is generally unsuitable for on-site use as a monitor. In the ozone oxidation method, since the oxidizing power in the neutral region is weak, both the oxidation of the nitrogen compound and the oxidation of the phosphorus compound are p
A mechanism for adjusting H is required, and the structure of the device becomes complicated. Further, a pH adjusting solution of an acid and an alkali is also required as a consumable. As described above, the conventional analysis method cannot not only measure the nitrogen compound and the phosphorus compound in common, but also increases the cost and lacks suitability as a continuous monitor.
Difficult to use.

Accordingly, an object of the present invention is to provide an analysis method which enables common measurement of a nitrogen compound and a phosphorus compound in a sample water and enables continuous analysis for a long time. . Another object of the present invention is to provide an apparatus which is advantageous for oxidizing a nitrogen compound and a phosphorus compound together to convert them into nitrate ions and phosphate ions by such an analysis method.

[0008]

The analysis method of the present invention includes the following steps (A) to (C) for analyzing nitrogen compounds and phosphorus compounds in water. (A) Sample water at 50-100 ° C
An oxidation step of irradiating the sample water with ultraviolet rays in the presence of a photo-oxidation catalyst, (B) a step of measuring nitrate ions of the oxidized sample water by an absorption spectrophotometry, and (C) an oxidized sample A step of adding a color former that selectively reacts with phosphate ions to water, and measuring the color developing solution by an absorption spectrophotometric method.

As the photo-oxidation catalyst, TiO ₂ and silver halide can be used. In a preferred embodiment, AgCl, A
Silver halides such as gI and AgBr are used. In another preferred embodiment, a gas containing oxygen or ozone is blown into the sample water during ultraviolet irradiation.

The photo-oxidative decomposition apparatus of the present invention has a sample water inlet / outlet, a photo-oxidation catalyst in a tank, and simultaneously oxidizes nitrogen compounds and phosphorus compounds in the sample water to convert nitrate ions into nitrate ions and phosphorus compounds. An oxidation reaction tank that generates phosphate ions, an ultraviolet light source that irradiates ultraviolet rays into the oxidation reaction tank,
Heating means for heating the sample water in the oxidation reaction tank to 50 to 100 ° C. When using a batch type photo-oxidative decomposition device, the sample water is supplied to the oxidation reaction tank discontinuously and a flow path is taken out discontinuously. And a flow path for continuously supplying the liquid to the air.

[0011] The analyzer of the present invention can be used to supply a sample water of 50 to 10
Heated to 0 ° C and irradiates the sample water with ultraviolet light in the presence of a photo-oxidation catalyst to simultaneously oxidize the nitrogen and phosphorus compounds in the sample water to produce nitrate ions from the nitrogen compound and phosphate ions from the phosphorus compound An oxidation reaction tank to be connected, an absorption measurement cell made of quartz glass, which is connected to the oxidation reaction tank by a flow path, and supplied with sample water from the oxidation reaction tank, and selectively emits phosphate ions to the oxidation reaction tank or the absorption measurement cell. A color developing solution addition flow path for adding a reacting color developing solution, a light source unit for irradiating ultraviolet and near infrared rays as measurement light to the absorption measurement cell, and a transmission light on the measurement light transmission optical path of the absorption measurement cell; A demultiplexing means for demultiplexing into two optical paths, and a first means for selecting an absorption wavelength specific to nitrate ions on one of the demultiplexed optical paths and detecting light of the wavelength as sample light of nitrate ions. Optical system and the other split optical path A second optical system that selects an absorption wavelength specific to the color developing solution that has reacted with phosphate ions, and detects light of that wavelength as sample light of phosphate ions; and a first optical system and a second optical system. An arithmetic processing unit that calculates the nitrogen compound concentration and the phosphorus compound concentration based on the detection signal. In a preferred embodiment of the analyzer, the absorption measurement cell is disposed at a position lower than the oxidation reaction tank, and no pump is disposed in the flow path of the sample water from the oxidation reaction tank to the drainage via the absorption measurement cell, The sample water is transferred by the head.

[0012]

The silver halide is widely used as a photographic material. Its light absorption characteristics are also well known and almost absorb the emission spectrum of a low-pressure mercury lamp. However, it is not known that silver halide has a catalytic action when oxidizing nitrogen compounds and phosphorus compounds in water.

Although the function of silver halide as a photooxidation catalyst is not clear, it is known that electrons in the valence band are excited into the conduction band by light absorption to generate free electrons and holes. It is considered that these free electrons and holes act on electrons bonded to nitrogen or phosphorus to break the bond, leading to oxidation.

When a gas containing oxygen or ozone is blown when irradiating the sample water with ultraviolet rays, the following reaction occurs, and oxygen atoms and ozone are generated in the water. The oxygen atoms and ozone promote the oxidation of nitrogen and phosphorus together with the action of the silver halide photooxidation catalyst. O ₂ + UV (18
5 nm) → 2O O + O ₂ → O ₃ O ₃ + UV (254 nm) → O + O ₂

Since oxygen atoms and ozone have oxidizing power, nitrogen compounds and phosphorus compounds in the sample water are oxidized and converted into nitrate ions and phosphate ions, respectively. 50 water samples
The reason for heating to に 100 ° C. is that the heating greatly accelerates the photooxidative decomposition reaction.

[0016]

FIG. 1 shows an embodiment of the method of the present invention in the order of steps, and FIG. 2 shows a schematic configuration of a measuring apparatus. In the configuration diagram of FIG. 2, reference numeral 2 denotes a photo-oxidation decomposition tank, which is provided with a heating means so as to be able to heat to 50 to 100 ° C., means for supplying oxygen or air to the sample water, and irradiation of the sample water with ultraviolet rays. There is also a means to do it. The sample water after the nitrogen and phosphorus compounds are oxidized to nitrate ions and phosphate ions by ultraviolet irradiation in the photo-oxidative decomposition tank 2 is led to the measurement tank 8. Reference numeral 10 denotes an absorptiometer that measures the absorbance of nitrate ions in the sample water in the measurement tank 8 and the amount of color developed by the phosphate ions after the addition of the coloring agent as the absorbance. In order to measure phosphate ions, an ammonium molybdate solution and an L-ascorbic acid solution are measured and mixed by the measuring devices 12 and 14, respectively, and supplied to the measuring tank 8. Wash water is supplied to the photo-oxidative decomposition tank 2 and the measurement tank 8 for washing.

FIG. 3 shows an example of the photo-oxidative decomposition tank. A low-pressure mercury lamp 22 as a light source is mounted inside a reaction vessel 40 made of Pyrex glass, and about 150 ml of sample water 41 can be stored in the reaction vessel 40 with the low-pressure mercury lamp 22 mounted. Stabilized power supply (power transformer) for low-pressure mercury lamp 22
23 has a capacity of 54 W, a current of 0.6 A, a primary voltage of 100 V, and a secondary voltage of 190 V (please specify). An air inlet 24 for supplying air is provided at the center of the bottom of the reaction tank 40, and 10 ml / min of air is supplied into the reaction tank 40. The supply of air is for supplying oxygen and stirring the sample water 41. At the bottom of the reaction tank 40, a sample water inlet 26 and a sample water outlet 28 are further provided.
On / off valves are provided at the air inlet 24, the sample water inlet 26, and the sample water outlet 28, respectively. A side tube 30 is provided at the upper part of the reaction tank 40, and the overflowed sample water is discharged from the side tube 30.

Inside the reaction tank 40, the height along the wall is 100 mm, the circumference is 200 mm, and the thickness is 0.0.
An Ag thin film 110 having a 5 mm AgCl thin film on its surface is
AgCl is attached so as to be in contact with the sample water.

The temperature of the sample water in the reaction tank 40 is set to 50 to 10
In order to maintain a constant temperature between 0 ° C., an aluminum protection tank as a heat sink 42 is provided in contact with the reaction tank 40 outside the reaction tank 40. The heat sink 42 has a cartridge heater (sheath heater) 32 of about 30 W.
Are embedded, and a thermocouple is embedded as the temperature sensor 34. The temperature controller 37 is set to adjust the temperature of the sample water to 90 ° C. as an example. The temperature of the sample water depends on the heat from the heat sink 42 and the low-pressure mercury lamp 22.
The temperature rises sharply to 90 ° C. due to the heat generated by the heating.

The ultraviolet radiation source is not limited to the low-pressure mercury lamp 22, and any light source that can emit ultraviolet light with strong energy, such as an excimer laser, a deuterium lamp, a xenon lamp, and a Hg-Zn-Pb lamp, can be used. it can. Low-pressure mercury lamps are advantageous because they are inexpensive and have a long life and are suitable as monitors. At the time of oxidative decomposition, the low-pressure mercury lamp 22 is turned on, ultraviolet rays are irradiated on the sample water in the reaction tank 40, and air is supplied from the air inlet 24.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. The sample water is supplied to the reaction tank 40 through the sample inlet 26 while being measured, after large dirt is removed by a filter or the like in advance. Reaction tank 40
In this case, the sample water 41 is heated to 90 ° C., and while the air is supplied from the air inlet 24, the sample water is irradiated with ultraviolet rays by the low-pressure mercury lamp 22 for 45 minutes. It is considered that the ultraviolet irradiation causes the following reaction in the reaction tank 40 together with the oxidation reaction of the photooxidation catalyst by AgCl. O ₂ + UV (185 nm) → 2O O + O ₂ → O ₃ O ₃ + UV (254 nm) → O + O ₂ O + O ₃ → 2O ₂ (O, O ₃ ) + (nitrogen compound, phosphorus compound) → nitrate ion, phosphate ion (O , O ₃ ) + unsaturated compound → saturated compound, CO ₂ ,
H ₂ O

After the completion of the photo-oxidative decomposition, a part or all of the sample water in the reaction tank 40 is taken out to the measuring tank 8 and the spectrophotometer 10
Is measured at a wavelength of 220 nm. next,
An ammonium molybdate solution and an L-ascorbic acid solution are added to the measuring tank 8 to cause a color reaction. Phosphate ions of the colored solution are measured at a wavelength of 880 nm by the absorptiometer 10.

FIG. 4 shows the photo-oxidation catalyst AgCl used in FIG.
3 shows a method of forming a thin film 110. NaC
An Ag thin plate 114 of a main material serving as a photo-oxidation catalyst is immersed in an aqueous solution 112 (about 1 mol) as an anode, and Pt serving as a counter electrode is
The thin plate 116 is set so as to have the same surface area as the Ag thin plate 114. Both electrodes 114 and 11 from DC power supply 118
When a voltage of about 0.3 V is applied between 6
The surface of the Cl thin plate 114 is sufficiently plated to form an AgCl thin film.

When forming an AgI thin film or an AgBr thin film, they can be formed in the same manner by using an aqueous solution of NaI or an aqueous solution of NaBr, respectively. Instead of setting an Ag thin plate having an AgCl thin film inside the reaction tank 40 as shown in FIG.
A thin film is formed, and the Ag thin film is made of NaC in the same manner as in FIG.
An AgCl thin film can be obtained by performing an electrolytic treatment in an aqueous solution. Further, the inner surface of the reaction tank 40 may be coated with a silver paste to form an AgCl thin film in the same manner.

FIG. 5 shows the decomposition efficiency when the photooxidation catalyst AgCl is used in comparison with other methods. “AgCl” is represented by (NH ₄ ) ₂ S as a representative example of the hardly decomposable ammonia nitrogen using the photo-oxidative decomposition tank of FIG.
Using O ₄ , a concentration of 1.5 ppmN (nitrogen-converted concentration of 1.
5 ppm) of the sample water. "Pt" indicates the case where a Pt thin film was used as the photo-oxidation catalyst, and "No catalyst" indicates the case where no photo-oxidation catalyst was used. From this result, Ag
It can be seen that the catalytic effect is remarkable when Cl is used as the photo-oxidation catalyst. Although Pt is known as an oxidation catalyst, when oxidizing a nitrogen compound or a phosphorus compound as in the present invention, it means that the catalytic activity is lower than that of AgCl.

In the present invention using the photo-oxidation catalyst, when irradiating the sample water with ultraviolet rays, it is not an essential condition to blow a gas containing oxygen or ozone into the sample water. FIG. 6 shows an example of a photo-oxidative decomposition tank in which ultraviolet light is irradiated without blowing such an oxidizing gas into the sample water. (A) is a top view and (B) is a front sectional view. A low-pressure mercury lamp 22 for irradiating ultraviolet rays is provided in a glass reaction tank 40 such as Pyrex, and directly contacts sample water in the reaction tank 40. The low-pressure mercury lamp 22 has a luminance at a short wavelength ultraviolet ray, for example, 185 nm. A sample water inlet 26 and a sample water outlet 28 are provided at the bottom of the reaction tank 40. A side tube 30 is provided at the upper part of the reaction tank 40 to discharge the overflow liquid when the sample liquid is introduced. Reaction tank 40
Inside is Ag with AgCl thin film on the surface as a photo-oxidation catalyst
The thin plate 110 is attached so that the AgCl thin film can come into contact with the sample water. At the side and bottom of the reaction tank 40, a heat sink 42 of a metal protective tank having good heat conductivity is provided in contact with the outside of the reaction tank 40.
Has a cartridge heater 32 and a temperature sensor 34 embedded therein. The outside of the heat sink 42 is covered with a heat insulating material 36.

In the photo-oxidative decomposition tank of FIGS. 3 and 6, the sample inlet 26 is not limited to the bottom but may be provided on the side or on the top. Also, when the air inlet is provided when the sample inlet is provided at the bottom, the sample inlet and the air inlet merge,
In a portion connected to the reaction tank, a common inlet may be provided.

FIG. 7 shows the difference in oxidation efficiency between the case where air is blown and the case where air is not blown when the sample water is irradiated with ultraviolet rays. Blowing air shows higher oxidation efficiency, but when air is not blown, the photooxidation catalyst also shows higher oxidation efficiency. From this result, a sufficient oxidation efficiency can be obtained by increasing the contact area between the oxidation catalyst and the sample water without blowing an oxidizing gas such as air.

Irradiation with ultraviolet rays in the presence of a photo-oxidation catalyst increases the efficiency of oxidation of nitrogen compounds and phosphorus compounds by ultraviolet rays, so that a flow-type photo-oxidative decomposition apparatus for oxidizing a sample water while continuously flowing it can also be constructed. . 8 and 9
Shows an example of a flow type photo-oxidative decomposition apparatus.
In the photo-oxidative decomposition apparatus of (A), A
Catalyst 110 having AgCl thin film formed on the surface of thin plate
Is provided so that the AgCl thin film is brought into contact with the sample water. A sample water inlet 122 is formed at the bottom of the reaction tank 120, and an outlet 124 is provided at the upper end. A low-pressure mercury lamp 22 is installed in a reaction tank 120 and a stabilizing power supply 23
Is lit by. A heat sink 42 having a heater and a temperature sensor is provided outside the reaction tank 120.

In the photo-oxidative decomposition apparatus (B), Ag is applied to the inner surface.
A reaction tank 130 provided with a Cl thin film catalyst 110 is installed in an oblique direction, a sample water inlet 122 is provided at the bottom, and an outlet 124 is provided at the upper end. Reaction tank 13
A low-pressure mercury lamp 22 is installed in the center of the
A spiral plate 132 is provided between the reaction vessel 2 and the reaction tank 130, and the sample water supplied from the inlet 122 is supplied to the spiral plate 13.
2 around the low pressure mercury lamp 22 along exit 2
4. A heat sink 42 having a heater and a temperature sensor is provided outside the reaction tank 130.

In the photo-oxidative decomposition apparatus (C), Ag is applied to the inner surface.
The reaction tank 140 provided with the Cl thin film catalyst 110 has a U-shaped cross section, and has an inlet 122 at one upper end and an outlet 124 at the other upper end. A U-shaped low-pressure mercury lamp 142 is mounted inside the reaction tank along the U-shape of the reaction tank 140. A heat sink 42 having a heater and a temperature sensor is provided outside the reaction tank 140.
Is provided.

The photo-oxidative decomposition apparatus (D) is characterized in that the catalyst is not a thin film, but rather AgCl particles 152.
Is different from the photo-oxidative decomposition device of The reaction tank 150 has a sample water inlet 122 at the lower end and an outlet 124 at the upper end. A low-pressure mercury lamp 154 is installed at the center of the reaction tank,
AgCl particles are filled between the low-pressure mercury lamp 154 and the reaction tank 150. An air inlet 156 is provided at the center of the bottom of the reaction tank 150, and the reaction tank 150 is irradiated with ultraviolet light.
Air can be supplied to the inside of the cylinder.
The AgCl particles 152 are obtained by coating Ag on the surface of a sphere such as glass or alumina to change it to AgCl, or by coating an AgCl thin film. In the figure (D), the light from the low-pressure mercury lamp 154 is the catalyst A
Air is supplied to stir the sample water because it is obstructed by the gCl particles 152.

In each of the various photo-oxidative decomposition apparatuses shown in FIGS. 8 and 9, the decomposition efficiency of the nitrogen compound and the phosphorus compound is 1 unit.
In order to approach 00%, it is necessary to adjust the flow rate of the sample water, but it is not always necessary to increase the capacity of the reaction tank.

FIGS. 10 and 1 show an example in which a batch type photo-oxidative decomposition apparatus is used to construct an analyzer for nitrogen compounds and phosphorus compounds.
It is shown in FIG. FIG. 10 shows a reaction section, and FIG. 11 shows a measurement section. Reference numeral 202 denotes a photo-oxidative decomposition tank that oxidizes a nitrogen compound to nitrate ions and oxidizes a phosphorus compound to phosphate ions by ultraviolet irradiation, and has an AgCl thin film catalyst provided on an inner surface thereof. A supply pipe 20 for supplying sample water, air and cleaning water is provided at the bottom of the oxidation reaction vessel 204 of the photo-oxidative decomposition tank 202.
6 and an extraction tube 20 for extracting the sample water after the completion of the oxidation reaction.
8 is connected, and a discharge pipe 210 for discharging the overflowing sample water, washing water, and air is provided at the upper part of the oxidation reaction vessel 204.
And a calibration liquid supply pipe 216 for supplying a calibration liquid 212 via a valve 214. A discharge valve V5 is connected to the discharge pipe 210, and the sample water or the like is discharged through the valve V5.

In the oxidation reaction vessel 204, a short-wavelength ultraviolet ray, for example, a low-pressure mercury lamp 226 having a luminance of 185 nm is disposed as a light source for photo-oxidative decomposition. At the time of oxidative decomposition, the low-pressure mercury lamp 226 is turned on by the power supply 228 to irradiate the sample water in the oxidation reaction vessel 204 with ultraviolet rays.

The oxidation reaction vessel 204 includes an oxidation reaction vessel 20.
A heater 230 is provided to maintain the sample water in the sample 4 at a predetermined temperature of 50 to 100 ° C., and can be controlled to a predetermined temperature by a temperature controller via a temperature sensor 232. The sample water in the oxidation reaction vessel 204 is, for example, 90 ° C.
Temperature is controlled. The heater 230 may be embedded in the oxidation reaction container 4 together with the temperature sensor 232 as a cartridge heater. If necessary, the outside of the oxidation reaction vessel 204 may be covered with a heat insulating material.

The supply pipe 206 at the lower part of the oxidation reaction vessel 204
In order to supply the sample water via the
And a pinch valve V3. Valve 234 and V
The flow path between 3 is connected to a flow path for draining via a valve V4. In order to supply air for aerating the sample water during the oxidation reaction to the supply pipe 206, an air supply channel is provided with a filter 238, a pump 240, and a flow meter 242 with a needle.
And a valve V1.

The supply tube 206 further includes an oxidation reaction vessel 2
In order to supply clean water for cleaning the flow passages such as the fluid flow passage 04 and the measuring cell, the clean water supply passage is provided with a ball valve 244 and a solenoid valve V.
2, connected via a pure water device 246 and a check valve 248. A drain valve 250 is connected to the supply pipe 206, and the liquid remaining in the oxidation reaction vessel 204 and the supply pipe 206 can be discharged through the valve 250. An outlet pipe 208 provided at the bottom of the oxidation reaction vessel 204 is connected to the bottom of the absorption measurement cell 252 via a valve V6. The absorption measurement cell 252 can be drained from the bottom through a valve V8, and a discharge pipe having a valve V7 is connected to the top of the cell to discharge the overflowing sample water and washing water.

The absorption measurement cell 252 has a transmission window made of quartz glass for transmitting sample water and transmitting measurement light in a range from ultraviolet to near infrared. In order to irradiate the measurement light to the absorption measurement cell 252,
A xenon flash lamp 254 is provided. As a light source for measurement, a deuterium lamp on the short wavelength side and a tungsten lamp on the long wavelength side can be used. However, since the structure becomes complicated when there are two types of light sources, a xenon lamp that can cover the wavelength range necessary for measurement is preferable.
A xenon flash lamp is advantageous because a xenon lamp that is continuously lit has a high temperature and has a short life. Xenon flash lamp 254 generates less heat,
Long service life. Reference numeral 256 denotes a power supply for the light source. In the absorption measurement cell 252, the coloring agents 218 and 220 are filled with the peristaltic pump 2.
A coloring agent supply pipe 224 that supplies the coloring agent via the tube 22 is connected. The coloring agents 218 and 220 react with phosphate ions to form a color. The coloring agent 218 is an ammonium molybdate solution, and the coloring agent 220 is an L-ascorbic acid solution.

The absorption measurement cell 252 has a quartz window through which ultraviolet light can pass, which is arranged on the measurement optical path. The optical path length of the absorption measurement cell 252 is 10 mm. A half mirror 262 for splitting the transmitted light is installed on the transmitted light optical path of the absorption measurement cell 252, and a quartz condenser lens 258 is arranged on the optical path between the absorption measurement cell 252 and the half mirror 262. Light transmitted through the measurement cell 252 is focused on the half mirror 262. On the optical path between the condenser lens 258 and the half mirror 262, a calibration filter 262 is arranged.

The reflected light from the half mirror 262 is 80
The half mirror 262 has a transmission optical path for measuring a nitrogen compound, and a reflection optical path for measuring a phosphorus compound. The light having a wavelength characteristic of 0 nm or more and the transmitted light having a wavelength of 240 nm or less is used. . A silicon photodiode 266 is disposed as a nitrogen-side photodetector on the transmission optical path of the half mirror 262, and a transmission wavelength of 220 is provided on the optical path between the half mirror 262 and the photodiode 266.
nm optical filter 264 is disposed. On the other hand, a silicon photodiode 270 is arranged as a phosphor-side photodetector on the reflection optical path of the half mirror, and an optical filter 268 having a transmission wavelength of 880 nm is arranged on an optical path between the half mirror 262 and the photodiode 270. I have. The half width of the optical filters 264 and 268 is 10 to 30.
nm. Photodetector silicon photodiode 26
No. 6,270 uses a material having a wide range of sensitivity in the ultraviolet to near infrared region.

In order to amplify the detection outputs of the photodiodes 266 and 270, the preamplifiers 272 and 2
The detection output amplified by the preamplifiers 272 and 274 is input to the arithmetic unit 278 via the preprocessing circuit 276. The pre-processing unit 276 performs differential amplification and logarithmic amplification, and the calculation unit 278 calculates the concentrations of the nitrogen compound and the phosphorus compound, and displays them on the display unit 280. Reference numeral 284 denotes a power supply for the operation unit. The measured value can also be taken out as an analog output, for example, DC 0 to 1 V or DC 4 to 20 m
It can be output as the value of A. The control unit 282 performs temperature control during measurement and sequence control of each electromagnetic valve (pinch valve, electromagnetic valve), peristaltic pump, air pump, and the like.

FIG. 12 shows an example of a nitrogen compound and phosphorus compound analyzer using a flow type photo-oxidative decomposition apparatus. In the case of the flow type, there is a difference in the flow path configuration from the case of the batch type shown in FIGS. (A) shows the photo-oxidative decomposition device 3
The sample water from 00 is continuously flowing to the measurement cell 302, and the pump 212 does not operate when measuring nitrogen,
When the coloring agents 218 and 220 are not supplied, the absorption spectrometer 3
In step 04, the absorbance of nitrate ions is measured. On the other hand, when measuring phosphorus, the pump 212 is operated and the reaction tank 3 is measured.
A coloring agent is supplied to the flow path from 00 to the measurement cell 302,
The absorbance of the coloring solution is measured by the absorptiometer 304. The operation of the pump 212 and the switching of the measurement wavelength of the absorption photometer 304 are controlled by the sequence control unit 306.

In (B), the sample water from the photo-oxidative decomposition tank 300 is divided into two flow paths, one of which is
Directly led to 2N, the absorbance of nitrate ions is measured by the absorptiometer 304N. The other flow path has a pump 212
218 and 220 are constantly supplied from the measurement cell 3
The absorbance of the sample water introduced into 02P by the coloring agent is measured by the absorptiometer 304P. In (B), the measurement of nitrogen and the measurement of phosphorus can be performed simultaneously in parallel.

FIG. 13 shows the reaction section of FIG. 12 (A) in detail. The sample water is sent by the pump 310 and adjusted to a predetermined flow rate in the adjusting tank 312. The sample water from the adjustment tank 312 is guided to the flow type photo-oxidative decomposition tank 300. The reaction tank 300 is the reaction tank illustrated in FIG. 8 and FIG. The sample water flow path from the reaction tank 300 is connected to the manifold 322. In order to supply clean water for cleaning the measuring cell 302, the clean water supply passage is connected to the ball valve 31.
4, via a solenoid valve 316, a pure water device 318, and a check valve 320, the manifold 322 joins the flow path of the sample water.
The color formers 218, 220 are supplied via a pump 212,
It merges with the manifold 322 via the valve 324. The flow path from the manifold 322 is led to the measuring section shown in FIG.

FIG. 14 shows the details of the pre-processing section 276 and the calculating section 278 in the measuring section of FIG. The detection signal of the photodiode 266 on the nitrogen side is
2, a logarithmic amplifier 284 is connected to the output side of the preamplifier 272 to convert the amplified output to a logarithmic value. The output of logarithmic amplifier 284 is V / I converter 29
At step 6, it is converted to a current value and taken out as an output. On the phosphorus side, logarithmic amplifiers 286 and 284 are connected in parallel to the output side of the preamplifier 274 to convert the detection output amplified by the preamplifier 274 into a logarithmic value. The output of the logarithmic amplifier 286 is also converted to a current value by the V / I converter 400 and the output can be taken out. Since the relationship between the concentration of the nitrogen compound and the phosphorus compound and the absorbance obey the Lambert-Beer law, the signals of the photodiodes 266 and 270 are logarithmically converted so that the output signal is proportional to the concentration.

Reference numeral 290 denotes a nitrogen side differential amplifier which can amplify the difference between the logarithmic values converted by the logarithmic amplifiers 284 and 286 and take out the output from the V / I converter 298 as a nitrogen side measured value. The logarithmic conversion value of the logarithmic amplifier 286 is also held in the hold circuit 292, and the phosphorus side differential amplifier 294 receives the phosphorus side measurement value from the logarithmic amplifier 288,
The output of the logarithmic amplifier 286 at the time of measurement on the nitrogen side held in the hold circuit 292 is input to amplify the difference between the two, and V / I
The converter 402 outputs the measured value on the phosphorus side.

In the case of measuring the nitrogen compound concentration, the light transmitted through the half mirror 262 becomes the sample light, and the reflected light becomes the comparison light.
The difference between the simultaneous detection signals of the two photodiodes 266 and 270 is obtained by the differential amplifier 290 and output from the V / I converter 298 as a nitrogen compound concentration measurement value.

In the case of measuring the phosphorus compound concentration, a detection signal from the photodiode 270 at the time of measuring the nitrogen compound concentration is held in the hold circuit 292 as comparison light, and the measurement liquid (when a coloring agent is added to the sample water) at the time of measuring the phosphorus compound. The reflected light from the half mirror 262 due to the addition of the sample becomes the sample light, and the difference between the signal from the logarithmic amplifier 288 and the signal held in the hold circuit 292 is amplified by the differential amplifier 294, and the phosphorus compound concentration measurement value is obtained. Is output from the V / I converter 402.

The following is an example in which ultraviolet light is irradiated in the presence of a photo-oxidation catalyst according to the present invention, and nitrogen compounds and phosphorus compounds are measured by flowing air at about 10 ml / min. Table 1 shows an example in which a standard sample was measured. The standard sample is a sample prepared by dissolving a reagent in pure water.

[0051]

[Table 1]

Table 2 shows an example of measurement of a wastewater sample prepared by diluting factory wastewater with pure water, and shows a comparison between a measured value according to the official method and a measured value according to the present invention.

[0053]

[Table 2]

FIG. 15 shows an embodiment of the analyzer of the present invention in which the sample water is caused to flow by utilizing the height difference of the flow path.
In (A), the adjustment tank 312 is arranged at the highest position,
The flow-type photo-oxidation decomposition tank 300 to which the sample water is supplied from the adjustment tank 312 is disposed at a lower position than the flow-type photo-oxidation decomposition tank 300.
The measurement cell 252 to which the sample water subjected to the photo-oxidation treatment at 00 is supplied is arranged at a position lower than the reaction tank 300.

The sample water is sent to the adjusting tank 312 by the pump 310 and adjusted to a predetermined flow rate in the adjusting tank 312. The sample water from the adjusting tank 312 is guided to the photo-oxidative decomposition tank 300 by a head, and the sample water photo-oxidized and decomposed in the photo-oxidative decomposition tank 300 also flows to the measurement cell 252 by the head, and is discharged from the measurement cell 252 to the drain. Is done.

In (B), a water supply flow path is connected via a switching valve 330 to a flow path from the regulating tank 312 to the photo-oxidative decomposition tank 300, and the measuring cell 25 is connected to the photo-oxidative decomposition tank 300.
2 is connected to a standard liquid supply channel via a switching valve 332. The switching valves 330 and 332 are set in the sample water flow path when performing measurement while flowing the sample water,
Switching valve 3 when supplying clean water to measure the flow path
The switching valve 332 is switched to the side of the standard liquid supply flow path when the reference numeral 30 is switched to the water supply path and the standard liquid is measured. Also in this case, the sample water flows from the adjustment tank 312 to the downstream side due to a head.

In the analysis method of the present invention, the reaction product is not necessarily 10
It does not mean that it must be used at 0% conversion. For example, the conventional method using oxidation with an oxidizing agent and a spectrophotometric method and the method of the present invention having a conversion of 1
By preliminarily measuring a certain correlation with the analysis value in a state of less than 00%, it is possible to use even a state in which the conversion is less than 100%.

[0058]

According to the present invention, the sample water is heated to 50 to 100 ° C., and the sample water is irradiated with ultraviolet rays in the presence of a photo-oxidation catalyst to cause an oxidation reaction. Are converted to nitrate and phosphate ions, respectively, and then the nitrate and phosphate ions are respectively analyzed, so that nitrogen compounds and phosphorus compounds can be measured under the same conditions, and one analyzer Can analyze both the nitrogen compound and the phosphorus compound.

Since the photo-oxidation catalyst is used, the oxidation rate is increased, and it can be expected as a total nitrogen analyzer or a total phosphorus analyzer. In addition, elemental analysis of nitrogen and phosphorus is also possible, and can be expected as an elemental analyzer for a laboratory. Since the method uses physical means of irradiating the sample water with ultraviolet rays in the presence of the photo-oxidation catalyst, consumables are extremely small, and maintenance work is facilitated. Oxidation efficiency is increased by heating the sample water and supplying a gas containing oxygen or ozone. Thus, the use of the method of the present invention makes it possible to monitor nitrogen compounds and phosphorus compounds at low cost. Also, the configuration is simple.

[Brief description of the drawings]

FIG. 1 is a flowchart of an embodiment showing an analysis method of the present invention.

FIG. 2 is a block diagram schematically showing an example of an apparatus for realizing the analysis method of the present invention.

FIG. 3 is a sectional view showing a photo-oxidative decomposition reaction apparatus according to one embodiment.

FIG. 4 is a schematic view showing a method for producing a photo-oxidation catalyst used in the example.

FIG. 5 is a diagram showing the photo-oxidative decomposition rate when a photo-oxidation catalyst is used and when it is not used.

FIGS. 6A and 6B are diagrams illustrating an example of a batch-type photo-oxidative decomposition apparatus according to an embodiment, wherein FIG. 6A is a top view and FIG.

FIG. 7 is a diagram of measured data showing the effect of oxygen on the photooxidative decomposition reaction of a nitrogen compound.

FIGS. 8A and 8B are cross-sectional views each showing an example of a flow type photo-oxidative decomposition apparatus.

FIGS. 9C and 9D are cross-sectional views each showing an example of a flow type photo-oxidative decomposition apparatus.

FIG. 10 is a configuration diagram showing a reaction unit in one embodiment of the analyzer.

FIG. 11 is a configuration diagram showing a measurement unit in the embodiment of the analyzer.

FIGS. 12A and 12B are flow charts schematically showing an analyzer.

FIG. 13 is a flow chart showing a reaction section in the flow-type analyzer.

FIG. 14 is a block diagram illustrating an optical system and a signal processing system in the measurement unit in FIG. 10;

FIGS. 15A and 15B are flow charts showing an example in which a sample water is made to flow using a height difference in a flow type analyzer. It is a figure which shows the absorption spectrum of a nitrate ion and a phosphate ion (coloring agent addition).

[Explanation of symbols]

2,202,300 Photo-oxidative decomposition tank 8 Measurement tank 12,14 Measuring instrument 10 Spectrophotometer 22,142,152,226 Low-pressure mercury lamp 24 Air inlet 26,122, Sample water inlet 28 Sample outlet 32 Heater 34 Temperature sensor 37 Temperature Conditioner 40, 120, 130, 140, 150 Reaction tank 110 AgCl catalyst 224 Chromogen supply tube 252, 302, 302N, 302P Absorption measurement cell 276 Preprocessing unit 278 Operation unit

Claims (5)

(57) [Claims] 1. An oxidation method having a sample water inlet / outlet, a photo-oxidation catalyst in a tank, and simultaneously oxidizing a nitrogen compound and a phosphorus compound in the sample water to produce nitrate ions from the nitrogen compound and phosphate ions from the phosphorus compound. A reaction tank, an ultraviolet light source for irradiating the oxidation reaction tank with ultraviolet light, a heating means for heating the sample water in the oxidation reaction tank to 50 to 100 ° C., and a flow path for supplying and taking out the sample water to the oxidation reaction tank A photo-oxidative decomposition device comprising: 2. The photo-oxidation apparatus according to claim 1, wherein the flow path is a flow path for supplying the sample water to the oxidation reaction tank discontinuously and taking the sample water discontinuously, and the photo-oxidation decomposition apparatus is a batch type. Disassembly device. 3. The photo-oxidation apparatus according to claim 1, wherein the flow path is a flow path for continuously supplying and continuously taking out sample water to the oxidation reaction tank, and the photo-oxidative decomposition apparatus is a flow type. Disassembly device. 4. An analysis method comprising the following steps (A) to (C) for analyzing nitrogen compounds and phosphorus compounds in water. (A) an oxidation step of heating the sample water to 50 to 100 ° C. using the photo-oxidative decomposition apparatus according to claim 1 and irradiating the sample water with ultraviolet rays in the presence of a photo-oxidation catalyst; (B) Measuring the nitrate ions of the oxidized sample water by a spectrophotometric method; (C) adding a color former that selectively reacts with phosphate ions to the oxidized sample water, and measuring the color developing solution by the spectrophotometric method Process. 5. The sample water is heated to 50 to 100 ° C. by using the photo-oxidative decomposition apparatus according to claim 1, and the sample water is irradiated with ultraviolet rays in the presence of a photo-oxidation catalyst. A photo-oxidation decomposition tank for simultaneously oxidizing the nitrogen compound and the phosphorus compound to generate nitrate ions from the nitrogen compound and phosphate ions from the phosphorus compound; and
A quartz glass absorption measurement cell to which the sample water from the oxidation reaction tank is supplied; and a coloring solution addition flow path for adding a coloring solution that selectively reacts with phosphate ions to the oxidation reaction tank or the absorption measurement cell. A light source unit that irradiates ultraviolet light and near-infrared light as measurement light to the absorption measurement cell; and a demultiplexing unit that is on a measurement light transmission optical path of the absorption measurement cell and splits the transmitted light into two optical paths. A first optical system that selects an absorption wavelength specific to nitrate ions on one of the demultiplexed optical paths and detects the light of that wavelength as a sample light of nitrate ions; A second optical system that selects an absorption wavelength specific to the color developing solution that is on the road and has reacted with the phosphate ions, and detects light of the wavelength as sample light of the phosphate ions; and the first and second optical systems. Nitrogen compound concentration and recovery based on system detection signals Analyzer is characterized in that an arithmetic processing unit for calculating the compound concentration.