JP2013246053A - Measuring device and method for total organic carbon concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring device and a measuring method for a total organic carbon concentration capable of simply measuring an amount of carbon dioxide generated from oxidation of an organic matter with a high degree of accuracy.SOLUTION: A measuring device for a total carbon concentration comprises: an oxidation decomposition section which oxidizes and decomposes an organic matter contained in a liquid sample to generate carbon dioxide by irradiating the sample liquid with ultraviolet light and extricates the carbon dioxide from the sample liquid; a carbon dioxide absorption section which absorbs the extricated carbon dioxide; and a measurement section which measures an amount of the absorbed carbon dioxide. The oxidation decomposition section has: a reaction container where the organic matter contained in the sample liquid is oxidized and decomposed; an ultraviolet light source which is arranged to irradiate the reaction container; and gas transfer means which is connected to the reaction container and bubbles the sample liquid inside the reaction container. The carbon dioxide absorption section has an absorption container to store liquid which has alkalinity to absorb the carbon dioxide transferred from the reaction container and contains metallic ions to form insoluble carbonate. The measurement section has a turbidity meter which measures turbidity of the liquid in the absorption container.

Description

  The present invention relates to an apparatus and a measurement method for measuring the concentration of total organic carbon contained in a sample solution.

  Total organic carbon (hereinafter referred to as TOC) is one of water quality indexes represented by the carbon content of organic substances contained in water. The concentration of TOC is measured for water samples such as tap water, industrial water, industrial wastewater, sewage and environmental water that require water quality management, and the water quality is evaluated based on the measured value.

  The TOC concentration is measured by oxidizing and decomposing an organic substance contained in a sample into carbon dioxide, and measuring the amount of carbon dioxide produced. As a process of oxidatively decomposing organic matter, there are a combustion oxidation method in which an organic matter contained in a measurement sample is burned at a high temperature using a catalyst such as platinum, and a wet oxidation method in which an organic matter is oxidatively decomposed using ultraviolet rays. Generally, the combustion oxidation method is used when measuring samples with high TOC concentrations such as sewage and industrial wastewater, and the wet oxidation method is used when measuring samples with low TOC concentrations such as tap water, tap water, and pure water. Is used.

  As a step of measuring the amount of carbon dioxide produced, carbon dioxide produced by either combustion oxidation method or wet oxidation method is a highly sensitive non-dispersive infrared gas analyzer (hereinafter referred to as “NDIR”). ) Is generally employed.

  Patent Document 1 describes a method for separating carbon dioxide generated by a wet oxidation method through a gas-permeable membrane and quantifying it with a conductivity sensor in order to reduce the size of a TOC concentration measuring device. Yes.

JP 2006-90732 A

  In measuring a sample containing a large amount of organic matter such as sewage and industrial wastewater, a measurement apparatus that mainly combines the above-described combustion oxidation method and a non-dispersive infrared gas analyzer (NDIR) is used. However, in this measuring apparatus, since the temperature of the combustion furnace that performs the oxidation reaction is set to 900 ° C. or more, the power consumption is large, and it is necessary to replace the oxidation catalyst such as expensive platinum every time it deteriorates. There was a problem of high cost. In addition, since the combustion furnace is large and a high-sensitivity NDIR, which is a precision optical instrument, is incorporated, there is a problem that the apparatus becomes large and the price of the apparatus itself is high, making it difficult to introduce the apparatus. It was.

  Moreover, in the measuring apparatus which combined the wet oxidation method of patent document 1, and the measurement of the amount of carbon dioxide by electrical conductivity, it respond | corresponds about the sample containing high concentration organic substances, such as a sewage and an industrial wastewater. It was not possible, and it remained in the apparatus for evaluating the sample containing low concentration organic substances, such as tap water.

  Furthermore, when the wet oxidation method is adopted, an oxidizing agent such as peroxodisulfate or perchlorate with a high concentration is added to the sample to promote the oxidation reaction. If not used, the oxidative decomposition efficiency for samples containing high concentrations of organic substances such as sewage and industrial wastewater was low and could not be handled.

  In this way, an efficient wet oxidation method for organic matter in a sample and simple carbon dioxide produced by an oxidation reaction that can meet the need to easily analyze the TOC concentration of a sample containing a large amount of organic matter such as sewage and industrial wastewater. No simple measurement method and a small and inexpensive TOC concentration measurement device combining them.

  The present invention has been devised in view of the above points, and its purpose is to easily and accurately measure the amount of carbon dioxide produced by oxidation of organic matter without using NDIR or conductivity measuring equipment. An object of the present invention is to provide a measuring apparatus and a measuring method that can be used.

  Another object of the present invention is to provide a high-concentration organic substance contained in a sample solution such as sewage or industrial wastewater without using an oxidizing agent such as peroxodisulfate or perchlorate in the wet oxidation method. Is to provide a measuring apparatus and a measuring method capable of measuring the total organic carbon concentration with high accuracy.

  Another object of the present invention is to provide an inexpensive TOC concentration measuring device by adopting the above-described new measuring method, whereby the entire device is small in size.

  In order to solve the above problems, the total organic carbon measuring apparatus of the present invention irradiates a sample liquid with ultraviolet rays, oxidatively decomposes organic substances contained in the sample liquid to generate carbon dioxide, and releases carbon dioxide from the sample liquid. An oxidative decomposition part, a carbon dioxide absorption part that absorbs the released carbon dioxide, and a measurement part that measures the amount of absorbed carbon dioxide, and the oxidative decomposition part oxidizes organic matter contained in the sample liquid A reaction vessel for performing decomposition, an ultraviolet light source disposed so as to irradiate the reaction vessel, and a gas transfer means connected to the reaction vessel for bubbling the sample liquid in the reaction vessel. An absorption container that contains a liquid containing metal ions that form an insoluble alkali carbonate that absorbs carbon dioxide transferred from the container, and the measurement unit is a turbidity that measures the turbidity of the liquid in the absorption container. Meter It is provided.

  The organic matter in the sample solution is oxidized and decomposed into carbon dioxide by the ultraviolet rays irradiated from the ultraviolet light source in the reaction vessel of the oxidation decomposition portion. At this time, by bubbling the sample liquid in the reaction vessel with the gas transfer means, the amount of received UV light of the sample liquid increases, the efficiency of oxidative decomposition increases, and the generated carbon dioxide is released as carbon dioxide gas. The The released carbon dioxide gas is transferred from the reaction vessel to the carbon dioxide absorption part, and is absorbed by the alkaline solution in the absorption container of the carbon dioxide absorption part to become carbonate ions. Further, the absorbed carbon dioxide, that is, carbonate ions, reacts with a cation such as a metal ion that forms a hardly soluble carbonate to form a hardly soluble carbonate to form fine particles. The amount of the fine particles of the hardly soluble carbonate is quantified by a turbidimeter of the measuring unit, and the concentration of organic matter contained in the sample solution, that is, the total organic carbon concentration is measured.

  In addition, the ultraviolet light source of the total organic carbon concentration measuring apparatus of the present invention has a plurality of irradiation units, and irradiates the reaction container from a plurality of directions and is close to the sample liquid in the reaction container. It is also preferred that they are arranged. By irradiating the sample liquid with ultraviolet rays in close proximity from a plurality of directions, the amount of received ultraviolet light is increased and the sample liquid is suitably warmed, and the reactivity of oxidative decomposition of organic substances in the sample liquid is increased. Therefore, carbon dioxide can be generated by reliably oxidizing and decomposing organic substances in the sample solution.

  The gas transfer means of the total organic carbon concentration measuring device of the present invention is configured to increase the liquid level of the sample liquid by 15% to 70% by bubbling the sample liquid in the reaction vessel. It is also preferable. The sample liquid in the reaction vessel is agitated with air bubbles, and the titanium oxide particles used as the sample liquid and catalyst are mixed and dispersed uniformly, and the ultraviolet light receiving area, that is, the amount of ultraviolet light received increases. Can be reliably oxidatively decomposed to generate carbon dioxide.

  Further, the gas transfer means is preferably configured to circulate and transfer the gas between the reaction vessel and the absorption vessel. By circulating for a certain period of time, the carbon dioxide generated and released in the reaction vessel can be surely absorbed by the alkaline liquid in the absorption vessel, so that the total organic carbon concentration can be measured with high accuracy. .

  Furthermore, it is also preferable that the metal ion of the measuring apparatus for the total organic carbon concentration of the present invention is an alkaline earth metal ion. Thereby, the substance which suitably insolubilizes the carbon dioxide absorbed by the absorption liquid as a hardly soluble carbonate is selected. Carbon dioxide absorbed in the liquid in the absorption container forms fine particles of alkaline earth metal carbonate.

  Furthermore, it is also preferable that the alkaline earth metal ion used in the measuring apparatus for the total organic carbon concentration of the present invention is a strontium ion. Thereby, the substance which insolubilizes carbon dioxide more suitably is selected. Carbon dioxide absorbed in the absorbing solution forms fine particles such as strontium carbonate.

  The method for measuring total organic carbon according to the present invention includes a step of irradiating a sample solution with ultraviolet rays to oxidatively decompose organic substances contained in the sample solution to generate carbon dioxide, and bubbling the sample solution under acidic conditions. , A step of releasing carbon dioxide from the sample solution, a step of absorbing the released carbon dioxide in an absorbing solution exhibiting alkalinity, carbon dioxide absorbed in the absorbing solution, and metal ions that form a hardly soluble carbonate. And a step of producing a poorly soluble carbonate in the absorbent and a step of measuring the turbidity of the absorbent containing the poorly soluble carbonate.

  Organic matter contained in the sample solution is oxidized and decomposed by ultraviolet rays, and carbon dioxide is generated in the sample solution. By bubbling this sample solution under acidic conditions, almost all of the carbon dioxide contained in the sample solution is released from the sample solution as carbon dioxide gas. The released carbon dioxide gas is absorbed by the alkaline absorbent and becomes carbonate ions. Furthermore, the carbonate ions in the absorption liquid react with cations such as metal ions that form a poorly soluble carbonate to form a poorly soluble carbonate and form fine particles in the absorbent. By measuring the turbidity of this absorbing solution, the concentration of organic substances contained in the sample solution, that is, the total organic carbon concentration is measured.

  The step of generating carbon dioxide in the total organic carbon measurement method of the present invention preferably includes irradiating the sample liquid with ultraviolet rays from a plurality of directions and heating the liquid temperature of the sample liquid. By irradiating the sample solution with ultraviolet rays from a plurality of directions and heating the sample solution, the oxidative decomposition efficiency of the organic matter in the sample solution is enhanced. Therefore, carbon dioxide can be generated by reliably oxidizing and decomposing organic substances in the sample solution.

  Moreover, it is also preferable that the step of generating carbon dioxide in the method for measuring total organic carbon of the present invention includes bubbling the sample liquid so as to increase the height of the liquid surface of the sample liquid by 15% to 70%. . The sample liquid is agitated with bubbles to uniformly mix and disperse the sample water and titanium oxide particles used as a catalyst, and the amount of received UV light per sample liquid volume also increases. Therefore, carbon dioxide can be generated by reliably oxidizing and decomposing organic substances in the sample solution.

  And it is also preferable that the poorly soluble carbonate of the method for measuring total organic carbon of the present invention is an alkaline earth metal carbonate. Thereby, the substance which suitably insolubilizes the carbon dioxide absorbed by the absorption liquid as a hardly soluble carbonate is selected. The carbon dioxide absorbed in the absorbing liquid forms alkaline earth metal carbonate microparticles.

  Moreover, it is also preferable that the alkaline earth metal carbonate in the method for measuring total organic carbon of the present invention is strontium carbonate. Thereby, the substance which insolubilizes carbon dioxide more suitably is selected. The carbon dioxide absorbed in the absorbing solution forms strontium carbonate microparticles.

ADVANTAGE OF THE INVENTION According to this invention, the measuring apparatus and measuring method of the total organic carbon density | concentration which have the following outstanding effects can be provided.
(1) Carbon dioxide generated by the oxidation reaction of organic matter can be quantified easily and with high accuracy without using expensive equipment such as NDIR or conductivity measuring instrument.
(2) Without using a catalyst such as platinum and a combustion furnace, or an oxidizing agent, it is possible to efficiently oxidize and decompose high-concentration organic substances contained in the sample solution and measure the total organic carbon concentration with high accuracy. it can.
(3) The whole apparatus is small, the apparatus itself is very inexpensive, and the measuring apparatus for the total organic carbon concentration can be obtained at a low cost for measurement.

It is the schematic of the measuring apparatus of the total organic carbon concentration which concerns on one Embodiment of this invention. It is a flowchart which shows schematically the measuring method of all the organic carbon which concerns on embodiment of FIG. It is a graph which shows the example of the relationship between the strontium chloride density | concentration and the turbidity by the fine particle of strontium carbonate. It is a graph which shows the example of the relationship between turbidity and each carbon concentration.

  Hereinafter, a total organic carbon concentration measuring apparatus according to an embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, the total organic carbon concentration measuring apparatus 1 according to the present embodiment irradiates a sample liquid W with ultraviolet rays, oxidatively decomposes organic substances in the sample liquid W, and generates carbon dioxide as carbon dioxide. An oxidative decomposition unit 2 is provided which is released as carbon gas. The oxidative decomposition section 2 is a reaction vessel 20 in which an oxidative decomposition reaction of the sample liquid W introduced therein is performed, and the vicinity of the reaction vessel 20 so as to irradiate the sample liquid W introduced into the reaction vessel 20 with ultraviolet rays. And a gas transfer means connected to the reaction vessel 20 for bubbling the sample liquid W in the reaction vessel 20, that is, the air pump 5 and each flow path. Further, the measuring device 1 includes a carbon dioxide absorbing section 3 that absorbs carbon dioxide generated and released by the oxidative decomposition section 2, and a measuring section 4 that measures the amount of carbon dioxide absorbed by the carbon dioxide absorbing section 3. It has. The carbon dioxide absorption unit 3 includes an absorption container 30, which is connected to the upper part of the reaction container 20 via a gas flow path L _3, and the flow path L to the lower part of the reaction container 20. ₁ , the cock 22, the gas flow path L ₂ , the air pump 5 and the gas flow path L ₄ are connected. Thereby, the gas is transferred through the gas flow path L ₃ , the gas flow path L ₄ , the air pump 5, the gas flow path L ₂ , the cock 22 and the flow path L ₁ , and between the reaction container 20 and the absorption container 30. Is circulated from the upper part of the reaction vessel 20 toward the absorption vessel 30. Inside the absorption vessel 30, the reaction vessel 20 through the gas flow path L ₃ absorbs the transported carbon dioxide absorbing liquid 31 to be insoluble by forming a carbonate sparingly soluble is accommodated. The measuring unit 4 that measures the amount of carbon dioxide has a turbidimeter 40 that measures the turbidity of the absorbent 31 and a power source 41.

  The sample liquid W which is a measurement target of the measuring apparatus 1 is not particularly limited, but examples thereof include sewage and industrial wastewater containing TOC at a high concentration, as well as environmental water and clean water. It is done.

Next, the structure of the carbon dioxide absorption part 3 in this embodiment is demonstrated in detail. The carbon dioxide absorption part 3 is roughly comprised from the absorption container 30 and the absorption liquid 31 accommodated in it. The absorption container 30 includes a gas inflow portion 301 and a gas outflow portion 302, and an absorption liquid 31 is accommodated inside the absorption container 30. Absorption vessel 30 is connected via an upper and a gas flow path L ₃ of the reaction vessel 20 of the oxidative decomposition unit 2, the gas A ₂ which is transported through the gas flow path L ₃ is inlet to the absorption vessel 30 Inflow from 301. The position of the inflow portion 301 is disposed so as to be sufficiently below the liquid surface of the absorbing liquid 31. Further, the gas outflow portion 302 is disposed above the absorption container 30 so as to be above the liquid surface of the absorption liquid 31 so that the absorption liquid 31 does not flow out. In this embodiment, since the absorption container 30 is also used as a measurement cell (measurement container) of the turbidimeter 40 described later, its outer peripheral surface and bottom are formed of a material such as transparent glass or transparent resin. When not used as a measurement cell, it is not limited to this.

The absorbing liquid 31 is alkaline and contains a metal salt that forms a hardly soluble carbonate. Generated by the oxidative decomposition reaction of organic matter carried out in a reaction vessel 20, the released carbon dioxide gas is transported through the gas channel L _3, and flows into the absorption liquid 31 from the inlet portion 301 of the liquid storage container 30. Since the absorbing liquid 31 is alkaline, carbon dioxide in the gas A ₂ is absorbed by the absorbing liquid 31 and becomes carbonate ions. Since the absorbing liquid 31 contains metal ions that form a hardly soluble carbonate, the carbonate ions in the absorbing liquid 31 form a hardly soluble carbonate to generate fine particles.

  The absorbing liquid 31 only needs to exhibit alkalinity to such an extent that carbon dioxide that has flowed in can be sufficiently absorbed. Although it does not specifically limit in order to exhibit alkalinity, Sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water, calcium hydroxide, barium hydroxide, strontium hydroxide, etc. are used suitably. Moreover, the density | concentration of the substance which exhibits alkalinity shall be 1 mmol / L or more, and the carbon dioxide which generate | occur | produces from a high concentration organic substance can also be absorbed reliably by making it especially 10 mmol / L or more.

  As described above, the absorption liquid 31 in the present embodiment contains metal ions that form a hardly soluble carbonate. As the metal ion, any metal ion may be used as long as it forms a slightly soluble carbonate by forming a slightly soluble carbonate with carbonate ion. Specifically, Group II elements containing alkaline earth metals, metal ions such as cobalt, lead, zinc, nickel or manganese are preferably used. From the viewpoint of high safety and low environmental impact, More preferably, an alkali metal ion is used, and an alkaline earth metal ion such as calcium, barium, magnesium, or strontium is more preferably used. In particular, strontium ions having low carbonate solubility are preferred. In order to contain these metal ions in the absorption liquid 31, it is preferable to dissolve the chlorides, nitrates, sulfates, phosphates or hydroxides of the metal ions in the absorption liquid 31. Further, the concentration of metal ions contained in the absorbing liquid 31 is relatively high in order to sufficiently form fine particles of hardly soluble carbonate when the concentration of carbonate ions contained in the absorbing liquid is low. Metal ions are required. For example, when alkaline earth metal strontium is used, when the TOC concentration of the sample solution is about 5 mg-C / L, the concentration of the strontium salt is preferably about 50 mmol / L or more. When the TOC concentration is 15 mg-C / L or more, the concentration of the strontium salt is preferably about 25 mmol / L or more. In the present embodiment, a metal ion that forms a poorly soluble carbonate is included in a solution exhibiting alkalinity as an absorbing liquid, and a hardly soluble carbonate is formed simultaneously with absorption. It is good also as a structure which provides the means to add the metal ion which forms the above-mentioned hardly soluble carbonate after absorbing carbon dioxide, using the liquid which exhibits this.

  Next, the configuration of the measurement unit 4 in the present embodiment will be described in detail. The measuring unit 4 is schematically configured from a turbidimeter 40 and a power source 41, and the turbidimeter 40 is arranged so that the turbidity of the absorbent 31 can be measured. In the present embodiment, the absorption container 30 itself of the carbon dioxide absorption unit 3 is configured as a measurement cell of the turbidimeter 40, and the absorbing liquid is obtained by applying the light source of the turbidimeter 40 from the side surface of the absorption container 30. A turbidity of 31 is measured. As the turbidimeter 40, various methods such as a transmitted light measurement method, a scattered light measurement method, and a transmitted light / scattered light calculation method are used. Moreover, it is good also as a structure which puts a turbidity sensor directly in the absorption liquid 31 in the absorption container 30, and measures turbidity, or after transferring the absorption liquid 31 from the absorption container 30 to another container, turbidity. It is also possible to adopt a configuration that measures

Next, the structure of the oxidative decomposition part 2 of this embodiment is demonstrated in detail. The oxidative decomposition part 2 is roughly constituted by a reaction vessel 20, an ultraviolet light source 21, and an air pump 5 which is a gas transfer means in the present embodiment. Does this reaction vessel 20 is provided with an inlet 201 of the gas A ₁ for bubbling into or sample solution in the sample liquid W, which flows into the sample liquid W into the reaction vessel 20, the bubbling of the sample liquid whether flows the gas a ₁ for, is selected by the cock 22. Similarly, the reaction vessel 20 is provided with a gas outflow portion 202, and the reaction vessel 20 is connected to the absorption vessel 30 of the carbon dioxide measurement unit 3 through the outflow portion 202 and the gas flow path L _3. ing.

  The shape of the reaction container 20 is such that the ultraviolet light irradiated from the ultraviolet light source 21 reaches the depth of the reaction container 20, the ultraviolet light is irradiated to the entire width direction of the reaction container 20, and an appropriate amount of sample liquid can be put. Shape is desirable. Here, when the depth of the reaction vessel 20 (when the reaction vessel 20 is an elliptical cylindrical shape, the minor axis of the ellipse) is 8 mm, the ultraviolet ray of water in which 250 mg / L of titanium oxide is suspended is transmitted. When the rate was measured, the transmittance was about 10% and the light utilization rate was about 90%. From this, it has been found that even when the depth of the reaction vessel 20 is larger than 8 mm, the light utilization efficiency hardly increases. From this, the depth of the reaction vessel 20 is desirably 8 mm or less, and the titanium oxide concentration may be 500 mg / L or more. Therefore, the depth of the reaction vessel 20 is more desirably 5 mm or less.

  Moreover, since the ultraviolet light source 21 used in this embodiment has a tube diameter of about 15 mm to 25 mm in order to reduce the size of the entire apparatus, the width of the reaction vessel 20 (reaction vessel 20 If the ellipse has a cylindrical shape of 30 mm or more, the reaction vessel 20 has a portion that is difficult to receive ultraviolet irradiation from a plurality of directions or strong ultraviolet irradiation at close distances. . Furthermore, if the size of the reaction vessel 20 is too small, the amount of sample liquid to be measured decreases, resulting in a decrease in the amount of generated carbon dioxide, and there is a possibility that high accuracy cannot be obtained in measured values. If the size of the reaction vessel 20 is too large, the liquid level becomes low when the amount of the sample liquid is small, and only a part of the ultraviolet light source 21 is used effectively. It will take time. From this, the width of the reaction vessel 20 is desirably 5 mm to 30 mm, and the length of the reaction vessel is desirably about 100 mm to 400 mm.

In the present embodiment, the sample liquid W is injected into the reaction vessel 20 from the inflow section 201 through the sample liquid inlet 23 of the oxidative decomposition section 2 through the flow path L ₀ , the cock 22 and the flow path L ₁ . The ultraviolet light source 21 irradiates the sample liquid W in the reaction vessel 20 with ultraviolet light to cause an oxidative decomposition reaction, and the organic matter in the sample liquid W is oxidized to carbon dioxide. In order to promote this oxidative decomposition reaction, it is desirable to use titanium oxide as a photocatalyst, and anatase type or rutile type titanium oxide is particularly preferably used. The amount of titanium oxide added to the sample liquid W varies depending on the TOC concentration of the sample liquid W. However, when measuring a sample liquid containing a high concentration TOC such as sewage or industrial wastewater, the titanium oxide concentration is It is preferably 200 mg / L or more, and more preferably 500 mg / L or more.

  Furthermore, the pH can be adjusted when performing the oxidative decomposition reaction of the sample liquid W in the reaction vessel 20. At the time of oxidative decomposition reaction, if the pH of the sample liquid W is about 3 to 9, the organic matter in the sample liquid W is almost completely oxidatively decomposed. However, when the pH is 3 or lower or 10 or higher, the oxidative decomposition rate decreases. Therefore, the pH of the sample liquid W is preferably 3-9. Furthermore, it is more preferable to adjust the sample liquid W to about pH 3 to 7 in the acidic range from the viewpoint that carbon dioxide generated by oxidative decomposition is efficiently released from the sample liquid as carbon dioxide gas under acidic conditions.

The sample liquid W put in the reaction vessel 20 flows from the inflow portion 201 through the gas transfer means, that is, the gas flow path L ₄ , the air pump 5, the gas flow path L ₂ , the cock 22 and the flow path L ₁ . the gas _{A 1,} is bubbled. Bubbling is performed by adjusting the aeration line speed with the air pump 5 and is preferably bubbled so as to increase the height of the liquid surface of the sample liquid W by 10% or more, and so as to increase by 15% to 70%. More preferably. In the present invention, “increasing the liquid level” means that the sample liquid in the reaction vessel 20 is driven by the bubbling bubbles based on the height of the sample liquid W in the reaction vessel 20 before bubbling. The height of the apparent liquid level which W increased from below and increased. By sending air from the inflow portion 201 of the reaction vessel 20 and bubbling the sample liquid W, (1) the amount of received ultraviolet light per sample liquid volume increases, and the oxidative decomposition efficiency increases. Titanium oxide used as a photocatalyst is prevented from precipitating in the sample solution, and the suspended / dispersed state is maintained, so that the oxidative decomposition efficiency increases. (3) Carbon dioxide generated by oxidative decomposition is carbon dioxide gas As an effect of being released from the sample liquid.

As described above, in the present embodiment, the gas is configured to circulate between the reaction vessel 20 of the oxidative decomposition unit 2 and the absorption vessel 30 of the carbon dioxide absorption unit 3 by the gas transfer means. That is, the gas flowing into the inflow portion 201 through the gas flow path L ₄ , the air pump 5, the gas flow path L ₂ , the cock 22 and the flow path L ₁ is a gas A ₂ containing carbon dioxide generated in the reaction vessel 20. And flows out from the outflow portion 202 of the reaction vessel 20. The gas A ₂ containing carbon dioxide flows into the absorption container 30 from the inflow portion 301 via the gas flow path L ₃ and passes through the absorption liquid 31, so that the carbon dioxide contained in the gas A ₂ is absorbed. Removed. The gas A ₁ from which carbon dioxide has been removed flows out from the outflow portion 302 of the absorption container 30 and returns to the air pump 5 through the gas flow path L ₄ . Therefore, by circulating the gas by the gas transfer means for a certain period of time, the carbon dioxide generated in the reaction vessel 20 can be surely absorbed in the absorption liquid 302 of the absorption vessel 30, and the total organic carbon concentration can be accurately determined. Can be measured. Further, since the gas A ₂ containing carbon dioxide generated in the reaction container 20 circulates so as to be sucked into the absorption container 30, the carbon dioxide released in the reaction container 20 can be reliably sucked into the absorption container 30. The total organic carbon concentration can be measured with high accuracy.

Further, before the ultraviolet light source 21 is turned on, the gas circulating in the measuring device 1 is transferred to the inflow portion 201 of the reaction vessel 20 via the gas flow path L ₂ , the cock 22 and the flow path L ₁ by the gas transfer means. Inflow is caused to flow out from the outflow portion 202 of the reaction vessel 20, and is caused to flow in from the inflow portion 301 of the absorption container 30 through the gas flow path L ₃ , and the absorbent 31 is passed through. Thereby, before the oxidative decomposition of the organic substance, the carbon dioxide contained in the gas can be reliably absorbed in advance and removed. Therefore, in the gas circulation after the oxidative decomposition is started by turning on the ultraviolet light source, carbon dioxide other than that generated by the oxidative decomposition is not mixed in the measuring apparatus 1, and the total organic carbon concentration is measured with high accuracy. be able to. Moreover, since carbon dioxide in the gas can be reliably removed in advance as described above, indoor air can be suitably used as the gas used in the measuring apparatus 1. Therefore, it is not necessary to separately prepare carbon dioxide-free air, nitrogen gas, or the like, and measurement can be performed easily and without cost. In addition, by devising the shape of the absorption container 30, without circulating the gas, the gas not containing carbon dioxide is changed from the inflow part 201 to the outflow part 202 of the reaction container 20 and from the inflow part 301 to the outflow part 302 of the absorption container. after then air may be reliably absorbed carbon dioxide by a method that does not connect the gas passage L ₄ to the air pump 5.

While performing the circulation of carbon dioxide or a gas by oxidative decomposition and gas transfer means of the organic matter in the sample liquid W, the reaction vessel 20, the absorption vessel 30, the flow path L ₀ ~L ₁ and / or gas flow path L ₂ When carbon dioxide enters and exits to the outside through ~ L ₄ or the like, the amount of carbon dioxide generated by oxidative decomposition may not be accurately measured. Therefore, the reaction vessel 20 uses a material that easily transmits ultraviolet rays and does not easily transmit carbon dioxide, and the absorption vessel 30, the flow paths L _{0 to} L _{1, the} gas flow paths L _{2 to} L _{4, and the} like are also oxidized. It is necessary to use a material that does not easily transmit carbon. Although not particularly limited, for example, the reaction vessel 20 hardly absorbs ultraviolet rays, and has a carbon dioxide transmission coefficient (thickness of 1 mm, area of 1 cm 2, transmission cc per second when the carbon dioxide partial pressure is 1 cm of mercury). The thing made from a fluororesin below 2 * 10 < ^-9 > cc / mm * cm <2> * s * cmHg is used suitably. For the absorption container 30 or the flow paths L _{0 to} L _4, etc., a plastic material having a small carbon dioxide permeability coefficient (for example, 2 × 10 ⁻⁹ cc / mm · cm 2 · s · cm Hg or less) and a thickness of 0.5 mm or more. A material having low gas permeability such as metal or glass is preferably used.

  The ultraviolet light source 21 is disposed so as to irradiate ultraviolet rays in the vicinity of the reaction vessel 20, and is connected to a power source (not shown) via the socket 210. The ultraviolet light source 21 may be any light source capable of emitting ultraviolet light. Specifically, a long wavelength ultraviolet lamp, a medium wavelength ultraviolet lamp, a low wavelength ultraviolet lamp, a low pressure mercury lamp, an ultraviolet LED, or the like is used. In particular, from the viewpoint of increasing the oxidation efficiency of titanium oxide, which is a photocatalyst, a black light lamp that emits ultraviolet light having a wavelength of around 360 nm is preferably used. In addition, as the ultraviolet light source 21 of the present embodiment, a U-shaped black light lamp that is compact and has a relatively large amount of electric power of 20 W or more is used, but a plurality of straight tube type black light lamps are arranged in parallel. Those configured as described above are also preferably used. Thus, by using the ultraviolet light source 21 having a plurality of irradiation surfaces, the reaction vessel 20 can be irradiated with ultraviolet rays from a plurality of directions, so that the oxidative decomposition efficiency is improved. It is also possible to decompose organic substances in the sample solution in a short oxidative decomposition time.

  The reaction vessel 20 and the ultraviolet light source 21 are arranged close to each other in order to increase the oxidative decomposition efficiency. In the present embodiment, the reaction vessel 20 is disposed in close contact with the center of the two tubes of the U-shaped black light fluorescent lamp. By arranging the reaction vessel 20 in the center of the two tubes, ultraviolet rays are simultaneously irradiated from both directions at a short distance, and the amount of received ultraviolet light received by the sample solution W in the reaction vessel 20 is increased and the sample solution W is suitably used. Can be warmed. That is, it is preferable to arrange the reaction vessel 20 close to the ultraviolet light source 21 so that the sample solution W is heated, and the temperature of the sample solution W is set to 60 ° C. or higher, so that the oxidative decomposition efficiency is increased. More preferably, the reaction container 20 is closely attached to the ultraviolet light source 21, and the temperature of the sample liquid W is set to 60 ° C. or higher. Furthermore, a reflecting plate is disposed on the outer periphery of the ultraviolet light source 21 and the reaction vessel 20, the back side of the ultraviolet light source 21, etc., and the reaction vessel 20 is irradiated with the ultraviolet rays that have not been directly irradiated to the reaction vessel 20 by the reflecting plate. It can also be configured as follows.

  Next, a method for measuring the total organic carbon concentration and a method for using the total organic carbon concentration measuring apparatus according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 2, the method for measuring the concentration of total organic carbon according to the present embodiment prepares a sample liquid W, and prepares a sample liquid W in a pre-preparation step S0, which removes carbon dioxide contained in the apparatus. Step S1 for oxidatively decomposing an organic substance to generate carbon dioxide, Step S2 for releasing the generated carbon dioxide from the sample liquid W, Step S3 for absorbing the released carbon dioxide in the absorbing liquid 31, and Absorbing in the absorbing liquid 31 Step S4 for reacting the carbon dioxide thus formed with metal ions that form a poorly soluble carbonate to form a poorly soluble carbonate to insolubilize, Step S5 for measuring the turbidity of the absorbent 31, and measurement Step S6 for obtaining the TOC concentration from the turbidity value.

(Preparation process)
First, the preparation step S0 shown in FIG. 2 will be described. The sample liquid W is injected into the sample liquid inlet 23 using a syringe or the like. The sample liquid W flows into the reaction container 20 from the inlet 201 of the reaction container 20 through the flow path L ₀ , the cock 22 and the flow path L ₁ . Next, after preparing the absorption liquid 31 in the absorption container 30, the air pump 5 is operated and the air is circulated between the reaction container 20 and the absorption container 30. The air A ₁ driven by the air pump 5 through the outflow part 302 and the gas flow path L ₄ of the absorption container 30 is supplied to the inflow part 201 of the reaction container 20 through the gas flow path L ₂ , the cock 22 and the flow path L _1. The sample liquid W in the reaction vessel 20 is bubbled. Then, the outlet portion 202 of the reaction vessel 20 the air in the reaction vessel 20 to flow out, and flows into the absorption liquid 31 from the inflow portion 301 of the liquid storage container 30 via the flow path L _3. After circulating the air by the air pump 5 for a predetermined time, the air pump 5 is temporarily stopped, and the turbidity of the absorbent 31 is measured by the turbidimeter 40 to obtain a blank value.

By this operation, carbon dioxide existing in each of the flow paths L _{1 to} L ₄ , the reaction container 20 and the absorption container 30 can be absorbed by the absorption liquid 31 and removed. In addition, by adjusting the pH of the sample liquid W to about 3 to 7 in the acidic range in advance, the inorganic carbon contained in the sample liquid W is released as carbon dioxide gas and absorbed by the absorbing liquid 31. Therefore, the organic carbon concentration of the sample liquid W can be measured with higher accuracy.

(Oxidative decomposition process)
Next, step S1 related to the oxidative decomposition reaction will be described. A sufficient amount of titanium oxide is added to the reaction vessel 20 to adjust the pH value of the sample solution W to about 3 to 7 in the acidic range. The addition of titanium oxide to the sample solution W and the adjustment of pH may be performed in the preparatory step S0. Next, the ultraviolet light source 21 is turned on and the reaction container 20 is irradiated with ultraviolet rays. Since the ultraviolet light source 21 in the present embodiment is U-shaped and has a plurality of irradiation surfaces, the sample liquid W inside the reaction vessel 20 is irradiated with ultraviolet rays from a plurality of directions. By irradiating the sample liquid W with ultraviolet rays, the organic matter contained in the sample liquid W is oxidized and decomposed to generate carbon dioxide. At this time, since the ultraviolet light source 21 is disposed in close contact with the reaction vessel 20, the sample liquid W is gradually heated by receiving irradiation heat from the ultraviolet light source 21, and the oxidative decomposition efficiency is increased.

In the oxidative decomposition step S <b> 1, it is preferable to circulate air between the reaction vessel 20 and the absorption vessel 30 by moving the air pump 5. The air A ₁ transferred from the air pump 5 flows from the inflow portion 201 of the reaction vessel 20 through the gas flow path L ₂ , the cock 22, and the flow path L ₁ , and bubbles the sample liquid W in the reaction container 20. The bubbling is preferably performed so that the height of the apparent liquid level lifted by the bubbling is increased by 15% to 70% as compared with the height of the liquid level of the sample liquid W in the reaction container 20. Specifically, the bubbling is adjusted by adjusting the air line velocity of the air pump 5. When the sample liquid W is bubbled during the oxidative decomposition, the amount of ultraviolet light received per amount of the sample liquid is increased, and the oxidative decomposition efficiency is increased. Further, this bubbling prevents the photocatalyst titanium oxide from precipitating in the sample liquid W and maintains the suspended / dispersed state, so that the oxidative decomposition efficiency is further enhanced.

(CO2 emission process)
Next, step S2 for releasing the generated carbon dioxide from the sample liquid W will be described. Carbon dioxide generated by oxidative decomposition exists in the state of inorganic carbon ions such as carbon dioxide or ionized carbon dioxide in the sample liquid W. By making the sample liquid W acidic conditions and bubbling the sample liquid W, the generated carbon dioxide can be efficiently released from the sample liquid W as carbon dioxide gas. In the present invention, the oxidative decomposition step S1 and the carbon dioxide releasing step S2 are performed continuously. That is, the carbon dioxide generated by oxidative decomposition is sequentially released as carbon dioxide gas without being dissolved in the sample liquid W as carbonate ions or the like. Specifically, since the carbon dioxide generated from the sample liquid W in the reaction vessel 20 has the pH of the sample solution W adjusted to an acidic range, and bubbling from the bottom of the reaction vessel 20 is appropriately performed, The sample liquid W is immediately released as carbon dioxide gas. Released carbon dioxide is aspirated into the absorption vessel 30 from the outlet 202 of the reaction vessel 20 through the gas flow path L _3.

(CO2 absorption process)
Next, step S3 for causing the absorbing liquid 31 to absorb the generated carbon dioxide will be described. The generated gas A ₂ containing carbon dioxide flows into the absorption container 30 through the gas flow path L ₃ and further through the inflow port 301. Since the inflow port 301 is provided at the lower part of the liquid surface of the absorbing liquid 31, carbon dioxide in the gas A ₂ is absorbed by the absorbing liquid 31 exhibiting alkalinity to form carbonate ions, and remains in the absorbing liquid 31. . The gas A ₁ after passing through the absorption liquid 31 flows from the outflow portion 302 of the absorption container 30 to the gas flow path L ₄ , the air pump 5, the gas flow path L ₂ , the cock 22, the flow path L ₁ , the reaction container 20, and the gas flow. through the road _{L 3} returns to the inflow portion 301 of the liquid storage container 30. Therefore, even if carbon dioxide remains in the gas A ₁ after passing through the absorbing liquid 31, the carbon dioxide can be reliably absorbed in the absorbing liquid 31 by sufficiently circulating the gas.

(Insolubilization process)
The step S4 for insolubilizing carbon dioxide absorbed in the absorbent 31 as a hardly soluble carbonate will be described. Carbon dioxide (carbonate ions) absorbed in the absorption liquid 31 in the absorption container 30 reacts with metal ions that form a poorly soluble carbonate in the absorption liquid 31, thereby generating a hardly soluble carbonate. Specifically, the alkaline earth metal carbonate is formed by reacting with an alkaline earth metal ion that is contained in the absorbent 31 in advance or added after carbon dioxide is absorbed. Since the alkaline earth metal carbonate has extremely low solubility, it is insolubilized to form fine particles, and the absorbent 31 becomes cloudy.

(Measure turbidity and calculate TOC concentration)
Next, step S5 related to turbidity measurement and step S6 related to TOC concentration measurement will be described. The turbidity of the absorbing liquid 31 containing fine particles is measured using the turbidimeter 40 by the insolubilization step S4 described above. The TOC value is obtained by applying the turbidity value obtained by the measurement to the calibration curve obtained from the standard substance. At that time, a value with higher accuracy can be obtained by subtracting the blank value obtained in the pre-preparation step S0 from the obtained measurement value.

  Hereinafter, the present invention will be described in detail with reference to examples.

1. Quantification of carbon concentration by turbidity In the apparatus according to one embodiment of the present invention shown in FIG. 1, the carbon concentration is 20 mg-C / L in the absorption container of the carbon dioxide measuring unit (the alkaline absorbing solution is not contained). 8 mL of an aqueous sodium carbonate solution was added. Next, an aqueous strontium chloride solution is added to the above-mentioned sodium carbonate aqueous solution so that the concentration of strontium chloride is 10 mmol / L, 25 mmol / L, 50 mmol / L, or 100 mmol / L. Generated. The turbidity of the liquid containing strontium carbonate microparticles at each strontium chloride concentration was measured with a turbidimeter, and the relationship between the strontium chloride concentration and the turbidity of the liquid due to strontium carbonate microparticles was observed. A similar test was performed on 15 mg-C / L and 5 mg-C / L aqueous sodium carbonate solutions.

  The results are shown in FIG. The horizontal axis indicates strontium chloride concentration, and the vertical axis indicates turbidity. When the carbon concentration was 20 mg-C / L, the turbidity showed a constant value (about 0.69) at a strontium chloride concentration of 25 mmol / L or more. From this, in order to sufficiently insolubilize carbonate ions in an aqueous sodium carbonate solution having a carbon concentration of 20 mg-C / L (1.67 mmol / L) as strontium carbonate, about 15 times the reaction equivalent of strontium chloride is used. I found that it was necessary. Similarly, when the carbon concentration is 15 mg-C / L (1.26 mmol / L), the turbidity shows a constant value (about 0.52) at a strontium chloride concentration of 25 mmol / L or more, It was found that about 20 times the reaction equivalent of strontium chloride was required. When the carbon concentration is 5 mg-C / L (0.42 mmol / L), the turbidity shows a constant value (about 0.17) at a strontium chloride concentration of about 50 mmol / L or more, It was found that about 120 times the reaction equivalent of strontium chloride was required. Next, FIG. 4 shows the relationship between the turbidity showing the above constant value and each carbon concentration. The horizontal axis represents carbon concentration (mg-C / L), and the vertical axis represents turbidity. It was shown that the carbon concentration and turbidity are in a linear relationship, and the carbon concentration corresponding to the turbidity measured from this calibration curve can be obtained.

  From these, by adding an alkaline earth metal salt such as strontium chloride to an aqueous solution having carbonate ions, microparticles of hardly soluble alkaline earth metal carbonate were formed, and it became cloudy due to the formation of the microparticles It was found that the carbon concentration contained in the aqueous solution can be obtained by measuring the turbidity of the liquid.

2. Absorption of carbon dioxide generated in reaction vessel and determination of carbon concentration by turbidity In the apparatus according to one embodiment of the present invention shown in FIG. 1, 8 mL of 100 mmol / L strontium chloride aqueous solution is placed in the absorption vessel of the carbon dioxide measuring unit. And then about 1.3 mmol of lithium hydroxide was added and dissolved. Next, 6 mL of an aqueous sodium carbonate solution having a carbon concentration of 20 mg-C / L is placed in a reaction vessel (width 15 mm × height 300 mm × depth 3 mm) in the oxidative decomposition section, and sulfuric acid is added so that the pH of the aqueous sodium carbonate solution is 4. Added. An air pump was used to circulate and vent between the reaction container and the absorption container at a linear velocity of 130 cm / min to bubble the reaction container and suck carbon dioxide gas generated in the reaction container into the absorption container. The turbidity of the liquid in the absorption container during a predetermined circulation aeration time was measured, and the relationship between the circulation aeration time and the turbidity was observed. The results are shown in Table 1. The turbidity results measured for the aqueous sodium carbonate solution having a carbon concentration of 20 mg-C / L in Example 1 are also shown in Table 1.

  The turbidity corresponding to the measured value when carbonate ion and strontium ion were reacted in the absorption container performed in Example 1 was measured by circulating aeration for 3 minutes. From this, by bubbling the aqueous solution in the reaction vessel under acidic conditions for a short time, almost all of the carbonate ions contained in the aqueous solution are released from the aqueous solution as carbon dioxide gas. It has been shown that almost the entire amount is absorbed in the alkaline solution and that the absorbed carbon dioxide reacts with alkaline earth metal ions to form microparticles of sparingly soluble alkaline earth metal carbonates. That is, it was found that the concentration of carbon contained in the aqueous solution in the reaction vessel can be obtained by measuring the turbidity of the liquid turbid due to the formation of alkaline earth metal carbonate fine particles.

3. Measurement by turbidity of TOC concentration of sewage and industrial wastewater Using the apparatus described in one embodiment of the present invention shown in FIG. 1 above, the TOC concentration of two types of sewage treated water and two types of industrial wastewater by the following method Was measured. 6 mL of each sample solution such as sewage and titanium oxide were added at a concentration of 500 mg / L in the reaction vessel of the oxidative decomposition unit, and the pH of the sample solution was adjusted to 3.5 with sulfuric acid. 8 mL of a 100 mmol / L strontium chloride aqueous solution was placed in the absorption container of the carbon dioxide measuring section, and then about 1.3 mmol of lithium hydroxide was added and dissolved. A 27W U-shaped UV lamp (Sankyo Electric Co., Ltd., compact type BLB lamp, product number FPL27BLB) is turned on to irradiate the reaction vessel and circulate between the reaction vessel and the absorption vessel at a linear velocity of 130 cm / min using an air pump The reaction vessel was bubbled, and the carbon dioxide gas generated in the reaction vessel was sucked into the absorption vessel. The temperature of the sample liquid at this time was 75 ° C., and the liquid level of the sample liquid was increased by about 40% due to bubbling. The TOC concentration was determined by measuring the turbidity of the liquid in the absorption container after 20 minutes of ultraviolet irradiation and air circulation. Moreover, about the sample liquid, the TOC density | concentration was measured using the combustion oxidation-NDIR type TOC analyzer (Shimadzu Corporation, TOC5000 type | mold).

  The method of the present invention has proved that organic carbon such as sewage and industrial wastewater containing colloidal substances can be analyzed with high accuracy.

4). Oxidative degradation rate of organic matter by ultraviolet light source In a wet oxidation type TOC concentration measuring apparatus having an ultraviolet light source, usually a short straight tube ultraviolet lamp of about 6 W to 8 W is used in order to reduce the size of the entire apparatus. Yes. Therefore, in the total organic carbon concentration measuring apparatus used in Example 3 above, a straight tube type black light lamp (power 8 W, length 287 mm, Sankyo Electric Co., Ltd., product number FL8BLB) generally used, The efficiency of the oxidative decomposition reaction of a U-shaped black light lamp (power 27 W, length 265 mm, Sankyo Electric Co., Ltd., product number FPL27BLB) having the same length and used in the present invention was examined.

  The above two types of black light lamps were each attached to the total organic carbon concentration measuring apparatus used in Example 3, and a reaction vessel (width 15 mm × height 300 mm × depth 3 mm) was attached in close contact with each black light lamp. After adding 6 mL of 18 mg / L glucose standard solution in terms of carbon as a sample solution to the reaction vessel of the oxidative decomposition unit, titanium oxide is added to a concentration of 500 mg / L, and the pH of the sample solution is set to 3. Adjusted to 5. In the same manner as in Example 3, the turbidity of the absorbing solution when each black light lamp was used with a reaction time of 10 to 50 minutes was measured to determine the TOC concentration, and the oxidative decomposition rate was determined. The results are shown in Table 3.

  As a result, by using a U-shaped black light lamp having a plurality of ultraviolet irradiation sections and capable of irradiating the reaction vessel with ultraviolet rays from a plurality of directions, it is significantly more than that using a single straight tube type black light lamp. It was found that oxidative decomposition can be performed efficiently. Furthermore, when a U-shaped black light lamp was used, it was shown that the organic matter in the sample solution was decomposed 100% within 20 minutes without using an oxidizing agent. Note that the decomposition rate can be improved by irradiating ultraviolet rays from a plurality of directions using a plurality of straight tube black light lamps instead of the U-shaped black light lamp used in the present embodiment.

5. Oxidative decomposition rate of organic matter by temperature The relationship between the oxidative decomposition efficiency of organic matter contained in the sample solution and the temperature of the sample solution was investigated. The heating of the sample liquid was performed by heating the ultraviolet lamp by irradiation with ultraviolet light, and specifically, it was adjusted by the arrangement distance between the ultraviolet lamp and the reaction vessel and the air cooling of the fan. After adding 6 mL of 18 mg / L glucose standard solution in terms of carbon as a sample solution to the reaction vessel of the oxidative decomposition unit of the measuring apparatus used in Example 3, titanium oxide was added to a concentration of 500 mg / L, The pH of the sample solution was adjusted to 3.5 with sulfuric acid. The arrangement distance between the ultraviolet lamp and the reaction vessel was adjusted so that the temperature of the sample solution was 40 ° C to 90 ° C. In the same manner as in Example 3, oxidative decomposition was performed in the reaction vessel for 20 minutes, and the turbidity of the absorbing solution was measured to determine the TOC concentration and the oxidative decomposition rate. The results are shown in Table 4.

  As a result, under the conditions of this example, the decomposition rate was slightly low when the temperature of the sample solution was 40 ° C., but it was found that most organic substances contained in the sample solution could be oxidatively decomposed under the condition of about 60 ° C. or higher. In addition, when the sample solution was 90 ° C., the sample solution was significantly evaporated. Thus, although the temperature at which complete decomposition is possible varies depending on the type of organic substance, titanium oxide concentration, reaction time, and the like, the higher the temperature, the higher the reaction rate and the higher the decomposition rate. For these reasons, in order to increase the efficiency of the oxidative decomposition reaction in the sample solution, the sample solution in the reaction vessel is placed at an appropriate temperature of 90 ° C. or less by placing the reaction vessel close to the ultraviolet lamp, that is, It has been shown that it is effective to heat to 60 ° C to 90 ° C.

6). Oxidative degradation rate of organic substances by bubbling In order to increase the oxidative degradation efficiency of the sample solution, a method of increasing the amount of UV irradiation of the sample solution was investigated. Therefore, it was studied to increase the amount of UV light received per amount of sample liquid by sending air from the bottom of the reaction vessel and bubbling the sample liquid. In addition, it was considered that this method can prevent titanium oxide, which is mainly used as a photocatalyst for the oxidative decomposition reaction, from precipitating at the bottom of the reaction vessel and not acting as a photocatalyst. After adding 6 mL of 18 mg / L glucose standard solution in terms of carbon as a sample solution to the reaction vessel of the measurement apparatus used in Example 3, titanium oxide was added to a concentration of 500 mg / L. The pH was adjusted to 3.5 with sulfuric acid. The air pump was adjusted to have a linear flow rate of 20 cm / min to 250 cm / min, and the sample solution in the reaction vessel was bubbled. The water surface height of the sample liquid increased by bubbling was measured and obtained as the rate of increase in the light receiving area. Furthermore, oxidative decomposition was carried out in a reaction vessel for 20 minutes by the same method as in Example 3, and the turbidity of the absorbent was measured to determine the TOC concentration and the oxidative decomposition rate. The results are shown in Table 5.

  As a result, under the conditions of this example, when the air line velocity was 20 cm / min, a part of titanium oxide was precipitated and the water surface height was increased only by 6%. In addition, by adjusting the aeration line speed to 30 cm / min or more and increasing the water surface height by about 10% or more, titanium oxide was not precipitated in the reaction vessel, and the state suspended in the sample solution was maintained. . However, since the light receiving area is increased only by 9%, the oxidative decomposition rate was slightly low. Further, when the air line velocity was 250 cm / min, a part of the liquid sometimes overflowed from the reaction vessel. Therefore, the increase rate of the water surface height is preferably about 15 to 70%, and it has been found that the oxidative decomposition efficiency can be increased by increasing the water surface height in this way.

  In this way, by generating bubbles in the sample solution, the titanium oxide in the reaction vessel is always kept in a floating state, the amount of light received per sample solution amount can be increased, and the organic matter contained in the sample solution can be reduced. It was found that it can be efficiently oxidized and decomposed.

7). Oxidative degradation rate of organic matter depending on the amount of photocatalyst The relationship between the amount of photocatalyst added to the sample solution and the oxidative degradation efficiency of organic matter was investigated. Specifically, anatase type titanium oxide powder was used as the photocatalyst. After putting 6 mL of 18 mg / L glucose standard solution in terms of carbon as a sample solution into the reaction vessel of the oxidative decomposition unit of the measuring apparatus used in Example 3, the concentration of titanium oxide is 50 mg / L to 500 mg / L. The pH of the sample solution was adjusted to 3.5 with sulfuric acid. In the same manner as in Example 3, oxidative decomposition was performed in the reaction vessel for 20 minutes, and the turbidity of the absorbing solution was measured to determine the TOC concentration and the oxidative decomposition rate. The results are shown in Table 6.

  As a result, in the present invention, when measuring a high concentration TOC (18 mg / L in terms of carbon) as in the conditions of the example, the titanium oxide concentration is set to 500 mg / L, so that it is included in the sample solution. It was shown that almost all organic substances can be oxidatively decomposed. In addition, it is thought that the addition density | concentration of a titanium oxide can also be 500 mg / L or less if the titanium oxide with a larger oxidative decomposition promotion effect of organic substance than the titanium oxide used in the present Example is used.

8). Oxidative degradation rate of organic matter depending on pH of sample solution The relationship between pH of sample solution and oxidative degradation efficiency of organic matter was investigated. After adding 6 mL of 18 mg / L glucose standard solution in terms of carbon as a sample solution to the reaction vessel of the oxidative decomposition unit of the measurement apparatus used in Example 3, it was added so that the titanium oxide concentration was 500 mg / L. The pH of the sample solution was adjusted to 2.2 to 12.6. In the same manner as in Example 3, oxidative decomposition was performed in the reaction vessel for 20 minutes, and the turbidity of the absorbing solution was measured to determine the TOC concentration and the oxidative decomposition rate. The results are shown in Table 7.

  From this result, it was shown that when the pH of the sample solution is about 3 to 9, the oxidative decomposition is almost complete, but when the pH is 3 or less or 10 or more, the oxidative decomposition rate decreases. Accordingly, it has been found that the pH of the sample solution is preferably set to more than 3 and less than 9 in order to increase the oxidative decomposition efficiency of the organic matter contained in the sample solution. On the other hand, in order to release carbon dioxide generated by oxidative decomposition of organic matter from the sample liquid as carbon dioxide gas, it is necessary to make the carbon dioxide generated in the sample liquid difficult to ionize, that is, an acidic condition. The pH of the sample solution is preferably more than 3 and less than 7.

  The present invention is not limited to the above-described embodiments or examples, and various design changes within the scope not departing from the gist of the invention described in the claims are also included in the technical scope. .

DESCRIPTION OF SYMBOLS 1 Measuring apparatus of total organic carbon concentration 2 Oxidation decomposition part 20 Reaction container 201,301 Inflow part 202,302 Outflow part 21 Ultraviolet light source 210 Socket 22 Cock 23 Sample liquid inlet 3 Carbon dioxide absorption part 30 Absorption container 31 Absorption liquid 4 Carbon dioxide Measurement unit 40 Turbidimeter 41 Power source 5 Air pump L _{0 to} L ₁ flow path W Sample liquid L _{2 to} L ₄ Gas flow path A _{1 to} A ₂ gas

Claims (7)

The sample liquid is irradiated with ultraviolet rays, the organic matter contained in the sample liquid is oxidized and decomposed to generate carbon dioxide, and carbon dioxide is released from the sample liquid, and the carbon dioxide that absorbs the released carbon dioxide Having an absorption part and a measurement part for measuring the amount of absorbed carbon dioxide,
The oxidative decomposition unit includes a reaction vessel that oxidizes and decomposes organic substances contained in the sample solution, an ultraviolet light source that is arranged to irradiate the reaction vessel, and a sample solution in the reaction vessel that is connected to the reaction vessel. A gas transfer means for bubbling
The carbon dioxide absorption part includes an absorption container that contains a liquid containing metal ions that form an alkali that absorbs carbon dioxide transferred from the reaction container and forms a hardly soluble carbonate.
The measuring unit includes a turbidimeter for measuring the turbidity of the liquid in the absorption container.   The ultraviolet light source has a plurality of irradiation units, and is arranged in close proximity so as to irradiate the reaction container from a plurality of directions and to heat a sample solution in the reaction container. Item 2. The total organic carbon concentration measuring device according to Item 1.   2. The gas transfer means is configured to increase the liquid level of the sample liquid by 15% to 70% by bubbling the sample liquid in the reaction vessel. Or the measuring apparatus of the total organic carbon concentration of 2.   The total organic carbon concentration according to any one of claims 1 to 3, wherein the gas transfer means is configured to circulate and transfer gas through the reaction vessel and the absorption vessel. Measuring device.   The said organic ion is alkaline-earth metal ion, The measuring apparatus of the total organic carbon concentration of any one of Claims 1-4 characterized by the above-mentioned.   6. The apparatus for measuring the total organic carbon concentration according to claim 5, wherein the alkaline earth metal ions are strontium ions. Irradiating the sample liquid with ultraviolet rays to oxidatively decompose organic substances contained in the sample liquid to generate carbon dioxide;
Bubbling the sample solution under acidic conditions to release carbon dioxide from the sample solution;
A step of absorbing the released carbon dioxide in an absorbing solution exhibiting alkalinity;
Reacting carbon dioxide absorbed in the absorbent with metal ions that form a poorly soluble carbonate to form a poorly soluble carbonate in the absorbent;
Measuring the turbidity of the absorbing solution containing a hardly soluble carbonate, and a method for measuring total organic carbon.

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