JP5552977B2 - Method for measuring dissolved substance concentration - Google Patents

Description

The present invention relates to measuring how the dissolved substance concentration, particularly relates to a preferred way to measure the concentration of organic substances in the water.

  High-concentration chemicals and detergents and a large amount of pure water are used for rinsing them for cleaning and surface treatment of electronic components. Improvement of water quality and reduction of usage due to advancement of electronic components. The improvement of the water recovery rate by wastewater recovery aiming at the problem has become an issue. Efficiently reducing the organic component (TOC) in water to a lower concentration is an important issue in terms of both improving water quality and improving the water recovery rate, and monitoring the concentration online is important. It is.

  As a method for measuring TOC online in an ultrapure water system, a TOC monitor based on the UV method is mainly used. This is a method of irradiating a sample water with low-pressure UV light of 185 nm, oxidizing and decomposing TOC in the sample water to lower the molecular weight / ionization, and obtaining the TOC concentration from the resistivity before and after that (Patent Document 1, Patent Document 1). 2).

However, this method has a problem that a TOC component that does not absorb 185 nm UV light, such as urea, cannot be measured because it is not decomposed by UV.
JP 2004-177164 A JP 2008-1111721 A

The present invention aims at providing a measuring how the dissolved substance concentration which can be organic such as urea measured with high accuracy.

  The dissolved substance concentration measuring method of the present invention (Claim 1) includes a step of supplying hydrogen to a container filled with a platinum group metal catalyst, and a step of passing sample water containing dissolved oxygen and dissolved substances through the container. Thereafter, hydrogen water is passed through the container, a specific substance concentration in the effluent water or a characteristic value corresponding thereto is measured, and a dissolved substance concentration in the sample water is obtained from the measurement result.

  A method for measuring a dissolved substance concentration according to claim 2 is characterized in that, in claim 1, the dissolved substance is an organic substance.

  The method for measuring the dissolved substance concentration according to claim 3 is the method according to claim 1 or 2, wherein a sample water having a known dissolved substance concentration is used to obtain a correlation between the characteristic value and the dissolved substance concentration in the sample water. The dissolved substance concentration in the sample water is obtained based on the characteristic value measured for the sample water whose substance concentration is unknown and the correlation.

  The dissolved substance concentration measuring method according to claim 4 is characterized in that, in any one of claims 1 to 3, the dissolved substance is urea, and the resistivity of the effluent water is measured as the characteristic value. It is.

  A method for measuring a dissolved substance concentration according to claim 5 is the method according to any one of claims 1 to 4, wherein a plurality of the containers are provided in parallel, and a separate process is performed in some containers and other containers. It is characterized by.

In the measurement how the dissolved substance concentration of the present invention, first supplying hydrogen to the vessel such as a column filled with a platinum group metal catalyst is adsorbed hydrogen on platinum group metal catalyst. Next, the sample water with the dissolved oxygen concentration adjusted is passed through the container, and the dissolved substances in the sample water are adsorbed on the platinum group metal catalyst. Thereafter, hydrogen is supplied again to the container, the adsorbed substance is desorbed from the platinum group metal catalyst, and the concentration of the desorbed substance is measured to measure the concentration of the substance in the sample water.

According to this method, it becomes possible concentration measurement of UV flame decomposable substance such as urea could not be monitored in conventional monitors.

Is a system diagram showing an embodiment of the measuring how the dissolved substance concentration of the present invention. It is a graph which shows the result of an Example.

  Hereinafter, the present invention will be described in more detail.

  Examples of dissolved substances in sample water to be measured in the present invention include urea, amines (ethanolamine, methylamine, diethanolamine, triethanolamine, trimethylamine, etc.), DMSO, and the like, but are not limited thereto.

  When the dissolved substance is urea, the concentration in the sample water is preferably about 0.5 to 10 μg / LasC, particularly about 0.5 to 5 μg / LasC as the carbon concentration. Examples of water having such a urea concentration include pure water and ultrapure water used for electronic component manufacturing.

  Examples of the platinum group metal of the platinum group metal catalyst include ruthenium, rhodium, palladium, osmium, iridium and platinum. These platinum group metals can be used individually by 1 type, and can also be used in combination of 2 or more type. It can also be used as an alloy made of two or more metals. Moreover, the refined product of the mixture produced naturally can also be used without isolate | separating into a single-piece | unit. Among these, platinum, palladium, a platinum / palladium alloy alone or a mixture of two or more of them is particularly suitable because of its strong catalytic activity.

  The platinum group metal catalyst may be a platinum group metal fine particle or a metal supported catalyst in which platinum group metal nanocolloid particles are supported on the surface of a carrier. In addition, the platinum group metal catalyst may be formed by forming a coating of a platinum group metal such as platinum on a substrate such as a ceramic ball by plating or the like.

  There is no particular limitation on the method for producing platinum group metal nanocolloid particles, and examples thereof include a metal salt reduction reaction method and a combustion method. Among these, the metal salt reduction reaction method can be suitably used because it is easy to produce and stable metal nanocolloid particles can be obtained. In the case of the metal salt reduction reaction method, for example, 0.1 to 0.4 mmol / L aqueous solution of platinum group metal such as platinum, nitrate, sulfate, metal complex, etc., alcohol, citric acid or a salt thereof, By adding a reducing agent such as formic acid, acetone, or acetaldehyde 4 to 20 equivalents with respect to the platinum group metal and boiling for 1 to 3 hours, platinum group metal nanocolloid particles can be produced. Further, for example, by dissolving 1-2 mmol / L of hexachloroplatinic acid, potassium hexachloroplatinate, etc. in an aqueous polyvinylpyrrolidone solution, adding a reducing agent such as ethanol, and heating and refluxing in a nitrogen atmosphere for 2 to 3 hours, Nanocolloid particles can be produced.

  The weight average particle diameter of the platinum group metal nanocolloid particles is preferably 1 to 50 nm, more preferably 1.2 to 20 nm, and still more preferably 1.4 to 5 nm. If the weight average particle diameter of the metal nanocolloid particles is less than 1 nm, the catalytic activity for TOC decomposition and removal may be reduced. When the weight average particle diameter of the metal nanocolloid particles exceeds 50 nm, the specific surface area of the nanocolloid particles becomes small, and the catalytic activity for TOC decomposition and removal may be reduced.

  There is no particular limitation on the carrier for supporting the platinum group metal nano colloidal particles. Can be mentioned. Of these, anion exchange resins are preferred. Since the platinum group metal nanocolloid particles have an electric double layer and are negatively charged, they are stably supported on the anion exchange resin and are difficult to peel off. This anion exchange resin is preferably a strongly basic anion exchange resin based on a styrene-divinylbenzene copolymer, and more preferably a gel resin. The exchange group of the anion exchange resin is preferably in the OH form. The amount of platinum group metal nanocolloid particles supported on a carrier such as an anion exchange resin is preferably 0.01 to 0.2% by weight, more preferably 0.04 to 0.1% by weight. .

  Next, a dissolved substance concentration measuring apparatus according to an embodiment of the present invention and a dissolved substance concentration measuring method using this apparatus will be described with reference to FIG.

  As shown in FIG. 1, a sample water supply pipe 1 is connected to a catalyst packed column 3. This column 3 is packed with a platinum group metal catalyst 3a. A dissolved oxygen concentration meter 2 is provided in the vicinity of the column 3 of the pipe 1. A hydrogen supply pipe 4 and an oxygen supply pipe 5 are connected to the pipe 1 upstream of the dissolved oxygen concentration meter 2. The hydrogen supply pipe 4 may be connected to the downstream side of the dissolved oxygen concentration meter 2 or may be directly connected to the column 3. The sample water pipe 1 and the oxygen supply pipe 5 are preferably made of a metal such as stainless steel having a low oxygen permeability, nylon, or the like. An outlet pipe 6 having a resistivity meter 7 is connected to the outlet of the column 3.

  The hydrogen supplied to the hydrogen supply pipe 4 may be hydrogen gas or hydrogen water (hydrogen-dissolved water), but hydrogen water is used to prevent gas lock when sample water is circulated in the adsorption process. It is preferable to use it.

  The procedure for measuring the dissolved substance concentration in the sample water is preferably as follows.

(1) Hydrogen adsorption step First, hydrogen water is passed from the hydrogen supply pipe 4 to the catalyst-filled column 3 to adsorb hydrogen to the catalyst 3a. The hydrogen concentration at this time is preferably about 0.1 to 1.6 mg / L, particularly about 0.2 to 1.6 mg / L. Moreover, when the sum of the volume of the hydrogen supply pipe and the volume of the catalyst packed column is 1, the supply amount of hydrogen water is preferably about 0.1 to 10, particularly about 1 to 5. When the volume of the platinum group metal catalyst is used as a reference, it is preferable to pass hydrogen water 1 to 5 times, particularly 1 to 3 times, the volume of the platinum group metal catalyst 3a.

(2) Dissolved substance adsorption process Next, while supplying sample water to the piping 1, oxygen water is added to the sample water in this piping 1 from the oxygen supply piping 5 as needed. The amount of oxygen water added at this time is preferably adjusted so that the dissolved oxygen concentration detected by the dissolved oxygen meter 2 is about 5 to 500 μg / L, particularly about 10 to 100 μg / L. When the dissolved oxygen concentration in the sample water before addition of oxygen water is excessively high, oxygen water is not added, and a degassing mechanism is provided in the pipe 1 upstream of the dissolved oxygen meter 2 so that the dissolved oxygen meter 2 It is preferable to deaerate so that the detected dissolved oxygen concentration in the above range falls within the above range.

  When the sample water having the dissolved oxygen concentration adjusted in this way is passed through the column 3, dissolved substances such as urea contained in the sample water are adsorbed by the platinum group metal catalyst adsorbing hydrogen. The mechanism by which dissolved substances are adsorbed on the platinum group metal catalyst is that in the presence of the platinum group metal catalyst, the hydrogen adsorbed on the platinum group metal catalyst and oxygen in the sample water are combined, and electrons are unevenly distributed on the surface of the metal catalyst. It is inferred that this is because a rough portion of electrons is generated on the surface of the metal catalyst, and the unshared electron pair inherent in N atoms such as urea is bonded to the rough portion of the electrons.

When the platinum group metal catalyst 3a is an anion exchange resin in which 0.01 to 0.2% by weight of platinum group metal nonanocolloid particles are supported, the water flow rate (SV) of the sample water to the catalyst packed column 3 is 10 to 500 hr ^−1, especially about 50 to 300 hr ⁻¹ is preferable, but not limited thereto.

(3) Desorption Step Next, hydrogen water from the hydrogen supply pipe 4 is passed through the column 3 that has adsorbed dissolved substances in the adsorption step (2). As a result, the adsorbed material adsorbed on the catalyst is desorbed and flows out to the pipe 6. At this time, the adsorbed material adsorbed on the platinum group metal catalyst 3a is ionized or ionized and reduced in molecular weight. The reason why this ionization proceeds is not necessarily clear, but hydrogen in the hydrogen water supplied in the step (3) reacts with oxygen adsorbed on the catalyst to produce water, It is speculated that this is because the bond of the lone pair is also broken and the hydrolysis partially proceeds to urea.

  The amount of substance adsorbed on the platinum group metal catalyst is proportional to the dissolved substance concentration in the sample water, and the amount of substance desorbed from the platinum group metal catalyst while ionizing is proportional to the amount of adsorbed substance on the catalyst. The ion concentration in the water is proportional to the dissolved substance concentration in the sample water. The detected resistivity of the resistivity meter 7 decreases as the ion concentration in the desorbed water increases.

  Therefore, a calibration curve between the dissolved substance concentration and the resistivity of desorbed water was obtained in advance using sample water with a known dissolved substance concentration, and sample water with an unknown dissolved substance concentration was passed under the same conditions as when the calibration curve was created. The dissolved substance concentration in the sample water can be detected from the detected value of the desorbed water at that time.

The water flow SV in this desorption step is preferably about 3 to 60 hr ^−1, especially about 5 to 50 hr ⁻¹ . Moreover, it is preferable to employ | adopt the value which became the highest after the water-flow start of hydrogenous water as a detected value of the resistivity by the resistivity meter 7.

  When the desorption process is continued, the detected value of the resistivity meter 7 gradually increases. In the middle of this desorption process, the process proceeds to the hydrogen adsorption process of (1). When the detected resistivity of the resistivity meter 7 reaches a predetermined value or less, the hydrogen adsorption process is terminated, and the dissolution of (2) above Move on to substance adsorption process.

  Thus, by repeating the desorption and hydrogen adsorption step by the sample water flow step → hydrogen water flow step, the dissolved substance concentration in the sample water can be repeatedly measured.

  It should be noted that a plurality of catalyst packed columns 3 are provided in parallel, and another process such as a desorption process is performed in another catalyst packed column when a sample water flow process is performed in a part of the catalyst packed columns. Good. By doing in this way, a dissolved substance density | concentration can be measured with high frequency.

  Examples and comparative examples will be described below.

[Example 1]
Using the apparatus shown in FIG. 1, the sample water having a known urea concentration was passed under the following conditions to measure the resistivity of the effluent water.

As a platinum group metal catalyst (catalyst resin), 500 mL of “Nano Saver” (platinum nano colloid support resin) manufactured by Kurita Kogyo Co., Ltd. was packed in a 30 mm diameter column. Hydrogen water having a hydrogen concentration of 1.2 mg / L was passed through the column at SV = 12 hr ⁻¹ for 10 minutes.

Next, sample water having a dissolved oxygen concentration of 30 μg / L and a urea concentration of 0.2 μg / LasC was passed for 30 min at SV = 60 hr ⁻¹ .

After passing the sample water, hydrogen water having the above concentration was passed at SV = 12 hr ⁻¹ and the column effluent resistivity was measured. The results are shown in FIG.

  Hydrogen water, sample water, and hydrogen water were sequentially passed in the same manner except that sample water having a urea concentration of 1.4 μg / LasC, 2.8 μg / LasC, or 3.8 μg / LasC was used as the sample water. Then, the resistivity of the column effluent was measured. The results are shown in FIG.

As shown in FIG. 2, a linear relationship between the urea concentration of the sample water and the resistivity is such that the resistivity decreases as the urea concentration increases (in FIG. 2, y = 0.3775x ² −0.3481x + 17 .443, R ² = 0.9997), and the urea concentration in the sample water can be monitored from the resistivity of the effluent.

[Comparative example]
Using a UV method TOC online monitor (ANATEL A1000-XP, manufactured by Hack Ultra Co., Ltd.), the sample water was irradiated with low-pressure ultraviolet light having a wavelength of 185 nm, and the change in resistivity before and after that was measured. Was not detected, and the urea concentration could not be monitored.

2 dissolved oxygen concentration meter 3 catalyst packed column 3a platinum group metal catalyst 7 resistivity meter

Claims (5)

Supplying hydrogen to a container filled with a platinum group metal catalyst;
Passing sample water containing dissolved oxygen and dissolved substances through the container;
Thereafter, hydrogen water is passed through the container, the specific substance concentration in the effluent water or the characteristic value corresponding thereto is measured, and the dissolved substance concentration in the sample water is obtained from this measurement result;
Method for measuring the concentration of dissolved substances having   2. The method for measuring a dissolved substance concentration according to claim 1, wherein the dissolved substance is an organic substance.   3. The characteristic value measured in the sample water according to claim 1 or 2, wherein a correlation between the characteristic value and the dissolved substance concentration in the sample water is obtained using a sample water having a known dissolved substance concentration, and the dissolved substance concentration is measured. And measuring the dissolved substance concentration in the sample water based on the correlation.   4. The dissolved substance concentration measuring method according to claim 1, wherein the dissolved substance is urea, and the resistivity of the effluent water is measured as the characteristic value.   5. The dissolved substance concentration measuring method according to any one of claims 1 to 4, wherein a plurality of the containers are provided in parallel, and a separate process is performed in some containers and other containers.

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