JP2009156692A - Continuous monitoring method and device of test water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous monitoring method and a device of test water capable of enriching an analysis object material to a target concentration continuously by a small-sized device, and monitoring continuously the concentration of the enriched analysis object material, even in the case of an extremely small amount of the analysis object material in the test water. <P>SOLUTION: The test water is subjected to RO membrane separation processing to be separated into enriched water wherein the analysis object material is enriched and permeated water wherein the analysis object material concentration is reduced, and a part of the enriched water is subjected to circulation processing by an RO membrane module. Then, the analysis object material concentration is measured relative to residual enriched water, and the analysis object material concentration in the test water is operated based on the result. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and apparatus for continuous monitoring of test water, and in particular, while separating the supplied test water into concentrated water with an increased concentration of the analyte and water with a reduced concentration of the analyte. The present invention relates to a continuous monitoring method and apparatus for continuously measuring the concentration of an analysis target substance in concentrated water in which the analysis target substance is concentrated.

  INDUSTRIAL APPLICABILITY The sample monitoring method and apparatus of the present invention are useful for continuous monitoring analysis of sample water containing trace amounts of analytes such as ultrapure water in the semiconductor industry, electric power / nuclear power industry, pharmaceutical industry, and all other industrial fields. It is.

  In semiconductor manufacturing plants, ultrapure water is used that has been highly purified by removing impurities. Examples of water quality management items for ultrapure water include resistivity, fine particles, viable bacteria, TOC (Total Organic Carbon), dissolved oxygen, silica, cation ions, anion ions, heavy metals, and the like.

  Currently, ultra-pure water continuous analyzers (online monitors) use resistivity meters, fine particle meters, TOC meters, silica meters, dissolved oxygen meters, metal analyzers, and the like. These analyzers have measurable lower limit values. For example, in a metal element monitor, the measurable lower limit values are about 0.1 to 400 μg / L for Na and Ca, and about 10 ng / L for Fe. It is.

  On the other hand, the required water quality of ultrapure water used in the semiconductor industry, the electric power / nuclear power industry, the pharmaceutical industry, etc. has been increasing in recent years. Therefore, in order to perform water quality management with the above-described analyzer using ultrapure water containing an analyte such as a trace amount of metal ions as the test water, the analyte lower limit value of the analyzer is used for the analysis of the analyte in ultrapure water. It is necessary to concentrate to the above concentration. In addition, even in the case of an analysis target substance that is contained above the measurement lower limit value, it may be necessary to concentrate the analysis target substance in order to obtain a more accurate analysis result.

Conventionally, as a method for continuously concentrating and monitoring a substance to be analyzed in ultrapure water, as described in JP-A-2004-77299, a reverse osmosis membrane device and an electrodeionization device are provided in multiple stages. Therefore, a method for highly concentrating the substance to be analyzed has been proposed.
JP 2004-77299 A

  However, in the method of Japanese Patent Application Laid-Open No. 2004-77299, since the reverse osmosis membrane device and the like are provided in at least two stages, the device is increased in size, and thus cannot be put into practical use as a monitoring device. In addition, when ultrapure water containing only a very small amount of each metal ion concentration of 1 ng / L or less is to be concentrated, two stages are insufficient for concentrating to the target concentration, and more devices are used. Since it cannot be concentrated to the target concentration unless it is provided, the apparatus is further increased in size.

  The present invention solves the above-mentioned conventional problems, and even if the amount of the analyte to be analyzed is extremely small, the analyte is continuously concentrated to the target concentration by a small device, and the concentrated analyte It aims at providing the continuous monitoring method and apparatus of the sample water which can monitor the density | concentration of water continuously.

  The continuous monitoring method for sample water of the present invention (Claim 1) is a method for continuously monitoring the concentration of a substance to be analyzed in the sample water, and the substance to be analyzed is concentrated by subjecting the sample water to reverse osmosis membrane separation treatment. Concentration process for separating the concentrated water and permeated water having a reduced concentration of the analyte, a return process for returning a part of the concentrated water from the concentration process before the concentration process, and analysis of the remaining concentrated water An analysis step for measuring the concentration of the target substance and a calculation step for calculating the concentration of the target substance in the test water based on the analysis result of the analysis step are characterized.

  The continuous water monitoring method according to claim 2 is the method according to claim 1, wherein in the returning step, the concentrated water is returned so that the membrane surface flow velocity of the reverse osmosis membrane in the concentration step is 25 to 600 m / Hr. Features.

  The continuous monitoring method of sample water according to claim 3 is the method according to claim 1 or 2, wherein the pH of the water subjected to the reverse osmosis membrane separation treatment is in the range of 3.0 to 6.95 prior to the concentration step. It includes a pH adjusting step for adjusting.

  The continuous monitoring method of sample water according to claim 4 is the method according to any one of claims 1 to 3, wherein the sample water is ultrapure water having a metal ion concentration of each metal of 1 ng / L or less. The target substance is a metal ion.

  The continuous monitoring apparatus for test water of the present invention (Claim 5) is an apparatus for continuously monitoring the concentration of the analyte in the test water, and the analyte is concentrated by subjecting the test water to reverse osmosis separation. Reverse osmosis membrane separation means for separating the concentrated water into permeated water having a reduced analyte concentration, a return means for returning a part of the concentrated water to the upstream side of the reverse osmosis membrane separation means, An analysis unit that measures the concentration of the analysis target substance in the concentrated water and a calculation unit that calculates the concentration of the analysis target substance in the test water based on the analysis result of the analysis unit are characterized.

  The continuous water monitoring apparatus according to claim 6 is characterized in that, in claim 5, in the return means, the concentrated water is returned so that the membrane surface flow rate in the reverse osmosis membrane separation means is 25 to 600 m / Hr. And

  The continuous monitoring apparatus for sample detection according to claim 7 is the pH adjustment according to claim 5 or 6, wherein the pH of water introduced into the reverse osmosis membrane separation means is adjusted to be in the range of 3.0 to 6.95. Means.

  The continuous water monitoring device according to claim 8, wherein the water sample is ultrapure water in which the metal ion concentration of each metal is 1 ng / L or less. The target substance is a metal ion.

  In the present invention, even if the reverse osmosis membrane separation means as the concentration means is a single stage, a trace amount analysis in the sample water is performed by circulating a part of the concentrated water and increasing the membrane surface flow velocity of the reverse osmosis membrane. The target substance can be concentrated at a high concentration rate. Further, during the concentration, there is no change in the form of the analyte in the test water, and there is almost no problem of contamination. For this reason, it is possible to accurately and continuously monitor a very small amount of component, which is difficult to analyze by the conventional method, with a small apparatus.

  According to the present invention, sample water containing an extremely small amount of an analyte to be analyzed that is less than the lower limit of measurement, such as ultrapure water, can be easily obtained with a small device without causing a change in the form of the analyte and contamination of the sample. In addition, it is possible to continuously concentrate and efficiently perform continuous analysis, greatly improving the analysis efficiency, greatly reducing the time required for analysis, and reflecting the analysis results to operation management etc. at an early stage. It becomes possible.

  In particular, in the present invention, by adding an acid to the test water and lowering the pH, it is possible to obtain a highly accurate analysis result by highly concentrating trace components in the test water at a high speed through the concentrated water side. And its industrial utility is extremely large.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a system diagram showing an embodiment of a continuous sample monitoring apparatus of the present invention.

  In this continuous monitoring device, after adjusting the pH by adding an acid to the test water, it is permeated through the reverse osmosis (RO) membrane module 1 to reduce the concentration of the analyte and the concentration of the analyte. A part of the concentrated water obtained by separating into permeated water is returned to the inlet side of the RO membrane module 1 by the circulation pump P. Further, the remainder of the concentrated water is fed to an analysis means (in FIG. 1, an ion chromatograph 2 and a spectrophotometer 3), and the concentration of the analyte in the concentrated water is measured. Calculate the analyte concentration.

  Examples of the acid added to the test water include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid. In the test water, such an acid is added, and the pH of water flowing into the RO membrane (hereinafter sometimes referred to as “RO membrane water supply”) is 3.0 to 6.95, particularly 6 to 6.95. It is adjusted to become. Thus, by setting the pH of the RO membrane water supply to a weak acidity of 3.0 to 6.95, it is possible to concentrate a very small amount of analyte in the test water at a high concentration rate in the RO membrane. . This is due to the effect of preventing deposition by ionizing a metal that is easily deposited by forming a hydroxide due to weak acidity. If this adjusted pH value exceeds the above upper limit value, the above effect cannot be sufficiently obtained, and if it is less than the above lower limit value, there is a possibility of causing performance deterioration of the constituent members of the RO membrane.

  The higher the concentration factor in the RO membrane, the higher the concentration of the analyte in the test water in the concentrated water. Therefore, the analysis accuracy in the subsequent analysis means increases, but excessively high concentration means the analyte in the concentrated water. There is a possibility that the concentration becomes high and the analyte is deposited on the membrane surface and cannot be recovered. Therefore, the concentration of RO membrane expressed by the ratio of the amount of test water introduced into the system with respect to the amount of concentrated water discharged out of the system (the amount of concentrated water supplied to the ion chromatograph 2 and spectrophotometer 3 in FIG. 1). The magnification is preferably 2 to 2000 times, particularly about 10 to 100 times, and the concentration of the substance to be analyzed in the concentrated water is preferably 2 to 3 times the measurement lower limit value of the analysis means.

  The present invention is characterized in that a part of the concentrated water in the RO membrane is returned to the upstream side of the RO membrane module 1, and the concentrated water is circulated in this way, so that the pole in the sample water in the one-stage RO membrane can be obtained. This makes it possible to concentrate a very small amount of a substance to be analyzed with high concentration. The higher the amount of concentrated water returned, the better the concentration of the analyte, but the larger the amount of circulating water, the larger the amount of retained water in the system, and the larger the capacity of the device. Connection is undesirable. From the viewpoint of high concentration and downsizing of the apparatus, the concentrated water is preferably circulated so that the membrane surface flow velocity at the RO membrane is 25 to 600 m / Hr, particularly 400 to 450 m / Hr. The reason why the concentration efficiency is improved by circulating a part of the concentrated water and increasing the membrane surface flow velocity at the RO membrane is due to the effect of reducing the concentration polarization of the membrane surface and suppressing metal adhesion to the membrane surface. Is.

  For the circulation of the concentrated water, a highly clean circulating pump, for example, a member made of fluororesin (including fluororesin processed products) such as polytetrafluoroethylene is used, and there is no magnetic contact between the members by the motor. It is preferable to use a floating pump or the like in order to reduce analysis errors due to contamination from the circulation pump.

  Of the concentrated water of the RO membrane module 1, the remaining concentrated water that is not returned to the inlet side of the RO membrane module 1 is supplied to the analysis means and analyzed for the concentration of the substance to be analyzed. The analysis means is not particularly limited and is appropriately determined according to the type of the substance to be analyzed. For the analysis of metal ions, either or both of the ion chromatograph 2 and the spectrophotometer 3 shown in FIG. Can be used. In addition, a resistivity meter, a fine particle meter, a TOC meter, a silica meter, a dissolved oxygen meter and the like can also be used. When using a plurality of analysis means, these may be arranged in series or in parallel.

  From the analysis target substance concentration in the concentrated water analyzed by the analysis means, the analysis target substance concentration in the test water can be calculated as follows.

That is, as in the present invention, when the sample water is continuously concentrated by the RO membrane and a part of the concentrated water is circulated, the flow rate of the sample water in the system is stable in a substantially steady state. If the sample water flow rate, circulating water volume, and concentrated water withdrawal volume are kept constant, the concentration rate at the RO membrane can be considered to be constant, and analysis of the concentrated water as shown in the following formula (1). A value obtained by dividing the target substance concentration by the concentration factor can be used as the analysis target substance concentration of the test water.
Supply amount of test water to RO membrane: Ff
Concentrated water to be extracted out of the system: Fb
Concentration of analyte in concentrated water (monitoring detection value): Cm
RO membrane concentration factor = Ff / Fb
Analyte concentration in the sample water = Analyte concentration in the concentrated water / RO membrane concentration rate
= Cm / (Ff / Fb)

  In the present invention, the sample water to be monitored is not particularly limited, but generally, the concentration of the substance to be analyzed is low, and concentration is necessary for water quality analysis. A typical example is ultrapure water used in semiconductor factories and the like.

  Examples of the analytes that can be monitored include cations, silica, metals, organic acids and the like when an ion chromatograph is used as an analysis means. In addition, when a spectrophotometer is used as the analysis means, cations, silica, heavy metals, and the like can be given.

  The present invention is particularly effective when continuously monitoring the metal ion concentration of ultrapure water in which the metal ion concentration of each metal is 1 ng / L or less.

  In addition, there is no restriction | limiting in particular in the RO membrane used for concentration of test water.

  In the present invention, the RO membrane module can be provided in two or more stages. However, according to the present invention, the test water can be sufficiently concentrated by the one-stage RO membrane, and the monitoring device For the purpose of downsizing, the RO membrane module is usually provided in only one stage.

  Hereinafter, the present invention will be described more specifically with reference examples and examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

  In the following reference examples and examples, continuous monitoring of sample water was performed using the apparatus shown in FIG.

  As the RO membrane of the RO membrane module 1, a reverse osmosis membrane “ES-20-D4” (4 inch) manufactured by Nitto Denko Corporation is used, and as a circulating pump P for concentrated water of the RO membrane, Levitro magnetic levitation type manufactured by Iwaki Co., Ltd. A pump “LEV300F” (maximum discharge amount 40 L / min, maximum lift 20 m, maximum rotation speed 6200 rpm, withstand pressure 0.30 MPa) was used. Further, “FIAMO” manufactured by FIAMO was used as the spectrophotometer 3, and “IC-7000” manufactured by Yokogawa Electric Co., Ltd. was used as the ion chromatograph 2.

  Ultrapure water (pH 7.0) is used as test water, and trace analysis of Na ion, Ca ion, and Fe ion in ultrapure water is monitored and analyzed, and Na ion and Ca ion are monitored and evaluated by ion chromatography. The Fe ion was monitored and evaluated with a spectrophotometer.

[Reference Example 1]
With the circulation pump stopped, ultrapure water was supplied to the RO membrane at 500 mL / min, concentrated water 50 mL / min (10-fold concentration) was taken out, and the entire amount was supplied to the analysis system. At this time, the membrane surface flow velocity of the RO membrane is 427 m / Hr.
FIG. 2 shows analysis values for the ultrapure water to be monitored, analysis values for the concentrated water, and values (monitoring detection values) detected by an ion chromatograph and a spectrophotometer. FIG. 3 shows the relationship between the monitoring detection value and the concentrated water analysis value. The analytical value of ultrapure water and concentrated water is a value measured by an inductively coupled plasma mass spectrometer (ICP-MS).
2 and 3, it is possible to analyze metal ions in ultrapure water with an RO membrane to a concentration higher than the lower limit of quantification of ion chromatograph and spectrophotometer. I understand.
The recovery rate of each metal ion in Reference Example 1 (ratio of the amount of the analyte in the concentrated water to the amount obtained by subtracting the amount of the analyte in the permeated water from the amount of the analyte in the test water) is shown in FIG. It was street.

[Reference Example 2]
Monitoring was performed in the same manner as in Reference Example 1 except that acid (nitric acid) was added to ultrapure water and the pH of the RO membrane feed water was adjusted to about 6.5.
As a result, as for the concentrated water analysis value and the monitoring detection value, an excellent correlation was obtained as in Reference Example 1. Furthermore, as shown in FIG. 4, the recovery rate was very good.

[Example 1]
In Reference Example 2, the same operation was performed except that the circulation pump was operated and a part of the concentrated water was circulated at high speed so that the membrane surface flow velocity of the RO membrane was 427 m / Hr to the inlet side of the RO membrane module. Monitoring.
As a result, as for the concentrated water analysis value and the monitoring detection value, an excellent correlation was obtained in the same manner as in Reference Examples 1 and 2, and as shown in FIG. 4, a much higher result was obtained for the recovery rate. .

  From the above results, it can be seen that according to the present invention, a very small amount of an analyte of 1 ng / L or less in test water can be continuously highly concentrated to obtain a highly accurate analysis result.

It is a systematic diagram which shows embodiment of the continuous monitoring apparatus of the test water of this invention. It is a graph which shows the continuous monitoring analysis result of the ultrapure water in the reference example 1. It is a graph which shows the correlation of the concentrated water analysis value and monitoring detection value in the reference example 1. 4 is a graph showing metal ion recovery rates in Reference Examples 1 and 2 and Example 1.

Explanation of symbols

1 RO membrane module 2 Ion chromatograph 3 Spectrophotometer

Claims (8)

In the method of continuously monitoring the concentration of the analyte in the sample water,
A concentration step for separating the test water into a concentrated water in which the analyte is concentrated and a permeated water in which the analyte concentration is reduced by subjecting the test water to reverse osmosis membrane separation;
A return step of returning a portion of the concentrated water from the concentration step before the concentration step;
An analysis process for measuring the concentration of the analyte in the remaining concentrated water;
And a calculation step of calculating the concentration of the substance to be analyzed in the test water based on the analysis result of the analysis step.   The continuous monitoring method according to claim 1, wherein in the returning step, the concentrated water is returned so that the membrane surface flow velocity of the reverse osmosis membrane in the concentration step is 25 to 600 m / Hr.   3. The method according to claim 1, further comprising a pH adjustment step of adjusting the pH of the water subjected to the reverse osmosis membrane separation treatment to be in a range of 3.0 to 6.95 prior to the concentration step. Continuous monitoring method of sample water.   4. The sample water according to claim 1, wherein the sample water is ultrapure water having a metal ion concentration of each metal of 1 ng / L or less, and the analysis target substance is a metal ion. Continuous monitoring method of sample water. In a device that continuously monitors the concentration of the analyte in the sample water,
A reverse osmosis membrane separation means for separating the test water into a concentrated water in which the analyte is concentrated and a permeated water in which the concentration of the analyte is reduced by subjecting the test water to reverse osmosis membrane separation;
A return means for returning a part of the concentrated water to the upstream side of the reverse osmosis membrane separation means;
An analytical means for measuring the concentration of the analyte in the remaining concentrated water;
And a calculation unit for calculating a concentration of a substance to be analyzed in the test water based on an analysis result of the analysis unit.   The continuous monitoring apparatus according to claim 5, wherein in the returning means, the concentrated water is returned so that a membrane surface flow rate in the reverse osmosis membrane separating means is 25 to 600 m / Hr.   7. A continuous water sample according to claim 5, further comprising pH adjusting means for adjusting the pH of the water introduced into the reverse osmosis membrane separation means to be in the range of 3.0 to 6.95. Monitoring device.   8. The sample water according to claim 5, wherein the sample water is ultrapure water having a metal ion concentration of each metal of 1 ng / L or less, and the analysis target substance is a metal ion. A continuous monitoring device for water sampling.

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