JP2020134434A - Method of evaluating organic substances in ultrapure water, and organic substance identification method in ultrapure water production system - Google Patents

Abstract

To provide a method of evaluating organic substances in ultrapure water of an ultrapure water production system and a method of identifying a causative substance and a place of occurrence in membrane fouling at outlets of the system.SOLUTION: A method of evaluating organic substances includes: a first step (sampling step A) of sampling ultrapure water of an ultrapure water production system; a second step (adhesion step B) of passing the sampled ultrapure water through a porous body and causing organic substances in the ultrapure water to be absorbed onto the porous body; a third step (eluting step C) of eluting the organic substances from the porous body in which the organic substances are concentrated to obtain an eluate; a fourth step (measurement step D) of measuring the eluate by fluorography; and a fifth step (evaluation step E) of evaluating the organic substances in the ultrapure water on the basis of the measurement in the fourth step. Identifying a location of membrane fouling is identifying, by fluorography, a location where the same fluorescence peaks occur by comparing the fluorescence peaks of the organic substances on the filtration membrane in which membrane fouling occurs with the fluorescence peaks obtained by the above method from the outlet water of each device of the production system.SELECTED DRAWING: Figure 1

Description

The present invention relates to an organic substance evaluation method in ultrapure water for evaluating organic substances contained in ultrapure water in an ultrapure water production system. The present invention also relates to a method for identifying organic substances in an ultrapure water production system.

High-quality ultrapure water is required for cleaning processes for manufacturing liquid crystals, semiconductors, and electronic components. As an ultrapure water production system, in order to meet this demand, a pretreatment, a primary pure water production system, a secondary ultrapure water production system, and the like are known as a unit.

An ultrafiltration membrane (UF membrane) is often placed at the outlet of the ultrapure water production system, but a very small amount of organic matter remains even in the ultrapure water that contains almost no impurities, and this very small amount Organic matter can result in blockage of the exit UF membrane, so-called membrane fouling. At the stage when this membrane fouling occurs, the trace amount of organic matter is due to elution from functional materials and constituent members such as the ion exchange resin and membrane material used, and organic matter of biological origin existing in the system. Can be predicted.

As an analytical method for identifying a membrane fouling substance, a method of extracting an occluded component from an actually occluded membrane with a chemical and a method of directly measuring a membrane surface deposit are known.

For example, in Patent Document 1, it is a method of analyzing the contaminated state of the separation membrane used for filtering the water to be filtered, and the separated membrane after filtration is subjected to either fluorescence spectroscopy or near-infrared spectroscopy or We are proposing a method for measuring using both.

Japanese Unexamined Patent Publication No. 2016-107235

Patent Document 1 employs a method of directly evaluating the membrane surface because it takes time and effort to extract the blocked matter component from the closed membrane by a chemical. When the organic matter concentration is on the order of ppm, it can be easily measured by directly observing the film surface or analyzing the sample water.
However, in the ultrapure water production system, before the membrane fouling occurs, the concentration of organic substances in the ultrapure water is about extremely low (0.Xppb to several ppb). It is not possible to grasp the cause, and it is difficult to identify the cause.

Further, it is very difficult to evaluate the organic matter in the ultrapure water having such an extremely low concentration even if the ultrapure water is directly analyzed. Therefore, when evaluating organic substances in a sample containing only a very small amount of organic substances such as ultrapure water, an operation by concentration is indispensable.

However, even if it is said to be concentrated, it is difficult to find out the exact cause because the organic matter of biological origin is denatured by heat concentration. In addition, heat concentration requires a large amount of ultra-pure water to be concentrated, resulting in a large cost.

Therefore, an object of the present invention is to provide a method for evaluating an organic substance at low cost without denaturing the organic substance in ultrapure water. Another object of the present invention is to provide a method for identifying where a causative substance of membrane fouling is generated in an ultrapure water production system.

The present inventor can concentrate the organic matter in ultrapure water on a porous body and analyze it in the state of the eluate in which it is eluted by the fluorescence fluorescence method, so that the organic matter can be specified inexpensively without being denatured. We found what we could do and came to complete the present invention.

That is, in the present invention, the first step of sampling ultrapure water in an ultrapure water production system and the sampled ultrapure water are passed through a porous body to allow organic substances in the ultrapure water to be made porous. The second step of adhering to the body, the third step of eluting the organic substance from the porous body to which the organic substance is attached to obtain an eluent, the fourth step of measuring the eluate by the fluorescence photometric method, and the above. The present invention relates to an evaluation method characterized by having a fifth step of evaluating organic substances in the ultrapure water based on the measurement in the fourth step.

Further, the present invention includes a first step of sampling ultrapure water at each outlet of a plurality of devices in front of a filtration membrane provided at the outlet of an ultrapure water production system.
The second step of passing the sampled ultrapure water through the porous body and adhering the organic matter in the ultrapure water onto the porous body.
The third step of eluting the organic matter adhering to each porous body to obtain an eluate, and
The fourth step of eluting the organic matter adhering to the filtration membrane to obtain a control eluate, and
Each eluate obtained in the third step and a control eluate obtained in the fourth step are measured by a fluorescence intensity method in a fifth step.
The fluorescence peak appearing in the control eluate and the fluorescence peak appearing in each of the eluents obtained from the measurement result of the fifth step are compared, and the organic substance identified by the fluorescence peak appearing in the control eluate is contained. The sixth step of identifying the ultrapure water and
The present invention relates to a method for identifying an organic substance in an ultrapure water production system, which comprises the above.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for evaluating an organic substance by concentrating it at low cost without denaturing the organic substance in ultrapure water. Further, the present invention can provide a method for identifying where in the ultrapure water production system the causative substance of membrane fouling is generated.

It is a flow figure explaining the process of the organic matter evaluation method of this invention. It is the schematic explaining the structure of the ultrapure water production system and the sampling place. It is a flow figure explaining the process of the method of identifying the occurrence place of the membrane fouling of this invention. The fluorescence three-dimensional spectrum of the eluate eluted by IPA from the closed UF membrane (A) and the new UF membrane (B) is shown. The difference spectrum which subtracted FIG. 4 (B) from FIG. 4 (A) is shown. The fluorescence three-dimensional spectrum of ultrapure water collected from a pure water tank is shown.

As shown in the flow chart of FIG. 1, the method according to the present invention involves a sampling step A for sampling ultrapure water in an ultrapure water production system and passing the sampled ultrapure water through a porous body. Adhesion step B in which the organic substance in the ultrapure water is adhered onto the porous body, elution step C in which the organic substance is eluted from the porous body to which the organic substance is adhered to obtain an eluent, and the eluent is fluorescent. It has a measurement step D for measuring by the photometric method and an evaluation step E for evaluating organic substances in ultrapure water based on the measurement in the measurement step D.
In the present invention, water from which impurities are highly removed and having a specific resistance of 10 MΩ · cm or more is defined as ultrapure water.

First, a sampling step A for sampling ultrapure water is performed. As will be described later, when identifying the causative substance of membrane fouling, the outlet water of each device of the ultrapure water production system in front of the filtration membrane in which membrane fouling is generated is sampled. ..

Next, the adhesion step B is carried out in which the sampled ultrapure water is passed through the porous body and the organic substances in the ultrapure water are adhered onto the porous body.

Generally, an ultrafiltration membrane (UF membrane) is used as the filtration membrane at the outlet of the ultrapure water production system. Since the UF membrane is a porous membrane having a molecular weight cut off of several thousand, the molecular weight of the organic substance captured therein is several thousand or more. That is, it can be said that the molecular weight of the organic substance that causes the membrane fouling is 1000 or more. Therefore, for the concentration of a very small amount of organic matter in ultrapure water, a porous body having the same molecular weight cut-off or a porous body having adsorption performance is used, and the organic substance is adhered onto the porous body and concentrated. To do.

Here, the adhesion step B is carried out until the concentration that can be analyzed by the analyzer, that is, the organic matter in the ppb order ultrapure water is concentrated to the ppm order.

As the porous body to be used, an ultrafiltration membrane (UF membrane) used as a filtration membrane, a monolith resin, or a synthetic adsorbent can be used.

In the attachment step B, it is preferable to use a concentration kit in which the porous body is arranged on a tubular member having a predetermined diameter.
For example, when a UF membrane is used, a commercially available pencil-type module containing the UF membrane can be used as a concentration kit. For monolith resin and synthetic adsorbent, connect a tube to the connection pipe of the ultrapure water production system, and attach a connector to the tube to a column filled with monolith resin or synthetic adsorbent to form a concentration kit, and configure the concentration kit, flow rate and time. Can be adjusted to carry out the adhesion step B.

As the UF membrane for the concentration kit, one having a molecular weight cut-off equal to or slightly lower than that used for the filtration membrane provided at the outlet of the ultrapure water production system can be used. In order to accelerate the concentration, it is preferable to optimize the filtration area and the amount of water flow, and concentrate faster than the organic matter trapping by the filtration membrane at the outlet.

The monolith resin is an ion exchange group introduced into the skeleton of the monolithic organic porous body, and the monolith anion exchanger is introduced so that the anion exchange groups are uniformly distributed in the skeleton of the monolithic organic porous body. The porous body and the monolithic cation exchanger are the porous bodies in which the cation exchange groups are introduced so as to be uniformly distributed in the skeleton of the monolithic organic porous body. The monolithic organic porous body is a porous body in which the skeleton is formed of an organic polymer and has a large number of communication holes serving as flow paths for the reaction solution between the skeletons.

The structure of the monolith anion exchanger is an organic porous body consisting of a continuous skeleton phase and a continuous pore phase, the thickness of the continuous skeleton is 1 to 100 μm, the average diameter of the continuous pores is 1 to 1000 μm, and the total pore volume. Is 0.5 to 50 mL / g.

The thickness of the continuous skeleton of the monolith anion exchanger in the dry state is 1 to 100 μm. If the thickness of the continuous skeleton of the monolith anion exchanger is less than 1 μm, the anion exchange capacity per volume decreases, and the mechanical strength decreases, especially when the monolith anion is passed at a high flow velocity. It is not preferable because the exchange body is greatly deformed. Further, the contact efficiency between the reaction solution and the monolith anion exchanger is lowered, and the catalytic activity is lowered, which is not preferable. On the other hand, if the thickness of the continuous skeleton of the monolith anion exchanger exceeds 100 μm, the skeleton becomes too thick, it takes time to diffuse the substrate, and the catalytic activity decreases, which is not preferable. The thickness of the continuous skeleton is determined by SEM observation.

The average diameter of the continuous pores of the monolith anion exchanger in the dry state is 1 to 1000 μm. If the average diameter of the continuous pores of the monolith anion exchanger is less than 1 μm, the pressure loss during water flow increases, which is not preferable. On the other hand, if the average diameter of the continuous pores of the monolith anion exchanger exceeds 1000 μm, the contact between the liquid to be treated and the monolith anion exchanger becomes insufficient and the removal performance deteriorates, which is not preferable. The average diameter of the continuous pores of the monolith anion exchanger in the dry state is measured by the mercury intrusion method and refers to the maximum value of the pore distribution curve obtained by the mercury intrusion method.

The total pore volume of the monolith anion exchanger in the dry state is 0.5 to 50 mL / g. If the total pore volume of the monolith anion exchanger is less than 0.5 mL / g, the contact efficiency of the liquid to be treated becomes low, which is not preferable, and further, the amount of permeated liquid per unit cross section becomes small, and the treatment amount Is not preferable because it reduces. On the other hand, if the total pore volume of the monolith anion exchanger exceeds 50 mL / g, the anion exchange capacity per volume decreases and the removal performance deteriorates, which is not preferable. Further, the mechanical strength is lowered, and the monolith anion exchanger is significantly deformed especially when the liquid is passed at a high speed, and the pressure loss at the time of passing the liquid rises sharply, which is not preferable. The total pore volume is measured by the mercury intrusion method.

Examples of the structure of such a monolith anion exchanger include the open cell structure disclosed in JP-A-2002-306976 and JP-A-2009-62512, and JP-A-2009-67982. Examples thereof include a co-continuous structure, a particle-aggregated structure disclosed in JP-A-2009-7550, and a particle-composite-type structure disclosed in JP-A-2009-108294.

The synthetic adsorbent is a spherical crosslinked polymer having a porous macro reticular structure (MR structure), and is mainly styrene-based, acrylic-based, or phenol-based crosslinked copolymer particles. As a synthetic adsorbent used in the present invention. Those having a specific surface area of 150 to 1000 m ² / g and a pore volume of 0.3 to 2.0 cm ² / g are preferable. Such synthetic adsorbents are synthetic adsorbents sold by the applicant, such as Amberlite® XAD2000, XAD4, FPX66, XAD1180N, XAD7HP, XAD-2, XAD761 (all of which are trade names and are Amber). Light (registered trademark) XAD (registered trademark) series) and the like can be used.

Next, an elution step C is carried out in which an organic substance adhering to the porous body is eluted to obtain an eluate. A suitable solvent is used to elute the organic matter from the porous material. As the solvent that can be used, a solvent that is compatible with water and has little effect on organic substances and porous materials is selected. Specifically, it is appropriately selected from alcohols such as isopropyl alcohol (IPA), an aqueous acid solution such as dilute nitric acid, tetramethylammonium hydroxide (TMAH) and the like. In particular, IPA having excellent elution of various organic substances can be preferably used. Although a part of the organic matter constituting the porous body may be eluted, it can be distinguished from the target attached organic matter (hereinafter, also referred to as a target organic matter) by having a different fluorescence wavelength.

The amount of the solvent used is such that the organic matter in the obtained eluate is on the order of ppm, for example, when about 5000 L of ultrapure water is passed, elution can be carried out with 100 ml of IPA. Further, the eluate may be further concentrated as known as long as it does not affect the target organic matter.

Subsequently, step D of measuring the obtained eluate by the fluorescence intensity method is carried out. The fluorometric method is a method for identifying an organic substance by putting a target liquid in a cell and acquiring a three-dimensional fluorescence spectrum. LC-OCD (Dissolved Organic Carbon Separation Measuring Device), which is known as a method for identifying organic substances, cannot measure a target organic substance due to the influence of the organic solvent when an organic solvent is introduced. Further, FT-IR has low sensitivity, and it is necessary to further increase the concentration rate, which is not practical. On the other hand, in the fluorometric method, it is possible to identify the target organic substance by eliminating the influence of the solvent on the order of ppm. In particular, in the fluorescence intensity method, organic substances can be identified by the position of the fluorescence peak (Reference: Environment.sci.Technol.2003,37,5701-5710 Chen et al.). For example, it is said that by-products of microorganisms are strongly detected at excitation wavelengths of 250 nm to 340 nm and fluorescence wavelengths of 300 nm to 380 nm, and aromatic proteins are strongly detected at excitation wavelengths of 200 nm to 250 nm and fluorescence wavelengths of 280 nm to 380 nm. In the fluorometric method, an organic substance having a π bond such as a double bond or a benzene ring emits fluorescence, but an inorganic compound or an organic substance having no π bond such as IPA does not generate fluorescence. Therefore, the target organic matter can be identified without being affected by the solvent. Finally, the evaluation step E for evaluating the organic matter in the ultrapure water is carried out based on the measurement result of the step D as described above. As described above, since the ultrapure water is concentrated without heating, the organic substance can be evaluated inexpensively without denaturing the organic substance.

Next, a method for identifying the cause of contamination such as membrane fouling of the filtration membrane provided at the outlet of the ultrapure water production system will be described.
FIG. 2 shows an arrangement example of an ultrapure water production system to which the present invention is applied, and mainly shows a secondary ultrapure water production system. The necessary equipment is arranged between the pure water tank 11 in which the pure water obtained in the primary pure water production system is stored and the UF membrane 15 at the outlet of the ultrapure water production system. In this example, the pump 12, the UV device 13, and the resin tower 14 are arranged, but the present invention is not limited to this. Further, FIG. 3 shows a flow chart illustrating a method for specifying the present embodiment. Hereinafter, the method of the present embodiment will be described with reference to FIGS. 2 and 3.

Concentration kit 21A for adhering organic substances in ultrapure water to the porous body in the front stage of the UF membrane 15 and in the rear stage of each device in order to identify the source of the causative substance of the clogging in the UF membrane 15. ~ 21D is installed. Using the concentration kits 21A to 21D, the sampling step A'for sampling the ultrapure water at the outlets of the plurality of devices in front of the filtration membrane and the sampled ultrapure water are passed through the porous body, respectively. The adhesion step B'for adhering the organic matter in the ultrapure water onto the porous body is carried out. The elution step C'is carried out by eluting the attached organic substances from each concentration kit to obtain eluates A to D. Further, since the organic substance causing the membrane fouling is also adsorbed on the UF membrane 15, the elution step C ″ is carried out to obtain the eluate E (control eluate) by eluting from the UF membrane 15 as well. A measurement step D'for measuring the eluate E and the eluates A to D by the fluorescence intensity method is carried out. The fluorescence peak appearing in the eluate E in the measurement step D'is compared with the fluorescence peak appearing in the eluates A to D, and the ultrapure water at the outlet of the apparatus containing the organic substance identified by the fluorescence peak appearing in the eluate E is compared. Perform comparison / identification step E'to identify water. That is, the comparison / identification step E'identifies which device causes the organic substance identified by the fluorescence peak appearing in the eluate E by comparing the fluorescence peaks. From the above, it is possible to identify the cause of membrane fouling (causative substance and its occurrence location).

The sampling step A'and the adhesion step B'are carried out on-site in each concentration kit, and the elution steps C'and C'and the measurement step D'are performed after the concentration kit is removed from the water treatment system. Backwash the concentration kit, collect the porous body in the field or in a laboratory, immerse it in a solvent to obtain an eluate, and analyze the eluate with a fluorometer installed in the laboratory. Just do it.

In addition, when membrane fouling occurs, the fouling substance may be deposited on the bottom of the UF membrane installation tank. Therefore, the water at the bottom of the tank may be sampled and used as it is for analysis by the fluorescence intensity method without being concentrated.

In this way, by identifying the causative substance of membrane fouling and identifying the location of occurrence, the components of the device can be changed to a material that does not easily cause membrane fouling, or the causative substance can be separately washed or sterilized. It can be removed and microorganisms can be removed. As a result, the occurrence of membrane fouling can be suppressed.

Hereinafter, the present invention will be specifically described with reference to Examples.
FIG. 4 shows a three-dimensional fluorescence spectrum of the eluate eluted by IPA from the closed UF membrane (A) and the new UF membrane (B).
As the occluded UF membrane, a new UF membrane in which water was passed at 4 m ³ / hr for about 120 days was used. The organic matter adhering to the occluded UF membrane was eluted with about 10 L of IPA to obtain an eluate, and the eluate was further diluted 5-fold with IPA and measured by the fluorescence fluorescence method. An eluate was obtained for the new UF membrane by the same operation.
FIG. 5 shows a difference spectrum obtained by subtracting FIG. 4 (B) from FIG. 4 (A). That is, the causative substance of the membrane fouling is shown in the spectrum shown in FIG. According to FIG. 5, soluble microbial by-products are detected at an excitation wavelength of 250 nm to 340 nm and a fluorescence wavelength of 300 nm to 380 nm, and a strong fluorescence peak of an aromatic protein is detected at an excitation wavelength of 200 nm to 250 nm and a fluorescence wavelength of 280 nm to 380 nm.

FIG. 6 shows a three-dimensional fluorescence spectrum of the outlet water of the pure water tank (here, the water at the bottom of the pure water tank is collected). In FIG. 6, soluble microbial by-products are detected at excitation wavelengths of 250 nm to 340 nm and fluorescence wavelengths of 300 nm to 380 nm, and strong fluorescence peaks of aromatic proteins are detected at excitation wavelengths of 200 nm to 250 nm and fluorescence wavelengths of 280 nm to 380 nm.

It can be analyzed from FIG. 5 that the organic substances causing the blockage of the UF membrane are soluble microbial by-products and aromatic proteins, and that they are generated in the pure water tank according to FIG. It was also confirmed that soluble microbial by-products and aromatic organic substances can be identified as trace amounts of organic substances in ultrapure water.

11 Pure water tank 12 Pump 13 UV device 14 Resin tower 15 Outlet filtration membrane (UF membrane)
21A-21D Concentration Kit

Claims (8)

The first process of sampling ultrapure water in an ultrapure water production system,
The second step of passing the sampled ultrapure water through the porous body and adhering the organic matter in the ultrapure water onto the porous body.
The third step of eluting the organic substance adhering to the porous body to obtain an eluate, and
The fourth step of measuring the eluate by the fluorescence intensity method, and
A method for evaluating an organic substance in ultrapure water, which comprises a fifth step of evaluating the organic substance in the ultrapure water based on the measurement in the fourth step. The first step is to sample the ultrapure water in front of the filtration membrane provided at the outlet of the ultrapure water production system.
The method for evaluating an organic substance in ultrapure water according to claim 1, wherein the porous body is one selected from a filtration membrane having a molecular weight cut-off equal to or less than that of the filtration membrane, a monolith resin, and a synthetic adsorbent. .. The method for evaluating an organic substance in ultrapure water according to claim 1 or 2, wherein the solvent for eluting the organic substance in the third step is one selected from alcohols, an acid aqueous solution, and an alkaline aqueous solution. The method for evaluating an organic substance in ultrapure water according to any one of claims 1 to 3, wherein the organic substance has a fluorescence intensity of an excitation wavelength of 200 nm to 340 nm and a fluorescence wavelength of 280 nm to 380 nm. The first step of sampling the ultrapure water at each outlet of a plurality of devices in front of the filtration membrane provided at the outlet of the ultrapure water production system, and
The second step of passing the sampled ultrapure water through the porous body and adhering the organic matter in the ultrapure water onto the porous body.
The third step of eluting the organic matter adhering to each porous body to obtain an eluate, and
The fourth step of eluting the organic matter adhering to the filtration membrane to obtain a control eluate, and
Each eluate obtained in the third step and a control eluate obtained in the fourth step are measured by a fluorescence intensity method in a fifth step.
The fluorescence peak appearing in the control eluate and the fluorescence peak appearing in each of the eluents obtained from the measurement result of the fifth step are compared, and the organic substance identified by the fluorescence peak appearing in the control eluate is contained. A method for identifying an organic substance in an ultrapure water production system, which comprises a sixth step of identifying the ultrapure water. The organic substance identification in the ultrapure water production system according to claim 5, wherein the porous body is one selected from a filtration membrane having a molecular weight cut-off equal to or less than that of the filtration membrane, a monolith resin, and a synthetic adsorbent. Method. The ultrapure water production according to claim 5 or 6, wherein the solvent for eluting the organic substance in the third step and the fourth step is one selected from alcohols, an acid aqueous solution, and an alkaline aqueous solution. How to identify organic matter in the system. The method for identifying an organic substance in an ultrapure water production system according to any one of claims 5 to 7, wherein the organic substance has a fluorescence intensity of an excitation wavelength of 200 nm to 340 nm and a fluorescence wavelength of 280 nm to 380 nm.