Water treatment system, ion exchange device and measurement method

Abstract

To perform high-accuracy management of a metal content of an ion exchange resin.SOLUTION: There is provided a water treatment system including a non-regenerative ion exchange device 105 filled with an ion exchange resin whose metal content satisfies a predetermined standard, wherein the metal content of the ion exchange resin is a value obtained on the basis of metal concentration of an analytical sample which obtained by putting a mixture liquid obtained by adding an acid of specific concentration to the ion exchange resin into a container in which a metal elution amount eluted from an inner wall into the acid when the acid of predetermined concentration is put and analysis is performed using a microwave decomposition method, and decomposing the ion exchange resin by using the microwave decomposition method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water treatment system, an ion exchange device, and a measurement method. [Background technology]

[0002] In the manufacturing process of semiconductor devices and liquid crystal devices, ultrapure water from which impurities have been highly removed is used for various purposes such as cleaning processes. Ultrapure water is generally produced by sequentially treating raw water (river water, groundwater, industrial water, etc.) in a pretreatment system, a primary pure water system, and a secondary pure water system (subsystem). Some of the primary pure water systems and subsystems include an ion exchange device filled with ion exchange resin inside. In particular, in the subsystem, a non-regenerative ion exchange device (cartridge polisher) filled with a mixed bed of highly purified cation exchange resin and anion exchange resin is preferably used to meet the strict water quality requirements for ultrapure water (e.g., metal concentration at the pg / L level). If ion components such as metal ions leak from such a non-regenerative ion exchange device into the treated water, the water quality of the ultrapure water will not meet the required level. For this reason, a method has been proposed for managing the treated water quality of a non-regenerative ion exchange device by using an anion exchange resin with a metal elution amount below a threshold value as the anion exchange resin to be filled into the non-regenerative ion exchange device (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5499433 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the amount of metal (metal concentration) eluted from anion exchange resin used in a non-regenerative ion exchange device into an acid solution is analyzed by shaking with acid (putting anion exchange resin in a container, adding an acid solution to it and shaking it). However, among the metals adsorbed to the ion exchange resin, there is a possibility that some metals are adsorbed to the ion exchange resin by ion exchange, for example, by coordinate bonds if it is a metal element, or by hydrophobic bonds or intermolecular forces if it is a substance containing organic matter. These metals are difficult to elute from the ion exchange resin even when contacted with acid, and are difficult to elute from the anion exchange resin into the acid solution by shaking with acid. Therefore, there is a problem that such metals may affect the quality of the treated water (for example, metal concentration at the pg / L level) of the non-regenerative ion exchange device. For example, if a part of the reagent (sodium hydroxide) used in the regeneration treatment of the anion exchange resin remains on the anion exchange resin, the metal ions derived from the reagent are not adsorbed to the anion exchange resin by ion exchange. Therefore, the concentration of metal ions contained in the treated water when ultrapure water is passed through the anion exchange resin may be higher than the amount of metal eluted in the acid solution. In other words, the behavior of the amount of metal elution from the anion exchange resin treated water (especially when the metal concentration is at the pg / L level) cannot be tracked by simply measuring the amount of metal adsorbed by the ion exchange reaction. This causes a problem in that it is difficult to control the quality of the treated water from the ion exchange device with high accuracy.

[0005] An object of the present invention is to provide a water treatment system capable of controlling the quality of treated water from an ion exchange device with high precision, an ion exchange device, and a method for measuring the amount of metal contained in an ion exchange resin for use in producing ultrapure water. [Means for solving the problem]

[0006] The water treatment system of the present invention comprises: The present invention provides an ion exchange apparatus filled with an ion exchange resin having a metal content that satisfies a predetermined standard, The amount of metal contained in the ion exchange resin is a value obtained based on the metal concentration of an analytical sample obtained by adding an acid of a specific concentration to the ion exchange resin, placing the resulting mixed solution in a container in which an amount of metal eluted from the inner wall into the acid is equal to or less than a threshold value when a predetermined concentration of acid is added and the mixed solution is decomposed using a microwave decomposition method, and the ion exchange resin is decomposed using a microwave decomposition method.

[0007] The ion exchange apparatus of the present invention further comprises: The ion exchange resin is filled with an ion exchange resin whose amount of metal contained satisfies a predetermined standard, and the amount of metal contained in the ion exchange resin is a value obtained based on the metal concentration of an analytical sample obtained by adding an acid of a specific concentration to the ion exchange resin, placing the resulting mixed liquid in a container in which the amount of metal eluted from the inner wall into the acid is equal to or less than a threshold value when the ion exchange resin is decomposed using a microwave decomposition method with an acid of a specific concentration.

[0008] The measurement method of the present invention further comprises the steps of: A method for measuring the amount of metal contained in an ion exchange resin filled in an ion exchange device, comprising the steps of: A mixed solution obtained by adding an acid of a specific concentration to the ion exchange resin is placed in a container in which the amount of metal eluted from the inner wall into the acid when a predetermined concentration of acid is added and decomposition is performed using a microwave decomposition method is equal to or less than a threshold value, and the ion exchange resin is decomposed using a microwave decomposition method; A value obtained based on the metal concentration of the analytical sample obtained after the decomposition is taken as the amount of contained metal. Effect of the Invention

[0009] In the present invention, the quality of treated water from an ion exchange device can be controlled with high precision. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing an embodiment of an ultrapure water producing system of the present invention. [Diagram 2]FIG. 1 shows an example of a container used for measurement and the measured values ​​of the amount of elution of each element depending on the cleaning method thereof. [Diagram 3] 1 is a graph showing an example of the relationship between the measured amount of sodium content and the quality of treated water from a CP. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The microwave decomposition method is one method for preparing samples (hereinafter referred to as analytical samples) used in analyzing ion exchange resins. In the microwave decomposition method, a solution containing a mineral acid is first added to an ion exchange resin, and the resulting mixture is placed in a sealed container. The ion exchange resin is completely decomposed by irradiating the sample in the sealed container with microwaves to prepare an analytical sample. This sample solution is then analyzed using an analytical device such as an inductively coupled plasma mass spectrometry (ICP-MS) to quantify the amount of all metals contained in the ion exchange resin.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the amount of eluted metal eluted from an ion exchange resin is defined as the amount of metal eluted in acid, measured using a conventional hydrochloric acid elution method or a hydrochloric acid shaking method. The amount of contained metal is defined as the amount of metal quantified using a microwave decomposition method. The metal concentration in treated water is defined as the concentration of metal contained in the treated water of a non-regenerative ion exchange device.

[0013] FIG. 1 is a diagram showing an embodiment of an ultrapure water production system of the present invention. As shown in FIG. 1, the ultrapure water production system 100 in this embodiment has a plurality of water treatment devices, including a water tank 101, a pump 102, a heat exchanger (HEX) 103, an ultraviolet oxidizer (UVox) 104, a non-regenerative ion exchanger (CP) 105 which is an ion exchanger, a degassing membrane device (MD) 106, and an ultrafiltration membrane device (UF) 107. The ultrapure water production system 100 may be equipped with other water treatment devices. Also, as shown in FIG. 1, the ultrapure water production system 100 in this embodiment includes a main pipe 109, a circulation pipe 108, and a branch pipe 110. Note that the present invention is applicable not only to ultrapure water production systems, but also to water treatment systems such as pure water production systems.

[0014] The water tank 101 is a tank in which primary pure water is stored. The water tank 101 also stores primary pure water supplied from the outside and circulating water (return water) in which a part of ultrapure water supplied from the ultrafiltration membrane device 107 through the main pipe 109 is circulated through the circulation pipe 108. The pump 102 pumps up the primary pure water and circulating water stored in the water tank 101 and supplies them to the heat exchanger 103. The primary pure water and circulating water pumped up by the pump 102 are sequentially processed in the heat exchanger 103, the ultraviolet oxidation device 104, the non-regenerative ion exchange device 105, the degassing membrane device 106, and the ultrafiltration membrane device 107, and are sent to the use devices 200-1 to 200-3 through the main pipe 109, the circulation pipe 108, and the main pipe 109 and the branch pipe 110. Branch pipes 110 are pipes that branch off from main pipe 109 and connect to each of usage devices 200-1 to 200-3. Therefore, the number of branch pipes 110 is at least the number of usage devices 200-1 to 200-3.

[0015] The use devices 200-1 to 200-3 are devices that use ultrapure water supplied from the ultrapure water production system 100. The use devices 200-1 to 200-3 may be devices that use ultrapure water to clean parts of semiconductor devices or liquid crystal displays. The use devices 200-1 to 200-3 may also be devices that use ultrapure water to clean medical products. The use devices 200-1 to 200-3 may also be devices that use ultrapure water in a steam generator of a power generation turbine.

[0016] The treatments in the heat exchanger 103, the ultraviolet oxidation device 104, the degassing membrane device 106 and the ultrafiltration membrane device 107 may be the same as the general water treatments carried out in these devices.

[0017] The non-regenerative ion exchange device 105 is disposed at the last stage of the ultrapure water production system 100 as a water treatment device for removing metal ion components from the primary pure water stored in the water tank 101 and the water to be treated, which is the circulating water. The ion exchange resin filled in the non-regenerative ion exchange device 105 is a mixture of a cation exchange resin and an anion exchange resin. The sodium content, which is the metal content of the cation exchange resin, is 100 μg-Na / L-CER, more preferably 50 μg-Na / L-CER, and even more preferably 10 μg-Na / L-CER or less. The sodium content, which is the metal content of the anion exchange resin, is 50 μg-Na / L-AER, more preferably 30 μg-Na / L-AER, and even more preferably 10 μg-Na / L-AER or less. The mixed-bed ion exchange resin filled in the non-regenerative ion exchange device 105 preferably has a sodium content, which is the metal content, of 50 μg-Na / LR or less. Furthermore, the metal contained in the ion exchange resin is not limited to sodium, and is not particularly limited as long as a correlation can be obtained between the amount of contained metal obtained using this method and the quality of treated water.

[0018] The amount of metal contained in the ion exchange resin filled in the non-regenerative ion exchange device 105 is measured using the following method. First, the following is selected as a container used to measure the amount of metal contained in the ion exchange resin. An acid with the same concentration and amount as that used to decompose the ion exchange resin is added to the container, and microwaves are irradiated under the same conditions as when the ion exchange resin was decomposed, to prepare an analysis sample. When the prepared analysis sample is analyzed using an analysis device such as an inductively coupled plasma mass spectrometry (ICP-MS), it is preferable that the concentration of each element constituting the container contained in the analysis sample is 100 ng / L or less. A container that satisfies these conditions is selected.

[0019] FIG. 2 is a diagram showing an example of the measured values ​​of the elution amount of each element according to the container used for the measurement and the cleaning method thereof. As shown in FIG. 2, the elution amount of each element (Na, Mg, Al, K, Ca, Fe, Zn, Pb) is measured after cleaning each of a plurality of containers using various cleaning methods. The measured elution amount of each element may be different from each other, for example, even if the containers are made of the same material, due to different cleaning methods. Examples of containers include fluororesins such as PTFE (polytetrafluoroethylene) and quartz. From these measured values, a container and a cleaning method that satisfy a predetermined condition are selected. The selected container is cleaned using the selected cleaning method, and the container is used to measure the amount of metal contained in the ion exchange resin filled in the non-regenerative ion exchange device. Furthermore, the containers may be selected based on the elution amount of each element due to multiple uses. In this case, a container that has less change in the elution amount of each element even when used multiple times is selected.

[0020] A mixed solution in which a predetermined concentration of acid is added to an ion exchange resin serving as a target sample is placed in a container selected using the above-mentioned method, the amount of metal eluted from the inner wall into the acid being equal to or less than a threshold value. The container containing the mixed solution is irradiated with microwaves to completely decompose the ion exchange resin to prepare an analysis sample. The analysis sample is then analyzed using an analyzer such as an inductively coupled plasma mass spectrometry (ICP-MS) to quantify the amount of all metals contained in the ion exchange resin from the metal concentration contained in the analysis sample. As the decomposition reaction of the ion exchange resin proceeds, the solution containing the mineral acid added to the ion exchange resin is consumed, so that the acid concentration of the analysis sample differs depending on the type and amount of the ion exchange resin. For accurate measurement, it is required to avoid the influence of ionization interference due to differences in acid concentration and physical interference due to differences in viscosity of the analysis sample. Therefore, it is necessary to correct the difference in acid concentration and the difference in viscosity of the analysis sample by making the acid concentration uniform in the process of diluting the analysis sample or adding an internal standard substance to the analysis sample. The acid used in the measurement is, for example, nitric acid. The metal concentration (e.g., ng / L) of the obtained analytical sample is converted into a unit to calculate (obtain) the amount of metal contained in the ion exchange resin (amount of sodium contained μg / LR). Note that the present invention is also applicable to the case where only one of the anion exchange resin and the cation exchange resin is packed alone in the non-regenerative ion exchange device 105 (single bed).

[0021] An ion exchange resin whose value measured by a microwave decomposition method satisfies a predetermined condition is packed into a non-regenerative ion exchange device 105 .

[0022] FIG. 3 is a graph showing an example of the relationship between the measured amount of sodium content and the treated water quality of the CP. As shown in FIG. 3, the higher the measured amount of sodium content, the lower the quality of the treated water treated by the CP (deionization device). These relationships change linearly. Therefore, by using an ion exchange resin with a lower measured amount of sodium content, the quality of the treated water treated by the deionization device filled with the ion exchange resin can be made high quality. Furthermore, based on these relationships, the quality of the treated water treated by the deionization device filled with the ion exchange resin can be predicted from the measured amount of sodium content.

[0023] The amount of metal elution measured by the conventional hydrochloric acid elution method or hydrochloric acid immersion is the amount of metal components physically attached to the surface of the ion exchange resin. On the other hand, the metal content measured by the microwave decomposition method used in the present invention is the amount of metal components contained in the ion exchange resin. Therefore, in order to manage the quality of treated water from a non-regenerative ion exchange device with high accuracy (e.g., metal concentration at the pg / L level), the metal content measured by the microwave decomposition method is more suitable for measuring the metal components contained in the ion exchange resin. The difference between the amount of eluted metal measured by the hydrochloric acid elution method or hydrochloric acid shaking method and the amount of contained metal measured by the microwave decomposition method is particularly noticeable in the anion exchange resin that constitutes the ion exchange resin.

[0024] In this way, in the present invention, a mixed solution in which an acid of a predetermined concentration is added to an ion exchange resin is added to a container in which the amount of metal eluted from the inner wall into the acid is equal to or less than a threshold value under immersion in an acid of a predetermined concentration, and the ion exchange resin is decomposed using a microwave decomposition method, and the metal concentration of the analysis sample obtained is measured as the amount of metal contained in the ion exchange resin. The ion exchange resin whose measured value satisfies a predetermined condition is filled into a mixed bed deionization device. Therefore, the treated water quality of the non-regenerative ion exchange device can be controlled with high accuracy (for example, metal concentration at the pg / L level). In addition, the ion exchange resin obtained by this management can also be applied to a system in which a water treatment device equipped with an ion exchange device filled with the ion exchange resin is installed between a subsystem and a use point. As a result, even if the ultrapure water supplied from the subsystem contains a trace amount of impurities due to elution from piping, etc., the ultrapure water from which the impurities have been removed can be supplied to the use point. Note that the above-mentioned prior art documents do not describe metal impurities eluted from a container used for measuring the concentration of the ion exchange resin. In addition, the microwave decomposition method has been disclosed for use with ion exchange resins for the production of pure water and soft water for the power industry, but its use with highly purified ion exchange resins for the production of ultrapure water has not been disclosed. Furthermore, only the evaluation results of single-bed ion exchange resins have been disclosed for the microwave decomposition method, and there is no record of its use with mixed-bed ion exchange resins. Furthermore, the analytical precision of the microwave decomposition method is low (mg / L-ion exchange resin level) to apply it to the field of ultrapure water production. Furthermore, there is no disclosure regarding the amount of metal eluted from a sealed container during decomposition using the microwave decomposition method.

[0025] As described above, in the configuration shown in Fig. 1, the non-regenerative ion exchange device 105 is an ion exchange device (an ion exchange device filled with an ion exchange resin) arranged at the last stage of the ultrapure water production system 100. In a configuration in which ion exchange devices (ion exchange devices filled with an ion exchange resin) are arranged at a stage further downstream of the non-regenerative ion exchange device 105, for example, in a plurality of branch pipes 110, the ion exchange device arranged at the branch pipes 110 becomes the ion exchange device arranged at the last stage of the ultrapure water production system 100. Even in this case, the non-regenerative ion exchange device 105 may be arranged at the position shown in Fig. 1, and the ion exchange resin evaluated using the present method may be filled in the non-regenerative ion exchange device 105. Furthermore, for example, in a configuration in which an ion exchange device (an ion exchange device filled with ion exchange resin inside) is arranged only in the branch pipe 110 connected to the use apparatus 200-1 among the multiple branch pipes 110, further downstream from the non-regenerative ion exchange device 105, the ion exchange device arranged in the branch pipe 110 on the path to the use apparatus 200-1 is the ion exchange device arranged in the final stage of the ultrapure water producing system 100, and the non-regenerative ion exchange device 105 is the ion exchange device arranged in the final stage of the ultrapure water producing system 100 on the path to the use apparatus 200-2, 200-3. [Explanation of symbols]

[0026] 100 Ultrapure Water Production System 101 Aquarium 102 Pump 103 Heat exchanger 104 Ultraviolet Oxidation Device 105 Non-regenerative ion exchange device 106 Degassing membrane device 107 Ultrafiltration Membrane Device 108 Circulation piping 109 Main Pipe 110 Branch piping 200-1~200-3 Equipment used

Claims

1. The present invention provides an ion exchange apparatus filled with an ion exchange resin having a metal content that satisfies a predetermined standard, The amount of metal contained in the ion exchange resin is a value obtained based on the metal concentration of an analytical sample obtained by adding an acid of a specific concentration to the ion exchange resin, placing the resulting mixed solution in a container in which an acid of a predetermined concentration is added and decomposing the ion exchange resin using a microwave decomposition method, the amount of metal eluted from the inner wall into the acid being equal to or less than a threshold value.

2. 2. The water treatment system according to claim 1, The water treatment system has an ion exchange resin having a metal content, ie, a sodium content, of 50 μg-Na / LR or less.

3. The water treatment system according to claim 2, The ion exchange device is filled with a mixture of a cation exchange resin and an anion exchange resin as the ion exchange resin, the sodium content of the cation exchange resin is 100 μg-Na / L-CER, and the sodium content of the anion exchange resin is 50 μg-Na / L-AER or less.

4. The water treatment system according to claim 2, A water treatment system in which the acid concentration of the obtained analytical sample is adjusted to be constant.

5. In the water treatment system according to any one of claims 1 to 4, The ion exchange device is a device for removing metal ion components from the water to be treated that is supplied to the water treatment system, and is disposed at the final stage of the water treatment system.

6. An ion exchange device which is filled with an ion exchange resin having a metal content that satisfies a predetermined standard, and the metal content of the ion exchange resin is a value obtained based on the metal concentration of an analytical sample obtained by adding an acid of a specific concentration to the ion exchange resin, placing the resulting mixed solution in a container in which the amount of metal eluted from the inner wall into the acid is equal to or less than a threshold value when the mixed solution is decomposed using a microwave decomposition method with an acid of a predetermined concentration.

7. A method for measuring the amount of metal contained in an ion exchange resin filled in an ion exchange device, comprising the steps of: A mixed solution obtained by adding an acid of a specific concentration to the ion exchange resin is placed in a container in which the amount of metal eluted from the inner wall into the acid when a predetermined concentration of acid is added and decomposition is performed using a microwave decomposition method is equal to or less than a threshold value, and the ion exchange resin is decomposed using a microwave decomposition method; The amount of metal contained in the analytical sample is determined based on the metal concentration of the analytical sample obtained after the decomposition.

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