JPH0545351A - Method for measuring concentration of dilute ionic solution - Google Patents

Abstract

(57) [Summary] [Objective] To provide a method for measuring the concentration of a stock solution by extremely efficiently adsorbing, collecting and concentrating a stock solution having a low ion concentration in water. [Structure] A dilute ionic solution is filtered through one or more of a cation, an anion, or a porous membrane having chelate exchange functionality, and the ions adsorbed on the porous membrane are desorbed and concentrated with a regenerant, A method for measuring a diluted ion solution concentration, which comprises measuring the ion concentration of an original diluted ion by detecting the ion concentration. [Effect] The dilute solution can be concentrated 1,000 times or more, and the concentration of the stock solution can be specified with an error of 1% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention provides highly efficient supplemental concentration of ions from a dilute ion solution such as ultrapure water.
The present invention relates to a method for measuring the ion concentration in a solution extremely efficiently.

[0002]

2. Description of the Related Art Generally, when measuring the ion concentration in water, if the concentration becomes low below the detection limit of the measuring instrument, concentration operation such as evaporation by a special device in the clean room is required. come. However, the lower the concentration, the more the required concentration ratio must be increased, which complicates the operation and increases the measurement error such as contamination of impurities. It is said that.

When concentration is considered with a cation, anion or ion exchange resin having a chelate exchange function,
It is difficult to adsorb low-concentration ions, and if the regenerant is run until the resin in the column is completely regenerated to desorb the ions, due to the restrictions imposed by the structure of the column, It requires an enormous amount of regenerant liquid and does not require concentration operation.

[0004]

SUMMARY OF THE INVENTION The present invention aims to detect the ion concentration of the original solution extremely efficiently and accurately by concentrating the ion concentration of the low concentration ion solution and measuring the ion concentration. It is intended.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that in a step of concentrating ions in water, a dilute ionic solution is provided with cation, anion or chelate exchange functionality. The present invention has been completed based on the finding that this can be achieved by performing filtration treatment on any one or more of the porous membranes that are provided and desorbing adsorbed ions with a regenerant.

That is, according to the present invention, a dilute ionic solution is filtered through one or more of a cation, an anion, and a porous membrane having chelate exchange functionality, and the ions adsorbed on the porous membrane are regenerated as a regenerating liquid. The method for measuring the concentration of a diluted ionic solution is characterized by measuring the ion concentration of the above-mentioned diluted ionic solution by desorbing and concentrating with, and detecting the ion concentration.

The present invention will be specifically described below. As the material of the membrane used in the present invention, most of the materials currently on the market can be used, for example, cellulose (di or tri) acetate, polysulfone, polyvinylidene fluoride, polyamide, polyethylene, polyolefin such as polypropylene, or A copolymer of a polyolefin and a halogenated olefin, such as an ethylene-tetrafluoroethylene copolymer, may be mentioned. As the structure of the porous membrane, a flat membrane shape (pleats, spiral shape), a tube shape, a hollow fiber shape or the like is used, but a hollow fiber shape is particularly preferable.

The porous membrane used in the present invention is preferably made of polyolefin, a copolymer of polyolefin and a halogenated olefin, polyvinylidene fluoride or polysulfone, and the material of the inner and outer surfaces of the membrane and the surface of pores is It is preferable to use a porous membrane in which at least a part of cations, anions, or a functional group having a chelate exchange function is chemically bound, and the binding of the functional group to the porous membrane is
It may be directly or in the case where a polymer having a functional group is bound.

More preferably, the material of the porous membrane is polyolefin, and the membrane structure has a three-dimensional network structure, and cations, anions, or anions are formed on at least a part or the whole of the inner and outer surfaces of the membrane and the surface of the pores. It is preferable to use a hollow fiber-like porous membrane in which a functional group having a chelate exchange function or a polymer having a functional group is chemically bound.

In the present invention, the ionic species to be concentrated include, for example, alkali metals such as Li, Na and K, Be,
Alkaline earth metals such as Mg, Ca, Fe, Co, Ni,
Transition metals such as Cu, Group IIIb such as B, Al and In, C
Examples thereof include halogens such as l, Br and I, water-soluble organic compounds such as organic carboxylic acids, organic sulfonic acids, acidic dyes and basic dyes.

The water ion concentration measuring device used in the present invention is, for example, an atomic absorption spectrophotometer, a plasma emission spectrophotometer (ICP), a plasma mass spectrometer (ICP-MS), an ion chromatograph analyzer, A spectrophotometer or the like. In the present invention, examples of the functional group having a cation exchange function that binds to the porous membrane include H ⁺ type or metal salt type of sulfonic acid group, carboxylic acid group, and phosphoric acid group. Examples of the functional group having an anion exchange function include quaternary ammonium groups, primary amines, secondary amines, tertiary amines and salts thereof. Examples of the functional group having a chelate exchange function include H ⁺ type such as iminodiacetic acid group and metal salt type.

It is preferable that these functional groups are contained in an amount of 0.1 meq to 5 meq per 1 g of the film. When it is less than this range, the metal ion adsorption capacity of the film is deteriorated, and when it exceeds this range, other properties of the film, for example, mechanical properties are deteriorated. The average pore diameter of the porous membrane is preferably in the range of 0.01 μm to 5 μm. If it is less than this range, the water permeability is not sufficient for practical use, and the time required for concentration becomes enormous, and if it is more than this range, there is a problem in the ion adsorption performance.

Although there are many methods for measuring the average pore size,
The present invention is based on the method described in ASTM F316-70, which is called the normal air flow method, which measures from the air permeation flow rate of a dry membrane and a wet membrane when the air pressure is changed. The porosity of the porous film is preferably in the range of 20% to 80%. Here, the porosity is measured by immersing the membrane in a liquid such as water in advance and then drying it, and measuring the weight change before and after that. When the porosity is outside the above range, it is not preferable in terms of permeation rate and mechanical properties.

The thickness of the porous film is preferably in the range of 10 μm to 5 mm. If it is less than this range, problems occur in the mechanical strength of the membrane, and if it exceeds this range, the water permeability is not practically sufficient. Various pore structures of the porous film can be formed by a molding method. For example, polysulfone can be made into a three-dimensional network structure film by adopting a so-called wet method in which a solvent is used as a mixed solvent and then it is discharged from a nozzle into a hollow fiber shape and molded with a coagulant or the like. In the case of polyolefin, it is possible to form a porous film by so-called stretching method or chemical treatment after electron beam irradiation, that is, so-called etching radiation, but as a pore structure, fingers obtained by the stretching method or etching radiation are used. Rather than a structure-like or through-hole type hole structure, for example, Japanese Patent Publication No. 59-37292 and Japanese Patent Publication No. 40-957.
Those having a three-dimensional network structure formed by the micro phase separation method, the mixing extraction method, or the like disclosed in JP-B No. 47-17460 and JP-B No. 47-17460 are preferable in terms of practical performance. However, the method is not limited to this. In particular, by using the porous membrane having the structure disclosed in JP-A-55-131028, it is possible to achieve excellent adsorption performance that cannot be obtained by the conventional technique.

As a method of introducing a functional group having a cation exchange function into the side chain of the polymer constituting the membrane, for example,
As disclosed in JP-A-3-68425, a method of reacting with sulfuric acid anhydride in a non-reactive solvent or sulfuric acid, or reacting with sulfuric acid anhydride in a gas state is adopted. Alternatively, a method may be used in which after irradiating the porous membrane with ionizing radiation, styrene is grafted and then the sulfonation is performed.

In the case of introducing a carboxylic acid group, for example, a method of irradiating the film with an electron beam or the like in advance and then grafting acrylic acid can be used. As a method of introducing a functional group having an anion group into the side chain of the polymer constituting the membrane, for example, as disclosed in JP-A-3-68425,
After irradiating the porous membrane with ionizing radiation, a method of grafting glycidyl methacrylate to add an organic amine or directly adding an organic amine is used.

As a method of introducing a functional group having a chelate group into the side chain of a polymer constituting a membrane, for example, a method of introducing an iminodiacetic acid group into the side chain of polyethylene, it is disclosed in JP-A-3-94883. As described above, after irradiating the polyethylene film with an electron beam or the like, grafting chloromethylstyrene and then introducing an iminodiacetic acid group, or after irradiating the polyethylene film with an electron beam or the like in advance, graft reaction with glycidyl methacrylate is performed. Then, a method of reacting with iminodiacetic acid is adopted.

In order to introduce the above-mentioned functional group into the side chain of the polymer constituting the porous membrane, it may be introduced before forming into the membrane, but after forming into the membrane, the inside and outside surfaces and pores of the membrane are formed. A method of chemically adding-bonding to at least a part of the surface portion of is preferred. It is desirable that the functional groups are bonded to each surface of the membrane as uniformly as possible, but in some cases it may be better to preferentially bond to the surface of the pores of the membrane.

The amount of the functional group in the present invention is determined by the amount of the porous film 1
It refers to milliequivalents per g, but here, 1 g of film means a value based on the weight of the entire film, for example, the weight obtained by taking out a part of the film surface or a part of the inside. is not. In order to bond the functional group while maintaining the excellent mechanical properties of the film, it is preferable to allow the functional group to exist uniformly and preferentially on the surface of the pores of the film as much as possible. Homogeneity is acceptable. Therefore, the meaning of the film 1g mentioned here indicates a value which is uniformly measured over the entire surface of the film, and does not mean the weight from an extremely microscopic viewpoint.

The role of the porous membrane having cation, anion and chelate groups in the present invention is very important.
That is, when using the above-mentioned porous membrane having a side chain to which a functional group is bound, excellent ion adsorption characteristics of adsorbing even low concentration of ions can be obtained as compared with the case of using an ion exchange resin, and the membrane used. The amount is small, and above all, the amount of regenerant liquid is remarkably small, and ions are completely desorbed. This is to increase the concentration efficiency of the liquid,
This is an extremely significant advantage, and it can be effectively used as a sample concentrator for low ion concentration detectors, which must completely adsorb low-concentration ions, desorb with a small amount of desorption liquid, and concentrate to a high concentration. ..

Further, in the case of a membrane, scale-up is easy, and it can be applied to a small scale such as a concentrator of an ion concentration detector to a plant scale concentrator for industrial use. Furthermore, it is possible to reduce various ion concentrations by introducing these ion adsorption porous membranes into the ultrapure water production system in the semiconductor field by taking advantage of the property of efficiently adsorbing extremely low concentration ions. Therefore, it is possible to obtain higher purity ultrapure water. In particular, introduction of a chelate-type ion exchange membrane is effective for reducing heavy metal ions, which is a problem in semiconductor manufacturing.

The present invention will be described below with reference to examples, but they do not limit the present invention.

[0023]

【Example】

[0024]

[Reference Example] Preparation of Cation Exchange Membrane 22.1 parts by weight of finely divided silicic acid [Nippon Aerosil Co., Ltd., trade name, Aerosil R-972], 55 parts by weight of dibutyl phthalate (DBP), polyethylene resin powder [Asahi Kasei Co., Ltd., trade name, SH-800 grade] 23 parts by weight of the composition were premixed, and then extruded into a hollow fiber having an inner diameter of 2 mm and a thickness of 0.5 mm with a 30 mm twin-screw extruder. DBP was extracted by immersing it in 1,1-trichloroethane for 60 minutes. Caustic soda 4 with a temperature of 60 ℃
After immersing in a 0% aqueous solution for about 20 minutes to extract finely divided silicic acid, it was washed with water and dried [hereinafter referred to as porous membrane (A)].

The obtained porous film was irradiated with γ-rays in an N ₂ atmosphere at 100 KGy, and then styrene (including divinylbenzene) was graft-polymerized in a gas phase at 70%, washed and dried, and then ethylenedichloroethane (EDC). Sulfonated with SO _{3 in} to obtain an average pore diameter of 0.25 μm and a porosity of 62
%, Sulfone group 1.2 meq / g membrane.
Here, the graft ratio of the obtained membrane and the quantification of the sulfone group were as follows. -Definition of graft ratio Graft ratio (%) = [weight of graft-polymerized membrane (g) -weight of unreacted membrane (g)] / weight of unreacted membrane (g) -Quantification of sulfone group A sulfonated porous membrane was used. 1N HClaq. Dip in H
After forming into a mold, it is washed with water, and then 1N CaCl ₂ aq. And release the released HCl to 0.1 N NaOHaq. Was titrated with phenolphthalein as an indicator.

Preparation of Anion Exchange Membrane The above-mentioned porous membrane (A) was used as an untreated membrane having no functional group. The obtained porous film (A) was irradiated with 100 KGy of γ-ray in an N ₂ atmosphere, and then about 100% of glycidyl methacrylate was graft-polymerized in a gas phase, washed and dried, and then HN (CH ₃ ) ₂ was used alone. At 80 ° C. for 24 hours. Then, it was further reacted with ethylene chlorohydrin at 80 ° C. for 4 hours to obtain a porous membrane (B).
The total ion exchange capacity of the obtained anion exchange groups was 0.5.
It was 0 meq / g polymer. The anion exchange capacity is measured by Hiroshi Shimizu “Ion Exchange Resin” Kyoritsu Shuppan Co., Ltd. The measuring method according to 89 was followed. Preparation of Chelate Exchange Membrane The above-mentioned porous membrane (A) was used as an untreated membrane having no functional group. The obtained porous membrane (A) was irradiated with 100 KGy of γ-rays in an N ₂ atmosphere, and about 100% of glycidyl methacrylate was graft-polymerized in the gas phase, washed and dried, and the pH was adjusted to 12 with sodium carbonate. The graft membrane was immersed in a prepared 0.4 mol / l aqueous solution of sodium iminodiacetate and reacted at 80 ° C. for 24 hours to give a chelate having an iminodiacetic acid group of 1.7 mmol (3.4 meq) per 1 g of the membrane. An exchange membrane was obtained. The quantification of iminodiacetic acid groups was calculated by two methods, a gravimetric method and a metal adsorption equilibrium method.

[0027]

Examples 1 to 3 and Comparative Examples 1 to 3 The ion exchange membrane modules shown in Table 1 below are used as Examples 1 to 3, and the ion exchange resin columns shown in Table 2 below are used as Comparative Examples 1 to 3. Then, the concentration of the dilute ionic solution was measured.

[0028]

[Table 1]

[0029]

[Table 2]

The water-permeable liquid structure and water-permeable conditions used are as follows. Water-permeable liquid composition and water-permeable conditions Example 1 and Comparative Example 1 Water-permeable liquid: Composition Fe ion, 100 ppb, 8.0 liters Water permeation rate 10 ml / min Desorption liquid: Composition 2N H ₂ SO ₄ , 5 ml Water permeation rate 1 ml / min Example 2 and Comparative Example 2 Water permeation liquid: composition Cl ion, 100 ppb, 8.0 liters Water permeation rate 10 ml / min Desorption liquid: Composition 1N NaOH, 5 ml Water permeation rate 1 ml / min Example 3 and Comparative Example 3 Water permeation liquid: composition Ni ions, 100 ppb, 8.0 liter Water permeation rate 10 ml / min Desorbent: Composition 2N H ₂ SO ₄ , 5 ml Water permeation rate 1 ml / min The dilute ion solution concentration measuring methods of Examples 1 to 3 and Comparative Examples 1 to 3 are described below, The results are shown in Table 3.

Example 1 and Comparative Example 1 A column of 5 ml of cation exchange resin and a module of 5 cm of hollow fiber cation exchange membrane having an outer diameter of 3.5 mm and an inner diameter of 2.5 mm were used as a module. 10
A 100 ppb Fe ion solution was subjected to 8.0 liter permeation filtration by a total filtration method at ml / min. The Fe ion is adsorbed on the column of 5 ml of caton-exchange resin,
As an ion desorption liquid, 5 ml of 2N H ₂ SO ₄ was permeated at a water permeation rate of 1 ml / min, and the Fe ion concentration of the liquid desorbed from the cation exchange resin was 40.3 pp.
It was m. The concentration of the stock solution (water-permeable solution) calculated from that value was 25.2 ppb, and the concentration of the stock solution could not be specified. In addition, ₂ NH ₂ was also used as a desorption solution for Fe ions in this cation exchange membrane 5 cm 1 module.
When 5 ml of SO ₄ was permeated at a water permeation rate of 1 ml / min, the Fe ion concentration of the liquid desorbed from the cation exchange membrane was 159.0 ppm. The concentration of the stock solution (water-permeable solution) calculated from that value was 99.4 ppm, and the concentration of the stock solution could be detected with an error of 1% or less.

However, the water-permeable liquid used was prepared by using Fe ion in a clean bench using ultrapure water and measuring the concentration with an atomic absorption photometer. The Fe ion concentration of the desorption solution was also measured by an atomic absorption spectrophotometer after the desorption solution was diluted with ultrapure water to an appropriate concentration within the detection range.

Example 2 and Comparative Example 2 A column having 5 ml of anion exchange resin and a module having 5 cm of a hollow fiber-like anion exchange membrane having an outer diameter of 3.5 mm and an inner total of 2.5 mm are used as a module. Speed 10
At 100 ml / min, a 100 ppb Cl ion solution was permeated through 8.0 liters by a total filtration method. The column of 5 ml of anion exchange resin on which the Cl ions are adsorbed is
As an ion desorption liquid, 5 ml of 1N NaCl was permeated at a water permeation rate of 1 ml / min, and the Cl ion concentration of the liquid desorbed from the anion exchange resin was 24.7 pp.
It was m. The concentration of the stock solution (water-permeable solution) calculated from that value was 15.4 ppb, and the concentration of the stock solution could not be specified. In addition, 1NNa was similarly used as a desorption liquid for Cl ions in this anion exchange membrane 5 cm1 module.
When 5 ml of Cl was permeated at a water permeation rate of 1 ml / min, the Cl ion concentration of the liquid desorbed from the anion exchange membrane was 158.7 ppm. The concentration of the stock solution (water-permeable solution) calculated from the value was 99.2 ppb, and the concentration of the stock solution could be detected with an error of 1% or less. However, the water-permeable liquid used was one in which Cl ions were prepared in a clean bench using ultrapure water and the concentration was measured by ion chromatography. The Cl ion concentration of the desorption solution was also similarly measured by ion chromatography after the desorption solution was diluted with ultrapure water to an appropriate concentration within the detection range.

Example 3 and Comparative Example 3 A column having 5 ml of chelate exchange resin and an outer diameter
3.5ml, 2.5ml inner diameter hollow fiber chelate exchange
Permeability rate of 10 for a module with a membrane of 5 cm
100 ppb Ni ion solution was completely filtered at ml / min.
By filtration, 8.0 liter of water was filtered. That Ni Io
On the column of 5 ml of chelate-exchange resin that has absorbed nitrogen.
2NH as ion desorption liquid₂SO_FourPermeate 5 ml
When water permeates at a speed of 1 ml / min, chelate exchange
The Ni ion concentration of the liquid desorbed from the resin is 15.8 pp
It was m. Concentration of undiluted solution (permeable liquid) calculated from the value
Is 9.9 ppb, and specifying the concentration of the stock solution is
could not. Also, chelate exchange membrane 5 cm 1 piece module
In the same manner as a desorption liquid for Ni ions. ₂
SO_FourWhen 5 ml was permeated at a water permeation rate of 1 ml / min
The Ni ion concentration of the liquid desorbed from the chelate exchange membrane.
The degree was 159.3 ppm. Hara calculated from that value
The concentration of the liquid (water-permeable liquid) is 99.6 ppb, 1% or less.
The concentration of the stock solution could be detected with the error below.

However, as the water-permeable liquid, Ni ion was prepared in a clean bench using ultrapure water, and the concentration was measured by an atomic absorption photometer. The Ni ion concentration of the desorption solution was also measured by an atomic absorption spectrophotometer after the desorption solution was diluted with ultrapure water to an appropriate concentration within the detection range.

[0036]

[Table 3]

The concentration ratio here is defined by the following formula. Concentration factor = ion concentration in 5 ml of desorption solution / ion concentration of stock solution

[0038]

The method of the present invention is capable of efficiently concentrating metal ions in water, so that a sample of a metal ion concentration measuring instrument in water, particularly a sample having a low concentration, is concentrated and the concentration thereof is efficiently measured. It is suitable for

Claims (1)

[Claims] 1. A dilute ionic solution is filtered through one or more of a cation, an anion, and a porous membrane having chelate exchange functionality, and the ions adsorbed on the porous membrane are desorbed and concentrated by a regenerant. Then, the ion concentration of the diluted ion solution is measured by detecting the ion concentration, and the diluted ion solution concentration measuring method is characterized.