JPS59142803A - Selective separation membrane for ion - Google Patents

Abstract

PURPOSE:To obtain an ion selective separating membrane having superior strength coated with an ion permselective film on one side and a film of a material having oxidation/reduction function on another side, of a porous membrane. CONSTITUTION:A selective separation membrane for ions 10 is provided with a film 11 comprising a cellulosic polymer; an ion permselective film 12 comprising a plasma polymer of styrene is coated on one side 11a thereof, and a film made of an oxidation/reduction functional material 13 consisting of Pt etc. is coated on another side 11b. The periphery of the product except a part of the surface of the ion permselective film 12 is covered by an insulating body 14 such as ''Teflon'', and a lead wire 15 is connected to the Pt film 13. The ion selective separation film permeates specified ions, particularly H<+> selectively, and oxidation/reduction functional material serves as an ion sensor for detecting the concentration of the specific ion by the response of the electrode potential.

Description

[Detailed description of the invention] 10 Background of the invention 〔Technical field〕 This invention relates to an ion selective separation membrane.

[Prior art and problems]

For example, in body fluids where various ions, sugars, acids (amino acids, aspartic acid, lactic acid, uric acid, etc.), flea beetles, etc. coexist, specific ions can be selectively permeated to concentrate, separate, and
Recovery and measurement of specific ion concentrations are desired in biochemistry, food, industrial chemistry, and medical fields. Various functional membranes are being studied in an attempt to achieve this objective. When such a membrane is immersed in a sample solution, it may swell, and if the membrane is a composite membrane, gaps may be created between the membranes due to crotch separation or differences in expansion/contraction, making it impossible for the membrane to perform its intended function. There was something I couldn't do.

(1) Object of the Invention Therefore, an object of the present invention is to provide an ion selective separation membrane that does not have the above-mentioned drawbacks.

According to this invention, a porous membrane is used as a support, an ion selective permeable membrane is attached to one side of the porous membrane, and a redox functional material membrane is attached to the other side of the porous membrane. An ion-selective separation membrane is provided that exhibits the following characteristics.

The porous membrane is preferably made of cellulose polymer.

Further, the ion selectively permeable membrane is preferably made of a plasma polymer of styrene.

Furthermore, it is preferable that the redox functional material is platinum.

DETAILED DESCRIPTION OF THE m6 INVENTION The present invention will now be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, an ion selective separation membrane 10 of the present invention
is provided with a porous membrane I, on one side 11h of which is coated an ion selective permeation layer 1m12, and on the other side 11b is coated with a redox functional material membrane 13, respectively. The ion selectively permeable membrane 12, except for a part of its surface, is often covered with an insulator 14 such as Teflon, and if the membrane 13 is made of platinum or the like, which will be described later, a lead wire 15 is connected to it. be done.

The porous membrane 11 is strongly supported by the ion-selective permeable membrane 12 and the redox elid material A on both sides, and even if immersed in the electrolyte solution for a long period of time, these membranes will not peel off.
It does not swell. Further, this porous membrane 1 functions to allow ions, excluding giant ions, to pass therethrough, and to prevent substances having a large molecular weight, such as small molecules, from passing through. The pore size of this porous membrane 11 itself is around 10 μm, but since it is surrounded by the ion selectively permeable membrane 12, the effective pore size is thought to be around 0.001 μm. Such a porous membrane 1 is made of cellulose polymers (cellulose, acetyl cellulose, cellulose cellulose, ethyl cellulose, triacetyl cellulose, cellulose acetate butyrate, etc.), polycarbonate, polyvinyl chloride and their comonomers, polyvinylidene chloride. , polyamide (e.g. nylon), silicone rubber, fluororesin, (e.g. Teflon), Nafion, polynulfone, polyethylene,
It is made of polyacrylonitrile, polymethyl methacrylate, etc. Cellulose polymers are preferred.

The ion selective permeation membrane 12 has a function of selectively permeating only specific ions and hydrogen ions from among the various ions coexisting in the solution, and as a result, only the specific ions pass through the porous membrane 11 and have a redox function. The liquid material layer 13 is reached. Such an ion-permselective membrane can be induced by plasma polymerization of a hydroxy aromatic compound, a vinyl aromatic compound (such as styrene), an amino group-containing aromatic compound, or the like.

Plasma polymerization can be carried out using the apparatus shown in FIG. This device has a tube body 21 whose lower end 21a is closed and whose upper end 21b is connected to a vacuum system (not shown).The tube body 21 is branched and communicated with a conductive film provided with an ion-sensitive membrane. A branch pipe 2 with a closed tip that serves as a holding part for the base body C
2 is formed. On the lower side of this branch pipe 22 and above the lower end 21a, it is symmetrical about the pipe body 21.
An anode electrode 23 and a ground electrode 24 are arranged at specific positions. The anode electrode 23 is connected to a high frequency generator 25 via a lead wire 1.1. On the other hand, the ground electrode 24 is connected to the high frequency generator 25 via the lead aL, and is grounded (GND) together with the high frequency generator 250 case 7 via the branch lead wire Ls. The porous membrane C is held within the branch pipe 22 so as to face the pipe body 21.

In order to form a plasma polymerized film of a desired organic monomer on the porous membrane C using such a plasma polymerized tube, first, the organic monomer M is placed in the bottom of the tube 21; Pipe body 2
The pressure is reduced to about 10-'torr using a vacuum system to remove air or oxygen within the tube body 2. Next, the vapor pressure of the organic monomer in the tube body 21 is adjusted to about 1 torr VC, and plasma is irradiated with high frequency power of 10 W to 100 W for 3 to 120 seconds. In this way, the organic monomer excited by the plasma polymerizes in the porous membrane and forms a crotch.

The redox functional material film 13 may be one that itself performs a redox reaction with specific ions, or one that can receive and receive electrons in a redox reaction, such as a platinum group metal, particularly platinum. The former materials include polymeric compounds with redox reaction active centers such as ferrocene conductor, polynitrostyrene, polyaniline, etc., as well as polymeric ligand compounds and metal complex compounds such as polyvinylpyridine (PVP). Coordinated ruthenium complexes or polymeric complex compounds prepared by electrostatic interaction between a polyelectrolyte compound and an ionic interpolant, such as protonated 3-/4-protonated PVP immobilized in PA. Mo (CN) a
There are complexes, complex compounds of polyxylyl viologen and poly7-tyrene sulfonic acid, and the like. The latter metal is
Can be applied using gututa or vapor deposition.

■1 The ion-selective separation membrane having the above-described configuration selectively permeates only specific ions, especially hydrogen ions, in a solution, and when the redox-functional material is a metal, the redox-functional material remains unchanged (1); When the functional material itself undergoes an oxidation-reduction reaction, by supporting it on a conductive substrate, such as a carzene substrate, it acts as an ion sensor that measures the ion concentration of the specific ion in response to electrical potential.

Examples of this invention will be described below.

Example 1 A commercially available cellulose acetate membrane (Cusolophane on one side of the chest,
A plasma polymerized sample of styrene was deposited using the plasma polymerization apparatus shown in FIG.

The plasma polymerization conditions were as follows.

Styrene monomer vaporization pressure: about 1 torr Plasma generation power: 100 W Plasma irradiation time: about 6 seconds A polystyrene film with a thickness of about 0.1 μm was formed on one side of the cellulose acetate film by this plasma polymerization.

Next, the other side of the cellulose acetate membrane was coated with a platinum thin film using the bipolar high-speed Nu-Sentsuta method (200 W x 15 seconds), and a copper wire was connected to the end of this platinum thin film using silver paste. did. Next, the periphery of the polystyrene membrane except for a part of the surface was covered with epoxy resin, and the desired ion-selective separation membrane was assembled. This ion-selective separation membrane was inserted into the cell shown in FIG. 3.

This cell has an electrolyte v37 and an air chamber 32 communicating with each other on both sides.
and is equipped with an insertion part J3i' for an ion selective separation membrane in the center. First, a phosphate buffer solution with a pH of 6.86 is placed in the electrolyte chamber, an ion selective separation membrane is inserted into the insertion part 33 so that the polystyrene membrane is in contact with the phosphate buffer solution, and a commercially available sodium chloride saturated calomel electrode ( SSCE)
When the equilibrium potential value was measured at 25°±01°C, it showed a constant value of 285.2 mV. Next, when the H of the phosphate buffer in the electrolyte chamber 3 was changed and the equilibrium potential value was measured, the pH was 2.0 to 8.0, as shown by the straight line a in Figure 4. The Nernst linear relationship was shown in the range of . The slope of this straight line a is approximately 56 mV/p
It is H. Further, the time in the trench (response time) for the equilibrium potential value to reach a constant value was within about 1 minute.

From the above results, it can be seen that this ion-selective separation membrane has excellent hydrogen ion permselectivity and can be used as a pH sensor.

Example 2 An ion selective separation membrane was prepared in the same manner as in Example 1 except that a cellophane membrane was used instead of the cellulose acetate membrane.

When the equilibrium potential value for a phosphate buffer solution of pH 6.86 was measured in the same manner as in Example 1, it showed a constant value of about 197 mV. When we measured the equilibrium potential W with respect to change, as shown in the straight line in Figure 4, p
The Nernst @ line relationship was shown in the range of H2,0 to 8.0. The slope of this straight line was about 59 mV/pH, and the response time was within about 1 minute.

Next, the dissolved carbonic acid partial pressure PCO and the acid part 7 partial pressure Po2 of the phosphate buffer with pH 6 and 86 were changed, respectively.
The effect on the equilibrium potential was investigated. At this time, the nitrogen gas partial pressure was kept constant at 237.75 Hg. The results are shown in Figure 5 as a and b, respectively. As can be seen from this conclusion, PCO and Po2 are each 178.25.
mmHg i can measure hydrogen ion concentration without being affected by dissolved carbon dioxide and oxygen.

■8 Specific Effects of the Invention The ion selective separation membrane of the present invention described above can firmly bond the ion selective permeation membrane and the redox functional material layer due to the presence of the porous membrane, so that the ion selective separation membrane and the redox functional material layer can be strongly bonded over a long period of time. Function can be expressed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the ion selective separation membrane of the present invention, FIG. 2 is a schematic diagram of a plasma polymerization apparatus used for producing the ion selective separation membrane of the present invention, and FIG. 3 is a sectional view of the ion selective separation membrane of the present invention. Cell used for measuring membrane properties, No. 4
5 and 5 are graphs showing the characteristics of the one ion selective separation membrane of the present invention. 11...Porous membrane, J2...Ion selective permeation membrane, 1
3...Redox functional material film. Applicant's agent Patent attorney Takehiko Suzue Figure 1
Figure 2ND Figure 3

Claims (4)

[Claims] (1) A porous membrane is used as a support, an ion selective permeable membrane is adhered to one side of the porous membrane, and an oxidation ring functional material membrane is adhered to the other side of the porous membrane. An ion-selective separation membrane featuring: (2) The ion selective separation membrane according to claim 1, wherein the porous membrane is made of a cellulone polymer. (3) The ion selective separation membrane according to claim 1 or 2, wherein the ion selective permeation membrane is made of a plasma polymer of styrene. (4) The ion selective separation membrane according to any one of claims 1 to 3, wherein the redox functional material is platinum.