JP6469515B2 - Ion exchange method and ion exchanger using ion channel - Google Patents

Description

  The present invention relates to an ion exchange method using an ion channel and an ion exchanger.

  Conventionally, an ion exchange method using an ion exchanger is known and used in various fields such as water treatment, food, medicine / medical treatment, industrial wastewater treatment, and the like.

  This ion exchange method is a separation method using a reaction in which ions in an ion exchanger are released into an electrolyte solution and replaced by taking in the ions in the electrolyte solution to cause phase transfer.

  However, this ion exchange method has a problem that it is difficult to completely separate the target ions because it is impossible to prevent contamination of impurities.

  Therefore, a metal ion separation method has been proposed to eliminate this inconvenience. More specifically, a selective capture agent (for example, a crown ether) that is a cyclic compound and forms a complex only with a metal ion having a binding constant suitable for the ring size includes a plurality of types of metal ions. It is added to the aqueous solution, and unnecessary metal ions are retained in the aqueous solution by the selective trapping agent. Next, the aqueous solution is brought into contact with an ion-exchangeable solid phase (ion exchange resin), so that only desired metal ions are obtained. A method of moving to this solid phase has been proposed. It is described that by such a method, separation can be performed while preventing impurities from being mixed, and a specific type of metal ion can be obtained at a high concentration (for example, see Patent Document 1).

JP 2002-121623 A

  However, in the method described in Patent Document 1, an ion selective trapping agent is present in a solution, and unnecessary ions are trapped and held in an aqueous solution. It is a method to collect by. For this reason, when the desired ions are present at a low concentration, it is necessary to lower the concentration of the unwanted ions more than the concentration of the desired ions by capturing the unwanted ions with the capture agent. The method is difficult due to the problem of inclusion equilibrium constants. For this reason, there was a problem that ion exchange at a relatively low concentration is difficult.

  In addition, the method described in Patent Document 1 requires a general ion exchange agent in addition to the ion trapping agent, which increases the number of steps, increases costs, and requires a long time for processing. There was a problem.

  Therefore, the present invention has been made in view of such a point, and in a solution containing a plurality of types of metal ions, even if the metal ions have a relatively low concentration, the exchange can be reliably performed, and the ions By providing a single material that combines the functions of a capture agent and an ion exchanger, the number of processing steps can be reduced, and an efficient ion exchange method and ion exchanger can be provided in terms of cost and processing time. Objective.

  In order to achieve the above object, the ion exchange method of the present invention is a method in which an ion conductive crystal formed by ionic bonding of a crown ether encapsulating lithium ions and a dithiolate metal complex is converted into metal ions other than lithium ions. It is characterized in that lithium ions in the ion conductive crystal are exchanged with metal ions by being immersed in a solution in which is dissolved.

  According to the present invention, it is possible to reliably exchange even a relatively low concentration of metal ions by an inexpensive and simple method.

It is a figure which shows the combined state of the ion conductive crystal which concerns on embodiment of this invention. It is a figure which shows the IR spectrum of the ion conductive crystal before the ion exchange in the Example of this invention, and the ion conductive crystal after ion exchange. It is a figure which shows the IR spectrum of the ion conductive crystal before the ion exchange in the Example of this invention, and the ion conductive crystal after ion exchange. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the IR spectrum of the ion conductive crystal before the ion exchange in the Example of this invention, and the ion conductive crystal after ion exchange. It is a figure which shows the IR spectrum of the ion conductive crystal before the ion exchange in the Example of this invention, and the ion conductive crystal after ion exchange. It is a figure which shows the IR spectrum of the ion conductive crystal before the ion exchange in the Example of this invention, and the ion conductive crystal after ion exchange. It is a figure which shows the IR spectrum of the ion conductive crystal before the ion exchange in the Example of this invention, and the ion conductive crystal after ion exchange. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention. It is a figure which shows the part which performed the EPMA measurement in the ion conductive crystal after the ion exchange in the Example of this invention.

  In the solid ion exchange method of the present invention, an ion conductive crystal formed by ionic bonding of a crown ether encapsulating lithium ions and a dithiolate metal complex is converted into metal ions other than lithium ions (hereinafter simply referred to as “metal ions”). Is a method for exchanging lithium ions in ion-conductive crystals with metal ions by immersing them in a solution in which the solution is dissolved.

  And by such a method, it becomes possible to exchange reliably even if it is a metal ion of a relatively low density | concentration in the solution containing a multiple types of metal ion by an inexpensive and simple method.

  Moreover, the target metal ion can be easily recovered by recovering the ion-exchanged crystal (that is, the ion exchanger).

The ion conductive crystal has a structure in which crown ether (18-crown-6) encapsulating lithium ions and a dithiolate nickel complex (Ni (dmit) ₂ ) are electrically attracted to each other.

More specifically, the ion conductive crystal used in the present invention includes a crown ether (Li ⁺ (18-crown-6)) that includes lithium ions, which are monovalent cations as a whole, and a monovalent cation. The dithiolate nickel complex (Ni (dmit) ₂ ), which is an anion, is electrically attracted and bound by Coulomb force (that is, by ionic bonding).

  FIG. 1 shows a structural diagram of an ion conductive crystal represented by the formula (1). As shown in FIG. 1, an ion conductive crystal 1 is composed of three crown ethers 3, two dithiolate nickel complexes 4, and four water molecules 5 with respect to two lithium ions 2, and has the following chemical formula. It is represented by

(In the formula, dmit represents 1,3-dithiol-2-thione-4,5-dithiolate.)
Then, as shown in FIG. 1, three crown ethers 3 are formed as one unit, and these are stacked one-dimensionally, whereby ion channels 9 are formed in the crystal, and are included in the crown ether 3. Lithium ions 2 can move in ion channels 9 made of crown ether 3. Therefore, the crystal represented by the above formula (2) has ionic conductivity.

  Next, the outline of the manufacturing method of the ion conductive crystal in this embodiment is shown in the following reaction scheme 1.

<Reaction Scheme 1>
From a crown ether (Li ⁺ (18-crown-6)) that is clathrated with lithium ions that are monovalent cations as a whole and represented by formula (4), and a dithiolate nickel complex that is a monovalent anion. In order to obtain the ion conductive crystal, first, a solution in which 18-crown-6 of formula (3) and lithium perchlorate (LiClO ₄ ) are dissolved in acetonitrile is prepared.

Also, TBA · Ni (dmit) ₂ (bis (1,3-dithiol-2-thione-4,5-dithiolate) nickel (III) tetrabutylammonium) was synthesized, and this TBA · Ni (dmit) ₂ was synthesized. Dissolve in acetonitrile to prepare a solution containing the dithiolate nickel complex. TBA · Ni (dmit) ₂ can be synthesized by a known method (see, for example, Steinmecke, G .; Sieler, HJ; Krimes, R .; Hoyer, E. Phosphorus Sulfur 1979, 7, 49). it can.

  Next, an acetonitrile solution (hereinafter referred to as “solution A”) in which lithium perchlorate and crown ether (18-crown-6) are dissolved is poured into a sample tube, and an acetonitrile solution in which the dithiolate nickel complex is dissolved (hereinafter referred to as “solution A”). Solution B ”) is poured into the sample tube so that solution A and solution B do not mix rapidly.

Next, without covering the sample tube, the lithium ion shown in the formula (4) was included as shown in the above formula (1) by leaving it in the dark at room temperature for 3 to 4 days. Lithium-crown ether (Li ⁺ (18-crown-6)) and a dithiolate nickel complex are electrically attracted to obtain an ion conductive crystal represented by the formula (2).

  Further, the ion conductive crystal used in the present invention can be selected in accordance with other metal ions exchanged with lithium ions.

  More specifically, it is possible to use this metal ion when the binding constant of another metal ion to be exchanged with respect to the crown ether contained in the ion conductive crystal is larger than the binding constant of the lithium ion. (Note that the binding constant between crown ether and metal ion can be found in RM Izatt, JS Bradshaw, SA Nielsen, JD Lamb, and JJ Christensen, Chem. Rev., 85, 271-339 (1985), RM Izatt, K. Pawlak, and JS Bradshaw, Chem. Rev., 91, 1721-2085 (1991), RA Samant, VS Ijeri, and AK Srivastava, J. Chem. Eng. Data, 48, 203-207 (2003)).

For example, when the metal ion to be exchanged is potassium ion (K ⁺ ), the binding constant of potassium ion to crown ether (18-crown-6) is 6.24, which is lithium for (18-crown-6). Since the ion coupling constant is larger than 2.69, an ion conductive crystal having a crown ether (18-crown-6) can be used as an ion exchanger.

For example, when the metal ion to be exchanged is lanthanum ion (La ³⁺ ), the binding constant of lanthanum ion to crown ether (15-crown-5) is 6.49, which is (15-crown-5). Since the binding constant of lithium ion with respect to is larger than 4.26, an ion conductive crystal having crown ether (15-crown-5) can be used as an ion exchanger.

That is, an ion conductive crystal containing lithium ions and having lithium ion-crown ether (Li ⁺ (15-crown-5)) which is a monovalent cation as a whole is used.

  In this case, the production method of the ion conductive crystal is the same as that in the case of using the above-mentioned 18-crown-6, and the following 18-crown-6 is produced by substituting 15-crown-5. An ion conductive crystal represented by the formula (5) can be obtained.

  Here, since the binding constant of the metal ion to the crown ether depends on the size of the crown ether, a plurality of kinds of metals can be selected by selecting the size of the crown ether having a large binding constant corresponding to the metal ion to be exchanged. In a solution containing ions, even if the target metal ion is a metal ion having a relatively low concentration, it is possible to reliably perform ion exchange without depending on the principle of ion exchange equilibrium.

  In addition, it does not specifically limit as metal ion used as exchange object, For example, other alkali metal ions, alkaline earth metal ions with different valences, transition metal ions, and lanthanoids other than the above-mentioned potassium ions and lanthanum ions An ion etc. can be mentioned.

  Next, the solid ion exchange method according to the embodiment of the present invention will be described.

  In the solid ion exchange method of the present invention, ion conduction is performed by immersing an ion conductive crystal formed by ionic bonding between a crown ether encapsulating lithium ions and a dithiolate metal complex in a solution in which metal ions are dissolved. This is a method of exchanging lithium ions in metal crystals with metal ions.

  Here, from the viewpoint of surely performing ion exchange of metal ions, the concentration of metal ions in the solution is preferably 0.01 to 1M.

  Similarly, from the viewpoint of reliably performing ion exchange of metal ions, the temperature of the solution is preferably 20 to 40 ° C., and the reaction time (that is, the ion conductive crystal is immersed in a solution in which metal ions are dissolved). Time) is preferably 2 hours or more.

  In addition, you may change the said embodiment as follows.

In the above embodiment, a dithiolate nickel complex (Ni (dmit) ₂ ) is used as the dithiolate metal complex, but the dithiolate metal complex is not limited to this, and may be an anion for keeping the charge neutral. . For example, a configuration using a dithiolate palladium complex (Pd (dmit) ₂ ), a dithiolate platinum complex (Pt (dmit) ₂ ), or a dithiolate gold complex (Au (dmit) ₂ ) may be used.

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.

(Synthesis of ion-conductive crystals)
18-crown-6 (trade name 18-crown-6-Ether, manufactured by Tokyo Chemical Industry Co., Ltd.) of formula (3) and lithium perchlorate (anhydrous) (trade name, Lithium perchlorate, manufactured by Kanto Chemical Co., Inc.) , anhydrous) was dissolved in 5 ml of acetonitrile (manufactured by Nacalai Tesque) to obtain solution A.

Further, TBA · Ni (dmit) ₂ was synthesized by a known method, and then 7 mg of this TBA · Ni (dmit) ₂ was dissolved in 5 ml of acetonitrile (manufactured by Nacalai Tesque) to obtain a dithiolate nickel complex. A solution B containing was obtained.

  Next, after pouring 5 ml of the solution A into the 10 ml sample tube, the sample tube is prepared so that the solution A and the solution B are not mixed rapidly (so as not to disturb the interface of the solution A). Slowly poured into.

  Next, the sample tube into which the solution A and the solution B were poured was not covered, and left at room temperature for 3 to 4 days in a dark place. As a result, a black (dark green) plate crystal was precipitated at the bottom of the sample tube, and an ion conductive crystal represented by the formula (2) was obtained.

(Solid ion exchange)
Next, the obtained ion conductive crystal was immersed in 1M aqueous potassium chloride solution (manufactured by Nacalai Tesque, Inc., liquid temperature: 30 ° C.) for 24 hours, and lithium ions in the ion conductive crystal were converted to potassium ions. Exchanged.

(IR spectrum measurement)
Next, IR spectra of the ion conductive crystal before ion exchange and the ion conductive crystal after ion exchange were measured. The above results are shown in FIGS.

  The IR spectrum was measured using an infrared spectrometer (trade name: FT-IR660Plus, manufactured by JASCO Corporation, trade name: FT-IR660Plus), grinding the KBr tablet (about 30 mg) and the sample to be measured about 20 times. A KBr disk was prepared by applying pressure, and this was measured.

As shown in FIG. 2, it can be seen that a broad peak derived from the OH group in the vicinity of 3500 cm ⁻¹ disappears in the sample after ion exchange. Therefore, it is considered that water molecules coordinated to lithium ions were desorbed in the ion conductive crystal (Li ⁺ (18-crown-6)) before the exchange by ion exchange.

Further, as shown in FIG. 3, a peak shift was observed in the region of 800 to 1500 cm ⁻¹ . Here, it is known that the peak derived from C—O—C stretching of the crown ether near 1100 cm ⁻¹ shifts depending on the type of metal cation included in the crown ether (T. Akutagawa, et. al., Chem. Eur. J., 2001, 7, 4902). Also in this example, it can be seen that the peak is shifted to the lower wavenumber side by ion exchange.

From the above, in the ion conductive crystal (Li ⁺ (18-crown-6)) before exchange, the metal cation included in the crown ether was a lithium ion. It turns out that it was exchanged.

(EPMA measurement)
Next, EPMA (Electron Probe Micro Analyzer) measurement of the ion conductive crystal after ion exchange was performed. More specifically, the sample after ion exchange is divided, the cross section is irradiated with an electron beam, the spectrum of the characteristic X-rays generated is obtained, and the component of the sample (( That is, the atomic ratio of nickel, sulfur and potassium based on nickel was analyzed.

  In addition, EPMA measurement was performed with respect to each of the cross-sectional parts 1-5 of the sample shown in FIG. 4 using the EPMA measuring apparatus (JEOL Co., Ltd. make, brand name: JXA-8200). Further, an acceleration voltage was set to 15 kV, an irradiation current amount was set to 10 nA, and an electron beam having a beam diameter of 10 μm was irradiated for 20 seconds. The results are shown in Table 1.

As shown in Table 1, potassium was detected in any of the cross-sectional portions 1 to 5 after the crystal was cut. From this, it can be seen that lithium ions were exchanged for potassium ions by ion exchange. Moreover, as shown in Table 1, the ratio of nickel and potassium with respect to nickel is about 1: 1, and the ion conductive crystal (Li ⁺ (18-crown-6)) before exchange Since the ratio of nickel to lithium in is 1: 1, it is understood that ion exchange from lithium ions to potassium ions has been performed.

(Ion selectivity of crown ether)
Next, an aqueous solution in which lithium chloride and potassium chloride are dissolved is prepared, and the obtained ion conductive crystal (Li ⁺ (18-crown-6)) is immersed in this aqueous solution, whereby ion selectivity of crown ether is obtained. It was confirmed.

  More specifically, as shown in Table 2 below, the concentration of lithium ions and potassium ions in the solution is changed and the total concentration of ions in the solution (that is, the sum of the concentrations of lithium ions and potassium ions in the solution). ) Was prepared to be about 0.1M.

In addition, 10 ml of an aqueous solution is placed in a sample tube (10 ml), and 5 to 10 mg of ion conductive crystal (Li ⁺ (18-crown-6)) is added to the aqueous solution, and potassium ions in the solution with respect to lithium ions in the crystal are added. In a state where the concentration is excessive (that is, the amount of lithium present in 1 mg of crystals is about 7.7 × 10 ⁻³ mg, whereas the aqueous solution having the lowest potassium ion concentration (Li: K = 9: 1) Since the amount of potassium ions present in 1 ml is 0.47 mg, in each sample shown in Table 2, the concentration of potassium ions in the solution relative to the lithium ions in the crystal is Ion exchange was performed in an excess state.

  Next, the EPMA measurement of each ion conductive crystal after ion exchange was performed in the same manner as the above-mentioned EPMA measurement. In addition, about the sample after ion exchange at the time of using the aqueous solution of the sample (Li: K = 9: 1) shown in Table 2, EPMA measurement was performed with respect to each of the cross-sectional parts 6-10 shown in FIG. It was. Moreover, about the sample after ion exchange at the time of using the aqueous solution of the sample shown in Table 2 (Li: K = 4: 6), EPMA measurement was performed with respect to each of the cross-sectional parts 11-15 shown in FIG. It was. Moreover, about the sample after ion exchange at the time of using the aqueous solution of the sample (Li: K = 7: 3) shown in Table 2, EPMA measurement is performed with respect to each of the cross-sectional parts 16-20 shown in FIG. It was. Moreover, about the sample after ion exchange at the time of using the aqueous solution of the sample (Li: K = 8: 2) shown in Table 2, EPMA measurement was performed with respect to each of the cross-sectional parts 21-23 shown in FIG. It was. Moreover, about the sample after ion exchange at the time of using the aqueous solution of the sample (Li: K = 9: 1) shown in Table 2, EPMA measurement was performed with respect to each of the cross-sectional parts 24-26 shown in FIG. It was. The above results are shown in Table 3.

As shown in Table 3, potassium was detected in any of the cross-sectional portions 6 to 26. From this, when the metal ion with which lithium ions are exchanged is potassium ion (K ⁺ ), the binding constant of potassium ion to crown ether (18-crown-6) is 6.24, which is (18-crown). It can be seen that lithium ions were selectively exchanged for potassium ions because the binding constant of lithium ions for -6) was larger than 2.69.

  Further, from the results of the above-mentioned examples (using 1M potassium chloride aqueous solution) and the examples shown in Table 2 (using 0.012-0.090M potassium chloride aqueous solution), metal ions (potassium ions) in the solution were obtained. ) In the range of 0.01 to 1M, it can be seen that ion exchange from lithium ions to potassium ions is reliably performed.

(Reaction temperature evaluation)
Next, the temperature of the 1M potassium chloride aqueous solution was changed to 4 ° C, 20 ° C, 40 ° C, 50 ° C, and 60 ° C in the solid ion exchange step (temperature of the 1M potassium chloride aqueous solution: 30 ° C). Thus, lithium ions in the ion conductive crystal were exchanged with potassium ions.

  Subsequently, the IR spectrum of the ion conductive crystal before ion exchange and the ion conductive crystal after ion exchange at each reaction temperature were measured by the same method as the IR spectrum measurement described above. The above results are shown in FIGS.

As shown in FIG. 10, in the spectrum of the sample exchanged with an aqueous solution at 20 ° C., a peak shift attributed to C—O—C stretching of the crown ether was observed at 1103 cm ⁻¹ . In addition, as shown in FIG. 11, the spectrum of the sample subjected to the exchange experiment at 40 ° C. also shows a peak attributed to C—O—C stretching of crown ether at 1103 cm ⁻¹ , as in the case of 20 ° C. A shift was observed. On the other hand, as shown in FIG. 10, in the spectrum of the sample exchanged with an aqueous solution at 4 ° C., a peak (a peak near 1400 cm ⁻¹ ) showing typical characteristics before the exchange experiment is observed, and C of crown ether The peaks of —O—C stretching were 1103 cm ⁻¹ and 1113 cm ⁻¹ (the ones with 1103 cm ⁻¹ should be shoulders). From the above, it is assumed that ion exchange is not performed in the ice bath.

Moreover, as shown in FIG. 11, in the spectrum of the sample exchanged with an aqueous solution at 50 ° C. or higher, the peak of C—O—C stretching of the crown ether was 1103 cm ^−1. The sample collapsed just by touching. In addition, the region of 1200 to 1300 cm ⁻¹ is greatly changed in the spectrum. From these facts, it is considered that in the temperature region of 50 ° C. or higher, exchange to potassium ions is possible, but solid-phase ion exchange in this crystalline state becomes difficult.

  From the above, it can be seen that the temperature suitable for ion exchange is 20 to 40 ° C.

(Reaction time evaluation)
Next, in the above solid ion exchange step (reaction time: 24 hours), the reaction time is 1 hour, 2 hours, 5.5 hours, 7 hours, 9 hours, 10.5 hours, 12 hours, 24 hours, 48 hours. The time was changed to 96 hours, and lithium ions in the ion conductive crystal were exchanged with potassium ions.

  Subsequently, the IR spectrum of the ion-conducting crystal after ion exchange in each reaction time was measured by the same method as the IR spectrum measurement described above. The above results are shown in FIGS.

As shown in FIGS. 12 and 13, in the spectrum of the sample whose reaction time is 1 hour, the above-mentioned typical peak (peak near 1400 cm ⁻¹ seen only in the spectrum of the sample before ion exchange) is observed. However, these peaks were not observed in the sample having a reaction time of 2 hours or more. Further, no peak shift attributed to C—O—C stretching of the crown ether was observed only in the 1 hour sample. From the above, it can be seen that ion exchange to potassium ions is reliably performed by setting the reaction time to 2 hours or more.

  Next, in the same manner as the above-mentioned EPMA measurement, EPMA measurement was performed on the ion conductive crystal after ion exchange was performed with the reaction time set to 1 hour, 2 hours, 7 hours, and 10.5 hours.

  In addition, about the sample after ion exchange in case reaction time is 1 hour, EPMA measurement was performed with respect to each of the cross-sectional parts 27-35 shown in FIG. Moreover, about the sample after ion exchange in case reaction time is 2 hours, EPMA measurement was performed with respect to each of the cross-sectional parts 36-40 shown in FIG. Moreover, about the sample after ion exchange in case reaction time is 7 hours, EPMA measurement was performed with respect to each of the cross-sectional parts 41-44 shown in FIG. Further, for the sample after ion exchange when the reaction time was 10.5 hours, EPMA measurement was performed on each of the cross-sectional portions 45 to 49 shown in FIG. The results are shown in Table 4.

  As shown in Table 4, in the sample having a reaction time of 1 hour, the cross-sectional portion exchanged with potassium is small, and it can be seen that ion exchange is not sufficiently performed in most of the crystals. On the other hand, in the samples with reaction times of 2 hours, 7 hours, and 10.5 hours, it can be seen that lithium ions are exchanged for potassium ions in the entire crystal.

  From the above, it can be seen that the reaction time (that is, the time for immersing the ion conductive crystal in the solution in which potassium ions are dissolved) is preferably 2 hours or more.

  Examples of utilization of the present invention include ion exchange methods and ion exchangers using crown ether.

DESCRIPTION OF SYMBOLS 1 Ion conductive crystal 2 Lithium ion 3 Crown ether 4 Dithiolate nickel complex 5 Water molecule 6 Solid electrolyte 7 Positive electrode sheet 8 Negative electrode sheet 9 Ion channel

Claims (5)

By immersing an ion conductive crystal formed by ionic bonding between a crown ether encapsulating lithium ions and a dithiolate metal complex, the ion conductive crystal is immersed in a solution in which metal ions other than the lithium ions are dissolved. Exchanging the lithium ion with the metal ion in
An ion exchange method, wherein the crown ether is 15-crown-5, the ion conductive crystal is represented by the following formula (1), and the metal ions are sodium ions.
(In the formula, dmit represents 1,3-dithiol-2-thione-4,5-dithiolate, and M represents any metal of Ni, Pd, Au, and Pt.) The ion exchange method according to claim 1 , wherein M is Ni. The ion exchange method according to claim 1 or 2 , wherein the concentration of the metal ions in the solution is 0.01 to 1M. The temperature of the said solution is 20-40 degreeC, The ion exchange method of any one of Claims 1-3 characterized by the above-mentioned. The ion exchange method according to any one of claims 1 to 4 , wherein the immersion time is 2 hours or more.