Method for producing copper iodide

Abstract

To provide a method for producing copper iodide that can reduce the amount of unreacted copper residue.SOLUTION: The method for producing copper iodide of the present invention comprises a reaction step of adding metallic copper to an aqueous solution containing polyiodide ions and reacting the polyiodide ions with metallic copper to obtain copper iodide.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing copper iodide.

Background Art

[0002] Various developments have been made on methods for producing copper iodide. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes a method of subjecting metallic copper and solid iodine to a solid-phase reaction using a salt of an inorganic strong acid such as sodium hydrogen sulfate as a catalyst. Further, Patent Document 2 describes a method for producing copper iodide in which iodine is reacted with metallic copper.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of investigations by the present inventor, it has been found that there is room for improvement in terms of the amount of unreacted copper remaining in the method for producing copper iodide described in Patent Document 1 above.

Means for Solving the Problems

[0005] As a result of further investigations by the present inventor, it has been found that by using polyiodide ions having high water solubility instead of solid iodine (I2) having low water solubility, the amount of unreacted copper remaining in the method for producing copper iodide can be reduced, and the present invention has been completed.

[0006] According to one aspect of the present invention, there is provided a method for producing copper iodide as follows.

[0007] 1. A method for producing copper iodide, comprising a reaction step of adding metallic copper to an aqueous solution containing polyiodide ions and reacting the polyiodide ions with the metallic copper to obtain copper iodide. 2. The method for producing copper iodide according to 1., including a preparation step of preparing an aqueous solution containing polyiodide ions before the reaction step, wherein in the preparation step, a catalyst is reacted with solid iodine in an aqueous solvent to obtain the aqueous solution containing polyiodide ions. A method for producing copper iodide. 3. The method for producing copper iodide according to 2., wherein the catalyst contains at least hydroiodic acid. A method for producing copper iodide. 4. The method for producing copper iodide according to any one of 1. to 3., wherein the concentration of copper iodide in the aqueous solution containing polyiodide ions obtained in the reaction step is 5% by mass or more and 60% by mass or less. A method for producing copper iodide. 5. The method for producing copper iodide according to any one of 1. to 4., wherein in the reaction step, the liquid temperature of the aqueous solution containing polyiodide ions is 5°C or more and 55°C or less. A method for producing copper iodide. 6. The method for producing copper iodide according to any one of 1. to 5., wherein in the reaction step, the pH of the aqueous solution containing polyiodide ions is 7 or less. A method for producing copper iodide. 7. The method for producing copper iodide according to any one of 1. to 6., wherein in the reaction step, the iodine concentration measured by thiosulfate titration in the aqueous solution containing polyiodide ions immediately before adding the metallic copper is 1% by mass or more. A method for producing copper iodide. 8. The method for producing copper iodide according to any one of 1. to 7., wherein in the aqueous solution containing polyiodide ions after the reaction step, the iodine concentration measured by thiosulfate titration is 5% by mass or less. A method for producing copper iodide. 9. The method for producing copper iodide according to any one of 1. to 8., A method for producing copper iodide, wherein the metallic copper contains copper powder having a median diameter of 100 μm or less as measured by the wet laser diffraction method. 10. The method for producing copper iodide according to 2 or 3, wherein a separation liquid is recovered from the reaction liquid obtained in the reaction step by solid-liquid separation, and hydroiodic acid contained in the recovered separation liquid is reused as the catalyst in the preparation step. 11. The method for producing copper iodide according to any one of 1 to 10, wherein the polyiodide ion contains one or more selected from the group consisting of triiodide ion, pentaiodide ion, and heptaiodide ion.

Advantages of the Invention

[0008] According to the present invention, there is provided a method for producing copper iodide with a reduced amount of unreacted copper residue.

Embodiments for Carrying Out the Invention

[0009] The outline of the method for producing copper iodide of the present embodiment will be described.

[0010] The method for producing copper iodide of the present embodiment includes a reaction step of adding metallic copper to an aqueous solution containing polyiodide ions and reacting the polyiodide ions with the metallic copper to obtain copper iodide.

[0011] According to the findings of the present inventors, it has been found that the amount of unreacted copper residue in the method for producing copper iodide can be reduced by reacting polyiodide ions having high water solubility with metallic copper in an aqueous solvent. Although the detailed mechanism is not clear, it is presumed that the use of polyiodide ions having higher water solubility than solid iodine (I2) in water can enhance the reactivity with metallic copper, thereby reducing the amount of unreacted copper residue. The reaction step of the present embodiment mainly involves the reaction between a solid metal and polyiodide ions, and the reaction mechanism is different from that generated by the reaction between a solid metal and solid iodine. In addition, in the method for producing copper iodide according to the present embodiment, since the operation of sequentially adding solid iodine when reacting metallic copper with solid iodine is unnecessary, the production efficiency can be improved.

[0012] Hereinafter, each configuration of the method for producing copper iodide according to the present embodiment will be described in detail.

[0013] An example of an embodiment of the method for producing copper iodide is a preparation step of preparing an aqueous solution containing polyiodide ions, and a reaction step of adding metallic copper to the aqueous solution containing polyiodide ions prepared in the preparation step and reacting the polyiodide ions with the metallic copper to obtain copper iodide.

[0014] In the preparation step, in an aqueous solvent, a catalyst is reacted with solid iodine to obtain an aqueous solution containing polyiodide ions (referred to as "aqueous solution containing polyiodide ions" in this specification). By carrying out the preparation step before the reaction step, an aqueous solution containing an appropriate amount of polyiodide ions can be produced. In addition, in the preparation step, the order of adding the aqueous solvent, solid iodine, and the catalyst into the container is not particularly limited. As an example, the catalyst may be added to the aqueous solvent, and then solid iodine may be added. Further, each component may be added not all at once but in divided additions in a plurality of times.

[0015] As the catalyst used in the preparation step, any catalyst can be used as long as it promotes the reaction of converting solid iodine into polyiodide ions. In this specification, polyiodide ions are represented by the general formula [I n m- (where n is an integer of 3 or more and is selected from 3 to 29, and m is selected from 1 to 3 according to the value of n). These may be included alone or in combination of any two or more. Specific polyiodide ions are, for example, triiodide ions (I3 - ), pentaiodide ions (I5 - ), and heptaiodide ions (I7​- It contains one or more selected from the group consisting of. The aqueous solution containing polyiodide ions may be an aqueous solution containing one or more of the above polyiodide ions, and preferably an aqueous solution containing triiodide ions (I3 - ). In the aqueous solution containing triiodide ions, the content ratio of triiodide ions (I3 - ) in 100% by mass of polyiodide ions is not particularly limited, but it may be, for example, 50% by mass or more as mainly containing triiodide ions (I3 - ). Specific catalysts include, for example, iodide-based catalysts such as hydroiodic acid and / or sodium iodide, but are not limited thereto. Among iodide-based catalysts, from the viewpoint of further reducing the residual amount of unreacted copper, it is preferable to contain at least hydroiodic acid. The HI concentration in hydroiodic acid is not particularly limited, but from the viewpoint of catalyst efficiency, a relatively high concentration is preferable, and for example, it may be 55% by mass to 58% by mass.

[0016] The addition amount of the catalyst is, for example, 0.1 mol to 1.5 mol, preferably 0.3 mol to 1.3 mol, more preferably 0.75 mol to 1.1 mol, when the iodine equivalent of solid iodine in the preparation step is based on 1 mol. When the addition amount of the catalyst is equal to or more than the above lower limit value, the residual amount of unreacted copper can be further reduced.

[0017] The water solvent may be a solvent containing H2O, and other solvents may be contained as long as the above catalytic reaction is not inhibited.

[0018] The upper limit of the iodine concentration in the aqueous solution containing polyiodide ions immediately before the addition of metallic copper obtained in the preparation step is, for example, 50% by mass or less, preferably 35% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less. Thereby, the increase in viscosity in the aqueous solution containing polyiodide ions can be suppressed, and the ease of stirring in the next reaction step can be enhanced. Also, by setting it to 20% by mass or less, the residual amount of unreacted copper can be further reduced. On the other hand, from the viewpoint of productivity by improving volumetric efficiency, the lower limit of the iodine concentration content is, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more. The iodine concentration in the aqueous solution containing polyiodide ions can be measured by thiosulfate titration.

[0019] In the aqueous solution containing polyiodide ions obtained in the preparation step, immediately before the addition of metallic copper, it is preferable that no solid iodine is contained, or even if solid iodine is contained, the content of solid iodine is 5% by mass or less. Thereby, the reactivity with copper powder can be enhanced. Here, solid iodine means undissolved I2 (solid) that does not dissolve in the aqueous solution containing polyiodide ions.

[0020] In the reaction step, metallic copper is added to the aqueous solution containing polyiodide ions, and if necessary, stirred to react polyiodide ions with metallic copper. Metallic copper may be added all at once from the viewpoint of productivity, or may be added in divided portions multiple times.

[0021] The metallic copper used in the reaction step preferably contains powdered metallic copper from the viewpoint of stirrability in the liquid.

[0022] There is no particular limitation on the production method of metallic copper. For example, it may be produced by any production method such as electrolysis, pulverization, atomization, chemical reduction, plasma rotating electrode method, uniform droplet spraying method, heat treatment method, etc.

[0023] The upper limit of the median diameter measured by the wet laser diffraction method of powdered metallic copper (which may be referred to as copper powder) is, for example, 100 μm or less, preferably 50 μm or less, more preferably 30 μm or less. Thereby, sedimentation of copper powder during stirring can be suppressed, and the reactivity with polyiodide ions can be enhanced. The lower limit of the median diameter of the above copper powder is, for example, 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more. Thereby, dust scattering can be suppressed and the ease of operation can be improved.

[0024] In this specification, the median diameter means the particle diameter at the point where the cumulative volume from the small particle side is 50% in the volume frequency particle size distribution measured by the laser diffraction scattering method. Specifically, copper powder and a surfactant (e.g., Tween 20) are put into water, and using an ultrasonic cleaning device, they are dispersed at a frequency of 24 kHz for 10 minutes to prepare a measurement sample. The particle size distribution of the copper powder in the measurement sample can be measured using a particle size distribution meter (e.g., MT-3300EXII manufactured by Nikkiso Co., Ltd.).

[0025] In the reaction step, the liquid temperature of the aqueous solution containing polyiodide ions is, for example, 5°C or higher and 55°C or lower, preferably 5°C or higher and 40°C or lower, more preferably 15°C or higher and 30°C or lower.

[0026] Also, in the reaction step, the aqueous solution containing polyiodide ions has a pH of, for example, 7 or lower, preferably 3 or lower, and more preferably 2 or lower from the viewpoint of reactivity.

[0027] The reaction end point of the reaction step can be, for example, indicated by a predetermined unreacted copper residue amount (%).

[0028] Through the above reaction step, an aqueous solution containing polyiodide ions (reaction solution) containing copper iodide is obtained. The upper limit of the iodine concentration in the aqueous solution containing polyiodide ions after the reaction step is, for example, 5% by mass or lower, preferably 2% by mass or lower, more preferably 1% by mass or lower. On the other hand, the lower limit of the content of the above iodine concentration is not particularly limited, but it may be 0.1% by mass or higher.

[0029] The upper limit of the copper iodide concentration in the aqueous solution containing polyiodide ions obtained in the reaction step is, for example, 60% by mass or lower, preferably 40% by mass or lower, more preferably 25% by mass or lower. This can enhance the ease of stirring. On the other hand, from the viewpoint of productivity, the lower limit of the content of the above copper iodide concentration is, for example, 5% by mass or higher, preferably 15% by mass or higher, more preferably 20% by mass or higher.

[0030] Copper iodide can be obtained by separating copper iodide from the reaction solution. As a method for separating copper iodide, known methods can be used.

[0031] The reaction solution obtained by the method for producing copper iodide according to this embodiment does not substantially contain sulfate ions. Therefore, there is no need for the trouble of washing the copper iodide recovered from the reaction solution. That is, the recovered copper iodide has high handleability in the subsequent process.

[0032] In addition, in this embodiment, the reaction solution obtained in the reaction step may be separated by solid-liquid separation to recover the separation liquid, and hydroiodic acid contained in the separation liquid recovered in the recovery step may be reused as a catalyst in the preparation step.

[0033] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the scope capable of achieving the object of the present invention are included in the present invention.

Example

[0034] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the descriptions of these examples at all.

[0035] <Experiment A: Iodine Concentration> (Example A1) The procedure for the method for producing copper iodide is as follows. Into a 1 L separable flask equipped with a thermometer and a stirrer, 200 g of ion-exchanged water and 200 g of hydroiodic acid with a HI concentration of 57% by mass were placed. After stirring, 204 g of solid iodine was further added, and while maintaining the liquid temperature at 30°C, stirring was carried out at 300 rpm for 10 minutes to prepare an aqueous solution containing polyiodide ions with a pH of less than 1 (preparation step). The obtained aqueous solution containing polyiodide ions mainly contained triiodide ions as polyiodide ions. 100 g of copper powder (median diameter: 30 μm) was sequentially added to the obtained aqueous solution containing polyiodide ions over 20 minutes, and while maintaining the liquid temperature at 30°C, the mixture was stirred at 300 rpm for 60 minutes to react the polyiodide ions with the copper powder, obtaining an aqueous solution containing copper iodide (reaction step). The aqueous solution containing copper iodide was filtered, washed, and dried to obtain dried copper iodide (dried product).

[0036] The copper iodide concentration (mass %) of the aqueous solution (slurry) containing copper iodide obtained in the reaction step was calculated from "dried copper iodide (g) / aqueous solution containing copper iodide (g)". In the reaction step, the iodine concentration (mass %) of each iodine in the aqueous solution containing polyiodide ions before adding copper powder / after the reaction step was measured by the thiosulfate titration method. In the thiosulfate titration method, the iodine amount (g) of I2 was measured, and the iodine concentration (mass %) was calculated based on "iodine amount (g) / solution amount (g) used for titration". The amount of unreacted copper remaining was determined by putting a predetermined amount (g) of the dried product obtained by the above method for producing copper iodide into DMSO, dissolving copper iodide, and quantifying (g) the unreacted copper that did not dissolve as insoluble matter, and calculating based on the weight ratio (%) of "insoluble matter amount / predetermined amount of dried product". The purity of the produced copper iodide was measured by volumetric analysis using an EDTA·2Na standard solution. The above results are shown in a table.

[0037] The median diameter of the copper powder was determined as the particle diameter at the point where the cumulative volume from the small particle side was 50% in the volume frequency particle size distribution measured by the laser diffraction scattering method obtained when copper powder and a surfactant (Tween 20) were put into water, dispersed for 10 minutes at a frequency of 24 kHz using an ultrasonic cleaning device to prepare a measurement sample, and the particle size distribution of the copper powder in the measurement sample was measured using a particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., MT-3300EXII).

[0038] (Examples A2 to A4) In the preparation step, cuprous iodide was obtained in the same manner as in Example A1, except that the amount of ion-exchanged water was changed to 400 g, 500 g, and 700 g. (Example A5) In the preparation step, cuprous iodide was obtained in the same manner as in Example A1, except that the amount of solid iodine was changed to 102 g and the amount of copper powder was changed to 50 g.

[0039]

Table 1

[0040] Examples A3 to A5 showed that, compared with Examples A1 and A2, the amount of unreacted copper residue was lower and the yield was further increased. This result is presumably due to the high stirrability of copper powder in the aqueous solution. In preliminary experiment A, in which the iodine concentration of the polyiodide ion-containing aqueous solution immediately before adding copper powder was set to 51% by mass in the same manner as in Example A1 except that no ion-exchanged water was used, it was found that the stirring operation of copper powder in the aqueous solution was difficult compared with Examples A1 to A5.

[0041] The purity of the cuprous iodide obtained in Example A4 was 99.93%. Also, even when the stirring time in the reaction step of Example A4 was shortened from 60 minutes to 20 minutes, a result was obtained in which the amount of unreacted copper residue was comparable to that of Example A4. As a reference example, the same conditions as in Example A1 were used except that hydroiodic acid and solid iodine were added to the aqueous solution containing copper powder and ion-exchanged water in this order. As a result, the amount of unreacted copper residue increased compared with Example A1.

[0042] <Experiment B: Liquid temperature> (Examples B1 to B4) In the reaction step, cuprous iodide was obtained in the same manner as in Experimental Example A4, except that the liquid temperature of the polyiodide ion-containing aqueous solution was changed to 10°C, 20°C, 40°C, and 50°C.

[0043] Examples B1 to B4 all showed a result of 0% unreacted copper residue, similar to Experimental Example A4. From this result, it was found that in the method for producing copper iodide of the present invention, when the copper iodide concentration is appropriate, the degree of freedom of temperature becomes higher.

[0044] <Experiment C: pH, solution composition> (Examples C1 to C3) In the preparation step, 200 g of hydroiodic acid was changed to 100 g of hydroiodic acid and 100 g of sodium iodide, 20 g of hydroiodic acid and 180 g of sodium iodide, and 200 g of sodium iodide. Otherwise, in the same manner as in Example A4, dried copper iodide was obtained.

[0045] [Table 2]

[0046] From the results of Experiment C, it was found that the polyiodide ion-containing aqueous solution contains protons, that is, the lower the pH, the higher the yield tends to be.

[0047] <Experiment D: catalyst amount> (Example D1) In the preparation step, dried copper iodide was obtained in the same manner as in Example A4, except that the amount of ion-exchanged water was changed to 750 g and the amount of hydroiodic acid was changed to 150 g. The addition amount of hydroiodic acid (catalyst) was 1 mol in Example A4 and 0.75 mol in Example D1 when the iodine equivalent of solid iodine in the preparation step was based on 1 mol. Example D1 showed a result of 0% unreacted copper residue. Also, in a preliminary experiment D in which the addition amount of hydroiodic acid (catalyst) was set to 0.5 mol in the same manner as in Example A except that the amount of ion-exchanged water was changed to 780 g and the amount of hydroiodic acid was changed to 100 g, the unreacted copper residue was higher than that in Example A4 and Example D1.

Claims

1. A method for producing copper iodide, comprising a reaction step of adding metallic copper to an aqueous solution containing polyiodide ions and reacting the polyiodide ions with the metallic copper to obtain copper iodide.

2. The method for producing copper iodide according to Claim 1, including a preparation step of preparing an aqueous solution containing polyiodide ions before the reaction step, wherein, in the preparation step, a catalyst is reacted with solid iodine in an aqueous solvent to obtain the aqueous solution containing polyiodide ions.

3. The method for producing copper iodide according to Claim 2, wherein the catalyst contains at least hydroiodic acid.

4. The method for producing copper iodide according to Claim 1 or 2, wherein the concentration of copper iodide in the aqueous solution containing polyiodide ions obtained in the reaction step is 5% by mass or more and 60% by mass or less.

5. The method for producing copper iodide according to Claim 1 or 2, wherein, in the reaction step, the liquid temperature of the aqueous solution containing polyiodide ions is 5°C or more and 55°C or less.

6. The method for producing copper iodide according to Claim 1 or 2, wherein, in the reaction step, the pH of the aqueous solution containing polyiodide ions is 7 or less.

7. The method for producing copper iodide according to Claim 1 or 2, wherein, in the reaction step, the iodine concentration measured by thiosulfate titration in the aqueous solution containing polyiodide ions immediately before adding the metallic copper is 1% by mass or more.

8. The method for producing copper iodide according to Claim 1 or 2, wherein, after the reaction step, the iodine concentration measured by thiosulfate titration in the aqueous solution containing polyiodide ions is 5% by mass or less.

9. The method for producing copper iodide according to Claim 1 or 2, wherein the metallic copper contains copper powder having a median diameter of 100 μm or less measured by a wet laser diffraction method.

10. The method for producing copper iodide according to Claim 2, wherein the reaction solution obtained in the reaction step is separated by solid-liquid separation to recover a separation liquid, and hydroiodic acid contained in the recovered separation liquid is reused as the catalyst in the preparation step.

11. The method for producing copper iodide according to Claim 1 or 2, A method for producing copper iodide, wherein the polyiodide ion contains one or more selected from the group consisting of triiodide ion, pentaiodide ion, and heptaiodide ion.

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