JP5532886B2 - Method for producing metallic indium - Google Patents

Description

  The present invention relates to a method for producing metallic indium from a metallic indium-containing alloy.

  Indium is a rare metal that is not contained in a specific ore at a high concentration and is contained as a trace component in zinc ore and the like. In recent years, indium-tin oxide (ITO) containing indium as a main component has been used for a transparent conductive film of a liquid crystal display device, and the demand for it has increased rapidly. Therefore, it is expensive by refining and recovering metal indium from scraps containing indium generated from within the ITO manufacturing process and scrap after using ITO as a target (collectively referred to as “ITO scrap”). Various methods for recycling metal indium have been studied.

  As one of these methods, a method for producing metal indium by a molten salt electrolysis method is known. For example, a method is known in which metal indium is collected at the cathode by molten salt electrolysis using mercury (indium-tin amalgam) containing metallic indium-tin as an anode and a molten salt electrolyte as a medium (for example, Patent Documents). 1). In this method, since the standard precipitation potentials of metal indium and tin are close, in ordinary molten salt electrolysis, tin is mixed into metal indium. Therefore, by using amalgam, indium can be selectively oxidized and dissolved. It has been.

  Although it is possible to recover purified metallic indium containing almost no impurities such as tin by this method, since mercury is used for the anode and molten salt electrolysis is performed at a temperature of 160 ° C. or higher, a part of the mercury is generated. It is a method that requires consideration for health and the environment, such as vaporizing as vapor. In addition, the metal indium deposited on the cathode contains a small amount of mercury, and it was necessary to combine further advanced purification techniques to remove the mercury.

  In addition, as a method for recovering metallic indium from an alloy containing indium, a method is also known in which an indium-containing alloy is used as an anode, electrolytic purification is performed using a molten salt electrolyte containing indium monochloride, and metallic indium is deposited on the cathode. (For example, refer to Patent Document 2). However, when the molten salt containing indium chloride comes into contact with air having a normal gas composition, that is, a high water vapor concentration, the moisture content of the molten salt increases, and the molten salt is denatured by a chemical reaction, increasing the cell voltage and the cathode. The quality of metallic indium deposited on the steel is lowered. Moreover, it is necessary to exchange part or all of the molten salt deteriorated by moisture absorption.

  Moreover, in this patent document 2, the content of indium chloride is preferably 50 to 67% by weight, and the reason is that when it is lower than 50% by weight, zinc is mixed in the deposited indium, which is not preferable, and 67% by weight. If it is higher, tin is mixed in the deposited indium, which is not preferable.

  Further, in a method of electrolytic purification using a mixed molten salt containing indium chloride and zinc chloride using an alloy containing indium metal as an anode, a method of adding ammonium chloride for the purpose of improving the oxidation resistance of the mixed molten salt is also known. (For example, see Patent Document 3). However, the addition of ammonium chloride increases the melting point of the molten salt, so that the electric resistance of the molten salt increases, the electrolytic cell voltage increases, the impurity content increases, and the odor of ammonia, which is a decomposition product of ammonium chloride, increases. In order to worsen the working environment, there were many problems such as the need for an exhaust gas treatment facility as a countermeasure.

  On the other hand, an aluminum chloride-based molten salt electrolyte bath mainly composed of aluminum chloride and containing at least one chloride is used for electroplating aluminum or aluminum alloy. When the amount of impurities such as moisture contained in the electrolyte bath increases, it becomes difficult to form a smooth plating film. Therefore, in order to remove this impurity, the composition of the electrolyte bath is adjusted so that the aluminum chloride content is 50 mol% or less. There is known a method of purifying an electrolyte bath by adjusting so that the precipitated impurities are separated from the bath (see, for example, Patent Document 4).

  By this method, electrochemical operation such as electroplating is possible, but since this molten salt is mainly composed of aluminum chloride, it is highly hygroscopic, has a remarkable hydrolyzability, and slightly leaks into the gas phase. The molten salt may be altered by moisture. In addition, since aluminum chloride has a high vapor pressure, a part of the aluminum chloride evaporates, the composition changes, and industrially long-term stable operation is difficult. In addition, the present inventors made this aluminum chloride as a molten salt and produced metal indium from a metal indium-containing alloy. As a result, it has been found that there are many problems such as a part of metal aluminum being electrodeposited in metal indium and reducing the purity of indium.

Japanese Patent Publication No.46-2734 WO2006-046800 Soviet Patent No. 531380 JP 04-254600 A

  An object of the present invention is to provide an effective and efficient method for producing metal indium capable of solving various problems of the conventional method, that is, highly purified metal indium from a metal indium-containing alloy over a long period of time. An object of the present invention is to provide a method for producing at a high recovery rate.

  As a result of intensive studies on the technology for producing metal indium from an alloy containing metal indium, the present inventors have optimized the type and composition of the electrolyte used for molten salt electrorefining and optimized the water content in the molten salt. As a result, it was found that the purity of the metal indium deposited on the cathode can be increased, the electrolyte of the molten salt is stabilized, and the metal indium can be efficiently electrodeposited and recovered, and the present invention has been completed.

  That is, the present invention uses metal indium for the anode and cathode of a metal indium-containing alloy, uses an indium chloride-zinc chloride molten salt mainly composed of indium chloride as an electrolyte, and indium from the anode by molten salt electrolysis. In the method for producing metal indium, which is eluted as a cation and electrodeposits metal indium on the cathode, the indium chloride content in the indium chloride-zinc chloride molten salt is 68% by weight or more, and the water content in the molten salt is 0.00. The present invention relates to a method for producing metallic indium, characterized by being 5% by weight or less.

The moisture content in the present invention is a value based on the moisture content of the molten salt, and the moisture content indicates the moisture content per unit weight of the molten salt containing moisture (edited by the Powder Engineering Society). (See "Handbook of Powder Engineering", page 588 (1986))
Hereinafter, the present invention will be described in detail.

  In the present invention, a metal indium-containing alloy is used for the anode. The alloy in the present invention refers to a metal-like material composed of indium metal and one or more other metal elements and / or non-metal elements, and the bonding state thereof is not particularly limited. The content of metal indium is not particularly limited. That is, it can be suitably used regardless of whether metal indium is a main component or a trace amount. The metal indium content in the metal indium-containing alloy is preferably 100 ppm by weight to 99.999% by weight, more preferably 1% by weight to 99.99, from the degree of metal indium purification, indium recovery, and indium productivity. % By weight, more preferably 60% by weight to 99.9% by weight.

  The type of metal other than metal indium in the metal indium-containing alloy is not particularly limited. For example, Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co , Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Sb, Te, Cs, Ba, Ta, W, Re , Os, Ir, Pt, Au, Tl, Pb, Bi.

  Among these, metals having good separation and purification from indium in molten salt electrolysis are Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu. , Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Cs, Ba, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb Bi, especially Sn, Cu, Fe, Si, Ni, Pb, Na, Ca and Mg are preferable because they can be easily separated and purified from indium.

  Further, as the metal indium-containing alloy, used indium solder after using metal indium as solder, metal indium-containing alloy obtained by reducing the indium compound, and the like can also be used. The indium compound is not particularly limited as long as it is a compound containing indium. Specific examples include indium oxide, indium hydroxide, indium chloride, indium sulfate, indium nitrate, and ITO scrap.

  For example, as a method of obtaining an alloy containing indium metal from ITO scrap, a method of reducing the ITO scrap with a reducing agent, dissolving the ITO scrap in an acidic aqueous solution such as hydrochloric acid, nitric acid, sulfuric acid, or a mixed acid thereof, After obtaining indium chloride, indium sulfate, indium nitrate or the like, and then adding an alkali to form a compound containing indium hydroxide, and further converting the compound containing indium hydroxide into indium oxide by heat treatment, a reducing agent Or a solution containing indium chloride, indium sulfate or indium nitrate, and then adding a base metal rather than indium, specifically metallic aluminum or metallic zinc. The metal indium containing alloy is deposited by substitution, and the metal indium containing alloy is deposited. That method and the like can be mentioned.

  As a molten salt used in the present invention, first, a salt containing indium is naturally essential.

  In the present invention, indium chloride is used because of its low melting point, excellent oxidation resistance, and low electrical resistance. However, using indium chloride alone is not economical because indium is a rare metal and expensive.

  Therefore, although it is used as a mixed molten salt containing a salt other than indium chloride, zinc chloride is used in combination in consideration of the features of low hygroscopicity and hydrolyzability and relatively low melting point.

  It is essential that the content of indium chloride in the molten salt is 68% by weight or more, and that the water content of the molten salt is 0.5% by weight or less. When the content of indium chloride is less than 68% by weight, that is, when the zinc chloride content is 32% by weight or more, zinc is considerably electrodeposited on the cathode, and the purity of metallic indium is lowered. Furthermore, zinc chloride has a low electrical conductivity in the molten salt, and if it is contained at 32% by weight or more, the liquid resistance increases, the electrolytic cell voltage increases, and the running cost increases, which is not economical. In the molten salt in the present invention, the electrolytic cell voltage can be lowered, the melting point can be lowered, and the operating temperature can be lowered by containing 68% by weight or more of indium chloride. Accordingly, the content of indium chloride in the molten salt is preferably 70% by weight or more, and more preferably 75% by weight or more.

  In addition, as described above, in Patent Document 2, when the content of indium chloride is higher than 67% by weight, it is described that tin is mixed in the precipitated indium, which is not preferable. Not only the content of indium chloride is set to 68% by weight or more, but also the water content of the molten salt is set to 0.5% by weight or less, so that tin is not mixed in indium, and further the conductivity in the molten salt is increased. The liquid resistance is reduced, the electrolytic cell voltage is lowered, and the running cost is reduced, so that it is economical and the present invention has been completed.

  In the molten salt used in the present invention, the content of indium chloride is 68% by weight or more, and the water content of the molten salt is 0.5% by weight or less. At the time of melting in the above-mentioned Patent Document 4, it is described that the water content in the molten salt is 0.5 wt% or less, but the indium chloride content in this prior document is 50 mol% or less ( = 53 wt% or less), and the indium chloride content and its action are completely different from those of the present invention.

Indium chloride contained in the molten salt includes InCl, InCl ₂ , and InCl ₃ whose indium valences are monovalent, divalent, and trivalent, and it is essential to include at least one of them. More preferred is InCl that has a low melting point and enables molten salt electrolysis at a lower temperature. The molten salt electrolyte bath containing InCl, since indium move univalent preferable from the fact that compared to InCl ₃ is trivalent, it triples the production rate of In in the same amount of electricity.

  The water content of the molten salt of the present invention is 0.5% by weight or less. If the water content exceeds 0.5% by weight, solids are deposited in the molten salt, inhibiting the deposition of indium metal on the cathode, leading to a decrease in current efficiency. However, this is because the impurity content in the metal indium deposited on the cathode becomes high and sufficient purification may not be possible.

  In addition, the water content in the molten salt in the present invention indicates the water content at any time during the operation from the beginning of molten salt electrolysis to the end of molten salt electrolysis. The most preferred embodiment is to dehydrate the water in the molten salt before the start of operation, reduce the water content in the molten salt to 0.5 wt% or less, prevent water absorption of the molten salt even during operation, % Or less. Furthermore, the water content of a preferable molten salt is 0.4% by weight or less.

  The water vapor concentration in the gas phase part in contact with the molten salt is not particularly limited, but when the water vapor concentration is low, the water content of the molten salt evaporates, but when it is high, the molten salt absorbs moisture and the water content increases. Sometimes. Therefore, as one method for keeping the water content low, there is a method for keeping the water vapor concentration in the gas phase portion in the electrolytic cell low. Specifically, the water vapor concentration in the gas phase part is preferably 1% by volume or less, more preferably 0.5% by volume or less. Moreover, the component of the gaseous phase part which is contacting with molten salt is not specifically limited, For example, air, nitrogen, argon, helium, hydrogen, carbon monoxide, a carbon dioxide etc. can be used. Preferably, the oxygen concentration in the gas phase is set to 10% by volume or less, so that the dissolved oxygen concentration in the molten salt can be kept low, and oxidation of the molten salt and electrodeposited indium is prevented. More preferably, the main component is at least one selected from nitrogen, argon and helium.

  The shape of the electrolytic cell used for molten salt electrolysis is not particularly limited as long as the anode chamber and the cathode chamber are not in contact with each other and electricity does not flow directly. In other words, it is sufficient if the anode chamber and the cathode chamber are separated from each other. For example, normal use as described in the book “Molten salt technology is a key technology in the 21st century (Application of Molten Salt (IPC Publishing))” A molten salt electrolyzer can be applied. The appropriate electrolytic cell shape differs depending on the operation method such as whether the anode and the cathode are solid or liquid, and whether the operation is a continuous type or a batch type, and may be appropriately selected.

Specifically, when the metal indium-containing alloy in the anode chamber is melted and the metal indium in the cathode chamber is also melted, the cathode chamber and the anode chamber are partitioned by a partition, and the upper part of both electrodes is a molten salt electrolyte bath. Examples include an electrolytic cell in which a salt bridge structure or an electrolytic cell shape is cylindrical, and an anode is placed in an insulating container in the center of a molten salt electrolyte bath, and a cathode is disposed so as to surround the anode. be able to. As described above, the gas atmosphere in the molten salt electrolyzer may sometimes improve the stability of the molten salt by lowering the water vapor concentration and the oxygen concentration. Furthermore, depending on the structure of the molten salt electrolysis tank, the area where the molten salt comes into contact with the gas phase part may be reduced, and moisture absorption of the molten salt may be suppressed. Preferably, the contact area with the gas phase part is 0.1 to 100 m ² / m ³ per unit molten salt capacity, and more preferably 0.2 to 80 m ² / m ³ .

In such molten salt electrolysis method, a One of the features that can increase the current density, the current density is preferably from 1~200A / dm ^2. When operating at less than 1 A / dm ² , the production rate per unit electrode area may decrease. From the viewpoint of productivity, the higher the current density, the better. However, at a current density exceeding 200 A / dm ² , when metal indium is deposited on the cathode, impurities may be taken in and it may be difficult to obtain high-purity indium. The current density is more preferably ^{2 to} 100 A / dm ² and further 3 to 50 A / dm ² .

  Moreover, the operation temperature of molten salt electrolysis will not be specifically limited if it is more than melting | fusing point of a molten salt electrolyte bath. 90-500 degreeC is preferable and 100-450 degreeC is more preferable from the operation | use operation surface of corrosion of apparatus material and molten salt electrolysis.

  Furthermore, the time required for the molten salt electrolysis is sufficient if it is sufficient to perform electrolysis of 50 to 100% of indium contained in the alloy in order to avoid a sufficient recovery rate and mixing of impurities.

  By electrolyzing under the proper operating conditions described above, high-purity metal indium can be deposited on the cathode, but if the metal indium has not achieved the target purity, the same operation is performed. Molten salt electrolysis may be further performed one or more times, and purification may be performed until the target purity is reached. Or depending on the kind of impurity, you may implement combining the purification method of the metal indium known conventionally. Specifically, alkali casting methods using alkali metal hydroxides and chlorination methods using chlorinating agents such as ammonium chloride can be adopted, and by combining these purification techniques as appropriate, more effective and efficient Indium metal can be manufactured.

  According to the method of the present invention, highly purified metal indium can be produced from a metal indium-containing alloy with a high recovery rate over a long period of time.

It is the figure which represented typically the H-type electrolytic cell used in the Examples 1, 2 and Comparative Example 1. It is the figure which represented typically the H type continuous electrolytic cell used by the present Example 3 and Comparative Examples 2, 3, and 4. FIG.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited only to these Examples.

  In the present invention, the water content in the molten salt is measured by dissolving the molten salt in a dehydrated methanol solvent, sampling a part thereof, and Karl Fischer reagent (trade name “Hydranal Composite 5” manufactured by Sigma-Aldrich). ) And titrated.

Example 1
As raw material for the metal indium-containing alloy, 1814 g of ITO scrap (91.1 wt% indium oxide, 8.9 wt% tin oxide) generated during the production of the ITO target was ground to an average particle size of 51 μm with a crusher, and reduced to 1735 g of ground powder. 170.9 g of graphite (product name “KS-75”, manufactured by Lonza) was mixed, and the mixture was placed in a magnetic crucible having an internal volume of 1 L and charged into an electric furnace. After replacing the inside of the electric furnace with nitrogen gas, the temperature of the furnace wall was raised to 1100 ° C. in 6 hours and held at 1100 ° C. for 3 hours. After completion of the reaction, the inside of the electric furnace was cooled and the total weight of the reduction product and the unreacted raw material powder was measured to be 1456.3 g.

  When the processed product was analyzed with an X-ray diffractometer, the diffraction peak of indium oxide in the scrap became weak, and instead a strong peak of metal indium was observed, so the reduction of indium oxide in the ground ITO scrap was reduced. Was confirmed to be good. Also, almost all of the tin oxide was converted to metal tin, and it was confirmed that the reduction product was an indium-tin alloy.

  Next, molten salt electrolysis was performed to purify and recover metallic indium from the alloy. The electrolytic cell is an H-type electrolytic cell having an inner diameter of 2 cm and a height of 13 cm made of Pyrex (registered trademark) glass as shown in FIG. 1, and 63.2 g of an indium-tin alloy as a reduction product is formed on the anode. The cathode was charged with 29.9 g of indium metal having a purity of 99.999% by weight. The weight of the molten salt charged was 70.3 g, and the composition was 73.5 wt% (= 71.5 mol%) indium monochloride and 28.5 mol% zinc chloride. The water content at this time was 0.4% by weight.

Next, platinum conducting wires were inserted into the anode and cathode of the electrolytic cell, and the electrolytic cell was placed in an electric muffle furnace, and the temperature of the electrolytic cell was 240 ° C., and molten salt electrolysis was performed. Molten salt electrolysis was carried out for 8 hours using a constant current device (Kikusui Electronics Co., Ltd., trade name “PMC18-5”) at a current value of 0.94 A and a current density of 30 A / dm ² .

  As a result, 31.5 g of metal indium was dissolved from the indium-tin alloy charged in the anode chamber, and 61.1 g of metal indium was obtained from the cathode chamber. The water content in the molten salt at the end of electrolysis was 0.3 wt. %Met. Since the amount charged into the cathode chamber was 29.9 g, the amount of electrodeposition was 31.2 g.

  Moreover, the electrolytic cell voltage changed at 4.5V.

  A part of the metal indium on the cathode is taken out, dissolved in hydrochloric acid, the impurity content is obtained with an ICP analyzer, and the tin content in the electrodeposited metal indium corrected by the amount and purity of the charged metal indium is as low as 95 ppm by weight. The zinc content was also as low as 2 ppm by weight.

  Indium oxide was produced using the recovered metal indium as a raw material, an ITO target was produced from the indium oxide and tin oxide, and the sputtering performance as the ITO target was evaluated. As a result, the generation of nodules was hardly observed, and it was reusable as a raw material for producing the ITO target.

Example 2
Using the indium-tin alloy recovered by the reduction in Example 1, the molten salt electrolytic purification was performed using the same Pyrex (registered trademark) glass H-type electrolytic cell as in Example 1.

  The anode chamber was charged with 61.7 g of the alloy, and the cathode chamber was charged with 30.4 g of 99.999 wt% metallic indium prepared separately. The weight of the molten salt charged was 75.4 g, and its composition was 73.6% by weight of indium monochloride (= 71.6% by mole), 28.4% by mole of zinc chloride, and 0.5% by weight of water content. Platinum lead wires were inserted into the anode and cathode of the electrolytic cell, and the electrolytic cell was placed in an electric muffle furnace, and the temperature of the electrolytic cell was 240 ° C., and molten salt electrolysis was performed.

Molten salt electrolysis was carried out for 14 hours using the constant current device used in Example 1 with a current value of 0.94 A and a current density of 30 A / dm ² .

  As a result, 55.8 g was dissolved from the indium-tin alloy charged in the anode chamber, and 86.1 g was obtained from the cathode chamber. The water content in the molten salt at the end of electrolysis was 0.3% by weight. It was. Since the amount charged into the cathode chamber was 30.4 g, the amount of electrodeposition was 55.7 g. A part of the metal indium on the cathode is taken out, dissolved in hydrochloric acid, the impurity content is obtained with an ICP analyzer, and tin in the deposited metal indium corrected from the amount and purity of the charged metal indium is 520 ppm by weight, the zinc content Was also as low as 3 ppm by weight. Further, the weight of indium electrodeposited in the cathode chamber was 55.7 g against the indium weight of 56.5 g charged in the anode chamber, and the recovery rate was 98.6%, which was good.

  Moreover, the electrolytic cell voltage changed at 4.8V.

Comparative Example 1
Using the indium-tin alloy recovered by the reduction in Example 1, the molten salt electrolytic purification was performed using the same Pyrex (registered trademark) glass H-type electrolytic cell as in Example 1. The anode chamber was charged with 63.3 g of the alloy, and the cathode chamber was charged with 30.1 g of indium metal having a purity of 99.999 wt% prepared separately. The weight of the molten salt charged was 70.8 g, and the composition was 73.5% by weight of indium monochloride (= 71.5% by mole) and 28.5% by mole of zinc chloride. The water content was adjusted to 0.9% by weight by adding water to the molten salt.

Platinum lead wires were inserted into the anode and cathode of the electrolytic cell, and the electrolytic cell was placed in an electric muffle furnace, and the temperature of the electrolytic cell was 240 ° C., and molten salt electrolysis was performed. Molten salt electrolysis was carried out for 14 hours in the same manner as in Example 2, using the constant current device used in Example 1 and setting the current value to 0.94 A and the current density to 30 A / dm ² .

  As a result, 53.8 g was dissolved from the indium-tin alloy charged in the anode chamber, and 83.7 g was obtained from the cathode chamber. The water content in the molten salt at the end of electrolysis was 0.8% by weight. It was. Since the amount charged into the cathode chamber was 30.1 g, the amount of electrodeposition was 53.6 g. A part of the metal indium on the cathode was taken out, dissolved in hydrochloric acid, the impurity content was determined with an ICP analyzer, and tin in the electrodeposited metal indium corrected from the amount and purity of the charged metal indium was 1860 ppm by weight, the zinc content Was as high as 52 ppm by weight. In addition, the weight of indium electrodeposited in the cathode chamber was 53.7 g, the indium recovery rate was 93.9%, which was lower than 98.6% in Example 2, compared to 57.2 g of indium charged in the anode chamber.

  In addition, the electrolytic cell voltage was unstable and increased to initial 5.2V and to 6.1V just before the end of operation.

Example 3
In order to purify and recover metallic indium from used indium solder, molten salt electrolytic purification was performed. The used indium solder contained 99.22 wt% of the main component indium, 4580 wt ppm of tin, which is an impurity, and 3220 wt ppm of copper.

  For the molten salt electrolytic purification, an H-type continuous electrolytic cell made of Pyrex (registered trademark) glass shown in FIG. 2 was used. The anode chamber was charged with 143.9 g of the alloy, and the cathode chamber was charged with 49.1 g of 99.999 wt% metallic indium prepared separately. The weight of the molten salt charged was 127.1 g, and the composition was 68.1% by weight of indium monochloride (= 65.9% by mole) and 34.1% by mole of zinc chloride. The water content at this time was 0.4% by weight. Stainless steel wires are inserted into the anode and cathode of the electrolytic cell, the electrolytic cell is placed in an electric muffle furnace, the temperature of the electrolytic cell is set to 290 ° C., and nitrogen gas is continuously introduced into the electrolytic cell at 1.2 L / hr. Molten salt electrolysis was carried out while circulating the product. At this time, the water vapor concentration in the nitrogen gas was 0.1 vol%.

Molten salt electrolysis was carried out continuously for 30 days using the constant current apparatus used in Example 1 with a current value of 0.45 A and a current density of 20 A / dm ² . Since indium in the anode chamber is electrolyzed and the holding amount decreases, 46.3 g of used indium solder is supplied once a day. The metal indium electrodeposited in the cathode chamber was recovered by continuously flowing out from the overflow tube.

  As a result, the weight of metal indium recovered from the cathode chamber, the current efficiency of the cathode chamber, and the contents of impurities tin, copper, and zinc are shown in Table 1 below.

この表から、３０日間の連続運転にも拘らず、陰極室からは金属インジウムが電流効率９９％以上で回収でき、更に、３０日間に亘って、不純物スズ、銅、亜鉛の含有量は少なく、良好な結果であった。又、運転終了後に溶融塩中の水分含有量を測定した結果０．２重量％と低く良好であった。

From this table, despite the continuous operation for 30 days, metal indium can be recovered from the cathode chamber with a current efficiency of 99% or more, and over 30 days, the content of impurities tin, copper, zinc is small, It was a good result. Further, the water content in the molten salt was measured after the operation was completed, and as a result, it was as low as 0.2% by weight and good.

  The electrolytic cell voltage was as high as 3.5 V immediately before supplying the indium solder to the anode chamber because the maximum distance between the electrodes was 2.5 V, and immediately after the insertion, the distance between the electrodes was minimum and became 2.5 V. This electrolytic cell voltage remained substantially constant over 30 days.

Comparative Example 2
In order to purify and recover metallic indium from the used indium solder used in Example 3, molten salt electrolytic purification was performed.

  As in Example 3, the molten salt electrolytic purification used an H-type continuous electrolytic cell made of Pyrex (registered trademark) glass as shown in FIG. The anode chamber was charged with 140.3 g of the alloy, and the cathode chamber was charged with 50.4 g of metallic indium of 99.999 wt% prepared separately. The weight of the molten salt charged was 125.6 g, and the composition was 63.1% by weight of indium monochloride (= 60.8% by mole) and 39.2% by mole of zinc chloride. The water content at this time was 0.4% by weight. Stainless steel wires are inserted into the anode and cathode of the electrolytic cell, the electrolytic cell is placed in an electric muffle furnace, the temperature of the electrolytic cell is set to 290 ° C., and nitrogen gas is continuously introduced into the gas phase of the electrolytic cell at 1.2 L / hr. Molten salt electrolysis was carried out while circulating. At this time, the water vapor concentration in the nitrogen gas was 0.1 vol%.

Molten salt electrolysis was carried out continuously for 30 days using the constant current apparatus used in Example 1 with a current value of 0.45 A and a current density of 20 A / dm ² . Since indium in the anode chamber is electrolyzed and the holding amount decreases, 45.2 g of used indium solder was supplied once a day. The metal indium electrodeposited in the cathode chamber was recovered by continuously flowing out from the overflow tube.

  As a result, the moisture content in the molten salt was measured after the operation was completed, and the result was as low as 0.3% by weight. Table 2 below shows the weight of metal indium recovered from the cathode chamber, the current efficiency of the cathode chamber, and the contents of impurities tin, copper, and zinc.

この表から、３０日間の連続運転中、電流効率は約９７％で、実施例３の９９％以上よりも低く生産性が劣り、不純物の亜鉛含有量も多く、十分な精製ができなかった。

From this table, during the continuous operation for 30 days, the current efficiency was about 97%, which was lower than 99% or more of Example 3, the productivity was inferior, the impurity zinc content was large, and sufficient purification could not be performed.

Comparative Example 3
Using the used indium solder used in Comparative Example 2, electrolytic purification was performed using the same Pyrex (registered trademark) glass H-type continuous electrolytic cell as in Example 3. The anode chamber was charged with 145.7 g of the alloy, and the cathode chamber was charged with 50.4 g of metallic indium with a purity of 99.999 wt% prepared separately. The weight of the molten salt charged was 128.6 g, and the composition was 63.2% by weight of indium monochloride (= 61.5% by mole) and 38.5% by mole of zinc chloride. The water content was 0.7% by weight by adding water to the molten salt. Stainless steel wires are inserted into the anode and cathode of the electrolytic cell, the electrolytic cell is placed in an electric muffle furnace, the temperature of the electrolytic cell is set to 290 ° C., and the gas phase of the electrolytic cell is 1% of water having a water vapor concentration of 1.5 vol%. Molten salt electrolysis was performed while continuously flowing at 2 L / hr.

Molten salt electrolysis was carried out continuously by using the constant current device used in Example 1 with a current value of 0.45 A and a current density of 20 A / dm ² . Since indium in the anode chamber is electrolyzed and the holding amount decreases, used indium solder is supplied once a day. The metal indium electrodeposited in the cathode chamber was recovered by continuously flowing out from the overflow tube.

  As a result, a large amount of white solid was produced in the molten salt, and the current efficiency dropped to 76% on the 10th day from the start of operation, so it was stopped. Table 3 below shows the operation results during this period, that is, the weight of recovered metal indium, the current efficiency of the cathode chamber, and the contents of impurities tin, copper, and zinc.

この表から、陰極室の電流効率は９５．５％から７６．０％に急激に低下し、又、不純物スズ、銅の含有量は高く十分な精製ができなかった。１０日間の連続運転終了後に溶融塩中の水分含有量を測定した結果３．５重量％に増加していた。

From this table, the current efficiency of the cathode chamber dropped rapidly from 95.5% to 76.0%, and the contents of impurities tin and copper were high, and sufficient purification was not possible. As a result of measuring the water content in the molten salt after the continuous operation for 10 days, it was increased to 3.5% by weight.

Comparative Example 4
Using the used indium solder used in Comparative Example 2, electrolytic purification was performed using the same Pyrex (registered trademark) glass H-type continuous electrolytic cell as in Example 3. The anode chamber was charged with 141.7 g of the alloy, and the cathode chamber was charged with 48.5 g of 99.999 wt% metallic indium prepared separately. The weight of the molten salt charged was 135.3 g, and the composition thereof was 46.6% by weight of indium monochloride (= 45.3% by mole), 54.7% by mole of zinc chloride, and the water content was 0.4% by weight. . Stainless steel wires are inserted into the anode and cathode of the electrolytic cell, the electrolytic cell is placed in an electric muffle furnace, the temperature of the electrolytic cell is 290 ° C., and nitrogen gas having a water vapor concentration of 0.1 vol% is added to the gas phase of the electrolytic cell. Molten salt electrolysis was performed while continuously flowing at 1.2 L / hr.

Molten salt electrolysis was carried out continuously by using the constant current device used in Example 1 with a current value of 0.45 A and a current density of 20 A / dm ² . Since indium in the anode chamber is electrolyzed and the holding amount decreases, used indium solder is supplied once a day. The metal indium electrodeposited in the cathode chamber was recovered by continuously flowing out from the overflow tube.

  Table 4 below shows the recovered metal indium weight, the current efficiency of the cathode chamber, and the contents of impurities tin, copper, and zinc.

この表から、陰極室から回収したインジウム中には亜鉛含有量が非常に高く、精製が不十分であったため、運転を３日間で停止した。

From this table, the indium recovered from the cathode chamber had a very high zinc content and was not sufficiently purified, so the operation was stopped in 3 days.

Comparative Example 5
Using the used indium solder used in Comparative Example 2, electrolytic purification was performed using the same Pyrex (registered trademark) glass H-type continuous electrolytic cell as in Example 3. The anode chamber was charged with 137.5 g of the alloy, and the cathode chamber was charged with 51.6 g of 99.999% by weight metallic indium prepared separately. The weight of the molten salt charged was 115.4 g, and its composition was 26.2% by weight of indium monochloride (= 25.5% by mole) and 74.5% by mole of aluminum chloride. The water content at this time was 0.5% by weight. Stainless steel wires were inserted into the anode and cathode of the electrolytic cell, and the electrolytic cell was placed in an electric muffle furnace, and the temperature of the electrolytic cell was 250 ° C. Molten salt electrolysis was conducted by setting the current value to 0.45 A and the current density to 20 A / dm ² . Molten salt electrolysis was performed while continuously flowing nitrogen gas having a water vapor concentration of 0.3 vol% at 1.2 L / hr in the gas phase of the electrolytic cell.

  As a result, 13 hours after starting operation, white solids were scaled in the exhaust gas line, the line was blocked, and continuous operation became difficult, so the operation was stopped. Table 5 below shows the impurity content in the indium flowing out of the cathode chamber immediately before the shutdown.

この表から、陰極室から回収したインジウム中にはアルミニウム含有量が非常に多く、精製が不十分であった。

From this table, the indium recovered from the cathode chamber had a very high aluminum content and was not sufficiently purified.

  The present invention relates to a method for purifying and recovering metal indium from an alloy containing metal indium.

1: Anode (chamber) crude In alloy 2: Cathode (chamber) purified In
3: Molten salt 4: Anode conductor (platinum conductor with protective tube)
5: Cathode conductor (platinum conductor with protective tube)
6: Anode (chamber) crude In alloy 7: Cathode (chamber) purified In
8: Molten salt 9: Anode conductor (SUS wire)
10: Cathode conductor (SUS wire)
11: Crude In alloy inlet 12: Purified In overflow port 13: Gas inlet 14: Exhaust gas outlet 15: Gas communication pipe

Claims (9)

Metal indium is used as the anode and cathode of the metal indium-containing alloy, and indium chloride-zinc chloride molten salt containing indium chloride as the main component is used as the electrolyte, and indium is eluted from the anode as a cation by molten salt electrolysis. In the method for producing metallic indium, in which metallic indium is electrodeposited on the cathode, the indium chloride content in the indium chloride-zinc chloride molten salt is 68% by weight or more, and the molten salt has a water content of 0.5% by weight or less. A method for producing metal indium. 2. The method for producing metal indium according to claim 1, wherein the indium chloride is indium monochloride. The method for producing metal indium according to claim 1 or 2, wherein molten salt electrolysis is performed in a gas atmosphere having a water vapor concentration of 1 vol% or less. The method for producing metal indium according to any one of claims 1 to 3, wherein molten salt electrolysis is performed in a gas atmosphere having an oxygen concentration of 10% by volume or less. The method for producing metal indium according to claim 3 or 4, wherein the gas atmosphere is one or more selected from nitrogen, argon, and helium. The operation temperature of molten salt electrolysis is 140-500 degreeC, The manufacturing method of the metal indium in any one of Claims 1-5. The method for producing metal indium according to any one of claims 1 to 6, wherein the metal indium-containing alloy is an alloy obtained by reducing an indium compound. The method for producing metal indium according to claim 7, wherein the indium compound is an indium oxide-containing substance. 9. The method for producing metal indium according to claim 8, wherein the indium oxide-containing material is ITO scrap.

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