JP5028563B2 - Indium recovery method - Google Patents

Description

  The present invention relates to a method for recovering indium from an indium-containing workpiece containing gallium as an impurity.

  Demand for indium is increasing as a raw material for compound semiconductors such as InP and InAs, and for ITO used as a transparent electrode film for liquid crystal which has recently been rapidly growing. Indium is a metal element obtained in a trace amount as a by-product of the zinc smelting process together with gallium and the like, but recently, raw materials with a high indium content such as ITO target material scrap and semiconductor material scrap are increasing.

Among them, several methods for recovering indium using ITO target scraps as raw materials have been proposed. For example, there is a method using solvent extraction (see Patent Document 1), but this method is sufficient for separating and recovering indium from an object to be treated such as semiconductor scrap in which a large amount of the gallium of the family element is confused. Absent.
Japanese Patent Laid-Open No. 08-091838

  The present invention solves the above-mentioned problems in the conventional indium recovery method, has a simple process in wet refining of metal, and has good separability from gallium and the like, which are impurities of the same family, at low cost and high yield. A method that can recover indium at a high rate is proposed.

  Usually, indium-treated materials generated from semiconductor scrap are often in the form of metals in which homologous elements such as gallium, which are difficult to separate, are dissolved, and in the form of intermetallic compounds. At the same time, after the whole raw material is decomposed with an acid and made into a solution, it is common to take a means of separating impurities with a solvent or separating them while precipitating as a salt. It was thought to be ineffective. Therefore, as a result of intensive studies and studies to solve the above-mentioned problems, the present inventor brought a large amount of an alkaline agent into contact with an indium-containing workpiece containing a family impurity such as gallium at a predetermined temperature. The present inventors have found that gallium and the like, which are impurities of the same family, can be selectively eluted to easily separate and concentrate indium to be collected.

That is, an alkali hydroxide at least equal to the indium-containing object to be processed containing gallium as an impurity by mass is added to the indium-containing object, water is added to dissolve the impurity in the liquid, and then solid-liquid separation is performed. An indium concentrate is obtained, and the indium concentrate is leached with sulfuric acid, and hydrogen sulfide is blown into the indium concentrate to precipitate and separate as indium sulfide. The indium sulfide is then leached with hydrochloric acid and an oxidizing agent, and the leachate is hydroxylated. An indium recovery method for obtaining indium metal by adding alkali and converting indium to hydroxide, then dissolving the hydroxide with hydrochloric acid, subjecting the indium-containing hydrochloric acid solution to an indium electrowinning process as an electrolytic base solution, and performing electrowinning I will provide a.

  Further, the present invention provides a method of adding water after adding the alkali hydroxide to the indium-containing object to be processed in a solid state and performing heat treatment in advance. By this method, the rate of migration of impurities into the liquid such as gallium can be further increased. The heat treatment temperature is preferably 200 ° C. or higher.

  According to the indium recovery method of the present invention, it is cheaper and simpler than the conventional method, and it can be easily separated from homologous impurities such as gallium, and indium can be recovered in a high yield. Therefore, the present invention is extremely useful as a method for separating and concentrating indium from an indium-containing object containing gallium, which is a family impurity.

  FIG. 1 is a flowchart showing a schematic configuration of an indium recovery method according to an embodiment of the present invention. The indium recovery method according to the embodiment of the present invention will be described below with reference to FIG.

  The flow shown in FIG. 1 includes a step of adding an alkali hydroxide to an indium-containing object containing gallium as an impurity and subjecting it to heat treatment, a step of cooling, adding water and stirring at a predetermined liquid temperature after the heat treatment, The process is divided into liquid separation to obtain an indium concentrate. Further, the obtained indium concentrate is dissolved with a mineral acid such as sulfuric acid, and a sulfurizing agent such as hydrogen sulfide is added to further separate indium from the remaining impurities such as gallium to separate indium as sulfide. Sulfides containing indium are leached using hydrochloric acid containing an oxidizing agent. After neutralizing this hydrochloric acid leaching solution, it is again dissolved in hydrochloric acid and used as an electrolytic source solution in the indium electrowinning step, and electrolyzed to recover metallic indium.

  Examples of indium-containing objects include scraps generated in semiconductor epitaxial processes, ITO target material scraps used as liquid crystal transparent electrode films, etc., but the present invention is generally difficult to separate and recover from impurities such as gallium. This is especially effective for metal-shaped scrap.

  Solid alkali hydroxide such as flakes, powders, and granules is added to the indium-containing object containing gallium as the impurity. As the alkali hydroxide, sodium hydroxide and potassium hydroxide are preferable, but sodium hydroxide is preferable in view of cost. The amount of alkali hydroxide added is preferably equal to or greater than 20 times the mass of the indium workpiece. If the amount is less than the same amount, the gallium of the family impurity cannot be removed, and if it exceeds 20 times, the impurity separation effect is large, but the indium loss to be recovered increases and the yield decreases.

  When the indium-containing object to be processed containing gallium as an impurity is in a metal shape, a heat treatment step is indispensable, but in advance, other recovery steps, for example, a salt such as a hydroxide obtained in a recovery step from a zinc smelting by-product When indium is included in the form, the removal rate of impurities can be increased by adding water after adding the above alkali hydroxide without passing through the heat treatment step. The separation effect from gallium is also increased. Further, a sufficient separation effect can be obtained even if alkali hydroxide is used as a solution in advance.

  When the indium-containing object to be processed containing gallium as an impurity is in a metal shape or an intermetallic compound, it is desirable to perform heat treatment after adding the alkali hydroxide. The heat treatment temperature is preferably 200 ° C. or higher, more preferably 300 ° C. or higher, in view of the removal rate of gallium or the like that is a family impurity. The container can be made of PTFE up to 250 ° C., and SUS can be used for more than that. PTFE is preferable when impurities such as iron are a concern. The heat treatment time is 1 hour or longer, preferably 5 hours or longer. After heat treatment, it is preferable to cool in consideration of bumping in the next step.

  After standing to cool, leaching is carried out while adding water and stirring. The temperature of the liquid is 50 ° C or higher. The stirring speed is preferably 300 RPM or more.

  For solid-liquid separation in the next step, decantation, filter press, centrifugation, or normal filtration may be selected depending on the size of the batch. However, in small batches, the salt concentration is high, so centrifugation is followed by pressurization. Filtration is preferred. The liquid temperature may be returned to room temperature, but it is preferable to perform the liquid temperature at 50 ° C. or higher in consideration of filterability.

  The solid after the solid-liquid separation is concentrated with indium and separated from the impurity gallium in the liquid. The solid substance, that is, the indium concentrate, can be recovered as indium metal by the following process shown below.

  The indium concentrate is leached with sulfuric acid, and the free sulfuric acid concentration in the leachate is adjusted to 80 g / L or less. When a sulfurizing agent exceeding 80 g / L is added, indium sulfide formation is insufficient, and the recovery rate of indium is lowered. Next, a sulfurizing agent is added by means such as blowing hydrogen sulfide into the leachate, and the oxidation / reduction potential is adjusted to a range of −50 mV to 50 mV with an Ag / AgCl electrode, thereby leaving impurities such as gallium in the liquid. Indium can be separated and recovered as a sulfide precipitate. The precipitate can be separated into solid and liquid using a filter press or the like. If the oxidation-reduction potential is less than −50 mV, gallium starts to precipitate, and if it exceeds 50 mV, indium sulfide is not sufficiently generated, and the recovery rate of indium is lowered.

  The indium sulfide precipitate obtained above is leached with an oxidizing agent such as hydrochloric acid containing NaClO3. The leaching solution can be neutralized with an alkali and then filtered, and the hydroxide precipitate can be again leached with hydrochloric acid and used as an electrolysis solution for indium electrowinning.

  Moreover, if there is no restriction | limiting in particular in the purity of the indium metal obtained, an indium concentrate can be directly leached with hydrochloric acid, and the obtained indium-containing hydrochloric acid solution can be used as an electrolytic base solution for indium electrowinning.

  50 g of granular sodium hydroxide is added to 50 g of indium-containing material to be recovered as a hydroxide as a zinc smelting by-product (containing 10.6 g of In and 9.8 g of Ga), and made up to 1000 ml with water, and stirred at a liquid temperature of 50 ° C. and 300 rpm. While maintaining this state for 1 hour, the mixture was filtered to separate the precipitate. The indium concentration and gallium concentration in the precipitate were measured with an ICP emission spectroscopic analyzer, and the recovery rate was calculated. As a result, 98.5% of indium was recovered in the precipitate, and only 0.6% of gallium was removed in the solution.

  Metal indium scrap 50 g (In 25.4 g, containing Ga 24.5 g) generated from semiconductor scrap was used as an indium-containing workpiece, 250 g of granular sodium hydroxide was added, and heat treatment was performed at 200 ° C. for 1 hour. After cooling to room temperature, water was added to make 1000 ml, and this state was maintained for 1 hour with stirring at a liquid temperature of 50 ° C. and 300 rpm, followed by filtration to separate the precipitate. The indium concentration and gallium concentration in the precipitate were measured with an ICP emission spectroscopic analyzer, and the recovery rate was calculated. As a result, 99.1% of indium was recovered in the precipitate and 73.9% of gallium was removed in the solution.

  The same procedure as in Example 2 was performed except that the heat treatment temperature was 350 ° C. As a result, 98.1% of indium was recovered in the precipitate and 95.2% of gallium was removed in the solution.

  The same procedure as in Example 2 was performed except that the amount of granular sodium hydroxide to be added was 1000 g and the heat treatment temperature was 350 ° C. As a result, as a result, indium precipitates 96.3. % Was recovered and 97.7% of the gallium was removed in the solution.

  The same procedure as in Example 2 was performed except that the alkali hydroxide to be added was potassium hydroxide and the heat treatment temperature was 350 ° C. As a result, 98.5% of indium was recovered in the precipitate and 90.2% of gallium was removed in the solution.

  The same procedure as in Example 2 was performed except that the heat treatment operation was not performed. As a result, 99.8% of indium was recovered in the precipitate and 15.1% of gallium was removed in the solution.

  The precipitate obtained in Example 4, ie, 25 g of indium concentrate was leached at 160 g of sulfuric acid (1 + 1) at a liquid temperature of 80 ° C., and water was added to make a total volume of 1000 ml. The free sulfuric acid concentration in the leachate was 48 g / L. Next, hydrogen sulfide was blown into this leachate, and the oxidation-reduction potential was adjusted to −40 mV with an Ag / AgCl electrode. After the reaction, the resulting slurry was filtered to obtain a precipitate of indium sulfide. As a result of analyzing the precipitate, 98.8% of indium was recovered and 99.7% of the impurity gallium could be removed in the liquid.

1N Hydrochloric acid (500 ml) was added to the indium sulfide precipitate obtained above, and 150 ml of 20% sodium chlorate solution was further added, and leaching was performed at 30 ° C. The leachate was adjusted to pH = 9.5 with a 30% aqueous sodium hydroxide solution. The resulting indium hydroxide precipitate was filtered off. The obtained indium hydroxide was dissolved in hydrochloric acid and adjusted to pH = 1.5 with a 30% aqueous sodium hydroxide solution, and this solution was used as an electrolytic base solution at a liquid temperature of 40 ° C. and a current density of 0.02 A / cm 2. Electrolysis was performed to obtain indium metal.

It is a flowchart which shows schematic structure of the indium recovery method concerning one Embodiment of this invention.

Claims (4)

A method of recovering indium from an indium-containing object to be treated containing gallium as an impurity, wherein an alkali hydroxide having a mass equal to or more than that of the indium-containing object is added to the indium-containing object, and water is added. After dissolving some of the impurities in the liquid, solid-liquid separation to obtain an indium concentrate ,
The indium concentrate is leached with sulfuric acid, a sulfurizing agent is added to the sulfuric acid leachate, and indium is precipitated and separated as a sulfide. The sulfide is then leached with hydrochloric acid and an oxidizing agent, and an alkali hydroxide is added to the leachate, and indium is added. An indium recovery method for obtaining an indium metal by electrolysis by dissolving the hydroxide with hydrochloric acid to obtain an indium-containing hydrochloric acid solution, using the indium-containing hydrochloric acid solution as an electrolytic base solution for an indium electrowinning step . The heat treatment is performed after the alkali hydroxide is added to the indium-containing workpiece.
The indium recovery method described in 1. The method for recovering indium according to claim 2, wherein the heat treatment is performed at a temperature of 200 ° C. or higher. 2. The alkali hydroxide is sodium hydroxide.
The method for recovering indium according to any one of to 3.

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