JP4915015B2 - Purification method of gallium-containing solution - Google Patents

Description

  The present invention relates to a method for purifying a gallium-containing solution, and in particular, removes impurities from a gallium-containing solution, such as a gallium electrolyte used as an electrolytic solution to recover gallium metal by electrowinning, thereby purifying the gallium-containing solution. Regarding the method.

  Gallium is generally used for compound semiconductors, and in particular, high purity gallium of 6 to 7 N grade is used for manufacturing compound semiconductors such as GaAs and GaP, and is used for ICs, LSIs, light emitting diodes, and the like. Further, the use of a gallium alloy as a catalyst for alcohol decomposition and compounding has attracted attention, and high-purity gallium is required.

  Gallium is a metal element that is recovered in a small amount as a by-product of zinc smelting and aluminum smelting, and has recently been recovered from scrap containing gallium. In order to obtain gallium from smelting by-products and scrap containing gallium, gallium-containing smelting by-products and scrap are generally dissolved in an alkali solution and concentrated, and then recovered as metal by electrowinning. To be done.

  It is desirable that the gallium electrolyte used for such electrowinning does not contain any components that hinder the electrowinning, such as metals that are intended for collection, that is, impurity metals other than gallium. However, since the solution of smelting by-products and scrap dissolved in alkali contains various impurity metals other than gallium, electrolytic collection of impurity metals, etc. by adding chemicals or solid-liquid separation before electrolytic collection. The component which becomes the obstruction factor is removed.

  In addition, the composition of the gallium electrolyte is important because the purity of gallium obtained by electrowinning is almost determined by the composition of the gallium electrolyte. The electrolytic source solution that is the source of the electrolytic solution may contain impurity metals such as iron, copper, lead, tin, and indium. If these metals are contained even in trace amounts, Impurity metals are electrodeposited together with gallium metal, which not only lowers the quality of gallium metal, but also places a heavy burden on the high purity purification process that further increases the purity of gallium.

As a purification method of gallium electrolyte, indium precipitate formed by adding alkali metal oxalate to gallium electrolyte is filtered, or alkaline earth metal hydroxide or oxide is added to gallium electrolyte. There has been proposed a method for removing indium and vanadium by filtering the precipitate of vanadium formed by adding (see, for example, Patent Document 1). In addition, by maintaining the cathode current density at a low current density of 0.05 to 0.1 A / dm ² and performing electrolysis of a gallium electrolyte containing impurities such as indium, copper, and lead, indium, copper, A method has been proposed in which impurities such as lead are electrodeposited on the cathode side to be separated and removed from the electrolytic solution (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 63-496 (2nd page) JP-A-6-192875 (paragraph numbers 0008-0012)

  However, the method of Patent Document 1 is a method of removing indium or vanadium and copper from a gallium electrolyte, and cannot be applied to the purification of a gallium electrolyte containing iron, lead, tin or the like as impurities.

  Moreover, the method of patent document 2 is a method of removing indium, copper, and lead, and cannot fully purify the gallium electrolyte solution which contains iron, tin, etc. as an impurity. In addition, this method requires a long time to remove impurities and requires an electrolytic facility for purifying the gallium electrolyte, which increases the cost.

  In addition, when the gallium electrolyte is alkaline, a method is desired that can be used as a gallium electrolyte for obtaining high-purity gallium by simply removing impurities from the electrolytic base solution in a short time. ing. Furthermore, even when various impurities are contained in the source solution, such as when the source solution contains tin in addition to copper, lead, and indium, impurities can be easily removed from the source solution. A method that can be removed in a short time is desired.

  Therefore, in view of such conventional problems, the present invention can remove impurities from a gallium-containing solution containing at least one of copper, iron, lead, tin and indium as impurities easily and in a short time. An object of the present invention is to provide a method for purifying a gallium-containing solution.

  As a result of diligent research to solve the above problems, the present inventors have added gallium to a solution containing at least one of copper, iron, lead, tin, and indium as impurities and gallium, thereby obtaining gallium. It has been found that impurities can be easily removed from the contained solution in a short time, and the present invention has been completed.

  That is, the method for purifying a gallium-containing solution according to the present invention is characterized by adding metal zinc to a solution containing at least one of copper, iron, lead, tin and indium and gallium and then filtering. In this gallium-containing solution purification method, the solution is preferably an alkaline solution, the free NaOH concentration in the solution is preferably adjusted to 150 g / L or less, and the temperature of the solution is preferably adjusted to 40 ° C. or less. . The zinc metal is preferably zinc dust. Furthermore, the filtrate after filtration can be used as a gallium electrolyte for recovering gallium metal by electrowinning.

  According to the present invention, impurities are easily removed in a short time from a gallium-containing solution containing at least one of copper, iron, lead, tin and indium as impurities, and the concentration of impurities in the gallium-containing solution is extremely low. Can be a concentration. By performing electrowinning using the gallium electrolyte solution thus obtained, high-purity gallium can be recovered.

  In an embodiment of the method for purifying a gallium-containing solution according to the present invention, zinc metal is added to a solution containing at least one of copper, iron, lead, tin and indium and gallium, stirred, and then filtered to obtain a filtrate. to recover.

  As the metallic zinc, zinc powder in powder form, granular form or flake form can be used. The form of metallic zinc should just be a form which can react in a liquid. The shape of the metallic zinc is not particularly limited, but may be in a state of being dispersed in the liquid in order to improve mixing with the liquid and reactivity, and the size of the metallic zinc is about several μm to several mm. Good. Moreover, the purity of zinc should just be 99% or more, However, Even if it is a case where another metal component etc. are included, the other metal component should just not elute in an alkaline solution or an electrolysis original solution.

Moreover, the following reaction will advance rapidly that the reaction temperature of metallic zinc is 40 degreeC or more. That is, the natural dissolution of zinc powder proceeds rapidly while generating hydrogen gas, the reaction is completed in a short time, and a sufficient substitution reaction cannot be performed. In addition, zinc is eluted in the liquid, resulting in an increase in zinc concentration. Therefore, it is preferable to adjust the temperature of the solution to 40 ° C. or lower, and the lower the temperature, the more preferable.
Zn + 2OH ⁻ = ZnO ₂ ²⁻ + H ₂ ↑

Moreover, it is preferable that the free NaOH concentration in a solution is 150 g / L or less, and it is so preferable that it is low. This is because when the free NaOH concentration is 150 g / L or more, the ability to remove lead, tin, indium and the like, which are impurities with a low ionization tendency, decreases. This cause is also these impurities is temporarily reduced to the metal, respectively HPbO ₂ ^- or ^{_{PbO 3 2-, SnO 3 -,}} InO 2 - remelting process proceeds as a result, the removal capacity as a total decrease It is thought that it is from.

  Thus, the free NaOH concentration in the solution is preferably 150 g / L or less, and the reaction temperature of the zinc powder is preferably 40 ° C. or less, and a sufficient equilibrium is reached in a reaction time of about 30 minutes.

  The filtrate obtained by the method for purifying a gallium-containing solution according to the present invention can be used as a gallium electrolyte for recovering gallium metal by electrowinning. Metal elements other than gallium in the gallium electrolyte greatly affect the composition of gallium metal obtained by electrowinning. Therefore, this electrolytic solution is alkaline, and the total content of copper, iron, lead, tin and indium as impurities in the electrolytic solution is preferably 5 ppm or less. If the total content of copper, iron, lead, tin and indium as impurities in gallium metal is 5 ppm or less, the quality of gallium metal will be 99.999 mass% or more, and it can be used as a material for semiconductors and catalysts. become. Furthermore, it can be used in a purification process for producing high-purity 6N (99.9999 mass%) and 7N (99.99999 mass%) gallium, and can greatly reduce the burden on additives and equipment in the purification process. And cost can be reduced.

  Examples of the method for purifying a gallium-containing solution according to the present invention will be described in detail below.

[Example 1]
First, an electrolytic base solution recovered by zinc smelting was prepared as a gallium-containing solution. This electrolytic base solution had the composition shown in Table 1.

Next, the electrolytic treatment of the electrolytic base solution was performed. That is, the electrolytic base solution was reverse neutralized with H ₂ SO ₄ to adjust the free NaOH concentration to 103 g / L, and 1.1 L of this solution was placed in a beaker, and 2 g of zinc dust was added while stirring with a stirrer. The mixture was reacted at a temperature of 40 ° C. for 30 minutes, and then filtered with suction through C filter paper to obtain a filtrate.

Next, 1 L of the obtained solution was used as an electrolytic solution, and one cathode made of SUS316L (cathode liquid contact area: 0.0153 m ² ) and two anodes were arranged, the current flow was 6.38 A, the cathode current The density was 417 A / m ² , the energization time was 17 hours, and it was confirmed that the gallium concentration at the end of electrolysis was 1 g / L or less, and electrowinning was performed to recover gallium metal. Table 2 shows the quality of impurities in the obtained gallium metal. As shown in Table 2, impurities in gallium metal were only slightly detected.

[Examples 2 to 4]
Electrolyte obtained by the same method as in Example 1 except that the temperature at which the zinc powder was reacted was 35 ° C. (Example 2), 30 ° C. (Example 3), and 25 ° C. (Example 4), respectively. Gallium metal was recovered by electrowinning in the same manner as in Example 1. Table 2 shows the quality of impurities in the obtained gallium metal. As shown in Table 2, the amounts of impurities in gallium metal were all below the lower limit of analytical quantification.

[Comparative example]
Gallium metal was recovered by electrowinning as in Example 1 using the same electrolytic base solution as in Example 1. Table 2 shows the quality of impurities in the obtained gallium metal. As shown in Table 2, in this comparative example, the amount of impurities in the gallium metal was much larger than in Examples 1 to 4. Therefore, in Examples 1-4, it turns out that the quantity of various impurities can be reduced to a very low level by a simple method in a short time, and an impurity can fully be removed.

Claims (5)

A method for purifying a gallium-containing solution, comprising adding metal zinc to an alkaline solution containing at least one of copper, iron, lead, tin, and indium and gallium, followed by filtration. The method for purifying a gallium-containing solution according to claim 1, wherein the concentration of free NaOH in the alkaline solution is adjusted to 150 g / L or less. And adjusting the temperature of the alkaline solution to 40 ° C. or less, the purification method of the gallium-containing solution according to claim 1 or 2. The method for purifying a gallium-containing solution according to any one of claims 1 to 3 , wherein the metallic zinc is zinc dust. The method for purifying a gallium-containing solution according to any one of claims 1 to 4 , wherein the filtrate after filtration is a solution used as a gallium electrolyte for recovering gallium metal by electrowinning.