JP4915016B2 - 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 as a material for compound semiconductors. 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. Yes. 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 inventors of the present invention contact a solution containing at least one of copper, iron, lead, tin, and indium as impurities and a mixture of zinc metal and activated carbon. As a result, it was found that impurities can be easily removed from the gallium-containing 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 in that a solution containing at least one of copper, iron, lead, tin and indium and gallium is brought into contact with a mixture of metallic zinc and activated carbon. 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. The solution brought into contact with the mixture of metallic zinc and activated carbon can be used as a gallium electrolyte solution for recovering gallium metal by electrolytic collection.

  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, a solution containing at least one of copper, iron, lead, tin, and indium and gallium is added to a layer of a mixture of metallic zinc and activated carbon such as zinc dust. Pass through the liquid.

  Zinc powder is preferably used as the metallic zinc. The finer the zinc powder, the better and preferably less than 150 mesh. In order to bring the gallium-containing solution into contact with the zinc dust, it is preferable to pass the gallium-containing solution through a column filled with a mixture of zinc dust and activated carbon. For example, as shown in FIG. 1, a commercially available filter bag (filter housing) 12 is installed in a column container 10, and a punching pipe 14 having a large number of through holes 14 a is formed at the center of the filter bag 12. The mixture is filled with zinc dust and activated carbon 16 around and under the punching pipe 14 in the filter bag 12, the activated carbon 18 is filled in the punching pipe 14, and the gallium-containing solution is introduced into the inlet of the container 10. What is necessary is just to introduce | transduce from 20, flow in a column, and to make it discharge | emit from the discharge port 22 of the container 10. In addition, when only zinc dust is packed in the column container 10, the pressure loss increases and liquid passage becomes impossible. Therefore, zinc powder is mixed with activated carbon and packed. Further, in order to pass the liquid through the entire filter bag 12, a punching pipe 14 is inserted into the center of the filter bag 12, and only the activated carbon 18 is filled in the punching pipe 14. Further, as shown in FIG. 2, the density of the through holes 14 a increases toward the lower side of the punching pipe 14 so as to ensure liquid passage to the bottom. The activated carbon to be used may be a commercially available activated carbon, and for example, activated carbon such as palm coal M manufactured by Taihei Chemical Industry Co., Ltd. or Kuraray Coal KW manufactured by Kuraray Chemical Co., Ltd. may be used.

Moreover, the following reaction will advance rapidly that the reaction temperature of metallic zinc is 40 degreeC or more. That is, the spontaneous 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 carried out, resulting in a sudden increase in pressure, which is dangerous. 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.

  The solution 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.

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

  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, 1000 L of this electrolytic base solution was passed through the column as shown in FIG. 1 at a solution temperature of 31 ° C. and SV (space velocity) = 100 hr ⁻¹ for 2 hours. As the filter bag 12, a × 100 filter housing (trade name) manufactured by Elepon Chemical Machinery Co., Ltd. is used, and as activated carbon, coconut M (granular activated carbon manufactured by Taihei Chemical Industry Co., Ltd., packing density: 0) .47 g / mL) was used. Only the activated carbon 16 is filled in the punching pipe 14, and activated carbon: zinc powder = 1: 1.4 (weight ratio) is placed around and below the punching pipe 14 in the filter bag 12. Zinc dust (zinc powder of less than 150 mesh) was mixed well and filled (the filling amount of this mixture was 3.8 L). The pressure inside the filter bag 12 when the liquid was passed was 0.07 MPa, and there was no problem.

Next, two electrowinning tanks with 9 cathodes and 10 anodes made of SUS316L per tank were placed in series, and the liquid passed through was put into the tank, and the current flow was 1,000 A (cathode) Current density: 417 A / m ² ), energization time was 48 hours, 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, the amount of main impurities in gallium metal was below the lower limit of analytical quantification.

[Comparative example]
Example 1 was prepared the same electrolyte source solution 1L and placed in a bath of arranging the cathode one and two anodes consisting of SUS316L, 6.38A energization current, 417A / ^{m 2} current density in the cathode, current Electrolysis was performed at a time of 17 hours to recover gallium metal. 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 the example. Therefore, it can be seen that the embodiment can sufficiently remove impurities by reducing the amount of various impurities to a very low level in a simple method and in a short time.

It is sectional drawing which shows schematically the column which lets a gallium containing solution flow. It is a perspective view which shows roughly the punching pipe used for the column of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Container 12 Filter bag 14 Punching pipe 14a Through-hole 16 Mixture of zinc dust and activated carbon 18 Activated carbon 20 Inlet 22 Outlet

Claims (5)

A method for purifying a gallium-containing solution, comprising contacting an alkaline solution containing at least one of copper, iron, lead, tin and indium and gallium with a mixture of metallic zinc and activated carbon. 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. The method for purifying a gallium-containing solution according to claim 1 or 2 , wherein the temperature of the alkaline solution is adjusted to 40 ° C or lower. 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 solution in contact with the mixture of the zinc metal and activated carbon, characterized in that it is a solution used as a gallium electrolyte for the recovery of gallium metal by electrowinning, according to any one of claims 1 to 4 A method for purifying a gallium-containing solution.

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