JP6086801B2 - Separation method of gallium and zinc - Google Patents

Description

  The present invention is a method for separating gallium and zinc from a gallium aqueous solution containing zinc by adjusting pH.

  Gallium is mainly used in light emitting diodes (LEDs), laser diodes (LDs), integrated circuits (ICs) and the like as compound semiconductors such as gallium arsenide and gallium phosphide. Recently, semiconductor IGZO (Indium-Gallium-Zinc-Oxide) composed of indium, gallium, zinc, and oxygen has been attracting attention because of its low power consumption.

  In this way, gallium is an important metal material for electronic equipment, but gallium is mainly used in the production of alumina from bauxite, retort residue of zinc distillate from zinc blende, sulfuric acid leaching residue from zinc roasted ore, etc. A small amount is recovered as a by-product. Recently, it is also recovered from scraps discarded from the manufacturing process of the electronic material. These raw materials often contain a plurality of impurities such as heavy metals, which must be separated in order to reuse gallium.

  As a technique for separating gallium from impurities, for example, Patent Document 1 adds metal gallium to a solution containing gallium, deposits and separates noble impurities from gallium by a substitution reaction, and further precipitates impurities by adjusting the pH. .

  In Patent Document 2, a solution containing a small amount of gallium and a large amount of impurities is passed through an ion exchange resin to adsorb and elute gallium, and then gallium is recovered as a hydroxide by pH adjustment. It is described that the impurity concentration can be further reduced by repeatedly passing the resin through the resin.

  Both Patent Documents 1 and 2 combine a plurality of purification means. As the types of processes increase, the required equipment increases and operations become complicated. In addition, the metal gallium added by the method of Patent Document 1 is expensive, and the resin used in Patent Document 2 is expensive in itself, and also costs chemicals used for cleaning and regeneration.

JP 2012-193396 A JP 59-193230 A

  Provided is a simple and inexpensive method for separating gallium from impurities.

  In order to solve the above problems, the inventor has intensively studied a method for separating gallium from impurities only by adjusting the pH of the gallium aqueous solution and performing precipitation separation, and as a result, has found that it can be realized by the following method. That is, the present invention adjusts the pH of a gallium aqueous solution containing zinc to 3 to 5, removes the precipitate containing gallium and zinc, and the precipitate obtained in the first step from pH 13 The pH of the alkaline aqueous solution containing the gallium and zinc obtained in the second step, and the gallium and zinc obtained in the second step is adjusted to 12 to 13, and the aqueous solution containing gallium and the precipitate containing zinc are added. It is characterized by including the 3rd process to isolate | separate.

  In addition, it is preferable to adjust the pH of the aqueous solution containing gallium and zinc to 4 to 5 in the first step because precipitates easily aggregate.

  According to the present invention, since zinc and gallium can be separated by adjusting the pH, it is not necessary to use an expensive additive such as metallic gallium, a resin, or a chemical used for cleaning and collecting the resin. Necessary equipment is only pH adjustment equipment and solid-liquid separation equipment, and there is no need for equipment for adding metal gallium, resin building, and cleaning / elution of resin. Furthermore, since gallium is taken out as a solid and dissolved, gallium can be easily concentrated even when the gallium concentration of the raw material is low. If the pH of the aqueous solution is adjusted to 4 to 5 in the first step, the gallium-containing precipitate is aggregated and easily separated from the liquid.

  The present inventors paid attention to pH adjustment as a method for separating gallium and impurities. Since pH adjustment requires less cost for chemicals than metal substitution and resin, and the equipment may be simple, it was considered that the above-mentioned problems could be solved if gallium could be separated and recovered only by pH adjustment.

  Since gallium is soluble in both acid and alkali, it is clear that it can be separated from an element insoluble in at least acidic or alkaline by pH adjustment. However, since zinc exhibits the same behavior as gallium, it is considered difficult to separate. The raw materials of Patent Documents 1 and 2 also contain zinc, but are separated by metal substitution or resin. Therefore, the present inventors diligently studied a method for separating gallium and zinc by adjusting pH.

As a result, it was found that when the pH of the gallium aqueous solution was 3 to 5, gallium hydroxide was precipitated while zinc was dissolved, and conversely, when the pH was adjusted to 12 to 13, zinc was precipitated while gallium was dissolved. .
As a result of further investigations, when the pH of the aqueous gallium solution is 3 to 5, several percent of zinc contained in the aqueous solution is precipitated together with gallium, whereas when the pH is 12 to 13, the aqueous solution before pH adjustment. It can be seen that the solubility of zinc hydroxide is reduced to about 10 mg / L when the pH is 12 regardless of the zinc concentration. The conclusion was reached that it is favorable for separation.

  However, even if the pH is set to 12 to 13, a part of zinc remains in the solution. Therefore, in order to increase the purity of the gallium aqueous solution, it is necessary to increase the gallium concentration before adjusting the pH. Therefore, in order to obtain a solution having a high gallium concentration, first, the pH of the gallium aqueous solution was adjusted to 3 to 5 to obtain gallium hydroxide once and dissolved in a small amount of liquid, thereby completing the present invention. . Hereinafter, the present invention will be described in detail.

(Gallium solution)
The gallium aqueous solution may be acidic or alkaline. Specific examples include a residue obtained by recovering zinc from the zinc ore and a solution obtained by dissolving IGZO with an acid. In addition to zinc, the impurity may contain any element that exhibits a behavior different from that of gallium in the pH range in each step of the present invention. For example, indium, iron, titanium, zirconium and the like can be separated from gallium according to the present invention. There is no restriction | limiting in particular in the gallium density | concentration of the said aqueous solution, What is necessary is just to exist to such an extent that gallium is melt | dissolving and a gallium precipitates at a 1st process. The lower the gallium concentration, the better the separation from zinc in the first step, and the higher the gallium concentration, the higher the recovery rate of gallium in the first step.

(First step)
In the first step, the pH of the gallium aqueous solution is adjusted to 3 to 5 to precipitate gallium hydroxide. As described above, a part of zinc is mixed in gallium hydroxide. In addition to zinc, trivalent iron can also be separated. When the pH is less than 3, the solubility of gallium increases, so the gallium recovery rate decreases, and when the pH exceeds 5, the solubility of zinc decreases, so the separation between gallium and zinc becomes worse. For the pH adjustment method, a known technique can be used without particular limitation. For example, there is a method in which acid or alkali is added while stirring the aqueous solution, and the pH is measured continuously or intermittently using a pH meter or pH test paper. Common acids such as hydrochloric acid, sulfuric acid, nitric acid, alkali alkali metal or alkaline earth metal hydroxide, and ammonia can be used as the acid. The obtained precipitate can be taken out by a known solid-liquid separation technique such as filtration, decantation, and centrifugation. As a result of detailed observation of the behavior of precipitates in the above pH range by the present inventors, it was found that when the pH was adjusted to 4 to 5, the precipitates aggregated and the separability from the liquid was improved. Therefore, when a large amount of hydroxide precipitates, it is preferable to adjust the pH to 4-5.

(Second step)
The gallium precipitate obtained in the first step is dissolved again. By adjusting the amount of the solvent, a solution having a desired gallium concentration can be obtained. Gallium hydroxide dissolves in both acid and alkali, but in the third step, the pH is adjusted to the alkali side, so it is preferably dissolved in an alkaline aqueous solution from the viewpoint of reducing the amount of chemical used. When an alkaline aqueous solution is used, divalent iron, indium, titanium, zirconium, and the like are insoluble and can be separated. As the alkaline aqueous solution, an aqueous solution of the above alkali metal or alkaline earth metal hydroxide salt, ammonia or the like can be used. As described above, in order to increase the purity of the gallium solution obtained in the third step, it is preferable to obtain an aqueous solution having a high gallium concentration by reducing the amount of solvent in this step as much as possible. The preferable gallium concentration is 5 g / L or more, more preferably 40 g / L or more. When dissolving in an alkaline aqueous solution, an aqueous solution having a pH greater than 13 is used. The higher the alkali concentration, the easier the gallium hydroxide dissolves, and the alkali concentration is preferably 0.5 N or higher.

(Third process)
The pH of the solution obtained in the second step is adjusted to 12 to 13, and zinc mixed in the gallium hydroxide obtained in the first step is precipitated and separated. If the pH is less than 12, gallium also precipitates, and the yield of gallium decreases. If the pH exceeds 13, the solubility of zinc hydroxide increases, and the separability between zinc and gallium decreases. A more preferable pH range is 12.5 to 13.0. As for the pH adjustment method, the chemical used for pH adjustment, and the solid-liquid separation method, known techniques, general acids and alkalis can be used as in the first step.

  It is important to adjust the pH of the present invention in the order of the first step → second step → third step from the viewpoint of improving the separation of gallium from zinc and performing the treatment efficiently. The reason is as follows. As described above, in the first step, several percent of zinc contained in the gallium aqueous solution is precipitated together with gallium. In addition, the amount of zinc remaining in the liquid in the third step is almost determined depending on the pH. Therefore, if it implements in order of a 3rd process-> 1st process, the amount of zinc in the gallium obtained will be substantially decided by the liquid quantity of raw material gallium aqueous solution, and the pH of a 3rd process. On the other hand, if the pH is adjusted in the order of the first step → the second step → the third step as in the present invention, the gallium concentration can be arbitrarily determined in the second step with the solubility of gallium as the limit. Zinc can be further separated as compared with the case of carrying out.

Example 1
The pH of 397 mL of an aqueous solution (acid concentration 0.4 N) having the composition shown in Table 1 was adjusted to 5, and the precipitate was filtered. The composition of the precipitate was as shown in Table 2. Water and a 24% aqueous sodium hydroxide solution were added to the precipitate to adjust the alkali concentration to 1N, and the entire precipitate was dissolved. The liquid volume was 143 mL. The pH of the solution was adjusted to 12.5, and the precipitate was filtered. The amount of filtrate was 364 mL, and the composition was as shown in Table 3. From Tables 1 to 3, it can be seen that according to the present invention, gallium and zinc or other impurities can be separated only by pH adjustment.

Claims (2)

  The pH of the gallium aqueous solution containing zinc is adjusted to 3 to 5, the precipitate containing gallium and zinc is taken out, and the precipitate obtained in the first step is dissolved in an alkaline aqueous solution having a pH higher than 13. A second step of adjusting the pH of the alkaline aqueous solution containing gallium and zinc obtained in the second step to 12 to 13, and separating into an aqueous solution containing gallium and a precipitate containing zinc A method for separating gallium and zinc, comprising:   The method for separating gallium and zinc according to claim 1, wherein the pH of the aqueous solution containing gallium and zinc is adjusted to 4 to 5 in the first step.