JP2020050943A - Recovery method of gallium - Google Patents

Abstract

To provide a method for recovering gallium while suppressing contamination of cobalt from a processing object.SOLUTION: A processing object containing at least an iron group element and gallium is impregnation treated in a solution of hydroxide of alkali metal prepared at 1 mol/L to 13.8 mol/L at temperature of less than 120°C. The temperature of the solution is preferably 70°C and further impregnation time is more preferably 10 min. or more. Alternatively, the impregnation time is preferably 48 hr. or longer, and further the temperature of the solution is more preferably 50°C or higher. The processing object may be a magnet sludge of rare earth element-iron-boron-based permanent magnet, or a residue mainly containing iron oxide obtained by removing a rare earth element from the magnet sludge.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for recovering gallium from a treatment target containing at least iron, cobalt, and gallium.

  An RTB-based permanent magnet (R is at least one of the rare earth elements and always contains Nd, T is at least one of the transition metal elements and always contains Fe, and B is boron) is an excellent magnet. Because of its characteristics, it is used in various fields such as automobiles, industrial machines, and electronic devices. Its usage is expected to increase with the spread of electric vehicles and electronic devices. On the other hand, as the production volume of magnets increases, the amount of machining waste (hereinafter, referred to as “magnet sludge”) such as cutting waste and grinding waste generated in the magnet manufacturing process has also increased. Since valuable metal elements are contained in magnet sludge, collecting and reusing them is an important technical issue. In particular, rare earth elements are actively recycled because they are expensive.

  Some RTB-based permanent magnets use gallium (Ga) as an additive. Gallium is mainly produced as a by-product of aluminum smelting, but its production is small, and there is concern over long-term stable procurement. Therefore, collecting and reusing gallium, which is a rare metal, from waste such as magnet sludge is an important issue from the viewpoint of material procurement.

  As a method of separating and recovering gallium from a compound containing gallium, there are known a method of electrolytic refining described in Patent Document 1 and a method of mixing and dissolving an alkali metal hydroxide described in Patent Document 2. I have.

  In the electrolytic refining method described in Patent Literature 1, electrolysis is performed using an aqueous solution containing an electrolyte and a raw material containing gallium as an anode. Gallium dissolved from the anode is electrodeposited on the cathode, but by setting the temperature of the electrolytic solution to be equal to or higher than the melting point of gallium, the electrodeposited gallium can be melted and dropped, and collected as a liquid. However, powders that have been oxidized, such as magnet sludge, have a low electrical conductivity, and are therefore very difficult to treat by this method.

  The method described in Patent Literature 2 is a method in which a raw material containing gallium as a main component is mixed with an alkali metal hydroxide, heated, converted to a hydroxide, and then dissolved and recovered in water. However, when the content of gallium is small, such as magnet sludge, it is difficult to efficiently convert gallium to hydroxide.

In addition, the magnet sludge contains a component that elutes into a strongly alkaline aqueous solution such as cobalt (Co). After the gallium is eluted from the object to be treated, it is reduced to metallic gallium by electrolysis or the like. At this time, if a metal that is nobler than gallium, such as cobalt, is present in the solution, it is preferentially reduced over gallium, and may form a cobalt-gallium alloy. In a gallium-cobalt alloy, the two-phase coexistence state of Ga and Ga ₃ Co is stable up to a cobalt concentration of 22 wt%, and the Ga phase is liquefied at about 30 ° C., so that gallium can be easily recovered at a low temperature. On the other hand, if the cobalt concentration exceeds 22% by weight, the Ga phase cannot be stably present, so that the melting point of the product increases, making it difficult to recover gallium at a low temperature.

JP-A-6-192877 Japanese Patent No. 50029090

  Therefore, an object of the present invention is to provide a method for recovering gallium while suppressing the incorporation of cobalt from a treatment object.

In the gallium recovery method of the present invention made in view of the above points, in the exemplary embodiment 1, the treatment target containing at least iron, cobalt and gallium, the temperature is less than 120 ° C., 1 mol / L or more, This is a method of recovering gallium by immersion treatment in an aqueous solution of an alkali metal hydroxide adjusted to 13.8 mol / L or less.
In the aspect 2, the gallium recovery method according to the aspect 1, wherein the temperature of the aqueous solution is 70 ° C. or higher.
In the aspect 3, the gallium recovery method according to the aspect 2, wherein the immersion time of the aqueous solution is 10 minutes or more.
In the aspect 4, the gallium recovery method according to the aspect 1, wherein the immersion time of the aqueous solution is 48 hours or more.
In the fifth aspect, the method for recovering gallium according to the fourth aspect, wherein the temperature of the aqueous solution is 50 ° C. or higher.
In the sixth aspect, the processing object according to the first to fifth aspects, wherein the object to be treated is magnet sludge of an RTB-based permanent magnet or a residue mainly composed of iron oxide obtained by removing a rare earth element from the magnet sludge. It is a gallium recovery method.

  ADVANTAGE OF THE INVENTION According to the method of this invention, gallium can be collect | recovered, suppressing elution of cobalt from the to-be-processed object containing at least iron, cobalt, and gallium.

4 is a graph showing the relationship between the concentration of sodium hydroxide and the concentrations of Co and Ga in a filtrate. It is a graph which shows the relationship between temperature and Ga concentration in a filtrate in each sodium hydroxide concentration. It is a graph which shows the relationship between temperature and Co density | concentration in a filtrate in each sodium hydroxide density | concentration. It is a graph which shows the relationship between temperature and Ga concentration in a filtrate in each immersion time. It is a graph which shows the relationship between temperature and Co density | concentration in a filtrate in each immersion time.

In the method for recovering gallium of the present invention, an object to be treated containing at least iron, cobalt, and gallium is treated with an alkali metal water adjusted such that the temperature is lower than 120 ° C. and 1 mol / L or more and 13.8 mol / L or less. Gallium is eluted while suppressing the elution of cobalt by immersion treatment in an aqueous solution of an oxide.
Hereinafter, details of the present invention will be described.

  First, the treatment target containing at least iron, cobalt, and gallium, to which the method of the present invention is applied, may contain a rare earth element, boron, or the like as another element. Specifically, an RTB-based permanent magnet may be used. In particular, it can be suitably applied to magnet sludge generated in the manufacturing process.

  At this time, the magnet sludge may be in a completely oxidized state or an unoxidized state. The concentrations of gallium, cobalt, and iron contained in the magnet sludge are, for example, 0.02 to 0.6 wt%, 0.76 to 1.46 wt%, and 34.6 to 54.8 wt%.

  Further, it may be a residue after recovering (removing) the rare earth element from the magnet sludge. As a method of recovering (removing) the rare earth element, for example, after completely oxidizing the magnet sludge with a rotary kiln, dispersing it in water, and adjusting the pH to 3 or more, recovering (removing) the acid by dropping it. )do it. In addition to this, the completely oxidized magnet sludge is immersed in an acid containing 3 times or more moles of hydrogen ions of the rare earth element contained in the magnet sludge, and heated at 60 ° C. or more for 8 hours or more. Can also be collected (removed). The main component of the residue obtained by these operations is iron oxide. The concentrations of gallium and cobalt in the residue are, for example, 0.03 to 0.32 wt% and 1.09 to 2.09 wt%.

  In order to sufficiently exert the effects of the present invention on the object to be treated, the object to be treated is desirably in the form of powder having a particle diameter d50 of 10 μm or less. If the particle diameter d50 of the processing object exceeds 10 μm, gallium inside the particles may not be sufficiently eluted.

  As the alkali metal hydroxide used in the present invention, sodium hydroxide or potassium hydroxide can be used. One or two of these alkali metal hydroxides are dissolved in water and used (hereinafter, this aqueous solution is referred to as "treatment liquid"). At this time, the concentration of the hydroxide of the alkali metal is preferably 1 mol / L or more and 13.8 mol / L or less. If the concentration of the hydroxide of the alkali metal exceeds 13.8 mol / L, the solubility at room temperature will be exceeded, and the addition will be useless. When the concentration of the alkali metal hydroxide is less than 1 mol / L, the effect of eluting gallium is reduced. When the concentration of the alkali metal hydroxide is more than 5 mol / L, the concentration of the alkali metal hydroxide is 5 mol, considering that the ability to collect gallium is difficult to increase (close to a saturated state). / L or less is more preferable.

  The temperature of the treatment liquid is preferably lower than 120 ° C. When the temperature of the treatment liquid is 120 ° C. or higher, the amount of cobalt eluted is large, making it difficult to reduce gallium metal at a low temperature by subsequent electrolysis.

  The lower limit of the immersion time in the treatment liquid varies depending on the treatment temperature. When the temperature of the treatment liquid is 70 ° C. or more and less than 120 ° C., it is preferably 10 minutes or more. When the temperature of the treatment liquid is 50 ° C. or more, the treatment time is preferably 48 hours or more. When the immersion time is shorter than these lower limits, the amount of cobalt eluted increases, and the ratio of the cobalt concentration to the sum of the gallium concentration and the cobalt concentration cannot be reduced to 22 wt% or less. The upper limit of the immersion time is preferably 96 hours or less in consideration of productivity.

  As described above, the treatment is performed by immersing the object to be treated in the treatment solution in which the concentration and temperature of the alkali metal hydroxide are adjusted. At this time, in order to promote the reaction between the processing solution and the processing target, it is preferable to perform stirring as necessary. As a stirring method, a stirring method using a stirring blade or a stirring method by bubbling air can be used. In particular, the method of stirring by bubbling air is preferable in that oxygen in the air acts as an oxidizing agent to suppress the elution of cobalt.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not construed as being limited to the following description.

Gallium concentration and cobalt concentration of the object to be treated Magnet sludge having a particle diameter d50 of about 10 μm generated in the process of manufacturing the RTB-based permanent magnet as the object to be treated (stored in water to prevent spontaneous ignition) ) Was dehydrated by suction filtration. This magnet sludge was further heat-treated at 900 ° C. for 2 hours, and then subjected to ICP analysis (device used: ICPV-1017 manufactured by Shimadzu Corporation). As a result, the gallium concentration was 0.30 to 0.38 wt%, and the cobalt concentration was 0.58 to 0.61 wt%.

Examples 1 to 5:
Next, five 100 ml (treatment solutions) of sodium hydroxide (NaOH) aqueous solution adjusted to have different concentrations of 1 mol / L from 1 mol / L to 5 mol / L were prepared, and each of them was subjected to suction-filtered magnet sludge (while wet). ) Was immersed and treated at 70 ° C. for 6 hours. The residue after the treatment was subjected to suction filtration, and the filtrate was subjected to ICP analysis. The samples were designated as Examples 1 to 5, and the results are shown in FIG. FIG. 1 is a graph showing the relationship between the concentration of sodium hydroxide and the concentrations of Co and Ga in the filtrate. Table 1 shows the concentration of sodium hydroxide, the concentration of Co in the filtrate, the concentration of Ga, the yield of Ga, and the concentration of Co in the filtrate. 2 shows specific numerical values of the mass% of Co in a Co—Ga alloy considered to be generated from Ga and Ga.

  From the results shown in FIG. 1 and Table 1, at a temperature of 70 ° C., the elution amount of gallium increased as the concentration of the alkali metal hydroxide increased. The amount of cobalt eluted was smaller than that of gallium, and the mass% of cobalt in the Co—Ga alloy predicted to be produced from the filtrate was 8.3 wt% or less in all the results, and the amount of elution was very low. It was small. Therefore, when reducing to metallic gallium by electrolysis or the like, it is considered that recovery of gallium at a low temperature is facilitated. From the above, it was found that the elution amount of gallium was affected by the concentration of the hydroxide of the alkali metal, but was less affected by the elution amount of cobalt.

Examples 6 to 15, Comparative Examples 1 to 8:
Prepare 100 ml (treatment solution) of sodium hydroxide aqueous solution adjusted to have a concentration different from 5 mol / L to 12.5 mol / L by 2.5 mol / L, and suction-filtered magnet sludge (wet state) ) 10 g was immersed and treated for 6 hours at different temperatures (in the range of 30 ° C to 140 ° C) for each concentration. The magnet sludge used was different from the magnet sludge used in Examples 1 to 5.

  When the concentration of the aqueous sodium hydroxide solution is 5 mol / L, at a temperature of 70 ° C. for Example 6, 80 ° C. for Example 7, 90 ° C. for Example 8, 100 ° C. for Example 9, and 110 ° C. for Example 10. Processing was performed.

  When the concentration of the aqueous sodium hydroxide solution was 7.5 mol / L, the treatment was performed at a temperature of 100 ° C. as Example 11 and at 120 ° C. as Comparative Example 1.

  When the concentration of the aqueous sodium hydroxide solution was 10 mol / L, the treatment was performed at a temperature of 100 ° C. as Example 12, 110 ° C. as Example 13, 120 ° C. as Comparative Example 2, and 130 ° C. as Comparative Example 3.

  When the concentration of the aqueous sodium hydroxide solution is 12.5 mol / L, the temperature of 100 ° C. as Example 14, 110 ° C. as Example 15, 120 ° C. as Comparative Example 4, 130 ° C. as Comparative Example 5, and 140 ° C. as Comparative Example 6 The treatment was performed at a temperature.

  When the concentration of the aqueous sodium hydroxide solution was 5 mol / L, the treatment was performed at 30 ° C. as Comparative Example 7 and at 50 ° C. as Comparative Example 8.

  After the treatment, the residue was subjected to suction filtration, and the filtrate was subjected to ICP analysis. The results are shown in FIGS. 2 and 3 and Table 2. FIG. 2 is a graph showing the relationship between the temperature and the Ga concentration in the filtrate at each sodium hydroxide concentration, and FIG. 3 is a graph showing the relationship between the temperature and the Co concentration in the filtrate at each sodium hydroxide concentration. Table 2 shows that the concentration of Co in the filtrate, the concentration of Ga, the yield of Ga, and the Co-Ga alloy in the Co-Ga alloy considered to be generated from Co and Ga in the filtrate for each sodium hydroxide concentration and each temperature. It shows specific numerical values of the mass% of Co.

  From the results shown in FIG. 2 and Table 2, it was found that the amount of gallium eluted tended to gradually increase as the temperature increased. In the concentration range higher than 5 mol / L, no significant difference was found in the amount of elution due to the difference in the concentration of sodium hydroxide. On the other hand, from the results shown in FIG. 3 and Table 2, the elution amount of cobalt rapidly increased from 110 ° C. to 120 ° C., but no significant difference was observed due to the difference in the concentration of sodium hydroxide. In addition, even at a low temperature of 50 ° C. or less, the amount of cobalt eluted was high. Further, in the examples, the mass% of cobalt in the Co—Ga alloy predicted to be generated from the filtrate was 22 wt% or less. Therefore, when reducing to metallic gallium by electrolysis or the like, it is considered that recovery of gallium at a low temperature is facilitated.

Examples 16 to 26, Comparative examples 9 to 11:
10 g of suction-filtered magnetic sludge (in a wet state) was immersed in 100 ml of a 5 mol / L aqueous sodium hydroxide solution (treatment liquid) and treated at 50 ° C. to 110 ° C. for 6 to 48 hours. The magnet sludge used was different from the magnet sludge used in Examples 1 to 15 and Comparative Examples 1 to 8.

  When the temperature was 50 ° C., the treatment was performed for 6 hours as Comparative Example 9, 12 hours as Comparative Example 10, 24 hours as Comparative Example 11, and 48 hours as Example 16.

  When the temperature was 70 ° C., the treatment was performed for 6 hours in Example 17, 12 hours in Example 18, 24 hours in Example 19, and 48 hours in Example 20.

  When the temperature was 90 ° C., the treatment was performed for 6 hours as Example 21, 12 hours as Example 22, and 48 hours as Example 23.

  When the temperature was 110 ° C., the treatment was performed for 6 hours as Example 24, 24 hours as Example 25, and 48 hours as Example 26.

  After the treatment, the residue was subjected to suction filtration, and the filtrate was subjected to ICP analysis. The results are shown in FIGS. 4 and 5 and Table 3. FIG. 4 is a graph showing the relationship between the temperature and the Ga concentration in the filtrate at each immersion time, and FIG. 5 is a graph showing the relationship between the temperature and the Co concentration in the filtrate at each immersion time. Table 3 shows that the Co concentration in the filtrate, the Ga concentration, the Ga yield for each temperature and each immersion time, and the amount of Co in the Co-Ga alloy considered to be generated from Co and Ga in the filtrate. It shows specific numerical values of mass%.

  From the results shown in FIG. 4 and Table 3, it was observed that the amount of gallium eluted tended to gradually increase with the immersion time. On the other hand, from the results shown in FIG. 5 and Table 3, it was found that the amount of cobalt eluted tended to gradually decrease with the immersion time. Further, in the examples, the mass ratio of cobalt in the Co—Ga alloy predicted to be generated from the filtrate was 22 wt% or less. Therefore, when reducing to metallic gallium by electrolysis or the like, it is considered that recovery of gallium at a low temperature is facilitated.

  From the above, the elution amount of gallium is influenced by the concentration of the alkali metal hydroxide, and is particularly affected at a concentration of 1 mol / L or more and 5 mol / L or less, and the elution amount of cobalt is higher than that of gallium. The effect of the concentration of the substance was found to be small. On the other hand, the amount of gallium eluted gradually increases as the temperature rises, and the amount of cobalt eluted increases when the temperature is lower than 50 ° C or 120 ° C or higher. I understood. It was also found that the amount of cobalt eluted decreased with time. Therefore, in order to recover gallium while suppressing the incorporation of cobalt, the gallium is preferably immersed in an aqueous solution of an alkali metal hydroxide adjusted to 1 mol / L or more and 13.8 mol / L or less, and treated at less than 120 ° C. Preferably, the temperature is 70 ° C. or more, and the immersion time is more preferably 10 minutes or more. Alternatively, desirably, it is preferable to immerse in an aqueous solution of an alkali metal hydroxide adjusted to 1 mol / L or more and 13.8 mol / L or less, and treat at less than 120 ° C. for 48 hours or more, and when the temperature is 50 ° C. or more. It is considered better.

The present invention provides gallium, which is a rare metal whose production is small and whose long-term stable procurement is concerned, from a treatment target containing iron, cobalt and gallium, such as magnet sludge of an RTB-based permanent magnet. It has industrial applicability in that it can be recovered.

Claims (6)

  Recovery of gallium by immersion treatment of an object containing at least iron, cobalt and gallium in an aqueous solution of an alkali metal hydroxide adjusted to a temperature of less than 120 ° C. and 1 mol / L or more and 13.8 mol / L or less Method.   The method of claim 1, wherein the temperature of the aqueous solution is 70 ° C. or higher.   The gallium recovery method according to claim 2, wherein the immersion time of the aqueous solution is 10 minutes or more.   The gallium recovery method according to claim 1, wherein the immersion time of the aqueous solution is 48 hours or more.   The gallium recovery method according to claim 4, wherein the temperature of the aqueous solution is 50 ° C or higher.   The said object to be processed is a magnet sludge of an RTB-based permanent magnet or a residue mainly composed of iron oxide obtained by removing rare earth elements from the magnet sludge. Gallium recovery method.

Images