JP6346402B2 - Cobalt recovery method - Google Patents

Description

  The present invention relates to a method for recovering cobalt.

  Cobalt is used in steel for wear resistance, high temperature resistance, high strength, and high toughness as an alloy material, and although it is highly industrially important, the majority of them rely on imports. Therefore, recovery of metallic cobalt from a cobalt-containing aqueous solution is significant even at a low concentration.

  Generally, when obtaining electrocobalt by electrowinning, if the electrolyte contains a base metal rather than cobalt, the metal is deposited before cobalt, so the quality of the obtained electrocobalt is degraded. It is known. Therefore, in order to obtain high-quality electric cobalt, it is necessary to remove impurity elements other than cobalt from the electrolytic solution before electrolytic purification of cobalt.

  In order to remove a sulfur-containing elemental impurity such as copper contained in the cobalt-containing aqueous solution, a method of removing sulfide precipitate is common. This makes it possible to selectively remove copper, but it is disadvantageous in terms of cost because it requires generation of hydrogen sulfide gas, the sulfurating agent is very expensive, and a step of recovering precipitated copper is required. is there. In addition, as another method, there is a method in which metallic iron, metallic aluminum, or the like is added and copper in the solution is separated and recovered as metal by cementation. In this method, since the metal to be added dissolves in the solution, a step for removing the dissolved metal from the solution is necessary, and this method is also disadvantageous in terms of cost.

  On the other hand, in recent years, a method for removing copper by solvent extraction has been developed as disclosed in JP-A No. 2004-162135 (Patent Document 1).

JP 2004-162135 A JP 2011-208272 A

N.B.Devi a, K.C.Nathsarma a, V. Chakravortty, “Separation of divalent manganese and cobalt ions from sulphate solutions using sodium salts of D2EHPA, PC 88A and Cyanex 272”, Hydrometallurgy, 54 (2000), p.117-131

  By the way, the solvent extraction is useful for the liquid in which the impurity copper contained in the solution is relatively low or the cobalt concentration in the solution is high with respect to the impurities, and the Cu concentration in the liquid There is no mention of copper separation from an acidic aqueous solution containing a high concentration of copper with a ratio of / Co concentration of 5 or more, and cobalt is efficiently efficiently applied to a solution containing such a high concentration of impurities. Whether it can be extracted is unknown.

  In Patent Document 2, in order to solve such problems, after reducing the copper concentration by solvent extraction, the solution after extraction is passed through the resin to further remove copper, and the copper concentration in the solution before electrolytic purification There has been proposed a technique for obtaining high-purity electrocobalt by lowering.

  Here, in the method of Patent Document 2, it is possible to increase the purity of the obtained electric cobalt, but in order to increase the value of product cobalt, cobalt is obtained with high purity and a higher cobalt recovery rate is achieved. From this point of view, there was still room for improvement.

  Therefore, the present invention minimizes the loss of cobalt while removing most copper from an acidic aqueous solution having a high impurity concentration that contains at least copper and cobalt, and the Cu concentration is 5 times or more than the Co concentration. The purpose is to recover high purity cobalt at a high recovery rate.

  From the viewpoint of recovering high-purity cobalt by electrolytic purification, it is desirable to remove copper as much as possible when removing copper from an acidic aqueous solution containing high-concentration copper by solvent extraction. However, if copper is excessively removed by solvent extraction, even cobalt is extracted together, so that the recovery rate decreases even though the purity of cobalt can be increased.

  On the other hand, as in the technique described in Patent Document 2, it is clear that the solvent extraction may be stopped before reaching the extraction equilibrium and the remaining copper may be removed by resin adsorption. From the viewpoint of the allowable amount of copper, there is a possibility that copper that cannot be removed by resin adsorption may remain in the solution even if the copper concentration after solvent extraction is too high. Quality will not be constant.

  From the above viewpoints, the present inventors have intensively studied to solve the above-mentioned problems. Regarding the solvent extraction of copper, the copper at the latter stage of the solvent extraction is determined by setting the end point where the copper is reduced to a certain concentration. Thus, the present invention was completed by finding that high-purity cobalt can be obtained at a higher recovery rate.

That is, (1) a method of recovering cobalt from an aqueous solution having a copper concentration of 10 g / L or more, a cobalt concentration of 5 g / L or less, and a ratio of the copper concentration / the cobalt concentration of 5 or more,
A copper extraction step of extracting copper with a solvent using a carboxylic acid-based extractant;
A copper adsorption step of passing the extracted liquid containing copper through an acidic chelate resin;
A cobalt extraction step for solvent extraction of cobalt contained in the solution from which copper has been removed;
A cobalt recovery step of recovering cobalt by electrolytic treatment of a solution containing cobalt;
In the copper extraction step, the copper concentration is 200 mg / L or less.
(2) The method according to (1), wherein the copper extraction step is performed at pH 5.0 or less.
(3) In the method according to (1) or (2),
In the copper adsorption step, the functional group of the acidic chelate resin is used after being replaced with sodium ion as a counter ion.
(4) In the method according to any one of (1) to (3),
In the copper adsorption step, the copper concentration in the liquid is reduced to 2 mg / L or less.
(5) In the method according to any one of (1) to (4),
In the cobalt extraction step, a phosphate ester-based extractant is used.

  According to the present invention, it is possible to recover high-purity cobalt at a high recovery rate while removing most of copper from an acidic aqueous solution having a high impurity concentration while minimizing the loss of cobalt.

An aspect of the processing flow of the present invention is shown. It is a graph which shows the relationship between pH and the extraction rate of copper and cobalt. It is a graph which shows the relationship between the copper concentration of the solution which permeate | transmits resin, and time to breakthrough. It is a graph which shows the relationship between the form of the terminal of resin, and the adsorption capacity of copper.

  In the present invention, the target aqueous solution is an acidic aqueous solution containing copper and low concentration cobalt. More specifically, it is an acidic aqueous solution containing copper having a copper concentration of 10 g / L or more, a cobalt concentration of 5 g / L or less, and a Cu concentration / Co concentration ratio of 5 or more.

  As an embodiment of the present invention, as shown in FIG. 1, there is a method for recovering cobalt from such a copper-containing aqueous solution, in which copper is extracted with a solvent using a carboxylic acid-based extractant (S1). ), A copper adsorption step (S2) for passing the extracted liquid containing copper through the acidic chelate resin, a cobalt extraction step (S3) for solvent extraction of cobalt contained in the solution from which copper has been removed, and cobalt. And a cobalt recovery step (S4) for recovering cobalt by electrolytically processing the solution.

Hereinafter, this embodiment will be described.
In step (S1), copper solvent extraction is performed.
As an example of this solvent extraction, an acidic aqueous solution (aqueous phase) and a carboxylic acid-based extractant (organic phase) are brought into contact, and these are typically stirred and mixed with a mixer to react copper with the extractant.

  FIG. 2 is a graph showing the relationship between the extraction pH and the extraction rate of copper and cobalt when Versic Acid 10 (manufactured by Shell Chemical Co., Ltd., hereinafter referred to as VA-10) is used as the carboxylic acid-based extractant. That is, VA-10 was diluted with liquid paraffin (manufactured by Shell Chemical Co., Shellsol), and 20 vol. % Is a graph obtained by plotting the results of extraction performed by varying the volume ratio of the copper-containing acidic aqueous solution and the extractant to 1: 2.5 and the extraction pH between 2 and 8. is there.

  According to FIG. 2, the extraction pH is a range in which cobalt is not extracted and copper is selectively extracted, preferably 3.0 or more, more preferably 3.5 or more, and preferably 5. 0 or less, preferably 4.0 or less. In addition, it is preferable to implement solvent extraction on normal temperature (example: 15-25 degreeC)-60 degrees C or less, or the conditions under atmospheric pressure.

  FIG. 3 shows the concentration and breakthrough of copper contained in the solution after the solvent extraction of copper when the solution after the solvent extraction of copper (solution before passing through the resin: the previous solution) was subjected to the resin adsorption in the subsequent stage. The relationship with the time until is shown. Particularly at low concentrations, the time to breakthrough is faster with respect to the increase in copper concentration, and according to FIG. 3, the time to breakthrough is 90 minutes or more, which is realistic from the viewpoint of removing impurities by resin adsorption. It can be seen that the copper concentration in the solution to be passed through the resin is approximately 200 mg / L or less. In the range where the copper concentration exceeds 200 mg / L, it has been found that even if the amount of resin used is increased, the time until breakthrough does not change greatly. Therefore, even if the amount of resin used is increased, the copper concentration is 200 mg / L. It is clear that it is meaningful to remove copper by solvent extraction up to L or less.

  Thus, in step (S1), copper is removed to such an extent that no excessive load is applied to the resin adsorption in the subsequent step (S2) and cobalt is not co-extracted. For example, the solvent extraction may be performed until the copper concentration is 200 mg / L or less, which generally does not impose a burden on the resin.

In step (S2), the copper remaining in step (S1) is removed by a resin adsorption process.
Although copper is a noble metal than cobalt, for example, when cobalt electrolysis is performed on the extracted liquid obtained in step (S1), copper is involved and low-grade electric cobalt is obtained. Therefore, it is necessary to further reduce the copper concentration. Therefore, after the solvent extraction step, the solution is passed through the resin and reduced to a copper concentration that does not impair the quality of the electric cobalt, for example, 2 mg / L or less. At this time, the solution after solvent extraction can be passed through the resin without adjusting pH or the like.

The adsorption procedure of this step (S2) may follow a conventional method. An example is the column method. The column is filled with an acidic chelate resin, and an acidic aqueous solution containing metal ions (that is, a solution after copper solvent extraction) is passed therethrough to react copper and the resin. The contact temperature with the resin is from room temperature (eg, 15 to 25 ° C.) to 100 ° C.
Specific examples of the acidic chelating agent include UR-10S and UR-40H (manufactured by Unitika) whose functional groups are iminodiacetic acid.

FIG. 4 is a graph showing the relationship between the form of the end of the copper adsorption resin and the copper adsorption capacity. That is, each type of resin was packed in a column having an inner diameter of 16 mm so that the height of the resin layer was 80 mm (the amount of the resin was 20 mL), and there was 1 liter of an aqueous solution of 800 mg / L of copper and 2000 mg / L of cobalt (0. 001 m ³ ) was passed over 6 hours, and after elution, the copper concentration in the solution was measured to evaluate the copper adsorption capacity of each resin.
In FIG. 4, “UR-40H” means that the terminal functional group of the acidic chelate resin is free base (hydrogen), and “UR-10S” is the same resin as “UR-40H”, It has a terminal functional group with a sodium ion as a counter ion. In addition, “UR-40H” was pretreated with 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L NaOH to replace the terminal functional group with sodium ion. The results used are also shown.

  According to FIG. 4, in the copper adsorption step (S2), the terminal functional group of the acidic chelate resin has a sodium ion as a counter ion, and the copper adsorption ability is maintained even when a large amount of the copper-containing solution is flowed. From this, it can be seen that it is suitably used as the copper adsorption resin in step (S2). The acidic chelate resin whose terminal functional group is a sodium ion counter ion is a free-base acidic chelate resin, in which the terminal functional group is substituted with sodium using an aqueous sodium hydroxide solution in advance, and the sodium ion is used as the counter ion. It may be used.

  The reason for removing most of the copper in step (S1) is that there is an effective amount of copper that can be adsorbed in the resin adsorption process in step (S2). Accordingly, if copper can be removed by solvent extraction in step (S1) until the copper concentration can be effectively removed in step (S2), the copper can be removed from the copper-containing aqueous solution containing cobalt without wasting cobalt. As a result, high-purity cobalt can be obtained at a high recovery rate.

Subsequently, in step (S3), cobalt contained in the cobalt-containing aqueous solution from which copper has been removed is subjected to solvent extraction.
As an example of this solvent extraction, a cobalt-containing aqueous solution (aqueous phase) and an extractant (organic phase) are brought into contact, and these are typically stirred and mixed with a mixer to react cobalt with the extractant.
Examples of the cobalt extractant include PC-88A (produced by Daihachi Chemical Co., Ltd.), which is an acidic phosphate ester extractant. In addition, as described in Non-Patent Document 1, generally, the extraction rate of cobalt tends to be better as the extraction pH is higher, but from the viewpoint of reducing reagent costs, preventing precipitation of other metals, and the like. The extraction pH of cobalt is preferably 6.3 or less, more preferably 4.5 or less.
In addition, the solvent extraction is preferably performed under normal temperature (eg, 15 to 25 ° C.) to 60 ° C. or less or under atmospheric pressure in order to prevent the deterioration of the extractant.

In step (S4), cobalt is recovered by subjecting the solution containing cobalt obtained in step (S3) to electrolytic treatment.
Although it is the electrolysis conditions here, the conditions of the electrolysis purification of normal cobalt containing aqueous solution are employable. For example, the electrolysis conditions as seen in Japanese Patent Application No. 11-75438 pH: 1~3, current density: may be electrolyte as 10~1000A / m ^2.

  From the viewpoint of obtaining high-purity cobalt, electrolytic cobalt as a raw material is required to contain 8 ppm or less of copper contained as an impurity. To achieve this, the copper concentration in the electrolyte must be 0.2 mg / L or less, and the copper distribution ratio in the cobalt extraction step (S3) is 0.83. In this case, copper needs to be reduced to 2 mg / L or less.

Further, the copper extracted in the organic phase in the copper extraction step (S1) is subjected to simple washing and back extracted with sulfuric acid to obtain a copper sulfate solution. Further, the copper adsorbed on the resin in the copper adsorption step (S2), for example, passes sulfuric acid to elute the copper to obtain a copper sulfate solution.
Further, in step (S5), this copper sulfate solution is subjected to electrolytic treatment to obtain electrolytic copper, and copper is also recovered. In addition, the solvent of the organic phase from which copper was removed can be repeatedly used as the extraction solvent in the copper extraction step in step (S1).

Examples of the present invention will be described below, but the present invention is not limited to the examples.
Example 1
About the acidic Cu pre-extraction solution having the composition shown in Table 1, the volume ratio of the pre-extraction solution and the extractant is 1: 2.5 using a carboxylic acid-based extractant VA-10 (manufactured by Shell Chemical Co., Ltd.) Two-stage extraction of copper was performed at room temperature and atmospheric pressure. VA-10 is diluted with shell sol, 20 vol. In each stage, the extraction pH was set to 4.5 using a mixture adjusted to%, and after stirring and mixing with a mixer, the mixture was allowed to stand for 15 minutes for two-layer separation. Table 1 shows the results of measuring the content of each component in each of the aqueous phase after extraction (liquid after Cu extraction) and the organic phase (organic phase after Cu extraction).

  According to Table 1, it can be seen that the extraction of copper selectively extracted copper into the organic phase while cobalt remained in the aqueous phase.

  Subsequently, for the Cu extraction liquid having the composition shown in Table 2, DP-8R (manufactured by Daihachi Chemical Co., Ltd.) is used as a non-chelating resin, and the volume ratio of the Cu extraction liquid and the extractant is 1: 1. Three-stage extraction of calcium was performed at room temperature and atmospheric pressure. DP-8R was diluted with IsoperM and diluted with 10 vol. %, The extraction pH was set to 2.0 at each stage, and after stirring and mixing with a mixer, the mixture was allowed to stand for 15 minutes for two-layer separation. Table 2 shows the results of measuring the content of each component in each of the aqueous phase after extraction (liquid after Ca extraction) and the organic phase (organic phase after Ca extraction).

  According to Table 2, it can be seen that the extraction of calcium selectively extracted calcium into the organic phase, while cobalt remained almost in the aqueous phase.

  Subsequently, using UR-10S as the acidic chelate resin, 20 mL of the degassed resin was packed into the column, and the Ca post-extraction solution having the composition shown in Table 3 was filled in this column at a linear velocity (LV) of 1 m / hr. The liquid was passed under conditions. A solution after extraction of Ca obtained through the acidic chelate resin was obtained as a solution after Cu adsorption, and the content of each component was measured. On the other hand, the amount of each metal component adsorbed on the resin after Cu adsorption is about the eluent obtained by passing sulfuric acid through the Ca post-extraction solution and eluting the metal adsorbed on the resin. The content of each component was measured. The results are shown in Table 3.

  According to Table 3, the acid chelate resin adsorbs most of the copper remaining in the solution after Ca extraction, that is, the copper remaining in the copper extraction step of step (S1), and the concentration of copper contained in the solution after Cu adsorption. It can be seen that is selectively made smaller.

  Subsequently, for the post-Cu adsorption liquid having the composition shown in Table 4, the volume ratio of the post-Cu adsorption liquid and the extractant using PC-88A (manufactured by Daihachi Chemical Co.), which is an acidic phosphate ester extractant. The two-stage extraction of cobalt was performed at 1: 0.2, normal temperature and atmospheric pressure. PC-88A was diluted with IsoperM and diluted with 20 vol. In each stage, the extraction pH was set to 4.5 using a mixture adjusted to%, and after stirring and mixing with a mixer, the mixture was allowed to stand for 15 minutes for oil-liquid separation. Table 4 shows the results of measuring the content of each component in each of the aqueous phase after extraction (liquid after Co extraction) and the oil phase (oil after Co extraction).

  Subsequently, the organic phase after the Co extraction having the composition shown in Table 4 was subjected to nickel scrubbing to remove nickel. Specifically, a nickel scrubbing solution having a Co concentration higher than the Co concentration in the organic phase after the Co extraction and having a nickel concentration lower than the nickel concentration, for example, a Ni scrubbing having the composition shown in Table 5 The pre-solution was brought into contact with the organic phase after the Co extraction to replace nickel incorporated in the organic phase with cobalt. This operation was a two-stage extraction in which the volume ratio of the Ni scrubbing pre-solution and the Co-extracted oil was 1: 0.2, and the extraction pH was 4.5 at each stage. In this way, a post-Ni scrubbing oil was obtained, and this post-Ni scrubbing oil was subjected to the electrolytic treatment described below. The Ni scrubbing post-liquid (aqueous phase) is recovered and can be subjected to Ni scrubbing again.

  According to Tables 4 and 5, it can be seen that cobalt was selectively extracted by extraction of cobalt, and nickel extracted together with cobalt was removed by Ni scrubbing treatment.

Further, the Ni scrubbed organic phase having the composition shown in Table 5 was stripped with 1N sulfuric acid. The strip solution was subjected to electrolytic purification of cobalt by energizing for 40 hours under the condition of a current density of 200 A / m ² . The purity of the obtained electrocobalt was 99.98%, and the recovery rate of cobalt based on the initial Cu pre-extraction solution was 95%.

Claims (4)

A method for recovering cobalt from an aqueous solution having a copper concentration of 10 g / L or more, a cobalt concentration of 5 g / L or less, and a ratio of the copper concentration / the cobalt concentration of 5 or more,
A copper extraction step of extracting copper with a solvent using a carboxylic acid-based extractant;
A copper adsorption step of passing the extracted liquid containing copper through an acidic chelate resin;
A cobalt extraction step for solvent extraction of cobalt contained in the solution from which copper has been removed;
A cobalt recovery step of recovering cobalt by electrolytic treatment of a solution containing cobalt;
The copper extraction step is performed at a pH of 4.0 or less, and the copper concentration is set to 200 mg / L or less without co-extracting cobalt.
A method characterized in that the time until breakthrough of the acidic chelate resin is 90 minutes or more. The method of claim 1, wherein
In the copper adsorption step, the functional group of the acidic chelate resin is used after being replaced with sodium ion as a counter ion. The method according to claim 1 or 2 ,
In the copper adsorption step, the copper concentration in the liquid is reduced to 2 mg / L or less. The method according to any one of claims 1 to 3
In the cobalt extraction step, a phosphate ester-based extractant is used.

Images