JPH10310437A - Method for refining nickel sulfate containing cobalt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly purified nickel sulfate soln. and to effectively recover cobalt at the time of producing refined nickel sulfate from a crude nickel sulfate soln. by reducing the consumption of a neutralizer and the waste water treating cost and removing such impurities as cobalt, calcium, magnesium, iron, zinc, copper, sodium and ammonia contained in the crude nickel sulfate soln. SOLUTION: Nickel is extracted from a crude nickel sulfate soln. having high contents of sodium and ammonia with an acidic org. extractant to obtain a nickel-holding org. phase. The nickel-holding org. phase is cleaned with a nickel-contg. cleaning soln., the cleaned org. phase is allowed to react with an aq. crude nickel sulfate soln. having especially a high content of cobalt to substitute the nickel in the org. phase for the impurities in the aq. acrude nickel sulfate soln., and a refined nickel sulfate soln. and an org. phase concentrated in cobalt are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying nickel sulfate containing cobalt, and more particularly to ammonia, sodium, cobalt, and the like contained in a crude nickel sulfate solution containing a large amount of cobalt.
The present invention relates to a method for obtaining a high-purity purified nickel sulfate solution by removing impurities such as iron, copper, zinc, calcium, and magnesium, and for recovering cobalt.

[0002]

2. Description of the Related Art Nickel sulfate is widely used in industrial applications of nickel, for example, in general electroplating, nickel electroless plating for computer hard disks, and more recently, nickel for secondary batteries. Nickel sulfate is increasingly used as a raw material.

However, among these uses,
In many cases, the content of ammonia, sodium, cobalt, iron, zinc, copper, calcium, magnesium and the like contained as nickel sulfate impurities must be minimized. Conventionally, crude nickel sulfate has been purified by a solvent extraction method. Generally, an acidic extractant such as an organic phosphoric acid-based acidic extractant, that is, an acidic phosphonate or an acid phosphinate is used. A method of extracting and separating impurities in a crude nickel sulfate solution into an organic extractant and purifying, or extracting nickel into the extractant,
Although a method of obtaining a purified nickel sulfate solution from a nickel-containing organic phase by a sulfuric acid back-extraction method has been adopted, no matter which method is employed, when using an acidic extractant,
In order to release hydrogen ions when extracting impurities or nickel in the raw material solution, it is necessary to use sodium hydroxide or ammonia as a neutralizing agent.

[0004] For example, when a method of extracting impurities from a crude nickel sulfate solution into an acidic extractant is employed, by adjusting the pH at the time of extraction, cobalt, calcium, which is usually extracted at a lower pH side than nickel, By extracting iron, zinc, copper, and the like into the extractant, these impurities can be separated and removed from the extractant to obtain a purified nickel sulfate solution. Na ⁺ and NH ₄ ⁺ ions in the wetting agent were mixed in the purified aqueous solution of nickel sulfate, which was a problem because it contaminated the purified nickel sulfate solution.

On the other hand, if an attempt is made to extract only the nickel component from a crude nickel sulfate solution containing these impurities with an acidic extractant into the acidic extractant, the pH is lower than that of nickel.
The impurity element extracted on the side is also extracted into the extractant at the same time. In addition, it is inevitable that some sodium and ammonia are extracted simultaneously with the extraction of nickel, and the use of a neutralizing agent to adjust the extraction pH is unavoidable as described above. All of them will be allowed to be mixed, and only by performing a back-extraction operation using sulfuric acid that is usually performed to recover nickel in the organic phase after extraction, all of these impurity elements can be separated. It is difficult.

Therefore, sodium and ammonia are separated by vigorously washing the extracted organic agent, and the other impurities are separated from nickel sulfate obtained by sulfuric acid back-extraction using different types of extractants. , A re-purification process for extracting and separating the same had to be repeated. Therefore, in such a conventional method, not only a large amount of washing water is required for washing the nickel-containing extraction organic agent, but also wastewater treatment and the accompanying nickel loss can be considered, and further, other nickel such as cobalt can be considered. In order to remove impurities, it was economically disadvantageous, for example, that it was necessary to have a different solvent extraction facility. Also, when a relatively large amount of cobalt is contained in the crude nickel sulfate solution to be purified, the cobalt remaining in the organic phase after purification is an expensive valuable material. Economically advantageous.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for obtaining purified nickel sulfate from a crude nickel sulfate solution containing a large amount of cobalt while reducing the amount of a neutralizing agent used in the solvent extraction method and the cost of wastewater treatment. Cobalt, calcium, magnesium, iron, zinc, contained in raw nickel sulfate solution
It is an object of the present invention to provide a method for removing nickel, sodium, ammonia, and other impurities to obtain a highly purified nickel sulfate solution, and to effectively recover cobalt.

[0008]

In order to achieve the above object, the present invention provides an extraction step of extracting nickel from a crude nickel sulfate solution containing a large amount of sodium and ammonia with an acidic organic extractant to obtain a nickel-retaining organic phase. And washing the nickel-retaining organic phase obtained in the extraction step with a nickel-containing washing solution, and reacting the washed nickel-retaining organic phase obtained in the washing step with an aqueous solution of nickel sulfate containing a large amount of cobalt, A step of substituting nickel in the nickel-retaining organic phase with impurities such as cobalt in the crude nickel sulfate aqueous solution, thereby obtaining a purified nickel sulfate solution and obtaining a cobalt-concentrated organic phase by the substitution. The method is characterized by:

In the present invention, the organic phase containing impurities such as cobalt obtained in the substitution step is sent to a nickel selective back extraction step in which nickel is selectively back extracted with dilute sulfuric acid, and is obtained in the selective back extraction step. It is preferable to supply the nickel sulfate solution as a part of the nickel sulfate solution containing impurities used in the replacement step. Further, the organic phase containing cobalt and other impurities obtained in the selective extraction step can be sent to a cobalt recovery step of back-extracting cobalt with hydrochloric acid, and the cobalt in the organic phase can be recovered as cobalt hydrochloride.

Further, the organic phase having impurities other than cobalt after the recovery of cobalt is washed, and then sent to an impurity back-extraction step for back-extracting impurities other than cobalt into sulfuric acid using sulfuric acid, and the organic phase in the extracted organic phase is washed. Impurities in sulfuric acid,
It is preferable that a part of the organic phase containing no impurities obtained in the impurity back-extraction step is refluxed to the extraction step and used repeatedly as the acidic organic extractant in the extraction step. In addition, the remainder of the extracted organic phase containing no impurities obtained in the impurity back-extraction step can be used for diluting the nickel-retaining organic phase obtained in the washing step.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the present invention extracts nickel from a crude nickel sulfate aqueous solution containing a large amount of impurities extracted at a higher pH than nickel such as sodium and ammonia by using an acidic organic extractant to retain nickel. An extraction step of obtaining an organic phase, a step of washing the nickel-retaining organic phase obtained in the extraction step with a washing liquid containing nickel, and washing the nickel-retaining organic phase obtained in the washing step and a part thereof with an acid. Reacting the diluted organic phase diluted with the organic extractant with a crude nickel sulfate aqueous solution containing a large amount of cobalt,
A method for purifying crude nickel sulfate containing cobalt, which comprises a substitution step of replacing impurities in the crude nickel sulfate aqueous solution with nickel in the extracted organic phase.

Hereinafter, the technical idea underlying the present invention will be described. As mentioned above, iron, zinc, copper, cobalt,
In the case where impurities or nickel are solvent-extracted from a nickel sulfate solution containing sodium, ammonia, or the like using an acidic organic extractant, in any case, sodium hydroxide, ammonia, or the like is generally used as a neutralizing agent. These are undesirably mixed into the nickel sulfate solution to be purified. By the way, the crude nickel sulfate solution, which is a starting material for solvent extraction, contains a large amount of impurities extracted at a higher pH than nickel when performing solvent extraction with an acidic extractant such as sodium or ammonia due to its production history. And those containing more impurities extracted at a lower pH than nickel, such as cobalt, iron, copper, zinc, calcium, and magnesium. The present invention utilizes the above-described extraction characteristics of impurities contained in the crude nickel sulfate solution to remove impurities from the crude nickel sulfate solution by selectively using a solvent extraction method and a substitution method depending on the raw material. The present invention has established a method for obtaining purified nickel sulfate in a comprehensive and economically advantageous manner by efficiently recovering valuable substances, particularly cobalt, contained in the nickel.

That is, in the present invention, first, in the extraction step, nickel in a crude nickel sulfate solution containing more impurities such as sodium and ammonia extracted at a higher pH than nickel using an acidic organic extractant is subjected to solvent extraction. A crude nickel sulfate solution that contains a large amount of impurities extracted at a lower pH than nickel, such as sodium and ammonia, by extracting into an organic extractant to prepare a nickel-retaining organic phase containing less sodium and ammonia. To replace the nickel component in the nickel-containing organic phase with impurities such as cobalt in the crude nickel sulfate solution, and transfer most of these impurities in the crude nickel sulfate solution to the organic phase. Thus, impurities are separated and removed from the crude nickel sulfate solution.

According to the present invention, the step of extracting nickel with an acidic extractant that requires the use of a neutralizing agent is performed by the following substitution step, in which nickel contained therein and impurities in the crude nickel sulfate solution are removed. Is carried out to prepare a nickel-retaining organic agent in which nickel is contained in an organic phase in order to replace the crude nickel sulfate solution. Unlike the purification method, the amount of the neutralizing agent used and the wastewater treatment cost to be performed thereafter can be significantly reduced, and the neutralization agent is not used in the replacement step. In the nickel sulfate solution, it is possible to avoid at least the incorporation of sodium and ammonium due to the use of the neutralizing agent. In addition, according to the present invention, by performing the substitution step, from the crude nickel sulfate solution containing a large amount of cobalt in the impurities, the contained cobalt can be concentrated in the organic phase obtained in the substitution step, and thereafter, In the cobalt recovery step performed in step (1), efficient cobalt recovery can be performed, so that the overall economic effect in the purification of the crude nickel sulfate solution can be increased.

FIG. 1 shows a schematic process chart of the nickel sulfate refining method of the present invention. Hereinafter, the present invention will be described in the order of steps with reference to FIG. The extraction step is a step of extracting nickel in the crude nickel sulfate solution by a solvent extraction method with an acidic organic extractant to prepare a nickel-retaining organic phase. Therefore, as the nickel source, in addition to the nickel sulfate solution, a nickel chloride solution, a nickel nitrate solution, and the like can be used. However, it is appropriate to use a crude nickel sulfate solution in view of the object of the present invention and its availability. is there. For the extraction of nickel, a general multistage countercurrent solvent extraction tank conventionally used in this type of solvent extraction method, for example, a countercurrent multistage mixer settler or the like is used, and an acidic organic extractant is supplied to the uppermost stage thereof. The raw material crude nickel sulfate solution is supplied to the lowermost stage to cause an extraction reaction in countercurrent. As the acidic organic extractant, as the extractant, for example, Cyanex 27
2, an organic acid-based acidic organic extractant such as D2EHPA or PC-88A may be used.

In performing the extraction, the pH at the time of the extraction reaction should be higher than the conventional nickel extraction pH of 5.5 to 6.5 in order not to leave nickel as much as possible in the extraction residue. It is desirable to work in the pH range of 6.5 to 7.0. Further, it is desirable to maintain the nickel concentration in the extracted and retained organic phase as high as possible. This means that simultaneous extraction of sodium, ammonia, etc. is likely to occur due to extraction at high pH, but increases the nickel concentration in the organic phase and exceeds the nickel retention stoichiometry originally held by the acidic organic extractant. The amount is based on a new finding by the present inventors that the amount of sodium and ammonium extracted into the extracted organic phase simultaneously with nickel can be suppressed. Therefore, the supply amount of the acidic organic extractant to be supplied to the extraction step needs to be kept to a necessary minimum. The nickel-retaining organic phase contained cobalt, iron, copper, and the like contained in the crude nickel sulfate solution.
Most of the impurities extracted into the organic phase at a lower pH than nickel such as zinc, calcium and magnesium are co-extracted and contained.

The nickel-bearing organic phase obtained in the extraction step is sent to a washing step. In the washing step, the nickel-bearing organic phase is washed with a nickel-containing solution. The use of a nickel-containing solution as a cleaning solution involves a substitution reaction between nickel in the cleaning solution and sodium and ammonium in the organic agent,
This is because the removal of sodium and ammonium from the nickel-containing organic agent is promoted, so that the removal of sodium and ammonia can be performed more efficiently than using ordinary washing water containing no nickel. Generally, the cleaning liquid supplied to the cleaning step has a nickel content of 10 to 20 g / Ni.
A solution obtained by diluting a nickel sulfate solution with water so that the volume becomes 1 liter is used. The dilution ratio may be adjusted according to the sodium and ammonia concentrations in the solution. Since the washing waste liquid discharged in this washing step can be returned to the extraction tank as it is, no special waste liquid treatment is required.

The nickel-bearing organic phase that has undergone the washing step is sent to the replacement step. In the replacement step, a multi-stage continuous counter-current reaction tank having at least three-stage reaction tanks, for example, a multi-stage counter-current mixer settler is used. Using a three-stage countercurrent mixer settler for the substitution reaction, the top stage, ie, the first stage mixer settler, is supplied with the nickel-retaining organic phase, and the bottom stage, ie, the third stage mixer settler, is charged with cobalt to be purified. A crude nickel sulfate solution containing impurities as a main component is supplied to cause a countercurrent reaction between the two. In this manner, impurities in the crude nickel sulfate solution, such as cobalt, iron, zinc, copper, calcium, and magnesium, and nickel in the nickel-retaining organic phase are exchanged by a substitution reaction, and nickel in the organic phase is converted into an aqueous phase. In addition, impurities such as cobalt in the crude nickel sulfate solution move into the organic agent phase, respectively, and a highly purified purified nickel sulfate solution can be obtained.

In this case, if the concentration of impurities contained in the nickel-supporting organic phase is excessively high, the transition of the impurities from the aqueous phase to the nickel-holding organic phase occurs when the impurity concentration in the aqueous phase decreases. Therefore, it is necessary to reduce the impurity concentration in the nickel-supporting organic phase. For this reason, a part of the nickel-retained extracted organic phase is replaced with a new acidic organic extractant having the same kind of organic phase composition, or the organic phase after removing impurities by back extraction from the organic phase containing impurities obtained in the substitution step. It is preferable to adjust the concentration of impurities in the nickel-supporting organic agent which is diluted with and subjected to the substitution reaction. In a reaction system using this kind of acidic organic extractant, when the cobalt concentration in the organic phase in the process exceeds 11 g / liter, the viscosity of the organic phase sharply increases, and the separation between the organic phase and the aqueous phase becomes difficult. It has been confirmed by experiments conducted by the present inventors that the concentration of the compound decreases and the substitution reaction becomes difficult to proceed. Therefore, the operation of diluting the nickel-supporting organic phase supplied to the substitution step is performed so that the cobalt concentration in the organic phase at the final stage of the substitution reaction at which the cobalt concentration in the organic phase becomes the highest does not exceed 11 g / liter. It is important from the point of view.

The substitution reaction between nickel and impurities in the substitution step is suitably carried out at a pH of 4 to 5. In this case, unlike the extraction reaction in the previous extraction step, since there is no release of hydrogen ions from the extractant, it is possible to always maintain an appropriate pH without adjusting the pH using a neutralizing agent. it can.
Therefore, in this case, unlike the extraction step by solvent extraction using a normal acidic extractant, there is no release of hydrogen ions from the extractant, so that the pH is usually 4 to 6 without using a neutralizing agent. Since it is kept within the range, it is possible to avoid mixing of sodium and ammonium into the purified nickel sulfate solution by using a neutralizing agent.

Since the purified nickel sulfate solution is usually recovered as nickel sulfate crystals by performing a concentration operation, the nickel concentration in the purified nickel sulfate solution obtained in the replacement step should be maintained as high as possible. Is desirable. When the crude nickel sulfate solution containing impurities is subjected to the substitution reaction with the nickel-retaining organic phase, the amount of nickel in the nickel-retaining organic phase must be somewhat higher than the equivalent of the impurity to be substituted. Phase, i.e., the transfer by replacement with nickel sulfate solution becomes difficult,
The progress of the substitution reaction with impurities is hindered. Therefore, it is desirable that the nickel concentration in the nickel-supporting organic phase be an excessive amount such that a certain amount of nickel remains in the organic phase obtained after the substitution reaction. According to the experiments of the present inventors, when the nickel concentration in the nickel-retaining organic phase supplied to the substitution step is set to 1.3 equivalents or more of the amount of impurities to be substituted present in the supplied crude nickel sulfate solution, the substitution is performed. The amount of nickel remaining in the organic phase discharged after the reaction was 3 g /
It was confirmed that the substitution reaction was carried out smoothly at this time, and that when the amount of nickel became 1.3 equivalents or less, the pH in the substitution reaction became 4 or less and the substitution reaction did not proceed. Here, the amount of impurities to be replaced means impurities contained in the crude nickel sulfate solution and extracted at a lower pH than nickel when solvent extraction is performed with an acidic organic extractant, for example, cobalt, iron, or the like. zinc,
It refers to the total amount of impurities such as copper, cobalt, calcium, and magnesium.

The purified nickel sulfate solution obtained by the substitution reaction can be used as it is or concentrated to produce nickel sulfate crystals as a product. In addition, the organic phase containing impurities is sequentially sent to a series of recovery steps such as a nickel back extraction step, a cobalt recovery step, a post-collection washing step, and a final back extraction step. The organic phase is purified by recovering cobalt, which is evaluated as an important recovery valuable material, and removing impurities other than cobalt. This organic phase is again extracted from the crude nickel sulfate solution by the nickel extraction step. It is economical because it can be used as an acidic organic extractant for the preparation of the organic phase and a diluent for the washed nickel-retaining organic phase sent to the displacement step.

In the nickel back-extraction step, most of the residual nickel in the organic phase is selectively extracted into sulfuric acid by reacting with sulfuric acid at a pH of around 4.0.
Since the aqueous phase obtained in the nickel back-extraction step is a solution mainly composed of nickel sulfate, it can be directly refluxed to the substitution step.

The organic phase after the nickel is back-extracted is sent to a cobalt recovery step, where cobalt, which is evaluated as a valuable resource other than nickel, is adjusted to a pH of 1.4 to 2.0 using hydrochloric acid. By adjusting to a range, it can be back-extracted into hydrochloric acid and recovered as a cobalt chloride solution. The cobalt chloride solution needs to be further purified because calcium, magnesium, copper, zinc and the like are simultaneously back-extracted and contained. The organic phase after the recovery of cobalt is washed with dilute sulfuric acid and sent to the final back-extraction step where 3 to 6N sulfuric acid is used to remove impurities such as iron and zinc remaining in the organic phase. I do. The organic phase is thus purified through a series of recovery steps,
It can be regenerated as a clean acidic organic extractant.

As described above, in the present invention, a crude nickel sulfate solution containing sodium and ammonium is subjected to nickel extraction with an acidic organic extractant at a high pH of 6.5 to 7.0. Simultaneous extraction of sodium and ammonium in the crude nickel sulfate solution into the organic phase is suppressed by holding nickel in the organic phase in an amount equal to or greater than the stoichiometric amount of nickel held by the acidic organic extractant. The nickel-retaining organic phase is prepared as described above, and then the nickel-retaining organic phase is reacted with a crude nickel sulfate solution containing a large amount of cobalt, whereby the nickel contained in the nickel-retaining organic phase and the crude nickel sulfate solution are contained. To purify the crude nickel sulfate solution by substituting impurities such as cobalt, iron, zinc, copper, calcium, and magnesium. As a result, it is possible to obtain a high-purity purified nickel sulfate solution while reducing the amount of the neutralizing agent used and the waste liquid treatment cost, and it is also possible to reduce the cobalt contained in the crude nickel sulfate solution by the organic phase obtained by the substitution step. Since it can be obtained by concentrating it inside, effective cobalt recovery can be performed in the subsequent cobalt recovery step, which is extremely economically advantageous.

[0026]

Embodiments of the present invention will be described below. Example 1 In this example, an experiment was conducted to verify the relationship between the nickel extraction conditions in the extraction step for obtaining a nickel-retaining organic phase and the sodium and ammonium removal effects in the washing step. In the experiment, PC-88A (manufactured by Daihachi Chemical Co., Ltd.) was used as an acidic organic extractant, and Cleansol G was used.
(Nippon Oil Co., Ltd.) diluted to 20% (V / V) was used. In the extraction experiment, a mixer setter with an effective volume of 1.72 liters and a settler portion of 10.3 liters was used in duplicate. Using a two-stage continuous countercurrent mixer settler, an acidic organic extractant was introduced into the first-stage mixer settler, and a nickel sulfate solution containing sodium was introduced into the second-stage mixer settler, and the acidic organic extractant was used. The nickel was then countercurrently extracted from the nickel sulfate solution.

At this time, the pH of the extraction reaction was 7.2 and 7.0, and the neutralizing agent for adjusting the pH was 200
g / liter of caustic soda was used. The temperature of the extraction reaction was set at 40 ° C., and the temperature was kept constant by keeping each mixer settler in hot water at the same temperature. In this extraction experiment, the nickel concentration of the sodium sulfate solution containing sodium introduced into the second-stage mixer settler was 9.3.
The concentration was varied in the range of ３４34.6 g / liter, but the concentration of sodium was kept constant at 0.53 g / liter. Also, the flow rate of the nickel sulfate solution was 7.3 liter / liter in order to change the concentration of the extracted organic nickel obtained after the washing.
hr to 10.0 liters / hr. As a result of these operations, the amount of sodium supplied to the extraction step with the sodium sulfate solution containing sodium supplied in the extraction experiment was 3.9 to 5.4 g / hr.

In the subsequent washing experiment, a three-stage continuous countercurrent mixer settler using three mixer setters having the same specifications as the extraction experiment was used as the washing tank, and the nickel-retaining organic phase obtained in the extraction experiment was used. The nickel-containing organic phase was washed by introducing it to the first-stage mixer settler and introducing the nickel-containing washing solution to the third-stage mixer settler. Table 1 shows the nickel concentration of the nickel-retaining organic phase obtained in the extraction step, the flow rate of the nickel-retaining organic phase supplied from the extraction step to the cleaning step, the flow rate and the nickel concentration of the cleaning solution introduced into the cleaning step, and the supply to the cleaning step. Total nickel content,
The results of measurement of the nickel concentration in the extraction residue after washing, the flow rate of the residue, and the pH during extraction are shown. Table 2 shows the nickel and sodium concentrations of the nickel-retaining organic phase after the washing experiment, the washing ratio (the flow rate of the organic phase / the flow rate of the washing solution), the Na / Ni distribution ratio of the washing solution, and the Na / Ni distribution ratio of the supply washing waste liquid, and The measurement results were shown for the sodium removal rate.

[0029]

[Table 1] Extraction flow rate Ni concentration total supply of Ni concentration phase after organic extraction after organic washes washing after Ni raffinate extraction phase Ni concentration flow pH Ni (g / l) ( l / hr) (l / nr) (g / l) (g / hr) (g / l) (l / hr ) 30.4 11.8 5.28 16.8 347.9 0.01 15.0 7.2 26.7 14.3 5.40 18.1 382.2 0.02 15.1 7.0 21.1 18.1 5.40 18.8 382.2 0.08 15.1 7.0 15.1 9.53 7.02 7.37 144.7 0.04 17.6 7.0 12.6 18.0 6.00 18.1 226.2 0.01 14.1 7.0

[0030]

[Table 2] Washing solution in organic phase after washing Na removal rate Ni concentration Na concentration Washing ratio Na / Ni Na / Ni (g / l) (g / l) (ppm) (ppm) (%) 30.4 0.0005 0.45 16 1.4x10 ⁴ 99.9 26.7 0.004 0.38 150 1.2x10 ⁴ 98.7 21.1 0.003 0.30 199 1.2x10 ⁴ 98.8 15.1 0.009 0.74 596 3.7x10 ⁴ 98.4 12.6 0.51 0.33 4.0x10 ⁴ 1.7x10 ⁴ −

As can be seen from the nickel concentration in the extraction residue after washing shown in Table 1, when the pH during the extraction reaction is set to around 7, most of the nickel contained in the nickel sulfate solution can be extracted. , Its extraction rate is a high value of 99.5% or more. In addition, from the results in Table 2, it can be seen that as to the removal of sodium, the higher the concentration of nickel retained in the nickel-retaining organic phase supplied to the washing step, the more efficient sodium removal can be performed. That is, when the nickel concentration in the nickel-retaining organic phase is higher than about 20 g / liter, the removal rate of sodium is almost 90%.
On the other hand, when the washing ratio is lower than around 15 g / liter, the amount of the washing solution is increased to increase the washing ratio. However, the amount of nickel is increased to increase the Na / Ni distribution ratio, thereby reducing the amount of sodium in the organic phase. Even if the substitution reaction with nickel in the cleaning solution is promoted, improvement in the sodium removal rate cannot be expected.
This means that when the pH of the extraction reaction is around 7, the higher the nickel retention concentration in the extracted organic phase, the more the amount of sodium that is simultaneously extracted from the raw crude nickel sulfate solution into the extracted organic phase during extraction is suppressed. Has a relationship with

The concentration of P used in this experiment was 20%.
The stoichiometry for nickel extraction of the C-88A acidic organic extractant is 18.3 g / l. In other words, when nickel is used in the organic phase in an amount equal to or more than the stoichiometric amount possessed by the acidic organic extractant from this experiment, simultaneous extraction of sodium into the extracted organic phase is suppressed, and a detergent containing nickel must be used. It is presumed that the sodium removal efficiency in the extracted organic phase could be further increased in combination with the effect of replacing the nickel in the detergent with the trace amount of sodium present in the extracted organic phase.

Example 2 In this example, an experiment was conducted to verify the amount of nickel in the organic phase holding nickel and the efficiency of removing impurities in the crude nickel sulfate solution to be purified in the substitution step. In the substitution experiment, a four-stage continuous countercurrent mixer settler using four mixer settlers having the same specifications as in Example 1 was used as a substitution reaction tank, and the nickel-retaining organic phase obtained in Example 1 was diluted with an organic phase for dilution. Together with the crude nickel sulfate solution to be purified, and a crude nickel sulfate solution containing a large amount of impurities, particularly cobalt, which is extracted at a lower pH than the nickel by the acidic organic extractant, is introduced into the fourth stage. Each was introduced into a mixer settler and reacted countercurrently.

In the replacement step, the flow rate of the nickel-retaining organic phase supplied to the first-stage mixer settler, including the organic phase for dilution, is from 10.8 liter / hr to 18.8 liter / hr.
r. Also, the flow rate of the crude nickel sulfate solution for purification supplied to the fourth-stage mixer settler was 10.
It was changed from 7 liters / hr to 18.6 liters / hr. The concentration of the supplied crude nickel sulfate solution is 100 g for convenience.
/ Liter, but the nickel and impurity concentrations of the organic phase and the aqueous phase were varied in order to examine various equilibrium states. Table 3 shows the compositions of the organic phase and the purified nickel sulfate solution obtained by the substitution reaction experiment. In addition,
In the substitution reaction, the release of hydrogen ions from the extracted organic phase does not occur, and its pH is adjusted to 4.0 to 4.0 without any particular adjustment.
The range of 5.0 was always maintained and stable.

[0035]

[Table 3] Organic phase after substitution Purified nickel sulfate solution Ni Co Ca Mg Zn Cu Ni Co Ca Mg Zn Cu (g / l) (g / l) (mg / l) (mg / l) (mg / l) (mg / l) (g / l) (g / l) (mg / l) (mg / l) (mg / l) (mg / l) 6.44 4.85 843 65 38 15 101 3 3 19 <0.1 <0.1 4.94 5.53 793 62 35 15 98.9 4 3 18 <0.1 <0.1 3.07 8.76 558 59 61 26 97.9 4 3 24 <0.1 <0.1 2.74 7.29 776 45 34 14 95.8 7 2 21 <0.1 <0.1 3.60 11.8 552 52 69 41 117 12 7 10 <0.1 <0.1 2.41 8.56 662 52 57 25 97.9 20 3 27 <0.1 <0.1 0.71 10.9 457 30 62 25 90.7 26 5 27 <0.1 <0.1

From the results shown in Table 3, it was found that most of the impurities were transferred into the organic phase by the substitution step, and a purified nickel sulfate solution having a small impurity content could be obtained.
Further, although the substitution rate of cobalt among the impurities is remarkably large, the cobalt concentration in the purified nickel sulfate solution is 10 m
It has been found that in order to reduce the concentration to less than g / liter, it is necessary to adjust the nickel concentration in the organic phase to at least 3 g / liter. Table 4 shows the results of estimating the required amount of nickel with respect to the total amount of impurities to be replaced from the nickel concentration of the organic phase after replacement, based on the cobalt concentration in the purified nickel sulfate solution obtained in the replacement step. . From this result, it is determined that the necessary nickel equivalent in the nickel-supporting organic phase for effectively replacing impurities in the crude nickel sulfate solution is 1.3 mol or more.

[0037]

[Table 4] Required nickel equivalent Purified nickel sulfate (Ni + impurity) / impurity Co concentration in solution (Mol / Mol) (mg / l) 2.03 3 1.71 4 1.31 4 1.31 7 1.28 12 1.25 20 1.06 26

Example 3 In order to efficiently remove impurities in the crude nickel sulfate solution in the replacement step, in addition to controlling the amount of nickel in the nickel-retaining organic phase, the phase separation property between the aqueous phase and the organic phase was determined. Management is required. It is known that if the concentration of cobalt in the organic phase is excessively high, the viscosity of the organic phase is increased and the phase separation property is lowered. Therefore, in this example, the effect of the cobalt concentration in the organic phase on the phase separation property is considered. An experiment was performed. In the experiment, an organic phase was prepared in which the concentration of cobalt was changed using the acidic organic extractant used in Example 1, and this was mixed with the purified nickel sulfate solution obtained in Example 2 at a ratio of 1: 1. 400 ml of the mixture was placed in a container equipped with a rotary stirrer having a rotation speed of 1200 rpm, stirred at 35 ° C. for 20 minutes, and then allowed to stand to measure a phase separation time between an organic phase and an aqueous phase. Table 5 shows the results. From the results shown in Table 5, the phase separation can be smoothly performed in a relatively short time until the cobalt concentration in the organic phase becomes 11 g / liter. It was found that it was not possible to perform a typical substitution reaction.

[0039]

[Table 5] 4th stage organic phase 4th stage aqueous phase Phase separation time Co concentration Ni concentration Co concentration Ni concentration (g / l) (g / l) (g / l) (g / l) (sec) 4.85 8.92 0.22 132 90 9.33 0.06 0.015 109 81 11.8 3.60 0.010 117 5400

Example 4 In this example, a comprehensive continuous purification test including purification of a crude nickel sulfate solution and recovery of cobalt was performed according to the process sequence shown in FIG. In each of the extraction, washing, and replacement steps, a multistage countercurrent continuous mixer settler of the same specification and the same number of stages as the mixer settler used in the previous examples was used, and the same temperature conditions were used. The crude nickel sulfate solution was purified. Table 6 shows the number of stages of the multistage countercurrent mixer settler used in each step, the pH at the time of the reaction in each step, and the chemicals used for pH adjustment in each step (however, the concentration of the neutralizing agent in the extraction step). Was. Table 7 shows the liquid compositions of the organic phase and the aqueous phase in each step together with the flow rates.

[0041]

[Table 6] Step Number of steps pH Extraction of chemicals for pH adjustment 2 6.9-7.0 200g / l NaOH washing 3 No adjustment-Substitution 4 No adjustment-Ni back extraction 3 3.9-4.0 3N-H ₂ SO ₄ Co recovery 2 1.8-2.0 6N-HCl Organic phase washing 1 0-1.0 3N-H ₂ SO ₄ Final back extraction 1 <0 3N-H ₂ SO ₄

[0042]

[Table 7]  Process liquid flow rate Ni Co Ca Mg Cu Zn Na NH_Three (l / hr) (g / l) (g / l) (mg / l) (mg / l) (mg / l) (mg / l) (mg / l) (mg / l) Extracted sulfuric acid Ni solution 11.9 16.1 0.06 89 82 52 3 875 180 Wash solution 8.0 10.3-----78-Reverse extraction organic phase 12.7-0.002------Extract residue 20.9 0.01-----10 100 102 After washing Organic phase 12.7 20.7 0.064 84 97 49 69 3 1 Organic phase after dilution 11.8 79.4 15.4 600 54 134 34 27 20 Organic phase after washing 10.0 6.54 0.021 27 31 16 22 1-Ni-substituted sulfate solution 9.5 20.7 0.064 84 97 49 69 3 1 Purified Ni sulfate solution 11.8 96.1 0.005 2 34--30 20 Replaced organic phase 19.5 3.35 9.33 415 75 80 66--Ni recovered liquid 4.8 13.5 8.9 276 78----Ni recovered organic phase 19.5 0.01 8.2 346 55 80 66 --Co chloride solution 1.7 0.02 45.2 379 2300--2100-Co recovery solution 2.2 0.05 100 2900 2300 557 14 1700-Organic phase after Co recovery 19.5-0.09 54-23 64--Liquid after organic washing 3.9-4.3 82-- ---Organic phase after organic washing 19.5-0.035 54-6 64--Final back extract 3.0-0.23 380-44 451--  Note:-is <0.001g / l

In the extraction step, the extraction pH was adjusted to 7 as in the example.
Using a 20% PC-88A acidic organic extractant, nickel in the crude nickel sulfate solution was extracted and held at 1.13 equivalents. The nickel-retained organic phase after the washing was partly diluted with the cleaned organic phase obtained from the final back-extraction step, and the concentration of cobalt contained therein was adjusted to 30 mg / liter, and the nickel-retained organic phase in the replacement step was removed. The mixture was introduced into the second-stage mixer settler at a flow rate of 10 L / hr, and after washing the remainder, the nickel-retaining organic phase was introduced into the third-stage mixer.

Calculating from the nickel and the impurity concentration in the organic phase obtained from the fourth stage mixer settler after the reaction in the substitution step, the amount of nickel supplied to the substitution step is the amount of the impurity removed in the substitution step. It turns out that it is 1.3 equivalent or more. After the substitution reaction, a purified nickel sulfate solution is obtained from the fourth stage mixer settler. In order to express the degree of impurity purification according to the present invention, Table 8 shows the ratio of each impurity to Ni in the purified nickel sulfate solution obtained and in the crude nickel sulfate solution before purification.

[0045]

[Table 8] Ni ratio (ppm) Co Ca Mg Cu zn Na NH ₃ Before purification 1.5x10 ⁵ 6.7x10 ³ 1.3x10 ³ 1.8x10 ³ 361 9.4x10 ³ 2.0x10 ³ After purification 52 21 354 <10 <10 312 208

The nickel selective back-extraction step performed for recovering nickel in the organic phase obtained in the substitution step includes three steps:
This was performed using a stepwise countercurrent mixer settler. Using 3N sulfuric acid in which distilled water was adjusted to a pH of about 4.0 with sulfuric acid as a back extract, nickel remaining in the organic phase could be extracted into the back extract as nickel sulfate. What is important in the nickel selective back-extraction step is to sufficiently recover nickel without leaving nickel in the organic phase after nickel recovery, and send it to the next cobalt recovery step as an organic phase containing almost no nickel. This is because, when cobalt is recovered as cobalt chloride in the next cobalt recovery step, if nickel is mixed in the recovery liquid, the obtained cobalt chloride is further electrolytically purified to prevent cobalt.
According to Table 7, Ni / Co in the organic phase obtained in the nickel selective back-extraction step according to the present invention is about 0.001, and it can be seen that sufficiently satisfactory results have been obtained. . The nickel sulphate solution obtained by the nickel selective back-extraction contains some impurities that are extracted simultaneously and is therefore refluxed to the displacement step for purification.

The organic phase after the nickel back extraction step was sent to the next cobalt recovery step, in which cobalt contained in the organic phase was separated and recovered. In this step, the organic phase after nickel recovery was reacted with the back extract, and the pH was adjusted to 1 with 6N hydrochloric acid.
The concentration was adjusted to 4 to 2.0, and most of the cobalt in the organic phase could be recovered as a cobalt chloride solution having a concentration of about 45 g / liter. The reason why cobalt was recovered as cobalt chloride in this step is based on the assumption of electrolytic purification of cobalt chloride, and may be recovered as cobalt nitrate using nitric acid. In the case of recovery as cobalt chloride, the concentration can be reduced to 100 g / liter, so that the subsequent cobalt purification step can be performed economically.

Next, the organic phase after the recovery of cobalt is washed with distilled water and sulfuric acid in an organic phase washing step, which is performed to remove chloride ions contained in the organic phase. At this time, a small amount of cobalt and calcium remaining in the organic phase is back-extracted into the washing solution.However, by performing operations such as neutralization, cobalt can be separated and recovered from calcium. It is. Further, as a final back-extraction step, the washed organic phase is reacted with 3N sulfuric acid,
Back extraction of copper, zinc and residual cobalt and calcium was performed, and these elements could be separated and removed from the organic phase. When iron is contained in the organic phase, it can be separated and removed from the organic phase in the same manner. In addition, it is also possible to recover cobalt as cobalt hydroxide by oxidizing cobalt from the back extract. The purified organic phase of impurities obtained in the final back extraction step is
It can be refluxed in the first extraction step and used as an acidic organic extractant for extracting the crude nickel sulfate solution.

[0049]

As described above, according to the present invention, by using both the organic acidic solvent extraction method and the substitution method, it is difficult to mix sodium and ammonia with the conventional solvent extraction method alone. It is possible to easily obtain a purified nickel sulfate solution without using a neutralizing agent and to reduce wastewater treatment cost, and to effectively recover cobalt from a crude nickel sulfate solution having a high cobalt content. Therefore, it is extremely effective economically.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a high-purity nickel sulfate refining and cobalt recovery step according to the present invention.

Claims (6)

[Claims] 1. An extraction step in which nickel is extracted from a crude nickel sulfate solution rich in sodium and ammonia with an acidic organic extractant to obtain a nickel-retaining organic phase, and the nickel-retaining organic phase obtained in the extraction step contains nickel. A step of washing with a washing solution, and reacting the washed nickel-retaining organic phase obtained in the washing step with an aqueous solution of nickel sulfate containing a large amount of cobalt, wherein nickel in the nickel-retaining organic phase and cobalt in the crude nickel sulfate aqueous solution are reacted. A method for purifying nickel sulfate, comprising the steps of: obtaining a purified nickel sulfate solution and obtaining a cobalt-concentrated organic phase by the replacement. 2. The nickel sulfate according to claim 1, wherein the nickel content of the nickel-retaining organic phase obtained in the extraction step is larger than the nickel-retaining stoichiometry of the acidic organic agent. Purification method. 3. The extracted organic phase containing impurities obtained in the substitution step is sent to a nickel selective back extraction step in which nickel is selectively back extracted with dilute sulfuric acid, and the sulfuric acid obtained in the nickel selective back extraction step is transferred to the nickel selective back extraction step. 2. The method for purifying nickel sulfate according to claim 1, wherein the nickel solution is refluxed as a nickel sulfate solution containing impurities used in the substitution step. 4. The method according to claim 3, wherein the organic phase obtained in the nickel selective extraction step is sent to a cobalt recovery step in which cobalt is back-extracted with hydrochloric acid, and the cobalt is recovered as cobalt hydrochloride in the step. A method for purifying nickel sulfate. 5. After washing the organic phase containing impurities other than cobalt after recovering cobalt, the organic phase is sent to an impurity back-extraction step of back-extracting impurities other than cobalt into sulfuric acid using sulfuric acid. 2. The nickel sulfate according to claim 1, wherein a portion of the impurity-free organic phase obtained in the impurity back-extraction step is refluxed as an acidic organic extractant in the extraction step. Purification method. 6. The method according to claim 5, wherein the remainder of the organic phase containing no impurities obtained in the impurity back-extraction step is used for diluting the nickel-retaining organic phase obtained in the washing step.
A method for purifying nickel sulfate as described above.