JPH11229056A - Production of high purity nickel aqueous solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high purity nickel aq. solution by removing zinc and iron from a zinc-and iron-containing nickel aq. solution. SOLUTION: The high purity nickel aq. solution is recovered by adding a oxidizing agent and a neutralizer into an acidic nickel aq. solution containing zinc and iron as impurities, such as a nickel raw material solution, to increase the pH to remove zinc with iron as a deposit. On the other hand, nickel in the deposit is dissolved and recovered in an acid cleaning liquid by cleaning the deposit with an acidic solution and after the resultant acid cleaning liquid is brought into contact with an alkyl phosphonic ester to extract zinc in the acid cleaning liquid, the acid cleaning liquid is returned to the nickel raw material solution. In such a case, the alkyl phosphonic ester used as the extractant is preferably 2-ethylhexyl phosphonic mono-2-ethylhexyl ester and it is effective when the resultant high purity nickel aq. solution is a nickel sulfate aq. solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-purity nickel aqueous solution by removing these impurity elements from a nickel aqueous solution containing zinc and iron as impurities.

[0002]

2. Description of the Related Art Nickel salts are used as a raw material for plating materials, aluminum color formers, various catalysts, and battery materials. With the recent technological innovation, nickel salts having higher purity have been desired. Have been. The higher the purity of nickel salts used for such applications, the better the purity, especially those containing no iron, copper, zinc, etc., and a manufacturing process for that is required. I have.

[0003] For example, nickel sulfate, which is one of nickel salts, is produced by the following method. After dissolving raw materials such as nickel-containing sulfides and metal scraps in sulfuric acid, impurities such as iron, copper, and cobalt are removed. The liquid is concentrated by heating and evaporating, followed by cooling,
Crystals of nickel sulfate precipitate. In order to produce high-purity nickel sulfate, it is important to dissolve the raw materials and set the conditions of the crystallization step to precipitate crystals, but it is most important to reduce impurities in the aqueous solution of nickel sulfate before crystallization. It is.

[0004] Usually, sulfides and metal scraps used as a raw material of nickel sulfate contain impurities such as iron, copper and zinc in addition to nickel. These impurities are leached into the liquid together with nickel when the raw material is dissolved. In order to produce high-purity nickel sulfate, it is necessary to remove these elements from the liquid by some method.

Similarly, nickel chloride dissolves and crystallizes a nickel-containing raw material. In this case, too, in order to produce nickel chloride with high purity, it is necessary to remove impurities from the solution before crystallization.

[0006] In recent years, high purity nickel alloys and metal nickel used for plating have been desired, and an electrolytic solution from which impurities have been completely removed before the electrolytic operation is required.

[0007] It is known that iron can be removed as a hydroxide by increasing the pH in an oxidized solution. Therefore, removing iron from the solution of the raw material can be achieved relatively easily. At this time, if the pH of the solution is sufficiently high, not only iron but also zinc and copper, which are relatively easily hydrolyzed, precipitate and are removed from the solution. However, under such conditions, a large amount of nickel, which is the object of recovery, also precipitates, and a deposit having a high nickel content is generated. If this artifact is extracted out of the system without any treatment, nickel contained in the artifact cannot be recovered, resulting in loss.

Therefore, the obtained neutralized residue is usually washed with an acid. In order to sufficiently recover nickel from the neutralized deposit, it is necessary to lower the pH of the cleaning solution. However, when washing at a low pH, impurities such as zinc contained in the deposit are dissolved again. Therefore, the solution contains not only nickel but also impurities such as zinc. The solution containing nickel and zinc etc.
To recover nickel, it is desirable to mix it with the solution of the raw material. However, since the cleaning solution contains impurities such as zinc, the impurities cannot be extracted out of the system by directly mixing the cleaning solution with the nickel solution and repeating the process. For this reason, it has not been possible to treat this acid cleaning solution until now.

Since impurities such as copper are noble metals compared to nickel, it is conceivable to directly remove them from the nickel raw material solution by cementation utilizing the oxidation-reduction potential difference of the metals. Generally, iron metal is often used, but iron dissolves in the solution as the reaction proceeds.
Therefore, the purification liquid load for iron removal increases.

[0010] Nickel can also be used as a reducing agent. In this reaction, the contact area with the metal is rate-determining, and it is important to secure a surface area. Plates and massive metallic nickel do not react well, and to increase reactivity,
It is disadvantageous because it is necessary to use powdered nickel.
In addition, zinc is a metal that is lower than nickel, and therefore cannot be removed by cementation.

It is also conceivable to remove as sulfide. In this case, not only copper but also zinc is removed, which is convenient. However, in order to reduce the concentration of copper and zinc in the solution to a sufficient concentration, it is necessary to add a large amount of a sulfurizing agent such as hydrogen sulfide gas, and as a result, coprecipitation of a large amount of nickel is inevitable. In addition, a small amount of a sulfurizing agent such as hydrogen sulfide remains even after the completion of the reaction, and sulfide precipitates are gradually formed in a later step, and the reaction is scaled in a reaction tank or the like, or a deaeration operation for removing the odor of hydrogen sulfide is performed. Necessary or complicated.

Solvent extraction has been developed as a method for removing the above-mentioned impurities. In recent years, highly selective solvents have been developed, and solvent extraction is an effective means. Solvent extractants are roughly classified into acidic extractants, neutral extractants, and basic extractants. For the extraction of copper and zinc, phosphoric acid-based compounds such as 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester are used. Acidic extractants are suitable. In solvent extraction, selective extraction is important, but it is extremely important how the amount of organic solvent dissolved or suspended in an aqueous solution can be reduced in order to be established as a process. In the treatment methods proposed so far, a solvent extraction operation is required for all the solutions of the nickel raw material. When targeting such a large amount of solution, the solvent loss to the aqueous solution becomes extremely large, and as a result, solvent extraction cannot be adopted.

As described above, according to the conventional methods, it has not been possible to remove these elements from the aqueous nickel sulfate solution containing iron, zinc and copper to produce a high-purity nickel aqueous solution.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a method for producing a high-purity nickel aqueous solution by removing these elements from a nickel aqueous solution containing zinc and iron. And

[0015]

The present invention provides an acidic nickel aqueous solution containing zinc and iron as impurities, for example, an oxidizing agent and a neutralizing agent added to a nickel raw material solution to raise the pH, The zinc is removed as a deposit, and a high-purity nickel aqueous solution is recovered.

On the other hand, by washing the formed residue with an acidic solution, nickel in the residue is dissolved and recovered in an acid washing solution, and the resulting acid washing solution is brought into contact with an alkylphosphonate to form an acid. This is a method for producing a high-purity nickel aqueous solution, characterized in that after extracting zinc in a washing solution, an acid washing solution is repeatedly used as a nickel raw material solution.

The alkyl phosphonate used as the extractant at this time is preferably 2-ethylhexyl phosphonate mono-2-ethylhexyl ester. When the obtained high-purity nickel aqueous solution is a nickel sulfate aqueous solution, It is effective.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention utilizes the property that zinc precipitates together with iron during the formation of a neutralized precipitate, and that zinc is more easily extracted into an alkylphosphonate than nickel. As described above, iron ions present in the solution can be removed from the solution as hydroxides by oxidizing to trivalent. Therefore, if a neutralizing agent is added to the nickel raw material solution together with the oxidizing agent, iron is easily precipitated as a hydroxide. Oxidation of iron ions may be performed using a general oxidizing agent such as hydrogen peroxide, chlorine, oxygen, and air. Solution pH
As the concentration of iron decreases, the reaction proceeds generally at pH 4 or higher, and the reaction proceeds to 0.001 g /
The iron concentration can be less than one liter.

At this time, zinc in the solution tends to precipitate together with iron, and can be removed from the solution by utilizing this property. The removal of zinc is more efficient at higher pH,
The pH is adjusted to 5.0 or higher, preferably 5.5 or higher. Increasing the pH improves the removal of iron and zinc. However, at this time, nickel also precipitates at the same time and is contained in the deposit. Therefore, removing iron and zinc by oxidizing and neutralizing them, and recovering a high-purity nickel aqueous solution and reducing the transfer rate of nickel to precipitation are both conflicting phenomena. It is difficult even if the pH at the time of sum is finely controlled.

Therefore, the nickel-containing artifact is
Wash with a low pH solution whose pH has been adjusted with hydrochloric acid or sulfuric acid, and recover nickel in the acid washing solution. The lower the pH, the better the nickel recovery, but the iron begins to redissolve. Therefore, considering that iron ions normally precipitate efficiently as hydroxides at pH 3 or higher, desirably at pH 4 or higher as described above, a p of 4 or higher is considered.
What is necessary is just to wash with H liquid.

When washed at pH 4, about 90% of the nickel in the deposits can be eluted and recovered. At this time, zinc which has been removed together with iron elutes in the washing solution. When acid washed at pH 4, 82% of the zinc in the deposit elutes. Therefore, since this solution cannot be returned to the nickel solution as it is, it is necessary to further separate nickel and zinc. A solvent extraction method is applied to this separation.

Alkyl phosphonic acid esters and alkyl phosphinic acids have a high extraction ability for iron and zinc.
In particular, monoethyl 2-ethylhexyl 2-ethylhexylphosphonate is an extractant suitable for the purpose of the present invention.
This extractant also extracts nickel. However, the extractability of the present extractant with respect to nickel is lower than that of other metal ions, and can be achieved only by increasing the pH of the aqueous solution. Therefore, by adjusting the pH of the aqueous solution so as not to extract nickel, zinc in the acid washing solution can be selectively extracted.

According to the present invention, since the solvent extraction step of the present invention is directed to an acid washing solution of a neutralized residue, which has a small volume, loss of the organic solvent can be minimized.

Usually, the pH of an acidic extractant such as 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester decreases as the extraction proceeds, and a neutralizing agent is required to further proceed the extraction. In 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester, zinc is extracted at a pH of about 1 to 3.

In this solvent extraction step, only the zinc dissolved during the acid washing of the neutralized residue should be extracted and removed, and the amount of metal ions to be extracted is small. Therefore, if the organic solvent and the acid washing solution having a pH of 4 are mixed and contacted without adding a neutralizing agent, the pH of the aqueous phase becomes 2 to 3, which is a pH suitable for zinc extraction. Since the amount of the processing solution is small and the addition of the neutralizing agent is not required, the process is greatly simplified as compared with the case where the solvent extraction operation is applied to the starting solution, for example, the entire amount of the nickel raw material solution. The device can extract zinc.

The alkyl phosphonic acid ester used here has a high viscosity and is usually used after dilution. If a high-concentration extractant can be used, a large amount of impurities can be extracted with a small amount of the organic solvent, but the viscosity will increase and hinder the extraction operation. The dilution rate is not particularly limited, and may be used according to the impurity concentration.
It is desirable to use within the range.

Although the temperature at the time of extraction is not particularly limited, the viscosity of the aqueous solution and the extractant decreases as the temperature increases, and the time required for two-phase separation of the aqueous phase and the organic phase after the extraction reaction can be shortened. The extraction reaction is desirably performed at a high temperature. However, the operation at 20 to 60 ° C. is desirable because the extractant and the diluent added to reduce the viscosity of the extractant may volatilize with temperature or may catch fire.

According to the present invention, a high-purity nickel aqueous solution can be produced, and high-purity nickel salts can be recovered by concentrating this solution by heating and evaporating. Alternatively, high-purity metallic nickel can be produced by electrolyzing the solution. Hereinafter, examples of the present invention will be described.

[0029]

EXAMPLE Calcium hydroxide was added to a solution of nickel sulfate containing 83.5 g / l of nickel while blowing air into the solution to raise the pH, thereby producing iron-based deposits. After reacting at 60 ° C. for 1 hour, the solution was filtered to separate a residue and an aqueous solution, and the aqueous solution was recovered as a high-purity nickel sulfate aqueous solution. By this operation, not only iron but also zinc and copper precipitated and were removed from the solution. The higher the pH of the solution, the more efficiently these impurities can be removed.
A high purity nickel sulfate aqueous solution having a very low impurity concentration was obtained. Table 1 shows the results.

[0030] Subsequently, the generated neutralized residue was washed while adjusting the pH with sulfuric acid. Washing was carried out for 1 hour at 50 ° C. using 1 liter of an acid solution of 200 g of the neutralized residue. As shown in Table 2, the lower the pH during washing, the higher the nickel recovery. In acid washing at pH 4, 87 of the nickel in the neutralized precipitate
% And 82% of zinc eluted, but no elution of iron.

[0031] Next, the organic solvent obtained by diluting 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester to 20% by volume with an aromatic diluent was contact-mixed with the acid washing solution obtained by the above operation. The contact mixing was performed at room temperature, and the volume ratio between the organic solvent and the aqueous solution was 1: 1 or 1: 3. No neutralizing agent such as sodium hydroxide was added at all. The results are shown in Table 3. The zinc in the acid washing solution was extracted and removed, and a high-purity nickel aqueous solution was obtained. Although the obtained high-purity nickel aqueous solution can be used as a high-purity nickel aqueous solution, it was repeatedly used as a nickel solution in the raw material dissolving step.

[0032]

[0033]

According to the method of the present invention, the impurities can be efficiently removed from a nickel aqueous solution containing zinc and iron as impurities, and a high-purity nickel aqueous solution can be produced.

Continued on the front page (72) Inventor Kazuyuki Takaishi 3-5-3 Nishihara-cho, Niihama-shi, Ehime Prefecture Sumitomo Metal Mining Co., Ltd. Besshi Works (72) Inventor Naoyuki Tsuchida 3-5-3, Nishihara-cho, Niihama-shi, Ehime Metal Mining Co., Ltd.

Claims (3)

[Claims] An oxidizing agent and a neutralizing agent are added to an acidic nickel aqueous solution containing zinc and iron as impurities, and zinc is removed together with iron as a deposit to recover a high-purity nickel aqueous solution. The nickel in the deposit is dissolved and recovered in an acid washing solution by washing the material with an acidic solution,
A method for producing a high-purity nickel aqueous solution, further comprising: contacting the obtained acid washing solution with an alkylphosphonic ester to extract zinc, and repeating the acid washing solution as a part of a nickel aqueous solution as a starting solution. 2. The method according to claim 1, wherein the alkyl phosphonic acid ester is 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester. 3. The method for producing a high-purity nickel aqueous solution according to claim 1, wherein the high-purity nickel aqueous solution is a nickel sulfate aqueous solution.