JPS582166B2 - Method for removing cobalt from aqueous nickel sulfate solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of adding secondary nickel hydroxide to an aqueous solution of nickel sulfate containing cobalt and separating cobalt as a precipitate.

Conventional methods for removing cobalt ions in the nickel refining process include: 1) Adding a neutralizing agent such as nickel carbonate or slaked lime and an oxidizing agent such as chlorine gas to a nickel sulfate aqueous solution and/or nickel chloride aqueous solution containing cobalt to remove cobalt ions. 2) A method in which ions are precipitated and removed as trivalent hydroxide; 2) A slightly excess amount of sodium hydroxide than the neutralization amount is added to an aqueous nickel sulfate solution, and the resulting slurry is electrolytically oxidized to produce secondary water. There is a method of separating the cobalt as a precipitate by adding the resulting precipitate to an aqueous solution of nickel sulfate containing cobalt.

However, the disadvantage of method 1) is that a considerable amount of chlorine ions are mixed into the nickel sulfate aqueous solution, which corrodes equipment used in the nickel manufacturing process, resulting in a significant increase in repair costs or initial investment costs for equipment to withstand corrosion. There is.

In the case of method 2), there is no contamination of chlorine ions, but the current efficiency during electrolytic oxidation is extremely low, so hydroxide with a high proportion of secondary nickel hydroxide cannot be efficiently obtained, and therefore cobalt removal is difficult. There are drawbacks such as a low filtering rate and poor filterability of the second nickel hydroxide obtained, such as requiring large equipment for filtration and cleaning.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a method for efficiently removing cobalt contained in nickel sulfate as a precipitate.

In order to achieve this objective, the present invention first develops secondary nickel hydroxide [Ni (
This was obtained through research on the manufacturing method of OH)3 and many experiments on the addition method, etc.
After adding a slightly excess aqueous alkali hydroxide solution to the nickel sulfate aqueous solution to form a slurry, the amount of nickel is adjusted to 1.2 equivalents or less and an aqueous sodium hypochlorite solution is added to precipitate second nickel hydroxide. The precipitate is added to an aqueous solution of nickel sulfate containing cobalt, and diluted sulfuric acid is added in an amount of 2 or more equivalents of nickel based on the amount of cobalt in the solution to adjust the pH of the aqueous solution to 3 to 5, preferably 4 to 5. The amount of cobalt is adjusted to within this range, and cobalt is separated as a precipitate.

The present invention will be explained in more detail below.

In the present invention, the aqueous nickel sulfate solution for producing the second nickel hydroxide preferably does not contain cobalt, but it is also possible to use a solution containing about several g/l of cobalt.

There is no particular limitation on the concentration of nickel, but it is usually 50 to 1.
It is desirable to use one with a concentration of about 509/l at room temperature to 60°C.

The alkaline hydroxide aqueous solution to be added to the nickel sulfate aqueous solution is not particularly limited, but sodium hydroxide or potassium hydroxide, for example, 2
It is preferable to use an amount that makes the pH of the nickel sulfate aqueous solution about 11 to 12 at room temperature at a concentration of 0 to 30% by weight.

Other than alkali hydroxide, such as sodium carbonate, can also be used, but as seen in the comparative example, the filterability is slightly improved, but the cobalt removal rate is significantly lowered.

The nickel sulfate aqueous solution to which alkali hydroxide has been added is the first
A precipitate of nickel hydroxide [Ni(OH)2] is formed to form a slurry. Next, this slurry solution is preferably diluted to about 1.5 times with water and further heated to 50 to 60°C.
After heating the sodium hypochlorite to 1.0 to 1.2 equivalents, preferably 1.0 to 1.2 equivalents of available chlorine to the amount of nickel,
．． Add 1 equivalent with gentle stirring.

The reason why the slurry-like solution is preferably maintained at 50 to 60° C. for the reaction is to improve the filterability of the formed precipitate.

The nickel hydroxide precipitate thus formed is at least 8
Contains 0% secondary nickel hydroxide [Ni(OH)3].

Then, it is separated from the mother liquor by the above-mentioned precipitation pulp method or filtration and washing, and then used as a cobalt precipitant either as a cake or after drying in the air.

Next, usually 50 to 150 g/l of nickel and several g of cobalt.
Add a small amount of dilute sulfuric acid to an aqueous solution of nickel sulfate containing /l and maintain the pH of the solution in the range of 3 to 5, preferably 4 to 5, while stirring lightly. It is added in an amount of 2 or more equivalents, preferably 3 to 4 equivalents, of the amount of cobalt in the aqueous solution.

In this case, about one hour is sufficient to separate the cobalt as a precipitate.

The reason why the amount of sodium hypochlorite added to form a precipitate of secondary nickel hydroxide is set to 1.2 equivalents or less, preferably 1.1 equivalents in terms of effective chlorine amount is that if the amount exceeds that amount, the amount of chlorine increases. Since it would be undesirable to increase the amount, it is set to the minimum necessary level.

Further, the reason why the pH of the cobalt-containing nickel sulfate aqueous solution when adding the second nickel hydroxide is adjusted to a range of 3 to 5 is that the removal rate of cobalt decreases when both of the pH values are outside of this range.

Although the reason for this is not clear, it is presumed that when the pH is higher than 5.0, the surface of the trivalent hydroxide is covered with the divalent hydroxide, which inhibits the oxidation of cobalt ions.

The amount of secondary nickel hydroxide is nickel and the amount of cobalt is 2.
The reason for adding at least an equivalent amount, preferably 3 to 4 equivalents, is that if the amount is less than 2 equivalents, the removal of cobalt will be insufficient.
This is because an amount of 4 equivalents or more is not necessary in practice, and adding an unnecessarily large amount of nickel will undesirably increase the mixing rate of nickel in the cobalt precipitate that is precipitated when cobalt is removed.

The second nickel hydroxide obtained by the first step of the method of the present invention has very good filterability and purity as seen in the examples below, so it can contain several g/l of cobalt by adding a small amount. It is possible to efficiently remove 95% or more to a concentration of 0.1 g/l or less.

If the amount added is further increased, for example, to 4 equivalents or more, the removal rate can be further improved to a concentration of 99% or more and 0.01 g/l or less.

The present invention can also be applied to the removal of cobalt from an aqueous nickel chloride solution containing cobalt.

Examples will be described below.

Example 1 Put 1 liter of nickel sulfate aqueous solution with pH 1.0 containing 125 g/l of nickel into a 3 liter beaker, add 20 parts by weight of sodium hydroxide aqueous solution until the pH reaches 12.0, and add 1 liter of nickel sulfate aqueous solution with pH 1.0 containing 125 g/l of nickel until the pH reaches 12.0. Processed for minutes.

Next, add 500ml of water to the obtained slurry, then place the beaker in a water bath maintained at 50°C, and lightly stir a sodium hypochlorite solution containing 12% by weight of available chlorine (1.1 equivalent to nickel). After 1 hour of treatment, the formed precipitate was lightly filtered using qualitative filter paper, and the precipitate was transferred to another beaker, water was added to make the concentration 100 g/l, and then Nutsche filtration was performed using qualitative filter paper. The mixture was vacuum filtered using a vacuum filter and further dried in air to obtain a precipitate having the composition shown in Table 1.

Next, pH5.5, Ni104g/l, Co1.9g/l
Take 1 liter of cobalt-containing nickel sulfate aqueous solution in a 2-liter beaker, add 7 to 14 g of the second nickel hydroxide cake shown in Table 1 as a dry weight, and add a small amount of dilute sulfuric acid to the nickel aqueous solution to adjust the pH to 4. 5 and was added while adjusting the concentration to 5, and was treated for a predetermined period of time.

The results are shown in Table 2.

As is clear from Table 2, the treatment time differed slightly depending on the amount of secondary nickel hydroxide, but in all cases a cobalt removal rate of 96% or higher (initially expected value was 95% or higher) was obtained.

When the amount of nickel was three times or more the amount of cobalt, a treatment time of 30 minutes was enough to give satisfactory results.

Example 2 Using the second nickel hydroxide obtained in Example 1, the pH of the aqueous solution during cobalt removal was 4.2 to 5.5, the treatment time was 60 minutes, and the amount of second nickel hydroxide used was 7g dry weight (
Cobalt removal treatment was carried out in the same manner as in Example 1, except that the ratio of nickel to cobalt amount was 2 times.

The results are shown in Table 3.

As is clear from Table 3, when the pH during treatment was 5.0 or higher, the cobalt removal rate decreased significantly, but in all other cases a removal rate of 96% or higher was obtained.

Example 3 The procedure was the same as in Example 1, except that the amount of sodium hypochlorite aqueous solution added when producing second nickel hydroxide was changed, and the amount of second nickel hydroxide added was 14 g (dry). Processed.

The cobalt removal treatment time was 30 minutes in each case.

The results are shown in Table 4.

As shown in Table 4, increasing the amount of sodium hypochlorite added does not have any particular adverse effect on the cobalt removal rate, but it is not preferable because the amount of chlorine increases and corrodes the equipment.

Example 4 A process was carried out in the same manner as in Example 1, except that the effective chlorine concentration of the sodium hypochlorite aqueous solution used in producing the second nickel hydroxide was changed.

The results are shown in Table 5.

As can be seen from Table 5, there was a tendency for the cobalt removal rate to improve as the hypochlorous acid concentration increased.

Comparative Example A 20% by weight aqueous sodium hydroxide solution was added to 1 liter of the nickel sulfate aqueous solution used in Example 1 so that the pH value became 8 to 10, or sodium carbonate was used to adjust the pH to 1.
2, the amount of second nickel hydroxide added was 14 g, and the treatment was performed in the same manner as in Example 1, except that the treatment time was 1 hour.

The results are shown in Table 6.

As is clear from Table 6, the removal rate of cobalt was significantly reduced when the pH value at the time of green precipitation was low and when carbonate was used as the alkali.

Claims (1)

[Claims] 1. To the nickel hydroxide slurry obtained by adding a slightly excess alkali hydroxide aqueous solution to the neutralization amount to the nickel sulfate aqueous solution, 1.2% of the nickel amount in the slurry is added.
A first step of adding an equivalent amount or less of an aqueous sodium hypochlorite solution and separating the resulting precipitate, and adding the precipitate obtained in the first step to an aqueous nickel sulfate solution containing cobalt, depending on the amount of cobalt in the solution. 2 equivalents or more as nickel, pH
A method for removing cobalt from an aqueous nickel sulfate solution, comprising the steps of adding cobalt in steps 3 to 5 and separating cobalt as a precipitate. 2 Claim 1 in which an alkali hydroxide aqueous solution is added to a nickel sulfate aqueous solution so that the pH becomes 11-12.
A method for removing cobalt from an aqueous nickel sulfate solution as described in .