JP2015227489A - Solution purification method of cobalt chloride solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solution purification of a cobalt chloride solution which can reduce the loss of cobalt and the unit consumption of a sulfurizing agent.SOLUTION: In a solution purification method of a cobalt chloride solution, the pH of the cobalt chloride solution is adjusted to 1.15-1.35, and the addition amount of the sulfurizing agent is a mol equivalent of 9-11 times the amount of impurities contained in the cobalt chloride solution, in removing impurities as sulfide precipitation by adding a sulfurizing agent and a pH adjustment agent. The method can reduce the Co/Cu ratio of the sulfide precipitation, allow reduction of the loss of cobalt while removing impurities sufficiently, minimize the addition amount of the sulfurizing agent to an amount necessary for removal of impurities and thereby reduce the unit consumption of the sulfurizing agent.

Description

  The present invention relates to a method for purifying a cobalt chloride solution. More specifically, the present invention relates to a method for purifying a cobalt chloride solution for removing impurities from a cobalt chloride solution containing at least copper as an impurity.

  In the hydrometallurgical process for recovering nickel and cobalt from sulfides, the clarification process removes impurities from the resulting leachate by leaching the nickel matte and nickel-cobalt mixed sulfide (MS) as raw materials. After that, electrolytic nickel and electrolytic cobalt are recovered in the electrolysis process.

  As shown in FIG. 1, the leachate obtained from the leaching step is sent to the cobalt solvent extraction step after removing copper in the cementation step and removing impurities such as iron and arsenic in the deironing step. In the cobalt solvent extraction step, nickel and cobalt are separated by solvent extraction to obtain a crude nickel chloride solution and a crude cobalt chloride solution. Impurities are further removed from the crude nickel chloride solution to obtain a high purity and sent to the nickel electrolysis process. In the nickel electrolysis process, electric nickel is produced by electrowinning. On the other hand, the cobalt chloride solution is further purified by removing impurities and sent to the cobalt electrolysis process. In the cobalt electrolysis process, electrolytic cobalt is produced by electrowinning.

  The liquid purification process of the crude cobalt chloride solution includes a plurality of detailed processes, including a copper removal process. In the copper removal step, impurities such as copper and lead are removed as sulfide starch by adding a sulfurizing agent to the crude cobalt chloride solution. Since the pH of the treatment liquid is lowered by the addition of the sulfiding agent, in order to prevent this, a pH adjuster is added to adjust the pH of the treatment liquid.

  However, in the copper removal step, a part of valuable cobalt is co-precipitated together with impurities copper and lead and removed as sulfide starch. For this reason, there is a problem of loss of valuables. In addition, when the sulfurized starch is repeated in the leaching process for the recovery of cobalt contained in the sulfurized starch, there is a problem that the operation efficiency is lowered.

  Patent Document 1 discloses that in the copper removal step, the redox potential (Ag / AgCl electrode reference) is adjusted to 50 mV or less and the pH is adjusted to 0.3 to 2.4. Patent Document 2 discloses that in the step of removing lead from the cobalt chloride solution, the redox potential (Ag / AgCl electrode standard) is adjusted to -50 to 0 mV and the pH is adjusted to 1.0 to 2.0.

  However, since the oxidation-reduction potential is not stable due to the influence of cobalt, which is the main component of the cobalt chloride solution, there is a problem that it is difficult to adjust the addition amount of the sulfiding agent using the oxidation-reduction potential as an index. Therefore, in actual operation, excessive addition of a sulfiding agent is performed in order to reliably remove impurities, which increases the basic unit of sulfiding agent (the amount of sulfiding agent used per cobalt production). There's a problem.

JP 2004-285368 A JP 2008-274382 A

  An object of this invention is to provide the liquid purification method of the cobalt chloride solution which can reduce the loss of cobalt and can make a sulfidizing agent basic unit low in view of the said situation.

The method for purifying a cobalt chloride solution according to the first aspect of the present invention is to add a sulfurizing agent and a pH adjuster to a cobalt chloride solution containing at least copper as an impurity to remove impurities as a sulfide starch. The pH is adjusted to 1.15 to 1.35, and the addition amount of the sulfurizing agent is 9 to 11 times the molar equivalent of the amount of impurities contained in the cobalt chloride solution.
The cobalt chloride solution purification method of the second invention is characterized in that, in the first invention, the pH of the cobalt chloride solution is adjusted to 1.15 to 1.25.
According to a third aspect of the present invention, in the first or second aspect, the sulfiding agent is hydrogen sulfide.
According to a fourth aspect of the present invention, in the first, second or third aspect, the pH adjusting agent is cobalt carbonate.

According to the first invention, since the pH of the cobalt chloride solution is adjusted to 1.15 to 1.35, the Co / Cu ratio of the sulfide starch can be lowered, and the loss of cobalt can be reduced while sufficiently removing impurities. Further, since the addition amount of the sulfiding agent is 9 to 11 times the molar equivalent of the impurity amount, the addition amount of the sulfiding agent can be suppressed to an amount necessary for removing the impurities, and the sulfiding agent basic unit can be lowered.
According to the second invention, since the pH of the cobalt chloride solution is adjusted to 1.15 to 1.25, the Co / Cu ratio of the sulfide starch can be further reduced, and the loss of cobalt can be further reduced.
According to the third invention, since the sulfiding agent is hydrogen sulfide, it is possible to prevent other metals from being mixed into the cobalt chloride solution.
According to the fourth invention, since the pH adjuster is cobalt carbonate, it is possible to prevent other metals from being mixed into the cobalt chloride solution.

It is a whole process figure of a hydrometallurgical process. It is a detailed process drawing of a copper removal process. It is a graph which shows Co / Cu ratio of the sulfide starch with respect to pH of a cobalt chloride solution. It is a graph which shows transition of pH of a cobalt chloride solution, and a sulfidizing agent basic unit.

Next, an embodiment of the present invention will be described with reference to the drawings.
The cobalt chloride solution purification method according to an embodiment of the present invention is applied to a nickel and cobalt hydrometallurgical process described below. The method for purifying a cobalt chloride solution according to the present invention is applicable to any process as long as it is a process for purifying a cobalt chloride solution containing at least copper as an impurity, regardless of the origin of the cobalt chloride solution.

  As shown in FIG. 1, in the nickel and cobalt hydrometallurgical process, first, the raw material nickel / cobalt mixed sulfide (MS: mixed sulfide) and nickel matte are leached with chlorine to obtain a leachate. The main component of the leachate is a nickel chloride solution, which contains impurities such as iron, copper and lead in addition to cobalt.

  The leachate obtained from the leaching step is sent to the cobalt solvent extraction step through a cementation step and a deironing step. In the cobalt solvent extraction step, cobalt contained in the leachate is separated by solvent extraction to obtain a nickel chloride solution and a cobalt chloride solution. For convenience of explanation, the nickel chloride solution and the cobalt chloride solution obtained from the cobalt solvent extraction step are referred to as a crude nickel chloride solution and a crude cobalt chloride solution, respectively. The crude cobalt chloride solution contains copper, lead and the like as impurities.

  In the crude cobalt chloride solution, impurities are removed in the liquid purification step to obtain a high purity cobalt chloride solution, which is sent to the cobalt electrolysis step. In the cobalt electrolysis process, electrolytic cobalt is produced by electrowinning.

  The liquid purification process of the crude cobalt chloride solution includes a plurality of detailed processes, including a copper removal process. As shown in FIG. 2, in the copper removal step, a sulfurizing agent is added to the crude cobalt chloride solution supplied to the reaction vessel to precipitate copper and lead as impurities as sulfide starch. In addition, since the pH of the treatment liquid is lowered by the addition of the sulfurizing agent, in order to prevent this, a pH adjuster is added to adjust the pH of the treatment liquid.

  Although it does not specifically limit as a sulfurizing agent, For example, water-soluble sulfides, such as hydrogen sulfide, sodium sulfide, sodium hydrosulfide, are used. Among these, hydrogen sulfide is preferable because it can prevent mixing of other metals into the cobalt chloride solution.

  As the pH adjusting agent, an alkaline or acidic pH adjusting agent is selected depending on the pH of the treatment liquid and / or the sulfurizing agent. The pH adjuster is not particularly limited, but an alkaline salt such as sodium hydroxide, calcium hydroxide, sodium carbonate, cobalt carbonate or the like can be used as the alkaline pH adjuster, and mineral such as hydrochloric acid or sulfuric acid can be used as the acidic pH adjuster. An acid can be used. Of these, cobalt carbonate is preferred because it can prevent other metals from being mixed into the cobalt chloride solution.

  The intermediate slurry discharged from the reaction tank is sent to a solid-liquid separation device such as a filter press device and separated into a high-purity cobalt chloride solution and sulfide starch. In this way, impurities can be removed as sulfide starch.

  The obtained high-purity cobalt chloride solution is supplied to the cobalt electrolysis step through other steps as necessary. Further, the sulfurized starch is repeated in the leaching step, and cobalt and the like contained in the sulfurized starch are recovered.

  In this embodiment, in the copper removal step of the above hydrometallurgical process, the pH of the cobalt chloride solution is adjusted to 1.15 to 1.35, preferably 1.15 to 1.25, and the addition amount of the sulfiding agent is included in the cobalt chloride solution. It is characterized in that the molar equivalent is 9 to 11 times the amount of impurities. Here, pH adjustment can be performed by adjusting the addition amount of a pH adjuster. Moreover, the amount of impurities means the amount of impurities such as copper and lead, for example, the sum of the amount of copper and the amount of lead.

  The inventor of the present application measured the cobalt / copper weight ratio (hereinafter referred to as Co / Cu ratio) of the sulfide sulfide with respect to the pH of the cobalt chloride solution in the reaction vessel in the copper removal step. The results shown in FIG. Got.

  FIG. 3 shows that the Co / Cu ratio can be lowered as the pH of the cobalt chloride solution is lower. That is, as the pH of the cobalt chloride solution is lowered, the coprecipitation amount of valuable cobalt can be reduced while removing copper as impurities. Specifically, the Co / Cu ratio is drastically lowered by adjusting the pH of the cobalt chloride solution to 1.35 or less, and the Co / Cu ratio is reduced to about 1.3 or less by adjusting the pH of the cobalt chloride solution to 1.25 or less. It turns out that it can be suppressed.

  As described above, by adjusting the pH of the cobalt chloride solution to 1.35 or less, preferably 1.25 or less, the Co / Cu ratio of the sulfide starch can be lowered, and the loss of cobalt can be reduced while sufficiently removing impurities. Moreover, since the loss of cobalt can be reduced, it is possible to reduce the sulfiding agent conventionally consumed for sulfiding cobalt, and to reduce the amount of sulfiding agent added.

  However, if the pH of the cobalt chloride solution is less than 1.15, the particle size of the sulfide starch is reduced, and poor filtration occurs in the solid-liquid separation device. Therefore, it is preferable to adjust the pH of the cobalt chloride solution to 1.15 or more. .

Moreover, when this inventor investigated the addition amount of the sulfurizing agent with respect to the impurity amount processed at a copper removal process, 9-11 times mole equivalent of the impurity amount was found to be appropriate.
This survey was conducted according to the following procedure. In the copper removal step, the addition amount of the sulfiding agent was changed between 6 to 12 molar equivalents relative to the amount of impurities in the crude cobalt chloride solution (hereinafter referred to as impurity amount (crude)). At each sulfurizing agent addition amount, the amount of impurities contained in the sulfided starch obtained by the sulfurization reaction (hereinafter referred to as impurity amount (starch)) and the amount of cobalt contained in the sulfided starch (hereinafter referred to as cobalt amount (starch). ) Was analyzed. As a result, when the addition amount of the sulfiding agent is less than 9 times the molar equivalent of the impurity amount (crude), the impurity amount (starch) rapidly decreases with respect to the impurity amount (coarse), and the impurity removal amount is 90%. It was found that it was less than% by weight, which was insufficient. If the amount of sulfurizing agent added exceeds 11 times the amount of impurities (crude), coprecipitation is accelerated rapidly, and the amount of cobalt (starch) is reduced to 5% by weight of the amount of cobalt in the crude cobalt chloride solution. I understood that it would exceed.

  That is, if the addition amount of the sulfiding agent is less than 9 times the molar equivalent of the amount of impurities, the impurities cannot be sufficiently converted to sulfide starch. Moreover, when the addition amount of the sulfiding agent exceeds 11 times the molar equivalent of the impurity amount, the coprecipitation amount of cobalt increases and the sulfiding agent basic unit deteriorates.

  From the above, the addition amount of the sulfiding agent can be suppressed to the amount necessary for removing the impurities by setting the molar equivalent of 9 to 11 times the amount of impurities contained in the cobalt chloride solution. The sulfiding agent unit can be lowered.

  Further, since the addition amount of the sulfiding agent is adjusted based on the impurity amount, the addition amount can be easily adjusted as compared with the conventional case where the oxidation-reduction potential is used as a reference. Therefore, it is not necessary to add an excessive sulfurizing agent.

  As described above, loss of valuable cobalt can be reduced, and the sulfidizing agent basic unit can be lowered. In addition, since the amount of cobalt contained in the sulfide starch is reduced, the amount of cobalt repeated in the leaching step is also reduced, so that the amount of chlorine used in the leaching step can be reduced and the amount of hydrochloric acid used in the cobalt solvent extraction step can be reduced. .

Next, examples will be described.
(Common conditions)
In the copper removal step of the wet refining process, the cobalt chloride solution was purified. Details of the cobalt chloride solution are as follows. In addition, hydrogen sulfide was used as the sulfiding agent, and cobalt carbonate was used as the pH adjusting agent.
Cobalt chloride solution flow rate: 90 ~ 120L / min
Cobalt chloride solution valuable material concentration: Co 60 ~ 70g / L
Cobalt chloride solution impurity concentration: Cu 60-110mg / L, Pb 1-10mg / L

Example 1
The addition amount of the pH adjuster was adjusted so that the pH of the cobalt chloride solution in the reaction vessel was 1.35. Moreover, the addition amount of the sulfiding agent was 10 times the molar equivalent with respect to the amount of copper to be treated in the copper removal step. As shown in Fig. 4, as a result of operation for 8 months from October 2012 to June 2013, the sulfidizing agent basic unit was in the range of 7.0 to 8.0 kg / t, and the average value was about 7.3 kg / t. It was. The Co / Cu ratio of the sulfide starch was 2.9 on average.

(Comparative Example 1)
The addition amount of the pH adjuster was adjusted so that the pH of the cobalt chloride solution in the reaction vessel was 2.0 to 2.5. The sulfurizing agent was added at a constant flow rate. As shown in FIG. 4, as a result of operation for 6 months from April to September 2012, the sulfidizing agent basic unit was in the range of 8.0 to 12.0 kg / t, and the average value was about 9.3 kg / t. The Co / Cu ratio of the sulfide starch was 4.9 on average.

  From the above, it was confirmed that Example 1 can reduce the sulfidizing agent basic unit by about 20% compared with Comparative Example 1. It was also confirmed that the Co / Cu ratio can be reduced by about 40%.

Claims (4)

In removing a impurity as a sulfurized starch by adding a sulfurizing agent and a pH adjuster to a cobalt chloride solution containing at least copper as an impurity,
Adjust the pH of the cobalt chloride solution to 1.15-1.35,
A method for purifying a cobalt chloride solution, wherein the addition amount of the sulfiding agent is 9 to 11 times the molar equivalent of the amount of impurities contained in the cobalt chloride solution. The method for purifying a cobalt chloride solution according to claim 1, wherein the pH of the cobalt chloride solution is adjusted to 1.15 to 1.25. The method for purifying a cobalt chloride solution according to claim 1 or 2, wherein the sulfurizing agent is hydrogen sulfide. 4. The method for purifying a cobalt chloride solution according to claim 1, wherein the pH adjuster is cobalt carbonate.