JP2008156713A - Method of chlorine leaching of nickel/cobalt-containing mixed sulfide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical and efficient method of chlorine leaching for recovering nickel and cobalt from a nickel/cobalt-containing mixed sulfide obtained by wet sulfuration reaction at a high leaching ratio of ≥95%. <P>SOLUTION: The method of chlorine leaching of nickel/cobalt-containing mixed sulfide obtained by wet sulfuration reaction is characterized in that the powder properties of the mixed sulfide used for raw materials are preadjusted, and controlled so that the specific surface area reaches ≥1.50 m<SP>2</SP>/g or the specific surface area (F) per unit particle diameter satisfies inequality; F=a/d≥0.05 m<SP>2</SP>/g/μm, and thereafter nickel and cobalt are recovered by chlorine leaching treatment at a leaching ratio of ≥95; wherein, a denotes the specific surface area (m<SP>2</SP>/g) of the mixed sulfide; and d denotes the 50% diameter (μm) of a particle diameter distribution. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for leaching a mixed sulfide containing nickel and cobalt, and more specifically, in a method for leaching a mixed sulfide containing nickel and cobalt obtained by a wet sulfidation reaction, which is produced from a wet sulfidation reaction step. When using raw mixed sulfides or mixed sulfides that have been pulverized thereafter as raw materials, nickel and nickel and The present invention relates to a practical and efficient chlorine leaching method for recovering cobalt at a high leaching rate of 95% or more.

Conventionally, as a sulfide raw material containing nickel and cobalt, nickel matte obtained mainly by smelting sulfide ore has been mainly used, but in recent years, it has been hydrometallized from oxide ore that is abundant on the earth. Attention has been focused on mixed sulfides containing nickel and cobalt obtained by the method.
Nickel mats are solidified by cooling the sulfide melted in the smelting process, and have a structure in which the Ni ₃ S ₂ phase, which is the main component, and the metal phase mainly composed of nickel are densely precipitated. ing. On the other hand, the mixed sulfide is a powder that is precipitated mainly from a sulfuric acid solution by a sulfurization reaction, and the main component is NiS containing coprecipitated cobalt.

  In general, as a leaching method of nickel and cobalt, various methods such as an oxidative leaching method, an alkali leaching method, and a chlorine leaching method are already known. Among these, a chlorine leaching method has attracted attention for nickel mats that have been widely used as a raw material, and finely pulverized raw materials are used in this method. This is because sulfur can be separated as solid elemental sulfur by the chlorine leaching reaction, and a high leaching rate of nickel and cobalt can be obtained. For example, in chlorine leaching from a nickel mat, it has been reported that a leaching rate of 95% or more of nickel and cobalt can be obtained with a raw material pulverized to a particle size of 100 mesh (opening: 150 μm) or less (for example, , See Patent Document 1). In the case of nickel mats, it is also known that the leaching rate increases as the pulverized particle size becomes finer. Therefore, the nickel leaching rate is controlled by using a raw material having a predetermined particle size distribution by pulverization. Things were going on.

  On the other hand, the leaching of nickel and cobalt using the chlorine leaching method has also been studied for mixed sulfides. Since mixed sulfides are usually produced by a wet process, the particle size distribution can be easily adjusted by controlling the sulfiding conditions in the production. Taking advantage of this, the mixed sulfides can be used as raw materials. Attempts have been made to improve the leaching rate by using a fine distribution, but this is greatly different from the case of the nickel mat described above, and even if the particle size distribution is comparable, a significant increase in the nickel leaching rate is obtained. I couldn't.

This reason is said to be mainly due to the difference in the mineral composition of nickel mat and mixed sulfide and the mechanism of the leaching reaction associated therewith, as will be described next.
As described above, in the nickel mat, since the metallic nickel phase is present inside the powder particles in addition to the sulfide phase, the following reaction formula (1) and reaction formula (2) proceed simultaneously and leaching occurs. move on. That is, the reaction formula (1) is a reaction in which chlorine gas is ionized and nickel is leached at the same time when S ^{2− of} NiS representing sulfide becomes S ⁰ . Reaction formula (2) is a reaction of elution of nickel ions (Ni ²⁺ ) and ionization of chlorine gas.

Reaction formula (1): NiS + Cl ₂ → Ni ²⁺ + S ⁰ + 2Cl ⁻
Reaction formula (2): Ni ⁰ + Cl ₂ → Ni ²⁺ + 2Cl ⁻

  That is, in the nickel mat, since the trace of the metal nickel phase leached becomes a cavity and forms a new surface, chlorine gas can enter the mat particles, so that the reaction formulas (1), (2 ) Reaction occurs continuously and the reaction proceeds sufficiently to the inside of the particles.

On the other hand, in the mixed sulfide, since there is no metallic nickel phase, the leaching reaction proceeds only by the reaction formula (1), so that elemental sulfur (S ⁰ ) remains on the particle surface of the mixed sulfide. Thus the particle surface because it is blocked by S ^0, together with the area of effective reaction interface leaching is reduced, it prevents the progress of the reaction to the particle interior.

  When the difference in reactivity between the two is shown in terms of a specific leaching rate, the same conditions as the particle size distribution conditions for obtaining a high leaching rate in the case of nickel mat, for example, the 50% diameter of the particle size distribution (the integrated value of the integrated particle size distribution) (It may be referred to as “D50” hereinafter.) Using a mixed sulfide produced to be 45 μm or less, and leaching under the same conditions as the nickel mat, The leaching rates of nickel and cobalt were not limited to 95%, and sometimes only a low result of 90% or less was obtained.

As countermeasures, in order to improve the leaching rate of nickel and cobalt from mixed sulfides, increase the amount of chlorine gas injected during chlorine leaching, or leaching chlorine after melting mixed sulfides into a mat. A method such as a method has been studied. However, each of these methods has problems. That is, an increase in the amount of chlorine gas blown in leads to oxidation of elemental sulfur produced in the reaction, and the sulfur component dissolves into the leachate as sulfate ions, for example, accelerates the deterioration of the anode electrode during electrowinning. Or an increase in the amount of neutralizing agent for discharging sulfate ions affects the subsequent processes. In addition, smelting of mixed sulfides is technically possible, but it requires high energy consumption in the drying process and generation of SO ₂ during smelting, and it is necessary to deal with environmental problems and pollution problems. However, the leach rate is improved, but there is a problem in economy because it leads to an increase in cost. Other methods include extension of chlorine leaching time, repeated leaching of leaching residues that have not been sufficiently leached, re-leaching after pulverizing the leaching residues, etc., but all methods are time, process, energy, etc. There was a problem that it increased, leading to an increase in cost.

  Under these circumstances, it is practical and efficient to recover nickel and cobalt from mixed sulfides at a high leaching rate of 95% or more without significantly changing the conventional leaching process and conditions. New developments and proposals are needed.

Japanese Patent Publication No. 7-91599 (first page, fifth page, sixth page)

  In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a mixed sulfide that is produced from a wet sulfide reaction step in a method for leaching a mixed sulfide containing nickel and cobalt obtained by a wet sulfide reaction. In addition, when any of the mixed sulfides pulverized thereafter is used as a raw material, 95% or more of nickel and cobalt are mixed from the mixed sulfide without greatly changing the process and conditions of the conventional chlorine leaching method. It is to provide a practical and efficient chlorine leaching method for recovering at a high leaching rate.

  In order to achieve the above object, the present inventors have conducted extensive research on a method for leaching a mixed sulfide containing nickel and cobalt obtained by a wet sulfidation reaction. The body characteristics were adjusted in advance, and the specific surface area or the specific surface area per unit particle size (F) was controlled to a specific value or more, and then subjected to chlorine leaching treatment. The inventors have found that nickel and cobalt can be recovered and completed the present invention.

That is, according to the first aspect of the present invention, in the method for leaching a mixed sulfide containing nickel and cobalt obtained by a wet sulfidation reaction,
The powder characteristics of the mixed sulfide used as a raw material are adjusted in advance, and the specific surface area is 1.50 m ² / g or more, or the specific surface area (F) per unit particle diameter satisfies the following formula (1) Thus, a chlorine leaching method for mixed sulfides is provided, which is subjected to a chlorine leaching treatment and recovers nickel and cobalt at a leaching rate of 95% or more.
F = a / d ≧ 0.05 m ² / g / μm (1)
(Wherein, a represents the specific surface area (m ² / g) of the mixed sulfide, and d represents the 50% diameter (μm) of the particle size distribution.)

  Further, according to the second invention of the present invention, in the first invention, the above-mentioned powder characteristics adjust the sulfiding conditions when the mixed sulfide is produced by the wet sulfidation reaction or the obtained mixed sulfidation. A method for chlorine leaching of mixed sulfides, characterized in that it is controlled by either grinding the product.

  According to a third aspect of the present invention, there is provided the chlorine leaching method for mixed sulfides according to the first aspect, wherein the 50% diameter of the particle size distribution is 5 to 50 μm.

  According to a fourth aspect of the present invention, in the first aspect, the mixed sulfide is obtained by adding a sulfiding agent to a sulfuric acid aqueous solution containing nickel and cobalt and precipitating the nickel and cobalt as sulfides. A method for leaching a mixed sulfide leaching is provided.

  According to a fifth aspect of the present invention, in the first aspect, the chlorine leaching controls a redox potential so as to suppress oxidation of sulfur while blowing chlorine gas into the mixed sulfide slurry. A method for leaching a mixed sulfide leaching is provided.

  The chlorine leaching method for mixed sulfides containing nickel and cobalt according to the present invention includes leaching of mixed sulfides produced as a result of wet sulfidation reaction and mixed sulfides after pulverization. Since the powder characteristics of the mixed sulfide can be controlled based on the above index that can control the rate, and the leaching rate of nickel and cobalt of 95% or more can be stably achieved, its industrial value is Very large.

Hereinafter, the chlorine leaching method of the mixed sulfide containing nickel and cobalt of the present invention will be described in detail.
The chlorine leaching method of the present invention is a method for chlorine leaching of mixed sulfides containing nickel and cobalt obtained by a wet sulfidation reaction. The powder characteristics of mixed sulfides used as raw materials are adjusted in advance, and the specific surface area is 1.50 m. ² / g or more, or the specific surface area per unit particle size (F) is controlled by satisfying the following formula (1), and then subjected to a chlorine leaching treatment, and nickel with a leaching rate of 95% or more. And cobalt is recovered.
F = a / d ≧ 0.05 m ² / g / μm (1)
(Wherein, a represents the specific surface area (m ² / g) of the mixed sulfide, and d represents the 50% diameter (μm) of the particle size distribution.)

In the method of the present invention, as a raw material for leaching, a powder having a specific surface area of 1.50 m ² / g or more, or a specific surface area per unit particle size (F) of 0.05 m ² / g / μm or more. It is important to use mixed sulfides with controlled properties. Thereby, when using any of the mixed sulfides produced by the wet sulfidation reaction and the mixed sulfides pulverized thereafter as a raw material, for example, the specific surface area of the produced mixed sulfides is 1.50 m. When it is ² / g or more, it is directly used as a raw material, whereas when the specific surface area is less than this, the specific surface area (F) per unit particle diameter of the mixed sulfide is 0.05 m ² / g / μm. By controlling the powder characteristics as described above, the leaching rate can be managed in a practical and efficient manner, and a high leaching rate can be obtained.

The specific surface area per unit particle diameter (F) employed in the present invention is the specific surface area (a, unit is m ² / g) of the mixed sulfide, 50% diameter (d, unit is the unit). It is a value divided by μm, and is calculated by F = a / d. This is an index representing the difficulty of leaching, and in order to take into account the effect of the reduction of the specific surface area associated with the pulverization process, the relative surface area of the particles having the same particle size is relatively compared. It is an index consisting of physical quantities. That is, if the specific surface area (F) per unit particle diameter is large, it means that the particles are more easily leached. Specifically, in the case of particles having the same particle diameter, the value of a / d is larger than the particles having a large specific surface area such as irregularities in the surface state, and the particles having a small specific surface area because the surface state is smooth. growing.

  From this point of view, the phenomenon that the particle size observed in the pulverization process of the mixed sulfide is refined but does not contribute to the increase of the specific surface area is that the mixed sulfide particles are first compacted and then pulverized during the pulverization. The cause is presumed to be through the process. That is, the mixed sulfide particles produced by the wet sulfidation method are originally low in density unlike the nickel mat produced by smelting, and therefore, when pulverized, they are easily deformed into a flat shape, for example, and the specific surface area is reduced. This is because the specific surface area (F) per unit particle diameter decreases because this exceeds the increase in specific surface area due to the decrease in particle size. However, as a matter of course, at a certain particle size level, the specific surface area (F) per unit particle size increases due to the particle size decrease as in the case of the nickel mat.

By the way, the figure below shows how each affects the nickel leaching rate when the particle size distribution and the specific surface area, which are the basis of the specific surface area per unit particle size (F), are individually adjusted. It explains using.
First, FIG. 1 shows the relationship between the 50% diameter of the mixed sulfide (MS) produced from the sulfurization reaction step and the nickel leaching rate, and the mixed sulfide obtained by the grinding treatment. It is a figure showing the relationship between the 50% diameter of a particle size distribution, and a nickel leaching rate. Here, the pulverization treatment is performed by changing the pulverization time in the planetary ball mill using an unground pulverized mixed sulfide having a particle size D50 of 85 μm. In addition, the mixed sulfide used here is obtained by wet sulfidation reaction of sulfuric acid aqueous solution in the sulfuric acid leaching method of nickel oxide ore.

  FIG. 2 shows the relationship between the specific surface area of the mixed sulfide (MS) produced from the sulfurization reaction step and the nickel leaching rate, and the specific surface area of the mixed sulfide obtained by the grinding treatment. It is a figure showing the relationship of a nickel leaching rate.

1 and 2, it is more important that the correlation between the 50% diameter of the particle size distribution and the nickel leaching rate and the correlation between the specific surface area and the nickel leaching rate are different between the unground product and the pulverized product. This means that when the specific surface area of the mixed sulfide as produced is 1.50 m ² / g or more, a high leaching rate can be obtained without pulverization, and the particle size of the mixed sulfide can be obtained by pulverization. In spite of the 50% diameter of the distribution becoming smaller, the specific surface area becomes smaller without increasing. For example, the specific surface area is 1.3 m ² / g when the 50% diameter of the particle size distribution of the unground product is 36 μm, whereas the specific surface area of the pulverized product is 0.1 μm when the 50% diameter of the particle size distribution is 31 μm. 79m ² / g, and it can be seen, the 50% size of the particle size distribution is the specific surface area when the 19μm is 0.75 m ² / g. In addition, it can be seen that making the particle size finer by pulverization does not necessarily directly contribute to the improvement of the nickel leaching rate, but may decrease.

In other words, the mixed sulfides produced from the wet sulfidation reaction process and the mixed sulfides that were subsequently pulverized were not found to be identical in the relationship between the powder characteristics and the nickel leaching rate. It can be seen that the rate cannot be uniquely managed solely by its particle size distribution or specific surface area. And when the specific surface area of the mixed sulfide as produced here is less than 1.50 m ² / g, the specific surface area per unit particle diameter (F) calculated from both the particle size distribution and the specific surface area Has technical significance.

The specific surface area (F) per unit particle size used in the method of the present invention is 0.05 m ² / g / μm or more. That is, in the mixed sulfide having a specific surface area (F) per unit particle size of less than 0.05 m ² / g / μm, the leaching property is low, so that nickel and cobalt are leached at a high leaching rate of 95% or more. I can't. In addition, when the specific surface area of the mixed sulfide as produced is 1.50 m ² / g or more, the specific surface area (F) per unit particle diameter is 0.05 m ² / g / μm or more. It is done.

Although it does not specifically limit as 50% diameter of the particle size distribution of this invention, 5-50 micrometers is preferable. That is, if the 50% diameter of the particle size distribution is less than 5 μm, it is excessively pulverized and the cost increases. On the other hand, if the 50% diameter of the particle size distribution exceeds 50 μm, elemental sulfur (S ⁰ ) remains on the particle surface in the leaching reaction, and the leaching reaction does not proceed.

Control of the powder characteristics used in the above method is not particularly limited, but the powder characteristics of the mixed sulfide produced by adjusting the sulfiding conditions in the wet sulfidation reaction are controlled or produced. When the specific surface area (F) per unit particle size of the mixed sulfide is less than 0.05 m ² / g / μm, the mixing sulfide is preferably pulverized to control the powder characteristics. . As a result, the mixed sulfides can be controlled based on the above index, which can control the leaching rate, regardless of whether the mixed sulfides produced by the wet sulfidation reaction or the mixed sulfides after pulverization are used as raw materials. By controlling the powder characteristics, it is possible to stably achieve a high leaching rate of 95% or more.

  The mixed sulfide used in the above method is not particularly limited, and those produced from various liquid leachates are used. Among them, hydrogen sulfide gas or the like is added to a sulfuric acid aqueous solution containing nickel and cobalt. Those obtained by adding a sulfiding agent and precipitating nickel and cobalt as sulfides are preferably used. For example, in the sulfuric acid leaching method of nickel oxide ore, valuable metals are once concentrated and separated as sulfides from an aqueous sulfuric acid solution containing valuable metals such as nickel and cobalt obtained from the leaching process, and then from the obtained sulfides. The valuable metals are separated and recovered individually.

  The chlorine leaching used in the above method is not particularly limited. For example, when chlorine gas is blown into the mixed sulfide slurry, the oxidation / reduction potential is controlled so as to suppress sulfur oxidation. Are preferably used. That is, under the leaching conditions that do not suppress the oxidation of sulfur, the leaching hindrance due to the precipitation of elemental sulfur according to the reaction formula (1) as described above becomes small, so that the leaching characteristic peculiar to mixed sulfides is deteriorated. Does not happen.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the analysis method of the metal used by the Example and the comparative example, the particle size distribution, and the evaluation method of a specific surface area are as follows.
(1) Metal analysis: ICP emission analysis was performed.
(2) Measurement of particle size distribution: It was carried out with a particle size distribution measuring device (MICROTRAC HRA model: 9320-X100).
(3) Measurement of specific surface area: The specific surface area was measured by a BET specific surface area measurement method using a high-speed specific surface area and pore distribution measuring device (YUASAIONICS NOVA1000).

(Example 1)
As raw material, unsintered mixed sulfide A (Ni grade: 56 wt%, Co grade: 4.2 wt%, D50: 15.4 μm) produced from the sulfurization step of high pressure sulfuric acid leaching of nickel oxide ore, specific surface ^area: using ^{2.20m 2 /g,F:0.14m 2 / g / μm} ) 30g, performs chlorine leached with leaching under the following conditions, then, to determine the nickel leaching rates. The results are shown in Table 1.

[Chlorine leaching conditions]
Reaction tank: 500 mL titanium stirring tank Leached liquid and amount: Nickel chloride aqueous solution (liquid composition (g / L): Ni; 165, Co: 0.9, Cu: 30, Fe: 0.5, S: 4.5) 300 mL
Slurry concentration: 100 g / L
Chlorine gas injection control: 520 mV (redox potential (Ag / AgCl electrode standard))
Rotation speed: 400rpm (titanium shaft with 4 blades)
Leaching time: 3 hours

(Example 2)
As a raw material, mixed sulfide B obtained by pulverizing mixed sulfide produced from the sulfidation process of nickel oxide ore under high pressure sulfuric acid leaching method (Ni grade: 59 wt%, Co grade: 3.5 wt%, D50: 3.9 .mu.m, specific surface ^{area: 1.87m 2 /g,F:0.48m 2 / g /} μm) except using the a similar manner to example 1, then, to determine the nickel leaching rates. The results are shown in Table 1.

(Example 3)
As a raw material, mixed sulfide C obtained by pulverizing mixed sulfide produced from the sulfidation process of nickel oxide ore under high pressure sulfuric acid leaching method (Ni grade: 59 wt%, Co grade: 3.5 wt%, D50%) : 8.4 .mu.m, specific surface ^{area: 1.19m 2 /g,F:0.14m 2 / g /} μm) except using the a similar manner to example 1, then, to determine the nickel leaching rates. The results are shown in Table 1.

(Comparative Example 1)
As raw materials, unsintered mixed sulfide E (Ni grade: 57 wt%, Co grade: 3.9 wt%, D50: 35.5 μm) produced from the sulfurization step of high pressure sulfuric acid leaching of nickel oxide ore, specific surface ^{area: 1.33m 2 /g,F:0.04m 2 / g /} μm) except using the a similar manner to example 1, then, to determine the nickel leaching rates. The results are shown in Table 1.

(Comparative Example 2)
As raw materials, unsintered mixed sulfide F (Ni grade: 58 wt%, Co grade: 3.3 wt%, D50: 84.5 μm, produced from the sulfidation step of high pressure sulfuric acid leaching of nickel oxide ore, specific surface ^{area: 0.51m 2 /g,F:0.01m 2 / g /} μm) except using the a similar manner to example 1, then, to determine the nickel leaching rates. The results are shown in Table 1.

(Comparative Example 3)
As a raw material, mixed sulfide G obtained by pulverizing mixed sulfide produced from the sulfidation step of nickel oxide ore under high pressure sulfuric acid leaching method (Ni grade: 60 wt%, Co grade: 3.4 wt%, D50: 31.4Myuemu, specific surface ^{area: 0.79m 2 /g,F:0.03m 2 / g /} μm) except using the a similar manner to example 1, then, to determine the nickel leaching rates. The results are shown in Table 1.

(Comparative Example 4)
As a raw material, mixed sulfide D obtained by pulverizing mixed sulfide produced from the sulfiding process of high pressure sulfuric acid leaching of nickel oxide ore (Ni grade: 59 wt%, Co grade: 3.3 wt%, D50%) : 19.2 μm, specific surface area: 0.75 m ² / g, F: 0.04 m ² / g / μm) was used in the same manner as in Example 1, and then the nickel leaching rate was determined. The results are shown in Table 1.

From Table 1, in Examples 1 to 3, in leaching, as a raw material, the specific surface area is 1.50 m ² / g or more, or the specific surface area (F) per unit particle diameter is 0.05 m ² / g / μm or more. It can be seen that a nickel and cobalt leaching rate of 95% or more can be achieved because the mixed sulfide having controlled powder characteristics is used. On the other hand, in Comparative Examples 1 to 4, the specific surface area or the specific surface area per unit particle diameter does not meet these conditions, so that satisfactory results cannot be obtained with the nickel and cobalt leaching rates.
From the above, the specific surface area is 1.50 m ² / g or more per unit particle size when using any of the mixed sulfides produced from the wet sulfidation reaction process and the mixed sulfides that have been pulverized thereafter as raw materials. By controlling the specific surface area (F) to 0.05 m ² / g / μm or more, a stable operation with a high leaching rate can be performed.

  As is clear from the above, the chlorine leaching method of the mixed sulfide containing nickel and cobalt of the present invention uses either the mixed sulfide as produced by the wet sulfidation reaction or the mixed sulfide that has been pulverized thereafter as a raw material. In particular, it is suitable as a method for stably achieving the leaching rate of nickel and cobalt of 95% or more by controlling the powder characteristics of the mixed sulfide based on the above-mentioned index capable of managing the leaching rate. . Moreover, it can apply widely in the leaching reaction of sulfides other than the mixed sulfide.

Represents the relationship between the 50% diameter of the particle size distribution of the unmixed mixed sulfide (MS) and the nickel leaching rate, and the relationship between the 50% diameter of the particle size distribution of the mixed sulfide obtained by the pulverizing treatment and the nickel leaching rate. FIG. It is a figure showing the relationship between the specific surface area of unmixed mixed sulfide (MS) and nickel leaching rate, and the relationship between the specific surface area of mixed sulfide obtained by pulverization and nickel leaching rate.

Claims (5)

In a method of leaching a mixed sulfide containing nickel and cobalt obtained by a wet sulfidation reaction,
The powder characteristics of the mixed sulfide used as a raw material are adjusted in advance, and the specific surface area is 1.50 m ² / g or more, or the specific surface area (F) per unit particle diameter satisfies the following formula (1) The method of leaching mixed sulfides characterized in that nickel and cobalt are recovered at a leaching rate of 95% or more after being controlled by leaching.
F = a / d ≧ 0.05 m ² / g / μm (1)
(Wherein, a represents the specific surface area (m ² / g) of the mixed sulfide, and d represents the 50% diameter (μm) of the particle size distribution.)   The powder characteristics are controlled by either adjusting a sulfiding condition when producing a mixed sulfide by a wet sulfidation reaction or by pulverizing the obtained mixed sulfide. Chlorine leaching method of the described mixed sulfide.   The method for leaching a mixed sulfide according to claim 1, wherein the 50% diameter of the particle size distribution is 5 to 50 µm.   The mixed sulfide chlorine according to claim 1, wherein the mixed sulfide is obtained by adding a sulfiding agent to a sulfuric acid aqueous solution containing nickel and cobalt and precipitating the nickel and cobalt as sulfides. Leaching method.   2. The chlorine leaching of mixed sulfide according to claim 1, wherein the chlorine leaching is performed by controlling a redox potential so as to suppress sulfur oxidation while blowing chlorine gas into the slurry of mixed sulfide. Method.

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