JP6127902B2 - Method for leaching nickel and cobalt from mixed sulfides - Google Patents

Description

  The present invention relates to a hydrometallurgical process of nickel and cobalt, and more particularly to a method for leaching nickel and cobalt from a mixed sulfide produced by a wet sulfidation reaction.

  As a smelting method of nickel and cobalt, for example, as described in Patent Document 1, chlorine gas is blown into a raw material containing nickel sulfide such as nickel mat and a trace amount of cobalt sulfide, and leaching and leaching are performed. A method of producing nickel and cobalt as electrolytic nickel and cobalt by electrolytically collecting nickel and cobalt has been put into practical use. This method has a simple process and realizes economical production such that chlorine gas generated by electrowinning can be reused for leaching.

  Nickel sulfide such as nickel matte used as a raw material in the above smelting method is, for example, nickel sulfide obtained by melting nickel sulfide ore in a smelting furnace, or melting in a nickel oxide ore and melting in an electric furnace The nickel sulfide obtained by the so-called dry smelting method, such as nickel sulfide obtained in this way.

  On the other hand, in recent years, it is possible to produce nickel sulfide by hydrometallurgy using raw material of nickel oxide ore of low nickel grade that can be mined relatively easily because it is abundant and is near the surface. It is done. Specifically, nickel oxide ore is subjected to pressure acid leaching (high pressure acid leaching, commonly referred to as HPAL), impurities such as iron are removed from the pressure acid leaching solution, and then wet sulfide reaction is performed, for example, hydrogen sulfide gas. Nickel sulfide is produced by injecting into the leachate.

  The nickel sulfide produced by the wet sulfidation reaction in this nickel oxide ore wet smelting process is also a sulfide containing nickel and cobalt, similar to the nickel sulfide obtained by a dry smelting method such as nickel matte. Patent Document 2 discloses a method of hydrometallizing nickel and cobalt using a sulfide containing nickel and cobalt produced by this wet sulfidation reaction (hereinafter sometimes referred to simply as mixed sulfide) as a raw material. There is a technology to which the above-mentioned Patent Document 1 is applied.

  That is, after repulping the mixed sulfide into an aqueous chloride solution, chlorine and gas were blown into the slurry to leached nickel and cobalt into the aqueous chloride solution, which contained divalent copper chloro complex ions as the oxidizing agent. Nickel in the nickel mat is leached by bringing the crushed nickel mat into contact with the chlorine leaching solution and performing a substitution reaction between copper and nickel. Thereafter, the substitution leachate is purified to remove impurities such as iron and lead, and cobalt in the substitution leachate is separated using a method such as solvent extraction. Next, nickel is electrolytically collected to produce electric nickel. In addition, about cobalt, the further refinement | purification liquid is performed by the process route different from nickel, and it is commercialized as an electric cobalt by electrowinning.

  However, if the mixed sulfide produced by wet sulfidation reaction is wet smelted using the method described in Patent Document 2 above, the leaching rate of nickel and cobalt is significantly higher than when nickel mat is used as the raw material. To drop. For this reason, nickel and cobalt that have not been leached out from the chlorine leaching residue through a sulfur recovery process, and the actual yield of nickel and cobalt is reduced.

Furthermore, when a mixed sulfide produced by a wet sulfidation reaction is used as a raw material, a sulfur leaching rate (hereinafter referred to as an oxidation rate only for sulfur) is higher than when a nickel mat is used as a raw material. The concentration of sulfate radicals (SO ₄ ^2- ions) in the chlorine leachate increases. Since SO ₄ ²⁻ ions in this chlorine leachate are supplied to the electrowinning process as an electrolytic solution via the substitution leach and clean solution, an increase in power costs due to an increase in the electrolytic cell voltage in the electrowinning process, and from the anode This caused problems such as a decrease in the chlorine recovery rate due to the generation of oxygen gas. Therefore, it is desired industrially to suppress the sulfur oxidation rate to 2 to 3% or less.

These problems are presumed to be mainly due to the difference in the precipitation composition between the nickel matte and the mixed sulfide and the accompanying difference in the mechanism of the leaching reaction. For example, Patent Document 3 states that “in general, mixed sulfides have lower nickel quality and higher sulfur quality than nickel mats, so that the behavior in chlorine leaching is different from that of nickel mats. Since sulfur increases, if the temperature of the reaction system is high or the reaction heat generated is large, sulfur softens and coalesces easily to form aggregates, which tends to cause leaching inhibition. As described above, the nickel mat has a structure in which the Ni ₃ S ₂ phase, which is the main component, and the metal nickel phase are densely precipitated. Therefore, the amount of sulfur generated with the progress of the reaction is relatively small. "Leaching inhibition due to the fusion of sulfur to the reaction interface is unlikely to occur."

As can be seen from the description in Patent Document 3, the main components of the nickel mat are Ni ₃ S ₂ and Ni (metallic nickel), and the Ni ₃ S ₂ phase and the metallic nickel phase are dense, that is, small crystals are homogeneous. Since it has a dispersed and precipitated structure, in the nickel leaching of chlorine, traces of metallic nickel leaching become voids, and the leaching reaction, which is a reaction between solid and liquid or solid and gas, proceeds inside the particles. Since it becomes easy, it is thought that the leaching reaction of Ni ₃ S ₂ is promoted.

On the other hand, the mixed sulfide produced by the wet sulfidation reaction is recovered as a precipitate by reacting with hydrogen sulfide gas in a sulfuric acid acidic solution containing nickel and cobalt. % CoS. In addition, a small amount of Ni ₃ S ₄ and elemental sulfur are also contained. Therefore, in the case of chlorine leaching of mixed sulfides, there is no metallic nickel phase. Therefore, it is considered that the leaching reaction is difficult to proceed inside the particles.

  In response to the above-described problems in chlorine leaching of mixed sulfides, Patent Document 3 discloses that the mixed sulfides are finely pulverized using means such as pre-pulverization to increase the surface area of particles involved in the leaching reaction. Has proposed a method for improving the leaching rate of nickel and cobalt. Similarly, in Patent Document 3, after the mixed sulfide is repulped into a chloride aqueous solution containing a predetermined amount of copper and then leached with chlorine, the generated excess elemental sulfur is fixed as copper sulfide, A method for preventing a decrease in the leaching rate of nickel and cobalt due to fusion and at the same time preventing an increase in the sulfur oxidation rate has been proposed.

  However, according to the method described in Patent Document 3, the leaching rate of nickel is improved to 95% or more, but the leaching rate of cobalt remains at 90% or less. That is, as is well known to those skilled in the art, CoS is thermodynamically more stable than NiS and it is difficult to separate cobalt and sulfur, so that the leaching rate of cobalt is lower than that of nickel. Challenges still remain.

  Further, as a means for increasing the cobalt leaching rate, for example, a method of increasing the amount of chlorine gas blown in is conceivable. However, since the oxidizing power of chlorine gas is strong, the sulfur oxidation rate is increased. Problems occur. Furthermore, there may be a method in which the leaching residue that has not been sufficiently leached with chlorine is pulverized and then leached again. However, in this case, equipment, processes, energy, etc. will increase, leading to an increase in cost. there were.

Japanese Patent Publication No. 07-091599 JP 2008-240009 A JP 2010-1000093

  In the present invention, when leaching a mixed sulfide containing nickel and cobalt produced by a wet sulfidation reaction in a wet smelting process of nickel oxide ore with chlorine, the mixed sulfide is pulverized in advance. It is possible to leach nickel and cobalt from mixed sulfides at a high leaching rate without using a method of pulverizing and re-leaching the chlorine leaching residue, and to keep the sulfur oxidation rate low. The aim is to provide a possible, efficient and economical leaching method.

  In order to achieve the above object, the present inventor examined the difference in the precipitation composition of the mixed sulfide and the mechanism of the leaching reaction accompanying the precipitation, particularly focusing on the leaching rate of cobalt. It was found that by leaching sulfides under relatively weak oxidation conditions compared to chlorine leaching, the leaching rate of nickel was improved and at the same time the leaching rate of cobalt was increased, and the present invention was completed. It is.

That is, the method for leaching nickel and cobalt from a mixed sulfide according to the present invention is a method for leaching nickel and cobalt from a mixed sulfide containing nickel and cobalt produced by a wet sulfidation reaction in a wet smelting process of nickel oxide ore. A first leaching step of leaching the mixed sulfide with a chloride aqueous solution having an oxidation-reduction potential of 0 mV to 400 mV (Ag / AgCl electrode standard) at a temperature of 70 ° C. to 100 ° C .; A second leaching step in which the residue obtained by solid-liquid separation of the slurry obtained in the leaching step is made into a slurry with an aqueous chloride solution and then leached by blowing chlorine gas into the slurry, and the first leaching step In the method, an aqueous chloride solution of cupric chloride is used as the oxidizing agent .

  According to the present invention, there is no need to pulverize the mixed sulfide in advance using means such as pulverization, and the leaching residue of the leaching of chlorine is pulverized and re-leached without taking a method. Nickel and cobalt can be leached with a high leaching rate from the mixed sulfide produced by the wet sulfidation reaction in the hydrometallurgical process, and at the same time, the sulfur oxidation rate can be kept low.

  Therefore, the leaching method of nickel and cobalt according to the present invention is effective when the nickel sulfide ore is smelted in the wet smelting process of nickel oxide ore using the mixed sulfide produced by the wet sulfidation reaction as a raw material. Since nickel and cobalt can be leached economically, it is extremely useful industrially.

  The method for leaching nickel and cobalt from a mixed sulfide according to the present invention uses a mixed sulfide containing nickel and cobalt produced by a wet sulfidation reaction as a raw material, and this mixed sulfide has an oxidation-reduction potential of 0 mV to 400 mV or less (Ag First leaching step (so-called oxidation leaching) at a temperature of 70 ° C. to 100 ° C. or less with an aqueous chloride solution based on (AgCl electrode standard), and the slurry obtained in the first leaching step is separated into solid and liquid, After the residue is made into a slurry with an aqueous chloride solution, a second leaching step of leaching (so-called chlorine leaching) by blowing chlorine gas into the slurry is included.

The mixed sulfide containing nickel and cobalt as raw materials is subjected to pressure acid leaching (HPAL) of nickel oxide ore of low nickel grade, and after removing impurities such as iron from the pressure acid leaching solution, wet sulfidation reaction It is manufactured by. This mixed sulfide containing nickel and cobalt contains NiS as a main component, contains about 8% CoS, and also contains a small amount of Ni ₃ S ₄ and elemental sulfur.

  The aqueous chloride solution used in the first and second leaching steps is a general term for aqueous solutions containing chloride ions as anions. In the present invention, the main component is nickel chloride and a small amount of impurities. An aqueous solution containing is preferred. Specifically, in the nickel and cobalt smelting method as described in Patent Documents 1 and 2, the electrolytic waste liquid produced from the nickel electrolysis step can be used.

  Next, the leaching method of nickel and cobalt from the mixed sulfide according to the present invention will be described in detail for each leaching step.

[First leaching process]
First, in the first leaching step, the mixed sulfide as a raw material is oxidatively leached with an aqueous chloride solution having an oxidation-reduction potential of 0 mV to 400 mV (Ag / AgCl electrode standard). The oxidative leaching in the first leaching step is performed as a pretreatment for the chlorine leaching in the second leaching step, and is under relatively weak oxidation conditions as compared with chlorine leaching of the mixed sulfide, that is, 0 to 400 mV. It is characterized by leaching at the oxidation-reduction potential.

That is, as described above, by oxidizing and leaching the mixed sulfide under relatively weak oxidation conditions where the oxidation-reduction potential is 0 mV or more and 400 mV or less, as shown in the following chemical formula 1, the mixed sulfide containing NiS as a main component can be obtained. At the same time that a part of Ni is leached into the aqueous chloride solution, NiS in the mixed sulfide changes into the form of Ni ₃ S ₄ and remains in the residue.

[Chemical 1]
4NiS + 2CuCl ₄ ²⁻ → Ni ²⁺ + Ni ₃ S ₄ + 2Cl ⁻ + 2CuCl ₃ ²⁻

In addition, it was found that NiS, which is the main component of the mixed sulfide, changes in form to Ni ₃ S ₄ due to the oxidative leaching in the first leaching step, thereby forming voids in the mixed sulfide. In addition, elemental sulfur is not substantially generated in the oxidative leaching in the first leaching step.

As described above with reference to Patent Document 3, when voids are formed in the mixed sulfide, the reaction easily proceeds to the inside of the particles, so that the leaching reaction of nickel and cobalt is promoted. On the other hand, the elemental sulfur generated in the leaching and remaining in the mixed sulfide is considered to cause fusion and inhibit the leaching of nickel and cobalt. Therefore, in the present invention, by oxidatively leaching before chlorine leaching, the main component NiS can be transformed into Ni ₃ S _{4 under the} condition that sulfur is not generated, and nickel and cobalt are efficiently leached at a high leaching rate. It is extremely important in doing so.

  In the first leaching step, the reason why the oxidation-reduction potential at the time of oxidative leaching with an aqueous chloride solution is 0 mV or more and 400 mV or less is that if the oxidation-reduction potential is less than 0 mV, nickel in the mixed sulfide is contained in the chlorine leaching solution. This is because the oxidative leaching reaction itself does not proceed. On the other hand, if the oxidation-reduction potential exceeds 400 mV, nickel leaching reaction is promoted and elemental sulfur may be generated, which is not preferable.

  In order to maintain the oxidation-reduction potential of the aqueous chloride solution used in the first leaching step at 0 mV or more and 400 mV or less, an oxidizing agent having an oxidizing power capable of leaching nickel in the mixed sulfide, that is, the oxidation-reduction potential is set to 0 mV or more. It is preferable to use an oxidizing agent that can be retained. As such an oxidizing agent, any oxidizing agent having an oxidative leaching action on nickel in the mixed sulfide may be used, and for example, ferric chloride or a chloric acid oxidizing agent may be used. However, considering the action of fixing a small amount of elemental sulfur present in the mixed sulfide as copper sulfide, a divalent copper chloro complex ion, for example, a chloride aqueous solution of cupric chloride is preferable.

Although ozone, oxygen, oxygen-enriched air, and air can be used as the oxidant, it is not a preferable method. When these are used as oxidizing agents, SO ₄ ²⁻ ions may be generated by the oxidative leaching reaction. As described above, SO ₄ ²⁻ ions in the leachate cause problems such as an increase in power cost due to, for example, a voltage increase in the electrowinning process and a decrease in chlorine recovery rate due to generation of oxygen gas from the anode. Because.

In the first leaching step, the temperature of the aqueous chloride solution during the oxidative leaching reaction is set to 70 ° C. or higher and 100 ° C. or lower. When the temperature of the aqueous chloride solution is less than 70 ° C., the oxidizing power of an oxidizing agent such as a divalent copper chloro complex ion cannot be fully utilized. Therefore, NiS that is the main component of the mixed sulfide is Ni ₃ S _4. Since it takes a long time to change the shape, it is not preferable. On the contrary, when the temperature of the aqueous chloride solution exceeds 100 ° C., a trace amount of elemental sulfur present in the mixed sulfide may be fused to inhibit leaching.

  The slurry obtained in the first leaching step is separated into a solid (residue) and a leachate by solid-liquid separation. As specific solid-liquid separation means, centrifugal filtration, suction filtration, pressure filtration using a filter press or the like can be used. The separated residue is made into a slurry with an aqueous chloride solution and then supplied to the second leaching step. On the other hand, the post-leaching solution (chloride aqueous solution) from which the solid content has been separated is supplied to the step of recovering the leached nickel and cobalt.

  It is preferable to add hydrochloric acid so that the slurry of the solid-liquid separated residue is supplied at a pH of 0.4 or more and 0.6 or less before being supplied to the next second leaching step. Since the mixed sulfide constituting the residue is in the form of a fine powder having a particle size of the order of 10 μm, an oxide is easily formed on the particle surface by air oxidation. Since the oxide on the surface of the particles inhibits the leaching of nickel and cobalt, the leaching of chlorine in the second leaching step can be promoted by previously adding hydrochloric acid to dissolve the oxide on the surface.

[Second leaching process]
In the second leaching step, chlorine gas is blown into the slurry supplied from the first leaching step, that is, the slurry of the residue obtained by solid separation of the slurry obtained in the first leaching step and the aqueous chloride solution. Leaches chlorine.

Chlorine leaching in the second leaching step is to dissolve a target metal such as nickel in an aqueous chloride solution, and indirectly oxidizes copper chloro complex ions and the like as shown in the following chemical formulas 2 and 3. The copper chloro complex ion or the like ionizes the target metal such as nickel, and the reaction of ionizing the target metal such as nickel by the oxidizing power of chlorine gas as shown in the following chemical formula 4. Ni ₃ S ₄ in which the shape of NiS, which is the main component of the mixed sulfide, is changed by oxidative leaching in the first leaching step is leached according to Chemical Formula 5 and Chemical Formula 6.

[Chemical formula 2]
2CuCl ₃ ²⁻ + Cl ₂ → 2CuCl ₄ ²⁻
[Chemical formula 3]
NiS + 2CuCl ₄ ²⁻ → Ni ²⁺ + S ⁰ + 2Cl ⁻ + 2CuCl ₃ ²⁻
[Chemical formula 4]
NiS + Cl ₂ → Ni ²⁺ + S ⁰ + 2Cl ⁻

[Chemical formula 5]
Ni ₃ S ₄ + 6CuCl ₄ ²⁻ → 3Ni ²⁺ + 4S ⁰ + 6Cl ⁻ + 6CuCl ₃ ²⁻
[Chemical 6]
Ni ₃ S ₄ + 3Cl ₂ → 3Ni ²⁺ + 4S ⁰ + 6Cl ⁻

  In chlorine leaching in the second leaching step according to the present invention, chlorine leaching conditions that have been generally performed can be employed. For example, in the chlorine leaching reaction in the second leaching step, it is preferable that the redox potential of the aqueous chloride solution is 480 to 550 mV and the temperature is 105 to 115 ° C.

In general, CoS is thermodynamically more stable than NiS and cobalt and sulfur are difficult to separate, so the leaching rate of cobalt is lower than the leaching rate of nickel. However, according to the present invention, in the first leaching step, NiS, which is the main component of the mixed sulfide, changes its shape to Ni ₃ S ₄ so that voids are formed, and it is fused and inhibits leaching. As a result, the leaching reaction of nickel and cobalt is promoted. As a result, not only the nickel leaching rate can be improved, but also the leaching rate of cobalt, which has poor solubility compared to nickel, can be improved.

[Example 1]
As a raw material, a mixed sulfide produced by a wet sulfidation reaction in a nickel oxide ore wet smelting process and having a composition shown in Table 1 below was used.

First, a mixed sulfide having the composition shown in Table 1 is charged into an aqueous chloride solution containing 40 g / l of a divalent copper chloro complex ion as an oxidizing agent so as to have a slurry concentration of 350 g / l. Then, oxidation leaching was carried out for 8 hours at an oxidation-reduction potential of 300 mV and a temperature of 90 ° C. using a reaction vessel with an acid-resistant brick lining having a total effective capacity of 480 m ³ (first leaching step). The slurry after oxidative leaching was subjected to solid-liquid separation, and the composition of the mixed sulfide obtained after oxidative leaching as a residue was measured by IPC emission spectroscopy.

  In addition, a mixed sulfide having the composition shown in Table 1 was used as a raw material, and the oxidation-reduction potential during the leaching reaction was changed within the range of 0 to 400 mV for each sample. Oxidative leaching was performed. For each sample, the slurry after oxidative leaching was subjected to solid-liquid separation, and the composition of the mixed sulfide obtained as a residue after oxidative leaching was measured in the same manner as described above.

  The results of measuring the composition of the mixed sulfide after the oxidative leaching are shown in Table 2 below. The numerical values of the composition and molar ratio in Table 2 below show the range of the minimum value and the maximum value of a total of four samples obtained by oxidative leaching using the mixed sulfide having the composition of Table 1 as a raw material. The dry weight percent and the molar ratio represent the molar ratio (dimensionless number) when S is 1 mole.

  Since the sum of the molar ratio of nickel and cobalt in the mixed sulfide shown in Table 1 is 1.0, nickel and cobalt contained in the mixed sulfide used as a raw material are in the form of NiS and CoS. It can be estimated that there is. Moreover, it can be estimated from the molar ratio of nickel shown in Table 2 that 12 to 15% of nickel in the mixed sulfide is leached by oxidative leaching.

  Next, the mixed sulfide of each sample after oxidative leaching obtained as a residue by solid-liquid separation was repulped with an aqueous chloride solution to obtain a slurry. At that time, the slurry concentration of the mixed sulfide after the oxidative leaching was adjusted so that the copper ion concentration of the chlorine leaching solution obtained by the next chlorine leaching reaction was 40 g / l.

Each of the obtained slurries was subjected to conditions of an oxidation-reduction potential of 550 mV (based on Ag / AgCl electrode), a temperature of 111 ° C., and a residence time of 12.5 hours, using a reaction vessel having an acid-resistant brick lining with a total effective capacity of 350 m ^3. Leached chlorine (second leaching step).

  After the chlorine leaching was completed, the obtained slurry of each sample was subjected to solid-liquid separation, and the nickel leaching rate, the cobalt leaching rate, and the sulfur oxidation rate were determined as average values of a total of 4 samples. The obtained results are shown in Table 3 below.

[Conventional example]
The mixed sulfide having the composition shown in Table 1 is subjected to the same method as the chlorine leaching in Example 1 without performing the oxidative leaching, that is, the copper ion concentration of the chlorine leaching solution obtained by the chlorine leaching reaction. The slurry concentration of the mixed sulfide was adjusted so as to be 40 g / l, and chlorine leaching was performed under the conditions of a redox potential of 550 mV (Ag / AgCl electrode standard), a temperature of 111 ° C., and a residence time of 12.5 hours.

[Comparative Example 1]
The mixed sulfide having the composition shown in Table 1 was subjected to oxidation leaching in the same manner as in Example 1 except that the oxidation / reduction potential at the time of reaction was set to -50 mV as the oxidation leaching condition. The resulting oxidative leaching residue was leached with chlorine in the same manner as in Example 1 above.

[Comparative Example 2]
The mixed sulfide having the composition shown in Table 1 was subjected to oxidation leaching in the same manner as in Example 1 except that the oxidation / reduction potential at the time of reaction was set to 450 mV as the oxidation leaching condition. The resulting oxidative leaching residue was leached with chlorine in the same manner as in Example 1 above.

[Comparative Example 3]
The mixed sulfide having the composition shown in Table 1 was oxidatively leached in the same manner as in Example 1 except that the temperature during the reaction was 60 ° C. as the oxidative leaching condition. The resulting oxidative leaching residue was leached with chlorine in the same manner as in Example 1 above.

[Comparative Example 4]
The mixed sulfide having the composition shown in Table 1 was oxidatively leached in the same manner as in Example 1 except that the temperature during the reaction was 110 ° C. as the oxidative leaching condition. The resulting oxidative leaching residue was leached with chlorine in the same manner as in Example 1 above.

  Also for the above-described conventional examples and Comparative Examples 1 to 4, after the chlorine leaching was completed, the obtained slurry was subjected to solid-liquid separation, the nickel leaching rate and the cobalt leaching rate, and the sulfur oxidation rate were obtained, and the obtained results were obtained. These are shown in Table 3 below.

  As shown in Table 3 above, according to the examples of the present invention, it can be seen that, together with the excellent nickel leaching rate, a particularly high cobalt leaching rate is obtained as compared with the conventional example, and the oxidation rate of sulfur is also kept low. . On the other hand, Comparative Examples 1 and 3 had low cobalt leaching rates, and Comparative Examples 2 and 4 had high sulfur oxidation rates.

Claims (2)

A method of leaching nickel and cobalt from a mixed sulfide containing nickel and cobalt produced by a wet sulfidation reaction in a hydrometallurgical process of nickel oxide ore, wherein the mixed sulfide has an oxidation-reduction potential of 0 mV to 400 mV ( A first leaching step leached at a temperature of 70 ° C. to 100 ° C. with a chloride aqueous solution of Ag / AgCl electrode) and a residue obtained by solid-liquid separation of the slurry obtained in the first leaching step. And a second leaching step in which chlorine gas is blown into the slurry and leached, and a cupric chloride aqueous solution is used as an oxidizing agent in the first leaching step. And leaching method of nickel and cobalt from mixed sulfide. The slurry prior to leaching in the second leaching step, pH is characterized by the addition of hydrochloric acid to be 0.4 to 0.6, nickel from mixed sulfide according to claim 1 And cobalt leaching method.