JP6943141B2 - Leaching method of mixed sulfide containing nickel and cobalt - Google Patents

Description

The present invention relates to a method of leaching nickel and cobalt from a mixed sulfide containing nickel and cobalt.

As a method for producing nickel and cobalt, for example, as described in Patent Document 1, chlorine gas is blown into a raw material such as a nickel mat containing nickel sulfide and a trace amount of cobalt sulfide to leached and leached chlorine gas. A method of commercializing nickel and cobalt as electric nickel and electric cobalt by electrolytically collecting them has been put into practical use. In this method, the process is simple and the chlorine gas generated by electrowinning can be reused for leaching, so that smelting can be performed economically. The raw materials such as the nickel mat are produced by a pyrometallurgical method including, for example, a step of melting nickel sulfide ore in a blast furnace and a step of melting nickel oxide ore charged with sulfur in an electric furnace.

On the other hand, low nickel grade nickel oxide ore such as laterite ore, which has abundant reserves and is located near the surface of the earth, is treated by a hydrometallurgy method to produce nickel sulfide. Is being manufactured. Specifically, high pressure acid leaching (commonly known as HPAL) is applied to nickel oxide ore to remove impurities such as iron from the obtained leachate, and then, for example, hydrogen sulfide gas is added to the leachate. Nickel sulfide is produced by blowing in and performing a wet sulfide reaction.

The nickel sulfide produced from nickel oxide ore by the hydrometallurgy method as described above is also a sulfide containing nickel and cobalt, like the nickel sulfide such as nickel matte produced by the above-mentioned pyrometallurgy method. Patent Document 2 describes a method for hydrometallurgy of nickel and cobalt using a mixed sulfide containing nickel and cobalt produced by this hydrometallurgy method (hereinafter, may be simply referred to as a mixed sulfide) as a raw material. A technique applying the above-mentioned Patent Document 1 as described has been proposed.

The technique of Patent Document 2 obtains nickel and cobalt by leaching nickel and cobalt into the chloride aqueous solution (chlorine leaching step) by repulping the mixed sulfide into the chloride aqueous solution and then blowing chlorine gas into the obtained slurry. By bringing the pulverized nickel mat into contact with the chlorine leachate containing the divalent copper chloro complex ion as the oxidizing agent, the chlorine leachate undergoes a substitution reaction between copper and nickel to leach nickel in the nickel mat. We are doing (semination process).

The replacement leachate residue (also referred to as cementation residue) after this cementation step (also referred to as CM step) is treated in the chlorine leaching step, while the replacement leachate (also referred to as cementation final solution) is iron or lead in the purification step. Etc. are removed, and cobalt in the replacement leachate is separated and recovered by a method such as solvent extraction. After being treated in the above liquid purification step, electrolytic nickel is produced by electrowinning. Cobalt is further purified by a treatment route different from that of nickel, and then commercialized as electric cobalt by electrowinning.

Special Fair 07-091599 Japanese Unexamined Patent Publication No. 2008-240009

A mixed sulfide containing nickel and cobalt (also referred to as MS (Mixed Sulfide)) produced by a wet refining method such as a high-pressure sulfuric acid leaching method from the above low nickel grade oxide ore recovers nickel from an aqueous solution by sulfide precipitation. Nickel metal is not included because it does. As described above, since the mixed sulfide has poor reducing power and the substitution reaction with copper ions does not easily proceed, the method of directly adding it to the chlorine leaching step as described in Patent Document 2 is efficient. However, the mixed sulfide has a problem that the stability as a sulfide is high and the leaching reaction efficiency is low as compared with the nickel matte produced by the pyrometallurgical method and the cementation residue produced by the cementation reaction. rice field.

By the way, in the leaching of metal in the raw material in the reaction tank where chlorine is leached, the absorption reaction of chlorine gas into the liquid phase using copper ions as a medium as shown in the following reaction formula 1 (chloride complex ion of divalent copper). Treatment by a two-step reaction consisting of an oxidation reaction of sulfide by absorbed chlorine gas (chloride complex ion of oxidized divalent copper) as shown in the following reaction formulas 2 and 3. Is done.

[Reaction formula 1]
Cl ₂ + 2CuCl ₃ ^2- → 2CuCl ₄ ^2-
[Reaction equation 2]
^{_{6CuCl 4 2+ Ni 3 S 2 →}} 3Ni 2+ + 6Cl - + 6CuCl 3 2+ 2S
[Reaction equation 3]
^{_{2CuCl 4 2+ MS → M 2+ +}} 2Cl - + 2CuCl 3 2+ S
However, M = Ni, Co, Fe, Cu

When a copper-containing raw material, that is, a cementation residue after performing a substitution reaction between copper and nickel in a chlorine leachate and leaching nickel in a nickel mat, leaching is carried out by the leaching reaction represented by the above reaction formula 3. After the generated copper ions form a chloride complex and contribute to the leaching reaction, they act as a chlorine absorber in Reaction Formula 1, so that the amount of chlorine gas absorbed increases as the leaching reaction of the raw material progresses. Since the mixed sulfide contains almost no copper, the amount of copper ions contained in the liquid at the start of the reaction determines the amount of chlorine gas absorbed, and even if excess chlorine gas is blown at one time, it is contained in the liquid. There was a problem that it could not be absorbed and did not contribute to the leaching reaction.

Further, if only the mixed sulfide is continuously charged into the above-mentioned reaction tank for leaching chlorine, the copper supply into the reaction tank is depleted, chlorine gas cannot be absorbed into the liquid, and the leaching reaction does not proceed and the gas phase Chlorine gas leaks into it. In order to solve this problem, it is conceivable to add a nickel matte raw material containing Cu or a cementation residue to the reaction vessel, but since these raw materials have better leaching reaction efficiency than mixed sulfide, chlorine gas is preferentially added. It is difficult to increase the amount of mixed sulfide, which is an economically advantageous raw material, because chlorine gas does not effectively contribute to the leaching reaction of nickel in the mixed sulfide. The chlorine leaching residue produced from the chlorine leaching step remained in the chlorine leaching residue because it was discharged to the copper smelting process for the purpose of recovering trace precious metals after recovering the sulfur in the chlorine leaching residue as a product. There is a loss for nickel. Therefore, an optimal mixed sulfide leaching method that minimizes the nickel grade in the chlorine leaching residue has been desired.

The present invention has been made in view of the above-mentioned conventional problems, and the chlorine leaching reaction of the mixed sulfide is efficiently promoted by securing the amount of copper required for chlorine absorption, and the mixture occupies all the raw materials. It is an object of the present invention to provide a method for leaching mixed sulfide capable of increasing the ratio of sulfide.

In order to achieve the above object, in the mixed sulfide leaching method according to the present invention, 40 to 60% of the mixed sulfide raw material containing nickel and cobalt produced by the wet smelting method is added to a copper-containing nickel chloride aqueous solution. The first leaching step of leaching nickel from the mixed sulfide by adding and reducing the divalent copper ion in the aqueous solution to the monovalent copper ion, and the first slurry obtained in the first leaching step are dry-made. A second leaching step of adding a nickel sulfide raw material produced by the wrought method, immobilizing monovalent copper ions in the first slurry in the form of copper sulfide, and leaching nickel from the nickel sulfide raw material. It has a third leaching step of leaching and the balance residue and the mixture sulfide material obtained by the second slurry to solid-liquid separation obtained in the second leaching step with chlorine gas, the copper containing nickel chloride The chlorine leachate obtained by solid-liquid separation of the third slurry obtained in the third leaching step is used as the aqueous solution, and the cementation final solution obtained by solid-liquid separation of the second slurry is treated in the purification step. It is characterized in that nickel is recovered after being sulfurized.

According to the present invention, the mixed sulfide can be efficiently subjected to chlorine leaching treatment, and the ratio of the mixed sulfide to the total raw materials can be increased.

It is a block flow figure which shows a specific example of the leaching method of the mixed sulfide of this invention. It is a graph which shows the relationship between the ratio added to the cementation step in the whole mixed sulfide raw material, and the nickel grade in the chlorine leaching residue produced in the chlorine leaching step.

Hereinafter, a specific example of the nickel sulfide leaching method of the present invention will be described with reference to FIG. In the leaching method of a specific example of the present invention, first, in the crushing step S1, the mixed sulfide raw material containing nickel and cobalt produced by the hydrometallurgy method is crushed, and the obtained mixed sulfide raw material after crushing is crushed. A chloride aqueous solution such as an electrolytic waste solution is added to the mixture to form a slurry.

Next, in the first leaching step (crude cementation step) S2, a part of the slurry mixed sulfide raw material is added to a copper-containing nickel chloride aqueous solution, and the divalent copper ions in the aqueous solution are converted into monovalent copper ions. Nickel is leached from the mixed sulfide by reduction. Next, in the second leaching step (fine cementing step) S3, a nickel sulfide raw material produced by a dry smelting method is added to the first slurry obtained in the first leaching step S2, and the nickel sulfide raw material is added to the first slurry. The monovalent copper ion is immobilized in the form of copper sulfide, and nickel is leached from the nickel sulfide raw material.

Next, in the third leaching step (chlorine leaching step) S4, the residue obtained by solid-liquid separation of the second slurry obtained in the second leaching step S3 and the remainder of the mixed sulfide raw material are leached with chlorine gas. .. The chlorine leaching final solution produced in the third leaching step S4 is used as the above-mentioned copper-containing nickel chloride aqueous solution in the first leaching step S2. On the other hand, the sulfur content contained in the raw material is not leached and remains as a solid, so that it is recovered in the sulfur recovery step S5.

Since impurities such as Co and Fe are present in the cementation final liquid obtained by solid-liquid separation of the second slurry obtained in the second leaching step S3, for example, oxidation neutralization in the liquid purification step S6. It is removed as a purified liquid starch such as hydroxide by the method. This purified liquid starch is treated in the purified liquid starch treatment step S8. Further, the liquid purification step S6 may include a solvent extraction step. On the other hand, the final solution of the purification process from which impurities have been removed is pure nickel chloride, and after adjusting the pH, it is separated into electric nickel and chlorine gas by an electrowinning method in the electrolysis step S7. The generated chlorine gas is repeated in the third leachation step S4 and the liquid purification step S6. The electrolytic solution after the treatment in the electrolytic step S7 is treated in the dechlorination / chlorine recovery step S9, and chlorine gas and the electrolytic waste liquid are recovered. Hereinafter, the main steps constituting the leaching method of a specific example of the present invention will be specifically described.

[Crushing step S1]
In the pulverization step S1, for example, a mixed sulfide containing nickel and cobalt containing NiS as a main component, which is produced from nickel oxide ore by hydrometallurgy, has an average particle size (preferably by a wet pulverizer such as a tower mill or a bead mill). It is pulverized until D50) is 80 μm or less, preferably 20 μm or less, and more preferably 10 μm or less. By pulverizing in this way, the copper ions contained in the copper-containing nickel chloride aqueous solution can be efficiently reduced in the first leaching step S2 of the subsequent step, and the copper ion removal efficiency can be improved. The average particle size (D50) is a particle size at which the cumulative volume is 50% as measured by laser particle size distribution measurement.

The mixed sulfide pulverized as described above is repulped with an aqueous chloride solution to form a slurry. Here, the chloride aqueous solution is a general term for aqueous solutions containing chloride ions as anions, but in one specific example of the present invention, an aqueous solution containing nickel chloride as the main component and containing a trace amount of impurities is particularly preferable. Examples of such a nickel chloride aqueous solution include an electrolytic waste liquid produced in the dechlorination / chlorine recovery step S9 described later.

[First leaching step S2]
The first leaching step S2 is a step of performing crude cementing (also simply referred to as crude CM), and the chlorine leaching final solution as a copper-containing nickel chloride aqueous solution produced in the third leaching step S4 described later is pulverized as described above. The mixed sulfide raw material slurried in step S1 is added. At that time, instead of adding all of the mixed sulfide raw materials, 40 to 60%, preferably 45 to 55% of the total mixed sulfide raw materials are added, and the rest is used as a raw material for the chlorine leaching step described later. .. As a result, divalent copper ions in the copper-containing nickel chloride solution are reduced to monovalent copper ions, so that nickel is leached from the mixed sulfide raw material. In other words, divalent copper ions are efficiently reduced to monovalent copper ions by the reducing power of nickel sulfide contained in the mixed sulfide. Specifically, in the first leaching step S2, for example, the reactions shown in the following reaction formulas 4 and 5 occur.

[Reaction equation 4]
_{^{2CuCl 4 2+ 4NiS → Ni 2+ +}} 2Cl - + Ni 3 S 4 + 2CuCl 3 2-
[Reaction equation 5]
^{NiS + 2Cu + → Ni 2+ +} Cu 2 S

That is, by adding the mixed sulfide to the copper-containing nickel chloride solution produced in the third leaching step S4, the main component of the mixed sulfide, nickel sulfide (NiS), is converted into the copper-containing nickel chloride solution. The divalent copper ion inside is reduced to monovalent copper ion (reaction formula 4). Further, as the main component NiS is immobilized as a monovalent copper ions of copper sulfide _(Cu 2 S) (Scheme 5).

However, the reducing power of NiS, which is the main form in nickel sulfide, is weak, and the effect of fixing monovalent copper ions as copper sulfide is weak. Therefore, in the first leaching step S2, the reaction (reaction formula 4) for reducing the divalent copper ions in the copper-containing nickel chloride solution to the monovalent copper ions mainly proceeds. Then, the reduced monovalent copper ions are mainly reduced by the nickel sulfide raw material produced by the dry smelting method in the second leaching step S3 in the subsequent stage, and used as sulfur in the nickel sulfide raw material, preferably as a sulfur source. It is immobilized as copper sulfide by the sulfur in the added chlorine leaching residue.

The copper concentration (in terms of monovalent copper) contained in the copper-containing nickel chloride solution at the end of the reaction in the first leaching step S2 is preferably 30 g / L or less, and thus the second leaching step S3 in the subsequent step is performed. The copper concentration in the subsequent copper-containing nickel chloride solution can be efficiently removed to 0.1 g / L or less. The sulfide such as copper sulfide produced in the first leaching step S2 is treated as a cementation residue in the third leaching step S4 through the second leaching step S3.

The copper-containing nickel chloride solution used in the first leaching step S2, that is, the chlorine leaching final solution produced in the third leaching step S4 has a copper ion concentration of 30 to 50 g / L, a nickel concentration of 150 to 270 g / L, and a pH of 0. It is preferably 5 to 2.0. As for the form of copper ions in the copper-containing nickel chloride solution, for example, the divalent copper ion ratio is preferably 60 〜 90%, and the monovalent copper ion ratio is preferably 10 to 40%. Further, the copper-containing nickel chloride solution used in the first leaching step S2 has a redox potential (based on the Ag / AgCl electrode) of 450 to 550 mV, and the redox potential (based on the Ag / AgCl electrode) in the first leaching step S2. It is preferable to carry out the leaching treatment under the condition of 400 mV or less.

The temperature condition at the time of leaching in the first leaching step S2 is preferably 80 to 110 ° C, and more preferably 90 to 95 ° C. By setting the temperature condition to 80 ° C. or higher, the reduction treatment of copper ions in the copper-containing nickel chloride solution can be efficiently advanced, and the copper ion removal efficiency can be improved in the second leaching step S3 described later. Can be done. If the temperature condition is higher than 110 ° C, the efficiency of removing copper from the copper-containing nickel chloride solution is improved, but the equipment cost due to the heat-resistant specifications and the operating cost due to the increase in the amount of steam are incurred, and efficient operation may not be possible. There is.

As described above, the reason why a part of the mixed sulfide is treated in the crude CM step and the rest is treated in the chlorine leaching step described later is the amount of nickel leached in the crude CM step depending on the amount of Cu in the copper-containing nickel chloride aqueous solution. This is because the leaching rate can be improved by distributing and adding the mixed sulfide to the cementation step and the chlorine leaching step as described above. In addition, nickel sulfide (NiS) in the mixed sulfide raw material is not completely leached out and remains partly _{as a solid of Ni 3} S ₄ , so if the amount added is too large, the load of the solid-liquid separation treatment in the subsequent stage increases. Therefore, the capital investment cost of the solid-liquid separator and the like is high.

That is, in general, the amount of Ni leached in the cementation step is determined by the copper concentration of the leaching starting liquid, and it is difficult to completely leached NiS. When the copper concentration in the starting liquid is increased aiming at complete leaching of NiS, the amount of nickel matte added for complete sulfide of copper in the second leaching step S3 increases, and as a result, the mixed sulfide in the total raw material is mixed. The ratio cannot be increased. Further, if the distribution ratio of the mixed sulfide to the cementation step is increased, the unreacted mixed sulfide contained in the cementation residue is only increased, but the mixed sulfide that is difficult to be leached in the chlorine leaching step is leached out. It becomes impossible to separate the easy cementation residue, and as a result, the nickel leaching rate of the mixed sulfide decreases. Further, it is economically unfavorable because the load on the solid-liquid separator of the slurry produced in the cementation step increases.

On the other hand, in order to maximize the ratio of mixed sulfide to the total raw materials, it is necessary to keep the starting solution copper concentration in the cementation process as low as possible and reduce the amount of nickel matte raw materials added. As shown in Patent Document 2 described above, when the copper concentration of the starting liquid is lowered as described above, the chlorine leaching rate in the third leaching step S4 is lowered, so that the lower limit of the copper concentration of the starting liquid is 30 g / L. Is preferable. The distribution ratio of the mixed sulfide to the cementation step is a suitable requirement for satisfying all of these constraints.

[Second leachation step S3]
The second leaching step S3 is a step of performing precision cementation (also simply referred to as refined CM), and a dry smelting method of nickel mat or the like is added to the first slurry containing the copper-containing nickel chloride solution obtained in the first leaching step S2. The nickel sulfide raw material produced in the above is added to reduce divalent copper ions to monovalent copper ions, and nickel metal or the like as the nickel sulfide raw material is converted into nickel ions by the oxidizing power of divalent and monovalent copper ions. It is exuded. In addition, monovalent copper ions are immobilized as sulfides such as copper sulfide.

Like the mixed sulfide described above, the nickel sulfide raw material such as the nickel matte is also preferably added after being pulverized and then repulped with an electrolytic waste solution suitable as an aqueous chloride solution to form a slurry. In this second leaching step S3, as shown by the following reaction formulas 6 to 9, nickel sulfide (Ni ₃ S ₂ ) in a nickel sulfide raw material such as nickel matte, which has a higher leaching efficiency than the mixed sulfide, or The following leaching reaction occurs due to nickel metal (Ni).

[Reaction equation 6]
^{_{2CuCl 4 2+ Ni 3 S 2 →}} Ni 2+ + 2Cl - + 2NiS + 2CuCl 3 2-
[Reaction equation 7]
^{_{2CuCl 4 2+ Ni → Ni 2+ +}} 2Cl - + 2CuCl 3 2-
[Reaction equation 8]
Ni + 2CuCl ₃ ^2- + S → Ni ²⁺ + 6Cl ⁻ + Cu ₂ S
[Reaction equation 9]
Ni ₃ S ₂ + 6CuCl ₃ ² + S → ^{3 Ni 2+} + 18Cl ⁻ + 3Cu ₂ S

As shown in the above reaction formulas 6 and 7, in the second leaching step S3, the nickel metal (Ni) and nickel sulfide (Ni ₃ S ₂ ) contained in the added nickel mat remain in the copper-containing nickel chloride solution. The divalent copper ion is reduced to the monovalent copper ion. As described above, the divalent copper ions remaining without being reduced in the first leaching step S2 are reduced by the nickel mat in the second leaching step S3.

Further, as shown in the reaction formulas 8 and 9, in the second leaching step S3, the monovalent copper ions reduced in the first leaching step S2 and the second leaching step S3 are contained in the nickel mat as Ni or Ni. ₃ by S ₂ and sulfur is fixed as a sulfide. The copper fixed as the sulfide is separated as a cementation residue and a cementation final liquid by solid-liquid separation. The separated cementation residue is treated in the third leaching step (chlorine leaching step) S4. By the way, the Nikke sulfide raw material produced by a dry smelting method such as nickel matte contains a trace amount of copper as an impurity. As described above, the copper-containing nickel sulfide added as a raw material in the second leaching step S3 is cemented in the second leaching step S3 and then treated in the third leaching step S4. Therefore, when nickel sulfide such as nickel matte is used as a raw material in the second leaching step S3, the amount of copper circulating in the system inevitably increases.

The temperature condition of the leaching reaction in the second leaching step S3 is preferably 70 to 100 ° C, more preferably 80 to 90 ° C. By setting the temperature condition to 70 ° C. or higher, the reaction of reducing the remaining divalent copper ions to monovalent copper ions and efficiently immobilizing the monovalent copper ions with sulfur can proceed. When the temperature condition is higher than 100 ° C., the copper removal efficiency from the copper-containing nickel chloride solution is not improved any more, and it is preferably 100 ° C. or lower from the viewpoint of operating efficiency. Further, in the second leaching step S3, it is preferable to carry out the leaching treatment under the condition that the redox potential (based on the Ag / AgCl electrode) is 0 to 100 mV.

By the way, in the cementation step in the conventional electronickel manufacturing process, a nickel mat is repulped together with a nickel chloride solution with respect to a copper-containing nickel chloride aqueous solution which is a chlorine leaching final solution obtained by leaching mixed sulfide with chlorine. The obtained slurry was added, and a nickel leaching residue was added as a sulfur source. In this case, the divalent copper ions in the copper-containing nickel chloride aqueous solution are reduced to monovalent copper ions by the nickel metal and nickel sulfide in the nickel matte raw material, and are immobilized as copper sulfide by the sulfur in the chlorine leaching residue. It had been.

However, in the chlorine leaching step, the monovalent copper ion absorbs chlorine gas and is oxidized to the divalent copper ion, and the metal in the raw material is leached by the oxidizing power of the divalent copper ion. It is necessary to secure a copper concentration above a certain amount. At this time, if the treatment amount of the mixed sulfide is increased for the purpose of increasing the production of electrolytic nickel, the flow rate of the treatment liquid in the chlorine leaching step and the cementation step increases, and as a result, the circulation amount of copper in the system increases. It will be. However, copper ions cannot be efficiently and effectively removed as copper sulfide by adding only nickel matte in the cementation step, and the amount of mixed sulfide processed for the purpose of increasing the production of electrolytic nickel is increased. Could not be dealt with appropriately.

Therefore, in the leaching method of a specific example of the present invention, as described above, first, in the first leaching step S2, a mixed sulfide is added to the copper-containing nickel chloride aqueous solution to reduce the divalent copper ion to the monovalent copper ion. do. Then, in the second leaching step S3, a nickel sulfide such as a nickel mat is added to the first slurry produced thereby to immobilize the monovalent copper ion as a sulfide such as copper sulfide, and the copper-containing nickel chloride solution is used. Copper is being removed.

In this way, instead of reducing and immobilizing divalent copper ions only with the nickel metal and nickel sulfide contained in the nickel sulfide, first, the copper-containing nickel chloride aqueous solution maximizes the reducing power of the mixed sulfide. The divalent copper ion inside is reduced to monovalent copper ion, and then the monovalent copper ion is immobilized as a sulfide with nickel sulfide. As a result, the copper circulating in the system can be efficiently decopperized, and copper can be reliably removed from the copper-containing nickel chloride aqueous solution.

When a nickel matte was added to the copper-containing nickel chloride aqueous solution in the first leaching step S2 and a mixed sulfide was added in the second leaching step S3, divalent copper ions were added to the nickel metal and nickel sulfide. The function of reducing the monovalent copper ion is prioritized, and then the function of fixing the monovalent copper ion to copper sulfide occurs. On the other hand, although nickel sulfide in the mixed sulfide has the ability to reduce divalent copper ions, it has a low ability to fix monovalent copper ions as copper sulfide, so the copper ions are removed in the second leaching step S3. I can't cut it. Therefore, in this case, the efficient copper removal treatment cannot be performed as in the conventional case.

Further, even when the mixed sulfide raw material and the nickel matte raw material are collectively added to the copper-containing nickel chloride aqueous solution in the cementation step, the reaction of nickel metal and nickel sulfide in the nickel matte is similarly prioritized. , The reducing power of nickel sulfide in the mixed sulfide cannot be utilized, and copper cannot be sufficiently immobilized and removed.

As described above, in the second leaching step S3, monovalent copper is reduced to copper sulfide by the nickel sulfide produced by a dry smelting method such as a nickel matte raw material having a higher leaching efficiency than the mixed sulfide, that is, a high copper reducing ability. By doing so, the mixed sulfide can be efficiently treated in the smelting step.

[Third leaching step S4]
In the third leaching step (chlorine leaching step) S4, the cementation residue obtained by solid-liquid separation of the second slurry obtained in the second leaching step S3 of the previous step and the remainder of the above-mentioned slurry-ized mixed sulfide raw material. On the other hand, by blowing the chlorine gas recovered in the electrolysis step S7, the reactions of the above-mentioned reaction formulas 1 to 3 are caused. As a result, metals such as nickel in the metal sulfide raw material such as the mixed sulfide are oxidatively leached by divalent copper ions oxidized by chlorine gas to generate a chlorine leachate as a copper-containing nickel chloride aqueous solution. The chlorine leachate produced in the third leaching step S4 is sent to the first leaching step S2 described above. On the other hand, in the third leaching step S4, since the chlorine leaching residue containing sulfur as a main component remains in the solid phase, sulfur is recovered by the treatment in the sulfur recovery step S5.

[Purification process S6]
In the purification step S6, impurities other than nickel are removed from the cementation final solution (nickel leachate) obtained by solid-liquid separation of the second slurry produced in the second leaching step S3, and nickel chloride for electrowinning. Get the solution. This liquid purification step S6 includes, for example, an iron removal step, a cobalt removal step, a lead removal step, and a zinc removal step. In these steps, as a method for removing impurities from the nickel leachate which is the final solution of cementation, for example, an oxidation neutralization method using chlorine gas as an oxidizing agent and nickel carbonate as an alkali agent can be used. The oxidation-neutralization method utilizes the property that heavy metals such as cobalt and iron tend to become hydroxides in the low pH range when they become higher-order oxide ions. It is a method that is widely used for wastewater treatment including.

Generally, as the chemical used in the oxidation neutralization method, hypochlorous acid, oxygen, air or the like can be used as the oxidizing agent in addition to chlorine gas. Further, as the alkaline agent, in addition to carbonate, hydroxides such as caustic soda, ammonia and the like can be used. Although these chemicals are used in a combination suitable for the process conditions, it is preferable to use chlorine gas as an oxidizing agent and carbonate, particularly nickel carbonate, as an oxidizing agent in the nickel hydrometallurgy process. The reason for using chlorine gas as the oxidizing agent is that chlorine gas is a strong oxidizing agent generated in the process and is easy to use. Further, the reason why nickel carbonate is used as the alkaline agent is that it is possible to suppress the introduction of sodium or the like as an impurity and the reactivity at the time of oxidative neutralization is excellent. Further, a solvent extraction method using various organic extractants may be used to separate nickel and cobalt contained in the nickel chloride aqueous solution. In the solvent extraction method for separating nickel and cobalt, a phosphoric acid ester-based acidic extractant such as D2EHPA (Di- (2-ethylhexyl) phosphoric acid) or an amine such as TNOA (Tri-n-octylamine) is used as an organic extractant. A system extractant is used.

[Electrolysis step S7]
In the electrolytic step S7, electrolytic nickel is produced by electrowinning the nickel chloride solution purified in the above-mentioned liquid purification step S6. That is, in electrowinning, nickel ions in the nickel chloride solution are precipitated as metal (electronickel) on the cathode side. On the other hand, on the anode side, chlorine ions in the nickel chloride solution are generated as chlorine gas. The generated chlorine gas can be used as the recovered chlorine gas, for example, in the third leaching step S4 or the like.

A mixed sulfide raw material containing nickel and cobalt produced by a hydrometallurgical method and a nickel matte raw material produced by a pyrometallurgical method were leached using chlorine gas, and the nickel leaching rate at that time was evaluated. .. Specifically, first, an electrolytic waste solution was prepared as an aqueous nickel chloride solution, and crushed mixed sulfide was added to the electrolytic waste solution so that the concentration after addition was about 400 g / L to prepare a raw material slurry. 28% of this raw material slurry was charged into a reaction vessel, and chlorine gas was blown into it to perform chlorine leaching treatment.

The remainder of the raw material slurry (that is, 72 of the raw material slurry) was added to the chlorine leaching final solution (that is, a copper-containing nickel chloride aqueous solution) having a copper ion concentration of 35 g / L obtained by solid-liquid separation of the slurry after the chlorine leaching treatment. %) Was added, and a crude cementation treatment was performed at a reaction temperature of 90 ° C. Nickel mat was added to the slurry after the crude cementation treatment so that the concentration after the addition was 32 g / L, and the precision cementation treatment was carried out at a reaction temperature of 86 ° C. The cementation residue obtained by solid-liquid separation of the slurry after the refinement cementation treatment was treated in a chlorine leaching step. The Ni quality of the chlorine leaching residue produced in the chlorine leaching step was measured. The measurement was performed with a fluorescent X-ray analyzer.

Further, the distribution ratio between the chlorine leaching treatment and the crude cementation treatment of the raw material slurry was changed in the range of 28:72 to 62:38 instead of the above 28:72, and leaching was performed in the same manner as above. The treatment was carried out, and the Ni quality of the chlorine leaching residue was measured. FIG. 2 shows a graph in which the Ni grade in the obtained chlorine leaching residue is plotted on the horizontal axis for the distribution ratio of the entire mixed sulfide raw material to the CM process.

From the graph of FIG. 2, by setting the distribution ratio of the mixed sulfide to the CM process in the range of 40 to 60%, the Ni grade in the chlorine leaching residue can be suppressed to a low value of less than 3%, that is, It can be seen that a high Ni leaching rate can be achieved. However, when the distribution ratio of the mixed sulfide to the CM process exceeds 60%, it can be seen that the Ni grade in the chlorine leaching residue rapidly increases, that is, the Ni leaching rate decreases. This is because when the distribution ratio of the mixed sulfide to the CM process exceeds 60%, the residual load in the CM process increases and the amount of unleached mixed sulfide present in the chlorine leaching residue increases. Conceivable.

S1 crushing process S2 first leaching process (coarse cementation process)
S3 Second leaching step (fine cementation step)
S4 Third leaching process (chlorine leaching process)
S5 Sulfur recovery process S6 Purification process S7 Electrolysis process S8 Purification starch treatment process S9 Dechlorination / chlorine recovery process

Claims (4)

To add 40 to 60% of a mixed sulfide raw material containing nickel and cobalt produced by a wet smelting method to a copper-containing nickel chloride aqueous solution, and reduce divalent copper ions in the aqueous solution to monovalent copper ions. In the first leaching step of leaching nickel from the mixed sulfide and the first slurry obtained in the first leaching step, a nickel sulfide raw material produced by a dry smelting method is added to the first slurry. A residue obtained by solid-liquid separation of a second leaching step in which monovalent copper ions are immobilized in the form of copper sulfide and nickel is leached from the nickel sulfide raw material, and a second slurry obtained in the second leaching step. the mixed sulfide raw material and balance have a third leaching step of leaching with chlorine gas, the copper containing the aqueous nickel chloride solution by solid-liquid separation a third slurry obtained in the third leaching step and A method for leaching mixed sulfide, which comprises recovering nickel after being treated in a purification step in the cementation final liquid obtained by solid-liquid separation of the second slurry using the obtained chlorine leaching solution. .. The method for leaching a mixed sulfide according to claim 1 , wherein the copper ion concentration of the copper-containing nickel chloride aqueous solution is 30 to 50 g / L. The chlorine leachate has an oxidation-reduction potential (Ag / AgCl electrode reference) of 450 to 550 mV, and the first leaching step is characterized in that the leaching treatment is performed under the condition that the redox potential (Ag / AgCl electrode reference) is 400 mV or less. The method for leaching the mixed sulfide according to claim 2. The method for leaching a mixed sulfide according to claim 3 , wherein in the second leaching step, the leaching treatment is performed under the condition that the redox potential (based on the Ag / AgCl electrode) is 0 to 100 mV.

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