Processing method of nickel sulfide raw material

Abstract

To provide a method that enables effective control of distribution of iron and arsenic to a chlorine leaching residue in a hydrometallurgical process using, as a raw material, a nickel sulfide including iron and arsenic.SOLUTION: A processing method of a nickel sulfide raw material including iron and arsenic includes: a cementation step of mixing a nickel sulfide raw material with a copper-containing and iron-containing crude nickel chloride aqueous solution containing a bivalent copper ion, and substituting and leaching nickel in the nickel sulfide raw material to generate a cementation slurry to obtain a cementation final solution with the copper ion removed and a cementation residue; and a chlorine leaching step of blowing a chlorine gas into a residue slurry of the cementation residue to obtain a chlorine leachate and a chlorine reaching residue. In the cementation step, a pH of a liquid phase of the cementation slurry is adjusted to control an arsenic output amount calculated by (an arsenic concentration in the cementation final solution)×(a flow rate of the cementation final solution).SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for treating a nickel sulfide feedstock, which allows for the control of the distribution of iron and arsenic in a chlorine leach residue in a hydrometallurgical process using nickel sulfide as a feedstock, the nickel sulfide containing nickel, cobalt, copper and sulfur, and also containing iron and arsenic as impurities. [Background technology]

[0002] In the nickel hydrometallurgical refining process (hereinafter also referred to as the "MCLE process"), the raw material nickel matte or nickel-cobalt mixed sulfide (MS: mixed sulfide) is leached with chlorine, and the resulting leachate (chlorine leachate) is subjected to a purification process to remove impurities, and nickel and cobalt are recovered in the form of electrolytic nickel and electrolytic cobalt in an electrolytic process. The technology of the MCLE process is disclosed in, for example, Patent Document 1 and Patent Document 2.

[0003] As shown in FIG. 1, the chlorine leaching solution obtained from the chlorine leaching process is subjected to removal of excess copper in the copper removal electrolysis process provided between the cementation process and the cementation process, and impurities such as iron and arsenic are removed in the iron removal process, and then the solution is sent to the cobalt solvent extraction process. In the cobalt solvent extraction process, nickel and cobalt are separated by solvent extraction to obtain a crude nickel chloride solution (NiCl2) and a crude cobalt chloride solution (CoCl2). The crude nickel chloride solution is further purified by removing impurities in the solution purification process and sent to the nickel electrolysis process. Then, in the nickel electrolysis process, electrolytic nickel is produced by electrolytic winning. Meanwhile, the crude cobalt chloride solution is also further purified by removing impurities in the solution purification process and sent to the cobalt electrolysis process, where electrolytic winning is produced.

[0004] On the other hand, the chlorine leaching residue obtained by separating it from the chlorine leaching solution in the chlorine leaching process is mainly composed of sulfur, but also contains metallic sulfides such as nickel as undissolved raw materials. Therefore, the chlorine leaching residue obtained from the chlorine leaching process is heated to melt the sulfur content, and then separated into solid and liquid using a filter such as an ultrafilter (UTF) to recover the sulfur. Since the solid content contains nickel, etc., it is sent back to the chlorine leaching process, etc., to recover valuable metals such as nickel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-3104 A [Patent Document 2] JP 2019-81920 A Summary of the Invention [Problem to be solved by the invention]

[0006] The nickel sulfide raw material to be treated in the MCLE process is processed using raw materials from various sources, and depending on the raw material treatment configuration, the load of various impurities may increase, and the amount of iron and arsenic to be removed may also increase. If the impurity load of iron or arsenic increases, the distribution amount of the iron or arsenic to the chlorine leaching residue obtained from the chlorine leaching process also increases, which may deteriorate the filterability (liquid permeability) of the filter when recovering sulfur from the chlorine leaching residue.

[0007] As a method for suppressing the distribution of iron and arsenic to the chlorine leaching residue, the applicant of the present application has proposed a method in which hydrochloric acid is added to the chlorine leaching slurry in the chlorine leaching step, and the hydrochloric acid concentration of the resulting chlorine leaching solution is adjusted to adjust the ratio of the iron concentration to the arsenic concentration (iron / arsenic) in the cementation final solution. According to this method, the pH of the chlorine leaching solution can be kept almost constant, and the distribution behavior of iron and arsenic is stabilized, making it possible to efficiently remove iron ions and arsenic ions from the cementation final solution.

[0008] However, the above-mentioned method has a problem that it increases the material cost of the acid and increases the cost of the neutralizing agent in the solution purification step (iron removal step), that is, it increases the production cost of electrolytic nickel.

[0009] The present invention has been proposed in view of the above circumstances, and has an object to provide a method that enables effective control of distribution of iron and arsenic to a chlorine leaching residue obtained from a chlorine leaching step, without increasing material costs, in a hydrometallurgical process using nickel sulfide containing iron and arsenic as impurities as a raw material. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, in a raw material treatment process including a cementation step of removing copper ions from a copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions, and a chlorine leaching step of obtaining a chlorine leachate by chlorine leaching a cementation residue slurry, and repeating the chlorine leachate obtained as a copper-containing, iron-containing crude nickel chloride aqueous solution, the inventors have found that the distribution of iron and arsenic to the chlorine leach residue can be effectively controlled by controlling the arsenic output amount calculated by (arsenic concentration in the cementation final liquid)×(flow rate of the cementation final liquid) with respect to the cementation final liquid in the cementation step by adjusting the pH of the liquid phase of the cementation slurry, and have completed the present invention.

[0011] (1) The first invention of the present invention is a method for treating a nickel sulfide raw material containing iron and arsenic as impurities, comprising a cementation step of mixing a copper-containing and ferrous crude nickel chloride aqueous solution containing divalent copper ions with a nickel sulfide raw material, and displacing and leaching nickel in the nickel sulfide raw material with the copper ions in the copper-containing and ferrous crude nickel chloride aqueous solution to produce a cementation slurry which is a mixture of the ferrous crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide, and separating the resulting mixture into a cementation end liquid and a cementation residue by solid-liquid separation; and a cementation step of repulping the cementation residue to produce a cementation residue slurry, and then separating the resulting cementation slurry by solid-liquid separation. and a chlorine leaching step of injecting chlorine gas into a cementation residue slurry to leach heavy metals in the cementation residue to produce a chlorine leaching slurry, and separating the chlorine leaching solution and the chlorine leaching residue by solid-liquid separation, and the chlorine leaching solution is repeatedly produced as the copper-containing, iron-containing crude nickel chloride aqueous solution, in which the cementation step controls the arsenic output amount of the cementation final liquid, which is calculated by (arsenic concentration in the cementation final liquid) x (flow rate of the cementation final liquid), by adjusting the pH of the liquid phase of the cementation slurry.

[0012] (2) A second aspect of the present invention is a method for treating a nickel sulfide raw material according to the first aspect of the present invention, wherein in the cementation step, the amount of arsenic output is controlled by adjusting a pH of a liquid phase of the cementation slurry in accordance with an amount of arsenic input calculated by (amount of nickel sulfide raw material) x (arsenic content in the nickel sulfide raw material) for the nickel sulfide raw material.

[0013] (3) A third invention of the present invention is a method for treating a nickel sulfide raw material according to the second invention, wherein, in the cementation step, when the amount of arsenic output is to be reduced, a pH of the liquid phase of the cementation slurry is increased, and when the amount of arsenic output is to be increased, a pH of the liquid phase of the cementation slurry is decreased.

[0014] (4) A fourth aspect of the present invention is a method for treating a nickel sulfide raw material according to the second aspect of the present invention, wherein in the cementation step, a pH of the liquid phase of the cementation slurry is adjusted based on a correlation between a pH of the cementation end liquid and an arsenic concentration in the cementation end liquid so that the arsenic output amount becomes a predetermined amount according to the arsenic input amount.

[0015] (5) A fifth aspect of the present invention is a method for treating a nickel sulfide raw material according to the fourth aspect of the present invention, wherein in the cementation step, a pH of the liquid phase of the cementation slurry is adjusted based on a correlation between a pH of the cementation end liquid and an arsenic concentration in the cementation end liquid so that the arsenic input amount and the arsenic output amount are substantially equal to each other depending on the arsenic input amount.

[0016] (6) A sixth aspect of the present invention is a method for treating a nickel sulfide raw material according to any one of the first to fifth aspects of the present invention, wherein in the cementation step, a pH of the liquid phase of the cementation slurry is adjusted by adding a neutralizing agent containing nickel carbonate. Effect of the Invention

[0017] According to the present invention, it is possible to effectively control the distribution of iron and arsenic to the chlorine leaching residue obtained from the chlorine leaching step without increasing material costs and the like. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a process diagram showing a schematic flow of a nickel hydrometallurgical process (MCLE process). [Diagram 2] FIG. 1 is a process diagram showing an example of a flow when the nickel sulfide raw material processing method is applied to processing in an MCLE process. [Diagram 3] 1 is a graph showing the relationship between the iron content and the arsenic content in cementation residue. [Figure 4]1 is a graph showing the relationship between the iron content and the arsenic content in a chlorine leaching residue. [Diagram 5] 1 is a graph showing the relationship between the pH of the final cementation liquid and the arsenic concentration in the final cementation liquid. [Figure 6] This is a graph showing the changes in the pH of the cementation end liquor, the arsenic content of the nickel sulfide raw material (arsenic load from the raw material, i.e., arsenic input amount), the balance between the arsenic load in the raw material and the amount of arsenic discharged from the cementation end liquor, and the arsenic content in the chlorine leaching residue. [Figure 7] 1 is a graph showing the relationship between the pH of a chlorine leachate and the maximum arsenic concentration in the chlorine leachate. [Figure 8] 1 is a graph showing the relationship between the pH of the chlorine leachate and the arsenic content in the chlorine leach residue, stratified by the arsenic content in the cementation residue. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the gist of the present invention.

[0020] The method for processing a nickel sulfide raw material according to the present embodiment is a method for processing a nickel sulfide raw material containing iron and arsenic as impurities.

[0021] For example, the nickel sulfide raw material may be a raw material used as a raw material in a nickel hydrometallurgical process (MCLE process). Therefore, as described in detail below, the processing method can be applied to processing in the MCLE process, which includes a cementation step and a chlorine leaching step.

[0022] 2 is a process diagram showing an example of a flow when this processing method is applied to processing in an MCLE process. Specifically, the processing method for nickel sulfide raw material according to this embodiment includes a cementation step S1 in which a copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions is mixed with a nickel sulfide raw material, and nickel in the nickel sulfide raw material is substituted and leached by the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution to remove the copper ions in the aqueous solution, and a chlorine leaching step S2 in which the cementation residue is repulped to form a cementation residue slurry, and then chlorine gas is blown into the cementation residue slurry to leach heavy metals to obtain a chlorine leachate and a chlorine leachate residue, and the chlorine leachate is repeatedly converted into a copper-containing, iron-containing crude nickel chloride aqueous solution, which is a raw material processing process.

[0023] Although the notation methods are different, Figure 1 and Figure 2 are both flow diagrams of the electrolytic nickel production process (MCLE process), and the "iron removal process," "cobalt solvent extraction process," and "liquid purification process" in Figure 1 are all included in the "liquid purification process S3" in Figure 2. In addition, the "copper removal electrolysis process" shown in Figure 1 is omitted in Figure 2, and <sulfur recovery> shown in Figure 2 is omitted in Figure 1.

[0024] This treatment method is characterized in that the amount of arsenic output, calculated as (arsenic concentration in final cementation liquid) x (flow rate of final cementation liquid), is controlled by adjusting the pH of the liquid phase of the cementation slurry in the cementation process.

[0025] Then, the amount of arsenic output is controlled by adjusting the pH of the liquid phase of the cementation slurry as described above according to the amount of arsenic input, which is calculated by (amount of nickel sulfide raw material) x (arsenic content in the nickel sulfide raw material) for the nickel sulfide raw material.

[0026] According to the method for treating nickel sulfide raw material according to the present embodiment, even if the impurity load of iron and arsenic derived from the nickel sulfide raw material increases, it is possible to effectively control the distribution of iron and arsenic to the chlorine leaching residue obtained from the chlorine leaching step without increasing the material cost, etc. This makes it possible to prevent a decrease in the liquid permeability of a filtration filter such as an ultrafilter (UTF) during the operation of recovering sulfur from the chlorine leaching residue.

[0027] <1. Cementation process> In the cementation step S1, a copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions is mixed with a nickel sulfide raw material to fix and remove the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution.

[0028] Nickel sulfide raw materials contain iron and arsenic as impurities, and examples of the nickel sulfide raw materials include mixed sulfide (MS) containing nickel and cobalt produced by a hydrometallurgical process using nickel oxide ore as a raw material, and nickel matte produced by a nickel pyrometallurgical process.

[0029] More specifically, in the cementation step S1, a nickel sulfide raw material containing iron and arsenic as impurities is mixed with a copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions, and the nickel in the nickel sulfide raw material is leached by substitution with the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution, thereby immobilizing and removing the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution. This cementation reaction produces a cementation slurry, which is a mixture of the iron-containing crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide produced by immobilizing the copper ions as sulfides.

[0030] The copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions, which is mixed with the nickel sulfide raw material, is a chlorine leachate obtained through a chlorine leaching treatment in the chlorine leaching step S2 described below. Thus, the process in this treatment method is a raw material treatment process that is configured by repeatedly converting the chlorine leachate into a copper-containing, iron-containing crude nickel chloride aqueous solution.

[0031] In the cementation step S1, the produced cementation slurry is subjected to solid-liquid separation to obtain a cementation end liquid (iron-containing crude nickel chloride aqueous solution) and a cementation residue (a precipitate containing copper sulfide). The method of solid-liquid separation is not particularly limited, and can be performed by a well-known method such as a centrifuge or a filter press, and the precipitate of copper sulfide, which is the cementation residue, can be efficiently separated.

[0032] The cementation end liquid obtained through the cementation step S1 is sent to a liquid purification step S3 including an iron removal step. As will be described in detail later, the iron removal step removes iron, which is an impurity contained in the cementation end liquid (iron-containing crude nickel chloride aqueous solution).

[0033] On the other hand, the cementation residue containing the copper sulfide immobilized in the cementation step S1 is sent again to the chlorine leaching step S2 and subjected to chlorine leaching treatment.

[0034] Here, as a result of research by the present inventors, it was found that there is a positive correlation between the iron content and the arsenic content in the cementation residue obtained in the cementation step S1, and that the molar ratio is approximately iron (Fe):arsenic (As) = 3:2, as shown in the graph of Figure 3. It was also found that there is a positive correlation between the iron content and the arsenic content in the chlorine leaching residue obtained in the chlorine leaching step S2, and that the weight ratio is approximately iron (Fe):arsenic (As) = 0.8:1.1, as shown in the graph of Figure 4. Since the atomic weight of iron is 55.8 and the atomic weight of arsenic is 74.9, this weight ratio can be converted to a molar ratio of 0.014:0.015, which is approximately 1:1. Therefore, it is estimated that FeAsO4 is mainly produced in the chlorine leaching residue produced in the chlorine leaching step S2, which has a high oxidation-reduction potential (ORP), while Fe3(AsO4)2 is mainly produced in the cementation residue produced in the cementation step S1, which has a low ORP.

[0035] Furthermore, from the graph shown in Figure 5, which shows the relationship between the pH of the cementation final liquid and the arsenic concentration in the cementation final liquid, it was found that the lower the pH of the liquid phase in the reaction in the cementation step S1, the higher the arsenic concentration in the cementation final liquid.

[0036] Usually, arsenic input from nickel sulfide raw material into the MCLE process is removed from the cementation end solution obtained through the cementation process S1 in the next process of solution purification process S3 (iron removal process) and sent out of the MCLE process. However, when the amount of arsenic discharged from the cementation process, expressed as "(flow rate of cementation end solution) x (arsenic concentration)", becomes small relative to the arsenic load from the nickel sulfide raw material, the arsenic is distributed to the cementation residue. When the arsenic is distributed to the cementation residue, as shown in the process diagram of Figure 2, the arsenic is sent to the chlorine leaching process S2 via the cementation residue, leached by chlorine leaching, and repeated again to the cementation process S1. That is, the arsenic is gradually concentrated in the leaching system in which a loop is formed by the cementation process S1 and the chlorine leaching process S2.

[0037] Then, when the amount of arsenic circulating between the cementation step S1 and the chlorine leaching step S2 increases and exceeds the amount of arsenic leaching in the chlorine leaching step S2, which is expressed as "(arsenic concentration in the chlorine leaching solution) x (flow rate of the chlorine leaching solution)", the distribution of arsenic to the chlorine leaching residue increases. When the amount of arsenic distributed to the chlorine leaching residue increases in this way, a problem occurs in that the liquid permeability of a filter such as an ultrafilter (UTF) decreases when recovering sulfur from the chlorine leaching residue.

[0038] Therefore, the method for processing the nickel sulfide raw material according to the present embodiment is characterized in that in the cementation step S1, the "arsenic output amount" for the cementation final liquid is controlled by adjusting the pH of the liquid phase of the cementation slurry, which is calculated by (arsenic concentration in the cementation final liquid) x (flow rate of the cementation final liquid).

[0039] More preferably, the amount of arsenic output, calculated as (arsenic concentration in the final cementation liquid)×(flow rate of the final cementation liquid), of the final cementation liquid is controlled by adjusting the pH of the cementation slurry according to the amount of arsenic input.

[0040] Here, the "arsenic input amount" refers to the amount calculated by "amount of nickel sulfide raw material) x (arsenic content in nickel sulfide raw material)" for the nickel sulfide raw material. Also, the "arsenic output amount" refers to the amount calculated by "(arsenic concentration in cementation final liquid) x (flow rate of cementation final liquid)" for the cementation final liquid generated in the cementation process, as described above. The "arsenic output amount" refers to the amount of arsenic discharged from the cementation final liquid.

[0041] As described above, the lower the pH of the liquid phase in the reaction in the cementation step S1, the higher the arsenic concentration in the final cementation liquid. For this reason, for example, in the cementation step S1, when the amount of arsenic output is to be reduced according to the amount of arsenic input, the pH of the liquid phase of the cementation slurry is adjusted to be increased. On the other hand, when the amount of arsenic output is to be increased, the pH of the liquid phase of the cementation slurry is adjusted to be decreased.

[0042] Furthermore, according to this treatment method, the pH of the liquid phase of the cementation slurry can be adjusted so that the "arsenic output amount" contained in the cementation end liquid becomes a predetermined amount according to the "arsenic input amount." The pH of the liquid phase of the cementation slurry can be adjusted so that the "arsenic output amount" becomes a predetermined amount based on a correlation graph (table data) between the pH of the cementation end liquid and the arsenic concentration in the cementation end liquid, for example, as shown in Figure 5. Note that a correlation graph such as that shown in Figure 5 can be created by analyzing operation data, etc.

[0043] For example, a case will be described in which the pH of the liquid phase of the cementation slurry is adjusted so that the "arsenic output amount" is approximately equal to the "arsenic input amount" according to the "arsenic input amount". In this case, the "arsenic input amount" is first calculated from "(amount of nickel sulfide raw material) x (arsenic content in nickel sulfide raw material)". Next, the pH of the cementation end liquid that correlates with the "arsenic output amount" that is approximately equal to the calculated "arsenic input amount" is derived from a correlation graph such as that shown in Figure 5. Then, the pH of the cementation slurry obtained from the cementation process is adjusted so as to match the derived pH.

[0044] In addition, "arsenic input amount" and "arsenic output amount" being "almost equal" means that the difference between the amounts is within a range of ±10%.

[0045] As described above, in the processing of the nickel sulfide raw material according to the present embodiment, in the cementation step S1, the pH of the liquid phase of the cementation slurry is adjusted to control the arsenic output amount calculated by (arsenic concentration in the cementation final liquid)×(flow rate of the cementation final liquid), thereby making it possible to efficiently control the “arsenic output amount” contained in the cementation final liquid.

[0046] For example, by adjusting the pH of the liquid phase of the cementation slurry according to the "arsenic input amount" so that the "arsenic input amount" and the "arsenic output amount" become approximately equal, it is possible to suppress an increase in the arsenic content in the cementation residue and maintain it at a low level, and as a result, it is possible to maintain the arsenic content in the chlorine leaching residue at a low level.

[0047] As described above, according to the nickel sulfide raw material processing method of the present embodiment, even if the impurity load of iron or arsenic originating from the nickel sulfide raw material increases, it is possible to effectively control the distribution of iron and arsenic to the chlorine leaching residue obtained from the chlorine leaching step S2 without increasing material costs, etc.

[0048] The pH of the liquid phase of the cementation slurry can be adjusted by adding a neutralizing agent such as nickel carbonate, although there is no particular limitation to this. The neutralizing agent such as nickel carbonate is a neutralizing agent used in the oxidation neutralization reaction in the liquid purification step S3 (iron removal step) described below. Therefore, a part of the neutralizing agent such as nickel carbonate may be added in the cementation step S1 as well.

[0049] The cementation process in the cementation step S1 can be performed using a cementation processing device equipped with a plurality of reaction tanks (a total of n reaction tanks) connected in series, and the pH adjustment of the liquid phase of the cementation slurry can be performed in the final (nth) reaction tank of the plurality of reaction tanks connected in series. In this way, by adjusting the pH by adding a neutralizing agent or the like in the final reaction tank, the final pH of the liquid phase of the cementation slurry can be accurately adjusted.

[0050] FIG. 4 is a graph showing the relationship between the iron content and the arsenic content in the chlorine leaching residue. As shown in the graph of FIG. 4, iron and arsenic have a positive correlation with respect to distribution to the chlorine leaching residue, and iron and arsenic behave similarly in chlorine leaching. As for the distribution behavior of iron in the cementation process, similar to the arsenic shown in FIG. 5, the lower the pH of the liquid phase, the higher the iron concentration in the final cementation liquid. Therefore, in the cementation process, as described above, by adjusting the pH of the liquid phase of the cementation slurry according to the "arsenic input amount", it is possible to efficiently and effectively control the distribution of not only arsenic but also iron to the chlorine leaching residue.

[0051] <2. Chlorine leaching process> In the chlorine leaching step S2, the cementation residue produced in the above-mentioned cementation step S1 is repulped with an aqueous solution to form a slurry (cementation residue slurry), and then chlorine gas is blown into the cementation residue slurry to perform chlorine leaching. By this chlorine leaching treatment, heavy metals such as nickel and copper in the cementation residue are leached into the aqueous solution.

[0052] In the chlorine leaching step S2, the chlorine leaching slurry produced through the chlorine leaching treatment is subjected to solid-liquid separation to obtain a chlorine leaching solution and a chlorine leaching residue. As described above, the obtained chlorine leaching solution is a solution obtained by leaching heavy metals such as nickel and copper into an aqueous solution. The chlorine leaching solution also contains iron. Therefore, the chlorine leaching solution is a copper-containing, iron-containing crude nickel chloride aqueous solution.

[0053] The chlorine leaching process will now be described more specifically. In the chlorine leaching step S2, for example, reactions shown in the following formulas [1] to [3] occur. Cl2+2Cu + → 2Cl - +2Cu 2+ [1] NiS+2Cu 2+ → Ni 2+ +S 0 +2Cu + [2] Cu2S+2Cu 2+ → 4Cu + +S 0 [3]

[0054] That is, in the chlorine leaching step S2, when the cementation residue slurry is pumped, metal components such as nickel sulfide (NiS) and copper sulfide (Cu2S) contained in the cementation residue are oxidized and leached by "divalent copper ions" oxidized by chlorine gas. This produces a nickel chloride aqueous solution containing copper ions, which is the chlorine leaching solution. As shown in formula [1], it is estimated that oxidative leaching using divalent copper ions as electron carriers is carried out in the chlorine leaching step S2. In addition, NiS in formula [2] represents the main component of MS, and Cu2S in formula [3] represents the main component of cementation residue.

[0055] The chlorine leaching solution produced in the chlorine leaching step S2 is repeatedly used as an aqueous solution of copper-containing, iron-containing, nickel chloride containing divalent copper ions, and is sent to the cementation step S1 as described above, where it is mixed with the nickel sulfide raw material and treated to remove the copper ions by precipitation. 0 The chlorine leaching residue, mainly composed of, remains in the solid phase.

[0056] As described above, in the method for treating nickel sulfide raw material according to the present embodiment, in the cementation step S1, the arsenic output amount calculated by (arsenic concentration in the cementation final liquid)×(flow rate of the cementation final liquid) is controlled by adjusting the pH of the liquid phase of the cementation slurry.Then, the arsenic output amount is controlled by adjusting the pH of the liquid phase of the cementation slurry according to the arsenic input amount calculated by (amount of nickel sulfide raw material)×(arsenic content in the nickel sulfide raw material) for the nickel sulfide raw material.

[0057] In this way, since the amount of arsenic output can be effectively controlled, the migration of iron and arsenic to the cementation residue can be controlled, and as a result, it becomes possible to control the distribution of iron and arsenic to the chlorine leaching residue obtained from the chlorine leaching step S2. In other words, even if the impurity load of iron and arsenic derived from the nickel sulfide raw material increases, it becomes possible to control the distribution of iron and arsenic to the chlorine leaching residue obtained from the chlorine leaching step S2 without increasing the material cost, etc.

[0058] <3. Iron removal process> As described above, the cementation end solution obtained through the cementation step S1 is sent to the solution purification step S3 including the iron removal step. The cementation end solution is an iron-containing crude nickel chloride aqueous solution from which copper ions have been removed in the cementation step S1, but is an aqueous nickel chloride solution containing iron ions and arsenic ions as impurities (iron-containing arsenic nickel chloride aqueous solution).

[0059] Specifically, in the iron removal process, the cementation end liquid is oxidized and neutralized, causing the iron in the cementation end liquid to precipitate as a neutralized precipitate, and the iron-depleted end liquid and iron-depleted precipitate are obtained by solid-liquid separation. The oxidation neutralization method utilizes the property that heavy metals such as iron, when they become highly oxidized ions, tend to become hydroxides in the low pH range.

[0060] In the iron removal process, the impurity iron is removed through the reaction shown in equation [4] below. 2Fe 2+ +Cl2+3NiCO3+3H2O→ 2Fe(OH)3+3Ni 2+ +2Cl - +3CO2···[4]

[0061] As shown in equation [4], in the iron removal process, hydroxide precipitates of impurity elements such as iron to be removed are formed from the iron-containing arsenic nickel chloride aqueous solution, which is the cementation end liquid, to obtain a nickel chloride aqueous solution from which impurities have been removed (iron-removed end liquid).

[0062] In general, the chemicals used in the oxidation neutralization method include hypochlorous acid, oxygen, air, and the like as the oxidizing agent in addition to chlorine gas. Also, hydroxides such as caustic soda, ammonia, and the like as the neutralizing agent in addition to nickel carbonate. These chemicals are used in combinations suited to the process conditions, but in a wet smelting process using a nickel sulfide raw material, it is preferable to use chlorine gas as the oxidizing agent and nickel carbonate as the neutralizing agent. For example, chlorine gas is a strong oxidizing agent that is generated in the process and is easy to use. Also, the reason for using nickel carbonate as the neutralizing agent is that it can control the ion concentrations of nickel, sodium, sulfuric acid, and the like throughout the process, and has excellent reactivity during oxidation neutralization.

[0063] Although the iron removal step has been described as the solution purification step S3, the solution purification step S3 can be combined with other steps for removing impurities depending on the impurity composition of the cementation end solution. For example, in addition to the iron removal step by the above-mentioned oxidation neutralization method, a cobalt removal step by a solvent extraction method, a lead removal step by an oxidation neutralization method under different conditions, a zinc removal step by an ion exchange method, etc. can be combined. Through such solution purification step S3, a high-purity aqueous nickel chloride solution can be obtained.

[0064] In addition, the high-purity nickel chloride aqueous solution obtained through the solution purification step S3 including the iron removal step is then sent to the electrolysis step S4, and electrolytic nickel is produced from the high-purity nickel chloride aqueous solution by electrowinning. EXAMPLES

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0066] [Example] In the MCLE process using nickel sulfide as a raw material, the amount of arsenic distributed in the chlorine leaching residue was investigated depending on whether or not the pH of the cementation end solution obtained from the cementation step was adjusted.

[0067] Figure 6 is a graph showing the trends in the pH of the cementation end liquor, the arsenic content of the nickel sulfide raw material (arsenic load from the raw material, arsenic input amount), the balance between the arsenic load in the raw material and the amount of arsenic removed from the cementation end liquor, and the arsenic content in the chlorine leaching residue.

[0068] As shown in the graph in Figure 6, when the arsenic load from the raw material increases, if the pH of the cementation end liquid is not adjusted, the amount of arsenic discharged from the cementation end liquid (arsenic output amount), expressed as "(arsenic concentration in cementation end liquid) x (flow rate of cementation end liquid)", becomes less than the amount of arsenic input from the raw material. In this case, it is believed that arsenic is distributed to the cementation residue, increasing the amount of arsenic flowing into the chlorine leaching process, and as a result, the arsenic content in the chlorine leaching residue increases.

[0069] Here, Figure 7 is a graph showing the relationship between the pH of the chlorine leachate and the maximum arsenic concentration in the chlorine leachate. Since the pH of the chlorine leachate is lower than that of the cementation end solution, the arsenic concentration in the chlorine leachate is relatively high, but the concentration increases as the pH decreases, just like the cementation end solution. If an excessive amount of arsenic flows into the chlorine leachate process beyond the amount of arsenic discharged from the chlorine leachate, which is expressed as "(arsenic concentration in the chlorine leachate) x (flow rate of the chlorine leachate)", the amount of arsenic distributed to the chlorine leachate residue increases. This shows that it is necessary to take measures to lower the pH of the chlorine leachate. However, if the pH of the chlorine leachate is to be lowered, a large amount of acid is required because the pH is in the strong acid region around zero, and a large amount of neutralizing agent is required to neutralize the chlorine leachate whose pH has been lowered in the cementation process. In this regard, according to the method for treating nickel sulfide raw material according to the present embodiment, the pH of the liquid phase of the cementation slurry, which has a pH of about 3, is adjusted, so that the amount of a pH adjusting agent, basically a neutralizing agent, required is small.

[0070] Figure 8 is a graph showing the relationship between the pH of the chlorine leaching solution and the arsenic content in the chlorine leaching residue, stratified by the arsenic content in the cementation residue. As shown in Figure 8, during the period when the arsenic content in the cementation residue decreased, that is, when the arsenic load (inflow amount of arsenic) to the chlorine leaching process decreased, it was found that the distribution of iron and arsenic to the chlorine leaching residue was suppressed even without adjusting the hydrochloric acid concentration of the hydrochloric acid leaching solution.

[0071] In this way, it was found that by adjusting the pH of the liquid phase of the cementation slurry produced in accordance with the amount of arsenic input in the nickel sulfide raw material and controlling the amount of arsenic output in the cementation end liquid, it is possible to effectively control the distribution of iron and arsenic to the chlorine leaching residue while reducing material costs, without the need to adjust the pH of the chlorine leaching solution in the chlorine leaching process.

Claims

1. A method for treating a nickel sulfide raw material containing iron and arsenic as impurities, comprising the steps of: a cementation step of mixing a copper-containing, ferrous, crude nickel chloride aqueous solution containing divalent copper ions with a nickel sulfide raw material, and displacing and leaching nickel in the nickel sulfide raw material with the copper ions in the copper-containing, ferrous, crude nickel chloride aqueous solution to generate a cementation slurry which is a mixture of the ferrous crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide, and separating the resulting cementation slurry into a cementation final liquid and a cementation residue by solid-liquid separation; a chlorine leaching step of repulping the cementation residue to prepare a cementation residue slurry, injecting chlorine gas into the cementation residue slurry to leach heavy metals in the cementation residue to produce a chlorine leached slurry, and separating the slurry into a chlorine leached solution and a chlorine leached residue by solid-liquid separation; The chlorine leachate is repeatedly used as the copper-containing, iron-containing crude nickel chloride aqueous solution, In the cementation process, the pH of the liquid phase of the cementation slurry is adjusted to control an arsenic output amount calculated by (arsenic concentration in the cementation final liquid) x (flow rate of the cementation final liquid) for the cementation final liquid. Method for processing nickel sulfide raw materials.

2. In the cementation step, The arsenic output amount is controlled by adjusting the pH of the liquid phase of the cementation slurry according to an arsenic input amount calculated by (amount of nickel sulfide raw material) x (arsenic content in the nickel sulfide raw material) for the nickel sulfide raw material.

2. The method for treating nickel sulfide raw material according to claim 1.

3. In the cementation step, To decrease the arsenic output, the pH of the liquid phase of the cementation slurry is increased; In order to increase the arsenic output, the pH of the liquid phase of the cementation slurry is decreased. The method for treating nickel sulfide raw material according to claim 2.

4. In the cementation step, The arsenic output amount is adjusted to a predetermined amount according to the arsenic input amount. The pH of the liquid phase of the cementation slurry is adjusted based on the correlation between the pH of the cementation final liquid and the arsenic concentration in the cementation final liquid. The method for treating nickel sulfide raw material according to claim 2.

5. In the cementation step, In response to the arsenic input amount, the arsenic input amount and the arsenic output amount are approximately equal to each other. The pH of the liquid phase of the cementation slurry is adjusted based on the correlation between the pH of the cementation final liquid and the arsenic concentration in the cementation final liquid. The method for treating nickel sulfide raw material according to claim 4.

6. In the cementation step, a pH of the liquid phase of the cementation slurry is adjusted by adding a neutralizing agent containing nickel carbonate. A method for treating a nickel sulfide raw material according to any one of claims 1 to 5.

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