Oxidation-neutralization treatment method for nickel chloride aqueous solution

Abstract

To provide an oxidation-neutralization treatment method for a nickel chloride aqueous solution having high manganese removal rate.SOLUTION: There is provided an oxidation-neutralization treatment method for a nickel chloride aqueous solution which comprises an oxidation-neutralization step of blowing chlorine gas as an oxidizing agent while continuously supplying a nickel chloride aqueous solution containing manganese to a plurality of reaction tanks connected in series, followed by adding a neutralizing agent to generate a neutralized precipitate containing manganese by an oxidation-neutralization reaction. The amount of chlorine gas blown into the nickel chloride aqueous solution per unit volume in the final reaction tank, which is the most downstream of a plurality of reaction tanks, is 0.5 kg / (m3 h) or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for oxidizing and neutralizing an aqueous solution of nickel chloride, and more particularly to a method for removing manganese contained in an aqueous solution of nickel chloride by an oxidizing and neutralizing method. [Background technology]

[0002] In the nickel hydrometallurgical process, nickel sulfide is leached with chlorine, impurities are removed from the resulting aqueous nickel chloride solution, and electrolytic nickel is recovered by electrowinning. The oxidation neutralization method is known as a method for removing impurities from an aqueous nickel chloride solution. For example, Patent Document 1 describes the removal of impurities such as lead contained in an aqueous nickel chloride solution by the oxidation neutralization method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-171972 Summary of the Invention [Problem to be solved by the invention]

[0004] If manganese is contained in the aqueous nickel chloride solution subjected to electrowinning, the current efficiency will decrease and the operating cost will increase, so it is necessary to remove manganese from the aqueous nickel chloride solution.

[0005] In view of the above circumstances, an object of the present invention is to provide a method for oxidizing and neutralizing an aqueous nickel chloride solution, which has a high manganese removal rate. [Means for solving the problem]

[0006] The first aspect of the method for oxidizing and neutralizing an aqueous solution of nickel chloride comprises an oxidation and neutralization step of continuously supplying an aqueous solution of nickel chloride containing manganese to a plurality of reaction tanks connected in series, while blowing chlorine gas as an oxidizing agent therein and adding a neutralizing agent therein to produce a neutralized precipitate containing manganese by an oxidation and neutralization reaction, and the amount of chlorine gas blown into the final reaction tank, which is the most downstream of the plurality of reaction tanks, per unit volume of the aqueous solution of nickel chloride is 0.5 kg / (m 3 ·h) characterized in that: The second aspect of the method for oxidizing and neutralizing a nickel chloride aqueous solution is the same as the first aspect, except that the amount of chlorine gas blown into the nickel chloride aqueous solution in the final-stage reaction tank is 0.4 kg / (m 3 ·h) characterized in that: The third aspect of the method for oxidizing and neutralizing an aqueous nickel chloride solution is characterized in that, in the first or second aspect, the pH of the aqueous nickel chloride solution in the final-stage reaction tank is 4.6 to 4.8, and the oxidation-reduction potential (Ag / AgCl electrode standard) is 1,000 to 1,030 mV. [Effects of the Invention]

[0007] According to the present invention, the amount of chlorine in the final stage reaction vessel is 0.5 kg / (m 3 By keeping the manganese removal rate below 100%, the manganese removal rate can be increased. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing the overall process of nickel hydrometallurgy. [Figure 2] FIG. 2 is a detailed process diagram of the lead removal process. [Figure 3] FIG. 2 is an explanatory diagram of an oxidation neutralization facility. [Figure 4] 1 is a graph showing the relationship between the amount of chlorine in the final-stage reaction tank and the final-stage manganese removal rate. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, an embodiment of the present invention will be described with reference to the drawings. The oxidation neutralization treatment method according to one embodiment of the present invention is a method for removing manganese contained in an aqueous solution of nickel chloride by oxidation neutralization. The aqueous solution of nickel chloride may contain other impurities such as iron, lead, and cobalt. The aqueous solution of nickel chloride undergoes oxidation neutralization treatment to remove the impurities.

[0010] The oxidation neutralization treatment method of this embodiment is suitably applied to the de-ironization step and the de-leading step, particularly the de-leading step, of the nickel hydrometallurgical refining process described below. Therefore, the de-leading step will be described below as an example. However, the oxidation neutralization treatment method of this embodiment is not limited to the de-leading step, and can be applied to any process step as long as it is a step of removing manganese from an aqueous nickel chloride solution by oxidation neutralization treatment.

[0011] As shown in Figure 1, in the nickel hydrometallurgical process, the raw material nickel sulfide is first treated in the leaching process to obtain leachate. Nickel sulfide can be nickel matte or nickel-cobalt mixed sulfide.

[0012] The leaching process includes a chlorine leaching process and a cementation process. In the chlorine leaching process, the oxidizing power of chlorine gas injected into the leaching tank causes substantially all of the metals contained in the solids in the raw slurry to be leached into the liquor. In the cementation process, the chlorine leaching solution is brought into contact with nickel sulfide, preferably nickel matte, to carry out a substitution reaction between copper and nickel. As a result, for example, nickel in the nickel matte is leached into the liquor, and copper ions in the liquor are precipitated in the form of copper sulfide or metallic copper. The leachate obtained in the leaching process is mainly composed of an aqueous nickel chloride solution and contains impurities such as copper, iron, and lead in addition to cobalt.

[0013] In the iron removal process, impurities such as iron and arsenic are removed from the leachate (nickel chloride aqueous solution) by oxidation neutralization. In this process, an oxidizing agent is applied to the leachate to adjust the oxidation-reduction potential (based on an Ag / AgCl electrode, the same applies below) to 400-1,100 mV, while a neutralizing agent is added to adjust the pH to 1.5-3. Chlorine gas, for example, is used as the oxidizing agent. Nickel carbonate, for example, is used as the neutralizing agent. The oxidation neutralization reaction precipitates impurities such as iron and arsenic contained in the leachate as hydroxides or oxides. The precipitate is removed by solid-liquid separation, yielding a deionized final solution from which impurities have been removed.

[0014] In the solvent extraction step, the cobalt contained in the iron-removal final liquor is separated by solvent extraction to obtain an aqueous nickel chloride solution and an aqueous cobalt chloride solution. Hereinafter, for ease of explanation, the aqueous nickel chloride solution and the aqueous cobalt chloride solution obtained in the solvent extraction step will be referred to as the crude nickel chloride solution and the crude cobalt chloride solution, respectively. The nickel concentration in the crude nickel chloride solution is 160 to 200 g / L. The crude nickel chloride solution also contains impurities such as lead, manganese, cobalt, and zinc. The cobalt contained in the iron-removal final liquor is extracted into the organic solvent and selectively separated from the nickel chloride in the iron-removal final liquor, but trace amounts of cobalt still remain in the extraction residue (crude nickel chloride solution).

[0015] The crude cobalt chloride aqueous solution is purified in a solution purification process to remove impurities, resulting in a high-purity cobalt chloride aqueous solution that is sent to the cobalt electrolysis process, where electrolytic cobalt is produced by electrowinning.

[0016] The crude nickel chloride aqueous solution undergoes a deleading process to remove impurities, resulting in a high-purity nickel chloride aqueous solution. The deleading process will be described in detail later. After the deleading process, other solution purification treatments may be performed as needed. For example, trace amounts of zinc remaining in the nickel chloride aqueous solution may be removed by adsorption onto an anion exchange resin. The high-purity nickel chloride aqueous solution is sent to a nickel electrolysis process. In the nickel electrolysis process, electrolytic nickel is produced by electrowinning.

[0017] As shown in Fig. 2, the deleading process has three sub-processes: a dilution process, an oxidation / neutralization process, and a solid-liquid separation process. In the following description, the term "crude aqueous nickel chloride solution" is used to mean not only the starting solution of the deleading process, but also the water to be treated in the dilution process and the oxidation / neutralization process.

[0018] In the dilution step, a diluent is added to the crude nickel chloride aqueous solution to dilute it and thereby reduce the nickel concentration. For example, the crude nickel chloride aqueous solution (nickel concentration 160 to 200 g / L) obtained in the solvent extraction step is diluted so that the nickel concentration becomes 90 to 130 g / L. Note that, since the main component of the crude nickel chloride aqueous solution is nickel chloride, the nickel concentration can be used as an index of the chloride ion concentration of the crude nickel chloride aqueous solution.

[0019] If the nickel concentration of the crude nickel chloride aqueous solution is 130 g / L or less, the low chloride ion concentration destabilizes the chloro complex, making it easier for impurities, especially cobalt, to precipitate in the oxidation neutralization process. Furthermore, if the nickel concentration of the crude nickel chloride aqueous solution is 130 g / L or less, nucleation of precipitate particles is promoted, resulting in larger particle sizes, improving filterability in the solid-liquid separation process. If the nickel concentration of the crude nickel chloride aqueous solution is 90 g / L or more, the amount of diluent added can be reduced, preventing a significant increase in the volume of the crude nickel chloride aqueous solution, eliminating the need to increase facility capacity.

[0020] It is preferable to use nickel electrolysis waste liquid as the diluent. Nickel electrolysis waste liquid is obtained as waste liquid after using a high-purity nickel chloride aqueous solution as an electrolyte in the nickel electrolysis process. By using nickel electrolysis waste liquid as a diluent, it is possible to prevent an increase in the total amount of liquid in the hydrometallurgical process system. Industrial water may be used as the diluent instead of nickel electrolysis waste liquid. If industrial water is used, the crude nickel chloride aqueous solution can be diluted to the target nickel concentration with a smaller amount of liquid than if nickel electrolysis waste liquid is used.

[0021] The diluted crude nickel chloride aqueous solution is sent to the oxidation neutralization step. In the oxidation neutralization step, an oxidizing agent and a neutralizing agent are added to the crude nickel chloride aqueous solution to produce a neutralized precipitate through an oxidation neutralization reaction. The main reaction in the oxidation neutralization reaction is to produce nickel hydroxide or oxide. At the same time, hydroxides or oxides of impurities such as lead, manganese, and cobalt contained in the crude nickel chloride aqueous solution are produced. Therefore, the main components of the neutralized precipitate are nickel hydroxide and oxide (nickel precipitate). Note that hereinafter, the manganese hydroxide and oxide contained in the neutralized precipitate will be referred to as manganese precipitate.

[0022] Chlorine gas is used as the oxidizing agent. Nickel carbonate, sodium carbonate, calcium carbonate, nickel hydroxide, sodium hydroxide, calcium hydroxide, etc. can be used as the neutralizing agent. Of these, nickel carbonate and nickel hydroxide are preferred because they do not increase the impurities in the high-purity nickel chloride aqueous solution.

[0023] The slurry containing the neutralized precipitate is separated into a high-purity aqueous nickel chloride solution and the neutralized precipitate in a solid-liquid separation step. Since the main components of the neutralized precipitate are nickel hydroxide and oxide, the neutralized precipitate can be reused, for example, as a raw material for nickel sulfate.

[0024] In the oxidation neutralization step, an oxidation neutralization equipment AA shown in FIG. 3 is used. The oxidation neutralization equipment AA has multiple reaction tanks 10A, 10B, and 10C connected in series. The number of reaction tanks 10A, 10B, and 10C is not particularly limited, as long as it is two or more. The aqueous crude nickel chloride solution is continuously supplied to the most upstream reaction tank 10A (first tank) and flows sequentially to the downstream reaction tanks 10B and 10C. The flow rate of the aqueous crude nickel chloride solution is, for example, 2,200 to 3,000 L / min.

[0025] The dilution step may be carried out in a concentration adjusting tank, or the dilution step and the oxidation / neutralization step may be carried out in the same reaction tank 10 A. In the latter case, both the crude nickel chloride aqueous solution before dilution and the diluent may be supplied to the reaction tank 10 A.

[0026] An oxidizing agent (chlorine gas) and a neutralizing agent are continuously supplied to each of the reaction vessels 10A, 10B, and 10C. Each of the reaction vessels 10A, 10B, and 10C is also equipped with an agitator for stirring the crude nickel chloride aqueous solution with the oxidizing agent (chlorine gas) and neutralizing agent. Chlorine gas is blown into the crude nickel chloride aqueous solution in the reaction vessels 10A, 10B, and 10C as an oxidizing agent, and a neutralizing agent is added to produce a neutralized precipitate through an oxidation-neutralization reaction. By carrying out the oxidation-neutralization treatment in stages using multiple reaction vessels 10A, 10B, and 10C, the efficiency of the oxidation-neutralization treatment is improved and the impurity concentration in the treated solution can be reduced.

[0027] The pH and oxidation-reduction potential of the aqueous crude nickel chloride solution may be changed in a stepwise manner. For example, from the viewpoint of maintaining good filterability of the produced neutralized precipitate, the pH of the first tank 10A may be set to the highest, and the pH of the second tank 10B and subsequent tanks may be decreased in a stepwise manner, with no neutralizing agent being added to the most downstream final-stage reaction tank 10C.

[0028] For example, when three reaction tanks 10A, 10B, and 10C are used for the oxidation neutralization treatment, the pH of the crude nickel chloride aqueous solution in the first reaction tank 10A, which is the most upstream, is preferably 4.9 to 5.2, and the redox potential is preferably 980 to 1,050 mV. In the second reaction tank 10B, the pH of the crude nickel chloride aqueous solution is preferably 4.7 to 4.9, and the redox potential is preferably 980 to 1,050 mV. In the final reaction tank 10C, which is the most downstream, the pH of the nickel chloride aqueous solution is preferably 4.6 to 4.8, and the redox potential is preferably 1,000 to 1,030 mV. Strictly speaking, the pH and redox potential mentioned above refer to the average pH and average redox potential.

[0029] The term "average" here means the average of the entire aqueous crude nickel chloride solution in the reaction tank. When the aqueous crude nickel chloride solution in the reaction tank is stirred with a stirrer or the like, the measurements of the pH meter and ORP meter installed in the reaction tank will be the average pH value and the average oxidation-reduction potential value, respectively.

[0030] The slurry containing the neutralized precipitate produced by the neutralization reaction is continuously discharged from the final-stage reaction tank 10C.

[0031] The inventors of the present application have found that in such an oxidation neutralization treatment, if the amount of chlorine gas blown into the final-stage reaction tank 10C is reduced, the manganese removal rate will be increased. Specifically, the amount of chlorine gas blown into the final-stage reaction tank 10C per unit volume of the aqueous solution of crude nickel chloride (hereinafter referred to as the "chlorine amount") is set to 0.5 kg / (m 3 The manganese removal rate can be sufficiently increased by controlling the amount of chlorine gas blown into the final-stage reaction vessel 10C (kg / h) relative to the volume (m 3 ) is the value divided by

[0032] The reason why the manganese removal rate increases when the amount of chlorine in the final-stage reaction tank 10C is reduced is presumed to be as follows: In a facility in which multiple reaction tanks 10A, 10B, and 10C are connected in series, the majority of the oxidation and neutralization reaction basically takes place in the first tank 10A. Therefore, most of the manganese contained in the crude nickel chloride aqueous solution also becomes a precipitate in the first tank 10A.

[0033] If the amount of chlorine in the final-stage reaction tank 10C is large, the oxidation-reduction potential of the crude nickel chloride aqueous solution will locally increase, and it is believed that some of the manganese precipitate produced in the first tank 10A will redissolve. This will result in a decrease in the final manganese removal rate. Conversely, if the amount of chlorine in the final-stage reaction tank 10C is small, the oxidation-reduction potential of the nickel chloride aqueous solution will not locally increase, and the redissolution of manganese precipitate can be suppressed. As a result, it is believed that the manganese removal rate can be increased.

[0034] It is considered that the manganese removal rate can be increased by reducing the amount of chlorine not only in the final-stage reaction tank 10C but also in any reaction tank downstream of the first tank 10A, that is, in the second tank 10B and thereafter.

[0035] From the viewpoint of suppressing redissolution of manganese precipitate, there is no lower limit to the amount of chlorine in the final-stage reaction tank 10C. However, the amount of chlorine affects the oxidation-reduction potential of the crude nickel chloride aqueous solution. It is preferable to adjust the amount of chlorine so that the oxidation-reduction potential of the crude nickel chloride aqueous solution in the final-stage reaction tank 10C is in a range suitable for oxidation-neutralization treatment, specifically, 1,000 to 1,030 mV. [Example]

[0036] Next, an example will be described. The nickel hydrometallurgical refining process shown in Figure 1 was carried out. In the deleading step shown in Figure 2, impurities contained in the crude nickel chloride aqueous solution were removed by an oxidation neutralization method. The nickel concentration of the crude nickel chloride aqueous solution at the time of supply to the oxidation neutralization step was 90 to 130 g / L, and the manganese concentration was 1 to 20 mg / L.

[0037] The oxidation and neutralization process used three reactors connected in series, each with a capacity of 50 m 3 An oxidizing agent and a neutralizing agent were added to the first and second tanks. Only an oxidizing agent was added to the third tank (the final reactor). Chlorine gas was used as the oxidizing agent, and basic nickel carbonate was used as the neutralizing agent.

[0038] The pH of the crude nickel chloride aqueous solution in the first tank is 4.9 to 5.2, and the redox potential is 980 to 1,050 mV. The pH of the crude nickel chloride aqueous solution in the second tank is 4.7 to 4.9, and the redox potential is 980 to 1,050 mV. The pH of the crude nickel chloride aqueous solution in the final reaction tank is 4.6 to 4.8, and the redox potential is 1,000 to 1,030 mV. The temperature of the crude nickel chloride aqueous solution in each tank is 50 to 60°C.

[0039] Below, the manganese removal rate in the deleading process will be examined in two stages: the first tank and the second tank and beyond. The manganese removal rate in the second tank and beyond is referred to as the "second-stage manganese removal rate." The second-stage manganese removal rate refers to the manganese removal rate achieved by operations in the second tank and beyond, including the solid-liquid separation process. The second-stage manganese removal rate is calculated using the following procedure. The slurry discharged from the first tank is sampled and filtered through filter paper, and the manganese concentration ρ1 of the filtrate is measured using atomic absorption spectrometry. The manganese concentration ρ2 of the filtrate (high-purity nickel chloride aqueous solution) obtained in the solid-liquid separation process is measured using atomic absorption spectrometry. The second-stage manganese removal rate R is then calculated from these measured values ​​using the following formula: R=(ρ1-ρ2) / ρ1

[0040] The relationship between the amount of chlorine in the final-stage reaction tank and the subsequent manganese removal rate is shown in Figure 4. The horizontal axis of the graph in Figure 4 represents the amount of chlorine in the final-stage reaction tank, which is the value obtained by dividing the amount of chlorine gas blown into the final-stage reaction tank by the volume of the crude nickel chloride aqueous solution in the final-stage reaction tank.

[0041] As can be seen from the graph in Figure 4, the lower the amount of chlorine in the final stage reaction tank, the higher the subsequent manganese removal rate R. 3 If the chlorine content is 0.4 kg / (m 3 If the temperature is set to 0.15°C or less, the secondary manganese removal rate R will be 90% or more. Furthermore, the variation in the secondary manganese removal rate can be reduced. If the secondary manganese removal rate R is high, the overall manganese removal rate in the deleading process will also be high.

Claims

1. an oxidation-neutralization step in which an aqueous nickel chloride solution containing manganese is continuously supplied to a plurality of reaction tanks connected in series, while chlorine gas is blown in as an oxidizing agent and a neutralizing agent is added to produce a neutralized precipitate containing manganese by an oxidation-neutralization reaction; The amount of chlorine gas blown into the nickel chloride aqueous solution in the final stage reaction tank, which is the most downstream of the plurality of reaction tanks, is 0.5 kg / (m ３ h) is less than or equal to 1. A method for oxidizing and neutralizing an aqueous nickel chloride solution.

2. The amount of chlorine gas blown into the nickel chloride aqueous solution in the final stage reaction vessel per unit volume was 0.4 kg / (m ３ h) is less than or equal to 2. The method for oxidizing and neutralizing an aqueous nickel chloride solution according to claim 1.

3. The pH of the nickel chloride aqueous solution in the final-stage reaction tank is 4.6 to 4.8, and the oxidation-reduction potential (based on an Ag / AgCl electrode) is 1,000 to 1,030 mV.

3. The method for oxidizing and neutralizing an aqueous nickel chloride solution according to claim 1 or 2.

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