JP2022006900A - Production method of nickel sulfate aqueous solution - Google Patents

Abstract

To provide a method for efficiently producing a high-purity nickel sulfate aqueous solution at low cost.SOLUTION: Provided is a production method of a nickel sulfate aqueous solution for producing a high purity nickel sulfate aqueous solution from a crude nickel sulfate aqueous solution including at least cobalt by a solvent extraction process using an acidic organic extractant. The solvent extraction process has an exchange stage in which the acidic organic extractant and the crude nickel sulfate aqueous solution are introduced into a mixer-settler-type solvent extraction device of a plurality of stages in a countercurrent way relative to each other to carry out continuous extraction treatment, thereby causing nickel preliminarily extracted into the acidic organic extractant and cobalt in the crude nickel sulfate aqueous solution to carry out exchange reaction for substitution. Of the plurality of stages, a preceding stage of a rearmost stage, the rearmost stage, and the other stages are controlled so as to have an aqueous phase of pH 4.4 to 5.0, pH 2.5 to 4.0, and pH 4.0 to 4.5, respectively.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for producing a nickel sulfate aqueous solution, and more particularly to a method for producing a high-purity nickel sulfate aqueous solution through a solvent extraction step using an acidic organic solvent as an extractant.

Nickel sulfate is used not only for nickel plating but also for a wide range of applications such as aluminum coloring, catalysts, and positive electrode materials for secondary batteries. Examples of the method for producing nickel sulfate include nickel mats produced by dry smelting, nickel auxiliary raw materials generated in copper smelters, and nickel discharged from the lead removal step of the wet production process of electric nickel. A method is known in which a lead starch is used as a raw material to obtain a high-purity nickel sulfate aqueous solution through a pressure leaching step, a dissolution step, a purification step, a solvent extraction step and the like.

In the solvent extraction step included in the above-mentioned method for producing a nickel sulfate aqueous solution, a so-called COB-SX (Crowding Organic Bipath-Solvent Operation) process using an acidic organic extractant is used as disclosed in Patent Document 1. Has been proposed. In the COB-SX process shown in Patent Document 1, an extraction stage for extracting nickel from an extraction system crude nickel sulfate aqueous solution to obtain a nickel-retaining organic phase using an acidic organic extractant, and a nickel-retaining organic obtained in the extraction stage. By introducing a cleaning stage in which the phase is washed with a cleaning solution containing nickel, a nickel-retaining organic phase after cleaning, and an exchange-type crude nickel sulfate aqueous solution into a countercurrent flow, cobalt and the like contained in the exchange-type crude nickel sulfate aqueous solution can be used. It consists of an exchange stage that replaces the impurities in the nickel with nickel contained in the nickel-retaining organic phase.

A multi-stage mixer settler is used in the above-mentioned exchange stage, and among these multiple stages (n exchange stage) of the mixer settler, one stage before the last stage is used for the purpose of producing a high-purity nickel sulfate aqueous solution. The pH of the mixer settler (n-1th exchange stage) may be intentionally set high. As a result, the amount of impurities brought from the aqueous phase of the n-1 exchange stage to the mixer settler in the previous stage can be reduced, so that a high-purity nickel sulfate aqueous solution can be produced. The n-stage mixer settler constituting the above-mentioned exchange stage is referred to as a first exchange stage, a second exchange stage, ..., An n-1 exchange stage, and an n-th exchange stage in the order of the flow direction of the organic phase. There is.

Japanese Unexamined Patent Publication No. 10-310437

As described above, for example, in an exchange stage composed of four stages, a high-purity nickel sulfate aqueous solution can be obtained by making the pH of the third exchange stage higher than that of the other first, second, and fourth exchange stages. However, by repeating the following (3) to (5), as shown by the white arrow in FIG. 1, a large amount of Co circulates between the third exchange stage and the fourth exchange stage, which is a problem. It happened to be.
(1) In the fourth exchange stage, a part of Co in the aqueous phase is sent to the third exchange stage without being extracted into the organic phase and remaining in the aqueous phase.
(2) In the third exchange stage, the residual Co in the aqueous phase is extracted into the organic phase, and an organic phase having a high Co concentration is generated.
(3) The organic phase having a high Co concentration is sent from the third exchange stage to the fourth exchange stage.
(4) In the fourth exchange stage, Co in the organic phase is back-extracted into the aqueous phase, and the aqueous phase containing the back-extracted Co is sent to the third exchange stage.
(5) In the third exchange stage, Co in the aqueous phase containing the back-extracted Co is extracted into the organic phase, and an organic phase having a high Co concentration is generated.

As a result, the conventional exchange stage has the following two problems.
1. 1. Since the back extraction reaction of Co extracted in the third exchange stage occurs, a large amount of acid is required in the fourth exchange stage, and the acid intensity becomes high.
2. 2. The Co concentration in the organic phase of the third exchange stage may temporarily rise sharply due to fluctuations during operation, which causes the viscosity of the organic phase to rise and causes poor oil-water separation in the mixer settler.

Further, in the exchange stage of FIG. 1, the problem is that Ni circulates between the third exchange stage and the fourth exchange stage by repeating the following [1] to [2] as in the case of the above Co. May become.
[1] In the third exchange stage, Ni in the aqueous phase is extracted into the organic phase, and the organic phase containing an excess of Ni is sent to the fourth exchange stage.
[2] In the fourth exchange stage, Ni in the organic phase is back-extracted into the aqueous phase.

In the crude nickel sulfate aqueous solution treated by the above COB-SX process, the Co load as an impurity is reduced due to fluctuations in the raw material species and their treatment ratio, fluctuations in the content in the raw materials, process changes, process condition changes, etc. In that case, lower cost operation is desired. The present invention has been made in view of the above circumstances, and by reducing the amount of Co and Ni circulating between the n-1th exchange stage and the nth exchange stage, a high-purity nickel sulfate aqueous solution can be obtained. The challenge is to provide a method that can be manufactured efficiently at low cost.

In order to achieve the above object, the method for producing a nickel sulfate aqueous solution according to the present invention is a nickel sulfate aqueous solution for producing a high-purity nickel sulfate aqueous solution from a crude nickel sulfate aqueous solution containing at least cobalt by a solvent extraction step using an acidic organic extractant. In the solvent extraction step, the acidic organic extractant and the crude nickel sulfate aqueous solution are introduced into a countercurrent flow into a multi-stage mixer settler type solvent extractor to perform a continuous extraction process. It has an exchange stage in which nickel previously extracted by the acidic organic extractant and cobalt in the crude nickel sulfate aqueous solution are exchanged and replaced, and among the plurality of stages, one stage before the last stage. The pH of the aqueous phase of the above is 4.4 to 5.0, the pH of the aqueous phase of the last stage is 2.5 to 4.0, and the pH of the aqueous phase of the other stages is 4.0 to 4.5. It is characterized by controlling each.

According to the present invention, it is possible to efficiently produce a high-purity nickel sulfate aqueous solution at a lower cost.

It is a schematic flow diagram which shows the circulation of Co between the 3rd exchange stage and the 4th exchange stage of a COB-SX process. It is a block flow figure of the manufacturing method of the nickel sulfate aqueous solution which concerns on embodiment of this invention. It is a schematic flow chart of the COB-SX process performed in the solvent extraction step of FIG. It is a schematic flow chart of the exchange stage of the COB-SX process of FIG. It is a graph which shows the ratio with respect to the metal equivalent to be extracted of sulfuric acid consumed in the exchange stage of the COB-SX process performed in the Example and the comparative example of this invention.

Hereinafter, a method for producing an aqueous nickel sulfate solution according to an embodiment of the present invention will be described in detail. As shown in FIG. 2, the method for producing an aqueous nickel sulfate solution according to an embodiment of the present invention includes a nickel mat produced by pyrometallurgy, a deleaded starch produced in an electronickel manufacturing process, and a copper smelter. It uses crude nickel sulfate generated in such cases as a raw material. Of these, the nickel mat is preferably pulverized to a predetermined size and then leached under high temperature and high pressure conditions in the pressure leaching step to obtain a crude nickel sulfate aqueous solution.

The deleaded starch is dissolved in sulfuric acid in the sulfuric acid dissolution step and then reduced and dissolved in a reducing agent such as SO ₂ gas in the reduction dissolution step to obtain a crude nickel sulfate / cobalt mixed aqueous solution. The deleaded starch is produced in the deleading step of the so-called MCLE method (Matte Chlorine Leach Electrowinning method). This MCLE method is a process for producing electric nickel by repulping nickel matte and nickel-cobalt mixed sulfide (MS: Mixed Sulfide) with an electrolytic waste liquid and then treating this with a cementation step and a chlorine leaching step. Yes, the deleaded starch is recovered in the deleading step after the cementation step.

The mixed aqueous solution of the crude nickel sulfate aqueous solution and the crude nickel sulfate / cobalt mixed aqueous solution produced from the above nickel matte and the deleaded starch, respectively, is composed of a crude nickel sulfate aqueous solution containing at least cobalt from which iron is removed in the iron removal step. It becomes the exchange system de-Fe final solution. On the other hand, after the crude nickel sulfate is dissolved in the dissolution step, Zn and Cd are removed in the Zn removal / Cd removal step, and iron is removed in the iron removal step. Will be.

The extraction-based de-Fe final solution and the exchange-based de-Fe final solution, which are separately generated from the above two raw material processing routes, are then processed in a solvent extraction step by the COB-SX process to produce a high-purity nickel sulfate product. An aqueous solution and a crude cobalt chloride aqueous solution are produced. This solvent extraction step consists of an extraction stage, a cleaning stage, an exchange stage, a Ni recovery stage, a Co recovery stage, and a reverse extraction stage. In each stage, a general mixer-settler type solvent extraction device is connected in series. Multi-stage countercurrent continuous extraction processing is performed by using the apparatus. A general organic phosphoric acid-based acidic organic extractant can be used as the organic solvent circulating in this solvent extraction step, and 2-ethylhexylphosphonate mono-2-ethylhexyl having the structural formula shown in Chemical formula 1 below can be used. It is preferable to use it for the above-mentioned acidic organic extractant.

The COB-SX process described above will be specifically described with reference to FIG. 3. In the extraction stage, an extraction system de-Fe final solution, which is a crude nickel sulfate aqueous solution containing no cobalt, is supplied and discharged from the back extraction stage. After the reverse extraction, Ni is mainly extracted by the extraction reaction represented by the following formula 1, for example, and sodium, ammonia and the like having a lower extraction rate than Ni are separated and removed on the aqueous phase side. In the following formula 1, R represents an acidic organic extractant excluding H of the hydroxy group.
[Equation 1]
2 (RH) + Ni ²⁺ → R-Ni-R + 2H ⁺

The post-extraction organic discharged from the extraction stage is then supplied to the cleaning stage, where sodium and ammonia remaining in the organic phase are removed by replacing Ni in the cleaning liquid by cleaning with the cleaning liquid. To. Further, by replacing the fine droplets suspended in the organic phase called entrainment with a cleaning liquid, impurities retained in the organic phase as entrainment are removed. The cleaning solution is preferably an aqueous solution of nickel sulfate having a low impurity concentration. For example, a high-purity nickel sulfate aqueous solution discharged from the exchange stage or a dehydrated mother liquor produced from the manufacturing process of high-purity nickel sulfate crystals diluted with water. Is preferably used.

The post-cleaning organic that has left the cleaning stage is then introduced from the first stage side into an exchange stage composed of, for example, a four-stage mixer settler, and here, the exchange system de-Fe introduced from the fourth stage side. Countercurrent contact with the final liquid is performed. As a result, Ni contained in the organic after cleaning and impurities such as Co contained in the exchange-based de-Fe final solution are replaced by, for example, the exchange reaction of the following formula 2, and the impurities in the exchange-based de-Fe final solution are organic. Extracted to the phase.
[Equation 2]
R-Ni-R + Co ²⁺ → R-Co-R + Ni ²⁺

As a result, a high-purity nickel sulfate aqueous solution is generated on the aqueous phase side. This high-purity nickel sulfate aqueous solution is shipped as a product as it is, or is supplied to a crystallization facility and concentrated and crystallized by heating to produce nickel sulfate crystals. As described above, since Co is extracted by the extractant from which Ni has been extracted in advance in the exchange stage, a neutralizing agent for pH adjustment becomes unnecessary. This makes it possible to prevent contamination of the high-purity nickel sulfate aqueous solution with Na, which is a problem when NaOH is used as a neutralizing agent, for example. Further, since Ni is back-extracted corresponding to the extraction of Co, the Ni concentration can be maintained high.

In the above exchange stage, if the concentration of impurities contained in the organic after washing is too high, when the concentration of impurities in the aqueous phase becomes low due to the substitution reaction, the migration of the impurities from the aqueous phase to the organic phase is less likely to occur. Therefore, as shown in FIGS. 3 and 4, a part of the organic substance after the back extraction regenerated in the back extraction stage is extracted, the extraction stage and the washing stage are bypassed, and the organic material is introduced from the first stage side of the exchange stage. After washing, it is used as an organic diluent. In addition, the organic after washing is partially extracted and introduced into the third stage of the exchange stage in order to carry out the substitution reaction more efficiently in the mixer settler in the subsequent stage where the impurity concentration in the aqueous phase is high. There is.

The exchanged organic that has left the exchange stage is then supplied to the Ni recovery stage, where Ni contained in the exchanged organic is recovered in the dilute sulfuric acid on the aqueous phase side. The Ni recovery liquid containing Ni recovered in this way is repeated in the nickel sulfate manufacturing process as necessary. The organic after Ni recovery from the Ni recovery stage is then supplied to the Co recovery stage, where Co contained in the organic after Ni recovery is recovered to hydrochloric acid on the aqueous phase side. The crude Co chloride aqueous solution containing Co recovered in this manner is supplied to the electrowinning step after impurities such as zinc, manganese, copper and cadmium are removed to obtain a high-purity cobalt chloride aqueous solution in a further purification step. And electric cobalt is manufactured. After the Co recovery from the Co recovery stage, the organic substance is finally introduced into the back extraction stage, where impurities such as iron are back-extracted with dilute sulfuric acid.

In solvent extraction using an acidic organic extractant as described above, hydrogen ions are involved in the extraction reaction, so the extraction rate changes depending on the pH. The extraction rate differs depending on the metal, and it is easy to extract in the order of Fe> Zn> Cu> Mn> Co> Ca> Mg> Ni. Therefore, by lowering the pH in the order of the extraction stage, cleaning stage, exchange stage, nickel recovery stage, cobalt recovery stage, and reverse extraction stage, which are the order of the flow of the organic phase, different metals can be separated and recovered in each stage. can do.

In the exchange stage of the above COB-SX process, an acid preferably composed of sulfuric acid is added to each of the first to fourth exchange stages to individually control the pH. Specifically, the third exchange stage controls the pH within the range of 4.4 to 5.0, and the first and second exchange stages control the pH within the range of 4.0 to 4.5. The fourth exchange stage controls the pH within the range of 2.5 to 4.0. This makes it possible to produce a high-purity nickel sulfate aqueous solution while suppressing the problem of circulation of Co and Ni between the third exchange stage and the fourth exchange stage described above as much as possible.

When the pH of the third exchange stage is lower than 4.4, the distribution of impurities such as calcium and magnesium to the organic phase decreases, and the concentration of impurities in the obtained high-purity nickel sulfate aqueous solution increases. On the contrary, if the pH of the third exchange stage is higher than 5.0, the circulation amount of Co and Ni between the above-mentioned third exchange stage and the fourth exchange stage cannot be reduced, and the above-mentioned acid cannot be reduced. It becomes impossible to suppress the problem that the basic unit becomes high and the problem that the viscosity of the organic phase temporarily becomes high.

As described above, in the method for producing high-purity nickel sulfate according to the embodiment of the present invention, for example, in an exchange stage composed of four stages, the pH of the third exchange stage is controlled to be lower than that of the conventional method. Since Co and Ni can be prevented from being excessively extracted into the organic phase in the third exchange stage, the amount of acid consumed in the exchange stage can be reduced. Further, since the Co concentration in the organic phase can be kept low in the third exchange stage, it is difficult for the viscosity to increase due to the temporary increase in the Co concentration in the organic phase when the load of Co fluctuates, and there is a risk that the oil-water separability deteriorates. Can be significantly reduced. As a result, the quality is stable and the productivity is improved.

[Example]
A nickel sulfate aqueous solution was produced along the block flow of the nickel sulfate aqueous solution shown in FIG. At that time, a COB-SX process as shown in the flow chart of FIG. 3 was adopted for the solvent extraction step, and a four-stage mixer settler having the configuration shown in FIG. 4 was used for the exchange stage. In addition, PC-88A, which is an organic phosphoric acid-based acidic organic extractant manufactured by Daihachi Chemical Industry Co., Ltd., is used as the extractant, and Teclean, which is a diluent composed of saturated hydrocarbons manufactured by JXTG Energy Co., Ltd., is used. It was diluted with N-20 so that the concentration of the extractant in the organic solvent was about 15 to 25% by volume. The organic solvent thus prepared was adjusted so that the ratio of the organic phase flow rate to the aqueous phase flow rate, so-called O / A, was 1 to 4, and the exchange stage was operated.

Further, the pH of the first and second exchange stages is controlled to 4.0 to 4.5, the pH of the fourth exchange stage is controlled to 2.5 to 4.0, and the pH of the third exchange stage is 4. It was controlled to 8 ± 0.1. Under these conditions, a high-purity nickel sulfate aqueous solution was produced for about one month. During that time, the sulfuric acid consumed in the exchange stage was about 85% of the metal equivalent to be extracted. The metal equivalent to be extracted can be obtained from the balance of Ni and Co in the organic phase. To show the specific procedure, organic flow rate after cleaning (L / min) x organic Ni concentration after cleaning (mol / L) -organic flow rate after replacement (L / min) x organic Ni + Co concentration after replacement (mol / L) ) = Metal equivalent to be extracted (H ⁺ required amount) (mol / min).

[Comparative Example 1]
A high-purity nickel sulfate solution was produced in the same manner as in the above Examples except that the pH of the third exchange stage was controlled to 5.5 ± 0.1. The sulfuric acid consumed during that period was about 101% of the metal equivalent to be extracted.

[Comparative Example 2]
A high-purity nickel sulfate solution was produced in the same manner as in the above Examples except that the pH of the third exchange stage was controlled to 5.2 ± 0.1. The sulfuric acid consumed during that period was about 92% of the metal equivalent to be extracted.

As can be seen from the graph of FIG. 5 in which the amount of sulfuric acid consumed in Examples 1 and 2 above is divided by the equivalent of the metal to be extracted, the pH of the third exchange stage is controlled under the condition satisfying the requirements of the present invention. In Comparative Example 1 in which the pH of the third exchange stage was controlled by 5.5 ± 0.1 and Comparative Example 2 in which the pH of the third exchange stage was controlled by 5.2 ± 0.1 as compared with the above-mentioned Examples. The amount of sulfuric acid used increased by 16% and 8%, respectively.

Claims (5)

A method for producing a high-purity nickel sulfate aqueous solution from a crude nickel sulfate aqueous solution containing at least cobalt by a solvent extraction step using an acidic organic extractant.
In the solvent extraction step, the acidic organic extractant and the crude nickel sulfate aqueous solution are introduced into a countercurrent flow of the acidic organic extractant and the crude nickel sulfate aqueous solution into a multi-stage mixer settler type solvent extractor to perform a continuous extraction process, whereby the acidic organic extractant is previously used. It has an exchange stage in which the extracted nickel and cobalt in the crude nickel sulfate aqueous solution are exchanged and replaced, and the pH of the aqueous phase of the first stage before the last stage of the plurality of stages is set to 4. The feature is that the pH of the aqueous phase of the last stage is controlled to 2.5 to 4.0, and the pH of the aqueous phase of the other stages is controlled to 4.0 to 4.5, respectively. A method for producing an aqueous solution of nickel sulfate. The method for producing a nickel sulfate aqueous solution according to claim 1, wherein the plurality of stages are four stages. The solvent extraction step has a cleaning stage in front of the exchange stage, and a part of the organic after cleaning discharged from the cleaning stage is discharged from the cleaning stage in the third stage of the exchange stage. The method for producing a nickel sulfate aqueous solution according to claim 2, wherein the organic residue after washing is introduced into the first stage of the exchange stage. The method for producing a nickel sulfate aqueous solution according to any one of claims 1 to 3, wherein the pH is controlled by adding a sulfuric acid aqueous solution. The method for producing an aqueous nickel sulfate solution according to any one of claims 1 to 4, wherein the acidic organic extractant is mono-2-ethylhexyl 2-ethylhexylphosphonate.

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