JP6471912B2 - Method for producing high purity cobalt sulfate aqueous solution - Google Patents

Description

The present invention relates to a method for producing a high purity cobalt sulfate aqueous solution.
More specifically, the present invention relates to a method for producing a high purity cobalt sulfate aqueous solution from a mixed aqueous solution of nickel chloride and cobalt chloride.

Cobalt is widely used in industry as an alloying element for special steels and magnetic materials. The special steel is used for aerospace, generators, and tools because of its excellent wear resistance and heat resistance, and the magnetic material is used for small headphones, small motors, etc. by taking advantage of strong magnetism.
Furthermore, cobalt is used as a raw material for the positive electrode material of lithium ion secondary batteries. Recently, lithium ion secondary batteries are used for mobile information processing terminals such as automobiles, power storage, small personal computers and smartphones. The demand for secondary batteries continues to increase.

  Cobalt is often associated with nickel and copper as a mineral resource, and most of it is produced as a by-product of nickel smelting and copper smelting. The separation of impurities, including the beginning, is an important technical element.

For example, when recovering cobalt as a by-product in nickel hydrometallurgy, to obtain an aqueous solution containing nickel and cobalt, the raw material is leached or extracted into an aqueous solution using a mineral acid or an oxidizing agent, or subjected to a dissolution treatment. To do.
Nickel and cobalt contained in the obtained acidic aqueous solution are generally separated and recovered by a solvent extraction method using various organic extractants.

  For example, from a mixed aqueous solution of nickel chloride and cobalt chloride containing impurities obtained by leaching a nickel raw material containing cobalt using the oxidizing power of chlorine gas, a solvent extraction method using an amine-based extractant is used. Cobalt is separated as a cobalt chloride aqueous solution containing impurities, and after purifying the cobalt chloride aqueous solution containing impurities by the method disclosed in Patent Document 1, the cobalt chloride aqueous solution is subjected to electrowinning to obtain a product as electric cobalt The method of making it practical has been put into practical use.

By the way, when the use of cobalt is a raw material for a positive electrode material of a lithium ion secondary battery, a positive electrode material such as lithium cobaltate is produced by a solution-based reaction. It is desirable to be in the form of a crystal or an aqueous solution.
Furthermore, a cobalt sulfate aqueous solution is more desirable.

Conventionally, this cobalt sulfate aqueous solution was manufactured by once dissolving commercialized electric cobalt (metal cobalt) in the sulfuric acid aqueous solution again.
Furthermore, a cobalt sulfate crystal was produced by concentrating, crystallizing, dehydrating and drying an aqueous cobalt sulfate solution obtained by dissolving electrocobalt in an aqueous sulfuric acid solution.
However, the process of directly producing an aqueous cobalt sulfate solution is more efficient without going through an expensive electrowinning step.

By the way, a high-purity cobalt sulfate aqueous solution with a low content of calcium as an impurity is desirable for the cobalt sulfate aqueous solution as a raw material of the positive electrode material of the lithium ion secondary battery.
Therefore, according to the electrowinning method, cobalt containing no calcium can be obtained in the process of metallization by electrolytic reduction. In other words, calcium can be separated and removed by the electrowinning step, and a liquid purification method of a cobalt chloride aqueous solution for providing a test solution suitable for the electrowinning method is proposed in Patent Document 2. .

On the other hand, as a process for producing a cobalt sulfate aqueous solution having a low calcium concentration without passing through an electrowinning step, Patent Document 3 discloses a method for producing a cobalt sulfate solution by a solvent extraction method using phosphonic acid or phosphinic acid. Is disclosed.
If the method disclosed in Patent Document 3 is used, an aqueous cobalt chloride solution obtained by solvent extraction using an amine-based extractant can be converted into an aqueous cobalt sulfate solution.

However, when impurities are contained in the cobalt chloride aqueous solution, the impurities are extracted into phosphonic acid or phosphinic acid, so that a washing step of washing the organic solvent from which cobalt is extracted with the cobalt sulfate aqueous solution is required.
Furthermore, since impurities remain in the washed cobalt sulfate aqueous solution obtained in the cleaning step, a step for removing the impurities is also necessary.
Therefore, the repetition amount of cobalt, that is, the amount of cobalt that is not commercialized increases, and a great cost is required.

Patent Document 4 discloses a method for extracting and separating impurities in a cobalt solution into an organic solvent using a mixed organic solvent extractant composed of an organic phosphate type and an oxime type. In the method disclosed in No. 4, it is necessary to recover cobalt extracted with a solvent together with impurities, and a step of removing impurities from the recovered cobalt solution is required.
Furthermore, the separation efficiency of calcium from cobalt is not high, and some calcium is distributed to the cobalt solution.

  That is, in both methods of Patent Document 3 and Patent Document 4, since an aqueous cobalt solution containing impurities is generated, labor is required for the treatment and costs are increased.

JP2015-203134A Japanese Patent Laid-Open No. 2006-14164 JP 2012-153546 A Japanese Patent Laid-Open No. 11-050167

  Accordingly, the present invention was invented in view of the above-mentioned problems of the prior art, and a high-purity cobalt sulfate aqueous solution that is a cobalt sulfate aqueous solution having a low impurity concentration and high cobalt purity from a mixed aqueous solution of nickel chloride and cobalt chloride. A method for producing a high-purity cobalt sulfate aqueous solution, which does not generate an aqueous cobalt solution containing impurities, and can particularly efficiently obtain a high-purity cobalt sulfate aqueous solution not containing calcium at a low cost. The purpose is to provide.

  In order to achieve the above object, the inventors of the present invention particularly relate to a method for producing a high-purity cobalt sulfate aqueous solution free of these impurities from a mixed aqueous solution of nickel chloride and cobalt chloride containing calcium, manganese, iron, and copper. As a result of intensive studies, it was found that a high-purity cobalt sulfate aqueous solution can be efficiently produced by using a non-calcium alkaline slurry or an aqueous solution as a pH adjuster, and the present invention has been completed.

  That is, the first invention of the present invention is a method for producing a high-purity cobalt sulfate aqueous solution from a mixed aqueous solution of nickel chloride and cobalt chloride containing at least calcium, manganese, iron, and copper. (1) At least the calcium, manganese, Amine-based extraction step of obtaining an amine-based organic solvent from which cobalt, manganese, iron, and copper are extracted by subjecting a mixed aqueous solution of nickel chloride and cobalt chloride containing iron and copper to solvent extraction using an amine-based extractant (2) By bringing a weak acidic hydrochloric acid aqueous solution into contact with the amine organic solvent from which cobalt, manganese, iron, and copper have been extracted, cobalt in the amine organic solvent is removed from the weakly acidic hydrochloric acid from the amine organic solvent. An amine-based back-extraction step that back-extracts into an aqueous solution to obtain a cobalt chloride aqueous solution containing a small amount of manganese and copper; (3) An oxidizing agent and a non-calcium alkaline slurry or aqueous solution are added to a cobalt chloride aqueous solution containing a small amount of manganese and copper, and a redox potential and pH of 800 or more and less than 1050 mV (Ag / AgCl electrode standard) are set to 2.0. By adjusting to ˜3.0, a manganese oxide precipitate is produced and separated to obtain a cobalt chloride aqueous solution in which the manganese concentration is removed to 0.001 g / L or less, (4) the manganese is A sulfurizing agent and a non-calcium alkaline slurry or aqueous solution are added to the removed cobalt chloride aqueous solution, and the oxidation-reduction potential and pH of −100 or more and −50 mV or less (Ag / AgCl electrode standard) are 1.3 or more. By adjusting to 5 or less, a copper sulfide precipitate is generated and separated, and the manganese concentration is 0.001 g / L or less and the copper concentration is 0. Decoppering step for obtaining a cobalt chloride aqueous solution removed to 0005 g / L or less, (5) Using the cobalt chloride aqueous solution obtained in the step (4) as an aqueous phase, and using a non-calcium alkaline aqueous solution to adjust the pH of the aqueous phase Acidic phosphate-based extraction step of obtaining an acidic phosphate-based organic solvent having a cobalt concentration of 10 g / L or less, which is an organic phase from which cobalt has been extracted, by subjecting it to solvent extraction using an acidic phosphate-based extractant while adjusting the pH (6) The sulfuric acid in which the cobalt in the acidic phosphoric acid organic solvent is brought into contact with the acidic phosphoric acid organic solvent from which the cobalt has been extracted, thereby converting the cobalt in the acidic phosphoric acid organic solvent from the acidic phosphoric acid organic solvent into an aqueous phase. High-purity characterized by including an acidic phosphoric acid-based back-extraction step that back-extracts into an aqueous solution to obtain a high-purity cobalt sulfate aqueous solution having a cobalt / calcium weight ratio of 2500 or more. It is a manufacturing method of cobalt sulfate aqueous solution.

  The second invention of the present invention is a weakly acidic hydrochloric acid aqueous solution used in the amine-based back extraction process in the first invention, a non-calcium alkaline slurry or aqueous solution used in the demanganese process, and a non-calcium system used in the copper removal process. As a solvent for an alkaline slurry or aqueous solution, a non-calcium alkaline aqueous solution used in the acidic phosphoric acid-based extraction step, and a sulfuric acid aqueous solution used in the acidic phosphoric acid-based reverse extraction step, pure water or soft water having a calcium concentration of 2 mg / L or less And a high-purity cobalt sulfate aqueous solution having a cobalt / calcium weight ratio of 15000 or more in the acidic phosphoric acid-based back extraction step.

  The third aspect of the present invention is the flow rate ratio obtained by dividing the aqueous phase pH of the acidic phosphoric acid extraction step in the first and second inventions from 4.0 to 5.0 and the flow rate of the organic phase by the flow rate of the aqueous phase. (O / A) is 7 to 9, and the aqueous phase pH of the acidic phosphoric acid-based back extraction step is 1.5 to 1.8.

  A fourth invention of the present invention is a high purity cobalt sulfate aqueous solution characterized in that the amine extractant in the first to third inventions is a tertiary amine and the acidic phosphate extractant is an acidic phosphate ester. It is a manufacturing method.

  According to a fifth aspect of the present invention, in the acidic phosphoric acid system extraction step according to the first to fourth aspects, a multistage counter-current type solvent extraction device having two stages is used, and in the acidic phosphoric acid system back extraction process, two stages are used. A method for producing a high-purity cobalt sulfate aqueous solution characterized by using a multistage counter-current solvent extraction apparatus comprising:

  According to the method for producing a high-purity cobalt sulfate aqueous solution of the present invention, a high-purity cobalt sulfate aqueous solution not containing calcium can be efficiently obtained at low cost without generating a cobalt aqueous solution containing impurities.

It is a schematic flowchart of the manufacturing process of the high purity cobalt sulfate aqueous solution of this invention. It is a schematic flowchart of the manufacturing process of the conventional high purity cobalt sulfate aqueous solution.

  In the present invention, (1) cobalt, manganese, iron and copper are extracted by subjecting a mixed aqueous solution of nickel chloride and cobalt chloride containing at least calcium, manganese, iron and copper to solvent extraction using an amine-based extractant. (2) by bringing a weakly acidic aqueous hydrochloric acid solution into contact with the amine organic solvent from which cobalt, manganese, iron, and copper obtained in the amine extraction step are obtained. An amine-based back-extraction step in which cobalt in the amine-based organic solvent is back-extracted from the amine-based organic solvent into a weakly acidic hydrochloric acid aqueous solution to obtain a cobalt chloride aqueous solution containing a small amount of manganese and copper; An oxidizing agent and a non-calcium alkaline slurry or aqueous solution are added to a cobalt chloride aqueous solution containing a small amount of manganese and copper obtained in the extraction step, and 80 As described above, by adjusting the oxidation-reduction potential and pH of less than 1050 mV (Ag / AgCl electrode standard) to 2.0 to 3.0, manganese oxide precipitates are generated and separated, and the manganese concentration is 0.001 g / A demanganese step for obtaining a cobalt chloride aqueous solution removed to L or less, (4) a sulfurizing agent and a non-calcium alkaline slurry or an aqueous solution are added to the cobalt chloride aqueous solution from which manganese obtained in the demanganese step is removed; By adjusting the oxidation-reduction potential and pH of −100 to −50 mV (Ag / AgCl electrode standard) to 1.3 to 1.5, copper sulfide precipitates are generated and separated, and the manganese concentration Is obtained by the copper removal step of obtaining a cobalt chloride aqueous solution from which the copper concentration is removed to 0.001 g / L or less and the copper concentration to 0.0005 g / L or less, (5) By using the aqueous solution of cobalt chloride in the aqueous phase as a non-calcium alkaline aqueous solution and adjusting the pH of the aqueous phase to solvent extraction using an acidic phosphate extractant, An acidic phosphoric acid-based extraction step for obtaining an acidic phosphoric acid-based organic solvent having a cobalt concentration of 10 g / L or less, (6) a sulfuric acid aqueous solution in the acidic phosphoric acid-based organic solvent from which cobalt obtained in the acidic phosphoric acid-based extraction step has been extracted The high-purity cobalt sulfate aqueous solution having a cobalt / calcium weight ratio of 2500 or more is obtained by back-extracting cobalt in the acidic phosphate organic solvent from the acidic phosphate organic solvent into an aqueous sulfuric acid solution as an aqueous phase. The entire process is constituted by the steps (1) to (6) of the acidic phosphate-based back extraction step to obtain a non-calcium alkaline slurry or pH adjuster. A non-calcium alkaline aqueous solution is used.

  Further, preferably, a weakly acidic hydrochloric acid aqueous solution used in the amine-based back extraction step, a non-calcium alkaline slurry or non-calcium alkaline aqueous solution used in the demanganese step, a non-calcium alkaline slurry or non-calcium used in the copper removal step As a solvent for aqueous alkaline solutions, non-calcium alkaline aqueous solutions used in acidic phosphoric acid-based extraction processes, and sulfuric acid aqueous solutions used in acidic phosphoric acid-based reverse extraction processes, pure water or soft water with a calcium concentration of 2 mg / L or less is used. To do.

  In the present invention, in particular, it is difficult to completely separate from cobalt with an acidic phosphoric acid-based extractant, and it is contained in a neutralizing agent such as calcium hydroxide, and is also contained to some extent in general industrial water. Can be produced.

  Here, as an embodiment of the present invention, a case where a high purity cobalt sulfate aqueous solution is produced from a mixed aqueous solution of nickel chloride and cobalt chloride obtained by a nickel hydrometallurgical process will be described below as an example.

[Nickel hydrometallurgical process]
First, in nickel smelting, for example, nickel sulfide obtained by melting nickel sulfide ore in a blast furnace, nickel sulfide obtained by adding sulfur to nickel oxide ore and melting in an electric furnace, so-called dry type Nickel mats mainly composed of nickel sulfide such as Ni ₃ S ₂ obtained by a smelting method are produced.

  On the other hand, nickel oxide ore of low nickel grade is subjected to pressure acid leaching, and impurities such as iron are removed from the pressure acid leaching solution, and then, for example, hydrogen sulfide gas is converted into nickel ions and cobalt ions by wet sulfidation reaction. A mixed sulfide (hereinafter referred to as a mixed sulfide) containing nickel and cobalt whose main components are sulfides such as NiS obtained by blowing into the leachate contained is also produced.

As a method of refining nickel and cobalt using the above nickel mat and mixed sulfide as raw materials, nickel mat and mixed sulfide are leached using the oxidizing power of chlorine gas, and the extracted nickel ions and cobalt ions are electrolyzed. A method of commercializing as electric nickel and cobalt by sampling has been put into practical use.
In this method, mixed sulfide is repulped into an aqueous chloride solution and then chlorine gas is blown into the slurry to leach nickel and cobalt into the aqueous chloride solution to form a chlorine leachate. The leaching solution containing divalent copper chloro complex ions as an oxidizing agent is brought into contact with the crushed nickel mat, and the substitution reaction between copper and nickel is performed to replace nickel in the nickel mat with the chlorine leaching solution. Leached to produce a substitution leachate.

The substitution leaching final solution obtained by this substitution leaching is sent to a liquid purification step comprising a deironing step, an amine solvent extraction step, a deleading step, and a dezincing step.
First, in the iron removal step, by adding chlorine gas as an oxidizer and nickel carbonate slurry as a neutralizer to the substitution leaching final solution, a precipitate mainly composed of ferric hydroxide is generated. A deiron-free final solution that has been subjected to the treatment for removing iron in the substitution leach final solution is obtained.
Since the pH of the final solution during the reaction in this iron removal step is about 2.0 to 2.5, only iron is selectively removed from the substitution leaching final solution in this step.

The final iron removal liquid obtained in the iron removal step is a mixed aqueous solution of nickel chloride and cobalt chloride containing impurities such as calcium, manganese, iron, copper, and zinc.
In the next amine-based solvent extraction step, tri-normal-octylamine (TNOA), which is an amine-based extractant, is mixed and brought into contact with this final iron-free solution, so that cobalt, copper, zinc, and iron are extracted from the aqueous phase. It transfers to an organic phase and the process which obtains the extraction residual liquid (aqueous phase) containing nickel from which cobalt, copper, zinc, and iron were removed is performed.

  In the deleading process of the next process, as in the deironing process, chlorine gas is added as an oxidizing agent, nickel carbonate slurry is added as a neutralizing agent, and the nickel chloride solution that is the extraction residual liquid after extraction with an amine solvent is added. This is a deleaded final solution containing nickel from which lead has been removed as lead oxide, and the pH of the extraction residual liquid in the deleading process is controlled to 4-5. A precipitate is formed as a product.

The deleaded final solution after deleading is sent to a dezincing step, and in this dezincing step, a small amount of zinc chloro complex ion of about 0.1 mg / L remaining in the deleading final solution is weakly anionic. A nickel chloride aqueous solution from which impurities are removed by adsorption onto an ion exchange resin is obtained.
The nickel chloride aqueous solution from which impurities have been removed through the liquid purification step as described above is sent to the electrolysis step after pH adjustment, and electronickel is produced by electrowinning.

This method is simple and realizes efficient and economical production such as reusing chlorine gas generated by electrowinning for leaching.
Moreover, about the cobalt isolate | separated by the amine type | system | group solvent extraction process, the further impurity is removed by the process route different from nickel, and it is commercialized as an electric cobalt by electrowinning.

Here, a solvent extraction method for separating nickel and cobalt used in the present invention will be described.
As an organic extractant used for extraction, an amine-based extractant such as tri-normal-octylamine (TNOA) or an acidic phosphate ester-based extractant such as di- (2-ethylhexyl) phosphonic acid (D2EHPA) is used.

  Both amine-based extractants and acidic phosphate-based extractants have excellent nickel and cobalt separation performance, but in general, when anions are sulfate ions, phosphate-based acidic extractants are used. Is a substance that produces a complex ion of cobalt and minus, such as chloride ions, an amine extractant is used.

For example, in the case of a chloride aqueous solution having a sufficiently high chloride ion concentration, cobalt forms chloro complex ions, but nickel does not form chloro complex ions. It has a higher cobalt and nickel separation factor than the agent.
In addition, it has high separation characteristics from other impurities that do not generate chloro complex ions.
In addition, zinc, iron, and copper, which are more likely to form chloro complex ions than cobalt, can be controlled by adjusting the aqueous phase chloride ion concentration to an appropriate range when cobalt is back-extracted. The cobalt can be selectively back-extracted while remaining in the organic solvent.

On the other hand, since an acidic phosphate ester-based extractant extracts cations as they are, most impurities other than nickel can be extracted, for example, by selecting an extractant having appropriate characteristics.
Therefore, it is advantageous to employ an acidic phosphate ester extractant when selectively separating nickel from a mixed aqueous solution of nickel and cobalt, and an amine extractant when selectively separating cobalt. It becomes.

However, the separation of nickel and cobalt by solvent extraction using an amine-based extractant is limited when cobalt produces negative complex ions.
Further, as the complex ion Cl ^- for anions like they are extracted together, the complexing anion OH ^- except when it is undesirable substance in some cases there is a problem that accompany the cobalt.
In other words, when cobalt is selectively separated from a mixed aqueous solution of nickel and cobalt, solvent extraction with an amine-based extractant is appropriate. However, since the resulting cobalt aqueous solution is a cobalt chloride aqueous solution, a cobalt sulfate aqueous solution is obtained. In such a case, chloride ions in the cobalt chloride aqueous solution become an undesirable substance accompanying cobalt.

  As one embodiment of the present invention, cobalt was separated from an iron-free final solution in the nickel hydrometallurgical process that has been outlined so far by an amine solvent extraction step, and obtained in the amine solvent extraction step. The present invention can be applied to a method for producing high purity cobalt sulfate from a crude cobalt chloride aqueous solution containing a small amount of manganese and copper.

[Production process of high-purity cobalt sulfate aqueous solution of the present invention]
FIG. 2 is a schematic flow diagram of a conventional process for producing a high purity cobalt sulfate aqueous solution.
Conventionally, an aqueous cobalt sulfate solution was produced by dissolving electrolytic cobalt in an aqueous sulfuric acid solution.

On the other hand, FIG. 1 is a schematic flow diagram of the production process of the high purity cobalt sulfate aqueous solution of the present invention.
The present invention is a process for directly producing an aqueous cobalt sulfate solution without going through an expensive electrowinning step, but does not contain calcium, which is an element that is difficult to remove without going through an electrowinning step, This is a process for producing a high purity cobalt sulfate aqueous solution.

The manufacturing process of the high purity cobalt sulfate aqueous solution of this invention is as above-mentioned. (1) Amine system extraction process, (2) Amine system back extraction process, (3) Demanganese process, (4) Decoppering process, (5 It consists of an acidic phosphoric acid-based extraction step and (6) an acidic phosphoric acid-based back extraction step.
Here, (1) amine-based extraction step and (2) amine-based back extraction step are amine-based solvent extraction steps, (5) acidic phosphoric acid-based extraction steps and (6) acidic phosphoric acid-based back extraction steps are acidic phosphoric acid. The system solvent extraction step will be collectively described.

(1) Amine solvent extraction step The amine solvent extraction step comprises at least an amine extraction step and an amine back extraction step.
For example, an amine cleaning step may be provided between the amine extraction step and the amine back extraction step.

  In the method, the solvent extraction is preferably a multi-stage counter-current method, for example, using a mixer-settler type extraction device. In the embodiment used for the description of the present invention, the amine-based extraction step has three steps, and the amine-based washing step also includes The three-stage, amine-based back extraction step is also composed of three stages.

The extraction agent is preferably a tertiary amine, more preferably tri-normal-octylamine (TNOA) or tri-iso-octylamine (TIOA).
An aromatic hydrocarbon is used as a diluent for the extractant.
Further, in order to adjust the viscosity of the organic phase, the concentration of the extractant in the organic phase (mixture of the extractant and the diluent) is set to 20 to 40% by volume.

  The tertiary amine used for the extractant has the ability to extract metal chloro complex ions as shown in the formulas (2) and (2 ′) by adding and activating hydrochloric acid according to the following formula (1). Moreover, it has excellent nickel and cobalt separation characteristics.

M in the above formula (2) represents a metal species forming a chloro complex ion such as Co, Cu, Zn, etc., but the form of the chloro complex ion differs depending on the valence of the metal ion. In this case, the above equation (2 ′) is followed. R represents an alkyl group.
In the formula (1), formula (2), and formula (2 ′), “:” represents a lone pair of nitrogen atoms.

In the amine-based extraction step, metal species that form chloro complex ions such as Co, Cu, Zn, and Fe are extracted into the organic phase by the reaction represented by Formula (2) or Formula (2 ′), and the metal element An amine carrying a chloro complex ion is produced.
Since nickel does not form chloro complex ions, it remains in the extraction residual liquid and is separated. Calcium also does not form chloro complex ions and can be separated from cobalt. In addition, manganese forms chloro complex ions, but its stability is lower than cobalt, so some is extracted into the organic phase.
Therefore, if the aqueous solution of nickel chloride contains a metal that is more likely to form chloro complex ions than cobalt, that is, chloro complex ions of copper, zinc, iron, etc. The metal is also extracted.

  On the other hand, in the amine-based back-extraction step, the organic phase after extraction, that is, an amine carrying cobalt chloro complex ions is brought into contact with a weak acidic hydrochloric acid aqueous solution, whereby cobalt is dissolved in the aqueous phase according to the following formula (3). Can be detached.

  In the amine-based extraction step, the chloride ion concentration in the mixed aqueous solution of nickel chloride and cobalt chloride containing impurities such as calcium, manganese, iron, copper, zinc, etc., which is the extraction starting solution, is as high as 200 to 250 g / L. Yes, because cobalt forms a stable chloro complex ion, cobalt is extracted into the organic phase.

On the other hand, in the amine-based back extraction step, the chloride ion concentration in the aqueous phase is low and is 70 to 100 g / L.
Therefore, at the chloride ion concentration of 70 to 100 g / L, cobalt chloro complex ions in the organic phase become unstable, and cobalt is back-extracted into the aqueous phase.
Furthermore, iron, copper, and zinc remain in the organic phase because the chloro complex ion is stable even at a chloride ion concentration of 70 to 100 g / L.
A part of manganese extracted in the amine-based extraction step elutes in the aqueous phase in the amine-based back extraction step.

Thus, in the amine-based solvent extraction step, cobalt can be extracted and back-extracted, that is, separated and recovered from nickel, by adjusting the chloride ion concentration in the aqueous phase to a specific range.
Furthermore, separation from cobalt and calcium that does not form chloro complex ions, and separation from iron, copper, and zinc that form chloro complex ions more easily than cobalt can be performed.

Preferably, pure water or soft water having a calcium concentration of 2 mg / L or less is used as the solvent for the weakly acidic hydrochloric acid aqueous solution used in the amine-based back extraction step.
This treatment is for avoiding re-mixing of calcium into the back extract from which calcium has been separated, that is, an aqueous cobalt chloride solution.

(2) Demanganese process The back extract obtained in the amine solvent extraction process, that is, the crude cobalt chloride aqueous solution, still contains trace amounts of manganese and copper.
In the demanganese process, an oxidizing agent is added to a cobalt chloride aqueous solution containing manganese and copper, and an oxidation-reduction potential (ORP: Ag / AgCl electrode standard, hereinafter all oxidation-reduction potential values are based on an Ag / AgCl electrode standard). Is adjusted to 800 mV or more and less than 1050 mV, and the pH is adjusted to 2.0 to 3.0 to produce and separate manganese oxide precipitate, and the manganese chloride is removed to 0.001 g / L or less. This is a step of obtaining an aqueous cobalt solution.

  Manganese in the aqueous solution of cobalt chloride is separated and removed from the aqueous solution by generating an oxide precipitate by a reaction in a highly oxidizing atmosphere with an oxidizing agent. This reaction in a highly oxidizing atmosphere can be expressed by the following formula (4), for example, when chlorine gas is used as an oxidizing agent and cobalt carbonate is used for pH adjustment.

In this demanganese process, the oxidation-reduction potential of the cobalt chloride aqueous solution is adjusted to 800 mV or more and less than 1050 mV, and the pH is set to 2.0 in order to sufficiently remove manganese as an oxide precipitate and suppress the coprecipitation of cobalt. It is important to adjust to ~ 3.0.
Here, the pH of the cobalt chloride aqueous solution separated and recovered in the amine solvent extraction step is less than 2.0, and an alkali or an alkaline aqueous solution is used as a pH adjuster.

In the present invention, a non-calcium alkaline slurry or an aqueous solution is used as a pH adjuster in order to produce a high-purity cobalt sulfate aqueous solution that does not contain calcium.
Examples of the non-calcium alkaline slurry or aqueous solution include an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution, but those containing calcium such as slaked lime slurry and calcium carbonate slurry cannot be used.

Preferably, pure water or soft water having a calcium concentration of 2 mg / L or less is used as the solvent for the non-calcium alkaline slurry or aqueous solution. Furthermore, it is desirable to use the cobalt carbonate slurry described above as the alkali.
Carbonic acid radicals in cobalt carbonate are converted into carbon dioxide gas by the reaction as shown in formula (4) and dissipated into the air. Therefore, impurities other than cobalt and chloride ions are mixed in the cobalt chloride aqueous solution obtained in the demanganese process. It is because there is no fear of doing.

(3) Copper removal step In the copper removal step, a sulfurizing agent is added to the cobalt chloride aqueous solution from which the manganese obtained in the manganese removal step is removed, and the oxidation-reduction potential (ORP) of the cobalt chloride aqueous solution is -100 to -50 mV. And adjusting the pH to 1.3 to 1.5 to produce and separate copper sulfide precipitate from the cobalt chloride aqueous solution, the manganese concentration is 0.001 g / L or less, the copper concentration is 0.0005 g / L. This is a step of obtaining an aqueous cobalt chloride solution removed below.

  Copper in the cobalt chloride aqueous solution is removed from the aqueous solution by forming a copper sulfide precipitate according to the following formula (5).

In the copper removal step, adjusting the oxidation-reduction potential (ORP) of the cobalt chloride aqueous solution to −100 to −50 mV and the pH to 1.3 to 1.5 sufficiently removes copper as a sulfide and It is important to suppress coprecipitation.
Moreover, since an acid produces | generates with reaction as shown to the said Formula (5), an alkali or alkaline aqueous solution is used as a pH adjuster also in a copper removal process.

In the present invention, a non-calcium alkaline slurry or an aqueous solution is used as a pH adjuster as in the demanganese process.
Preferably, pure water or soft water having a calcium concentration of 2 mg / L or less is used as the solvent for the non-calcium alkaline slurry or aqueous solution. Furthermore, it is desirable to use the cobalt carbonate slurry described above as the alkali.

(4) Acidic phosphoric acid-based solvent extraction step The acidic phosphoric acid-based solvent extraction step comprises at least an acidic phosphoric acid-based extraction step and an acidic phosphoric acid-based back extraction step.

For example, in the acidic phosphoric acid extraction process, fine droplets of cobalt chloride aqueous solution may be mixed in the organic phase, so in order to prevent chloride ions from mixing into the cobalt sulfate aqueous solution, An acidic phosphate washing step may be provided between the extraction step and the acidic phosphate back extraction step.
Specifically, the solvent extraction is performed using a multistage countercurrent system. For example, a mixer-settler type extraction device is used, and in the embodiment used in the description of the present invention, a multistage counter-current method is employed in which the acidic phosphoric acid-based extraction step is two stages and the acidic phosphoric acid-based back extraction process is also two stages. doing.

The extractant is preferably an acidic phosphate, more preferably mono-2-ethylhexyl 2-ethylhexylphosphonate (product name: PC-88A) or di- (2-ethylhexyl) phosphonic acid (D2EHPA). .
An aromatic hydrocarbon is used as a diluent for the extractant.
In order to adjust the viscosity of the organic phase, the concentration of the extractant in the organic phase (extractant and diluent) is 20 to 40% by volume.

The acidic phosphoric acid ester of the acidic phosphoric acid-based extractant is obtained by extracting cobalt from the cobalt chloride aqueous solution obtained in the above copper removal step according to the following formula (6), and having a cobalt concentration of 10 g / L or less. A system organic solvent is formed. In the process, acid is generated.
Here, R in the above formula (6) represents the whole organic compound containing a functional group.

Since it is necessary to maintain an appropriate pH in order to extract cobalt, an alkali or an alkaline aqueous solution is used as a pH adjuster in the acidic phosphoric acid extraction process.
In the present invention, a non-calcium aqueous alkali solution is used as a pH adjuster. As the non-calcium alkaline aqueous solution, an aqueous sodium hydroxide solution can be used.
Preferably, pure water or soft water having a calcium concentration of 2 mg / L or less is used as a solvent for the non-calcium alkaline aqueous solution.

The pH of the aqueous phase in the acidic phosphoric acid system extraction step is preferably 4.0 to 5.0.
When the pH is less than 4.0, the extraction rate of cobalt decreases, and thus the processing cost for recovering cobalt from the extraction residual liquid in the acidic phosphoric acid system extraction step increases. When the pH exceeds 5.0, cobalt forms a hydroxide precipitate, which causes a decrease in the extraction rate of cobalt in the same manner as described above. Further, the generated solid (precipitate) is separated into oil and water in the mixer settler. Cause defects.

In the acidic phosphoric acid-based back extraction step, according to the following formula (7), the extracted organic phase is brought into contact with an aqueous sulfuric acid solution, and the cobalt extracted in the organic solvent is back-extracted to obtain a cobalt / calcium weight ratio. Obtains a high-purity cobalt sulfate aqueous solution of 2,500 or more.
In other words, in the acidic phosphoric acid solvent extraction step, bath conversion from an aqueous cobalt chloride solution to an aqueous cobalt sulfate solution is performed. At the same time, since the organic solvent extractant is regenerated, the regenerated organic solvent is repeated for use in the acidic phosphoric acid extraction process.

The pH of the aqueous phase in the acidic phosphoric acid-based back extraction step is preferably 1.5 to 1.8.
If the pH is less than 1.5, impurities may be back extracted into the aqueous phase. On the other hand, when the pH exceeds 1.8, the amount of back extraction of cobalt into the aqueous phase decreases. Furthermore, in solvent extraction using acidic phosphate ester, since hydrogen ions are involved in the extraction reaction, the extraction rate varies depending on the pH value.

The extraction rate varies depending on the metal, and is easily extracted in the order of Fe>Zn>Cu>Mn>Ca>Co>Mg> Ni.
That is, if the pH is increased, the metal on the Ni side and more difficult to be extracted can be extracted, and if the pH is lowered, the more easily extracted metal on the Fe side is prevented from being extracted. be able to.

  The cobalt chloride aqueous solution obtained in the copper removal step does not contain Fe, Zn, Cu, or Mn, but as a pH adjuster in the manganese removal step or copper removal step, for example, a calcium-based alkaline slurry such as slaked lime slurry. Or when aqueous solution is used, Ca will be contained in the cobalt chloride aqueous solution.

Since this calcium is more easily extracted than cobalt, and furthermore, the extraction behavior is close to that of cobalt, a part of the extracted calcium is back-extracted together with cobalt in the acidic phosphoric acid-based back extraction process, so that the obtained cobalt sulfate It will be mixed into the aqueous solution.
Therefore, in the present invention, (1) amine extraction step, (2) amine back extraction step, (3) demanganese step, (4) copper removal step, (5) acidic phosphate extraction step, (6) In the entire process composed of the acidic phosphate-based back extraction step, a non-calcium alkaline slurry or an aqueous solution is used as a pH adjuster.

  Further, preferably, a weakly acidic hydrochloric acid aqueous solution used in the amine-based back extraction step, a non-calcium alkaline slurry or aqueous solution used in the demanganese step, a non-calcium alkaline slurry or aqueous solution used in the copper removal step, and acidic phosphoric acid As the solvent of the sulfuric acid aqueous solution used in the system back extraction step, pure water or soft water having a calcium concentration of 2 mg / L or less is used.

Moreover, it is desirable that the flow rate ratio (O / A) obtained by dividing the flow rate of the organic phase in the acidic phosphoric acid extraction step by the flow rate of the aqueous phase is 7 to 9.
Here, it is preferable to manage the cobalt concentration in the organic phase (extractant and diluent) at 10 g / L or less. When it exceeds 10 g / L, the viscosity of the organic phase increases and the oil-water separation performance decreases.

On the other hand, the higher the cobalt concentration in the cobalt chloride aqueous solution obtained in the above copper removal step, the more efficient, and the operation is actually performed at about 70 to 90 g / L.
Thus, although it is efficient to extract cobalt up to the upper limit of the extraction ability of the extractant, it is preferable to set O / A to 7 or more so that the cobalt concentration in the organic phase is 10 g / L or less.

In general, with respect to O / A, the smaller the flow rate of the organic phase, the smaller the size of the entire solvent extraction device including the pump and relay tank, which is advantageous in terms of equipment cost and operation cost. Become.
Therefore, if O / A is increased more than necessary, it is disadvantageous in terms of equipment cost and operation cost, so it is preferable that O / A be 9 or less.

  The present invention includes (1) amine extraction step, (2) amine back extraction step, (3) demanganese step, (4) decoppering step, (5) acidic phosphoric acid extraction step, (6) acidic phosphorus This is a high-purity cobalt sulfate production method composed of an acid-based back extraction step. For calcium, which is difficult to separate in the steps (2) to (6), a non-calcium alkaline slurry or aqueous solution is used as a pH adjuster. More preferably, as water used in each step, mixing of calcium is prevented by using pure water or soft water having a calcium concentration of 2 mg / L or less.

  As a result, a cobalt sulfate aqueous solution having a cobalt to calcium weight ratio (a value obtained by dividing cobalt weight by calcium weight) of 15000 or more while maintaining the cobalt extraction rate in the acidic phosphoric acid-based extraction step at 99.8% or more. Can be manufactured.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, the range of this invention is not specifically limited by description of a present Example and a comparative example.

The final iron removal liquid obtained in the deironing step in the nickel hydrometallurgical process was treated at a flow rate of 100 L / min in the amine solvent extraction step.
The composition of the iron removal final solution is as follows: Ni concentration is 180 g / L, Co concentration is 7.5 g / L, Ca concentration is 0.6 g / L, Cu concentration is 0.03 g / L, Fe concentration is 0.02 g / L. The Mn concentration was 0.005 g / L.

In the amine-based solvent extraction process, a mixer-settler type extraction device was used. The amine-based extraction process had three stages, the amine-based cleaning process had three stages, and the amine-based back-extraction process had three stages.
Tri-normal-octylamine (TNOA) was used as the extractant, Teclean N-20 manufactured by JX Nippon Mining & Energy was used as the diluent, and the extractant concentration in the organic solvent (mixture of extractant and diluent) was 20 An organic solvent diluted to volume% was used.

In the amine-based back extraction step, back extraction was performed with a dilute hydrochloric acid aqueous solution diluted with soft water.
The composition of the back-extracted solution is as follows: Co concentration is 70 g / L, Ca concentration is 0.002 g / L, Cu concentration is 0.2 g / L, Fe concentration is 0.001 g / L, and Mn concentration is 0.01 g / L. there were.

Next, the back extract obtained in the amine solvent extraction step was treated in the demanganese step.
In the demanganese process, the oxidation-reduction potential was adjusted to less than 800 to 1050 mV, and the pH was adjusted to 2.0 to 3.0.
Chlorine gas was blown as an oxidizing agent, and a soda ash aqueous solution in which soda ash was dissolved in soft water was added as a pH adjuster. Thereafter, the manganese removal treatment liquid was subjected to solid-liquid separation with a filter press to obtain a manganese removal final solution, which was supplied to the copper removal step.

In the copper removal step, the redox potential was adjusted to −100 to −50 mV, and the pH was adjusted to 1.3 to 1.5.
Hydrogen sulfide gas was blown in as a sulfiding agent, and a soda ash aqueous solution in which soda ash was dissolved in soft water was added as a pH adjuster. Thereafter, the copper removal treatment liquid was subjected to solid-liquid separation with a filter press to obtain a copper removal final liquid.

The copper removal final solution was treated at a flow rate of 11 L / min in the acidic phosphoric acid solvent extraction step.
In the acidic phosphoric acid-based solvent extraction process, a mixer-settler type extraction device is used, the acidic phosphoric acid-based extraction process (extraction stage), the acidic phosphoric acid-based washing process (washing stage), the acidic phosphoric acid-based back extraction process (reverse) The number of extraction stages) was changed according to each operating condition shown in Table 1, and was set to 1 to 2 extraction stages, 0 or 3 washing stages, and 2 back extraction stages.

Using Daihachi Chemical Industry Co., Ltd. PC-88A as the extractant and JX Nippon Mining & Energy Corporation Teclean N-20 as the diluent, the extractant concentration in the organic solvent (mixture of extractant and diluent) is An organic solvent diluted to 20% by volume was used.
As a pH adjuster, a 200 g / L aqueous sodium hydroxide solution was used.

As shown in Table 1, the operating conditions were the conditions of 6 cases in which the aqueous phase pH of the acidic phosphoric acid system extraction step was changed to 3.5 to 5.0, and O / A was changed to 7.0 and 8.8. Operated.
The diluted water of the caustic soda aqueous solution and the sulfuric acid aqueous solution was soft water for RUN1 to RUN4, and industrial water for RUN5 and RUN6.

The calcium concentration of industrial water was 0.012 g / L.
As evaluation items for each operating condition, the cobalt extraction rate was selected for the actual yield, the chemical solution usage was selected for the cost index, and the Co / Ca concentration ratio of the cobalt sulfate aqueous solution was selected for the quality index.
The Co and Ca concentrations in the liquid were measured by ICP emission spectroscopy.

The Co / Ca concentration ratio of the cobalt sulfate aqueous solution obtained with RUN1 was as high as 20000 or more at 20106, but the cobalt extraction rate remained at 97.14% by operating with one extraction stage.
In RUN2, in order to reduce cobalt loss, the number of extraction stages was increased from one to two, and low pH operation was performed.
As a result, the cobalt extraction rate fell to 95.00% because pH was 4 or less.

  In RUNs 3 and 4, the extraction stage was set to two stages and the operating pH was controlled to the same level as RUN1, so that the cobalt extraction rate reached 99.99% and 99.9% or more, and the cobalt sulfate aqueous solution Co / Ca concentration The ratio was over 15000.

In RUN5, instead of the soft water used in RUN1 to 4, industrial water with a calcium concentration of 0.012 g / L is used to perform an amine solvent extraction process, a demanganese process, a copper removal process, and an acidic phosphoric acid solvent extraction process. And an aqueous cobalt sulfate solution was produced.
As a result, although the cobalt extraction rate was 99.93% and 99.9% or more, the cobalt sulfate aqueous solution Co / Ca concentration ratio was 2646, which was lower than RUN1-4.

  In RUN6, instead of the soft water used in RUN1 to 4, industrial water with a calcium concentration of 0.012 g / L was used to carry out the operations of the amine-based solvent extraction process, the demanganese process, and the copper removal process. Obtained.

In the acidic phosphoric acid solvent extraction step, three washing stages were installed between the extraction stage and the back extraction stage, and the organic phase after extraction was washed with a high purity cobalt sulfate aqueous solution by a multi-stage countercurrent system.
As the washing start liquid, an aqueous cobalt sulfate solution was used in which 32% of the back-extraction stage aqueous phase was extracted and the cobalt concentration was adjusted to 50 g / L.
As a result, the cobalt extraction rate was 99.9% or more, but the cobalt sulfate aqueous solution Co / Ca concentration ratio was 8333, which was lower than that of RUN1 to RUN4.

(Comparative Example 1)
A high purity cobalt sulfate aqueous solution was manufactured by dissolving electric cobalt in a sulfuric acid aqueous solution in accordance with the schematic flow of the manufacturing process of the conventional high purity cobalt sulfate aqueous solution shown in FIG.
The operating conditions of the amine-based extraction process, the amine-based back extraction process, the demanganese process, and the copper removal process were as follows: calcium hydroxide slurry was used as the pH adjuster, weak acidic hydrochloric acid aqueous solution used in the amine-based back extraction process, Example 1 was the same as Example 1 except that industrial water having a calcium concentration of 0.012 g / L was used as dilution water for the calcium hydroxide slurry used in the manganese process and the calcium hydroxide slurry used in the copper removal process.

In the dezincification step, the cobalt chloride aqueous solution obtained in the decopperization step is passed through an ion exchange resin tower packed with 5 m ³ of a weakly basic anion exchange resin (Amberlite IRA96SB manufactured by Organo), thereby obtaining cobalt chloride. Zinc in the aqueous solution was removed by adsorption.

In the electrowinning process, an insoluble anode in which a titanium plate is coated with iridium oxide is used, and a thin plate of pure metal cobalt having a width of 0.8 m, a height of 1 m, and 5 to 7 kg per sheet is used as a cathode. Energization was performed for about 8 days at a current density of ˜260 A / m ² .

  In the sulfuric acid dissolution step, 240 to 250 g / L sulfuric acid aqueous solution is added to a dissolution tank charged with about 3 t of electric cobalt cut to 100 mm × 100 mm × 12.5 mm, and heated to 90 ° C. with steam. Thus, a high purity cobalt sulfate aqueous solution was produced.

In Comparative Example 1, the total cost of electricity, steam, chemicals, etc. per 1 ton of cobalt was 1.34 times that of RUN3 of Example 1.
Moreover, in the comparative example 1, when the energization time of about 8 days was taken into consideration, the number of days required for the nickel raw material to become a high-purity cobalt sulfate aqueous solution was about three times that of RUN3 of Example 1.

(Comparative Example 2)
Use of calcium hydroxide slurry as pH adjuster in demanganese process and copper removal process, weakly acidic hydrochloric acid aqueous solution used in amine-based back extraction process, calcium hydroxide slurry used in demanganese process, and copper removal process RUN3 of Example 1 except that the calcium hydroxide slurry used, the sodium hydroxide aqueous solution used in the acidic phosphoric acid system extraction step, and industrial water having a calcium concentration of 0.012 g / L were used as dilution water of the sulfuric acid aqueous solution. Under the same conditions, a high purity cobalt sulfate aqueous solution was produced.
As a result, the Co / Ca concentration ratio of the obtained aqueous cobalt sulfate solution was 152.

Claims (5)

In a method for producing a high-purity cobalt sulfate aqueous solution from a mixed aqueous solution of nickel chloride and cobalt chloride containing at least calcium, manganese, iron and copper,
(1) An amine from which cobalt, manganese, iron, and copper are extracted by subjecting a mixed aqueous solution of nickel chloride and cobalt chloride containing at least calcium, manganese, iron, and copper to solvent extraction using an amine-based extractant. An amine-based extraction step to obtain an organic solvent,
(2) By bringing a weak acidic hydrochloric acid aqueous solution into contact with an amine organic solvent from which cobalt, manganese, iron, and copper have been extracted, cobalt in the amine organic solvent is converted from the amine organic solvent to the weak acidic hydrochloric acid aqueous solution. An amine-based back-extraction step to obtain a cobalt chloride aqueous solution containing trace amounts of manganese and copper,
(3) An oxidizing agent and a non-calcium alkaline slurry or aqueous solution are added to the cobalt chloride aqueous solution containing a small amount of manganese and copper, and the oxidation-reduction potential and pH of 800 or more and less than 1050 mV (Ag / AgCl electrode standard) are set. Demanganese step of obtaining an aqueous cobalt chloride solution in which manganese oxide precipitate is generated and separated by adjusting to 2.0 to 3.0 to remove manganese concentration to 0.001 g / L or less,
(4) A sulfurizing agent and a non-calcium alkaline slurry or aqueous solution are added to the cobalt chloride aqueous solution from which manganese has been removed, and the oxidation-reduction potential and pH of -100 or more and -50 mV or less (Ag / AgCl electrode standard) are set to 1. .3 or more and 1.5 or less to produce a copper sulfide precipitate, which is separated and removed with a manganese concentration of 0.001 g / L or less and a copper concentration of 0.0005 g / L or less. A copper removal step to obtain an aqueous cobalt solution,
(5) Using the cobalt chloride aqueous solution obtained in the step (4) as an aqueous phase, subjecting it to solvent extraction using an acidic phosphoric acid-based extractant while adjusting the pH of the aqueous phase with a non-calcium alkaline aqueous solution. An acidic phosphoric acid-based extraction step for obtaining an acidic phosphoric acid-based organic solvent having a cobalt concentration of 10 g / L or less, which is an organic phase from which cobalt has been extracted,
(6) The sulfuric acid aqueous solution in which cobalt in the acidic phosphoric acid organic solvent is brought into an aqueous phase from the acidic phosphoric acid organic solvent by bringing the sulfuric acid aqueous solution into contact with the acidic phosphoric acid organic solvent from which the cobalt has been extracted. An acidic phosphate-based back extraction step to obtain a high purity cobalt sulfate aqueous solution having a cobalt / calcium weight ratio of 2500 or more,
A method for producing a high-purity cobalt sulfate aqueous solution, comprising: Weakly acidic hydrochloric acid aqueous solution used in the amine-based back extraction step,
A non-calcium alkaline slurry or an aqueous solution used in the demanganese step,
A non-calcium alkaline slurry or aqueous solution used in the copper removal step,
A non-calcium alkaline aqueous solution used in the acidic phosphoric acid-based extraction step;
And as a solvent of sulfuric acid aqueous solution used in the acidic phosphoric acid-based back extraction step,
A pure water or soft water having a calcium concentration of 2 mg / L or less is used, and a high-purity cobalt sulfate aqueous solution having a cobalt / calcium weight ratio of 15000 or more is obtained in the acidic phosphate-based back extraction step. 2. A method for producing a high-purity cobalt sulfate aqueous solution according to 1. The aqueous phase pH in the acidic phosphoric acid system extraction step is 4.0 to 5.0, and the flow rate ratio (O / A) obtained by dividing the flow rate of the organic phase by the flow rate of the aqueous phase is 7 to 9,
The method for producing a high purity cobalt sulfate aqueous solution according to claim 1 or 2, wherein the aqueous phase pH in the acidic phosphoric acid-based back extraction step is 1.5 to 1.8.   The said amine type extractant is a tertiary amine, and the said acidic phosphoric acid type extractant is acidic phosphate ester, The manufacture of the high purity cobalt sulfate aqueous solution of any one of Claims 1-3 characterized by the above-mentioned. Method. In the acidic phosphoric acid-based extraction step, a multistage countercurrent solvent extraction apparatus having two stages is used,
5. The method for producing a high-purity cobalt sulfate aqueous solution according to claim 1, wherein the acidic phosphoric acid-based back extraction step uses a two-stage multistage countercurrent solvent extraction apparatus.

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