JP6241617B2 - Method for producing cobalt powder - Google Patents

Description

  The present invention relates to a method for producing a fine cobalt powder that can be used as a seed crystal from a solution containing a cobalt sulfate ammine complex, and is particularly applicable to the treatment of an intermediate solution in a process generated from a wet cobalt smelting process. .

  As a method for producing fine cobalt powder, an atomizing method for obtaining fine powder by dispersing molten cobalt in gas or water, or volatilizing cobalt as shown in Patent Document 1 and reducing in a gas phase A dry method such as a CVD method for obtaining cobalt powder is known.

In addition, as a method for producing cobalt powder by a wet process, a method using a reducing agent as shown in Patent Document 2 or a cobalt solution in a reducing atmosphere at a high temperature as shown in Patent Document 3 There is a spray pyrolysis method in which cobalt powder is obtained by a thermal decomposition reaction by spraying.
However, these methods are expensive because they require expensive reagents and a large amount of energy.

  On the other hand, as shown in Non-Patent Document 1, a method of supplying cobalt gas to a cobalt sulfate ammine complex solution to reduce cobalt ions in the complex solution to obtain cobalt powder is industrially inexpensive and useful. . However, the cobalt powder particles obtained by this method are easily coarsened, and it has been difficult to produce a fine powder that can be used as a seed crystal.

  In particular, when generating and growing particles from an aqueous solution, a small amount of fine crystals called seed crystals are allowed to coexist in small quantities, a reducing agent is supplied thereto, and seed crystals are grown to obtain a powder having a predetermined particle size. The method is used. The seed crystal used in this method is often obtained by pulverizing a product, etc., but it is time consuming and leads to an increase in cost because the yield is reduced. In addition, seed crystals having an optimum particle size and properties are not necessarily obtained by pulverization, and a method for stably obtaining seed crystals has been demanded.

JP-A-2005-505695 JP 2010-242143 A Japanese Patent No. 4286220

“The Manufacture and properties of Metal powder produced by the gaseous reduction of the aquatic solutions”, Powder metallurgy, No. 1/2 (58).

  Under such circumstances, the present invention provides a method for producing a fine cobalt powder that becomes a seed crystal suitable for producing cobalt powder from a solution containing a cobalt ammine sulfate complex.

The first invention of the present invention that solves such problems is a solution containing a cobalt sulfate ammine complex in a shape having no corners such as a sphere or ellipse having a diameter of 0.1 to 3 mm insoluble in the solution , Cobalt contained in the mixed slurry by adding insoluble solids from which surface debris has been removed to form a mixed slurry, and charging the mixed slurry into the reaction tank and then blowing hydrogen gas into the mixed slurry. A reduction / precipitation process in which complex ions are reduced to form cobalt precipitates on the insoluble solid surface, and a separation process in which cobalt precipitates on the insoluble solid surface are separated from the insoluble solid surface to form cobalt powder. It is a manufacturing method of cobalt powder characterized by producing cobalt powder in order.

  2nd invention of this invention is a manufacturing method of cobalt powder characterized by the ammonium sulfate density | concentration in the solution containing the cobalt sulfate ammine complex in 1st invention being the range of 10-500 g / L.

  A third aspect of the present invention is a cobalt powder characterized in that the cobalt concentration in the solution containing the cobalt ammine sulfate complex in the first and second aspects is 50 g / L or more and 100 g / L or less. It is a manufacturing method.

  A fourth invention of the present invention is a method for producing cobalt powder, characterized in that the temperature of the mixed slurry at the time of blowing hydrogen gas in the reduction step of the first to third inventions is 150 to 200 ° C. .

  The fifth aspect of the present invention is characterized in that the pressure in the gas phase portion in the reaction tank when hydrogen gas is blown in the reduction steps of the first to fourth aspects is in the range of 1.0 to 4.0 MPa. It is a manufacturing method of cobalt powder made into.

  According to a sixth aspect of the present invention, the insoluble solid in the first to fifth aspects is a combination of one or more selected from cobalt, alumina, zirconia, iron, and silica. It is the manufacturing method of the cobalt powder characterized.

  According to the present invention, it is possible to provide a method for producing a fine cobalt powder optimal for a seed crystal used for producing a cobalt powder more economically and efficiently from a cobalt sulfate ammine complex solution using hydrogen gas. To do.

It is a manufacturing flow figure of the manufacturing method of cobalt powder concerning the present invention. 2 is an SEM image showing an appearance of cobalt powder generated in Example 1. FIG.

The present invention produces cobalt powder by blowing hydrogen gas into a slurry of a mixed slurry formed by adding an insoluble solid insoluble in this solution to the cobalt sulfate ammine complex solution, or the insoluble solid and a dispersant. It is the manufacturing method of the cobalt powder characterized by these.
Hereinafter, the manufacturing method of the cobalt powder of this invention is demonstrated with reference to the manufacturing flowchart shown in FIG.

[Cobalt sulfate ammine complex solution]
The cobalt sulfate ammine complex solution used in the present invention is not particularly limited, but one or a mixture selected from cobalt and cobalt mixed sulfide, crude cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt carbonate, cobalt powder and the like. Cobalt leachate (solution containing cobalt) obtained by dissolving cobalt-containing materials such as industrial intermediates composed of sulfuric acid or ammonia, and subjecting it to liquid purification processes such as solvent extraction, ion exchange, and neutralization A solution obtained by removing the impurity elements in the solution and adding ammonia to form a cobalt ammine sulfate complex solution is suitable, and cobalt is contained in the form of cobalt complex ions.

In the present invention, the cobalt concentration in the solution containing the cobalt sulfate ammine complex is 50 g / L or more and 100 g / L or less, preferably 50 g / L or more and 80 g / L or less.
This limitation on the range of cobalt concentration is that the solution containing cobalt sulfate before adding ammonia often contains trace amounts of calcium, but since calcium behaves the same as cobalt, the cobalt concentration is 100 g / L. This is because there is a concern that calcium is precipitated as gypsum in a solution that exists in excess of.

  Further, the solution containing cobalt sulfate is diluted by addition of ammonia, and further diluted by repeating the filtrate generated in the reduction step, as will be described later, so that it is too dilute at a concentration of less than 50 g / L. A decrease in production efficiency occurs, such as an increase in the scale of equipment to be processed. For this reason, it is preferable that it is a density | concentration of 50 g / L or more.

[Mixing process]
<Addition of insoluble solid>
In this step, an insoluble solid which is insoluble in the complex solution and becomes a base for precipitation is added to the cobalt sulfate ammine complex solution.
The insoluble solid added here is not particularly limited as long as it is insoluble in the cobalt sulfate ammine complex solution, ammonium sulfate aqueous solution or alkaline solution, or has a low solubility. For example, cobalt powder, iron powder, alumina powder, Zirconia powder, silica powder and the like can be used.

Furthermore, the ammonium sulfate concentration in the solution is preferably in the range of 10 to 500 g / L. If it is 500 g / L or more, the solubility is exceeded and crystals are deposited. In addition, since ammonium sulfate is newly generated by the reaction, it is difficult to achieve less than 10 g / L.
In addition, when adding an insoluble solid, a dispersant may be added to the cobalt sulfate ammine complex solution before the addition, and then an insoluble solid may be added. If the dispersant used has carboxylic acid, Although not particularly limited, polyacrylic acid is suitable as an industrially available product.

  In the present invention, it is not a method of precipitating a powder using a seed crystal that has been generally used in the past, and using the seed crystal as a product, but after the necessary precipitation (cobalt precipitation) on the surface of the insoluble solid is finished, Is separated from the deposited and grown powder (cobalt deposit), and only the powder portion is used as a product. According to such a method of the present invention, the product of the seed crystal itself has an impurity property. Can be avoided.

The amount of the insoluble solid added is not particularly limited, and an amount that can be mixed by stirring when added to the cobalt sulfate ammine complex solution is selected according to the type of the solid.
Although the shape and size are not particularly limited, the cobalt powder deposited on the surface by colliding with each other or applying vibration as described later may be separated. A surface having a gentle shape is suitable so that the powder can be effectively separated.
Considering effective separation between the insoluble solid and the cobalt powder, it is easy to use an actual operation having a shape with no corners such as a sphere or an ellipse having a diameter of about 0.1 to 3 mm.

Prior to depositing the cobalt powder, it is preferable to use it as the insoluble solid of the present invention after giving impacts or impacts in advance to remove residue on the surface of the insoluble solid.
Moreover, the insoluble solid after separating the cobalt powder can be used again after performing a pretreatment such as washing as necessary.

[Reduction / precipitation process]
Next, in this step, the slurry formed by adding the insoluble solid in the previous step is charged into the reaction vessel of the high pressure resistant high temperature vessel, and hydrogen gas is blown into the slurry stored in the reaction vessel. Cobalt complex ions in the slurry are reduced to deposit cobalt on the insoluble solid contained.
The temperature of the mixed slurry at this time, that is, the reaction temperature is preferably in the range of 150 to 200 ° C. If it is less than 150 degreeC, reduction efficiency will fall, and even if it is 200 degreeC or more, there is no influence on reaction, rather, since loss, such as a heat energy, increases, it is not suitable.

  Furthermore, the pressure of the gas phase portion in the reaction tank (representing the space in the reaction tank remaining after storing the solution in the reaction tank) during the reaction is maintained at 1.0 to 4.0 MPa by supplying hydrogen gas. It is preferable. If it is less than 1.0 MPa, the reaction efficiency decreases, and even if it exceeds 4.0 MPa, there is no influence on the reaction, and the loss of hydrogen gas increases. In addition, even if hydrogen gas is blown into the mixed slurry, the cobalt complex ions in the slurry can be reduced even if it is blown into the gas phase portion in the reaction vessel.

  By the reduction / precipitation treatment under such conditions, a cobalt precipitate is formed on the insoluble solid, and the cobalt contained in the solution can be extracted and recovered as a fine powdery cobalt precipitate.

[Separation process]
In this process, the cobalt precipitate produced in the previous process is stuck to the insoluble solid and cannot be used in that state, so the cobalt precipitate formed on the surface is separated from the insoluble solid and recovered as cobalt powder. It is.

  As a specific separation method, for example, in order not to oxidize due to heat generation, put insoluble solids in water, rotate and collide the insoluble solids with each other to separate the cobalt powder on the surface, rotate on a wet sieve, There are a method of sieving the separated cobalt powder at the same time, and a method of applying vibrations by applying ultrasonic waves to the liquid to separate them. If the mesh is finer than the size of the insoluble solid, it can be used.

  The cobalt powder produced as described above can be used, for example, as a cobalt paste which is an internal constituent material of a multilayer ceramic capacitor, and the particles are grown by repeating the hydrogen reduction using the recovered cobalt powder as a seed crystal. High purity cobalt metal can be produced.

  Hereinafter, the present invention will be described with reference to examples.

[Mixing process]
To a solution containing 75 g of cobalt (cobalt sulfate solution) and 330 g of ammonium sulfate, 191 ml of 25% ammonia water and 2.5 g of 40 wt% polyacrylic acid as a dispersing agent are added to adjust the total liquid volume to 1000 ml. A solution containing a cobalt ammine complex was prepared. To this solution, 190 g of zirconia balls having a diameter of 1 mm was added as an insoluble solid serving as a precipitation matrix to prepare a mixed slurry.

[Reduction / precipitation process]
Next, the mixed slurry was charged into the inner cylinder can of the autoclave, and then heated and maintained at 185 ° C. while stirring, hydrogen gas was blown into the mixed slurry, so that the pressure in the inner cylinder can of the autoclave was 3 Hydrogen gas was supplied to maintain the pressure at 5 MPa. After 120 minutes had passed since the supply of hydrogen gas, the supply of hydrogen gas was stopped and the inner cylinder can was cooled.

[Separation process]
After cooling, the mixed slurry in the inner cylinder can is filtered to take out the insoluble solid that has produced cobalt deposits on the surface, and then the insoluble solid taken out into a wet sieve with an opening of 500 μm is put into the base by adding vibration. The insoluble solid was separated from the precipitated cobalt powder.
When the collected cobalt powder was observed, it was confirmed that fine cobalt powder was generated as shown in FIG. Moreover, the production | generation reaction rate of cobalt powder was 86%.

(Comparative Example 1)
[Mixing process]
Add 191 ml of 25% ammonia water to a solution containing 75 g of cobalt (cobalt sulfate solution) and 330 g of ammonium sulfate, and add 5 g of 40 wt% polyacrylic acid to the dispersant, and adjust the total liquid volume to 1000 ml. A solution containing the complex was prepared. To this solution, the following operation was performed without adding the insoluble solid as a precipitation matrix.

[Reduction / precipitation process]
After charging the prepared solution into the inner cylinder can of the autoclave, the temperature inside the inner cylinder can of the autoclave is maintained at 3.5 MPa by blowing in hydrogen gas while being heated and maintained at 185 ° C. while stirring. Was supplied with hydrogen gas. After 60 minutes had passed since the supply of hydrogen gas, the supply of hydrogen gas was stopped and the inner cylinder can was cooled.

[Separation process]
After cooling, the solution in the inner cylinder can was filtered, but only 1 g of cobalt powder could be recovered, and about 15 g of plate-like cobalt scaling was generated on the side wall and stirrer in the inner cylinder can.

  As is clear from Example 1 and Comparative Example 1, fine cobalt powder can be efficiently produced from the mixed slurry containing insoluble solids, but in the absence of insoluble solids, the desired cobalt powder can be produced. There wasn't.

(Comparative Example 2)
[Mixing process]
To a solution containing 110 g of cobalt (cobalt sulfate solution) and 330 g of ammonium sulfate, 191 ml of 25% ammonia water and 2.5 g of 40 wt% polyacrylic acid as a dispersing agent are added, and the total liquid volume is adjusted to 1000 ml. A solution containing a cobalt sulfate ammine complex was prepared.
To this solution, 190 g of zirconia balls having a diameter of 1 mm was added as an insoluble solid serving as a precipitation matrix to prepare a mixed slurry.

[Reduction / precipitation process]
Next, the mixed slurry was charged into the inner cylinder can of the autoclave, and then heated and maintained at 185 ° C. while stirring, hydrogen gas was blown into the mixed slurry, so that the pressure in the inner cylinder can of the autoclave was 3 Hydrogen gas was supplied to maintain the pressure at 5 MPa. After 120 minutes had passed since the supply of hydrogen gas, the supply of hydrogen gas was stopped and the inner cylinder can was cooled.

[Separation process]
After cooling, the mixed slurry in the inner cylinder can is filtered to take out the insoluble solid that has produced cobalt deposits on the surface, and then the insoluble solid taken out into a wet sieve with an opening of 500 μm is put into the base by adding vibration. The insoluble solid was separated from the precipitated cobalt powder.

  When the collected cobalt powder was observed, it was confirmed that the same fine cobalt powder as in Example 1 was produced. However, the formation of gypsum was also observed and could not be used for the product as cobalt powder.

Claims (6)

A mixed slurry is formed by adding an insoluble solid from which surface debris has been removed to a solution containing a cobalt sulfate ammine complex and having no corners such as a sphere or ellipse having a diameter of 0.1 to 3 mm that is insoluble in the solution. A mixing step to
After charging the mixed slurry into a reaction tank, hydrogen gas is blown into the mixed slurry to reduce cobalt complex ions contained in the mixed slurry, thereby forming a cobalt precipitate on the insoluble solid surface. A precipitation process;
Separating the cobalt precipitate on the insoluble solid surface from the insoluble solid surface to form cobalt powder,
A method for producing cobalt powder, characterized in that cobalt powder is produced in order.   The method for producing cobalt powder according to claim 1, wherein the ammonium sulfate concentration in the solution containing the cobalt sulfate ammine complex is in the range of 10 to 500 g / L.   The method for producing cobalt powder according to claim 1 or 2, wherein a cobalt concentration in the solution containing the cobalt sulfate ammine complex is 50 g / L or more and 100 g / L or less.   The method for producing cobalt powder according to any one of claims 1 to 3, wherein the temperature of the mixed slurry when hydrogen gas is blown in the reduction step is 150 to 200 ° C.   5. The cobalt according to claim 1, wherein the pressure in the gas phase portion in the reaction tank when hydrogen gas is blown in the reduction step is in a range of 1.0 to 4.0 MPa. Powder manufacturing method.   6. The insoluble solid according to any one of claims 1 to 5, wherein the insoluble solid is one or a combination of two or more selected from cobalt, alumina, zirconia, iron, and silica. A method for producing cobalt powder.