JPS6017812B2 - Method for recovering cobalt from an aqueous solution containing cobalt ions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering cobalt in high yield by cementation from an aqueous solution containing cobalt ions using simple equipment and operations.

Aqueous solutions containing cobalt ions are obtained during wet processing such as sulfuric acid leaching of laterite ore, sulfuric acid leaching or hydrochloric acid leaching of manganese nodules, and during processing of waste catalysts. As methods for recovering cobalt from these solutions, the following sulfide precipitation methods and solvent extraction methods using various extraction reagents have been proposed, but each has its own drawbacks. [1]
In the sulfide precipitation method, the sulfide precipitate that is generated at low temperatures is generally fine and difficult to pass through the furnace.
Because the precipitation operation is carried out at such high temperatures, ``large-scale equipment is required.

■ Since solvent extraction can be combined with electrowinning to obtain high-purity metals, it has become the mainstream method for hydrometallurgical smelting of various nonferrous metals in recent years. Since it requires operational technology, it is not necessarily optimal when the L metal concentration is low or when the amount of treatment is small.

The present inventors have conducted various studies on methods for recovering cobalt ions in aqueous solutions using simple equipment and operations.
We have discovered that cobalt can be quantitatively cemented by controlling conditions such as the temperature and pH of an aqueous solution using metallic iron, and have arrived at the present invention. That is, the gist of the present invention is characterized in that metal iron is added to an aqueous solution containing cobalt ions in an inert gas atmosphere at a temperature of 60 qo or more and a pH of 5.5 or less to cause cobalt cementation. A method for recovering cobalt from an aqueous solution containing cobalt ions. Next, the progress that led to the present invention will be described. Cementation of cobalt ions by iron is fully possible in equilibrium terms, but generally, even if an aqueous solution containing cobalt ions is flooded and iron is added, cementation of cobalt ions will proceed only slightly. This is because the surface of ordinary metallic iron is covered with oxides, and even if it is highly pure and the oxide film on the surface is thin, when placed in an aqueous solution, dissolved oxygen will immediately form a thick oxide film. This is because this oxide film is formed and prevents contact between cobalt ions and the base metal. Furthermore, even if dissolved oxygen is present, if the pH of the aqueous solution is high, metallic iron will react with high-temperature water and an oxide film will be formed on its surface, preventing sufficient contact between cobalt ions and the base metal. Because of the obstruction, cementation still progresses slowly. In summary, the conditions necessary to promote the cementation of cobalt ions by iron, which is fully possible in terms of equilibrium theory, are to keep the surface of the added metal iron in a fresh state in an aqueous solution, and to bond cobalt ions and base metal. The purpose is to allow the metal iron to react and cementation to occur. To this end, the present invention combines the following industrial measures. '1} Create an inert gas atmosphere to prevent the formation of an oxide film due to oxygen present in the lacquer.

Nitrogen, argon, helium, etc. are suitable as the inert gas, and nitrogen is particularly advantageous in terms of cost. The pressure of the inert gas is not specified. {2) In order to prevent the formation of an oxide film within the range where cementation is possible or to dissolve the formed oxide film, the pH of the aqueous solution is adjusted to 5.5 or less while adding a key acid such as sulfuric acid. Preferably it is kept in the range of 5-3.

In this case, if the aqueous solution containing cobalt ions is dehydrated and its pH is kept low, cementation will proceed quickly, but on the other hand, the dissolution rate of iron in acid will also increase rapidly.
Since the amount of iron consumed increases unnecessarily, the above pH range is required in order to achieve effective cementation using the minimum necessary amount of iron. Furthermore, as for the reaction temperature, the cementation rate increases as the temperature rises, but the above {1},'
2} is satisfied, it is 6000 or more, preferably in the range of 70 to 90oo.

Various iron powders can be used as the replacement metal iron used in the present invention.

For example, electrolytic iron powder has high purity and the best reactivity, but it is expensive and therefore impractical. Although reduced iron powder is inferior in purity to electrolytic iron powder, it is the most practical because it has sufficient reactivity and is inexpensive. Iron powder can also be used, but since it has a much smaller specific surface area and poorer reactivity than iron powder, it needs to be used under harsher conditions than the iron powder. The amount of iron powder to be used is 2 to 3 times the theoretical amount. Regarding the coexistence of other metal ions, as long as the metal ions have a more base potential than cobalt ions, most of them do not have any adverse effects either in principle or in practice.

However, aluminum ions are an exception. This material hydrolyzes and becomes acidic, thereby dissolving iron and forming an aluminum hydroxide film on its surface, which prevents contact between cobalt ions and the base metal. Therefore, if a large amount of aluminum ions coexist, it is necessary to remove them to some extent in advance. Furthermore, if copper or nickel ions having a more noble potential than cobalt ions coexist, these will precipitate together with cobalt. If copper coexists, cobalt cementation is rather promoted. The potential of iron (m) ions is very noble, and therefore, it is reduced to iron (0) ions and consumes metallic iron, so it is desirable to remove them in advance like aluminum. As described above, the present invention provides a method for recovering cobalt in high yield by cementation from an aqueous solution containing cobalt ions using simple equipment and operations, and has great industrial value.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 An aqueous solution of cobalt sulfate (Co concentration 2/2) was placed in a round bottom flask, stirred at a speed of 300 to 40 pm, nitrogen gas was passed through the flask, and the flask was placed in a constant salt bath of 90 q0. (150 mesh, purity 98.5%) 4.85
After the cobalt concentration was added, IN sulfuric acid was added to maintain the pH of the aqueous solution at 4, and the reaction was allowed to proceed for 10 minutes, and the cobalt concentration of the aqueous solution was reduced to 0.03 cobalt/so.

Example 2 A mixed aqueous solution of cobalt sulfate and nickel sulfate (Co and Ni concentrations 2 nights/night each) was placed in a round bottom flask and operated in the same manner as in Example 1 to obtain reduced iron powder 9. When the pH of the aqueous solution was kept at 5 and the reaction was allowed to proceed for 10 minutes, the concentrations of cobalt and nickel were 0.035 and 0.013/2, respectively.
It declined.

Further, at a reaction time of 20 minutes, the concentrations of cobalt and nickel decreased to 0.010 and 0.001%, respectively, and both were almost completely precipitated. The amount of iron powder dissolved was 4.44 hours and 5.01 hours at reaction times of 10 minutes and 20 minutes, respectively, which were 1.18 times and 1.32 times the theoretical amount, respectively. Example 3 A mixed aqueous solution of cobalt sulfate, steel sulfate, and nickel sulfate (Co, Cu, and Ni concentrations of 2 tons each) was placed in a round bottom flask and reduced by operating the same machine under the same conditions as Example 1. When 12.50 tons of iron powder was added and reacted for 10 minutes while keeping the pH at 4, cobalt, nickel, and copper were almost completely precipitated.

Claims (1)

[Claims] 1. Cobalt from an aqueous solution containing cobalt ions, which is characterized by cementing cobalt by adding metallic iron to the aqueous solution containing cobalt ions in an inert gas atmosphere at a temperature of 60° C. or higher and a pH of 5.5 or lower. collection method.