Cobalt Extraction Process

Cobalt Extraction Process

Cobalt ores rarely occur alone in nature. They primarily occur in associated deposits of nickel, copper, pyrite, and arsenic. Cobalt ore concentrations are relatively low, making extraction relatively difficult. Cobalt ore resources primarily include nickel-cobalt sulfide and oxide ores, copper-cobalt ores, arsenic-cobalt ores, and cobalt-bearing pyrite. Cobalt smelting is characterized by low-grade raw materials, a long extraction process, and multiple extraction methods.

Cobalt extraction from nickel, copper, and sulfur converting slag: Cobalt-containing converting slag undergoes reduction and sulfidation smelting in a blast furnace or electric furnace to produce cobalt alloy or cobalt matte. This is concentrated by magnetic separation and then subjected to pressure acid leaching to release the cobalt into solution. After purification, the solution is added with oxalic acid to precipitate cobalt oxalate. Calcination of the cobalt oxalate yields refined cobalt oxide.

Cobalt extraction from nickel refining purification slag: Cobalt slag produced during the anolyte purification process of nickel electrolytic refining is an important raw material for cobalt extraction. Cobalt slag is leached with reducing sulfuric acid to release cobalt into solution as cobalt sulfate. The solution is then subjected to the natantium ferroalite method to remove iron, and extraction to remove impurities such as copper, zinc, and manganese. The solution is then separated from the nickel and cobalt to produce a pure cobalt chloride solution, which can then be used to produce cobalt oxide products or to obtain metallic cobalt products through electrowinning.

Cobalt extraction from cobalt-containing pyrite: Flotation of cobalt-containing pyrite yields a cobalt-sulfur concentrate containing 0.3% to 0.5% cobalt. Cobalt-sulfur concentrate is roasted with sulfuric acid to convert valuable elements such as cobalt, nickel, and copper into soluble sulfates. Roasted sand is then leached with water or acid to transfer the cobalt, nickel, and copper into solution. The leachate is purified to remove impurities such as iron, copper, zinc, and manganese. The solution is then separated by nickel and cobalt to produce a pure cobalt solution, which is then used to produce metallic cobalt through electrolysis.

Cobalt extraction from arsenic-cobalt ore: Arsenic-cobalt ore is roasted or smelted to volatilize the arsenic as As₂O₃, resulting in roasted sand or cobalt matte. This is then acid-leached to release the cobalt into solution. The solution is then removed of iron, arsenic, and impurities such as copper, zinc, and manganese before entering nickel and cobalt separation. The purified cobalt solution is then used to produce metallic cobalt or cobalt oxide products according to market demand.

Cobalt is often associated with other minerals and has a complex composition, resulting in numerous cobalt smelting methods and complex processes. Cobalt smelting generally involves three steps:

First, transfer the cobalt from the ore into solution, or prepare a crude cobalt alloy or cobalt matte, which is then transferred into solution;

Second, impurity removal and purification;

Third, extraction of the metal. Cobalt smelting processes can generally be divided into four categories: high-temperature smelting and enrichment followed by wet extraction of cobalt, sulfuric acid roasting followed by leaching to extract cobalt, reduction roasting and ammonia leaching, and pressure leaching.

Technical Development Directions: Pressure leaching offers a shorter process, higher nickel and cobalt leaching rates, and produces no harmful waste gas or wastewater, resulting in better environmental protection. This method is widely used in developed countries. Practice has proven that a single metallurgical furnace is always the most economical, regardless of plant size. Therefore, during renovations, multiple furnaces are converted to a single furnace. Another trend is to learn from and leverage various processes, leveraging their strengths and weaknesses to achieve continuous improvement.