How does leaching separate cobalt from roasted ore concentrates?

In the context of cobalt processing, leaching is a hydrometallurgical technique used to extract cobalt from roasted ore concentrates by dissolving it into a liquid solution.

For copper-cobalt sulfide ores, the concentrate is first roasted under controlled conditions to convert the cobalt into a water-soluble sulfate while keeping copper and iron in a less soluble state. When this roasted product undergoes leaching, the cobalt dissolves into the solution, allowing it to be separated from the remaining solid impurities. Once the solution is treated to remove any residual copper and iron, the cobalt is recovered through electrolysis.1

Alternatively, for certain concentrates such as those derived from arsenide ores, leaching can be used to bring the cobalt into solution, followed by precipitation using hydrogen. In other industrial applications, such as the ammonia pressure leaching of nickel, cobalt is similarly recovered from the resulting solution through reduction with hydrogen under pressure.12