How does ammonia pressure leaching recover cobalt from nickel ores?

In the context of nickel processing, ammonia pressure leaching is a method used to extract metals from ore. During this specific process, cobalt is recovered from the resulting pregnant solution through reduction with hydrogen under pressure.1

This technique is part of a broader category of extractive metallurgy known as leaching, where pressure and temperature are increased within an autoclave to accelerate the dissolution of minerals that would otherwise react too slowly at atmospheric pressure.2