Nickel Extraction from Nickel Sulfide Concentrates by Iron Addition: Ferronickel Formation Mechanism

The conventional process of nickel extraction from sulfide concentrates involves complex and costly steps, while also generating a considerable amount of sulfur dioxide. The solid-state extraction of nickel from nickel sulfide concentrates by iron addition was proposed as an alternative approach where the nickel was recovered into a ferronickel alloy in a simple process with minimal SO₂ emissions. Previous works have shown that approximately 97 pct of Ni in the concentrates was recovered into two types of ferronickel grains at 1073 K. One type contained low Ni but with large size; another type was smaller in size but contained high Ni. The present study investigated the formation mechanism and contribution of each type of grain to the extent of nickel extraction. Further, studies at higher temperature showed that liquid formation shifts the ferronickel formation process to another mechanism.