Promotion Effect of Cu Metal on Ni Leaching from NiS in Acidic Solution

The recovery of nickel from nickel sulfide (NiS) is an important process for the effective utilization of metal resources. In our previous work, the addition of metallic pieces, such as Fe and Sn, was found to enhance Ni leaching from NiS in acidic solutions containing a copper oxidant. This study investigates the promotional effect of metallic copper on this leaching process. The addition of metallic Cu was observed to significantly accelerate Ni leaching from NiS, even in the absence of a copper oxidant. Notably, when Cu was introduced as a powder, a complete Ni leach was achieved. Experimental results demonstrated that direct physical contact between the metallic Cu and NiS, as well as sufficient proton concentration, were essential factors for promoting the reaction. Furthermore, analysis of the residue by XRD confirmed the formation of Cu2S. These findings suggest that Ni leaching is enhanced by a solid-phase reaction between metallic Cu and NiS, leading to the formation of Cu2S.