Exploration of sodium thiosulfate for leaching of cobalt-containing pyrite: A DFT study

The paper presents the theoretical calculation results of exploratory research relating to the leaching of cobalt-containing pyrite using sodium thiosulfate as a lixiviant. It is well known that density functional theory (DFT) calculations can qualitatively evaluate the exchange of matter and energy between the mineral system and the surroundings, which greatly expands the breadth and depth of leaching process. Thus, DFT method was used to determine the effectiveness of sodium thiosulfate (Na₂S₂O₃) as a lixiviant for the leaching of cobalt-containing pyrite in this study. The analyses of DFT calculations illustrated that thiosulfate can be well adsorbed on the surface of cobalt-containing pyrite due to the formation of S-Fe and O-Co bonds between the S 3p orbital and O 2p orbital in sodium thiosulfate and the Fe 3d orbital and Co 3d orbital in cobalt-containing pyrite. Analysis of crystal orbital Hamilton population (COHP) indicated that Fe-S and S-Co bonds became longer when the thiosulfate adsorbed on the surface of the cobalt-containing pyrite, resulting in the weakening of interactions between S and Fe or Co atoms. Overall, the findings suggested that sodium thiosulfate was a promising lixiviant，favored the dissolution of Fe and Co.