Understanding Surface Characteristics and 2-Mercaptobenzothiazole Adsorption on Pyrite, Arsenopyrite and Chalcopyrite Surfaces Using DFT Approach

Enhanced recoveries of gold-bearing minerals, namely pyrite, chalcopyrite and arsenopyrite, are essential to meet the ever-increasing demand for the precious metal. Since flotation is the 1st step in the recovery of these minerals, a detailed understanding of their surface structure as well as the interaction of the collector molecules with these surfaces is essential to not only rationalize experimental observations but also design new task specific collector molecules. In the present work, we have employed density functional theory (DFT) simulations to understand the surface characteristics of pyrite, arsenopyrite and chalcopyrite and to evaluate the adsorption of a commonly used collector, 2-mercaptobenzothazole (MBT), on these surfaces. DFT calculations reveal that (001) and (100) surfaces of chalcopyrite undergo significant reconstruction, while (110) and (112) surfaces of chalcopyrite, (100) surface of pyrite and (001), (100), (011), (110) and (111) surfaces of arsenopyrite undergo only atomic relaxations. MBT (both the thione and thiol tautomers) chemisorbs on all the three minerals, with the adsorption strength varying in the following order: pyrite > arsenopyrite > chalcopyrite. A stronger adsorption of MBT on pyrite over chalcopyrite explains the experimentally observed selectivity of MBT for the former. Furthermore, results from these simulations provide detailed atomic scale insights into the bonding mechanisms at the surfaces, that are crucial for a rational design of novel flotation collectors with enhanced efficiencies.