Impact of mechanical activation on bioleaching of pyrite: A DFT study

•The impact of mechanical activation on bioleaching of pyrite is studied.•The interactions between cells and activited pyrite are studied by DFT.•The DFT results agree well with the experiments results.•Combining experiments with DFT is important for studying bioleaching process.•Mechanical activation significantly enhances the bioleaching of pyrite. The impact of mechanical activation on the bioleaching of pyrite was studied, and the mechanisms were elucidated by DFT (density functional theory). The characterization result of the pyrite that were mechanically activated showed that the average diameter of the pyrite particles decreased sharply when the activation time was up to 80 min and remained constant from 80 min to 120 min due to the sample agglomeration effect. The change in the specific surface area exhibited the opposite trend, and the contact angles of the pyrite particles decreased gradually as the grinding time increased from 0 to 120 min, which implied that the hydrophilic property of the pyrite increased. The pyrite lattices increased after mechanical activation, indicating the presence of S defect sites on the pyrite surface. Notably, all these changes favored the increase in the bioleaching rate of pyrite. The result showed that the leaching rate of pyrite increased noticeably after mechanical activation by Sulfobacillus thermosulfidooxidans (S.t), and the cell exhibited enhanced adsorption on the activated pyrite surface. The DFT result proved that the activated pyrite could be easily adsorbed by H2O and cells, with relatively large adsorption energies, strong bonds, and an increased number of electron transfers.