Molecular dynamics simulation and analysis of interfacial water at selected sulfide mineral surfaces under anaerobic conditions

• Sulfide minerals are naturally hydrophobic under anaerobic conditions.
• MDS of contact angles were performed for selected sulfide mineral surfaces.
• Interaction between water and a sulfide surface determines size of contact angle.
• Hydrophobic sulfide mineral surfaces have relatively weak interaction with water.
• Sphalerite (110) and molybdenite edge surfaces have only modest hydrophobicity.

In this paper, we report on a molecular dynamics simulation (MDS) study of the behavior of interfacial water at selected sulfide mineral surfaces under anaerobic conditions. The study revealed the interfacial water structure and wetting characteristics of the pyrite (100) surface, galena (100) surface, chalcopyrite (012) surface, sphalerite (110) surface, and molybdenite surfaces (i.e. the face, armchair-edge, and zigzag-edge surfaces), including simulated contact angles, relative number density profiles, water dipole orientations, hydrogen-bonding, and residence times. Two MDS force fields for the metal and sulfur atoms in selected sulfide minerals were created using UFF with partial charge determined by charge equilibration and using UFF with partial charge determined by Mulliken population analysis. Simulation results for the structural and dynamic properties of interfacial water molecules indicate the natural hydrophobic character for the selected sulfide mineral surfaces under anaerobic conditions as well as the relatively weak hydrophobicity for the sphalerite (110) surface and the two molybdenite edge surfaces.

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