Electronic simulations of alanine and water coadsorption over Defect-free and Sulfur-depleted sphalerite surfaces

Abstract

Understanding the interactions of amino acids with minerals is crucial for selecting the peptide-based reagents of interest in environmentally friendly ore separation applications. This study aimed to simulate archetypal alanine/water/ZnS complexes through DFT by including explicit water molecules on defectless and sulfur-deficient sphalerite. Swarms of water molecules up to a multilayer were introduced into the simulation cells in order to examine the different types of surface interactions in the solvated mode. Using the grand canonical Monte Carlo method, an efficient strategy was also proposed to diversify the highly plausible initial configurations. Our results revealed that solvated alanine disinclines to form a covalent bond with the defect-free sphalerite surface, thereby the higher affinity toward the neighboring water molecules. On the contrary, sulfur-depleted ZnS surfaces were the siege of stable monodentate bonds between the solvated alanine and Zn atoms around the pruned vacancy site. In particular, our study suggests that the level of interactions between solvated alanine and ZnS can be controlled by tuning the density of sulfur vacancy on the ZnS surface.