Anisotropic surface energies and adsorption behaviors of scheelite crystal

Anisotropic surface broken bond densities and surface energies of six surfaces of scheelite were calculated with density functional theory (DFT). The calculation results show that its surface energy is directly proportional to its surface broken bond density. {1 1 2} and {0 0 1} surfaces are the two predominant cleavage or exposed planes. The prediction of morphology is well consistent with our experimental observations based on XRD. Anisotropic adsorption behaviors and wettability of these two surfaces after being immersed in sodium oleate and DDA solutions were studied by means of contact angle measurement, AFM and flotation test. The contact angle values at a given NaOl concentration decreased in the order {1 1 2} > {0 0 1}. As for DDA, similar wettability for the two surfaces was observed. The results were interpreted by AFM and interaction energies for the adsorption of surfactants on each surface calculated in accordance with molecular dynamics (MD) simulation.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Anisotropic surface energies of scheelite were calculated by DFT calculations. ► Two predominantly cleavage planes, e.g. {1 1 2} and {0 0 1} surfaces were confirmed. ► Anisotropic adsorption behaviors oleate molecules at two surfaces were observed. ► Anisotropic adsorption behaviors were interpreted based on AFM and MD simulations.