Interactions at the organic/inorganic interface: binding motifs for phosphonates at the surface of barite crystals

Abstract

Synthetic barite crystals, prepared under conditions chosen to mimic those encountered in off-shore oil fields, have a simple rhombic plate-like morphology in which large (001) faces are bound by smaller (210) sides. The addition of certain stereochemically related diphosphonates produces a characteristic morphological change leading to disc and elliptical morphologies. These results are shown to be consistent with a binding model in which the diphosphonate ion replaces two sulphates in the (011) surface. The implications of these results to the case of gypsum precipitation is also considered.