Mechanisms of surface precipitation and dissolution of barite: A morphology approach

Barite (BaSO4) was synthesized at normal pressure and room temperature by mixing sodium sulfate and barium chloride solutions by gentle flow (0.5 ml/min.). The well-formed rectangular and rhombohedral crystals with smooth faces formed from solutions with low degrees of supersaturation. Most precipitates became single crystals. We employed the scanning electron microscope (SEM) to observe barite dissolution by chemical agent diethylenetrinitrilopentaacetic acid. Molecular modeling was used to assist the interpretation of the surface reaction. A kinetic model for the pit growth (initial dissolution) on the surface was evaluated. With SEM microanalysis of barite and kinetic model of pit growth, important surface phenomena and mechanisms of dissolution can be hypothesized. Surface phenomena and composition are very important in barite dissolution. Experimental results suggest that the initial dissolution starts on the two lowest energy surfaces: (001) and (210), and that the etch pits are elongated in one direction on the (210) surface and formed cavities on the (001) surface. The simulated surface structures by molecular modeling can aid the interpretation the pit formation on those selected surfaces. (C) 1999 Academic Press.