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

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