Barite Growth Rates as a Function of Crystallographic Orientation, Temperature, And Solution Saturation State

Barite growth kinetics was investigated as a function of crystallographic orientation for temperatures between 10 and 70 degrees C and initial saturation indices (SI) of 1.1 and 2.1. The growth rates were estimated for the (001), (210), and (101) faces using vertical scanning interferometry. Overall, face-specific barite growth rates (r(hkl)) can be successfully described by the rate law r((hkl)) = A((hkl)) exp(-E-a((hkl))/RT) (10(SI) - 1), where A((hkl)) and E-a((hkl)) represent the face-specific Arrhenius pre-exponential factor and activation energy, respectively, R is the gas constant, and T refers to the absolute temperature. In addition, because of the modest growth anisotropy of the various investigated faces, the following isotropic rate law can be used to satisfactorily account for the measured rate data: r((hkl)) = A exp(-E-a/RT)(10(SI) - 1) with average values of A = exp(13.59) nm h(-1) and E-a = 35.0 +/- 2.5 kJ mol(-1). Over the range of conditions investigated in the present study, our results suggest that the barite growth kinetics is surface-controlled, while possibly verifying the principle of detailed balancing and microreversibility. These results imply that previous modeling exercises of steady-state barite growth based on isotropic rate laws may remain valid, at least over the range of conditions investigated in the present study.