The kinetics of barite dissolution and precipitation in water and sodium chloride brines at 44–85°C

Abstract

The dissolution rate of natural barite cleavage fragments was measured in deionized water and NaCl brines over the temperature range 44–85°C. Dissolution followed first-order kinetics, with an activation energy of 24.9 ± 10.1 kJ/mol. The observed insensitivity to stirring rate and low absolute value of the rate constant (extrapolated k at 25° C = 3.30 ± 1.31 × 10 −3 L/ m 2 s) indicated desorption rather than volume diffusion as the rate-determining step. The NaCl concentration had no effect on k up to 0.1 M. Barite growth from supersaturated aqueous solutions was also studied. Precipitation followed a second order rate law, k 25° C = 162 ± 65 L 2/ sm 2mol, E a = 22.0 ± 14.3 kJ/mol, and was not sensitive to pH variation. A different rate law is likely to apply at high supersaturations, where a change in secondary growth morphology was observed.