Temperature dependence of calcite dissolution kinetics between 1 and 62°C at pH 2.7 to 8.4 in aqueous solutions

Details Temperature dependence of calcite dissolution kinetics between 1 and 62°C at pH 2.7 to 8.4 in aqueous solutions Temperature dependence of calcite dissolution kinetics between 1 and 62°C at pH 2.7 to 8.4 in aqueous solutions

Mar 1984

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984gecoa..48..485l&link_type=abstract

Geochimica et Cosmochimica Acta, vol. 48, Issue 3, pp.485-493

Computer Science

8

Scientific paper

The kinetics of calcite dissolution in aqueous KCl-solutions far from equilibrium, between 1 and 62°C in the pH-range 2.7 to 8.4 have been investigated using a rotating disc apparatus. At neutral and alkaline pH in the mixed kinetic regime the empirical apparent activation energy (EAAE) for the surface chemical reaction rate constant is 54 ± 4 kJ mole -1 for Carrara marble and 46 ± 4 kJ mole -1 for Iceland spar. Under similar conditions the EAAE of the transport rate constant increases with decreasing temperature, but has a mean value of 27 ± 2 kJ mole -1 . The corresponding diffusion coefficient has a mean EAAE of 37 ± 3 kJ mole -1 and this high EAAE is consistent with transport dependence on product diffusion in this H + -independent regime. In contrast, in acid solutions, where the rate approaches end-member transport control, the EAAE of the diffusion coefficient is 16 kJ mole -1 , also decreasing with increasing temperature. This is compatible with H + -diffusion to the surface being rate-controlling. In inhibitor-free natural systems, calcite dissolution kinetics far from equilibrium can be described in terms of three regimes: an H + -dependent regime (pH < 4 at 25°C), a transition regime (4 < pH < 5.5 at 25°C) and an H + -independent regime (pH > 5.5 at 25°C). At lower temperatures these boundaries move to higher pH values. The presence of inhibitors in natural systems may enhance surface controlled kinetics.

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