KINETICS OF CALCITE DISSOLUTION AS AFFECTED BY CARBON-DIOXIDE PARTIAL-PRESSURE

Research was conducted to determine the effect of CO2 on the kinetics of soil mineral dissolution. It was found that in soils or overburden materials in which CaCO3 is the dominant weatherable mineral, the kinetics of dissolution was not a simple diffusion controlled for first-order reaction. In these calcareous systems, the transfer of atmospheric CO2 to solution was an important rate limiting step in the kinetics of dissolution. At higher PCO2 values the dissolution of calcite was modeled by three simultaneous reactions on the surface of the calcite. It is postulated that the CO2 attack consists of an adsorption of CO2(Aq) on the calcite surface followed by hydrolysis of the CO2 to H2CO3. The hydrolysis is apparently catalyzed by the calcite surface because the aqueous hydrolysis, CO2(aq) + H2O .fwdarw. H2CO3, occurs too slowly for the observed rate of reaction.