The kinetics of calcite dissolution in acetic acid solutions

Abstract

The kinetics of calcite dissolution in acetic acid solutions was investigated over a wide range of pH using a rotating disk apparatus. The results show that the dissolution is influenced by the rate of transport of reactants to the surface, the kinetics of the reversible surface reaction, and the rate of transport of products away from the surface. Below about pH 2.9, the dissolution is influenced by the transport of both reactants and products, while above about pH 3.7, the dissolution is influenced predominantly by the kinetics of the surface reaction. A general model was developed to account for the combined effects of transport and reaction on the rate of dissolution. The effect of acetate ions on the rate of dissolution was investigated in alkaline solutions (pH 8.2 to 14) to eliminate the effects of hydrogen ion attack. The presence of acetate ions was found to have no significant affect on the rate of dissolution when compared to results in potassium chloride and sodium chloride solutions. The rate of dissolution was observed to decrease over this pH range and could not be described by previous reaction mechanisms. Therefore, a surface dissociation mechanism involving water was introduced and was shown to describe the rate of dissolution over the pH range of 8 to 14.