Dissolution kinetics of chrysotile at pH 7 to 10

The rate of chrysotile dissolution over five days was studied in constant-pH, batch suspensions at 25°C. After the first day, release of Mg occurred at a constant rate and exhibited a fractional dependence on pH, [H⁺]^(0.24). Interpreted in terms of a site-binding model for adsorption of protons on the surface. this fractional dependence implies that the rate is limited by a chemical reaction involving less than one adsorbed proton per Mg released into solution. The actual magnitude of the rate (10^(-15.7) mol cm⁻¹ s⁻¹ at pH 8) supports this interpretation. The inorganics NO³⁻, Cl⁻, HCO₃⁻ and SO₄⁻² and the organics catechol and oxalate affected the rate of Mg release only during the initial 12 to 24 hours of each experiment. Silica release was linear from the outset of each experiment, but showed no definite pH dependence