Controls on silicate dissolution rates in neutral and basic pH solutions at 25°C

Abstract

The pH-dependence of far from equilibrium steady-state dissolution rates of silicates can be understood by considering the detachment rates of their oxide components through surface protonation-deprotonation reactions. At high pH, where Si surface sites are deprotonated and therefore carry negative charge, detachment of silicon appears to control overall silicate dissolution rates. At low pH, near the zero point of charge of SiO 2 (where surface charge is dominated by the other oxide components), detachment of the non-silicon structure-forming oxides apparently controls dissolution rates of multi-oxide silicates. Correlations between metal-oxygen site potentials and pH-dependent surface detachment reactions permit estimation of dissolution rates of a large number of silicates from pH 5 to pH 12.