Is the glass phase dissolution rate always a limiting factor in the leaching processes of combustion residues?

The kinetic characteristics of waste glass phases in some coal fly ashes are simulated by the hydration free energy approach of multiple-component glass. A geochemical model is used to calculate the dissolution processes of waste glass in a low flow-through system for coal fly ashes. The contribution of waste glass dissolution for the leaching of solid waste is discussed on the basis of dissolution mechanisms and kinetics of glass phases, reaction time and disposal condition. It has been found that the dissolution rate of a glass phase is not always a limiting factor in the leaching processes of coal fly ashes. Additional retention mechanisms may retard the release of toxic elements but only under some limited conditions. The disposal environment together with kinetic properties of waste glass phases need to be accounted, for the dissolution of the glass phase. Glass dissolution under some, not improbable, circumstances may considerably contribute to the long-term release of toxic metals.