General chemical equilibrium model for stabilized/solidified wastes

Chemical equilibrium models have an important role in predicting the behavior of stabilized/solidified (s/s) wastes for risk assessment. Such a model has been developed for wastes treated by conventional solidification/stabilization and it is named SOLTEQ-B. This model is an improvement over a previous version (SOLTEQ) in terms of speed and reliability of convergence. The improvement is due primarily to use of a different method of describing the equilibrium characteristics of calcium silicate hydrate, which is the primary product of cement hydration. SOLTEQ-B was evaluated using experimental data from a series of batch equilibrium tests of pure s/s binder and s/s binder/waste mixtures. SOLTEQ-B accurately predicted pH during neutralization by CO2 or nitric acid and also accurately predicted concentrations of the primary components of cement (Ca, Si, Al, and SO4).

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