The effects of composition on glass dissolution rates: The application of four models to a data base

Abstract

PNL-6333 UC-70 Completion of the data base will help provide the data to demonstrate the composition/durability relationships needed to develop durable waste glasses •

Effect of glass composition on waste form durability: A critical review

“…To evaluate the relative merits of various models, it is important to have a consistent, relevant database of glass compositions and test results. For this purpose, we have employed a subset of the nearly 300 glass compositions discussed by Geldart and Kindle [196]. The following criteria were used to eliminate glass compositions not relevant to waste glass formulations from the data set.…”

“…Thus, the VO model is a hybrid of sorts between a predominantly thermodynamic model, such as the FEH model, and a purely structural model, such as the NBO model. The VO model has only seen significant application in analysis of the database of Geldart and Kindle [196] and the analysis of Abrajano et al [197].…”

“…where UB represents the number of unstable bonds, SB represents the number of stable bonds, Ostable is the number of oxygen atoms in "stable" oxides, and Ounstable is the number of oxygen atoms in "unstable" oxides [196]. Unstable bonds are defined as those formed by alkali cations, and, as there is technically one NBO bond per alkali, UB is simply two times the total alkali oxide concentration.…”

Linear Free Energy Relationships in Glass Corrosion

“…Other models have been proposed to explain the relationship between glass composition and durability without Invoking the concept of hydration free energies. For example, 1t was recently suggested that the contribution of cations to chemical durability of glasses depends primarily on their valence [9]. The fundamental basis of this hypothesis 1s yet to be explored in detail, but results based on the same data set used in the hydration model shows valence parameter correlation with In LR$j that is comparable to the hydration free-energy model (Figure lb).…”

Linear Free Energy Relationships in Glass Corrosion

“…Other discrepancies between the theoretical models and empirical observations are notable. For example, whereas the valence parameter nwdel was successful 1n predicting relative contributions of elemental groups, It failed to account for the relative durability effects within Individual groups suggested by the empirical analysis [9]. This contrasts with the fact that the relative durability contributions within the alkali and, to a lesser extent, alkaline earth element groups stipulated by the hydration model Is borne out by the empirical analysis.…”