THE INTERACTION OF SOLUTES WITH SILICATE GLASS AND ITS EFFECT ON DISSOLUTION RATES

The effect of the presence of solutes such as Mg and Al on the dissolution of soda-lime silicate glass in water at 90-degrees-C was measured. The leachant pH was 8.1 in the case of Mg and 9.5 in the case of Al. It was found that the retardation of the dissolution process in the presence of these additives could be described in terms of a simple Langmuir-type model. In the case of Mg, 1:1 exchange of Mg from the solution for Na, K and Ca in the glass was established. In the case of Al, the mechanism involves aluminosilicate formation rather than cation exchange, but the effect was described by a Langmuir-type expression. Na borate was used to buffer the pH during solute effect studies. Na effects on the dissolution of glass were measured. They included enhancement of Mg interaction with the glass when Na:Mg ratio was low and enhanced glass dissolution when this ratio was high. Na ions had little effect on the interaction between Al and the glass surface.