Effect of a siliceous additive on aqueous alteration of waste glass with engineered barrier materials

A simulated waste glass was leached in the presence of bentonite. iron and magnetite (as a corrosion product), with and without amorphous silica at 60 degreesC for 364 days. These experiments were carried out to assess the ef fect of silica on the aqueous alteration of waste glass in contact with eng ineered barrier materials. The weight losses of samples without amorphous s ilica increased with time, while the weights of samples with amorphous sili ca were almost unchanged. This shows that the concentration of silicic acid in the porewaters reached the solubility of amorphous silica quickly, so t hat the detrimental effects of the engineered barrier materials were effici ently reduced. We also conducted MCC-1 type experiments with the same glass using silica saturated solutions at 60 degreesC. 75 degreesC and 90 degree sC to understand the alteration mechanisms of glass under these conditions. The results show that the glass alteration under these conditions is domin ated by glass hydration, and the release of soluble elements from the waste glass closely follows a relationship dependent on the square root of time. (C) 2001 Elsevier Science B.V. All rights reserved.