Effect of chlorine and chromium on sulfur solubility in low-activity waste glass

According to an empirical sulfur solubility model developed from over 200 simulated low-activity waste (LAW) glasses, chlorine and chromium show strong effects on lowering sulfur solubility in glass. This work investigates the saturation concentrations of the sulfur, chlorine, and chromium anionic species coexisting in a glass matrix. A simplified LAW glass was prepared and saturated by sodium sulfate, sodium chloride, and sodium chromate salts as single components and as mixtures with different ratios at 25 mol%, 50 mol%, and 75 mol% of sulfate mixed with chloride or chromate. A crucible-scale salt-saturation was performed to determine saturation concentrations of sulfur, chromium, and chlorine incorporated into the simplified LAW glass. The glass compositions were analyzed by inductively coupled plasma-atomic emission spectroscopy, ion chromatography, and X-ray emission spectroscopy. The chemical analysis data show that the chromium and chlorine incorporated in the glass have strong negative effects on sulfur solubility, which can be qualitatively explained by the sulfur, chlorine, and chromium ions competing for voids in the glass matrix.