Single-pass flow-through experiments on a simulated waste glass in alkaline media at 40°C.: I. Experiments conducted at variable solution flow rate to glass surface area ratio

Dissolution of a borosilicate glass containing a complex mixture of simulated fission product oxides has been investigated in single-pass flow-through (SPFT) experiments in moderately alkaline media at 40°C. The experiments were designed such that the ratio of the solution flow rate to the glass surface area varied extensively over the experimental matrix. Dissolution of the glass is surface reaction-controlled under these experimental conditions. In Si-rich, alkaline solutions, the concentration of Al is moderated to very low levels by the development of secondary aluminosilicate gels. Rates of dissolution decrease linearly as the solution activity product a Al( OH) 4 − ( aq) 0.06 a H 4 SiO 4 0.51 increases. A rate law containing a mixed Al/Si affinity term gives good agreement with the experimental data.