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

Dissolution of a borosilicate glass containing a complex mixture of simulat ed fission product oxides has been investigated in single-pass flow-through (SPFT) experiments in moderately alkaline media at 40 degrees C. The exper iments were designed such that the ratio of the solution flow rate to the g lass surface area varied extensively over the experimental matrix. Dissolut ion of the glass is surface reaction-controlled under these experimental co nditions. In Si-rich, alkaline solutions, the concentration of Al is modera ted 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)(-) (0.06)((nq))a(H4SiO4)(0.51) increases. A rate law containing a mixed Al/Si affinity term gives good agreement with the experimental data. (C) 2000 Elsevier Science B.V. All rights reserved.