Dependence of albite dissolution kinetics on ph and time at 25°c and 70°c

The dissolution rate of albite has been measured as a function of pH and time at 25°C and 70°C in a single-pass flow-through leaching apparatus. Run times extended to 50 days in each experiment. Limited data were obtained at 25°C in the pH range 4–10. More extensive data were obtained at 70°C over the pH range 1.39–11.75. Dissolution rates were defined by release of Si, and in some cases also by Al and Na releases. Speciationsolubility calculations indicate the solutions were well undersaturated for all the likely possible secondary minerals. The fluid was maintained far from equilibrium with albite in all runs. Analysis of the data shows a general consistency with the transition state theory model of Helgesonet al. (1984). Feldspars leached at low and high pH at 70°C showed extensive development of prismatic etch pits demonstrating a surface reaction-controlled dissolution process.