Iron(II) in repository systems : a thermodynamic study of solubility and hydrolysis in dilute to concentrated chloride systems

Due to the extensive use as container material, metallic iron and its corrosion products are expected to strongly impact the geochemical conditions in the near-field of potential repositories for nuclear waste disposal. Solubility experiments with well-defined Fe(OH)2(cr) and Fe2(OH)3Cl(cr) solid phases were conducted in dilute to concentrated KCl/KOH systems. Solid phases were characterized by XRD. Eh, pH and the aqueous iron concentration were monitored. Experimental data was used to develop a new thermodynamic SIT activity model to accurately describe the Fe2+ K+ H+ OH- Cl--H2O(l) system. Results of the conducted solubility experiments will be discussed with special focus on potential impacts of crystal size and surface effects.