Ca-Montmorillonite; MINSORB code (2-site protolysis no electrostatics surface complexation and cation exchange model developed and incorporated into MINEQL); solid:liquid ratio 0.94 resp. 1g/L, fixed parameters: Zn inventory 1E-3mol/kg, Mn inventory 4E-4mol/kg, selectivity coefficient for cation exchange Ca-Ni=0.8