The sorption of thorium, uranium, neptunium, plutonium and americium on hydrotalcite, tobermorite, ettringite and calcium silicate hydrate gel were investigated in water, saturated NaCl solution and Q-brine at 25, 55 and 85 degrees C. Speciation was also studied. The data obtained will fulfil Freundlich's isotherm if the ion constituent is taken as a parameter but even Langmuir's isotherm will be valid if the ionic concentration of the various ionic species is taken into account. A theoretical parameter was found which permits the solution capability of the various cementitious materials to be compared with respect to the relevant ionic species present.
