10.26165/JUELICH-DATA/SECCU6 Marques Fernandes, Maria(Paul Scherrer Institut, Laboratory for Waste Management, 5232 Villigen PSI, Switzerland)Klinkenberg, Martina(Institute of Energy and Climate Research (IEK-6) – Nuclear Waste Management, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany)Baeyens, Bart(Paul Scherrer Institut, Laboratory for Waste Management, 5232 Villigen PSI, Switzerland)Brandt, Felix(Institute of Energy and Climate Research (IEK-6) – Nuclear Waste Management, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany) Jülich DATA 2023 The adsorption of Ba and 226Ra on Na-illite (Illite du Puy, IdP) was studied in single element experiments as a function of pH and ionic strength. In addition, 137Ba/133Ba isotherms at different pH values were measured and the adsorption of trace 226Ra was quantified as a function of increasing Ba concentrations. This dataset contains experimental data on pH-edges and isotherms. Klinkenberg, Martina(Institute of Energy and Climate Research (IEK-6) – Nuclear Waste Management, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany)Marques Fernandes, Maria(Paul Scherrer Institut, Laboratory for Waste Management, 5232 Villigen PSI, Switzerland)Brandt, Felix(Institute of Energy and Climate Research (IEK-6) – Nuclear Waste Management, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany)