TITLE:
Effect of pH and Ionic Strength on 152Eu Sorption to Granitic Rocks and Component Minerals
AUTHORS:
Fidelis Sameh Ebong, Gillian Nkeudem Asoba, Nick Evans
KEYWORDS:
Surface Complexation, Sorption Edge, Saline Environment, Immobilisation of Radionuclides
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.5,
May
28,
2026
ABSTRACT: The basic objective of radioactive waste management is to prevent unacceptable radiological risk for people today, and for future generations. The immobilisation of radionuclides in groundwater environments cannot be explained solely by the empirical models. The health and safety approach to the storage of radioactive waste in different geochemical media depends solely on the ability of rocks to retard through sorption any leach radionuclides from the near field. Sorption studies of 152Eu as a representative member of trivalent actinides were carried out in the lab at varying pH and different saline environment using different granitic rocks and minerals. To investigate the effect of ionic strength as well as pH, two sets of experiments, in the presence of 0.1 and 0.05 mol?dm?3 NaCl, were used with a control having no NaCl present. The effect of surface area has been taken into consideration in the surface complexation studies using the JChess geochemical code. NaCl is used to create a low concentration brine/seawater environment. With the possible disposal/storage of nuclear waste in deep geological repository. Sample separation was performed as described above and counting was performed for Eu counting was performed based on its gamma emitting properties using Cobra II Auto Gamma. Varying pH had no effect on sorption in 0.05 and 0.1 mol?dm?3 NaCl systems however, net sorption for all Eu species in solution was higher than for NaCl free system. Sorption varied with pH below pH 7 for sorption in NaCl free system. Saturation was attained after pH 8. Sorption in varying pH showed similar sorption profiles in both NaCl systems. Eu sorption is enhanced in the presence of NaCl. Surface complexation constants, Log K values for experimental data have been determined by fitting modelled data to experimental data. The modelling approach can be included efficiently in transport simulations having chemical gradients in space and time.