Adsorption and diffusion mechanism of cesium and chloride ions in channel of geopolymer with different Si/Al ratios: molecular dynamics simulation

Geopolymer is a kind of inorganic cementitious material, which is produced by geopolymerization of activator and aluminosilicate. It can be used for solidification of radionuclides. In this study, molecular dynamics simulation was applied to investigate that the adsorption and diffusion mechanism of radioactive nuclide cesium and chloride ions in the channel of geopolymer with different Si/Al ratios. The simulation results could be characterized by density distribution, radial distribution function (RDF), hydrogen bond, mean square displacement (MSD) and diffusion coefficient. Density distribution indicated that there is an obvious aggregation of Cs+ and Cl- on the channel surface. Moreover, the composition of geopolymer gel has a great influence on the dynamic characteristics of ions. With the decrease of Si/Al ratio, both MSD and diffusion coefficient of cesium and chloride ions gradually reduced. It showed that the adsorption of geopolymer channel for Cs+ and Cl- gradually enhanced, and diffusion ability of Cs+ and Cl- has steadily decreased.