A new approach to an efficient and selective extraction of Cs + ions from water, sea water enriched with Cs + and a radioactive solution simulating the effluents of the Fukushima reactors ( 137 Cs, 29 kBq L 21 ) was developed by using porous silica-or glass-based nanocomposites containing Prussian blue type nanoparticles, Co 2+ /[Fe(CN) 6 ] 32 , with sizes below 10 nm. A particular emphasis is given on the kinetics of cesium sorption fitted by using the classical reaction order model as well as a diffusion model in order to better understand the sorption mechanism. Compared to the amount of Co 2+ / [Fe(CN) 6 ] 32 nanoparticles, the sorption capacities of studied nanocomposites are more than three times higher than the ones observed for the respective bulk materials. These nanocomposites present a high selectivity to Cs + and extract it in trace amounts.