Fe3O4 nanoparticles were surface modified with Prussian blue (PB) and the nanoparticles were used for the removal of cesium (Cs) ion. The attachment of PB with the Fe3O4 and their morphology were explained based on the studies by transmission electron microscope and BET measurements. The Cs ion adsorption studies have shown that the Cs removal efficiency reached maximum within 120 min. The adsorption kinetics studies using Lagergren pseudo-first-order kinetic model suggest the values of the amount of metal ion adsorbed at equilibrium (q (e)) and adsorption rate constant (k (1)) as 22 mg/g and 0.015 min(-1), respectively. The capture efficiency of the prepared nanoparticles was studied by varying the flow channel diameter, applied magnetic field, and the fluid flow velocity. The study suggests that PB-Fe3O4 nanoparticles could be used for the detoxification of Cs where the flow velocity is in the range of few tens of cm/s.