Аннотация:Kinetics of cesium sorption by ferrocyanide-modified clinoptilolite (NPF-Cl sorbent and its calcium form) from solutions with cesium concentration more than 50 mg/L was studied. Three stages of the process of cesium sorption were found. It was shown that the first stage of cesium sorption occurs in macropores of the sorbents resulting in chemical transformation of the surface of ferrocyanide phase of the sorbents, decrease of macropores (≥120 nm) volume and increase of mesopores (5-100 nm) volume. The degree of chemical transformation of the surface and change of mesopores volume increased with the increase of initial concentration of cesium in the solution. Diffusion of cesium into the sorbent's grains occurred at the second stage of sorption process. The third stage of the sorption process is realized after cesium diffusion into small mesopores and it is conditioned by precipitation of mixed ferrocyanide phases containing cesium in pores with the diameter of 3.7-4.8 nm. Decrease of volume of small micropores was observed as a result of the third stage of cesium sorption.