Fe-silicalite nano- and microcrystals as heterogeneous Fenton-type catalysts have been synthesized and characterized by dynamic light scattering, X-ray diffraction, scanning and transmission electron microscopy, nitrogen adsorption measurements, inductively coupled plasma optical emission spectrometry, UV visible diffuse reflectance spectroscopy and temperature-programmed desorption of ammonia. Catalytic performance of Fe-silicalites was studied in mineralization of EDTA by H2O2 at 303-353 K and Co-60 removal from EDTA chelates. The effect of activation by the acid treatment on the state of active sites, catalytic activity and stability of Fe-silicalites was studied. Fe-silicalites nanocrystals are more efficient catalysts vs. microcrystals due to enhanced catalytic sites accessibility. (C) 2015 Elsevier B.V. All rights reserved.