The sorption-desorption processes in the systems ―radionuclide (137Cs, 90Sr)—natural clay minerals‖ and
―radionuclide (137Cs, 90Sr)—modified clay mineral forms with deposited humic acids and iron hydroxide‖ were
studied. It is found that the presence of humic acids and Fe(OH)3 on the surface of clay minerals increases 137Cs and
90Sr sorption in wide pH range (4 9). Ions Na+
and Ca2+ with the increase of their concentration in aqueous
solutions reduce the 137Cs and 90Sr fixation and promote their migration to the environment. It is shown that the
ammonium salts act as effective leaching reagents relative to the cesium ions and according to their desorption
capacity they can be arranged as follows: NH4Cl<NH4H2Cit<(NH4)2Ox<(NH4)2HCit

Keywords: radionuclides, 137Сs, 90Sr, sorption-desorption, natural and modified clay minerals, leaching agent