In some publications, the adsorption isotherms of some heavy metal ions, measured at different pH values on carbonic adsorbents, have inflection points followed by the increase of the adsorption values. In these works, however, the cause of the appearance of these points is not questioned. The purpose of the present work is to identify the causes of the appearance of the inflection points on the adsorption isotherms of the strontium ions on the activated carbons CAN-7 and CAN-8, obtained from walnut shells. The jumps on both adsorption isotherms are very clear and start on CAN-7 and oxidized CAN-8 at the same equilibrium concentrations of strontium ions. Probably, an important role in the adsorption process of strontium ions from aqueous solutions on these two active carbons has the surface chemistry of these adsorbents and the possibility of formation on the surface of the adsorbents of polymolecular layers. The appearance of the inflection points on the adsorption isotherms of the strontium ions on CAN-7 and CAN-8 oxidized active carbons are related to the interaction of the strontium ions with the nonhomogeneous surface of the adsorbents (based on the phosphatic groups, weak and strong carboxylic groups), subsequent formation of the polymolecular adsorbent layer, due to the hydrogen bonds formed between the Sr(OH)+ ions, but also to the collateral interactions between the strontium ions adsorbed at the interface. The interaction between hydrated strontium ions (Sr2+) and the supermicroporous and microporous surface of adsorbents will be totally different from that of the mesopores.