The present research concerns the possibility of adsorptive removal of the frequently used antibiotics – moxifloxacin and norfloxacin on natural zeolites – mordenite and its acid-modified form from aqueous solutions. The adsorption of the above-mentioned antibiotics on the selected natural zeolite samples was investigated under static and dynamic conditions. Adsorption experiment under dynamic conditions carried out using the specially constructed dynamic type of laboratory equipment. Based on the data of chemical, IR spectroscopic, X-ray diffraction analyses, it has shown that when the zeolite adsorbent is treated with an acid, an equivalent exchange of extra framework cations for a hydrogen ion and dealumination occurs and silanol groups are formed at the same time. The increase in the adsorption activity of mordenite as a result of its treatment with acid is associated with an increase in the pore size due to the unblocking of the adsorbent aluminosilicate framework channels during dealumination.