<p>Terrestrial ecosystems act as significant reservoirs for human and veterinary antibiotics. Given that the underlying mechanisms can be generalized to the broader group of amphoteric antibiotics, ciprofloxacin (CIPRO) (the most prescribed fluoroquinolone) and hematite and goethite (primary oxides of soils developed in the humid tropics) were selected. We have sought to integrate the information available in the literature on the fundamental characteristics (mainly the charge dynamics as a function of pH variations) of CIRO and Fe oxides and, thorough critical analysis and proposing the formation of a most stable double covalent bound, to elucidate the chemical principles governing both outer- and inner-sphere adsorptions of CIPRO on Fe oxides. As the pH rises above 4.1, the zwitterionic species of ciprofloxacin (CIPRO ±) increasingly predominates, enabling outer-sphere adsorption through the interaction of its negatively charged groups with the positively charged adsorption sites on Fe oxides. Considering the combination of dominant pH in soils (4–6) and the possibility of surface charges on Fe oxides and CIPRO, the following inner-sphere adsorption dynamics are expected: i) more acidic condition (pH ~ 4.0) – easer rupture of the FeO–H^−0.5 than that FeO–H₂^+0.5, CIPRO(NH₂⁺)-ferrol bond (FeOH-NH₂CIPRO and FeO-NH₂CIPRO monodentate complex formation) and H⁺ release; ii) less acid condition (pH ~ 6.0) – easer rupture of the Fe–OH₂^+0.5 than that Fe–OH^−0.5, CIPRO(COO⁻)-ferrol bond (Fe-COOCIPRO monodentate complex formation) and H₂O or OH⁻ release; iii) combination of inner-sphere adsorption by NH₂⁺ and COO⁻ groups and closing of the Fe-COO(CIPRO)NH₂-OHFe ring structure (bidentate complex formation). This wide range of charges and bond stability conditions ensure low CIPRO potential of groundwater contamination in highly weathered tropical soils.</p>