This study covers the evaluation of the structure and the capacity in adsorbing orthophosphate ions of kaolinites collected from sampling sites in Manaus (Brazil). The kaolinites were obtained using physical fractioning (sieving/siphoning) techniques and chemical treatment with HCl, H 2 SO 4 , H 2 O 2 and KCl. The investigation of the kaolinite lattices involved the Hinckley and Plançon indexes determined from X-ray diffraction data, Fourier transformed infrared spectroscopy, scanning electron microscopy and Mössbauer spectroscopy. The absorption capacity of orthophosphate ions was calculated by Freundlich and Langergren isotherms. A transitional state was observed in the crystallographic structure from kaolinites because of the isomorphic substitution of Al 3+ by Fe 3+. This isomorphic substitution occurs accompanied by the optical pleochroism behavior, but it also reduces the mean particle sizes and increases the number of structural defects and magnetic properties of these kaolinites. Mössbauer spectroscopy showed that the substituting Fe 3+ preferentially occupies octahedral sites. In the kaolinite lattices there are different octahedral sites of