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Mexican clinoptilolite- and mordenite-rich tuffs were modified to obtain their sodium, iron, and silver forms in order to elucidate the effects of metallic species on the sorption properties of the natural zeolitic materials for the removal of  from aqueous solutions. The interaction between the manganese solutions and the zeolitic materials was conducted by using a batch system. The unmodified and modified natural zeolites were characterized by scanning electron microscopy (SEM), X-ray diffraction, BET specific surface, and the points of zero charge. The amounts of Fe and Ag in both clinoptilolite- and mordenite-rich tuffs are similar (4.3±0.2 %wt. and 3.9±0.1 %wt., respectively). The morphology and the crystalline structure of both materials demonstrate no change when Fe or Ag is added into the zeolitic network; however, the textural characteristics and the point of zero charge were affected by the presence of these metallic species with respect to unmodified zeolitic materials. The kinetic data were best fit by a pseudo-second order model, and the Freundlich model described the isotherms. The clinoptilolite- and mordenite-rich tuffs modified with silver removed manganese more efficiently than those modified with iron or sodium did. Therefore, both zeolitic materials could be used for the removal of manganese from aqueous solutions, independent of their structural characteristics.

manganese, mordenite, clinoptilolite, sorption, kinetic, isotherms.