On the state of iron in a clinoptilolite

The characterization of an iron-containing natural zeolitic sample from the deposit of Tasajeras (Cuba) has been carried out by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS),57Fe Mossbauer spectroscopy and Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The results show that iron is mainly located (ca. 96%) as Fe3+ in an octahedral site of the clinoptilolite framework. No evidence of tetrahedrally coordinated Fe3+ was found. The remaining 4% Fe is located as Fe2+ in an extraframework octahedral site, probably as a solvated ion, within the clinoptilolite structure.