TY - JOUR
T1 - Evidence for controlled insertion of Fe ions in the framework of clinoptilolite natural zeolites
AU - Chávez-Rivas, F.
AU - Rodríguez-Fuentes, G.
AU - Berlier, G.
AU - Rodríguez-Iznaga, I.
AU - Petranovskii, V.
AU - Zamorano-Ulloa, R.
AU - Coluccia, S.
N1 - Funding Information:
F. Chávez-Rivas and R. Zamorano-Ulloa acknowledge the support of COFAA-IPN. This research was partially supported by Project IN110608 of DGAPA-UNAM and Project 102907 of CONACYT, Mexico. F. Chávez-Rivas acknowledge technical support from Ignacio Colin Duran from ESFM-IPN and Dr. Vasudev Shetti of Dipartimento di Chimica, Torino. Prof. Mario Chiesa (Dipartimento di Chimica, Torino) is gratefully acknowledged for fruitful discussions.
PY - 2013
Y1 - 2013
N2 - This work is focused on the spectroscopic characterization of a set of materials obtained by hydrothermal treatments from a natural clinoptilolite zeolite, NZ. OPAZ (orthophosphoric acid treatment on NZ), Fe2+-OPAZ (ferrous sulphate acid treatment on OPAZ) and Fe3+-OPAZ (ferric sulphate acid treatment on OPAZ) samples were characterized by HRTEM, UV-Vis, temperature dependent EPR and Infra Red spectroscopies in order to describe the structure, nuclearity and distribution of iron ions and iron oxides clusters and particles. Complementary pieces of information were obtained from the different techniques. In particular, HRTEM analysis suggested an effect of the hydrothermal treatments not only on the Fe speciation but also on the zeolite particles morphology and surface. The same technique could not clearly detect the presence of iron oxide phases, suggesting their very small size and high dispersion. A more detailed description of the isolated and clustered species could be in turn obtained by UV-Vis spectroscopy. This was confirmed by temperature dependent EPR spectroscopy, suggesting the presence of nanosized ferromagnetic magnetite-like particles. Finally, IR spectroscopy gave clear cut evidence about the insertion of Fe3+ ions in framework positions, with consequent generation of distinct Bronsted acidity, after hydrothermal treatments with iron salts. This transformation could be explained through the reaction with defective hydroxyl nests formed by mildly acid hydrothermal treatment with isolated Fe3+ ions.
AB - This work is focused on the spectroscopic characterization of a set of materials obtained by hydrothermal treatments from a natural clinoptilolite zeolite, NZ. OPAZ (orthophosphoric acid treatment on NZ), Fe2+-OPAZ (ferrous sulphate acid treatment on OPAZ) and Fe3+-OPAZ (ferric sulphate acid treatment on OPAZ) samples were characterized by HRTEM, UV-Vis, temperature dependent EPR and Infra Red spectroscopies in order to describe the structure, nuclearity and distribution of iron ions and iron oxides clusters and particles. Complementary pieces of information were obtained from the different techniques. In particular, HRTEM analysis suggested an effect of the hydrothermal treatments not only on the Fe speciation but also on the zeolite particles morphology and surface. The same technique could not clearly detect the presence of iron oxide phases, suggesting their very small size and high dispersion. A more detailed description of the isolated and clustered species could be in turn obtained by UV-Vis spectroscopy. This was confirmed by temperature dependent EPR spectroscopy, suggesting the presence of nanosized ferromagnetic magnetite-like particles. Finally, IR spectroscopy gave clear cut evidence about the insertion of Fe3+ ions in framework positions, with consequent generation of distinct Bronsted acidity, after hydrothermal treatments with iron salts. This transformation could be explained through the reaction with defective hydroxyl nests formed by mildly acid hydrothermal treatment with isolated Fe3+ ions.
KW - Bronsted sites
KW - FTIR
KW - Fe-zeolites
KW - Hydrothermal treatment
KW - Natural zeolites
UR - http://www.scopus.com/inward/record.url?scp=84871338237&partnerID=8YFLogxK
U2 - 10.1016/j.micromeso.2012.04.001
DO - 10.1016/j.micromeso.2012.04.001
M3 - Artículo
SN - 1387-1811
VL - 167
SP - 76
EP - 81
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
ER -