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Clays and Clay Minerals; April 2007; v. 55; no. 2; p. 165-176; DOI: 10.1346/CCMN.2007.0550206
© 2007 Clay Minerals Society
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Fe(III)-MODIFIED MONTMORILLONITE AND BENTONITE: SYNTHESIS, CHEMICAL AND UV-VIS SPECTRAL CHARACTERIZATION, ARSENIC SORPTION, AND CATALYSIS OF OXIDATIVE DEHYDROGENATION OF PROPANE

T. Grygar1,*, D. Hradil1, P. Bezdicka1, B. Dousová2, L. Capek3 and O. Schneeweiss4

1 Institute of Inorganic Chemistry ASCR, 250 68 Rez, Czech Republic
2 Institute of Chemical Technology in Prague, Technicka 5, 166 28 Prague 6, Czech Republic
3 University Pardubice, Cs. Legii 565, 532 10 Pardubice, Czech Republic
4 Institute of Physics of Materials ASCR, Zizkova 22, 616 62 Brno, Czech Republic

* E-mail address of corresponding author: grygar{at}iic.cas.cz

Two major species were identified in Fe-treated montmorillonite: monomeric or dimeric hydroxoaqua cations Fe(OH)x (3–x)+ (form I), and polymeric structures with edge-shared Fe(O,OH)6 (form II). These species have different electron spectra (absorption maximum is 29,600 cm–1 in form I, and 26,000 and 28,000 cm–1 in form II), chemical and thermal stability, and electrochemical behavior. Form I behaves as a partly exchangeable cation in interaction with Cu2+ from Cu-trien solution and Ni2+ from Ni-EDTA, that can be used for selective quantitative analysis. On heating above the dehydration temperature (~100–150°C) montmorillonite with Fe3+ in form I is converted to a mica-like structure and Fe3+ ions are fixed more strongly in the montmorillonite structure. Form II behaves similarly to hydrous ferric oxides, but its thermal crystallization to hematite is postponed to ~500–600°C. The Fe3+ cations in the interlayer space are much less thermally stable than Al pillars in pillared interlayered clays (PILCs). Form I is more active in oxidative dehydrogenation of propane, while form II is the active species in sorption of As and the non-specific combustion of propane. To produce only form II by the treatment of montmorillonite with Fe3+, its load must be kept below ~20 wt.%; otherwise the usual hydrous ferric oxides are formed.

Key Words: As sorption • Fe-montmorillonite • Fe-bentonite • Oxidative Dehydrogenation of Propane • Pillaring • Speciation of Fe






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