Al-doped maghemite examined as catalyst for the discoloration of methylene blue and for the decomposition of ammonium nitrate

A.F.CABRERA; C E RODRIGUEZ TORRES; S.J. STEWART

Social Science research Network

SSRN

Año: 2022

Nanostructured aluminium-doped magnetic iron (III) oxide (AlxFe2-xO3 with x= 0.33, 0.67 and 1) havebeen prepared by autocombustion method. The as-prepared samples were characterized by XRD,thermogravimetric analysis, UV-vis and Mössbauer spectroscopies and magnetometry. The cubicspinel is the main crystalline phase for all compositions. The presence of Al in the spinel phase causesa progressive decrease in both the cell parameter (a) and the grain size (L). The room temperatureMössbauer spectrum of x= 0.33 is mainly composed of a Fe3+ broad sextet while, for higher Alcontent, the spectra consist of a Fe3+ broad doublet corresponding to superparamagnetic maghemite.The saturation magnetization decreases with the Al doping and reaches a rather low value for the illcrystalline sample x = 1 (MS ~ 2 emu/g). The optical direct band gap of the samples is red-shifted withrespect to pure maghemite, with values close to 2 eV. The photocatalytic performance of AlxFe2-xO3tested in the decolorization of methylene blue dye showed a good efficiency for the oxide whoseband gap energy best matches the energy of the incident light (x= 0.33). The catalytic effect of thesesamples on the thermal decomposition of ammonium nitrate is more noticeable for those Alconcentrations that lead to the reaction being exothermic.Keywords: maghemite, Al-doped Fe2O3, photocatalysis, propelents, methylene blue, ammoniumnitrate