Formation of magnetite in highly alkaline media in the presence of small amounts of ruthenium

Krehula, Stjepko; Musić, Svetozar (2007) Formation of magnetite in highly alkaline media in the presence of small amounts of ruthenium. Croatica Chemica Acta, 80 (3-4). pp. 517-527. ISSN 0011-1643

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Abstract

The effect of small amounts of ruthenium on the formation of magnetite in highly alkaline media was investigated using X-ray powder diffraction (XRD), Mossbauer and FT-IR spectroscopies, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Acicular alpha-FeOOH particles precipitated in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH) were used as a reference material. Initial addition of small amounts of Ru(NO)(NO3)(3) to that precipitation system had a drastic effect on the formation of iron oxide phases and their properties. The addition of Ru(NO)(NO3)3 favoured the formation of stoichiometric Fe3O4. With an increase of the initial Ru(NO)(NO3)3 concentration in the precipitation systems less time was needed for the formation of Fe3O4 as a single Fe-bearing phase in the precipitates. Ruthenium ions made solid solutions alpha-(Fe,Ru)OOH; however, there was no indication of the formation of solid solutions with alpha-Fe2O3 and Fe3O4, Mossbauer and FT-IR spectroscopies supported the conclusion on the formation of solid solutions a-(Fe,Ru)OOH. FE-SEM showed the formation of octahedral Fe3O4 Particles of a mu m range size. Ruthenium particles (approximate to 20 nm in size) were deposited onto the surfaces of Fe3O4 particles. They were also present in the form of clusters containing octahedral Fe3O4 particles in the nanosize range (approximate to 100 nm or less). The formation of Fe3O4 was interpreted as a combining effect of the thermal decomposition products of TMAH under autoclaving conditions and the catalytic action of ruthenium. In such a way strong reductive conditions in the investigated precipitation system were created.

Item Type:	Article
Uncontrolled Keywords:	ruthenium; TMAH; magnetite; XRD; Mossbauer; FT-IR; FE-SEM; EDS; low-temperature phase; alpha-feooh; thermal-decomposition; verwey transition; mossbauer; ions; particles; goethite; fe3o4; catalysts
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Materials Chemistry
Projects:	Project title Project leader Project code Project type Sinteza i mikrostruktura metalnih oksida i oksidnih stakala [85111] Mira Ristić 098-0982904-2952 MZOS
Depositing User:	Stjepko Krehula
Date Deposited:	25 Oct 2013 12:27
URI:	http://fulir.irb.hr/id/eprint/844

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