Home >> Canadian Metallurgical Quarterly, Number 4, October-December 1996

Thermodynamic Analysis of the Reactions of Iron Oxides: Dissolution in Oxalic Acid

Authors: Panias, D.; Taxiarchou, M.; Douni, I.; Paspaliaris, I.; Kontopoulos, A.

Source: Canadian Metallurgical Quarterly, Number 4, October-December 1996 , pp. 363-373(11)

Publisher: Maney Publishing

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Abstract:

The mechanism of dissolution of pure iron oxides by means of organic acids comprises two different chemical pathways: (a) non-reductive dissolution and (b) reductive dissolution. In this paper, the thermodynamic analysis of these pathways for the iron oxides—oxalic acid system is presented. In low acid solutions (pH higher than 3) the only thermodynamically stable complex ions of bivalent and trivalent iron are [Fe2+(C2O4)2]− and [Fe3+(C2O4)3]3−, Uncomplexed Fe2+ ion can be identified only in high acid solutions, while uncomplexed Fe3+ ion is not likely to build-up in oxalic acid solutions. In the pH range 1—2 the [Fe3+(C2O4)2]− and [Fe3+C2O4]+ ions are stable, while at pH less than 1, the [Fe3+HC2O4]2+ is the only ion existing. Copyright © 1996 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd

Résumé

La dissolution d'oxides de fer purs par les acides organiques peut etre realisee selon deux mechanismes chimiques différents: (a) une dissolution non réductive et (b) une dissolution réductive. L'analyse thermodynamique de ces deux traitements chimiques pour Ie système oxide de fer–acide oxalique est présenté dans cet article. En solutions faiblement acides (pH> 3), les seuls complexes ioniques du fer bivalent et trivalent thermodynamiquement stables sont [Fe2+(C2O4)2]2− et [Fe3+(C2O4)3]3−, Les ions Fe2+ non compléxés ne peuvent être identifiés qu'en solution fortement acides, tandis que la présence d'ions Fe3+ non compléxés restent peu probable en solution d'acide oxalique. Dans une gamme de pH de 1—2, les ions [Fe3+(C2O4)2]− et [Fe3+C2O4]+ sont stables, tan dis qu'à pH < 1, la seule forme ionique existante est [Fe3+HC2O4]2+.

Document Type: Research Article

DOI: http://dx.doi.org/10.1179/000844396109608642

Publication date: 1996-10-01

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