INVESTIGADORES
ALVAREZ Mariana
congresos y reuniones científicas
Título:
Acid dissolution of synthetic manganese goethite before and after transformation to hematite by heating
Autor/es:
MARIANA ALVAREZ; ELSA E. SILEO; ELSA H. RUEDA
Lugar:
Bahía Blanca
Reunión:
Conferencia; 12th International Clay Conference; 2001
Institución organizadora:
The Clay Minerals Society
Resumen:
Dehydroxilation of goethite in soil with formation of hematite may occur in some environments due to natural and managed fires. The dehydroxilation of goethite can be influenced by Mn-substitution, particle size and structural defects. Acid dissolution of Mn-goethite and hematite provides evidence of the incorporation of Mn in the structure of these minerals. Dissolution kinetics may provide an indication of the effects of Mn substitution and heating on the solubility and stability of these minerals in the soil environment. If uniform crystals retain their shapes during dissolution, the dissolution process can be described by the cube-root law. Dissolution of mixtures of goethite and hematite does not follow the cube-root law. This situation may also apply to the dissolution of partly dehydroxylated goethite consisting in goethite and hematite. This work describes the dissolution kinetics of Mn-goethites synthetized by Stiers and Schwertmann method1, with some modifications introduced by Schwertmann and Cornell2, and its heated products. It examines the hypothesis that the non-uniform nature of these materials will result in complex dissolution kinetics. Measurements of the kinetics of acid dissolution of synthetic manganese goethites and corresponding hematites produced by heating of parent Mn-goethites at various temperatures were carried out in 6 mol dm-3 HCl at 30 °C. Chemical analysis, XRD, SEM and EDAX of the samples complete this study.   1.       STIERS, W. and SCHWERTMANN, U. (1985) Evidence for manganese substitution in synthetic goethite. Geochim. Cosmochim. Acta 49, 1909-1911. 2. SCHWERTMANN, U. and CORNELL, R.M. (1991) Iron oxides in the laboratory. Preparation and Characterization. VCH. Weinheim (Federal Republic of Germany). 137 pp.