Reductive dissolution and MiSssbauer spectroscopic study of Fe forms in the fine fractions of Slovak Fe-rich bentonites

ABSTRACT: Four samples of <2 ~tm fractions of Fe-rich bentonites from tile area of the Zvolensk ~ kotlina Basin (Slovakia) have been investigated byMiSssbauer spectroscopy and reductive dissolution in ammonium hydrogen oxalate (pH = 2.7). Both methods have shown the presence of goethite in the samples. The relative amount of Fe bound in goethite varied more within the samples of bentonite from Zvolensk ~ Slatina, which was redeposited after transport over a short distance, than in the authigenically altered bentonite from Hrochot'. The results of the fits of the reductive dissolution curves uggest size distribution, variation in Al-for-Fe substitution i goethite particles and/or different access of extracting solution to goethite particles present in the analysed fine fractions of bentonites. The fine fractions of bentonites frequently contain a part of Fe bound in iron oxides or oxyhydroxides, such as goethite or hematite, tc. (e.g. Murad, 1987; Goodman et al.; 1988; Lear et al., 1988; Vandenberghe et al., 1990; Lego et al., 1995)