Amorphous Fe Hydroxide Research Articles

Infrared study of the adsorption of hydroxycarboxylic acids onα-FeOOH and amorphous Fe (III)hydroxide

The adsorption of lactic acid, meso-tartaric acid,l-tartaric acid and citric acid onα-FeOOH and amorphous Fe(III)hydroxide was investigated by i.r. spectroscopy. The results indicate that adsorption is based on partial replacement of the surface hydroxyl groups by carboxylate groups. For meso-tartaric acid onα-FeOOH and for lactic acid andl-tartaric acid on amorphous Fe(III)hydroxide deprotonated alcoholic hydroxyl groups participate in the surface complex formation. A tentative model for the adsorption on the (100) face ofα-FeOOH is presented.

The Formation of Hematite from Amorphous Iron(III)Hydroxide

AbstractThe formation of hematite from amorphous Fe(III)hydroxide in aqueous systems at pH 6 and 70°C, both with and without oxalate, was followed by kinetic measurements, electron microscopy, i.r. spectroscopy and thermal analysis.In the absence of oxalate, small amorphous particles coalesce into aggregates which eventually become single crystals of hematite. When oxalate is present, crystal growth is much faster and does not proceed through the intermediate stage of aggregation. Aggregates, when formed, consist of groups of single crystals. It is suggested that oxalate accelerates the nucleation of hematite crystals by acting as a template, the Fe-Fe distance in Fe-oxalate ions being similar to that in hematite.

THE DISTRIBUTION OF IRON, MANGANESE, AND SCOTLAND ALUMINIUM IN SOME SOILS FROM NORTH‐EAST SCOTLAND

SummaryTwenty‐four soils from north‐east Scotland have been subjected to differential extraction techniques to determine the effect of hydromorphism on various Fe, Mn, and A1 fractions. There were pronounced losses of dithionite‐extractable Fe and Mn from gleyed horizons, but the 'silicate‐Fe’fraction appeared to be relatively unaffected. The oxalate‐extractable Fe and A1 fractions also decreased in response to gleying. The ratio of the oxalate‐ to dithionite‐extractable Fe fractions (Fe0/Fed) increased in gleyed horizons, presumably due to variations in the rate of ageing and crystallization of amorphous Fe oxides and hydroxides.