A Mössbauer study of the effect of dithionite/citrate/bicarbonate treatment on a vermiculite, a smectite and a soil

Abstract

When describing clay minerals of natural origin one often has to take into account the possibility that they contain other phases, e.g. iron oxides and hydroxides which may form a ‘coating’ on the clay mineral itself or occur as physically inseparable ultra-fine particles. These iron oxyhydroxides are sometimes difficult to detect by XRD as a consequence of their very small ‘domain volumes’ (Kodama et al., 1977). The iron oxyhydroxides are normally removed chemically prior to detailed characterization of the clay mineral. Removal of iron oxyhydroxide coatings facilitates dispersion and subsequent particle-size fractionation of minerals and soils and also enhances the parallel orientation, and therefore the intensity, of basal X-ray reflections of layer-silicates.