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Iron Oxide-Clay Mineral Association in Brazilian Oxisols: A Magnetic Separation Study

Published online by Cambridge University Press:  28 February 2024

Mauricio Paulo Ferreira Fontes
Mauricio Paulo Ferreira Fontes*
Affiliation:
Departamento de Solos, Universidade Federal De Viçosa, 36570 Viçosa, MG, Brasil
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Abstract

Selected Brazilian Oxisols were sampled and submitted to high-gradient magnetic separation (HGMS) to study the iron oxide-clay mineral associations. The soils, derived from four different parent materials, have mineralogy dominated mostly by hematite, goethite, and kaolinite. Gibbsite appears in most soil samples. The high-gradient magnetic separation showed good separation for some soils, as indicated by color differentiation and iron oxide segregation between magnetic and nonmagnetic fractions. Soils that showed a somewhat low surface area for the iron oxides associated with high phosphate adsorption were poorly separated by HGMS. This suggests a strong interaction between kaolinite and iron oxides, which would indicate a low estimation of their surface areas obtained by the difference method using BET-N2 data. A relative concentration of anatase and rutile in the magnetic portion of some of the samples was attributed to the presence of Fe, either as coatings on the crystals or within the structure of these two minerals.

Keywords

BrazilGoethiteHematiteMagnetic separationOxisols
Type
Research Article
Information
Clays and Clay Minerals , Volume 40 , Issue 2 , April 1992 , pp. 175 - 179
Copyright
Copyright © 1992, The Clay Minerals Society

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