Composition and molecular scale structure of nanophases formed by precipitation of biotite weathering products

Tamrat Wuhib Zewde, Rose Jérôme, Grauby Olivier, Doelsch Emmanuel, Levard Clément, Chaurand Perrine, Basile-Doelsch Isabelle. 2018. Composition and molecular scale structure of nanophases formed by precipitation of biotite weathering products. Geochimica et Cosmochimica Acta, 229 : 53-64.

Quartile : Q1, Sujet : GEOCHEMISTRY & GEOPHYSICS

Résumé : Because of their large surface area and reactivity, nanometric-size soil mineral phases have a high potential for soil organic matter stabilization, contaminant sorption or soil aggregation. In the literature, Fe and Al phases have been the main targets of batch-synthesized nanomineral studies while nano-aluminosilicates (Al and Si phases) have been mainly studied in Andic soils. In the present work, we synthesized secondary nanophases of Fe, Al and Si. To simulate a system as close as possible to soil conditions, we conducted laboratory simulations of the processes of (1) biotite alteration in acidic conditions producing a Al Si Fe Mg K leachate solution and (2) the following neoformation of secondary nanophases by titrating the leachate solution to pH 4.2, 5 and 7. The morphology of the nanophases, their size, crystallinity and chemistry were characterized by TEM-EDX on single particles and their local atomic structure by EXAFS (Extended X-ray Absorption Fine Structure) at the Fe absorption K-edge. The main nanophases formed were amorphous particles 10–60 nm in size whose composition (dominated by Fe and Si) was strongly controlled by the pH conditions at the end of the titration. At pH 4.2 and pH 7, the structure of the nanophases was dominated by the polymerization of Fe, which was hindered by Al, Si, Mg and K. Conversely, at pH 5, the polymerization of Fe was counteracted by precipitation of high amounts of Si. The synthetized nanophases were estimated to be rather analogous to nanophases formed in natural biotite-bearing soils. Because of their small size and potential high surface reactivity, the adsorption capacities of these nanophases with respect to the OM should be revisited in the framework of soil C storage.

Classification Agris : P33 - Chimie et physique du sol

Champ stratégique Cirad : Axe 6 (2014-2018) - Sociétés, natures et territoires

Auteurs et affiliations

• Tamrat Wuhib Zewde, Aix-Marseille université (FRA)
• Rose Jérôme, CNRS (FRA)
• Grauby Olivier, CINAM-Marseille (FRA)
• Doelsch Emmanuel, CIRAD-PERSYST-UPR Recyclage et risque (FRA) ORCID: 0000-0002-7478-4296
• Levard Clément, CNRS (FRA)
• Chaurand Perrine, Aix-Marseille université (FRA)
• Basile-Doelsch Isabelle, INRA (FRA) - auteur correspondant

Source : Cirad-Agritrop (https://agritrop.cirad.fr/587543/)

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