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Journal Articles Geochimica et Cosmochimica Acta Year : 2024

Role of the crystal chemistry on the dissolution kinetics of Fe(III)-rich smectites

Abstract

Smectites are reactive minerals that are present in surface environments. Most of the smectite dissolution kinetics reported in the literature are related to Al-rich smectites, whereas Fe(III)-rich smectites, which are commonly found in soils, have not been well studied. In this study, the impact Fe(III)/O 20 (OH) 4) and Al-rich smectites as the R Si =f(∆G) functions differ, with Fe(III)-rich smectites exhibiting greater instability than Al-rich smectites. Under the most acidic conditions investigated (pH 1.8 and 2), the crystal chemistry and mineralogy of the smectite changed during dissolution, with a relatively greater loss of tetrahedral Fe than of octahedral Fe and the formation of amorphous silica phases. These results show that the amount and location of structural Fe(III) in smectites impact the stability of the minerals. This suggests that the dissolution rate of smectites as a function of the ionic activity product classically used to describe reactive transport should consider the effects of the crystal chemistry, in particular, the amount of structural Fe(III), which is rather high, especially in soil smectites.
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Saturday, August 31, 2024
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Saturday, August 31, 2024
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Dates and versions

hal-04442866 , version 1 (06-02-2024)

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Delphine Masson, Valentin Robin, Emmanuel Joussein, Emmanuel Tertre, F. Baron. Role of the crystal chemistry on the dissolution kinetics of Fe(III)-rich smectites. Geochimica et Cosmochimica Acta, 2024, ⟨10.1016/j.gca.2024.01.028⟩. ⟨hal-04442866⟩
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