Unveiling the impact of nontronite NAu-2 on Akaganeite Bioreduction and Mineral Precipitation
Résumé
Fe-oxides and Fe-phyllosilicates coexist in sediments and aquifers, playing a pivotal role in nutrient and pollutant cycles due to their large specific surface area and high reactivity. Under anaerobic conditions, dissimilatory ironreducing bacteria use Fe(III)-bearing minerals, such as Fe-phyllosilicates and Fe-oxides, as electron acceptors during their metabolic processes. While the bioreduction behavior of individual Fe-oxide and Fe-phyllosilicate minerals is well-documented, much less is known about how their reactivity is altered when combined in a mixed system. This study investigates how low concentrations of Fe-phyllosilicates influence the bioreduction of Fe-oxide by Shewanella oneidensis MR-1, using akaganeite (Aka) and nontronite (NAu-2) as model minerals. The results reveal that the presence of NAu-2 significantly decreased both the rate and extent of Aka bioreduction. Additionally, while bioreduction of Aka led to the formation of magnetite, siderite, and chukanovite, only magnetite precipitated in the presence of NAu-2, as confirmed by XRD, Mössbauer spectroscopy and transmission electron microscopy. These findings suggest that the interaction and surface properties of the Aka-NAu-2 composite fundamentally alter Aka's transformation, highlighting the complexity of mineral reactivity in natural environments.