Influence of Silica Coatings on Magnetite-Catalyzed Selenium Reduction
journal contributionposted on 2021-02-19, 20:15 authored by Sara Goberna-Ferrón, Maria P. Asta, Bahareh Zareeipolgardani, Sarah Bureau, Nathaniel Findling, Laura Simonelli, Jean-Marc Greneche, Laurent Charlet, Alejandro Fernández-Martínez
The reactivity of iron(II/III) oxide surfaces may be influenced by their interaction with silica, which is ubiquitous in aquatic systems. Understanding the structure–reactivity relationships of Si-coated mineral surfaces is necessary to describe the complex surface behavior of nanoscale iron oxides. Here, we use Si-adsorption isotherms and Fourier transform infrared spectroscopy to analyze the sorption and polymerization of silica on slightly oxidized magnetite nanoparticles (15% maghemite and 85% magnetite, i.e., ∼2 maghemite surface layers), showing that Si adsorption follows a Langmuir isotherm up to 2 mM dissolved Si, where surface polymerization occurs. Furthermore, the effects of silica surface coatings on the redox-catalytic ability of magnetite are analyzed using selenium as a molecular probe. The results show that for partially oxidized nanoparticles and even under different Si surface coverages, electron transfer is still occurring. The results indicate anion exchange between silicate and the sorbed SeIV and SeVI. X-ray absorption near-edge structure analyses of the reacted Se indicate the formation of a mixed selenite/Se0 surface phase. We conclude that neither partial oxidation nor silica surface coatings block the sorption and redox-catalytic properties of magnetite nanoparticles, a result with important implications to assess the reactivity of mixed-valence phases in environmental settings.
Read the peer-reviewed publication
results showLangmuir isothermsilica surface coatingsredox-catalytic abilitySi adsorptionSe VISi-coated mineral surfacesX-ray absorption near-edge structur...anion exchangesurface behaviorSilica Coatingselectron transferSi surface coveragesMagnetite-Catalyzed Selenium Reductionredox-catalytic propertiesmixed-valence phasessurface polymerization2 mMmagnetite nanoparticlesuse Si-adsorption isothermsnanoscale iron oxidessilica surface coatings blockSe IV