Reversible Fe(ii) uptake/release by magnetite nanoparticles

Abstract

The reversible flow of Fe(ii) across the magnetite–solution interface impacts the stoichiometry and reactivity of magnetite nanoparticles.

Trace element and organic matter mobility impacted by Fe3O4-nanoparticle surface coating within wetland soil

“…The higher pH values observed in presence of both nFe3O4 after 10 PVs (t-test, p-values<0.05) might be the consequence of an oxidation of the nFe3O4. Peng et al 43,44 demonstrated that at pH 6, proton-promoted dissolution yields the release of Fe 2+ (aq) from magnetite nanoparticles, following the equation 1: where the square represents a cationic vacancy due to diffusive migration of iron cations 43,44 . Although the pH values observed during the leaching with both particles are similar, in the 10 first PVs the pH values of the leaching solution observed in presence of nFe3O4@DMSA were lower.…”

Probing the effects of redox conditions and dissolved Fe2+ on nanomagnetite stoichiometry by wet chemistry, XRD, XAS and XMCD

“…The surface properties of magnetite can be altered upon Fe(II)-recharge. Indeed, complex surface reactions can take place when stoichiometric magnetite is equilibrated with dissolved Fe(II), such as rapid atomic exchange 20 , redistribution of electron equivalents between bulk and the outermost surface of particles 21 , and surface-mediated electron transfer with redox-sensitive species in solution 22 . It is, therefore, necessary to thoroughly characterize both the bulk and surface of magnetite to accurately…”

“…XMCD spectra of magnetite typically show two negative peaks due to Fe(II) and Fe(III) on a O h site, and a positive one due to Fe(III) on a T d site, whose relative intensities allow determining the magnetite stoichiometry. For these reasons, XAS and XMCD at the Fe L 2,3 -edges were used in several studies to elucidate the structure and properties of magnetite surfaces 21,[24][25][26][27][28][29][30][31] .…”

Tunable Mn Oxidation State and Redox Potential of Birnessite Coexisting with Aqueous Mn(II) in Mildly Acidic Environments

“…Nevertheless, it is likely that electron transfer between birnessite and sorbed Mn 2+ impacts Mn AOS and oxidative reactivity of birnessite under mildly acidic conditions. Our recent studies showed that electron injection from sorbed Fe(II) to magnetite (Fe 3 O 4 ) can change the structural Fe(II)/Fe(III) ratio and the reduction potential of magnetite without the formation of secondary mineral phases, the extent of which depends on solution pH, magnetite loading, and initial concentrations of aqueous Fe(II) and redox-active organic molecules [22,23]. Similarly, the interfacial electron transfer between birnessite and Mn 2+ may induce electron injection and delocalization in Mn octahedral layers of birnessite, even though no detectable secondary phases are formed.…”