Issue 7, 2018

Reversible Fe(ii) uptake/release by magnetite nanoparticles


Magnetite commonly coexists with aqueous Fe2+ (Fe2+(aq)) in anoxic subsurface environments. Complex interactions between magnetite and Fe2+(aq) profoundly impact redox potential fluctuations in surrounding environment and biogeochemical cycles of important elements and contaminants. However, the ability of magnetite to act as a source/sink of electron equivalents through fluctuations in solution pH or the activity of Fe2+(aq) remains poorly quantified. We systematically studied the interrelationships between equilibrium Fe2+(aq) concentrations and structural versus surface-localized Fe(II)/Fe(III) ratios in magnetite using micro X-ray diffraction and synchrotron-based X-ray magnetic circular dichroism, respectively, under different controlled experimental conditions. Relative to pH 7, at pH 6 proton-promoted dissolution yields Fe2+(aq) release from magnetite nanoparticles, coupled to a decrease in the structural Fe(II)/Fe(III) ratio by electron hopping along the octahedral sublattice from the particle interior to the surface. At pH 8, magnetite sorbs Fe2+(aq), increasing both the structural and surface-localized Fe(II)/Fe(III) ratio. Amendments of Fe2+(aq) inhibit acidic Fe2+(aq) release and promote Fe2+(aq) uptake at more basic conditions, whereas increasing magnetite loading facilitates Fe2+(aq)–magnetite interaction at the same respective pH extremes. The reversible flow of Fe(II) across the magnetite–solution interface under different conditions implies that the redox reactivity of magnetite nanoparticles is quickly responsive to changes in environmental conditions, such as an increase in pH due to groundwater passing through carbonate-rich rocks, via a dynamic redistribution of electron equivalents between particle interiors and the solid/water interface.

Graphical abstract: Reversible Fe(ii) uptake/release by magnetite nanoparticles

Supplementary files

Article information

Article type
21 Mar 2018
04 Jun 2018
First published
05 Jun 2018

Environ. Sci.: Nano, 2018,5, 1545-1555

Author version available

Reversible Fe(II) uptake/release by magnetite nanoparticles

H. Peng, C. I. Pearce, W. Huang, Z. Zhu, A. T. N'Diaye, K. M. Rosso and J. Liu, Environ. Sci.: Nano, 2018, 5, 1545 DOI: 10.1039/C8EN00328A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity