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Ferrihydrite Nanoparticle Aggregation Induced by Dissolved Organic Matter

  • Luigi Gentile
  • Tao Wang
  • Anders Tunlid
  • Ulf Olsson
  • Per Persson
Publishing year: 2018
Language: English
Pages: 7730-7738
Publication/Series: Journal of Physical Chemistry A
Volume: 122
Issue: 38
Document type: Journal article
Publisher: The American Chemical Society

Abstract english

Ferrihydrite (Fh) nanoparticles are omnipresent in nature and often highly mobile because of their colloidal stability. Thus, Fh serves as a vector for iron as well as associated nutrients and contaminants. Here, we demonstrate, using small-angle X-ray scattering combined with cryo-transmission electron microscopy (cryo-TEM), that dissolved organic matter (DOM), extracted from a boreal forest soil, induce aggregation of Fh nanoparticles, of radius 3 nm, into fractal aggregates, having a fractal dimension D = 1.7. The DOM consists of both fractal-like colloids (>100 nm) and small molecular DOM, but the attractive Fh interparticle interaction was mediated by molecular DOM alone as shown by cryo-TEM. This highlights the importance of using soil extracts, including all size fractions, in studies of the colloidal behavior of DOM-mineral aggregates. The Fh nanoparticles also self-assemble during synthesis into aggregates with the same fractal dimension as the DOM-Fh aggregates. We propose that, in both the absence and presence of DOM, the aggregation is controlled by the Fh particle charge, and the process can be viewed as a linear polymerization into a self-avoiding random walk structure. The theoretical D value for this is 5/3, which is in close agreement with our Fh and DOM-Fh results.


  • Physical Chemistry


  • ISSN: 1089-5639
Tao Wang
E-mail: tao [dot] wang [at] biol [dot] lu [dot] se

Postdoctoral fellow


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