Combined AFM and STXM in situ study of the influence of Eu(III) on the agglomeration of humic acid

Markus Plaschke, Jörg Rothe, Thorsten Schäfer, Melissa A. Denecke, Kathy Dardenne, Susanne Pompe, Karl Heinz Heise

Research output: Contribution to journalArticlepeer-review


Humic acid (HA) agglomerates formed in aqueous solutions in the presence of trivalent Eu cations were investigated in situ with a combination of atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM). The micromorphologies of both natural HA and a melanoidine based synthetic HA observed by AFM in electrolyte solution are in fair agreement with previous AFM studies on humic substances. STXM micrographs of Eu(III) induced HA agglomeration reveal zones of high and low optical density with markedly distinct C K-NEXAFS, indicative of different humic functionalities. Particulate agglomerates observed by AFM can be correlated to the dense zones, whereas fibrous structures in AFM images can be associated with the low density areas. The Eu cation distribution within the agglomerates cannot be unambiguously deduced from their C K-NEXAFS spectra. The near edge X-ray absorption fine structure spectra can be correlated to a segregation of different HA fractions, possibly due to the presence of humic species with different affinities for metal cation complexation. STXM micrographs of purified Aldrich HA exhibit the presence of other yet unidentified, carbon-rich particles, independent of the addition of Eu(III). Both AFM and STXM results for the synthetic melanoidine based HA demonstrate a homogeneous morphology and chemical structure. © 2002 Elsevier Science B.V. All rights reserved.
Original languageEnglish
Pages (from-to)245-256
Number of pages11
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Issue number1-3
Publication statusPublished - 4 Feb 2002


  • Atomic force microscopy
  • Humic acid
  • Scanning transmission X-ray microscopy
  • Synthetic humic acid

Research Beacons, Institutes and Platforms

  • Dalton Nuclear Institute


Dive into the research topics of 'Combined AFM and STXM in situ study of the influence of Eu(III) on the agglomeration of humic acid'. Together they form a unique fingerprint.

Cite this