Iron, cobalt, and gadolinium transport in methanogenic granules measured by 3D magnetic resonance imaging

Jan Bartacek*, Frank J. Vergeldt, Josef Maca, Edo Gerkema, Henk Van As, Piet N.L. Lens

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

8 Citations (Scopus)

Abstract

Description of processes such as bioaccumulation, bioavailability and biosorption of heavy metals in biofilm matrixes requires the quantification of their transport. This study shows 3D MRI measurements of the penetration of free (Fe 2+ , Co 2+ and Gd 3+ ) and complexed ([FeEDTA] 2- and [GdDTPA] 2- ) metal ions in a single methanogenic granule. Interactions (sorption or precipitation) between free metals and the biofilm matrix result in extreme shortening of the spin-spin relaxation time (T 2 ) and a decrease of the amplitude (A 0 ) of the MRI signal, which hampers the quantification of the metal concentration inside the granular sludge matrix. MRI images clearly showed the presence of distinct regions (dead or living biomass, cracks, and precipitates) in the granular matrix, which influenced the metal transport. For the free metal ions, a reactive barrier was formed that moved through the granule, especially in the case of Gd 2+ . Chelated metals penetrated faster and without reaction front. Diffusion of [GdDTPA] 2- could be quantified, revealing the course of its transport and the uneven (0.2-0.4 mmolL -1 ) distribution of the final [GdDTPA] 2- concentration within the granular biofilm matrix at equilibrium.

Original languageEnglish
Article number13
JournalFrontiers in Environmental Science
Volume4
Issue numberMAR
DOIs
Publication statusPublished - 16 Mar 2016

Keywords

  • Granular biofilm
  • Magnetic resonance microscopy
  • Metal diffusion
  • Metal transport
  • Methanogenic granular sludge

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