Abstract
Microbial reduction of soluble hexavalent uranium (U(VI)) to sparingly soluble tetravalent uranium (U(IV)) has been explored as an in situ strategy to immobilize U. Organic ligands might pose a potential hindrance to the success of such remediation efforts. In the current study, a set of structurally diverse organic ligands were shown to enhance the dissolution of crystalline uraninite (UO2) for a wide range of ligand concentrations under anoxic conditions at pH 7.0. Comparisons were made to ligand-induced U mobilization from noncrystalline U(IV). For both U phases, aqueous U concentrations remained low in the absence of organic ligands (<25 nM for UO2; 300 nM for noncrystalline U(IV)). The tested organic ligands (2,6-pyridinedicarboxylic acid (DPA), desferrioxamine B (DFOB), N,N'-di(2-hydroxybenzyl)ethylene-diamine-N,N'-diacetic acid (HBED), and citrate) enhanced U mobilization to varying extents. Over 45 days, the ligands mobilized only up to 0.3% of the 370 μM UO2, while a much larger extent of the 300 μM of biomass-bound noncrystalline U(IV) was mobilized (up to 57%) within only 2 days (>500 times more U mobilization). This work shows the potential of numerous organic ligands present in the environment to mobilize both recalcitrant and labile U forms under anoxic conditions to hazardous levels and, in doing so, undermine the stability of immobilized U(IV) sources.
Original language | English |
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Pages (from-to) | 6369-6379 |
Number of pages | 11 |
Journal | Environmental Science & Technology |
Volume | 56 |
Issue number | 10 |
DOIs | |
Publication status | Published - 17 May 2022 |
Austrian Fields of Science 2012
- 106026 Ecosystem research
- 105906 Environmental geosciences
Keywords
- Biomass
- Ligands
- Oxidation-Reduction
- Uranium/chemistry
- Uranium Compounds/chemistry
- ion-exchange chromatography
- U redox speciation
- chelating ligands
- mobilization
- dissolution kinetics
- monomeric U(IV)
- uranium