Authors
Xin Li, Huixiang Zhang, Shanshan Yang, Juan Liu, Fei Liu
Published in
Environmental science & technology. Jun 13, 2025. Epub Jun 13, 2025.
Abstract
During the Fe(II)aq-catalyzed transformation of ferrihydrite, the abiotic reduction of organic contaminants is an important process in the natural attenuation of groundwater pollutants. However, during this transformation, the reduction capacity of the Fe(II)aq-Fe(III) oxyhydroxide system evolves substantially over time and its impacts on contaminant attenuation processes remain unclear. In this study, a single quantitative relationship between contaminant reduction rates (ksa) and shifts in the reduction capacity during the ferrihydrite transformation (log(ksa) = 0.91·(-EH/59 mV - pH) + 2.96) was established using nitrobenzene as a representative contaminant, despite variations in transformation pathways and product assemblages at different pH values and Fe(II)aq concentrations. The reduction capacity of such systems was dependent on the iron oxide composition when ferrihydrite was transformed to more thermodynamically stable Fe(III) oxyhydroxides. EH decreased from 1.5 and - 46.8 mV to -113.1 and -136.5 mV (all measurements vs. a standard hydrogen electrode) as ferrihydrite transformed to lepidocrocite and goethite, respectively. When structural Fe(II)-containing magnetite was formed, decreases in the pH and Fe(II)aq concentration increased EH from -159.7 to -79.9 mV. This work provides an effective method for predicting the abiotic attenuation of organic contaminants during complex mineral transformation processes and deepens our understanding of the natural transformation behavior of contaminants in aquifers.
PMID:
40513040
Bibliographic data and abstract were imported from PubMed on 14 Jun 2025.
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