How does organic matter affect Ce redox speciation and the formation of CeO2 nanoparticles?
Abstract
Understanding the interactions between trace metals and natural organic matter (OM) is crucial due to its influence on metal speciation, mobility, toxicity, and bioavailability. Cerium (Ce) is of particular interest due to its industrial use, natural occurrence, and unique redox chemistry. It exists in both the +III and +IV oxidation states, enabling redox cycling in surface environments. Here, advanced spectroscopic, microscopic analyses and thermodynamic modeling were used to elucidate the influence of OM on Ce(III) oxidation to Ce(IV) and potential CeO2 nanoparticle formation. The results showed a strong pH-dependent Ce(III) oxidation in the presence of OM and O2(g), with negligible Ce(IV) at pH 5 and nearly complete oxidation at pH 10. Dissolved O₂(g) was identified as the primary oxidant, as almost no Ce(IV) was detected under N2-atmosphere. At the lowest Ce to OM concentration ratios investigated, complexation of Ce(III) by OM was identified as a key mechanism limiting its oxidation to Ce(IV) whereas, at higher concentration ratios or in the absence of OM, oxidation was driven by hydrolysis and precipitation of CeO₂ nanoparticles. Beyond this control on Ce redox speciation, OM further impacted CeO₂ nanoparticle formation by (i) kinetically inhibiting crystal growth to ~2 nm crystallites that persist as a metastable phase over environmentally relevant time scale and (ii) accumulating Ce(III) within a ~1 nm-thick organic-rich layer around these nanoparticles. These findings highlight the dual role of OM in regulating Ce redox speciation and nanoparticle formation, with direct implications for Ce fate and mobility in OM-rich environments.
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BibTeX
@article{kiththangodage2026does,
title = {{How does organic matter affect Ce redox speciation and the formation of CeO2 nanoparticles?}},
author = {Terjini Kiththangodage and Yann Sivry and Jaimy Scaria and Mathieu Pédrot and Fadi Choueikani and Andreas Voegelin and Ralf Kaegi and Svetlana Tsareva and Xavier Devaux and Aline Dia and Rémi Marsac},
journal = {Environmental science.Nano},
year = {2026},
month = oct,
doi = {10.1039/d6en00805d},
url = {https://hal.science/hal-05802676v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - How does organic matter affect Ce redox speciation and the formation of CeO2 nanoparticles?
AU - Terjini Kiththangodage
AU - Yann Sivry
AU - Jaimy Scaria
AU - Mathieu Pédrot
AU - Fadi Choueikani
AU - Andreas Voegelin
AU - Ralf Kaegi
AU - Svetlana Tsareva
AU - Xavier Devaux
AU - Aline Dia
AU - Rémi Marsac
PY - 2026
DA - 2026/10/16
JO - Environmental science.Nano
DO - 10.1039/d6en00805d
UR - https://hal.science/hal-05802676v1
AB - Understanding the interactions between trace metals and natural organic matter (OM) is crucial due to its influence on metal speciation, mobility, toxicity, and bioavailability. Cerium (Ce) is of particular interest due to its industrial use, natural occurrence, and unique redox chemistry. It exists in both the +III and +IV oxidation states, enabling redox cycling in surface environments. Here, advanced spectroscopic, microscopic analyses and thermodynamic modeling were used to elucidate the influence of OM on Ce(III) oxidation to Ce(IV) and potential CeO2 nanoparticle formation. The results showed a strong pH-dependent Ce(III) oxidation in the presence of OM and O2(g), with negligible Ce(IV) at pH 5 and nearly complete oxidation at pH 10. Dissolved O₂(g) was identified as the primary oxidant, as almost no Ce(IV) was detected under N2-atmosphere. At the lowest Ce to OM concentration ratios investigated, complexation of Ce(III) by OM was identified as a key mechanism limiting its oxidation to Ce(IV) whereas, at higher concentration ratios or in the absence of OM, oxidation was driven by hydrolysis and precipitation of CeO₂ nanoparticles. Beyond this control on Ce redox speciation, OM further impacted CeO₂ nanoparticle formation by (i) kinetically inhibiting crystal growth to ~2 nm crystallites that persist as a metastable phase over environmentally relevant time scale and (ii) accumulating Ce(III) within a ~1 nm-thick organic-rich layer around these nanoparticles. These findings highlight the dual role of OM in regulating Ce redox speciation and nanoparticle formation, with direct implications for Ce fate and mobility in OM-rich environments.
SN - 2051-8153
ER -