TY - JOUR
T1 - MnO2-Induced Oxidation of Iodide in Frozen Solution
AU - Du, Juanshan
AU - Kim, Kitae
AU - Son, Seungwoo
AU - Pan, Donglai
AU - Kim, Sunghwan
AU - Choi, Wonyong
N1 - Publisher Copyright:
© 2023 American Chemical Society.
PY - 2023/4/4
Y1 - 2023/4/4
N2 - Metal oxides play a critical role in the abiotic transformation of iodine species in natural environments. In this study, we investigated iodide oxidation by manganese dioxides (β-MnO2, γ-MnO2, and δ-MnO2) in frozen and aqueous solutions. The heterogeneous reaction produced reactive iodine (RI) in the frozen phase, and the subsequent thawing of the frozen sample induced the gradual transformation of in situ-formed RI to iodate or iodide, depending on the types of manganese dioxides. The freezing-enhanced production of RI was observed over the pH range of 5.0-9.0, but it decreased with increasing pH. Fulvic acid (FA) can be iodinated by I-/MnO2 in aqueous and frozen solutions. About 0.8-8.4% of iodide was transformed to organoiodine compounds (OICs) at pH 6.0-7.8 in aqueous solution, while higher yields (10.4-17.8%) of OICs were obtained in frozen solution. Most OICs generated in the frozen phase contained one iodine atom and were lignin-like compounds according to Fourier transform ion cyclotron resonance/mass spectrometry analysis. This study uncovers a previously unrecognized production pathway of OICs under neutral conditions in frozen environments.
AB - Metal oxides play a critical role in the abiotic transformation of iodine species in natural environments. In this study, we investigated iodide oxidation by manganese dioxides (β-MnO2, γ-MnO2, and δ-MnO2) in frozen and aqueous solutions. The heterogeneous reaction produced reactive iodine (RI) in the frozen phase, and the subsequent thawing of the frozen sample induced the gradual transformation of in situ-formed RI to iodate or iodide, depending on the types of manganese dioxides. The freezing-enhanced production of RI was observed over the pH range of 5.0-9.0, but it decreased with increasing pH. Fulvic acid (FA) can be iodinated by I-/MnO2 in aqueous and frozen solutions. About 0.8-8.4% of iodide was transformed to organoiodine compounds (OICs) at pH 6.0-7.8 in aqueous solution, while higher yields (10.4-17.8%) of OICs were obtained in frozen solution. Most OICs generated in the frozen phase contained one iodine atom and were lignin-like compounds according to Fourier transform ion cyclotron resonance/mass spectrometry analysis. This study uncovers a previously unrecognized production pathway of OICs under neutral conditions in frozen environments.
KW - chemical reactions in ice
KW - manganese dioxide
KW - organoiodine compounds
KW - reactive iodine
KW - redox cycle of iodine species
UR - http://www.scopus.com/inward/record.url?scp=85151244507&partnerID=8YFLogxK
U2 - 10.1021/acs.est.3c00604
DO - 10.1021/acs.est.3c00604
M3 - Article
C2 - 36952586
AN - SCOPUS:85151244507
SN - 0013-936X
VL - 57
SP - 5317
EP - 5326
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 13
ER -