Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 56, Issue 2, Pages 1007-1016Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c06747
Keywords
iodination; reactions in ice; freeze-concentration effect; humic substances; reactive iodine formation
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Funding
- Leading Researcher program - Korea government (MSIT) through the National Research Foundation of Korea (NRF) [NRF-2020R1A3B2079953]
- Korea Polar Research Institute (KOPRI) project [PE21120]
- Korea Polar Research Institute of Marine Research Placement (KOPRI) [PE21120] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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The formation of organoiodine compounds (OICs) is significantly enhanced in frozen solutions containing Fe(III) and NOM, particularly after thawing. The freeze-thaw cycle is more efficient in producing OICs compared to continuous reactions in frozen solutions. Aromatic organic compounds induce higher OIC formation yields in freeze-thaw systems.
The formation of organoiodine compounds (OICs) is of great interest in the natural iodine cycle as well as water treatment processes. Herein, we report a pathway of OIC formation that reactive iodine (RI) and OICs are produced from iodide oxidation in the presence of Fe(III) and natural organic matter (NOM) in frozen solution, whereas their production is insignificant in aqueous solution. Moreover, thawing the frozen solution induces the further production of OICs. A total of 352 OICs are detected by Fourier transform ion cyclotron resonance mass spectrometry in the freeze-thaw cycled reactions of Fe(III)/I-/humic acid solution, which are five times as many as OICs in aqueous reactions. Using model organic compounds instead of NOM, aromatic compounds (e.g., phenol, aniline, o-cresol, and guaiacol) induce higher OIC formation yields (10.4-18.6%) in the freeze-thaw Fe(III)/I- system than those in aqueous (1.1-2.1%) or frozen (2.7-7.6%) solutions. In the frozen solution, the formation of RI is enhanced, but its further reaction with NOM is hindered. Therefore, the freeze-thaw cycle in which RI is formed in the frozen media and the resulting RI is consumed by reaction with NOM in the subsequently thawed solution is more efficient in producing OICs than the continuous reaction in frozen solution.
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