2024-05-30 パシフィック・ノースウェスト国立研究所(PNNL)
◆機械工学者のXiaoliang “Bryan” He、研究員のNik Qafoku、地球科学者のMark Rockholdが主導する多分野研究では、ラボ実験と数値モデリングを用いて、フェリハイドライトを放射性ヨウ素汚染の浄化戦略としてテストしました。フェリハイドライトは土壌や地下堆積物に存在し、高い親和性を持つナノミネラルです。
◆この研究は、American Chemical SocietyのEarth and Space Chemistry誌の表紙に掲載されました。研究はフェリハイドライトがヨウ素酸塩の吸着を強化し、その移動性を低下させ、地下水中の汚染物質濃度を減少させることを示しました。この研究は、PNNLの複雑なサイトの浄化技術を特定するための取り組みの一部です。
＜関連情報＞
- https://www.pnnl.gov/news-media/deep-vadose-zone-program-research-makes-acs-journal-cover
- https://pubs.acs.org/doi/full/10.1021/acsearthspacechem.3c00291
ハンフォード堆積物における放射性ヨウ素の収着と輸送に関する実験的および数値的研究 Experimental and Numerical Study of Radioiodine Sorption and Transport in Hanford Sediments
Xiaoliang He, Mark L. Rockhold, Yilin Fang, Amanda R. Lawter, Vicky L. Freedman, Rob D. Mackley, and Nikolla P. Qafoku
ACS Earth and Space Chemistry Published:January 16, 2024
DOI:https://doi.org/10.1021/acsearthspacechem.3c00291
Abstract
Radioiodine (129I) poses a potential risk to human health and the environment at several U.S. Department of Energy sites, including the Hanford Site, located in southeastern Washington State. Experimental studies and numerical modeling were performed to provide a technical basis for field-scale modeling of iodine sorption and transport behavior. The experiments were carried out using six columns of repacked contaminated sediments from the Hanford Site. Although iodate has been determined to be the dominant iodine species at the Hanford Site, the sorption and transport behaviors of different iodine species were investigated in a series of column experiments by first leaching sediments with artificial groundwater (AGW) followed by AGW containing iodate (IO3–), iodide (I–), or organo-iodine (2-iodo-5-methoxyphenol, C7H7IO2). Ferrihydrite amendments were added to the sediments for three of the columns to evaluate the impact of ferrihydrite on 129I attenuation. The results showed that ferrihydrite enhanced the iodate sorption capacity of the sediment and retarded the transport but had little effect on iodide or organo-I, providing a technical basis for developing a ferrihydrite-based remedial strategy for iodate under oxidizing conditions. Data from the column transport experiments were modeled using the linear equilibrium Freundlich isotherm model, the kinetic Langmuir adsorption model, and a distributed rate model. Comparisons of the experimental data and modeling results indicated that sorption was best represented with the distributed rate model with rates and maximum sorption extents varying by iodine species and ferrihydrite treatment. However, the linear Freundlich isotherm (Kd) model was also found to fit the laboratory experimental data relatively well, suggesting that the Kd model could also be used to represent iodine transport at the field scale.
