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測量應用案例-20210313
閱讀：144 發布時間：2021-3-10| 提 供 商 | 美國布魯克海文儀器公司 | 資料大小 | 3.8MB |
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The interactions between natural colloidal organic matter and actinides in solutions are complex
and not fully understood. In this work, a crew-cut PS-b-PAA micelle is proposed as a model
particle for humic acid (HA) colloid with the aim to better understand the sequestration,
aggregation, and mobility of HA colloids in the presence of uranyl ions. The effects of uranyl ions
on the structure of polystyrene-b-poly(acry1ic acid) (PS29k-b-PAA5k) micelles in aqueous solution
were mainly investigated by synchrotron small-angle X-ray scattering. A core-shell model,
accounting for the thickness and contrast changes of the PAA corona induced by the adsorption of
uranyl, was employed to analyze the scattering data. A combination of transmission electron
microscopy, dynamic light scattering and zetametry showed a strong affinity of uranyl ions for
PAA segments in water at pH 4-5 that resulted in the shrinkage and improved contrast of the PAA
corona, as well as colloidal destabilization at high uranyl concentration.
Keywords: polystyrene-b-poly(acry1ic acid), micelles, uranyl, SAXS, core-shell, adsorption
INTRODUCTION
Uranium is an essential element for nuclear energetic and military applications. In aqueous
media such as natural water and wet soil in acidic to near-neutral pH conditions uranium mainly
exists as linear and symmetric UO2 2+ (uranyl) ion, and its oxides and hydroxides [1, 2], including
cationic clusters, show extensive complexation reactions with inorganic and organic
contaminants. The behavior and fate of uranium species in ecosystem is an important issue because