Extended X-ray Absorption Fine Structure Investigation of Adsorption and Separation Phenomena of Metal Ions in Organic Resin

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• 作者：Atsushi Ikeda ; Tsuyoshi Yaita ; Yoshihiro Okamoto ; Hideaki Shiwaku ; Shinichi Suzuki ; Tatsuya Suzuki ; Yasuhiko Fujii
• 刊名：Analytical Chemistry
• 出版年：2007
• 出版时间：November 1, 2007
• 年：2007
• 卷：79
• 期：21
• 页码：8016 - 8023
• 全文大小：254K
• 年卷期：v.79,no.21(November 1, 2007)
• ISSN：1520-6882

文摘

Analytical technique using organic resins has already beenwell-developed, and its applications are employed invarious fields; nevertheless, the chemical phenomenaoccurring inside the resin remain unclear for the mostpart. In the present study, we apply EXAFS spectroscopyto elucidate the adsorption and separation phenomena ofmetal ions by organic resin. That is, the chemical speciesof trivalent lanthanides (Ln(III)) adsorbed in a tertiarypyridine resin from hydrochloric acid and nitric acidsolutions have been determined by EXAFS. The resultsin HCl solutions suggest that Ln(III) ions are partlydehydrated in the resin phase, enabling the pyridinegroups of the resin and chloride ions to coordinate to theLn(III) ions in their primary coordination sphere. On theother hand, Ln(III) ions are tightly coordinated by severalnitrate ions in HNO₃ solutions and they keep forming thenitrate complex even in the resin phase. The lighter Ln ofNd tends to form an anionic nitrate complex, [Nd(NO₃)₄·nH₂O]^-, in the resin phase, while the middle Lnof Sm exists as a cationic nitrate complex, [Sm(NO₃)₂·nH₂O]⁺, for the most part. On the basis of these EXAFSresults, the adsorption and separation mechanisms of thepyridine resin in HCl solutions are interpreted as thedirect coordination of pyridine groups to metal ions, whilethe mechanisms in HNO₃ solutions are mainly dominatedby the anion-exchange reaction between the protonatedpyridine groups and the anionic nitrate complexes of Ln(III). The obtained results demonstrate that the hydrationof metal ions weakens, and instead, other complexationsare enhanced in the resin phase.