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Lanthanide ion exchange properties of a coordination polymer consisting of di(2-ethylhexyl) phosphoric acid and trivalent metal ions (Ce super(3+), Fe super(3+), or Al super(3+))

Three kinds of coordination polymers ([M(dehp) sub(3)], M = Ce, Fe, or Al) were prepared by mixing the sodium form (Na(dehp)) of di(2-ethylhexyl) phosphoric acid and MCl sub(3) in an ethanol-water binary mixture. They have monoclinic crystalline structure with similar lattice parameters. The lanthan...

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Published in:Dalton transactions : an international journal of inorganic chemistry 2014-02, Vol.43 (12), p.4807-4812
Main Authors: Ooi, Kenta, Tasaki-Handa, Yuiko, Abe, Yukie, Wakisaka, Akihiko
Format: Article
Language:English
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Summary:Three kinds of coordination polymers ([M(dehp) sub(3)], M = Ce, Fe, or Al) were prepared by mixing the sodium form (Na(dehp)) of di(2-ethylhexyl) phosphoric acid and MCl sub(3) in an ethanol-water binary mixture. They have monoclinic crystalline structure with similar lattice parameters. The lanthanide ion (Ln super(3+) = La super(3+), Sm super(3+), Dy super(3+), or Yb super(3+)) exchange properties were studied in a 20 : 80 vol% ethanol-water binary mixture containing 2 mM Ln(NO sub(3)) sub(3) at room temperature. The rate of Ln super(3+) adsorption is relatively slow; it requires over 3 weeks to reach equilibrium. [M(dehp) sub(3)] has different Ln super(3+) affinities depending on the kind of central metal ions: the affinity order at 3 week adsorption is Yb super(3+) < La super(3+) < Dy super(3+) < Sm super(3+) for [Ce(dehp) sub(3)], La super(3+) < Sm super(3+) < Dy super(3+) < Yb super(3+) for [Fe(dehp) sub(3)], and La super(3+) < Sm super(3+), Dy super(3+), Yb super(3+) for [Al(dehp) sub(3)]. The difference in affinity order can be explained by two factors: the coordination preference and steric strain caused by the polymeric structure. The chemical and structural analyses suggested that the Ln super(3+) adsorption progresses first by the central M super(3+)/Ln super(3+) exchange, followed by a morphological change to a rod-like or fibrous form by a solid phase reaction. In the case of [Fe(dehp) sub(3)], the eluted Fe super(3+) may be hydrolyzed and precipitated as amorphous iron hydroxide.
ISSN:1477-9226
1477-9234
DOI:10.1039/c3dt53407c