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KMID : 1059519890330020232
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Journal of the Korean Chemical Society
1989 Volume.33 No. 2 p.232 ~ p.237
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Study on the Ion Exchange Mechanism of Rare Earth Elements in Several Elution Types (I)
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Cha Ki-Won
Hong Sung-Wook
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Abstract
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The elution mechanism of rare earth elements in cation exchange resin which was substituted with NH4+, Zn2+ or Al3+ as a retaining ion had been investigated. Rare earths or rare earths-EDTA complex solution was loaded on the top of resin bed and eluted with 0.0269M EDTA solution. When the rare earth-EDTA complex was adsorbed on the Zn2+ or Al3+ resin form, retaining ion was complexed with EDTA and liberated rare earths was adsorbed in the resin again. Adsorbed rare earths in resin phase could be eluted by the complexation reaction with EDTA eluent. On NH4+ resin form, the rare earth-EDTA complex which had negative charge could not adsorbed on the cation exchange resin because the complexation reaction between NH4+ and EDTA was impossible. So the elution time was much shorter than in Zn2+ or Al3+ resin form. When the rare earths solution was loaded on the Zn2+, Al3+ resin form bed, rare earths was adsorbed in the resin and the retaining ion was liberated. Adsorbed rare earths in resin bed was exchanged by EDTA eluent forming rare earths-EDTA complex, and eluted through these processes. On NH4+ resin form, rare earths loaded was adsorbed by exchange reaction with NH4+. As the EDTA eluent was added, rare earths was liberated from resin forming negatively charged rare earth-EDTA complex and eluted without any exchange reaction. So the elution time was greatly shortened and there was no metallic ion except rare earths in effluent. When the Zn2+ and Al3+ was used as retaining ion, the pH of efflent was decreased seriousely because the H+ liberated from EDTA molecule.
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