Ln³⁺ Adsorption into an Yttrium-Hdehp Coordination Polymer through Exchange with Coordinated Yttrium Ion

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An exchange between lanthanide ions (Ln³⁺) in a solution and coordinated yttrium ions (Y³⁺) takes place in a coordination polymer (CP) formed by Y³⁺ and di-(2-ethylhexyl) phosphoric acid (Hdehp). Through this cation exchange, Ln³⁺ is adsorbed on the CP depending on the coordination power with Hdehp. Accordingly, the Ln³⁺ with the larger atomic number is more preferably adsorbed into the CP. This adsorption is affected by the concentration of H⁺, C_H+, in the solution. For example, at C_H+=10^-5 M, Y³⁺ is replaced directly by the incoming Ln³⁺ with a 1:1 stoichiometry. In a limited higher C_H+ region, the CP becomes a gel and the Ln³⁺/Y³⁺ exchange is enhanced therein.