Kinetic Mass Transfer Behavior of Eu(III) in Nitrilotriacetamide-Impregnated Polymer-Coated Silica Particles

We investigated the distribution mechanism of Eu(III) in a single polymer-coated silica particle including nitrilotriacet-amide (NTA) extractants known as HONTA and TOD2EHNTA. We studied the kinetic rate constants of the distribution proc-ess at various concentrations of NO31 (CNO31) that were pre-pared using HNO3 and NaNO3 solutions. The rate-determining process during the distribution of Eu(III) was identified as the reaction process of Eu(III) for both extractants, that is, the reaction process of Eu(III) and two NTA molecules in the polymer layer of the silica particle. Furthermore, the reaction of Eu(III) with NO31 ions was found not to be involved in the rate-determining process. The forward (k1) and backward (k11) reaction kinetic constants for the reaction between Eu(III) and two NTA molecules were determined to be k1 = (5.7 +/- 2.2) x 102 M12 s11 and k11 = (2.3 +/- 4.4) x 1014 s11 for HONTA, and k1 = (6.5 +/- 3.0) x 102M12s11 in the NaNO3 system and k11 = (2.0 +/- 1.5) x 1014 s11 in both solutions for TOD2EHNTA. The present study provides a valuable approach for the evaluation and enhancement of the functionality of 'single extractant-impregnated polymer-coated silica particles'.