Eu(III) transfer in single N,N,N',N'-tetraoctyldiglycolamide-impregnated polymer-coated silica particle using fluorescence microspectroscopy: transfer mechanism and effect of polymer crosslinking degree.

A microcapillary manipulation system combined with fluorescence microspectroscopy enabled us to analyze mass transfer in a single particle. In this study, we revealed the Eu(III) distribution in a single diglycolamide-derivative extractant (TODGA)-impregnated polymer-coated silica particle. The reaction of Eu(III) with two TODGA molecules in the polymer layer was the rate-limiting process, which was revealed by the relationship between the rate constants (k1 and k-1) and concentrations of Eu(III) and HNO3. The decrease in the crosslinking degree of the polymer layer caused an increase in only k-1. This indicates that hydrophilic environments at lower crosslinking degrees enhance the stability of the charged Eu(III) species such as Eu3+, Eu(NO3)2+, and Eu(NO3)2+.