Improvement in the elution performance of an N,N,N',N-tetraoctyl diglycolamide impregnated extraction chromatography adsorbent using neodymium via micro-particle-induced X-ray emission analysis.

An adsorbent used for the recovery of trivalent minor actinides (MA(III); Am and Cm) from high level liquid waste generated from reprocessing of spent nuclear fuel was subjected to micro-particle induced X-ray emission (micro-PIXE) analysis to improve its elution performance. The experimental adsorbent comprised SiO2 particles, a polymer coating, and an N,N,N',N'-tetraoctyl diglycolamide (TODGA). The particles to be analyzed were subjected to Nd adsorption and an elution operation, but Nd in the adsorbent was found to be uniformly distributed. This might have been caused by individual differences in the amount of impregnated TODGA. The remaining Nd species were not localized to a specific part of the adsorbent after the adsorption operation. Some Nd elements were retained in the adsorbent after elution, probably because of the poor diffusion of the mobile phase inside the adsorbent. An adsorbent having a different microstructure from the first was then evaluated, and rapid elution was observed on new adsorbent along micro-PIXE analysis.

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+.

Extraction Mechanism of Lanthanide Ions into Silica-based Microparticles Studied by Single Microparticle Manipulation and Microspectroscopy.

Single porous silica microparticles coated with a styrene-divinylbenzene polymer (SDB) impregnated with octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) were injected into an aqueous 3 mol/L nitric acid solution containing trivalent lanthanide (Ln(III)), as a high-level liquid waste model. We used the microcapillary manipulation-injection technique; and the extraction rate of Ln(III), as an Ln(III)-CMPO complex, into the single microparticles was measured by luminescence microspectroscopy. The extraction rate significantly depended on the Ln(III), CMPO, or NO3- concentration, and was analyzed in terms of diffusion in the pores of the microparticles and the complex formation of Ln(III). The results indicated that the rate-determining step in Ln(III) extraction was diffusion in the pore solution of the microparticles.