Analytical Sciences

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

Toshiki OTAKA,* Tatsumi SATO,* Simpei ONO,** Kohei NAGOSHI,** Ryoji ABE,** Tsuyoshi ARAI,** Sou WATANABE,*** Yuichi SANO,*** Masayuki TAKEUCHI,*** and Kiyoharu NAKATANI*

*Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
**Shibaura Institute of Technology, Toyosu, Tokyo 135-8548, Japan
***Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1194, Japan

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.

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