Cesium extraction by calixarenes crown-ether; Diluent effect

Simonnet, M.; 宮崎 有史*; 鈴木 伸一; 矢板 毅

no journal, , 

Cs is a troublesome fission product for both nuclear waste reprocessing and the cleaning of contaminated areas (Fukushima). Because Cs belongs to the alkali elements, it is hard to separate from Na and K, whose natural abundances are high. Calixarenes crown-ether were found to be efficient alkali extractants, with the alkali selectivity determined by the number of ether functions. It was found that ligands with 6 ether functions are optimum for cesium whilst 4 is optimum for Na, yielding great Na separation factors. However, the resulting high oxygen contents yields a low solubility in aliphatic diluents. Different diluents were thus used in literature, such as alcohols, ketones, chloroform, nitrophenylalkylether or dodecane with a modifier. Whilst the distribution ratios greatly varied along with the diluent, few studies focused on understanding this phenomenon. The aim of the present work is thus to study the diluent effect at both macroscopic (distribution ratio and separation factor comparison) and microscopic (EXAFS analysis) scales. For the latter study, two diluents, chloroform and 2-nonanone, were chosen. Their properties (density, viscosity, dielectric constant, water solubility) are all different, except from the calixarene crown-ether solubility which is high in both cases. Additional interactions between the diluent and the counterion were also investigated. The study focuses on acidic aqueous solutions only.