Extraction Behavior of Phenyl-substituted Phosphine Oxides for Some Fission Product Elements

As potential multidentate extractants with specific high extraction behavior for metal species in aqueous acidic media, extraction behavior of 1,1,3,5,5-pentaphenyl-1,3,5- triphosphapentane trioxide (PPTPT) and 1,1,5,5,2’,2’-hexaphenyl-1,3,5,2’-tetraphospha- 3-ethylpentane tetraoxide (HPTEPT), one of the aprotic triphosphine trioxides and tetraphosphine tetraoxides, respectively, for fission products elements (FPs) was extensively investigated by using liquid-liquid extraction and solid-liquid adsorption in the form of a silica-supported impregnated adsorbent. It was found, from the examination up to 9 mol/dm3 (=M) HNO3 and HCl, that metal ions such as Fe(III), Zr(IV) and Nd(III) were in general highly extracted and adsorbed by both PPTPT and HPTEPT, and that the dependence of the extraction/adsorption behavior on the acid concentration varies depending on the metal ions. It was suggested, from the slope analysis for the extraction system of the two extractants for Nd(III) under 6 M HNO3 and HCl, that they extract Nd(III) differently, i.e., three molecules of PPTPT and one or two of HPTEPT were found necessary for the extraction of one molecule of Nd(III), respectively, where some of one HPTEPT molecule binds at least two Nd(III) ions by crosslinking from the steric viewpoint.