Removal of Pd(II), Zr(IV), Sr(II), Fe(III), and Mo(VI) from simulated high level liquid waste by extraction chromatography utilizing the macroporous silica-based polymeric materials

Abstract

To eliminate a few specific elements from highly active liquid waste (HLW), two macroporous silica-based N, N, N′, N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) and octyl(phenyl)- N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) impregnated polymeric composites, TODGA/SiO 2-P and CMPO/SiO 2-P, were synthesized. It was done by an advanced vacuum sucking technique through impregnation of the chelating agents into the pores of SiO 2-P particles support. The partitioning of Sr(II), Pd(II), Zr(IV), Mo(VI), and Cs(I) from a 3.0 M HNO 3 solution containing some typically simulated fission and non-fission products Ru(III), Rb(I), Fe(III), Na(I), K(I), and Ba(II) was performed at 298 and 323 K, respectively. In the first column packed with TODGA/SiO 2-P, Sr(II), Pd(II), and Zr(IV) were adsorbed and eluted effectively by 0.01 M HNO 3, 0.05 M DTPA-pH 2.5, and 0.5 M oxalic acid, respectively, while others showed very weak or almost no adsorption and flowed into effluent along with 3.0 M HNO 3. Cs(I), Fe(III), and Mo(VI) containing effluent was then applied to the second column packed with CMPO/SiO 2-P. Fe(III) and Mo(VI) were found to be adsorbed together and eluted utilizing 0.05 M DTPA-pH 2 at 323 K. The effective partitioning of Fe(III) was of great benefit to the evaporation, concentration, and finally geological disposal of HLW. The separation of Sr(II) and Mo(VI) was useful for the vitrification of HLW due to the Sr heat generator property and low solubility of Mo oxides in molten glass materials. Cs(I) can be separated by a novel silica-based 1,3-[(2,4-diethyl-heptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) impregnated polymeric composite (Calix[4]arene-R14/SiO 2-P). In terms of the results obtained, a highly specific partitioning process of Fe(III) and some specific fission products Sr(II), Pd(II), Zr(IV), Cs(I), and Mo(VI) from a simulated HLW by extraction chromatography was proposed.