SPEC: A New Process for Strontium and Cesium Partitioning Utilizing Two Macroporous Silica-Based Supramolecular Recognition Agents Impregnated Polymeric Composites

Abstract

To effectively separate two heat generators Cs(I) and Sr(II) from a highly active liquid waste (HLW), two macroporous silica-based polymeric composites (Calix[4]arene-R14 + M)/SiO₂-P and (DtBuCH18C6 + M)/SiO₂-P were synthesized. It was done by impregnating and immobilizing the supramolecular recognition agent, 1,3-[(2,4-diethylheptyl ethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) or 4,4′,(5′)-di-(tert-butylcyclo hexano)-18-crown-6 (DtBuCH18C6), into the pores of the macroporous SiO₂-P particles with a mean diameter of 50 µm. It was found that in the first column packed with (Calix[4]arene-R14 + M)/SiO₂-P, all of the tested elements were effectively eluted and separated into two groups: ( 1 Horwitz , E.P. ; Mark , L.D. ; Fisher , D.E. ( 1991 ) SREX: A new process for the extraction and recovery of strontium from acidic nuclear waste stream . Solvent Extr. Ion Exch. , 9 ( 1 ): 1 – 25 . [Taylor & Francis Online], [Web of Science ®] [Google Scholar] ) Na(I), K(I), Sr(II), Ba(II), Rh(III), Ru(III), Pd(II), Zr(IV), RE(III) (La-Lu and Y), and Mo(VI) (Sr-containing group), and ( 2 Wood , D.J. ; Law , J.D. ( 1997 ) Evaluation of the SREX solvent extraction process for the removal of ⁹⁰Sr and hazardous metal ions from acidic nuclear waste solutions containing high concentrations of interfering alkali metal ions . Sep. Sci. Technol. , 32 ( 1–4 ): 241 – 253 . [Taylor & Francis Online], [Web of Science ®] [Google Scholar] ) Cs(I)-Rb(I) (Cs-group) by eluting with 4.0 M HNO₃ and water, respectively, at 298 K. The heat emitting element Cs(I) flowed into the second group along with Rb(I), while Sr(II) showed no sorption and flowed into the Sr-containing group. In the second column packed with (DtBuCH18C6 + M)/SiO₂-P, the Sr-containing group was separated into ( 1 Horwitz , E.P. ; Mark , L.D. ; Fisher , D.E. ( 1991 ) SREX: A new process for the extraction and recovery of strontium from acidic nuclear waste stream . Solvent Extr. Ion Exch. , 9 ( 1 ): 1 – 25 . [Taylor & Francis Online], [Web of Science ®] [Google Scholar] ) Na(I), K(I), Rh(III), Ru(III), RE(III) (La-Lu and Y), Pd(II), Zr(IV), and Mo(VI) (non-sorption group), and ( 2 Wood , D.J. ; Law , J.D. ( 1997 ) Evaluation of the SREX solvent extraction process for the removal of ⁹⁰Sr and hazardous metal ions from acidic nuclear waste solutions containing high concentrations of interfering alkali metal ions . Sep. Sci. Technol. , 32 ( 1–4 ): 241 – 253 . [Taylor & Francis Online], [Web of Science ®] [Google Scholar] ) Sr(II)-Ba(II) (Sr-group), by eluting with 2.0 M HNO₃ and water, respectively. The heat emitting element Sr(II) adsorbed by (DtBuCH18C6 + M)/SiO₂-P flowed into the second group along with Ba(II). Based on the results, a new process entitled SPEC (Strontium/Cesium Partitioning from HLW by Extraction Chromatography) for heat generator partitioning from a simulated highly active liquid waste utilizing two macroporous silica-based supramolecular recognition composites has been developed.