Chromatographic separation of platinum group metals from simulated high level liquid waste using macroporous silica-based adsorbents.
To separate platinum group metals (PGMs) from high level liquid waste, three novel macroporous silica-based adsorbents, namely, (Crea+Dodec)/SiO2-P, (Crea+TOA)/SiO2-P and (MOTDGA+TOA)/SiO2-P, were synthesized by introducing extractants Crea (N',N'-di-n-hexyl-thiodiglycolamide), TOA (Tri-n-octylamine), MOTDGA (N,N'-dimethyl-N,N'-di-n-octyl-thiodiglycolamide) along with theirs modifier, Dodec (n-dodecyl alcohol), into 50μm diameter SiO2-P particles by impregnation. Chromatographic separation of PGMs from simulated high level liquid waste was investigated by column method. It was found that 100% of Pd(II) and Re(VII) could be eluted out from simulate HLLW in 3.0M HNO3 solution using three adsorbents. For Ru(III) and Rh(III), high temperature has distinct effect on the adsorption rate and a further study for Ru(III) and Rh(III) is necessary to separate them from HLLW completely. In all six column experiments, a relatively satisfactory chromatographic separation operating for PGMs from simulated HLLW was obtained using (Crea+TOA)/SiO2-P adsorbent packed column at 323K.
Study on selective separation of cesium from high level liquid waste using a macroporous silica-based supramolecular recognition absorbent
A macroporous silica-based supramolecular recognition absorbent (Calix[4] + Dodecanol)/SiO2–P, was prepared by successive impregnation and fixing the 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix[4]arene (Calix[4]arene-R14) and its molecule modifier 1-Dodecanol onto SiO2 silica-based polymer support. The characterization of (Calix[4] + Dodecanol)/SiO2–P was examined by thermal gravimetry and differential thermal analysis and electron probe microanalysis. Relatively large separation factors of Cs and other metal ions (αCs/Mn+) above 60 were obtained in the presence of 3 M HNO3. The adsorption data of Cs(I) fitted well with Langmuir isotherm and the maximum adsorption capacity was estimated to be 0.19 mmol g−1. The Cs(I) in 3 M HNO3 were also effectively adsorption on (Calix[4] + Dodecanol)/SiO2–P in the column operation, and the loaded Cs(I) was successfully eluted with an eluent of H2O. The column packed with (Calix[4] + Dodecanol)/SiO2–P had excellent reusability after three cycles.
Fission Product Extraction (FPEX): Development of a Novel Solvent for the Simultaneous Separation of Strontium and Cesium from Acidic Solutions
Abstract A synergistic extraction solvent for the simultaneous removal of cesium and strontium from acidic solutions has been investigated. The extraction solvent consists of, 4,4′,(5′)‐di‐(t‐butyldicyclo‐hexano)‐18‐crown‐6 (DtBuCH18C6), calix[4]arene‐bis‐(tert‐octylbenzo‐crown‐6) (BOBCalixC6), and 1‐(2,2,3,3‐tetrafluoropropoxy)‐3‐(4‐sec‐butylphenoxy)‐2‐propanol (Cs‐7SB modifier) in a branched aliphatic kerosene (Isopar® L). Extraction synergy for strontium was observed when DtBuCH18C6 was combined with the BOBCalixC6 cesium extractant solvent and Cs‐7SB modifier or if the Cs‐7SB modifier was substituted into the SREX (Strontium Extraction) solvent in place of TBP. The novel process extracted both cesium and strontium simultaneously from 1 M nitric acid solutions with distribution ratios of 8.8 and 7.7 for strontium and cesium, respectively, at ambient temperature. Distribution coefficients for cesium and strontium as a function of nitric acid concentration and temperature were also obtained with 0.5 M<[HNO3]<2.5 M giving favorable distribution ratios. This new process utilizing the combined solvent has been named the Fission Product Extraction Process (FPEX).