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).

Keywords:

• Calixarene
• cesium
• crown ether
• FPEX
• strontium

Acknowledgments

We wish to thank our collaborators Drs. Bruce A. Moyer, Laetitia H. Delmau and Peter V. Bonnesen at Oak Ridge National Laboratory for the BOBCalixC6, the Cs‐7SB modifier, CSSX solvent and helpful discussions. This research was sponsored by the US Department of Energy, Office of Nuclear Energy, Science and Technology under DOE Idaho Operations Office contract DE‐AC07‐99ID13727.