Partitioning of REE(III) and TPE(III) with an extractant based on chlorinated cobalt dicarbollide and polyethylene glycol

Abstract

Theoretical principles and practical characteristics are reported for an extraction process for REE and TPE partitioning using an extractant based on chlorinated cobalt dicarbollide (CCD) and polyethylene glycol (PEG). Joint extraction of REE and TPE is performed from a ≤1 M HNO3 solution with a solution of CCD and PEG in a polar diluent. The TPE stripping is performed with an aqueous solution of a complexing agent (diethylenetriaminepentaacetic acid) and an organic base (urea or thiourea). Trials on an extraction rig in Gatchina showed that the process can be successfully used for exhaustive recovery of REE and TPE from real Purex process raffinates and for their subsequent partitioning, with reaching the required process parameters. The results of semicommercial trials of the REE/TPE partitioning process on the extraction installation of the Mayak Production Association are reported. The trials were performed on such scale for the first time in the world. In reprocessing of 40 m3 of high-level raffinates, good results were obtained with respect to the process hydrodynamics, REE/TPE partitioning, and their separation from impurity elements. The process has high potential for use in HLW reprocessing technologies at new radiochemical plants.