Investigation of tris(2-methylbutyl) phosphate for U/Th separation from U-Th and U-Th-REE solutions by cross current mode

Abstract

ABSTRACT Conventional U/Th separation is carried out using tri-n-butyl phosphate (TBP) as the extractant. While processing the thorium-based feed solutions with TBP, third phase formation is a major concern due to the presence of large quantities of Th(IV). In a systematic investigation to overcome the limitations and retaining the properties of TBP, a branched isomer of higher homologue of TBP, tris(2-methylbutyl) phosphate (T2MBP) has been explored as a potential extractant for nuclear fuel reprocessing with lesser third phase formation tendency. In this context, T2MBP has been investigated for the complete recovery and separation of actinides (U, Th) from the THOREX and monazite ore processing feed solutions in cross current mode, and the results are compared with TBP-based systems. The co-extracted thorium in the separation process was further improved by scrubbing. The influence of the structural effect, organic-to-aqueous (O/A) phase ratio and scrub acid concentration on the U/Th separation process have been determined using T2MBP as the extractant. Overall, these studies indicated that T2MBP exhibits higher U/Th separation factor, and it has the ability to recover and separate individual actinides (U, Th) without third phase formation compared to TBP.