Comparison of uranyl third-phase formation in 30% TBP-nitric acid in dodecane and HPT using UV-visible spectroscopy

Third phase formation behavior was studied in the uranyl / 30% tri-n-butyl phosphate/high molar nitric acid system. Using metal ion titration coupled with UV-visible spectroscopy, a comparison was made between the diluents dodecane and hydrogenated polypropylene tetramer (HPT). This work presents the first quantitative comparison of dodecane with HPT, which is commonly used in the French reprocessing program. As anticipated, higher metal loading prior to third phase formation was observed in the HPT system due to the branched configuration of the diluent. Spectral evidence of differences in speciation between each phase, as well as a change in the single organic phase speciation prior to phase splitting is presented.