Solvent extraction of selenium in nitric acid: evaluation of multiple extractants and proposal of a novel separation process.

Solvent extraction behaviors of Se (VI) from nitric acid solutions were investigated with multiple extractants used for uranium, plutonium, minor actinides, and rare earth elements separation processes from high-level liquid waste. During the processes, Se remained in the residual aqueous solutions, as all extractants showed distribution ratios < 1. In contrast, Se showed distribution ratios > 1 with o-phenylenediamine in dilute nitric acid (< 2 M HNO₃), octanol as the organic phase, and concentrated nitric acid (8 M HNO₃) for back extraction, suggesting a potential new single separation process and recovery of Se. [ABSTRACT FROM AUTHOR]