Extraction of heptavalent technetium from nuclear waste streams with 2-nitrophenyl octyl ether

Technetium-99, in the form of Tc(VII), is one of major problems in the mana gement and disposal of nuclear waste in view of its long half-life in combi nation with high geochemical mobility. Solvent extraction is an important s eparation technique to remove Tc-99 from liquid nuclear waste streams. 2-ni trophenyl octyl ether (NPOE) shows high extraction ability for Tc(VII) from water and NaOH solutions (> 99.5%) in spite of the lack of donating atoms. Upon extraction from alkaline solutions, TcO4- associates with NPOE molecu les in 1:1 stoichiometry where the co-extracted cation is expected to play an important role in the extraction mechanism. At pH > 4 the Tc(III) distri bution is relatively insensitive towards changes in pH, while at decreasing pH (<4) the distribution ratio decreases sharply. The strong dependency of the Tc(VII) distribution on the acidity is very useful for developing effi cient extraction-stripping systems. This study showed that NPOE is an excel lent compound for the removal of technetium from alkaline nuclear wastes.