Efficient and Selective Extraction of 99mTcO4– from Aqueous Media Using Hydrophobic Deep Eutectic Solvents

Extraction of trace pertechnetate (99mTcO4–) from aqueous media using hydrophobic deep eutectic solvents (DESs) is reported for the first time. The hydrophobic DESs studied comprise a 1:2 molar ratio of a tetraalkylammonium or tetraalkylphosphonium halide mixed with a monocarboxylic acid (i.e., saturated fatty acid). Quantitative (>99%) removal of tracer levels of 99mTcO4– from an aqueous phase in the presence of a large excess of competing anions (e.g., Cl–, NO3–, HCO3–, H2PO4–, SO42–) within 5–60 min at 25 °C without the aid of a formal extracting agent (e.g., ionophore) demonstrates an efficient and selective extraction. At infinite dilution of pertechnetate, very high distribution ratios in excess of 103 are observed. Attempts to strip technetium from the DES extractant phase by reduction with SnCl2 are also reported. Overall, these outcomes provide the basis for considering hydrophobic DESs as an alternative platform for 99TcO4– waste management.