Process for separation of technetium from alkaline low level waste using di-tert-butyldibenzo-18-crown-6 + isodecyl alcohol/n-dodecane solvent

Di-tert-butyldibenzo-18-crown-6 ether (CE) dissolved in a mixture of isodecyl alcohol and n-dodecane has been investigated for separation of technetium from alkaline low level waste (LLW). Technetium present as TcO4− pairs with sodium ion-crown ether complex formed due to high sodium nitrate concentration in the waste solution results in extraction of TcO4− by ion-pair formation of the kind Na+·CE·TcO4−. Stoichiometry of the extracted complex as determined by slope analysis of log-log plot of technetium distribution ratio (DTc) vs. the CE concentration suggests a combining ratio of 1 TcO4− to 1 CE. Extraction of TcO4− was examined from aqueous phase with varying NaNO3 and NaOH concentrations. DTc was found to increase with increase in Na+ concentration having NO3− or OH− as counter ions, however, above 5 M concentrations of them, DTc remained constant for NaOH while it decreases for NaNO3 due to a strong competitive extraction of NO3− ion compared to OH−. Quantitative stripping of TcO4− was achieved in three consecutive contact of loaded organic with deionized water.