The Extraction of Th(IV) and U(VI) by Dihexyl-<i>N, N</i>-diethylcarbamoylmethylphosphonate from Aqueous Nitrate Media

Abstract

Abstract The extraction behavior of Th(IV) and U(VI) from nitrate media was studied using relatively pure dihexyl-N, N-diethylcarbamoylmethylphosphonate (DHDECMP). The data were compared with analogous measurements obtained with dibutyl butylphosphonate (DB[BP]). It was found that the extractant dependency is second power for U(VI) with both DHDECMP and DB[BP]. However, the extractant dependency for Th(IV) is third power for DB[BP] but varied from 2.5 to 2.0 power for DHDECMP depending on the total nitrate concentration. The Kd data do not support the theory that DHDECMP is an effective chelating agent for actinide ions. Significant differences between DHDECMP and DB[BP] do appear in the extraction behavior of Th(IV) from 1 to 5 M HNO3. These differences are explained by the ability of DHDECMP to buffer itself against the effects of HNO3 by protonation of the amide group.