Synergistic extraction of uranium(VI) by alamine 336 in the presence of neutral oxodonors

The distribution behaviour of U(VI) from H2SO4 (similar to 0.1 M) employing U-233 as tracer using mixtures of Alamine 336 with three different neutral oxodonors, viz. dihexyl octanamide (DHOA), tri-n-butyl phosphate (TBP) and tri-n-octyl phosphine oxide (TOPO) in several diluents has been investigated. The stoichiometry of species extracted in dodecane medium was found to vary with the nature of oxodonor. Whereas in the case of the Alamine 336-DHOA mixture, {R3NH}(4)UO2(SO4)(3). DHOA appears to dominate; in the cases of TBP and TOPO, mixed species were formed. Synergistic enhancement in D-U values varied in the order DHOA < TBP < TOPO, which follows the trend of their basicities. in nitrobenzene medium where antagonism was observed for TBP and DHOA, neither synergism nor antagonism occurred in the case of TOPO. The mechanism of synergism appears to involve the replacement of water molecules from the inner coordination sphere of U by oxodonor molecules. The stoichiometry of the species extracted with amine alone changes with the nature of the diluent.