Organophosphinic, phosphonic acids and their binary mixtures as extractants for molybdenum(VI) and uranium(VI) from aqueous HCl media

Synergistic extraction of U(VI) with mixtures of 2-ethyl hexyl phosphonic acid-mono-2-ethyl hexyl ester (PC-88A) and TBP, TOPO or Cyanex 923

The extraction of uranium (VI) from hydrochloric acid medium with PC-88A (H2A2 in dimeric form) and neutral organo phosphorous donors like TBP, TOPO and Cyanex 923 (S) in dodecane is reported. Experiments were performed with PC-88A, TOPO and Cyanex 923 alone and with the mixtures of PC-88A with TBP, TOPO or Cyanex 923. The presence of neutral donors in PC-88A solutions gave synergistic enhancement in the extraction of uranium (VI), the order being Cyanex 923>TOPO>TBP. The species extracted with PC-88A alone is UO2(HA2)2, whereas with TOPO or Cyanex 923 alone, it is UO2Cl2·2S and with the synergistic mixtures it is UO2(HA2)2·S. The power dependencies of S and PC-88A under experimental conditions have also been evaluated using non-linear regression analysis. The equilibrium constants of synergistic extraction have been calculated and the mechanism of the extraction is discussed. The effect of different organic diluents on uranium (VI) extraction with PC-88A has also been examined.