Novel diglycolamide-functionalized calix[4]arenes for actinide extraction and supported liquid membrane studies: Role of substituents in the pendent arms and mass transfer modeling

Several calix[4]arene-functionalized diglycolamide (C4DGA) ligands were evaluated for the extraction as well as supported liquid membrane (SLM) transport of actinides and fission product elements from nitric acid feed solutions. The extraction efficiency of the C4DGA ligands for Am(III) was orders of magnitude higher than that of the commonly proposed diglycolamide ligand, TODGA (N,N,NcN'-tetra-n-octyl diglycolamide). The extraction efficiency of Am(III) with C4DGA increased with increasing the alkyl chain length attached to the N atom of the DGA moieties closer to the calix[4]arene platform. The facilitated transport of metal ions through SLM containing the C4DGA ligands followed the efficiency: Am(III)similar to Eu(III)similar to Np(IV) > Pu(IV) >> U(VI) > Sr(II) > Cs(I). The permeability coefficient (P) and diffusion coefficient (D-o) values for the transported species were calculated. A mathematical model was developed to predict the transport of Am(III) through the SLM, which was successfully verified with the experimental results. The model describes the membrane flux over a wide range of feed composition, chemical composition of metal-ligand complex and revealed that the membrane diffusion processes mainly controls the membrane permeability under different experimental conditions. Present study revealed the possible application of these exotic ligands for recovery of minor actinides from acidic waste solution using liquid membrane technique, where the ligand inventory is extremely low. (C) 2012 Elsevier B.V. All rights reserved.