Extraction of Am(iii) using novel solvent systems containing a tripodal diglycolamide ligand in room temperature ionic liquids: a ‘green’ approach for radioactive waste processing

Abstract

Extraction of Am 3+ from acidic feed solutions was investigated using novel solvent systems containing a tripodal diglycolamide (T-DGA) in three room temperature ionic liquids (RTIL), viz. [C 4 mim][NTf 2 ], [C 6 mim][NTf 2 ] and [C 8 mim][NTf 2 ]. Compared to the results obtained with N,N,N9,N9-tetra-n-octyl diglycolamide (TODGA), T-DGA gave significantly higher distribution coefficients in these RTILs. The D Am values decreased with increasing carbon chain length in the RTILs, which was related to the solubility of the RTIL in the aqueous phase. The distribution studies included the effect of equilibration time, aqueous phase acid concentration variation and T-DGA concentration variation. In general, significantly higher equilibration times were observed for the extraction systems, which was partly due to the viscous RTIL phase and partly due to the slow conformational changes of the T-DGA ligand during complexation. Apart from Am 3+ , extraction of Pu 4+ , UO 2 2+ , Eu 3+ , Sr 2+ and Cs + was also investigated, since they have significant implications in radioactive waste processing. Stripping studies indicated .99% stripping in three stages using 0.5 M EDTA or DTPA in 1 M guanidine carbonate. Slope analysis indicated the extraction of 1 : 1 complexed species of Am(III) with T-DGA. Time resolved laser fluorescence spectroscopy (TRLFS) studies showed a strong complexation with no inner-sphere water molecules in the Eu(III)-T-DGA complexes for [C 4 mim][NTf 2 ] as the diluent. Radiolytic degradation studies of the solvent systems containing T-DGA in the three RTILs were also carried out and while the D Am values decreased marginally when the solvents were exposed to 500 kGy absorbed dose, a relatively sharp decrease (60%) was seen when the solvents were exposed further to 1000 kGy absorbed dose, suggesting the possibility of recycling. Extraction studies were also carried out at varying temperatures and the thermodynamic parameters were calculated.

Luminescence investigation on Eu–pillar[5]arene-based diglycolamide (DGA) complexes: Nature of the complex, Judd–Ofelt calculations and effect of ligand structure

“…Similarly, the site symmetry around Eu 3+ ion in complexes of diglycolamide functionalized calix [4]arenes and its structural modification was also reported to be C 4v [17]. The splitting pattern of each transition in emission profiles of Eu-TODGA, Eu-L1, Eu-L2 and Eu-L3 were presented in Fig.…”

“…We have recently reported the results of a TRLIFS study of DGAfunctionalized calix [4]arenes using the obtained J-O parameters. We arrived at a site symmetry of C 4v and a tentative structure of the complexes was presented with possible coordinating sites [17].…”

“…Formation of reverse micelle aggregation by four TODGA molecules was reported to be responsible for unusually high extraction efficiency of trivalent actinides and lanthanides over other oxidation states [2][3]. In view of the above fact, several attempts were reported to study the actinide extraction using tripodal diglycolamide, where three diglycolamide moieties are attached in C pivotal position [4], diglycolamide functionalized calix [4] arenes and their different structural modifications, where diglycolamide moieties are anchored on a calix [4]arene molecular platform [5][6][7]. Recently, pillararene platform tethered with functional groups were reported by us to be a novel class of extractants for Ln/An separation [8].…”

Probing of the local environment and calculation of J.O. parameters for Eu3+ CMPO functionalized pillararene complexes by time resolved fluorescence spectroscopy

“…The Eu 3 þ complexes of CMPO functionalized pillararenes were found to be more symmetric compared to the diglycolamide functionalized pillararenes. Among the various supramolecular ligands, the asymmetric factors for the Eu 3 þ complexes followed the trend of ligands as tripodal diglycolamide [44] oDGA functionalized ionic liquid with NTf 2 − anion [45] o CMPO pillararene LI oCMPO pillararene LII oDGA Calixarene LI [46] oDGA functionalized ionic liquid with PF 6 − anion [45] oTODGA [45] oCMPO pillararene LIII oDGA Calixarene LII [46] oDGA pillararene LI [47] oPyrazine functionalized calixarene L4 [48] oboth side DGA calixarene [49] oDGA pillararene LII [46] o Pyrazine functionalized calixarene L6 [48] oDGA pillararene LIII [47] olower rim DGA calixarene [49]. …”

Alkylation and pre-organisation of diglycolamide ligands on flexible platforms for nuclear waste treatment

“…concentrations. 159 The following step is the pre-organisation of the ligand on calix [4]arenes, which gave…”