Highly Promising Method for the Decontamination of Europium from Americium Using an Extraction Chromatography Resin Containing a Tripodal Diglycolamide and SO₃Ph-BTP as Eluent

Separation of Am3+ from Eu3+ was demonstrated by extraction column chromatography using a tripodal diglycolamide ligand (T-DGA). A clean separation was achieved by selective complexation of Am3+ in the feed with 2,6-bis(5,6-di(sulfophenyl)-1,2,4-triazin-3-yl)pyridine (SO3Ph-BTP) with a separation factor of about 2000. The extraction chromatography resin material with particle size in the range of 175-250 μm contained only 7.4% T-DGA ligand (53 μmol/g) and is one of the most efficient materials used for this purpose until date. Parameters such as feed acidity and SO3Ph-BTP concentration were varied, while keeping the other parameters constant for getting the best optimized condition for the separation of Am3+ from Eu3+ ions. The optimized feed condition was 0.1 M HNO3 containing 10 mM SO3Ph-BTP for the clean separation of Am3+ from the Eu3+ fraction. In the feed solution containing Eu3+ and Am3+, the latter was complexed with SO3Ph-BTP and, therefore, was not retained on the column, whereas the uncomplexed Eu3+ could be efficiently held onto the column. Finally, the loaded Eu3+ from the column was eluted with 0.1 M HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid), giving a sharp and narrow elution curve. The radiation stability of the resin was excellent up to 1000 KGy gamma dose, and an identical separation efficiency of the resin was noted with the irradiated resin column, as was obtained with the pristine resin.</p

Solvent systems containing diglycolamide-functionalized calix[4]arenes in room temperature ionic liquid for metal ion extraction: studies with simulated high-level wastes

The extraction of actinide ions such as Am(III), Pu(IV), Np(IV), U(VI) and Pu(VI) was studied from simulated high-level waste (SHLW) solutions using several diglycolamide-functionalised calix[4]arene (Calix-DGA) ligands dissolved in the room temperature ionic liquid (RTIL) [C8mim][NTf2]. The Calix-DGA ligands were three lower-rim functionalised ligands with varying alkyl substituents (L-I, L-II and L-III), an upper-rim functionalised ligand (L-IV) and an upper- and lower-rim functionalised ligand (L-V). The SHLW solutions used contained 0.5 M HNO3 and the extraction trend of the actinides was found out to be Am(III) > Pu(IV)∼Np(IV)≫ and the extraction efficiency of the Calix-DGA ligands for Am(III) being L-V>L-I>L-II>L-IV>L-III. Reasonably, good extraction of Am(III) was obtained with 5.0 × 10− 4 M ligand solutions suggesting that higher concentrations of the ligand can be used for a higher loading of the metal ions. The extraction of other metal ions representing fission products, structural materials and process chemicals was studied by Inductively Coupled Plasma –Atomic Emission Spectroscopy analysis. The extraction mechanism follows the cation-exchange mechanism often observed with RTIL-based extraction systems. Enthalpy changes were measured from van't Hoff plots and were found to be significantly different than those observed with tracer studies reported previously

Effect of an alkyl substituent and spacer length in benzene-centered tripodal diglycolamides on the sequestration of minor actinides

Three benzene-centered tripodal diglycolamide (Bz-T-DGA) ligands, where diglycolamide (DGA) moieties are tethered to the central benzene ring through a methylene spacer and having either a hydrogen atom (LI) or an isopentyl group (LII) attached to the N-atom, and DGA moieties attached via an ethylene spacer and having an isopentyl group attached to the N-atom (LIII), were studied for their complexation and extraction abilities towards trivalent actinides and lanthanides. The distribution ratio of Am(iii) and Eu(iii) with 1 mmol L-1 ligand in 5% iso-decanol/n-dodecane followed the order: LII &gt; LIII &gt; LI. The substitution of the H atom with the isopentyl group on the N-atom of the DGA moieties resulted in two orders of magnitude enhancement in the extraction ability of the ligand. On the other hand, increase in the spacer length between the benzene ring and the DGA moieties resulted in several fold reduction in the extraction ability of the ligand. Spectroscopic studies with Eu3+ ions in acetonitrile also confirmed the metal/ligand complex formation constant in the order: LII &gt; LIII &gt; LI. Luminescence decay lifetimes of Eu3+/ligand complexes confirmed the absence of water molecules and that all the primary coordination sites of the metal ion are occupied by the ligands.</p

Liquid-liquid extraction and facilitated transport of f-elements using an N-pivot tripodal ligand

Diglycolamide (DGA)-functionalized tripodal ligands offer the required nine-coordinated complex for effective binding to a trivalent lanthanide/actinide ion. A N-pivot tripodal ligand (TREN-DGA) containing three DGA pendant arms was evaluated for the extraction and supported liquid membrane transport studies using PTFE flat sheets. Solvent extraction studies indicated preferential extraction of 1:1 (M:L) species, while the metal ion extraction increased with increasing HNO3 concentration conforming to a solvated species extraction. Flat sheet-supported liquid membrane studies, carried out using 4.0 × 10−3 M TREN-DGA in 95% n-dodecane + 5% iso-decanol indicated faster mass transport for Eu3+ ion as compared to Am3+ ion. The determined transport parameters indicated slow diffusion of the M-TREN-DGA (M = Am or Eu) complex being the rate-determining step. The transport of lanthanides and actinides followed the trend: Eu3+ &gt; Am3+∼ Pu4+ &gt;&gt; UO22+ and Am can be selectively separated from a mixture of U and Pu by oxidizing the latter to its +6 oxidation state. The liquid membrane stability was not encouraging and was deteriorating the transport efficiency with time, which was attributed to carrier loss into the aqueous phases.</p

Evaluation of a novel PVC-based efficient potentiometric sensor containing a tripodal diglycolamide (TREN-DGA) ionophore for europium(III) estimation

Polymeric membrane-based electrodes containing a multiple diglycolamide (DGA), such as a N-pivot diglycolamide (diglycolamide-TREN (TREN-DGA) and a C-pivot diglycolamide (tripodal diglycolamide) (T-DGA) as ionophore, and polyvinyl chloride (PVC) as the base polymer were fabricated. These membranes were tested for the potentiometric determination of europium ions in acidic feed solutions. The membrane with a composition of 81.5% PVC and 18.5% TREN-DGA showed a wide dynamic range (3.2 × 10−7 to 1.0 × 10−2 M) with a slope of 17.2 ± 0.4 mV per decade for europium ion. The presence of sodium tetraphenyl borate (NaTPB) as ionic additive in the DGA-TREN containing membrane marginally improved the dynamic range in the detection of europium ion. On the other hand, the membrane with a composition of 77.3% PVC and 22.7% T-DGA does not show any systematic potential response against variation of the concentration of europium ions in the external solution containing 1 M HNO3. The physical characterization of these membranes was carried out using techniques such as thermogravimetry (TGA), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) in order to understand the effect of the different constituents of the membrane on the potential response for europium ion. AFM measurements revealed that the morphology of the membrane remained intact even after prolonged use of the membrane. The interference effect of Ca2+, Mg2+, Cu2+, Fe3+, Bi3+, Zn2+, Cd2+ and UO2 2+ on the potential response was investigated. The response time of the proposed sensor was found to be less than five seconds. The lifetime of the sensor electrode was found to be three months under proper storing conditions. The membrane sensor was employed in the determination of Eu3+ in synthetic water samples.</p

A highly efficient sensor for europium(III) estimation using a poly(propylene imine) diaminobutane diglycolamide dendrimer as the ionophore:Potentiometric and photoluminescence studies

Multiple-diglycolamide (DGA) based ligands are known as highly promising extractants for the selective and efficient extraction of trivalent lanthanides/actinides from acidic feed solutions and therefore they have a great potential for the low level detection of these metal ions when used as ionophores in a potentiometric sensor. However, their use as ionophores in a potentiometric sensor is not much explored. Here in, we report the potentiometric sensing of Eu(III) ion in acidic medium using three novel multiple DGA-functionalized dendrimers: viz., generation zero (G0), one (G1) and two (G2) poly(propylene imine) diaminobutane dendrimers as ionophores doped in a polyvinyl chloride (PVC) matrix containing 2-nitrophenyl octyl ether (NPOE) as the plasticizer and sodium tetraphenylborate (NaTPB) as the ionic additive. Out of these three dendrimers, the G1 membrane gave very encouraging results and the G2 membrane did not work properly. On the other hand, the G0 membrane showed a narrower linear dynamic range (LDR), and a higher limit of detection (LOD) than the G1 membrane. The membrane with 4.1 % G1, 31.1 % PVC, 62.2 % NPOE, 2.6 % NaTPB exhibited a linear response behaviour from 6.6 × 10-7 M to 1.5 × 10-2 M Eu(III) with a slope of 15.6 ± 0.2 mV/decade and a LOD of 5.0 × 10-7 M. The response time and lifetime of this sensor were found to be &lt; 10 s and more than three months, respectively, and showed reasonably high selectivity with respect to mono- and divalent cations as well as the uranyl ion. All the sensor membranes contained two types of Eu(III) species as seen by luminescence spectroscopy. The sensor efficiency was checked by the ‘spike recovery method’. The G1 membrane sensor was also employed for the potentiometric titration of Eu(III) as an indicator electrode. Both methods showed more than 95 % recovery with excellent matching with the X-ray fluorescence (XRF) results. The sensor can also be used in the estimation of europium ion in a laboratory bearing waste and in a lamp phosphor waste leached which compared well with XRF and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) results, respectively.</p