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

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

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

Liquid–Liquid Extraction and Supported Liquid Membrane Transport of Neptunium(IV) Across a Flat-Sheet Supported Liquid Membrane Containing a TREN-DGA Derivative

Liquid–liquid extraction and liquid membrane transport behavior of tetravalent actinide ions viz. Th(IV), Np(IV), and Pu(IV) were investigated for the first time using a diglycolamide (DGA) based dendrimer with a tris(2-aminoethyl)amine (TREN) scaffold as the organic extractant. The generation of 1 dendrimer with six DGA pendent moieties (termed as TREN-G1-DenDGA) extracted Np(IV) more effectively than the other two ions, the trend being Np(IV) > Pu(IV) > Th(IV). The extraction studies of Np(IV) from 3 M HNO3 indicated a 1:1 (metal:ligand) species and the extraction efficiency increased with increasing nitric acid concentration (1–6 M). The transport efficiency of Np(IV) increased with the nitric acid concentration (1–6 M) as well as with the ligand concentration. A very low concentration of 5.75 × 10−4 M ligand, when used as the carrier, resulted in the transport of ca. 25% metal ion transport in 5 h, which increased to >85% with 4.4 × 10−3 M ligand. The transport efficiency of the metal ion across the SLM followed the trend Np(IV) > Th(IV) > Pu(IV). The membrane stability was not satisfactory as seen over a period of 5 days suggesting long-term use may require regular replenishment of the carrier solvent. The effective diffusion coefficient (D eff) of Np(IV)-TREN-G1-DenDGA were determined by the lag-time method and was found to be 5.1 × 10−8 cm2/s

Evaluation of three novel benzene-centered tripodal diglycolamide ligands for the pertraction of americium(III) through flat sheet membranes for nuclear waste remediation applications

Three benzene-centered tripodal diglycolamide (Bz-T-DGA) ligands were evaluated for the pertraction of Am3+ across PTFE flat sheet membranes. The feed phase contained a tracer spiked nitric acid solution (3 M), while the receiver phase contained 1 M α-hydroxyisobutyric acid (AHIBA). The transport of Am3+ was quantitative with ligand LI, with ethyl groups appended to the benzene ring at the 1,3,5-positions and two spacer atoms between the ring and the DGA group. Ligand LIII, with a butoxy tether between the ring and the DGA unit, displayed a much better transport efficiency than ligand LII having an ethylamide linkage, although in both cases the transport rates are lower than that of LI. The transport efficiency of the actinide ions was Am3+ > Pu4+ ≫ UO22+ suggesting that Am and Pu can be easily decontaminated from U in a mixture. The membrane stability was reasonably good with LI, while it was poor for the other two ligands

Unique Eu(III) transport selectivity seen using a supported liquid membrane containing a diglycolamide dendrimer ligand

Dendrimers are exotic multi-functional ligands and are expected to give rise to better extraction/transport results as compared to the mono-functional ligands. Diglycolamide (DGA) based dendrimers are scarcely reported and literature on their transport studies are very limited. Transport of Am(III) and Eu(III) across a PTFE (polytetrafluoroethylene) based flat sheet supported liquid membrane containing a generation 1 dendrimer of tris(2-aminoethyl)amine (TREN), containing six diglycolamide (DGA) pendent arms (termed as TREN-G1-DenDGA) was investigated from nitric acid feed solutions. The transport studies involved 5.75 × 10−4 M ligand solution in 5% isodecanol modified n-dodecane. Am(III) transport was slower than that of Eu(III) under identical conditions. The transport of both Am(III) and Eu(III) increased with increasing nitric acid concentration from 1 to 6 M HNO3 suggesting a solvation extraction mechanism with nitrate ions playing a significant role. A unique preferential Eu(III) transport over Am(III) was seen at 3 M HNO3 with a transport selectivity factor (ratio of permeability coefficient values) of 6.2 which decreased upon changing the acid concentration. Carrier ligand concentration also played a significant role in transport selectivity. Membrane parameters such as permeability coefficient and effective diffusion coefficient (D eff) values were determined experimentally. The liquid membrane stability studies were also carried out

Pertraction of americium(III) through supported liquid membranes containing benzene-centered tripodal diglycolamides (Bz-T-DGA) as an extractant/carrier

Two novel benzene-centered tripodal diglycolamide (Bz-T-DGA) ligands with affinity for actinide ions were employed for the solvent extraction as well as flat sheet supported liquid membrane (SLM) transport of trivalent americium (Am3+), considered as one of the most important minor actinide ions in the high level waste (HLW). Bz-T-DGA ligands with isopentyl substituents and varying spacer lengths in the DGA arms, viz. methylene (TPAMTEB) and ethylene (TPAETEB) groups were employed for actinide extraction for possible application in nuclear waste remediation. With both the ligands, the extraction of Am3+ increased with the concentration of nitric acid (1–6 M HNO3), the distribution ratio (D) values being 16.6 and 3.71 at 3 M HNO3 and 35.1 and 44.4 at 6 M HNO3 for 6.6 × 10−4 M TPAMTEB and TPAETEB, respectively taken in a 5% isodecanol and 95% n-dodecane diluent mixture. A stripping study showed a relatively slow stripping of Am3+ from the loaded membrane with TPAETEB even in the presence of a complexing agent. Am3+ transport rates were rather slow in polypropylene (PP) flat sheets as compared to previous, analogous studies suggesting slow migration of the complexed ions. Am3+ transport was 4.8 times slower in TPAETEB than in TPAMTEB with diffusion coefficients of 4.5 × 10−8 and 2.16 × 10−7 cm2/s, respectively

Americium pertraction across supported liquid membranes containing multiple diglycolamide ligands: Role of alkyl substitution and spacer length in carrier ligands

Liquid–liquid extraction and subsequent supported liquid membrane (SLM) transport studies involving Am3+ ion were carried out from nitric acid feed solutions using three N-pivot tripodal diglycolamide (DGA) ligands with varying substituent at the inner carboxamide N atom and spacer length. The ligand with an isopropyl substituent and with C2 spacer is termed as iPr3-TREN-DGA, while the one without alkyl substituent is termed as TREN-DGA. The third ligand with no substituent but a C3 spacer is termed as TRPN-DGA. The trend of metal ion extraction was iPr3-TREN-DGA > TRPN-DGA > TREN-DGA when solutions of ca. 1.0 × 10−3 M ligand in 95% n-dodecane + 5% isodecanol were used. Stripping studies were carried out using 0.01 M HNO3, 0.01 M EDTA (at pH 3.0) and 1 M α-HIBA (α-hydroxyisobutyric acid) The extraction and stripping kinetics studies suggested attainment of equilibrium in about 30 minutes. The SLM studies were carried out in a two-compartment cell with 20 mL feed as well as receiver phase volumes and PTFE (polytetrafluoroethylene) flat sheets as the solid support. The transport rates followed the same trend as that of the metal ion extraction study, suggesting comparable diffusion coefficients of the complexes (obtained by the lag-time method). Membrane stability studies indicated the best stability for the TRPN-DGA ligand