Liquid Membrane Transport Studies Research Articles

Unique Selectivity Reversal in the Complexation of Uranium(VI) and Plutonium(IV) with Two Novel C-Pivoted Tripodal Amide Ligands: Extraction and Liquid Membrane Transport Studies

ABSTRACT Two new carbon pivoted tripodal amide-containing ligands with different spacers (L I : -CH2- spacer; L II : -CH2-CH2- spacer) have been investigated for the liquid–liquid extraction of tetravalent plutonium and hexavalent uranium from nitric acid feed solutions. The studies were carried out using the ligand solutions prepared in 95% n-dodecane + 5% isodecanol. Pu(IV) extraction was higher than that of U(VI) at 3 M HNO3 for ligand L I which was just the opposite for ligand L II . Increase of the nitric acid concentration resulted in increasing extraction of both metal ions. Isodecanol variation studies exhibited decrease in the extraction of Pu(IV) and U(VI) with increasing isodecanol content in the organic phase. Greater that 98% stripping of Pu(IV) and U(VI) was obtained from the complexes of L I and L II using 0.5 M HNO3 + 0.1 M HEDTA and 1 M Na2CO3, respectively. The slope analysis study suggested the formation of 1:2 (ML2) species with Pu(IV) as well as U(VI) with both ligands at 3 M HNO3. Temperature variation studies showed that the extraction of U(VI) and Pu(IV) with both ligands is exothermic in nature. Supported liquid membrane transport experiments using 0.11 M ligands (L I and L II ) in 95% n-dodecane + 5% isodecanol indicated poor transport (<10% after 2 h) of U(VI) and Pu(IV).

Supported liquid membrane transport studies of Pu(IV) using OTDA, a novel diamide

Liquid Membrane (LM) transport studies of Pu(IV) were investigated in detail using a novel rationally designed conformationally constrained oxatricyclodiamide (OTDA). Detailed parametric investigations were carried out to understand the transport mechanism and to optimize the transport conditions. Efforts were also made to investigate the effect of diluent on the extraction as well as transport of Pu(IV) across the membrane with OTDA. Mass transfer modeling of the transport process was performed and a good agreement between the experimental results and theoretically values was found. The optimized conditions for transport was found to be a PTFE membrane support of 0.45 μm, 4 M HNO3 as feed acidity, 0.1 M OTDA in 30% IDA/n-dodecane as carrier and in the strippant side a mixture of 0.2 M HAN + 0.3 M HNO3. Under the optimized conditions, the permeability co-efficient value was found to be (2.11 ± 0.08) × 10−3 cm/s. Diffusion coefficient value of 1.06 × 10-6 cm2/s was obtained for Pu(IV)-OTDA system.

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+ > Am3+∼ Pu4+ >> 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.

New extractant N,N′-dimethyl-N,N′-dicyclohexyl-2,(2′-dodecyloxyethyl)-malonamide (DMDCDDEMA) for radiotoxic acidic waste remediation: Synthesis, extraction and supported liquid membrane transport studies

N,N′-dimethyl-N,N′-dicyclohexyl-2,(2′-dodecyloxyethyl)-malonamide (DMDCDDEMA) has been synthesized by a simpler route; with a better yield, than conventional pentaalkyl substituted diamide synthesis procedures. This route involves simple purification procedures like crystallization leading to desired molecule with high purity. The key step of 1-tosyloxy-3-oxa-pentadecane synthesis has been achieved by selective monoprotection of glycol with simpler chemical transformations. The synthesized product has been tested for radiotoxic metal ions (such as 241Am, 237Np, 239Pu, 233U) extraction and their transport behavior across a supported liquid membrane from nitric acid solutions. The effects of various experimental parameters on the possible radiotoxic waste remediation by this diamide have been evaluated quantitatively. The performance of DMDCDDEMA has been evaluated vis-à-vis other proposed carrier extractants for actinide partitioning under conditions of study. The study suggests that the relatively easier synthesis and its application in membrane based separations may help in scale up operations in radiotoxic waste remediation.

Studies on the separation of 90Y from 90Sr by solvent extraction and supported liquid membrane using TODGA: role of organic diluent

Solvent extraction and supported liquid membrane transport studies on Y(III) and Sr(II) were carried out using both nitric as well as hydrochloric acid feed conditions using N,N,N′,N′-tetra-octyldiglycolamide (TODGA) in several organic diluents. The solvent extraction studies indicated extremely large separation factor (SF) values with chloroform, carbon tetrachloride, 1-decanol and hexone when 6 M HNO3 was used as the feed. On the other hand, the SF values were 1–2 orders of magnitude lower when the nitric acid concentration was 3 M HNO3. Significantly large SF values were also obtained from 6 M HCl when xylene, carbon tetrachloride, n-dodecane and hexone were used as the diluent. Though mass transfer was not very promising in the supported liquid membrane studies with most of the diluent systems, quantitative Y(III) transport was observed with 0.1 M TODGA in xylene with negligible Sr(II) transport suggesting possibility of obtaining carrier free 90Y. The purity of the radiotracer was checked by half-life method.

Prodigious Azocalix[4] Pyrrole Super-molecule: Effective Reagent for Liquid-liquid Extraction, Preconcentration and Transport of Cu(II) Ions

A novel series of eight prodigious calix(4)pyrrole super-molecules bearing azo-moiety at the meso position of the macrocycle have demonstrated the ability for liquid-liquid extraction, preconcentration and transport of Cu(II) ions across a liquid membrane. Various significant extraction parameters such as effect of pH, effect of solvent and effect of reagent concentration were investigated which showed high affinity and selectivity towards Cu(II) in the presence of large quantities of associated metal ions. The wavelengths of maximum extraction (λ max) and molar absorptivity (e) have also been determined. The stoichiometry of complex was evaluated by slope ratio method. The system obeys Beer's law over the range 0.5-10.0 μg mL -1 . Liquid membrane transport studies of Cu(II) were carried out from source to the receiving phase under controlled conditions and a mechanism of transport is proposed. To check the validity of the proposed method, Cu(II) was analyzed in natural and ground water samples of Ahmedabad city, Gujarat, India.

Supported liquid membrane transport studies on Am(III), Pu(IV), U(VI) and Sr(II) using irradiated TODGA

Transport behaviour of actinides viz. Am3+, Pu4+ and UO22+ was investigated from nitric acid feed conditions using PTFE (polytetrafluoroethylene) flat sheet supported liquid membranes (SLM) containing an irradiated solvent system comprising of N,N,N′,N′-tetra-n-octyldiglycolamide (TODGA) as the carrier extractant and N,N-di-n-hexyloctanamide (DHOA) as the phase modifier. The present studies were carried out in order to understand the effect of irradiation on the long term reusability of the SLM and the decontamination behaviour in the absorbed dose range of 0–100MRad. The studies using irradiated carrier included those with irradiated TODGA without any phase modifier and with 0.1M as well as 0.5M DHOA as the phase modifier. Transport behaviour of all the metal ions were found to be seriously affected with increasing radiation dose which was reflected in the decreasing percentage transport (%T) as well as permeability co-efficient (P) values. Though Sr(II) transport was quite significant with all the three unirradiated solvent systems, it was surprisingly low (<5%) when solvents exposed to 100MRad dose were used in the SLM. Separation factors (S.F.) of the actinides over Sr(II) were calculated and were found to increase at higher radiation doses suggesting possibility of getting better decontamination on prolonged use of the supported liquid membrane system.

Liquid–liquid extraction and flat sheet supported liquid membrane studies on Am(III) and Eu(III) separation using 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine as the extractant

Solvent extraction and supported liquid membrane transport studies for the preferential removal of Am 3+ from feeds containing a mixture of Am 3+ and Eu 3+ was carried out using 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine ( n-Pr-BTP) as the extractant. Diluent plays an important role in these studies. It was observed that the distribution coefficients deteriorate significantly for both Am 3+ and Eu 3+ though the separation factors were affected only marginally. The transport studies were carried out at pH 2.0 in the presence of NaNO 3 to result in the preferential Am 3+ transport with high separation factors. Effect of different experimental parameters, viz. feed composition, stripping agents, diluents of the organic liquid membrane and membrane pore size was studied on the transport and separation behaviour of Am 3+ and Eu 3+. The supported liquid membrane studies indicated about 85% Am 3+ and 6% Eu 3+ transport in 6 h using 0.03 M n-Pr-BTP in n-dodecane/1-octanol (7:3) diluent mixture for a feed containing 1 M NaNO 3 at pH 2 and a receiver phase containing pH 2 solution as the strippant. Consequently, a permeability coefficient of (1.75 ± 0.21) × 10 −4 cm s −1 was determined for the Am 3+ transport. Stability of the n-Pr-BTP and its SLM was also studied by carrying out the distribution and transport experiment after different time intervals.

Design and synthesis of series of receptors and their use in extraction and liquid membrane transport studies of amino acids

Design and synthesis of series of receptors and their use in extraction and liquid membrane transport studies of amino acids

Characterization of Anthraquinone-DerivedRedox Switchable Ionophores and Their Complexes with Li+, Na+, K+, Ca+, and Mg+Metal Ions

Anthraquinone derived redox switchable ionophores 1,5 bis (2-(2-(2-ethoxy) ethoxy) ethoxy)anthracene-9,10-dione (V1) and 1,8-bis(2-(2-(2-ethoxy)ethoxy)ethoxy) anthracene—9,10-dione (V2) have been used for isolation, extraction and liquid membrane transport studies of Li+, Na+, K+, Ca2+and Mg2+metal ions. These isolated complexes were characterized by melting point determination, CV and IR,1H NMR spectral analysis. Ionophore V2shows maximum shift in reduction potential(ΔE)with Ca(Pic)2. The observed sequence for the shifting in reduction potential(ΔE)between V2and their complexes is V2calcium picrate (42 mV) &gt; V2potassium picrate (33 mV) &gt; V2lithium picrate (25 mV) &gt; V2sodium picrate (18 mV) &gt; V2magnesium picrate (15 mV). These findings are also supported by results of extraction, back extraction and transport studies. Ionophore V2complexed with KPic and showed much higher extractability and selectivity towards K+than V1. These synthetic ionophores show positive and negative cooperativity towards alkali and alkaline earth metal ions in reduced and oxidized state. Hence, this property can be used in selective separation and enrichment of metal ions using electrochemically driven ion transport.

Supervanadophile: Complexation, preconcentration and transport studies of vanadium by octa functionalized calix[4]resorcinarene-hydroxamic acid

A new octa functionalized calix[4]resorcinarene bearing eight hydroxamic acid groups (OFCHA) has been synthesized and its analytical properties have been investigated. To elucidate the structure of the compound, elemental analysis, FT-IR and 1H NMR spectral data have been used. The compound showed high affinity and selectivity for vanadium(V) in presence of large quantities of associated metal ions. The complexation of vanadium(V) with OFCHA has a 4:1 metal: ligand stoichiometry as evaluated by Job’s plot. A spectrophotometric method is proposed for the extractive determination of vanadium(V) in an acidic medium in the presence of diversified matrix, and verified by ICP-AES. Under the optimum condition of acidity, solvent, interfering ions and OFCHA concentration, the molar absorptivity of the complex is 5630 l mol-1 cm-1 at 495 nm. The system obeys Beer’s law over the range 0.125–8.75 μg ml-1 of vanadium(V) with Sandell sensitivity 0.009 μg cm-2. The preconcentration factor and overall stability constant evaluated at 25 °C were 142 and 14.18, respectively. The complexation is characterized by favorable enthalpy and entropy changes. Liquid membrane transport studies of vanadium(V) were carried out from source to the receiving phase under controlled conditions and a mechanism for transport is suggested. To check the validity of the proposed method, vanadium is determined in environmental, biological samples and some standard reference materials from NIST and BCS.

Extraction &amp; Bulk Liquid Membrane Transport Studies of Biologically Important Metal Ions (Li+, Na+ and K+) by Synthetic Ionophores

Extraction &amp; Bulk Liquid Membrane Transport Studies of Biologically Important Metal Ions (Li+, Na+ and K+) by Synthetic Ionophores

Extraction and Liquid Membrane Transport Studies of Alkali Metal Ions Using Chromogenic Ionophores

Article Extraction and Liquid Membrane Transport Studies of Alkali Metal Ions Using Chromogenic Ionophores was published on December 1, 2008 in the journal Main Group Metal Chemistry (volume 31, issue 6).

Enhanced Li+ ion-selective ionophoric properties of double armed diaza-12-crown-4 derivatives

Abstract A variety of double armed crown ethers were prepared in which amine, amide, ester, nitrile and pyridine moieties were attached as cation-ligating sidearms to diaza-12-crown-4 ring. FAB-MS and 7Li/13C/23Na NMR binding and liquid membrane transport studies revealed that most of them exhibited Li+ cation selectivity, though corresponding single armed lariat ethers showed Na+ cation selectivity. Among them, amine-armed diaza-12-crown-4 derivative offered the highest Li+ ion-selective ionophoric property. Its transport efficiency and selectivity were particularly superior to those of commercially available Li+ ion-selective ionophores.

Ag+ Ion-selective lariat ethers: high pressure syntheses and cation recognition properties

A new series of lariat ethers have been prepared by a high pressure SNAr reaction, in which various heteroaromatics are directly connected to the nitrogens of 12-, 15- and 18-membered aza-crown ethers. Liquid membrane transport studies demonstrated that lariat ethers having thiazole, oxazole, pyrazine and pyridazine rings on their sidearms exhibited excellent Ag+ ion selectivity. 13C NMR binding experiments revealed that these lariat ethers selectively formed encapsulated Ag+ complexes in a different fashion from that of double armed crown ethers. Cooperative action between the heteroaromatic sidearm and the aza-crown ring afforded unique cation recognition.