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Selective separation of 99Tc from aqueous process streams is of vital importance in view of its high fission yield, radioactivity, the long half-life, and high mobility in the environment. To this ...

A novel functionalized ionic liquid, namely, malonamide-functionalized ionic liquid (MFIL) was synthesized and evaluated for the liquid–liquid extraction of rare-earth metals (REMs), transition, and other base metals from a hydrochloric acid medium. Theoretical calculations coupled with FT-IR studies were used to establish the mode of complexation between metal ions and the extracting moiety of MFIL. Uptake studies with multimetal feed solutions showed very good selectivity for REMs over other transition and base metals. Quantitative back extraction of REMs from loaded MFIL was accomplished using an acidic solution. MFIL showed preferential uptake of REMs over base and transition metals typically found in lamp phosphors.

A simple and rapid method based on solid phase extraction chromatography (SPEC) has been developed for the determination of 90Sr in environmental samples. The SPEC method consists of three steps, namely, (1) carbonate precipitation of alkaline earths, (2) column separation of strontium using 4,4′(5′)-bis(tert-butylcyclohexano)-18-crown-6 based Sr spec resin and (3) beta counting of SrCO3 using low background gas flow counter. Minimum detection limit (MDL) of low beta gas flow counter is 1.42 Bq/kg for 10,000 s counting time. The capacity of the column for strontium was about 12.2 ± 0.5 mg of Sr per g of Sr spec resin. The SPEC method using Sr spec resin was standardized with 90Sr spiked samples and tested on sediment samples of Mumbai harbour bay. The average activity concentration of 90Sr in sediment samples was found to be 2.2–13.7 Bq/kg. The results obtained by SPEC method have been found to be in good agreement with conventional gravimetric method.

The paper reports a new rapid radioanalytical procedure for the determination of plutonium (Pu) in sediments by solid phase extraction chromatography (SPEC) using Bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) grafted resin, abbreviated as Benzodioxodiamide (BenzoDODA) grafted resin. The resin was synthesized and evaluated for its sorption behaviour towards Pu in batch and column mode to determine its efficacy for selective recovery of Pu from sediment samples. The analytical procedure was based on the radiochemical separation of samples by acid digestion, followed by preconcentration of actinides by co-precipitation with Fe(OH)3 and finally selective recovery of Pu by SPEC using a column filled with BenzoDODA grafted resin. Pu was then radiometrically assayed by preparing alpha disc sources with electro-deposition followed by alpha spectrometry. The method was further validated with IAEA reference materials. This method gives reliable and reproducible results for the activity concentration of Pu in sediment samples within 24 h.

Novel task specific ionic liquid, namely, N -methyl- N,N,N -trioctyl ammonium-bis-(2-ethylhexyl) phosphonate (MTOABEHP) was synthesized by metathesis route and, its extraction efficiency in n -dodecane was evaluated for Gd(III) using liquid-liquid extraction technique. Extraction kinetics was found to be fast, quantitative uptake was attained within ten minutes of equilibration. Increase in pH of aqueous feed solution resulted in the increase of uptake of Gd(III) up to pH = 4, afterward the extraction decreased significantly. Stoichiometry of the extracted complex was found to be Gd(NO 3 ) 3 ·3MTOABEHP using log-log plot method. Temperature variation studies have shown that the extraction is enthalpy driven (ΔH 0 = −27.5 kJ mol −1 ), showing very strong interactions between the ionic liquid moiety and Gd(III). FT-IR and 31 P NMR studies have shown the participation of phosphoryl oxygen of task specific ionic liquid moiety in bond formation with gadolinium ions. Efficient back-extraction could be achieved with 0.1 M Ethylene diaminetetraacetic acid (EDTA) and deionized (DI) water (pH ∼ 7, ⩾50 °C), thus providing the option of recyclability of the extractant.

New preorganised 1,2-diamide functionalised, bidentate ligand-embedded hydrophobic ionic liquids (DAILs) were synthesised, which enabled efficient extraction of lanthanides from an aqueous phase. The selective metal binding ability of the functionalised ionic liquid was examined by NMR, FTIR and a structure optimisation calculation. The selective liquid–liquid extraction behavior with DAILs was demonstrated.

N,N,N ’, N ’-Tetra-(2-ethylhexyl)-dithiodiglycolamide were impregnated onto XAD-16 resin and evaluated for the sorption of palladium from acidic medium. The sorption kinetics for Pd on the resin was fast, equilibrium was attained within 60–90 min. The pseudo-first order kinetics model closely matches with the experimental data of sorption kinetics. The sorbed palladium can be eluted using 0.01 M thiourea in 0.1 M HNO 3 solutions. Freundlich sorption isotherm model fit well with the isothermal sorption data with maximum sorption capacity of ≈ 29 mg/g. Sorption studies with simulated HLW solution have shown high uptake of palladium and very small co-extraction of lanthanides.

Imino diacetamide styrene divinyl benzene resin was evaluated for separation of palladium from simulated high level liquid waste (HLLW). The kinetics of sorption was found to be fast, and the kinetic data were fitted well to the pseudo-second-order kinetics model. Very high Kd (~103) were obtained for Pd for feed solutions having acidity from 0.25 M to 4.0 M HNO3. The loading studies of the resin showed the maximum sorption capacity of 54 mg/g. Back extraction studies showed that sorbed Pd can be effectively back extracted using 0.01 M thiourea in 0.2 M HNO3. Studies with simulated HLLW showed preferential sorption of Pd over other metal ions.

Facilitated transport of Pu(IV) from nitric acid medium was studied using a novel extractant, BenzoDODA in supported liquid membrane mode. BenzoDODA is a highly selective ligand for Pu(IV), providing very high decontamination factor from other fission products present in high level waste (HLW) solution (nitric acid medium). Various process parameters such as feed acidity, concentration of BenzoDODA, membrane pore size etc., were optimized to achieve effective transport of Pu(IV). Near quantitative (∼97%) transport of Pu(IV) was observed in ∼360 min using 0.1 M BenzoDODA as carrier in n-dodecane employing 0.45 μm PTFE as membrane support when 0.2 M N2H4 in 0.6 M HNO3 was used as strippant. Transport studies with diluted HLW of PUREX origin showed near negligible transport of other elements present in the solution when near quantitative transport of Pu(IV) was observed. The maximum permeability coefficient (P) value was found to be 2.50 × 10−4 cm/s at 3.85 M HNO3 as feed acidity using 0.1 M BenzoDODA as carrier. The membrane was found to be stable over six cycles of operation. Thus, this system can be used for separation of Pu(IV) from acidic process streams.

BenzoDODA encapsulated polymeric beads were synthesized by phase inversion technique and evaluated for the separation of plutonium from nitric acid medium. The beads were characterized by FT-IR, TGA and SEM techniques to gain insight into their structure and morphology. Kinetics studies showed that the sorption of plutonium was fast and, equilibrium was achieved within 60 min of equilibration. Sorption isotherm studies have indicated that uptake increases with the increase of metal ion concentration, the sorption data fitted well to Langmuir model. Back extraction was effectively carried out using 0.3 M Hydrazine + 0.5 M HNO3. Reusability of the beads was established by multiple sorption–desorption experiments. The beads were found to be quite stable as no significant structural deformation or leaching out of the extractant was observed in 4.0 M HNO3 solution, up to studied equilibration time of 8 days.

A novel Plutonium (Pu) (IV) selective ligand, bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) acetamide (BenzoDODA) was studied for its Pu(IV) extraction behavior in presence of 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide {[C n mim][Tf 2 N]}ionic liquids. BenzoDODA was observed to behave differently in RTIL compared to n-dodecane toward Pu(IV) extraction. The presence of C 4 mimTf 2 N tends to bring about significant enhancement in the extraction of Pu in both the acidic media (HCl and HNO 3 ) as compared to that of using n-dodecane as diluent. The investigation of the extraction mechanism revealed that while using in RTIL (as diluent), the cation-exchange prevails up to 3 M acidity, in contrast to anion exchange mechanism ruling above 3 M acidic strength. However, in n-dodecane (as diluent) the metal extraction takes place via formation of anion-assisted neutral complex formation only at all acidities. Studies on the nature of species formed by Pu(IV) and BenzoDODA in both HNO 3 and HCl medium showed formation of a di-solvate species for RTIL in contrast to mono-solvate formed in n-dodecane. Selectivity of BenzoDODA-RTIL system appears to be lost at lower acidities due to significant extent of extraction of other matrix elements along with target metal ion. However at higher nitric acid concentration (7 M) BenzoDODA was found to be selectively extracting Pu(IV).

Palladium selective ligand, N , N , N ′, N ′-tetra-(2-ethylhexyl)-dithiodiglycolamide (DTDGA), was encapsulated in polymeric composite beads under simple laboratory conditions. The composite beads were evaluated for separation and recovery of palladium from simulated spent automobile catalyst dissolver (SSACD) solution. Batch extraction studies were carried out to understand the influence of various parameters on the sorption behavior of palladium. The beads showed maximum uptake of Pd at 3.0 M HCl. Pd sorption kinetics is found to be fast, and the kinetics data fit well in to the pseudo second-order equation model for the sorption of palladium ions onto the composite beads. Different sorption isotherm models were applied to the experimental data. Equilibrium data are represented well by the Langmuir isotherm equation, with a monolayer sorption capacity of 1.37 mg/g for the swollen beads. The process mechanism is found to be complex, consisting of both intraparticle diffusion and film diffusion. More than 99% of palladium was back extracted in single contact using 0.01 M thiourea in 0.1 M HCl. Batch extraction studies with SSACD solution showed negligible uptake of Fe, Cr, Ni and Pt thus showing very high selectivity and extractability of the composite beads for palladium.

A new solid supported ionic liquid (SSIL) has been synthesized and evaluated for the separation of uranium from acidic aqueous streams. SSIL has provided an opportunity to exploit the anchored task specific ionic liquid (TSIL) moiety for the sorption of uranium from aqueous streams and thus overcoming the limitations encountered during liquid–liquid extraction processes involving the use of TSILs.

Imino diacetamide styrene divinyl benzene (IDAA SDVB) resin was synthesized and evaluated for separation of molybdenum (Mo) from simulated dissolver solution of irradiated uranium–aluminium alloy. Detailed studies were carried out to understand the influence of various parameters on sorption of Mo. The kinetics of Mo sorption is found to be fast and the kinetics data fit well to the pseudo-second order kinetic equation. Sorption of Mo is found to decrease with the increase of feed acidity. The loading capacity of resin is determined to be 30 mg g−1, the sorption isotherm data fit well to the Langmuir model. Batch sorption experiments with simulated dissolver solution showed quantitative uptake of Mo along with some co-extraction of iodine (I). Column runs have demonstrated that co-extracted ‘I’ could be scrubbed easily with solutions of feed acidity. Finally, sorbed Mo could be eluted with 3.0 M HNO3. XAFS and FT-IR studies of Mo sorbed on to IDAA SDVB resin have shown that Mo is sorbed in the +6 oxidation state (in the form of MoO42−), wherein the complex attains octahedral geometry with contribution from four oxygen atoms of the molybdate anion and two oxygen atoms of the amidic moiety of the imino-diacetamide ligand.

Novel ligand, namely, N , N , N ′, N ′-tetra-(2-ethylhexyl)-dithiodiglycolamide (DTDGA) has been evaluated for separation and recovery of palladium from simulated spent catalyst dissolver (SSCD) solution. Liquid–liquid batch extraction studies were carried out to understand the influence of various parameters on the extraction behavior of palladium. Extraction equilibrium studies showed near complete extraction of palladium within 5 min. With the increase in hydrochloric acid concentration, the extraction of palladium increased up to 3.0 M HCl and then remained constant on further increase in acidity. Stoichiometry of the extracted species was determined to be PdCl 2 ⋅DTDGA by mole ratio plot. The effect of various diluents on the extraction of palladium was studied and it was found that there is quantitative uptake in n -paraffinic diluents and the extraction decreases with increase in polarity of diluent. More than 99% of palladium was back extracted in single contact using 0.01 M thiourea in 0.1 M HCl. Extraction studies with SSCD solution showed negligible uptake of Fe, Cr, Ni, and Pt, thus showing very high selectivity and extractability of DTDGA for palladium.

Detailed liquid–liquid extraction studies of Pu(IV) with BenzoDODA have been carried out to evaluate the efficacy of BenzoDODA in the separation and recovery of Pu(IV) from acidic solutions. Acid uptake constant (KH) was determined to be 0.44. Incorporation of tertiary butyl group in the aromatic moiety of BenzoDODA resulted in the increase in extractability of Pu(IV) but at the expense of decrease in the selectivity for Pu(IV) vis a vis other metal ions. Among the various diluents studied, the normal paraffinic hydrocarbons, namely, n-dodecane/kerosene were found to be the most preferred diluents. BenzoDODA was found to be stable in radiation environment, with good extraction ability up to 20 MRad. Number of stages required for the effective recovery of plutonium from the feed solution has been determined by McCabe Thiele’s plot. It was found that even at higher loadings of Pu(IV), there is no third formation which is remarkable since at these loading TBP/n-dodecane solvent system has shown considerable third phase formation. Thus, BenzoDODA/n-dodecane solvent system can be used for recovery of Pu(IV) from concentrated processing streams as well.

A novel ligand, namely, N , N , N ′, N ′-tetra-(2-ethylhexyl)dithiodiglycolamide (DTDGA) has been explored as a carrier across a supported liquid membrane (SLM) to study the transport behavior of Pd(II) from nitric acid medium. Almost quantitative transport of Pd(II) was observed in ~2 h time interval using 0.025 M DTDGA in n-dodecane as carrier from 4.0 M HNO 3 feed solution with 0.01 M thiourea in 0.2 M HNO 3 as strippant. During this time interval almost negligible transport of other fission products present in high level waste (HLW) solution was observed. Various parameters were optimized to achieve maximum transport rate viz., feed acidity, DTDGA concentration in membrane phase, membrane porosity etc. Highest permeability co-efficient value of 2.37×10 −3 cm/s was observed for 0.025 M DTDGA as carrier keeping the feed acidity at 4 M HNO 3 and using 0.2 µm PTFE as membrane support. The membrane was found to be stable over six cycles of operation.

The extraction properties of N,N,N',N'-tetra-(2-ethylhexyl) dithiodiglycolamide (DTDGA) have been evaluated for separation and recovery of palladium from simulated high-level liquid waste (SHLW) solution. Extraction of Pd was found to increase with increase in nitric acid concentration up to 4.0 M, above which the extraction remains almost constant. Acid uptake studies show 1:1 stoichiometry between DTDGA and HNO3 at nitric acid concentration above 3.0 M. The acid uptake constant (KH) was found to be 0.60 which could be due to the presence of two carbonyl groups of amidic moiety. DTDGA has shown very high extractability and selectivity for Pd over other metal ions present in SHLW. The separation factor (SF) for Pd over other metal ions was found to be more than 104. Almost complete back extraction of palladium from organic phase was achieved with 0.01 M thiourea in 0.1 M nitric acid. Reusability studies of the extractant indicate that DPd remains almost constant even after five successive cycles of extrac...

DTDGA solvent system was evaluated for hydrolytic and radiolytic stabilities to ascertain its application in separation and recovery of palladium from High Level Liquid Waste (HLW) solutions. Hydrolysis of DTDGA solvent system was not observed when it was kept in contact with 3.0 M nitric acid solution for two weeks. Moreover, contrary to other ‘S’ donor extractants used for the said purpose, the oxidation of thioetheric sulphur to sulphoxide or sulphones was also not observed. On the other hand, radiolysis of DTDGA solvent system was notably observed, which was found to increase with increase in absorbed dose. At gamma radiation dose of 0.2 MGy, no significant loss of DTDGA was observed. Aliphatic diluent namely n-dodecane was found to have sensitization effect on degradation of DTDGA. The degradation products were identified by GC-MS, the major ones were found to be formed by cleavage of thioetheric and amidic bonds of DTDGA molecule. The liquid–liquid extraction studies of palladium with irradiated solvent indicate that there was no significant change in D Pd up to an absorbed dose of 0.2 MGy above which it decreases gradually. Further, the radiolysis does not affect the stripping behavior of palladium. Extraction studies of Simulated High Level Liquid Waste (SHLW) elements with irradiated solvent system showed that, except palladium, any other element is hardly extracted thus retaining its remarkable selectivity.

Amberlite XAD-16 has been functionalized with 2-acteyl pyridine by coupling it with 2-chloro pyridine after acetylation. The resulting resin (AP-XAD 16) has been characterized by various techniques like FT-IR, TGA, elemental analysis, etc. and has been evaluated for the solid phase extraction of palladium and other metal ions present in high level waste (HLW) solution. Sorption equilibrium was attained within 30–45 min. The pseudo-second order kinetics model yielded the best fit for the experimental data of sorption kinetics. Pd sorption was found to decrease gradually with increase in aqueous phase acidity. The sorption process involves the complex formation between Pd(II) and the resin which contains the carbonyl group and soft ‘N’ atom of pyridine moiety with lone pair of electrons. The loaded palladium can be effectively eluted using acidic thiourea solutions. The adsorption isotherm data fitted well with Langmuir as well as Freundlich models. The maximum sorption capacity of the resin was found to be 8 mg/g which is in agreement with the equilibrium adsorption capacity. Sorption studies carried out with simulated high level waste solution have shown very high uptake of palladium as compared to the other elements, thus showing the potential for possible use of the resin for efficient separation and recovery of palladium from HLW solution.

A novel carrier, N,N,N',N'-tetra-(2-ethylhexyl) thiodiglycolamide, T(2EH)TDGA has been studied for transport of Pd(II) from nitric acid medium across a supported liquid membrane (SLM). Pd(II) was found to be almost quantitatively transported (≈ 99.9%) within 2h from 3.0M HNO(3) medium using 0.05 M T(2EH)TDGA in n-dodecane as carrier and 0.01 M thiourea in 0.2M HNO(3) as strippant. Pd(II) transport was also studied against various parameters like feed acidity, carrier concentration, membrane pore size, etc. Palladium transport was found to be diffusion controlled and the diffusion co-efficient value was found to be 3.56 × 10(-5)cm(2)/s. Selectivity of T(2EH)TDGA for palladium over other fission products was found to be quite high, with the separation factors for Pd, with respect to different fission products being >10(3). With respect to leaching out of carrier from the membrane support, the membrane was found to be stable for six consecutive cycles. Thus, T(2EH)TDGA can be used as an efficient carrier of Pd(II) from nitric acid medium.

Extraction behaviour of Y(III) from hydrochloric acid medium by octyl phenyl phosphinic acid (OPPA) has been investigated over a wide range of experimental conditions such as feed acidity, yttrium concentration, OPPA concentration, diluents, temperature, stripping reagents. The extraction mechanism of Y(III) with OPPA was established using distribution data obtained by slope analysis technique and it showed the formation of Y(HA2)3 type of neutral species in the organic phase. This was also confirmed by non-linear least square regression of the distribution data to the mathematical expression correlating percentage extraction and acidity. The extraction constant (log Kex ) of the two phase reaction has been evaluated to be 3.2. Distribution ratio (D) decreased with the increase in temperature with ΔH = –16 kJ/mole. Amongst the reagents studied, 7 M H2SO4 was found to be better with 70% stripping of Y(III) in a single contact. Extraction of Y(III) in different diluents followed the order: dodecane...

Hydrolytic and radiolytic stability of T(2EH)TDGA solvent system has been investigated to establish its application in separation and recovery of palladium from High Level Liquid Waste (HLW) solutions. Hydrolysis of T(2EH)TDGA solvent system with nitric acid was not observed. Moreover, unlike other “S” donor extractants used for the said purpose, the oxidation of thioetheric sulphur to sulphoxide or sulphones was also not observed. However, radiolytic degradation was notably observed and found to increase with increase in absorbed dose. n-dodecane was found to sensitize the degradation of T(2EH)TDGA. At gamma radiation dose of 0.2 MGy, no significant loss of T(2EH)TDGA was observed. The degradation products were identified by GC-MS. The major products were found to be formed by cleavage of thioetheric and amidic bonds of T(2EH)TDGA molecule. The extraction studies of palladium with irradiated solvent indicate that with 0.025 M T(2EH)TDGA/n-dodecane, there was no significant change in D Pd up to an absorbed dose of 0.2 MGy above which it decreases significantly. However, with 0.05 M T(2EH)TDGA/n-dodecane, there is gradual decrease in D Pd with increase of absorbed dose. Further, the radiolysis does not affect the stripping behavior of palladium. Extraction studies of Pd(II) and other fission products from simulated high level liquid waste (SHLW) solutions to irradiated solvent system showed that, except palladium, any other element is hardly extracted thus retaining its remarkable selectivity.

The extraction properties of N,N,N′,N′-tetra(2-ethylhexyl)thiodiglycolamide T(2EH)TDGA have been evaluated for the separation and recovery of palladium from simulated high-level liquid waste (SHLW). T(2EH)TDGA has shown very high selectivity for Pd (II) over other metal ions present in SHLW. The separation factor (SF) for Pd (II) over other metal ions was found to be more than 105. Reusability studies of the extractant indicate that DPd remained almost constant even after five successive cycles of extraction and stripping. Palladium was quantitatively recovered from thiourea strip solution by treating it with ammonia and filtering the precipitate of palladium sulphide. The acid uptake constant (KH) was found to be 0.62 which could be due to the presence of two carbonyl groups of amidic moiety. To account for very high extractability of palladium with T(2EH)TDGA over other ‘S’ donor extractants, namely Bis-(2-ethylhexyl)sulphoxide (BESO), FTIR, as well as Raman studies were carried out. FTIR and Raman stud...

To establish the use of TEHDGA/isodecylalcohol/n-dodecane solvent system for actinide partitioning from HLW, the hydrolytic and radiolytic stability of the solvent was investigated. Hydrolysis of TEHDGA with nitric acid at room temperature was not observed. Radiolytic degradation was observed and found to increase with increase in absorbed dose. It was found that the presence of n-dodecane enhances the degradation of TEHDGA whereas isodecyl alcohol, the phase modifier, has no such effect. At gamma-radiation dose as high as 0.2 MGy, no significant loss of TEHDGA was observed. The degradation products were identified by GC-MS, the main products were formed by cleavage of ether and amide bonds of TEHDGA molecule. The extraction behavior of Am(III) at 4.0 M HNO3 does not vary much with increase in absorbed dose, however stripping behavior is affected by the presence of acidic degradation products formed during radiolysis. The findings indicate that the solvent retains its expected extraction and stripping properties up to a high gamma-radiation dose of 0.2 MGy. Irradiated solvent was purified and made suitable for reuse by treating it with 5% w/v Na2CO3 solution, basic alumina and finally by distillation at reduced pressure.

Facilitated transport of Am(III) in nitric acid medium using tetra(2-ethyl hexyl) diglycolamide (TEHDGA) in n-dodecane as carrier was studied. It was aimed at finding out the physico-chemical model for the transport of Am(III) using TEHDGA/n-dodecane as carrier under various experimental parameters like feed acidity, carrier concentration, varying strippant, varying membrane pore size, etc. The feed acidity and carrier concentrations were varied from 1 M to 6 M HNO3 and 0.1 M to 0.3 M TEHDGA/n-dodecane, respectively. The transport of Am(III) increased with increase in feed acidity and carrier concentration reaching maximum at 3 M HNO3 and 0.2 M TEHDGA/n-dodecane, respectively. Several stripping agents were tested and 0.1 M HNO3 was found to be the most suitable stripping agent for this system. Almost quantitative transport of Am(III) was observed at about 180 min with feed acidity of 3 M HNO3, 0.1 M HNO3 as strippant and 0.2 M TEHDGA/n-dodecane as carrier. The pore size of the membrane support was varied from 0.20 μm to 5 μm and the permeation coefficient increased with increase in pore size up to 0.45 μm (2.43 × 10−3 cm/s), and then decreased with further increase in pore size. The plot between permeation coefficient vs. (membrane thickness)−1 was linear which showed that the Am(III) transport was membrane diffusion limited. The membrane diffusion coefficient calculated from the graph was found to be 1.27 × 10−6 cm2/s and its theoretical value was 1.22 × 10−6 cm2/s. The stability of the carrier against leaching out of the membrane support as well as the integrity of membrane support was studied over a period of 30 days and was found to be satisfactory within the studied time period.

The extraction behavior of uranium, thorium and nitric acid has been investigated for the TEHDGA/isodecyl alcohol/n-dodecane solvent system. Conditional acid uptake constant (KH) of TEHDGA/n-dodecane and the ratio of TEHDGA to nitric acid were obtained as 1.72 and 1:0.96, respectively. The extracted species of uranium and thorium in the organic phase were found to be UO2(NO3)2·2TEHDGA and Th(NO3)4·2TEHDGA. A workable separation factor (DTh/DU) of the order of 300 was observed between thorium and uranium in the nitric acid range of 0.5M to 1.5M. Similar separation factor was also achieved at higher acidity when thorium was present in large concentration compared to uranium. These results indicate that TEHDGA solvent system could be a potential candidate for separation of thorium from uranium.

A new ligand grafted polymeric resin (BenzoDODA SDVB) was synthesized by covalently attaching plutonium selective ligand (BenzoDODA) on to styrene divinyl benzene (SDVB) polymer matrix. BenzoDODA SDVB resin was evaluated for separation and recovery of plutonium(IV) from nitric acid medium. Sorption of Pu(IV) was found to decrease with the increase in nitric acid concentration, with very small sorption above 7.0 M HNO 3 . Sorption kinetics was fast enough to achieve the equilibrium within 60 min of contact where the kinetic data fitted well to pseudo-second-order model. Sorption isotherm data fitted well to Langmuir model suggesting chemical interaction between the BenzoDODA moiety and plutonium(IV) ions. Sorption studies with some of representative radionuclides of high level waste showed that BenzoDODA SDVB is selective and therefore could be a promising solid sorbent for separation and recovery of plutonium. Further, the theoretical calculations done on BenzoDODA SDVB resin suggested Pu(NO 3 ) 4 ·BenzoDODA (1:1) sorbed complex conformed to generally observed square antiprism geometry of the plutonium complexes, with contributions from oxygen atoms of four nitrate ions as well as from four oxygen atoms present in BenzoDODA (two phenolic ether oxygen atoms and two carbonyl oxygen atoms of amidic moiety).

A novel extractant, namely, Benzodioxodiamide (BenzoDODA) has been synthesized and evaluated for its extraction behaviour towards plutonium and other elements present in the spent nuclear fuel. High separation factors for plutonium over other elements were observed, indicating the high selectivity of the extractant for plutonium. The extractant is quite promising for the selective separation of plutonium from dissolver solution and various acidic waste streams.

Review: evaluation of various liquid-liquid extraction processes for Pd separation from liquid waste generated during reprocessing of spent nuclear fuels; 63 refs.

A precise, sensitive and selective method for the spectrophotometric determination of palladium (II) using N , N , N ′, N ′-tetra(2-ethylhexyl) thiodiglycolamide T(2EH)TDGA as an extractant is described. Palladium (II) forms yellow colored complex with T(2EH)TDGA which exhibits an absorption maximum at ∼300 nm. The colored complex obeys Beer's law in the concentration range 1.0–15.0 μg ml −1 of palladium with a molar absorptivity of 1.29 × 10 5 M −1 cm −1 . The effects of various experimental parameters have been studied to establish the optimum conditions for the extraction and determination of palladium. The precision of the method has been evaluated and the relative standard deviation has been found to be less than 0.5%. The method has been successfully applied to the determination of palladium in simulated high level liquid waste (SHLW) solution.

Imino diacetamide styrene divinyl benzene (IDAA SDVB) resin was evaluated for the sorption of uranium from sulphuric acid medium. Uranium sorption on to the resin was fast, the kinetic data fitted well in pseudo second order kinetics model. Sorption of uranium was found to increase with the increase in initial concentration of uranium in aqueous feed solution, the sorption isotherm data fitted closely in to Langmuir isotherm model. The sorption of uranium is observed to decrease with the increase in initial feed acidity thereby, allowing sorption and desorption at lower (0.1 M H2SO4) and higher (1.0 M H2SO4) acidities, respectively.

The present paper provides a review of the various processes/schemes developed for the separation and recovery of palladium from high level liquid waste (HLLW) generated during reprocessing of spent nuclear fuel. This separation is necessary in view of various problems posed by the presence of palladium during vitrification of HLLW. Further, to meet the ever increasing demand for palladium in various applications, HLLW can be considered as one of the possible secondary sources of this valuable metal. In this regard several processes are proposed involving liquid–liquid extraction, solid phase extraction, precipitation electro-deposition, for recovering palladium from HLLW. The focus of the present review is to evaluate various liquid–liquid extraction processes proposed for palladium separation from HLLW.

The structure of the extraction complexes of palladium(II) with novel ligands, namely, N,N,N′,N′-tetra-(2-ethylhexyl) thiodiglycolamide (T(2EH)TDGA) and N,N,N′,N′-tetra-(2-ethylhexyl) dithiodiglycolamide (DTDGA), have been determined by extended X-ray absorption fine structure spectroscopy (EXAFS). The interpretation of the EXAFS data is well supported by theoretical calculations of the complex geometry based on density functional theory (DFT). T(2EH)TDGA, having one thioetheric ‘S’ atom, forms a square planar complex with the Pd(II) ion, exhibiting 2 : 1 stoichiometry with one sulphur atom and one carbonyl oxygen atom from each T(2EH)TDGA molecule interacting with Pd(II) at distances of 2.24 and 2.04 A, respectively. On the other hand, DTDGA, having two ‘S’ atoms in addition to two carbonyl groups, forms a square planar complex with Pd(II), exhibiting 1 : 1 stoichiometry, wherein both the sulphur atoms and the carbonyl oxygen of DTDGA interact with Pd(II) at distances of 2.29 and 2.05 A, respectively. The slight distortion from the perfect square planar geometry could be attributed to the steric hindrance imposed by the bulky alkyl group of the amidic moieties. DFT calculations for the Pd–ligand complexes show that the Pd(II)–DTDGA complex with 1 : 1 stoichiometry is energetically more stable than the Pd(II)–T(2EH)TDGA complex with 1 : 2 stoichiometry. Among the two possible Pd(II)–T(2EH)TDGA complex geometries, the cis configuration appears more favorable. The methodology of fitting the EXAFS data has been validated by fitting the EXAFS data of a Pd(II)–aquo complex which showed square planar geometry with two axial water molecules constituting the secondary hydration sphere.

A theoretical study of stacking patterns of various hydrogen-bonded base pair complexes has been undertaken. Modified Rayleigh-Schrodinger perturbation theory for intermediate range interactions, has been employed to evaluate the stacking interactions using multicentered-multipole expansion method. Net atomic charge and corresponding dipole components located at each of the atomic centers have been computed by CNDO/2 method. An analysis of the intermolecular forces involved in the stable formation of the various base pair complexes, has been presented and the results have been discussed in the light of experimental as well as other theoretical observations. The possibility of relative preference of the left-handed configuration for alternating sequences has been quantitatively explored.

The ordering of mesogenic compounds in the liquid phase has been investigated using intermolecular interaction energy calculations taking Anisaldehyde azine (CH3 – O – C6H4 - CH = N – N = CH - C6H4...