Technetium elimination is a very challenging task, particularly for nuclear wastewater and contaminated groundwater, due to their large volume and presence of various interfering ions. For this purpose, some commercially available anion exchange resins with different specifications like polymeric network, pore diameter, bead size etc., were selected to appraise their impact on the decontamination process. Fundamental extraction properties, including the effect of solution pH, equilibration time, and temperature, were determined to obtain the optimum extraction condition. The resins were characterized using BET, SEM, EDS, XPS, TG-DSC-EGA, FTIR, CP/MAS 13C NMR to decipher the extraction mechanism and structure-extraction correlation. To quantify the loading capacity (as high as 745 +/- 14 mg/g) and ascertain the reaction mechanism, a non-radioactive surrogate, ReO4 - has been used. Competition studies with common anions found in groundwater indicate that, even in the presence of high concentration (10,000 times relative concentration) of these anions, TcO4 - can be selectively extracted by the resins, confirming their effectiveness towards 99Tc-contaminated groundwater. Dynamic column experiment using these resins with actual industrial wastewater collected from a 99mTc radiopharmaceutical production facility exhibits a cost-effective, high-throughput, and efficient decontamination performance.

A series of bidentate, viz., 1,1'-(1,2-ethylene)-3,3'-dimethyldiimidazoline-2,2'-diylidene (L1), 1-methyl-3-(2-pyridylmethyl)-imidazoline-2-ylidene (L2) and tridentate, viz., 1,3-bis(2-pyridyl)-imidazoline-2-ylidene (L3) ligands have been obtained from their corresponding imidazolium salts through deprotonation reactions. Treatment of UO2Cl2(THF)(3) with one equivalent L3 produces air-stable U(VI)-carbene complex 3, characterized by elemental analysis, FTIR, NMR spectroscopy as well as extended X-ray absorption fine structure (EXAFS) analysis. EXAFS result indicates that the ligand is bonded through one C and two N-atoms to the uranium atom. Attempts to synthesize uranyl complexes derived from L1 and L2 were also successful but these complexes are decomposed quickly within one hour at room temperature. 3 produces pure UO2 powder when heated under an argon atmosphere from room temperature to 600 degrees C with constant heating rate of 5 degrees C/min. The solid-state UV-Vis spectrum of the compound shows absorption peaks at 332 and 450 nm. The excitation spectrum of 3 (at lambda(em) = 520 nm) exhibits two almost symmetrical peaks at 273 and 368 nm. Density functional theory-based quantum mechanical calculations indicate that a partial covalent interaction exists between the carbene C and U while a weak non-covalent interaction exists between carbene N and U atoms.

99Tc removal from contaminated aqueous solution was explored using some commercially available anion exchange resins with various specifications. Various combinations of physicochemical parameters like polymeric network, pore diameter, percent cross-linking, bead size etc. were selected to appraise their impact on 99Tc uptake. Fundamental extraction properties such as effect of solution pH, equilibration time, effect of temperature were determined for obtaining the optimum extraction condition. The resins were characterized using BET, SEM, EDS, XPS, TG, FTIR spectroscopy to decipher the structure-extraction correlation and extraction mechanism. In order to quantify the loading capacity (745 mg/g as maximum) and ascertain the reaction mechanism, non-radioactive surrogate of TcO4-, i.e, ReO4- have been used. ReO4- quantity in solution was measured using UV-Vis spectrophotometry with λmax at 204 nm. 4M HNO3 was found be an effective reagent towards desorption from the loaded resins. The capture performance was found to deteriorate with γ-radiation particularly at higher absorbed dose (500 kGy onwards). Competition studies with most common anions found in ground water as well as soil such as Cl-, NO3-, SO42-, CO32-, PO43- indicate that, even in presence of high concentration (1:10000 molar ratio) of these interfering anions, TcO4- can be selectively extracted by the resins confirming their effectiveness towards the decontamination of real ground water with respect to 99Tc.

A set of new oxidovanadium(IV) complexes, [VO(4-NO2C6H4CH = CHCONHO)(2)] (1), [VO(4-NO2C6H4CH = CHCONHO)(2)(2-CNC5H4N)] (2) and [VO(4-NO2C6H4CH = CHCONHO)(2)(4-CNC6H4NH2)] (3), have been synthesized and characterized by different analytical techniques (magnetic susceptibility, molar conductivity, elemental analysis) and spectroscopic techniques, viz. FTIR, UV-vis, EPR, and mass spectrometry. The magnetic susceptibility, EPR, and ESI-MS data indicate that 1 exists as monomer and a distorted square pyramidal geometry around vanadium is ascertained. The electrochemical study of 1 has shown that it is electrochemically active exhibiting VOV/VOIV quasi-reversible redox couple. The biological activity of 1-3 has been studied against various pathogenic bacteria Staphylococcus epidermidis, Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, Salmonella paratyphi, and Salmonella typhi, and fungi Brachypsectra fulva, Candida albicans, and Fusarium oxysporum by minimum inhibitory concentration (MIC) method. In some cases, the synthesized complexes showed superior antibacterial and antifungal activity than the well-known standard drugs tetracycline hydrochloride and fluconazole. The cytotoxicity of 1-3 has been studied on a human cervix carcinoma HeLa cell derivative (mammalian transformed cell line Hep2c) by MTT assay. Density functional theory (DFT) studies have been carried out to determine their relative free energy of formation and optimized molecular structures of 1-3. Time-dependent density functional theory (TD-DFT) based calculations have been performed to find out the frontier molecular orbitals and corroborate with the experimentally observed electronic transitions of 1. Other parameters like HOMO, LUMO energies, and global reactivity descriptors clearly support higher biological activity of 2 and 3 than 1.

A solvent extraction-based technique has been utilized to study the separation of ruthenium from simulated alkaline solution using Aliquat 336 as the extractant and isodecyl alcohol (IDA) as the phase modifier in n-dodecane. The effects of various experimental parameters such as solution pH, mixing time, concentration of Aliquat 336 and IDA, role of citric acid as the aqueous phase modifier/complexing agent, and stripping agents have been evaluated. It was observed that with the increase in the solution pH, the extraction efficiency increases gradually. However, when citric acid was added into the aqueous solution, an overall increase (from ∼20 to 91%) in ruthenium extraction is observed. 20 min of the mixing time was found to be sufficient to reach the extraction equilibrium. Solution composition was optimized as 50% Aliquat 336 and 10% IDA in n-dodecane (v/v) for maximum extraction. The stripping of ruthenium from the loaded organic phase has been studied using HCl and HNO3. The result indicates that in the presence of 8 M HNO3, ∼73% of ruthenium can be back extracted to the aqueous phase in a single contact. The stripping efficiency of HNO3 was found to be higher than that of HCl. Active studies with 106Ru as the radiotracer were also performed and monitored using a HPGe detector. The same method was implemented for extraction studies with real waste solution in the presence of other radionuclides such as 137Cs, 90Sr, and 125Sb. The presence of the chemical species in aqueous as well as organic phase has been identified using UV-vis spectrophotometry, Fourier transform infrared spectroscopy, and Raman spectroscopy. Density functional theory-based quantum mechanical calculations have been performed in order to unravel the extraction mechanism with the present solvent system.

The title complex [PdCl(L)] (1), is obtained from the reaction of SCS pincer ligand HL (where, HL = N,N'-di-tert-butylbenzene-1,3-dicarbothioamide) with lithium tetrachloropalladate (II) in methanol. The compound 1 is characterized by elemental analysis, FTIR, 1H, and 13C-NMR spectroscopy, UV-Vis spectroscopy, powder X-ray diffraction and X-ray crystallographic techniques. At room temperature, 1 emits luminescence light of wavelength 460 nm in the solid state upon excitation by UV light of wavelength 280 nm. The average emission lifetime indicates that, both the ligand and complex emission is fluorescence in nature and involves mainly ligand centers π-π* deexcitation. It also shows good catalytic activity towards Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions of aryl bromides with tert-butyl acrylate and p-tolylboronic acid respectively. For both type of reactions, more than 99% conversion of the substrates is found to occur for electronically activated p-nitro bromobenzene using 1 mol % of 1. Further, modern DFT calculations are performed to decipher the mechanistic insight on the preferable pathways of the Mizoroki-Heck cross-coupling reaction. Stepwise free energy of reactions for various probable reaction pathways suggest that the catalytic route has profound preference for Pd(0)-Pd(II) over Pd(II)-Pd(IV) pathway.

In this study the coordination chemistry of three ligands, C5H4NOCONRR' (where, R, R' = (C3H7)-C-i (L1); R, R' = (C4H9)-C-i (L2); and R = H, R' = (C4H9)-C-t (L3) composed of N-oxide and carboxamide groups have been explored with uranyl nitrate and some selected lanthanide (La, Sm, and Eu) nitrates. All the synthesized ligands as well as their complexes (1-12) of type UO2(NO3)(2)L (where, L = L1, L2, and L3 for 1, 2, and 3 respectively) and Ln(NO3)(3)(H2O)L-2 (where, Ln = La, L = L1 for 4, L = L2 for 5, and L = L3 for 6; Ln = Sm, L = L1 for 7, L = L2 for 8, and L = L3 for 9; Ln = Eu, L = L1 for 10, L = L2 for 11, and L = L3 for 12) have been characterized by elemental analysis, spectroscopic analyses such as FTIR, H-1 NMR, and electrospray ionization mass spectrometry (ESI-MS). Solid-state structural analysis of L1, 3, and 10 is carried out by X-ray crystallographic technique. The CO and NO groups of L1 are placed almost mutually perpendicular to each other in the crystal structure of L1. The X-ray data show that in [UO2(NO3)(2){C5H4NOCONH ((C4H9)-C-t)}] (3), the ligand acts as a bidentate chelating ligand and is bonded through both the N-oxo and amide oxygen atoms, whereas, in [Eu(NO3)(3)(H2O){C5H4NOCON((C3H7)-C-i)(2)}(2)] (10), the ligands show monodentate behavior and are bonded only through N-oxo oxygen atoms. Quantum mechanical calculation at DFT level corroborates the possibility of various bonding modes of these ligands towards uranium and europium nitrate with the preference of bonding as observed in the synthesized complexes. Solvent extraction studies using N,N-dioctyl N-oxo pyridine 2-carboxamide ligand (L4) in n-dodecane with UO22+, Pu4+, Am3+ and Eu3+ indicate the trend Pu4+ > UO22+ > Am3+ > Eu3+ at acidity range from 0.01 M to 6 M HNO3. The ligands show good radiation stability at gamma dose up to 500 kGy and chemical stability at 3 M HNO3 for up to 200 h without much affecting the metal ion extraction. Theoretical calculations show the possibility of presence of different metal species in the organic phase, other than the products obtained from dichloromethane during the solvent extraction of UO22+ and Eu3+ in water/dodecane biphasic media. Energy decomposition analysis supports the higher extraction coefficient of UO22+ than Eu3+ with an evidence of higher orbital interaction of the ligands with UO22+. (C) 2021 Elsevier Ltd. All rights reserved.

The oxidovanadium(IV) complex [VO(HL)2] (1) (where, HL = 4-nitrocinnamohydroxamate; 4-NO2C6H4CH=CHCONHOH) has been synthesized by the condensation reaction of VOSO4∙5H2O and potassium 4-nitrocinnamohydroxamate in methanol-water medium. The complex is characterized by elemental analysis, molar conductivity, magnetic susceptibility measurement, FTIR, UV-Vis, Electron Paramagnetic Resonance (EPR) spectral techniques and mass spectrometry. The bidentate linkage of hydroxamate ligand involving O,O-coordination through hydroxamic and carbonyl oxygen atoms has been deduced. The magnetic susceptibility, EPR and mass spectra (ESI-MS) indicate that the complex exists as monomer and a distorted square pyramidal geometry around vanadium is proposed. The electrochemical study of 1 has shown it is to be electrochemically active exhibiting VOV/VOIV quasi-reversible redox couple. The thermal study of the complex yielded VO2 as sole decomposition product. The coordination compounds 2 and 3 have been isolated from the reaction of complex 1 with 2-cyanopyridine (2-CNPy) and 4-aminobenzonitrile (4-CNAn) respectively and characterized by physicochemical and IR spectral study. The biological activity of 1-3 has been studied against various pathogenic bacteria E. coli, S. aureus, S. typhi, S. paratyphi, S. epidermidis, K. pneumonia and fungi C. albicans, B. fulva, and F. oxysporum by minimum inhibitory concentration (MIC) method. The complexes exhibit enhanced antimicrobial activity relative to both the free ligand and vanadyl sulphate. The cytotoxicity of 1-3 has been studied on mammalian transformed cell line Hep2c, a derivative of human cervix carcinoma HeLa cells by MTT assay. 2 and 3 exhibit higher cytotoxic activity than 1 and reveal a marked effect of the coordination of nitrogen bases. Density functional theory studies have been carried out to determine the relative free energy of formation and stable molecular structures of 1-3. Time dependent density functional theory (TD-DFT) based calculation have been performed to find out the frontier molecular orbitals and to corroborate with the experimentally observed UV-Vis spectrum of 1. Other parameters like HOMO, and LUMO energies, density of state (DOS), and global reactivity descriptors clearly support higher biological activity of 2 and 3 than 1.

The manuscript deals with efficient separation of hexavalent UO22+ and tetravalent Th4+ from aqueous acidic waste solution in 'green way' using ionic liquid with novel picolinamide (L I) and N-oxo picolinamide (L II) based ligands. A comparative evaluation was carried out to understand the extraction mechanism, kinetics, thermodynamics, speciation, radiolytic stability and stripping behaviour of UO22+ and Th4+ in ionic liquid vis-a-vis molecular diluent. The investigation demonstrates the predominance of 'cation exchange' mechanism in ionic liquid and 'solvation' mechanism in n-dodecane based systems. The slower extraction kinetics in ionic liquid was attributed to the 'viscosity effect'. The extractive mass transfer processes were found to be spontaneous, endothermic and entropically driven in nature. The picolinamide and N-oxo picolinamide ligands were found to form inner-sphere complexes in ionic liquid as well as n-dodecane. In molecular diluent, the species involved for separation of UO22+ were UO2(NO3)(2). 2 LI and UO2(NO3)(2). L II, respectively, whereas in ionic liquid thet were [UO2(NO3).2L](+) and [UO2(NO3).L](+). For Th4+, in molecular diluent, the most plaussible extracted species were Th(NO3)(4). 2 LI and Th(NO3)(4). L II, while in ionic liquid they were [Th(NO3)(2). 2 L](2+) and [Th(NO3)(2). L](2+), respectively. Ionic liquid based solvent systems exhibited more radiolytic stability compared to that in molecular diluent. The CO32- was more effective aqueous phase complexing agent to back extract UO22+, while C2O42- exhibited the same for Th4+. (c) 2021 Elsevier B.V. All rights reserved.

Three N,N-substituted pyridine 2-carboxamide ligands, C5H4NCONRR' (where, R, R' = (C3H7)-C-i (L-1); R, R' = (C4H9)-C-i (L-2); and R = H, R' = (C4H9)-C-t (L-3), as well as their coordination complexes (1-3) of uranyl nitrate have been synthesized. All the ligands and their corresponding complexes were characterized by CHN elemental analysis, infrared (FTIR) and NMR spectroscopy. The crystal structure of the complex 1 shows that the central uranium atom occupies a distorted hexagonal bipyramidal geometry, where the four oxygen atoms of the bidentate nitrate ligands with the oxygen and nitrogen atoms of the ligand L-1 form the hexagonal plane and two axial oxygen atoms of uranyl occupy the trans axial position. Here, the ligand acts as a bidentate chelating ligand. The preliminary structural analysis of the complex 3 also indicates similar kind of structure as that of the complex 1. Quantum mechanical calculation at DFT level is supportive with the solid state structure obtained from X-ray crystallographic analysis. (C) 2019 Elsevier Ltd. All rights reserved.

The separation of different metal ions can be successfully accomplished by using picolinamide-based ligands. We herein report the first X-ray structure of picolinamide-based ligands of the type C5H4NCONR2 (where R=(C3H7)-C-1 (L1) and (C4H9)-C-1 (L2)) and C5H4NCONHR (R=(C4H9)-C-t (L3)) with palladium(II) ion. We have synthesized and characterized the structures of two palladium complexes, [PdCl2(L1)(2)](1) and [PdCl2 L-3] (3). In 1, ligand L1 forms a 2 : 1 complex with palladium(II) chloride, whereas in 3, the ligand L3 forms a 1 : 1 complex. Further, in 1, the ligand L1 acts as a monodentate ligand and is bound only through pyridyl-N atom, whereas in 3, the ligand L3 acts as a bidentate chelating ligand and is bound through both the pyridyl-N and amido-O atoms to the Pd(II) center. Electronic structure calculations are carried out to understand the experimental coordination diversity in the Pd complexes. Our calculations clearly suggest that a combination of steric hindrance of the ligand and the electronic effect of metal ions may modulate the coordination preferences.

The selective separation of uranyl ions from an aqueous solution is one of the most important criteria for sustainable nuclear energy production. We report herein a known, but unexplored extractant, tetraalkyl urea, which shows supreme selectivity for uranium in the presence of interfering thorium and other lanthanide ions from a nitric acid medium. The structural characterization of the uranyl complex (UO2X2·2L, where X = NO3(-), Cl(-) and Br(-)) by IR, NMR and single crystal X-ray diffraction provides insight into the strong interaction between the uranyl ion and the ligand. The origin of this supreme selectivity for uranyl ions is further supported by electronic structure calculations. Uranyl binding with the extractant is thermodynamically more favourable when compared to thorium and the selectivity is achieved through a combination of electronic and steric effects.

Carbamoyl pyrazole compounds of palladium(II) chloride of the type [PdCl2L2] (where L = C3H3N2CONR2 or C5H7N2CONR2; R = CH3, C2H5 or iC3H7) have been synthesized and characterized by IR, 1H NMR, ES-MS, elemental analysis and single crystal X-ray diffraction methods. The centrosymmetric structure of [PdCl2(C3H3N2CON{C2H5}2)2] (2) shows that the palladium(II) ion is surrounded by two pyrazolyl nitrogen and two chlorine atoms in a square planar arrangement and the two nitrogen atoms of the carbamoyl group are weakly bonded to the metal centre in axial positions. In the centrosymmetric structure of [PdCl2(C5H7N2CON{C2H5}2)2] (5), the palladium(II) ion is surrounded by two pyrazole nitrogen and two chlorine atoms form a square planar arrangement and the two oxygen atoms of the carbamoyl group are weakly bonded to the metal centre in axial positions. The ligands are bonded through the soft pyrazole nitrogen to palladium(II) chloride in mutually trans positions. The carbamoyl pyrazole groups displayed an anti conformation. Theoretical studies on compound 5 show that the axial interactions involve donation from the filled pz orbital of the oxygen atom to the dxz orbital of the palladium(II) ion.

New bifunctional pyrazole based ligands of the type [C(3)HR(2)N(2)CONR'] (where R = H or CH(3); R' = CH(3), C(2)H(5), or (i)C(3)H(7)) were prepared and characterized. The coordination chemistry of these ligands with uranyl nitrate and uranyl bis(dibenzoyl methanate) was studied with infrared (IR), (1)H NMR, electrospray-mass spectrometry (ES-MS), elemental analysis, and single crystal X-ray diffraction methods. The structure of compound [UO(2)(NO(3))(2)(C(3)H(3)N(2)CON{C(2)H(5)}(2))] (2) shows that the uranium(VI) ion is surrounded by one nitrogen atom and seven oxygen atoms in a hexagonal bipyramidal geometry with the ligand acting as a bidentate chelating ligand and bonds through both the carbamoyl oxygen and pyrazolyl nitrogen atoms. In the structure of [UO(2)(NO(3))(2)(H(2)O)(2)(C(5)H(7)N(2)CON {C(2)H(5)}(2))(2)], (5) the pyrazole ligand acts as a second sphere ligand and hydrogen bonds to the water molecules through carbamoyl oxygen and pyrazolyl nitrogen atoms. The structure of [UO(2)(DBM)(2)C(3)H(3)N(2)CON{C(2)H(5)}(2)] (8) (where DBM = C(6)H(5)COCHCOC(6)H(5)) shows that the pyrazole ligand acts as a monodentate ligand and bonds through the carbamoyl oxygen to the uranyl group. The ES-MS spectra of 2 and 8 show that the ligand is similarly bonded to the metal ion in solution. Ab initio quantum chemical studies show that the steric effect plays the key role in complexation behavior.

Chitosan tripolyphosphate (CTPP) beads were prepared at two different cross-linking densities and adsorption of Cr(III) onto it were studied as a function of different operational parameters such as solution pH, equilibration time and initial Cr(III) ion concentration. Higher cross-linked beads were found to have more adsorption capacity at all the experimental pH employed (pH = 3–5), whereas adsorption capacity is found to increase with increase in pH. Adsorption data were analyzed using Langmuir and Freundlich isotherm models. Langmuir model is found be more suitable to explain the experimental results with a monolayer adsorption capacity of 469.5 mg/g. Among the kinetic models used, pseudo-second order kinetic model could best describe the adsorption process. Competition experiments done in presence of Na(I), Mg(II), Ca(II), Al(III) and Fe(III) revealed that, except in the case of Al(III), adsorption of Cr(III) is not significantly affected by the presence of foreign cations. NaCl is found to be a suitable leaching agent for the desorption of adsorbed Cr(III) from CTPP beads. FTIR spectroscopic investigations confirmed that phosphate groups are the principal binding site responsible for the sorption of Cr(III) onto CTPP beads.

Magnetite (Fe3O4) nanoparticle was synthesized using a solid state mechanochemical method and used for studying the sorption of uranium(VI) from aqueous solution onto the nanomaterial. The synthesized product is characterized using SEM, XRD and XPS. The particles were found to be largely agglomerated. XPS analysis showed that Fe(II)/Fe(III) ratio of the product is 0.58. Sorption of uranium on the synthesized nanomaterials was studied as a function of various operational parameters such as pH, initial metal ion concentration, ionic strength and contact time. pH studies showed that uranium sorption on magnetite is maximum in neutral solution. Uranium sorption onto magnetite showed two step kinetics, an initial fast sorption completing in 4–6 h followed by a slow uptake extending to several days. XPS analysis of the nanoparticle after sorption of uranium showed presence of the reduced species U(IV) on the nanoparticle surface. Fe(II)/Fe(III) ratio of the nanoparticle after uranium sorption was found to be 0.48, lower than the initial value indicating that some of the ferrous ion might be oxidized in the presence of uranium(VI). Uranium sorption studies were also conducted with effluent from ammonium diuranate precipitation process having a uranium concentration of about 4 ppm. 42% removal was observed during 6 h of equilibration.