Complexes Of Th Research Articles

Innovative g-C3N4/AX composite electrode for effective thorium elimination from aqueous solutions

Electrosorption is a technique that combines electrical and adsorption processes and has been established to displace Th(IV) from aqueous solutions. The present study successfully synthesised a novel electrode, where graphitic carbon nitride was modified with amidoxime amidoxime groups (g-C3N4/AX) via the hydrothermal method. The batch experiments conducted in this study revealed that the g-C3N4/AX electrode possessed a favourable thorium adsorption capacity of 275.74 mg.g−1 and a swift elimination equilibrium of within 30 min. Furthermore, the removal efficiency at − 1.0 V (84.46 %) of the electrode was almost threefold greater than the removal efficiency at open circuit potential (24.09 %). The results were due to the free electrical charges on the g-C3N4/AX electrode, which induced the electrical driving force and facilitated the adsorption of Th(IV) ions onto the g-C3N4/AX surface. The shifted bands from the Fourier transform-infrared (FT-IR) spectrum post-electrosorption demonstrated a substantial complexation of Th(IV) with the amine groups of amidoxime and g-C3N4. A significant transference in energy band peaks was also observed during the XPS assessment, indicating that the electrosorption process included oxygen (O), carbon (C), and nitrogen (N) species. In the practical real wastewater involving rare earth residue, which contains Ce, La, Nd and Pr ions, g-C3N4/AX exhibited good capabilities in selectively adsorbing Th(IV). The electrode synthesised in this study also exhibited the ability to regenerate with a reasonable ∼ 80 % removal ratio after five runs. The results indicated that the amidoxime-modified graphitic carbon nitride electrode demonstrated a good potential in removing thorium from aqueous solutions via electrosorption applications.

Thermodynamics of Thorium(IV) complexes with N-methylethylenediamine-N,Nʹ,Nʹ-triacetate in aqueous solutions: Potentiometry and microcalorimetry

The thermodynamic parameters of the complexes of Th with N-methylethylenediamine-N,Nʹ,Nʹ-triacetic acid (MEDTA; denoted as H3L with three dissociable protons) were studied. Potentiometry and microcalorimetry were used to determine formation constants and enthalpies, respectively. Thermodynamic analysis revealed two successively formed complexes, namely, ThL+ and ThL22− (L3− denotes the totally deprotonated MEDTA). Results indicated that both complexation reactions were exothermic and driven by entropic force. The first stepwise reaction (Th4+ ​+ ​L3− = ThL+) was mainly driven by entropy with minimal effect on enthalpy change. The second stepwise reaction (ThL+ ​+ ​L3− = ThL22−) was more exothermic and showed less entropic change than the first stepwise reaction. The strong chelation of MEDTA would inhibit the hydrolysis of Th4+ and increase solubility.

Covalent bond shortening and distortion induced by pressurization of thorium, uranium, and neptunium tetrakis aryloxides

Covalency involving the 5f orbitals is regularly invoked to explain the reactivity, structure and spectroscopic properties of the actinides, but the ionic versus covalent nature of metal-ligand bonding in actinide complexes remains controversial. The tetrakis 2,6-di-tert-butylphenoxide complexes of Th, U and Np form an isostructural series of crystal structures containing approximately tetrahedral MO4 cores. We show that up to 3 GPa the Th and U crystal structures show negative linear compressibility as the OMO angles distort. At 3 GPa the angles snap back to their original values, reverting to a tetrahedral geometry with an abrupt shortening of the M-O distances by up to 0.1 Å. The Np complex shows similar but smaller effects, transforming above 2.4 GPa. Electronic structure calculations associate the M-O bond shortening with a change in covalency resulting from increased contributions to the M-O bonding by the metal 6d and 5f orbitals, the combination promoting MO4 flexibility at little cost in energy.

Studies on some binary complexes of Th (IV) and UO2 with vitamin-U At constant temperature

Studies on some binary complexes of Th (IV) and UO2 with vitamin-U At constant temperature

Characterization of Thorium-Pyrazinoic acid complexation and its decorporation efficacy in human cells and blood

Thorium (Th) exposure to the human beings is a radiochemical hazard and the chelation therapy by suitable drugs is the major prevention approach to deal with. The present studies aimed at usage of pyrazinoic acid (PCA), which is a prodrug to treat tuberculosis, for its usage as decorporating agent for thorium from human body. The present studies provide a comprehensive knowledge on the chemical interaction and biological efficacy of pyrazinoic acid (PCA) for decorporation of Thorium from the human body. The thermodynamic parameters for Th-PCA speciation are determined by both experiment and theory. The potentiometric data analysis and Electro-Spray Ionization Mass Spectrometry (ESI-MS) studies revealed the formation of MLi (i = 1–4) species with the decrease in stepwise stability constants. All the species formations are endothermic reactions and are predominantly entropy-driven. Biological experiments using human erythrocytes, whole blood and normal human lung cells showed cytocompatibility and decorporation ability of PCA for Thorium. Density functional calculations have been carried out to get insights on interaction process at molecular level. The experimental results and theoretical predictions found to be in line with each other. Present findings on complexation of Th by PCA and its evaluation in human cells and blood would further motivate determination of its safety levels and decorporation efficacy in animal models.

Complexes of Th(iv) with neutral O–N–N–O hybrid ligands: a thermodynamic and crystallographic study

The thermodynamics of Th(iv) complexes with N,N,N',N'-tetramethyl-2,2'-bipyridine-6,6'-dicarboxamide (TMBiPDA) and N,N,N',N'-tetramethyl-1,10-phenanthroline-2,9-dicarboxamide (TMPhenDA) in CH3OH/10%(v)H2O (CH3OH : H2O = 9 : 1 by volume) were determined by spectrophotometry and calorimetry. The ligand TMBiPDA/TMPhenDA coordinates with the central Th atom by the tetradentate (O-N-N-O) mode, which is validated by 1H NMR in solution and crystallography in the solid. The single crystal X-ray diffraction data show that ten-coordinated thorium coordinates with two ligand molecules and two solvent molecules (water or methanol). Both ThL and ThL2 complexes (L = TMPhenDA or TMBiPDA) were detected in solution. In thermodynamics, the formation of all complexes is driven by both enthalpy and entropy. In a comparison, enthalpy is more favorable to the formation of TMBiPDA complexes, while entropy is more favorable to the formation of TMPhenDA complexes; the entropy advantages of the TMPhenDA complexes override the enthalpy advantages of the corresponding TMBiPDA complexes, giving the TMPhenDA complexes higher stability constants than the TMBiPDA complexes. In crystallography, ligand distortions occur in ThL2 complexes, and TMBiDA distorts more than TMPhenDA does; the Th-O and Th-N bonds involving TMBiPDA are slightly shorter than those involving TMPhenDA.

Peroxo Complexes of Th(IV) and Zr(IV) Ions Containing Aspartic Acid and Amine Bases as Potential Biological Agents

Eight new peroxo complexes of the type [MO(O2)(Asp)L] have been synthesized and characterized by conductivity, magnetic moments, UV-Vis, IR, ESI-MS and 1H NMR spectra, TLC, and elemental analyses [M = Th(IV) and Zr(IV), Asp= deprotonated aspartic acid, L = quinoline, isoquinoline, 8-hydroxyquinoline, and 1,10-phenanthroline]. IR spectra indicate that the ligands coordinate to the metal ions via nitrogen of the amino group of aspartic acid and heterocyclic amines, oxygen of the carboxylate group of deprotonated aspartic acid and the peroxo group (O–O). ESI-MS spectral data and magnetic moment values coupled with electronic spectral data suggest an octahedral geometry for all the complexes. The molar conductance values indicate that all the complexes behave as 1 : 2 electrolytes except complexes of 8-hydroxyquinoline that behaves as 1 : 3 electrolytes. Antibacterial activity of the complexes has been tested against four pathogenic bacteria, two Gram-positive Staphylococcus aureus and Bacillus subtilis and two Gram-negative Escherichia coli and Shigella dysenteriae using Kanamycin (K-30) as a standard. The MIC values for complexes hve been measured. Antifungal activity of the complexes has been tested against four pathogenic fungi Aspergillus flavus, Penicillium species, Candida species, and Aspergillus niger using Fluconazole-50 as a standard. The complexes K2[ThO(O2)(Asp)(IQ)] and K2[ZrO(O2)(Asp)(Q)] demonstrate the highest antibacterial activity, and K2[ZrO(O2)(Asp)(1,10-Phen)] exhibits the highest antifungal activity against all the tested pathogens.

Azerbaijan and the Security Complex of Th e South Caucasus

Azerbaijan and the Security Complex of Th e South Caucasus

Complexation of thorium with pyridine monocarboxylate-N-oxides: Thermodynamic and computational studies.

The feed wastes and waste water treatment plants are the major sources for the entry of N-oxides into the soils then to aquatic life. The complexation of actinides with potentially stable anthropogenic ligands facilitate the transportation and migration of the actinides from the source confinement. The present study describes the determination of thermodynamic parameters for the complexation of Th(IV) with the three isomeric pyridine monocarboxylates (PCNO) namely picolinic acid-N-oxide (PANO), nicotinic acid-N-oxide (NANO) and isonicotinic acid-N-oxide (IANO). The potentiometric and isothermal calorimetric titrations were carried out to determine the stability and enthalpy of the formations for all the Th(IV)-PCNO complexes. Th-PANO complexes are more stable than Th-NANO and Th-IANO complexes which can be attributed to chelate formation in the former complexes. Formation of all the Th-PCNO complexes are endothermic and are entropy driven. The geometries for all the predicted complexes are optimized the energies, bond distances and charges on individual atoms are obtained using TURBOMOLE software. The theoretical calculation corroborated the experimental determinations.

Complexation of Th(IV) with sulfate in aqueous solution at 10–70 °C

The applicability of spectrophotometry or H+-potentiometry to the studies of the complexation of thorium(IV) in aqueous solutions is limited because Th(IV) does not have characteristic optical absorption in UV/Vis/Near IR region and H+-electrode is not sensitive in solutions of high acidity that needs to be maintained to prevent the hydrolysis of Th(IV). In the present work, the technique of calorimetric titration was used to determine the heat of reaction for the complexation of Th(IV) with sulfate in the temperature range of 10–70°C. The equilibrium constants and enthalpy of complexation were determined simultaneously from the calorimetric data. It was observed that the enthalpy of complexation is endothermic at 10°C, and become more endothermic as the temperature is increased. Despite of this, the complexes, Th(SO4)2+ and Th(SO4)2(aq), become more stable at higher temperatures due to the increasingly more positive entropy of complexation that exceeds the increase of enthalpy. The trends in the stability of sulfate complexes with tetravalent actinides (Th4+, U4+, Np4+, and Pu4+) are discussed in terms of electrostatic interactions that correlate with the ionic radii of the metal cations.

Synthesis and Characterization of Some Mixed Ligand Complexes of Th(IV) with Salicylyl hydrazine and its Derivatives

Synthesis and Characterization of Some Mixed Ligand Complexes of Th(IV) with Salicylyl hydrazine and its Derivatives

Sorption mechanism of Th(IV) at iron oxyhydroxide (IOHO)/water interface: Batch, model and spectroscopic studies

In this study, sorption mechanism of Th(IV) at iron oxyhydroxide (IOHO)/water interface was studied under ambient conditions to explore the retardation effects of IOHO on actinides in the engineering barrier system of the high-level radioactive waste geological repository. The sorption of Th(IV) on IOHO was strongly dependent on pH, and the intra-particle diffusion was the rate-controlling step. The presence of humic acid can enhance the sorption of Th(IV) on IOHO below pH~3.5, while slightly inhibit Th(IV) sorption above pH3.5 due to the competing effect of humic acid remaining in aqueous phase. The surface complexation model (SCM) confirmed that the bi-dentate complex of (FeO)2Th2+ and mono-dentate complexes of FeOThOH2+, FeOTh(OH)2+ and FeOTh(OH)30 are controlling the sorption process of Th(IV) on IOHO. Th(IV) sorption on IOHO is favorable to high temperature with respect to the hydrolysis effect of Th(IV). XPS analysis also confirmed the above mono- and bi-dentate surface complexes of Th(IV) on IOHO, which are very sensitive to environmental conditions. Mössbauer spectroscopy showed a decreasing geometry of each components of IOHO after Th(IV) sorption, indicating the chemisorption of Th(IV) on IOHO. Moreover, the contributions from Fe3O4(A) and Fe3O4(B) components to Th(IV) sorption were higher under high temperature and initial Th(IV) concentration in comparison with α-FeOOH and amorphous Fe3O4 components. The mono-dentate FeOThOH2+ and FeOTh(OH)2+complexes formed at Fe3O4(A) and Fe3O4(B) surfaces, whereas the bi-dentate (FeO)2Th2+ complex was preferring forming at the surface of α-FeOOH and amorphous Fe3O4.

Sorption behavior of thorium onto granite and its constituent minerals

ABSTRACTThe sorption behavior of thorium (Th) onto granite and its major constituent minerals, feldspar, quartz and mica were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. Distribution coefficients (Kd) decreased with increased carbonate concentrations and showed the minimal value at around pH 10. This sorption tendency was seen for all the rock and mineral samples, and it was due to the formation of aqueous hydroxo–carbonate complexes of Th in the solutions. The order of sorbability for Th was mica > feldspar > quartz ≈ granite. The sorption behaviors of Th were analyzed by the non-electrostatic surface complexation model with the Visual Minteq computer program. The Kd for granite were calculated by component additivity approaches. The model calculations were able to explain the experimental results reasonably well. It was shown that the sorption behavior of Th onto granite can be explained by the complexation with the surface sites of mainly biotite and feldspar.

Structure, Stability, and Electronic Properties of Dimethyl Sulfoxide and Dimethyl Formammide Clusters Containing Th(4.).

By using accurate density functional theory calculations, we have studied the complexes of Th(4+) with dimethyl-sulfoxide (DMSO) and dimethyl-formammide (DMF) molecules. These solvents are prototypes for oxygen-donor organic environments in which the oxygen atom is connected to S and C atom, respectively. Extended structural, energetic, and electronic structure analysis has been performed to provide a complete picture of the physical properties at the basis of the interaction of Th(4+) with the two solvents. By using a cluster grow approach, we have found that, very likely, the first solvation shell contains nine molecules in the case of DMSO, while it contains eight molecules for DMF. The theoretical results shown here are in agreement with experimental data taken from the literature.

Synthesis and Elucidation of Some Mixed Ligand Complexes of Th(IV) with N-(1-morpholinobenzyl)semicarbazide

Synthesis and Elucidation of Some Mixed Ligand Complexes of Th(IV) with N-(1-morpholinobenzyl)semicarbazide

Th(IV) complexes with cis-ethylenebis(diphenylphosphine oxide): X-ray structures and NMR solution studies

The complexation of Th(NO3)4 with the rigid diphosphoryl ligand cis-ethylenebis(diphenylphosphine oxide) has been investigated using X-ray crystallography, IR, NMR and CHN analysis. Three crystal polymorphs were grown out of methanolic solution where the 1:3 Th(IV)–ligand complex is ten-coordinate, and the metal is bound by three bidentate ligands and two nitrato groups. An additional metal–ligand complex with similar geometry was also grown from the non-coordinating solvent CHCl3. Analysis of CD3OD and CDCl3 solutions of this complex using 1H and 31P NMR reveals that ligand exchange rates are fast on the NMR time scale in methanol-d4, and slow on the NMR time scale in chloroform-d. Further, three additional crystal structures are reported describing the 1:1 and 1:2 Th(IV)–ligand complex, the 1:3 Th(IV)–ligand complex with an extra aqua ligand, and a serendipitous 1:3 Th(IV)–ligand structure where one ligand bears an epoxide.

The separation of Th(IV)/U(VI) via selective complexation with graphene oxide

The separation of Th(IV)/U(VI) is of great importance in the development of thorium-based reactors. Here, we report our studies of Th(IV)/U(VI) separation by graphene oxide (GO). Firstly, variation of media conditions such as the pH, contact time, ionic strength, as well as the presence of different anionic ligands were conducted. The results showed that GO exhibited great selectivity for Th(IV) and the separation factor of Th(IV)/U(VI) reached as high as 36.3 after 2h of contact at pH 3.8 and minimum ionic strength, and increasing the ionic strength caused the separation factor of Th(IV)/U(VI) to decrease. The presence of sulfate strongly influenced the separation factor of Th(IV)/U(VI) by GO. Secondly, competitive adsorption studies, as well as SEM–EDS, XRD, FT-IR, and XPS characterization were employed to gain further understanding of the mechanism of GO’s selective complexation of Th(IV)/U(VI). FT-IR and XPS characterizations showed that GO adsorbed Th(IV)/U(VI) through coordination of functional groups such as CO and CO on GO. The results of the competitive adsorption studies suggested that GO had a selective affinity for Th(IV) over U(VI). SEM–EDS exhibited a uniform distribution of both Th(IV) and U(VI) on GO. XRD indicated that the interlayer distances of the prepared GO, GO–Th(IV), GO–U(VI), and GO–Th(IV)/U(VI) were 8.24, 8.20, 7.86, and 8.26Å, respectively. These results suggested that the adsorption of U(VI) caused a decrease of the interlayer distance of GO, which is probably inhibits GO’s ability to adsorb metal ions due to increased inter-planar repulsion and induced steric hindrance that limits adsorption of more metal ions. Therefore, a spatial feature based mechanism of GO was proposed.

Humic acid complexation of Th, Hf and Zr in ligand competition experiments: Metal loading and pH effects

The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories.Here, we present conditional equilibrium binding constants (Kc,MHA) of thorium, hafnium, and zirconium–humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE–ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000Da membrane were also performed to validate the CE–ICP-MS analysis. Experiments were performed at pH3.5–7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE–ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal–humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc,MHA several orders of magnitude above REE–humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc,MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc,MHA values attained at very low metal loading conditions are compared to existing literature data. Overall, experimental data suggest that the tetravalent transition metal/-actinide–humic acid complexation is important over a wide range of pH values, including mildly acidic conditions, and thus, these complexes should be included in speciation models.

Extraction and separation of thorium and rare earths with 5,11,17,23-tetra (diethoxyphosphoryl)-25,26,27,28-tetraacetoxycalix[4]arene

A calixarene derivative, 5,11,17,23-tetra(diethoxyphosphoryl)-25,26,27,28-tetraacetoxycalix[4]arene (L), was studied for the extraction and separation of thorium and rare earths in nitrate medium. Thorium was extracted into the organic phase by a complex of Th(NO3)4·L with the logarithm of the equilibrium constant of 2.77. Thermodynamic functions, ΔH, ΔG and ΔS were calculated to be −2.49, −15.55 kJ/mol and 44.53 J/(mol·K), respectively. The results indicated that this calixarene derivative might be used to separate thorium from rare earths and the separation factors were larger than 26. However, the salting-out agents affected the separation.

Aqueous Complexation of Thorium(IV), Uranium(IV), Neptunium(IV), Plutonium(III/IV), and Cerium(III/IV) with DTPA

Aqueous complexation of Th(IV), U(IV), Np(IV), Pu(III/IV), and Ce(III/IV) with DTPA was studied by potentiometry, absorption spectrophotometry, and cyclic voltammetry at 1 M ionic strength and 25 °C. The stability constants for the 1:1 complex of each trivalent and tetravalent metal were calculated. From the potentiometric data, we report stability constant values for Ce(III)DTPA, Ce(III)HDTPA, and Th(IV)DTPA of log β(101) = 20.01 ± 0.02, log β(111) = 22.0 ± 0.2, and log β(101) = 29.6 ± 1, respectively. From the absorption spectrophotometry data, we report stability constant values for U(IV)DTPA, Np(IV)DTPA, and Pu(IV)DTPA of log β(101) = 31.8 ± 0.1, 32.3 ± 0.1, and 33.67 ± 0.02, respectively. From the cyclic voltammetry data, we report stability constant values for Ce(IV) and Pu(III) of log β(101) = 34.04 ± 0.04 and 20.58 ± 0.04, respectively. The values obtained in this work are compared and discussed with respect to the ionic radius of each cationic metal.