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Two new aqueous UIV complexes were synthesized by the interaction between the tetravalent uranium cation and the (1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetra(methylene phosphonic acid) (DOTP) macrocyclic ligand. Two distinct homonuclear complexes were identified; the first was characterized by X‐ray crystallography as a unique "out‐of‐cage", [U(DOTPH6)2] complex, in which the UIV cation is octa‐coordinated to 4 phosphonic arms from each ligand in a square anti‐prism geometry, with a C4 symmetry. The second is the "in‐cage" [U(DOTPH4)] complex, in which the tetravalent cation is located between the macrocycle O4 and N4 planes. With the help of UV‐Vis absorption, 1H/31P NMR, ATR‐IR, and MALDI‐TOFMS analytical techniques, the chemical interchange between both species is presented. It is shown that the one‐way transition is governed by the formation of a multiple number of soluble oligomeric species consisting of varied stoichiometric ratios of both characterized homonuclear complexes. [ABSTRACT FROM AUTHOR]

In this study, the native and 2,5-diaminobenzene sulfonic acid (DABSA) attached Lentinus concinnus biomasses were utilized for removal of U(VI) ions from solutions. At 25 °C, the maximum uranium ion adsorption capacity of the native and DABSA attached fungal biomasses were found to be 118.6 and 539.2 mg/g, respectively, at pH 6.0. The negative ΔG° values of U(VI) removal showed that the adsorption procedure were spontaneous. ATR-FTIR data showed that U(VI) ions adsorption the adsorbents was mainly attributed by amine, carboxyl and sulfate groups. [ABSTRACT FROM AUTHOR]

An efficient natural bioextractant, orange peel extractant, was applied to recover uranium as one of hazardous elements. Batch experiments were carried out to determine the effect of various factors on the uranium extraction using a synthetic standard solution. These factors include the diluent type, pH, solvent concentration, contact time, and temperature. Under the optimum conditions (pH 4, A/O = 3/1), the maximum saturation capacity of the orange peel extractant for uranium reaches approximately 54.5 mg/g. The extracted uranium ions were almost completely eluted with NaCl/H2SO4 (1 M each). The procedure was applied to real sulfate leach liquor of a clay stone sample from Southeastern Sinai, Egypt. [ABSTRACT FROM AUTHOR]

Results are presented of a study concerned with the dissolution of uranium and plutonium compounds, carried out to diminish the amount of wastes in the form of a scrap formed in manufacture of a mixed nitride uranium-plutonium (MNUP) fuel. The optimal conditions of dissolution in nitric acid of uranium and plutonium compounds contained in the scrap were determined. The influence exerted by the concentration of nitric acid, process temperature, and addition of fluoride ions to the solution on the dissolution process were examined. [ABSTRACT FROM AUTHOR]

Room temperature reaction of the uranium(IV)–carbene [U{C(SiMe3)(PPh2)}(BIPMTMS)(μ-Cl)Li(TMEDA)(μ-TMEDA)0.5]2 (1, BIPMTMS = C(PPh2NSiMe3)2) with white phosphorus (P4) produces the organo-P5 compound [P5{C(SiMe3)(PPh2)}2][Li(TMEDA)2] (2) and the uranium(IV)–methanediide [U{BIPMTMS}{Cl}{μ-Cl}2{Li(TMEDA)}] (3). This is an unprecedented example of cooperative metal–carbene P4 activation/insertion into a metal–carbon double bond and also an actinide complex reacting with P4 to directly form an organophosphorus species. Conducting the reaction at low temperature permits the isolation of the diuranium(IV) complex [{U(BIPMTMS)([μ-η2:η2-P2]C[SiMe3][PPh2])}2] (4), which then converts to 2 and 3. Thus, surprisingly, in contrast to all other actinide P4 reactivity, although this reaction produces catenation overall it proceeds via P4 cleavage to functionalised P2 units. Hence, this work establishes a proof of concept synthetic cycle for direct fragmentation, catenation, and functionalisation of P4. [ABSTRACT FROM AUTHOR]

C-term magnetic circular dichroism (MCD) spectroscopy is a powerful method for probing d–d and f–f transitions in paramagnetic metal complexes. However, this technique remains underdeveloped both experimentally and theoretically for studies of U(V) complexes of Oh symmetry, which have been of longstanding interest for probing electronic structure, bonding, and covalency in 5f systems. In this study, C-term NIR MCD of the Laporte forbidden f–f transitions of [UCl6]− and [UF6]− are reported, demonstrating the significant fine structure resolution possible with this technique including for the low energy Γ7 → Γ8 transitions in [UF6]−. The experimental NIR MCD studies were further extended to [U(OC6F5)6]−, [U(CH2SiMe3)6]−, and [U(NC(tBu)(Ph))6]− to evaluate the effects of ligand-type on the f–f MCD fine structure features. Theoretical calculations were conducted to determine the Laporte forbidden f–f transitions and their MCD intensity experimentally observed in the NIR spectra of the U(V) hexahalide complexes, via the inclusion of vibronic coupling, to better understand the underlying spectral fine structure features for these complexes. These spectra and simulations provide an important platform for the application of MCD spectroscopy to this widely studied class of U(V) complexes and identify areas for continued theoretical development. [ABSTRACT FROM AUTHOR]

The synthesis, electronic structure, and reactivity of a uranium metallacyclopropene were comprehensively studied. Addition of diphenylacetylene (PhC≡CPh) to the uranium phosphinidene metallocene [η5‐1,2,4‐(Me3C)3C5H2]2U=P‐2,4,6‐tBu3C6H2 (1) yields the stable uranium metallacyclopropene, [η5‐1,2,4‐(Me3C)3C5H2]2U[η2‐C2Ph2] (2). Based on density functional theory (DFT) results the 5f orbital contributions to the bonding within the metallacyclopropene U‐(η2‐C=C) moiety increases significantly compared to the related ThIV compound [η5‐1,2,4‐(Me3C)3C5H2]2Th[η2‐C2Ph2], which also results in more covalent bonds between the [η5‐1,2,4‐(Me3C)3C5H2]2U2+ and [η2‐C2Ph2]2− fragments. Although the thorium and uranium complexes are structurally closely related, different reaction patterns are therefore observed. For example, 2 reacts as a masked synthon for the low‐valent uranium(II) metallocene [η5‐1,2,4‐(Me3C)3C5H2]2UII when reacted with Ph2E2 (E=S, Se), alkynes and a variety of hetero‐unsaturated molecules such as imines, ketazine, bipy, nitriles, organic azides, and azo derivatives. In contrast, five‐membered metallaheterocycles are accessible when 2 is treated with isothiocyanate, aldehydes, and ketones. [ABSTRACT FROM AUTHOR]

New syntheses have been developed for the synthesis of (borohydrido-κ³H)tris[η5-(trimethylsilyl)cyclopentadienyl]uranium(IV), [U(BH4)(C8H13Si)3] or Cp'3U(BH4) (Cp' = C5H4SiMe3) and its structure has been determined by single-crystal X-ray crystallography. This compound crystallized in the space group P... and the structure features three η5-coordinated Cp' rings and a κ³-coordinated (BH4)- ligand. [ABSTRACT FROM AUTHOR]

Sodium fluorouranates were studied to get the refined value of one of the fundamental constants with determination of differences between various uranium isotopes contained in these compounds. Such compounds as sodium heptafluorouranate can be classified as molecular substances with covalent bonds. The approach to the assessment of decomposition temperature of sodium fluoride compounds with various uranium isotopes based on the Mendeleev and Karapetyants methods, as well as on the quantum Landau representations is proposed. The Landau equation for the boiling point of isotopic compounds was corrected. The estimated decomposition (boiling) temperatures of sodium heptafluorouranates containing uranium isotopes 235U, 234U, and 232U were 453.8, 453.0, and 451.4 K respectively. The sublimation temperature of 271SgF6 was estimated. [ABSTRACT FROM AUTHOR]

A TiO2 aerogel with a high removal percentage and adsorption capacity was manufactured via template synthesis. Subsequently, the as-prepared TiO2 aerogel was characterized by various techniques and applied as an adsorbent for the removal of U(VI). The results revealed that the U(VI) adsorption was very rapid and reached apparent equilibrium within 100 min. The maximum removal percentage was 97.1%, which was calculated using the pseudo-second-order kinetic model (T = 298 K, t = 180 min, pH = 5, m/V = 0.1 g L−1 and C0 = 10 mg g−1). The Langmuir isotherm model was used to determine the maximum adsorption capacity and it achieved 638.0 mg g−1 (T = 298 K, pH = 5 and m/V = 0.1 g L−1). In addition, the removal of U(VI) on the TiO2 aerogel was relatively good in acidic solution and the removal behavior was independent of the influence of ionic strength. The removal percentage of the as-prepared TiO2 aerogel was higher than 90% after five cycles. Due to these excellent properties such as easy recovery, fast adsorption kinetics, high adsorption capacity and high removal percentage, the TiO2 aerogel might become an extremely employable adsorbent for the extraction of U(VI) in seawater. [ABSTRACT FROM AUTHOR]

The determination of free acidity and uranium in a radioactive uranyl nitrate solution inside a hot cell has to be done remotely. It generally involves the addition of complexing agents or the application of sophisticated analytical methods and modelling. To make the analyses uncomplicated, a simple acid–base conductometric titration method was developed to determine the free acidity and the uranium concentration simultaneously. Uranyl nitrate solutions containing nitric acid from 0.02 to 0.83 mmol and uranium from 0.32 to 15.90 mg per aliquot were determined by this method. The precision and accuracy of the method were found to be within ± 5%. For the titrations carried out at higher temperatures, the bias was found to be within ± 10%. [ABSTRACT FROM AUTHOR]

Oxide is an attractive linker for building polymetallic complexes that provide molecular models for metal oxide activity, but studies of these systems are limited to metals in high oxidation states. Herein, we synthesized and characterized the molecular and electronic structure of diuranium bridged UIII/UIV and UIII/UIII complexes. Reactivity studies of these complexes revealed that the U−O bond is easily broken upon addition of N‐heterocycles resulting in the delivery of a formal equivalent of UIII and UII, respectively, along with the uranium(IV) terminal‐oxo coproduct. In particular, the UIII/UIII oxide complex effects the reductive coupling of pyridine and two‐electron reduction of 4,4′‐bipyridine affording unique examples of diuranium(III) complexes bridged by N‐heterocyclic redox‐active ligands. These results provide insight into the chemistry of low oxidation state metal oxides and demonstrate the use of oxo‐bridged UIII/UIII complexes as a strategy to explore UII reactivity. [ABSTRACT FROM AUTHOR]

Oxide is an attractive linker for building polymetallic complexes that provide molecular models for metal oxide activity, but studies of these systems are limited to metals in high oxidation states. Herein, we synthesized and characterized the molecular and electronic structure of diuranium bridged UIII/UIV and UIII/UIII complexes. Reactivity studies of these complexes revealed that the U−O bond is easily broken upon addition of N‐heterocycles resulting in the delivery of a formal equivalent of UIII and UII, respectively, along with the uranium(IV) terminal‐oxo coproduct. In particular, the UIII/UIII oxide complex effects the reductive coupling of pyridine and two‐electron reduction of 4,4′‐bipyridine affording unique examples of diuranium(III) complexes bridged by N‐heterocyclic redox‐active ligands. These results provide insight into the chemistry of low oxidation state metal oxides and demonstrate the use of oxo‐bridged UIII/UIII complexes as a strategy to explore UII reactivity. [ABSTRACT FROM AUTHOR]

Activation of dinitrogen (N2, 78 %) and dioxygen (O2, 21 %) has fascinated chemists and biochemists for decades. The industrial conversion of N2 into ammonia requires extremely high temperatures and pressures. Herein we report the first example of N2 and O2 cleavage by a uranium complex, [N(CH2CH2NPiPr2)3U]2(TMEDA), under ambient conditions without an external reducing agent. The N2 triple bond breaking implies a UIII–PIII six‐electron reduction. The hydrolysis of the N2 reduction product allows the formation of ammonia or nitrogen‐containing organic compounds. The interaction between UIII and PIII in this molecule allows an eight‐electron reduction of two O2 molecules. This study establishes that the combination of uranium and a low‐valent nonmetal is a promising strategy to achieve a full N2 and O2 cleavage under ambient conditions, which may aid the design of new systems for small molecules activation. [ABSTRACT FROM AUTHOR]

Activation of dinitrogen (N2, 78 %) and dioxygen (O2, 21 %) has fascinated chemists and biochemists for decades. The industrial conversion of N2 into ammonia requires extremely high temperatures and pressures. Herein we report the first example of N2 and O2 cleavage by a uranium complex, [N(CH2CH2NPiPr2)3U]2(TMEDA), under ambient conditions without an external reducing agent. The N2 triple bond breaking implies a UIII–PIII six‐electron reduction. The hydrolysis of the N2 reduction product allows the formation of ammonia or nitrogen‐containing organic compounds. The interaction between UIII and PIII in this molecule allows an eight‐electron reduction of two O2 molecules. This study establishes that the combination of uranium and a low‐valent nonmetal is a promising strategy to achieve a full N2 and O2 cleavage under ambient conditions, which may aid the design of new systems for small molecules activation. [ABSTRACT FROM AUTHOR]

Eight cyclopentadienyl U(III) iodide complexes have been synthesized from UI3 and crystallographically characterized to show the variations that can occur with this ligand set and uranium in the +3 oxidation state: (C5Me5)2UI(THF), {[K(OEt2)2][(C5Me5)2U(µ–I)2]}2, [K(18-crown-6)][(C5Me5)2U(µ–I)2], [K(2.2.2-cryptand)][(C5Me5)2UI2], [Li(THF)4][(C5Me5)2UI2], [Li(THF)3][(C5Me5)2UI(µ–I)], {[K(18-crown-6)]2(µ–toluene)}{[C5H3(SiMe3)2]2UI(µ–I)}2 and [(C5Me5)U]3(µ3–I)2 (µ–I)3I(THF)2. The structures show that small modifications in synthetic and crystallization procedures lead to changes in the coordination mode of the isolated product such that many structural options are available that can only be defined by X-ray crystallography. These variations highlight the many low energy options available in the reaction chemistry of this combination of metal and ligands. [ABSTRACT FROM AUTHOR]

The paper presents experimental and numerical simulation of the bioremediation in nitrate-, -sulfate-ions and uranium polluted aquifers near the Novosibirsk Chemical Concentrates Plant (NCPP) sludge storage facility. We used two HCh 4.4 (MSU) and PHREEQC 2.18 (USGS) software packages for geochemical modeling and found that the microbial consumption of oxidizers (oxygen and nitrate ions) led to a decrease in the redox potential to –400 mV. The latter plays a key role in the reduction of uranyl ions and stabilization (immobilization) of uranium in low soluble biogenic sediments containing calcium phosphates, sulfides of iron and associated heavy metals. Results of experimental and numerical simulation turned out to be consistent with the composition of mineral phase collected in situ in a discharge area of polluted aquifer. [ABSTRACT FROM AUTHOR]

• Sustainable MnO 2 @chitosan (CTS) composite aerogel beads were designed and synthesized. • The millimeter-scale MnO 2 @CTS gathered merits of easy separation and high capacity. • Mechanical strength was improved through in-situ growth of Nano-MnO 2 on CTS beads. • The maximum adsorption capacity for uranium reached 410.7 mg/g at pH eq 6. • During adsorption, MnO 2 @CTS partially reduced U(VI) to U(V/IV). To address the imperative need for efficient removal of uranium-containing wastewater and mitigate radioactive contamination risks associated with nuclear energy, the development of materials with high removal efficiency and facile separation is crucial. This study designed and synthesised MnO 2 @chitosan (CTS) composite aerogel beads by in-situ growing δ-MnO 2 on porous CTS aerogel beads. This approach not only mitigates the agglomeration of MnO 2 nanospheres but also significantly enhances the porous structure and surface area of MnO 2 @CTS. These cost-effective and eco-friendly millimeter-scale spherical aerogels exhibited convenient separation properties after adsorption. These characteristics help mitigate the risk of equipment seam blockage and secondary pollution that are often associated with powdered adsorbents. Additionally, MnO 2 @CTS exhibited remarkable mechanical strength (stress approximately 0.55 MPa at 60 % strain), enabling rapid separation and easy regeneration while maintaining high adsorption performance even after five cycles. Significantly, MnO 2 @CTS exhibited a maximum adsorption capacity of 410.7 mg/g at pH 6 and 298 K, surpassing reported values for most CTS/MnO 2 -based adsorbents. The chemisorption process of U(VI) on MnO 2 @CTS followed the pseudo-second-order kinetic and Dubinin-Radushkevish models. X-ray photoelectron spectroscopy analysis further confirmed the reduction of U(VI) to U(V/IV). These findings highlight the substantial potential of MnO 2 @CTS aerogel beads for U(VI) removal from aqueous solutions, positioning them as a promising solution for addressing U(VI) contamination in wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Phosphorylation Mg-Fe layered dioxides nanosheets with favorable memory effect, for uranium extraction from wastewater. • A simple modification strategy was provided calcination coupled in-situ phosphorylation. • The P-Mg-Fe LDOs showed a high adsorption capacity of 909.09 mg g−1. • The adsorption mechanisms were surface complexation, mineralization reaction, dissolution-precipitation and memory effect. As the nuclear industry boomed, lots of uranium has entered the water environment and caused great damage to ecological environment. Designing and preparing efficient uranium adsorption materials is essential to solve the problem. Phosphorylated Mg-Fe layered dioxides (P-MF LDOs) nanosheets with a favorable memory effect were prepared by calcination and in-situ phosphorylation for uranium extraction from wastewater (UEW). The unique phosphating method resulted in a uniform distribution of phosphate functional groups in the surface of LDOs, which gave it great ability for capture of uranium. The adsorption capacity of P-MF LDOs was 2.31 times that of pure MF LDOs. According to the Langmuir model, the theoretical extraction capacity of P-MF LDOs was as high as 909.09 mg g−1, which was significantly higher than that of similar sorbents. Additionally, it exhibited excellent anti-interference ability. The results of the adsorption mechanism study revealed that the binding modes included surface complexation, mineralization reaction, dissolution-precipitation, and memory effect. In conclusion, P-MF LDOs represent a type of highly efficient uranium adsorbent with simple preparation and high adsorption capacity for UEW. This study provides new insights into the development of inorganic clay-based uranium adsorbents. [ABSTRACT FROM AUTHOR]

The dynamic reactions of uranium (U) with iron (Fe) minerals change its behaviors in soil environment, however, how the coexisted constituents in soil affect U sequestration and release on Fe minerals during the transformation remains unclear. Herein, coupled effects of lead (Pb) and dissolved organic matter (DOM) on U speciation and release kinetics during the catalytic transformations of ferrihydrite (Fh) by Fe(II) were investigated. Our results revealed that the coexistence of Pb and DOM significantly reduced U release and increased the immobilization of U during Fh transformation, which were attributed to the enhanced inhibition of Fh transformation, the declined release of DOM and the increased U(VI) reduction. Specifically, the presence of Pb increased the coprecipitation of condensed aromatics, polyphenols and phenols, and these molecules were preferentially maintained by Fe (oxyhydr)oxides. The sequestrated polyphenols and phenols could further facilitate U(VI) reduction to U(IV). Additionally, a higher Pb content in coprecipitates caused a slower U release, especially when DOM was present. Compared with Pb, the concentrations of the released U were significantly lower during the transformation. Our results contribute to predicting U sequestration and remediating U-contaminated soils. [Display omitted] • A lower U:Pb ratio enhanced the stability of U during Fh transformation. • The presence of Pb increased the coprecipitation of DOM molecules with Fh. • The concentration of the released U was significantly lower compared with Pb. • The coexistence of DOM and Pb slowed down U release from Fe (oxyhydr)oxides. [ABSTRACT FROM AUTHOR]

The chemistry of linear uranyl(V/VI) dioxo cations, [Oyl–U–Oyl]+/2+, is dominated by coordination of uranium in the equatorial plane. Effects of this constraint were evaluated by experiment and theory for gas‐phase mixed‐valence UV/VI coordination dimers in which uranyl moieties are linked by alkyl dicarboxylates, [(UO2+)(UO22+)(OOC‐(CH2)n‐2‐COO2–)2]– (n = 3–12). Faster O2‐addition to dimers with short linkers n = 3 and 4, vs. n ≥ 5, suggests a structural difference. Computed structures with the shortest linkers have bridging dicarboxylates and nearly parallel, non‐interacting uranyls. Longer linkers, n = 5–7, accommodate uranyl orientations with distinct UV–UVI end‐on cation‐cation interactions (CCIs), whereby Lewis base Oyl from UV coordinates to the acid UVI, denoted as UVOyl···UVI. The dimer structure for n = 8 has a UV–UVI side‐on diamond‐shape CCI, with UVOyl···UVI and UVIOyl···UV interactions. Addition of O2 to the n = 4 and 5 dimers yields [(UO22+)2(OOC‐(CH2)n‐2‐COO2–)2(O2–)]–, with UV oxidized to UVI and O2 reduced to O2–. Whereas O2 can associate to and oxidize the exposed UV center for dimers with n = 3 and 4, the more crowded UV site in the CCI structures inhibits O2 addition. The results demonstrate rational structural control of uranyl‐uranyl bonding and reactivity in small coordination complexes. [ABSTRACT FROM AUTHOR]

Uranium, a double-edged sword with high-efficiency energy and radioactive toxicity, attracts people to enjoy the advantages by generating power, but at the same time brings potential harm by nuclide migration. Therefore, it is necessary to develop a highly-efficient sensor to monitor uranyl ions in the field. However, the designed processes of the reported sensors are random, time-consuming and difficulty. It is urgent to find a new strategy to rationally, quickly and effectively screen out the required molecule for efficient uranium detection. Herein, with the guidance from the rational design method, the parameter, E gap , was applied to judge the chromatic aberration between the designed PADAP derivate and its uranyl complex. And the optimized structure sensor, 2-((3-bromo-5-(9,9-dioctyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-fluoren-2-yl)-2-pyridylazo)-5-(diethylamino)phenol (abbr. W1H), was screened and successfully synthesized. W1H exhibited significant color change (red to blue) after binding uranyl ions, and its detection limit for uranium was as low as nanomolar. More meaningfully, the coordination mechanism of W1H toward uranium was clarified by theoretical calculation of the electron cloud density distribution, E bind , and 1H NMR, IR and MS for the first time. With the more excellent uranyl sensitivity, selectivity, and recyclability, W1H and its colorimetric test strip have been applied to the detection of low-concentration uranium in environmental samples around the uranium tailings, providing a useful on-site method to monitor trace uranium in actual samples. Image 1 • A high selective and sensitive uranyl sensor named W1H was screened and synthesized with the help of rational design strategy. • The W1H detection limit by UV spectrophotometry was as low as nanomolar level, which was superior to the most reported colorimetric/UV sensors. • The binding mode of uranyl-W1H were identified by DFT calculation of the electron cloud density distribution, 1H NMR, IR and MS for the first time. • Stability constants of interfering metal ion toward W1H shows the reason why W1H can specifically recognize uranium than the other metal ions. • W1H and its colorimetric test strip has been applied to detect uranium in real sample, providing a useful method to detect contaminants in environment. [ABSTRACT FROM AUTHOR]

The first stable base‐free terminal uranium phosphinidene metallocene is presented; and its structure and reactivity have been studied in detail and compared to that of the corresponding thorium derivative. Salt metathesis reaction of the methyl iodide uranium metallocene Cp"'2U(I)Me (2, Cp"'=η5‐1,2,4‐(Me3C)3C5H2) with Mes*PHK (Mes*=2,4,6‐(Me3C)3C6H2) in THF yields the base‐free terminal uranium phosphinidene metallocene, Cp"'2U=PMes* (3). In addition, density functional theory (DFT) studies suggest substantial 5f orbital contributions to the bonding within the uranium phosphinidene [U]=PAr moiety, which results in a more covalent bonding between the [Cp"'2U]2+ and [Mes*P]2− fragments than that for the related thorium derivative. This difference in bonding besides steric reasons causes different reactivity patterns for both molecules. Therefore, the uranium derivative 3 may act as a Cp"'2U(II) synthon releasing the phosphinidene moiety (Mes*P:) when treated with alkynes or a variety of hetero‐unsaturated molecules such as imines, thiazoles, ketazines, bipy, organic azides, diazene derivatives, ketones, and carbodiimides. [ABSTRACT FROM AUTHOR]

Mesoporous ZrO2/SBA-15 materials were prepared for the first time by a one-step method using ZrO2 as zirconium source and their uranium (U(VI)) adsorption behavior were studied. The influence of ZrO2 content on the structure, morphology and hydrothermal stability of the obtained ZrO2/SBA-15 was investigated. It was found that the structural order of ZrO2/SBA-15 decreased with increasing ZrO2 content. The hydrothermal stability of SBA-15 was improved by loading of ZrO2. Furthermore, the effects of pH, initial U(VI) concentration, contact time, temperature and ZrO2 content on the U(VI) adsorption capacity were studied. The results demonstrated that the U(VI) adsorption capacity decreased with increasing ZrO2 content and temperature. The adsorption process was found to be well fitted to the Langmuir and pseudo-second-order model. The calculated maximum adsorption capacities were 326 and 294 mg·g−1 for 0.4ZrO2/SBA-15 and 0.8ZrO2/SBA-15 samples at 283 K, respectively. Furthermore, the analysis of thermodynamic parameters (ΔG, ΔH, and ΔS) revealed that the process of U(VI) adsorption onto ZrO2/SBA-15 was feasible, spontaneous and exothermic. [ABSTRACT FROM AUTHOR]

Bifunctional amidophosphonate derivatives, already known as efficient ligands in uranium extraction from phosphoric media, have been evaluated and compared to the conventional tri-n-butyl phosphate (TBP) for uranium extraction from nitrate medium. The efficiency of U extraction and its selectivity towards competing elements such as Th, Zr, Mo, Fe, and V was evaluated with various ligand structures. It was found that extractant molecules containing a monosaponified phosphonate moiety instead of phosphonate moieties are less effective and selective. Furthermore, it was observed that the alkylation of the methylene bridge linking the two functional groups prevents the formation of precipitates during the uranium loading. Effects of acidity as well as ligand concentration were also investigated in order to estimate the loading capacity of the molecules. More detailed stoichiometry and transfer energy were further determined by the slope analysis method and a thermodynamic study. The possible uranium recovery from the organic phase has moreover been demonstrated thanks to stripping steps at low nitric acid concentration. [ABSTRACT FROM AUTHOR]

Reaction of the uranium(III) metallocenium salt [(CpiPr4)2U][B(C6F5)4] with tert-butyl isocyanide (tBuNC) yielded the dicationic uranium(IV) complex [(CpiPr4)2U(CNtBu)4][B(C6F5)4]2 (1), which displays a linear metallocene geometry. Use of crude mixtures of [(CpiPr4)2U][B(C6F5)4], which contain a soluble source of iodide, led instead to isolation of the monocationic uranium(IV) iodide complex [(CpiPr4)2U(I)(CNtBu)2][B(C6F5)4] (2). Adduct formation with no change in oxidation state was observed upon addition of tBuNC to the neutral uranium(III) species (CpiPr4)2UI, resulting in isolation of (CpiPr4)2U(I)(CNtBu) (3). X-ray crystallographic and IR spectroscopic studies both showed effects ascribed to the presence of multiple strongly donating isocyanide ligands in 1. [ABSTRACT FROM AUTHOR]

The crystal structures of S,S′-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) diacetate (1_ac), S,S′-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) dichloride (1_Cl), 1_U complex, S,S′-naphthalene-1,4-diylbis(methylisothiouronium) dichloride (2_Cl), and 2_U complex were determined for the first time. The supramolecular structures of the compounds obtained are mainly based on hydrogen bonding and ionic interactions between the isothiouronium cations and the counter anions Cl−, CH3COO−, and [UO2(CH3COO)3]−. Their structural and spectroscopic properties were studied, and the results of DFT calculations were compared with the experimental findings to provide insights into the properties of these new compounds. The DFT calculations indicate a strong preference for the formation of the outer-sphere complex (ion-pair) between the uranyl species and an isothiouronium cation, and very large stabilization energies of the interactions, which can be utilized for the selective binding of U(VI). The compounds obtained are the first f-element and isothiouronium salt complexes described so far. [ABSTRACT FROM AUTHOR]

Treatment of [Ph3EMe][I] with [Na{N(SiMe3)2}] affords the ylides [Ph3E=CH2] (E=As, 1As; P, 1P). For 1As this overcomes prior difficulties in the synthesis of this classical arsonium‐ylide that have historically impeded its wider study. The structure of 1As has now been determined, 45 years after it was first convincingly isolated, and compared to 1P, confirming the long‐proposed hypothesis of increasing pyramidalisation of the ylide‐carbon, highlighting the increasing dominance of E+−C− dipolar resonance form (sp3‐C) over the E=C ene π‐bonded form (sp2‐C), as group 15 is descended. The uranium(IV)–cyclometallate complex [U{N(CH2CH2NSiPri3)2(CH2CH2SiPri2CH(Me)CH2)}] reacts with 1As and 1P by α‐proton abstraction to give [U(TrenTIPS)(CHEPh3)] (TrenTIPS=N(CH2CH2NSiPri3)3; E=As, 2As; P, 2P), where 2As is an unprecedented structurally characterised arsonium‐carbene complex. The short U−C distances and obtuse U‐C‐E angles suggest significant U=C double bond character. A shorter U−C distance is found for 2As than 2P, consistent with increased uranium‐ and reduced pnictonium‐stabilisation of the carbene as group 15 is descended, which is supported by quantum chemical calculations. [ABSTRACT FROM AUTHOR]

Treatment of [Ph3EMe][I] with [Na{N(SiMe3)2}] affords the ylides [Ph3E=CH2] (E=As, 1As; P, 1P). For 1As this overcomes prior difficulties in the synthesis of this classical arsonium‐ylide that have historically impeded its wider study. The structure of 1As has now been determined, 45 years after it was first convincingly isolated, and compared to 1P, confirming the long‐proposed hypothesis of increasing pyramidalisation of the ylide‐carbon, highlighting the increasing dominance of E+−C− dipolar resonance form (sp3‐C) over the E=C ene π‐bonded form (sp2‐C), as group 15 is descended. The uranium(IV)–cyclometallate complex [U{N(CH2CH2NSiPri3)2(CH2CH2SiPri2CH(Me)CH2)}] reacts with 1As and 1P by α‐proton abstraction to give [U(TrenTIPS)(CHEPh3)] (TrenTIPS=N(CH2CH2NSiPri3)3; E=As, 2As; P, 2P), where 2As is an unprecedented structurally characterised arsonium‐carbene complex. The short U−C distances and obtuse U‐C‐E angles suggest significant U=C double bond character. A shorter U−C distance is found for 2As than 2P, consistent with increased uranium‐ and reduced pnictonium‐stabilisation of the carbene as group 15 is descended, which is supported by quantum chemical calculations. [ABSTRACT FROM AUTHOR]

Homoleptic σ‐bonded uranium–alkyl complexes have been a synthetic target since the Manhattan Project. The current study describes the synthesis and characterization of several unprecedented uranium–methyl complexes. Amongst these complexes, the first example of a homoleptic uranium–alkyl dimer, [Li(THF)4]2[U2(CH3)10], as well as a seven‐coordinate uranium–methyl monomer, {Li(OEt2)Li(OEt2)2UMe7Li}n were both crystallographically identified. The diversity of complexes reported herein provides critical insight into the structural diversity, electronic structure and bonding in uranium–alkyl chemistry. [ABSTRACT FROM AUTHOR]

Homoleptic σ‐bonded uranium–alkyl complexes have been a synthetic target since the Manhattan Project. The current study describes the synthesis and characterization of several unprecedented uranium–methyl complexes. Amongst these complexes, the first example of a homoleptic uranium–alkyl dimer, [Li(THF)4]2[U2(CH3)10], as well as a seven‐coordinate uranium–methyl monomer, {Li(OEt2)Li(OEt2)2UMe7Li}n were both crystallographically identified. The diversity of complexes reported herein provides critical insight into the structural diversity, electronic structure and bonding in uranium–alkyl chemistry. [ABSTRACT FROM AUTHOR]

Calcium chloride (CaCl2) roasting and nitric acid (HNO3) leaching were combined to remove uranium and radioactivity from uranium tailings. The results show that the uranium and gross α and β radioactivity removal efficiencies improve with increasing CaCl2 addition and HNO3 leaching time and reach maximum values of 81.5%, 87.9% and 86.5%, respectively, after roasting with 50% CaCl2 for 120 min, followed by 1 mol L−1 HNO3 leaching. The uranium leaching rate is 62.3% higher than with direct acid leaching. The mineralogical characteristics of the roasted clinker show that roasting uranium tailings with CaCl2 changes their mineral phase, and Ca2+ becomes incorporated into the silicate matrix, which is beneficial for removing uranium and other radionuclides by acid leaching. [ABSTRACT FROM AUTHOR]

Salinity, selenium, and uranium pose water‐quality challenges for the Arkansas River in southeastern Colorado and other rivers that support irrigation in semiarid regions. This study used 31 years of continuous discharge and specific conductance (SC) monitoring data to assess interannual patterns in water quality using mass balance on a 120‐km reach of river. Discrete sampling data were used to link the SC records to salinity, selenium, and uranium. Several important patterns emerged. Consumptive use reduced discharge by a median value of 33% and drove corresponding increases in salinity and uranium concentrations. Increased water availability for irrigation from rainfall and upstream snowpack in 1995–1999 flushed additional salinity and uranium into the river in 1996–2000; average annual total dissolved solids (salinity) concentrations increased 25%, and loads increased 131%. Smaller flushing events have occurred, sometimes lagging an increase in water availability by about one year. The pattern indicates flushing of salts temporarily stored, evaporatively concentrated, or of geologic origin. Mobilization of selenium from the reach was minor compared to salinity and uranium, and net selenium removal from the river was suggested in some years. Several processes related to irrigation could be removing selenium. The results provide context for efforts to improve water quality in the Arkansas River and rivers in other semiarid regions. Research Impact Statement: Wet years flushed salts from the landscape to the Arkansas River the same or following year; dry years stored salts in the landscape, and net removal of selenium is indicated in some years. [ABSTRACT FROM AUTHOR]

The π coordination of arene and anionic heteroarene ligands is a ubiquitous bonding motif in the organometallic chemistry of d‐block and f‐block elements. By contrast, related π interactions of neutral heteroarenes including neutral bora‐π‐aromatics are less prevalent particularly for the f‐block, due to less effective metal‐to‐ligand backbonding. In fact, π complexes with neutral heteroarene ligands are essentially unknown for the actinides. We have now overcome these limitations by exploiting the exceptionally strong π donor capabilities of a neutral 1,4‐diborabenzene. A series of remarkably robust, π‐coordinated thorium(IV) and uranium(IV) half‐sandwich complexes were synthesized by simply combining the bora‐π‐aromatic with ThCl4(dme)2 or UCl4, representing the first examples of actinide complexes with a neutral boracycle as sandwich‐type ligand. Experimental and computational studies showed that the strong actinide–heteroarene interactions are predominately electrostatic in nature with distinct ligand‐to‐metal π donation and without significant π/δ backbonding contributions. [ABSTRACT FROM AUTHOR]

This paper reports a study of leaching of uranium and P2O5 from Syrian phosphate using commercial nitric and hydrochloric acids. The effect of different parameters such as the liquid:solid ratio, the acid concentration, the leaching time and the reaction temperature is studied aiming optimization of various process parameters and hence maximization of uranium and P2O5 recovery. The optimal dissolution efficiency of uranium and P2O5 in hydrochloric acid referring to 88.46 % and 91.37 %, respectively, is obtained under the following conditions: a liquid:solid ratio of 5:1 mL:g, an acid concentration of 29.6 %, contact time of 25 min and a reaction temperature of 40°C. The optimal dissolution efficiency of uranium and P2O5 in nitric acid referring to 94.16 % and 93.07 %, respectively, is obtained under the following conditions: a liquid:solid ratio of 6:1 mL:g, an acid concentration of 40.9 %, contact time of 20 min and a reaction temperature of 50°C. [ABSTRACT FROM AUTHOR]

Crystals of a new uranyl sulfate (C2N4H8S2)[UO2(SO4)2]·0.3H2O (1) templated by a relatively rare bis‐isothiouronium cation, were formed upon evaporation of aqueous solutions containing uranyl acetate, thiourea, and excess sulfuric acid. The new compound is orthorhombic, P212121, a = 6.928(2) Å, b = 13.398(3) Å, c = 15.225(3) Å, Z = 2. Its crystal structure is comprised of [UO2(SO4)2] moieties linked by hydrogen bonds formed between the template cations and terminal oxygen atoms of the sulfate tetrahedra. The C2N4H8S22+ template is most likely formed in situ during a redox reaction between uranyl cation and thiourea in a strongly acidic medium, with UO22+ partially reduced to U4+. [ABSTRACT FROM AUTHOR]

We describe the functionalisation of the previously reported uranium(III) β-diketiminate complex (BDI)UI2(THF)2 (1) with one and two equivalents of a sterically demanding 2,6-diisopropylphenolate ligand (ODipp) leading to the formation of two heteroleptic complexes: [(BDI)UI(ODipp)]2 (2) and (BDI)U(ODipp)2 (3). The latter is a rare example of a tetrahedral uranium(III) complex, and it shows single-molecule magnet behaviour. [ABSTRACT FROM AUTHOR]

With the depletion of uranium terrestrial deposits, researchers have focused on the development of adsorbents to extract radioactive uranium from seawater/wastewater. However, the artificial manipulation of adsorbents for the cost-effective extraction of radioactive uranium from large numbers of water samples is still significantly challenging. Herein, a facile yet versatile stepwise strategy has been reported for the fabrication of adsorbents. Magnesium hydroxide (Mg(OH)2) was fabricated via the in situ conversion of a natural ore powder (magnesite), whose unique internal pore structure is highly suitable for the development of highly efficient sorbents. The coordination interaction of the synthesized adsorbent with uranium was enhanced by further introducing inexpensive molecules with water-locking properties, which resulted in superior extraction capacity and low production cost. After careful calculation, the cost per kilogram of the adsorbent was found to be about $0.21. The adsorption behaviors of the synthesized adsorbent CMC–PAM/Mg(OH)2 were investigated by batch adsorption, flow-through column adsorption (in laboratory), and field adsorption experiments in natural seawater and river. Representatively, CMC–PAM/Mg(OH)2 was exceptional in extracting uranium not only at high concentrations with sufficient capacities in a wide pH range (1584.67 mg g−1 and 454.55 mg g−1 at pH = 5 and pH = 8, respectively), but also in trace quantities including uranium in a flow-through column (55.68 mg g−1), natural seawater (8.6 mg g−1), and river (6.7 mg g−1). Inspired by this excellent performance, the effects of competitive ions on the selective adsorption of uranium by CMC–PAM/Mg(OH)2 in simulated wastewater and seawater environments were further studied. Using a combination of FTIR spectroscopic and XPS studies, it was revealed that the amine and hydroxyl groups enhanced the overall uranyl affinity of the CMC–PAM/Mg(OH)2 composite. [ABSTRACT FROM AUTHOR]

Quinoline Silicate Lewatit Composite and activated Lewatit were prepared and tested for uranium removal from sulfate solution. Uranium sorption capabilities of the tested adsorbents was estimated under different conditions; uranium initial concentration, pH, contact time, temperature, adsorbent dose and interfering ions. Experimental data obeyed Langmuir isotherm model with 69.44 mg/g and 217.39 mg/g theoretical capacity for AL and QSLC, respectively. Thermodynamic studies indicated an exothermic behavior with a decrease in randomness. Kinetics studies showed that the adsorption process obeyed pseudo-second order model. Optimum conditions were carried out for uranium recovery from a rock sample, producing uranium concentrate with 93.33% purity. [ABSTRACT FROM AUTHOR]

High radioactive anomalies were recorded in the variegated claystones at the middle member of Um Bogma Formation, the eU-content reaches 1030 ppm, while eU/eTh ratio was equivalent to 11.7 times of Clark value. Associated elements with economic values as rare earth elements, vanadium and molybdenum were detected. Beside this, work focusing on uranium recovery from collected samples was investigated using different reagents and leaching techniques. Pug-leaching process using sulfuric acid at 100 °C is the most efficient leaching condition. Selective separation of uranium with high grade (38%) was obtained using synthetic quaternary ammonium sorbent grafted on silica particles. [ABSTRACT FROM AUTHOR]

The material of organic–inorganic hybrid polymers combine the functional organic and the advantages of a thermally stable and robust inorganic substrate, resulting in strong binding affinities toward selected metal ions and relatively high metal ion adsorption capacities. The aim of this work is to synthesize the polymer‐inorganic hybrid composite adsorbent base on amidoxime zeolite (zeolite–AMO) using simultaneous radiation technique; to characterize the adsorbent using FTIR and zeta potential; and to test the adsorption capacity of adsorbent for uranium (VI) using batch adsorption test in aqueous system. The solvent system of acrylonitrile monomer is water emulsion, with the concentration of 30%. The irradiation dose is 100 kGy with the dose rate of 2 kGy h−1. The hydroxylamine solution with the concentration of 6% in a mixture of water–methanol with ratio of 1:1 at 80 °C for 3 hours of reaction time uses for the amidoximation process. The result shows that the highest degree of grafting is 20.31%. Furthermore, the amidoxime density is 5.82 mmol g−1 and the optimum pH is 5.9. The sorption process follows the pseudo‐second‐order kinetic model and fits with the Freundlich model analysis. [ABSTRACT FROM AUTHOR]

New, simple and rapid spectrophotometric methods were described for the micro-determination of some rare earth metal ions uranium(VI), samarium(III) and cerium(III) using a new synthesized sulfacetamide azo dye derivative [2-((4-(N-acetylsulfamoyl)phenyl)diazenyl)-3,4,5-trihydroxybenzoic acid] (APDB). The new reagent was reacted with the three rare earth metal ions forming colored complexes at 500, 535 and 540 nm for U(VI), Sm(III) and Ce(III), respectively. The complexes were formed in alkaline medium using borate buffer at pH = 9 for U(VI) and Sm(III) and at pH = 8 for Ce(III). The absorbance of U(VI) and Sm(III)-APDB complexes was enhanced in the presence of CTAB as a cationic micellar media while that of Ce(III)-APDB complex was improved by using aerosol GPG surfactant. The proposed methods were also improved by using acetone and DMF as organic solvents for only U(VI) and Sm(III)-APDB complexes, respectively. The three metal ions complexes were formed by 1:2 (metal:ligand) ratio. Beer's law was followed over the concentration range of 5–80, 10–160 and 10–80 µg mL−1 for U(VI), Sm(III) and Ce(III), respectively. The proposed methods showed 0.8910, 2.454 and 2.750 µg mL−1 limit of detection and 2.700, 7.436 and 8.335 µg mL−1 quantification limit (LOQ) for U(VI), Sm(III) and Ce(III) complexes, respectively. The relative standard deviation was also calculated to be 0.00899, 0.00461 and 0.0180 for U(VI), Sm(III) and Ce(III) complexes, respectively. The interference effect of various diverse ions was also investigated. The proposed methods were successfully applied for the determination micro-amounts of the selected metal ions in some industrial, biological and plant samples. [ABSTRACT FROM AUTHOR]

Attempts to synthesize plutonium(IV) silicate, PuSiO4, have been made on the basis of results recently reported in the literature for CeSiO4, ThSiO4, and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4via applying the conditions reported for thorium and uranium, an efficient method of PuSiO4 synthesis was established by applying the conditions optimized for the CeSiO4 system. This method was based on the slow oxidation of plutonium(III) silicate reactants under hydrothermal conditions at 150 °C in hydrochloric acid (pH = 3–4). These results shed new light on the potential behavior of plutonium in reductive environments, highlighting the representative nature of cerium surrogates when studying plutonium under such conditions and providing some important pieces of information regarding plutonium chemistry in silicate solutions. [ABSTRACT FROM AUTHOR]

The molten flux synthesis of a uranium gallophosphate and a uranium gallate, Cs4[UO2Ga2(PO4)4] (1) and Cs2UO2Ga2O5 (2), and four uranium phosphates, [Rb2Rb3.93Cl0.93][(UO2)5(PO4)5] (3), Rb11[(UO2)8(PO4)9] (4), Rb7.6[(UO2)8O8.6F0.4(PO4)2] (5), and Rb6[(UO2)5O2(PO4)4] (6), is reported. A systematic exploration of the UF4–GaPO4–ACl (A = Cs, Rb) phase space resulted in the synthesis of targeted Cs4[UO2Ga2(PO4)4] (1) and Cs2UO2Ga2O5 (2), which are gallium analogs of the previously reported aluminates, Cs4[UO2Al2(PO4)4] and Cs2UO2Al2O5. The exploration of this phase space simultaneously led to the synthesis and characterization of four new uranium phosphate phases: [Rb2Rb3.93Cl0.93][(UO2)5(PO4)5] (3), a salt inclusion material, and Rb11[(UO2)8(PO4)9] (4), both of which have complex 3D, porous, framework structures, and Rb7.6[(UO2)8O8.6F0.4(PO4)2] (5) and Rb6[(UO2)5O2(PO4)4] (6), both of which are layered structures related to the U3O8 topology. Fluorescence spectroscopy data are reported for all the compositions and are found to be typical for uranyl compounds. [ABSTRACT FROM AUTHOR]

The amidoxime-functionalized biopolymer/graphene oxide gels were prepared and their performance in the application of the adsorption separation of uranium (VI) in aqueous solution has been studied. The prepared gels were characterized by using scanning electron microscopy, energy dispersive spectroscopy, Fourier transformed infrared spectra, and X-ray diffraction to determine the microscopic morphology, chemical composition and crystal structure. The adsorption performance of the gels including the effects of solution pH and contact time on the adsorption capacity has been evaluated by a batch adsorption technology. The adsorption isotherms and kinetics were measured, and the experimental data were analyzed and shown to be agreed with the Langmuir isotherm and the pseudo-second-order kinetic model. The results demonstrated that the adsorption process was the rate-limiting step in the separation process. [ABSTRACT FROM AUTHOR]

Uranium is carcinogenic ion and if present in water above its permissible limit, is very harmful to living beings. The main objective of this study is the removal of uranium from water sample using nano zero-valent copper prepared by green synthesis from Anacardium occidentale testa extract by a fully environment-friendly and cost-effective process without involvement of any hazardous chemicals. The formation of the A. occidentale-Cu nanoparticle is characterized through UV–Visible spectroscopy, FTIR, SEM–EDS, XRD and HR-TEM analysis. The adsorption capacity of copper nanoparticles, effect of pH, adsorbent and adsorbate dosage and contact time are studied and analyzed by Langmuir and Freundlich adsorption isotherm. [ABSTRACT FROM AUTHOR]

This present research aims to synthesize and investigate the adsorption potential of sugarcane bagasse (SCB) impregnated with 8 hydroxy quinolone 8‐(HQ) and 1,10 phenethroline (phen) to prepare impregnated sugarcane bagasse (ISCB) for removal UVI and ThIV. The effects of the operating parameters, including pH of the solution, contact time, initial concentration, temperature, dose and interfering ions on the adsorption efficiency were investigated to identify an optimal condition. The characterization of SEM‐EDX and FTIR analyses shows that ISCB has a porous structure and carbon‐containing functional groups. The adsorption result revealed that ISCB removed 98 % for both UVI and ThIV. The result obtained fitted well for Langmuir isotherms model with 185.19 mg·g–1 and 250 mg·g–1 as theoretical capacity for UVI and ThIV respectively. The adsorption process followed the pseudo‐second‐order kinetic model. In conclusion, this study proved that ISCB has the potential to be used as an effective and low‐cost adsorbent to remove UVI and ThIV. Finally we obtain products from thorium as ThO2 and uranium as Na2U2O7 from Abu Rushied leach liquor. [ABSTRACT FROM AUTHOR]

Reaction of (CpiPr4)2UI with NaN3 resulted in formation of tetrameric uranium(III) azide-bridged 'molecular square' [(CpiPr4)2U(μ-η1:η1-N3)]4 (1). Addition of B(C6F5)3 to 1 induced loss of N2 at room temperature, yielding the uranium(V) borane-capped nitrido (CpiPr4)2U(μ-N)B(C6F5)3 (2). [ABSTRACT FROM AUTHOR]