Effect of Porogen Type on the Synthesis of Uranium Ion Imprinted Polymer Materials for the Preconcentration/Separation of Traces of Uranium

Ion Imprinted Polymer (IIP) materials were prepared from different porogens by copolymerization of UO₂²⁺-5,7,dichloroquinoline-8-ol-4-vinylpyridine ternary complex in the presence of styrene as monomer, divinyl benzene as crosslinking agent and 2,2-azobisisobutyronitrile as initiator. The uranyl ion was removed on leaching with 50% (v/v) HCl, which leaves cavities in the polymer particles. Of the various porogens tested, 2-methoxy ethanol gave a higher retention/adsorption capacity for uranium and better selectivity for uranium over thorium. The optimum pH value for quantitative enrichment is 5.0–7.0, and desorption can be achieved with 5mL of 1M HCl. The retention capacity of the uranyl ion imprinted polymer particles was found to be 34.0mgg^–1 for uranium, which is much higher than blank or ion recognition polymer. More significantly, the selectivity coefficient (S_U/Th) is much higher (99.0) with 2-methoxy ethanol as porogen. The polymer particles obtained from this porogen have been characterized by IR, TGA, DTA, XRD, SEM and EDS analysis. Five replicate determinations of 40µg of uranyl ion present in 1000mL of aqueous solution with Arsenazo III spectrophotometric method gave a mean absorbance of 0.185 with a relative standard deviation of 2.46%. The detection limit corresponding to 3 times the standard deviation of the blank was found to be 2ngmL^–1.     

A Highly Efficient Chelating Polymer for the Adsorption of Uranyl and Vanadyl Ions at Low Concentrations

A new polymer containing double amidoxime groups per repeating unit was synthesized to enhance the metal ion uptake capacity. The adsorption properties of this new polymeric adsorbent, amidoximated poly(N,N-dipropionitrile acrylamide), for U(VI), V(V), Cu(II), Co(II) and Ni(II) ions were investigated by batch and flow-through processes at very low concentration levels (ppb). The chelating polymer showed high adsorption capacity for uranyl as well as vanadyl ions. In selectivity studies from a mixture of metal ions in aqueous solutions, the adsorbent showed high selectivity for uranyl and vanadyl ions in the following order: U(VI) > V(V) Co(II) = Cu(II) Ni(II) as determined by calculating the distribution coefficients D, of corresponding ions. The adsorption of uranyl and vanadyl ions from natural seawater by the new adsorbent was also examined in flow through mode.     

Radiation synthesis and uranyl‐ion adsorption of poly(2‐hydroxyethyl methacrylate/maleic acid) hydrogels

A new kind of copolymeric hydrogel adsorbent containing hydrophilic groups that both provides swelling in water and chelates with uranyl ions was synthesized, and its adsorptive ability for recovering uranium from aqueous media was investigated. The uranyl adsorption capacities of poly(2‐hydroxyethyl methacrylate/maleic acid) hydrogels were determined with a polarographic technique to be 3.2–4.8 (mg UO/g dry gel) from a 15‐ppm uranyl nitrate solution at pH, 6 depending on the molar content of maleic acid in the hydrogel. Adsorption studies showed that other stimuli, the temperature, and the ionic strength of the solution also have important roles in the uranyl‐ion adsorption capacity of these hydrogels. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 277–283, 2001     

Violation of Vavilov’s law upon excitation of luminescence of uranyl solutions at the short-wavelength absorption band (200–240 nm)

It was found that in the UV spectral region (200–240 nm) where intense absorption bands of the UO ₂ ²⁺ ion are located, excitation of its luminescence in solutions is not observed, thereby contradicting Vavilov’s law about independence of luminescence quantum yields from the excitation light wavelength. The violation of Vavilov’s law is explained in terms of nonradiative deactivation processes as the result of photoinduced electron transfer to the uranyl ion with its reduction to the pentavalent state and the subsequent disproportionation reaction to form uranium(IV). The presence of uranium(IV) ions during UV irradiation of uranyl solutions was proved by the chemiluminescent method.     

N,N,N′,N′-tetrabutylmalonamide as a new extractant for extraction of nitric acid and uranium(VI) in toluene

N,N,N,N-tetrabutylmalonamide (TBMA) was synthesized and used for extraction of uranyl(II) ion from nitric acid media in toluene. The effects of nitric acid concentration, extractant concentration, temperature and salting-out agent (LiNO₃) on distribution coefficients of uranyl(II) ion have been studied. The extraction of nitric acid is also studied. The main adduct of TBMA and HNO₃ is HNO₃. TBMA in 1.0 mol/l nitric acid solution. The 1:2:3 complex of uranyl(II) ion, nitrate ion and TBMA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBMA, and found that the NO ₃ ^– in the extraction species UO₂(NO₃)₂·3TBMA did not participate in coordination of uranyl(II) ion. The values of thermodynamic parameters have also been calculated.     

Spectrophotometric study of the complexation reaction between uranium/VI/ and one semicarbazone /SAS/

Salicylaldehyde-semicarbazone /SAS/ forms a complex with uranyl ion at pH 3.8±0.1 which has been studied spectrophotometrically. The results of Job's and moral ratio methods indicate 14 composition for the complex which at 230 nm obeys Beer's law in the range of 1 to 2500 ppb of uranium/VI/.     

Ditertiary phosphine derivatives of the heteronuclear cluster RuOs3(μ-H)2(CO)13

The heteronuclear cluster RuOs₃(μ-H)₂(CO)₁₃ (1) reacted readily with a number of ditertiary phosphines under chemical activation with trimethylamine-N-oxide. The solid-state and solution structures of these derivatives have been examined. Six structural types have been characterized crystallographically, including one in which a phenyl group migrates from the ditertiary phosphine ligand to the metal framework. There are many more isomers present in solution, most of which are rapidly inter-converting via hydride migrations.     

Solvent extraction of uranyl (II) ion with N,N,N,N-tetrabutylsucinylamide from nitric acid solution

N,N,N,N-tetrabutylsuccinylamide (TBSA) in a diluent composed of 50% trimethylbenzene (TMB) and 50% kerosene (OK) can extract uranyl (II) ion from nitric acid solution. The results of extraction study suggested the formation of the 121 uranyl (II) ion, nitrate ion and N,N,N,N-tetrabutylsuccinylamide complex as extracted specis. The values of thermodynamic functions have been calculated.     

Extraction of uranium/VI/ with di-2-ethylhexyldithiophosphoric acid in different organic solvents

Solvent extraction of uranium/VI/ from aqueous perchlorate media into cyclohexane, chloroform and carbon tetrachloride solutions of di-2-ethylhexyldithiophosphoric acid /HEhdtp/ was investigated. The treatment of the partition data showed that the extraction occurs via an ion-exchange mechanism similar to that established in benzene. The species extracted in the oxygen-free noncoordinating solvents mentioned are 12 complexes of uranyl ion with phosphorodithioato group. The high distribution ratio obtained is due to the long and branched alkyl chain /2-ethylhexyl/ of phosphorodithioato ligand, which increases the solubility of the uranium/VI/ chelate in the organic phase and decreases considerably its solubility in the aqueous phase.     

Performance for PAN-3 chelate fiber for adsorbing and separating trace uranium—determination by ICP-OES

An ICP-OES method is established for polyacrylamidoxime-carboxylic acid chelate fiber (PAN-3) adsorbing and separating trace uranium in waste water. The conditions for quantitative enrichment and desorption uranyl ions are investigated. The stability and the reuse performance of the chelate fiber are discussed. The interference of co-existent ions on uranyl ions as well as the analyses of samples are performed with satisfactory results. The lowest concentration of uranium determined by ICP-OES is 5 g/l, its RSD is 2.6%.     

Interaction of uranyl ions with snake venom proteins fromLachesis muta muta

The reaction product of uranyl nitrate with whole-protein Bushmaster snake venom in nitrate buffer at pH 3.5 has been studied. The maximum uptake of uranium was 291 mol U·g^–1 of venom. The infrared spectrum of the product showed an asymmetric O–U–O vibration at 921 cm^–1 typical of complex formation with the uranyl ion. Stability measurements with the UO ₂ ²⁺ -protein complex in neutral medium indicated moderate hydrolytic stability, with 14% dissociation after 16 hours at 0°C. Neutron irradiation and desorption studies with a²³⁵U-labelled complex showed that generated fission products such as lanthanides and barium were readily lixiviated at pH 7, whereas Ru and Zr were highly retained by the protein substrate.     

Spectrophotometrie determination of microgram quantities of hexavalent uranium

Summary A method is presented for the spectrophotometric determination of microgram amounts of hexavalent uranium by means of the azodyes Monochrome Black Blue G und Diamond Black PBB respectively.These two azodyes react with uranyl ions in an acetate buffered hydrochloric acid-methanolic medium under formation of colored chelates. 10 or 20 g uranium(VI)/10 ml measuring solution can still be determined with relatively high accuracy.

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Zusammenfassung Es wird eine Methode zur spektrophotometrischen Bestimmung von Mikrogrammengen Uran(VI) mittels der Azofarbstoffe Monochromschwarzblau G bzw. Diamantschwarz PBB angegeben. Diese beiden Azofarbstoffe reagieren mit Uranylionen in acetatgepuffertem salzsauermethanolischem Medium unter Bildung gefärbter Chelate. 10 bzw. 20 gUran(VI)/10ml Meßlösungkönnennoch mitrelativ hoher Genauigkeit bestimmt werden.

     

Extraction of uranium into a third phase of thorium nitrate—tributyl phosphate

Extraction of 0.05–0.25M uranyl nitrate into 30% tributyl phosphate (TBP) in dodecane from nitric acid solutions of thorium nitrate at equilibrium with its salt has been studied. Under investigated conditions a third (second organic) phase is formed. As the heavy organic phase extracts uranium, the calculated ratio of TBP to thorium and uranium sum decreases from 2.7 to less than 7. Electronic spectra show that in heavy organic phase approximately 80% of uranium is found as trinitrate complex, while in the light organic phase this complex is not detected. The measurements of dielectric constant () of the heavy phase reveal a frequency dependence of . The data obtained point to the existence of an ordered structure in the heavy organic phase.     

Theoretical prediction of a graphene-like 2D uranyl material with p-orbital antiferromagnetism

Versatile graphene-like two-dimensional materials with s-, p- and d-block elements have aroused significant interest because of their extensive applications while there is a lack of such materials with f-block elements. Herein we report a unique one composed of the f-block element moiety of uranyl (UO₂²⁺) through a global-minimum structure search. Its geometry is found to be similar to that of graphene with a honeycomb-like hexagonal unit composed of six uranyl ligands, where each uranyl is bridged by two superoxido groups and a pair of hydroxyl ligands. All the uranium and bridging oxygen atoms form an extended planar 2D structure, which shows thermodynamic, kinetic and thermal stabilities due to σ/π bonding as well as electrostatic interactions between ligands. Each superoxido ligand has one unpaired (2p_π*)¹ electron and is antiferromagnetically coupled through uranyl bridges with 2p_π*–5f_δ–2p_π* superexchange interactions, forming a rare type of one-dimensional Heisenberg chain with p-orbital antiferromagnetism, which might become valuable for application in antiferromagnetic spintronics.

An unprecedented graphene-like 2D uranyl material with p-orbital antiferromagnetism is found to be stable by computational investigations.     

η2-acylcarbonylvanadium-verbindungen

Substituted vanadium carbonyl compounds with η²-bonded acyl ligands (η²-RCO)V(CO)₃

(

= ditertiary phosphines or arsines: dppe, dppp, dppm, diars, arphos, dpase) have been prepared by photochemical reaction of [V(CO)₄

] with various substituted benzoyl chlorides and cyclopropanylcarbonyl chloride.Effects of aromatic substituents and

upon the thermal stability of the η²-acylcarbonylvanadium compounds are discussed. IR ν(CO) force constants and ⁵¹V NMR signals are linearly correlated with Hammett's σ constants of the aromatic substituents.The preparation of V(CO)₂Cl(diars)₂ is described.     

Diphenylarsinoderivate des Maleinsäureanhydrids und verwandte Verbindungen. Kristall- und Molekülstruktur des 2,3-Bis(diphenylstibino)maleinsäureanhydrids

The unusual properties of bis(diphenylphosphino)maleic anhydride and similar ditertiary phosphines has prompted the synthesis of analogous arsines and stibines. Bis(diphenylarsino)maleic anhydride,-maleic thioanhydride and-N-methyl maleic imide, bis(diphenylstibino)maleic anhydride (5) and-maleic thioanhydride are obtained as crystalline yellow or red compounds by the reaction of the corresponding 2,3-dichloromaleic acid derivatives with diphenyl(trimethylsilyl)arsine and-stibine resp. The uv/vis spectra and characteristic i.r. bands of selected compounds are given and compared with those of the corresponding phosphines. The strong shift of _C=C to lower wavenumbers observed in all compounds has caused the determination of crystal and molecular structure of5 by x-ray diffraction. Bond distances and angles are given. The complex formation of the new diarsine ligands has been examined by the preparation of Ni-, Cr- and Mo-carbonyl derivatives. As the first organylsulfane substituted maleic acid derivatives bis(phenylthio)maleic thioanhydride,-N-methyl-maleic imide and-maleic acid dimethylester are synthesized and described.

     

Photoluminescence of Uranium(VI): Quenching Mechanism and Role of Uranium(V)

The photoluminescence of uranium(VI) is observed typically in the wavelength range 400–650 nm with the lifetime of several hundreds μs and is known to be quenched in the presence of various halide ions (case A) or alcohols (case B). Here, we show by density functional theory (DFT) calculations that the quenching involves an intermediate triplet excited state that exhibits uranium(V) character. The DFT results are consistent with previous experimental findings suggesting the presence of photoexcited uranium(V) radical pair during the quenching process. In the ground state of uranyl(VI) halides, the ligand contributions to the highest occupied molecular orbitals increase with the atomic number (Z) of halide ion allowing larger ligand‐to‐metal charge transfer (LMCT) between uranium and the halide ion. Consequently, a larger quenching effect is expected as Z increases. The quenching mechanism is essentially the same in cases A and B, and is driven by an electron transfer from the quencher to the UO₂²⁺ entity. The relative energetic stabilities of the triplet excited state define the “fate” of uranium, so that in case A uranium(V) is oxidized back to uranium(VI), while in case B uranium remains as pentavalent.     

Influence of binary/ternary complex of imprint ion on the preconcentration of uranium(VI) using ion imprinted polymer materials

Ion imprinted polymer (IIP) materials were prepared for uranyl ion (imprint ion) by forming binary (5,7-dichloroquinoline-8-ol (DCQ) or 4-vinylpyridine (VP)) or ternary (5,7-dichloroquinoline-8-ol and 4-vinylpyridine) complexes in 2-methoxy ethanol (porogen) and copolymerizing in the presence of styrene and divinyl benzene as functional and crosslinking monomers, respectively and 2,2′-azobisisobutyronitrile as initiator. IIP particles were obtained by leaching the imprint ion in these polymer materials with 50% (v/v) hydrochloric acid, filtering, drying in an oven at 50 °C and grinding. Control polymer particles were also prepared under identical conditions. The above synthesized polymer particles were characterized by IR, CHN, X-ray diffraction, and pore size analyses. These leached polymer particles can now pick up uranyl ions from dilute aqueous solutions. The IIP particles obtained with ternary complex of uranyl ion alone gave quantitative enrichment of traces of uranyl ions from dilute aqueous solutions. The optimal pH for quantitative enrichment is 4.5-7.5 and eluted completely with 10 ml of 1.0 M HCl. The retention capacity of uranyl IIP particles was found to be 34.05 mg of uranyl ion per gram of polymer. Further, the percent extraction, distribution ratio, and selectivity coefficients of uranium and other selected inorganic ions were also evaluated. Five replicate determinations of 25 μg of uranium present in 1.0 l of aqueous solution gave a mean absorbance of 0.036 with a relative standard deviation of 2.50%. The detection limit corresponding to three times the standard deviation of the blank was found to be 5 μg l⁻¹.     

Colloidal Regularities of the Interaction between Uranium(VI) and the Cells of Metal-Resistant Bacillus cereus AUMC 4368 Bacterial Culture

Sorption of uranium(VI) by the cells of metal-resistant Bacillus cereus AUMC 4368 bacterium was studied in aqueous solutions as a function of pH, equilibrium concentration of metal, and the presence of co-ions with account of the changes in phase state of metals and biocolloids. Experimental data indicate that the sorption of uranium(VI) by negatively charged biocolloids is maximal at pH 4.2–4.5 (1.2 mM per 1g of dry biomass), when metal is present in the form of positively charged hydroxocomplexes. At pH 8, the interaction between uranium(VI) and the cells is inhibited due to the formation of negatively charged water-soluble hydroxocarbonate complexes and uranate ions. Co, Sr, Cu, Ca, Mg, and Zn ions do not influence the efficiency of sorption of uranium(VI) in a weakly acidic medium, but can cause inhibiting effect in neutral pH region. The most pronounced effect expressed in broadening of sorption range and in the heterocoagulation of uranyl is observed in the presence of Fe³⁺ ions. It was established that the binding of uranium(VI) occurs by the carboxyl surface groups of Bacillus cereuscell surface. Uranium(VI) is irreversibly bound by the carboxyl groups of cell surface and its efficient desorption is possible only during the interaction with citric acid or sodium hydrocarbonate with the formation of water-soluble complexes transferred to aqueous phase. It was shown that uranyl in the form of organocomplexes (citric, humatic, and fulvatic) is not sorbed by biocolloids.     

Cryoscopic Studies of the Uranyl Sulfate–Water, Uranyl Nitrate–Water, and Uranyl Nitrate–Nitric Acid–Water Systems

Freezing point lowerings of aqueous solutions of uranyl sulfate in the concentration range m 0.40 mol-kg^–1 and the activity and osmotic coefficients, which were calculated using the Pitzer equations for 2:2 electrolytes, are presented. Crystallization temperatures are reported for 0 to 13 molar nitric acid and 10–150 g uranium per liter uranyl nitrate–nitric acid–water solutions.