N,N,N',N'-Tetrabutyladipicamide as a new extractant in toluene of nitric acid and uranium (VI)

N,N,N',N'-Tetrabutyladipicamide (TBAA) was used for the extraction of nitric acid and uranyl(II) ion from nitric acid media into toluene. The effects of nitric acid, uranyl(II) ion, and extractant concentration, temperature and back extraction on the distribution coefficient of uranyl(II) ion have been studied. The main adduct of TBAA and HNO₃ is TBAA·HNO₃ in 1.0 mol/l nitric acid solution. The 1:2:2 complex of uranyl(II) ion, nitrate ion and TBAA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBAA. The values of the thermodynamic parameters have also been calculated.     

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.     

Nuclear magnetic resonance studies of edta in the presence of excess calcium or strontium

The equilibria which exist between metal ions, ethylenediaminetetraacetic acid (EDTA), and the resulting chelates have been thoroughly investigated by many techniques, emphasis being placed on the study of complexes containing a 1:1 ratio of metal ion to ligand. The results presented here are concerned with the observation of the chemical shift of the nonlabile protons of EDTA when excess calcium or strontium ions are present. The results yield evidence for a 2:1 complex. Formation constants for the equilibria believed to be in effect are given and a possible structure of the 2:1 complex is discussed.     

Complex formation of uranyl ions with polyaminopolycarboxylic acids

The complex formation of uranyl ions with ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid and triethylenetetraminehexaacetic acid has been studied by pH titrations, with computer evaluation of the titration data. For each ligand, the formation constants of a series of mono- and di-nuclear complexes were determined in 0.1 M KNO₃ at 25.0°C. The hydrolysis constants for uranyl ions and the dissociation constants of the ligands were also calculated. A novel approach was used to obtain realistic estimates of the uncertainties in the respective constants. Certain likely structures of the complexes are suggested.     

Ion chromatographic analysis of tetracyclines using polymeric column and acidic eluent

High-performance ion chromatography (HPIC) is first successfully used to analyze tetracycline antibiotics (TCs) in this work. The TCs are well separated on a solvent compatible polymeric cation-exchange column within 12 min. Isocratic elution with acetonitrile-hydrochloride is very advantageous for routine analysis. HPIC may be seen as a specific variant of the more common high-performance liquid chromatography (HPLC) for water-soluble and polar pharmaceuticals with low hydrophobicity. The detection limits (signal-to-noise ratio=3:1) of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), doxycycline (DC) are 10, 10, 20 and 20 microg l(-1), respectively. Samples are prepared by vortex mixing with an ethylenediaminetetraacetic acid disodium salt (Na2EDTA)-McIlvaine buffer (pH 4.0) solution and the mixture filtrates through a molecular weight cut-off filter. The method has been successfully applied to monitor the OTC removal rate through every reactor in the process of OTC manufacturing wastewater treatment by bio-chemical technology. It is also applicable to determine the TCs residues in milk and milk powder with satisfying results.     

Polyhydroxamic Acid Sorbents for Uranium Recovery

Crosslinked polyacrylamides were synthesized by solution polymerization using benzoyl peroxide as the radical initiator. The water–insoluble polymer obtained was functionalized by reacting with hydroxylamine to convert the amide group into hydroxamic acid group. The resultant functionalized polymer was characterized in terms of moisture uptake, elemental composition, IR spectra, thermal stability, exchange capacity and heavy metal sorption. The sorbent, obtained in particulate form, was investigated for its sorption properties with respect to uranium from uranyl nitrate solutions under unstirred batch conditions. This paper will concentrate on preparation, characterization and performance evaluation with respect to uranium sorption as a function of concentration, time, solution pH and temperature. The potential of this sorbent for uranium and other heavy metal ion recovery from sea water is ascertained.     

Interaction of uranium(VI) with phthalic acid

Phthalic acid, a ubiquitous organic compound found in soil, water, and in domestic and nuclear wastes can affect the mobility and bioavailability of metals and radionuclides. We examined the complexation of uranium with phthalic acid by potentiometric titration, electrospray ionization-mass spectroscopy (ESI-MS), and extended X-ray absorption fine structure (EXAFS) analysis. Potentiometric titration of a 1:1 U/phthalic acid indicated uranyl ion bonding with both carboxylate groups of phthalic acid; above pH 5 the uranyl ion underwent hydrolysis with one hydroxyl group coordinated to the inner-sphere of uranium. In the presence of excess phthalic acid, ESI-MS analysis revealed the formation of both 1:1 and 1:2 U/phthalic acid complexes. EXAFS studies confirmed the mononuclear biligand 1:2 U/phthalic acid complex as the predominant form. These results show that phthalates can form soluble stable complexes with uranium and may affect its mobility.     

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.     

Polarogkaphy of uranyl-malate complexes at moderately low temperature

The polarographic behavior of uranyl ion at ther dropping mercury electrode was examined in malic acid solution at 15°. The limiting regions of complex formation, polymerization, and reversibility as functions of pH value and ligand concentration were studied. The dimerization of the complexes was demonstrated by the currentvoltage curves and conductometric measurements. Three kinds of complex species with metal-ligand ratio of 2:1, 2:2, and 2:3 were identified.     

Polarographic studies of uranyl complexes with trans-and cis-butenedioic acids

The complexation of uranyl ion with fumaric and maleic acids was investigated by polarography and conductometry. The uranyl complexes of the two isomers differ: with fumaric acid, UO₂(HFum)₂ and UO₂Fum₂^2- were observed whereas with maleic acid, only one chelate, UO₂Mal₂^2-, was obtained. The dissociation constants obtained from the half-wave potential vs. pH plots were pK₁=3.05 and pK₂=4.55 for fumaric acid and pK₁=1.90 and pK₂=5.60 for maleic acid.     

Spectrophotometric Determination of Uranium with Sorbohydroxamic Acid as Reagent

Sorbohydroxamic acid forms with uranium an orange red, water soluble complex. The mole ratio of uranyl ion to compound is 1 to 1 under the investigated conditions. The formation constant of this chelate was also determined by the Likussar—Boltz method at a constant ionic strength of 0.1 M at 30°C as 2.10×10². The recommended procedure obeys Beer's law between 3.98ppm and 166.6ppm of uranyl ion at pH 3.8±0.1. Tolerances to cerium (IV) and thorium have been investigated. The procedure for the determination of uranium are made more specific by applying preliminary extraction of uranium by ether.     

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.     

Spectrophotometric studies on the uranyl-ascorbate complex

A systematic spectrophotometric study on the complexation of uranyl ions with ascorbic acid (vitamin C) is carried out. Factors influencing the sensitivity or selectivity of uranyl ascorbate are studied, and adequate elimination or control of the procedure is suggested. Results of the absorbance of uranyl ascorbate developed in HNO₃, HCl, and H₂SO₄ acid media within the concentration range (1.0–8.0) × 10⁻N show a marked dependence on the nature and concentration of the acid used. The observed decrease in color intensity at higher acidities is explained on the basis of the decomposing effect of hydrogen ions on uranyl ascorbate and the complexing effect on uranyl ions. Study of the stoichiometry of uranium:ascorbic acid complex in acid medium by continuous variation and molar ratio methods indicated the formation of 1:1 and 1:2 complexes. The formation constant of the 1:1 complex as calculated by these two methods was found to be 4.8 × 10⁴ and 5.0 × 10⁴, respectively. Best suitable conditions for stabilizing and increasing the color intensity of uranyl ascorbate, dependent on the nature of the medium and pH of the solution, are suggested for the determination of ascorbic acid in pharmaceutical preparations using this method.     

STUDY OF LUMINESCENT FORMS OF THE URANYL ION

Luminescence spectra and luminescence decay kinetics of uranyl sulphate water and uranyl nitrate acetone solutions of different concentrations have been studied. Similar experiments have been done with uranyl sulphate powder under vacuum. It has been experimentally shown that the hydrolysis of uranyl sulphate in water takes place, and under low salt concentrations (0.1-4.0 times 10^-4 M) a luminescence of a basic form of the photoexcited ion with a tentative structure of UO₂OH⁺* has been observed. The luminescence of the acidic form UO⁺* has been observed under higher salt concentrations (1–4 times 10^-2 M) in water and under any salt concentration in acetone. The acidic form has the characteristic emission spectrum possessing vibrational structure. The luminescence concentrational quenching of both photoexcited uranyl forms and exciplex emission have not been observed. The effect of a number of organic quenchers and molecular oxygen on uranyl luminescence has been studied. There is no luminescence quenching by O₂ up to 2 times 10⁶ Pa (20 atm) pressure. The low effectiveness of energy transfer from the photoexcited uranyl forms has been explained in terms of strong steric screening of 5f-uranium (VI) orbital by oxygen atoms and by external filled up uranium electronic shells.     

Complexation of poly(acrylic acid)s with uranyl ion

The complexation of uranyl ion (UO₂²⁺) in aqueous solution with polymers containing carboxylic acid groups was studied potentiometrically. Overall formation constants of the uranyl complexes with poly(methacrylic acid) and crosslinked poly(acrylic acid) were much larger than those with the corresponding low molecular carboxylic acids. Decrease in the viscosity of the polymer solution on adding uranyl ion indicated that poly(acrylic acid) forms intra-polymer chelates with uranyl ion. The crosslinked poly(acrylic acid) adsorbed uranyl ions at higher efficiency than transition metal ions.     

堆积模型在萃取中的应用I: 水相介质协同效应

根据推积模型提出一种新的协萃体系,即:(简单阴离子)1+(简单阴离子)2+萃取剂,并以实验证实了水相混合介质的协同效应.研究了UO2/OAc,C1/TBP-二甲苯体系的协萃效应,测定了萃合物的组成以及各种影响分配比的因素.     

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     

In Process Citation

A colorimetric micromethod is proposed for determination of phosphates in various materials (biological substances, pharmaceuticals and food). It is based on precipitation of magnesium uranyl phosphate, which is then dissolved in dilute sulphuric acid, and the uranyl ion is determined spectrophotometrically via the dark red colour of uranyl ferrocyanide. The sensitivity is 0.01 mg of P, and the average error 1%. The method is very simple and applicable to many types of sample.     

Thorium(IV) and uranium(VI) complexes with some heterocyclic azo dyes in absolute ethanol

Thorium(IV) and uranium(VI) chelate complexes with PAN, PAR, TAN and TAR have been studied in absolute ethanol. The uranyl ion forms complexes with PAN, PAR, TAN and TAR in the metal to ligand molar ratio of 1:1. Thorium(IV) forms complexes with PAR, TAR and TAN in the molar ratio of 1:2. In case of Th(IV)-PAN complexes the molar ratio is 1:2.4. The stability constants for all the above complexes have been worked out using the mole ratio method. The kinetics of aquation of Th(IV)-PAN complexes indicate that PAN acts as a tridentate ligand.     

Uranyl luminescence decay in phosphoric acid solution

Uranyl luminescences in phosphoric acid system has been studied. Uranyl excited by a nitrogen laser shows single or biexponential luminescence decays in the phosphoric acid system. When the uranyl ion or phosphoric acid concentration are lower, a single exponential luminescence decay appears, whereas at higher uranyl ion or phosphoric acid concentrations, biexponential decay is observed. Time-resolved spectra of uranyl in this system are measured. The reasons of the phenomena are tentatively established.