Uptake Of Uranyl Ions Research Articles

Grafting of poly(vinyl pyrrolidone) with citric acid using gamma irradiation

Ternary mixtures of poly(vinyl pyrrolidone) (PVP), citric acid (CA) and water were irradiated at various gamma ray doses. Copolymer swelling and gelation% were determined with respect to the irradiation dose and PVP/CA composition. The gelation% increases with increasing the irradiation dose, but decreases with increasing the CA content in the graft copolymer. The swelling% of the prepared hydrogels decreases with increasing the irradiation dose and CA content in the copolymer, as a result of an increase in the crosslink density and the hydrogen bonds, respectively. The ion exchange capacity and the uptake of uranyl ions increase with increasing the CA content in the graft copolymer.

Uranyl Ion Uptake from Aqueous Solutions by Chemically Cross-linked Polyelectrolyte CAMA Hydrogels

Uranyl ion adsorption from aqueous solutions has been investigated by chemically cross-linked polyelectrolyte acrylamide/maleic acid (CAMA) hydrogels. CAMA hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), maleic acid (MA), and water by free radical polymerization in aqueous solution using multifunctional cross-linkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4-butanediol dimethacrylate (BDMA). Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of adsorbent on the uranyl ion adsorption were examined. In the experiments of the sorption, L type sorption in the Giles classification system was found. Some binding parameters such as initial binding constant (K i ), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (Ô) for CAMA hydrogel-uranyl ion binding system were calculated by using Langmuir linearization method. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 3.29 × 10−4 − 15.87 × 10−4 mol uranyl ion per gram for CAMA hydrogels. Adsorption of uranyl ion was changed range 8.17–48.10%.

Enhancement of uranyl ion uptake by the prestructuring of poly(2‐hydroxyethyl methacrylate itaconic acid) hydrogels in the presence of lead and cadmium ions/polarographic determination

AbstractPoly(2‐hydroxyethyl methacrylate/itaconic acid) [P(HEMA/IA)] hydrogels were prepared by the γ‐ray irradiation of aqueous solutions. In the presence of lead and cadmium ions, the UO ion uptake on P(HEMA/IA) hydrogels was investigated with two types of hydrogel systems prepared by nonprestructuring and prestructuring methods. A differential pulse polarographic technique was used for the determination of trace quantities of uptake elements by the measurement of the reduction peak currents at −200, −410, and −580 mV for UO, Pb(II), and Cd(II) ions, respectively. Hydrogels prestructured with UO ions took up approximately 45% more UO ions than hydrogels prepared by the usual procedure. The UO ion uptake capacity of the hydrogels increased with an increasing percentage of itaconic acid in the hydrogel systems and an increasing concentration of UO ions in the presence of Pb(II) and Cd(II) ions. Uptake studies showed that other stimuli, such as the temperature and ionic strength of the solutions, also influenced the UO ion uptake capacity of the P(HEMA/IA) hydrogels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2385–2390, 2003

Quinoline-8-ol-immobilized Amberlite XAD-4: synthesis, characterization, and uranyl ion uptake properties suitable for analytical applications.

Amberlite XAD-4 has been functionalized by coupling it with 5-aminoquinoline-8-ol after acetylation. The resulting resin has been characterized by elemental analysis and IR spectra and has been used for preconcentrating uranyl ions prior to its determination by spectrophotometry. The optimum pH value for quantitative sorption is 4-6, and desorption can be achieved by using 5 mL of 1 mol L(-1) HCl. The sorption capacity of the resin is 11.5 mmol g(-1). The effect of various cations and anions on the preconcentration of uranium in conjunction with the determination procedure has been studied and we have found that none of the ions interfere except thorium. The enrichment factor for preconcentration of uranium was found to be 200. Ten replicate determinations of 40 micro g of uranium present in 1 L of sample gave a mean absorbance of 0.185 with a relative standard deviation of 2.64%. The detection limit corresponding to three times the standard deviation of the bank was found to be 2 micro g L(-1). The validation of the developed preconcentration procedure was carried out by successfully analyzing standard marine sediment reference material. The uranyl content of sediment and soils is estimated by spectrophotometry after its preconcentration with the above chelating resin.

Enhancement of uranyl ion uptake by prestructuring of acrylamide-maleic acid hydrogels

Acrylamide–maleic acid (AAm–MA) hydrogels were prepared by gamma-irradiation of their aqueous solutions. UO2+2 ion uptake on P(AAm–MA) hydrogels was investigated using two types of gel systems prepared by a simple irradiation method and a prestructured reaction. It has been observed that gels prestructured with UO2+2 ions adsorbed approximately 15–20% more UO2+2 ions than gels prepared in pure water (the usual method). It was also found that the uranyl ion adsorption capacity of hydrogels increased with an increasing amount of maleic acid in the gel system and an increasing concentration of uranyl ion in the solution. A possible interaction mechanism between the groups in the copolymeric gels and UO2+2 ion has been proposed based on the stoichiometry and the spectroscopic evidence. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 284–289, 2000

Factors affecting the extraction of uranyl ions from radioactive waste using natural materials

Uranium is considered to be one of the most important elements used in nuclear technology. Different authors have worked deeply with developing the methods and materials used for uranium separation, concentration, and refining. In this work, uptake and release behavior of uranyl ions by wood powder from nitrate medium was studied. The factors affecting both processes were discussed.

Behaviors of Acrylamide/Itaconic Acid Hydrogels in Uptake of Uranyl Ions from Aqueous Solutions

Abstract In this study, adsorptions of uranyl ions from two different aqueous uranyl solutions by acrylamide-itaconic acid hydrogels were investigated by a spectroscopic method. The hydrogels were prepared by irradiating with γ-radiation. In the experiment of uranyl ions adsorption, Type II adsorption was found. One gram of acrylamide-itaconic acid hydrogels sorbed 178–219 mg uranyl ions from the solutions of uranyl acetate, 42–76 mg uranyl ions from the aqueous solutions of uranyl nitrate, while acrylamide hydrogel did not sorb any uranyl ion. For the hydrogel containing 40 mg of itaconic acid and irradiated to 3.73 kGy, swelling of the hydrogels was observed in water (1660%), in the aqueous solution of uranyl acetate (730%), and in the aqueous solution of uranyl nitrate (580%). Diffusions of water onto hydrogels were a non-Fickian type of diffusion, whereas diffusions of uranyl ions were a Fickian type of diffusion.

Amidoxime resins based on poly(acrylonitrile‐co‐vinylidene chloride‐co‐divinylbenzene) and their behavior in uptake of uranium from sea water

AbstractAmidoxime resins were derived from poly(acrylonitrile‐co‐vinylidene chloride‐co‐divinyl‐benzene) beads, which were prepared by suspension polymerization of the ternary monomeric mixtures in the presence of 4‐methyl‐2‐pentanone (MIBK) or 1,2‐dichloroethane (DCE) as the diluent (porogen), in order to clarify the effect of copolymerized vinylidene chloride on properties of the resulting amidoxime resins. Pore structure analyses of the copolymers as well as of their amidoximated derivatives clarified that MIBK yields larger pores than does DCE and then the latter gives larger specific surface areas than does the former. On the other hand, chemical properties of the amidoximated resins, such as anionexchange capacities and uranyl ion uptake, were not eseentially affected by the diluent species, indicating that both MIBK and DCE as the porogen lead to the amidoxime resins with almost the same ability in recovery of uranium from sea water. The uranium recovery decreased with increase in the vinylidene chloride content, but the decrease in the recovery was minor up to the 10 mol % of vinylidene chloride. It was also clarified that the uranium recovery by the amidoxime resins containing vinylidene chloride is greatly enhanced by the alkali treatment. © 1994 John Wiley & Sons, Inc.

Uptake of uranyl ions by new sorbing polymers: discussion of adsorption isotherms and pH effect

Chitosan is a natural polymer well known for its efficient uptake of heavy metals. The modification of this polymer by the substitution of functional groups from organic acids allows new sorbents with high sorption capacities to be obtained: NDTC with ascorbic acid and glutamate glucan with oxo-2-glutaric acid. The mechanism of sorption is investigated and several sorption models are applied such as the Freundlich, Langmuir and Temkin models which fit experimental results well. These results are explained by the heterogeneity of the polymer surface, the variability of metal species in solution and possible interactions between the molecules sorbed. The effects of several parameters such as pH and metal ion concentration are examined and demonstrate the relative importance of metal speciation on sorption performances and mechanisms. The grafting of functional groups creates some heterogeneity of sorption energy, which explains the selectivity seen in the best models. Metal ions are firstly bound onto more energetic sites (nitrogen groups) and later onto other substituting functions.

The effect of anions on uranium accumulation by free and immobilized cells of aCitrobactersp. Implications for the treatment of metal‐bearing liquid wastes

Abstract Many metal‐bearing wastes are highly acidic and neutralization prior to treatment yields liquid effluents of high ionic strength. The interfering effects of an excess of chloride, sulfate and nitrate ions on metal accumulation by a Citrobacter sp. were investigated. Sulfate ion (300 mM) did not interfere with metal accumulation although 15–20% of the activity was lost in the presence of nitrate ion. This was attributable to an effect on the phosphatase enzyme responsible for metal uptake. Chloride ion interfered with uranyl ion uptake by cells immobilized in a flow‐through bioreactor but had little effect on metal accumulation by batch cell suspensions. These results have implications for the choice of bioreactor design for bioprocess use.

Uranium accumulation in the lichen Cladonia rangiferina. Part I. Uptake of cationic, neutral, and anionic forms of the uranyl ion

Evidence from published work is first reviewed to show that cationic, neutral, and anionic complexes of the uranyl ion are available to plants growing in uranium-enriched environments. The results of a study on the uptake of uranyl ions by the lichen Cladonia rangiferina L. Wigg. are then presented. Uptake was examined from three different uranyl solutions each predominantly containing a single species: namely, the cation [Formula: see text] (in distilled water), the neutral 1:1 complex with phthalate (UO2L), and the anionic complex of oxalate [Formula: see text]. Uptake decreased along the chemical speciation series: cation [Formula: see text] neutral species [Formula: see text] anion. Maximum observable capacities for this series were, respectively, 49, 17, and 1.6 μmol/g for 1-g samples in 100 mL containing 840 μmol of total uranium. The [Formula: see text] uptake curve was observed to be monophasic, while biphasic patterns appeared to apply for the phthalate and oxalate buffers. Heat-killed tissues showed marginally higher uptake capacities than live material.

A study of positive staining for electron microscopy using collagen as a model system—II. Staining by uranyl ions

The staining behaviour of uranyl salts was studied using reconstituted periodic-banded collagen fibrils as a model system and comparing electron-optical data and collagen sequence data by a computer-aided correlation procedure. Because it is only weakly dissociated and a variety of ionic uranyl complexes (cationic, neutral and anionic) coexist in aqueous solution, uranyl acetate stains not only negatively-charged but also positively-charged side-chains on the collagen. The relative uptake on charged groups of opposite sign depends on several factors, including the concentration and pH of the staining solution and the presence of extraneous phosphate groups (from the buffer used to reconstitute the fibrils), but no conditions could be found which allowed uranyl acetate to stain negative charges only. When the stain was uranyl nitrate, known to dissociate strongly in aqueous solution, uptake of uranyl ions was predominantly (although not exclusively) on negative charges on the collagen, provided that extraneous phosphate had previously been removed by dialysis.

Uptake and Binding of Uranyl Ions by Barley Roots

After undergoing the processing for electron microscopy, bound uranyl ions are revealed as characteristic electron-opaque crystals. Meristematic walls and associated vesicles become heavily labeled, while pinocytotic accumulation into vacuoles seems probable in cap cells and those just behind the meristem. The endodermal Casparian strip and suberinized lamella are effective barriers to the passage of uranyl ions.