Biochar derived from Salvadora persica branches biomass as low-cost adsorbent for removal of uranium(VI) and thorium(IV) from water

Journal of Radioanalytical and Nuclear Chemistry - In recent years, biochar based adsorbents have been given more attention for organic and inorganic pollutants removal. Therefore, in this study, a...     

Salvadora Persica branches biomass adsorbent for removal of uranium(VI) and thorium(IV) from aqueous solution: kinetics and thermodynamics study

Adsorption isotherms of U(VI) and Th(IV) in water were obtained and removal kinetics was studied. The main functional groups on the surface of Salvadora Persica branches adsorbent were identified using a Fourier-transform infrared and the surface morphology of adsorbent was characterized by a Scanning Electron Microscope. Effects of the U(VI) and Th(IV) initial concentrations, contact time, the mass of adsorbent loading, pH of the solution were investigated at 25?±?0.3 °C. The efficiencies with which this adsorbent removes U(VI) and Th(IV) from their solutions in water are reported. The adsorption isotherm fitted the Freundlich model. The adsorption of U(VI) and Th(IV) follows the pseudo-second order kinetic with squared correlation coefficients (R²) close to 1.0. The thermodynamic parameters (i.e. the free energy (\(\Delta G_{\text{ads}}^{o}\)), the enthalpy (\(\Delta H_{\text{ads}}^{o}\)) and the entropy of adsorption (\(\Delta S_{\text{ads}}^{o}\)) for the adsorption of U(VI) and Th(IV) on the Salvadora Persica branches adsorbent were reported.

     

Pomegranate peel waste biomass modified with H3PO4 as a promising sorbent for uranium(VI) removal

Journal of Radioanalytical and Nuclear Chemistry - Modified pomegranate peel was utilized as a sorbent for the biosorption of uranium(VI) from the aqueous solution. The biosorbent was characterized...     

Use of immobilized tannin adsorbent for removal of Cr(VI) from water

PIXE studies on pure metal targets surrounded by insulating material produced enhanced X-ray yields at comparatively low proton energies. Specially prepared metal discs of selected transition elements were embedded in Macor target holders and irradiated with 700 keV protons. Improved X-ray yields of up to more than 300% were observed. It was found that the enhanced yields were affected by the incident beam current due to a “leakage” effect. The recorded time-dependent spectra showed similar charge build-up and discharge patterns as those originally obtained for non-conducting samples. A possible mechanism for the enhancement is discussed.     

The removal of uranium (VI) from aqueous solutions onto natural sepiolite

The adsorption of uranium (VI) from aqueous solutions onto natural sepiolite has been studied using a batch adsorber. The parameters that affect the uranium (VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, and temperature, have been investigated and optimized conditions determined. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of sepiolite and experimental results showed this to be 34.61 mg · g^?1. The experimental results were correlated reasonably well by the Langmuir adsorption isotherm and the isotherm parameters (Q_o and b) were calculated. Thermodynamic parameters (ΔH° = ?126.64 kJ · mol^?1, ΔS° = ?353.84 J · mol^?1 · K^?1, ΔG° = ?21.14 kJ · mol^?1) showed the exothermic heat of adsorption and the feasibility of the process. The results suggested that sepiolite was suitable as sorbent material for recovery and adsorption of uranium (VI) ions from aqueous solutions.     

Efficient adsorption of uranium (VI) from aqueous solution by a novel modified steel slag adsorbent

Journal of Radioanalytical and Nuclear Chemistry - Using steel slag as a raw material, a new type of adsorption material has been prepared by acid modification method. The preparation conditions of...     

Highly efficient removal of uranium(VI) from aqueous solutions by poly(acrylic acid-co-acrylamide) hydrogels

In this study, poly(acrylic acid-co-acrylamide) (PAAAM) hydrogels were used to remove uranium (VI) ions in wastewater and characterized by FTIR, SEM, EDX. The effects of pH value, coexistence of ionic strength, contact time, initial U (VI) ion concentration and adsorption temperature were also studied. Adsorption data fitted well with pseudo-second-order, intra-particle diffusion model and Langmuir isotherm mode, the maximum adsorption capacity of U(VI) was 713.24 mg g^?1. Thermodynamic analysis shows that the adsorption of U(VI) is spontaneous endothermic. PAAAM hydrogel has excellent regeneration performance, after five time adsorption–desorption cycles, the adsorbent still maintained 99.24% adsorption capacity.     

Characterization of the sorption of uranium(VI) on different complexing resins

The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs–Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions.The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with log_110i=–1.16, in more acidic solution, and ML₂ with log_120i=–5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML₂, in more acidic solution, with log_120i=–3.16. In the presence of the ligand EDTA, the complex ML₂(OH)₂ was characterized with log_12–2i=–5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered.     

Determination of uranium(VI) in natural waters after preconcentration on adsorbent containing m-aminophenol fragments

Sorption and complexing properties of a modified adsorbent based on a maleic anhydride-styrene copolymer towards uranium(VI) are studied and the main quantitative characteristics of the metal ion sorption are determined. An adsorbent containing m-aminophenol fragments is proposed for the selective sorption of uranium(VI) from solutions. The optimal sorption conditions have been found. The recovery of uranium(VI) under the optimal conditions exceeds 95%. A procedure of the sorption photometric determination of uranium(VI) in sea water is developed.     

Microdetermination of uranium (VI)

Summary A new method has been evolved for the separation and estimation of UO₂ ²⁺ from Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺, Ga³⁺, In³⁺, Tl³⁺, La³⁺, Ti⁴⁺, Zr⁴⁺ and Th⁴⁺ with the sodium salt of benzilic acid as precipitating and chelating agent andn-butanol as solvent for solvent extraction. All these cations except UO₂ ²⁺ are precipitated by benzilic acid; UO₂ ²⁺ forms a deep yellow complex extractable byn-butanol. The uranium can be determined in the organic phase spectrophotometrically at 430 nm. The pH range over which the separation can be carried out is 2.6–4.0. Few anions and cations interfere.

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Zusammenfassung Eine neue Methode der Trennung und Bestimmung von UO₂ ²⁺ neben Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺, Ga³⁺, In³⁺, Tl²⁺, La³⁺, Ti⁴⁺, Zr⁴⁺ und Th⁴⁺ wurde ausgearbeitet. Das Natriumsalz der Benzilsäure dient als Färbungs- und Komplexbildungsmittel und n-Butanol zur Extraktion. Alle angeführten Kationen mit Ausnahme von UO₂ ²⁺ werden von Benzilsäure gefällt; UO^{2 2+} bildet einen tiefgelben, mit n-Butanol extrahierbaren Komplex und kann in der organischen Phase spektrophotometrisch bei 430 nm bestimmt werden. Die Trennung kann bei pH 2,6 bis 4,0 durchgeführt werden. Nur wenige Anionen und Kationen stören.

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Résumé On développe une nouvelle méthode pour la séparation et l'évaluation de UO₂ ²⁺ dans Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺, Ga³⁺, In³⁺, Tl³⁺, La³⁺, Ti⁴⁺, Zr⁴⁺ et Th⁴⁺, par le sel de sodium de l'acide benzilique comme agent précipitant et chélatant et le N-butanol comme solvant pour l'extraction par solvant. Tous ces cations, sauf UO₂ ²⁺, précipitent par l'acide benzilique; UO₂ ²⁺ forme un complexe jaune intense que l'on peut extraire par le N-butanol. On peut doser l'uranium en phase organique par spectrophotométrie à 430 nm. La séparation peut s'effectuer dans le domaine de pH de 2,6 à 4,0. Peu d'anions et de cations interfèrent.

     

The removal of uranium(VI) from aqueous solutions onto activated carbon: kinetic and thermodynamic investigations

The adsorption of uranium(VI) from aqueous solutions onto activated carbon has been studied using a batch adsorber. The parameters that affect the uranium(VI) adsorption, such as contact time, solution pH, initial uranium(VI) concentration, and temperature, have been investigated and optimized conditions determined (contact time 240 min; pH 3.0+/-0.1; initial uranium concentration 100 mg/L; temperature 293.15 K). The experimental data were analyzed using sorption kinetic models (pseudo-first- and pseudo-second-order equations) to determine the equation that fits best our experimental results. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of activated carbon and experimental results showed this to be 28.30 mg/g. The Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) models have been applied and the data correlate well with Freundlich model and that the sorption is physical in nature (the activation energy Ea=7.91 kJ/mol). Thermodynamic parameters (DeltaHads0=-50.53 kJ/mol, DeltaSads0=-98.76 J/mol K, DeltaGads(293.15 K)0=-21.61 kJ/mol) showed the exothermic heat of adsorption and the feasibility of the process.     

Extraction of uranium(IV) and uranium(VI) by primary and tertiary-amines from sulphate solutions

In developing a method for possible low level isotopic enrichment, which uses to advantage the equilibrium isotope effect observed during U(1V)-U(VI) electron exchange reaction in sulphate solutions, details of a solvent extraction process involving high concentration of a mixture of U(IV) and U(VI) and at low acid concentrations, are described. The extraction behaviour of uranium under these conditions is discussed. During the extraction with amines, U(IV) tended to get oxidised in sulphate solutions.     

Application of Brazilian kaolinite clay as adsorbent to removal of U(VI) from aqueous solution: Kinetic and thermodynamic of cation-basic interactions

The compound N¹-[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of ²⁹Si and ¹³C. The well-defined peaks obtained in the ¹³C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k₂ values 16.0 and 25.1 mmol g⁻¹ min⁻¹ ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations.     

LIX 84 as an extractant for throium(IV), uranium(VI) and molybdenum(VI)

The extraction order of Th(IV), U(VI) and Mo(VI) based on pH_0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H₂SO₄>HNO₃>HClO₄ and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H₂SO₄, HNO₃ and HClO₄ acid solutions. The diluents C₆H₆, CCl₄ and CHCl₂ are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.     

Hydrothermal leather waste by hydrothermal method for uranium (VI) removal from a Simulated Saline Solution

Hydrothermal leather waste was prepared by hydrothermal method, using leather waste as the precondition and applying the adsorption of uranium (VI) in solution. The effects of pH value, adsorption time and initial concentration of uranium (VI) on the adsorption efficiency were investigated. The adsorption process was in accordance with the pseudo‐second‐order kinetic model and Freundlich adsorption isotherm model. Kinetic and thermodynamic studies showed that the adsorption process was endothermic and spontaneous, and it reached adsorption equilibrium in 240 min. In the simulated high salinity environment, the adsorbent exhibited excellent adsorption rate on the trace of uranium (VI). The adsorbent was characterized by scanning electron microscopy, flourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, and it was found that the adsorption mechanism was coordinated complex.