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Abstract  

The sorption of uranium(VI) from aqueous solutions was investigated using synthesized magnesium silicate hollow spheres as a novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, contact time and initial U(VI) concentrations on uranium sorption efficiency. The desorbing of U(VI) and the effect of coexisting ions were also investigated. Kinetic studies showed that the sorption followed a pseudo-second-order kinetic model. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 25–400 mg/L. The maximum uranium sorption capacity onto magnesium silicate hollow spheres was estimated to be about 107 mg/g under the experimental conditions. Desorption of uranium was achieved using inorganic acid as the desorbing agent. The practical utility of magnesium silicate hollow spheres for U(VI) uptake was investigated with high salt concentration of intercrystalline brine. This work suggests that magnesium silicate hollow spheres can be used as a highly efficient adsorbent for removal of uranium from aqueous solutions.

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Abstract  

In this study, radiocesium sorption on ceramic clay was investigated as a function of particle size and initial 137Cs concentration using a batch method. Ceramic clay samples taken from the Söğüt(İnisar) clay deposit were composed of kaolinite, dickite and quartz. The equilibrium time and the liquid–solid ratio were determined as 60 min and 250 mL g−1, respectively. The distribution coefficients (K d) for variable liquid–solid ratio and the percentage adsorption (P Ad) were calculated. The values of K d and P Ad ranged from 483 to 3165 mL g−1 and 34–93%, respectively. The K d and P Ad values increased with increasing particle size, but decreased with increasing initial concentration. The sorption data were interpreted in terms of a Langmuir isotherm. The results indicated that the Söğüt(İnhisar) ceramic clay has good sorption capacity for cesium.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: G. Lujanienė, P. Beneš, K. Štamberg, J. Šapolaitė, D. Vopalka, E. Radžiūtė, and T. Ščiglo

Abstract  

Sorption of Cs, Pu and Am on natural clay of complex composition was studied to better understand the sorption mechanisms. It was found that cesium sorption to natural clay was affected by its coatings and by the ionic strength of solution. The sorption of Pu and Am on the clay was compared with that on synthetic goethite, hematite and magnetite, representing components of the clay coatings. The sorption was quantitatively interpreted using models assuming ion exchange and/or complex formation on the “layer sites” and “edge sites” of the clay and its coatings. Constants characterizing properties of the sites and sorption equilibria were determined.

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Abstract  

A novel composite adsorbent, magnetite/hydroxyapatite (Fe3O4/HAP) composites, was prepared by biowaste chicken eggshell for the purpose of removing radiocobalt from aqueous solutions. It highlighted that more than 92% Co(II) could be removed by using the developed composites under the experimental conditions. The maximum sorption capacity of Co(II) on Fe3O4/HAP composites was 6.9 × 10−4 mol/g. The coexisted foreign ions, e.g., ClO4 , NO3 , Cl, Na+ and K+, did not interfere the elimination of Co(II) from aqueous solutions, while Mg2+ did. The sorption process was found to be controlled well by pseudo-second-order and intra-particle diffusion models, and the equilibrium data were simulated by Langmuir model very well with high correlation coefficients. The thermodynamic parameters confirmed the spontaneity and endothermic nature of Co(II) sorption processes. After sorption, the Fe3O4/HAP composites could be effectively and fleetly separated from aqueous solutions by magnetic separation technique in large scale. The Fe3O4/HAP composites are suitable materials in the preconcentration of Co(II) from large volumes of aqueous solutions.

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Abstract  

MX-80 bentonite was characterized by XRD and FTIR in detail. The sorption of Th(IV) on MX-80 bentonite was studied as a function of pH and ionic strength in the presence and absence of humic acid/fulvic acid. The results indicate that the sorption of Th(IV) on MX-80 bentonite increases from 0 to 95% at pH range of 0–4, and then maintains high level with increasing pH values. The sorption of Th(IV) on bentonite decreases with increasing ionic strength. The diffusion layer model (DLM) is applied to simulate the sorption of Th(IV) with the aid of FITEQL 3.1 mode. The species of Th(IV) adsorbed on bare MX-80 bentonite are consisted of “strong” species

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{YOHTh}}^{4 + }$$ \end{document}
at low pH and “weak” species
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{XOTh(OH)}}_{3}$$ \end{document}
at pH > 4. On HA bound MX-80 bentonite, the species of Th(IV) adsorbed on HA-bentonite hybrids are mainly consisted of
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{YOThL}}_{3}$$ \end{document}
and
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{XOThL}}_{1}$$ \end{document}
at pH < 4, and
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{XOTh(OH)}}_{3}$$ \end{document}
at pH > 4. Similar species of Th(IV) adsorbed on FA bound MX-80 bentonite are observed as on FA bound MX-80 bentonite. The sorption isotherm is simulated by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models, respectively. The sorption mechanism of Th(IV) on MX-80 bentonite is discussed in detail.

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Abstract  

The bentonite from Gaomiaozi county (Inner Mongolia, China) (denoted as GMZ bentonite) was characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The effect of pH, contact time, ionic strength, humic acid (HA) and Eu(III) concentrations on Eu(III) sorption to the GMZ bentonite was studied by batch technique under ambient conditions. The sorption of Eu(III) on GMZ bentonite was strongly dependent on pH and independent of ionic strength. The sorption of Eu(III) on GMZ bentonite was mainly dominated by surface complexation rather than by ion exchange. The presence of HA enhanced Eu(III) sorption at low pH values, but decreased Eu(III) sorption at high pH values. The enhanced sorption of Eu(III) on GMZ bentonite at low pH was attributed to the strong complexation of Eu(III) with surface adsorbed HA on GMZ bentonite and the reduced sorption of Eu(III) at high pH was attributed to the formation of soluble HA–Eu complexes in aqueous solution. The strong sorption of Eu(III) on GMZ bentonite suggested that the GMZ bentonite could be used as the backfill material in nuclear waste disposal.

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Abstract  

LIII edge X-ray Absorption Fine Structure (XAFS) spectroscopic study of Eu(III) sorbed on γ-alumina from aqueous solutions of different pH (values ranging from 6 to 8) has been carried out at XAFS beam line of Elettra Synchrotron facility, Italy, in transmission mode. Extended X-ray Absorption Fine Structure spectra of reference compounds, namely, Eu2O3, Eu(OH)3 and Eu-aquo complex in solution, were also measured. The data were analyzed using the IFEFFIT suite of code. XAFS spectra of the sorption samples is dominated by the Eu–O near neighbor co-ordination at distance 2.4 ± 0.1 Å. 8–9 oxygen atoms, coming from both coordinating water molecule and oxygen atoms from alumina surface, surround the Eu(III) in the surface complex. Next near neighbor atoms in all the sorption samples consist of Al at distance ~3.6 and 3.8 Å, which on comparison with literature data indicates towards Eu(III) bidentate binding to apical oxygen of two different alumina octahedra on γ-alumina surface.

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Abstract  

The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions. The removal of 60Co(II) from wastewaters by MnO2 was studied as a function of various environmental parameters such as shaking time, pH, ionic strength, foreign ions, and humic substances under ambient conditions. The results indicated that the sorption of 60Co(II) on MnO2 was strongly dependent on pH and ionic strength. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on MnO2 surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of HA/FA enhances 60Co(II) sorption at low pH values, whereas reduces 60Co(II) sorption at high pH values. The Langmuir and Freundlich models were used to simulate the sorption isotherms of 60Co(II) at three different temperatures of 298.15, 318.15 and 338.15 K. The thermodynamic parameters (ΔH 0, ΔS 0 and ΔG 0) calculated from the temperature dependent sorption isotherms indicated that the sorption process of 60Co(II) on MnO2 was endothermic and spontaneous.

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Abstract  

Sorption of Th(IV) on Zr2O(PO4)2 as a function of contact time, reaction temperature, pH, ionic strength and solid-to-liquid ratio (m/V) is studied under ambient condition by using batch technique. Effects of fulvic acid (FA), phosphate, sulfate and citrate on Th(IV) sorption are investigated in detail. A pseudo-second-order rate equation is used to simulate the kinetic sorption. The removal of Th(IV) increases with increasing pH and hardly depends on ionic strength. Sorption of Th(IV) increases with increasing m/V and reaction temperature. The presence of FA and phosphate enhances the sorption of Th(IV) on Zr2O(PO4)2 while sulfate and citrate decrease the sorption. The Langmuir and Freundlich models are used to simulate the sorption isotherm of Th(IV) on Zr2O(PO4)2 at different temperatures. The thermodynamic data (i.e., ∆H 0, ∆S 0, ∆G 0) are calculated from temperature dependent sorption isotherms. The results suggest that the sorption process of Th(IV) on Zr2O(PO4)2 is spontaneous and endothermic.

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Abstract  

The sorption of U(VI) from aqueous solution on MX-80 bentonite was studied as a function of contact time, pH, ionic strength, solid contents, humic acid (HA), fulvic acid (FA) and temperature under ambient conditions using batch technique. The results indicate that sorption of U(VI) on MX-80 bentonite is strongly dependent on pH and ionic strength. The removal of U(VI) to MX-80 bentonite is rather quick and the kinetic sorption data is simulated well by a pseudo-second-order rate equation. The presence of HA enhances the sorption of U(VI) on MX-80 bentonite obviously, but the influence of FA on U(VI) sorption is not obvious. The thermodynamic parameters (ΔH 0, ΔS 0, and ΔG 0) for the sorption of U(VI) calculated from temperature dependent sorption suggest that the sorption reaction is endothermic and spontaneous.

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