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Abstract  

The aim of this study is the radiometric determination of uranium in waters by liquid scintillation counting (LSC) after pre-concentration of the element by cloud point extraction (CPE). For CPE, tributyl phosphate (TBP) is used as the complexing agent and (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol (Triton X-114) as the surfactant. The measurement is performed after phase separation by mixing of the surfactant phase with the liquid scintillation cocktail. The effect of experimental conditions such as pH, reactant ratio (e.g. m(TBP)/m(Triton), ionic strength (e.g. [NaCl]) and the presence of other chemical species (e.g. Ca2+ and Fe3+ ions as well as humic acid and silica colloids) on CPE has been investigated. According to the experimental results the total method efficiency is (13 ± 2)% and the chemical recovery (50 ± 10)% at pH 4 and reactant ratio (V(TBP)/V(Triton) = 0.1). Regarding the other parameters, generally Ca2+ and Fe3+ ions as well as the presence of colloidal species in solution (even at low concentrations) results in significant decrease of the chemical recovery of uranium. On the other hand increasing NaCl concentration leads to enhancement of chemical recovery. The detection limit under optimum experimental conditions has been found to be 0.5 Bq L−1 indicating that the method could be applied only to waters samples with increased uranium concentration. Moreover, the negative effect of the chemical species found in natural waters limits the applicability of the method with the respect to environmental radioactivity measurements.

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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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1988 Camaron, R.S. — Swift, R.S. — Thronton, B.K. — Posner, A.M.: 1972. Calibration of gel permeation chromatography materials for use with humic acid

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. Talajvizsgálati módszerkönyv Barabančíková, G., Senesi, N. & Brunetti, G., 1997. Chemical and spectroscopic characterization of humic acids isolated from different Slovak soil types

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–46. Li, Y., Yue, Q. & Yao, B., 2010. Adsorption kinetics and desorption of Cu(II) and Zn(II) from aqueous solution onto humic acid. J. Haz. Mat. 178. 455–461. Murányi A. & Füleky Gy., 1997. Ammóniumfelvétel

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. & Stotzky, G., 1998. Binding of DNA on humic acids: effect on transformation of Bacillus subtilis and resistance to DNase. Soil Biol. Biochem. 30. 1061–1067. Dauphin, L. A., Moser, B. D. & Bowen, M. D., 2009. Evaluation of five

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Gonet, S. S., Wegner, K. (1993): Effect of long-term mineral and organic fertilizer application on properties of soil humic acids. Zes. Nar. H. Koll. Zes. Nauk. (Krakow) , 37 , 51–63. Wegner K

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. Immunopathol. 114 , 209 – 223 . doi: http://dx.doi.org/10.1016/j.vetimm.2006.07.007 Islam , K. M. S. , Schumacher , A. and Gropp , J. ( 2005 ): Humic acid substances in animal

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Anderson, M. A., Hung, A. Y. C., Mills, D., Scott, M. S. (1995): Factors affecting the surface tension of soil solutions and solutions of humic acids. Oil Sci. , 160, 111-116. Factors

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., 1995. Sequential extraction of soils for multielement analysis by ICP-AES. Chemical Geology. 124. 109–123. Mackowiak, C. L., Grossl, P. R. & Bugbee, B. G., 2001. Beneficial effects of humic acid on micronutrient availability

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