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
Authors:Songsheng Lu, Zhiqiang Guo, Caicai Zhang, and Shouwei Zhang
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
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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Dauphin, L. A., Moser, B. D. & Bowen, M. D., 2009. Evaluation of five
Authors:Péter Sipos, Chung Choi, Tibor Németh, Zoltán Szalai, and Teréz Póka
., 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 humicacid on micronutrient availability