Authors:Sharayu Kasar, Sumit Kumar, Aishwarya Kar, K. Krishnan, N. Kulkarni, and B. Tomar
Sorption of Eu(III), an analogue of trivalent actinides (Am, Cm), by amorphous titania as well as different crystalline phases
of titania, namely anatase and rutile, have been studied as a function of pH, using 154Eu (half life = 8.8 yrs, Eγ = 123,247 keV) as a radiotracer. The objective of this study was to investigate the effect of the crystalline phase of the
titania on their sorption behaviour towards the metal ion. Amorphous titania was prepared by organic route and was converted
into anatase and rutile by heating at elevated temperatures based on the differential thermal analysis studies. Eu(III) sorption
by all forms of titania rises sharply with the pH of the suspension, with the sorption edge shifting to higher value in the
order; amorphous < anatase < rutile. However, the normalization of the sorption data to the surface area of the sorbents resulted
in the overlapping of the sorption curves for amorphous and anatase phases, with the data being higher for rutle in the lower
pH region, indicating the effect of the crystal phase on sorption behaviour of Eu(III).
Authors:Songsheng Lu, Lei Chen, Yunhui Dong, and Yixue Chen
Iron oxide/multiwalled carbon nanotube magnetic composites (denoted as magnetic composites) were synthesized and characterized
in detail. The magnetic composites can be separated from aqueous solution easily by using magnetic separation method. The
application of magnetic composites in the removal of Eu(III) from large volumes of aqueous solutions was studied. The results
indicated that the sorption of Eu(III) on the magnetic composites was strongly dependent on pH values and weakly dependent
on ionic strength. The sorption of Eu(III) on the magnetic composites was mainly dominated by inner-sphere surface complexation.
The linear sorption isotherms of Eu(III) suggested that Eu(III) sorption on the magnetic composites was far from saturation.
The large sorption capacity and the easy magnetic separation method indicate that the magnetic composites may be a promising
suitable material in nuclear waste management in future.
Effects of pH, Eu(III) concentration, ionic strength, temperature and humic acid (HA) on Eu(III) sorption to iron oxides were
investigated in detail. The sorption of Eu(III) to iron oxides was significantly dependent on pH and weakly dependent on ionic
strength, and higher temperature was gainful to Eu(III) sorption. In the presence of HA, Eu(III) sorption was enhanced significantly
at low pH; whilst obvious negative effect was observed in higher pH range. Below 12 mg/L HA, HA could obviously enhanced Eu(III)
sorption to iron oxides, nevertheless Eu(III) sorption decreased steeply with increasing HA while HA exceeded 12 mg/L. The
results were helpful for understanding radionuclides behaviors in natural environment.
Authors:Liming Zuo, Shaoming Yu, Hai Zhou, Jun Jiang, and Xue Tian
The adsorption behavior of Eu(III) from aqueous solution to mesoporous molecular sieves (Al-MCM-41) is investigated as a function
of contact time, solid content, ionic strength, pH, foreign ions and temperature by using batch technique. The experimental
results show that Eu(III) adsorption is strongly dependent on pH values, but independent of ionic strength and foreign cations
under our experimental conditions. The kinetic process is described by a pseudo-second-order rate model very well. The adsorption
isotherms are simulated by Langmuir model very well. The thermodynamic parameters (∆G°, ∆S°, ∆H°) are calculated from the temperature dependent adsorption isotherms at 293, 313 and 333 K, respectively, and the results
suggest that the adsorption of Eu(III) on Al-MCM-41 is a spontaneous and endothermic process. Desorption studies indicate
that the adsorbed Eu(III) is very difficult to be desorbed from the solid surface. Al-MCM-41 is a suitable material for the
preconcentration and solidification of Eu(III) from large volumes of aqueous solutions.
Authors:Lu Songsheng, Xu Hua, Wang Mingming, Song Xiaoping, and Liu Qiong
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.
Authors:Sumit Kumar, Aishwarya Kar, D. Bhattacharyya, and B. Tomar
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.
Authors:Wang Mingming, Xie Hongqin, Tan Liqiang, Qiu Jun, Tao Xingquan, and Wu Cuiping
Herein, the sorption properties of Eu(III) on Na-attapulgite were performed by using batch sorption experiments under different
experimental conditions, such as contact time, pH, ionic strength, humic acid and temperatures. The results indicated that
the sorption of Eu(III) on Na-attapulgite was strongly dependent on pH and temperature. At low pH values, the sorption of
Eu(III) was influenced by ionic strength, whereas the sorption was not affected by ionic strength at high pH values. The sorption
of Eu(III) was mainly dominated by ion exchange or outer-sphere surface complexation at low pH values, and by inner-sphere
surface complexation or surface precipitation at high pH values. The sorption of Eu(III) onto Na-attapulgite increased with
increasing temperature. The Langmuir and Freundlich models were applied to simulate the sorption isotherms, and the results
indicated that the Langmuir model simulated the sorption isotherms better than the Freundlich model. The thermodynamic parameters
(∆Go, ∆So, ∆Ho) were calculated from the temperature dependent sorption isotherms at 293, 313 and 333 K, respectively, and the results indicated
that the uptake of Eu(III) on Na-attapulgite was an endothermic and spontaneous process. The results of high Eu(III) sorption
capacity on Na-attapulgite suggest that the attapulgite is a suitable material for the preconcentration and immobilization
of Eu(III) ions from large volumes of aqueous solutions.
Authors:Keliang Shi, Fuqiang Liu, Yuanlv Ye, Zhijun Guo, and Wangsuo Wu
Metal ions sorption can be significantly affected by the presence of other sorbates, especially of complexing ligands. In
this study, the effect of Se(IV) on Eu(III) sorption onto TiO2 at different pH and Eu(III) concentration was investigated. Se(IV) was found to enhance Eu(III) sorption as a function of
Se(IV) concentration. Constant capacitance model was successfully used to interpret the sorption experimental data. The solubility
product of Eu2(SeO3)3 at ambient temperature was investigated to highlight the sorption mechanism of ternary sorption system. The pKsp value of Eu2(SeO3)3 was found to be 31.51 ± 0.95.
Authors:Y. Suzuki, T. Nankawa, T. Yoshida, T. Ozaki, T. Ohnuki, A. J. Francis, S. Tsushima, Y. Enokida, and I. Yamamoto
We have investigated the structure of Eu(III)-citrate complexes in aqueous solution and their degradability by Pseudomonas fluorescens. Analysis of 1:1, 1:2, and 1:5 Eu(III):citrate solutions at pH 7 by electrospray ionization mass spectrometry (ESI-MS) showed
that the 2:2 Eu(III)-citrate complex is the predominant complex species at a low citrate/Eu(III) ratio, while at a high ratio,
a 1:2 Eu(III)-citrate complex is formed preferably. Studies on the biodegradation of Eu(III)-citrate complex by P. fluorescens have shown that a 2:2 Eu(III)-citrate complex is resistent to degradation while a 1:2 complex transforms to a 2:2 complex
with the degradation of excess citric acid.
Authors:D. Xu, Q. L. Ning, X. Zhou, C. L. Chen, X. L. Tan, A. D. Wu, and X. Wang
Effects of ionic strength and of fulvic acid on the sorption of Eu(III) on alumina were investigated by using a batch technique.
The experiments were carried out at T=25±1 °C, pH 4-6 and in the presence of 1M NaCl. The results indicate that sorption isotherms of Eu(III) are linear at low
pH values. The sorption-desorption of Eu(III) on alumina at pH 4.4 is reversible, but a sorption-desorption hysteresis is
found at pH 5.0. Fulvic acid has an obvious positive effect on the sorption of Eu(III) on alumina at low pH values. The migration
of Eu(III) in alumina was studied by using column experiments and 152+154Eu(III) radiotracer at pH 3.8. For column experiments, Eu(III) sorbed on alumina can be desorbed completely from the solid
surface at low pH values. The findings are relevant to the evaluation of lanthanide and actinide ions in the environment.