ABSTRACT
In the original publication Fig. 10b was erroneously plotted due to the authors' carelessness and unintentional misoperation.
ABSTRACT
Efficient removal of radioactive 90Sr from nuclear waste solutions and natural water systems is of vital importance due to its radioactive nature and high mobility. We present here an anionic layered compound (NC4H12)(NC2H8)2[In3(pydc)6]·13.1H2O (SZ-6; pydc = 2,5-pyridinedicarboxylic acid) with the potential remediation ability towards radioactive Sr2+ from seawater. This material exhibits excellent ß and γ radiation resistance both in air and in aqueous solutions. Besides, this material could maintain its structural integrity in real seawater for 77 days. The adsorption experiment results show that SZ-6 exhibits superior Sr2+ removal capability over a wide pH range from 4 to 12 with fast adsorption kinetics and high selectivity. The effective removal of 90Sr from real seawater was demonstrated as well. Our results strongly suggest the potential application of SZ-6 for selectively capturing radionuclides in natural water systems.
ABSTRACT
The competitive binding trends of Ni(II) and Eu(III) on montmorillonite in the absence/presence of Na-oxalate are explored by using batch sorption/desorption technique, speciation modeling, and X-ray diffraction (XRD) analysis. With a series of molar Ni:Eu ratios (i.e., 1:1, 5:1, 10:1, 1:5, and 1:10), the coexisting Ni(II) did not affect the sequestration behaviors and immobilization mechanisms of Eu(III). In contrast, the presence of Eu(III) obviously suppressed the sorption percentages of Ni(II) in the acidic pH range. Even though no obvious influence of Eu(III) on the macroscopic binding trends of Ni(II) was observed under alkaline conditions, the fraction of Ni(II) adsorbed by the inner-sphere complexation mechanism decreased and that of Ni(II) precipitation increased with rising molar Ni:Eu ratio. The coexisting Na-oxalate did not influence Eu(III) sorption, while inhibited the sorption of Ni(II). The XRD analysis indicated the potential formation of two Eu-oxalate precipitate phases (i.e., Eu2(C2O4)3·xH2O(s)-1 and Eu2(C2O4)3·xH2O(s)-2) at different pH values (4.0 and 6.5) and Na-oxalate concentrations (ranging from 0.5 to 5.0 mM). Interestingly, the Eu2(C2O4)3·xH2O(s)-2 phase would be transformed into the Eu2(C2O4)3·xH2O(s)-1 solid with the increase of Na-oxalate concentration. The research findings could provide essential data for evaluating the fate of coexistent Eu(III) and Ni(II) in the complicated aquatic environment.
Subject(s)
Bentonite/chemistry , Europium/chemistry , Nickel/chemistry , Oxalic Acid/chemistry , Adsorption , Ions/chemistryABSTRACT
Deferiprone (3-hydroxy-1,2-dimethyl-4(1H)-pyridone, DFP), which is a drug clinically used for removing heavy metals in vivo, was explored for its removal efficiency towards uranium. The reaction of uranyl nitrate hexahydrate with DFP at room temperature yielded the compound [(UO2)(H2O)(C7NO2H8)2]·4H2O (1), which crystallizes from a mixed solution of methanol and water (pH = 7.0). X-ray diffraction shows that the stable complexation of uranyl occurs from the coordination of two bidentate DFP ligands perpendicular to the O[double bond, length as m-dash]U[double bond, length as m-dash]O unit with a fifth coordinating oxygen atom coming from one water molecule, resulting in a pentagonal bipyramidal geometry. The formation constants of uranyl and DFP complexes were measured and the species distribution diagram illustrates that UO2L2 (94.6%) is the dominant uranyl-DFP complex in 0.1 M KCl solution at physiological pH = 7.4. The results from both crystallographic and potentiometric studies imply that the metal : ligand ratio is 1 : 2. The effectiveness of using DFP to remove uranium was examined at the cellular level, and the results suggest that it can significantly reduce the cellular uptake and increase the cellular release of U(vi) in renal proximal tubular epithelial cells (NRK-52E).
