Journal
GEOCHIMICA ET COSMOCHIMICA ACTA
Volume 166, Issue -, Pages 129-145Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2015.06.020
Keywords
-
Categories
Funding
- National Natural Science Foundation of China [41203086, 21225730, 91326202]
- 973 Projects [2011CB933700]
- Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection
- Key Laboratory of Marine Chemistry Theory and Technology (Ocean University of China), Ministry of Education
Ask authors/readers for more resources
Heavy metal ions that leach from various industrial and agricultural processes are simultaneously present in the contaminated soil and water systems. The competitive sorption of these toxic metal ions on the natural soil components and sediments significantly influences their migration, bioavailability and ecotoxicity in the geochemical environment. In this study, the competitive sorption and selectivity order of Cu(II) and Ni(II) on montmorillonite are investigated by combining the batch experiments, X-ray diffraction (XRD), electron paramagnetic resonance (EPR), surface complexation modeling and X-ray Absorption Spectroscopy (XAS). The batch experimental data show that the coexisting Ni(II) exhibits a negligible influence on the sorption behavior of Cu(II), whereas the coexisting Cu(II) reduces the Ni(II) sorption percentage and changes the shape of the Ni(II) sorption isotherm. The sorption species of Cu(II) and Ni(II) on montmorillonite over the acidic and near-neutral pH range are well simulated by the surface complexation modeling. However, this model cannot identify the occurrence of surface nucleation and the co-precipitation processes at a highly alkaline pH. Based on the results of the EPR and XAS analyses, the microstructures of Cu(II) on montmorillonite are identified as the hydrated free Cu(II) ions at pH 5.0, inner-sphere surface complexes at pH 6.0 and the surface dimers/Cu(OH)(2)(s) precipitate at pH 8.0 in the single-solute and the binary-solute systems. For the Ni(II) sorption in the single-solute system, the formed microstructure varies from the hydrated free Ni(II) ions at the pH values of 5.0 and 6.0 to the inner-sphere surface complexes at pH 8.0. For the Ni(II) sorption in the binary-solute system, the coexisting Cu(II) induces the formation of the inner-sphere complexes at pH 6.0. In contrast, Ni(II) is adsorbed on montmorillonite via the formation of Ni phyllosilicate co-precipitate/alpha-Ni(OH)(2)(s) precipitate at pH 8.0. The selective sequence of Cu(II) > Ni(II) for binding on montmorillonite can be ascribed to the differences in the metal properties and the compatibility between the configurations of the montmorillonite binding sites and those of the Cu(II)O-6/Ni(II)O-6 polyhedra. The derived findings in this study could provide significant information for the evaluation of the competitive sorption behaviors at solid/water interfaces and the fate of the coexisting heavy metal ions in multicomponent environmental systems. (C) 2015 Elsevier Ltd. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available