Journal
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
Volume 336, Issue 1-3, Pages 123-129Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.colsurfa.2008.11.032
Keywords
Uranium(VI); Phosphate; gamma-Alumina; Sorption; Surface complexation; Modeling
Categories
Funding
- National Natural Science Foundation of China [20501010, J0630962]
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The sorption of U(VI) and phosphate on gamma-alumina was investigated in binary (phosphate/gamma-alumina; U(VI)/gamma-alumina) and ternary (U(VI)/phosphate/gamma-alumina) systems as functions of contact time, pH, ionic strength, solid-to-liquid ratio and U(VI) and/or phosphate concentrations by using a batch experimental method. It was found that the sorption of phosphate on gamma-alumina increases with pH from 2.5 to 5.2 and then decreases with pH from 5.2 to 9.4. The sorption of phosphate on gamma-alumina is insensitive to ionic strength. On the other hand, the sorption of U(VI) on gamma-alumina increases with increasing pH over the range of 4-6. The sorption of U(VI) on gamma-alumina increases slightly with decreasing ionic strength. In the ternary sorption system, it was found that the presence of phosphate increases the sorption of U(VI), whereas the presence of U(VI) has little effect on the sorption of phosphate. The sorption of U(VI) and phosphate in binary and ternary systems were interpreted in terms of surface complexation models. The effects of gamma-alumina dissolution and CO(2) in the sorption systems were considered in modeling calculations. Four surface complexes of phosphate, XOHAlHPO(4)(+), XH(2)PO(4), XHPO(4)(-) and XPO(4)(2-), and two surface complexes of U(VI), XOUO(2)(+) and XOUO(2)(OH)(2)(-), were respectively used to reproduce the sorption of phosphate in phosphate/gamma-alumina system and U(VI) sorption in U(VI)/gamma-alumina system. The co-sorption of U(VI) and phosphate in the ternary sorption system was interpreted by a model which combines the surface complexation models for the binary sorption systems together in addition to considering the formation of a ternary surface complex, XOUO(2)HPO(4)(-). (C) 2008 Elsevier B.V. All rights reserved.
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