Sorption mechanisms and sorption models
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Ion exchange and surface complexation are the main models used to quantify the sorption processes. Through a multidisciplinary approach, we have shown that the sorption processes are numerous and often do not correspond to simple models. The sorption on hydroxyapatites may proceed, depending on the element, by substitution of superficial species of the solid or by precipitation. On hexacyanoferrates, we can observe ion exchange or formation of new solid phases. On metal oxyhydroxides, the process corresponds to the surface complexation, but several different models of this type can fit the experimental data. Furthermore, slow kinetics, solubility and evolution of the solid, and the presence of impurities can disturb the surface reactivity determination. A better understanding of sorption processes can be achieved by using high-purity materials with controlled structure and morphology, by a multidisciplinary study of sorption mechanisms and by developing more accurate models.
Keywords:apatite / hexacyanoferrate / ion exchange / oxides / radionuclides / sorption / surface complexation / toxic elements / water transport
Source:Materials Science Forum, 2004, 453-454, 305-314
- Progress in Advanced Materials and Processes, 5th Conference of the Yugoslav-Materials-Research-Society (Yu-MRS 2003), Sep 15-19, 2003, Herceg Novi, Yugoslavia