Molecular modeling of surface modification of Wyoming and Cheto montmorillonite by methylene blue |
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Authors: | Petr Kovář Miroslav Pospíšil Petr Malý Zdeněk Klika Pavla Čapková Petra Horáková Marta Valášková |
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Affiliation: | (1) Charles University in Prague, Faculty of Mathematics and Physics, Ke Karlovu 3, 121 16 Prague, Czech Republic;(2) VŠB-Technical University Ostrava, 708 33 Ostrava-Poruba, Czech Republic |
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Abstract: | The surface area of various types of montmorillonites (MMT) with different values of layer charge plays a very important role in surface arrangement of methylene blue cations (MB). Photoluminescence measurements can be strongly or partially influenced by this surface arrangement of cations. For these reasons and on the basis of our previous results, molecular simulations were performed for various types of montmorillonites covered with methylene blue cations. Adsorption of methylene blue cations on Na-Wyoming MMT surface is different from Ca-Cheto MMT. In the case of Wyoming with a lower layer charge, MB cations lie parallel to the silicate layer for all investigated samples. On the other hand, Cheto surface is covered with a higher amount of MB cations. The results obtained from molecular modeling indicate that MB lies parallel to low loading case and become tilted with respect to layer for a higher loading. Moreover, a higher amount of MB cations covering the silicate layer are much less energy-stable. A higher loading of MB cations leads to aggregates but at low loading MB cations degrade to monomers. |
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