Adsorption of tiabendazole on organically modified montmorillonite

P. KOVÁř; M. GAMBA; R. M. TORRES SÁNCHEZ

Dresden

Conferencia; MECC14 7th MID-EUROPEAN CLAY CONFERENCE; 2014

Water contamination by fungicides is a significant problem that has been solved for years. A possible way of water decontamination in agricultural regions is using organically modified clay. We calculated the structure of interlayer space of Wyoming montmorillonite (Wy-MMT) intercalated with octadecyltrimethylammonium cations (ODTMA) and the adsorption of tiabendazole molecule (TBZ) on Wy-MMT and on Wy-MMT intercalated by ODTMA (Wy-ODTMA). The results of modeling showed a parallel orientation of ODTMA with respect to the MMT layers, ODTMA cations are horizontally shifted with respect to each other and the shift equals approximately to a half of ODTMA chain. We obtained a few possible basal spacings (1.94 nm, 2.00 nm and 2.10 nm) with a small difference of total energy. It is in qualitative agreement with experimental findings, where a mixture of two basal spacings was observed (ca 2.0 and 2.1 nm). The calculations of adsorption of TBZ molecule on Wy-MMT and on Wy-ODTMA surface showed that TBZ molecule interacts mainly via electrostatic interactions with sodium cations located in hexagonal cavities of MMT layer. The adsorption energy of TBZ between Wy-MMT and Wy-ODTMA is very similar and is of about -50 kcal/mol. If TBZ molecule is adsorbed together with ODTMA cations on the Wy-ODTMA surface the adsorption energy ranges from -10 kcal/mol to -5 kcal/mol. The differences in adsorption energy confirm experimental measurements where in case of Wy-ODTMA the desorption of TBZ was of 83% while in case of Wy-MMT no TBZ desorption was observed.