Adsorption of Polychlorinated Aromatics in EMT-Type Zeolites: A Combined Experimental-Simulation Approach

A combination of molecular simulation tools with the gravimetric experiments has been employed to explore the adsorption of dichlorinated aromatics in (EMT)-type zeolites at a microscopic scale. A suited combination of classical and quantum simulation tools provided a clear overall picture of the adsorption process, from both local and global points of view, well matching with the gravimetric measurement data. The adsorbate preferential locations, adsorbate/zeolite interaction nature and geometry, and the adsorption energy were extracted from density functional theory calculations. Furthermore, on the basis of classical force fields, the Gibbs ensemble Monte Carlo simulations made it possible to predict room temperature dichlorobenzene adsorption isotherms in the EMT-type zeolite in both purely siliceous and aluminosilicate forms. Finally, we accomplished a detailed analysis of the microscopic mechanism of the adsorption process, with a special highlight to understanding the interaction geometry of the molecule with the sodium cation, according to its crystallographic site. Thus, we could depict that adsorbates under study preferentially adsorb within the smaller cage, called hypocage. Then, the larger cages, designed as hypercages, start filling only once all hypocages are at least partially occupied.