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

Abstract

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.

Insights into Water Adsorption in Potassium-Exchanged X-type Faujasite Zeolite: Molecular Simulation and Experiment

“…Indeed, the adsorption, as a surface phenomenon, favors the occupation of smaller cages by adsorbent species, maximizing the adsorbate−adsorbent interactions. Such evidence was previously brought in analogous zeolites such as EMT possessing two types of cages with various sizes 5 or LTA with smaller β-cages and bigger α-cages. 31 Furthermore, the sodalite cage as the most energetically favorable adsorption site has been suggested from the experimental 40−42 as well as simulation point of view 43 for the sodium Y-type faujasite (Na−Y).…”

“…Zeolites, aluminosilicate crystalline materials with an ordered microporous structure, formed by linking silicon and aluminum tetrahedra, aroused a huge scientific interest related to a wide number of their potential applications, in particular, in environmental remediation. − Among the approximately 250 identified zeolite structures, the faujasite ( FAU ) has attracted a special attention due to its interesting structural, textural, and chemical properties. Indeed, FAU-type zeolites possess a large microporous volume, accessible even to pollutants with a significant molecular size .…”

“…In order to computationally determine the potassium cation distribution of the activated zeolite, we first carried out the classical potential-based geometry optimization, as described in Section 2.1.1, followed by DFT-based energy minimization. The resulting potassium cation distribution is detailed in Table2and illustrated in Figure2b 5.…”

Simulation-based evaluation of zeolite adsorbents for the removal of emerging contaminants

“…In the view of the widespread use of computational chemistry methods in zeolite science, 43,44 this appears somewhat surprising. In the field of molecular mechanics calculations, force-field based Monte Carlo (MC) and molecular dynamics (MD) simulations have been employed to study the adsorption and/or diffusion of organic molecules in all-silica zeolites for several species of considerable complexity, including substituted aromatics, [45][46][47][48][49][50][51] organic structure-directing agents (OSDAs), [52][53][54][55][56][57][58] and glucose. 59 In contrast to this, applications of force field methods to study the interaction of pharmaceuticals with zeolites are scarce, with the MD investigation of salbutamol and theophylline diffusion in zeolite beta by Fatouros et al being a rare example.…”

Simulation-Based Evaluation of Zeolite Adsorbents for the Removal of Emerging Contaminants

“…In the view of the widespread use of computational chemistry methods in zeolite science, [43,44] this appears somewhat surprising. In the field of molecular mechanics calculations, force-field based Monte Carlo (MC) and molecular dynamics (MD) simulations have been employed to study the adsorption and/or diffusion of organic molecules in all-silica zeolites for several species of considerable complexity, including substituted aromatics, [45][46][47][48][49][50] organic structure-directing agents (OSDAs), [51][52][53][54][55][56][57] and glucose. [58] In contrast to this, applications of force field methods to study the interaction of pharmaceuticals with zeolites are scarce, with the MD investigation of salbutamol and theophylline diffusion in zeolite beta by Fatouros et al being a rare example.…”