The role of water in DCE adsorption from aqueous solutions onto hydrophobic zeolites

In this study, we have investigated the adsorption processes of 1,2-dichloroethane (DCE) from aqueous solutions onto ZSM-5 and Y organophilic zeolites. The presence of this organic molecule in the zeolite channel systems was revealed by X-ray structure analyses carried out using the Rietveld method. Difference Fourier maps allowed us to determine the exact location of these DCE molecules, as well as that of the water molecules inside extraframework sites. Rietveld refinement clearly revealed the incorporation of DCE molecules within Y and ZSM-5 selected zeolites, in very good agreement with the weight loss given by TG analyses and with the saturation capacity determined by the adsorption isotherms. The distances between the oxygen atoms in the water molecules and the chlorine atoms in the DCE solutions suggest that different DCE molecules could be connected by means of hydrogen bonds through water, to form DCE-water complexes, thus influencing the DCE trans-gauche conformational equilibrium. The presence of these complexes causes variations in unit cell parameters, as well as remarkable framework deformations, clearly indicating that water strongly controls the diffusion and adsorption processes in zeolite materials. (C) 2012 Elsevier Inc. All rights reserved.