The aim of this work is to investigate the structural modifications in ZSM-5 during desorption of 1,2-dichloroethane (DCE) by ‘in situ' time-resolved X-ray powder diffraction. DCE is an important environmental pollutant due to its high toxicity, inertness and widespread application in industry (Gavaskar et al. 1995). Recently, the effective adsorption of 1,2-dichloroethane from aqueous solutions onto highly siliceous ZSM-5 zeolite has been demonstrated by Pasti et al. (2012) by combining diffraction and gas chromatography. In this work the step by step thermal desorption process of ZSM-5 organophilic zeolite (CBV28014, Zeolyst International, SiO2/Al2O3 ~280) loaded with DCE has been studied “in situ” by synchrotron radiation powder diffraction. Time-resolved diffraction data were collected (temperature range 25°-600°C) at the ID31 beamline at ESRF (Grenoble), using a fixed wavelength of 0.40003(1) Å. Kinetics and adsorption isotherm batch data were obtained via Headspace Solid Phase Microextraction -Gas Chromatography. Rietveld refinements were carried out on 19 consecutive powder patterns in the temperature range from 25°C to 600°C. The evolution of the structural features monitored by full profile Rietveld refinements reveals that a monoclinic (P21/n) to orthorhombic (P212121) phase transition occured at 70°C (Figure 1). The decomposition and expulsion of DCE was accompanied by changes in the unit-cell parameters, as well as in the channel apertures. Complete DCE degradation and expulsion was achieved upon heating at about 300 °C. This kind of information is crucial for designing and optimizing the regeneration treatment of zeolite used as adsorbents in water and wastewater remediation treatment technologies. Gavaskar A.R., Kim B.C., Rosansky S.H., Ong S.K., & Marchand E.G., 1995. Crossflow air stripping and catalytic oxidation of chlorinated hydrocarbons from groundwater Environ. Prog. 14 33–40. Pasti, L., Martucci, A., Nassi, M., Cavazzini, A., Alberti, A., & Bagatin, R. 2012. The role of water in DCE adsorption from aqueous solutions onto hydrophobic zeolites Microporous and Mesoporous Materials. 160, 182-193.
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|Titolo:||Temperature - induced transformations in ZSM-5 after 1,2-dichloroethane adsorption by “in situ” time resolved synchrotron powder diffraction|
|Data di pubblicazione:||2014|
|Appare nelle tipologie:||04.2 Contributi in atti di convegno (in Volume)|