Desorption of chlorobenzene confined in Y zeolite: a combined in situ synchrotron X-ray powder diffraction and chromatographic study

Volatile organic compounds (VOCs) such as chlorobenzene are common pollutants present in groundwater. Because of their human and ecosystems toxicity and their tendency to persist in water the removal of these contaminants it is in the public interest. Recently, the state of the art highlighted that hydrophobic zeolites are environmentally friendly materials, efficient as contaminants adsorbents and perfectly regenerable without changing their initial adsorption capacity (Martucci et al., 2015; Leardini et al., 2015; Martucci et al., 2015; Martucci et al., 2014; Pasti et al., 2012, Rodeghero et al., in press; Pasti et al., submitted). Structural and kinetic dynamic data are required to full understanding the behaviour of zeolites during the fuel-based compounds desorption process. Actually no in situ structural investigation of the VOCs kinetics desorption has been performed on Y zeolite. The challenge of this work is understanding the structural modifications undergoing on this hydrophobic material (HSZ-390HUA, SiO2/Al2O3 = 200, Tosoh Corporation) loaded with chlorobenzene (Cl-B) upon thermal treatment. To obtain this goal the study was carried out with two approaches. Firstly adsorption isotherm from distilled water was performed on zeolites in batches at RT and the concentration of contaminants in aqueous solution was obtained by gas chromatography and mass spectrometry. Then the in situ heating allowed us to simulate the regeneration process, which is usually subjected exhausted zeolites after adsorption of hydrocarbons. The desorption process was continuously monitored at the ID22 beamline (ESRF-Grenoble) as a function of temperature (heating rate 20°C/min) from room temperature up to 600°C. The results obtained with Rietveld method indicate that after thermal treatment zeolite does not show any significant crystallinity loss and when all the organic have been ejected (about 300°C), non-equilibrium distortions in the framework are relaxed and channel apertures become more circular. Achieving the reactivation of these materials and its reuse as pollutants adsorbent would expand their capabilities in environmental applications. Additionally, understanding this process can help in optimizing and the design the water remediation technologies (e.g. Permeable Reactive Barriers) and using zeolites as “molecular sieves” to remove fuels-based pollutants from water. Leardini, L., Quartieri, S., Vezzalini, G., Arletti, R. (2015): Thermal behaviour of siliceous faujasite: Further structural interpretation of negative thermal expansion. Microporous and Mesoporous Materials, 202, 226–233. Martucci, A., Braschi, I., Marchese, L., Quartieri, S. (2014): Min. Mag., 2014, 1115–1140. Martucci, A., Braschi, I., Bisio, C., Sarti, E., Rodeghero, E., Bagatin, R. and Pasti, L. (2015): Influence of water on the retention of methyl tertiary-butyl ether by high silica ZSM-5 and Y zeolites: a multidisciplinary study on the adsorption from liquid and gas phase. RSC Adv., 106, 86997-87006. Martucci, A., Rodeghero, E., Pasti, L., Bosi, V., Cruciani, G. (2015): Adsorption of 1,2-dichloroethane on ZSM-5 and desorption dynamics by in situ synchrotron powder X-ray diffraction. Microporous and Mesoporous Materials, 215, 175-182. Pasti, L., Rodeghero, E., Sarti, E., Bosi, V., Cavazzini, A., Bagatin R., and Martucci, A.: Competitive Adsorption of VOCs from binary aqueous mixtures on zeolite ZSM-5. RSC Adv., Submitted. 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. Micropor. Mesopor. Mat., 160, 182–193. Rodeghero, E., Martucci, A., Cruciani, G., Bagatin, R., Sarti, E., Bosi, V., Pasti, L. (2015): Kinetics and dynamic behaviour of toluene desorption from ZSM-5 using in situ high-temperature synchrotron powder X-ray diffraction and chromatographic techniques. Catalysis Today, In Press