Volatile organic compounds (VOCs) such as toluene, chlorobenzene, 1,2-dichloroethane and methyl-tert-buthyl-ether are commonly found in natural and drinking water. When these compounds are dissolved in groundwater are considered dangerous for the health of human and ecosystems already at low concentration [1]. For this reason, the removal of this organics from natural water is of considerable interest. Actually, a reliable alternative to obtain this goal is based on the adsorption technique by means of high-silica zeolites. The efficiency of the hydrophobic zeolites adsorption, from aqueous solution, has been highlighted in recent studies and its success is due to both selectivity and flexibility of the framework of these materials [2-4]. Moreover, the process does not induce the formation of dangerous secondary molecules for the environment. On the basis of as reported, in this work the interaction and mobility of some VOCs pollutants have been studied. Those VOCs have characterized by different chemical properties and molecular dimensions, and they are adsorbed in organophilic synthetic zeolites (ZSM-5 and Y with MFI and FAU topology, respectively) which differ in topology, channel systems and free window apertures. Furthermore, it has been checked the efficiently of these materials paying attention on the pollutants adsorption in presence of common competitors, such as humic monomers (e.g. caffeic acid and para-hydroxybenzaldheyde), by monitoring the structural features. Indeed, the presence of organic matter could influence the process of adsorption of pollutants in the waters competing for the available adsorption sites, either by limiting access to the micro-pores. The selected organophilic and hydrophobic zeolites were commercial as-synthesized with high SiO2/Al2O3 (up to 200). Kinetics and adsorption isotherm batch data were obtained via Headspace Solid Phase Microextraction-GC. After pollutants adsorption the structural characterization was obtain by using X-ray powders diffraction data collected on a Bruker D8 Advance diffractometer equipped with SOL-X detector. To determinate the total weight loss of zeolites loaded with fuel-based compounds thermal analyses (TG and DTA) were performed in air up to 900°C at 10°C/min. This combined study allowed us to: a) measure the sorption capacity of hydrophobic zeolite materials weighed against organic pollutants dissolved in water; b) characterise the structure after contaminants adsorption; c) localise the organic species in the zeolite channel systems; d) highlight the role of humic monomers in the pollutants removal; e) probe the interaction between the adsorbate and the zeolite framework. [1] P.V.O. Trindade, L.G. Sobral, A.C.L. Rizzo, S.G.F. Leite, Chemosphere, 2005, 58, 515–522. [2] A. Martucci, I. Braschi, C. Bisio, E. Sarti, E. Rodeghero, R. Bagatin, L. Pasti, RSC Advances, 2015, 5(106), 86997. [3] A. Martucci, E. Rodeghero, L. Pasti , V. Bosi, G. Cruciani , Microporous and Mesoporous Materials, 2015, 215, 175. [4] E. Rodeghero, A. Martucci, G. Cruciani, R. Bagatin, E. Sarti, V. Bosi, L. Pasti, Catalysis Today, 2016, In Press (doi:10.1016/j.cattod.2015.11.031).
Structural evidences of competitive adsorption of VOCs and humic monomers from water on high-silica zeolites: a combined X-ray powder diffraction and chromatographic study
RODEGHERO, Elisa;PASTI, Luisa;MARTUCCI, Annalisa;
2016
Abstract
Volatile organic compounds (VOCs) such as toluene, chlorobenzene, 1,2-dichloroethane and methyl-tert-buthyl-ether are commonly found in natural and drinking water. When these compounds are dissolved in groundwater are considered dangerous for the health of human and ecosystems already at low concentration [1]. For this reason, the removal of this organics from natural water is of considerable interest. Actually, a reliable alternative to obtain this goal is based on the adsorption technique by means of high-silica zeolites. The efficiency of the hydrophobic zeolites adsorption, from aqueous solution, has been highlighted in recent studies and its success is due to both selectivity and flexibility of the framework of these materials [2-4]. Moreover, the process does not induce the formation of dangerous secondary molecules for the environment. On the basis of as reported, in this work the interaction and mobility of some VOCs pollutants have been studied. Those VOCs have characterized by different chemical properties and molecular dimensions, and they are adsorbed in organophilic synthetic zeolites (ZSM-5 and Y with MFI and FAU topology, respectively) which differ in topology, channel systems and free window apertures. Furthermore, it has been checked the efficiently of these materials paying attention on the pollutants adsorption in presence of common competitors, such as humic monomers (e.g. caffeic acid and para-hydroxybenzaldheyde), by monitoring the structural features. Indeed, the presence of organic matter could influence the process of adsorption of pollutants in the waters competing for the available adsorption sites, either by limiting access to the micro-pores. The selected organophilic and hydrophobic zeolites were commercial as-synthesized with high SiO2/Al2O3 (up to 200). Kinetics and adsorption isotherm batch data were obtained via Headspace Solid Phase Microextraction-GC. After pollutants adsorption the structural characterization was obtain by using X-ray powders diffraction data collected on a Bruker D8 Advance diffractometer equipped with SOL-X detector. To determinate the total weight loss of zeolites loaded with fuel-based compounds thermal analyses (TG and DTA) were performed in air up to 900°C at 10°C/min. This combined study allowed us to: a) measure the sorption capacity of hydrophobic zeolite materials weighed against organic pollutants dissolved in water; b) characterise the structure after contaminants adsorption; c) localise the organic species in the zeolite channel systems; d) highlight the role of humic monomers in the pollutants removal; e) probe the interaction between the adsorbate and the zeolite framework. [1] P.V.O. Trindade, L.G. Sobral, A.C.L. Rizzo, S.G.F. Leite, Chemosphere, 2005, 58, 515–522. [2] A. Martucci, I. Braschi, C. Bisio, E. Sarti, E. Rodeghero, R. Bagatin, L. Pasti, RSC Advances, 2015, 5(106), 86997. [3] A. Martucci, E. Rodeghero, L. Pasti , V. Bosi, G. Cruciani , Microporous and Mesoporous Materials, 2015, 215, 175. [4] E. Rodeghero, A. Martucci, G. Cruciani, R. Bagatin, E. Sarti, V. Bosi, L. Pasti, Catalysis Today, 2016, In Press (doi:10.1016/j.cattod.2015.11.031).I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
