Fuel-based compounds, such as toluene and n-hexane, are common pollutants present in water and wastewater. Due to their tendency to persist in air, water and soil and to bioaccumulate through the food chain, they are included among the most hazardous compounds for human health and environment. Acquatic ecosystems are especially vulnerable because of the frequent use of water bodies as recipients of potentially toxic liquids and solids from domestic, agricultural and industrial wastes. Hence, the removal of fuel-based compounds, through adsorption onto inorganic sorbents is of considerable interest. Due to their selectivity towards organic contaminant and fast adsorption kinetics, it has been recently highlighted that High Silica Zeolites are hydrophobic sorbent materials suitable for adsorption processes (Martucci et al., 2015; Pasti et al., 2016). The aim of this work is to determine the ZSM-5 zeolite degree of selectivity and its structural changes when a competitive adsorption of toluene and n-hexane occurs. A sample of ZSM- 5 zeolite (MFI topology, SiO2/Al2O3 ratio=280), was provided by Tosoh Corporation and loaded with a binary mixture of toluene and n-hexane. Kinetics and adsorption isotherm data were obtained via Headspace Solid Phase Microextraction-GC. Powders patterns were collected before and after adsorption on a Bruker D8 Advance diffractometer equipped with SOL-X detector. Thermal (TG and DTA) analysis were performed in air up to 900°C at 10°C/min. This multidisciplinary approach allowed us to: 1) measure the sorption capacity of zeolite materials weighed against organic pollutants dissolved in water; 2) characterise the sorbent structure after pollutant adsorption; 3) localise the organic species in the zeolite channel systems; 4) probe the interaction between the adsorbate and zeolite framework. Rietveld refinements provide information about the relative position of molecules inside the structure after toluene, nhexane and their mixture adsorption. Data reveal that 1) n-hexane and toluene are preferentially adsorbed whether as single components than as binary mixture; 2) zeolite selectivity is higher towards the n-hexane than toluene. Differences Fourier maps analysis shows that n-hexane, water, and toluene have been adsorbed at about 8.95%, 2.2%, and 1.59%, respectively, in good agreement with both adsorption data and thermal analysis. As a matter of fact, ZSM-5 zeolite preferably adsorbs n-hexane, even in presence of a competitor, such as toluene. Martucci, A., Braschi, I., Bisio, C., Sarti, E., Rodeghero, E., Bagatin, R., 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., 5, 86997-87006. Pasti, L., Rodeghero, E., Sarti, E., Bosi, V., Cavazzini, A., Bagatin, R., Martucci, A. (2016): Competitive adsorption of VOCs from binary aqueous mixtures on zeolite ZSM-5. RSC Adv., 6, 54544-54552.
Toluene and n-hexane competitive adsorption on high-silica ZSM-5 zeolite
Rodeghero E.
;Beltrami G.;
2017
Abstract
Fuel-based compounds, such as toluene and n-hexane, are common pollutants present in water and wastewater. Due to their tendency to persist in air, water and soil and to bioaccumulate through the food chain, they are included among the most hazardous compounds for human health and environment. Acquatic ecosystems are especially vulnerable because of the frequent use of water bodies as recipients of potentially toxic liquids and solids from domestic, agricultural and industrial wastes. Hence, the removal of fuel-based compounds, through adsorption onto inorganic sorbents is of considerable interest. Due to their selectivity towards organic contaminant and fast adsorption kinetics, it has been recently highlighted that High Silica Zeolites are hydrophobic sorbent materials suitable for adsorption processes (Martucci et al., 2015; Pasti et al., 2016). The aim of this work is to determine the ZSM-5 zeolite degree of selectivity and its structural changes when a competitive adsorption of toluene and n-hexane occurs. A sample of ZSM- 5 zeolite (MFI topology, SiO2/Al2O3 ratio=280), was provided by Tosoh Corporation and loaded with a binary mixture of toluene and n-hexane. Kinetics and adsorption isotherm data were obtained via Headspace Solid Phase Microextraction-GC. Powders patterns were collected before and after adsorption on a Bruker D8 Advance diffractometer equipped with SOL-X detector. Thermal (TG and DTA) analysis were performed in air up to 900°C at 10°C/min. This multidisciplinary approach allowed us to: 1) measure the sorption capacity of zeolite materials weighed against organic pollutants dissolved in water; 2) characterise the sorbent structure after pollutant adsorption; 3) localise the organic species in the zeolite channel systems; 4) probe the interaction between the adsorbate and zeolite framework. Rietveld refinements provide information about the relative position of molecules inside the structure after toluene, nhexane and their mixture adsorption. Data reveal that 1) n-hexane and toluene are preferentially adsorbed whether as single components than as binary mixture; 2) zeolite selectivity is higher towards the n-hexane than toluene. Differences Fourier maps analysis shows that n-hexane, water, and toluene have been adsorbed at about 8.95%, 2.2%, and 1.59%, respectively, in good agreement with both adsorption data and thermal analysis. As a matter of fact, ZSM-5 zeolite preferably adsorbs n-hexane, even in presence of a competitor, such as toluene. Martucci, A., Braschi, I., Bisio, C., Sarti, E., Rodeghero, E., Bagatin, R., 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., 5, 86997-87006. Pasti, L., Rodeghero, E., Sarti, E., Bosi, V., Cavazzini, A., Bagatin, R., Martucci, A. (2016): Competitive adsorption of VOCs from binary aqueous mixtures on zeolite ZSM-5. RSC Adv., 6, 54544-54552.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
