Due to their biological origin, humic monomers, such as p-hydroxybenzaldehyde (p-HBA), are usually present in soils and water. Phenolic and aromatic compounds, such as p-HBA, arise from the degradation of natural organic matter (NOM), which can assume different molecular structures creating natural and synthetic compounds. The removal of these compounds from water is of increasing interest due to the possibility of negative interference with water remediation systems. Indeed, they usually assume the role of intermediary or precursor of many hazardous contaminants. Moreover, when high concentrations are present in water, they become phytotoxic for plants. It has been highlighted that hydrophobic zeolites are eco-friendly materials, which can be exploited for their adsorption properties in the removal of contaminants from water bodies and their possibility of regeneration through thermal treatment, without changing their initial adsorption capacity (Braschi et al., 2016; Wang et al., 2016). Since the presence of natural organic matter (NOM) can affect organic pollutants adsorption, the effect of lignin-derived phenolic monomers on the adsorption properties was investigated. The aim of this work is to study the structural modifications induced by adsorption/desorption process undergoing on a hydrophobic Y zeolite (HSZ-390HUA, SiO2/Al2O3 = 200, Tosoh Corporation) loaded with p-HBA upon thermal treatment. To obtain this goal, chromatographic, diffractometric and thermal (TG and DTA) analysis were carried out. Kinetics and adsorption isotherm batch data were obtained via Headspace Solid Phase Microextraction-GC in order to quantify the amount of p-HBA adsorbed into zeolite channels system.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 to 600°C) to investigate high-temperature structural modifications and probe the host-guest interactions. Experimental results confirm that p-HBA is highly adsorbed on zeolites. Rietveld refinements reveal that the extraframework content is completely desorbed at about 570°C; these results are in good agreement with the total weight loss registered by thermal analysis. After thermal treatment, zeolite does not show any significant loss of crystallinity and non-equilibrium distortions in the framework are relaxed. Moreover, the regenerated zeolites regain almost the same unit-cell parameters of the bare material and no relevant structural deformations are registered in channel geometry. Braschi, I., Blasioli, S., Buscaroli, E., Montecchio, D., Martucci, A. (2016): Physicochemical regeneration of high silica zeolite Y used to clean-up water polluted with sulfonamide antibiotics. J. Environ. Sci., 43, 302-312. Wang, X., Li, B.Q., Zhai, H.L., Xiong, M.Y., Liu, Y. (2016): An efficient approach to the quantitative analysis of humic acid in water. Food Chem., 190, 1033-1039.
Study of adsorption/desorption process of p-HBA into Y zeolite: a model system for water treatment contaminated by humic acids
Tallarigo N.
;Pasti L.;Beltrami G.;
2017
Abstract
Due to their biological origin, humic monomers, such as p-hydroxybenzaldehyde (p-HBA), are usually present in soils and water. Phenolic and aromatic compounds, such as p-HBA, arise from the degradation of natural organic matter (NOM), which can assume different molecular structures creating natural and synthetic compounds. The removal of these compounds from water is of increasing interest due to the possibility of negative interference with water remediation systems. Indeed, they usually assume the role of intermediary or precursor of many hazardous contaminants. Moreover, when high concentrations are present in water, they become phytotoxic for plants. It has been highlighted that hydrophobic zeolites are eco-friendly materials, which can be exploited for their adsorption properties in the removal of contaminants from water bodies and their possibility of regeneration through thermal treatment, without changing their initial adsorption capacity (Braschi et al., 2016; Wang et al., 2016). Since the presence of natural organic matter (NOM) can affect organic pollutants adsorption, the effect of lignin-derived phenolic monomers on the adsorption properties was investigated. The aim of this work is to study the structural modifications induced by adsorption/desorption process undergoing on a hydrophobic Y zeolite (HSZ-390HUA, SiO2/Al2O3 = 200, Tosoh Corporation) loaded with p-HBA upon thermal treatment. To obtain this goal, chromatographic, diffractometric and thermal (TG and DTA) analysis were carried out. Kinetics and adsorption isotherm batch data were obtained via Headspace Solid Phase Microextraction-GC in order to quantify the amount of p-HBA adsorbed into zeolite channels system.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 to 600°C) to investigate high-temperature structural modifications and probe the host-guest interactions. Experimental results confirm that p-HBA is highly adsorbed on zeolites. Rietveld refinements reveal that the extraframework content is completely desorbed at about 570°C; these results are in good agreement with the total weight loss registered by thermal analysis. After thermal treatment, zeolite does not show any significant loss of crystallinity and non-equilibrium distortions in the framework are relaxed. Moreover, the regenerated zeolites regain almost the same unit-cell parameters of the bare material and no relevant structural deformations are registered in channel geometry. Braschi, I., Blasioli, S., Buscaroli, E., Montecchio, D., Martucci, A. (2016): Physicochemical regeneration of high silica zeolite Y used to clean-up water polluted with sulfonamide antibiotics. J. Environ. Sci., 43, 302-312. Wang, X., Li, B.Q., Zhai, H.L., Xiong, M.Y., Liu, Y. (2016): An efficient approach to the quantitative analysis of humic acid in water. Food Chem., 190, 1033-1039.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
