Performance evaluation of wash-coated MCM-48 monolith for adsorption of volatile organic compounds and water vapors

The adsorption equilibrium and column dynamics of five organic molecules (acetone, benzene, n-hexane, toluene, trichloroethene) and water vapors on the wash-coated MCM-48 were studied to investigate the applicability of a monolithic adsorber in the adsorption based areas. The wash-coated samples were characterized by using X-ray diffraction (XRD), scanning electron microscopic (SEM) images and nitrogen adsorption–desorption isotherms. To obtain the pure component adsorption equilibrium data at different temperatures (300.15–322.15 K), a gravimetric method was used. The wash-coated MCM-48 showed the unique feature of mesoporous media without any defects although the adsorption capacities for selected adsorbates decreased. The hybrid adsorption isotherms, presented in our recent works [J.W. Lee, J.W. Lee, W.G. Shim, S.H. Suh, H. Moon, J. Chem. Eng. Data 48 (2003) 381–386; J.S. Oh, W.G. Shim, J.W. Lee, J.H. Kim, H. Moon, G. Seo, J. Chem. Eng. Data 48 (2003) 1458–1462; J.W. Lee, W.G. Shim, H. Moon, Micropor. Mesopor. Mater. 73 (2004) 109–119; W.G. Shim, J.W. Lee, H. Moon, Micropor. Mesopor. Mater. 88 (2006) 112–125] satisfactorily correlated the adsorption equilibrium data obtained. The adsorption equilibrium amounts for water vapor were about 5–6 times higher than those of the corresponding organic compounds. To examine the behavior of adsorption breakthrough curves, we employed axi-symmetric model with hybrid isotherms for single component and a simple extended hybrid Langmuir–Sips (EHLS) equation for multicomponent. The current work demonstrates that the adsorption breakthrough patterns are significantly dependent on the equilibrium adsorption isotherm shape. In the case of multi-component mixture systems, we found that there are cooperative and competitive relationships between soluble chemicals and water vapor. Moreover, considering the prediction works, the hybrid isotherm model agrees well with the single component experimental data while the EHLS model fails to explain the multi-component systems.