Removing Polycyclic Aromatic Hydrocarbons From Water by Adsorption on Silicagel

This study investigates a specific topic of water purification by the adsorption onto silicagel of polycyclic aromatic hydrocarbons (PAHs), which are carcinogenic, toxic and persistent in the environment. Acenaphthene, a representative low molecular PAH with moderate solubility in water, is selected as target compound. Batch kinetic experimental studies were undertaken. Kinetic results were modelled using pseudo-first and pseudo-second-order equations, and equilibrium data were described by the traditional Langmuir and Freundlich isotherms. It can be concluded that the lower molecular mass PAHs, such as acenaphthene, are well represented by the pseudo-first-order equations. Adsorption mechanisms were moreover analyzed using boundary layer mass transfer and intra-particle diffusion models, indicating intra-particle diffusion as the dominant adsorption controlling step. Isotherm equations may be applied to predict the silicagel quantity necessary to remove a given concentration of the PAH using a recommended fixed-bed batch adsorber system.