Aqueous phase adsorption of toluene in a packed and fluidized bed of hydrophobic aerogels

Surface-treated hydrophobic silica aerogel granules (Cabot Nanogel^®) are contacted by a downward flow of a dilute toluene-water solution in either a packed bed or an inverse fluidized bed mode. The toluene adsorption efficiency and capacity of the Nanogel granules in both the packed or inverse fluidized bed are studied. The results show that the major factors which affect the toluene adsorption efficiency and capacity are the weight of the Nanogel granules (bed height) and fluid superficial velocity. In the fluidized bed adsorber the breakthrough time is considerably shorter than in the packed bed adsorber due to solids mixing in the fluidized bed; the outlet toluene concentrations at short times are also much higher and the toluene adsorption efficiencies are relatively low. The Nanogel granules adsorb about 4% of their weight in toluene. Simple models were used to predict the packed bed and inverse fluidized bed experimental results based on batch equilibrium and batch kinetic measurements of the Nanogel granules and the toluene solution. Good agreement between the models and experimental results were obtained.