Removal of emulsified oil from water by inverse fluidization of hydrophobic aerogels

Different size ranges of surface-treated hydrophobic silica aerogels (Nanogel®) provided by Cabot Corporation are fluidized by a downward flow of an oil-in-water emulsion in an inverse fluidization mode. Surface areas, pore size distributions, and pore diameters are investigated by using BET and contact angle is measured by a goniometer. The hydrodynamics characteristics of the Nanogel granules of different size ranges are studied by measuring the pressure drop and bed expansion as a function of superficial water velocity. The density of the Nanogel granules is calculated from the plateau pressure drop after the bed is fully fluidized. The oil removal efficiency of a dilute (1000 ppm COD or lower), stabilized (using the emulsifier Tween 80) oil-in-water emulsion and the capacity of the Nanogel granules in the inverse fluidized bed are also studied. A model was developed to predict the inverse fluidized bed experimental results based on equilibrium and kinetic batch measurements of the Nanogel granules and the stabilized oil-in-water emulsion. The results show that the major factors which affect the oil removal efficiency and capacity are the size of the nanogel granules, bed height, fluid superficial velocity and the proportion of emulsifier in the oil-in-water emulsion. The Nanogel particles can absorb as much as 2.8 times their weight of oil by the inverse fluidization process.