(187a) Separation of Oil and Other Organics From Water Using Inverse Fluidization of Hydrophobic Aerogels

Surface-treated hydrophobic aerogel (Cabot Nanogel®) granules of size range of about 1 mm are fluidized by a downward flow of oil-contaminated water in an inverse fluidization mode. Nanogel particles are nanostructured, extremely light and porous, have a very large surface area per unit mass, and are sufficiently robust to be fluidized. Their hydrophobic surface gives them a strong affinity for oil and other organic molecules, with the exclusion of water. Furthermore, as they adsorb/absorb oil they become heavier, lose their buoyancy and eventually leave the column. Hence the fluidized bed can be operated continuously by adding fresh Nanogel at the same rate as the saturated Nanogel is removed from the bed.

The hydrodynamic characteristics of the inverse fluidized bed of Nanogel and the granule density were obtained by measuring the pressure drop and bed expansion as a function of the superficial water velocity. Either pure vegetable oil, or an oil-in-water emulsion using 1 and 4 % Tween 80 as a surfactant to keep the emulsion stable, were mixed with de-ionized water in a static mixer before entering the inverse fluidized bed. Microscopic examination of the inlet mixture showed that the oil droplets were less than 20 microns in size for the emulsified oil, but larger than 20 microns for the pure oil However, the oil removal efficiency (breakthrough curve) and capacity of the Nanogel granules in the inverse fluidized bed were found to depend on the amount of stabilizer added, indicating that the Tween 80 was affecting the aerogel surface and allowing some water to enter as well as oil.