(667a) Adsorption on Light Solid Sorbents

Aerogels and metal organic frameworks are new groups of microporous porous materials with very different structure:  one  is amorphous and the other crystalline.  However, one common feature of these two groups of materials is that they are highly porous with a low density, less or around 1 g/cm³. This paper will discuss some unique features of adsorption on these two groups of porous materials using experimental data of sorption of five volatile organic compounds from the vapor or liquid phase on hydrophobic silica aerogel granules, and diffusion carbon dioxide on MOF-5 crystals measured by different methods.  The rate of adsorption on silica aerogels decreases in the order: pure liquid>liquid solution>vapor. Transient measurement of diffusion of gases in MFO-5 gives diffusivities much lower than that measured by the steady-state membrane diffusion method.   Due to high porosity and low density, both the silica aerogels and MOF have much lower thermal conductivity than the conventional porous solids such as zeolites.The unusual adsorption results can be explained by a mathematical model considering both mass and heat transfer during the adsorption process. The results show the limitation of using these groups of light sorbents for gas/vapor separation.  However, these sorbents will find applications for liquid separation as demonstrated by removal of organics from wastewater by inversed fluidization bed.