Testing adsorbents capacities for indoor volatile organic compounds at optimum operating conditions

Measurements of adsorption isotherms for three VOCs (toluene, 1,2 dichlorobenzene and 1,1,1 trichloroethane) on five adsorbents (polyacrylonitrile carpet fibers, silica alumina, silica alumina impregnated with KMnO4, granulated activated carbon and pellets of activated carbon) were performed. Various temperatures and relative humidity were tested. VOCs concentrations were altered in the range of presence in indoor environments in Kuwait. The adsorbed weight was measured in a thermogravimetric analyser. Linear isotherms were observed in all cases with values of the Henry coefficient ranging from 0.01 to 0.941 mm. Silica alumina activated by KMnO4 showed highest adsorption rates. At low temperatures and minimum humidity in air high equilibrium constants were observed, since adsorption rate is higher than desorption rates at lower temperatures. In addition, increasing humidity will decrease adsorption rates due to moisture occupation of the available voids for adsorption, especially for hydrophilic adsorbents. There was good agreement between the equilibrium and kinetic constants obtained in the TGA. It may therefore be concluded that, in the present case at least, adsorption data obtained using small samples of adsorbent in the laboratory can be successfully scaled-up and used in combination with the theory described in this work to model indoor air quality in much larger chambers.