Adsorption of benzene vapor on natural silicate clay minerals under different moisture contents and binary mineral mixtures

Abstract

Benzene, as the representative compound in volatile organic chemicals (VOCs), widely exists in contaminated sites. Adsorption performance of clay minerals can retard the transport of VOCs gas phase to some extent. Static adsorption experiments were conducted to investigate the adsorption capacity of benzene vapor on natural silicate clay minerals (smectite, illite, chlorite and kaolinite) under different temperatures, moisture contents and mineral mixtures. The results of adsorption isotherms for oven-dried clay minerals implied that the distinct adsorption capacity for benzene was mainly attributed to the specific surface areas and pore volume of clay minerals. The amount of adsorption benzene reduced to the minimum, and then gradually increased as the moisture content raised. The existences of water molecule competed the adsorption sites with benzene on the surface of clay minerals at the low moisture content, whereas the dissolutions of benzene molecule in the adsorbed water and the gravitational water could facilitate the adsorption process of clay minerals its adsorption with a saturated water content. Except for the mixture of smectite-kaolinite samples which showed obstruction of pores and declined the adsorption amount of benzene vapor, the experimentally observed adsorption values of benzene on binary mineral mixtures were equal to the theoretically linear sum of the contributions of each individual minerals.