Lindane adsorption isotherms interpreted in terms of interaction free energies with porous media

Lindane adsorption isotherms on silica sand and alluvial loam were investigated by batch and column experiments and related to lindane interaction free energies with the porous media. These interaction free energies were highly dependent on the physico-chemical characteristics of lindane and the porous media and could be calculated by their surface thermodynamic properties. Silica sand displayed a single adsorption domain and lindane had a linear adsorption isotherm on silica sand. In contrast, alluvial loam exhibited dual adsorption domains, which could be interpreted by two linear adsorption isotherms. For heterogeneous porous media with multiple adsorption domains, such as alluvial loam, lindane first adsorbed onto domains of high adsorption potentials. When these domains were occupied, lindane began to adsorb onto domains of low adsorption potentials.