Sorption of Monoaromatic Hydrocarbons to Wood

Abstract

The sorption of benzene, toluene and o-xylene to wood, a common subsurface fill material, was characterized. Sorptive equilibrium was attained within 24 h for water-saturated Douglas fir and Ponderosa pine chips of centimeter-sized dimensions, consistent with predictions of retarded diffusive transfer into the wood. Sorption to the chips exhibited linear sorption isotherms. When wood−water partition coefficients were normalized to the wood's lignin content, the resulting lignin−water partition coefficients, Klignin, agreed to within a factor of 2 with literature values reported for chemically isolated lignins. Wood sorption was substantially overpredicted by an organic carbon-based model (i.e., Koc). Wood−water partition coefficients for nonionic sorbates (10 < Kow < 104) can be predicted as the product of the wood's fractional lignin content, flignin, and a Klignin estimated from the linear free energy relationship: log Klignin = (0.74 ± 0.09) log Kow − (0.04 ± 0.25).