Polycyclic aromatic hydrocarbon extraction from a coal tar-contaminated soil using aqueous solutions of nonionic surfactants

The efficiency and kinetics of surfactant facilitated extraction of phenanthrene and anthracence - two exemplar PAH compounds - from a coal tar-contaminated soil, using five surfactants have been investigated. Three of the surfactants used were ethylene oxide/propylene oxide block copolymers in which the propylene oxide (PO) block was of constant length but the ethylene oxide (EO) block lengths were varied. Steady state extraction values - for PAH removal - were obtained after 50 hours for four of the five surfactants. The extraction efficiency - calculated as the fraction of PAH removed in one washing - is shown to be related to the EO/PO ratio for the block copolymers. Apparent soil/aqueous surfactant solution distribution coefficients (K(d)) were also obtained and suggest that the surfactants can reduce K(d) by several orders of magnitude. Finally the kinetic data is readily fitted to the Elovich equation an essentially empirical equation which has been used, previously, to fit phosphate adsorption data. (C) 1999 Elsevier Science Ltd. All rights reserved.