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