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