Desorption of selected PAHs as individuals and as a ternary PAH mixture within a water-soil-nonionic surfactant system

Abstract

Remediation of soil contaminated with polycyclic aromatic hydrocarbons (PAHs) is a major environmental concern due to the toxic and carcinogenic properties of these compounds. Desorption and partitioning of anthracene, fluorene and pyrene within soil–aqueous systems in the presence of the nonionic surfactants, Triton X-100 and Tween 80,were studied. The results showed that the addition of Tween 80 solution at 10 g/L initial concentration enhanced the desorption of PAHs by 49.6%, 10.7% and 70.2% for anthracene, fluorene, and pyrene, respectively, from soil into aqueous phase at 72 h equilibration, while the addition of Triton X-100 could enhance the desorption of PAHs from soil by 59.5%, 17.4% and 86.3% for anthracene, fluorene and pyrene, respectively, at similar experimental conditions. The desorption behaviour of the tested PAHs in a ternary mixture was changed relatively since, in the presence of less hydrophobic solutes, the solubility of more hydrophobic solutes was increased leading to a higher desorption rate. The results showed that hydrophobicity is the primary property that controls PAH desorption from soil and surfactant sorption onto the soils (Q _m) in which the latter were found to be 3.75×10⁻⁶ and 4.82×10⁻⁶ mol/g for Triton X-100 and Tween 80, respectively.

Keywords:

• soil contamination
• PAHs desorption
• soil washing
• nonionic surfactant
• hydrophobicity

Acknowledgements

This work was funded by the Petroleum Research and Development Centre, Ministry of Oil, Iraq. The authors are grateful to the Ibn-Sina Company and the Department of Petroleum Engineering, University of Baghdad, for their technical support.