Ultrasonic Soil Washing with Fish Oil Extract to Remove Polychlorinated Dibenzo-p-dioxins (PCDDs), Dibenzofurans (PCDFs) from Highly Contaminated Field Soils

PCDD/F-contaminated soil of a coastal region formerly involved in the production of pentachlorophenol (PCP) in Tainan City in southern Taiwan, has drawn wide concern throughout the island. This main goal of this study was to find an effective and environmentally friendly means of removing PCDD/Fs from its contaminated fields. We performed a soil washing experiment with fish extract using a combination of ultrasonification and mechanical double-blade stirring. The experiments were conducted under ambient temperature, at a soil/liquid ratio of 1:2.5, 700 rpm, and over a short duration. This combined method using fish extract removed 94.12% of the pollutant in moderately contaminated soils (5 washing cycles) and 94.51% in highly contaminated soils (10 washing cycles), mostly via particle collision and penetration. These findings highlight the benefits of PCDD/F partitioning between the particles and fish oil extract. This study is the first to use fish oil extract, a natural solvent, to treat soils highly contaminated with dioxins. Because fish oil extract is rich in non-toxic bio-surfactants (e.g., alcohols, acids, ketones, etc.), it may be used in this process to improve bioavailability and bioactivity of the soil making bio-attenuation and full remediation safer and more efficient.