The investigation of fluorene removal with chemical oxidation after soil washing

Abstract

a b s t r a c tSoils contaminated by polycyclic aromatic hydrocarbons (PAHs) pose potential risks to human health and the environment. In this study a combined physical-chemical treatment involving soil washing and advanced oxidation was investigated. A fluorene contaminated loamy soil was treated with a washing solution containing a non-ionic surfactant polyoxyethylene 20 cetyl ether (Brij 58). The washing solution containing fluorene (48.5-54.3 mg/L) was afterwards treated with Fenton and electro-Fenton oxidation. The conventional Fenton oxidation results revealed a fast removal of fluorene (>84%) within the first 15 min. COD removal representing the general destruction of washing solution remained at about 10%, but increased to 81% when the reaction time was increased to 480 min using 2% hydrogen peroxide (H 2 O 2 ). The corresponding fluorene removal was about 98%. The pseudo-second order rate constants observed for fluorene (0.0016 L/mg min) and COD (1.5 × 10 -6 L/ mg min) oxidation supported these results by indicating to a faster oxidation of fluorene. Increase in the H 2 O 2 concentration similarly influenced the oxidation of COD rather than fluorene. The COD removal efficiency increased from 43% to 97% when the H 2 O 2 concentration was increased from 2% to 10% for a treatment time of 120 min. Electro-Fenton oxidation studies with a current density of 15 mA/cm 2 and an electrolyte conductivity of 2 mS/cm revealed even better results enabling a reduction in reaction time. 60 min of reaction time with 2% H 2 O 2 represented removal efficiencies of 98% and 91% for fluorene and COD, respectively.