Photo-assisted removal of fuel oil hydrocarbons from wood and concrete

Abstract

A novel photo-treatment to decontaminate building structural elements polluted with fuel oil hydrocarbons as a result of spillage and/or a catastrophic flood was examined. A proof-of-concept study evaluating the photocatalytic removal of hydrocarbons (n-hexadecane and fuel oil #2) from contaminated wood (southern yellow pine) and concrete was conducted using scintillation counting (with 14C-labeled n-hexadecane) and gas chromatography. Contaminated samples were irradiated by UV or fluorescent light in the absence or presence of a photocatalyst, TiO2. As a result of the treatment, under various scenarios, up to 80–98% of the originally applied n-hexadecane was removed, within a wide range of contaminant concentrations (4–250 mg/g wood). The essential treatment time increased from 1–7 days for low concentrations to several weeks for high concentrations. Mass balance experiments showed that the only product formed from 14C-labeled n-hexadecane in detectable amounts was 14CO2. For low amounts of applied hydrocarbon (4–20 mg/g wood), the overall process rate was limited by the contaminant transport/mobility whereas for high n-hexadecane concentrations (150–250 mg/g, corresponding to 50–80% filling of wood pores), the key factor was the photochemical reaction. Photodegradation experiments conducted with standard heating fuel oil #2 (a representative real-world contaminant) resulted in a significant (up to 80%) photochemical removal of mid-size hydrocarbons (C13–C17) in 3 weeks whereas heavier hydrocarbons (> C17) were not affected; light hydrocarbons (< C12) were removed by evaporation. These results point toward a promising technique to reclaim wooden and concrete structures contaminated with semi-volatile chemicals.