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.

Keywords:

• Fuel oil
• hydrocarbons
• photocatalysis
• wood

Acknowledgments

Funding for this work was provided by the USDA Forest Products Laboratory (FPL) via cooperative agreements#04-JV-11111120-070 and 05-JV-11111120-102. The authors are immensely grateful to Dr. A. Kubatova (UND Chemistry Dept.) and Dr. C. R. Frihart (USDA Forest Products Lab, Madison, WI) for providing access to essential equipment and fruitful discussion of the manuscript. Our thanks are to Dr. D. S. Muggli (UND Chemical Engineering Dept.) for reviewing the manuscript and to G. V. Baglayeva for measuring the maximum absorption of n-hexadecane in wood.

Notes

¹Blanks with such high n-hexadecane amounts held steady, at ca. 100% (not shown).