Technical Note Photocatalytic pre-treatment with food-grade TiO 2 increases the bioavailability and bioremediation potential of weathered oil from the Deepwater Horizon oil spill in the Gulf of Mexico Jonathon A. Brame a , Seok Won Hong b , Jaesang Lee b , Sang-Hyup Lee b , Pedro J.J. Alvarez a,⇑ a Rice University-Department of Civil and Environmental Engineering, 6100 Main St. Houston, TX 77005, United States b Center for Water Resource Cycle Research, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea highlights " Food-grade TiO 2 has potential as an environmentally benign photocatalyst. " Photocatalysis can be used to jump- start oil spill bioremediation. " Photocatalytic pre-treatment increased weathered oil solubility and biodegradability. graphical abstract article info Article history: Received 4 September 2012 Received in revised form 12 October 2012 Accepted 14 October 2012 Available online 22 November 2012 Keywords: Photocatalyst Oil Recalcitrant Remediation Bioremediation Biodegradation abstract Using the 2010 Deepwater Horizon oil spill in the Gulf of Mexico as an impetus, we explored the potential for TiO 2 -mediated photocatalytic reactive oxygen species (ROS) generation to increase the bioavailability (solubility) and biodegradability of weathered oil after a spill. Food grade TiO 2 , which is FDA approved for use as food additive in the United States, was tested as a photocatalyst for this novel application. Photocatalytic pre-treatment (0.05 wt.% TiO 2 , UV irradiation 18 W m 2 , 350–400 nm) for 24 h in a bench top photoreactor increased the soluble organic carbon content of weathered oil by 60%, and enhanced its subsequent biodegradation (measured as O 2 consumption in a respirometer) by 37%. Photocatalytic pre-treatment was also tested outdoors under sunlight illumination, but no significant increase in solubility or biodegradation was observed after 11 d of exposure. Although sunlight irradiation of food-grade TiO 2 generated ROS (assessed by the degrada- tion of 4-chlorophenol as a probe compound), the efficacy of weathered oil pre-treatment was appar- ently hindered by sinking of the photocatalysts under quiescent conditions and illumination occlusion by the oil. Overall, results indicate that photocatalytic pre-treatment to stimulate bioremediation of weathered oil deserves further consideration, but controlling the buoyancy and surface hydrophobic- ity of the photocatalysts will be important for future efforts to enable ROS generation in proximity to the target compounds. Ó 2012 Elsevier Ltd. All rights reserved. 0045-6535/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2012.10.009 ⇑ Corresponding author. Tel.: +1 713 348 5903; fax: +1 713 348 5268. E-mail addresses: jon.brame@gmail.com (J.A. Brame), swhong@kist.re.kr (S.W. Hong), lee39@kist.re.kr (J. Lee), alvarez@rice.edu (P.J.J. Alvarez). Chemosphere 90 (2013) 2315–2319 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere