Oxidative degradation of pyrene in contaminated soils by δ-MnO2 with or without sunlight irradiation

The enhanced oxidative degradation of pyrene in quartz sand and alluvial and red soils by micro-nano size birnessite (delta-MnO2) in the presence and absence of sunlight was investigated. The degradation of pyrene by delta-MnO2 in quartz sand showed very little synergistic effect of sunlight irradiation on delta-MnO2 oxidizing power. However, pyrene degradation by delta-MnO2 in alluvial and red soils was greater under solar irradiation than the combination of photooxidation of pyrene and oxidation of pyrene by delta-MnO2. The oxidative degradation percentages of pyrene by delta-MnO2 under sunlight irradiation are 94.8, 97.7, and 100% for alluvial soil, red soil, and quartz sand, respectively. Oxidative degradation percentages of pyrene by delta-MnO2 in alluvial and red soils with irradiation of sunlight almost attained a maximum at 1 h with a 5% (w/w) dose of the amended oxidant. Due to their different total organic carbon (TOC) contents, the sequence of enhanced oxidative degradation of pyrene by delta-MnO2 in quartz sand and alluvial and red soils was quartz sand > red soil > alluvial soil. Further, this study revealed that delta-MnO2-enhanced oxidative degradation of pyrene is very pronounced in contaminated soils in situ even at deep soil layers where irradiation by sunlight is very limited. (C) 2011 Elsevier B.V. All rights reserved.