Combined photocatalytic and fungal treatment for the destruction of 2,4,6-trinitrotoluene (TNT)

The combined TiO2-assisted photocatalytic reduction of TNT in series with fungal mineralization by Phanerochaete chrysosporium was investigated. Previously unreported byproducts from the photocatalytic reduction of TNT (at pH 3.1 to 6.6 under a nitrogen atmosphere) were observed: 4-amino-2,6-dinitrotoluene, 2,4-diamino-6-nitrotoluene, 4-hydroxylamino-2,6-dinitrotoluene, 2,4-dihydroxylamino-6-nitrotoluene, and 2-hydroxylamino-4-amino-6-nitrotoluene. The extent of TNT mineralization was approximately 14% by biological transformation alone and improved to approximately 32% using the combined photocatalytic and fungal treatment. No significant mineralization was seen during photocatalytic reduction of TNT. Six hours of photocatalytic pretreatment resulted in the greatest extent of biological mineralization in the combined process. In addition, solubility and polarity of transformation products was increased in the combined treatment over that of fungal or photocatalytic transformation alone. HPLC, mass spectrometry and C-14-radiotracer analyses of the TNT transformations were conducted to show both qualitative and quantitative aspects of the photocatalytic reduction and biological oxidation sequences. This experimentation demonstrated that a combined photochemical and biological sequence of treatment may be a viable method of treating aqueous TNT wastes. (C) 1998 Elsevier Science Ltd. All rights reserved.