Coupled photocatalytic and biological degradation of 2,4,6-trinitrotoluene (TNT)

A recirculating batch, annular photoreactor in combination with cultures of the ligninolytic fungus, P. chrysosporium, was used to investigate degradation and ultimate mineralization of aqueous solutions of 2,4,6-trinitrotoluene (TNT), a ''pink water'' constituent. The photocatalytic pretreatments of TNT were performed under anaerobic conditions with the addition of EDTA as a reducing agent to promote TNT reduction. At pH 3.1 to 6.6, the major photoreaction products under a nitrogen atmosphere were 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. Follow-on biological treatment of the photoreactor degradation products performed under aerobic conditions using mycelial preparations of P. chrysosporium showed up to 32 percent mineralization of the parent C-TNT, depending on length of phototreatment. Longer photocatalytic treatment of the TNT resulted in a greater extent of mineralization. The combined processes of TiO2 assisted photocatalysis and follow-on biological mineralization have the potential to be an effective technology for the remediation of pink water constituents.