Enhancing Fenton oxidation of TNT and RDX through pretreatment with zero-valent iron

The effect of reductive treatment with elemental iron on the rate and extent of TOC removal by Fenton oxidation was studied for the explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using a completely stirred tank reactor (CSTR). The results support the hypothesis that TNT and RDX are reduced with elemental iron to products that are oxidized more rapidly and completely by Fenton's reagent. Iron pretreatment enhanced the extent of total organic carbon (TOC) removal by approximately 20% and 60% for TNT and RDX, respectively. Complete TOC removal was achieved for TNT and RDX solutions with iron pretreatment under optimal conditions. On the other hand, without iron pretreatment, complete TOC removal of TNT and RDX solutions was not achieved even with much higher H2O2 and Fe2+ concentrations. Nitrogen was recovered as NH4+ and NO3- when Fe(0)-treated TNT and RDX solutions were subjected to Fenton oxidation. The bench-scale iron treatment-Fenton oxidation integrated system showed more than 95% TOC removal for TNT and RDX solutions under optimal conditions. These results suggest that the reduction products of TNT and RDX are more rapidly and completely degraded by Fenton oxidation and that a sequential iron treatment-Fenton oxidation process may be a viable technology for pink water treatment. (C) 2003 Elsevier Ltd. All rights reserved.