Abstract
Picric acid (2, 4, 6-trinitrophenol) is one of the toxic nitroaromatic compounds present in over 1000 munition sites in the United States, and this constitutes a major environmental and human health hazard. In a laboratory study, 250 mg/l of picric acid was degraded in an aqueous medium with Fenton's reagent [acidified ferrous (Fe2+) solution and hydrogen peroxide (H2O2)]. Different dosages of Fe2+ and H2O2 were employed to investigate the efficiency of the degradation. The initial picric acid solution, the reaction intermediates and byproducts of the degradation were monitored as total organic carbon (TOC) with the TOC analyzer as the Fenton reaction progressed. The oxidation process was fast and it was noted that the residual Fe2+ and H2O2 left in the mixture after 5 min of treatment was less than 10% of the starting concentration. Approximately 90% of the picric acid was mineralized within 60 min of reaction, as indicated by the reduction in TOC levels. The optimum pH for the removal of TOC with a one-step addition of Fenton's reagent was pH 2–3 under ambient laboratory temperatures. Formation of an intermediate complex (greenish in color) was observed at the initial stages of the Fenton oxidation of picric acid. UV-visible, HPLC and GC-MS analyses revealed that the picric acid ring structure was destroyed after treatment with Fenton's reagent and the reaction byproducts include nitrates, CO2, NH4 + and carboxylic acids.