Oxidizing 2,4,6-trinitrotoluene with pyrite-H 2O 2 suspensions

Abstract

A modified Fenton reagent, using solid pyrite in the place of soluble ferrous iron salt, has been used to clean-up pure water spiked with 2,4,6-trinitrotoluene (TNT). Water treatment was conducted at pH 3 with 1.8–28.6 mM Fe (II) (as pyrite) + 0.015-0.029 M of H 2O 2 and compared with Classic Fenton (CF) reaction: 1.8 mM Fe (II) (as ferrous sulfate) + 0.029-0.29 M H 2O 2. All experiments were conducted in the dark and in the light by using an artificial light source of 200-W. The pseudo-first order rate constant, k, of TNT degradation did not significantly increased as a function of peroxide addition like in CF reagent, where all Fe (II) was in solution. When both reagents were used at the concentrations of 1.8 mM Fe (II) + 0.029 M H 2O 2 complete oxidation of TNT with modified Fenton reagent was slower respect to classic Fenton reagent (48 h vs. 24 h). However mineralization of TNT with 1.8 mM Fe(II) from pyrite + 0.029 M H 2O 2 under Dark/Light conditions was of the same order of magnitude ( 42 85 %) as with CF using a 10 times higher concentration of peroxide (0.29 M H 2O 2). Even though reuse of oxidized pyrite after a first oxidation treatment, prolonged the time of TNT disappearance from a second solution (48 h vs 24 h with 5.4 mM Fe 2+ from pyrite + 0.029 M H 2O 2) the extent of mineralization remained unvaried (− 45%).