Oxidation of TNT by photo-Fenton process.
A series of photo-Fenton reactions have been performed for the degradation of 2,4,6-trinitrotoluene (TNT) in a 4.2-l reactor. The degradation reaction rate of TNT followed a pseudo-first-order behavior; and the rate constants for 2.4mW cm(-2)UV only, 2.4mW cm(-2)UV/H(2)O(2), Fenton, photo-Fenton (2.4mW cm(-2)) and photo-Fenton (4.7mW cm(-2)) were 0.002min(-1), 0.007min(-1), 0.014min(-1), 0.025min(-1) and 0.037min(-1), respectively. Increasing the intensity of UV light, and the concentrations of ferrous ions and hydrogen peroxide promoted the oxidation rate under the experimental conditions in this study. The weighting factor (f), the Fe(II)-promoted efficiency (r) and the promoted-UV light efficiency (p) were calculated to clarify their effects on the TNT oxidation. Moreover, the inhibition effect of hydroxyl radical was also observed in both Fenton and photo-Fenton oxidation when the concentration of Fe(II) were higher than 2.88mM. Solid phase micro-extraction was first applied to the separation of the organic byproducts from TNT oxidation. GC/MS was employed to identify the byproducts during the Fenton and photo-Fenton oxidation of TNT. These compounds were clarified as 1,3,5-trinitrobenzene, 1-methyl-2,4-dinitrobenzene 2,5-dinitrobenzoic acid and 1,3-dinitrobenzene. By these byproducts, the mechanisms of the methyl group oxidation, decarboxylation, aromatic ring breakage, and hydrolysis can be recognized and demonstrated. The pathway of TNT oxidation by photo-Fenton process was also proposed in this study.
Liou
Ming-Jer
MJ
Institute of Environmental Engineering, National Chiao Tung University, Hsinchu 300, Taiwan.
Lu
Ming-Chun
MC
Chen
Jong-Nan
JN
D008401:Gas Chromatography-Mass Spectrometry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D010777:Photochemistry; D014303:Trinitrotoluene / Q000737:chemistry*; D014466:Ultraviolet Rays
C045076:Fenton's reagent; D014303:Trinitrotoluene; D006861:Hydrogen Peroxide; D007501:Iron