Degradation of Nitrobenzene and Nitrophenols in Homogeneous Aqueous Solution

Degradation reactions of aqueous nitrobenzene (1), 2-nitrophenol (2), and 2,4-dinitrophenol (3) by means of the photolysis in the presence of the Fenton reagent (FeCL2/H2O2) (I) were investigated. The results were compared with those for 4-nitrophenol (4) as well as for direct photolysis (II), the photolysis in the presence of hydrogen peroxide (III) and the dark Fenton reaction (IV) of (1)–(3), reported elsewhere. In all the cases, decomposition of the aromatic nitrocompounds was observed. The best results were obtained when the solutions of nitrophenols 2–4, containing the Fenton reagent, were irradiated with the polychromic UV light. The rates of the compounds 1–4 degradation depend on their electronic structures in the ground and excited states. The mechanisms of the degradation of 1–4 by means of direct photolysis, the Fenton reaction, the photochemical reactions in the presence of hydrogen peroxide and the Fenton reaction are discussed. The developed method I is concluded to be more effective than II–IV, and therefore recommended for the elimination of the compounds 1–4 from waters and wastewaters.