Impact of Fenton and ozone on oxidation of wastewater containing nitroaromatic compounds

Abstract

Fenton and ozone treatment was investigated at laboratory scale for the degradation of aqueous solutions of nitrobenzene (NB). Effects of reactants concentration (03, H2O2, and Fe(II)), temperature, and pH on NB degradation were monitored. Reaction kinetic of these processes was also assessed. A rapid reaction took place for Fenton process at higher initial concentration of H2O2, higher temperatures, and more acidic conditions (pH 3). Similarly, ozonation reaction exhibited rapid rates for higher ozone dose, higher temperatures, and more basic conditions (pH 11). Complete NB degradation in 65 min was achieved using Fenton process. The conditions of complete elimination of 100 mgfL of initial NB concentration, were 250 mg/L of H2O2 concentration, pH 3, and 10 mg/L of Fe(II) concentration. Under these conditions, 55% organic carbon elimination was achieved. Total organic carbon mineralization was attained in 240 min reaction time by Fenton process with 900 mg/L of H2O2 concentration, and 30 mg/L of Fe(II) concentration. Fenton reaction showed a pseudo-first order kinetic; the reaction rate constant was ranged from 0.0226 to 0.0658 min(-1). Complete NB degradation was also achieved for an ozone dose of the order of 2.5 g/L. The ozonation was studied at different ozone doses, different initial pH (7-11) and at different temperatures (15-35 degrees C). NB ozonation kinetic was represented by a bi-molecular kinetic model which was reduced to pseudo-first order kinetic. The pseudo-first order reaction rate constant was determined to increase at 20 degrees C from 0.004 to 0.020 min(-1) as the used ozone increased from 0.4 to 1.9 g/L.