Kinetics and mechanism of nitrobenzene degradation by hydroxyl radicals-based ozonation process enhanced by high gravity technology

This study investigated the indirect oxidation of nitrobenzene (NB) by hydroxyl radicals (center dot OH) in a rotating packed bed (RPB) using competitive kinetics method with p-nitrochlorobenzene as a reference compound. The rate constants of NB with center dot OH are calculated to be between (1.465 +/- 0.113) x 10(9) L/(mol center dot s) and (2.497 +/- 0.192) x 10(9) L/(mol center dot s). The experimental data are fitted by the modified Arrhenius equation, where the activation energy is 4877.74 J/mol, the order of NB concentration, rotation speed, and initial pH is 0.2425, 0.1400 and 0.0167, respectively. The ozonation process of NB could be enhanced by RPB, which is especially effective for highly concentrated NB-containing waste-water under alkaline conditions. The high gravity technology can accelerate ozone mass transfer and self-decomposition of ozone to produce more center dot OH, resulting in an increase in the indirect oxidation rate of NB by center dot OH and consequently effective degradation of NB in waste-water.