The study herein investigated the effectiveness of simultaneous use of ozone and hydrogen peroxide (O-3/H2O2 process) to degrade o-phenylenediamine (o-PDA) in a simulated wastewater. A rotor-stator reactor (RSR) was employed to create a high-gravity environment in order to enhance ozone-liquid mass transfer rate and possibly improve the degradation rate of o-PDA. The degradation efficiency of o-PDA (eta) as well as the overall gas-phase volumetric mass transfer coefficient (K(G)a) were determined under different operating conditions of H2O2 concentration, initial o-PDA concentration, temperature of reaction, initial pH and rotation speed of RSR in attempt to establish the optimal conditions. Chemical oxygen demand reduction rate (r(COD)) of wastewater treated at a particular set of conditionswas also analyzed. Additionally, the intermediate products of degradation were identified using a gas chromatography-mass spectrometer (GC/MS) to further evaluate the extent of o-PDA degradation as well as establish its possible degradation pathway. Results were validated by comparison with those of sole use of ozone (O-3 process), and it was noted that., KGa and rCOD achieved by O-3/H2O2 process was 24.4%, 31.6% and 25.2% respectively higher than those of O-3 process, indicating that H2O2 can greatly enhance ozonation of o-PDA. This work further demonstrates that an RSR can significantly intensify ozone-liquidmass transfer rate and thus provides a feasible intensification means for the ozonation of o-PDA as well as other recalcitrant organics. (c) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.