The study herein investigated the effectiveness of simultaneous use of ozone and hydrogen peroxide (O

3

/H

2

O

2

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 (η) as well as the overall gas-phase volumetric mass transfer coefficient (K

G

a) were determined under different operating conditions of H

2

O

2

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 conditions was 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 o

zone (O

3

process)

and it was noted that η

K

G

a and r

COD

achieved by O

3

/H

2

O

2

process was 24.4%

31.6% and 25.2% respectively higher than those of O

3

process

indicating that H

2

O

2

can greatly enhance ozonation of o-PDA. This work further demonstrates that an RSR can significantly intensify ozone-liquid mass transfer rate and thus provides a feasible intensification means for the ozonation of o-PDA as well as other recalcitrant organics.