The influence of bicarbonate on degradation efficiency of nitrobenzene in aqueous solution by ceramic honeycomb supported manganese catalytic ozonation has been investigated. Under the lower concentration condition (25 and 50 mg L-1), bicarbonate enhances the degradation efficiency of nitrobenzene, while bicarbonate presents the inhibition effect at the higher concentration (100-250 mg L-1). The modification of ceramic honeycomb with Mn improves its resistibility to the negative effect of bicarbonate, and the inhibition effect of bicarbonate also can be decreased, respectively by increasing total applied ozone or amount of catalyst. The utilization efficiency of ozone increases with the increasing bicarbonate concentration (0-100 mg L-1). The formation of H2O2 and the initiation of hydroxyl radical ((OH)-O-center dot) reach a maximum at the bicarbonate concentration 75 and 50 mg L-1, respectively. The mechanism investigation suggests that bicarbonate plays an important role as a promoter of radical chain reactions accelerating the ozone mass transformation, causing the increases in the utilization efficiency of ozone, the formation of H2O2 and the initiation of (OH)-O-center dot at the lower concentration. Bicarbonate with the higher concentration exerts a negative effect on the degradation efficiency of nitrobenzene due to the predominance derived from its scavenging capacity of (OH)-O-center dot. (C) 2010 Elsevier B.V. All rights reserved.