The use of pumice for heterogeneous catalytic ozonation significantly enhances the degradation efficiency and the total organic carbon (TOC) removal of p-chloronitrobenzene (pCNB) in aqueous solution compared with ozonation alone because of the synergistic effect between ozone and the catalyst. The pCNB adsorption was too small to contribute significantly to the pCNB degradation during pumice-catalyzed ozonation. The decomposition rate of the aqueous ozone increased 1.374-fold in the presence of pumice. High pH also positively affected the pumice-catalyzed ozonation, as nearly uncharged surfaces (the solution pH was close to the point of zero charge) are favorable for catalytic pCNB ozonation. tert-Butanol remarkably decreases the removal efficiency of catalytic pCNB ozonation, which suggests that pCNB degradation follows the mechanism of hydroxyl radical oxidation. Increasing both the pumice and ozone concentrations enhanced the removal effectiveness of pCNB. Pumice is an efficient green catalyst for pCNB degradation in aqueous solution. (c) 2012 Elsevier B.V. All rights reserved.