Enhancement mechanism of heterogeneous catalytic ozonation by cordierite-supported copper for the degradation of nitrobenzene in aqueous solution.

The use of cordierite or Cu-cordierite for heterogeneous catalytic ozonation enhances significantly the degradation efficiency and the TOC removal of nitrobenzene in aqueous solution relative to ozonation alone, owing to the synergistic effect between ozone and the catalysts, and the modification process with Cu can increase the catalytic activity of cordierite forthe ozonation of nitrobenzene. The adsorption of nitrobenzene is too small to make a significant contribution to the degradation of nitrobenzene in either of the processes of catalytic ozonation. The initiation of hydroxyl radical (*OH) improves as the amount of Cu-cordierite catalyst is increased, meaning that the degradation of nitrobenzene is mainly attributed to *OH oxidation. The modification by loading Cu increases the density of surface hydroxyl groups and the pH at the point of zero charge (pH(PZC)) of raw cordierite. The investigation of the enhancement mechanism confirms that the modification by loading Cu causes changes of density of surface hydroxyl groups, pH(PZC), and /pH - pH(PZC)/, resulting in the acceleration initiation of *OH which can promote the degradation of nitrobenzene. The result shows that the optimal critical loading percentage of Cu is 3% under the present experimental conditions.