Heating activated red mud catalytic ozonation for degradation nitrobenzene from aqueous solution: performance and influence of preparation factors.

Red mud (RM), a waste residue of alumina refinery, has been used to develop an effective catalyst to enhance nitrobenzene (NB) removal from aqueous solution by ozonation. The result showed that the development of catalytic activity of RM was obtained by heating activation. The effects of different factors (heating temperature and time) have been examined in batch experiments. Sample prepared by heating RM at 400 degrees C for 4 h showed the highest activity in catalytic ozonation of NB. The temperature exhibited a significant effect on the performance of both NB removal and ozone decomposition. However, the effect of the heating time was insignificant. Experiments of both catalytic ozone decomposition and hydroxyl radical (*OH) inhibiting confirmed the existence of *OH in heated RM catalytic ozonation. According to the XRD pattern, the change of mineral content was the key reason for the development of catalytic activity, especially for hematite and magnetite.