The Recycle of Red Mud as NH 3 -SCR Catalyst by Acid Pretreatment: Insight into the Interaction Between Iron and Titanium Species

The red mud was activated by an acid leaching and reprecipitation approach to be used as NH 3 -SCR catalyst. The effect of acid concentration on the leaching rates of Fe, Ti, Al, Ca and Na was investigated, specifically, the interaction between Fe and Ti components in the obtained red mud-based catalysts was concerned. With the acid concentration increasing (below 3.1 mol/L), more Fe and Ti are leached out, meanwhile, Ti can be incorporated into Fe 2 O 3 phase and the crystallite size of Fe 2 O 3 becomes smaller, and the obtained catalyst exhibits better low-temperature activity and SO 2 resistance. The HRM3.1 catalyst obtained at the acid concentration of 3.1 mol/L possesses strongest reducibility, largest amount of surface chemisorbed oxygen and medium surface acidity. The in-situ DRIFTS results show that more NO can be adsorbed and oxidized over the HRM3.1 catalyst to generate more nitrate species, even though in the presence of SO 2 , alleviating the suppression of SO 2 on the NH 3 -SCR reaction, and thus the SO 2 tolerance is enhanced. Graphical Abstract