Adsorption mechanism of high concentration NH3 on modified red mud surface

Red mud enriched iron has potential advantages in catalyzing NH3 combustion to achieve high efficiency and low pollution. The adsorption of NH3 on surface of red mud is crucial in the process of NH3 catalytic combustion. The adsorption behavior of high concentration NH3 on modified red mud surface was studied using temperature programmed desorption (TPD), with a focus on the relationship between the physicochemical characteristics of modified red mud surface and NH3 adsorption performance. The results indicated that the NH3 adsorption capacity of modified red mud was 13.4% higher compared with red mud, suggesting that the modification treatment could enhance NH3 adsorption performance of red mud. It was related with generation of mesoporous structure and exposure of strong acid sites after modification according to the results of BET, XRF, XRD, NH3TPD, XPS, and FT-IR. The adsorption mechanism of NH3 on modified red mud surface was further investigated through molecular simulation. When the gaseous NH3 molecules were contacted with modified red mud, adsorption of NH3 included physical absorption, in particular chemical adsorption. The NH3 molecules would interact strongly with the modified red mud surface and adsorb onto the Fe atoms of Fe2O3 to form Fe-N bonds. The outcomes of this study were expected to enhance the understanding of adsorption mechanism of high concentration NH3 on modified red mud surface during red mud using for catalytic combustion of NH3.