Adsorption mechanism of high concentration NH3 on modified red mud surface

Abstract

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, NH₃-TPD, 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.