Study of dynamics and mechanism of HCl, SO₂, or NO removal by MnO₂/Mg–Al layered double hydroxide

The gas exhaust generated by waste incinerators contains toxic acid gases such as HCl, SO₂, and NO_x, which require appropriate treatment following their release. Although several methods exist for this purpose, they have various drawbacks. Thus, toward the search for a new removal method, the ability of Mg–Al layered double hydroxide (Mg–Al LDH) to eliminate HCl, SO₂, and NO gases from simulated exhaust gas was examined. In addition, the impact of the amount of LDH employed was investigated in terms of the toxic gas removal efficiencies and process temperature. Furthermore, the mechanism of removing HCl, SO₂, and NO by MnO₂/Mg–Al LDH was considered. More specifically, HCl removal proceeded mainly by the reaction of HCl with the CO₃²⁻ and OH⁻ species present between the Mg-Al LDH layers, while that of SO₂ took place through the adsorption of SO₂ onto the LDH and MnO₂ surfaces. Moreover, NO was removed through the oxidation of NO to NO₂ by MnO₂, followed by the reaction of NO₂ with the CO₃²⁻ and OH⁻ species present between the Mg–Al LDH layers. These results are expected to help pave the way for the use of Mg–Al LDH to remove toxic acid gases from the gas exhausts of waste incinerators, thereby addressing the various issues related to the use of current technologies.