Effect of MnO2/Mg–Al layered double hydroxide preparation method on the removal of NO

In this study, we prepared Mg–Al layered double hydroxide (LDH) by anion exchange and co-precipitation methods and investigated the influence of the preparation methods on the removal of NO. MnO2/Mg–Al LDH prepared using the rehydration and anion exchange methods exhibited very high NO removal rates, removing approximately 90% of NO even after 90 min. In contrast, MnO2/Mg–Al LDH prepared using the co-precipitation method demonstrated a poor NO removing ability. Although Mn3+ species were distributed within the LDH host layers when MnO2/Mg–Al LDH was prepared by co-precipitation, they did not affect the oxidation of NO. Conversely, MnO2 and Mn2O3 remaining in the form of bridges after the intercalation and subsequent reduction of MnO4- species contributed to NO oxidation, which was observed for MnO2/Mg–Al LDH prepared using both anion exchange and co-precipitation methods. Thus, bridging between the LDH layers by MnO2 and Mn2O3 is essential for removing NO.