Thermal decomposition behavior of MnO2/Mg-Al layered double hydroxide after removal and recovery of acid gas

Abstract

Acidic gases such as HCl, SO2, and NOx are compounds that are generated through the incineration of waste products. Hence, an efficient method of removing such gases is highly desired. In this study, we present a novel method for treatment of acidic gases by using an MnO2/Mg-Al layered double hydroxide (MnO2/Mg-Al LDH), which provides several advantages in removing NO when compared to other removal methods, in addition to enabling the removal of HCl and SO2. We tested the recovery of acidic gases using the dry process, which separates the adsorbed gases from the LDH and recovers them as gases again, allowing them to be reused, and the adsorbent to be regenerated. To achieve this, we analyzed the pyrolysis behavior of MnO2/Mg-Al LDH at different temperatures and with various acidic gases adsorbed, using thermogravimetry (TG) and evolved gas analysis-mass spectrometry (EGA-MS), and further studied the recovery of adsorbed acidic gases. For HCl, NO, and SO2, outlet concentrations of 4000, 1000, and 950 ppm, respectively, were achieved, with recovery rates above 99% for all three. Additionally, we identified that for removal of both HCl and NO, MnO2/Mg-Al LDH desorbed the acid gas and generated Mg-Al layered double oxide (Mg-Al LDO) as the LDH structure collapsed. Furthermore, for SO2 removal, MgAl2O4 and MgO were generated. Overall, we confirmed that acidic gases such as HCl, NO, and SO2, can be recovered with high efficiency and at a high concentration by using MnO2/Mg-Al LDH. This method of removal can have many potential applications.

Keywords

• MnO2/Mg-Al layered double hydroxide
• Thermal decomposition behavior
• Acid gas removal
• Acid gas recovery