Removal of HCl, SO2, and NO by treatment of acid gas with Mg–Al oxide slurry

Although effective treatment of acid gases such as HCl, SOx, and NOx is essential for preventing air pollution, current methods pose other environmental problems such as CaCl2 leaching, reduced landfill lifetimes, and solid waste production. Here we show that acid gases can be treated simply with a Mg–Al oxide slurry. The contribution of Mg–Al oxide to HCl and SO2 removal increased as a function of the quantity and temperature of Mg–Al oxide. HCl was removed by the reconstruction of Mg–Al layered double hydroxide (Mg–Al LDH) intercalated with Cl− dissociated from HCl in the slurry. SO2 was oxidized into SO3 by oxygen in the air flow, dissolved in an aqueous solution, and removed by the reconstruction of Mg–Al LDH intercalated with dissociated SO42-. Although less pronounced because of surface adsorption, NO was nonetheless removed by Mg–Al oxide. Our results suggest that simultaneous removal of HCl, SO2, and NO using a Mg–Al oxide slurry may be possible without the concomitant problems of conventional treatment methods.