Elimination behavior of nitrogen oxides from a NO 3−-intercalated Mg–Al layered double hydroxide during thermal decomposition

Abstract

The thermal properties of NO 3 −-intercalated Mg–Al layered double hydroxide (NO 3·Mg–Al LDH) were investigated using simultaneous thermogravimetry–mass spectrometry (TG–MS), and the elimination behavior of nitrogen oxides from this double hydroxide was examined. The TG–MS results showed that NO 3·Mg–Al LDH decomposed in four stages. The first stage involved evaporation of surface adsorbed water and interlayer water in NO 3·Mg–Al LDH. In the second and third stages, dehydroxylation of the brucite-like octahedral layers in NO 3·Mg–Al LDH occurred. The fourth stage mainly corresponded to the elimination of NO 3 − intercalated in the Mg–Al LDH interlayers to afford NO 2. Thermal decomposition of NO 3·Mg–Al LDH at 400–600 °C resulted in the formation of Mg–Al oxide, and the produced NO 2 reacted with H 2O and O 2 to form HNO 3 and HNO 2. The elimination of nitrogen oxides was found to increase with time and decomposition temperature. The synthesized Mg–Al oxide mixture could be used to remove nitric acid from aqueous solutions.