Zinc-aluminum layered double hydroxide and double oxide for room-temperature oxidation of sulfur dioxide gas

Abstract

Sulfur dioxide (SO2) gas at trace levels challenges the consumption of fuel gases and cleaning of flue gases originating from diverse anthropogenic sources. We have demonstrated Zn–Al layered double hydroxide (LDH) and layered double oxide (LDO) as low-cost and effective adsorbents in removing lowly concentrated SO2 gas at room temperature. Water in the adsorbent bed significantly improved the performance, where the maximum adsorption capacity of 38.0 mg g−1 was achieved for LDO. Based on the spectroscopic findings, the adsorbed gas molecules were oxidized to surface-bound sulfate/bisulfate species, showing complete mineralization of SO2 molecules. By employing an inexpensive NaOH–H2O2 solution-based regeneration strategy, we successfully regenerated the spent LDO, significantly restoring its gas uptake capacity. The regenerated oxide exhibited an increased gas uptake capacity ranging from 38.0 to 98.5 mg g−1, highlighting the practicality and economic feasibility of our approach. LDH/LDO materials are promising regenerable adsorbents for removing low concentrations of SO2 gas in ambient conditions.