Reactive Adsorption of SO<sub>2</sub> and NO<sub>2</sub> Gases over Black Mass Derived from Discarded Alkaline Batteries

Abstract

Disposable Mn-Zn alkaline batteries possess valuable metal-metal oxides that could function as reusable adsorbent-catalysts to eliminate harmful SO2 and NO2 gases under typical environmental conditions. This research has validated that a single AA Energizer alkaline battery provides enough material to capture 326 mg of SO2 (100 ppm) or 149 mg of NO2 (100 ppm) for three cycles at 20 degrees C and 80% relative humidity. The battery-derived black mass acted as an ambient temperature catalyst and oxidized adsorbed SO2 exclusively to sulfate ions. The composite exhibited redox behavior for NO2 by converting it to nitrite and nitrate ions. The spectroscopic analyses confirmed the formation of reactive species on the black mass after the NO2 and SO2 exposure. Theoretical calculations confirmed the chemical adsorption of acidic gases over the black mass with reactivity following the order ZnO > MnO2 > ZnMn2O4 > Zn for the black mass constituent phases. The black mass encapsulated in calcium alginate hydrogel beads possessed a large SO2 adsorption capacity of 82 mg g(-1), showing the excellent capability of the composite to work even as hydrogels.