Decomposition of O3 onto natural Gobi dust: From uptake to surface reactivity

• Under dry air and 20% RH, Gobi dust exceeds synthetic metal oxides for O 3 uptake. • Thermal regeneration of O 3 utake by Gobi is accessible at mild temperature (150 °C) • Oxide and peroxide surface groups are created along O 3 uptake on Gobi. • Al 2 Si 2 O 5 (OH) 4 and Al 2 O 3 are evidenced as the most contributive mineral phases of Gobi. • A five-step reaction mechanism is proposed to describe O 3 reactivity on Gobi surface. Beyond synthetic metal oxides, this work investigates natural mineral dust as a material of interest for O 3 uptake and decomposition. Ozone and Gobi dust interactions are addressed combining gas phase and adsorbed phase approach. It allows for determining: (i) the drivers of O 3 decomposition process on Gobi and (ii) surface reactions and mechanism. First, the steady catalytic decomposition of ozone onto Gobi is explored on a large O 3 concentration range: 20 ppb − 10 ppm, with steady uptake coefficients ranging from 2.6 x 10 -9 to 6.2 x 10 -8 . If moisture (20 % RH) does not impact initial uptake of O 3 it is evidenced to hinder the steady state behavior. Cyclic surface regeneration evidences that: (i) wet air flushing restores initial uptake properties, and (ii) mild thermal treatment (150 °C) restores the complete uptake process. Along O 3 decomposition, adsorbed phase monitoring using DRIFT allows for identification and dynamic monitoring of specific IR bands on Gobi surface. Oxide and peroxide surface species are created. To meet environmental conditions, the role of water on surface groups created by O 3 uptake is addressed through water molecule uptake experiments. Finally, a five-step mechanism is proposed to describe uptake and surface reactivity of O 3 on Gobi dust. This work provides a comprehensive evaluation of the surface properties and reactivity of Gobi dust towards O 3 , valuable for atmospheric, geocatalytic and plasma-catalytic processes.