Heterogeneous oxidation of sulfur dioxide by ozone on the surface of sodium chloride and its mixtures with other components

Abstract

[1] The heterogeneous oxidation of SO 2 by O 3 on NaCl particles has been studied using diffuse reflectance infrared Fourier transform spectroscopy. The formation of sulfite and sulfate on the surface was identified, and the roles of O 3 and water in the oxidation processes were determined. The results showed that in the presence of O 3 , SO 2 could be oxidized to sulfate on the surface of NaCl particles. The reaction is first order in O 3 and zero order in SO 2 . The initial reactive uptake coefficient for SO 2 [(0.6-9.8) Â 10 14 molecule cm À3 ] oxidation by O 3 [(1.2-12) Â 10 14 molecule cm À3 ] was determined to be (4.8-0.7) Â 10 À8 using the Brunauer-Emmett-Teller area as the reactive area and (9.8-1.4) Â 10 À5 using the geometric area at 40% relative humidity. A three-stage mechanism that involves the adsorption of O 3 results in an alkalescent surface, the adsorption of SO 2 followed by O 3 oxidation is proposed, and the adsorption of O 3 on the NaCl surface is the rate-determining step. The proposed mechanism can well explain the experiment results. Furthermore, the surface oxidation on mixtures of NaCl with other components such as CaCO 3 , Al 2 O 3 , TiO 2 , MgCl 2 6H 2 O, MgO, elemental carbon, and soot were studied. The reactivity of mixtures can be predicted from the reactivity of the single component with each component weighted by its abundance in the mixture. The catalytic and basic additives could enhance the production of sulfate on the NaCl surface.

Heterogeneous reaction of SO2 on TiO2 particles

“…With the reaction on -Al 2 O 3 , the presence of NO 2 improved the oxidation of SO 2 [17]. Li et al [11] studied the heterogeneous oxidation of SO 2 by ozone on the surface of sodium chloride and mixtures with other components using in situ DRIFTS and proposed a three-stage mechanism: (1) O 3 was adsorbed on the NaCl surface, which resulted in an alkalescent surface; (2) the adsorption of SO 2 was then followed by (3) O 3 oxidation. The adsorption of O 3 on the NaCl surface was the rate-determining step.…”

“…Studies since the 1970s have demonstrated that the uptake of SO 2 on particles leads to sulfite and sulfate formation [9]. The reaction mechanism and kinetics are related to the physical and chemical characteristics of the particles, such as surface active sites, acidity, and surface area [10][11][12][13]. Studies have focused on mineral particles and sea salts.…”

A preliminary analysis of the surface chemistry of atmospheric aerosol particles in a typical urban area of Beijing

“…Such transformations in aerosol particles affect both the environment and human health Tang et al, 2006;Wei et al, 2009). In the context of their close relationship to aerosol surface area, morphology, surface chemical composition, structure and other surface characteristics (Zhu et al, 2010;Lazzeri et al, 2003;Xu, 2006;Li et al, 2007;Li et al, 2010;Wu et al, 2009;Lu et al, 2013;Bluhm and Siegmann, 2009;Sobanska et al, 2014), study of the surface physicochemical characteristics of aerosol particles has become an important aspect of aerosol particle research.…”

Atmospheric hydrogen peroxide and organic hydroperoxides during PRIDE-PRD'06, China: their concentration, formation mechanism and contribution to secondary aerosols

“…It is worth noting that the calculated production of sulfate mentioned above includes only the production in the gas phase and in the aqueous bulk of droplets. The heterogeneous chemistry on the surface of droplets and aerosols is potentially important (Li et al, 2006(Li et al, , 2007Ammann and Pöschl, 2007;Pöschl et al, 2007;Chen et al, 2008), but it is not taken into account in the above estimation. Jayne et al (1990) observed that the uptake of SO 2 into water droplets was faster than predicted on the basis of the known kinetics in bulk solution, and they suggested that a surface complex was formed between SO 2 and H 2 O at the interface.…”