A Diffuse Reflectance Infrared Fourier Transform Spectroscopic Study of the Surface Reaction of NaCl with Gaseous NO2 and HNO3

In order to obtain reliable kinetic parameters, it is required to measure the reaction kinetics of important heterogeneous reactions at ambient relative humidity (RH). In this study, the uptake coefficients and HONO yields for the heterogeneous reaction of NO 2 on kaolin and hematite were measured at RH from 7% to 74% and at ambient pressure in the dark using a coated-wall flow tube reactor. The initial true uptake coefficient (g t,ini ) of NO 2 at RH 7% was measured to be (1.44 AE 0.10) Â 10 À7 and (1.58 AE 0.13) Â 10 À6 on kaolin and hematite, respectively, while it decreased notably on both minerals, accompanied by an increase of HONO yields, as RH increased. The average g t,ini at 32-74% RH was (4.42 AE 1.17) Â 10 À8 and (2.83 AE 0.84) Â 10 À7 on kaolin and hematite, respectively. The corresponding mean HONO yield was (36.0 AE 16.1)% and (75.9 AE 3.32)%, respectively.

Section: Hono Formation and Hono Yieldsmentioning

confidence: 99%

“…9,10 For example, heterogeneous reactions of NO x on soot and mineral dust can produce gaseous HONO, 3,4,11 which is a daytime source of OH radicals; 12 while reactions between NO x and sea salt might be a source of Cl radicals. 10 Mineral dust is an important component of APM, with a loading of 1000-3000 Tg per year.…”

Section: Introductionmentioning

confidence: 99%

Influence of relative humidity on heterogeneous kinetics of NO₂ on kaolin and hematite

Liu

Han

et al. 2015

“…It is well documented that passivation of such salt surfaces occurs during reactions with gases, which effectively terminates chemistry of the parent surface ions. [191][192][193][194][195][196] For example, Fig. 7a shows the TEM image of an unreacted single crystal of NaCl.…”

Section: View Article Onlinementioning

confidence: 99%

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

Finlayson-Pitts

2009

Self Cite

228

272

“…Previous studies using DRIFTS have shown that the IR signal is not restricted to the top few molecular layers of the sample; however, signals from lower portions of the pellet contribute significantly less to the total measured absorbance. 36 To examine the extent of the reaction at lower levels of the salt, a depth profile study of SO 4 2À within the salt sample was done by IC. After an experiment with an OH processed salt mixture treated similarly to the sample in Fig.…”

Section: Oxidation Of So 2 By O 3 In Region IImentioning

confidence: 99%

“…[28][29][30][31][32][33][34] Diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) is a powerful technique for following the chemistry of solid particles in real time under laboratory conditions. [35][36][37][38] It has the advantage of relatively strong signals due to the macroscopic amounts of sample used, but the matrix used must be infrared transparent. DRIFTS is not normally applicable to liquids where interface and bulk liquid phase reactions are important.…”

Section: Introductionmentioning

confidence: 99%

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol

Shaka

Robertson

Finlayson-Pitts

2007

Self Cite

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol. Diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) is a powerful technique for analyzing solid powders and for following their reactions in real time. We demonstrate that it can also be applied to studying the uptake and reactions of gases in liquid films. Within the DRIFTS cell, a 10% (w/w) mixture of MgCl 2 Á 6H 2 O in NaCl was equilibrated with air at 50% RH, which is above the deliquescence point of the magnesium salt but below that of NaCl. This mixture of NaCl coated with an aqueous magnesium chloride solution was then reacted with gas phase OH to generate hydroxide ions via a previously identified interface reaction. This treatment, hereafter referred to as OH-processing, was sufficient to convert some of the magnesium chloride to Mg(OH) 2 and Mg 2 (OH) 3 Cl Á 4H 2 O, making the aqueous film basic and providing a reservoir of alkalinity. Subsequent addition of SO 2 to the basic processed mixture resulted in its uptake and conversion to sulfite which was measured by FTIR. The sulfite was simultaneously oxidized to sulfate by HOCl/OCl À that was formed in the initial OH-processing of the salt. Further uptake and oxidation of SO 2 in the aqueous film took place when the salt was subsequently exposed to O 3 . These studies demonstrate that DRIFTS can be used to study the chemistry in liquid films in real time, and are consistent with the hypothesis that the reaction of gaseous OH with chloride ions generates alkalinity that enhances the uptake and oxidation of SO 2 under these laboratory conditions.