Ionic strength dependence of the oxidation of SO2 by H2O2 in sodium chloride particles

H. M. Ali; M. Iedema; X. Y. Yu; J. P. Cowin

doi:10.1016/j.atmosenv.2014.02.045

Ionic strength dependence of the oxidation of SO₂ by H₂O₂ in sodium chloride particles

H. M. Ali, M. Iedema, X. Y. Yu, J. P. Cowin

Research output: Contribution to journal › Article › peer-review

14 Scopus citations

Abstract

The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium chloride (brine) particles was studied by utilizing a cross flow mini-reactor. The reaction kinetics were followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely CCSEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry's law solubility of H₂O₂ in brine solutions to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to, eventually, a mixed NaHSO₄ plus H₂SO₄ brine solution. The reaction rate of the SO₂ oxidation by H₂O₂ was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted using established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H₂O₂. It also gives the first report of the dependence of the Henry's law constant of H₂O₂ on ionic strength.

Original language	English
Pages (from-to)	731-738
Number of pages	8
Journal	Atmospheric Environment
Volume	89
DOIs	https://doi.org/10.1016/j.atmosenv.2014.02.045
State	Published - Jun 2014
Externally published	Yes

Funding

The work was supported by the US Department of Energy under the auspices of the Atmospheric Science Program, under contract DE-AC05-76RL01830/KP1701000/57131, by the National Oceanic and Atmospheric Administration under the auspices of the Atmospheric Composition and Climate Program under the sub contract 47840, a DOE/BES Chemical Science grant (KC-0301020-16248). The research was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national user facility sponsored by the Department of Energy's Office of Biological and Environmental Research (OBER) and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by the US DOE by Battelle Memorial Institute. Some of the analysis was also performed at Arkansas State University – Jonesboro.

Funders	Funder number
OBER
U.S. Department of Energy	DE-AC05-76RL01830/KP1701000/57131
National Oceanic and Atmospheric Administration	47840
Basic Energy Sciences	KC-0301020-16248
Biological and Environmental Research
Pacific Northwest National Laboratory

Keywords

Brine
Ionic strength
Oxidation
Sodium chloride
Sulfate

Access to Document

10.1016/j.atmosenv.2014.02.045

Cite this

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title = "Ionic strength dependence of the oxidation of SO2 by H2O2 in sodium chloride particles",

abstract = "The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium chloride (brine) particles was studied by utilizing a cross flow mini-reactor. The reaction kinetics were followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely CCSEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry's law solubility of H2O2 in brine solutions to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to, eventually, a mixed NaHSO4 plus H2SO4 brine solution. The reaction rate of the SO2 oxidation by H2O2 was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted using established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H2O2. It also gives the first report of the dependence of the Henry's law constant of H2O2 on ionic strength.",

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AU - Ali, H. M.

AU - Iedema, M.

AU - Yu, X. Y.

AU - Cowin, J. P.

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AB - The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium chloride (brine) particles was studied by utilizing a cross flow mini-reactor. The reaction kinetics were followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely CCSEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry's law solubility of H2O2 in brine solutions to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to, eventually, a mixed NaHSO4 plus H2SO4 brine solution. The reaction rate of the SO2 oxidation by H2O2 was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted using established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H2O2. It also gives the first report of the dependence of the Henry's law constant of H2O2 on ionic strength.

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