Kinetics of oxidation of aqueous sulfur(IV) by nitrogen dioxide

Conference · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6567096

Lee, Y N; Schwartz, S E

The gas-liquid oxidation reaction of sulfur(IV) by NO/sub 2/ has been studied at neutral pH's, i.e., 6.40 and 5.80, and low reagent concentrations, i.e., (S(IV)) approx. = 1 x 10/sup -6/ M and p/sub NO/sub 2// approx. = 1 x 10/sup -7/ atm. Major products found under these reaction conditions are H/sup +/, NO/sub 2//sup -/, and SO/sub 4//sup =/, and the stoichiometry is consistent with 2NO/sub 2/ + HSO/sub 3//sup -/ + H/sub 2/O - > 3H/sup +/ + 2NO/sub 2//sup -/ + SO/sub 4//sup =/. The reaction rate was determined by following acid production via a pH-stat apparatus as a function of mixing time constant of the gas and liquid phases (tau/sub m/ = 1.6 - 5.3 s). The reaction rate was found to be significantly controlled by mass-transfer, even at the low reagent concentrations employed, and the extrapolation to the phase-mixed condition (tau/sub m/ = O) was able to yield only a lower-limit reaction rate constant. This rate constant, for reaction rate interpreted according to an overall second-order rate expression (R = k/sup (2)/ (S(IV))(NO/sub 2/)), was 2 x 10/sup 6/ M/sup -1/ s/sup -1/ at both pH 6.40 and 5.80. However, evidence is represented of a complex reaction mechanism apparently involving intermediates. As estimate of the contribution of NO/sub 2/-S(IV) reaction to acid production in cloud water made using the lower-limit second-order rate constant is 3 x 10/sup -5/ M hr/sup -1/ at pH 6 and p/sub SO/sub 2// = p/sub NO/sub 2// = 3 x 10/sup -9/ atm. Although the analysis is preliminary because of the use of a lower-limit value for k/sup (2)/ and the uncertainties in reaction mechanism, such a rate would constitute a significant contribution to cloud acidification.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6567096
• Report Number(s): BNL-32366; CONF-821136-15; ON: DE83005909
• Country of Publication: United States
• Language: English

Related Subjects

500100* -- Environment
Atmospheric-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
AQUEOUS SOLUTIONS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DISPERSIONS
FLUIDS
GASES
IONS
KINETICS
LIQUIDS
MIXTURES
NITRITES
NITROGEN COMPOUNDS
NITROGEN DIOXIDE
NITROGEN OXIDES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SOLUTIONS
STOICHIOMETRY
SULFATES
SULFUR COMPOUNDS
SULFUR IONS