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Sulfate Radical Scavenging by Mineral Surfaces in Persulfate-Driven Oxidation Systems: Reaction Rate Constants and Implications
Citation:
Rusevova Crincoli, K., C. Green, AND Scott G. Huling. Sulfate Radical Scavenging by Mineral Surfaces in Persulfate-Driven Oxidation Systems: Reaction Rate Constants and Implications. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 54(3):1955-1962, (2020). https://doi.org/10.1021/acs.est.9b06442
Impact/Purpose:
Inefficiency in sulfate radical (SO4•-)-driven treatment systems is a significant limitation of water, groundwater, or soil oxidative treatment systems. Previously, the assessment of the role(s) of non-target species have been focused entirely on aqueous phase species. However, solid species that react with reactive oxygen species (ROSs), may also be present, scavenge radicals, and negatively impact treatment efficiency. In this study, the role of solid phase media in oxidative treatment systems was measured for the first time. A kinetic analysis and laboratory testing methods were developed for the purpose of determining the surface scavenging rate constant (k≡S). k≡S was determined for alumina, a common mineral present in soil and aquifer material. The SO4•- surface scavenging rate for unconsolidated porous media comprised of 7% (wt/wt) alumina was projected to be 5 orders of magnitude greater than •OH reaction with aqueous phase species and scavengers. This research can be used to develop new methods and provide guidelines that limit surface scavenging and improve treatment efficiency.
Description:
Activated persulfate (PS) is a frequently applied method used to generate sulfate radicals (SO4•-), a powerful oxidant capable of degrading a broad array of environmental contaminants. The non-selective nature of SO4•- (i.e., reaction with non-target species) contributes significantly to treatment inefficiency. Radical scavenging in this manner has been quantified for non-target chemical species in the aqueous phase but has never been quantified for solid phase media. Analytical and kinetic analyses methods were developed to quantify the SO4•- scavenging rate constant (k≡S) for alumina, a common mineral in soil and aquifer materials. SO4•- were generated in UV- and thermally-activated persulfate (UV-APS, T-APS) batch systems, and the loss of rhodamine B (RhB) served as an indicator of SO4•- activity. k≡S for alumina was 2.42×104 m-2 s-1 and 2.03×104 m-2 s-1 for UV-APS and T-APS oxidative treatment systems, respectively. At concentrations >5 g L-1 alumina, the reaction of SO4•- with solid phase media increased over the aqueous phase reactions with RhB and scavengers. SO4•- scavenging by solid surfaces was orders of magnitude greater than reaction with the target compound and scavengers in the aqueous phase, underscoring the significant role of solid surfaces in scavenging SO4•-.
URLs/Downloads:
DOI: Sulfate Radical Scavenging by Mineral Surfaces in Persulfate-Driven Oxidation Systems: Reaction Rate Constants and Implications
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