Dataset Information

Hydroxyl radical scavenging by solid mineral surfaces in oxidative treatment systems: Rate constants and implications.

ABSTRACT: Advanced oxidation treatment processes used in various applications to treat contaminated soil, water, and groundwater involve powerful radical intermediates, including hydroxyl radicals (•OH). Inefficiency in •OH-driven treatment systems involves scavenging reactions where •OH react with non-target species in the aqueous and solid phases. Here, •OH were generated in iron (Fe)- and UV-activated hydrogen peroxide (Fe-AHP, UV-AHP) systems where the loss of rhodamine B served as a quantitative metric for •OH activity. Kinetic analysis methods were developed to estimate the specific •OH surface scavenging rate constant (k_?S). In the Fe-AHP system, k_?S for silica (2.85?×?10⁶ 1/m²?×?s) and alumina (3.92?×?10⁶ 1/m²?×?s) were similar. In the UV-AHP system, estimates of k_?S for silica (4.50?×?10⁶ 1/m²?×?s) and alumina (7.45?×?10⁶ 1/m²?×?s) were higher. k_?S for montmorillonite (MMT) in the UV-AHP system was ?4.22?×?10⁵ 1/m²?×?s. Overall, k_?S,silica???k_{?S, alumina}?>?k_?S,MMT indicating k_?S is mineral specific. Radical scavenging was dominated by surface scavenging at 10-50?g/L silica, alumina, or MMT, in both Fe-AHP and UV-AHP systems. The experimentally-derived surface •OH scavenging rate constants were extended to in-situ chemical oxidation (ISCO) treatment conditions to contrast •OH reaction rates with contaminant and aqueous phase reactants found in aquifer systems. •OH reaction was dominated by solid surfaces comprised of silica, alumina, and montmorillonite minerals relative to •OH reaction with trichloroethylene, the target compound, and H₂O₂, a well-documented radical scavenger. These results indicate that solid mineral surfaces play a key role in limiting the degradation rate of contaminants found in soil and groundwater, and the overall treatment efficiency in ISCO systems. The aggressive •OH scavenging measured was partially attributed to the relative abundance of scavenging sites on mineral surfaces.

SUBMITTER: Rusevova Crincoli K

PROVIDER: S-EPMC7530771 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Hydroxyl radical scavenging by solid mineral surfaces in oxidative treatment systems: Rate constants and implications.

Rusevova Crincoli Klara K Huling Scott G SG

Water research 20191031

Advanced oxidation treatment processes used in various applications to treat contaminated soil, water, and groundwater involve powerful radical intermediates, including hydroxyl radicals (•OH). Inefficiency in •OH-driven treatment systems involves scavenging reactions where •OH react with non-target species in the aqueous and solid phases. Here, •OH were generated in iron (Fe)- and UV-activated hydrogen peroxide (Fe-AHP, UV-AHP) systems where the loss of rhodamine B served as a quantitative metr ...[more]

PMID: 31706122

Similar Datasets

Project description:BackgroundFibrous chrysotile has been the most commonly applied asbestos mineral in a range of technical applications. However, it is toxic and carcinogenic upon inhalation. The chemical reactivity of chrysotile fiber surfaces contributes to its adverse health effects by catalyzing the formation of highly reactive hydroxyl radicals (HO•) from H2O2. In this Haber-Weiss cycle, Fe on the fiber surface acts as a catalyst: Fe3+ decomposes H2O2 to reductants that reduce surface Fe3+ to Fe2+, which is back-oxidized by H2O2 (Fenton-oxidation) to yield HO•. Chrysotile contains three structural Fe species: ferrous and ferric octahedral Fe and ferric tetrahedral Fe (Fe3+tet). Also, external Fe may adsorb or precipitate onto fiber surfaces. The goal of this study was to identify the Fe species on chrysotile surfaces that catalyze H2O2 decomposition and HO• generation.ResultsWe demonstrate that at the physiological pH 7.4 Fe3+tet on chrysotile surfaces substantially contributes to H2O2 decomposition and is the key structural Fe species catalyzing HO• generation. After depleting Fe from fiber surfaces, a remnant fiber-related H2O2 decomposition mode was identified, which may involve magnetite impurities, remnant Fe or substituted redox-active transition metals other than Fe. Fe (hydr)oxide precipitates on chrysotile surfaces also contributed to H2O2 decomposition, but were per mole Fe substantially less efficient than surface Fe3+tet. Fe added to chrysotile fibers increased HO• generation only when it became incorporated and tetrahedrally coordinated into vacancy sites in the Si layer.ConclusionsOur results suggest that at the physiological pH 7.4, oxidative stress caused by chrysotile fibers largely results from radicals produced in the Haber-Weiss cycle that is catalyzed by Fe3+tet. The catalytic role of Fe3+tet in radical generation may also apply to other pathogenic silicates in which Fe3+tet is substituted, e.g. quartz, amphiboles and zeolites. However, even if these pathogenic minerals do not contain Fe, our results suggest that the mere presence of vacancy sites may pose a risk, as incorporation of external Fe into a tetrahedral coordination environment can lead to HO• generation.

Dataset Information

Hydroxyl radical scavenging by solid mineral surfaces in oxidative treatment systems: Rate constants and implications.

Publications

Hydroxyl radical scavenging by solid mineral surfaces in oxidative treatment systems: Rate constants and implications.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets