Time dependent zero valent iron oxidation and the reductive removal of pertechnetate at variable pH

Kandel, Shambhu; Katsenovich, Yelena; Boglaienko, Daria; Emerson, Hilary P.; Levitskaia, Tatiana G.

doi:10.1016/j.jhazmat.2021.127400

Cited by 5 publications

(3 citation statements)

References 75 publications

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“…The variation suggests that a greater amount of iron oxides with Fe II and Fe III were formed in samples with lower levels of Cr(VI) (Figure S2). This finding supports the hypothesis that the variation in reduction rates at different Cr(VI) concentrations is attributed to a shift in iron oxidation . The inhibitory effect of Cr(VI) on the formation of iron oxides is responsible for influencing the shift in the iron oxidation rates.…”

Section: Resultssupporting

confidence: 88%

“…This finding supports the hypothesis that the variation in reduction rates at different Cr(VI) concentrations is attributed to a shift in iron oxidation. 8 The inhibitory effect of Cr(VI) on the formation of iron oxides is responsible for influencing the shift in the iron oxidation rates. Furthermore, it was observed that changes in pH were only significant in samples with lower Cr concentrations, where Tc reduction was relatively fast (Figure 5).…”

Section: Rates For Reduction Of Cr(vi) and Tc(vii)mentioning

confidence: 99%

“…Zero-valent iron (ZVI) is readily available and a cost-efficient material for large-scale remediation and the treatment of environmental contaminants. ZVI has been extensively studied for the reduction of redox-sensitive heavy metals and radionuclides from groundwater and solutions arising from the processing of nuclear wastes, including waste streams stored at the US Department of Energy Hanford Site. ,− Previous research has compared the efficiency of various ZVI products for Tc(VII) reduction and has demonstrated that ZVI produced by the electrolytic method and cast iron powder exhibits superior properties for treatment. , The particle size significantly affects the reduction capacity, with finer particle sizes more efficiently reducing Tc(VII) as they provide a more available surface area for reduction. However, nanosized ZVI particles led to more agglomeration, negating the potential benefits of increased surface area .…”

Section: Introductionmentioning

confidence: 99%

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Competitive Reduction of Pertechnetate and Chromate in Radioactive Waste Streams via Zero-Valent Iron

Williams,

Maria,

Katsenovich

et al. 2024

ACS Earth Space Chem.

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To prevent environmental release and exposure, it is essential to immobilize radioactive waste for long-term storage and disposal. One waste constituent, long-lived radionuclide technetium-99 ( 99 Tc), which is primarily produced during the irradiation of uranium fuels in nuclear reactors, represents a significant risk to human health and the environment. Zero-valent iron (ZVI) has shown promise in reducing highly soluble Tc(VII) into a less soluble Tc(IV) form. However, the presence of other redoxreactive elements can compete with Tc in the reduction process, potentially impeding its treatment. Cr(VI) is a hazardous, redoxactive contaminant commonly found at elevated concentrations in legacy waste streams. While simultaneous removal of Tc(VII) and Cr(VI) would be advantageous, the challenge lies in the typically higher concentrations of Cr(VI) compared to Tc(VII), potentially interfering with ZVI's reductive treatment of Tc. This study explores the removal of aqueous Cr(VI) and Tc(VII) by two different ZVI materials under alkaline pH 10 conditions (pH 10). Experiments were conducted across various Cr(VI) concentrations (1−50 mg/L) while maintaining a constant Tc(VII) concentration (1 mg/L) in 0.30 M NaCl solution for 30 days. The results indicate that ZVI can quantitatively reduce simultaneously present Tc(VII) and Cr(VI) when the Fe 0 :(Cr + Tc) molar ratio exceeds 106. However, a decrease in this stoichiometric ratio due to higher Cr(VI) content results in reduced Tc removal, possibly due to Cr(VI) inhibiting ZVI oxidation and saturating the ZVI surface.

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Section: Resultssupporting

confidence: 88%

Section: Rates For Reduction Of Cr(vi) and Tc(vii)mentioning

confidence: 99%