Reductive removal of pertechnetate and chromate by zero valent iron under variable ionic strength conditions

Yelena P Katsenovich; Antony Arun Maria; Jonathan Williams; Shambhu Kandel; Daria Boglaienko; Hilary P Emerson; Tatiana G Levitskaia

doi:10.1016/j.jhazmat.2022.130546

Reductive removal of pertechnetate and chromate by zero valent iron under variable ionic strength conditions

J Hazard Mater. 2023 Mar 5:445:130546. doi: 10.1016/j.jhazmat.2022.130546. Epub 2022 Dec 5.

Authors

Yelena P Katsenovich¹, Antony Arun Maria², Jonathan Williams², Shambhu Kandel², Daria Boglaienko³, Hilary P Emerson³, Tatiana G Levitskaia⁴

Affiliations

¹ Applied Research Center, Florida International University, 10555W Flagler St, Miami, FL 33174, USA. Electronic address: katsenov@fiu.edu.
² Applied Research Center, Florida International University, 10555W Flagler St, Miami, FL 33174, USA.
³ Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, USA.
⁴ Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, USA. Electronic address: Tatiana.Levitskaia@pnnl.gov.

PMID: 37055961
DOI: 10.1016/j.jhazmat.2022.130546

Abstract

Radioactive technetium-99 (Tc) present in waste streams and subsurface plumes at legacy nuclear reprocessing sites worldwide poses potential risks to human health and environment. This research comparatively evaluated efficiency of zero-valent iron (ZVI) toward reductive removal of Tc(VII) in presence of Cr(VI) from NaCl and Na₂SO₄ electrolyte solutions under ambient atmospheric conditions. In both electrolytes, anticorrosive Cr(VI) suppressed oxidation of ZVI at elevated concentrations resulting in the delay of initiation of Tc(VII) reduction to Tc(IV). In the absence of Cr(VI), no delay was observed in the analogous systems. At low ionic strength (IS), retarded ZVI oxidation inhibited Tc(VII) reduction. Higher IS favored reduction of both Tc(VII) and Cr(VI), which followed second-order reaction rates in both electrolytes attributed to the more efficient iron oxidation as evident from solids characterization studies. Magnetite was the primary iron oxide phase, and its higher fraction in the SO₄^2- solutions facilitated reductive removal of Tc(VII) and Cr(VI). In the Cl^- matrix, Cr(VI) promoted further oxidation of magnetite as well as formation of chromite diminishing overall reductive capacity of this system and resulting in less effective removal of Tc(VII) compared to the SO₄^2- solutions.

Keywords: Chloride; Chromate; Ionic strength; Pertechnetate; Sulfate; Zero valent iron.