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

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

doi:10.1016/j.jhazmat.2021.127400

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

J Hazard Mater. 2022 Feb 15;424(Pt B):127400. doi: 10.1016/j.jhazmat.2021.127400. Epub 2021 Sep 30.

Authors

Shambhu Kandel¹, Yelena P Katsenovich², Daria Boglaienko³, Hilary P Emerson⁴, Tatiana G Levitskaia⁵

Affiliations

¹ Applied Research Center, Florida International University, 10555W Flagler St, Miami, FL 33174, USA.
² Applied Research Center, Florida International University, 10555W Flagler St, Miami, FL 33174, USA. Electronic address: katsenov@fiu.edu.
³ Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, USA. Electronic address: daria.boglaienko@pnnl.gov.
⁴ Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, USA.
⁵ Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, USA. Electronic address: Tatiana.Levitskaia@pnnl.gov.

PMID: 34638077
DOI: 10.1016/j.jhazmat.2021.127400

Abstract

Elemental iron Fe⁰ is a promising reductant for removal of radioactive technetium-99 (Tc) from complex aqueous waste streams that contain sulfate, halides, and other inorganic anions generated during processing of legacy radioactive waste. The impact of sulfate on the kinetics of oxidation and reduction capacity of Fe⁰ in the presence of Tc has not been examined. We investigated the oxidative transformation of Fe⁰ and reductive removal of TcO₄^- in 0.1 M Na₂SO₄ as a function of initial pH (i.e., pH_i 4, 7, and 10) under aerobic conditions up to 30 days. Tc reduction was the fastest at pH_i 7 and slowest at pH_i 10 (Tc reduction rate pH_i 7 > 4 > 10). Aqueous fraction of Tc was measured at 0.4% at pH_i 7 within 6 h, whereas ≥ 97% of Tc was removed from solutions at pH_i of 4 and 10 within 24 h. Solid phase characterization showed that magnetite was the only oxidized crystalline phase for the first 6 h regardless of initial pH. Lepidocrocite was the most abundant oxidized product for pH_i 10 after 5 days, but was not observed at pH of 4 or 7.

Keywords: Iron oxides; Sulfate; Technetium-99; Zero valent iron.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Hydrogen-Ion Concentration
Iron*
Oxidation-Reduction
Sodium Pertechnetate Tc 99m*
Sulfates

Substances

Sulfates
Sodium Pertechnetate Tc 99m
Iron