8 Environmental Geoscience (Posters)

Monday, 18 April 2016
8:00 AM - 12:00 PM
Illinois Ballroom AB

EFFECTS OF HIGH PH AND NITRATE CONCENTRATIONS ON PERTECHNETATE REDUCTION KINETICS AT THE ZEROVALEN IRON-WATER INTERFACE

Paper number: 8-1
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

  • Brian A. Lenell Presenting Author
    University of Illinois at Urbana-Champaign, Urbana, IL
  • Yuji Arai
    University of Illinois at Urbana-Champaign, Urbana, IL

Abstract

Technetium-99 (99Tc) is a low level radioactive waste product resulting from uranium fission processes in nuclear reactors. Currently, the U.S. Department of Energy (DOE) has been investigating solidification and stabilization remediation methods via reductive precipitation of mobile Tc(VII)O4- to Tc(IV) oxides and sulfides for long term waste storage purposes. They are seeking effective reducing agents for the current saltstone cement formulation to optimize the Tc immobilization technology. In this study, the reducing capacity of synthetic zerovalent iron (ZVI) was evaluated using a chemical analog of 99TcO4- , perrhenate (ReO4-). The objective was to evaluate the kinetics Re(VII) reduction under simulated conditions (i.e., high pH and high nitrate concentrations) in low level radioactive waste storage tanks at DOE sites.

The synthetic ZVI [1] was used to conduct the Re(VII) sorption experiments at various pH and [NaNO3]. Perrhenate concentration was analyzed using a spectrophotometric method [2]. Batch methods were used for the reduction kinetic experiments using various carbonate buffer solutions (pH 8.3-10.2) under varying [nitrate]: 0, 0.001, 0.01 and 0.1M. Kinetic samples were taken at 10,30 min, 1, 3, 6, 12, and 24 hrs. The extent of Re(VII) removal and kinetic rate data were evaluated using pseudo-first and -second order kinetic models [3,4] The preliminary results showed that the extent of Re(VI) removal decreased with increasing pH and [nitrate].The rates were also affected by these variables. Implications of the research findings will be discussed with solid state characterization data of reaction products.

References:

1. Ponder S.M., Darab J.G., Mallouk T.E. (2000) Environ. Sci. Technol. 34,2564- 2569.

2. Lenell B.A. and Arai Y. (2016) Talanta. In Press, DOI: 10.1016/j.talanta.2015.10.063.

3. Ho Y.S. and McKay G. (1998) Process Biochem. 34,451-465.

4. Zhou et al. (2016) J. Colloid Interface Sci. 462, 200-207.

Geological Society of America Abstracts with Programs. Vol. 48, No. 5

doi: 10.1130/abs/2016NC-274343

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.