Characterization of Iron Sulfide Mineral Phases Associated with the Reductive Sequestration of Technetium
EMSL Project ID
35393
Abstract
Under reducing conditions, TcO4- is readily reduced to TcIV, which forms highly insoluble oxides such as TcO2-nH2O, but (re)oxidation of TcIV oxides can lead to remobilization. Under sulfidogenic conditions, most TcIV will be reduced and immobilized as Tc2S7, which is less readily remobilized, even under oxic conditions, so this may be a more sustainable way to remediate technetium-contaminated groundwater. This process should be favored by stimulation of sulfidogenic conditions, and addition of Fe0 or Fe0/S0 is an attractive way to achieve this. However, the biogeochemistry of such a system will be complex, so its performance under field conditions is hard to predict. The objective of this ERSP-funded project is to provide the fundamental understanding necessary to evaluate the feasibility of reductive immobilization of TcO4- in the vadose zone or groundwater by controlled injection of nano-sized Fe0 or Fe0/S0 to stimulate microbial sulfate reduction. The project objectives are structured around three hypotheses: (1) Fe0 or Fe0/S0 injection into relevant porous media produces stable sulfidogenic conditions, (2) sulfidogenic aquifer conditions reduce TcO4- to stabile TcIV sulfides, and (3) TcIV sulfides are resistant to remobilization upon reoxidation. To accomplish the goals of this project, it will be necessary to characterize the structure and composition of complex, oxygen-sensitive solid phases containing Fe, S, and sometimes bacterial cells and/or Tc. We propose to do some of this characterization with instrumentation at EMSL, using a potentially wide variety of techniques, but probably with emphasis on electrn probe microanalysis and Mossbauer spectroscopy.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2009-10-05
End Date
2012-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
1. Fan, D., R. P. Anitori, B. M. Tebo, P. G. Tratnyek, J. S. Lezama Pacheco, R. K. Kukkadapu, M. H. Engelhard, M. E. Bowden, L. Kovarik, and B. W. Arey. 2013. Reductive sequestration of pertechnetate (99TcO4?) by nano zero-valent iron (nZVI) transformed by abiotic sulfide. Environmental Science & Technology: ASAP.