Bacterial Pu(V) reduction in the absence and presence of Fe(III)-NTA: modeling and experimental approach

Journal Article · Thu Jan 10 04:00:00 EST 2013 · Biodegradation

DOI:https://doi.org/10.1007/s10532-010-9451-z· OSTI ID:1049566

Deo, Randhir P; Rittmann, Bruce E; Reed, Donald T ^[1]

---

1. AZU

Plutonium (Pu), a key contaminant at sites associated with the manufacture of nuclear weapons and with nuclear-energy wastes, can be precipitated to 'immobilized' plutonium phases in systems that promote bioreduction. Ferric iron (Fe³⁺) is often present in contaminated sites, and its bioreduction to ferrous iron (Fe²⁺) may be involved in the reduction of Pu to forms that precipitate. Alternately, Pu can be reduced directly by the bacteria. Besides Fe, contaminated sites often contain strong complexing ligands, such as nitrilotriacetic acid (NTA). We used biogeochemical modeling to interpret the experimental fate of Pu in the absence and presence of ferric iron (Fe³⁺) and NTA under anaerobic conditions. In all cases, Shewanella alga BrY (S. alga) reduced Pu(V)(PuO₂⁺) to Pu(III), and experimental evidence indicates that Pu(III) precipitated as PuPO_4(am). In the absence of Fe³⁺ and NTA, reduction of PuO₂⁺ was directly biotic, but modeling simulations support that PuO₂⁺ reduction in the presence of Fe³⁺ and NTA was due to an abiotic stepwise reduction of PuO₂⁺ to Pu4+, followed by reduction of Pu⁴⁺ to Pu³⁺, both through biogenically produced Fe²⁺. This means that PuO₂⁺ reduction was slowed by first having Fe³⁺ reduced to Fe²⁺. Modeling results also show that the degree of PuPO_4(am) precipitation depends on the NTA concentration. While precipitation out-competes complexation when NTA is present at the same or lower concentration than Pu, excess NTA can prevent precipitation of PuPO_4(am).

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: DOE - OTHER
• OSTI ID: 1049566
• Journal Information: Biodegradation, Journal Name: Biodegradation Journal Issue: (5) ; 2011 Vol. 22; ISSN BIODEG
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

54 ENVIRONMENTAL SCIENCES
ANAEROBIC CONDITIONS
BACTERIA
IRON
NTA
NUCLEAR ENERGY
NUCLEAR WEAPONS
PLUTONIUM
PRECIPITATION
SIMULATION
WASTES