Reduction of Np(V) and precipitation of Np(IV) by an anaerobic microbial consortium

Bruce E. Rittmann, James E. Banaszak, Donald T. Reed

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


A combination of experimental, analytical, and modeling investigations shows that an anaerobic, sulfate-reducing consortium reduced Np(V) to Np(IV), with subsequent precipitation of a Np(IV) solid. Precipitation of Np(IV) during growth on pyruvate occurred before sulfate reduction began. H2 stimulated precipitation of Np(IV) when added alone to growing cells, but it slowed precipitation when added along with pyruvate. Increasing concentrations of pyruvate also retarded precipitation. Accumulation of an intermediate pyruvate-fermentation product - probably succinate - played a key role in retarding Np(IV) precipitation by complexing the Np(IV). Hydrogen appears to have two roles in controlling Np precipitation: donating electrons for Np(V) reduction and modulating intermediate levels. That Np(V) is microbially reduced and subsequently precipitated under anaerobic conditions has likely beneficial implications for the containment of Np on lands contaminated by radionuclides, but complexation by fermentation intermediates can prevent immobilization by precipitation.

Original languageEnglish (US)
Pages (from-to)329-342
Number of pages14
Issue number5
StatePublished - 2002
Externally publishedYes


  • Anaerobic consortium
  • Bioreduction
  • Complexation
  • Hydrogen
  • Modeling
  • Neptunium
  • Precipitation
  • Succinate

ASJC Scopus subject areas

  • Environmental Engineering
  • Microbiology
  • Bioengineering
  • Environmental Chemistry
  • Pollution


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