Reoxidation of Biogenic Reduced Uranium: A Challenge Toward Bioremediation


Singh G., Sengoer S. S. , Bhalla A., Kumar S., De J., Stewart B., ...More

CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY, vol.44, no.4, pp.391-415, 2014 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Review
  • Volume: 44 Issue: 4
  • Publication Date: 2014
  • Doi Number: 10.1080/10643389.2012.728522
  • Title of Journal : CRITICAL REVIEWS IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY
  • Page Numbers: pp.391-415
  • Keywords: biogenic UO2, Fe(III)-(hydr)oxides, humics, Mn(IV) oxides, siderophores, CONTAMINATED SUBSURFACE SEDIMENTS, U(VI) REDUCTION, DESULFOVIBRIO-DESULFURICANS, IRON(III) (HYDR)OXIDES, COORDINATION CHEMISTRY, BIOLOGICAL REDUCTION, DISSOLVED-OXYGEN, U(IV) OXIDATION, FE(III) OXIDE, SULFATE

Abstract

Uraninite (UO2) is the most desirable end product of in situ bioreduction because of its low solubility under reducing conditions. For effective long-term immobilization of uranium (U), there should be no biotic or abiotic reoxidation of the insoluble biogenic U(IV). It is therefore critical to understand the long-term stability of U(IV) under oxic- and nutrient-limited conditions at U-contaminated subsurface sites. It has now been established that following in situ bioremediation of U(VI) via nutrient addition in the subsurface, a range of physical, chemical, and biological factors control the rate and extent of long-term stability of U(IV). Some of these factors are tied to site specific conditions including existence of oxidants such as Fe(III)(hydr)oxides, Mn(IV) oxides, oxygen, and nitrate; the presence of organic carbon and the reduced forms of U (e.g., mononuclear U(IV) or nanometer-sized uraninite particles); and the carbonate concentration and pH of groundwater. This review analyzes the contribution of these factors in controlling U(IV)-reoxidation, and highlights the competition among U(IV) and other electron acceptors and possible mechanisms of reoxidation of various forms of U(IV).