Uranium Immobilization by Sulfate-Reducing Biofilms

• Published in: Environmental science & technology Vol. 38; no. 7; pp. 2067 - 2074
• Main Authors: Beyenal, Haluk, Sani, Rajesh K, Peyton, Brent M, Dohnalkova, Alice C, Amonette, James E, Lewandowski, Zbigniew
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.2004
• Subjects: Absorption; Applied sciences; Bacteria; Biofilms; Biological and medical sciences; Biological treatment of waters; Biotechnology; Chemical Precipitation; Desulfovibrio desulfuricans; Earth sciences; Earth, ocean, space; Electrons; Engineering and environment geology. Geothermics; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Groundwaters; Hydrogen Sulfide - analysis; Industrial applications and implications. Economical aspects; Natural water pollution; Pollution; Pollution, environment geology; Radioactive wastes; Solubility; Sulfates - metabolism; Sulfur-Reducing Bacteria - physiology; Uranium; Uranium - chemistry; Uranium - isolation & purification; Wastes; Water Pollutants, Radioactive - isolation & purification; Water pollution; Water treatment and pollution; Radioactive waste; Sulfate-reducing bacteria; Radioactive pollution; XANES spectrometry; Immobilization; Hazardous waste; Liquid waste; Radioisotope; Chemical reduction; Sulfides; Bioreactor; Desulfovibrio desulfuricans; Transmission electron microscopy; Enzymatic activity; Decontamination; Chemical reaction; Uranium VI; Biofilm; Bacteria; Water pollution; Bioremediation; Ground water
• DOI: 10.1021/es0348703
• ISSN: 0013-936X

Hexavalent uranium [U(VI)] was immobilized using biofilms of the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans G20. The biofilms were grown in flat-plate continuous-flow reactors using lactate as the electron donor and sulfate as the electron acceptor. U(VI) was continuously fed into the reactor for 32 weeks at a concentration of 126 μM. During this time, the soluble U(VI) was removed (between 88 and 96% of feed) from solution and immobilized in the biofilms. The dynamics of U immobilization in the sulfate-reducing biofilms were quantified by estimating:  (1) microbial activity in the SRB biofilm, defined as the hydrogen sulfide (H2S) production rate and estimated from the H2S concentration profiles measured using microelectrodes across the biofilms; (2) concentration of dissolved U in the solution; and (3) the mass of U precipitated in the biofilm. Results suggest that U was immobilized in the biofilms as a result of two processes:  (1) enzymatically and (2) chemically, by reacting with microbially generated H2S. Visual inspection showed that the dissolved sulfide species reacted with U(VI) to produce a black precipitate. Synchrotron-based U L3-edge X-ray absorption near edge structure (XANES) spectroscopy analysis of U precipitated abiotically by sodium sulfide indicated that U(VI) had been reduced to U(IV). Selected-area electron diffraction pattern and crystallographic analysis of transmission electron microscope lattice-fringe images confirmed the structure of precipitated U as being that of uraninite.