Environmental Remediation Science at the Stanford Synchrotron Radiation Laboratory

Natural Mn oxide colloids and grain coatings are ubiquitous in the environment and have extremely high sorptive capacities for heavy metals, including U(VI). Mn(II) is a common ground water solute, which is bacterially oxidized to Mn(VI) oxide under microaerophilic conditions. In-situ stimulation of Mn oxide production provides a potential route to enhanced attenuation of ground water U(VI). We have used extended x-ray absorption fine structure (EXAFS) spectroscopy and synchrotron-based in-situ x-ray diffraction (SR-XRD) to probe the structural mechanisms of uranium binding by manganese oxides produced by Bacillus sp., strain SG-1. These results indicate that U(VI) is structurally bound within tunnel-structured Mn oxides