Effect of Staphylococcus epidermidis on U(VI) sequestration by Al-goethite

Abstract Effect of Staphylococcus epidermidis ( S. epidermidis ) on U(VI) sequestration by Al-goethite were conducted under different geologic conditions. The batch experiments showed that S. epidermidis significantly enhanced the adsorption rates of U(VI) at pH  S. epidermidis at pH 4.0 and 310 K were calculated from Langmuir equation to be 13.16 and 47.86 mg/g, respectively. The decreased adsorption of U(VI) on Al-goethite+ S. epidermidis at high carbonate and pH conditions were primarily driven by the electrostatic repulsion between negatively charged U(VI)-carbonate complexes and the negatively charged adsorbents. According to XPS analysis, the adsorbed U(VI) can be reduced to U(IV) by S. epidermidis, whereas inhibited reduction of U(VI) on Al-goethite + S. epidermidis at high pH could be attributed to the complexation of structural Fe(III) with the oxygen-containing functional groups of S. epidermidis . FT-IR analysis further demonstrated that the bonding of structural Fe(III) with functional groups (e.g., carboxyl and phosphate groups) of S. epidermidis . These results herein are important to understand the fate and transport of U(VI) on the mineral-bacteria ternary systems in the near-surface environment.