title: Bioreduction and reoxidation of uranium enhanced by thiol functional groups in natural organic matter.
abstract: Although natural organic matter (NOM) is known to affect biological reduction of U(VI) and subsequent reoxidation of U(IV), the underlying mechanisms remain unclear. This study investigated the redox reactions of sulfide with NOM to form thiol functional groups, which can greatly enhance U(VI) bioreduction and U(IV) reoxidation. Results showed that humic acid (HA) was found to be more effective than fulvic acid (FA) in producing thiol groups, both U(VI) bioreduction and U(IV) reoxidation rates increased with the increase of thiols content in HA and FA. These findings suggested that among other redox sites, thiol groups in NOM may play an important role in the electron transport between uranium and microbial cells, and are of great environmental implications because they provided direct proof that thiol groups are responsible for bioremediation and immobilization of uranium when it enters into the natural environments such as soil and groundwater.
authors.affiliation: CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China; Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge 37830, TN, USA; School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore. Electronic address: hwluo@ntu.edu.sg.
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Luo
authors.affiliation: CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Xu
keywords: Natural organic matter; Thiol functional groups; Uranium bioremediation