Sorption of trivalent cerium by a mixture of microbial cells and manganese oxides: Effect of microbial cells on the oxidation of trivalent cerium
Journal
Geochimica et Cosmochimica Acta
Journal Volume
163
Start Page
1
End Page
13
ISSN
0016-7037
Date Issued
2015-08
Author(s)
Ohnuki, Toshihiko
Jiang, Mingyu
Sakamoto, Fuminori
Kozai, Naofumi
Yamasaki, Shinya
Yu, Qianqian
Tanaka, Kazuya
Xia, Xiaobin
Yang, Ke
He, Jianhua
Abstract
Sorption of Ce by mixtures of synthetic Mn oxides and microbial cells of Pseudomonas fluorescens was investigated to elucidate the role of microorganisms on Ce(III) oxidative migration in the environment. The mixtures, upon which Ce was sorbed following exposure to solutions containing 1.0×10-4 or 1.0×10-5molL-1Ce(III), were analyzed by scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) and micro-X-ray fluorescence (micro-XRF) at synchrotron facilities. A Ce LIII-edge micro XANES spectra analysis was also performed to determine the oxidation states of Ce adsorbed to the Mn oxides and microbial cells in the mixtures. The distribution ratios (Kd) of Ce between the individual solids and solution increased with increasing pH of the solution, and was nearly the same in mixtures containing varying amounts of microbial cells. SEM-EDS and micro-XRF analyses showed that Ce was sorbed by both MnO2 and microbial cells (1.7×10-1 or 3.3×10-1gL-1). In addition, nano-particles containing Ce and P developed on the surface of the microbial cells. XANES analysis showed that lower fractions of Ce(III) were oxidized to Ce(IV) in the mixtures containing greater amounts of microbial cells. Micro-XANES analysis revealed that Ce was present as Ce(III) on the microbial cells and as Ce(IV) on Mn oxides. These results strongly suggest that the association of Ce(III) with the microbial cell surface and the formation of Ce phosphate nano-particles are responsible for suppressing the oxidation of Ce(III) to Ce(IV) in the mixtures.
Subjects
Pseudomonas fluorescens
absorption
cerium
manganese oxide
microbial activity
oxidation
scanning electron microscopy
X-ray fluorescence
XANES spectroscopy
Publisher
Elsevier BV
Type
journal article