摘要
To develop a microbe-based bioremediation strategy for cleaning up thorium-contaminated sites, we have investigated the biosorption behavior and mechanism of thorium on Bacillus sp. dwc-2, one of the dominant species of bacterial groups isolated from soils in Southwest China. Thorium biosorption depended on the p H of environment, and its rapid biosorption reached a maximum of up to 10.75 mg Th per gram of the bacteria(wet wt.) at pH 3.0. The biosorption agreed bettter with Langmuir isotherm model than Freundlich model, indicating that thorium biosorption was a monolayer adsorption. The thermodynamic parameters, negative change in Gibbs free energy and positive value in enthalpy and entropy, suggested that the biosorption was spontaneous,more favorable at higher temperature and endothermic process with an increase of entropy. Scanning electron microscopy(SEM) indicated that thorium initially binded with the cell surface, while transmission electron microscopy(TEM) revealed that Th deposited in the cytoplasm and served as cores for growth of element precipitation(e.g., phosphate minerals) or by self-precipitation of hydroxides, which is probably controlled by ion-exchange, as evidenced by particle induced X-ray emission(PIXE) and enhanced proton backscattering spectrometry(EPBS). Fourier Transform Infrared(FTIR) further indicated that thorium biosorption involved carboxyl and phosphate groups and protein in complexation or electrostatic interaction. Overall results indicated that a combined electrostatic interaction-complexation-ion exchange mechanism could be involved in thorium biosorption by Bacillus sp. dwc-2.
To develop a microbe-based bioremediation strategy for cleaning up thorium-contaminated sites, we have investigated the biosorption behavior and mechanism of thorium on Bacillus sp. dwc-2, one of the dominant species of bacterial groups isolated from soils in Southwest China. Thorium biosorption depended on the p H of environment, and its rapid biosorption reached a maximum of up to 10.75 mg Th per gram of the bacteria（wet wt.） at pH 3.0. The biosorption agreed bettter with Langmuir isotherm model than Freundlich model, indicating that thorium biosorption was a monolayer adsorption. The thermodynamic parameters, negative change in Gibbs free energy and positive value in enthalpy and entropy, suggested that the biosorption was spontaneous,more favorable at higher temperature and endothermic process with an increase of entropy. Scanning electron microscopy（SEM） indicated that thorium initially binded with the cell surface, while transmission electron microscopy（TEM） revealed that Th deposited in the cytoplasm and served as cores for growth of element precipitation（e.g., phosphate minerals） or by self-precipitation of hydroxides, which is probably controlled by ion-exchange, as evidenced by particle induced X-ray emission（PIXE） and enhanced proton backscattering spectrometry（EPBS）. Fourier Transform Infrared（FTIR） further indicated that thorium biosorption involved carboxyl and phosphate groups and protein in complexation or electrostatic interaction. Overall results indicated that a combined electrostatic interaction-complexation-ion exchange mechanism could be involved in thorium biosorption by Bacillus sp. dwc-2.
基金
Supported by National Natural Science Foundation of China(Nos.21071102 and 91126013)
Joint Funds of China National Natural Science Foundation and China Academy of Engineering Physics(No.U1330125)
the National Fund of China for Fostering Talents in Basic Science(No.J1210004)
关键词
离子交换机理
吸附行为
芽孢杆菌
FREUNDLICH模型
分离
土壤
静电相互作用
钍
Thorium Bacillus sp Biosorption Mechanism Transmission electron microscopy（TEM） Particle induced X-ray emission（PIXE） Enhanced proton backscattering spectrometry（EPBS）
