Biosorption behavior and mechanism of thorium on Bacillus sp. dwc-2 isolated from soil

• Published in: 核技术（英文版） 2015-12, Vol.26 (6), p.35-45
• Main Author: 兰图 丁聪聪 廖家莉 李晓龙 李兴亮 张杰 张东 杨吉军 罗顺忠 安竹 邬琦琦 杨远友 冯甦 唐军 刘宁
• Format: Article
• Language: English
• Subjects: Freundlich模型; 分离; 吸附行为; 土壤; 离子交换机理; 芽孢杆菌; 钍; 静电相互作用
• ISSN: 1001-8042; 2210-3147
• DOI: 10.13538/j.1001-8042/nst.26.060301

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.