以暹罗芽孢杆菌为研究对象, 它具有较高的表面积/体积比, 吸附性能良好。 前人关于暹罗芽孢杆菌的研究多集中在它降解纤维素淀粉或抗菌方面, 关于暹罗芽孢杆菌与放射性核素的作用及机制基本未涉及。 利用等离子发射光谱和等离子发射光谱-质谱研究溶液初始pH值、 铀初始浓度、 菌体用量等因素对暹罗芽孢杆菌去除铀的影响及作用过程中菌体释放的生物磷与铀去除的关系； 利用红外光谱和扫描电镜对与铀作用前后的暹罗芽孢杆菌形貌及基团变化进行表征； 利用X射线光电子能谱和扫描电镜能谱分析菌体表面元素分布情况和元素价态, 进而探讨暹罗芽孢杆菌对铀的去除机制。 结果表明, 由于不同pH条件下暹罗芽孢杆菌生长活性、 铀存在形态和磷元素释放量的不同, 其对铀的去除差异很大。 在pH 5.0时, 暹罗芽孢杆菌对铀的去除效果最好。 菌体用量增加有利于暹罗芽孢杆菌对铀的去除。 对实验结果进行Langmuir和Freundlich等温吸附拟合后发现： 暹罗芽孢杆菌对铀的去除行为符合Langmuir等温吸附模型； 铀浓度实验获得的最大吸附量高于理论计算的最大吸附量, 说明暹罗芽孢杆菌对铀的去除可能是物理和化学行为的共同作用。 暹罗芽孢杆菌能够有效去除水体中的铀, 实验获得的最大去除率为96.5%, 最高吸附量为450.3 mg·g-1, 高于大部分已报道的用于吸附铀的芽孢杆菌。 对反应前后菌体的扫描电镜测试发现, 与铀作用后暹罗芽孢杆菌表面出现鳞片状沉淀, X射线光电子能谱和扫描电镜能谱分析表明该沉淀为含磷铀物质。 结合红外光谱分析, 推测暹罗芽孢杆菌去除铀的机制为： 首先, 通过静电作用铀被快速吸引到暹罗芽孢杆菌表面, 随后以配位的形式被菌体上的磷酸基团、 氨基、 羟基、 羧基等活性基团吸附, 同时与菌体释放的含磷酸盐类物质相互作用, 形成含磷铀沉淀而被固定至细菌表面。 在此过程中, 少部分六价铀被菌体释放的胞内物质还原成四价铀而发生沉降。 推测菌体表面沉淀可能为铀的磷酸盐沉淀和含磷化合物与铀的络合物形成的混合物。

In this experiment, Bacillus Siamensis (B. siamensis) was taken as research object, and B. siamensis had a high ratio of surface area to volume, indicating that B. siamensis has a great performance on adsorbing heavy metals. However, the studies of previous experts and scholars on B. siamensis mostly focused on degradation of starch or cellulose and antifungal activity. And the mechanism of the interaction between B. siamensis and heavy metals or radionuclides was to tally not researched. Therefore, the purposes of this experiment were to use ICP-OES and ICP-MS to study the effects of pH value of solution, initial uranium concentration and biomass on removal of uranium by B. siamensis and the relationship between biological phosphorus released by cells and removal of uranium during the process, FTIR and SEM to characterize the morphology and group changes of B. siamensis before and after interaction with uranium, XPS and EDS to analyze the distribution and valence of elements on the surface of B. siamensis, and then the removal mechanism of uranium by B. siamensis was discussed. The results showed that the removal of uranium by B. siamensis under different pH varied greatly due to the difference of growth activities of B. siamensis, the existence forms of uranium and the amount of phosphorus element released by cells in the process under different pH values conditions. The removal effect was the best at pH=5.0. Increasing the biomass was beneficial to the removal of uranium by B. siamensis. The Langmuir and Freundlich adsorption isotherm models were used to fit the experimental data, and the fitting results showed that the removal behavior of uranium by B. siamensis conformed to the Langmuir isotherm adsorption model. And the maximum adsorption capacity obtained from the initial uranium concentration experiment was higher than the theoretical maximum adsorption capacity calculated from the Langmuir isotherm adsorption model, indicating that the removal of uranium by B. siamensis could be a combination of physical and chemical behavior. B. siamensis could effectively remove uranium from water. The maximum removal rate obtained in this experiment was 96.5% and the maximum adsorption capacity was 450.3 mg·g-1, which were higher than those of most of the Bacillus strains used to adsorb uranium. SEM test of B. siamensis before and after the reaction showed that scale-like precipitate appeared on the surface of the cells after the reaction. XPS and EDS showed that the precipitate was a phosphorus-containing uranium substance. Combined with FTIR analysis, it was presumed that the removal mechanism of uranium by B. siamensis is as follows: Firstly, uranium was rapidly attracted to the surface of B. siamensis through electrostatic action, then adsorbed by phosphate groups, amino groups, hydroxyl groups and carboxyl groups on the bacteria in coordination form, and at the same time interacting with phosphate-containing substances released by the bacteria to form phosphorus-containing precipitation of uranium and then immobilized on the surface of the bacteria. During this process, a part of the hexavalent uranium was reduced to tetravalent uranium by intracellular substances released by the B. siamensis and then settled. It was speculated that the precipitation on the surface of the cell might be the mixture of the phosphate precipitation of uranium and the complexes of phosphorus-containing compounds and uranium complexes.