灭活与非灭活条件下植物乳杆菌去除U(VI)的机理

在不同时间，pH值和生物量浓度条件下，进行了灭活与非灭活植物乳杆菌去除水中铀的对比试验，探讨了二者去除水中铀的机理，通过SEM-EDS、FTIR、XPS及XRD分析了铀与菌体表面的微观作用机理以及菌体表面沉积物的特征.结果表明：植物乳杆菌经灭活后，其吸附铀的能力得到显著的提高，当U（VI）初始浓度为10mg/L、pH值为6.0、37℃条件下，120min内灭活菌体对U（VI）的去除率为94.7%，而活菌体的去除率为88.9%.灭活菌体具有更高的铀吸附容量，在生物量浓度为0.06~0.24mg/L，pH值（3.0~7.0）条件下，灭活菌体与活菌体的U（VI）累积容量比W均大于1.SEM-EDS、FTIR分析结果表明，活细胞和灭活细胞都可通过细胞表面的羟基、酰基及羧基等官能团吸附、配位络合U（VI）.XRD分析表明，活菌体可生物磷酸矿化水中的U（VI）.活菌体的XRD谱图在2θ（18.023，25.492，27.343，40.813°处）有4个明显的磷酸铀酰晶体峰，而灭活菌体的XRD谱图显示为非晶态.XPS结果表明，活菌体可生物还原U（VI）.活菌体能谱图中U4f7/2和U4f5/2轨道出现了结合能为380.20eV和390.65eV的U（VI）分裂峰，而灭活菌体的能谱图中没有出现U（IV）的分裂峰.

Mechanism of U (VI) removal by Lactobacillus plantarum under inactivated and non-inactivated conditions

The uranium removal tests of inactivated and non-inactivated Lactobacillus plantarum were carried out under different pH and biomass concentration conditions, and the mechanism of uranium removal by Lactobacillus plantarum was discussed. Based on SEM-EDS, FTIR, XPS, and XRD, the microscopic mechanism of the interaction between uranium and microbial cell surface and the characteristics of sediments on the cell surface were analyzed. The ability of Lactobacillus plantarum to adsorb uranium was significantly improved after heat inactivation. With the pH 6.0, 37℃ and the 10mg/L U(VI), the removal efficiency of U(VI) by heat-killed cells was up to 94.7% during 120min, while the removal efficiency was only 88.9% by live cells. The inactivated bacteria had higher uranium adsorption capacity. At the biomass concentration of 0.06~0.24mg/L and pH value of 3.0~7.0, the rate(W) of accumulative capacity of U(VI) of inactivated bacteria to that of living bacteria is greater than 1. SEM-EDS、FTIR result illustrated the U(VI) could be adsorbed or coordinated on the surface of the active and inactivated cells through functional groups such as hydroxyl, acyl and carboxyl groups. There were 4 distinct crystal peaks of uranyl phosphate compound at 2θ(18.023, 25.492, 27.343 and 40.813°) in the XRD spectrum of living bacteria, while no crystal peaks in the spectrum of inactivated bacteria. XRD result indicated U(VI) can be precipitated with the form of uranyl phosphate by biological metabolism of live cells. There were the peaks attributed U(IV) at U 4f 7/2 with binding energy of 381.20eV and U 4f 5/2 with 390.95eV in the XPS energy spectrum of living bacteria. While There was no the peaks attributed U(IV) in the spectrum of inactivated bacteria. XPS result indicated that U(VI) can be induced to U(IV) by living bacteria.