Bacillus coagulans BP-2非活性菌株对Cd^(2+)的吸附特性及机理研究

Studies on Adsorption Characteristics and Mechanism of the Inactive Bacillus coagulans BP-2 on Cd^(2+)

为寻找Cd^(2+)经济、高效、环保的微生物吸附剂,探讨微生物对重金属的吸附特性和机理,从采自韶关大宝山矿区的土壤样品中分离、筛选耐镉功能菌株,以BP-2菌株为研究对象,采用16S r DNA方法对菌株进行了分子鉴定;通过批式试验系统研究了不同环境变量对菌株吸附Cd^(2+)的影响;利用等温吸附模型、动力学模型模拟了吸附过程;采用红外光谱(FTIR)、X射线衍射(XRD)和X射线光电子能谱(XPS)分析手段,探讨了菌株吸附镉的作用机理。结果表明,16S r DNA序列相似性表明该菌株隶属芽孢杆菌属,将其命名为Bacillus coagulans BP-2。当Cd^(2+)初始质量浓度为100 mg·L^(-1),吸附时间为80min,菌株生物量为2.5 g·L^(-1)时,菌株对Cd^(2+)的吸附效果最好,吸附量可达73.26 mg·g^(-1);菌株对Cd^(2+)的吸附过程符合Langmuir等温模型(r^2=0.991 1),最大吸附量为86.19 mg·g^(-1),二级动力学方程(r^2=0.981 4)能够更准确地描绘菌株对Cd^(2+)的吸附过程。XRD分析显示,吸附后在13.3°、39.1°处出现Cd^(2+)的特征峰,说明Cd^(2+)成功被吸附到菌株的表面。FTIR和XPS结果表明Bacillus coagulans BP-2细胞壁上的-OH、-NH和-C=O基团参与了Cd^(2+)的吸附。利用Bacillus coagulans BP-2非活性菌株作为经济、高效、环境友好生物材料能够有效吸附溶液中Cd^(2+)。该研究可为含镉重金属废水的去除提供理论基础和实践依据。

The aim of this paper is to isolate and screen Cd2＋-resistant functional strains, investigating the adsorption characteristics of Cd2＋, adsorption kinetics and mechanism. So that it can provide theoretical foundation and practical platform for the bioremediation of other heavy metals. The functional strain BP-2 was studied as research object, molecular identification was carried out based on 16S rDNA. The influence of different environmental variables on the adsorption of Cd2＋ was studied by batch test system, and the adsorption process was analyzed by isothermal adsorption model and kinetic model. The mechanism for the adsorption of Cd2＋ was discussed by Infrared spectroscopy （FTIR）, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analysis methods. The results indicated that the 16S rDNA sequence similarity of the strain belonged to be Bacillus, and named as Bacillus coagulans BP-2. The optimum adsorption capacity was achieved at initial Cd2＋ mass concentration of 100 mg·L-1, biomass 2.5 g·L-1 with the contact time of 80 min, and under this condition, the maximum adsorption capacity could reach 73.26 mg·g-1. The adsorption isotherm and kinetic models showed that the adsorption processes followed the pseudo-second-order kinetic model （r2=0.9919）, and were well described by Langmuir isotherm （r2=0.9814）. XRD characterization results exhibited that the area of 13.3 ° and 19.1 ° appeared a strong characteristic peak after adsorption, which implied the successfully adsorption of Cd2＋ to the surface of the inactive strain. The results of FTIR and XPS demonstrated that the functional groups such as -OH, -NH and -C=O on the surface of strain were the involvement of the adsorption for Cd2＋. Thus, the inactive strain Bacillus coagulans BP-2 can be employed as a potential economic, efficient and environmental-friendly biological material for the effective removal of Cd2＋ from the aqueous solutions, and it is of great practical significance to the sustainable development of ecological environment.