嗜酸氧化亚铁硫杆菌胞外聚合物与Cd^(2+)在吸附过程中的交互作用

Interaction between Extracellular Polymeric Substances of Acidithiobacillus ferrooxidans and Cd^(2+) during the Adsorption Process

从粤北大宝山酸性矿山废水(AMD)分离出具有较强耐镉活性的嗜酸氧化亚铁硫杆菌(Af菌),采用原子吸收分光光度技术和荧光光谱分析技术,研究Af菌胞外聚合物(EPS)与水中Cd^(2+)在吸附过程中的交互作用机制。分离获取的Af耐镉菌株最大耐受浓度为0. 03～0. 04 mol/L,表现出较强的耐镉活性;在Cd^(2+)的胁迫下,Af菌可通过产生EPS来抵御和去除Cd^(2+)的不利影响;当EPS吸附Cd^(2+)后,其类蛋白荧光峰强度增强,且在λ_(Em)=402 nm处产生一个新的宽大的荧光峰,并显示出较强的荧光强度。结果表明,Cd^(2+)与EPS间相互作用机制是电中和和离子架桥效应的协同过程,Cd^(2+)通过改变EPS表面电位和类蛋白疏水作用来介导EPS构象和絮凝体结构变化,进而促进EPS絮凝体的聚集,提高其絮凝效率和沉降性能。

A strain of Acidithiobacillus ferrooxidans(A.f)was isolated from the acid mine drainage of Dabaoshan Mine in North Guangdong and showed a strong cadmium resistance.The atomic absorption spectrophotometry and fluorescent spectrophotometry technique were used to explore the interaction between extracellular polymeric substances(EPS)of A.f.and Cd2+during the adsorption.The maximal tolerable concentration of A.f.to Cd2+ranged from 0.03 to 0.04 mol·L-1 and showed a strong cadmium resistance.Under the stress of Cd,A.f.could defend against Cd and decrease the harmful effect by producing and secreting EPS.After Cd2+was adsorbed onto the EPS,protein-like fluorescence intensities strengthened,and a new wide fluorescence spectral peak located at 402 nm appeared and showed great fluorescence intensity.The results indicated that the interaction between EPS of A.f.and Cd2+was one kind of collaborative process including charge neutralization and ion bridging effect.Cd2+could change the conformation of EPS and had an impact on structure of floc by the effect of surface potential of EPS and hydrophobic interaction of protein-like,which promoted the accumulation of the EPS floc and improved the efficiency of flocculation and settling performance.