Boonfueng Thipnakarin, Axe Lisa, Yee Nathan, Hahn Dittmar, Ndiba Peter K
Department of Civil and Environmental Engineering, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA.
J Colloid Interface Sci. 2009 May 15;333(2):439-47. doi: 10.1016/j.jcis.2009.02.033. Epub 2009 Feb 21.
Zinc sorption on sheathed Leptothrix discophora bacterium, the isolated extracellular polymeric substances (EPS) sheath, and Mn oxide-coated bacteria was investigated with macroscopic and spectroscopic techniques. Complexation with L. discophora was dominated by the outer membrane phosphoryl groups of the phospholipid bilayer while sorption to isolated EPS was dominated by carboxyl groups. Precipitation of nanoparticulate Mn oxide coatings on the cell surface increased site capacity by over twenty times with significant increase in metal sorption. XAS analysis of Zn sorption in the coated system showed Mn oxide phase contributions of 18 to 43% through mononuclear inner-sphere complexes. The coordination environments in coprecipitation samples were identical to those of sorption samples, indicating that, even in coprecipitation, Zn is not incorporated into the Mn oxide structure. Rather, through enzymatic oxidation by L. discophora, Mn(II) is oxidized and precipitated onto the biofilm providing a large surface for metal sequestration. The nanoparticulate Mn oxide coating exhibited significant microporosity (75%) suggesting contributions from intraparticle diffusion. Transient studies conducted over 7 months revealed a 170% increase in Zn loading. However, the intraparticle diffusivity of 10(-19) cm(2) s(-1) is two orders of magnitude smaller than that for abiotic Mn oxide which we attribute to morphological changes such as reduced pore sizes in the nanoparticulate oxide. Our results demonstrate that the cell-bound Mn oxide particles can sorb significant amounts of Zn over long periods of time representing an important surface for sequestration of metal contaminants.
采用宏观和光谱技术研究了锌在鞘铁细菌、分离出的细胞外聚合物（EPS）鞘以及锰氧化物包覆细菌上的吸附情况。与鞘铁细菌的络合作用主要由磷脂双层的外膜磷酰基主导，而对分离出的EPS的吸附则主要由羧基主导。细胞表面纳米颗粒状锰氧化物涂层的沉淀使吸附位点容量增加了二十多倍，金属吸附量显著增加。对包覆体系中锌吸附的X射线吸收光谱（XAS）分析表明，通过单核内球络合物，锰氧化物相的贡献为18%至43%。共沉淀样品中的配位环境与吸附样品相同，这表明即使在共沉淀过程中，锌也不会掺入锰氧化物结构中。相反，通过鞘铁细菌的酶促氧化作用，二价锰被氧化并沉淀在生物膜上，为金属螯合提供了一个大的表面。纳米颗粒状锰氧化物涂层表现出显著的微孔率（75%），表明颗粒内扩散起了作用。在7个月内进行的瞬态研究表明锌负载量增加了170%。然而，颗粒内扩散系数为10(-19) cm(2) s(-1)，比非生物锰氧化物的扩散系数小两个数量级，我们将其归因于形态变化，如纳米颗粒氧化物中孔径减小。我们的结果表明，细胞结合的锰氧化物颗粒可以在很长一段时间内吸附大量锌，这代表了一个用于螯合金属污染物的重要表面。
