Adsorption of Cu(II) to Bacillus subtilis: A pH-dependent EXAFS and thermodynamic modelling study
Adsorption of Cu(II) to Bacillus subtilis: A pH-dependent EXAFS and thermodynamic modelling study
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DOI：
10.1016/j.gca.2011.08.004
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发表时间：
2011-11
影响因子：
5
通讯作者：
E. Moon;C. Peacock
中科院分区：
文献类型：
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作者：
E. Moon;C. Peacock
细菌是非常有效的痕量金属吸附剂，它们在各种天然水系统中的丰度意味着生物吸附在许多元素的地球化学循环中起着重要作用。我们测量了吸附的Cu（II）枯草芽孢杆菌作为pH值和表面负载的函数。吸附边和XAS实验进行了高细菌-金属比，类似于自然地质和水环境中的铜吸收。我们报告了铜对B的显着吸附。枯草杆菌在整个pH范围内研究（pH值为2-7），与吸附增加pH值的最大值在pH值为6。首次直接测定了Cu吸附在B上。枯草杆菌作为（CuO 5 Hn）n− 8单齿，内球表面复合物，涉及羧基表面官能团。这种铜-羧基络合物是能够占所观察到的铜吸附在整个pH范围内研究。确定了Cu对B的分子吸附机理。枯草杆菌，我们已经开发了一个新的热力学表面络合模型铜吸附，是由EXAFS结果的通知和一致。我们使用1 pK基本斯特恩近似模型的表面静电。我们适合我们的吸附数据形成的单齿，内球RCOOCu+表面络合物。与以前的研究一致，这项工作表明，为了准确地预测的命运和流动性的铜在复杂的地球化学系统中，我们必须将形成的铜细菌表面复合物的反应性运输模型。为此，这项工作建议logKRCOOCu+=7.13的地质和含水系统一般高B。枯草杆菌与金属的比例
Bacteria are very efficient sorbents of trace metals, and their abundance in a wide variety of natural aqueous systems means biosorption plays an important role in the biogeochemical cycling of many elements. We measured the adsorption of Cu(II) to Bacillus subtilis as a function of pH and surface loading. Adsorption edge and XAS experiments were performed at high bacteria-to-metal ratio, analogous to Cu uptake in natural geologic and aqueous environments. We report significant Cu adsorption to B. subtilis across the entire pH range studied (pH ∼2–7), with adsorption increasing with pH to a maximum at pH ∼6. We determine directly for the first time that Cu adsorbs to B. subtilis as a (CuO5Hn)n−8monodentate, inner-sphere surface complex involving carboxyl surface functional groups. This Cu–carboxyl complex is able to account for the observed Cu adsorption across the entire pH range studied. Having determined the molecular adsorption mechanism of Cu to B. subtilis, we have developed a new thermodynamic surface complexation model for Cu adsorption that is informed by and consistent with EXAFS results. We model the surface electrostatics using the 1pK basic Stern approximation. We fit our adsorption data to the formation of a monodentate, inner-sphere RCOOCu+surface complex. In agreement with previous studies, this work indicates that in order to accurately predict the fate and mobility of Cu in complex biogeochemical systems, we must incorporate the formation of Cu-bacteria surface complexes in reactive transport models. To this end, this work recommends logKRCOOCu+=7.13 for geologic and aqueous systems with generally high B. subtilis-to-metal ratio.