Rutgers University, Department of Earth & Environmental Sciences, 101 Warren Street, Newark, New Jersey 07102, USA.
Environ Sci Technol. 2012 May 1;46(9):4894-901. doi: 10.1021/es2044807. Epub 2012 Apr 10.
The reactivity of aqueous Fe(II) with aluminum oxide in anoxic solutions was investigated with batch kinetic experiments combined with Fe K edge X-ray absorption spectroscopy measurements to characterize Fe(II) sorption products. Formation of Fe(II)-Al(III)-layered double hydroxides with an octahedral sheet structure similar to nikischerite (NaFe(II)(6) Al(3)(SO(4))(2)(OH)(18) (H(2)O)(12)) was observed within a few hours during sorption at pH 7.5 and aqueous Fe(II) concentrations of 1-3 mM. These Fe(II) phases are composed of brucite-like Fe(II)(OH)(2) sheets with partial substitution of Al(III) for Fe(II), charge balanced by anions coordinated along the basal planes. Their fast rate of formation suggests that these previously unrecognized Fe(II) phases, which are structurally and compositionally similar to green rust, may be an important sink of Fe(II) in suboxic and anoxic geochemical environments, and impact the fate of structurally compatible trace metals, such as Co(II), Ni(II), and Zn(II), as well as redox-reactive species including Cr(VI) and U(VI). Further studies are required to assess the thermodynamics, formation kinetics, and stability of these Fe(II) minerals under field conditions.
采用批式动力学实验结合 Fe K 边 X 射线吸收光谱测量研究了缺氧溶液中水中的 Fe(II)与氧化铝的反应活性，以表征 Fe(II)的吸附产物。在 pH 值为 7.5 和水相 Fe(II)浓度为 1-3mM 的吸附条件下，在几小时内观察到具有与 nikischerite（NaFe(II)(6)Al(3)(SO(4))(2)(OH)(18)(H(2)O)(12)）类似的八面体片层结构的 Fe(II)-Al(III)-层状双氢氧化物的形成。这些 Fe(II)相由类水镁石的 Fe(II)(OH)(2)片组成，其中 Al(III)部分取代了 Fe(II)，由沿基面配位的阴离子平衡电荷。它们的快速形成速率表明，这些以前未被识别的 Fe(II)相在结构和组成上与绿锈相似，可能是亚缺氧和缺氧地球化学环境中 Fe(II)的重要汇，并影响结构上相容的痕量金属（如 Co(II)、Ni(II)和 Zn(II)）以及氧化还原活性物质（如 Cr(VI)和 U(VI)）的命运。需要进一步研究来评估这些 Fe(II)矿物在野外条件下的热力学、形成动力学和稳定性。
