Rutgers University , Department of Earth & Environmental Sciences, Newark, New Jersey 07102, United States.
Environ Sci Technol. 2014 May 6;48(9):4937-45. doi: 10.1021/es500579p. Epub 2014 Apr 21.
Sorption of Fe(II) in anoxic aqueous suspensions of γ-Al2O3, smectitic clay and amorphous silica was studied as a function of pH (5.0-10.0) and reaction time (up to 110 days), using batch experiments complemented with synchrotron X-ray absorption spectroscopic analyses. Formation of secondary Fe(II) precipitates was observed at pH > 7 in all systems, with the rate of precipitation and the types of precipitates formed varying with pH and substrate type. Sorption of Fe(II) on γ-Al2O3 at pH ≥ 7.0 and onto clay at pH 7.0 and 7.5 led to formation of Fe(II)-Al(III) layered double hydroxides, whereas poorly crystalline trioctahedral Fe(II)-phyllosilicates formed in the amorphous SiO2 suspensions at pH > 7.5 and in the clay suspensions at pH 8.0. The rate and extent of Fe(II) sorption increased with pH, underscoring the importance of pH in regulating precipitate formation. Notably slower Fe(II) precipitation in the clay suspensions compared to γ-Al2O3 and SiO2 is attributed to relatively low availability of substrate-derived Al and Si. Our findings demonstrate that sorbent type, pH and reaction time are important factors affecting precipitation of secondary Fe(II) minerals in anoxic environments, and suggest substantial complexity in the type and reactivity of Fe(II) sorption products that may form.
研究了γ-Al2O3、蒙脱石粘土和无定形二氧化硅在缺氧水悬浮液中对 Fe(II)的吸附，考察了 pH 值（5.0-10.0）和反应时间（长达 110 天）的影响，实验采用了分批实验并辅以同步辐射 X 射线吸收光谱分析。在所有体系中，均观察到 pH > 7 时形成了次生 Fe(II)沉淀物，沉淀的速率和形成的沉淀物类型随 pH 值和基质类型而变化。在 pH ≥ 7.0 时，γ-Al2O3 对 Fe(II)的吸附以及在 pH 7.0 和 7.5 时粘土对 Fe(II)的吸附导致了 Fe(II)-Al(III)层状双氢氧化物的形成，而在 pH > 7.5 的无定形 SiO2 悬浮液中和在 pH 8.0 的粘土悬浮液中形成了结晶度差的三八面体 Fe(II)-层状硅酸盐。Fe(II)吸附的速率和程度随 pH 值的增加而增加，这突出了 pH 值在调节沉淀形成方面的重要性。值得注意的是，与 γ-Al2O3 和 SiO2 相比，粘土悬浮液中 Fe(II)沉淀的速度较慢，这归因于基质衍生的 Al 和 Si 的相对可用性较低。我们的研究结果表明，吸附剂类型、pH 值和反应时间是影响缺氧环境中次生 Fe(II)矿物沉淀的重要因素，并表明可能形成的 Fe(II)吸附产物的类型和反应性具有很大的复杂性。
