Department of Earth & Environmental Sciences, Rutgers University, 101Warren Street, Newark, New Jersey 07102, United States.
Environ Sci Technol. 2021 Aug 3;55(15):10411-10421. doi: 10.1021/acs.est.1c01442. Epub 2021 Jul 20.
The sorption of Ni(II) by green rust sulfate (GR-sulfate) was studied in anoxic pre-equilibrated suspensions at pH 7.0 and pH 7.8 with combined batch kinetic experiments, X-ray diffraction measurements, and Ni K-edge X-ray absorption spectroscopy (XAS) analyses. Continuous removal of aqueous Ni(II) was observed over the course of the reaction (1-2.5 weeks) at both pH values, with no concurrent changes in aqueous Fe(II) levels or detectable mineralogical modifications of the GR sorbent. XAS results indicate that Ni(II) is not retained as mononuclear adsorption complexes on the GR surface but rather incorporated in the octahedral layers of an FeNiFe(OH)-layered double hydroxide (LDH) phase with 0 < < 0.67. The combined macroscopic and spectroscopic data suggest that Ni(II) substitutes into the GR lattice during Fe(II)-catalyzed recrystallization of the sorbent and/or forms secondary Ni(II)/Fe(II)-Fe(III)-LDH phases with a higher stability than that of GR, complemented likely by Ni(II)-Fe(II) exchange at GR particle edges. The results of this study reveal GR to be a dynamic sorbent that engages in dissolution-reprecipitation and exchange reactions, causing extensive incorporation of trace metal Ni(II). Additional work is needed to further define the mechanisms involved and to assess the sorptive reactivity of GR with other trace metal species.
在 pH 值为 7.0 和 7.8 的缺氧预平衡悬浮液中，通过组合批式动力学实验、X 射线衍射测量和 Ni K 边 X 射线吸收光谱（XAS）分析研究了绿锈硫酸盐（GR-硫酸盐）对 Ni(II)的吸附。在两个 pH 值下，反应过程（1-2.5 周）中均观察到水溶液中 Ni(II)的连续去除，而水溶液中 Fe(II)水平没有同时变化，也没有检测到 GR 吸附剂的矿物学修饰。XAS 结果表明，Ni(II)不是作为单核吸附配合物保留在 GR 表面上，而是以 0 < < 0.67 的形式掺入到 FeNiFe(OH)层状双氢氧化物（LDH）相的八面体层中。宏观和光谱数据的综合表明，Ni(II)在 Fe(II)催化的吸附剂重结晶过程中取代 GR 晶格，或者形成比 GR 更稳定的次生 Ni(II)/Fe(II)-Fe(III)-LDH 相，可能伴随着 GR 颗粒边缘的 Ni(II)-Fe(II)交换。这项研究的结果表明，GR 是一种动态吸附剂，它会发生溶解-再沉淀和交换反应，导致痕量金属 Ni(II)的广泛掺入。需要进一步研究以进一步确定所涉及的机制，并评估 GR 对其他痕量金属物种的吸附反应性。
