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 Fe^II_0.67–xNi^II_xFe^III_0.33(OH)₂-layered double hydroxide (LDH) phase with 0 < x < 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)_aq. Additional work is needed to further define the mechanisms involved and to assess the sorptive reactivity of GR with other trace metal species.

中文翻译：

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绿锈硫酸盐吸附Ni(II)的机理研究

在 pH 7.0 和 pH 7.8 的缺氧预平衡悬浮液中，结合批次动力学实验、X 射线衍射测量和 Ni K-edge X 射线研究了绿锈硫酸盐（GR-硫酸盐）对 Ni(II) 的吸附吸收光谱 (XAS) 分析。在反应过程中（1-2.5 周），在两个 pH 值下均观察到 Ni(II) 水溶液的连续去除，而 Fe(II) 水溶液的含量没有同时发生变化，也没有可检测到的 GR 吸附剂的矿物学改变。XAS 结果表明 Ni(II) 没有作为单核吸附复合物保留在 GR 表面，而是结合在 Fe ^II _{0.67– x} Ni ^II _x Fe ^III _0.33 (OH) ₂的八面体层中-层状双氢氧化物 (LDH) 相，0 < x < 0.67。综合宏观和光谱数据表明，Ni(II) 在 Fe(II) 催化的吸附剂重结晶过程中取代了 GR 晶格和/或形成了二次 Ni(II)/Fe(II)-Fe(III)-LDH 相具有比 GR 更高的稳定性，可能由 GR 颗粒边缘的 Ni(II)-Fe(II) 交换补充。这项研究的结果表明 GR 是一种动态吸附剂，参与溶解-再沉淀和交换反应，导致微量金属 Ni(II) _{aq 的}大量掺入。需要额外的工作来进一步定义所涉及的机制并评估 GR 与其他痕量金属物种的吸附反应性。