Mechanistic Study of Ni(II) Sorption by Green Rust Sulfate
Mechanistic Study of Ni(II) Sorption by Green Rust Sulfate
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DOI：
10.1021/acs.est.1c01442
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发表时间：
2021-07-20
影响因子：
11.4
通讯作者：
Elzinga, Evert J.
中科院分区：
文献类型：
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作者：
Elzinga, Evert J.
在pH 7.0和pH 7.8的缺氧预平衡悬浮液中，采用间歇动力学实验、X射线衍射测量和Ni K边X射线吸收光谱（XAS）分析研究了绿色锈硫酸盐（GR-sulfate）对Ni（II）的吸附。在两种pH值下，在反应过程中（1-2.5周）观察到连续去除Ni（II）水溶液，同时没有同时发生Fe（II）水溶液水平的变化或GR吸附剂的可检测矿物学修饰。XAS结果表明，Ni（II）不是作为单核吸附络合物保留在GR表面上，而是结合在（Fe 0.67-xNixFe 0.33 III）-Ni-II-Fe-II（OH）（2）-层状双氢氧化物（LDH）相的八面体层中，其中0 < x < 0.67。结合的宏观和光谱数据表明，Ni（II）取代到GR晶格在Fe（II）催化的吸附剂的重结晶和/或形成二级Ni（II）/Fe（II）-Fe（III）-LDH相具有更高的稳定性比GR，补充可能由Ni（II）-Fe（II）交换在GR颗粒边缘。本研究的结果表明，GR是一个动态的吸附剂，从事溶解-再沉淀和交换反应，导致大量的微量金属Ni（II）（aq）的掺入。需要进一步的工作，以进一步确定所涉及的机制，并评估与其他微量金属物种的GR的吸附反应。关键词：铁，痕量金属，层状双氢氧化物，亚氧环境，吸附，沉淀，X射线吸收光谱，X射线衍射
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 (Fe0.67-xNixFe0.33III)-Ni-II-Fe-II(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. KEYWORDS: iron, trace metals, layered double hydroxides, suboxic environments, sorption, precipitation, X-ray absorption spectroscopy, X-ray diffraction