Low-Molecular-Weight Organic Acid Complexation Affects Antimony(III) Adsorption by Granular Ferric Hydroxide.
Low-Molecular-Weight Organic Acid Complexation Affects Antimony(III) Adsorption by Granular Ferric Hydroxide.
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DOI：
10.1021/acs.est.8b06297
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发表时间：
2019-04
影响因子：
11.4
通讯作者：
Xiaochen Li;T. Reich;M. Kersten;C. Jing
中科院分区：
文献类型：
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作者：
Xiaochen Li;T. Reich;M. Kersten;C. Jing
溶解的有机物通常会增强天然水生环境中锑(III) 的流动性。在吸附研究中，酒石酸通常用于与溶解的 Sb(III) 形成络合物并稳定其稳定。然而，这种低分子量有机酸络合与 Sb(III) 吸附之间的竞争很少受到关注，这促使我们测量水处理厂常用的羟基氧化铁吸附剂对 Sb(III) 的吸附量。 Sb K 边 X 射线吸收精细结构 (EXAFS) 谱给出了 Sb-O 和 Sb-Fe 距离和配位，其与具有与 Fe(O,OH)6 八面体共享角的三角 Sb(O,OH)3 多面体的二齿双核内球配合物以及与 Sb(O,OH)4 四面体共享角的二齿单核内球配合物在碱性 pH 值下相容。实验批量滴定数据使用电荷分布多位点表面络合（CD-MUSIC）模型进行拟合，受 EXAFS 分子水平信息的约束并考虑有机配体的竞争效应。随着 Sb(III) 浓度的增加，在酸性至中性 pH 值下吸附的比例减少。 CD-MUSIC 吸附模型表明，这完全是由溶液中酒石酸盐络合的强烈竞争引起的，这导致吸附常数高于未考虑这种竞争而得出的吸附常数。吸附模型结果允许使用 USGS PhreePlot 代码计算 pe-pH 优势图。该研究提供了一致的表面络合稳定性常数，使新数据库还可用于可靠地模拟缺氧水环境中有毒氧阴离子的吸附：例如，准确模拟 Sb(III) 和 As(III) 之间的竞争。
Antimony(III) mobility in natural aquatic environments is generally enhanced by dissolved organic matter. Tartaric acid is often used to form complexes with and stabilize dissolved Sb(III) in adsorption studies. However, competition between such low-molecular-weight organic acid complexation and adsorption of Sb(III) has received little attention, which prompted us to measure Sb(III) adsorption by iron oxyhydroxide adsorbents commonly used in water treatment plants. Sb K-edge X-ray absorption fine structure (EXAFS) spectra gave Sb-O and Sb-Fe distances and coordinations compatible with a bidentate binuclear inner-sphere complex with trigonal Sb(O,OH)3 polyhedra sharing corners with Fe(O,OH)6 octahedra and a bidentate mononuclear inner-sphere complex but with Sb(O,OH)4 tetrahedra at alkaline pH. Experimental batch titration data were fitted using the charge-distribution multisite surface complexation (CD-MUSIC) model, constrained by the EXAFS molecular level information and taking competitive effects by the organic ligand into consideration. The proportion adsorbed at acid to neutral pH decreased as the Sb(III) concentration increased. The CD-MUSIC adsorption model indicates that this was solely caused by strong competition from tartrate complexation in solution, which leads to adsorption constants higher than those derived without taking this competition into account. The adsorption model results allow for calculating a pe-pH predominance diagram using the USGS PhreePlot code. The study provides consistent surface complexation stability constants, allowing the new database to be used also to reliably model adsorption of toxic oxyanions in anoxic aqueous environments: for example, to accurately simulate competition between Sb(III) and As(III).