Surface complexation modeling of arsenate adsorption by akageneite (β-FeOOH)-dominant granular ferric hydroxide
Surface complexation modeling of arsenate adsorption by akageneite (β-FeOOH)-dominant granular ferric hydroxide
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DOI：
10.1016/j.colsurfa.2014.02.008
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发表时间：
2014-04-20
影响因子：
5.2
通讯作者：
Stanjek, Helge
中科院分区：
文献类型：
--
作者：
Kersten, Michael;Karabacheva, Svetlana;Stanjek, Helge
赤铁石（β - feooh）是一种颗粒状氢氧化铁（GFH）的主要化合物，在世界各地的地下水净化装置中用于去除砷和其他有毒污染物，首次建立了赤铁石的表面络合模型。与α - feooh多晶针铁矿的情况不同，目前还没有公开的表面络合模型来预测竞争的氧阴离子效应。这是由于一个连接的体-表面反应性，其中从隧道位置释放的未知数量的过量质子妨碍了酸滴定法对表面质子化的定量。因此，测量到的质子摄取超过了表面质子化中活性OH基团的预期。然而，氯离子以1:1的化学计量量共吸附，并与质子从隧道位置共释放，尽管动力学较慢。由于这种动力学，使用自动滴定器进行动态酸碱滴定对于可靠地估计表面电荷与pH曲线是不可行的。我们建议用至少一天的批平衡时间精确监测批滴定期间的氯化物交换。由此获得的氯化物数据用于校正pH依赖的大量质子交换，并重建真实的表面电位随pH的曲线，从而可靠地参数化CD-MUSIC表面络合模型。(C) 2014 Elsevier B.V.版权所有
A surface complexation model has been set up for the first time with akaganeite (beta-FeOOH), a major compound of granular ferric hydroxide (GFH) used in groundwater purification units worldwide for arsenic and other toxic pollutant removal. Unlike the situation for the alpha-FeOOH polymorph goethite, there is yet no published surface complexation model to predict competing oxyanion effects. This is due to a linked bulk-surface reactivity by which excess protons released in an unknown amount from tunnel sites hamper quantification of surface protonation by acid titration. The measured proton uptake thus exceeds what can be expected from OH groups active in surface protonation. However, chloride ions are co-sorbed in 1:1 stoichiometry and co-released with the protons from tunnel sites albeit with slow kinetics. Because of this kinetics, dynamic acid-base titrations using automatic titrators are not feasible for reliable estimation of surface charge vs. pH curves. We propose to precisely monitor the chloride exchange during batch titrations with at least one day batch equilibration times. The thus obtained chloride data were used to correct for the pH-dependent bulk proton exchange and to reconstruct the true surface potential vs. pH curves, and thus to reliably parameterize a CD-MUSIC surface complexation model for arsenate adsorption. (C) 2014 Elsevier B.V. All rights reserved.