Arsenic(III, V) adsorption on a goethite-based adsorbent in the presence of major co-existing ions: Modeling competitive adsorption consistent with spectroscopic and molecular evidence
Arsenic(III, V) adsorption on a goethite-based adsorbent in the presence of major co-existing ions: Modeling competitive adsorption consistent with spectroscopic and molecular evidence
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DOI：
10.1016/j.gca.2012.09.055
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发表时间：
2013-04-01
影响因子：
5
通讯作者：
Darby, Jeannie L.
中科院分区：
文献类型：
--
作者：
Kanematsu, Masakazu;Young, Thomas M.;Darby, Jeannie L.
研究了两种含氧阴离子砷酸根（As（V））和亚砷酸根（As（III））在常见针铁矿基颗粒多孔吸附剂上的吸附，磷酸盐、草酸、硫酸盐、碳酸盐、镁和钙），并使用扩展三层模型（ETLM）进行预测，该模型是一种与光谱和分子证据一致的偶极修改的单位点三层表面络合模型。根据先前的ETLM研究和已发表的实验光谱/理论分子信息选择所有离子的表面物种。所有离子的吸附平衡常数测定使用单溶质系统中获得的吸附数据。参考占位标准状态（由K-θ表示）的吸附平衡常数与文献中针铁矿的吸附平衡常数进行了比较。针铁矿基吸附剂的这些常数的值被发现是接近针铁矿先前研究的值。这些“约束”的吸附平衡常数确定在单溶质系统中使用的ETLM预测的竞争性相互作用的As（III，V）与共存的离子在二元溶质系统。的ETLM是能够预测As（III，V）吸附在含氧阴离子（磷酸盐，草酸，硫酸盐，碳酸盐）的存在下。这项研究提出了第一个成功的和系统的预测的竞争性相互作用的As（III，V）与这些含氧阴离子使用ETLM。的ETLM预测的表面（和水）形态也提供了见解的独特的吸附行为的As（III，V）的含氧阴离子的存在下。镁和钙在较高pH值下显著增强了As（V）的吸附，而对As（III）的吸附影响不大。增强吸附的As（V），但是，不能预测的ETLM使用的表面物种在以前的ETLM研究中提出的。进一步的研究是必要的，以确定三元配合物，特别是在高pH值。吸附等温线的As（V），在吸附水处理系统中的砷的主要形式，在共存离子的存在下，在水处理系统的相关条件下，也获得和预测的ETLM研究和比较共存离子对As（V）去除的效果。(C)2012爱思唯尔有限公司保留所有权利。
Adsorption of the two oxyanions, arsenate (As(V)) and arsenite (As(III)), on a common goethite-based granular porous adsorbent is studied in the presence of major co-existing ions in groundwater (i.e., phosphate, silicic acid, sulfate, carbonate, magnesium, and calcium) and predicted using the extended triple layer model (ETLM), a dipole modified single-site triple layer surface complexation model consistent with spectroscopic and molecular evidence. Surface species of all ions were selected according to the previous ETLM studies and published experimental spectroscopic/theoretical molecular information. The adsorption equilibrium constants for all ions were determined using adsorption data obtained in single-solute systems. The adsorption equilibrium constants referenced to the site-occupancy standard state (indicated by K-theta) were compared with those for goethite in the literature if available. The values of these constants for the goethite-based adsorbent are found to be close to the values for goethite previously studied. These "constrained" adsorption equilibrium constants determined in single-solute systems were used in the ETLM to predict the competitive interactions of As(III, V) with the co-existing ions in binary-solute systems. The ETLM is capable of predicting As(III, V) adsorption in the presence of oxyanions (phosphate, silicic acid, sulfate, and carbonate). This study presents the first successful and systematic prediction of the competitive interactions of As(III, V) with these oxyanions using the ETLM. The ETLM prediction of surface (and aqueous) speciation also provides insights into the distinct adsorption behavior of As(III, V) in the presence of the oxyanions. Magnesium and calcium significantly enhanced As(V) adsorption at higher pH values, while they had little effect on As(III) adsorption. The enhanced adsorption of As(V), however, could not be predicted by the ETLM using the surface species proposed in previous ETLM studies. Further studies are necessary to identify ternary complexes, especially at high pH. Adsorption isotherms of As(V), a dominant form of arsenic in adsorptive water treatment systems, in the presence of the co-existing ions under relevant conditions of water treatment systems are also obtained and predicted by the ETLM to study and compare the effect of the coexisting ions on As(V) removal. (C) 2012 Elsevier Ltd. All rights reserved.