A mechanistic description of Ni and Zn sorption on Na-montmorillonite .2. Modelling
A mechanistic description of Ni and Zn sorption on Na-montmorillonite .2. Modelling
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DOI：
10.1016/s0169-7722(97)00007-7
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发表时间：
1997-09-01
影响因子：
3.6
通讯作者：
Baeyens, B
中科院分区：
文献类型：
--
作者：
Bradbury, MH;Baeyens, B
第一部分报告了在各种条件下对钠蒙脱土进行的滴定和吸附边/等温线测量（Baeyens 和 Bradbury，1997）。这里使用称为 MINSORB 的计算机代码根据阳离子交换和表面络合机制对这些数据进行建模。该代码允许同时计算两种机制对放射性核素的吸收；还考虑到存在的其他阳离子的竞争反应。描述了逐步迭代拟合/建模过程。对于钠蒙脱石的情况，证明表面络合模型中不需要静电项。根据滴定结果的模型，推导出位点容量和质子化/去质子化常数的值。然后将这些值固定并用于吸附测量的所有进一步的表面络合建模。主要研究是用 Ni 进行的，但系统中存在的杂质阳离子，特别是 Zn，由于它们对 Ni 吸附的竞争作用，必须另外进行检查。详细研究了 Ni 和 Zn 的表面络合行为，给出了模型中两个 =SOH 型位点的固有表面络合常数。还考虑了锰的吸附，尽管不太详细，并且给出了该元素的估计表面络合常数。所有计算均包括阳离子交换。给出了 Ni-Na 和 Zn-Na 交换反应的测量选择性系数。该模型具有导出的参数，可以定量描述从滴定测量到吸附边缘到吸附等温线的所有实验数据。 (C) 1997 Elsevier Science B.V.
Titration and sorption edge/isotherm measurements, carried out under a wide variety of conditions on Na-montmorillonite, were reported in Part I (Baeyens and Bradbury, 1997). These data are modelled here in terms of cation exchange and surface complexation mechanisms using a computer code called MINSORB. This code allowed the uptake of radionuclides by both mechanisms to be calculated simultaneously; also taking into account competitive reactions from other cations present. A stepwise iterative fitting/modelling procedure is described. For the case of Na-montmorillonite it is demonstrated that an electrostatic term in the surface complexation model is not required. From the modelling of the titration results, values for site capacities and protonation/deprotonation constants were deduced. These values were then fixed and used in all further surface complexation modelling of the sorption measurements. The main study was carried out with Ni, but impurity cations present in the system, particularly Zn, had to be examined in addition due to their competitive effects on Ni sorption. The surface complexation behaviour of Ni and Zn was investigated in detail to give intrinsic surface complexation constants on two of the =SOH type sites included in the model. The sorption of Mn is also considered, though in less detail, and estimated surface complexation constants for this element are presented. Cation exchange was included in all of the calculations. Measured selectivity coefficients for Ni-Na and Zn-Na exchange reactions are given. The model, with the derived parameters, allowed all the experimental data from titration measurements through sorption edges to sorption isotherms to be quantitatively described. (C) 1997 Elsevier Science B.V.