Effect of major anions on arsenate desorption from ferrihydrite-bearing natural samples
Effect of major anions on arsenate desorption from ferrihydrite-bearing natural samples
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DOI：
10.1016/j.apgeochem.2008.01.006
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发表时间：
2008-06-01
影响因子：
3.4
通讯作者：
Fanfani, Luca
中科院分区：
文献类型：
--
作者：
Frau, Franco;Biddau, Riccardo;Fanfani, Luca
采用静态动力学实验和地球化学模拟方法，研究了背景电解质（Na 2 HPO 4中心点2 H（2）O、NaHCO 3、Na 2SO 4、NaNO 3和NaCl）对以水铁矿为主要含砷相的3个环境样品（尾矿、河床沉积物和表土）中As（V）解吸的影响。实验结果表明，溶解的磷酸盐和碳酸盐物种的存在下，砷（V）释放大大增加。类似于PO 43+，水铁矿和含水碳酸盐物种之间的强烈的内球型表面相互作用的建议。硝酸盐和Cl-对As（V）的解吸反应影响不大，SO4_2-则表现出中间行为，这取决于其溶解浓度，可能影响表面络合物的类型（即外球或内球）。As（V）的释放过程符合Lagergren修正的一级解吸速率方程，解吸速率常数k（des）大多在0.0012-0.0030 min（-1）之间。PHREEQC的解吸实验建模，与水铁矿作为主要的As-轴承相，表明pH值的影响是显着不太重要的比碳酸盐物种的置换作用，在确定量的As（V）释放到溶液中。当碳酸盐表面络合物从模型中排除时，As（V）解吸的模拟完全失败。在NaHCO_3实验中，尾矿样品的观测值与计算值之间的最佳匹配也包括在模型中的臭葱石和毒砂的溶解。此外，建模强调质量差的硫酸盐物种的吸附常数，导致强烈高估的As（V）解吸在pH 4和低估pH 7.5。虽然这项研究的结果与其他作者最近的研究结果一致，但它们不能推广或直接应用于自然系统。然而，环境影响有关的流动性，以及可能的应用在各个领域（如灌溉农业，土壤净化，水处理和矿山现场修复），可能来自这些研究结果。(C)2008爱思唯尔有限公司保留所有权利。
The influence of background electrolytes (Na2HPO4 center dot 2H(2)O, NaHCO3, Na2SO4, NaNO3 and NaCl) on arsenate (As(V)) desorption from 3 environmental samples (a tailings sample, a stream-bed sediment and a top soil) containing ferrihydrite as the main As-bearing phase has been studied by means of kinetic batch experiments and geochemical simulations. The experimental results indicate that As(V) release increases greatly in the presence of dissolved phosphate and carbonate species. Similarly to PO43+, a strong surface interaction of inner-sphere type between ferrihydrite and aqueous carbonate species is suggested. Nitrate and Cl- have negligible effects on the As(V) desorption reaction, whereas SO4_2- exhibits intermediate behavior depending on its dissolved concentration that probably influences the type of surface complex (i.e. outer-sphere or inner-sphere). The process of As(V) release follows the first-order rate equation of Lagergren modified for desorption; most values of the desorption rate constant k(des) are in the range of 0.0012-0.0030 min(-1). Modeling of the desorption experiments with PHREEQC, with ferrihydrite as the main As-bearing phase, indicates that the influence of pH is notably less important than the displacement action of carbonate species in determining the amount of As(V) released to solution. Simulation of As(V) desorption totally fails when the carbonate surface complexes are excluded from the model. In the NaHCO3 experiments with the tailings sample the best match between observed and calculated data is obtained also including dissolution of scorodite and arsenopyrite in the model. Moreover, modeling has stressed the poor quality of the adsorption constants for sulfate species that leads to strong overestimation of As(V) desorption at pH 4 and underestimation at pH 7.5. Although the findings of this study are consistent with the results of recent studies from other authors, they cannot be generalized or directly applied to natural systems. However, environmental implications concerning As mobility, as well as possible application in various fields (e.g. irrigation agriculture, soil decontamination, water treatment and mine site remediation), might be derived from these findings. (C) 2008 Elsevier Ltd. All rights reserved.