Arsenite and arsenate binding to ferrihydrite organo-mineral coprecipitate: Implications for arsenic mobility and fate in natural environments.
Arsenite and arsenate binding to ferrihydrite organo-mineral coprecipitate: Implications for arsenic mobility and fate in natural environments.
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DOI：
10.1016/j.chemosphere.2019.02.118
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发表时间：
2019-06
期刊：
影响因子：
8.8
通讯作者：
Qin Xue;Y. Ran;Yunzhi Tan;C. Peacock;H. Du
中科院分区：
文献类型：
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作者：
Qin Xue;Y. Ran;Yunzhi Tan;C. Peacock;H. Du
砷在土壤、沉积物和地下水系统中的流动性受氧化铁/水界面吸附的强烈控制，这种吸附的程度可能会受到天然有机质（NOM）的影响。本研究的目的是研究吸附的As（III）和As（V）上的共沉淀物与水铁矿（Fh）和腐殖酸（HA）与两个有机碳（OC）负载量为5和15重量%的OC。我们表明，HA与Fh的共沉淀可以显着降低保留的As（III）和As（V）在很宽的pH范围内（4-11），并与增加OC负载，有减少砷吸附。在pH > 6.5时，As（III）在Fh上的吸附量大于As（V（交换pH），而在HA存在下交换pH转变为更酸性的pH，这意味着在NOM存在下As（III）的结合比As（V）更有利。As（III）和As（V）都与铁羟基官能团络合，未检测到Fh-HA-As三元复合物。我们观察到，在纯Fh上，约40%的吸附的As（III）被氧化为As（V），而在Fh-HA共沉淀物上仅约29%的As（III）被氧化，这表明NOM阻碍了As（III）在铁（氢）氧化物上的氧化。本研究结果表明，NOM与砷的相互作用方式，促进砷的流动性，特别是促进相对于亚砷酸盐的砷酸盐的流动性，这对于评估砷在自然和污染环境中的迁移和生物有效性具有重要意义。
Arsenic mobility in soils, sediments and groundwater systems is strongly controlled by adsorption occurring at iron oxide/water interfaces, and the extent of this adsorption may be influenced by the presence of natural organic matter (NOM). This study aims to investigate the adsorption of As(III) and As(V) onto coprecipitates made with ferrihydrite (Fh) and humic acid (HA) with two organic carbon (OC) loadings of 5 and 15 wt% OC. We show that the coprecipitation of HA with Fh can significantly reduce the retention of both As(III) and As(V) over a wide pH range (4–11), and with increased OC loading, there is reduced arsenic adsorption. On pure Fh, As(III) is adsorbed to a greater extent than As(V) at pH > 6.5 (the crossover pH), whereas the crossover pH shifts to more acidic pH in the presence of HA, implying that the binding of As(III) is more favorable than As(V) in the presence of NOM. Both As(III) and As(V) are complexed with the ferric hydroxyl functional groups, and no ternary Fh-HA-As complexes are detected. We observe that ∼40% of the adsorbed As(III) is oxidized to As(V) on pure Fh, compared to only ∼29% of As(III) oxidation on the Fh-HA coprecipitate, indicating that NOM hinders As(III) oxidation on iron (hydr)oxide. The results of this study suggest that NOM interacts with arsenic in ways that promote arsenic mobility and especially promote the mobility of arsenate relative to arsenite, which is of great significance for evaluating the migration and bioavailability of arsenic in both natural and contaminated environments.