Abstract：
The contamination of arsenic (As) in aqueous environments has drawn widespread attention, and iron compounds may largely alter the migration ability of As. However, the stability of As(III) in Fe-As system with the intervention of organic matter (OM) remains unclear. Herein, we had explored the co-precipitation and co-oxidation processes of As-Fe system by using batch experiments combined with Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) in this research. The precipitation quantity of As(III) increased (28.85-92.41 %) when the As/Fe ratio decreased, and increased (24.20-64.20 %) with pH increased. The main active substance for oxidizing As(III) was H2O2, which was produced in the As-Fe system. FTIR and XPS revealed that As(III) was first oxidized in neutral, and then absorbed and enteredthe interior of Fe(OH)3 colloids. But under alkaline conditions, As(III) was adsorbed by Fe (Oxyhydr) oxides firstly, and then oxidized. The intervention of OM would inhibit the redistribution process of As(III) in aqueous environments. Functional groups and unsaturation of the carbon chain were the dominant factors that affected the precipitation and oxidation processes of As(III), respectively. Co-existing ions (especially PO43-) also signally affected the precipitation quantity of As(Ⅲ) in the system and, when coexisting with OM, could exacerbate this process. The influence of co-existing ions on the redistributive process of As(III) in the As-Fe system with/without OM were as follows: PO43- > SO42- > mixed ions > SiO32-. Moreover, high concentration of OM and PO43- might lead to morphological alterations of As, acting as a threat to aqueous environments. In summary, the present findings were to further understand and appreciate the changes of As toxicity in the aqueous environments. Particularly, the coexistence of OM and As can potentially increase the risk to drinking water safety.
摘要：
砷(As)在水环境中的污染已引起广泛关注,铁化合物可能在很大程度上改变As的迁移能力。然而,在有机质（OM）的干预下，Fe-As体系中As（III）的稳定性尚不清楚。在这里，在这项研究中，我们通过使用分批实验结合傅立叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）探索了As-Fe体系的共沉淀和共氧化过程。当As/Fe比降低时,As(III)的析出量增加(28.85-92.41%),并且随着pH的增加而增加（24.20-64.20％）。氧化As（III）的主要活性物质是H2O2，它是在As-Fe系统中产生的。FTIR和XPS表明As(III)首先在中性然后吸收并进入Fe（OH）3胶体内部。但在碱性条件下,As(III)首先被Fe(Oxyhydr)氧化物吸附，然后被氧化。OM的干预会抑制As（III）在水性环境中的再分配过程。碳链的官能团和不饱和度是影响As（III）沉淀和氧化过程的主要因素，分别。共存离子(尤其是PO43-)也显著影响了系统中As(Ⅲ)的析出量,当与OM共存时，可能会加剧这一过程。共存离子对含/不含OM的As-Fe体系中As（III）的再分配过程的影响如下：PO43->SO42->混合离子>SiO32-。此外，高浓度的OM和PO43-可能导致As的形态改变，对水性环境构成威胁。总之,本研究结果旨在进一步了解和理解As在水环境中的毒性变化。特别是,OM和As的共存可能会增加饮用水安全的风险。
